Park's Pediatric Cardiology for Practitioners, 6th Ed.

Left-to-Right Shunt Lesions

This chapter discusses common left-to-right shunt lesions such as atrial septal defect (ASD), ventricular septal defect (VSD), patent ductus arteriosus (PDA), endocardial cushion defect (ECD), and partial anomalous pulmonary venous return (PAPVR).

Atrial Septal Defect

Prevalence

Atrial septal defect (ostium secundum defect) occurs as an isolated anomaly in 5% to 10% of all congenital heart defects (CHDs). It is more common in females than in males (male-to-female ratio of 1:2). About 30% to 50% of children with CHDs have an ASD as part of the cardiac defect.

Pathology

1. Three types of ASDs exist: secundum defect, primum defect, and sinus venosus defect. Patent foramen ovale (PFO) does not ordinarily produce intracardiac shunts (see Chapter 15).

2. Ostium secundum defect is the most common type of ASD, accounting for 50% to 70% of all ASDs. This defect is present at the site of fossa ovalis, allowing left-to-right shunting of blood from the left atrium (LA) to the right atrium (RA) (Fig. 12-1). Anomalous pulmonary venous return is present in about 10% of cases.

3. Ostium primum defects occur in about 30% of all ASDs, if those that occur as part of complete ECD are included (see Fig. 12-1). Isolated ostium primum ASD occurs in about 15% of all ASDs. This is discussed in greater detail in the section on partial ECD.

4. Sinus venosus defect occurs in about 10% of all ASDs. The defect is most commonly located at the entry of the superior vena cava (SVC) into the RA (superior vena caval type) and rarely at the entry of the inferior vena cava (IVC) into the RA (inferior vena caval type). The former is commonly associated with anomalous drainage of the right upper pulmonary vein (into the RA), and the latter is often associated with anomalous drainage of the right lung into the IVC (“scimitar syndrome”) (see Chapter 15).

5. In coronary sinus ASD, there is a defect in the roof of the coronary sinus and the LA blood shunts through the defect and empties into the RA through the coronary sinus ostium, producing clinical pictures similar to other types of ASDs.

6. Mitral valve prolapse (MVP) occurs in 20% of patients with either ostium secundum or sinus venosus defects.

Clinical Manifestations

History

Infants and children with ASDs are usually asymptomatic.

Physical Examination (Fig. 12-2)

1. A relatively slender body build is typical. (The body weight of many is less than the 10th percentile.)

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FIGURE 12-1 Anatomic types of atrial septal defects (ASDs) viewed with the right atrial wall removed. IVC, inferior vena cava; SVC, superior vena cava.

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FIGURE 12-2 Cardiac findings of atrial septal defect. Throughout this book, heart murmurs with solid borders are the primary murmurs, and those without solid borders are transmitted murmurs or those occurring occasionally. Abnormalities in heart sounds are shown in black. Exp, expiration; Insp, inspiration.

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FIGURE 12-3 Tracing from a 5-year-old girl with secundum-type atrial septal defect.

2. A widely split and fixed S2 and a grade 2 to 3 of 6 systolic ejection murmur are characteristic findings of ASD in older infants and children. With a large left-to-right shunt, a mid-diastolic rumble resulting from relative tricuspid stenosis may be audible at the lower left sternal border.

3. Classic auscultatory findings (and electrocardiographic [ECG] and radiography findings) of ASD are not present unless the shunt is reasonably large (at least Qp/Qs of 1.5 or greater). The typical auscultatory findings may be absent in infants and toddlers, even in those with a large defect because the RV is poorly compliant.

Electrocardiography (Fig. 12-3)

Right axis deviation of +90 to +180 degrees and mild right ventricular hypertrophy (RVH) or right bundle branch block (RBBB) with an rsR′ pattern in V1 are typical ECG findings. In about 50% of patients with sinus venosus ASD, the P axis is less than +30 degrees.

Radiography Studies (Fig. 12-4)

1. Cardiomegaly with enlargement of the RA and right ventricle (RV) may be present.

2. A prominent pulmonary artery (PA) segment and increased pulmonary vascular markings are seen when the shunt is significant.

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FIGURE 12-4 Posteroanterior and lateral views of chest roentgenograms from a 10-year-old child with atrial septal defect. The heart is mildly enlarged with involvement of the right atrium (best seen in the posteroanterior view) and the right ventricle (best seen in the lateral view with obliteration of the retrosternal space). Pulmonary vascularity is increased, and the main pulmonary artery segment is slightly prominent.

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FIGURE 12-5 Diagram of two-dimensional echocardiography of the three types of atrial septal defects (ASDs). The subcostal transducer position provides the most diagnostic view. A, Sinus venosus defect. The defect is located in the posterosuperior atrial septum, usually just beneath the orifice of the superior vena cava. This defect is often associated with partial anomalous return of the right upper pulmonary vein. B, Secundum ASD. The defect is located in the middle portion of the atrial septum. C, Primum ASD. The defect is located in the anteroinferior atrial septum, just over the inflow portion of each atrioventricular valve. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.

Echocardiography

1. A two-dimensional echocardiographic study is diagnostic. The study shows the position as well as the size of the defect, which can best be seen in the subcostal four-chamber view (Fig. 12-5). In secundum ASD, a dropout can be seen in the midatrial septum. The primum type shows a defect in the lower atrial septum; the SVC type of sinus venosus defect shows a defect in the posterosuperior atrial septum.

2. Indirect signs of a significant left-to-right atrial shunt include RV enlargement and RA enlargement, as well as dilated PA, which often accompanies an increased flow velocity across the pulmonary valve. These findings indicate the functional significance of the defect.

3. Pulsed Doppler examination reveals a characteristic flow pattern with the maximum left-to-right shunt occurring in diastole. Color-flow mapping enhances the evaluation of the hemodynamic status of the ASD.

4. M-mode echocardiography may show increased RV dimension and paradoxical motion of the interventricular septum, which are signs of RV volume overload.

5. In older children and adolescents, especially in those with overweight, adequate imaging of the atrial septum may not be possible with the ordinary transthoracic echocardiographic study. Transesophageal echocardiography (TEE) may be used as an alternative.

Natural History

1. Earlier reports have indicated that spontaneous closure of the secundum defect occurs in about 40% of patients in the first 4 years of life (reported rates vary between 14% and 55% of patients). The defect may decrease in size in some patients. However, a more recent report indicates the overall rate of spontaneous closure to be 87%. In patients with an ASD smaller than 3 mm in size diagnosed before 3 months of age, spontaneous closure occurs in 100% of patients at 1½ years of age. Spontaneous closure occurs more than 80% of the time in patients with defects between 3 and 8 mm before 1½ years of age. An ASD with a diameter larger than 8 mm rarely closes spontaneously. Spontaneous closure is not likely to occur after 4 years of age.

It may be that “small ASDs” detected by color Doppler studies are not the true ASD; they may simply be incompetent foramen ovale which resolved to competent PFO without shunt. (Spontaneous closure of VSD is associated with high velocities across the defect with resulting platelet adhesion to a jet lesion on the septal leaflet of the tricuspid valve. Such hemodynamic abnormalities do not exist with ASD.)

2. Most children with an ASD remain active and asymptomatic. Rarely, congestive heart failure (CHF) can develop in infancy.

3. If a large defect is untreated, CHF and pulmonary hypertension begin to develop in adults who are in their 20s and 30s, and it becomes common after 40 years of age.

4. With or without surgery, atrial arrhythmias (flutter or fibrillation) may occur in adults. The incidence of atrial arrhythmias increases to as high as 13% in patients older than 40 years of age.

5. Infective endocarditis does not occur in patients with isolated ASDs.

6. Cerebrovascular accident, resulting from paradoxical embolization through an ASD, is a rare complication.

Management

Medical

1. Exercise restriction is unnecessary.

2. In infants with CHF, medical management (with a diuretic) is recommended because of its high success rate and the possibility of spontaneous closure of the defect.

Nonsurgical Closure

Nonsurgical closure using a catheter-delivered closure device has become a preferred method, provided the indications are met. Several closure devices that can be delivered through cardiac catheters have been shown to be safe and efficacious for secundum ASD closure. In the United States, currently only the Amplatzer septal occluder (AGA Medical) and Helex septal occluder (W.L. Gore and Associates) are approved for secundum ASD closure. Currently, there are no transcatheter devices designed for closure of sinus venosus, primum, or coronary sinus ASDs.

The use of the closure device may be indicated to close a secundum ASD measuring 5 mm or more in diameter (but less than 32 mm for Amplatzer device and less than 18 mm for Helex device) and a hemodynamically significant L-R shunt with clinical evidence of RV volume overload (i.e., Qp/Qs ratio of 1.5:1 or greater or RV enlargement). There must be enough rim (4 mm) of septal tissue around the defect for appropriate placement of the device, although some newer devices no longer require a septal rim present along the entire margin of the defect. The size of the rim around the ASD can be estimated by two-dimensional echocardiographic study as diagrammatically shown in Figure 12-6. The rim size is estimated in four directions: anterosuperior, anteroinferior, posterosuperior, and posteroinferior (Magni et al, 1997).

The timing of the device closure for secundum ASD is not entirely clear. Considering the possibility of spontaneous closure, it is wise not to use the device in infancy unless the patient is symptomatic with heart failure. ASD closure devices can be implanted successfully in children younger than 2 years of age, although common practice suggests that a weight greater than 15 kg may offer some technical advantages and simplify the procedure (Feltes et al, 2011). Closure rates are excellent with small residual shunts seen in fewer than 5% of patients at 1 year of follow-up.

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FIGURE 12-6 Two-dimensional echocardiographic estimates of the ASD rim size. The posterosuperior (PS) and posteroinferior (PI) rims are estimated in the bi–-vena cava view from the subcostal transducer position, the anteroinferior (AI) rim from the apical four-chamber view, and the anterosuperior (AS) (or retroaortic) rim from the parasternal short-axis view.

Complications are extremely rare. The overall risk of the procedure is 7.2% with the major complication rate of 1.6%, including device embolism with surgical removal. Other reported complications may include the following.

1. Early ECG abnormalities are common within the first 24 hours after implant, but most of these resolve quickly.

2. Probably the most feared complication with the Amplatzer device (but not with the Helex device) is early or late erosion of the device into the aortic root, with subsequent pericardial tamponade and rare death. It may be related to the oversizing of devices and deficiency of the anterosuperior (or retroaortic) rim (see Fig. 12-6).

3. Rarely thrombus formation in the right and left atrium occurs (2%–3%), but cerebral embolism is not more frequent than after surgical closure of the defect.

4. Release of nickel from the device (with peak at 1 month after implant) is a rare cause of significant allergic reaction.

Advantages of nonsurgical closure include a complete avoidance of cardiopulmonary bypass with its attendant risk, avoidance of pain and residual thoracotomy scars, a less than 24-hour hospital stay, and rapid recovery. All of these devices are associated with a higher rate of small residual leak than is operative closure.

Postdevice Closure Follow-up

The patients are prescribed aspirin 81 mg per day for 6 months. Postprocedure echocardiographic studies check for a residual atrial shunt and unobstructed flow of pulmonary veins, coronary sinus, and venae cavae, and proper function of the mitral and tricuspid valves. If 1-month and 1-year follow-up echocardiographic findings are normal, yearly or biennial follow-up will suffice. Some cardiologists prescribe aspirin 81 mg for patients with residual shunt to prevent paradoxical embolization, but most cardiologists do not.

Surgical Closure

Indications and Timing

Surgical closure is indicated only when device closure is not considered appropriate. Therefore, most patients with secundum ASD are not candidates for surgical closure of the defect.

1. A left-to-right shunt with a pulmonary-to-systemic blood flow ratio (Qp/Qs ratio) of 1.5:1 or greater is a surgical indication. Surgery is usually delayed until 2 to 4 years of age because the possibility of spontaneous closure exists.

2. If CHF does not respond to medical management, surgery is performed during infancy, again if device closure is considered inappropriate.

3. High pulmonary vascular resistance (PVR) (i.e., >10 units/m2, >7 units/m2 with vasodilators) may be a contraindication for surgery (or device closure).

Procedure

For secundum ASD, the defect is traditionally repaired through a midsternal incision under cardiopulmonary bypass by either a simple suture or a pericardial or Teflon patch. Recently, so-called minimally invasive cardiac surgical techniques with smaller skin incisions have become popular, especially for female patients. For ASDs (including simple primum ASDs and sinus venosus defects), one of the following techniques can be used: midline short transxiphoid incision with minimal sternal split (preferred), transverse inframammary incision with vertical or transverse sternotomy, or small lower midline skin incision with either partial or full median sternotomy. The benefit of this technique appears to be an improved cosmetic result; it does not reduce pain, hospital stay, or surgical stress.

For a sinus venosus defect without associated anomalous pulmonary venous return, the defect is closed using an autologous pericardial patch. When it is associated with pulmonary venous anomaly, a tunnel is created between the anomalous pulmonary vein and the ASD by using a Teflon or pericardial patch. A plastic or pericardial gusset is placed in the SVC to prevent obstruction to the SVC. Alternatively, one may use the Warden procedure. In this procedure, the SVC is divided above the level of the pulmonary venous entry. The cardiac end of the SVC is oversewn, and a pericardial baffle is placed in such a way to drain the pulmonary venous blood through the sinus venosus ASD into the LA. The proximal SVC is sewn to the right atrial appendage to drain the SVC blood to the RA.

For coronary sinus ASD, the ostium of the coronary sinus is closed with an autologous pericardium with care to avoid conduction tissues, provided it is not associated with persistent left SVC. This will result in drainage of coronary sinus blood into the left atrium.

Mortality

Fewer than 0.5% of patients die; however, there is a greater risk for small infants and those with increased PVR.

Complications

Cerebrovascular accident and postoperative arrhythmias may develop in the immediate postoperative period.

Postoperative Follow-up

1. Cardiomegaly on chest radiographs and enlarged RV dimension on echo as well as the wide splitting of the S2 may persist for 1 or 2 years after surgery. The ECG typically demonstrates RBBB (or RV conduction disturbance).

2. Atrial or nodal arrhythmias occur in 7% to 20% of postoperative patients. Occasionally, sick sinus syndrome, which occurs especially after the repair of a sinus venosus defect, may require antiarrhythmic drugs, pacemaker therapy, or both.

Ventricular Septal Defect

Prevalence

Ventricular septal defect is the most common form of CHD and accounts for 15% to 20% of all such defects, not including those occurring as part of cyanotic CHDs.

Pathology

1. The ventricular septum may be divided into a small membranous portion and a large muscular portion (Fig. 12-7A). The muscular septum has three components: the inlet septum, the trabecular septum, and the outlet (infundibular or conal) septum. The trabecular septum (also simply called the muscular septum) is further divided into anterior, posterior, mid, and apical portions. Therefore, VSD may be classified as a membranous, inlet, outlet (or infundibular), midtrabecular (or midmuscular), anterior trabecular (or anterior muscular, posterior trabecular (or posterior muscular), and apical muscular defect (Fig. 12-7B).

a. The membranous septum is a relatively small area immediately beneath the aortic valve. The membranous defect involves varying amounts of muscular tissue adjacent to the membranous septum (perimembranous VSD). According to the accompanying defect in the adjacent muscular septum, perimembranous VSDs have been called perimembranous inlet (atrioventricular [AV] canal type), perimembranous trabecular, or perimembranous outlet (tetralogy type) defects. Perimembranous defects are most common (70%).

b. Outlet (infundibular or conal) defects account for 5% to 7% of all VSDs in the Western world and about 30% in Far Eastern countries. The defect is located within the outlet (conal) septum, and part of its rim is formed by the aortic and pulmonary annulus. An aortic leaflet can prolapse through the VSD and cause aortic insufficiency (see later for further discussion). It has been called a supracristal, conal, subpulmonary, or subarterial defect.

c. Inlet (or AV canal) defects account for 5% to 8% of all VSDs. The defect is located posterior and inferior to the perimembranous defect beneath the septal leaflet of the tricuspid valve (see Fig. 12-7B).

d. Trabecular (or muscular) defects account for 5% to 20% of all VSDs. They frequently appear to be multiple when viewed from the right side. A midmuscular defect is posterior to the septal band. An apical muscular defect is near the cardiac apex and is difficult to visualize and repair. The anterior (marginal) defects are usually multiple, small, and tortuous. The “Swiss cheese” type of multiple muscular defect (involving all components of the ventricular septum) is extremely difficult to close surgically.

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FIGURE 12-7 Anatomy of ventricular septum and ventricular septal defect (VSD). A, Ventricular septum viewed from the right ventricular (RV) side. The membranous septum is small. The large muscular septum has three components: the inlet septum (I), the trabecular septum (T), and the outlet (or infundibular) septum (O). B, Anatomic locations of various VSDs and landmarks viewed with the RV free wall removed. a, outlet (infundibular) defect; b, papillary muscle of the conus; c, perimembranous defect; d, marginal muscular defect; e, central muscular defect; f, inlet defect; g, apical muscular defect. (From Graham TP Jr, et al: Moss’s Heart Disease in Infants, Children, Adolescents. Baltimore, Williams & Wilkins, 1989.)

2. The defects vary in size, ranging from tiny defects without hemodynamic significance to large defects with accompanying CHF and pulmonary hypertension.

3. The bundle of His is related to the posteroinferior quadrant of perimembranous defects and the superoanterior quadrant of inlet muscular defects. Defects in other parts of the septum are usually unrelated to the conduction tissue.

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FIGURE 12-8 Cardiac findings of a small ventricular septal defect. A regurgitant systolic murmur is best audible at the lower left sternal border; it may be holosystolic or less than holosystolic. Occasionally, the heart murmur is in early systole. A systolic thrill (dots) may be palpable at the lower left sternal border. The S2 splits normally, and the P2 is of normal intensity.

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FIGURE 12-9 Cardiac findings of a large ventricular septal defect. A classic holosystolic regurgitant murmur is audible at the lower left sternal border. A systolic thrill is also palpable at the same area (dots). There is usually a mid-diastolic rumble, resulting from relative mitral stenosis, at the apex. The S2 is narrowly split, and the P2 is accentuated in intensity. Occasionally, an ejection click (EC) may be audible in the upper left sternal border when associated with pulmonary hypertension. The heart murmurs shown without solid borders are transmitted from other areas and are not characteristic of the defect. Abnormal sounds are shown in black. Insp, inspiration.

4. In an infundibular defect, the right coronary cusp of the aortic valve may herniate through the defect. This may result in an actual reduction of the VSD shunt but may produce aortic regurgitation (AR) and cause an obstruction in the RV outflow tract (RVOT). A similar herniation of the right or noncoronary cusp occasionally occurs through perimembranous defects.

Clinical Manifestations

History

1. With a small VSD, the patient is asymptomatic with normal growth and development.

2. With a moderate to large VSD, delayed growth and development, decreased exercise tolerance, repeated pulmonary infections, and CHF are relatively common during infancy.

3. With long-standing pulmonary hypertension, a history of cyanosis and a decreased level of activity may be present.

Physical Examination (Figs. 12-8 and 12-9)

1. Infants with small VSDs are well developed and acyanotic. Before 2 or 3 months of age, infants with large VSDs may have poor weight gain or show signs of CHF. Cyanosis and clubbing may be present in patients with pulmonary vascular obstructive disease (Eisenmenger’s syndrome).

2. A systolic thrill may be present at the lower left sternal border. Precordial bulge and hyperactivity are present with a large-shunt VSD.

3. The intensity of the P2 is normal with a small shunt and moderately increased with a large shunt. The S2 is loud and single in patients with pulmonary hypertension or pulmonary vascular obstructive disease. A grade 2 to 5 of 6 regurgitant systolic murmur is audible at the lower left sternal border (see Figs. 12-8 and 12-9). It may be holosystolic or early systolic. An apical diastolic rumble is present with a moderate to large shunt (caused by an increased flow through the mitral valve during diastole) (see Fig. 12-9).

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FIGURE 12-10 Tracing from a 3-month-old infant with a large ventricular septal defect, patent ductus arteriosus, and pulmonary hypertension. The tracing shows biventricular hypertrophy with left dominance. Note that V2 and V4 are in ½ standardization.

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FIGURE 12-11 Posteroanterior and lateral views of chest roentgenograms of a ventricular septal defect with a large shunt and pulmonary hypertension. The heart size is moderately increased, with enlargement on both right and left sides of the heart. Pulmonary vascular markings are increased, with a prominent main pulmonary artery segment.

4. With infundibular VSD, a grade 1 to 3 of 6 early diastolic decrescendo murmur of AR may be audible. This murmur may be caused by herniation of an aortic cusp.

Electrocardiography

1. With a small VSD, the ECG findings are normal.

2. With a moderate VSD, left ventricular hypertrophy (LVH) and occasional left atrial hypertrophy (LAH) may be seen.

3. With a large defect, the ECG shows biventricular hypertrophy (BVH) with or without LAH (Fig. 12-10).

4. If pulmonary vascular obstructive disease develops, the ECG shows RVH only.

Radiography (Fig. 12-11)

1. Cardiomegaly of varying degrees is present and involves the LA, left ventricle (LV), and sometimes RV. Pulmonary vascular markings increase. The degree of cardiomegaly and the increase in pulmonary vascular markings directly relate to the magnitude of the left-to-right shunt.

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FIGURE 12-12 Selected two-dimensional echo views of the ventricular septum. These schematic drawings are helpful in determining the site of a ventricular septal defect (VSD). Different shading has been used for easy recognition of different parts of the ventricular septum. In the standard parasternal long-axis view (A1), the ventricular septum consists of (from the aortic valve toward the apex) the infracristal outlet (Inf-C outlet) septum (the VSD of tetralogy of Fallot is seen here) and the trabecular (mid- and apical) septum. In the parasternal right ventricular outlet tract (RVOT) view (A2), the septum consists of supracristal outlet (Sup-C outlet) septum and the trabecular septum. In the parasternal short-axis view showing the aortic valve (B1), the membranous septum is toward the 10 o’clock direction, the infracristal outlet septum at the 12 o’clock direction, and the supracristal outlet septum immediately adjacent to the pulmonary valve. The ventricular septum at the mitral valve (B2), the posterior muscular septum is inlet (INLET) septum. The ventricular septum at the papillary muscle (B3) is all trabecular septum, so that one can easily classify the defect into anterior (ANT), mid- (MID), and posterior (POST) trabecular defects. In the apical four-chamber view showing the coronary sinus (C1), the ventricular septum is the posterior (POST) trabecular septum. In the apical four-chamber view showing both atrioventricular (AV) valves (C2), the septum immediately beneath the tricuspid valve is the inlet septum (INLET) and the remainder is the mid- and apical septa. The thin septum between the insertion of the mitral and tricuspid valves is the AV septum (C2), a defect which can result in a left ventricle (LV)–to–right atrium (RA) shunt. In the standard apical four-chamber view, the membranous septum is not visible. In the apical “five-chamber” view (C3), the membranous (MEMB) septum is seen beneath the aortic valve, and below it is the infracristal outlet (Inf-C outlet) septum. The ventricular septum seen in the subcostal four-chamber view (D1) is similar to the apical four-chamber view (C2). With anterior angulation of the horizontal transducer, the LV outflow tract (LVOT) is seen (D2), and the septum seen here is similar to the apical “five-chamber” view (C3). With further anterior angulation, the RVOT is seen (D3). The superior part is the supracristal outlet (Sup-C outlet) septum, and the inferior part is the anterior (ANT) trabecular septum (D3). The subcostal short-axis view showing the RVOT (E1) is orthogonal to the standard subcostal four-chamber view and is an important view for evaluating the site and size of a VSD. In this view, both supracristal outlet (Sup-C outlet) and infracristal outlet (Inf-C outlet) septa (in that order) are seen beneath the pulmonary valve and the trabecular septum (ANT and POST) is seen apical ward. The ventricular septum seen at the papillary muscle (E2) is all trabecular septum and is similar to the parasternal short axis view (B3).

2. In pulmonary vascular obstructive disease, the main PA and the hilar PAs enlarge noticeably, but the peripheral lung fields are ischemic. The heart size is usually normal.

Echocardiography

Two-dimensional and Doppler echocardiographic studies can identify the number, size, and exact location of the defect; estimate PA pressure by using the modified Bernoulli equation; identify other associated defects; and estimate the magnitude of the shunt. Because the ventricular septum is a large, complex structure, examination for a VSD should be carried out in a systematic manner to be able to specify the exact location and size of the defect. When possible, more than one view should be obtained, preferably a combination of the long- and short-axis views.

The cardiac valves serve as markers of specific types of VSDs except for the trabecular septum. The membranous VSD is closely related to the aortic valve, the inlet VSD to the tricuspid (or AV) valve, and the infundibular VSD to the semilunar valves. Figure 12-12 is a collection of selected views of parasternal, apical, and subcostal views, which are useful in locating the site of VSDs.

The membranous septum is closely related to the aortic valve. In the apical and subcostal “five-chamber” views, it is seen in the LV outflow tract (LVOT) just under the aortic valve (Fig. 12-12C3). In the parasternal short-axis view at the level of the aortic valve, it is seen adjacent to the tricuspid valve (Fig. 12-12B1). These are the best views to confirm the membranous VSD. The membranous VSD is not visible in the standard parasternal long-axis view, but by tilting the transducer slightly to the right, away from the aorta, the membranous VSD becomes visible. Figure 12-13 shows a membranous VSD imaged in the apical “five-chamber” view.

The inlet septum is best imaged in the apical or subcostal four-chamber view beneath the AV valves (Fig. 12-12C2 and D1). It can also be seen equally well in the parasternal short-axis view in the posterior interventricular septum at the levels between the mitral valve and the papillary muscle (Fig. 12-12B2). Simple inlet VSD (not that associated with AV canal defect) is seen beneath the AV valve, but a small amount of tissue remains under the valves. In the AV canal type of VSD, the AV valves are at the same level. There may be straddling or overriding.

The infundibular (or outlet) septum lies inferior to the semilunar valves. The subpulmonary, supracristal infundibular VSD lies under the pulmonary valve (Fig. 12-12A2 and D3), and the subaortic infracristal VSD (tetralogy of Fallot [TOF] type, also called conoventricular VSD) lies under the aortic valve (Fig. 12-12A1 and D2). From the RV side, if the outlet septum lies inferior to the pulmonary valve, it is supracristal. The infracristal VSD lies much closer to the aortic valve but away from the pulmonary valve (Fig. 12-12, A1 and C3), and the supracristal is closer to the pulmonary valve (Fig. 12-12A2, D3, and E1).

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FIGURE 12-13 Two-dimensional echocardiogram showing membranous ventricular septal defect (VSD). The membranous VSD is seen underneath the aortic valve in the left ventricular outflow tract (in the apical “five-chamber” view). This view is equivalent to Figure 12-12, C3. AO, aorta; LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle; PV, pulmonary vein.

The trabecular septum is the largest portion of the ventricular septum and extends from the membranous septum to the cardiac apex. The four types of trabecular VSDs are (1) anterior, (2) midmuscular, (3) apical, (4) posterior. Echocardiographic views that show the locations of different types of trabecular VSDs are shown in Figure 12-12. The apical VSD occurs near the cardiac apex (Fig. 12-12A1, A2, C2, C3, D1,and D2). The entire ventricular septum seen at the papillary muscle level is the trabecular septum (Fig. 12-12B3 and E2). For imaging of an apical muscular VSD, the transducer must be maximally angled toward the cardiac apex.

Natural History

Understanding the natural history of a VSD is important when planning its management.

1. Spontaneous closure of perimembranous and muscular VSDs can occur. It occurs more frequently with small defects and during the first 6 months of life. About 60% of small to moderate muscular VSDs close spontaneously but not after 8 years of age. About 35% of small perimembranous VSDs close spontaneously but not after 5 years of age. These VSDs do not become bigger with age; rather, they decrease in size. However, inlet defects and outlet (infundibular) defects do not become smaller or close spontaneously.

2. CHF develops in infants with large VSDs but usually not until 6 to 8 weeks of age.

3. Pulmonary vascular obstructive disease may begin to develop as early as 6 to 12 months of age in patients with large VSDs, but the resulting right-to-left shunt usually does not develop until the teenage years.

4. Infundibular stenosis may develop in some infants with large defects and result in a decrease in the magnitude of the left-to-right shunt (i.e., acyanotic TOF), with an occasional occurrence of a right-to-left shunt.

Management

Medical

1. Treatment of CHF, if it develops, is indicated with diuretics (with or without) digoxin (see Chapter 27) for 2 to 4 months to see if growth failure can be improved. Some centers do not use digoxin. Addition of spironolactone may be helpful to minimize potassium loss from diuretics. Concomitant use of an afterload reducing agent, such as captopril, has gained popularity. Angiotensin-converting enzyme (ACE) inhibitors may raise the serum potassium level, and spironolactone or potassium supplementation should be discontinued. Frequent feedings of high-calorie formulas, either by nasogastric tube or oral feeding, may help. Anemia, if present, should be corrected by oral iron therapy. These measures often allow delay of surgical treatment and may promote spontaneous reduction or closure of the VSD.

2. No exercise restriction is required in the absence of pulmonary hypertension.

3. Nonsurgical device closure of selected muscular VSDs is possible in selected patients when the defect is not too close to cardiac valves and when it is difficult to access surgically. Some centers have used so-called hybrid procedures through left thoracotomy incision and performing “perventricular” device closure without the use of cardiopulmonary bypass to close muscular VSD in the operating room. Device closure is not popular for the perimembranous VSD because of the unacceptable rate of postprocedure heart block.

Surgical

Indications and Timing

1. Small infants who have large VSDs and develop CHF with growth retardation are managed with diuretics and afterload reducing agents, with or without digoxin. If growth failure cannot be improved by medical therapy, the VSD should be operated on within the first 6 months of life, preferably by 3 to 4 months of age. Surgery should be delayed for infants who respond to medical therapy.

2. Infants who have small VSDs and have reached the age of 6 months without CHF or evidence of pulmonary hypertension are usually not candidates for surgery.

3. If the PA pressure is more than 50% of systemic pressure, surgical closure should be done by the end of the first year.

4. After 1 year of age, a significant left-to-right shunt with Qp/Qs ratio of at least 2:1 indicates that surgical closure is needed, regardless of PA pressure. Surgery is not indicated for small VSD with Qp/Qs ratio less than 1.5:1.

5. Older infants with large VSDs and evidence of elevated PVR should be operated on as soon as possible.

6. Surgery is contraindicated in patients with a pulmonary to systemic vascular resistance ratio of greater than 0.5 or with pulmonary vascular obstructive disease with a predominant right-to-left shunt.

Procedure

1. PA banding as a palliative procedure is no longer performed unless additional lesions make complete repair difficult.

2. Direct closure of the defect is carried out under hypothermic cardiopulmonary bypass, preferably without right ventriculotomy. Most perimembranous and inlet VSDs are repaired by a transatrial approach. Outlet (conal) defects are best approached through an incision in the main pulmonary artery. Apical VSD may require apical right ventriculotomy.

As with the closure of ASDs, minimally invasive surgical techniques with smaller skin incisions are becoming popular for the closure of VSDs. The major benefit of this approach appears to be cosmetic.

Mortality

The surgical mortality rate is less than 1%. The mortality rate is higher for small infants younger than 2 months of age, infants with associated defects, and infants with multiple VSDs.

Complications

1. RBBB is frequent in patients repaired via right ventriculotomy. This is usually caused by the disruption of the Purkinje fibers, but it can also be caused by direct injury to the right bundle itself.

2. RBBB and left anterior hemiblock, which occurs in fewer than 10% of patients, is a controversial cause of sudden death. Complete heart block requiring pacemaker occurs in 1% to 2% of patients.

3. Residual shunt occurs in fewer than 5%. Intraoperative TEE echocardiography has reduced the incidence of the residual shunt.

4. The incidence of neurologic complications is directly related to the circulatory arrest time.

Surgical Approaches for Special Situations

1. VSD and PDA. If the PDA is large, the ductus alone may be closed in the first 6 to 8 weeks in the hope that the VSD is restrictive. If the VSD is large and not restrictive, PDA should be ligated at the time of VSD repair through the median sternotomy.

2. VSD and coarctation of the aorta (COA). A VSD is present in 15% to 20% of patients with COA. Several options exist in this controversial situation.

a. Initial repair of the COA alone if the VSD appears relatively small. The VSD is closed later, if indicated.

b. Coarctation repair and PA banding when the VSD appears unrestrictive.

c. Repair of both defects at the same time using one or two incisions.

3. VSD and AR syndrome. The prolapsed aortic cusp, with resulting AR, is usually associated with outlet VSD and occasionally with perimembranous VSD. It occurs in about 5% of patients with VSD, but the prevalence is much higher in Far Eastern countries (15%–20%). The adjacent (i.e., right or noncoronary) aortic valve cusps prolapse through the defect into the RVOT, actually reducing the VSD shunt. When AR appears, it gradually worsens. Surgery is usually performed promptly when AR is present even if the Qp/Qs ratio is less than 2:1, so that progression of AR (by Venturi effect through the open VSD) is either aborted or abolished. Some centers close the VSD even in the absence of AR if the aortic prolapse is demonstrated. When AR is trivial or mild, the VSD alone is closed. When AR is moderate or severe, the aortic valve is repaired or replaced. Not every case of VSD and AR results from the prolapsed aortic cusps; it may be the result of a VSD and bicuspid aortic valve.

Postoperative Follow-up

1. Office examination should be scheduled every 1 to 2 years.

2. Activity should not be restricted unless complications have resulted from surgery.

3. The ECG will show RBBB in 50% to 90% of patients who had VSD repair through right ventriculotomy and up to 40% of the patients who had repair through a right atrial approach.

4. Although rare these days, patients who had VSD and mild pulmonary hypertension and repair of the VSD after 3 years of age should be checked for possible progressive pulmonary vascular disease.

5. A patient with a postoperative history of transient heart block with or without pacemaker therapy requires long-term follow-up.

Patent Ductus Arteriosus

Prevalence

Patent ductus arteriosus occurs in 5% to 10% of all CHDs, excluding premature infants. It is more common in females than in males (male-to-female ratio of 1:3). PDA is a common problem in premature infants and will be presented under a separate heading in this chapter.

Pathology

1. There is a persistent patency of a normal fetal structure between the PA and the descending aorta, that is, about 5 to 10 mm distal to the origin of the left subclavian artery.

2. The ductus is usually cone shaped with a small orifice to the PA, which is restrictive to blood flow. The ductus may be short or long, straight, or tortuous.

Clinical Manifestations

History

1. Patients are usually asymptomatic when the ductus is small.

2. A large-shunt PDA may cause a lower respiratory tract infection, atelectasis, and CHF (accompanied by tachypnea and poor weight gain).

3. Exertional dyspnea may be present in children with a large-shunt PDA.

Physical Examination (Fig. 12-14)

1. Tachycardia and tachypnea may be present in infants with CHF.

2. Bounding peripheral pulses with wide pulse pressure (with elevated systolic pressure and lower diastolic pressure) are characteristic findings of a large PDA. With a small shunt, these findings do not occur.

3. With a large shunt, the precordium is hyperactive. A systolic thrill may be present at the upper left sternal border. The P2 is usually normal, but its intensity may be accentuated if pulmonary hypertension is present. A grade 1 to 4 of 6 continuous (“machinery”) murmur is best audible at the left infraclavicular area or upper left sternal border. An apical diastolic rumble may be heard when the PDA shunt is large. Patients with small ductus do not have the above findings.

4. If pulmonary vascular obstructive disease develops, a right-to-left ductal shunt results in cyanosis only in the lower half of the body (i.e., differential cyanosis).

Electrocardiography

The ECG findings in PDA are similar to those in VSD. A normal ECG or LVH is seen with small to moderate PDA. BVH is seen with large PDA. If pulmonary vascular obstructive disease develops, RVH is present.

Radiography

Radiographs are also similar to those of VSD.

1. Chest radiographs may be normal with a small-shunt PDA.

2. Cardiomegaly of varying degrees occurs in moderate-to large-shunt PDA with enlargement of the LA, LV, and ascending aorta. Pulmonary vascular markings are increased.

3. With pulmonary vascular obstructive disease, the heart size becomes normal, with a marked prominence of the PA segment and hilar vessels.

Echocardiography

Echocardiography has emerged as the procedure of choice in confirming the diagnosis and assessing functional significance.

1. The PDA can be imaged in most patients. Its size can be assessed by two-dimensional echo in a high parasternal view or in a suprasternal notch view (Fig. 12-15).

2. Doppler studies that are performed with the sample volume in the PA immediately proximal to the ductal opening provide important functional information (see discussion in PDA in Preterm Neonates).

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FIGURE 12-14 Cardiac findings of patent ductus arteriosus. A systolic thrill may be present in the area shown by dots.

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FIGURE 12-15 Parasternal short-axis view demonstrating patent ductus arteriosus (PDA) that connects the main pulmonary artery (MPA) and the descending aorta (Desc Ao). AO, aorta; LPA, left pulmonary artery; RPA, right pulmonary artery.

3. The dimensions of the LA and LV provide an indirect assessment of the magnitude of the left-to-right ductal shunt. The larger the shunt, the greater the dilatation of these chambers.

Natural History

1. Unlike PDA in premature infants, spontaneous closure of a PDA is rare in full-term infants and children. This is because the PDA in term infants results from a structural abnormality of the ductal smooth muscle rather than a decreased responsiveness of the ductal smooth muscle to oxygen.

2. CHF or recurrent pneumonia develops if the shunt is large.

3. Pulmonary vascular obstructive disease may develop if a large PDA with pulmonary hypertension is left untreated.

4. Although rare, an aneurysm of PDA may develop and possibly rupture in adult life.

Differential Diagnosis

The following conditions occur with a heart murmur, which is similar to the continuous murmur of PDA or with bounding pulses, and they require differentiation from PDA:

1. Coronary arteriovenous fistula: A continuous murmur is usually maximally audible along the right sternal border, not at the left infraclavicular area or upper left sternal border.

2. Systemic arteriovenous fistula: A bounding pulse with a wide pulse pressure and signs of CHF may develop without continuous murmur over the precordium. A continuous murmur is present over the fistula (i.e., head or liver).

3. Pulmonary arteriovenous fistula: A continuous murmur is audible over the back. Cyanosis and clubbing are present in the absence of cardiomegaly.

4. Venous hum: A venous hum is maximally audible in the right or left infraclavicular and supraclavicular areas when the patient is examined in a sitting position. It usually disappears when the patient lies in a supine position.

5. Collaterals in COA: A continuous murmur is audible in the intercostal spaces, usually bilaterally.

6. VSD with AR: A to-and-fro murmur, rather than a continuous murmur, is audible at the mid-left sternal border or lower left sternal border.

7. Absence of the pulmonary valve: A to-and-fro murmur (“sawing wood” sound) is audible at the upper left sternal border. Large hilar PAs on radiographic films and RVH on the ECG are characteristic. These patients are frequently cyanotic because this defect is usually associated with TOF.

8. Persistent truncus arteriosus: A continuous murmur is occasionally audible at the second right intercostal space or at the back in a cyanotic infant rather than in the upper left sternal border. The ECG may show BVH, and chest radiographic films show varying degrees of cardiomegaly and increased pulmonary vascularity. A right aortic arch is frequently found.

9. Aortopulmonary septal defect (aortopulmonary window): This extremely rare condition produces a bounding pulse, but the murmur resembles that of a VSD. CHF develops in early infancy.

10. Peripheral PA stenosis: A continuous murmur is audible all over the thorax. The ECG may show RVH if the stenosis is severe. This often accompanies Williams syndrome or rubella syndrome.

11. Ruptured sinus of Valsalva aneurysm: The sudden onset of chest pain and signs of severe heart failure with dyspnea develop. A continuous murmur or a to-and-fro murmur is present at the base. This condition is more commonly seen in patients with Marfan’s syndrome.

12. Total anomalous pulmonary venous return (TAPVR) draining into the RA: A murmur that sounds similar to a venous hum may be heard along the right sternal border in a child with mild cyanosis. The ECG shows RVH in the presence of cardiomegaly and increased pulmonary vascular markings on chest radiographic films.

Management

Medical

1. Unlike in premature infants with PDAs, indomethacin is ineffective in term infants and should not be used.

2. No exercise restriction is needed in the absence of pulmonary hypertension.

3. Nonsurgical occlusion of PDA has become a standard of care at many centers except in patients with very low birth weight.

Nonsurgical Closure

Large series of nonsurgical ductal closure in the United States and Europe reported 95% to 100% success rates.

1. Indications of PDA closure are as follows (Feltes TF, et al, 2011).

a. Closure of PDA is definitely indicated in patients with hemodynamically significant PDA with CHF, failure to thrive, pulmonary overcirculation, or enlargement of the LA and LV.

b. It is reasonable to close a small PDA when the murmur of PDA is audible by standard auscultation techniques.

c. There is controversy related to occlusion of so-called silent ductus. There are few data on the benefits of occluding the silent ductus because of lack of significant endothelial damage to cause endocarditis.

d. Ductal closure is contraindicated in patients with Eisenmenger’s syndrome or pulmonary vascular obstructive disease. The response of PVR to balloon occlusion or pulmonary vasodilators (e.g., oxygen or nitric oxide) is tested in the cardiac catheterization laboratory. If a good response is obtained, closure is advised. If the response is poor or equivocal, closure may not be recommended. A device closure (without additional surgical insult) may be considered in this setting. The presence of severe pulmonary hypertension with irreversible pulmonary vascular obstructive disease is a contraindication to surgery.

2. Procedure. Small ductus (<3 mm in diameter) are closed by various kinds of coils and larger ones by the Amplatzer PDA device.

a. Gianturco stainless steel coils have become the standard device for closure of PDA for all children with ducts smaller than 3 mm in diameter in the United States. In optimal candidates for the device, the ductus is 2.5 mm in size, but the use of multiple coils can close a ductus up to 5 mm. A retrograde approach is used from the femoral artery. The residual shunt rate is 5% to 15% at 12 months of follow-up. Overall, the procedure has 97% or greater success with zero mortality.

b. For larger PDA but smaller than 12 mm in diameter, specialized devices, such as the Amplatzer duct occluder, are available for catheter-based closure. The devices are implanted antegrade from the femoral vein. Although original recommendations from the manufacturer exclude patients who weigh less than 6 kg, successful use in infants as small as 2.5 kg has been reported. There is a 98% or greater closure rate at 6 months with minimal complications and no mortality.

The advantages of nonsurgical closure of the ductus include no need for general anesthesia, shorter hospital stay and convalescent period, and elimination of a thoracotomy scar. Disadvantages and potential complications include residual leaks, pulmonary artery coil embolization, hemolysis, left PA stenosis, aortic occlusion with the Amplatzer device, and femoral vessel occlusion.

Surgical Closure

Indications and Timing

Surgical closure is reserved for patients in whom a nonsurgical closure technique is not considered applicable. An interventional device rather than surgery is used to close small ductus with no hemodynamic significance by many centers.

Procedure

1. Ligation and division through left posterolateral thoracotomy without cardiopulmonary bypass is the standard procedure.

2. The technique of video-assisted thoracoscopic surgery (VATS) clip ligation has become the standard of care for surgical management of ductus with adequate length (to allow safe ligation), which is performed through three small ports in the fourth intercostal space.

Mortality

The surgical mortality rate is 0% for both techniques.

Complications

Complications are rare. Injury to the recurrent laryngeal nerve (hoarseness), the left phrenic nerve (paralysis of the left hemidiaphragm), or the thoracic duct (chylothorax) is possible. Recanalization (reopening) of the ductus is possible, although rare, occurring after ligation alone (without division).

Patent Ductus Arteriosus in Preterm Neonates

Prevalence

Clinical evidence of PDA appears in 45% of infants with a birth weight less than 1750 g and in about 80% of infants with a birth weight less than 1200 g. Significant PDA with CHF occurs in 15% of premature infants with a birth weight less than 1750 g and in 40% to 50% of those with a birth weight less than 1500 g.

Pathophysiology

1. PDA is a special problem in premature infants who are recovering from hyaline membrane disease. With improvement in oxygenation, the PVR falls rapidly, but the ductus remains patent because its responsiveness to oxygen is immature in premature newborns (see Chapter 8). The resulting large left-to-right shunt makes the lung stiff, and weaning the infant from the ventilator and oxygen therapy becomes difficult.

2. If the infant must remain on a ventilator and oxygen therapy for a long time, bronchopulmonary dysplasia develops, with resulting pulmonary hypertension (cor pulmonale) and right-sided heart failure.

3. Premature infants with significant left-to-right shunt may suffer from the consequences of prolonged hypoperfusion to many organs, which may include intracranial hemorrhage, renal dysfunction, myocardial ischemia, and necrotizing enterocolitis. Early recognition and appropriate management of PDA are keys to improving the prognosis of these infants.

Clinical Manifestations

1. The history is important in suspecting a significant PDA in a premature neonate. Typically, a premature infant with hyaline membrane disease shows some improvement during the first few days after birth. This is followed by an inability to wean the infant from the ventilator or a need to increase ventilator settings or oxygen requirements in 4- to 7-day-old premature infants. Episodes of apnea or bradycardia may be the initial sign of PDA in infants who are not on ventilators.

2. The physical examination commonly reveals bounding peripheral pulses, a hyperactive precordium, and tachycardia with or without gallop rhythm. The classic continuous murmur at the left infraclavicular area or upper left sternal border is diagnostic, but the murmur may be only systolic and is difficult to hear in infants who are on ventilators. Premature infants who are fluid overloaded or retaining fluid may also present with findings of PDA as described earlier (hyperdynamic precordium, systolic ejection murmur, bounding pulses, and wide pulse pressures), requiring differentiation from PDA.

3. The ECG is not diagnostic. It usually is normal but occasionally shows LVH.

4. Chest radiographs show cardiomegaly in larger premature infants who are not intubated. The infant may have evidence of pulmonary edema or increased pulmonary vascular markings, but these may be difficult to assess in the presence of hyaline membrane disease. In infants who are intubated and on high ventilator settings, chest x-ray films may show the heart to be either of normal size or only mildly enlarged.

5. Two-dimensional echocardiographic and color-flow Doppler studies provide accurate anatomic and functional information.

a. Two-dimensional echo provides anatomic information about the diameter, length, and shape of the ductus (see Fig. 12-15).

b. Doppler studies of the ductus (with the sample volume placed at the pulmonary end of the ductus) provide important functional information, such as ductal shunt patterns (pure left-to-right, bidirectional, or predominant right-to-left shunt), pressures in the PA, and magnitude of the ductal shunt or pulmonary perfusion status:

1) Ductal shunt pattern. A continuous positive flow indicates a pure left-to-right shunt with the PA pressure lower than the aortic pressure. In pure right-to-left shunts, flow is continuously negative away from the PA, indicating that the PA pressure is suprasystemic. A bidirectional shunting pattern (with an early negative flow in systole followed by a late positive flow in diastole) is found in infants with PDA and severe pulmonary hypertension.

2) Estimation of PA pressures. A high ductal flow velocity indicates a low PA pressure, and a low flow velocity indicates a high PA pressure. The pressure drop may be underestimated in patients with a small pulmonary end of the ductus, tortuous PDAs, or tunnel-like PDAs with diameters smaller than 3 mm and lengths longer than 10 mm (because of viscous energy loss). However, the easiest and most accurate estimate of the PA systolic pressure is obtained from the peak velocity of the TR, when it is present.

3) Perfusion status. Increased flow velocity in the left PA suggests a large left-to-right shunt through the ductus. High PA pressure and a lower flow velocity (with a pressure drop of <5 mm Hg) indicate poor perfusion of the lungs, which is a bad prognostic sign during the first 24 to 36 hours.

Management

For symptomatic infants, either pharmacologic or surgical closure of the ductus is indicated. A small PDA that does not cause symptoms should be followed medically for 6 months without surgical ligation because of the possibility of spontaneous closure.

Medical

1. Fluid restriction to 120 mL/kg per day and a diuretic (e.g., furosemide, 1 mg/kg two to three times a day) may be tried for 24 to 48 hours, but these regimens have a low success rate. Digoxin is not used because it has little hemodynamic benefit and a high incidence of digitalis toxicity.

2. Pharmacologic closure of the PDA can he achieved with indomethacin (a prostaglandin synthetase inhibitor). Indications and dosages vary from center to center (see later discussion). One popular approach is to give indomethacin (Indocin) 0.2 mg/kg intravenously every 12 hours for up to three doses in selected cases. A second course of indomethacin treatment is occasionally necessary to achieve adequate ductal closure. Contraindications to the use of indomethacin include high blood urea nitrogen (>25 mg/dL) or creatinine (>1.8 mg/dL) levels, low platelet count (<80,000/mm3), bleeding tendency (including intracranial hemorrhage), necrotizing enterocolitis, and hyperbilirubinemia.

Many dosage regimens exist and dose is dependent on postnatal age of the infant at time of first dose; one example is as follows. The dose is given intravenously every 12 hours a total of 3 doses. For infants less than 48 hours old, 0.2 mg/kg is followed by 0.1 mg/kg times 2. For infants 2 to 7 days old, 0.2 mg/kg times 3 is given, and for infants older than 7 days old, 0.2 mg/kg followed by 0.25 mg/kg times 2 is given.

3. A multicenter prospective study from Europe showed that intravenous ibuprofen (10 mg/kg followed at 24-hour intervals by two doses of 5 mg/kg) starting on the third day of life was as effective in closing the ductus in preterm newborns as indomethacin. Ibuprofen had a significantly lower incidence of oliguria, and it does not appear to have a deleterious effect on cerebral blood flow. Ibuprofen significantly reduces plasma concentrations of prostaglandin. An earlier study from Canada reported that intravenous ibuprofen 10 mg/kg given at 3 hours of age followed by 5 mg/kg given at 24 and 48 hours of age was effective in reducing the incidence of PDA without causing notable adverse drug reactions. Thus, ibuprofen appears to be a valuable alternative to indomethacin for both the treatment and the prophylaxis of PDA in preterm newborns. Ibuprofen may prove to be a better choice than indomethacin. A recent dose-finding study conducted in Europe confirmed the dosage of 10-5-5 mg/kg to be correct for ductal closure (Desfrere et al, 2005). Recent reports from Europe concluded that prophylactic use of ibuprofen in small preterm infants was not useful because, although it reduced the occurrence and the need for surgical ligation of the ductus, it did not reduce the frequency of intraventricular hemorrhage, mortality, or morbidity.

Surgical

If medical treatment is unsuccessful or if the use of indomethacin is contraindicated, surgical ligation of the ductus is indicated. The standard operative approach to PDA is through a posterolateral thoracotomy. The PDA is simply ligated or hemoclipped (without division). Many centers now perform PDA ligation in the neonatal intensive care unit at the bedside. The operative mortality rate is 0% to 3%.

Recently, the use of minimally invasive VATS has been reported for the management of PDA in low-birth-weight infants. This technique allows PDA interruption without the muscle cutting or rib spreading of a standard thoracotomy. Reduced compromise of respiratory mechanics and less chest wall deformity associated with a large thoracotomy incision may also be advantages.

Complete Endocardial Cushion Defect

Prevalence

Complete ECD (also known as AV canal defect, complete AV canal defect, or AV communis) occurs in 2% of all CHDs. Of patients with complete ECD, about 70% are children with Down syndrome. Of children with Down syndrome, about 40% have CHDs, and 50% of the defects are ECD. ECD is also a component of heart defects in asplenia and polysplenia syndromes (see Chapter 14).

Pathology

1. Abnormalities seen in complete ECD affect the structures normally derived from the endocardial cushion tissue. Ostium primum ASD, VSD in the inlet ventricular septum, and clefts in the anterior mitral valve and the septal leaflet of the tricuspid valve (forming the common AV valve) are all present in the complete form of ECD (Fig. 12-16). The combination of these defects may result in interatrial and interventricular shunts, LV-to-RA shunt, and AV valve regurgitation. Although rare, the entire atrial septum may be absent (common atrium). When two AV valve orifices are present without an interventricular shunt, the defect is called partial ECD or ostium primum ASD (which is presented under a separate heading in this chapter).

2. Both complete and partial forms of ECD are characterized by a deficiency of the inlet portion of the ventricular septum, with a “scooped-out” appearance of the muscular septum and an excessively long infundibular septum, as well as by an abnormal position of the aortic valve (i.e., displaced anterosuperiorly rather than being wedged between the right and left AV valves). The latter results in lengthening and narrowing of the LVOT, thereby producing the characteristic “goose-neck deformity” on angiocardiogram (see Fig. 12-21).

3. Whereas in complete ECD, a single valve orifice connects the atrial and ventricular chambers, in the partial form, there are separate mitral and tricuspid orifices. The common AV valve usually has five leaflets (see Fig 12-16). The arrangement of the LV papillary muscles may be abnormal in that either they are closer together or only one papillary muscle is present in the LV, which makes surgical repair difficult.

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FIGURE 12-16 Diagram of the atrioventricular (AV) valve and cardiac septa in partial and complete endocardial cushion defect (ECDs). A, Normal AV valve anatomy with no septal defect. B, Partial ECD with clefts in the mitral and tricuspid valves and an ostium primum atrial septal defect (ASD) (solid arrow). C, Complete ECD. There is a common AV valve with large anterior and posterior bridging leaflets. An ostium primum ASD (solid arrow) and an inlet ventricular septal defect (open arrow) are present. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.

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FIGURE 12-17 Rastelli’s classification of complete endocardial cushion defect. A, Type A. B, Type B. C, Type C. (See text for descriptions.) LV, left ventricle; RA, right atrium; RV, right ventricle.

4. In the majority of complete ECD cases, the AV orifices are equally committed to the RV and LV (“balanced” AV canal). In some patients, however, the orifices are committed primarily to one ventricle, with hypoplasia of the other ventricle (i.e., “unbalanced” AV canal with RV or LV dominance). Hypoplasia of one ventricle may necessitate one ventricular repair (i.e., Fontan operation).

5. A universally accepted classification for complete ECD does not exist. The Rastelli classification was based on the relationships of the anterior bridging leaflets to the crest of the ventricular septum or RV papillary muscles (Fig. 12-17). In type A, the anterior bridging leaflet is tightly tethered to the crest of the ventricular septum, occurring in 50% to 70%. This type is commonly associated with Down syndrome. In type B (3%), the anterior bridging leaflet is not attached to the ventricular septum; rather, it is attached to an anomalous RV papillary muscle and is almost always associated with unbalanced AV canal with right dominance. In type C (30%), a free-floating anterior leaflet is attached to the anterior papillary muscle. This type is often seen in visceral heterotaxia and conotruncal malformations.

6. Additional cardiac anomalies include TOF (called “canal tet,” occurring in 6% of patients), DORV with more than 50% overriding of the aorta (occurring in 6%), and transposition of the great arteries (occurring in 3%). Associated defects are rare in children with Down syndrome.

Clinical Manifestation

History

Failure to thrive, repeated respiratory infections, and signs of CHF are common.

Physical Examination (Fig. 12-18)

1. Infants with ECD are usually undernourished and have tachycardia and tachypnea (signs of CHF). This defect is common in infants with Down syndrome.

2. Hyperactive precordium with a systolic thrill at the lower left sternal border is common (shown as the area with dots in Fig. 12-18).

3. The S1 is accentuated. The S2 narrowly splits, and the P2 increases in intensity. A grade 3 to 4 of 6 holosystolic murmur is usually audible along the lower left sternal border. The systolic murmur may transmit well to the left axilla and be heard well at the apex when mitral regurgitation (MR) is significant. A mid-diastolic rumble may be present at the lower left sternal border or at the apex as a result of relative stenosis of the tricuspid or mitral valve.

4. Signs of CHF (e.g., hepatomegaly, gallop rhythm) may be present.

Electrocardiography

1. “Superior” QRS axis with the QRS axis between −40 and −150 degrees is characteristic of the defect (Fig. 12-19).

2. Most of the patients have a prolonged PR interval (first-degree AV block).

3. RVH or RBBB is present in all cases, and many patients have LVH, too.

Radiography

Cardiomegaly is always present and involves all four cardiac chambers. Pulmonary vascular markings are increased, and the main PA segment is prominent.

Echocardiography

Two-dimensional and Doppler echocardiographic studies allow imaging of all components of complete ECD and an assessment of the severity of these components. The following surgically important information can be gained: size of the ASD and VSD, size of the AV valve orifices, anatomy of leaflets, chordal attachment, relative and absolute size of the RV and LV (balance of the canal), and papillary muscle architecture (one vs. two) in the LV.

1. The apical and subcostal four-chamber views are most useful in evaluating the anatomy and the functional significance of the defect. These views show both an ostium primum ASD and an inlet muscular VSD (Fig. 12-20). Either the anterior bridging leaflet crosses the ventricular septum or the right and left AV valve leaflets can be seen at the same level from the crest of the ventricular septum. The full extent of the ASD and VSD can be imaged during systole when the common anterior leaflet is closed.

2. A combined use of the subcostal transducer position (i.e., about 45 degrees clockwise from a standard four-chamber view) and the parasternal short-axis examination may show a cleft in the mitral valve, the presence of bridging leaflets, the number of AV valve orifices (e.g., double orifice mitral valve), and the AV valve leaflets. These views may also image the abnormal position of the anterolateral papillary muscle, which is displaced posteriorly from its normal position, and the number (i.e., single or triple) of papillary muscles.

3. The subcostal “five-chamber” view may image a goose-neck deformity, which is characteristic of an angiocardiographic finding (Fig. 12-21).

4. In real time, the subcostal and apical four-chamber views can image the chordal attachment of the anterior bridging leaflet to the crest of the ventricular septum (type A), to the right side of the septum (type B), or to a papillary muscle at the apex of the RV or on its free wall (type C).

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FIGURE 12-18 Cardiac findings of complete endocardial cushion defect, which resemble those of a large ventricular septal defect. An apical holosystolic murmur (caused by mitral regurgitation) may transmit toward the left axilla. A systolic thrill may be present at the lower left sternal border (dotted area), where the systolic murmur is loudest. Insp., inspiration.

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FIGURE 12-19 Tracing from a 5-year-old boy with Down syndrome and complete atrioventricular canal. Note the “superior” QRS axis (–110 degrees) and right ventricular hypertrophy.

Natural History

1. Patients with complete ECD develop heart failure 1 to 2 months after birth, and recurrent pneumonia is common.

2. Without surgical intervention, most patients die by the age of 2 to 3 years.

3. In the latter half of the first year of life, survivors begin to develop pulmonary vascular obstructive disease. These survivors usually die in late childhood or as young adults. Infants with Down syndrome are particularly prone to the early development of pulmonary vascular obstructive disease during infancy. Therefore, surgery should be performed during infancy.

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FIGURE 12-20 Apical four-chamber views in systole (A) and diastole (B) from a patient with a complete endocardial cushion defect. In systole, an ostium primum defect and an inlet ventricular septal defect are imaged. The atrioventricular (AV) valve appears to be attached to the crest of the ventricular septum by chordae (type A). When the AV valve opens in diastole, a large deficiency in the center of the heart is visible. Note that there is a common AV valve, instead of two separate AV valves. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. (From Snider AR, Serwer GA: Echocardiography in Pediatric Heart Disease. St Louis, Mosby, 1990.)

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FIGURE 12-21 Frontal view of a left ventriculogram of a patient with partial endocardial cushion defect showing a goose-neck deformity. The left ventricular outflow tract is elongated and narrowed. The arrows point to the mitral cleft. AO, aorta: LV, left ventricle.

Management

Medical

1. In small infants with CHF, anticongestive management with diuretics and ACE inhibitors should be started. Digoxin may also be used (see Chapter 27).

2. Nutrition should be optimized.

Surgical

Indications

The presence of complete ECD indicates the need for surgery because an important hemodynamic derangement is usually present. Most of these infants have CHF that is unresponsive to medical therapy, and some have elevated PVR.

Timing

Although timing varies among institutions and with the hemodynamics of the defect, most centers perform the repair at 2 to 4 months of age. Early surgical repair is especially important for infants with Down syndrome with complete ECD because of their known tendency to develop early pulmonary vascular obstructive disease.

Procedures

Palliative

Banding of the PA in early infancy is no longer recommended unless other associated abnormalities make complete repair a high-risk procedure, such as those with “unbalanced” AV canal. The mortality rate for PA banding can be as high as 15%.

Corrective

Given two ventricles of suitable size and no additional defects, closure of the primum ASD and inlet VSD and construction of two separate and competent AV valves are carried out under cardiopulmonary bypass, deep hypothermia, or both. Some surgeons use a single patch to close the ASD and VSD and reconstruction of the left AV valve as a bileaflet valve; others use a two-patch technique, one patch for the VSD and a second for the ASD (Fig. 12-22). The left AV valve is allowed to persist as a trileaflet structure. A schematic drawing of the surgery is shown in Figure 12-21. This figure illustrates the complexity of the anatomy of the AV canal. Mitral valve replacement may become necessary in a few patients.

Patients with an unbalanced AV canal (with hypoplasia of RV or LV) may be treated by an earlier PA banding and later by a modified Fontan operation.

Mortality

The mortality rate has been 3% to 10%. The survival rate is the same for patients with and without Down syndrome. Factors that increase the surgical risk are young age, severe AV valve regurgitation, hypoplasia of the LV, increased and fixed PVR, and severe preoperative symptoms. Other defects (e.g., double-orifice mitral valve, single left-sided papillary muscle, additional muscular VSD) increase the surgical risk. The hospital mortality rate for complete ECD and TOF (“canal tet”) is around 10%.

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FIGURE 12-22 Schematic three-dimensional reconstructive surgery for complete atrioventricular canal defect. A, Single-patch technique. B, Two-patch technique. (From Backer CL, Mavroudis C: Atrioventricular canal defect. In Mavroudis C, Backer CL (eds): Pediatric Cardiac Surgery. Philadelphia, Mosby, 2003.)

Complications

1. MR becomes persistent or worsens 10% of the time.

2. Sinus node dysfunction resulting in bradyarrhythmias may occur.

3. Although complete heart block occurs rarely (in <5% of patients), it occurs more frequently when mitral valve replacement is required (up to 20% of patients).

4. Postoperative arrhythmias occur and are usually supraventricular.

Special Situations

1. Because of the early development of pulmonary vascular obstructive disease in patients with Down syndrome and complete ECD, cardiac catheterization should be performed before 3 months of age, and elective surgery should follow shortly thereafter. Down syndrome itself is not a risk factor.

2. Patients with “unbalanced” AV canal with severe hypoplasia of the LV and low PA pressure may receive a combination of the Damus-Kaye-Stansel operation (similar to Fig. 14-62) and a Fontan-type operation. The proximal PA is anastomosed end to side to the ascending aorta, and systemic venous return is channeled to the right PA, bypassing the RV.

3. In patients with TOF and complete ECD (i.e., “canal tet”) who are severely cyanotic, a systemic-to-PA shunt is carried out during infancy. A complete repair is done between 2 and 4 years of age.

4. Parachute deformity of the mitral valve may result in an obstructed mitral orifice. If there is a significant MR, valve replacement may be required.

5. Double-orifice mitral valve (found in 4%) is usually left alone. Incision of the valve may create more problems with MR.

Postoperative Follow-up

1. An office evaluation should be given every 6 months to 1 year.

2. Medications (e.g., diuretics, captopril, digoxin) may be required if residual hemodynamic abnormalities are present.

3. Some restriction of activities may be necessary if significant MR or other complications exist.

Partial Endocardial Cushion Defect

Prevalence

Partial ECD (partial AV canal defect or ostium primum ASD) occurs in 1% to 2% of all CHDs, which is considerably less than the prevalence of secundum ASD.

Pathology

1. In partial ECD, there is a defect in the lower part of the atrial septum near the AV valves without an interventricular communication (see Fig. 12-1). The anterior and posterior bridging leaflets are fused by a connecting tongue to form separate right and left AV orifices (see Fig. 12-16). There are “clefts” in the septal leaflets of the mitral and tricuspid valves. The conjoined leaflets are displaced into the ventricle and are usually firmly attached to the crest of the ventricular septum. The aortic valve and AV valves are distanced from one another, which accounts for the characteristic “goose-neck” deformity in angiocardiograms (see Fig. 12-21).

2. Less common forms of partial ECD include common atrium, VSD of the inlet septum (i.e., AV canal-type VSD), and isolated cleft of the mitral valve. A common atrium, in which the atrial septum is virtually absent, is either a characteristic lesion in patients with the Ellis-van Creveld syndrome or a component of complex cyanotic heart defects such as those associated with asplenia or polysplenia syndrome.

3. Occasional associated anomalies include secundum ASD and persistent left SVC that drains into the coronary sinus.

Clinical Manifestations

History

1. Patients with ostium primum ASD are usually asymptomatic during childhood.

2. History of symptoms such as dyspnea, easy fatigability, recurrent respiratory infections, and growth retardation may be present early in life if associated with major MR or common atrium.

Physical Examination

1. Cardiac findings are the same as those of secundum ASD (see Fig. 12-2), with the exception of a regurgitant systolic murmur of MR (owing to a cleft mitral valve), which may be present at the apex.

2. Mild cyanosis and clubbing may be present in patients with a common atrium.

Electrocardiography

1. “Superior” QRS axis with the QRS axis ranging from −30 to 150 degrees is characteristic of the condition (see Fig. 12-19).

2. RVH or RBBB (with rsR′ pattern in V1) is present, as in secundum ASD.

3. First-degree AV block (i.e., prolonged PR interval) is present in about 50% of cases.

Radiography

The radiography findings are the same as those of a secundum ASD (see Fig. 12-4) except for enlargement of the LA and LV when MR is significant. A characteristic “goose-neck” deformity is seen on a left ventriculogram (see Fig. 12-21).

Echocardiography

1. Two-dimensional and Doppler echocardiography allows accurate diagnosis of primum ASD. The defect is in the lower atrial septum (see Fig. 12-5). No visible or Doppler-detectable VSD is present. The septal portions of the AV valves insert at the same level on the crest of the ventricular septum.

2. A cleft in the anterior leaflet of the mitral valve is commonly imaged (which is directed toward the inlet septum or 9 o’clock direction in the parasternal short-axis view). (In case of “isolated mitral cleft,” the cleft is directed toward the LVOT or 11 o’clock direction in the short-axis view.) Rare abnormalities of the mitral valve include double-orifice mitral valve and parachute mitral valve.

3. The atrial septum may be completely absent (common atrium) in patients with Ellis-van Creveld syndrome.

4. Color-flow and Doppler studies are useful in the detection of stenosis or regurgitation of the AV valve and in the assessment of the RV and PA pressures.

Natural History

1. Spontaneous closure of the defect does not occur.

2. CHF may develop in childhood earlier than with secundum ASD. CHF is related to major MR or other associated defects.

3. Pulmonary hypertension (i.e., pulmonary vascular obstructive disease) develops in adulthood.

4. Arrhythmias occur in 20% of patients.

Management

Medical

1. No exercise restriction is indicated.

2. Anticongestive therapy with diuretics and ACE inhibitors may be indicated for some patients.

3. Device closure of the defect cannot be done.

Surgical

Indications and Timing

The presence of a partial AV canal (or primum ASD) is an indication for surgical repair. Elective surgery can be performed in asymptomatic children between 2 and 4 years of age. Surgery can be performed earlier in infants with CHF, failure to thrive, MR, or a common atrium.

Procedure

Under cardiopulmonary bypass, the primum ASD is closed, and the cleft mitral and tricuspid valves are reconstructed. Some surgeons leave the mitral valve as a trileaflet valve (without suturing the cleft) by performing various mitral annuloplasties. Recently, minimally invasive cardiac surgical techniques with smaller skin incisions have become popular, especially for female patients (discussed under Atrial Septal Defect).

Mortality

The surgical mortality rate is approximately 3%. Risk factors include the presence of CHF or cyanosis, failure to thrive, and moderate to severe MR.

Complications

1. Reoperation is needed in about 15% of the patients who have residual or worsening MR.

2. Atrial or junctional (nodal) arrhythmias occasionally occur.

3. Complete heart block rarely results and requires a permanent cardiac pacemaker.

4. Although rare, subaortic stenosis can develop after surgery.

Postoperative Follow-up

1. Usually no restriction in activity is indicated.

2. Sinus node dysfunction may require permanent pacemaker therapy.

3. Periodic echocardiographic evaluation for the development of subaortic stenosis and for worsening of MR should be performed. Subaortic stenosis develops more frequently after repair of partial ECD than complete ECD.

Partial Anomalous Pulmonary Venous Return

Prevalence

Partial anomalous pulmonary venous return occurs in less than 1% of all CHDs.

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FIGURE 12-23 Common types of partial anomalous pulmonary venous return. A, The right pulmonary veins drain anomalously to the superior vena cava (SVC). Sinus venosus atrial septal defect (ASD) is usually present. B, The right lower pulmonary vein drains anomalously into the inferior vena cava (IVC), usually without an associated ASD. C, The left pulmonary veins drain into the left innominate vein. D, The left pulmonary veins drain into the coronary sinus (CS). LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.

Pathology

1. One or more (but not all) pulmonary veins drain into the RA or its venous tributaries such as the SVC, IVC, coronary sinus, and left innominate vein. The right pulmonary veins are involved twice as often as the left pulmonary veins.

2. The right pulmonary veins may drain into the SVC, which is often associated with a sinus venosus defect (Fig. 12-23A), or drain into the IVC (Fig. 12-23B) in association with an intact atrial septum and bronchopulmonary sequestration (see simitar syndrome in Chapter 15).

3. The left pulmonary veins either drain into the left innominate vein (Fig. 12-23C) or into the coronary sinus (Fig. 12-23D). ASD is usually present with anomalous drainage of the left pulmonary veins.

Pathophysiology

1. Hemodynamic alterations are similar to those in ASD. Pulmonary blood flow increases as a result of recirculation through the lungs.

2. The magnitude of the pulmonary recirculation is determined by the number of anomalous pulmonary veins, the presence and size of the ASD, and the PVR.

Clinical Manifestations

History

Children with PAPVR are usually asymptomatic.

Physical Examination

1. Cardiac findings are similar to those of ASD (see Fig. 12-2).

2. When associated with ASD, the S2 is split widely and fixed. When the atrial septum is intact, the S2 is normal. A grade 2 to 3 of 6 midsystolic murmur is present at the upper left sternal border. A mid-diastolic rumble, resulting from relative tricuspid stenosis, may be present.

Electrocardiography

Right ventricular hypertrophy, RBBB, or a normal ECG may be seen.

Radiography

The findings are similar to those of secundum ASD (see Fig. 12-4).

1. Cardiomegaly involving the RA and RV, prominence of the PA segment, and increased pulmonary vascularity are all present.

2. Occasionally a dilated SVC, a crescent-shaped vertical shadow in the right lower lung (scimitar syndrome), or a distended vertical vein may suggest the site of anomalous drainage.

Echocardiography

The diagnosis of PAPVR requires a high index of suspicion. A systematic attempt to visualize each pulmonary vein should be made during any routine echocardiographic studies.

1. The inability to visualize all four pulmonary veins in the presence of mild dilatation of the RA and RV strongly suggests the diagnosis of PAPVR, especially in the presence of a demonstrable ASD.

2. PAPVR is frequently found in patients with ASD of any type and in those with persistent left SVC.

3. In sinus venosus defect, the chance of anomalous drainage of the right upper pulmonary vein is high.

Cardiac Magnetic Resonance Imaging

Cardiac magnetic resonance imaging can make correct diagnosis of partial anomalous pulmonary venous return, alternative to the invasive cardiac catheterization with exposure to radiation.

Natural History

1. Cyanosis and exertional dyspnea may develop during the third and fourth decades of life. This results from pulmonary hypertension and pulmonary vascular obstructive disease.

2. Pulmonary infections are common in patients with anomalous drainage of the right pulmonary veins to the IVC.

Management

Medical

1. No medical treatment is needed when asymptomatic.

2. Exercise restriction is not required.

Surgical

Indications and Timing

Indications for surgery include a significant left-to-right shunt with a Qp/Qs ratio of greater than 2:1 and, if the anatomy is uncomplicated, a ratio of greater than 1.5:1. Surgery is indicated in patients with scimitar syndrome with severe hypoplasia of the right lung even with a Qp/Qs ratio less than 2:1. Surgery is carried out between the age of 2 and 5 years. Isolated single-lobe anomaly without an ASD is usually not corrected.

Procedures

Surgical correction is carried out under cardiopulmonary bypass. The procedure to be performed depends on the site of the anomalous drainage.

1. To the RA. The ASD is widened, and a patch is sewn in such a way that the anomalous pulmonary veins drain into the LA (similar to that shown in Fig. 14-33B).

2. To the SVC. A tunnel is created between the anomalous vein and the ASD through the SVC and the RA by using a Teflon or pericardial patch. A plastic or pericardial gusset is placed in the SVC to prevent obstruction to the SVC.

3. To the IVC. In scimitar syndrome, the resection of the involved lobe(s) may be indicated without connecting the anomalous vein to the heart. When the anomalous venous drainage is an isolated lesion, the vein is reimplanted to the RA, and an intraatrial tunnel is created to drain into the LA.

4. To the coronary sinus. This defect is repaired in the same manner as for TAPVR to the coronary sinus (see Fig. 14-33, C).

Mortality

Surgical mortality occurs less than 1% of the time.

Complications

1. SVC obstruction for those patients with anomalous drainage into the SVC.

2. Postoperative arrhythmias (usually supraventricular) occur.

Postoperative Follow-up

1. An examination should be done every 1 to 2 years or at longer intervals.

2. No restriction in activities is indicated.