Congenital Heart Disease
BASIC SCIENCE QUESTIONS
1. The ductus arteriosus is derived from
A. The 2nd aortic arch
B. The 3rd aortic arch
C. The 4th aortic arch
D. The 6th aortic arch
The ductus arteriosus is derived from the sixth aortic arch and normally extends from the main or left PA to the upper descending thoracic aorta, distal to the left subclavian artery. In the normal fetal cardiovascular system, ductal flow is considerable (approximately 60% of the combined ventricular output), and is directed exclusively from the PA to the aorta. (See Schwartz 9th ed., p 597.)
2. The primary stimulus for closure of the ductus arteriosus after birth is
A. Loss of PGE2 made in the placenta
B. Increased PGI2 levels
C. Increased oxygen tension in the newborn’s blood
D. Decreased bradykinin
Locally produced and circulating prostaglandin E2 (PGE2) and PGI2 induce active relaxation of the ductal musculature, maintaining maximal patency during the fetal period. At birth, increased pulmonary blood flow metabolizes these prostaglandin products, and absence of the placenta removes an important source of them, resulting in a marked decrease in these ductal-relaxing substances. In addition, release of histamines, catecholamines, bradykinin, and acetylcholine all promote ductal contraction. Despite all of these complex interactions, the rising oxygen tension in the fetal blood is the main stimulus causing smooth muscle contraction and ductal closure within 10 to 15 hours postnatally. Anatomic closure by fibrosis produces the ligamentum arteriosum connecting the PA to the aorta. (See Schwartz 9th ed., p 598.)
3. Truncus arteriosus is often seen in patients with DiGeorge syndrome. This association suggests a common embryologic defect involving early development of
D. Neural crest
During embryonic life, the truncus arteriosus normally begins to separate and spiral into a distinguishable anterior PA and posterior aorta. Persistent truncus, therefore, represents an arrest in embryologic development at this stage. Other implicated events include twisting of the dividing truncus because of ventricular looping, subinfundibular atresia, and abnormal location of the semilunar valve anlages.
The neural crest may also play a crucial role in the normal formation of the great vessels, as experimental studies in chick embryos have shown that ablation of the neural crest results in persistent truncus arteriosus. The neural crest also develops into the pharyngeal pouches that give rise to the thymus and parathyroids, which likely explains the prevalent association of truncus arteriosus and DiGeorge syndrome. (See Schwartz 9th ed., p 602.)
1. Which of the following best describes the therapeutic approach to a child with hypoplastic left heart syndrome (HLHS)?
A. Palliation is the only option, repair is not possible
B. Reasonable palliation is not possible, repair must be attempted
C. Either palliation or repair is possible in the newborn period and the decision is made based on the physiology of the child
D. Palliation is possible in the newborn period with definitive repair later in childhood
Hypoplastic left heart syndrome (HLHS) includes a spectrum of conditions in which there is underdevelopment of the left-sided heart structures. The left heart is therefore inadequate to support the systemic circulation. Does this really answer the question? Shouldn’t the answer establish that the quote is about hypertrophic left heart syndrome? The traditional strategy of initial palliation followed by definitive correction at a later age, which had pervaded the thinking of most surgeons, began to evolve to one emphasizing early repair, even in the tiniest patients. Furthermore, some of the defects that were virtually uniformly fatal [such as hypoplastic left heart syndrome (HLHS)] now can be successfully treated with aggressive forms of palliation using cardiopulmonary bypass (CPB), resulting in outstanding survival for many of these children.
Because the goal in most cases of CHD is now early repair, as opposed to subdividing lesions into cyanotic or noncyanotic lesions, a more appropriate classification scheme divides particular defects into three categories based on the feasibility of achieving this goal: (a) defects that have no reasonable palliation and for which repair is the only option; (b) defects for which repair is not possible and for which palliation is the only option; and (c) defects that can either be repaired or palliated in infancy. It bears mentioning that all defects in the second category are those in which the appropriate anatomic components either are not present, as in HLHS, or cannot be created from existing structures. (See Schwartz 9th ed., p 592.)
2. The most common type of atrial septal defect (ASD) is
A. Sinus venosus defect
B. Ostium primum defect
C. Ostium secundum defect
D. Atrioventricular defect
ASDs can be classified into three different types: (a) sinus venosus defects, comprising approximately 5 to 10% of all ASDs; (b) ostium primum defects, which are more correctly described as partial AV canal defects; and (c) ostium secundum defects, which are the most prevalent subtype, comprising 80% of all ASDs. Ostium secundum defects are due to defects of the septum primum and those situated within the fossa ovalis. The secundum defects therefore included patent foramen ovales. (See Schwartz 9th ed., p 592.)
Ostium secundum defects are due to defects of the septum primum and those situated within the fossa ovalis. The secundum defects therefore include patent foramen ovales.
3. The most common type of ventricular septal defect (VSD) is
D. AV canal
VSD refers to a hole between the [left and right ventricles]. These defects are common, comprising 20 to 30% of all cases of CHD, and may occur as an isolated lesion or as part of a more complex malformation. VSDs vary in size from 3 to 4 mm to more than 3 cm, and are classified into four types based on their location in the ventricular septum: perimembranous, AV canal, outlet or supracristal, and muscular. Perimembranous VSDs are the most common type requiring surgical intervention, constituting approximately 80% of cases. These defects involve the membranous septum and include the malalignment defects seen in TOF. (See Schwartz 9th ed., p 619.)
4. The standard treatment for a small ASD is
A. Elective closure in infancy
B. Elective closure at age 4-5
C. Surgery or placement of an occlusion device only for symptomatic patients
D. Surgery or placement of an occlusion device for patients with a fixed PVR >12 U/ml
In general, ASDs are closed when patients are between 4 and 5 years of age. Children of this size can usually be operated on without the use of blood transfusion and generally have excellent outcomes. Patients who are symptomatic may require repair earlier, even in infancy. Some surgeons, however, advocate routine repair in infants .and children, as even smaller defects are associated with the risk of paradoxical embolism, particularly during pregnancy. (See Schwartz 9th ed., p 594.)
The advent of two-dimensional echocardiography with color flow Doppler has largely obviated the need for cardiac catheterization because the exact nature of the ASD can be precisely defined by echo alone. However, in cases where the patient is older than age 40 years, catheterization can quantify the degree of pulmonary hypertension present, because those with a fixed PVR greater than 12 U/mL are considered inoperable. (See Schwartz 9th ed., p 593.)
First performed in 1976, transcatheter closure of ASDs with the use of various occlusion devices is gaining widespread acceptance. Certain types of ASDs, including patent foramen ovale (PFO), secundum defects, and some fenestrated secundum defects, are amenable to device closure, as long as particular anatomic criteria (e.g., an adequate superior and inferior rim for device seating and distance from the [atrioventricular] valve) are met. Since the introduction of percutaneous closure, there has been a dramatic rise in device closure prevalence to the point where device closure has supplanted surgical therapy as the dominant treatment modality for secundum ASD. (See Schwartz 9th ed., p 594.)
5. Infants with critical aortic stenosis and good left ventricular function are initially treated with
A. Aortic valve replacement
B. Surgical aortic valvotomy
C. Balloon (catheter) valvotomy
D. Observation, with surgery planned when they achieve 10 kg weight
Patients who have a [left ventricle] capable of providing systemic output are candidates for intervention to relieve [aortic stenosis], generally through balloon valvotomy. Very rarely, if catheter-based therapy is not an option, relief of valvular AS in infants and children can be accomplished with surgical valvotomy using standard techniques of CPB and direct exposure to the aortic valve. Considerable debate exists, however, in the most accurate method to delineate patients in a morphologic grey zone, whereupon the decision between a single ventricle or biventricular strategy is unclear. The decision is critical as balloon valvotomy in a neonate without an adequate left ventricle can be disastrous. (See Schwartz 9th ed., p 595.)
Considerable debate exists, however, regarding the most accurate method to delineate patients in a morphologic gray zone, whereupon the decision between a single ventricle or biventricular strategy is unclear. The decision is critical as balloon valvotomy in a neonate without an adequate left ventricle can be disastrous.
6. The most common cause of death in patients with patent ductus arteriosus (PDA) is
A. Respiratory failure
B. Congestive heart failure
C. Respiratory infection
PDA is not a benign entity, although prolonged survival has been reported. The estimated death rate for infants with isolated, untreated PDA is approximately 30%. The leading cause of death is [congestive heart failure], with respiratory infection as a secondary cause. Endocarditis is more likely to occur with a small ductus and is rarely fatal if aggressive antibiotic therapy is initiated early. (See Schwartz 9th ed., p 598.)
7. Which of the following is the most common presenting manifestation in patients with supravalvular aortic stenosis?
C. Poor exercise tolerance
D. Asymptomatic murmur
The signs and symptoms of supravalvular AS are similar to other forms of [left ventricular outflow tract obstruction]. An asymptomatic murmur is the presenting manifestation in approximately one half of these patients. Syncope, poor exercise tolerance, and angina may all occur with nearly equal frequency. (See Schwartz 9th ed., p 597.)
8. The treatment of choice for an infant with coarctation of the aorta is
A. Catheterization with balloon dilation
B. Catheterization with placement of an aortic stent
C. Surgical aortoplasty
D. Resection with primary anastomosis
The routine management of hemodynamically significant COA [coarctation] in all age groups has traditionally been surgical. Transcatheter repairs are used with increasing frequency in older patients and those with recoarctation following surgical repair. Balloon dilatation of native coarctation in neonates has been used with poor results. The most common surgical techniques in current use are resection with end-to-end anastomosis or extended end-to-end anastomosis, taking care to remove all residual ductal tissue. Extended end-to-end anastomosis may also allow the surgeon to treat transverse arch hypoplasia which is commonly encountered in infants with aortic coarctation. The subclavian flap aortoplasty is another repair, although it is used less frequently in the modern era because of the risk of late aneurysm formation and possible underdevelopment of the left upper extremity or ischemia.
Although operative repair is still the gold standard, treatment of COA by catheter-based intervention has become more widespread. Both balloon dilatation and primary stent implantation have been used successfully. The most extensive study of the results of balloon angioplasty reported on 970 procedures: 422 native and 548 recurrent COAs. Mean gradient reduction was 74 ± 24% for native and 70 ± 31% for recurrent COA. This demonstrated that catheter- based therapy could produce equally effective results both in recurrent and in primary COA, a finding with far-reaching implications in the new paradigm of multidisciplinary treatment algorithms for CHD.
In summary, children younger than age 6 months with native COA should be treated with surgical repair, while those requiring intervention at later ages may be ideal candidates for balloon dilatation or primary stent implantation. Additionally, catheter-based therapy should be used for those cases of rest-enosis following either surgical or primary endovascular management. (See Schwartz 9th ed., p 601.)
9. Cor triatriatum results from division of which of the following chambers into two chambers?
A. Left atrium
B. Right atrium
C. Left ventricle
D. Right ventricle
Cor triatriatum is a rare CHD characterized by the presence of a fibromuscular diaphragm that partitions the left atrium into two chambers: a superior chamber that receives drainage from the pulmonary veins, and an inferior chamber that communicates with the mitral valve and the [left ventricle]. An ASD frequently exists between the superior chamber and the right atrium, or, more rarely, between the right atrium and the inferior chamber. (See Schwartz 9th ed., p 605.)
10. Which of the following is the most common associated anomaly in patients with coarctation of the aorta?
A. Rib notching
B. Bicuspid aortic valve
C. Ventricular septal defect (VSD)
D. Patent ductus arteriosus (PDA)
Other associated anomalies, such as VSD, PDA, and ASD, may be seen with COA, but the most common is that of a bicuspid aortic valve, which can be demonstrated in 25 to 42% of cases.
Rib notching is a result of coarctation, not an associated anomaly. Extensive collateral circulation develops, predominantly involving the intercostals and mammary arteries as a direct result of aortic flow obstruction. This translates into the well-known finding of ‘rib-notching’ on chest radiograph, as well as a prominent pulsation underneath the ribs. (See Schwartz 9th ed., p 601.)
11. Which of the following is the appropriate treatment of a newborn with TAPVC (total anomalous pulmonary venous connection)?
A. Pharmacologic treatment to maintain a patent ductus arteriosus
B. Surgical closure of any associated patent ductus arteriosus
C. Palliation with pulmonary artery banding
D. Definitive repair in the newborn period
Unique to this lesion is the absence of a definitive form of palliation. Thus, TAPVC with concomitant obstruction represents one of the only true surgical emergencies across the entire spectrum of congenital heart surgery.
Operative correction of TAPVC requires anastomosis of the common pulmonary venous channel to the left atrium, obliteration of the anomalous venous connection, and closure of the atrial septal defect (ASD). (See Schwartz 9th ed., p 604.)
12. Which of the following lesions is exclusively treated with a palliative operation rather than definitive repair as the first stage of treatment?
A. Tricuspid atresia
B. Coarctation of the aorta
C. Tetralogy of Fallot
D. Truncus arteriosus
Tricuspid atresia and hypoplastic left heart syndrome represent two forms of single ventricle physiology, and are therefore universally treated with palliation as a first stage of repair. Tricuspid atresia, however, is a more favorable morphologic subtype, as the right ventricle is underdeveloped rather than the left ventricle. The left ventricle, therefore, becomes the systemic ventricle.
The treatment for tricuspid atresia in the earlier era of palliation was aimed at correcting the defect in the pulmonary circulation. That is, patients with too much pulmonary flow received a pulmonary band, and those with insufficient flow received a systemic-to-PA [pulmonary artery] (PA) shunt. Systemic-to-PA shunts, or Blalock-Taussig (B-T) shunts, were first applied to patients with tricuspid atresia in the 1940s and 1950s. Likewise, PA banding was applied to patients with tricuspid atresia and congestive failure in 1957. However, despite the initial relief of either cyanosis or CHF, long-term mortality was high, as the single ventricle was left unprotected from either volume or pressure overload.
Recognizing the inadequacies of the initial repairs, Glenn described the first successful cavopulmonary anastomosis, an end-to-side SVC-to-RPA shunt in 1958, and later modified this to allow flow to both pulmonary arteries. This end-to-side SVC-to-RPA anastomosis was known as the bidirectional Glenn, and is the first stage to final Fontan repair in widespread use today. (See Schwartz 9th ed., p 608.)
13. Which valve is primarily affected in Ebstein’s anomaly?
Ebstein’s anomaly is a rare defect, occurring in less than 1% of CHD patients. The predominant maldevelopment in this lesion is the inferior displacement of the tricuspid valve into the [right ventricle], although Bove and others have emphasized that Ebstein’s anomaly is primarily a defect in right ventricular morphology rather than an isolated defect in the tricuspid valve. (See Schwartz 9th ed., p 613.)
14. Which of the following is almost universally present in a patient with TAPVC (total anomalous pulmonary vein connection)?
A. Atrial septal defect
B. Ventricular septal defect (VSD)
C. Patent ductus arteriosus (PDA)
D. Pulmonary valve stenosis
Total anomalous pulmonary venous connection (TAPVC) occurs in 1 to 2% of all cardiac malformations and is characterized by abnormal drainage of the pulmonary veins into the right heart, whether through connections into the right atrium or into its tributaries. Accordingly, the only mechanism by which oxygenated blood can return to the left heart is through an ASD, which is almost uniformly present with TAPVC. (See Schwartz 9th ed., p 603.)
15. The Norwood procedure is used in the treatment of
A. Coarctation of the aorta
B. Aortic stenosis
C. Hypoplastic left heart syndrome
D. Tetralogy of Fallot
In 1983, Norwood and colleagues described a two-stage palliative surgical procedure for relief of HLHS103 that was later modified to the currently used three-stage method of palliation. Stage 1 palliation, also known as the modified Norwood procedure, bypasses the LV by creating a single outflow vessel, the neoaorta, which arises from the RV. (See Schwartz 9th ed., p 611.)
16. Which valve is most often congenitally abnormal?
The spectrum of aortic valve abnormality represents the most common form of CHD, with the great majority of patients being asymptomatic until midlife. (See Schwartz 9th ed., p 594.)
17. Which of the following can be seen in an infant with severe aortic stenosis?
A. Crying during feeding
B. Upper body cyanosis
C. Hyperactive precordium
D. Machinery murmur
Neonates and infants with severe valvular AS may have a relatively nonspecific history of irritability and failure to thrive. Angina, if present, is usually manifested by episodic, inconsolable crying that coincides with feeding. As discussed previously, evidence of poor peripheral perfusion, such as extreme pallor, indicates severe left ventricular outflow tract obstruction (LVOTO). Differential cyanosis is an uncommon finding, but is present when enough antegrade flow occurs only to maintain normal upper body perfusion, while a large PDA produces blue discoloration of the abdomen and legs.
Hyperactive precordium and machinery murmur are typical findings in a patient with a patent ductus arteriosus. (See Schwartz 9th ed., p 595.)
18. The Fontan procedure is used to treat
A. Hypoplastic left heart syndrome
B. Tetralogy of Fallot
C. Total anomalous pulmonary venous connection (TAPVC)
D. Mitral stenosis
Although surgical palliation with the Norwood procedure is still the mainstay of therapy for infants with HLHS, a combined surgical and percutaneous option (hybrid procedure), which consists of bilateral PA banding and placement of a ductal stent, has emerged as a promising alternative that obviates the need for CPB in the fragile neonatal period. The hybrid procedure can also be used as a bridge to heart transplantation in those infants with severe AV valve regurgitation or otherwise unsuitable single-ventricle anatomy.
Following stage 1 palliation, the second surgical procedure is the creation of a bidirectional cavopulmonary shunt or hemi-Fontan, generally at 3 to 6 months of life when the [pulmonary vascular resistance] has decreased to normal levels. This is the first step in separating the pulmonary and systemic circulations, and it decreases the volume load on the single ventricle. The existing innominate artery-to-pulmonary shunt (or RV-to-pulmonary artery shunt) is eliminated during the same operation.
The third stage of surgical palliation, known as the Fontan procedure, completes the separation of the systemic and pulmonary circulations and is performed between 18 months and 3 years of age, or when the patient experiences increased cyanosis (i.e., has outgrown the capacity to perfuse the systemic circulation with adequately oxygenated blood) from inadequate flow through their superior cavopulmonary anastomosis. (See Schwartz 9th ed., pp 611-612.)
19. The best initial treatment of D-transposition of the great arteries (D-TGA) in a 6-month-old child is
A. Atrial septectomy
B. Atrial septectomy and PA banding
C. Senning procedure (atrial repair)
D. Arterial switch
Complete transposition is characterized by connection of the atria to their appropriate ventricles with inappropriate ventriculoarterial connections. Thus, the aorta arises anteriorly from the RV, while the PA arises posteriorly from the LV. Van Praagh and coworkers introduced the term D-transposition of the great arteries (D-TGA) to describe this defect, while L-TGA describes a form of corrected transposition where there is concomitant [atrioventricular] discordance.
Blalock and Hanlon introduced the first operative intervention for D-TGA with the creation of an atrial septectomy to enhance intracardiac mixing. Later, Rashkind and Cuaso developed a catheter-based balloon septostomy, which largely obviated the need for open septectomy. These early palliative maneuvers, however, met with limited success, and it was not until the late 1950s, when Senning and Mustard developed the first “atrial repair,” that outcomes improved. The Senning operation consisted of rerouting venous flow at the atrial level by incising and realigning the atrial septum over the pulmonary veins and using the right atrial free wall to create a pulmonary venous baffle (Fig. 20-1). Although the Mustard repair was similar, it made use of either autologous pericardium or synthetic material to create an intraatrial baffle. (See Schwartz 9th ed., pp 614-615.)
Despite the improved early survival rates, long-term problems, such as [systemic venous or pulmonary venous obstruction], baffle leak, arrhythmias, tricuspid valve regurgitation, and right ventricular failure, prompted the development of the arterial switch procedure by Jatene in 1975. The arterial switch procedure involves the division of the aorta and the PA, posterior translocation of the aorta (Lecompte maneuver), mobilization of the coronary arteries, placement of a pantaloon shaped pericardial patch, and proper alignment of the coronary arteries on the neoaorta. [The arterial switch operation is now the standard of care for neonates with transposition and coronary artery morphology amenable to transfer].
The most important consideration is the timing of surgical repair, because the arterial switch should be performed within 2 weeks after birth, before the LV loses its ability to pump against systemic afterload. In patients presenting later than 2 weeks, the LV can be retrained with preliminary PA banding and aortopulmonary shunt followed by definitive repair. (See Schwartz 9th ed., p 615.)
FIG. 20-1. The Senning operation. A. The atrial septum is cut near the tricuspid valve, creating a flap attached posteriorly between the caval veins. B. The flap of atrial septum is sutured to the anterior lip of the orifices of the left pulmonary veins, effectively separating the pulmonary and systemic venous channels. C. The posterior edge of the right atrial incision is sutured to the remnant of the atrial septum, diverting the systemic venous channel to the mitral valve. D. The anterior edge of the right atrial incision (lengthened by short incisions at each corner) is sutured around the cava above and below to the lateral edge of the LA incision, completing the pulmonary channel and diversion of pulmonary venous blood to the tricuspid valve area. (Reproduced with permission from D-Transposition of the great arteries, in Mavroudis C, Backer CL (eds): Pediatric Cardiac Surgery, 2nd ed. St. Louis: Mosby, 1994, p 345.)
20. Which of the following is NOT one of the four anomalies found in the Tetralogy of Fallot?
A. Atrial septal defect (ASD)
B. Overriding aorta
C. Right ventricular outflow obstruction
D. Right ventricular hypertrophy
The original description of TOF by Ettienne Louis Fallot, as the name implies, included four abnormalities: a large perimembranous VSD adjacent to the tricuspid valve; an overriding aorta; a variable degree of RVOT obstruction, which might include hypoplasia and dysplasia of the pulmonary valve as well as obstruction at the subvalvular and PA level; and right ventricular hypertrophy. More recently, Van Praagh and colleagues pointed out that TOF could be more correctly termed monology of Fallot, because the four components are explained by the malposition of the infundibular septum. When the infundibular septum is displaced anteriorly and leftward, the RVOT is narrowed and its anterior displacement results in failure of fusion of the ventricular septum between the arms of the trabecula-septomarginalis. (See Schwartz 9th ed., pp 617-618.)
21. The most significant late complication in patients who have had repair of a Tetralogy of Fallot is
B. Myocardial ischemia or infarction
C. Ventricular aneurysm
D. Brain abscess
Arrhythmias are potentially the most serious late complication following TOF repair. In a multicenter cohort of 793 patients studied by Gatzoulis and colleagues, a steady increase was documented in the prevalence of ventricular and atrial tachyarrhythmia and sudden cardiac death in the first 5 to 10 years following intracardiac repair. Clinical events were reported in 12% of patients at 35 years after repair. Prevalence of atrial arrhythmias from other studies, however, ranges from 1 to 11%, which is a reflection of the strong time dependence of arrhythmia onset.
Underlying causes of arrhythmia following repair are complex and multifactorial, resulting in poorly defined optimum screening and treatment algorithms. Older repair age has been associated with an increased frequency of both atrial and ventricular arrhythmias. Impaired ventricular function secondary to a protracted period of cyanosis before repair might contribute to the propensity for arrhythmia in older patients. (See Schwartz 9th ed., p 619.)
22. What is the probability of spontaneous closure for a VSD diagnosed in the 1st week of life?
VSDs may close or narrow spontaneously, and the probability of closure is inversely related to the age at which the defect is observed. Thus, infants at 1 month of age have an 80% incidence of spontaneous closure, whereas a child at 12 months of age has only a 25% chance of closure. This has an important impact on operative decision making, because a small or moderatesize VSD may be observed for a period of time in the absence of symptoms. Large defects and those in severely symptomatic neonates should be repaired during infancy to relieve symptoms and because irreversible changes in PVR may develop during the first year of life. (See Schwartz 9th ed., p 621.)
23. The Ross procedure is used to treat
A. Mitral insufficiency
B. Aortic stenosis
C. Coarctation of the aorta
D. Patent ductus arteriosus
The use of allografts and the advent of the Ross procedure have made early definitive correction of critical [aortic stenosis] a viable option. Donald Ross first described transposition of the pulmonary valve into the aortic position with allograft reconstruction of the pulmonary outflow tract in 1967. The result of this operation is a normal trileaflet semilunar valve made of a patient’s native tissue with the potential for growth to adult size in the aortic position in place of the damaged aortic valve. The Ross procedure has become a useful option for aortic valve replacement in children, because it has improved durability and can be performed with acceptable morbidity and mortality rates. The placement of a pulmonary conduit, which does not grow and becomes calcified and [either insufficient or] stenotic over time, does obligate the patient to reoperation to replace the right-ventricle to [pulmonary artery] conduit. [However, the advent of percutaneously placed pulmonary valves may obviate the need for surgical intervention]. (See Schwartz 9th ed., p 596.)