Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

CHAPTER 3 – Congenital Heart Disease

William C. Oliver Jr., MD,
James J. Lynch, MD

  

 

Classification and Nomenclature

  

 

General Pathophysiology Principles

  

 

Noncardiac Surgery and CHD 

  

 

Preoperative Assessment and Preparation

  

 

Premedication

  

 

Monitoring

  

 

Ventilation

  

 

Circulatory Support

  

 

Anesthetic Techniques

  

 

Muscle Relaxants

  

 

Anatomic Defects Associated with Increased Pulmonary Blood Flow 

  

 

Atrial Septal Defect (ASD)

  

 

Atrioventricular Septal Defects

  

 

Ventricular Septal Defect (VSD)

  

 

Patent Ductus Arteriosus (PDA)

  

 

Truncus Arteriosus

  

 

Total Anomalous Pulmonary Venous Connection (TAPVC)

  

 

Single Ventricle

  

 

Hypoplastic Left Heart Syndrome (HLHS)

  

 

Anatomic Defects Associated with Decreased Pulmonary Blood Flow 

  

 

Tetralogy of Fallot (TOF)

  

 

Pulmonary Atresia with VSD

  

 

Transposition of the Great Arteries (TGA)

  

 

Tricuspid Atresia (TA)

  

 

Ebstein's Anomaly

  

 

Eisenmenger's Syndrome

  

 

Obstruction of Blood Flow

  

 

Coarctation of the Aorta 

  

 

Congenital Aortic Stenosis

  

 

Conclusion

Isolated congenital heart disease (CHD) represents the most common category of birth defects, afflicting approximately 1% of liveborn infants.[1] The incidence of all forms of CHD is 75/1000 live births but 6 to 8/1000 live births when limited to moderate and severe forms. [2] [3] From 1940 to 2002 about 1 million individuals with simple congenital heart defects, and half that number each with moderate or complex defects, were born in the United States.[4] The incidence of infants born with severe CHD remains low at 2.5 to 3.0/1000 live births, whereas moderately severe forms of CHD account for another 3/1000 live births.[2] Interestingly, compared with prior studies of CHD, the incidence has been steadily rising by three to nine times, in large measure owing to echocardiography, because earlier studies reflected only patients referred to the major centers for angiography.[2]

Previously, 41% of individuals with CHD died within 1 year of birth and 25% died in the first week of life.[5] Advances in surgery and management of CHD are allowing 85% of these infants and children to reach adulthood[6] with a life expectancy approaching that of the general population. Not only are neonates and infants doing better with treatment, but their preoperative mortality has decreased. In the not too distant future there will be more adults with CHD than children. It is estimated that in the United States alone, at least 800,000 to 1 million adults currently have CHD. [7] [8] The number of affected individuals is growing at an annual rate of 5% per year. Because of the increasing longevity of children, adolescents, and adults with CHD, greater numbers are undergoing noncardiac surgical procedures of both the minor and major variety. [9] [10]

The condition of patients with CHD may vary significantly before noncardiac surgery. They may require noncardiac surgery with their CHD totally uncorrected, palliated, or completely corrected. Some individuals may have very mild CHD, requiring relatively little medical attention, whereas others have complex disease that demands significant medical expertise and resources.[2] “Corrective” surgery does not ensure that an individual is “normal” and unaffected by his or her CHD but instead may struggle with a range of problems, such as arrhythmias, congestive heart failure (CHF), and pulmonary hypertension (PAH).[11] Thus, anesthetic management of these persons will be highly individualized and complex, even though the CHD may be the same. Additionally, the crossover of CHD from pediatric to adult places both pediatric and adult anesthesiologists in unique positions, because one may be more familiar with CHD and the other more familiar with adults. This chasm impacts adults with CHD more than pediatric patients, with regard to noncardiac surgery and anesthesia. Patients with CHD who require noncardiac surgery provide a great challenge for anesthesiologists. In the following pages we will describe some of the more common congenital heart defects that an anesthesiologist may encounter in a noncardiac surgical environment from an anatomic, pathophysiologic, and anesthetic perspective.

CLASSIFICATION AND NOMENCLATURE

Defects of CHD are classified in many different ways, each with their own merits, but no one system has been totally satisfactory. From the standpoint of the anesthesiologist caring for these infants, children, and adults, three basic categories are useful from a functional point of view ( Table 3-1 ). The defect will be classified according to increased pulmonary blood flow or decreased pulmonary blood flow. If there is no shunting of blood, the third category is obstruction of blood flow. The clinical representation of this classification is largely CHF or cyanosis. This simple classification will facilitate formulation of an anesthetic strategy and its delivery.


TABLE 3-1   -- Flow Characteristics of Various Congenital Cardiac Lesions

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Presently, there is no unified system of nomenclature for CHD. The terminology and classification suggested by Anderson and colleagues[12] is subsequently modified and used for this chapter. The orientation of the heart in the chest is defined by the direction in which the ventricles are aligned from base to apex ( Fig. 3-1 ). Levocardia is the most common orientation. Because some of these heart defects are also associated with abnormalities of other organ systems, visceral sidedness (situs) is important to note. The cardiovascular, respiratory, and digestive systems acquire asymmetry during a point in embryologic development. Visceral sidedness is characterized as normal (situs solitus), mirror-image (situs inversus), and isomeric or indeterminate (situs ambiguus). Cardiac sidedness is determined by the position of the right atrium (RA), not the direction of the apex of the ventricle. The morphologic RA is normally right sided.[13] Another term, connection, is an anatomic term that indicates a direct link between two structures, whereas drainage indicates the direction of blood flow. Cardiac morphology is relatively constant compared with the anatomy but is important because it reflects the heart's potential for hemodynamic performance. The morphologic RA is characterized by a large pyramidal appendage and terminal crest ( Fig. 3-2 ). The morphologic left atrium (LA) is very different from the RA in that it does not have a terminal crest or pectinate muscles, and the main body is smooth ( Fig. 3-3 ). The atrioventricular (AV) valves are fibrous tissue flaps that connect ventricles and atria anatomically but separate them electrically. References to right or left AV valve minimize confusion that may occur with tricuspid or mitral valve nomenclature. The morphology of the AV valves typically follows the morphology of the ventricles of entry, not the atria of exit. A morphologic right ventricle is characterized by numerous small papillary muscles arising from the septal and free wall ( Fig. 3-4 ). In contrast, the morphologic left ventricle has two groups of papillary muscles that arise from the free wall of the left ventricle ( Fig. 3-5 ). The positions of the great vessels are generally described in relation to the position of the pulmonary trunk. Normally, the aorta is positioned right and posterior.

 
 

FIGURE 3-1  The cardiac base-apex axis is independent of cardiac position or sidedness. The three types are shown schematically. A, atrium; V, ventricle.  (Reprinted with permission from Edwards WD: Classification and terminology of cardiovascular anomalies. In Emmanouilides GC, Riemenschneider TA, Allen HD, Gutgesell HP [eds: Moss and Adams Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult. Baltimore, Williams & Wilkins, 1995, p 108.)

 

 

 

 
 

FIGURE 3-2  Interior of right atrium. Ant, anterior; CoS, coronary sinus; CT, crista terminalis (terminal crest); IVC, inferior vena cava; MP, musculi pectinati (pectinate muscles); Post, posterior; Sept, septal; Sept I, septum primum; Sept II, septum secundum; SVC, superior vena cava; TS, tinea sagittalis (sagittal worm); TV, tricuspid valve.  (Reprinted with permission from Van Praagh R: Cardiac anatomy. In Chang E [ed: Pediatric Cardiac Intensive Care. Baltimore, Williams & Wilkins, 1998, p 4.)

 

 

 

 
 

FIGURE 3-3  Interior of LA, left atrium. LAA, left atrial appendage; LV, morphologically left ventricle; MV, mitral valve; PV, pulmonary veins.  (Reprinted with permission from Van Praagh R: Cardiac anatomy. In Chang E [ed: Pediatric Cardiac Intensive Care. Baltimore, Williams & Wilkins, 1998, p 5.)

 

 

 

 
 

FIGURE 3-4  A, Interior of RV, right ventricle. AP, anterior papillary muscle; FW, free wall; LV, morphologically left ventricle; MB, moderator band; ML, muscle of Lancisi; PA, pulmonary artery; PB, parietal band; S, septum; SB, septal band; TV, tricuspid valve. B, The four main anatomic and developmental components of the right ventricle: (1) atrioventricular canal; (2) sinus; (3) septal band (proximal conus); and (4) parietal band (distal subsemilunar conus). Components 1 and 2 = RV inflow tract. Components 3 and 4 = RV outflow tract.  (Reprinted with permission from Van Praagh R: Cardiac anatomy. In Chang E [ed: Pediatric Cardiac Intensive Care. Baltimore, Williams & Wilkins, 1998, p 7.)

 

 

 

 
 

FIGURE 3-5  A, Interior of LV, left ventricle. AL, anterolateral (papillary muscle); AL of MV, anterior leaflet of mitral valve; Ao, aorta; FW, free wall; LC, left coronary (ostium); PP, posteromedial papillary (muscle); RC, right coronary (ostium); S, septum. B, The four main anatomic and developmental components of the LV: (1) atrioventricular canal; (2) sinus; (3) proximal conus; and (4) distal or subsemilunar conus. Components 1 and 2 = LV inflow tract. Components 1, 3, and 4 = LV outflow tract.  (Reprinted with permission from Van Praagh R: Cardiac anatomy. In Chang E [ed: Pediatric Cardiac Intensive Care. Baltimore, Williams & Wilkins, 1998. p 9.)

 

 

 

In describing the heart, three connections exist: venoatrial, atrioventricular, and ventriculoatrial. Venoatrial connections include the superior and inferior vena caval veins connecting to the morphologic RA and the pulmonary veins connecting to the morphologic LA. There are four combinations of AV connections: concordant, discordant, univentricular, and ambiguous ( Fig. 3-6 ). Concordant is the normal state, whereas discordant has the RA connected to the left ventricle. If both atria are connected to one ventricle, it is univentricular. The connection to the heart, not the heart itself is defined as univentricular.[13] The ventriculoarterial connections occur in four combinations: concordant, discordant, and double, single, and common outlets ( Fig. 3-7 ). The concordant description is the normal state. Discordant involves a right ventricular origin of the aorta and a left ventricular origin of the pulmonary artery. If both great arteries arise from only one ventricular cavity, it is called double outlet. A single outlet refers to the situation of only one artery arising from a ventricular chamber without another vessel arising at all. A common outlet refers to one vessel that contains both the pulmonary and aorta as undivided roots. More detail regarding the nomenclature complexities of CHD is available.[13]

 
 

FIGURE 3-6  The possible atrioventricular connections are shown schematically. Concordance is synonymous with the normal state, and discordance is synonymous with ventricular inversion. For either right or left cardiac isomerism, the atrioventricular connection is always ambiguous. There are three possible univentricular forms of connection: double, single, and common inlet. RA, right atrium; RV, right ventricle; LA, left atrium; LV, left ventricle; V, ventricle.  (Reprinted with permission from Edwards WD: Classification and terminology of cardiovascular anomalies. In Emmanouilides GC, Riemenschneider TA, Allen HD, Gutgesell HP [eds: Moss and Adams Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult. Baltimore, Williams & Wilkins, 1995, p 121.)

 

 

 

 
 

FIGURE 3-7  The possible ventriculoarterial connections are shown schematically. Concordance indicates the normal state, and discordance is synonymous with transposition of the great arteries. There are three other possible connections: double, single, and common outlet. RV, right ventricle; LV, left ventricle; Ao, aorta; RPA, right pulmonary artery; LPA, left pulmonary artery; PT, pulmonary trunk; TA, truncus arteriosus.  (Reprinted with permission from Edwards WD: Classification and terminology of cardiovascular anomalies. In Emmanouilides GC, Riemenschneider TA, Allen HD, Gutgesell HP [eds: Moss and Adams Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult. Baltimore, Williams & Wilkins, 1995, p 123.)

 

 

 

Copyright © 2008 Elsevier Inc. All rights reserved. - www.mdconsult.com

Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

GENERAL PATHOPHYSIOLOGY PRINCIPLES

Knowledge of the pathophysiology of CHD is important for anesthetic management of these of individuals. Not all defects of CHD include shunting, but an understanding is helpful. Ohm's law (V = IR) is the basic principle of shunt physiology represented as:

With the addition the of Hagen-Poiseuille equation that describes the relationship between flow through a cylinder of constant size and length, a formula can be devised that demonstrates anatomic factors that influence blood flow in CHD:

where Q = blood flow, P = pressure gradient, D = diameter, and R = resistance. Another major concept is the relationship between pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR). The equations to calculate these two values are:

The units for these values are mm Hg/L/min, commonly referred to as Wood's unit. PVR is usually below 3 units, whereas the SVR varies between 15 and 30 units.

Pulmonary blood flow can be calculated using the Fick principle with hemoglobin (Hb) concentration, saturations, and oxygen consumptions. Consequently, pulmonary blood flow (Q) is determined by:

Many catheterization reports will report the ratio of pulmonary blood flow to systemic blood flow (Qp/Qs) to express the degree of shunt. Excessive pulmonary blood flow is more than a Qp/Qs of 3. Inadequate pulmonary blood flow is a Qp/Qs of less than 1.

In the following pages, various defects of CHD are described concerning anatomy and pathophysiology and important concerns are presented regarding administration of anesthesia to the affected individuals.

Copyright © 2008 Elsevier Inc. All rights reserved. - www.mdconsult.com

Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

NONCARDIAC SURGERY AND CHD

The Mayo clinic reported on 276 patients younger than the age of 50 years with CHD who underwent 480 procedures (surgical or diagnostic) during a 5-year period.[9] Forty-two percent of patients underwent two or more procedures during this interval. The congenital heart defects of the patients are displayed in Table 3-2 . Left-to-right shunt was the most common defect found in 56% of the patients, with cyanotic CHD at 25% and obstructive CHD accounting for 17%. The median age at the time of the first procedure was 7 years.[9] The mortality rate (2.6%) was higher than the operative mortality of pediatric patients undergoing cardiac surgery with cardiopulmonary bypass (CPB), which is also the case with mortality for adults (4%) who undergo noncardiac surgery with CHD.[6] Mortality associated with noncardiac surgery in patients with CHD has been reported to be as high as 12% overall and 16% for major procedures.[10]

TABLE 3-2   -- Primary Pathophysiologic Finding or Diagnosis in Study Patients with Congenital Heart Disease (N = 276)[*]

Primary Diagnosis

No. of Patients

Shunt

155

 Isolated VSD

58

 Patent ductus arteriosus

36

 ASD[†]

35

 Complete AV septal defect

10

 Double-outlet right ventricle

7

 Primum ASD and cleft left AV valve

4

 Truncus arteriosus

3

 Other

2

Cyanotic CHD

68

 Single ventricle, excluding heterotaxia

25

 Tetralogy of Fallot

15

 Pulmonary valve atresia and VSD

10

 Complex complete TGA

8

 Ebstein's anomaly of the tricuspid valve

5

 Simple complete TGA

4

 Heterotaxia syndromes

1

Obstructive CHD

48

 Pulmonary stenosis[‡]

21

 Coarctation syndrome, including interrupted arch

18

 Complex TGA

6

 Vascular ring

3

Other

5

 Congenital aortic regurgitation

1

 Congenitally corrected TGA

1

 Other anomalies

3

Reprinted with permission from Warner MA, Lunn RJ, O’Leary PW, Schroeder DR: Outcomes of noncardiac surgical procedures in children and adults with congenital heart disease. Mayo Clin Proc 1998;73:729.

ASD, atrial septal defect; AV, atrioventricular; CHD, congenital heart disease; TGA, transposition of the great arteries; VSD, ventricular septal defect.

 

*

Who underwent a noncardiac surgical procedure between January 1987 and November 1992.

Excluding ostium primum ASD and including partial anomalous pulmonary veins.

Including subvalvular and supravalvular stenosis.

 

 

The challenge in the anesthetic management of patients with CHD corresponds to the multiple facets a particular congenital defect may consist of for each patient. This is supported by the fact that 5.4% of individuals with various types of CHD experienced a perioperative complication with their first noncardiac procedure.[9] The incidence more than doubles to 12.9% if the patient is younger than 2 years of age.

The importance of the preoperative assessment and preparation cannot be overestimated. The presence of more severe defects and associated risk factors clearly makes these patients individuals who require the highest degree of care.

Preoperative Assessment and Preparation

For patients with CHD, it is especially important to thoroughly examine prior medical and surgical records to recognize any change in cardiac physiology and identify new or previously existing risk factors. Clearly, prior surgical or catheterization procedures may have resulted in physiologic changes that may impact patient care. A child with hypoplastic left heart syndrome (HLHS) has markedly different anesthetic considerations before and after a Norwood procedure.

Irrespective of whether cyanosis or CHF is present, neurologic, hematologic, renal, and pulmonary systems are profoundly affected.[6] To evaluate the severity of the CHD before surgery, certain characteristics such as arterial saturation less than 75% (cyanosis), Q/P greater than 2, left ventricular outflow tract gradient greater than 50 mm Hg, elevated PVR, and hematocrit (HCT) greater than 60% are established risk factors.[14] Accordingly, medications to treat CHF, inpatient surgical procedures, and higher ASA physical status have been associated with more complications in patients with CHD undergoing noncardiac surgery.[10] PAH is especially important to identify before surgery, because it has been associated with a complication rate of 15%, compared with 4.7% without PAH for patients undergoing noncardiac surgery.[9] Furthermore, differences in the respiratory system and ventilator management accompany the onset of PAH compared with those who do not develop it.[15]

Beyond the expected congenital heart risk factors, it is also important to identify common health disorders such as diabetes, hypertension, renal disease, or extracardiac anomalies that may be overshadowed by the CHD during the preoperative assessment and that are normally expected to increase surgical risk. Extracardiac anomalies are present in 20% to 35% of patients with CHD and tend to be mostly musculoskeletal or involve the central nervous system and renal-urinary system. [3] [5] Sixty percent of individuals with extracardiac anomalies and CHD were affected by more than one system, excluding the cardiac anomaly.[16] Table 3-3 includes the most recognized chromosomal abnormalities with extracardiac anomalies to be associated with CHD.[1] Twenty-five percent of extracardiac anomalies exist in those with ventricular septal defect (VSD), tetralogy of Fallot (TOF), patent ductus arteriosus (PDA), complex coarctation, complex VSD, malpositions, and atrial septal defect (ASD). Trisomy 21 accounts for 71% of chromosomal abnormalities in those with CHD. Following trisomy 21, chromosome 22q11, referred to as CATCH, includes c left palate, abnormal facies, thymic aplasia, cardiac defect, and hypocalcemia.[1] Genetic syndromes associated with CHD have been reviewed.[17]


TABLE 3-3   -- Chromosomal Causes of Congenital Heart Disease

Mechanism

Chromosome/Region

Eponym

Characteristic Heart Defect(s)

Tetrasomy

22pter-q11

Cat's-eye syndrome

TAPVR, Persistent left SVC

Trisomy

13

Patau syndrome

VSD, PDA, ASD, dextroposition

 

18

Edwards syndrome

VSD, ASD, PDA

 

21

Down syndrome

VSD, AVSD, ASD

Monosomy

X

Turner syndrome

LVOT and aorta malformation

Deletion

3p

3p-syndrome

AVSD

 

4p

Wolf-Hirschhorn

ASD

 

5p

Cri du chat syndrome

Variable (in 30%)

 

8 p

8p-syndrome

AVSD

 

9p

9p-syndrome

VSD, PDA, PS

Microdeletion

7q11

Williams syndrome

SVAS, PPAS, PS

 

17p11.2

Smith-Magenis syndrome

PS, ASD, VSD, AV valve malformation

 

17p13.3

Miller-Dieker syndrome

TOF, VSD, PS

 

22q11.2

Di George syndrome[*]

Outflow tract and aortic arch anomalies

Reprinted with permission from Brennan P, Young ID: Congenital heart malformation: Aetiology and association. Semin Neonatol 2001;6:18.

ASD, atrial septal defect; AV, atrioventricular; AVSD, atrioventricular septal defect; LVOT, left ventricular outflow tract; PDA, patent ductus arteriosus; PPAS, peripheral pulmonary artery stenosis; PS, pulmonary valve stenosis; SVAS, supravalvar aortic stenosis; TAPVR, PAPVR, total/partial anomalous pulmonary venous return; TOF, tetralogy of Fallot; VSD, ventricular septal defect.

 

*

Related syndromes caused by 22q11 microdeletion: velocardiofacial (Shprintzen) syndrome, conotruncal anomaly-face syndrome.

 

 

Musculoskeletal abnormalities must be identified because they may cause obstacles to intubation and ventilation. A high index of suspicion is valuable because symptoms are usually nonspecific. Up to 25% of individuals with CHD may have an extracardiac anomaly involving the airway. Besides musculoskeletal abnormalities, enlarged cardiac or pulmonary vascular structures may threaten airway patency by extrinsic compression in these patients.[18] Careful inspection of the airway in anticipation of tracheal intubation is critical, because respiratory reserve is significantly limited. Obstruction is common with aortic dilation secondary to pulmonary atresia with VSD and major aortopulmonary collaterals and right aortic arch.[19]

It is rare to encounter coronary artery disease in patients with CHD, but chronic myocardial injury may be present in up to 40% of some defects, possibly related to inadequate perfusion for various reasons, but not atherosclerosis. Right-sided myocardial ischemia is more likely in those with right-sided cardiac defects.[14] PDA, coarctation of the aorta, and TOF have been associated with myocardial damage in infancy.[20] Although electrocardiographic (ECG) evidence may be lacking, individuals with CHF are especially at risk for myocardial ischemia.[20] Doppler color flow velocity is a good option to noninvasively assess coronary flow.[21]

Unless surgery is emergent, optimal physical condition is valuable for individuals with CHD. Evidence of worsening CHF with tachypnea or rales should at least delay surgery pending further investigation. However, respiratory abnormalities are often difficult to differentiate from cardiovascular abnormalities with CHD. Wheezing may be evidence of a new pulmonary infection or a manifestation of CHD.

Arrhythmias are common in patients with CHD, especially adolescents and adults.[22] It is important to identify a history of arrhythmias in these patients, because they may be occult or chronic, contributing to a slow hemodynamic deterioration.[23] In adults, Holter monitoring may be recommended to identify occult arrhythmias. Atrial dysrhythmias are especially common since volume loads predispose to dilated atria. The most common arrhythmias to occur in patients with CHD are the intra-atrial reentrant tachycardias (IART). They primarily originate in the RA. Similar to atrial flutter, IART have longer cycle lengths and multiple variations of P wave morphology. Management of these arrhythmias is complicated and has been reviewed.[24] Atrial fibrillation is less common than IART but is as difficult to treat at times, requiring a Maze procedure. Ventricular tachycardia is rare in CHD compared with other arrhythmias, but ventriculotomy may cause electrical instability and ventricular ectopy. Underperfused myocardium due to hypertrophy is predisposed to ventricular dysrhythmias. Sinoatrial node dysfunction and AV conduction abnormalities are also common in CHD, but pacemaker implantation may be challenging.[24] Certain congenital heart defects are more often associated with arrhythmias ( Table 3-4 ). Ebstein's anomaly and corrected transposition of the great arteries (TGA) have a high incidence of accessory AV pathways.[24] In many cases, electrophysiologic sequelae in this population are due to the arrhythmogenic potential of myocardium subjected to septal patches and suture lines in intra-atrial or intraventricular locations, chronic cyanosis, and abnormal volume-pressure physiology. [23] [24] Reentrant tachycardias are especially common following certain operations for CHD, such as repair of TOF, Mustard or Senning operation, and Fontan procedure. More recently, these procedures have been modified to reduce the likelihood of arrhythmias.


TABLE 3-4   -- Arrhythmias and Commonly Associated Congenital Heart Defects

Arrhythmia

Associated Defects

Tachycardias

Wolff-Parkinson-White syndrome

Ebstein's anomaly

 

“Corrected” transposition

Intra-atrial reentrant tachycardia

Postoperative Mustard

 

Postoperative Senning

 

Postoperative Fontan

 

Other

Atrial fibrillation

Mitral valve disease

 

Aortic stenosis

 

Single ventricle

Ventricular tachycardia

Tetralogy of Fallot

 

Aortic stenosis

 

Other

Bradycardias

SA node dysfunction

Postoperative Mustard

 

Postoperative Senning

 

Postoperative Fontan

 

Other

Congenital AV block

AV septal defects

 

“Corrected” transposition

Acquired AV block

VSD closure

 

Tetralogy of Fallot repair

 

Other

SA, Sinoatrial; AV, atrioventricular; VSD, ventricular septal defect. Reprinted with permission from Walsh EP: Arrhythmias in patients with congenital heart disease. Cardiac Electrophysiol Rev 2002;6:423.

 

 

 

Although neurologic integrity is not at the same risk with noncardiac surgery compared with cardiac surgery, and circulatory arrest in those with CHD, necropsy studies have shown that 2% to 10% of individuals with CHD have central nervous system malformations, increasing the risk of further injury with any subsequent operation.[25] Increased red blood cell mass has also been associated with a higher risk of cerebrovascular injury, often attributed to hyperviscosity of an elevated HCT of cyanotic CHD. In instances of primarily venous, not arterial, thrombosis, the incidence may reach 20% in these patients.[26] Children with polycythemia are at greater risk for thrombosis than adults.[14] Phlebotomy has been recommended by some as a prophylactic measure to reduce the risk of thrombosis but more recently has been associated with an increased risk of stroke, as 50% of patients with cerebrovascular events underwent phlebotomy.[26]

Laboratory evaluation will depend on the congenital heart defect and the complexity of the impending surgery. A recent preoperative Hb concentration is advisable to establish the baseline oxygen delivery needs of patients, especially those with cyanotic CHD, where the Hb may reside in the range of 15 to 20 g/dL. The effectiveness of oxygen delivery with an Hb beyond 20 g/dL is unclear. In the neonate or infant for surgery, a Hb of greater than 20 mg/dL may be associated with acidosis or infarction.[27] However, therapeutic phlebotomy is not uniformly recommended.

Hemostasis is an important consideration for surgery, especially since 70% of patients with CHD may have coagulation abnormalities.[28] Excessive bleeding in infants and children may have devastating outcomes. Coagulation derangements may actually be more serious than routine testing can detect. The exact mechanism and pathologic processes responsible for hemostatic abnormalities are not entirely understood, but individuals with CHD are more likely to experience profuse bleeding even with minor surgery.[29] This risk affects both adult and pediatric patients similarly.[27] Medications should be carefully screened to detect the use of warfarin (Coumadin) and aspirin, because these agents may be additive with the abnormalities of coagulation associated with CHD. Certain congenital hemostatic abnormalities such as von Willebrand's disease may be associated with CHD.

In a prospective study of 235 patients younger than the age of 34 years scheduled for cardiac surgery who underwent preoperative evaluation of prothrombin time (PT), activated partial thromboplastin time (APTT), platelet count, thrombin time, and bleeding time, 19% of participants had an abnormality of one laboratory value that was significantly higher than the expected incidence of abnormal coagulation tests in a control population.[30] Seven percent of individuals with CHD had two abnormal coagulation values. Poor cardiac performance, cyanosis, and elevated HCT were associated with the highest incidence of coagulation abnormalities. Goel and coworkers[29] confirmed the hemostatic abnormalities of CHD. Platelet count, PT, APTT, fibrinogen, D-dimer, and factors VII and VIII were obtained on 25 cyanotic and acyanotic children and compared with controls. Twenty-eight percent of both cyanotic and acyanotic individuals had isolated coagulation abnormalities, but 64% of cyanotic patients had more than one coagulation abnormality, as compared with only 20% of acyanotic individuals. Thirty-eight percent of these children with CHD also appeared to be in a state of disseminated intravascular coagulation (DIC), according to D-dimer elevations. A state of accelerated fibrinolysis has been reported by some to be associated with CHD.[31] Platelet function and number have been reported to be abnormal in patients with CHD.[31] Hemostasis is also related to the degree of hypoxia and HCT. [14] [28] Cyanotic children are significantly more likely to have evidence of platelet activation than acyanotic ones.[31] Thrombocytopenia has been shown to correlate with arterial saturation.

Age is a factor to consider when evaluating hemostatic considerations, because a large percentage of those with CHD are infants and children. The neonate may be subject to hepatic immaturity, defective clot retraction, DIC, low plasma factor levels, and qualitative platelet dysfunction.[32] As one ages, coagulation profiles change until transitioning to the adult profile ( Fig. 3-8 ). Mean factor prothrombin, VII, IX, and X concentrations remain below adult levels throughout childhood, appearing as prolongation of the APTT and PT.[33] Impaired synthesis of the vitamin K clotting factors is not uncommon in these patients.

 
 

FIGURE 3-8  Development of coagulation factors during childhood. Plasma concentrations of selected contact, vitamin K-dependent, and cofactors of coagulation from term through childhood. It is useful to think of the major changes as occurring in three periods: from birth through the first 6 months of life, from the first year until early adolescence, and during or by the end of adolescence.  (Reprinted with permission from Richardson MW, Allen GA, Monahan PE: Thrombosis in children: Current perspective and distinct challenges. Thromb Haemost 2002;88:900.)

 

 

 

Although patients with CHD should have a recent preoperative chest radiograph to compare with a previous chest radiograph, their value is minimal for a majority of pediatric patients. The most important feature is the pattern and degree of pulmonary vascularity. Evidence of interstitial fluid may suggest CHF.

A recent ECG is helpful to establish baseline rhythm, especially in view of the propensity of arrhythmias to occur in both adults and children. The pediatric ECG may be especially difficult to interpret and should be reviewed by a cardiologist.

Copyright © 2008 Elsevier Inc. All rights reserved. - www.mdconsult.com

Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

Premedication

Beyond the normal value of the preoperative visit to relieve anxiety, individuals with CHD generally benefit greatly from premedication. Many of these patients have undergone surgery and may be fearful, and they may also have a higher risk of adjustment problems, such as depression, low self-esteem, and dependence. Consequently, premedication and a preoperative visit are important for these patients.[34]The age to initiate premedication is unclear, but most agree that infants younger than 6 months of age do not require it.

For many years the goal of premedication was to heavily sedate children to prevent arterial desaturation during induction but not to overly depress the myocardium.[35] A vagolytic agent was included in the premedication to preserve heart rate during induction; however, the move away from halothane for inhalation induction has lessened the need for it. This is advantageous, because its use predisposed to arrhythmias.[35] Although secretions may be slightly greater without a preoperative anticholinergic, there is no evidence of complications without it.[36]

The choices of sedative and analgesic agents for premedication are quite numerous but should be evaluated in terms of the CHD, myocardial function, age, and associated medical conditions. Heavy sedation has been thought to have minimal impact on oxygen saturation, even in cyanotic patients.[37] Recent evidence seems to contradict such a premise. DeBock and colleagues[38] demonstrated a fall of more than 10% in pulse oximeter measurements in 30% of the cyanotic children with premedication consisting of morphine, scopolamine, and barbiturate, whereas acyanotic children experienced a clinically insignificant drop in saturation.

Intramuscular injection is rarely used now, because there are good oral alternatives. Infants between the age of 6 months and 9 months may receive oral pentobarbital (2 to 4 mg/kg). Recently, substitution of oral midazolam (0.75 to 1.0 mg/kg) has proven safe and effective for barbiturate, morphine sulfate, and atropine premedication without a decrease in pulse oximeter derived oxygen saturation (Spo2). In a comparison between intramuscular injection of morphine and atropine with oral midazolam in children ranging from 1 to 6 years of age scheduled for elective cardiac congenital heart surgery, intramuscular injection led to a significant reduction in saturation, from 84% to 76%, which was absent with oral midazolam.[39] Oral midazolam does not appear to compromise respiratory rate or cardiovascular stability. Because 10% to 30% of children are still not sedated with 1.0 mg/kg of oral midazolam, 1.5 mg/kg of oral midazolam was compared with 1.0 and 0.5 mg/kg in children younger than 2 years of age undergoing congenital heart surgery. Only 4% of those receiving 1.5 mg/kg of midazolam were inadequately sedated.[40] Eight patients of 193 developed hypotension greater than 20% with sedation, but there was no statistically significant difference in the blood pressure or saturation between the infants who received 1.5 mg/kg of midazolam compared with the lower doses.

Oral transmucosal fentanyl citrate has been studied and found to provide adequate sedation in over three fourths of this patient population compared with conventional premedication. [36] [41] However, a 38% incidence of vomiting was noted. Lowering the dose of fentanyl to 15 to 20 μg/kg reduced the incidence of nausea and preinduction vomiting to14%,[41] but this technique is not extremely popular.

It is important to carefully observe individuals with CHD for sensitivity to sedatives that may lead to upper airway obstruction, decreases in Spo2, and hypoventilation, especially if PAH is present. PAH can lead to a rapid hemodynamic deterioration on account of a rising Pco2. With CHD, an increase in the Paco2 from 40 to 45 mmHg raises the mean pulmonary artery pressure from 41 to 47 mm Hg.[42]Increases in Paco2were followed with transcutaneous CzO2 in patients with CHD with either oral midazolam or intramuscular morphine and scopolamine ( Fig. 3-9 ).[43] Importantly, of the 16 patients with PAH, 9 experienced clinically significant changes in transcutaneous CO2 and oxygen saturation.[43] A similar sensitivity to CO2 has been seen in adults with PAH.[44]

 
 

FIGURE 3-9  Changes in transcutaneous Pco2 (mean ± SD) in children with congenital heart disease after premedication with either morphine and scopolamine (open diamonds) or midazolam (closed diamonds). *P < .05 compared with baseline.  (Reprinted with permission from Alswang M, Friesen RH, Bangert P: Effect of preanesthetic medication on carbon dioxide tension in children with congenital heart disease. J Cardiothorac Vasc Anesth 1994;8:416.)

 

 

 

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Monitoring

Besides routine monitoring for administration of anesthesia, monitoring for patients with CHD undergoing noncardiac surgery depends on the congenital defect, severity of illness, functional reserve, and surgery.

Indirect blood pressure monitoring is adequate in some cases, because the accuracy of the Dinamap oscillometric monitor compares favorably in both adults and infants with direct intra-arterial measurements, particularly regarding the systolic blood pressure. [45] [46] It is necessary to identify any prior operations that involved creating systemic to pulmonary artery shunts that affect the flow to that extremity. A simple Blalock-Taussig shunt on the left will necessitate blood pressure and pulse oximeter monitoring on the right extremity. In circumstances in which both upper extremities have been affected by shunts, cannulation of a femoral artery is an option. Femoral artery blood pressure monitoring is not associated with more complications than the radial artery in those with CHD, except for neonates who may experience some temporary perfusion abnormalities.[47] Access to arterial blood gas (ABG) analysis with direct arterial monitoring may be desirable and an excellent reason for invasive monitoring.

The need for central venous access and monitoring in patients with CHD depends on the CHD and surgery. Success may be very challenging because of previous operations, chronic vessel occlusion, abnormal anatomy and blood flow, and broad age range. It is difficult to obtain central venous access in about 10% of patients with CHD.[48] Experience is especially important for successful central venous catheter placement with infants weighing less than 5 kg.[49] The incidence of noninfectious complications such as pneumothorax, hemothorax, air embolism, thoracic duct injury, and nerve damage is 1% to 7%, consistent with the challenge of central venous catheter placement. [50] [51]

A major concern with central venous catheter placement in patients with CHD is accidental arterial puncture and subsequent large-bore catheter placement. It may cause vascular damage, stroke, airway obstruction, and even death.[52] The incidence of carotid puncture varies from 0% to 23%, depending on the technique and patient's age ( Fig. 3-10 ).[53] A high approach to central venous cannulation in infants and young children will lessen the chance of morbidity. CHD increases the risk of carotid puncture (14.1%) in both adult and pediatric patients compared with others (9.3%). Carotid puncture is also more likely in infants younger than 3 months of age.[54] Although carotid puncture may cause injury, subsequent large catheter insertion causes most of the serious morbidity or mortality.

 
 

FIGURE 3-10  Success rate (A) and arterial puncture rate (B) as a function of age. Numbers in parentheses indicate the number of patients in each age group.  (Reprinted with permission from Oliver WC, Nuttall GA, Beynen FM, et al: The incidence of artery puncture with central venous cannulation using a modified technique for detection and prevention of arterial cannulation. J Cardiothorac Vasc Anesth 1997;11:853.)

 

 

 

To minimize this complication when attempting central venous access, an external jugular vein may be substituted for the internal jugular vein. However, success is less than 80% in children[55] and adults. Furthermore, the internal jugular vein is preferred by most for central venous monitoring. The challenge of securing central venous access is especially great in infants younger than 3 months and weighing less than 4 kg,[56] with a success rate below that in adults.[53] Failure rate has varied between 4[49] and 10%.[48] The relationship of the right internal jugular vein to the carotid artery in children may partially explain the poorer success rate. The position of the right internal jugular vein is not as well defined in children compared with adults and is also more unpredictable in children with CHD than in those without CHD.[57]The right internal jugular vein may be anterior to the carotid artery in 10% to 60% of patients with CHD, depending on the approach to the vein and the position of the head. [57] [58]A 45-degree angle with the head and midline will better align the carotid and internal jugular vein to obtain central venous placement.

To facilitate central venous access and avoid complications, ultrasound guidance has been recommended. Ultrasound reduces the number of carotid punctures and increases success rate, especially for less experienced clinicians. [54] [58] [59] The incidence of carotid puncture in infants and children without ultrasound may be as high as 23%. Ultrasound not only decreased the incidence of carotid puncture but increased the success rate to 100% in infants younger than 12 months of age, compared with a 77% success rate in highly experienced clinicians using conventional techniques.[54] Ultrasound is also valuable to assess the internal jugular vein. In a series of 500 infants and children with CHD receiving central venous access, the right internal jugular vein was unsuitable for cannulation in 3.2% of patients.[49] Approximately 3% of internal jugular veins may be too small. Table 3-5 displays the recommended length of the central venous catheter for different ages of patients to minimize complications.[60]


TABLE 3-5   -- Recommended Length of Central Venous Catheter (CVC) Insertion in Pediatric Patients Based on Weight

Patient Weight (kg)

Length of CVC Insertion (cm)

2–2.9

4

3–4.9

5

5–6.9

6

7–9.9

7

10–12.9

8

13–19.9

9

20–29.9

10

30–39.9

11

40–49.9

12

50–59.9

13

60–69.9

14

70–79.9

15

≥80

16

Reprinted with permission from Andropoulos DB, Bent ST, Skjonsby B, Stayer SA: The optimal length of insertion of centra venous catheters for pediatric patients. Anesth Analg 2001;93;885.

 

 

 

Pulse oximetry is a reliable, noninvasive, and continuous method to monitor arterial oxygen saturation (Sao2) without the necessity for recurrent ABG measurements.[61] However, poor peripheral perfusion or severe oxygen desaturation affects its accuracy and reliability. [62] [63] Most do not view an Spo2 of 80% as alarming because efforts to improve oxygenation have usually been initiated before such a saturation is reached. However, patients with CHD are a heterogeneous group with saturations regularly below 90% and not infrequently below 80%. A narrow margin of safety characterizes patients with CHD, so significant declines in Spo2 may not be tolerated. Adding to the uncertainty, pulse oximeters in patients with CHD tend to overread the Sao2, delaying the therapeutic response. Moreover, current pulse oximeters may fail to read on average for about one third of the surgery, further complicating patient care decisions.[64]

Masimo Corporation (Laguna Hills, CA) has developed a pulse oximeter that represents a fundamental change in oximetry technology. Signal Extraction Technology (SET) reduces pulse oximeter failure and inaccuracies associated with low perfusion. Recently, in a comparison with Agilent Merlin and the Nellcor N-395, better accuracy and precision in the perioperative period, with saturations below 90% in patients ranging in age from birth to 53 years with CHD undergoing congenital heart repair, were noted.[65] However, accuracy and precision are still lacking for saturations below 70% by all pulse oximeter monitors.

Monitoring arterial oxygen saturation may provide the most complete and accurate information regarding Qp/Qs.[66] Anesthesia management of CHD is influenced by Qp/Qs to a larger or lesser degree depending on the specific congenital heart anomaly. Excessive pulmonary flow may lead to hypoperfusion of the systemic circulation, evidenced by metabolic acidosis whereas insufficient pulmonary blood flow may result in severe hypoxia. Although Spo2 is valuable to assess Qp/Qs, [67] [68] arterial saturation reaches a certain point where the pulmonary ratio of flow may continue to rise with no ability to be discriminate. Consequently, systemic arterial oxygen saturations do not allow one to specify whether the Qp/Qs is 1 or 3, and the arterial saturation will plateau.[66] Acidosis may be the final indication of hypoperfusion from excessive pulmonary blood flow. Thus, systemic venous saturations may provide a better estimate of the pulmonary blood flow ratio ( Fig. 3-11 ). [66] Although better, systemic venous saturation can be two tailed, in that it may be low with a low ratio or low with a high pulmonary blood flow ratio. One needs to measure and observe both the arterial and venous saturations to make the correct therapeutic decision.[66]

 
 

FIGURE 3-11  Systemic oxygen delivery as a function of the Qp/Qs ratio. Superimposed curve represents function generated by nonlinear regression analysis, demonstrating two-tailed function.  (Reprinted with permission from Riordan CJ, Randsbaek F, Storey JH, et al: Balancing pulmonary and systemic arterial flows in parallel circulations: The value of monitoring system venous oxygen saturations. Cardiol Young 1997;7:76.)

 

 

 

Because of the relationship between Paco2 and PVR, accurate monitoring of Paco2 is crucial in those with CHD. Even with severe PAH, a degree of PAH is dynamic vasoconstriction and thus reversible.[42]Hypocarbic alkalosis is effective in reducing pulmonary artery pressures in children and infants ( Fig. 3-12 ).[42] End-tidal CO2 (ETco2) is routinely used intraoperatively to monitor Paco2 and has been shown to closely approximate it in most patients. Accuracy of ETco2 with Paco2 depends on ventilation-perfusion match, pulmonary blood flow, cardiac output, physiologic dead space, and venous admixture. As a result, significant gradients exist with ETco2 and Paco2 in those with cyanotic CHD. ETco2 commonly underreads Paco2.[69] The gradient also varies depending on the congenital defect (Fig. 3-13 ) because those with acyanotic lesions have less gradient.[69]

 
 

FIGURE 3-12  Values for mean pulmonary artery pressure (MPAP) at physiologic pH and arterial partial pressure of CO2 (Paco2) (period 3) compared with values obtained during hypocarbic alkalosis (periods 1, 2, 4, 5).  (Reprinted with permission from Morry JP, Lynn AM, Mansfield PB: Effect of pH and Pco2 on pulmonary and systemic hemodynamics after surgery in children with congenital heart disease and pulmonary hypertension. J Pediatr 1988;113:476.)

 

 

 

 
 

FIGURE 3-13  The mean (±SD) of the arterial to end-tidal CO2 partial presure difference (Pa-ETco2) in the four groups. The Pa-ETco2 in the cyanotic patients is greater than in the acyanotic patients. There is no statistically significant difference from the control Pa-ETco2 in the normal, acyanotic-shunting, or mixing groups of patients, but in the cyanotic-shunting group, the Pa-ETco2 calculated at times 3 and 4 were significantly greater than the values at control, time 1 and time 2.  (Reprinted with permission from Lazzell VA, Burrows FA: Stability of the intraoperative arterial to end-tidal carbon dioxide partial pressure difference in children with congenital heart disease. Can J Anaesth 1991;38:862.)

 

 

 

Another method used to monitor Paco2 is transcutaneous CO2. It has been shown to have a bias of 0.58 mm Hg and precision of 2.1 mm Hg in comparison with Paco2 in patients undergoing surgery for CHD. Transcutaneous CO2 is generally only accurate for infants younger than 6 months of age.[70] Accuracy is diminished with poor skin perfusion often present with vasoactive medications.

Echocardiography has become routine for all pediatric cardiac surgical procedures and may be helpful in selected noncardiac cases to assess shunt flow or myocardial function. Filling pressures may not correlate with volume measurements, so end-diastolic volume measurements per echocardiography may aid in hemodynamic management. Transesophageal echocardiography is generally tolerated, but 1% to 2% of infants and children may develop airway obstruction. Pulmonary function tests measured before and after placement of the echocardiographic probe reveal minimal changes, even in infants weighing 2 to 5 kg.[71] The hemodynamic effects of transesophageal echocardiography on infants with CHD were found to be minimal as well.[72]

It is problematic in patients with CHD to assess the cardiac output, so they may be susceptible to multiple organ failure. Quantitative measures of cardiac output in conjunction with residual shunts are inaccurate. Doppler echocardiography has not demonstrated agreement with invasive measures of cardiac output. Poor cardiac output can be reflected in mixed venous saturation, base deficit, and serum lactate measurement. Superior vena caval saturation is frequently obtained for cardiac output assessment instead of a true mixed venous blood saturation, but a slight gradient between superior vena caval saturation and mixed venous saturation exists.[73] Even if pulmonary artery catheters were available for determination of cardiac outputs in these patients, markers of tissue perfusion appear more valuable for assessing the patient's status than actual cardiac output.[74]

Additionally, two other important physiologic parameters to monitor include temperature and urine output. Temperature control is crucial, especially in infants and children with CHD, because hypothermia will increase SVR, and if hypothermia leads to shivering, metabolic demand will increase dramatically. The leftward shift of the oxygen-dissociation curve will add to oxygen deficit, because it is more difficult to unload oxygen. The room should be warmed to reduce conductive heat loss and a Bair Hugger® should be utilized.

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Ventilation

The manner and degree of ventilation is essential in patients with CHD to stabilize PVR and hemodynamics. Ventilators commonly associated with anesthesia machines do not provide the same degree of gas exchange compared with ventilators used in the intensive care unit, especially in individuals with respiratory failure.[75] The Siemens 300D (Siemens Elema/Maquet, Solna, Sweden) ventilator delivered the greatest mean inspiratory flow at all airway pressures, which is pressure independent in contrast to anesthetic ventilators.[76] Infants with CHD have altered lung compliance and airway resistance, causing them to be very sensitive to changes in ventilation.[77] The presence of PAH further increases the airway resistance, making ventilation even more critical. Children with acyanotic CHD are much more likely to have decreased respiratory compliance than those with cyanotic CHD. Compliance is more related to the pulmonary artery pressure than pulmonary blood flow or shunt direction.

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Circulatory Support

Circulatory support for CHD patients undergoing noncardiac surgery may be necessary. The stress of surgery impacts these patients more than others undergoing noncardiac surgery. Stress can manifest as both metabolic and respiratory acidosis and have a prolonged impact.[14] Many patients with CHD have tenuous preoperative ventricular function, so the stress of surgery and anesthesia may diminish ventricular function, potentially causing circulatory failure. Inotropes may be necessary but may cause tachycardia, increased myocardial oxygen consumption, increased SVR, and arrhythmias. Alternatively, milrinone, a relatively new phosphodiesterase inhibitor (PDE), with a rapid onset, stimulates vascular muscle relaxation and myocardial contractility. In one of the few randomized blinded multicenter studies of infants, milrinone was associated with reduced mortality and improved hemodynamics compared with other conventional agents.[78] One must resist the temptation to give excessive fluids to either pediatric or adult patients with CHD to support hemodynamics because it can be catastrophic.[79] Adequate circulatory support is essential to maintain the blood flow of palliative shunts; otherwise, pulmonary perfusion may be reduced significantly, risking further hypoxia and possible shunt thrombosis.[79]

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Anesthetic Techniques

There is not one anesthetic technique that can be recommended for patients with CHD, since these individuals vary significantly according to congenital defect and age.[14] A thorough understanding of CHD and the stresses that may accompany surgery are necessary. Anesthetic considerations include shunt flow, myocardial contractility, ventricular dilation or hypertrophy, arrhythmias, PVR, and outflow tract obstruction. Goals should include maintaining shunt flow to provide optimal cardiac output and systemic perfusion, minimizing myocardial depression, and avoiding exacerbating PVR ( Table 3-6 ). The factors that affect PVR are listed in Table 3-6 and are essentially applicable to both children and adults with CHD. In many respects, patients with CHD may behave almost normally; consequently, they may tolerate a conventional anesthetic.[79] In contrast, some patients may have serious functional limitations that require a more complex approach to anesthetic and perioperative management.

TABLE 3-6   -- Factors Affecting Pulmonary Vascular Resistance (PVR)

Decrease in PVR

Increase in PVR

Increasing PaO2

Sympathetic stimulation

Hypocarbia

 Light anesthesia

Alkalemia

 Pain

Minimizing intrathoracic pressure

Acidemia

 Spontaneous ventilation

Hypoxia

 Normal lung volumes

Hypercarbia

 High frequency and jet ventilation

Hypothermia

Avoidance of sympathetic stimulation

Increased intrathoracic pressure

 Deep anesthesia

 Controlled ventilation

Pharmacologic methods

PEEP

 Isoprenaline

Atelectasis

 Phosphodiesterase III inhibitors

 

 Prostaglandin (Pg) infusion (PgE1 and PgI2)

 

 Inhaled nitric oxide

 

Reprinted with permission from Lovell AT: Anaesthetic implications of grown-up congenital heart disease. Br J Anaesth 2004;93:131.

PEEP, positive end-expiratory pressure.

 

 

 

 

Sevoflurane is the agent of choice[22] for inhalation induction of infants and children without CHD because of its low partition coefficient, hemodynamic stability ( Fig 3-14A ), and its reduced effect on myocardial contractility compared with other volatile agents (see Fig 3-14B ).[80] Infants and children with CHD will tolerate sevoflurane concentrations of 8% with significantly less myocardial depression than halothane. [81] [82] Because sevoflurane is approximately four times less soluble in blood than halothane, inhalation induction is more rapid with lower inspired concentrations. Ventilation will have minimal effect on the speed of induction with sevoflurane.

 
 

FIGURE 3-14  A, Blood pressure was stable throughout the induction of anesthesia in both groups, children that receive either sevoflurane or halothane. Systolic blood pressure decreased at 1.0 minimal alveolar concentration (MAC) with halothane and sevoflurane, returning to baseline at 1.5 MAC. B, Left ventricular shortening fraction (SF; middle) and velocity of ventricular circumferential fiber shortening corrected for heart rate (VCFc; bottom) decreased with both anesthetic agents. Halothane decreased shortening fraction (two-way analysis of variance with repeated measures; P = .003) and VCFc (two-way analysis of variance with repeated measures; P = .018) more than sevoflurane.  (Reprinted with permission from Holzman RS, van der Velde ME, Kaus SJ, Body SC, et al: Sevoflurane depresses myocardial contractility less than halothane during induction of anesthesia in children. Anesthesiology 1996;85:1263.)

 

 

 

The effect of CHD on the uptake and distribution of anesthetic agents involves many factors. A right-to-left shunt will slow inhalation induction, because less anesthetic is absorbed from the lung, and mixing will further dilute blood that is passing to the left, decreasing the arterial concentration of the blood going to the brain, especially the less soluble agent. However, this is rarely problematic. An intravenous induction would be accelerated with a right-to-left shunt. The cyanotic child should be induced with a combination of nitrous oxide and a volatile agent, because it allows for a lower concentration of volatile agent to be given.

Although classically, the left-to-right shunt should promote the speed of inhalation induction, actually the clinical effect is insignificant.[83] Similarly, although intravenous induction should be slowed by a left-to-right shunt, unless the cardiac output is very poor, it is clinically irrelevant. Selection of the anesthetic agent (halothane, isoflurane, fentanyl/midazolam, sevoflurane) does not appear to affect the Qp/Qs ratio in those with left-to-right shunts, as long as the patients were mechanically ventilated at normocapnia and with 100% oxygen ( Fig. 3-15 ).[84] Individuals with single ventricles may be less tolerant of volatile agents. The reactive nature of the pulmonary vasculature will make the behavior of volatile agents unpredictable.

 
 

FIGURE 3-15  Individual patient pulmonary-to-systemic blood flow ratio (Qp:Qs) data for each anesthetic (halothane, n = 10; sevoflurane, n = 11; isoflurane, n = 10; and fentanyl/midazolam, n = 9). Heavy black line indicates mean value at each anesthetic concentration. (Reprinted with permission from Laird TH, Stayer SA, Rivenes SM, et al: Pulmonary-to-systemic blood flow ratio effects of sevoflurane, isoflurane, halothane, and fentanyl/midazolam with 100% oxygen in children with congenital heart disease. Soc Pediatr Anesth 2002;95:1204.)

 

 

 

Although isoflurane is not used for inhalation induction in children or adults owing to its pungent smell, it is well suited for anesthetic maintenance compared with halothane. Myocardial function is well preserved during isoflurane administration. [85] [86] Isoflurane concentration below 1.0 MAC will provide the same hemodynamic stability that fentanyl (75 μg/kg) and diazepam achieve in those with acyanotic CHD.[87] Similarly, sevoflurane maintains cardiac output and contractility in patients with CHD. [86] [88] A prospective study randomizing infants with CHD to either sevoflurane or halothane for inhalation induction for congenital heart surgery found that halothane had twice as many cardiovascular events (hypotension) as sevoflurane (P = .03) and a significantly greater lactate level before heparinization than those receiving sevoflurane.[89] The halothane group also had more episodes of bradycardia and emergency drug administration. Equal numbers of cyanotic and acyanotic infants were part of each group. Sevoflurane is associated with a lower incidence of arrhythmias compared with halothane.[86]

Intravenous anesthetics for patients with CHD are the preferred method of anesthetic induction and maintenance, excluding those that require inhalation induction.[90] Many intravenous agents are able to provide safe induction and anesthetic maintenance, but the margin for error with some choices is less.[79]

High-dose narcotic anesthesia has continued to be a popular anesthetic technique for patients with CHD based on the widely held idea of minimizing the hormonally mediated stress response, thereby minimizing pulmonary vascular reactivity and myocardial depression. This was concluded based on a study comparing a narcotic versus volatile agent-based anesthetic for congenital heart surgery. The presence of a metabolic acidosis with halothane was postulated to be the result of failure to attenuate the stress response compared with the narcotic.[91] The relationship between increased perioperative stress response and postoperative complications in newborns undergoing noncardiac operations questions the advisability of a volatile anesthetic in patients with CHD.[92] An opioid anesthetic was associated with a lower perioperative mortality in infants compared with halothane.[91] Fentanyl has remained popular for years in a range of dosages (10 to 150 μg/kg) for induction and maintenance of anesthesia in both pediatric and adult populations with CHD requiring cardiac surgery.[93]

The advantages of fentanyl for patients with CHD include minimal effect on pulmonary and systemic circulations and attenuation of response to intubation and incision. Fentanyl also attenuates the pulmonary vascular response to suctioning that may cause serious desaturation.[94] In conjunction with midazolam, fentanyl maintains contractility better than most volatile anesthetic agents in these patients.[86] Fentanyl has also been shown to maintain oxygen saturation and hemodynamics as effectively as ketamine in cyanotic CHD.[68] The same has been found concerning sufentanil and flunitrazepam in cyanotic children.[90] Although sufentanil has similar hormonal blocking properties as fentanyl, the hemodynamic predictability is not as good. The addition of a benzodiazepine with fentanyl compared with fentanyl alone in acyanotic infants and children showed better hemodynamic stability, indicating the value of a balanced anesthetic.[87] Shorter-acting agents such as alfentanil have some appeal, especially in noncardiac situations, for use as maintenance anesthetics, but there are some drawbacks.

Recently, the benefit of a narcotic anesthetic has been questioned, because there was no apparent evidence of a relationship between narcotics and outcome in neonates and infants undergoing CPB for cardiac surgery.[95]Furthermore, the addition of a benzodiazepine did not influence the stress response. It may be that “well compensated” CHD does not require or benefit as much from high-dose narcotic anesthetic technique, but further studies are necessary.[95]

Propofol is a substituted phenol agent that has a rapid onset and short duration of action. The use of propofol for anesthetic maintenance in patients with CHD is not recommended, based on some anecdotal reports of severe fatal metabolic acidosis in children who were critically ill.[96] The occurrence of propofol syndrome that includes metabolic lactic acidosis, myocardial dysfunction, and even death, has been found in critically ill patients, both pediatric and adult. [97] [98] In children with CHD undergoing cardiac catheterization, significantly more patients experienced a decrease of more than 20% of the mean arterial pressure (MAP) than those who received ketamine. The Spo2 in the propofol group fell more than 5% during induction, whereas ketamine was not associated with any reduction in Spo2.[99]Increased right-to-left shunting may have been responsible, as evidenced consistently during cardiac catheterization of both cyanotic and acyanotic children. Propofol reduces the SVR and hence increases right-to-left shunt, which further reduces pulmonary blood flow in cyanotic patients. Additionally, Sao2 has fallen as much as 10% in conjunction with decreased pH in cyanotic children.[100] If PVR is high, propofol may exacerbate pulmonary vasoconstriction, increasing ventricular afterload,[101] but does not appear to have any direct effect on PVR.[100] Patients with acyanotic CHD tolerate propofol as long as metabolic acidosis does not become excessive.

Ketamine has been frequently recommended for patients with cyanotic and acyanotic CHD and may be the agent of choice for induction of anesthesia in patients with cyanotic CHD.[102] Its effects are mediated through a centrally activated increase in sympathetic activity. Compared with halothane, it maintains the MAP significantly better in infants with cyanotic CHD. [67] [68] In those with CHD undergoing cardiac catheterization, ketamine has been shown to increase HR but causes no change in Qp/Qs.[102] It relaxes bronchial smooth muscle stimulated by endothelin.[103] As well as being superior to isoflurane in those with TOF,[104] ketamine provides excellent analgesia in contrast to propofol, which has no analgesic properties.

Etomidate and thiopental have been used in CHD. Etomidate provides excellent hemodynamic stability in teenagers and adults with CHD.[22] Thiopental has been used for induction in patients with CHD, but myocardial depression and vasodilation cause hemodynamic instability. Careful observation of the pulse oximeter during induction and anesthetic maintenance will help guide dosing to maintain hemodynamics ( Fig. 3-16 ).[68]

 
 

FIGURE 3-16  Oxygen saturations during the period of study for the five groups. Data are mean ± SEM. Time axis: Air = awake control measurements; Pre-Ind = preinduction following preoxygenation; 1 min, 3 min, 5 min = intervals post induction. LAR = laryngoscopy; 0.5 min, 1 min, 2 min = intervals post-intubation.  (Reprinted with permission from Laishley RS, Burrows FA, Lerman J, Roy WL: Effect of anesthetic induction regimens on oxygen saturation in cyanotic congenital heart disease. Anesthesiology 1986;65:675.)

 

 

 

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Muscle Relaxants

The choice of muscle relaxants for intubation and intraoperative maintenance will rest on the expected duration of the anesthetic, hemodynamics, airway assessment, and other associated medical conditions. The possibility of severe bradycardia with succinylcholine in infants and children limits its usefulness in hemodynamically compromised individuals. There are only a few reasons to use succinylcholine in infants and children with CHD. Pancuronium is a long-acting nondepolarizing neuromuscular blocker that tends to temporarily increase the heart rate and blood pressure through vagolysis, but these effects may be absent in some children with CHD.[105]Muscle relaxants are minimally affected by cyanotic or acyanotic CHD. Shorter-acting neuromuscular blocking agents such as vecuronium, cisatracurium, atracurium, and rocuronium or mivacurium may be selected if the clinical situation calls for it.

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ANATOMIC DEFECTS ASSOCIATED WITH INCREASED PULMONARY BLOOD FLOW

Excessive pulmonary blood flow has both cardiac and respiratory consequences. The increased pulmonary blood flow will result in volume overload of the ventricle, causing reduced myocardial function and low cardiac output. Increased pulmonary blood flow will increase left atrial pressure, causing increased pulmonary venous pressures and interstitial edema, ultimately leading to pulmonary vascular disease. The period of time until congenital heart repair occurs is important with respect to onset of pulmonary vascular disease. If repair occurs within 9 months, permanent effects from the defect are unlikely.[106] The period of time before irreversible pulmonary vascular obstructive disease sets in depends on the type of defect and complexity of lesion.

Atrial Septal Defect (ASD)

ASD represents about 30% of all CHD identified in adults. Women are affected two to three times as frequently as men.[8] Nearly 24% of newborns may have a communication between the atria, but only 8% are patent at 1 year of age after spontaneous closure of the defect.[107] Commonly present in low-birth-weight infants, these openings of the atrial septum are rarely associated with clinical symptoms. Those defects with valve openings may be differentiated from those that do not have valves and rarely close spontaneously.

Ostium secundum, ostium primum, patent foramen ovale (PFO), and sinus venosus are the types of ASD classified on the basis of anatomic location of the defect in the atrial septum ( Fig. 3-17A ). Ostium secundum is located in the area of the fossa ovalis. The ostium primum is located in the lower part of the atrium. The sinus venosus is located high in the atrial septal wall near the junction of the superior vena cava and RA. They occur primarily from excessive resorption of the septum primum or lack of growth of the septum secundum. Anomalous pulmonary venous connections may also be present in 10% of ASD. A PFO is located at the junction of the septum primum and septum secundum. It is not a proper ASD because the foramen ovale exists throughout fetal life and functionally closes as the left atrial pressure exceeds right atrial pressure after birth. In about 25% of people there is no anatomic closure of the foramen ovale, so a communication exists between the RA and LA.

 
 

FIGURE 3-17  A, Atrial septal anatomy. Schematic diagram showing the location of atrial septal defects, numbered in decreasing order of frequency: 1, secundum; 2, primum; 3, sinus venosus; 4, coronary sinus (CS) type. IVC, inferior vena cava; PT, pulmonary trunk; RV, right ventricle; SVC, superior vena cava. B, Secundum atrial septal defect (ASD). Right atrial view. SVC, superior vena cava; RAA, right atrial appendage; CS, coronary sinus; IVC, inferior vena cava; TV, tricuspid valve; RV, right ventricle.  (Reprinted with permission from Porter CJ, Feldt RH, Edwards WD, et al: Atrial septal defects. In Emmanouilides GC, Riemenschneider TA, Allen HD, Gutgesell HP [eds: Moss and Adams Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult. Baltimore, Williams & Wilkins, 1995, p 688.)

 

 

 

The simple ostium secundum is the most common form of ASD in both the pediatric and adult populations and one of the few defects that may truly manifest first in adulthood. It generally does not close spontaneously but may be unappreciated for years without symptoms. In the future, fewer patients will present with unrecognized ASD because of echocardiography. A murmur that was not recognized as pathologic often spurs the diagnosis by the age of 3 to 5 years.[108] Despite its left-to-right nature, severe CHF rarely occurs in the infant on the basis of a solitary ASD. However, it is similarly as rare to see survival past 70 years of age. People with large shunts rarely live to more than 30 to 40 years of age. Ongoing risks for these individuals include paradoxical emboli, bacterial endocarditis, and CHF.

Irrespective of the location of the ASD, the physiologic consequences of this defect are similar. The size of the left-to-right shunt will depend on the size of the defect and the diastolic filling characteristics of the ventricles, with the compliance of the chambers being more important in this respect. Infants will have little left-to-right shunting initially, because PVR is elevated and the right ventricle is hypertrophied (see Fig. 3-17 B). Eventually, increased flow to the RA results in volume overload of the right side of the heart, with enlargement of the RA and LA. If the shunt should exceed a Qp/Qs of 1.5, symptoms appear. Dyspnea on exertion will most likely be present by the age of 30 in approximately one third of patients. By age 40, right-sided heart failure with supraventricular tachyarrhythmias may appear in 10% of individuals.[109] Symptoms will progress to severe debilitation with aging.

A large ASD may be associated with a large palpable right ventricular or pulmonary artery impulse. There is wide and fixed splitting of the second heart sound. A systolic ejection flow murmur may be perceived at the left second intercostal space. However, the murmur may be so soft as to be confused with an “innocent” murmur of childhood. Most infants will not have the characteristic murmur. The ECG will frequently reveal a right bundle branch block, as well as right-axis deviation. Atrial tachyarrhythmias are especially common in an adult with an ASD. Atrial fibrillation is the most likely arrhythmia and may precipitate CHF. The chest radiograph may show evidence of increased pulmonary vascularity and PAH reflected by calcification of the pulmonary trunk.[110]

Although an individual with an ASD may be asymptomatic for many years, the systemic hypertension and ischemic heart disease often associated with aging will worsen the compliance of the left ventricle, causing more left-to-right shunt.[110] It is also not uncommon to find mitral insufficiency in 15% of these adult patients. Depending on the type of ASD, the incidence of PAH may vary significantly.[111]Survival with PAH caused by ASD and left-to-right shunt is much longer than primary PAH because the ASD appears to slow progression of pulmonary vasculopathy.

Because PAH occurs and the right ventricle tends to become less compliant with an ASD, eventually, the right ventricle may direct blood from right to left. It is uncommon for an adult with an ASD to develop Eisenmenger's syndrome.[8] Only about 10% of those with large defects of ASD will develop Eisenmenger's syndrome.[111] Patients with Eisenmenger's syndrome who require noncardiac surgery may be receiving some of the medications used to treat primary PAH.[111] Respiratory infections are also common with Eisenmenger's syndrome.

Anesthetic concerns for ASD include excessive pulmonary blood flow, left ventricular dysfunction, especially for adult ASD closure, and paradoxical embolism. Patients with ASD will usually tolerate most anesthetics, unless very severe CHF is present that will require an anesthetic with less myocardial depression. Inhalation or intravenous inductions can be tolerated in most circumstances. Great care should be taken to prevent even small amounts of air, because even a small amount may cause permanent neurologic deficit. For those who have undergone ASD closure as an adult, there remains an increased risk of atrial fibrillation.[34] If Eisenmenger's syndrome is present, refer to the anesthetic considerations of Eisenmenger's syndrome later in the chapter.

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Atrioventricular Septal Defects

This group of defects includes the AV septum and valves that result from a failure of the AV septum to develop. Also referred to as “endocardial cushion defects,” the two main defects are partial and complete AV septal defects. They represent 4% to 5% of CHD.[5]

The partial defect, accounting for 25% of AV septal defects, includes a primum ASD and a cleft mitral valve.[4] The failure of the septum primum to fuse with the endocardial cushions often results in a large ASD ( Fig. 3-18 ). Symptoms of the partial AV septal defect are more severe than a secundum ASD. CHF may appear as early as infancy with partial AV septal defect. Mitral regurgitation and left-to-right shunting may be severe. A crescendo-decrescendo murmur is heard in the upper lung fields, in association with a holosystolic murmur of mitral regurgitation at the apex. The chest radiograph shows a large heart and may display features consistent with a complete AV septal defect if the left-to-right shunt is large. Normal sinus rhythm is usually present on an electrocardiogram.[110] If the left-to-right shunt is not large, 75% of adult patients will be mildly symptomatic, some asymptomatic for as long as 20 years, but not late in adult life.[112] PAH rarely occurs.

 
 

FIGURE 3-18  Partial atrioventricular septal defect, with a primum atrial septal defect and a cleft anterior mitral leaflet. A, Right ventricular inflow view, showing widened commissure between septal (S) and anterior (A) tricuspid leaflets. B, Left ventricular inflow view showing cleft in anterior (A) mitral leaflet with abnormal chordal attachments to midportion of ventricular septum (arrows). ASD, Atrial septal defect; FO, fossa ovalis; LA, left atrium; LV, left ventricle; P, posterior leaflet; RA, right atrium; RV, right ventricle.  (Reprinted with permission from Porter CJ, Feldt RH, Porter CJ, et al: Atrioventricular septal defects. In Emmanouilides GC, Riemenschneider TA, Allen HD, Gutgesell HP [eds: Moss and Adams Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult. Baltimore, Williams & Wilkins, 1995, p 708.)

 

 

 

If the shunt is large, surgery to repair the defect is required early in life, with symptomatic relief in over 80% of patients and few complications beyond atrial arrhythmias.[112]

A complete AV septal defect involves not only failure of the septum primum to fuse with the endocardial cushions but also the cushions fail to fuse with each other, resulting in a common AV valve incorporating both atria and ventricles ( Fig. 3-19 ). The common AV valve is usually regurgitant. Figure 3-19 A depicts a type A complete AV septal defect. It is the most common type of AV septal defect and is associated with Down syndrome. Nearly 40% of those with Down syndrome have CHD, and 40% will have a complete AV septal defect.[113] Should the valves develop separately instead of forming a common AV valve, the leaflets of both valves will be abnormal and regurgitant (see Fig. 3-19 B).

 
 

FIGURE 3-19  A, The most frequent form of complete atrioventricular septal defect (type A), originally classified according to division of the anterior bridging leaflet (A) and attachment to the septum. Current interpretation has only the left-sided portion of the anterior leaflet as anterior bridging leaflet, and the right-sided portion is the true anterior tricuspid leaflet. P is the posterior bridging leaflet, and L represents the two lateral leaflets that correspond to posterior mitral and tricuspid leaflets. mitral valve (MV) and tricuspid valve (TV) indicate mitral and tricuspid portions of leaflets, and right atrial (RA) and right ventricular (RV) indicate right atrium and right ventricle respectively. B, Schematic four-chamber view of complete atrioventricular (AV) septal defect, showing common valve and atrial and ventricular communications.  (A, reprinted with permission from Porter CJ, Feldt RH, Porter CJ, et al: Atrioventricular septal defects. In Emmanouilides GC, Riemenschneider TA, Allen HD, Gutgesell HP [eds: Moss and Adams Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult. Baltimore, Williams & Wilkins, 1995, p 710; B, reprinted with permission from Castaneda AR, Jonas RA, Mayer Jr JE, Hanley FL [eds: Atrioventricular canal defect. In Cardiac Surgery of the Neonate and Infant, Philadelphia, WB Saunders, 1994, p 168.)

 

 

 

The newborn with complete AV septal defect may have an unremarkable physical examination. The precordium may be hyperdynamic and a systolic murmur may be detected along the left sternal border. The large left-to-right shunt will lead to systemic pressures in both ventricles by 1 year of age and PAH. Frequent respiratory infections and failure to thrive are also characteristic of this defect. Symptoms of CHF, such as poor feeding, poor growth, dyspnea, fatigability, and diaphoresis are common. Cardiomegaly will be present with prominent pulmonary vascular markings consistent with large left-to-right shunts on the chest radiograph ( Fig. 3-20 ). However, normal sinus rhythm is common on the ECG.

 
 

FIGURE 3-20  Chest radiograph of a patient with a complete atrioventricular septal defect showing cardiomegaly and increased pulmonary blood flow.  (Reprinted with permission from Spicer RL: Cardiovascular disease in Down syndrome. Sym Pediatr Cardiol 1984;31:1334.)

 

 

 

Complete repair during infancy is now common, although previously some patients underwent pulmonary artery band and complete repair later. Despite complete repair, 10% to 30% of patients may continue to experience mitral regurgitation, requiring another operation at some point.[114] Anesthetic considerations are similar to the partial AV septal defect, with larger left-to-right shunt and more significant mitral regurgitation.

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Ventricular Septal Defect (VSD)

VSD is the most common isolated congenital heart defect, constituting 20% to 33% of all CHD. [2] [5] The incidence varies from 1.5 to 3.5 per 1000 term infants.[115] A third of Down syndrome patients will have a VSD.[113] Spontaneous closure may occur in up to half of patients, explaining the lower prevalence of VSD in adults than infants. Extracardiac abnormalities accompany simple VSD in up to 50% of cases.[116] In many instances, repair of the extracardiac anomaly, such as tracheoesophageal fistula, is the reason for the exposure to anesthesia.

Eighty percent of VSDs are perimembranous (infracristal), found in the outflow tract of the left ventricle just beneath the aortic valve ( Fig. 3-21 ). Supracristal or outflow defects account for another 5% to 7% of VSDs. Inlet defects (canal defects) occur in the outflow tract of the right ventricle beneath the pulmonary valve and account for 8% to 11% of VSDs. Inlet defects are also associated with AV septal defects. Muscular defects are often multiple, having the appearance of a “Swiss cheese” defect, and represent 5% to 20% of VSDs.

 
 

FIGURE 3-21  Anatomic position of defects: a, outlet defect; b, papillary muscle of the conus; c, perimembranous defect; d, marginal muscular defects; e, central muscular defects; f, inlet defect; g, apical muscular defects.  (Reprinted with permission from Graham TP Jr, Gutgesell HP: Ventricular septal defects. In Emmanouilides GC, Riemenschneider TA, Allen HD, Gutgesell HP [eds: Moss and Adams Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult. Baltimore, Williams & Wilkins, 1995, p 726.)

 

 

 

The size of the VSD will determine the degree of left-to-right shunt.[113] Small to medium defects may limit left-to-right shunt, but a large defect has no resistance to flow and quickly causes volume overload and PAH. A small, moderate, and large VSD has a Qp/Qs ratio of less than 1.5, 1.5 to 2.0, and more than 2.0, respectively.[108] Not all VSDs will require surgical closure but may close spontaneously or simply restrict pulmonary flow as not to affect survival.

An infant with a VSD will encounter a dynamic shunt flow. Normally after birth, PVR decreases slowly over 2 to 4 weeks to adult levels, which is a protective measure against a rapid increase in pulmonary blood flow and possible pulmonary edema. Left-to-right shunt will increase, contingent on the normal decrease in PVR after birth.[115] If a large VSD is present, within the first 2 weeks to 1 year the infant will develop symptoms of CHF, especially poor feeding. The symptoms will very much resemble the patient with complete AV septal defect. The increased pulmonary blood flow will cause marked ventricular hypertrophy to develop. These infants may develop severe PAH and chronic pulmonary vascular disease even after a year without closure of the VSD.[113] Once pulmonary vascular disease becomes severe, options are restricted for successful treatment.[111] Early diagnosis of a VSD in a newborn is unlikely owing to the normally elevated PVR present at birth and elevated right ventricular pressure that minimize left-to-right shunt. Some patients may never experience a decrease in PVR; consequently, left-to-right shunt may be mild or even reverse. However, by the fourth decade, the right ventricle will have failed.[115]

If the right ventricular pressure and PVR decrease as expected in a patient with a VSD, a murmur becomes more prominent and diagnosis of the VSD is more likely.[34] On physical examination, a murmur may be heard only with a small VSD. Moderate defects will usually result in a harsh holosystolic murmur and hyperdynamic precordium owing to increased pulmonary blood flow. The large VSD may appear similar to other VSDs on examination, except sweating and tachypnea are more notable. The chest radiograph shows atrial enlargement, cardiomegaly, and increased pulmonary vascularity. The ECG may reveal ventricular hypertrophy if the VSD is moderate to large.

To prepare for noncardiac surgery in these children with unrepaired lesions, be aware of any extracardiac abnormalies.[116] Although rare, endocarditis is an issue and antibiotics should be administered. If the patient appears in CHF, surgery should be postponed to implement or increase some of the following: digoxin, furosemide, or captopril. Anesthetic management is similar to that for patients with increased pulmonary blood flow. Volatile agents should be used cautiously to avoid exacerbating myocardial depression.

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Patent Ductus Arteriosus (PDA)

The transition from fetal circulation after birth requires the functional closure of the ductus arteriosus, which is a communication between the left pulmonary artery and the descending aorta ( Fig. 3-22 ). Functional closure occurs 1 to 4 days after birth.[117] Anatomic closure of the ductus arteriosus is usually complete a month after birth, becoming the ligamentum arteriosum. Although a PDA may exist with other congenital heart defects, an isolated PDA is described here.

 
 

FIGURE 3-22  Patent ductus arteriosus with resultant left-to-right shunting. Some of the blood from the aorta crosses the ductus arteriosus and flows into the pulmonary artery (arrows).  (Reprinted with permission from Brickner ME, Hillis LD, Lange RA: Congenital heart disease in adults. N Engl J Med 2000;342:259.)

 

 

 

An isolated PDA occurs in every 2500 live births,[118] accounting for 10% to 14% of CHD. [5] [8] [108] It is rare for this anomaly to be missed in infancy or childhood. The incidence of isolated PDA increases as gestational maturity decreases. Approximately 80% of infants weighing less than 1200 g will have a PDA.[108] A PDA can be quite large and can extend from the posterior descending aorta near the origin of the left subclavian artery to the anterior surface of the main pulmonary artery. Various factors, such as hypoxemia, may prevent the normal closure of the ductus arteriosus after birth. A PDA rarely closes spontaneously after infancy.[8] In contrast to premature infants who have a functional problem with the ductus arteriosus, the term infant has an anatomic abnormality whereupon failure to constrict is structural, not functional.

A PDA is associated with left-to-right shunt and excessive pulmonary blood flow. The ductus arteriosus is not structurally identical to other vascular structures, so it has very poor contractile function. If the PDA is large, PVR will determine the degree of left-to-right shunt not the ductus arteriosus. Increased blood flow from PDA to LA may cause additional left-to-right shunting through a PFO, contributing further to left ventricular overload. As the pulmonary artery pressure increases, left-to-right shunting will decrease, but eventually pulmonary vascular changes will become permanent.[109]

If a PDA is small, it may only present problems related to bacterial endocarditis. A larger PDA may remain asymptomatic until childhood or adulthood, whereupon symptoms of fatigue, dyspnea, or palpitations may suddenly appear.[8] Early symptoms include tachypnea, diaphoresis, reduced exercise tolerance, failure to thrive, and recurrent pulmonary infections. PDA may lead to PAH in adulthood. Patients may live until the age of 60, even with CHF and PAH.[111] Mortality with a PDA in adults is 1.8%/year.[119]

A PDA has a characteristic continuous machine murmur, heard mostly at the first or second intercostal space on the left sternal border. Pulses may be bounding, and a widened pulse pressure may be seen with blood pressure monitoring. The ECG is usually unremarkable, except for some evidence of left ventricular hypertrophy if the left-to-right shunt is large. Increased pulmonary vascular markings, as well as an enlarged left atrium and ventricle, may be present on the chest radiograph.

PDA closure in adults is a very challenging operation compared with that in an infant or child.[34] Adults with PDA may be very ill. The PDA may become calcified and/or dilate, making the operation more risky on account of the amount of blood flowing through the PDA.[114]

Beyond the anesthetic considerations of defects with increased pulmonary blood flow, closure of the PDA may be performed through a thoracotomy, percutaneously, or thorascopically. Currently, interventional catheterization is achieving success at placing a Rashkind double umbrella occlusion device to obliterate the PDA and avoid a higher risk operation. Percutaneous measures have been relatively successful, with up to 98% at 1-year follow-up, but unsuccessful in patients weighing more than 5 kg.[120] Percutaneous PDA closure does not require anesthesia and thoracotomy. Residual leaks may occur in 25% of these procedures but are usually clinically insignificant. Thorascopic closure of PDA has also achieved good results with low complications and decreased hospital stay. [118] [121]Although good intravenous access is necessary should excessive blood loss occur with injury to the aorta, noninvasive monitoring is generally acceptable. One-lung ventilation is rarely required and usually not tolerated. Avoiding hyperoxia, especially in the neonatal period, is important to avoid increasing pulmonary blood flow any further. Infants who arrive in the operating room with severe CHF may require ventilation postoperatively.

Anesthesia should include low to moderate doses of fentanyl (25 μg/kg) with a plan for extubation and good analgesia. The diastolic pressure should be observed carefully with a large PDA, because coronary blood flow may suffer if the diastolic pressure is too low, especially because the left ventricular compliance is reduced from the large left-to-right shunt. There is slightly over 10% incidence of ischemic changes in patients with PDA on autopsy.[20] In the premature infant the Hb should not be allowed to drift because of the large amount of fetal Hb present. Anemia will further limit oxygen delivery.

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Truncus Arteriosus

Truncus arteriosus is a rare disorder, representing only 1% to 3% of CHD.[122] Nearly three fourths of infants with truncus arteriosus will die by 1 year of age. Truncus arteriosus is caused by a lack of separation of the great vessels in utero, so that only one major vessel, the truncal vessel, gives rise to the coronary arteries, aorta, and pulmonary arteries. There is also only one semilunar valve, the truncal valve, that may possess two to seven leaflets, which may be regurgitant in over half the cases. The truncal valve usually overrides both ventricles (80%) or may arise from the right ventricle alone (20%).

Because there are many different presentations, the classification is complex. Classification is based on the position of the main pulmonary artery and whether there is a VSD (type A) or not (type B). There are basically three types of truncus arteriosus, with the fourth type now referred to as pulmonary atresia with VSD. Type Ia, the most common, is present in 50% to 70% of individuals with truncus arteriosus ( Fig. 3-23 ). It is rare to find a truncus arteriosus defect without a VSD.

 
 

FIGURE 3-23  Various forms of truncus arteriosus. A, Type I with a short main pulmonary artery segment arising from the leftward, posterior, aspect of the ascending aorta. B, Type II with separate origins of the right and left pulmonary arteries arising close to each other on the posterior aspect of the ascending aorta. Note the left-sided aortic arch in A and B. C, Type III with separate origins of the right and left pulmonary arteries arising far apart from the posterolateral aspect of the ascending aorta. D, Type IV, which is more appropriately described as pulmonary atresia and ventricular septal defect; there are separate origins of the right and left pulmonary arteries arising from the descending aorta. Note there is a right-sided aortic arch in C and D.  (Reprinted with permission from Grifka RG: Cyanotic congenital heart disease with increased pulmonary blood flow. Pediatr Clin North Am 1999;46:413.)

 

 

 

With truncus arteriosus, the systemic and pulmonary circulations are not separated. The elevated PVR of the infant will initially direct blood systemically; however, as PVR falls, blood is directed to the pulmonary circulation, causing CHF. Ultimately, PVR increases to the degree that obstructive pulmonary vascular disease develops. Without treatment, Eisenmenger's syndrome will occur in about 50% of these people.[111] Some of these patients will develop pulmonary vascular obstruction to the degree that left-to-right shunting will be diminished and symptomatic improvement will occur, allowing survival into adulthood.[110] Occasionally, pulmonary artery stenosis may be present to limit pulmonary blood flow, but severe cyanosis will occur instead.

The infant with truncus arteriosus is critically ill with severe CHF secondary to a high Qp/Qs. The infant may be slightly cyanotic at birth, but as the PVR falls, the cyanosis will disappear. These children will rarely present for anything beyond cardiac surgery or catheterization. For patients with type Ia or IIa, it is critical to preserve systemic flow and minimize further pulmonary shunting. A high-dose fentanyl anesthetic is most commonly used to minimize changes in either pulmonary or systemic circulations. Hyperventilation and high-inspired FiO2 should be avoided so as to prevent further increasing pulmonary blood flow. Before complete repair at 2 months of age, these infants will receive digoxin, furosemide, and afterload reduction to reduce symptoms of pulmonary overcirculation and pulmonary blood flow.[122] Complete repair will involve creation of a conduit from the right ventricle to the pulmonary artery, closure of the VSD, and creation of a neoaortic valve from the truncal valve ( Fig. 3-24 ). The main reason for improvement in the prognosis for individuals with truncus arteriosus resides in the current strategy of early repair after birth, rather than delaying, which allows the excessive pulmonary blood flow to damage the pulmonary vasculature. Mortality and morbidity is increased if the repair is delayed more than 30 days after birth.[123] Later in life, almost all of these patients will require replacement of the pulmonary conduit, and others may even require repair or replacement of the neoaortic valve.[114] As the infant grows following complete repair, suprasystemic pressures may result in failure of the right ventricle that will require conduit replacement.

 
 

FIGURE 3-24  Repair of truncus arteriosus. The ventricular septal defect has been closed and a valved conduit has been interposed between the right ventricle and the pulmonary artery. Currently, this would typically be a homograft valve. The heart shown has a quadricuspid truncal (now aortic) valve.  (Reprinted with permission from Baum VC: The adult patient with congenital heart disease. J Cardiothorac Vasc Anesth 1996;10:273.)

 

 

 

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Total Anomalous Pulmonary Venous Connection (TAPVC)

This is a very uncommon anomaly, comprising about 1% of CHD. The two forms are partial and total. The partial defect includes pulmonary veins draining to the LA while other veins are draining to other venous connections in the chest. It accounts for only a fourth of anomalous pulmonary venous connections. There are four types of TAPVC: supracardiac, cardiac, infradiaphragmatic, and mixed ( Fig. 3-25). Some refer to the infradiaphragmatic as intracardiac. Because all the oxygenated blood returns to the RA, an ASD must exist. In the supracardiac and cardiac types of TAPVC with a large ASD the condition resembles an ASD with increased pulmonary blood flow and mixing that leads to less well-oxygenated blood delivered to the systemic circulation and thus cyanosis. The supracardiac type usually drains to the innominate vein and intracardiac type to the coronary sinus. With the infracardiac type, the drainage is usually to the portal vein, but the pulmonary venous flow is obstructed to a degree, resulting in PAH. With all types of TAPVC, the pulmonary veins come together in a confluence behind the heart and then connect to the systemic venous circulation.

 
 

FIGURE 3-25  Four classification of total anomalous pulmonary venous return. A, Type I; the four pulmonary veins drain into the vertical vein that enters the innominate vein. B, Type II; the pulmonary veins drain into the coronary sinus that enters the right atrium. C, Type III; the pulmonary veins join to form a descending vein that courses through the diaphragm and drains into the portal venous system. D, Type IV, mixed pulmonary venous return; the two right pulmonary veins and the left lower pulmonary vein drain to the coronary sinus, while the left upper pulmonary vein drains into a vertical vein. Note that in all four there is an atrial septal defect.  (Reprinted with permission from Grifka RG: Cyanotic congenital heart disease with increased pulmonary blood flow. Pediatr Clin North Am 1999;46:419.)

 

 

 

Patients with TAPVC may present in many different ways dependent on the pulmonary venous connections, size of the ASD, PVR, pulmonary venous obstruction, and other characteristics. The clinical presentation of TAPVC may vary, but cyanosis is present in all forms. Mild cyanosis and increased pulmonary blood flow from the RA as the PVR falls occur with the supracardiac and cardiac types of TAPVC. Right ventricular overload may occur owing to increased pulmonary blood flow. Surgery is not usually emergent, so medical management is often pursued with digoxin and furosemide. Surgical correction may be undertaken subsequently and electively. In contrast, infradiaphragmatic TAPVC presents with unstable hemodynamics and poor peripheral perfusion, and immediate inotropic support is necessary. Respiratory distress ensues quickly after birth and emergency surgery is necessary to prolong the infant's life. The obstruction to pulmonary venous return is associated with a very poor prognosis.[19] Anesthetic management is reviewed elsewhere. [122] [124]

Most patients with TAPVC will die without treatment in the first year.[125] Those who survive for 3 months have a 50% survival rate at 1 year.[125] Some patients have been known to survive to adulthood with TAPVC with a large, nonrestrictive ASD, minimal obstruction to pulmonary venous return, and little pulmonary vascular obstructive disease.[125] If the patient does not have pulmonary venous obstruction, a large ASD is present, and PVR is not excessive, the patient may be approached from an anesthetic standpoint as having an ASD with excessive pulmonary blood flow.

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Single Ventricle

The mortality of neonatal congenital heart repair involving two ventricles continues to decline, whereas patients with single-ventricle physiology continue to experience many challenges, accompanied by significant morbidity and mortality. Survival with a single ventricle is only 30% at 1 year after birth, although some individuals may live to adulthood.[126]

A wide variety of congenital heart defects are anatomically single-ventricle defects, which account for 1% to 2% of CHD.[126] However, other defects behave as single ventricles because they are unable to properly function as dual ventricle systems, such as HLHS, severe Ebstein's anomaly, tricuspid atresia, and an unbalanced AV septal defect. The ventricular morphology of two thirds of single ventricle defects is left ventricle. Approximately one fourth of single-ventricle anomalies have morphologic right ventricles. The remaining single-ventricle defects are classified as indeterminate but often are composed of both right and left ventricles. The great vessels appear discordant in 85% of these defects. Both morphology of the ventricle and the relationship of the great arteries are important to note when caring for these patients. Most single ventricles have an atretic AV valve or semilunar valve. Mixing of the systemic and pulmonary venous blood will necessarily occur, producing eventual ventricular overload. Ventricular ejection into either the systemic or pulmonary circulation is dynamic and will depend primarily on SVR and PVR, respectively. Consequently, surgical placement of either a systemic to pulmonary artery shunt or a pulmonary artery band will be required. The age of the patient is also important, because it will influence decisions regarding the care of individuals with the same single ventricle anatomy and physiology.

All current management options for a single-ventricle defect are suboptimal, but a Fontan procedure appears to offer many advantages.[127] The Fontan procedure is based on the principle that the right atrial pressure is capable of providing the force necessary to deliver deoxygenated venous blood to the pulmonary arteries and lungs, so that the well-oxygenated blood may return to the single ventricle without mixing with the deoxygenated venous blood. The solitary ventricle will then become the pump for this well-oxygenated blood to travel systemically, achieving a physiologic circulation without benefit of two ventricles. There have been many modifications of the Fontan operation ( Fig. 3-26 ) since its initial description.

 
 

FIGURE 3-26  The modifications of the Fontan procedure. A, Direct connection of the right atrial appendage to the side of the main pulmonary artery. B, Direct connection of the right atrial appendage of the end of the pulmonary trunk. C, Right atrial to right ventricular connection with a pericardial patch. D, Right atrial to right ventricular connection with a valved conduit. E, Total cavopulmonary anastomosis with an intra-atrial (lateral tunnel) baffle. F, Total cavopulmonary anastomosis using an extracardiac conduit.  (Reprinted with permission from Stayer SA, Andropoulos DB, Russell IA: Anesthetic management of the adult patient with congenital heart disease. Anesthesiol Clin North Am 2003;21:666.)

 

 

 

A Fontan operation is performed ideally from 18 months to 4 years of age but is also performed quite frequently during adulthood. The 15-year survival of 60% is the same for those who received a Fontan operation as a child or adult.[127] However, patients who received a Fontan operation as an adult may have different issues to contend with perioperatively and long-term compared with children who have undergone the procedure. One major concept that applies to both pediatric and adult patients is the importance of PVR. If PVR is high at the time of surgery, the Fontan operation will fail. However, strict characteristics once thought to be absolutely necessary to consider performing this procedure have been expanded, so that 80% of Fontan procedures are successful. This has been achieved through a variety of measures, but none is more important than the “fenestration” that is made between the atria. Fenestrations have allowed Fontan procedures to be performed in patients not previously considered candidates. The fenestration augments cardiac output at the expense of worse basal oxygenation. It also lessens the risk of complications. Chronic anticoagulation is required.

A patient who has had a Fontan procedure and who requires noncardiac surgery is an anesthetic challenge. Many physiologic changes occur with a Fontan operation. Some of these changes occur rapidly, whereas others may take years to occur. Certain changes are also associated specifically with Fontan procedures done more than 18 years ago that will not be present in more recent Fontan operations. Any history of prior palliative surgery should be noted, because these patients tend to have worse baseline myocardial function.

It is necessary to assess the current functional status of an individual who has had a Fontan operation, irrespective of previous functional class, because ventricular deterioration is inevitable. [127] [128] [129] [130] The reason for this gradual circulatory decompensation is not understood. Systolic ventricular function begins to slowly deteriorate at 1 to 5 years but is most discernible after 5 years.[127] The systolic function is more likely to be impaired if the ventricle is a morphologic right ventricle. Functional class and ejection fraction will be excellent during this slow deterioration. Along with reduced systolic function, Doppler echocardiography revealed in 25 patients with CHD that significant systolic incoordination, possibly attributed to the geometry of the muscles resulting from the CHD, was also present in these patients.[130] Even if systolic function is preserved, severe diastolic dysfunction may be present.[130] As the systolic function worsens, AV valve regurgitation may also appear. After 10 years an obvious decline in the functional class is readily apparent.[127] The amount of ventricular dysfunction is directly related to the number of years volume overload was present.

Another challenging characteristic of an individual with a Fontan operation is the propensity for arrhythmia that has become more prevalent as the number of years since surgery increases. Atrial dilation is a major focus, but decreased ventricular function and AV valve insufficiency also play a role in arrhythmogenesis. Arrhythmias are primarily IART,[23] with the most common being atrial flutter.[34] If atrial flutter occurs suddenly, rapid treatment is necessary because CHF may ensue rapidly.[131] Arrhythmias are more likely to occur in those with older-style Fontan operations than individuals with lateral tunnels and cavopulmonary connections.[23] Adults who received a Fontan operation are also more likely to have dysrhythmias. Forty-six percent of adults who underwent a Fontan procedure as adults will have arrhythmias by 10 years.[127] Modifications of the procedure, such as the use of a lateral tunnel, may ameliorate some of the ventricular dysfunction and other associated arrhythmias ( Fig. 3-27 ).[110]Atrial arrhythmias are especially difficult to treat.[23] Twenty percent of survivors will be taking at least one antiarrhythmic medication, excluding digitalis.[131]

 
 

FIGURE 3-27  Lateral tunnel modification of the Fontan operation in a heart with single ventricle. After resection of the native atrial septum, an intra-atrial baffle directs inferior vena caval return through the right atrium. The superior vena cava has been transected and both ends anastomosed to the right pulmonary artery. A hole has been placed in the baffle material to allow decompression of the right atrium if necessary. This may close spontaneously or may be closed by an intravascularly placed device in the catheterization laboratory, or a pursestring suture may be placed around it (the “adjustable atrial septal defect”) for later elective closure. The pulmonary artery has been ligated proximally. The coronary sinus (CS) has been incorporated into the low-pressure neo-left atrium, which will result in minor arterial desaturation. It can be appreciated that the cephalad-superior vena cava/right pulmonary artery anastomosis represents a bidirectional Glenn shunt.  (Reprinted with permission from Baum VC: The adult patient with congenital heart disease. J Cardiothorac Vasc Anesth 1996;10:272.)

 

 

 

Patients who have a Fontan operation tend to be receiving diuretics, afterload-reducing agents, and anticoagulants. Slightly more than half of individuals with a Fontan operation require chronic diuretics. Nearly one third of patients have had a thrombotic episode after the procedure, with biochemical evidence of thrombosis present long after surgery.[132] Beyond the well-recognized risk of perioperative thrombotic complications, long-term coagulation changes reveal a lowered protein C and S value compared with age-matched controls but no difference in antithrombin levels.[132] Fifty percent of Fontan patients have elevated levels of factor VIII.

Protein-losing enteropathy (PLE) is a major risk factor for anesthesia in patients who have had a Fontan procedure. It occurs in 10% of patients, characterized by significant peripheral edema, low serum albumin, hypomagnesemia, and hypocalcemia. [34] [131] The immune system is depressed, making these patients susceptible to respiratory tract infections. Especially important is that induction of anesthesia in these individuals has been noted to be a significant risk, with hemodynamic instability and even cardiovascular collapse not uncommon. Furthermore, several major classes of anesthetic agents, as well as other medications, are affected by the hypoalbuminemia. Any patient with PLE who requires surgery deserves special care to assess his or her current metabolic, protein, and hemodynamic status as well as their recent condition.

Anesthetic management of a patient who has had a Fontan operation has special considerations. The right atrial pressure must be adequate to maintain good cardiac output. Previous right atrial filling pressures should be noted. The right atrial pressure also reflects ventricular function, AV valve sufficiency and function, PVR, and pulmonary artery size.[131] There is a gradient between the RA and the LA that is partially fixed, due to the lungs, that determines the cardiac output. If PVR increases, the gradient between the RA and LA increases and the likelihood of poor cardiac output and systemic oxygen delivery increases; consequently, it is essential to minimize PVR. Parameters that are important to achieve to minimize PVR include hypocarbia, alkalosis, decreased intrathoracic pressures, normothermia, and minimal PEEP. Positive-pressure ventilation inhibits pulmonary blood flow, diminishes cardiac output, and increases PVR, whereas negative pressure does the opposite.[133] Afterload reduction may be used to reduce PVR and increase cardiac output. Inhaled nitric oxide (20 ppm) is beneficial in patients with a Fontan operation who have increased PVR and increased transpulmonary gradient because there is no change in systemic blood pressure, as can be caused by some pulmonary vasodilators.[134] The response to nitric oxide is rapid, or the individual may be a nonresponder. Nitric oxide may be instrumental in restoring oxygenation without hemodynamic consequences.[134]

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Hypoplastic Left Heart Syndrome (HLHS)

Before 1970 HLHS was considered fatal. It is the fourth most common congenital anomaly requiring neonatal surgery,[135] making up 7% of CHD.[3] Today, treatment involves either a heart transplant or a staged repair ending in a Fontan procedure to separate the pulmonary and systemic circulations. The anesthesiologist must understand the anatomic and physiologic issues to provide anesthesia to these patients for a noncardiac operation.

HLHS includes aortic valve atresia, hypoplasia of the ascending and arch of the aorta, and atresia or stenosis of the mitral valve. The apex of the heart is formed almost entirely by the right ventricle ( Fig. 3-28 ), while the left ventricle is nonfunctional. Pulmonary and systemic venous blood will mix in the RA. Systemic perfusion, especially coronary perfusion, will be supplied by the PDA. Excessive pulmonary blood flow will diminish systemic perfusion, leading to coronary hypoperfusion and shock. The mixed venous saturation is an excellent modality to detect anaerobic metabolism, especially if it is less than 30%. As long as PVR remains high, the infant will appear cyanotic, but systemic perfusion will be adequate.

 
 

FIGURE 3-28  Native anatomy in hypoplastic left heart syndrome (HLHS). Note the hypoplastic left ventricle, aortic valve atresia, and diminutive ascending aorta. Systemic blood flow is propelled by the right ventricle (RV) via the pulmonary artery (PA), and ductus arteriosus. Pulmonary venous return enters the right side of the heart through a foramen ovale or an atrial septal defect. LA, left atrium; RA, right atrium.  (Reprinted with permission from Nicolson SC, Steven JM, Jobes DR: Hypoplastic left heart syndrome. In Lake CL [ed: Pediatric Cardiac Anesthesia. Stamford, CT, Appleton & Lange, 1998, p 338.)

 

 

 

If a heart transplant is not performed for HLHS, ductal flow cannot continue to supply the systemic metabolic needs of the infant. A Norwood procedure is performed to create unobstructed systemic and coronary perfusion but also to ensure a stable source of pulmonary blood flow ( Fig. 3-29 ). A neoaorta is fashioned from the pulmonary artery and a shunt placed between the aorta and pulmonary artery to regulate pulmonary blood flow. Currently a Blalock-Taussig shunt is included in the “modified Norwood.”[19] Owing to advancements of the Norwood procedure, 85% to 94% of infants survive to a bidirectional cavopulmonary anastomosis[136] and 40% to 60% of infants will survive to be evaluated for a Fontan procedure.[137]

 
 

FIGURE 3-29  Norwood procedure. A,Dotted lines indicate transection points of the main pulmonary artery (PA) and ductus arteriosus. B, Atrial septectomy to avoid pulmonary venous hypertension. Patch closure of distal main PA. Longitudinal incision in aorta extending beyond ductus arteriosus, which has been divided and ligated. C and D. Construction of neoaorta using the proximal main PA, ascending aorta (Ao), and vascular allograft. E, Pulmonary blood flow supplied by a right modified Blalock-Taussig shunt connecting the right subclavian artery to the right PA.  (Reprinted with permission from Nicolson SC, Steven JM, Jobes DR: Hypoplastic left heart syndrome. In Lake CL [ed: Pediatric Cardiac Anesthesia. Stamford, CT, Appleton & Lange, 1998, p 342.)

 

 

 

Within a year of a Norwood procedure, a bidirectional cavopulmonary anastomosis or hemi-Fontan procedure is performed. With a hemi-Fontan procedure all pulmonary blood flow arises exclusively from the superior vena cava ( Fig. 3-30 ). The pulmonary veins deliver well-oxygenated blood to the single atrium while the inferior vena cava instead delivers desaturated blood to the single atrium, resulting in blood with a saturation of 85% for systemic delivery.[138] The hemi-Fontan procedure reduces the stress on the pulmonary vessels and PVR to handle the entire cardiac output; instead, the cardiac output is maintained by pulmonary venous blood derived from the superior vena cava and by deoxygenated blood derived from the inferior vena cava. It is the staging of the repair of HLHS that improved 5-year survival to 70%.[139] With improved survival there are more opportunities for these infants to undergo noncardiac surgery. After bidirectional cavopulmonary anastomosis or a hemi-Fontan procedure, a modified Fontan operation completes the staged repair of HLHS. The 10-year survival has still only reached 50% or less for patients with HLHS.[135]

 
 

FIGURE 3-30  A, Hemi-Fontan. The superior vena cava is associated with the augmented pulmonary arteries, and a dam is positioned to separate the common atrium from the caval-pulmonary anastomosis. B, Schematic illustration of the blood flow pattern in children after hemi-Fontan operation. Pulmonary blood flow is derived exclusively from superior vena cava (SVC) drainage flowing directly through the pulmonary bed. Venous return is split nearly equally between SVC flow that passes through the pulmonary circulation (PA and PV) entering the common atrium and inferior vena cava (IVC) blood that enters the atrium directly. The single ventricle (RV) need only supply sufficient flow to perfuse the systemic circulation; thus the volume load is equivalent to a normal systemic ventricle. Ao, aorta. (Reprinted with permission from Nicolson SC, Steven JM, Kurth CD, et al: Anesthesia for noncardiac surgery in infants with hypoplastic left heart syndrome following hemi-Fontan operation. J Cardiothoracic Vasc Anesth 1994;8:335.)

 

 

 

Anesthetic management for noncardiac surgery will depend on the stage of repair. Anesthesia for a Norwood procedure has been reviewed.[140] Fentanyl was associated with a more stable intraoperative course than halothane. Following a Norwood procedure but before the hemi-Fontan procedure, it is important to effectively balance systemic and pulmonary blood flow during a noncardiac operation. A Qp/Qs ratio maintained near 1.0 should provide optimal pulmonary, and especially systemic, perfusion. Two factors that will influence outcome the most in patients after a Norwood procedure include ventricular function and flow across the shunt.[141] Inhalation or intravenous induction may be used, depending on the ventricular function. Maintenance anesthesia should consist of a low-dose volatile agent and narcotics. Fentanyl will help stabilize systemic and pulmonary blood flows. Pao2 and Spo2 should be followed carefully but will not always accurately reflect the balance between pulmonary and systemic flows. A broader range of inspired oxygen concentrations and Pco2 is tolerated once there has been more time elapsed since the Norwood procedure.

After a bidirectional Glenn or hemi-Fontan operation, inhalation induction is tolerated quite well by infants and children. The PVR should not be allowed to increase, but it does not have to be low for a bidirectional Glenn or hemi-Fontan operation, in contrast to the modified Fontan procedure. Right atrial filling pressures must be maintained, especially if PVR is slightly elevated, because with adequate filling pressures the inferior vena cava can support the cardiac output.[138] Tidal volumes must be below normal even though moderate hypocarbia is desirable. If ventilation does not result in oxygen saturations at least as good as in the preoperative period, ventilation parameters should be reviewed. Regional block is recommended for analgesia to avoid significant respiratory depression associated with systemic narcotics.

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ANATOMIC DEFECTS ASSOCIATED WITH DECREASED PULMONARY BLOOD FLOW

Patients with cyanotic CHD may desaturate severely. In most cases, infants with cyanotic CHD do not survive very long without surgical intervention. The two most common defects of cyanotic CHD are TOF and Eisenmenger's syndrome.[142]

Tetralogy of Fallot (TOF)

TOF is the most common form of cyanotic CHD after 1 year of age, accounting for 10% of all CHD.[109] It is also the most common cyanotic defect encountered in adults.[110] Without surgery, a majority of patients die in childhood. Twenty-five percent will survive to adolescence without surgery but face a mortality rate of 6.4% per year.[110] Only 3% will survive until the age of 40.

TOF contains four main characteristics, although the essence of the defect has been argued for many years without resolution: a nonrestrictive VSD, obstruction of the right ventricular outflow tract with or without supravalvular pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta ( Fig. 3-31 ). There is a range of morphology, anatomy, signs, symptoms, and pathophysiologic consequences related primarily to the degree of pulmonary blood flow obstruction.[143] A feature that is consistently present with TOF is right ventricular infundibular narrowing. Until the infundibulum becomes more active and pulmonary blood flow becomes obstructed by closure of PDA, 25% of infants with TOF are acyanotic. However, pulmonary blood flow may be obstructed at levels other than the infundibulum. The pulmonary valve is stenotic in three fourths of individuals and absent in 2% to 6%.[144]

 
 

FIGURE 3-31  The interior of the right ventricle, showing the characteristic defects of tetralogy of Fallot: pulmonic stenosis, ventricular septal defect (VSD), overriding aorta, and right ventricular hypertrophy.  (Reprinted with permission from Stayer SA, Andropoulos DB, Russell IA: Anesthetic management of the adult patient with congenital heart disease. Anesthesiol Clin North Am 2003;21:663.)

 

 

 

Obstructed pulmonary blood flow at the level of the infundibulum with a VSD causes a right-to-left shunt that is largely fixed. However, changes in PVR and SVR can alter the amount of right-to-left shunt enough to precipitate “tet” spells. These episodes are profound states of cyanosis associated with increased right-to-left shunt, primarily occurring in infants 2 to 3 months of age that can progress to unconsciousness. These hypercyanotic spells are not limited only to TOF but occur in other cyanotic CHD. Treatment includes maneuvers to lessen the right-to-left shunt, such as increasing SVR or decreasing PVR. “Tet” spells may also be initiated by infundibular spasm in response to sympathetic stimulation or β-adrenergic medications. Adequate filling pressures and volume status are imperative in these patients, because hypovolemia may increase sympathetic stimulation or further reduce oxygen delivery, which may result in acidosis and, consequently, increase PVR, further exacerbating the right-to-left shunt. “Tet” spells are infrequent or absent by the age of 2 to 3 years and very rarely occur in children or adolescents. They do not occur in adults.[142]

Some patients with TOF may be palliated with a modified Blalock-Taussig shunt ( Fig. 3-32 ) until complete repair is warranted.[143] Although most patients will be repaired during infancy, adults also may undergo complete repair of TOF,[145] most commonly between the ages of 13 to 43 years. Surgical mortality is higher in adults (2.5% to 8.5%) than infants (<3.0%).[142] Furthermore, actuarial survival is less the older the patient is at the time of surgery.[146] Older patients often have previously undergone aortopulmonary shunts or have significant aortopulmonary collaterals that increase the difficulty of a complete repair. Once repaired, survival rates range from 80% to 94% over 20 years[34] and 80% of patients are symptom free.[147] Reoperation is necessary in less than 10% of patients.

 
 

FIGURE 3-32  Modified Blalock-Taussig shunt. Note the atretic main pulmonary artery (MPA) and the ligated ductus arteriosus (ductus). A Gore-Tex tube graft (shunt) is sewn side-to-side between the innominate artery and the right pulmonary artery. Size of the tube graft (3.5 mm, 4.0 mm, or 5.0 mm) is chosen at surgery depending on patient size and caliber of pulmonary artery. Some surgeons perform the shunt through a median sternotomy, and others choose a lateral thoracotomy; cardiopulmonary bypass is usually not required. AAo, ascending aorta.  (Reprinted with permission from Waldman JD, Wernly JA: Cyanotic congenital heart disease with decreased pulmonary blood flow in children. Pediatric Clin North Am 1999;46:388.)

 

 

 

Patients who require noncardiac surgery after TOF repair have several risk factors that need to be carefully monitored. These individuals have an increased risk of arrhythmias and sudden death, even though they have undergone repair. [23] [142] [147] On Holter monitoring, arrhythmias are detected in 40% to 50% of individuals after repair of TOF. Scarring from the atriotomy or ventriculotomy may contribute to this risk of arrhythmias. Atrial flutter or fibrillation is far more common than ventricular arrhythmias, especially because the age of repair is greater. These rhythm disturbances may cause considerable morbidity.[23] It has not been possible to identify which patients are at increased risk of sudden death after repair of TOF. It is not uncommon to see polymorphic ventricular ectopy by Holter monitoring in patients with TOF. Inducible VT is noted in 15% to 30% of patients.[23]

Before anesthesia, a patient who underwent TOF repair should be evaluated for evidence of pulmonary regurgitation. The right ventricle may dilate and develop worsening function and left ventricular failure with pulmonary regurgitation. However, the need for pulmonary valve replacement is not absolute with pulmonary regurgitation, because it may be tolerated well for years.[34] It is now questionable whether complete relief of the right ventricular to pulmonary artery gradient is even necessary at the time of repair, because significant infundibular resection is needed to accomplish it, and more than a third of patients at long-term follow-up have been identified with pulmonary regurgitation.[148] Obstruction of the right ventricular outflow tract is not uncommon and is the most common reason for reoperation. Assessment of the ventricular function is vital before any anesthetic because the function may deteriorate. However, if the repair is good, then the patient should be in condition to tolerate most operations.[147]

These patients may have a greater risk of developing myocardial ischemia during noncardiac surgery. Anomalous coronary arteries are present in 10% of those with TOF.[142] Thirty-five percent of infants with TOF have evidence of myocardial ischemia.[20]

Anesthetic management of infants with TOF will primarily occur in the catheterization laboratory or during a palliative or complete repair and has been reviewed.[149] Anesthetic induction can be achieved with ketamine, administered intramuscularly or intravenously with relative safety if ventilation is maintained. Ketamine has not been found to increase PVR in these patients[150] or precipitate “tet” spells.[102] It is effective at maintaining the SVR,[110] yet does not significantly alter Qp/Qs.[102] Ketamine provides superior hemodynamic control compared with isoflurane in infants with TOF, not just during induction but with anesthetic maintenance as well.[104] Fewer children and infants with TOF required inotropic support with ketamine than isoflurane before CPB.

An inhalation induction may also be safely performed in patients with TOF,[67] but the blood pressure must be carefully observed to avoid a decrease in SVR that may increase the right-to-left shunt. In general, anesthetic induction will improve peripheral saturation in those with cyanotic CHD. [67] [68] Fentanyl (10 to 25 μg/kg) and a very low inspired concentration of volatile agent is recommended for anesthesia maintenance in those with TOF.

Opioids offer several advantages, such as circulatory stability for anesthetic management of TOF, [87] [94] but benefit from the addition of other agents.[90] When flunitrazepam was added to a sufentanil-based anesthetic for infants and children undergoing complete repair of TOF, plasma levels of norepinephrine were suppressed more fully compared with the administration of sufentanil alone. Furthermore, the response to stimulation was not suppressed as well with opioids alone compared with opioids and benzodiazepines.[90]

If a patient is evaluated with TOF and absent pulmonary valve, extreme airway obstruction is a risk, secondary to the very large pulmonary arteries that lie on the bronchi.[144] Bronchomalacia is also a real concern. Any signs of respiratory infection should be carefully followed up, because the risk of these infections is significant.

Complete repair of TOF has not been achieved in some individuals. Poor pulmonary blood flow may have been remedied by aortopulmonary shunts that improved symptoms ( Fig. 3-33 ). These adults tend to have a less severe form of TOF. Although cyanotic, they have developed significant aortopulmonary collaterals that increased pulmonary blood flow. They may experience some dyspnea and limited exercise tolerance. Without complete repair, they have erythrocytosis, hyperviscosity, abnormal hemostasis, cerebral abscesses, or stroke and endocarditis.[142]Hemoptysis is possible and may be severe.[145] Severe volume overload resulting in CHF is also present in many of these individuals. Management of these patients from an anesthetic point of view should strive to maintain SVR, and fentanyl and ketamine accomplish this effectively.

 
 

FIGURE 3-33  Palliative aortopulmonary anastomoses. The anastomoses shown on this figure of a heart with tetralogy of Fallot represent the following: 1, modified Blalock-Taussig; 2, classic Blalock-Taussig; 3, Waterston (Waterston-Cooley); 4, Potts.  (Reprinted with permission from Baum VC: The adult patient with congenital heart disease. J Cardiothorac Vasc Anesth 1996;10:270.)

 

 

 

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Pulmonary Atresia with VSD

Pulmonary atresia with VSD makes up 2% of CHD. It is the most severe form of TOF, differentiated by pulmonary valve atresia and variable size and distribution of the pulmonary artery tree. The pulmonary arteries are much more abnormal than in TOF. The complex pulmonary anatomy sometimes relegates the patient to life-long chronic cyanosis. However, advances in surgical techniques have increased the number of patients capable of complete repair.

The central pulmonary arteries of pulmonary atresia have no anatomic connection with the right ventricle ( Fig. 3-34 A). In most cases the pulmonary trunk is little more than a cord or is altogether missing. If the right and left pulmonary arteries communicate, they are described as confluent. The blood supply to the lungs is largely derived from collateral vessels originating from the descending aorta or other systemic sources such as a PDA. The collateral vessels from the aorta follow the distribution of the pulmonary arterial branches to the lungs. The collateral vessels may travel to the lung segments alone or connect at some point with the pulmonary arterial vessels traveling to the same segments of the lung (see Fig. 3-34 B). The complexity of the pulmonary artery and collateral circulation to the lung results in many clinical scenarios for affected persons (see Fig. 3-34 C). The pulmonary blood supply is so variable and complex, whereas the intracardiac structure is straightforward. The pulmonary arteries may be quite hypoplastic, making complete surgical correction difficult or impossible. The VSD is nonrestrictive and connects morphologically distinct right and left ventricles.

 
 

FIGURE 3-34  Pulmonary atresia and ventricular septal defect. A, Anterior view of unopened specimen from an 18-year old shows dextroposed aorta (Ao), right aortic arch, and severely hypoplastic pulmonary trunk (PT) and left pulmonary artery (LPA). B, Posterior view of mediastinal structures from a 4-year old with pulmonary situs inversus, right aortic arch, and right atrial isomerism shows origin of large systemic collateral artery (arrow) to left lung from descending thoracic aorta. C, Anterior view of right aortic arch from an 8-year old shows mirror-image brachiocephalic branching, aberrant retroesophageal left subclavian artery (LSA), and origin of two small collateral arteries (arrows) and one large trifurcating collateral artery (*). LCCA, left common carotid artery; LV, left ventricle; RAA, right atrial appendage; RCCA, right common carotid artery; RSA, right subclavian artery; RV, right ventricle; Tr, trachea; TV, tricuspid valve.  (Reprinted with permission from Mair DD, Edwards WD, Julsrud PR, et al: Pulmonary atresia and ventricular septal defect. In Emmanouilides GC, Riemenschneider TA, Allen HD, Gutgesell HP [eds: Moss and Adams Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult. Baltimore, Williams & Wilkins, 1995, p 985.)

 

 

 

At birth these infants become very cyanotic, especially on PDA closure, or slightly cyanotic if significant collateral vessels are present. Eventually, patients will outgrow their collateral supply to become more cyanotic and require intervention. A number of operations, usually three, will be needed to centralize the complex pulmonary blood supply, referred to as “unifocalization.”[151] Unifocalization means that the central pulmonary arteries are confluent and continuous with all distal pulmonary arterioles. During the process of reaching unifocalization, these patients may appear for noncardiac procedures with various amounts of pulmonary blood flow.

To reach complete repair, the central arteries cannot be hypoplastic, or right ventricular failure would ensue. Most frequently, a staged operation is performed, when appropriate, with placement of a conduit from the right ventricle to the pulmonary arteries, followed by closure of the VSD.[151] The right ventricular-pulmonary artery conduit stimulates more pulmonary artery growth than aortopulmonary shunts. A single-stage complete repair for infants has been shown to achieve early cardiovascular physiologic normalization and avoid multiple operations.[152] It may also reduce the chance of obstructive pulmonary vascular disease that can occur with aortopulmonary collaterals.[152] The long-term results appear good with this one-stage approach, but additional studies will be necessary to validate it.[19]

As most patients with pulmonary atresia and VSD age, additional shunts or complete repair will be necessary. Those who have received complete repair will eventually require replacement of the right ventricle to pulmonary artery conduits later in life. These patients should be carefully evaluated for current and previous information regarding pulmonary artery distribution, cyanosis, and relative exercise tolerance. Anesthesia management is similar to those with TOF.

An important condition genetically transmitted that is associated with pulmonary atresia and VSD is the velocardiofacial syndrome. It is the second most common genetic condition associated with CHD. Velocardiofacial syndrome has many otolaryngologic manifestations, immune dysfunction, airway abnormalities, and reactive pulmonary airways. There is a propensity for chronic lung infections.[153] The anesthesiologist should be prepared for the possibility of severe bronchospasm. [152] [154]

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Transposition of the Great Arteries (TGA)

TGA constitutes 5% to 7% of CHD. [3] [5] It is the most frequent cyanotic defect.[5] The morphologic right ventricle gives rise to the aorta, and the morphologic left ventricle gives rise to the pulmonary artery ( Fig. 3-35 ). Without treatment, 95% of infants will die before 1 year of age. The operation of choice now is the arterial switch procedure. It is associated with low mortality, and patients should have a normal life expectancy. In contrast to many other congenital anomalies, additional cardiac surgery is unlikely. Extracardiac anomalies are rarely present with TGA.[34]

 
 

FIGURE 3-35  Normal heart (A) and a heart with transposition of the great arteries (TGA) (B). Note the right ventricle (RV) is in continuity with the main pulmonary artery (MPA), while the left ventricle (LV) is in continuity with the aorta (Ao). In the heart with TGA, the RV is in continuity with the Ao, and the LV is in continuity with the MPA.  (Reprinted with permission from Grifka RG: Cyanotic congenital heart disease with increased pulmonary blood flow. Pediatr Clin North Am 1999;46:407.)

 

 

 

TGA is usually designated with D or L. The “D” indicates that the aorta is anterior and to the right of the pulmonary artery, whereas “L” indicates the aorta is anterior and to the left of the pulmonary artery. TGA rarely contains an ASD or VSD but often has a large PDA. If there is AV discordance, the defect is referred to as a “corrected” TGA and it behaves in a physiologically normal manner.

TGA classically has parallel pulmonary and systemic circulations that result in severe cyanosis, which is made worse by the subsequent reduction in PVR that follows birth and the ensuing increased pulmonary blood flow that will ultimately cause pulmonary vascular disease. Without associated defects, the ductus arteriosus and PFO must provide communication between atria. Atrial communication generates improved oxygen saturation but may cause CHF. However, a small shunt such as an ASD or VSD may be associated with slightly better mortality than in those patients with severe cyanosis and no communication.

Infants with a restrictive ASD or obstructed aortic arch are severely cyanotic and have a poor prognosis with TGA. A communication may be required for viability, so a balloon septostomy is performed to increase oxygenation. Because the left atrial pressure is usually higher than the right atrial pressure, shunting will be in the direction of left to right. Most cases of TGA have an intact ventricular septum, but for those patients who have a VSD, cyanosis is mild but pulmonary blood flow is large. These individuals are prone to CHF and are often cyanotic and tachypneic. Early in their life they lead fairly normal lives, but myocardial function is depressed in contrast to normal hearts. A chest radiograph may frequently demonstrate an enlarged heart.[142] Although an anesthesiologist may interact with a patient who has TGA in the catheterization suite, contact will be minimal unless to provide anesthesia for the arterial switch.[155]

Although the arterial switch is currently utilized for most TGA infants, prior to its advent there were several surgical options to correct TGA. The Senning operation uses atrial native tissue to redirect blood from the RA to the left ventricle, whereas the Mustard procedure uses an intra-atrial baffle to direct systemic blood to the left ventricle ( Fig. 3-36 ).[110] The Rastelli procedure connects the pulmonary artery with RV and the LV with the aorta. Individuals who underwent a Senning, Mustard, or Rastelli procedure are likely to require an anesthetic for additional cardiac or noncardiac procedures. Long-term survival approaches 50% at 30 years.

 
 

FIGURE 3-36  Mustard operation. An intra-atrial baffle has been placed to redirect vena caval return posterior to the baffle to the left ventricle. The pulmonary veins enter to the right of the baffle; thus, pulmonary venous return is to the right atrium and then to the aorta. A Senning operation uses native atrial tissue to redirect blood flow, accomplishing the same result.  (Reprinted with permission from Baum VC: The adult patient with congenital heart disease. J Cardiothorac Vasc Anesth 1996;10:271.)

 

 

 

The primary problem with correction of TGA with a Senning or Mustard, procedure is right ventricular failure, because it supports the systemic circulation. The right ventricle remains the primary pump for systemic circulation, so eventually tricuspid regurgitation and right ventricular failure develop. Pulmonary obstructions may also occur in some instances. Besides gradual onset of circulatory failure, these patients have an increased risk for severe atrial dysrhythmias.[142] They may be present in 30% of cases[23] and are primarily reentry tachycardias attributed to trauma of the sinus node and atrial scarring.[23] Only 50% of individuals have sinus rhythm 20 years after surgery.[34] Ventricular arrhythmias are much less common than atrial arrhythmias and are rarely responsible for death. Another benefit of the arterial switch is the preservation of ventricular function compared with other operations for TGA.[34]

Patients with “corrected” transposition are functionally normal with respect to the pulmonary and circulatory circulation. It represents less than 1% of CHD. Median survival is approximately 45 years. Blood will be well oxygenated without surgical intervention, but they are not immune to right ventricular failure in adulthood because the systemic pump is a morphologic right ventricle.[34] Evidence of dysrhythmias and AV valve regurgitation should be sought before any surgery and anesthesia.[118]

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Tricuspid Atresia (TA)

TA represents about 3% of CHD but is the third most common cause of cyanotic CHD. It is defined as complete agenesis of the tricuspid valve without any direct communication between the RA and the right ventricle ( Fig. 3-37 ). An ASD or VSD is almost always present. In 70% of cases (type I), there is ventriculoarterial concordance. There are three subgroups of type of TA based on the presence of a VSD and pulmonary stenosis ( Fig. 3-38 ). Type Ib is the most common form of TA with a small VSD and pulmonary stenosis. TA is also uniformly associated with other cardiac anomalies that result in a variety of pulmonary blood flows and clinical manifestations. Extracardiac anomalies are present in 20% of those with TA.

 
 

FIGURE 3-37  Heart specimen illustrating a common variant of tricuspid atresia type IIc: D-transposition of the great arteries associated with coarctation of the aorta (c), hypoplasia of the aortic arch (a), patent ductus arteriosus (PDA), small ventricular septal defect (VSD), and hypoplasia of the right ventricle (RV). Note the adequate atrial septal defect (ASD).  (Reprinted with permission from Rosenthal A, Dick M: Tricuspid atresia. In Emmanouilides GC, Riemenschneider TA, Allen HD, Gutgesell HP [eds: Moss and Adams Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult. Baltimore, Williams & Wilkins, 1995, p 904.)

 

 

 

 
 

FIGURE 3-38  Type I: Tricuspid atresia without transposition of the great arteries. Type Ia: Pulmonary blood flow depends on a patent ductus arteriosus or bronchial collaterals because of pulmonary atresia. Type Ib: Restrictive pulmonary blood flow due to a small ventricular septal defect (VSD), small right ventricular cavity, and infundibular pulmonary stenosis. Type Ic: Normal or increased pulmonary blood flow due to a large VSD and an adequate pulmonary outflow tract.  (Reprinted with permission from Lowe DA, Stayer SA, Rehman MA: Abnormalities of the atrioventricular valves. In Lake CL [ed: Pediatric Cardiac Anesthesia. Stamford, CT, Appleton & Lange, 1998, p 409.)

 

 

 

Presentation at infancy will depend on whether pulmonary blood flow is reduced (cyanosis) or excessive (CHF). Excessive pulmonary blood flow is less common. A degree of cyanosis is still likely with excessive pulmonary blood flow, because significant mixing of systemic and pulmonary venous return is unavoidable. The size of the communication between the right and left sides of the heart also influences the degree of cyanosis. Factors that determine the physiology of TA are listed in Figure 3-39 . Hypoxic spells similar to “tet spells” may occur in infancy and can cause profound cyanosis.

 
 

FIGURE 3-39  Tricuspid atresia: physiology and common variations. Ventricular septal defect (VSD), right ventricle (RV), left atrium (LA), right atrium (RA), transposition of the great arteries (TGA), pulmonary stenosis (PS), main pulmonary artery (MPA), pulmonary blood flow (QP), aorta (Ao), ascending aorta (AAo).  (Reprinted with permission from Waldman JD, Wernly JA: Cyanotic congenital heart disease with decreased pulmonary blood flow in children. Pediatr Clin North Am 1999;46:393.)

 

 

 

Treatment in these infants is primarily surgical, with either an operation to increase pulmonary blood flow (shunt) or to decrease pulmonary blood flow (pulmonary artery band). Some type of surgical intervention is almost always required before 1 year of age. It is possible to achieve balanced pulmonary and systemic flows without intervention, with survival into the second decade. However, ventricular function will likely deteriorate, progressing to CHF. Brain abscesses and strokes are more common in these infants.

Anesthetic management of infants with TA for noncardiac procedures is challenging. Profound cyanosis may impair noninvasive monitoring of oxygen saturation.[65] Nitrous oxide and sevoflurane may be used for a gentle inhalation induction followed by a change to a narcotic-based anesthetic once intravenous access is established. The MAP must be kept up to maintain shunt patency. Although fluid deficits accumulate preoperatively, careful rehydration is necessary.

TA is the classic indication for a Fontan procedure.[156] It is usually performed between 2 and 15 years of age, if indicated.[156] Some of these patients may have undergone a superior cavopulmonary anastomosis before a Fontan procedure. This anastomosis involves end-to-side (bidirectional Glenn) or atrial dam (hemi-Fontan) to connect to the right pulmonary artery (see Fig. 3-30 ).[118] To complete the Fontan operation, an anastomosis of the inferior vena cava to the pulmonary artery will be necessary.

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Ebstein's Anomaly

Ebstein's anomaly represents 0.5% of patients with CHD.[3] They range from severely ill neonates to asymptomatic adults later in life. [157] [159] The mortality for infants may reach 20% in the first year. The mean age of death is approximately 20 years, with 15% alive at 60 years.[159]

Ebstein's anomaly includes an abnormal tricuspid valve and “atrialized” right ventricle that results in a poorly functioning right ventricle. Eighty percent of patients with Ebstein's anomaly will have an ASD or PFO.[142] Cyanosis is present in about half of these individuals.[158] VSD, pulmonary stenosis or atresia, and mitral valve abnormalities may accompany Ebstein's anomaly.

The main pathology of Ebstein's anomaly is derived from a tricuspid valve that is displaced downward toward the right ventricle, causing abnormalities of the septal and posterior leaflets of the valve. The level of valve displacement will largely determine the extent of valvular dysfunction and thus the degree of right ventricular dysfunction. Displacement of the valve also affects the leaflets ( Fig. 3-40 ). The posterior and septal leaflets are actually displaced below the “true” annulus into the right ventricle, with a large amount of “atrialized” right ventricle between the tricuspid valve annulus and the attachments of the leaflets ( Fig. 3-41 ). The anterior and posterior leaflets are very adherent to the endocardium. The anterior leaflet is usually malformed, large, and sail like. The posterior leaflet is usually tethered.

 
 

FIGURE 3-40  Ebstein's anomaly of the tricuspid valve. A, Normal anatomy, as would be seen in a subxiphoid four-chamber view, on echocardiogram. The mitral valve ring is more cephalad than the tricuspid ring, elevated by the membranous portion of the interventricular septum. The muscular septum separates the left ventricle (LV) and right ventricle (RV) cavities. B, Mild displacement of the septal and posterior leaflets that are tethered by fibrous chords to the septum. The anterior leaflet compensates by elongating and coapting downward within the RV cavity, creating a difference between tricuspid valve closure point and annulus. The valve itself is mildly regurgitant. This patient may be picked up incidentally as an asymptomatic child or adult. C, Moderate-to-severe downward displacement and tethering of two tricuspid valve leaflets. This valve is quite regurgitant, and there may be compromise of cardiac output. D, Because of right-to-left shunting through the associated atrial septal defect (ASD) and reduced pulmonary blood flow from functional as well as anatomic obstruction, this child would present as displaced down into the RV apex, the atrialized portion of the RV comprises most of the RV cavity, and there is probably secondary/associated pulmonary atresia. This child may well die in utero from cardiac output inadequate to sustain life.  (Reprinted with permission from Waldman JD, Wernly JA: Cyanotic congenital heart disease with decreased pulmonary blood flow in children. Pediatr Clin North Am 1999;46:403.)

 

 

 

 
 

FIGURE 3-41  Anatomy of the anomaly of the tricuspid valve as seen in Ebstein's anomaly. RA, right atrium; LA, left atrium.  (Reprinted with permission from Spitaels SEC: Ebstein's anomaly of the tricuspid valve complexities and strategies. Cardiol Clin 2002;20:432.)

 

 

 

The “atrialized” ventricle is thin and dilated, much like the atrium. The extent of “atrialized” right ventricle present indicates the hemodynamic capabilities.[160] There are also fewer cells in the Ebstein's right ventricle than are found in a normal right ventricle, which contributes to ventricular dilation in addition to the significant tricuspid regurgitation. The left ventricle may also be poorly contractile, along with mitral valve prolapse.[160] Functional class is an excellent gauge of the severity of Ebstein's anomaly before administering an anesthetic for a noncardiac procedure.

Slightly less than 7% of those with Ebstein's anomaly present in infancy, whereas others may even arrive as stillbirths. An infant with Ebstein's anomaly is very cyanotic owing to a large right-to-left shunt. Because of the “atrialized” right ventricle and corresponding poor ventricular function, tricuspid regurgitation is more severe, further raising the right atrial pressure beyond the left atrial pressure, and hence worsening cyanosis. Cyanosis from a right-to-left shunt adversely affects survival ( Fig. 3-42 ).[158] If a child survives the neonatal period, cyanosis may resolve as the infant ages and PVR is lowered. However, cyanosis may recur once right ventricular function begins to weaken further. Frequently, these infants will not survive surgery.[143]

 
 

FIGURE 3-42  Survival curve for 46 patients with Ebstein's anomaly on medical follow-up and survival pattern according to presence of cyanosis and aortic oxygen saturation. Survival curves for (▪) all 46 patients on medical follow-up, (◆) patients having cyanosis (Cy+), (Δ) patients with arterial oxygen saturation 85% or less (Sat = ↑ 85%) and (□) patients without cyanosis and patients with arterial oxygen saturation above 85% (Cy-, Sat > 85%).  (Reprinted with permission from Jaiswal PK, Balakrishnan KG, Saha A, et al: Clinical profile and natural history of Ebstein's anomaly of tricuspid valve. Int J Cardiol 1994;46:117.)

 

 

 

The most common presenting symptoms of Ebstein's anomaly are exertional dyspnea (71%), exertional palpitations (37%), and cyanosis (30%).[158] However, the clinical presentation of Ebstein's anomaly varies greatly. Older children may present with a murmur, and adolescents may be diagnosed with the onset of arrhythmias.[142] If the tricuspid valve is minimally displaced, tricuspid regurgitation may actually be mild enough to go unrecognized until adulthood. In fact, the diagnosis may be made by accident with few, if any, symptoms.[142] Older patients primarily complain of fatigue and dyspnea on exertion.[160] If the right ventricular function deteriorates enough, cyanosis may emerge during adulthood. Jugular venous distention is not common until the end because the RA is massively dilated ( Fig. 3-43 ).

 
 

FIGURE 3-43  Transthoracic echocardiogram. Parasternal four-chamber view shows a dilated right atrium (RA) and the atrialized right ventricle (aRV). The functional right ventricle (fRV) is small. The septal leaflet (SL) is completely adherent. The anterior leaflet (AL) has distal focal attachments to the ventricular wall, with a tongue of tissue completing the valvar ring at the junction of the inlet and trabecular components of the right ventricle.  (Reprinted with permission from Spitaels SEC: Ebstein's anomaly of the tricuspid valve complexities and strategies. Cardiol Clin 2002;20:434.)

 

 

 

A chest radiograph may reveal extreme cardiomegaly in a neonate. In a mild case, the chest radiograph may be almost normal. However, 60% of chest radiographs will show the heart to be enlarged, secondary to right atrial dilation. The electrocardiogram will show evidence of right bundle branch block or right atrial enlargement in over 50% of cases. [158] [159] Twenty-five percent of patients with Ebstein's anomaly will have Wolff-Parkinson-White syndrome, often evident by electrocardiography.[34] Invasive diagnostic measures such as cardiac catheterization are rarely necessary to confirm or diagnose Ebstein's anomaly any longer, because echocardiography is usually diagnostic.[159]

The anatomic relationship of the right ventricle in Ebstein's anomaly causes blood to be poorly directed to the pulmonary arteries. Consequently, the right ventricle may only be capable of delivering blood flow from the inferior vena cava to the pulmonary artery. To solve this problem, a bidirectional Glenn operation is performed ( Fig. 3-44 ). It connects the superior vena cava to the superior aspect of the right pulmonary artery, from which blood from the superior vena cava travels to the pulmonary artery, bypassing the right ventricle. It is referred to as a “one and a half repair.” It is a breakthrough in managing cyanotic CHD because it permits greater pulmonary blood flow without overloading the ventricle.[161] The right ventricle is already overloaded from tricuspid regurgitation.[110] The expectation with a bidirectional Glenn operation is that patients will maintain an Spo2 of 80% to 85% temporarily.[162] This operation is usually part of a staged procedure in infants younger than 6 months old. Before placement of a bidirectional Glenn operation, the cyanotic infant most likely underwent placement of an arterial shunt to improve pulmonary blood flow. However, patients have had a bidirectional Glenn procedure successfully performed when younger than age 2 months as the primary operation with good results.[152] Thrombosis is a great concern with a bidirectional Glenn operation, noted in up to 7% of infants. It produces severe morbidity and even mortality.

 
 

FIGURE 3-44  Two surgical techniques used to construct bidirectional superior cavopulmonary connections.  (Reprinted with permission from Bradley SM, Mosca RS, Hennein HA, et al: Bidirectional superior cavopulmonary connection in young infants. Circulation 1996;94(Suppl II):II-6.)

 

 

 

Replacement of the tricuspid valve occurs less often, owing to the success of tricuspid valve repair.[160] Repair is performed in 60% to 80% of patients with good long-term survival. [157] [163] The tricuspid valve is a more difficult valve to repair than other valves and more likely to result in complications postoperatively. Tricuspid valve repair involves plication of the free wall of the “atrialized” right ventricle, posterior tricuspid annuloplasty, and right atrial reduction. The repair is based on the construction of a monocusp valve fashioned by the use of the anterior leaflet of the tricuspid valve. If tricuspid valve repair is not possible, the valve is excised and replaced with a prosthetic one. At 1-year follow-up, 92% of patients with tricuspid repair were in NYHA class I or II and the heart size had even regressed in some.[157]

Anesthesia for patients with Ebstein's anomaly depends to a large degree on the clinical manifestations. The anatomic variation of the tricuspid valve and degree of valvular displacement, right-to-left shunt, right and left ventricular dysfunction, and occurrence of tachyarrhythmias are instrumental in assessing the status in those with Ebstein's anomaly. Once symptoms appear, the hemodynamics are usually more tenuous and arrhythmias a greater likelihood.[159] The right ventricular dysfunction makes these patients especially high risk for anesthesia. The right ventricular dysfunction is worsened by the tricuspid regurgitation. Any negative influence on the right ventricle may precipitate low cardiac output and right-sided heart failure, especially because these patients are prone to poor cardiac output, worsening of right-to-left shunt, and serious dysrhythmias. Similarly, poor left ventricular function is an especially ominous feature before anesthesia.[159] Loss of the atrial kick can abruptly worsen a tenuous hemodynamic status. If the patient is especially ill, an intravenous induction with ketamine and fentanyl is recommended. Ketamine is especially useful in patients with severe illness and unstable hemodynamics.

One must be very observant in Ebstein's anomaly patients during the perioperative period for the occurrence of arrhythmias. Supraventricular arrhythmias are known to occur in 25% to 30% of individuals and are frequently associated with reentry arrhythmias, such as Wolff-Parkinson-White syndrome. [158] [142] Wolff-Parkinson-White syndrome is especially common in patients with Ebstein's anomaly, in part because of the way the right atrium becomes incorporated into the ventricle, bypassing the annulus fibrosis of the tricuspid valve. Wolff-Parkinson-White syndrome may be found in approximately 25% of Ebstein's anomalies.[34] Electrophysiologic testing may be warranted in certain patients before anesthesia. Patients with Ebstein's anomaly may respond poorly to classic treatment for supraventricular arrhythmias like verapamil, especially if the arrhythmia is a reentrant type. Atrial fibrillation in association with Wolff-Parkinson-White syndrome can degenerate rapidly into ventricular fibrillation.

Ventricular arrhythmias are especially malignant and fatal in this defect.[157] It is important to review the chronic antiarrhythmic medications that the patient may be receiving. Even following tricuspid valve repair, ventricular fibrillation is still a major concern, because surgery does not alleviate the risk of lethal ventricular dysrhythmias. Radiofrequency ablation has been less successful in treating arrhythmias associated with Ebstein's anomaly than the general population.[142]

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Eisenmenger's Syndrome

Ten-year survival is approximately 80%.[142] The median survival is to the mid 30s,[79] with a mean age of death of 25 ±12 years, which is actually better than once believed. Survival greatly exceeds primary PAH. There seems to be something about the congenital heart defect that is protective compared to the patient who develops primary PAH.

Patients with Eisenmenger's syndrome began with CHD characterized by a left-to-right shunt with corresponding excessive pulmonary blood flow. The most common defects associated with Eisenmenger's syndrome are listed in Table 3-7 . An isolated VSD is by far the most common cause.[164] Over a period of time excessive pulmonary blood flow causes hypertrophy of the pulmonary vascular tree. Initially, only the pulmonary artery pressure rises and the PVR remains normal. As the medial hypertrophy of the pulmonary vessels occurs and the pulmonary artery pressure rises, the changes are still reversible. Eventually, the pulmonary vasculature is obliterated by the arteritis and thrombosis, which leads to the rise in PVR. The progression of the PVR is the final irreversible step that ultimately leads to a reversal of shunt direction, right to left.

TABLE 3-7   -- Distribution of Various Defects in 201 Patients of Eisenmenger's Syndrome

Diagnosis

Frequency

Percentage

Male

Female

VSD

67

33.33

35

32

ASD

60

29.85

30

30

PDA

29

14.43

13

16

VSD + ASD

4

1.99

1

3

VSD + PDA

6

2.98

4

2

ASD + PDA

1

0.49

1

0

Shunt lesion and aortic stenosis

3

1.49

0

3

Shunt lesion + mitral stenosis

1

0.49

0

1

Shunt lesion + coarctation of aorta

3

1.49

0

3

DORV, VSD, PAH

8

3.98

1

7

D-TGA VSD

3

1.49

1

2

Primum ASD

4

1.99

2

2

Complete atrioventricular septal defect

3

1.49

1

2

Single atrium

2

0.98

1

1

Sinus venosus ASD

2

0.98

1

1

Aortopulmonary window

3

1.49

1

1

L-TGA VSD

1

0.49

0

1

TAPVC

1

0.49

0

1

Total

201

100.00

92

109

Reprinted with permission from Saha A, Balakrishnan KG, Jaiswal PK, et al: Prognosis for patients with Eisenmenger syndrome of various aetiology. Int J Cardiol 1994;45:201.

ASD, atrial septal defect; DORV, double outlet right ventricle; D-TGA, dextro-transposition of great arteries; L-TGA, levo-transposition of great arteries; PAH, pulmonary arterial hypertension; PDA, patent ductus arteriosus; TAPVC, total anomalous pulmonary venous connection; VSD, ventricular septal defect.

 

 

 

 

Although the disease process begins early in life, symptoms of severe cyanosis and fatigue may not appear until late childhood or even adulthood. Erythrocytosis is common. Hemoptysis, palpitations, edema, and syncope are also common. Palpitations, present in almost 80% of patients,[164] are often due to atrial fibrillation. Syncope is important to note because it is associated with a worse prognosis. Central cyanosis, clubbing, and a right ventricular heave are some of the more prominent physical findings. It is helpful to know the extent of pulmonary vascular disease derived from cardiac catheterization. Pulmonary vascular disease is much more advanced in patients with Eisenmenger's syndrome than in other patients.[164] The degree of pulmonary vascular obstruction is the key to prognosis.

Hemodynamic data are important to know regarding any anesthetic for these individuals. The mean right atrial pressure is surprisingly normal in most, but the left atrial pressure is often elevated. If the right atrial pressure is more than 8 mm Hg, the prognosis is worse.[164] The mean pulmonary artery pressure has been found to be 68 ±15 mm Hg, in conjunction with an aortic pressure of 80 ±13 mm Hg.

Surgical procedures in these patients are associated with a high morbidity and mortality, even for relatively minor procedures.[165] Anesthesia considerations are important to minimize the risk for these patients. Meticulous attention must be paid to these patients to achieve good outcomes.

If the Hb is above 21 g/dL, then some have recommended prophylactic phlebotomy. More recently, Ammash and associates[165] found a higher mortality associated with those who had undergone prophylactic phlebotomy. Excessive Hb levels may contribute to excessive thrombosis, as well as bleeding. Although these patients are dependent on higher levels of Hb for adequate oxygen delivery to the tissues, the viscosity of the blood may actually reduce oxygen delivery at some point.

Although general anesthetics are usually performed for surgery, regional anesthesia has been more recently accepted.[79] Overall, patients with Eisenmenger's syndrome are highly preload dependent. Fluid shifts and hypovolemia are poorly tolerated. Because of the preoperative fast, intravascular volume depletion is common. It is important to maintain SVR. Decreases in SVR will exacerbate right-to-left shunting, will worsen cyanosis, and have been associated with sudden cardiovascular collapse.[79] Increases in SVR may exacerbate ventricular function but are generally better tolerated than decreases in SVR. Blood loss and volume depletion should be minimized. Central venous monitoring and arterial cannulation are highly recommended in these patients. The right atrial pressure may not always reflect an increase in PVR. One should strive to avoid situations that will increase the PVR, such as hypercarbia, PEEP, acidosis, and increased intrathoracic pressure. Because the PVR is fixed to a large extent, patients will not adjust rapidly to volume changes and hemodynamic changes. The pulse oximeter can be very helpful in determining the overall direction of shunting in these patients and may be the best method available to monitor PVR. Most selective pulmonary vasodilators will have little effect on the PVR in Eisenmenger's syndrome, although prostacyclin (epoprostenol) has demonstrated some benefit. One must be very careful to avoid paradoxical embolism, taking all the precautions.

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OBSTRUCTION OF BLOOD FLOW

If obstruction to either aortic or pulmonary valves occurs, then ventricular hypertrophy will likely ensue by childhood. Although these conditions are not complex, they occur very frequently and can have serious consequences.

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COARCTATION OF THE AORTA

Coarctation of the aorta is a discrete narrowing of the proximal thoracic aorta just opposite the insertion of the ductus arteriosus (juxtaductal), which, although a simple anatomic defect, has many different presentations ( Fig. 3-45 ). It appears in 6% to 8% of those with CHD.[3] Without treatment, coarctation carries significant morbidity and mortality, with a 25% mortality rate at 20 years, 50% at 30 years, and 75% at 50 years. [110] [166] The mean age of death without surgery for coarctation is 35 years,[34] which is more than a 50% reduction compared with a normal life span.

 
 

FIGURE 3-45  Coarctation of the aorta. Coarctation causes severe obstruction of blood flow in the descending thoracic aorta. The descending aorta and its branches are perfused by collateral channels from the axillary and internal thoracic arteries through the intercostal arteries (arrows).  (Reprinted with permission from Brickner ME, Hillis LD, Lange RA: Congenital heart disease in adults: I. N Engl J Med 2000;342:261.)

 

 

 

Coarctation of the aorta is associated with many other congenital anomalies, and only about a fourth of coarctations occur as isolated defects.[167] An example is the finding of coarctation in 25% of aortic stenosis and bicuspid aortic valve.[168] When coarctation exists with other congenital heart defects, it is referred to as a “complex coarctation.” Besides the association with cardiac defects, coarctation of the aorta is also more likely to be present with extracardiac anomalies such as Turner's syndrome, and other extra cardiac anomalies most commonly found in the musculoskeletal, gastrointestinal, or respiratory systems. [3] [16] In a large series from Johns Hopkins Hospital over a 30-year period, Turner's syndrome was the most common noncardiac congenital anomaly associated with coarctation.[169]Head and neck abnormalities are also common with coarctation. The importance of these associations resides in the potential for abnormalities of the airway.

The hemodynamics associated with coarctation of the aorta vary greatly. Cardiogenic shock and acidosis may be present in the newborn, because the entire cardiac output must traverse the obstruction. The newborn is less likely to be able to adapt rapidly to the severe obstruction to left ventricular flow. If collaterals or other defects are present, the obstruction to left ventricular outflow may be less severe. Nearly 75% of infants with coarctation and symptoms of CHF died without treatment, primarily due to the effect of coarctation on myocardial function.[167] Because the coarctation is usually before the ductus arteriosus, a neonate will tolerate it better if prostaglandin therapy is instituted to maintain the patency of the ductus arteriosus.

Infants are most likely to present with tachypnea and CHF in almost 50% of cases.[169] Others may develop chronic CHF over the ensuing months after birth. The heart will compensate for outflow obstruction with left ventricular hypertrophy. Children usually present asymptomatically, with the unexpected discovery of hypertension. Gradients between the left ventricular outflow tract and distal blood pressure may exceed 80 mm Hg. The gradient is at the systolic, not diastolic, blood pressure, so the pulse pressure is widened with a coarctation. Commonly, the difference will be in the upper versus lower extremities. Pulses below the coarctation will be diminished and delayed in timing compared with other pulses. The diagnosis will be made with routine physical examination that identifies discrepancies in the blood pressures in the arms and legs. The child with long-standing coarctation will often have evidence of left ventricular hypertrophy on the electrocardiogram and rib notching on the chest radiograph. However, 25% may have a normal electrocardiogram.[167] These patients have developed collaterals from the intercostals and subclavian arteries.

Patients normally become surgical candidates by the age of 3 to 5 years. Surgical repair has been discussed previously.[169] Surgical approaches include resection of the coarctation with an end-to-end anastomosis, subclavian flap aortoplasty, or aortoplasty with homograft or synthetic material ( Fig. 3-46 ). Surgical repair in adults is more difficult because the aorta is more sclerotic, aneurysms of the intercostal arteries are more common, and cardiovascular disease may be present.[34] Surgery for re-coarctation (0.5% to 4%) is much less common than in the past, when it was 8%. [118] [167] Surgery for re-coarctation still affects 16% of neonates who undergo repair for coarctation.[169] Surgical technique for correction of the coarctation can increase the risk of restenosis. It is more likely to occur 6 years after surgery.[169]

 
 

FIGURE 3-46  Surgical techniques for repair of coarctation. Illustrated are the several methods of surgical repair for coarctation of the aorta. A, Resection with end-to-end repair, the standard repair for patients beyond age 1. B, Patch aortoplasty, seldom used for primary repair because of a 5% (or higher) risk of late patch aneurysm but still used for recurrent coarctation. C, Subclavian flap, used primarily up to age 2. D, Dacron tube replacement, best when the coarctation segment is long.  (Reprinted with permission from Webb GD, Harrison DA, Connelly MS: Challenges posed by the adult patient with congenital heart disease. Adv Intern Med 1996;41:448.)

 

 

 

Balloon angioplasty is less invasive and is a viable alternative to surgery for coarctation of the aorta. Both surgery and angioplasty are recognized to leave a persistent gradient of 20 mm Hg or less that may cause problems in the future. Balloon angioplasty has been successful in 79% of children who developed restenosis after their initial surgery and 82% successful with “native” coarctation of the aorta.[170]Restenosis after balloon angioplasty is below 20%, except for infants without previous surgery, who develop restenosis with angioplasty in 71% of cases.[170] Awareness of this is important because a severe gradient may be present to affect hemodynamics during noncardiac surgery.[171]

Anesthetic management[172] has been reviewed for repair of coarctation. It is important to note the chance of worsening myocardial ischemia in an infant with coarctation of the aorta and CHF. Histopathologic examination has demonstrated evidence of myocardial ischemia in nearly 40% of infants, with coarctation of the aorta probably related to poor coronary perfusion and hypertrophied myocardium. Chronic ischemia may impact myocardial function, especially during noncardiac surgery.[20]

If the patient has undergone previous coarctation, comprehensive evaluation of the blood pressure in the extremities is warranted to identify any residual gradient.[118] Although children who undergo surgery will be normotensive after repair, 50% of adults will have persistent hypertension after repair[8] and will carry the same cardiovascular risk as anyone with hypertension and coronary artery disease.[110]

Congenital Aortic Stenosis

Congenital aortic stenosis accounts for 3% to 6% of CHD.[34] The prevalence of a bicuspid aortic valve may be 1% to 2%, with many cases “clinically silent.” Congenital bicuspid aortic stenosis is one of the most common congenital malformations of the heart. PDA and coarctation of the aorta occur commonly with congenital aortic stenosis.

Normally, the aortic valve has a surface area of 2 cm2/m2. Obstruction to left ventricular outflow may occur through different abnormalities: valvular (70%), subvalvular, and supravalvular aortic stenosis (Fig. 3-47 ). Infants and children with aortic stenosis have thickened and rigid valve tissue with various levels of commissural separation. Typically, the valve is bicuspid. As a consequence of the hemodynamically significant flow across the valve, the infant or child will develop concentric hypertrophy. This hypertrophied myocardium is at risk for coronary blood imbalances, as the demand is outstripped by the supply, especially in the subendocardial area. The pressure gradient across the valve is not a linear relationship, but is proportional to the square of the flow. So as the flow doubles, the gradient quadruples. A peak systolic gradient of 60 mm Hg in concert with a normal cardiac output results in a valve area of 0.5 cm2, which is considered critical obstruction. Left ventricular end-diastolic pressure is also frequently elevated. It should be noted that myocardial blood supply may be compromised, despite normal anatomic patency of the coronary arteries.[168]

 
 

FIGURE 3-47  Types of congenital aortic stenosis. A, Fibromuscular or tunnel-type of subaortic stenosis with obstruction to left ventricular emptying by muscular overgrowth of the entire outflow tract. B, Membranous subaortic stenosis in which a membrane is present 1 to 2 cm below the aortic valve orifice obstructing ventricular outflow. C, Thickened, domed, fused leaflets of congenital valvular stenosis. D, The “hourglass” narrowing of the supravalvular aorta producing supravalvular stenosis.  (Reprinted with permission from Rosen DA, Rosen KR: Anomalies of the aortic arch and valve. In Lake CL [ed: Pediatric Cardiac Anesthesia. Stamford, CT, Appleton & Lange, 1998, p 432.)

 

 

 

Congenital aortic stenosis in children may be associated with a severe obstruction that may appear essentially asymptomatic yet in other cases may manifest significant symptoms with a less dramatic gradient. Although severe aortic stenosis can be fatal during the neonatal period, most patients (84%) actually survive 15 years, although the long-term prognosis is largely unknown.[173]

Exertional fatigue may be the most common symptom, but many children will grow up without any knowledge of their condition. Under stress there is the possibility of sudden death. There is a harsh systolic crescendo-decrescendo murmur frequently present at the base of the heart. The electrocardiogram and chest radiograph may be normal despite the presence of severe aortic stenosis. Cardiac catheterization is rarely needed today to establish the site and severity of obstruction to the left ventricle. One cannot accurately follow the progression of aortic stenosis and left ventricular obstruction through such measures as electrocardiography, physical findings, or chest radiography, so echocardiographic Doppler ultrasound evaluations are required.

Management of congenital aortic stenosis may follow percutaneous balloon valvuloplasty or surgically performed aortic valvuloplasty. The surgical options include closed transventricular valvotomy, open valvotomy with inflow occlusion, or open valvotomy with extracorporeal circulation.

Most children with aortic regurgitation as well as outflow obstruction are receiving a Ross procedure.[19] A Ross procedure substitutes the aortic valve with a pulmonary autograft and places a pulmonary or aortic homograft between the right ventricle and the main pulmonary artery. Although many patients have impaired myocardium due to the aortic valve disease, the Ross is now being used in complex congenital heart operations. The 20-year assessment of these pulmonary autografts appears excellent so far, with few complications.[174] The Ross procedure avoids the need for anticoagulation in children and allows continued growth. The actuarial survival at 16 years was 74%.[175] The adult with aortic stenosis will frequently need a valve replacement.[34]

One needs to know that even if the infant has had an intervention for aortic stenosis, one may later anesthetize a patient with the possibility of restenosis, aortic regurgitation, and especially sudden death.[173] Moreover, almost all children will require some type of re-intervention following surgery in the ensuing 10 years.[173] In many of these children, aortic valve replacement may be necessary. The replacement of the aortic valve with the patient's own pulmonary valve has been reported with early short-term success[175] and offers the patient an option that continues to be evaluated but appears very promising.

Many pediatric patients with aortic stenosis are not in CHF and therefore may not require the high-dose narcotic anesthetic. It is important that the patients do not become profoundly hypovolemic, or severe reduction in blood pressure may result in myocardial ischemia to the hypertrophied myocardium. Inhalation induction may be tolerated unless there is severe CHF, whereupon intramuscular ketamine may be the ideal choice, with high-dose fentanyl after intravenous access is obtained. Severe bradycardia or tachycardia may not be tolerated very long.

Copyright © 2008 Elsevier Inc. All rights reserved. - www.mdconsult.com

Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

CONCLUSION

Because of advancements in surgery and medical management there are more individuals of all ages surviving longer with CHD. This has resulted in many patients requiring the same noncardiac operations as others who do not have CHD. These patients can do well with noncardiac surgery, but special consideration needs to be given to the native CHD, surgical interventions, and functional capacity. The aim is to obtain as much information as possible on the condition of the individual to develop the optimal anesthetic plan individualized for this particular patient to provide an anesthetic that will be safe and effective despite the great variation in age and physical condition.

Copyright © 2008 Elsevier Inc. All rights reserved. - www.mdconsult.com

Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

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