By far the most common clinically significant anomaly of the great systemic veins is persistence of the left superior vena cava (SVC). This vein, after being formed by the confluence of the left jugular and subclavian veins, descends into the chest parallel to the right superior vena cava and anterior to the left-lung hilus, usually entering the greatly dilated coronary sinus along a course normally occupied by the ligament and vein of Marshall. This topographic position is expected because embryologically, a persistent left SVC represents retention of the left anterior and common cardinal veins and the left sinus horn. Anatomically, the hemiazygos vein resembles the normal right-side azygos vein and may approximate it in size (see Plate 5-2).

The right SVC is usually present as well but may be absent. The two venae cavae may be equal in size, or one (generally the left) may be smaller than its counterpart. The left innominate vein, if present, is smaller than normal or may be more or less plexiform.

The coronary sinus ostium (coronary os) is very large because of the increased blood flow through it, detected easily by cardiac ultrasound. Occasionally, a defect is present in the wall between the sinus and left atrium (unroofed coronary sinus). Generally, such a defect results in a left-to-right shunt; that is, left atrial blood enters the coronary sinus and is carried to the right atrium. Hemodynamically, therefore, the anomaly resembles an atrial septal defect. If the defect is extremely large, particularly if the coronary os is small or atretic, the left SVC is said to “enter the left atrium.”

Patients with persistent left SVC present a typical clinical picture consisting of moderate central cyanosis without other symptoms. There is no murmur, and the heart is normal in size. The electrocardiogram (ECG) generally shows signs of left ventricular hypertrophy. Similar but more pronounced findings have been described in the rare cases of isolated drainage of the inferior vena cava into the left atrium.

Absence of the hepatic segment of the inferior vena cava (IVC) is an uncommon anomaly in which the prehepatic portion of the IVC drains into the right atrium by way of an enormously enlarged azygos vein. The hepatic veins empty into the right atrium by way of a short common stem that normally forms the most proximal part of the IVC (see Plate 5-2). Although azygos drainage of the IVC occurs rarely as an isolated lesion, usually it is associated with other serious cardiac anomalies (e.g., asplenia or polysplenia syndrome).

Other systemic venous anomalies, including double inferior vena cava (see Plate 5-2), generally involve the IVC bed and are of more importance to general surgeons and urologists than cardiologists and cardiac surgeons. Patients with significant cardiac anomalies associated with various types of partial inversion of the thoracic or abdominal viscera are particularly prone to harbor anomalies of the great systemic venous trunks. Because such anomalies may cause difficulties at surgery, their presence or absence should be clearly established as part of the diagnostic workup, most easily through angiocardiography, computed tomography (CT), or magnetic resonance imaging (MRI).

In total anomalous pulmonary venous connection (TAPVC), all the pulmonary venous blood enters the systemic venous system or the right atrium. An ASD or patent foramen ovale is always present. Types of TAPVC are distinguished by how the pulmonary venous blood enters the systemic circuit (see Plate 5-3). Embryologically, the intrapulmonary veins are derived from the venous plexus around the foregut and anastomose freely with the systemic veins early in the embryo. After the embryonic main pulmonary vein has appeared as an outgrowth of the primitive left atrium and established connections with the pulmonary venous plexus, the systemic and pulmonary venous anastomotic channels typically are obliterated. If the embryonic pulmonary vein does not develop at all or is obliterated secondarily, some of the anastomotic channels are retained, resulting in TAPVC.

In juxtaposition of the atrial appendages (auricles), the main bodies of the atria are normally located, but there is levoposition of the right atrial appendage. Instead of being to the right of the arterial trunks, the right atrial appendage crosses behind them to appear on their left, interposing itself between the great arteries and the left atrial appendage. Juxtaposition of the atrial appendages has no functional significance because it causes no hemodynamic disturbance itself. Its presence, however, always indicates the coexistence of other major cardiac anomalies. Transposition of the great vessels and a ventricular septal defect are invariably present, and atresia of the tricuspid valve is common. Plate 5-5 also depicts a double aortic arch.

In the rare cor triatriatum, a fibromuscular septum divides the left atrium into a posterosuperior part receiving the pulmonary veins and an anteroinferior part giving access to the mitral valve and left atrial appendage (see Plate 5-5). Cor triatriatum is probably caused by incomplete incorporation of the embryonic common pulmonary vein into the left atrium. The original pulmonary venous ostium is represented by an opening of variable size. Rarely, the septum is imperforate, and the distal pulmonary venous compartment drains through a defect into the right atrium or an anomalous vessel into the systemic venous system. Usually the fossa or foramen ovale is located between the anteroinferior compartment and right atrium.

The severity of symptoms depends on the size of the opening between the two compartments of the left atrium. Respiratory difficulties and dyspnea may be marked, and cardiac failure develops early. If the os is very small, death occurs within the first year of life; if it is larger, symptoms appear later and closely resemble those seen in mitral stenosis, i.e., chronic cough, dyspnea, fatigability, chest pain, and hemoptysis. Cyanosis may be present, and there is marked cardiomegaly. A mild or moderate systolic murmur is usually heard, but a diastolic murmur is seldom present. The ECG usually suggests right ventricular hypertrophy because the pulmonary pressure is elevated. Cor triatriatum is easily diagnosed with transthoracic cardiac ultrasound and other imaging modalities. Surgical repair is relatively simple; the anomalous membrane is excised.

Congenital absence of the spleen rarely occurs alone. Other visceral anomalies are present in most patients, about 60% of whom have the typical asplenia syndrome (see Plate 5-5). The most important feature of asplenia syndrome is the tendency for normally asymmetric organs (e.g., liver, lungs) to develop more or less symmetrically. The stomach may be located on either side or rarely in the midline. Both lungs are usually trilobed and resemble a normal right lung. The heart is generally severely malformed. A single or common ventricle is usually present and an endocardial cushion defect of the complete type often found. Transposition of the great vessels is the rule, usually associated with pulmonary stenosis. The atrial septum is reduced to a peculiar triangular band of muscle that crosses the common atrioventricular orifice. In typical cases, both the right atrium and the left atrium morphologically resemble a normal right atrium (isomerism of atria), meaning that both sinus horns have been incorporated into their corresponding atria. A coronary sinus is therefore absent. TAPVC is typically present. The great systemic veins also tend to develop symmetrically, at times with a bilateral SVC and a large vein entering on each side of the atrial floor, representing a bilateral persistence of the proximal vitelline veins. One of these drains a lobe of the liver (common hepatic vein), and the other drains the opposite lobe and the remainder of the IVC bed. The site of the viscera is impossible to determine (situs ambiguus, or heterotaxy syndrome).

The diagnosis of asplenia syndrome should be suspected in any infant with CHD associated with some form of partial visceral heterotaxy, particularly if cyanosis is present. Howell-Jolly and Heinz bodies are typically present in the peripheral blood smear. The prognosis is poor.

Of the two main types of ASD, the secundum type is more common and is one of the most frequently seen congenital cardiac anomalies (see Plate 5-6). The normal resorptive process that leads to the formation of the ostium secundum in the embryo is exaggerated, and most of the septum primum disappears. Most secundum ASDs are large, and the resulting left-to-right shunt is generally substantial, causing a several-fold increase in pulmonary blood flow. Both the right atrium and the right ventricle dilate and hypertrophy, and the pulmonary arteries enlarge considerably. Even though pulmonary venous return and therefore blood flow in the left atrium are increased, the left atrium does not enlarge because resistance to emptying into the left ventricle is higher than to the right ventricle, and thus it can readily “bleed off” through the defect into the more compliant right atrium. Systemic blood flow is generally at a low-normal rate or occasionally diminished.

The clinical features of ostium secundum ASD are not remarkable, considering the size of the defect and the magnitude of the shunt (see Plate 5-7). Only rarely are infants with ASD symptomatic; in fact, this anomaly is so well tolerated that disabling symptoms usually do not occur until adulthood, when it is the most common congenital cardiac defect. In children and young adults, the only symptoms are mild fatigability and dyspnea on exertion. Many patients are not even aware of the significance of ASDs, recognizing the defects only in retrospect after it has been corrected surgically and they have more energy and breathe more easily. Growth and development are generally normal. The heart is only slightly or moderately enlarged, and a thrill is extremely uncommon in isolated ASD. A left lower parasternal “heave” is often present, but a precordial bulge is seen only in patients with marked cardiomegaly. The murmur heard in ASD is not loud but rather systolic, medium pitched, and of the ejection type, best heard at the base to the left of the sternum. The ASD murmur is caused not by the left-to-right shunt itself but by the increased amount of blood passing through the otherwise-normal pulmonary valve. A similar mechanism is thought to cause the faint, short diastolic murmur heard in the tricuspid valve area (tricuspid flow murmur). Characteristically, the second sound at the upper left sternal border is split, and the splitting is fixed; unlike the variable splitting heard in normal children, the interval between the aortic (A₂) and pulmonic (P₂) components of S₂ remains constant through all phases of respiration; P₂ is often louder than A₂. An ejection click is rare in children but may be present in adults, indicating the presence of pulmonary hypertension.

The classic chest radiograph features of secundum ASD are mild to moderate cardiomegaly, prominent right-sided heart border caused by right atrial enlargement, evidence of right ventricular (RV) enlargement, prominent pulmonary artery segment at left upper heart border caused by dilatation of the pulmonary trunk, and marked hypervascularity of the lung fields. On fluoroscopy, distinct hilar pulsations can easily be seen, called the “hilar dance.” The left atrium is never enlarged, and therefore the esophagus is not displaced posteriorly.

The ECG features are usually unmistakable. Right-axis deviation is the rule, although the axis may be normal or rarely even oriented to the left. Prominent, peaked P waves may be seen in leads II and aV_F and in the right precordial leads. Most cases show an rSr′ or an rSR′ pattern over the right precordium, indicating mild to moderate RV enlargement. An rR′, an Rs, and particularly a qR pattern, not typically seen in children, indicate more severe RV hypertrophy, as seen with the development of pulmonary vascular changes and hypertension.

At cardiac catheterization, it is usually easy to enter the left atrium through the secundum defect, particularly when this is carried out from the femoral venous circulation. A distinct increase in oxygen content of the right atrium and an early opacification of the right atrium, on selective left atrial angiocardiography, demonstrate the presence of an ASD. RV and pulmonary artery pressures are normal or only slightly elevated in most children and young adults. Pulmonary hypertension may be present occasionally in early infancy or late in the disease course. A slight (10-15 mm Hg) pressure gradient across the pulmonary artery valve is common and does not, as a rule, indicate organic pulmonary valve stenosis, because it disappears after surgical closure of the defect.

Generally the clinical, chest radiograph, eECG, and cardiac ultrasound findings are so characteristic that many cardiologists do not hesitate to refer ASD patients to a surgeon, without catheterization or angiocardiographic studies. Medical treatment is often not required, but symptoms. (e.g., arrhythmias) should be treated as in any other cardiac condition. In children, cardiac failure rarely occurs, except in infants with very large defects. Bacterial endocarditis, the bane of many types of CHD, is extremely rare in uncomplicated ASD.

Surgical treatment ensures complete cure and should always be advised because surgery is easily done, employing cardiopulmonary bypass, and carries minimal risk. The ASD can usually be closed by direct suture. Because the defect is so well tolerated, surgery can safely be postponed until the child is 8 to 10 years or older. Percutaneous approaches using a septal occluder device (e.g., Amplatzer) have now become the transcatheter procedures of choice in patients, replacing the need for cardiopulmonary bypass (see Plate 5-8).

Extremely large secundum defects, involving practically all the septum and referred to as common atrium, are seldom seen. The symptoms tend to be more pronounced, and slight arterial desaturation may be present because of easy mixing of blood at the atrial level. A prosthesis, consisting of a free pericardial graft, is usually necessary to close the defect (see Plate 5-6).

In the sinus venosus type of ASD, the region of the fossa ovalis is normal, the defect being located high in the septum at the ostium of the superior vena cava, which tends to straddle the defect (see Plate 5-6). Partial anomalous pulmonary venous return is almost always present. Such anomalous veins usually drain the right upper lobe and the middle lobe. The embryology of this much rarer kind of atrial septal defect is not clear. The clinical picture and the radiographic and electrocardiographic findings are similar to those described above.

Surgical correction of this defect may require the use of a pericardial patch to reroute the anomalous venous return to the left atrium and simultaneously close the ASD without compromising the lumen of the superior vena cava or the pulmonary veins.

A third variety of anomalous interatrial communication is the “ostium primum” defect. Although some of its clinical features resemble other types of ASD, the ostium primum ASD differs significantly in other ways, and it is not truly a defect of the “atrial septum proper.” The primum ASD is caused by a developmental anomaly of the embryonic atrioventricular endocardial cushions (see Plates 5-9 and 5-10).

Characteristic clinical features include the early appearance of moderate to marked cyanosis, progressing with time and increasing with crying. Cerebral hypoxic spells, similar to those seen in tetralogy of Fallot are occasionally seen, consisting of a sudden deepening of cyanosis, crying, lethargy, and at times unconsciousness. The episodes usually last only a few minutes but may lead to the death of the infant (see Plate 5-11).

Clubbing of the digits is never present at birth and takes time to develop, generally not well marked until about 3 months of age. The few children who live for any length of time usually have dyspnea on exertion (or even at rest) and fatigability. Occasionally a child may squat, but this is not a characteristic feature as in tetralogy of Fallot. Cardiomegaly is typically absent in patients of tricuspid atresia, with no precordial bulge. A systolic thrill is rare. The apical heart sounds are unremarkable; S₂ at the base is normal or slightly increased and single, with P₂ greatly diminished or absent as a result of the reduced pulmonary blood flow. Typically, there is a harsh systolic murmur of moderate intensity, best heard at about the third left interspace parasternally.

On chest radiography the heart is either normal in size or only very slightly enlarged. The right border of the heart is prominent because of the enlarged right atrium; the left border may have a peculiar angulated or squared-off appearance, and the pulmonary artery segment is reduced or absent. The vascularity of the lung fields is diminished. The ECG is much more helpful in arriving at a diagnosis. Left-axis deviation, left ventricular (LV) hypertrophy, and right atrial hypertrophy are invariably present. These are so typical for tricuspid atresia and so unusual in other types of cyanotic CHD that any cyanotic baby showing left-axis deviation and LV hypertrophy on the ECG, and without cardiomegaly, should be considered to have tricuspid atresia. The P waves are generally tall and peaked (often very tall), indicating right atrial enlargement. Cardiac ultrasound and MRI can easily define the anatomic pathology, including shunts, valve regurgitation, and ventricular function.

Cardiac catheterization to obtain hemodynamic data generally should not be done; it contributes little to what is already known or suspected on clinical grounds, merely adding another stressful procedure for the very sick infant to undergo. If cardiac catheterization and angiography must be done, a simple venous angiocardiogram or a selective right atrial angiocardiogram confirms the diagnosis. Opacification of the right atrium is rapidly followed by visualization of the left atrium, left ventricle, and great vessels. Generally, there is a typical, more or less triangular filling defect between the opacified right atrium and the left ventricle. Cardiac magnetic resonance angiography (MRA) with contrast can confirm the anatomy as well. This area is normally occupied by the inflow portion of the right ventricle. An LV injection in the lateral position shows the diminutive right ventricular outflow portion to be filling by way of the VSD.

Treatment is surgical and can be only palliative. The surgery focuses on increasing pulmonary blood flow, which can also be accomplished in the newborn using prostaglandin E₁. PGE₁ relaxes smooth muscle in the ductus arteriosus and keeps it patent to provide temporary blood flow from the aorta to the pulmonary artery. This palliation allows time for patients with tricuspid atresia to mature to the point where a surgical procedure can be performed safely. Blalock-Taussig (subclavian to pulmonary artery anastomosis), classic Glenn (right atrium to pulmonary artery), or a Fontan (variations of vena cava to pulmonary artery) procedure provides flow to the pulmonary circulation in these patients, who depend on pulmonary blood flow for survival. These surgical procedures require the pulmonary artery pressure to be low in order for flow to enter the pulmonary circulation from the vena cava or right atrium.

A side-to-side anastomosis of the ascending aorta to the pulmonary artery can substitute for the Blalock-Taussig shunt. In the Glenn procedure, the proximal pulmonary artery is ligated, as is the superior vena cava, between the anastomotic site and the right atrium (see Plate 5-12). This operation has the considerable advantage of bringing blood directly from a large systemic vein to the right lung, thus entirely bypassing the right side of the heart. Unfortunately, it is not suitable in very small infants, who are at the highest risk and comprise the majority of cases of tricuspid atresia, because the low-pressure shunt between the small vessels has a strong tendency to thrombose, with disastrous results. This is also characteristic, but to a lesser extent, of the Blalock-Taussig operation. The Fontan procedure is another option to transfer venous blood directly into the pulmonary artery (see Plate 5-11).

Of the other (much rarer) forms of tricuspid atresia, those with a moderately large VSD and a normal to slightly increased pulmonary vascular resistance carry a much better prognosis and may not require surgery. A form that has a fairly good prognosis is that associated with transposition of the great vessels and a mild to moderate subpulmonic stenosis.

As an isolated malformation, Ebstein’s anomaly of the tricuspid valve is less common than tricuspid atresia. However, Ebstein’s malformation is of considerable clinical importance because most patients reach childhood, adolescence, or even adulthood, and therefore it must be much better tolerated than tricuspid atresia. In principle, Ebstein’s anomaly consists of a downward displacement of the tricuspid valve “origin.” The valve cusps, except for the medial two thirds of the anterior cusp, appear to originate from the right ventricular (RV) wall, often as low as the junction of the inflow and outflow portions of the right ventricle, instead of from the tricuspid annulus. The valve tissue is almost always redundant and wrinkled, and the chordae tendineae are poorly developed or absent (see Plate 5-13).

Embryologically, Ebstein’s malformation can be considered an abnormality in the undermining process of the RV wall, which normally leads to liberation of the inner layer of ventricular muscle. This process should continue until the atrioventricular junction is reached. Much of the apical portion of the valve “skirt” thus formed is normally resorbed, until only papillary muscles and narrow strands remain. The latter become fibrous (chordae tendineae), as do the valve cusps themselves. In Ebstein’s anomaly the process of undermining apparently is incomplete and does not reach the annulus. Individual cases vary greatly in this respect, and instead of cusps, chordae tendineae, and papillary muscles, there often are sheets of valve tissue with few or no chordae tendineae incorporating the papillary muscles. The anterior cusp is “liberated” very early in embryonic life, which may explain why this cusp always originates normally. The actual valve opening, located close to the crista supraventricularis, is usually much smaller than the normal tricuspid ostium, and the valve is almost always incompetent.

The downward displacement of the valve divides the right ventricle into two parts: (1) an “atrialized” part between the normal annulus and the abnormal valve origin and (2) the normal outflow portion of the right ventricle. The size of the “atrialized” portion of the right ventricle varies greatly, and its wall may be fibrous and paper thin or muscular and quite normally formed. Rarely, the valve is imperforate, or its free portion is practically nonexistent. The pulmonary valve may be stenotic or rarely atretic.

The clinical features are highly diverse, an expression of the considerable variability of the Ebstein’s pathology. In general, the larger and thinner walled the atrialized RV part, the smaller will be the remaining normally developed RV part. Also, the greater the insufficiency of the tricuspid valve, the more serious will be the hemodynamic situation. In severe cases, symptoms (cyanosis, dyspnea, feeding difficulty) may begin in the neonatal period (see Plate 5-14). The early occurrence of heart failure is an ominous sign and is usually followed by death within weeks. In milder cases, symptoms may not appear until later in childhood. Occasionally, the degree of malformation is slight and is compatible with a fairly active and normal life. Cyanosis and clubbing are usually present in older children, who tend to be underdeveloped and thin. Cyanosis in infancy often subsides temporarily, only to reappear later. Fatigue is a prominent symptom, along with exercise intolerance and dyspnea on effort. Cardiac arrhythmias are very common, usually consisting of some form of supraventricular tachycardia.

The patient with Ebstein’s anomaly almost always has considerable cardiomegaly on both the left and the right side, because of enlargement of the right atrium and the “atrialized” right ventricle, and the peripheral pulses are weak. The apical impulse is diffuse and poorly felt. A precordial bulge and thrill are unusual. S₁ is of normal intensity and often is split, with the second component loud; S₂ is generally normal. A loud, early diastolic S₃ is heard along the left lower sternal border, and S₄

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