In this chapter, congenital heart defects (CHDs) with a relatively low prevalence that have not been discussed previously are presented briefly.
Aneurysm of the Sinus of Valsalva
In aneurysm of the sinus of Valsalva (congenital aortic sinus aneurysm), there is a gradual downward protrusion of the aneurysm into a lower pressure cardiac chamber that eventually ruptures. Most of the aneurysm arises from the right coronary sinus (80%) and less frequently from the noncoronary cusp (20%). When a sinus of Valsalva aneurysm ruptures, a sinus of Valsalva fistula is formed. The fistula communicates most frequently with the right ventricle (RV) (75%) and less frequently with the right atrium (RA) (25%). Associated anomalies are common and include ventricular septal defect (VSD) (50%), aortic regurgitation (AR) (20%), and coarctation of the aorta. This rare anomaly has been reported primarily in the Asian population.
Unruptured aneurysm produces no symptoms or signs. A small sinus of Valsalva fistula may develop without symptoms. The aneurysm usually ruptures during the third or fourth decade of life. The rupture is often characterized by sudden onset of chest pain, dyspnea, a continuous heart murmur over the right or left sternal border, and bounding peripheral pulses. Severe congestive heart failure (CHF) eventually develops. Chest radiography shows cardiomegaly and increased pulmonary vascularity. The ECG may show biventricular hypertrophy (BVH), first- or second-degree atrioventricular (AV) block, or junctional rhythm.
Patients with small- to moderate-sized unruptured aneurysms probably do not need surgery. Unruptured aneurysms of the sinus of Valsalva that produce hemodynamic derangement should be repaired. When the aneurysm of the congenital sinus of Valsalva has ruptured or is associated with a VSD with or without aortic regurgitation, prompt operation is advisable.
Anomalous Origin of the Left Coronary Artery from the Pulmonary Artery (Bland-White-Garland Syndrome, ALCAPA Syndrome)
In anomalous origin of the left coronary artery from the pulmonary artery (PA), the left coronary artery arises abnormally from the PA. Patients usually are asymptomatic in the newborn period until the PA pressure falls to a critical level after birth. The direction of blood flow is from the right coronary artery, through intercoronary collaterals retrogradely, to the left coronary artery, and into the PA. This results in left ventricular insufficiency or infarction.
Symptoms appear at 2 to 3 months of age and consist of recurring episodes of distress (anginal pain), marked cardiomegaly, and CHF. Significant heart murmur usually is absent, with a rare exception of a heart murmur of mitral regurgitation secondary to myocardial infarction. The electrocardiogram (ECG) shows an anterolateral myocardial infarction pattern consisting of abnormally deep and wide Q waves, inverted T waves, and an ST segment shift in leads I and aVL and the left precordial leads (see Fig. 3-27). Chest radiography may show cardiomegaly (of the left atrium [LA] and left ventricle [LV]) with or without pulmonary edema in advanced cases. Cardiac enzyme changes probably occur, but the relatively slow development of myocardial infarction and the uncertainty of the exact time of infarction may make it difficult to interpret laboratory data. However, knowledge of cardiac enzyme changes seen in adult cases of myocardial infarction helps in the diagnosis of this condition (see Fig. A-2). Cardiac troponin I levels may also increase. The normal level of cardiac troponin I in children is 2 ng/mL or less and is frequently below the level of detection for the assay.
FIGURE 15-1 Doppler examination in the high parasternal short-axis view (left) and in the high parasternal long-axis view of the right ventricular (RV) outflow tract (right) from an infant with anomalous left coronary artery (ALCA) arising from the pulmonary artery (PA) (thin arrows). Heavy white arrows indicate retrograde (red) flow into the main PA from the ALCA as shown in both the frames. AO, aorta; LV, left ventricle. (From Snider AR, Serwer GA, Ritter SB. Echocardiography in Pediatric Heart Disease. Second Edition, 1997, Mosby, Philadelphia, Used with permission.) (see Expert Consult for the color figure).
Two-dimensional echocardiography with color-flow mapping is diagnostic and has replaced cardiac catheterization. The presence of normal origin of both the right and left coronary arteries from the aorta should be routinely checked in every echocardiographic study, especially in newborns. The absence of a normal left coronary artery raises the possibility of the condition and thus the diagnosis can be made in the newborn period before symptoms develop. Color Doppler examination may show retrograde flow into the proximal main PA (Fig. 15-1). The right coronary artery may be seen enlarged. The echocardiographic study also shows the size and function of the left heart. Increased echogenicity of papillary muscles and adjacent endocardium suggests fibrosis and fibroelastosis.
Computed tomography (CT) scans show high-resolution definition of coronary artery anatomy. The use of rapid acquisition (64-detector) scanners and pharmacologic slowing of the heart rate (with beta-blockers), especially in small infants, may be necessary to increase the ability to diagnose the condition.
Medical treatment alone carries an unacceptably high mortality (80%–100%). Therefore, all patients with this diagnosis need operation. The optimal operation in infancy remains controversial, but most centers prefer definitive surgery unless the patient is critically ill.
In critically ill infants, simple ligation of the anomalous left coronary artery close to its origin from the PA may be performed to prevent steal into the PA. This should be followed by a later elective bypass procedure (as described below).
Even for infants who are critically ill, many centers prefer to create a two-coronary system by performing one of the following procedures.
FIGURE 15-2 Intrapulmonary artery tunnel repair for anomalous origin of the left coronary artery (LCA) from the pulmonary artery (PA) (Takeuchi repair). A, Two dashed lines on the anterior wall of the PA are the proposed incision sites to create a flap of the PA. B, An aortopulmonary shunt is created after a punch hole (5–6 mm in size) is made in the contiguous wall of the aorta (Ao) and PA. C, The flap of the PA is sutured in place to form the convex roof of a tunnel through which aortic blood passes to the anomalous orifice of the left coronary artery. D, A piece of pericardium is used to close the opening in the anterior wall of the PA. E, Cross-sectional view of the tunnel operation when completed. LV, left ventricle; RA, right atrium; RV, right ventricle.
Intrapulmonary Tunnel Operation (Takeuchi Repair)
Intrapulmonary tunnel operation is the most popular among two-coronary repair surgeries (Fig. 15-2). Two circular openings are made in the contiguous wall of the aorta and the pulmonary trunk, and a 5- to 6-mm aortopulmonary window is created by suturing together these two openings. Two horizontal incisions are made in the anterior wall of the PA directly over the aortopulmonary window to create the flap of the PA wall. The flap is sutured in the posterior wall of the PA, and a tunnel is created that connects the opening of the aortopulmonary window and the orifice of the anomalous left coronary artery. The opening in the anterior wall of the PA is closed by a piece of pericardium. The mortality rate is near 0% but as high as more than 20% has been reported. Late complications of the procedure include supravalvular PA stenosis (75%), baffle leak (52%) causing coronary–PA fistula, and aortic insufficiency.
Left Coronary Artery Implantation
Left coronary artery implantation, with direct transfer of the anomalous left coronary artery into the aortic root, appears to be the most advisable procedure, but it is not always possible. The anomalous coronary artery is excised from the PA along with a button of PA wall, and the artery is reimplanted into the anterior aspect of the ascending aorta. If the direct implantation may result in excessive tension in the coronary artery, flaps can be developed from the anterior main PA wall and ascending aorta. These flaps are sutured to form a tube extension for the left coronary artery, which is then implanted to the aorta. The early surgical mortality rate is 15% to 20%.
Tashiro and colleagues (1993) reported a repair technique that was performed in adult patients. In this procedure, a narrow cuff of the main PA, including the orifice of the left coronary artery, is transected; the upper and lower edges of the cuff are closed to form a new left main coronary artery; and the aorta and the newly created left coronary artery are anastomosed side to end. The divided main PA is anastomosed end to end. This creates no obstruction to the PA. This technique has a potential application in the pediatric population, including small infants.
Subclavian–to–Left Coronary Artery Anastomosis
In subclavian–to–left coronary artery anastomosis, the end of the left subclavian artery is turned down and anastomosed end to side to the anomalous left coronary artery through a left thoracotomy approach. Aortic cross-clamping, which could be the source of ventricular impairment with postoperative low cardiac output and a high mortality rate, is avoided.
FIGURE 15-3 Diagram of aortopulmonary window (A) and persistent truncus arteriosus (B). These two conditions are similar from a hemodynamic point of view. Anatomically, however, there are two separate semilunar valves (aortic valve [AoV] and pulmonary valve [PV]) without associated ventricular septal defect (VSD) in aortopulmonary window, but there is only one truncal valve (TV) with associated VSD in persistent truncus arteriosus. AO, aorta; PA, pulmonary artery.
The need for simultaneous mitral valve reconstruction at the time of definitive surgery is controversial because spontaneous improvement of mitral regurgitation (MR) occurs after surgical revascularization. After successful two-coronary artery repair, LV systolic function and heart failure improve markedly, and the severity of the MR also decreases. Even the infarct pattern on ECG may eventually disappear.
Aortopulmonary Septal Defect
In aortopulmonary septal defect (also known as aortopulmonary window, aortopulmonary fenestration), a large defect is present between the ascending aorta and the main PA (Fig. 15-3). This condition results from failure of the spiral septum to completely divide the embryonic truncus arteriosus.
Hemodynamic abnormalities are similar to those of persistent truncus arteriosus and are more severe than those of patent ductus arteriosus (PDA). CHF and pulmonary hypertension appear in early infancy. Peripheral pulses are bounding, but the heart murmur is usually of the systolic ejection type (rather than continuous murmur) at the base.
The natural history of this defect is similar to that of a large untreated PDA, with development of pulmonary vascular disease in surviving patients. This defect has no known tendency to close spontaneously. Prompt surgical closure of the defect under cardiopulmonary bypass is indicated when the diagnosis is made. The surgical mortality rate is very low.
Arteriovenous Fistula, Coronary
Coronary artery fistulas are the most common congenital anomalies of the coronary artery, representing nearly half of all coronary artery anomalies. It can be isolated or associated with other CHDs, such as tetralogy of Fallot (TOF), atrial septal defect (ASD), PDA, and VSD. The right coronary artery is much more frequently involved than the left, and rarely both coronary arteries are involved.
These fistulas occur in one of two patterns.
1. “True” coronary arteriovenous fistula. This pattern occurs in only 7% of the cases of coronary fistulas (Fig. 15-4). This fistula involves a branching tributary from a coronary artery coursing along a normal anatomic distribution and eventually entering into the coronary sinus.
2. Coronary artery fistula (or coronary-cameral fistula). In the majority of cases (>90% of patients), the coronary fistula results from an abnormal coronary artery system with aberrant termination rather than true arteriovenous fistula. The right coronary is most commonly involved in coronary artery fistula. In more than 90% of reported cases, the fistula terminates in the right side of the heart (either to the RV or the PA; less commonly to the RA). It rarely terminates in the left side of the heart, but when it does, the majority enters the LA.
Patients usually are asymptomatic. However, congestive heart failure may develop if the shunt through the fistula is large. With a significant shunt, a continuous murmur, similar to the murmur of PDA, is audible over the precordium (rather than in the left infraclavicular area). The ECG usually is normal but may show right ventricular hypertrophy (RVH) or left ventricular hypertrophy (LVH) if the fistula is large. Chest radiography shows a normal heart size.
FIGURE 15-4 Aortogram showing coronary arteriovenous fistula in the distribution of the left circumflex artery (solid arrows). A, Anteroposterior projection. B, Lateral projection. The fistula empties through the coronary sinus (cs) and eventually into the right atrium (RA). The point of entry into the RA is marked by an open arrow. AO, aorta.
Echocardiographic studies usually suggest the sites and types of the fistulas. The presence of a massively dilated proximal portion of one coronary artery while the other coronary artery is of normal size suggests coronary artery or arteriovenous fistula. The dilatation is usually uniform. One can follow the course of the dilated coronary artery to its site of entry. The site of entry can usually be located with the help of color Doppler echocardiography by the detection of either continuous or diastolic high-velocity flow. Often selective coronary artery angiography is necessary for an accurate diagnosis before the intended intervention. If the flow through the fistula is large, then the chamber or vessel receiving the fistula will be dilated.
A tiny coronary artery fistula to the PA (coronary artery–to-PA fistula) that produces no symptom can only be detected incidentally by an echocardiographic study. Most children with this condition are asymptomatic. Spontaneous closure may occur in small fistulae. However, some patients may present with symptoms of dyspnea on exertion, increased fatigability, and possibly signs of high-output congestive heart failure. Rarely, adult patients may present with angina, palpitation, or signs of exercise-related coronary insufficiency.
Small fistulous connections in the asymptomatic patient may be monitored. For a moderate or large coronary artery fistula, transcatheter occlusion is reasonable using coils or other occluding devices. Elective surgery is indicated if not amenable to catheter occlusion. Using cardiopulmonary bypass, the fistula is ligated as proximal as can be done without jeopardizing flow in the normal arteries, and it is ligated near its entrance to the cardiac chamber. The surgical mortality rate is 0% to 5%.
Arteriovenous Fistula, Pulmonary
In this condition, the pulmonary arteries and veins communicate directly, bypassing the pulmonary capillary circulation. The fistulas may take the form of either multiple tiny angiomas (telangiectasis) or a large PA–to–pulmonary vein (PV) communication. About 60% of patients with pulmonary arteriovenous fistulas have hereditary hemorrhagic telangiectasis (Rendu-Osler-Weber syndrome), and 5% to 15% of patients with the syndrome have the fistula (see Table 2-1). Patients who have undergone a bidirectional Glenn operation are at risk of developing multiple pulmonary arteriovenous fistulas, although these malformations rarely occur after completion of a Fontan operation. This finding suggests that pulmonary circulation requires as yet undetermined hepatic factors, possibly vasoconstrictor prostaglandins, to suppress the development of arteriovenous malformations. Similarly, chronic liver disease can rarely be the cause of the arteriovenous fistula.
Desaturated systemic blood from the PAs reaches the PVs, bypassing the lung tissue, resulting in systemic arterial desaturation, cyanosis, and clubbing. The pulmonary blood flow and pressure remain unchanged, and there is no volume overload to the heart, unlike in systemic AV fistulas.
Physical examination may reveal cyanosis and clubbing. The peripheral pulses are not bounding. A faint systolic or continuous murmur may be audible over the affected lung in about 50% of patients. Polycythemia usually is present, and arterial oxygen saturation runs between 50% and 85%. Chest radiography shows normal heart size because there is no volume overload to the heart in pulmonary AV fistulas. One or more rounded opacities of variable size may be present in the lung fields. The ECG usually is normal. Occasional complications include stroke, brain abscess, rupture of the fistula with hemoptysis or hemothorax, and infective endocarditis.
The diagnosis can be made through contrast two-dimensional echocardiography by the appearance of microcavitations (bubbles) in the LA. In this technique, 4 to 10 mL of saline that has been agitated is injected into a peripheral vein while the appearance of bubbles in the atria is monitored. The bubbles appear first in the RA, and within 2 cardiac cycles, they appear in the LA. CT typically shows one or more enlarged arteries feeding a serpiginous or lobulated mass and one or more draining veins. Magnetic resonance imaging (MRI) has not been studied as much as CT in children. Pulmonary angiography remains the gold standard to determine the position and structure of abnormal vascular lesions in the lung before treatment.
Transcatheter occlusion is recommended for all symptomatic patients and for asymptomatic patients with discrete lesions with feeding arteries 3 mm or larger in diameter. Transcatheter occlusion has been proved to be effective with excellent long-term results. Diffuse microscopic pulmonary AV malformations are not amenable to transcatheter occlusion. Surgical resection of the lesions, with preservation of as much healthy lung tissue as possible, may be attempted in symptomatic children, but the progressive nature of the disorder calls for a conservative approach.
Arteriovenous Fistula, Systemic
Systemic arteriovenous fistulas may be limited to small cavernous hemangiomas or may be extensive. In large AV fistulas, there is direct communication (either a vascular channel or angiomas) between the artery and a vein without the interposition of the capillary bed. The two most common sites of systemic arteriovenous fistulas are the brain and liver. In the brain, it is usually a large type occurring in newborns in association with a vein of Galan malformation. In the liver, either localized or generalized hemangioendotheliomas (densely vascular benign tumors) are more common than fistulous arteriovenous malformations. With a large fistula, because of decreased peripheral vascular resistance, an increase in stroke volume (with a wide pulse pressure) and tachycardia result, leading to increased cardiac output, volume overload to the heart, and even CHF.
Physical examination reveals a systolic or continuous murmur over the affected organ. An ejection systolic murmur may be present over the precordium because of increased blood flow through the semilunar valves. The peripheral pulses may be bounding during the high-output state but weak when CHF develops. A gallop rhythm may be present with CHF. Chest radiography may show cardiomegaly and increased pulmonary vascular markings with a large fistula. The ECG may show hypertrophy of either or both ventricles.
Most patients with large cerebral arteriovenous fistulas and CHF die in the neonatal period, and surgical ligation of the affected artery to the brain is rarely possible without infarcting the brain. Surgical treatment of hepatic fistulas is often impossible because they are widespread throughout the liver. However, hemangioendotheliomas often eventually disappear completely. Large liver hemangiomas have been treated with corticosteroids, aminocaproic acid, local radiation, or partial embolization, but the beneficial effects of these management options are not fully established. Catheter embolization is becoming the treatment of choice for many symptomatic patients with AV fistula.
Atrial Septal Aneurysm
An aneurysmal tissue is present in part or all of the atrial septum that shows phasic septal excursion (of 10–15 mm in an adult) protruding into either atria. Atrial septal aneurysm (ASA) is present in 4% of the neonate using a different criterion (of marked mobility of the atrial septum). The prevalence of ASA varies between 0.2% and 1.9% of normal adult patients and up to 8% to 15% of adult stroke patients by transesophageal echocardiographic studies. It is commonly associated with patent foramen ovale (PFO), and together they might play a role in cryptogenic stroke in adult patients. ASA may prove to be a cause of atrial arrhythmias in some patients. See the section on PFO later in this chapter for further discussion of PFO or ASA versus stroke.
Cervical Aortic Arch
In this rare anomaly, the aortic arch is elongated, usually into the neck above the level of the clavicle. The aortic arch is usually right-sided and sometime with the descending aorta on the left, producing an anatomical vascular ring. Sometimes it is associated with arch hypoplasia or abnormal branching of the arch (e.g., anomalous subclavian artery, separate origin of the internal and external carotid arteries, and common origin of both carotid arteries). Rarely, discrete aortic coarctation or stenosis or atresia of the left subclavian artery is seen.
Infants with this condition may present with stridor, dyspnea, or repeated lower respiratory infection, similar to the signs of vascular ring. In adults, dysphagia is a common presenting complaint. A pulsating mass with associated thrill is present in the right supraclavicular fossa. A presumptive diagnosis of cervical aortic arch is made by noting loss of femoral pulses during brief compression of the pulsating mass. Chest radiographs may show a wide upper mediastinum with absence of the aortic knob. Echocardiography, CT, and MRI may be diagnostic. However, an aortogram is often necessary to make an accurate diagnosis of the condition with arch vessel abnormalities.
Treatment is necessary if the cervical arch is complicated by arch hypoplasia; symptomatic vascular ring; or rarely, aneurysm of the cervical arch itself.
Cleft Mitral Valve
Isolated cleft of the mitral valve is a very uncommon defect. There is a cleft in the septal leaflet of the mitral valve, not associated with endocardial cushion defect (ECD). About two thirds of cases are associated with other cardiac defects such as VSD (50%), left ventricular outflow tract (LVOT) obstructive lesions including aortic stenosis (AS) and subaortic stenosis (40%), secundum ASD (20%), and others. About 60% of the patients have syndromes, including trisomy 21, CHARGE association (see Table 2-1), heterotaxia, and others.
On the parasternal view of two-dimensional echocardiography, the cleft is seen in the septal mitral leaflet, directed toward the LVOT (11 o’clock direction) and associated with a varying degree of MR. This contrasts with the cleft associated with ECD that is directed toward the inlet (or posterior) septum (9 o’clock direction) in the same view.
More than half of these patients required surgical repair of the cleft because of an increasing severity of MR. During surgery, the cleft is usually buttressed by means of a Kaye anuloplasty or an anuloplasty band, depending on the age of the patient (Zhu et al, 2009).
Common Atrium (or Single Atrium)
In common atrium (single atrium, cor triloculare biventriculare), either the atrial septum is completely absent or only the vestigial element of a poorly developed atrial septum is present. This is a form of ECD with cleft mitral valve. Patients with asplenia syndrome (with other complex heart defects) have common atrium. This condition is also commonly seen with Ellis-van Creveld syndrome (see Table 2-1).
Symptoms may include shortness of breath and easy fatigability. Occasional infants may be critically ill with heart failure. Cyanosis varies from obvious to very mild, presenting only with exertion. The ECG shows left anterior hemiblock (“superior QRS axis”), as in ECD, and an rsR′ pattern in the right precordial leads, as in ASD. Surgery should be performed early in life because the patients usually have symptoms and are at risk for developing pulmonary vascular obstructive disease. Successful creation of a polyvinyl septum is possible.
Cor triatriatum is a rare congenital cardiac anomaly in which the LA is divided into two compartments by an abnormal fibromuscular septum with an opening (Fig. 15-5, A), producing varying degrees of obstruction of pulmonary venous return. Pulmonary venous and pulmonary arterial hypertension may result. Embryologically, this condition results from failure of incorporation of the embryonic common PV into the LA. Therefore, the upper compartment (accessory LA) is a dilated common PV, and the lower compartment is the true LA. Hemodynamic abnormalities of this condition are similar to those of mitral stenosis in that both conditions produce pulmonary venous and pulmonary arterial hypertension (see Chapter 10).
Important physical findings include dyspnea, basal pulmonary crackles, a loud S2, and a nonspecific systolic murmur. The ECG shows right-axis deviation and severe RVH and occasional right atrial hypertrophy. Chest radiography shows evidence of pulmonary venous congestion or pulmonary edema, a prominent PA segment, and right-sided heart enlargement. Echocardiography demonstrates a linear structure within the LA cavity (see Fig. 15-5, B). Surgical correction is always indicated. Pulmonary hypertension regresses rapidly in survivors if the correction is made early.
Double-Chambered Right Ventricle
Double-chambered RV (anomalous muscle bundle of the RV) is characterized by aberrant hypertrophied muscle bands that divide the RV cavity into a proximal high-pressure chamber and a distal low-pressure chamber. In the majority of patients, VSD or pulmonary valve stenosis is also present.
Clinical manifestations closely resemble those of pulmonary valvular or infundibular stenosis: a loud, grade 3 to 5 of 6 ejection systolic murmur along the upper and mid-left sternal border is present. Two-dimensional echocardiography is usually diagnostic in this lesion. The anomalous muscle bundle can be visualized best from either the subcostal or parasternal view. Color-flow Doppler assesses the severity and identifies the site of the obstruction. MRI may provide the same information as two-dimensional echocardiography. Cardiac catheterization and right ventriculogram should be performed before any intervention. Surgical resection of the bundle, as well as repair of other anomalies, is usually indicated as soon as the diagnosis is made.
FIGURE 15-5 Cor triatriatum. A, Diagram of cor triatriatum. B, Subcostal four-chamber view of an echocardiogram demonstrating a membrane (small arrows) in the left atrium (LA). AO, aorta; LV, left ventricle; PA, pulmonary artery; PV, pulmonary vein; RA, right atrium; RV, right ventricle; VC, vena cava.
In this extremely rare condition, the heart is partially or totally outside the thorax. Most reported cases of ectopia cordis are either thoracic (60%) or thoracoabdominal (40%); rarely, a case may be cervical or abdominal. The thoracic type is characterized by a sternal defect, absence of the parietal pericardium, cephalic orientation of the cardiac apex, epigastric omphalocele, and a small thoracic cavity. The thoracoabdominal type has partial absence or cleft of the lower sternum, an anterior diaphragmatic defect through which a portion of the ventricle protrudes into the abdominal cavity, a defect of the parietal pericardium, and an omphalocele. Intracardiac abnormalities are very common but not invariable; ASD, VSD, TOF, and tricuspid atresia are the most common intracardiac defects. One reported case of the abdominal type (1806) was a healthy French soldier, the father of three children, who died of pyelonephritis.
The treatment and prognosis of the defect are determined by the location of the defect, the extent of the cardiac displacement, and the presence or absence of intracardiac anomalies. Simple sternal cleft with minimal cardiac protrusion can be successfully treated in early infancy. However, in more severe cases, most surgical efforts to put the heart into the thorax have failed because of the smallness of the thorax and kinking of the blood vessels. Patients without omphalocele or intracardiac defects may remain largely asymptomatic and can undergo surgical repair later in childhood.
In hemitruncus arteriosus (origin of one PA from the ascending aorta), one of the PAs, usually the right PA, arises from the ascending aorta (Fig. 15-6). Associated defects such as PDA, VSD, and TOF are occasionally present. Hemodynamically, one lung receives blood directly from the aorta, as in PDA, with resulting volume or pressure overload, and the other lung receives the entire RV output, resulting in volume overload of that lung. Therefore, pulmonary hypertension of both lungs develops. CHF develops early in infancy, with respiratory distress and poor weight gain. A continuous murmur and bounding pulses may be present. The ECG shows BVH, and chest radiography shows cardiomegaly and increased pulmonary vascular markings.
FIGURE 15-6 Hemitruncus. Aortogram showing the right pulmonary artery (large arrow) originating anomalously from the ascending aorta (AO). Coronary arteries are also opacified (small arrows).
Definitive diagnosis is made by echocardiography, angiography, or other imaging modalities. Cardiac catheterization is needed to define the anatomy and assess pulmonary vascular resistance. Early surgical correction (anastomosis of the anomalous PA to the main PA) is indicated.
Idiopathic Dilatation of the Pulmonary Artery
In idiopathic dilatation of the PA (congenital pulmonary insufficiency), pulmonary regurgitation is present in the absence of pulmonary hypertension in asymptomatic children or adolescents. Many regard this as a very mild pulmonary valve stenosis with resulting poststenotic dilatation but subsequent loss of pressure gradient across the pulmonary valve.
A characteristic auscultatory finding is a grade 1 to 3 of 6 low-frequency, decrescendo diastolic murmur at the upper and mid-left sternal borders. The S2 is normal. The ECG usually is normal, but occasional right bundle branch block is present. Chest radiography shows a prominent main PA segment with normal peripheral pulmonary vascularity. Echocardiographic studies reveal a poststenotic dilatation of the main PA and varying degree of pulmonary regurgitation with little or no pressure gradient across the pulmonary valve but with a whirling of blood flow in the PA. The prognosis is generally good, but right-sided heart failure may occur in adult life.
Kartagener’s syndrome consists of the triad of situs inversus (with dextrocardia), paranasal sinusitis, and bronchiectasis. This disorder is inherited as an autosomal recessive trait; males and females are affected with equal frequency. The dextrocardia is a mirror image of normal and is functionally normal. Bronchiectasis is believed to result from a functional defect of the mucociliary epithelium with immotility of the cilia. In addition, affected males are infertile as a result of immobile spermatozoa.
Parachute Mitral Valve
Parachute mitral valve is a severe form of congenital mitral valve stenosis. In this anomaly, all chordae tendineae are thickened and shortened, and they attach to a single posteriorly located papillary muscles, producing severe mitral stenosis. The anterior papillary muscle is usually absent. The diagnosis can be suspected by two-dimensional echocardiography on the parasternal views. In the parasternal short-axis view, only one papillary muscle is imaged. Commonly associated conditions include supramitral ring, subvalvular or valvular AS and COA or the complete “Shone complex,” which is the combination of all or some of these abnormalities.
Patent Foramen Ovale
Patent foramen ovale is a tunnel between the septum secundum and the superior margin of the septum primum. The septum secundum is a thick, concave, muscular structure that expands from the posterosuperior wall and partially partitions the atria. The septum primum, a thin flap, extends from inferiorly and makes a tunnel. During fetal life, the tunnel (foramen ovale) is open and allows a direct flow of inferior vena cava (IVC) blood into the LA, sending blood with higher oxygen saturation to the LA (and eventually to the brain and coronary circulation).
Postnatally, when the pressure in the LA exceeds that in the RA as the result of lung expansion, and resulting increase in pulmonary venous return, the thin flap of the superior end of the septum primum is forced to shut against the septum secundum, thereby resulting in functional closure of the foramen. In most individuals, the foramen ovale is sealed shortly after birth, but for some reason, functional closure does not always occur, resulting in a small left-to-right atrial shunt detectable by color Doppler study. This condition is called “incompetent foramen ovale” (IFO) and is quite common in newborns, presenting in 75% of neonates. Probe patency of a competent foramen ovale is found in 25% of normal adults.
Patent Foramen Ovale Versus Stroke
There are controversies regarding the management of PFO, which has been proposed as a potential cause of cryptogenic stroke in adult patients. Some retrospective observational reports have shown a strong association (but not cause-and-effect relationship) between cryptogenic strokes and both PFO and ASA in adults. The prevalence of PFO was four times higher in stroke patients (40%) than in control participants (10%), and it was much higher (33 times) in patients with both PFO and ASA. Thus, paradoxical embolism via a PFO has been postulated as a possible cause of stroke. The proponents of the hypothesis of paradoxical embolization have advocated closing PFO for secondary prevention of stroke in patients with PFO and in high-risk adult patients without stroke.
However, some evidence casts doubts about this hypothesis, and thus the rationale of closing PFO to prevent recurrence of stroke remains controversial.
1. In these earlier observational studies, transient atrial fibrillation (with LA thrombus formation), emboli from aortic atherosclerotic plaques, and the hypercoagulable state were not ruled out (although the ability to rule out the hypercoagulable state is quite limited at this time).
2. Several recent studies (including a meta-analysis [Overell et al, 2000], a prospective case control study [Mas et al, 2001]), and a prospective population study [Meissner et al, 2006]) suggest that PFO alone does not appear to increase the odd ratio for stroke. ASA alone or in combination with PFO does not appear to substantially increase the odds ratio of stroke. In patients with isolated ASA (without PFO), paradoxical embolization cannot be the cause of stroke.
3. However, patients with ASA have been found to have a higher vulnerability to atrial fibrillation than those without it (Berthet et al, 2000). Atrial fibrillation, even a transient one, is a known cause of cardiogenic embolism.
4. Unless the RA pressure is elevated and frequent venous thrombus formation is demonstrated, hemodynamics do not favor paradoxical embolization in normal individuals with normal RA pressure.
Given these findings, the cause of stroke is more likely systemic embolization rather than paradoxical embolization through PFO; thus, closing of an isolated PFO may not be an effective or justifiable procedure for prevention of stroke. In fact, there is no evidence that closure of PFO (surgical or by device) is superior to medical management (aspirin, warfarin, or both) in preventing recurrence of strokes.
A recent guideline from the American Heart Association and American Stroke Association (Goldstein et al, 2006), which has been endorsed by the American Academy of Neurology, does not support closure of PFO for prevention of recurrent stroke at this time. Rather, it recommends antithrombotic therapy with aspirin or warfarin. PFO closure may be considered for patients with recurrent cryptogenic stroke despite medical therapy.
In the absence of convincing evidence for PFO as a cause of paradoxical embolization in adult patients and the absence of a superiority of PFO closure to medical therapy in adult patients, the rationale for closing PFOs in pediatric patients is at best controversial and may not be justified. It appears prudent to wait until this controversy is cleared before adopting the practice of closing PFOs in pediatric patients.
Pericardial Defect, Congenital
This rare congenital anomaly of the pericardium may be partial or complete. The majority of these cases occurs on the left side (85%), and they are more often complete (65%) than partial. About 30% to 50% of cases are associated with congenital anomalies of the heart (PDA, ASD, TOF, and mitral stenosis), lung, chest wall, or diaphragm. Pleural defect is almost always present.
Unless an associated cardiac anomaly is present, most patients are asymptomatic. Occasionally, a partial defect may produce chest pain, syncope, or systemic embolism secondary to herniation and strangulation of the left atrial appendage. A complete defect may produce vague positional discomfort in the supine or left lateral position.
Congenital pericardial defects are difficult to diagnose preoperatively. Occasionally, chest radiography may show a prominence of the left hilum or the PA caused by herniation of these structures through the partial defect. Complete absence of the left pericardium may be characterized by leftward displacement of the heart and aortic knob or a prominent PA. Echocardiography findings of complete absence of the left pericardium include an unusual cardiac hypermobility (cardioptosis), abnormal swing motion of the heart with each cardiac beat, and an abnormal systolic anterior motion of the ventricular septum (on M-mode). (These findings are similar to the echocardiographic findings of the transplanted heart, in which the donor heart is untethered and is placed in a large potential space.) Traditionally, the appearance of pneumopericardium after the introduction of air into the left pleural cavity was diagnostic. CT or MRI now permits better visualization of absence of the pericardium.
Surgical treatment is recommended only for symptomatic patients. Surgical procedures used in this condition include longitudinal pericardiotomy; partial pericardiectomy; primary closure; partial appendectomy (of the left atrial appendage); and pericardioplasty with pleural flaps, Teflon, or porcine pericardium.
Pseudocoarctation of the Aorta
Pseudocoarctation of the aorta is a condition in which the distal portion of the aortic arch and the proximal portion of the descending aorta are abnormally elongated and tortuous, with narrowing of the aortic isthmus but without significant obstruction. The elongation of the arch frequently produces an increased distance between the origin of the left common carotid and the left subclavian artery. Unlike cervical aortic arch, the aortic arch stays below the level of the clavicle. A variety of CHDs have been reported in association with pseudocoarctation. Physical examination and the ECG are normal when it is not associated with other cardiac defects.
Pseudocoarctation is not a benign entity as once believed because there is tendency for dilatation and aneurysm formation related to turbulent flow across the kink, and it may progress to show a substantial obstruction. Therefore, a close follow-up is required for asymptomatic patients who are without any associated anomalies. Cardiac catheterization (with measurement of pressure gradient) and angiography provide a definitive diagnosis for this condition. Similarly, CT is very helpful in the diagnosis. Surgical intervention may be required if dilatation compresses surrounding structures (e.g., esophagus), or aneurysm formation is present.
Pulmonary Artery Stenosis
PA stenosis accounts for more than 3% of all CHDs.
1. Stenosis of the PA occurs either at the main PA or in the peripheral pulmonary arteries. The most frequent site of stenosis is near the bifurcation as an isolated anomaly. More often it is seen with other CHDs such as valvular pulmonary stenosis, ASD, VSD, PDA, or TOF (in which 20% of the patients have associated peripheral PA stenosis).
2. When associated with cyanotic CHDs (e.g., pulmonary atresia with intact ventricular septum or TOF with pulmonary atresia), the stenosis usually involves multiple branches and multiple sites.
3. It may also be seen in association with other conditions such as rubella syndrome, Williams syndrome, and Alagille syndrome.
4. Some PA stenosis is secondary to surgical procedures, such as previous systemic-to-PA shunts.
1. Mild stenosis of the PAs causes no symptoms. If the stenosis is severe, the RV may hypertrophy.
2. An ejection systolic murmur grade 2 to 3 of 6 is audible at the upper left sternal border, with good transmission to the ipsilateral axilla and back. Occasionally, a continuous murmur is audible with severe stenosis. The S2 is either normal or more obviously split.
3. The ECG is normal with mild stenosis, but it shows RVH with severe stenosis.
4. Chest radiography findings usually are normal.
5. The echocardiogram may show stenosis in the main PA or near the bifurcation, but those in smaller branches cannot be imaged by echocardiography.
a. Significant PA stenosis is clearly present when (1) there is measurable pressure gradient of greater than 20 to 30 mm Hg, (2) RV or main PA pressure is higher than 50% of systemic pressure, or (3) lung perfusion scan shows a relative flow discrepancy between two lungs of 35%/65% or worse. (The normal right-to-left perfusion ratio was found to be 52.5 to 47.5 [±2.1%] rather than the often quoted 55/45 split, which was found to be more than 1 standard deviation greater than the mean [Cheng et al, 2006].)
b. Many significant stenoses may not be demonstrable by pressure gradient because of discrepant blood flow away from the stenotic area or because of low pulmonary flow situation (e.g., with Glenn shunt and Fontan circulation).
c. Lung perfusion scintigraphy had been a useful noninvasive method for determining relative pulmonary flows. However, washout effects from additional blood supply to the lung can make flow quantification inaccurate. Currently, MRI represents the gold standard for assessing differential blood flow to the lungs as derived by flow calculation in the branch pulmonary arteries. In patients with multiple previous stenting of the pulmonary tree, contrast-enhanced CT imaging is preferred. Angiocardiography is the best invasive tool in the diagnosis of peripheral PA stenosis.
1. Mild to moderate PA stenosis usually does not require treatment, but severe cases require some form of treatment.
2. The central (extraparenchymal) type is surgically amenable but the peripheral (intraparenchymal) type is not correctable by surgery; catheter therapy is often the only option.
3. For peripheral PA stenosis, treatment modalities include the use of standard balloon angioplasty, a cutting balloon, and the placement of endovascular stent.
a. Balloon angioplasty using low-pressure inflations has only a limited success rate, approximately 50%, with a 16% recurrence rate. Using high-pressure balloons (that can be inflated to 20–25 atm) appears to improve the effectiveness.
b. Using cutting balloons: Vessels resistant to high-pressure balloon angioplasty respond to either cutting balloon angioplasty alone or that followed by high-pressure ballooning. These techniques are best suited for small, lobar PA branches not amenable to stenting. Cutting balloons have three or four microsurgical blades with a cutting depth of 0.15 mm, which are activated when the balloons are inflated.
c. In contrast, stainless-steel balloon-expandable stents can overcome an obstruction, with an acute success rate close to 100% and a recurrence rate of only 2% to 3%. These stents are balloon dilatable to potential adult diameters of the vessel. This technique has become the primary mode of therapy for branch PA stenosis.
Pulmonary Vein Stenosis
Pulmonary vein stenosis is a very rare anomaly that can be either congenital (or “primary”) or acquired. The primary type is one that occurs without any inciting event, and the acquired type follows either a surgical or interventional procedure.
Congenital (“Primary”) Pulmonary Vein Stenosis
The congenital or “primary” form of stenosis can be isolated to a single PV but most often occurs in multiple veins simultaneously and the severity can be progressive, leading to partial or even total obstruction of flow. The stenosis can be a relatively discrete shelf, a longer segment of narrowing, or a diffuse hypoplasia of PVs. More than 50% of patients with PV stenosis have associated cardiac defects. On the other hand, nearly half of patients with PV stenosis have no associated cardiac anomalies (Latson et al, 2007). The disease may possibly be caused by abnormal proliferation of myofibroblasts in the PV.
Obstruction to pulmonary venous return results in pulmonary edema, pulmonary arterial hypertension, and increased pulmonary vascular resistance, similar to mitral stenosis. The number and severity of the stenosis of the PVs involved determine the timing and severity of symptoms. Most patients with the primary form of the disease present early in infancy with a history of significant respiratory symptoms (with tachypnea and recurrent pneumonias). If only one or two veins are involved, the manifestation may be delayed or the patient may remain asymptomatic for a long time. As the disease progresses, signs of pulmonary hypertension appear. Chest radiography may show localized or diffuse pulmonary edema depending on the number of PVs involved. Hemoptysis may develop in older surviving children.
Signs of pulmonary hypertension in the absence of a readily recognizable cause should raise the possibility of PV stenosis (Latson et al, 2007).
1. Echocardiographic study can visualize all PVs in nearly all patients. The finding of turbulent flow on color Doppler should raise the suspicion of PV stenosis. Monophasic flow or flow velocities above 1.7 m/sec indicate functionally significant stenosis. Normally, early diastolic flow velocity is less than 1 m/sec, and systolic flow velocity is much less than that.
2. MRI has been shown to be very useful in evaluation of PVs, although its applicability is limited by long acquisition time.
3. Multidetector CT angiography is an excellent technique for detailed analysis of the PVs.
4. Angiography provides the most selective detailed views of the PVs. It can be done by selective injection of contrast dye into the major branch or small branches of the PA.
5. Radionuclide imaging may demonstrate reduced flow to the affected portion of the lung that drains by affected PV(s).
Treatment and Prognosis
The prognosis is exceedingly poor in patients with involvement of most or all of the PVs, and long-term survival is rare without treatment. Most of the death is caused by pulmonary hypertensive crisis. Patients with only one or two PVs involved have much more benign courses. Patients with involvement of only one PV survive much longer.
Surgical as well as catheter intervention have a uniformly bad long-term outcome. Surgery can widen the narrowed veins, and interventional procedures can stretch the vessels, but the result is usually short-term solution because the stenosis typically recurs within 1 month to 6 weeks.
1. Surgical relief of stenosis by various techniques (including so-called sutureless techniques) has not improved survival significantly because of progression of the disease. Only 50% of patients survive for 5 years after surgery.
2. Catheter intervention offers only limited success. Balloon angioplasty with low-pressure dilatation follows quick recurrence in most of the patients. High-pressure balloon angioplasty or angioplasty with a cutting balloon may offer a better result. Use of stent has reported no better medium- or long-term results than cutting balloon angioplasty.
3. Pneumonectomy may be necessary for hemoptysis.
4. Lung transplantation can be an option in selected patients.
5. Use of chemotherapy drugs, such as Avastin or Gleevec (alone or in conjunction, depending on the child’s specific disease) is in experimental stage, which may inhibit proliferation of myofibroblast.
Acquired Pulmonary Vein Stenosis
Pulmonary vein stenosis may be secondary to surgery for anomalous pulmonary venous return. Significant stenosis of the PVs occurs in about 10% of patients after surgical repair of total anomalous pulmonary venous return. Rare causes of PV stenosis in adults include neoplasm growth, sarcoidosis, and fibrosing mediastinitis. The most common cause of PV stenosis in adults is radiofrequency ablation procedures done for treatment of atrial fibrillation. These patients usually present with shortness of breath.
In adults, balloon angioplasty of the involved vessels usually leads to a reasonably good initial result, but restenosis occurs in more than 50% of patients within 1 year. Use of cutting balloon angioplasty and further dilatation of stents has been successful in some cases. Use of drug (paclitaxel or zotarolimus)-eluting stents is gaining experience in adult patients with the condition; it appears to offer an excellent stent patency rate (De Potter et al, 2011).
All or some of the PVs from the lower lobe and sometimes the middle lobe of the right lung drain anomalously into the IVC, either just above or below the diaphragm. The appearance of chest radiography resembles a curved Turkish sword, a scimitar, with vertical radiographic shadow along the lower right cardiac border.
In symptomatic infants, associated anomalies (e.g., ASD, PDA, hypoplasia of the right lung and right PA, pulmonary venous obstruction, sequestration of right lung tissue receiving arterial supply from the aorta) are frequent. Left-sided obstructive lesions (e.g., hypoplastic LV, subaortic stenosis, aortic arch obstruction) also are frequently present. Anomalous systemic arterial supply originates in the descending aorta, usually supplies the right lung, and rarely supplies the left lung (pulmonary sequestration). Dextrocardia or mesocardia also is frequently found secondary to hypoplasia of the right lung.
For symptomatic infants, embolization or ligation of the systemic arterial supply to the right lung, if present, may result in improvement of pulmonary hypertension and signs of CHF. In infants with associated ASD, a pericardial tunnel of synthetic patch may be used to direct flow from the scimitar vein through the RA and into the LA. For most symptomatic infants with additional associated defects, the surgical mortality rate is high (up to near 50%).
Children and adults with the syndrome are either minimally symptomatic or asymptomatic, probably because they have a low incidence of associated anomalies. For older children, the anomalous pulmonary venous return can be redirected to the LA, but in patients with associated pulmonary sequestration, the involved lobes of the right lung may need to be resected. In selected older children and adult patients, the anomalous pulmonary venous return can be connected to the LA through a right thoracotomy without the use of cardiopulmonary bypass (Schwill et al, 2010).
Systemic Venous Anomalies
A wide variety of abnormalities appears in the systemic venous system; some of these have little physiologic importance, and others produce cyanosis. Recent developments in the diagnosis and treatment of cardiovascular disorders have brought these anomalies to the attention of cardiologists and thoracic surgeons. Some of these abnormalities produce difficulties in the manipulation of catheters during cardiac catheterization, and preoperative knowledge of systemic venous anomalies is important in cardiac surgery. Therefore, the search for common abnormalities of the systemic veins has become routine in the evaluation of pediatric cardiac patients during echocardiographic and cardiac catheterization.
Two well-known anomalies of systemic veins are persistent left superior vena cava (SVC) and infrahepatic interruption of the IVC with azygos continuation. Rarely, either a persistent left SVC or interrupted IVC drains into the LA, producing cyanosis.
Anomalies of the Superior Vena Cava
Persistent left SVC occurs in 3% to 5% of children with CHDs. The persistent left SVC is connected to the RA in 92% of cases and to the LA (producing cyanosis) in the remainder.
FIGURE 15-7 Schematic diagram of persistent left superior vena cava (LSVC). A, Left SVC drains via the coronary sinus (CS) into the right atrium (RA). The left innominate vein (LIV) and the right SVC (RSVC) are adequate. B, Uncommonly, the RSVC may be atretic. The coronary sinus is large because it receives blood from both the right and left upper parts of the body. C, The coronary sinus is absent, and the LSVC drains directly into the left atrium (LA). The atrial septum is intact. D, The LSVC connects to the LA, and there is a posterior atrial septal defect, which allows a predominant left-to-right atrial shunt. IVC, inferior vena cava; RIV, right innominate vein.
Persistent Left Superior Vena Cava Draining into the Right Atrium
In the most common type, the left SVC is connected to the coronary sinus (Fig. 15-7, A). As a rule, persistent left SVC is part of a bilateral SVC, but rarely the right SVC is absent (see Fig. 15-7, B). A bridging innominate vein is present in 60% of cases.
Isolated persistent left SVC (see Fig. 15-7) does not produce symptoms or signs. Cardiac examination is entirely normal. Chest radiography may show the shadow of the left SVC along the upper left border of the mediastinum. A high prevalence of leftward P axis (+15 degrees or less) has been reported on the ECG. Imaging of a enlarged coronary sinus is often the first clue to the diagnosis of persistent left SVC. Echocardiographic study provides 100% accurate diagnosis of the condition. Treatment for isolated persistent left SVC is not necessary.
Persistent Left Superior Vena Cava Draining into the Left Atrium
Rarely (in 8% of cases), a persistent left SVC drains into the LA, resulting in systemic arterial desaturation (Figs. 15-7, C and D). This is due to failure of invagination between the left sinus horn and LA; therefore, the coronary sinus is absent. Associated cardiac anomalies almost invariably are present. Complex defects, such as cor biloculare, conotruncal abnormalities, and asplenia syndrome, are commonly found. Defects of the atrial septum (single atrium, secundum ASD, primum ASD) are also frequently found.
Clinical manifestations are dominated by the associated complex cardiac defects. In the absence of complex defects, cyanosis is more marked when there is no atrial communication (see Fig. 15-7, C) than when there is an ASD. When there is an ASD (see Fig. 15-7, D), clinical findings resemble those of ASD with left-to-right shunt, with only mild arterial desaturation. Echocardiographic study with color-flow mapping usually provides an adequate diagnosis. MRI is increasingly used to establish the diagnosis of the condition. Cardiac catheterization and selective left SVC angiography establish the diagnosis.
Surgical correction is necessary. When there is an adequate-size bridging vein that connects two SVCs, simple ligation of the left SVC is performed. If the right SVC is absent or a bridging vein is inadequate, the left SVC is transposed to the RA.
Anomalies of the Inferior Vena Cava
Many abnormalities in the formation of the IVC have been reported. Among the significant anomalies are infrahepatic interruption of the IVC with azygos continuation and anomalous drainage of the IVC into the LA, producing cyanosis (Fig. 15-8).
Interrupted IVC with azygos continuation (see Fig. 15-8, A) has been reported in about 3% of children with CHDs. The IVC below the level of the renal veins is normal, but the hepatic portion of the IVC is absent. Instead of receiving the hepatic veins and entering the RA, the IVC drains via an enlarged azygos system into the right SVC and eventually to the RA. The hepatic veins connect directly to the RA. Bilateral SVC also is common. Azygos continuation of the IVC often is associated with complex cyanotic heart defects, such as polysplenia syndrome, double-outlet RV, cor biloculare, and anomalies of pulmonary venous return. Less often, a simple cardiac defect is associated. No case has been reported in association with asplenia syndrome. This defect creates difficulties during cardiac catheterization and can complicate surgical correction of an underlying cardiac defect. This condition is readily diagnosed by echocardiographic studies as well as by MRI. No specific treatment of this condition is indicated.
FIGURE 15-8 Schematic diagram of selected abnormalities of the inferior vena cava (IVC). A, Interrupted IVC with azygos continuation, the most common abnormality of the IVC. The hepatic veins (HVs) connect directly to the right atrium (RA). B, Right IVC draining into the left atrium (LA). C, Absence of the lower right IVC. The IVC drains into the LA through the left superior vena cava (SVC), and the RA drains through the hepatic portion of the IVC. D, Complete absence of the right IVC with communicating vein draining to the azygos vein. L, liver.
IVC connecting to the LA (see Fig. 15-8, B) is an extremely rare condition in which the IVC receives the hepatic veins, curves toward the LA, and makes a direct connection with the chamber. Pathologic persistence of the eustachian valve can result in a clinically similar situation in which a membrane completely excludes the IVC from the RA, with the IVC blood shunted to the LA through either an ASD or a PFO.
Two other extremely rare cases of IVC abnormalities are shown in Figure 15-8. In one of them, the lower end of the right IVC is absent, and the dominant left IVC drains into the LA (producing cyanosis) through the (left-sided) hemiazygos system and persistent left SVC (see Fig. 15-8, C). In the other case, the lower end of the right IVC is absent, and the left IVC drains through the (right-sided) azygos system (see Fig. 15-8, D).