Principles of Surgery, Companion Handbook - page 19

Chapter 17 Congenital Heart Disease

Principles of Surgery Companion Handbook

CHAPTER
17
CONGENITAL HEART DISEASE

 Classification
 Pathophysiology
 Examination
Principles of Care
Obstructive Left-Sided Lesions
 Coarctation of the Aorta
 Interrupted Aortic Arch
 Aortic Stenosis (Valvular/Subvalvular/Supravalvular)
 Congenital Mitral Valve Disease
 Cor Triatriatum
Increased Pulmonary Blood Flow (Left-to-Right Shunts)
 Patent Ductus Arteriosus (PDA)
 Aortopulmonary Window
 Ventricular Septal Defects
 Atrial Septal Defect (ASD)
 Incomplete Atrioventricular Septal Defect
 Complete Atrioventricular Septal Defects
Cyanotic Lesions
 Tetralogy of Fallot
 Pulmonary Stenosis/Pulmonary Atresia with Intact Ventricular Septum
 Tricuspid Atresia
 Single-Ventricle Complex
 Ebstein's Anomaly
Transposition of the Great Arteries (TGA)
 Double-Outlet Right Ventricle (DORV)
 Truncus Arteriosus
Other Complex Malformations
 Hypoplastic Left Heart Syndrome (HLHS)
 Total Anomalous Pulmonary Venous Return (TAPVR)
 Corrected Transposition
Other Anomalies
 Anomalous Origin of the Left Coronary Artery
 Vascular Rings
 Pulmonary Artery Sling

The incidence of congenital heart disease (CHD) is 8 per 1000 live births and is 10 times more frequent within family members. Etiology usually cannot be established, although rubella in the first trimester is known to cause patent ductus arteriosus (PDA). The genetic abnormality trisomy is associated with a high incidence of CHD.

The fetal heart develops between weeks 3 and 8 of gestation. Incomplete septal formation leads to the varieties of atrial septal defects (ASDs) and ventricular septal defects (VSDs). Abnormalities in septation of the primitive bulbus cordis lead to truncus arteriosus and other anomalies. Of the six branchial aortic arches, only the left fourth and sixth remain. They become the aortic arch and ductus arteriosus, respectively. Remnants of the remaining branchial arches lead to vascular ring malformations.

Fetal circulation is characterized by elevated vascular resistance and little pulmonary blood flow. Most of the blood entering the right atrium is shunted to the left atrium via the foramen ovale, whereas blood reaching the pulmonary artery is shunted into the aorta via the ductus arteriosus. With expansion of the lungs and decreased pulmonary vascular resistance, the flap valve of the foramen ovale is closed [since left atrial (LA) pressure exceeds right atrial (RA) pressure], and then within the first few days of life the ductus closes.

The seven most prominent CHDs are VSD (20 percent), (the following occur in 10–15 percent of patients) ASD, PDA, coarctation of the aorta, aortic stenosis, pulmonic stenosis, and transposition of the great arteries (TGA).

Classification

Congenital heart disease may be classified in five groups by the type of anatomic abnormality present: left-sided obstructive lesions, lesions producing increased pulmonary blood flow, lesions producing cyanosis, complex malformations with mixed physiology, and anomalous origin of vessels and vascular rings.

Pathophysiology

Physiologic abnormalities, such as pressure gradients across stenotic valves, shunts through septal defects, and elevated pulmonary artery pressure, can be diagnosed by echocardiography or cardiac catheterization. Untreated, patients may develop congestive heart failure or severe hypoxemia. Cardiac hypertrophy, irreversible ventricular function, or pulmonary vascular disease can occur.

Obstructive Left-Sided Lesions The most common disorders are aortic valvular stenosis and coarctation of the aorta. These lesions restrict systemic blood flow, resulting in systolic pressure overload and ventricular hypertrophy. Electrocardiogram (ECG) and magnetic resonance imaging (MRI, especially suited for older children) can identify ventricular hypertrophy.

With progressive disease, patients are susceptible to ventricular arrhythmias, and with aortic stenosis there is a risk of sudden death. Surgical intervention should be timed to prevent development of severe hypertrophy and ventricular dysfunction.

Left-to-Right Shunts A defect in the ventricular septum or a connection between the aorta and the pulmonary artery results in a shunt of oxygenated blood from the left-sided circulation to the right side. Shunting through an uncomplicated ASD is also left to right. A left-to-right shunt produces an increase in pulmonary blood flow. The most common defects producing left-to-right shunts are VSD, ASD, PDA, and atrioventricular septal defects.

Pulmonary Congestion Left-to-right shunt is significant when pulmonary blood flow is greater than systemic flow. Increased pulmonary vascular resistance is the late result of increased pulmonary blood flow resulting in an enlarged left ventricle.

Medical management includes vasodilator and diuretic therapy, often with digoxin. Operative intervention is indicated if an infant fails to grow despite medical therapy or if there are complications.

Increased Pulmonary Vascular Resistance Elevated pulmonary blood flow and pressure produce changes in the pulmonary vasculature resulting in a progressive increase in vascular resistance. Pulmonary hypertension subsides as soon as the cardiac defect is corrected. Elevated pulmonary vascular resistance can take longer to resolve, but if halted early, vascular changes may regress. Untreated, children and adolescents with large left-to-right shunts can have irreversible pulmonary vascular disease.

In evaluating pulmonary hypertension, if the pulmonary resistance is elevated, it is helpful to determine whether the vessels are reactive to oxygen, nitric oxide, or other pulmonary dilators. If the pulmonary vasculature bed is active and is capable of dilating in response to stimuli, a child may be a good candidate for operation.

Rarely do permanent pulmonary vascular changes occur before 1–2 years in uncomplicated VSD or PDA, but there is significant individual genetic variation in susceptibility. Infants with trisomy 21 and VSD or atrioventricular septal defect are at increased risk for fixed pulmonary vascular disease; repair at 2–3 months is advised. Most lesions that result in increased pulmonary vascular resistance should be corrected at 3–12 months. Transposition or truncus arteriosus requires operation in the first few weeks of life. Simple ASD rarely requires repair in infancy.

Cyanotic Lesions Right-to-left shunting of systemic venous blood back into the systemic circulation results in arterial hypoxemia and cyanosis. Cyanosis occurs because of the combination of an anatomic obstruction that results in decreased pulmonary blood flow and an intracardiac defect that allows right-to-left shunting of unoxygenated blood (e.g., tetralogy of Fallot, TGA, truncus arteriosus, or tricuspid atresia).

Most physiologic disturbances result from deficient oxygen transport to tissues. Cardiac failure and cyanosis can occur with complex lesions that produce mixing of blood with bidirectional shunting despite normal pulmonary blood flow.

The degree of cyanosis depends on the degree of anoxia and level of reduced hemoglobin (more easily seen in polycythemic states). About 5 g of reduced hemoglobin is required for visible cyanosis. Cyanosis in newborns may be difficult to detect because of higher levels of fetal hemoglobin.

Cyanosis from a pulmonary abnormality results in respiratory distress. Oxygen saturation of blood in the pulmonary veins of less than 95 percent suggests pulmonary disease. Cyanosis from an intracardiac shunt permits direct entry of venous blood into systemic circulation, which is only minimally responsive to inspired oxygen. An increase in pulmonary blood flow, even with a large shunt, can reduce cyanosis and improve oxygen transport.

Clinical features of chronic cyanosis include clubbing of digits or hypertrophic osteoarthropathy, which usually occurs after 2 years of age and slowly resolves after correction of anoxia. Polycythemia is a physiologic response of bone marrow and results in increased viscosity of blood with thrombotic complications (hematocrit > 80 percent associated with cerebral venous thrombosis in infants). Decreased exercise tolerance with dyspnea on exertion (DOE) is another sign. Hypercyanotic spells are a sign of cerebral anoxia and require emergent treatment. Treatment consists of placing the infant in the knee-chest position and administering oxygen, morphine, and phenylephrine. Urgent surgical placement of a systemic-to-pulmonary shunt or early total correction of the defect is indicated if the hypercyanotic spells develop. Brain abscesses may result because of the direct access of bacteria in venous-to-arterial circulation through a right-to-left-sided shunt when there is polycythemia and sluggish capillary flow. Cerebral injury can occur because of paradoxical venous thromboembolism; thrombus can migrate through the venous circulation, transverse the intracardiac defect, and reach the cerebral circulation.

In older children with chronic cyanosis, there is increase in bronchial circulation through the development of aortopulmonary collateral vessels. These may be of significance because of the risk of bleeding during operation and overperfusion of the lungs. Coordinating operative intervention with the occlusion of aortopulmonary collateral vessels is helpful.

Examination

History A maternal history of prenatal exposures, medications, or infections, as well a family history to eliminate hereditary disorders, should be taken. Note the age of the infant when the murmur or symptoms appeared (e.g., cyanosis, poor feeding, increased fatigue).

Physical Examination Assess the infant for growth and development (vital signs, height, weight, head circumference) and particularly for signs of cyanosis (clubbing), respiratory difficulty, or diaphoresis. Note any deformity of the left hemithorax. The chest is palpated for thrill, which indicates significant cardiac disease. Pulses in all four extremities should be felt with simultaneous palpation of the upper and lower extremity pulses to detect PDA or aortic regurgitation. During auscultation, a single second sound may be found in pulmonary valve atresia and tetralogy of Fallot. An excessively loud second sound signifies pulmonary hypertension or TGA. Murmurs should be characterized as to type, intensity, location, and transmission. The presence of rales suggests impaired left ventricular function with elevated pulmonary venous and capillary pressures. The hallmark of congestive failure is hepatic enlargement, which can regress rapidly in response to treatment.

Diagnostic Tests Heart size and contour, lung vascularity, rib notching, and changes in cardiac contour can be noted on chest radiographs. Electrocardiography (ECG) best determines ventricular hypertrophy, axis deviation, and conduction defects. Echocardiogram is noninvasive but precise and sensitive. It is the diagnostic method of choice. Transthoracic echocardiography during pediatric surgery can confirm preoperative diagnosis, monitor ventricular function, and assess adequacy of repair. Transesophageal echocardiography can be applied to infants weighing more than 3 kg. Doppler studies can detect and quantify intracardiac or great vessel shunts and the presence and severity of atrioventricular and semilunar valve regurgitation or stenosis.

Cardiac catheterization is an interventional procedure. It is used for the diagnosis and treatment of simple and complex arrhythmias. The advantages are precise pressure measurements, detection of abnormal shunts, visualization of ventricular or vascular morphology, and calculation of vascular resistance.

PRINCIPLES OF CARE

Preoperative Management Preoperative therapy is determined with attention to oxygenation, acid-base status, fluids, body temperature, and respiratory mechanics. Metabolic acidosis should be corrected immediately. Patients depending on a PDA should be started on intravenous infusion of prostaglandin E1 (0.05 µg/kg/min). Treatment with digitalis, diuretics, or inotropic agents may be necessary. It is not advisable to rush an unstable infant to the operating room before correction of underlying heart failure, correcting metabolic defects by improving perfusion, correcting acidosis, and stabilizing hemodynamics.

Intraoperative Management General anesthesia is induced with central venous access and arterial pressure monitoring. A percutaneous double-lumen internal jugular central venous catheter usually is inserted. A percutaneous radial artery line is inserted. A small Foley catheter is placed, and rectal and tympanic membrane temperatures are monitored.

The use of profound systemic hypothermia during cardiopulmonary bypass allows lower temperatures that give some end-organ protection and allow perfusion with lower flow rates. In patients with complicated anatomy, small infants, or neonates, deep hypothermia and total circulatory arrest may be used to allow safer, more precise intracardiac correction with a better visual field. After repair, the infant is rewarmed.

Hemodilution and systemic inflammatory effects can result in significant postoperative total body volume overload and may lead to transient dysfunction of the heart, lungs, and kidneys. Some suggest aggressive early postoperative ultrafiltration to improve cardiac performance, improve pulmonary compliance and alveolar oxygen transport, and diminish the risk of multiorgan injury.

Postoperative Management Four key areas are hemodynamics; fluids, electrolytes, and renal function; arrhythmias; and mechanical ventilation and respiratory therapy.

OBSTRUCTIVE LEFT-SIDED LESIONS

Coarctation of the Aorta

This occurs in 10–15 percent of patients; it is more common in males than females (3:1). It can represent a spectrum of disease including an isolated obstruction to diffuse hypoplasia, but preductal or “infantile” type represents a diffuse narrowing of the aorta between the subclavian artery and the ductus arteriosus, usually with ductus-dependent blood flow distally. Newborns present with acute heart failure. The condition is associated with other cardiac defects such as VSD, bicuspid aortic valve, and mitral valve anomalies. Coarctation of the aorta, subaortic stenosis, parachute mitral valve, and supravalvular left atrial ring are known as Shone's complex.

Pathophysiology and Clinical Manifestations Neonates present with congestive heart failure, which may include extreme acidosis, renal shutdown, and pulmonary congestion. Diagnosis can be confirmed by echocardiography.

Congestive heart failure after age 1 rarely occurs before age 20. Hypertension is a significant concern. Chest x-ray may establish the diagnosis by demonstrating bilateral notching of the ribs posteriorly; ECG will show signs of left ventricular hypertrophy and left ventricular strain. MRI or enhanced magnetic resonance angiography can establish the diagnosis. Without operative repair, patients die of rupture of the aorta, cardiac failure, rupture of an intracranial aneurysm, or bacterial endocarditis.

Adult type involves more localized narrowing at the site of insertion of the ligamentum arteriosus, and patients may be asymptomatic, presenting with hypertension later in childhood. Headaches, epistaxis, and leg fatigue are the most common symptoms. A combination of hypertension in the upper extremities and absent or decreased pulses in the lower extremities suggests coarctation. Before surgery, patients should be treated with beta-adrenergic blockers.

Operative Technique A left posterolateral thoracotomy in the fourth intercostal space is used. Coarctation usually is readily seen. The mediastinal pleura is incised, and the vagus nerve is retracted medially. The aortic arch proximal to the left subclavian artery, the left subclavian artery, the ligamentum arteriosum, and the distal aorta are serially mobilized. The intercostal arteries are isolated and preserved.

The proximal aorta, left subclavian artery, and distal aorta are occluded, and the coarctation is repaired by one of three techniques: subclavian flap arterioplasty, resection and end-to-end anastomosis, or wide resection with beveled hemiarch anastomosis.

In older children, the distal aortic pressure should be measured to determine the adequacy of flow through the collateral channels. Pressure should be more than 50–55 mmHg. Pressure of less than 45–50 mmHg increases the risk of spinal cord ischemia if the cross-clamp time exceeds 20 min.

After anastomosis, blood pressure should be measured proximal and distal to the site. For neonatal coarctation with VSD, pulmonary artery pressure is measured; if it remains elevated, immediate pulmonary artery banding is performed.

Interrupted Aortic Arch

This is a rare defect. Neonates with interrupted aortic arch (IAA) present 2–3 days after birth with congestive heart failure, acidosis, and hypoperfusion of the lower half of the body. Almost 30 percent of patients with Type B IAA have DiGeorge's syndrome, which is manifest by absence of thymic tissue, hypocalcemia, and immunologic abnormalities.

Anatomy and Physiology In Type A IAA, the interruption is distal to the left subclavian artery (40 percent of patients). Type B IAA results in total interruption of the arch between the left carotid and left subclavian arteries (55 percent of patients). In Type C IAA, the interruption occurs proximally between the innominate artery and the left carotid artery (5 percent of patients).

Most patients also have a large VSD, and some are associated with other left-sided obstructive lesions as well as varying degrees of hypoplasia of the left ventricular outflow tract (LVOT). The aortic valve is bicuspid in 40–50 percent of patients, the aortic annulus may be moderately to severely hypoplastic, and many patients with Type B IAA have subaortic obstruction.

Children with IAA depend on ductal flow for perfusion to the lower extremity; as the patent ductus begins to close, the child develops poor perfusion to the lower body with rapidly progressive metabolic acidosis and renal insufficiency. Severe pulmonary congestion and heart failure develop rapidly.

Diagnosis Diagnosis is made with echocardiography and MRI to determine the site of arch interruption.

Treatment After diagnosis, immediate infusion with prostaglandin E1 is begun. Acidosis is corrected, and inotropic agents are begun to lessen the degree of heart failure and enhance renal perfusion. Intubation and mechanical ventilation may be required. On correction, urgent operation is required.

Type A lesions are repaired through a left-sided incision in the fourth intercostal space. Resection and beveled hemiarch repair are performed. If VSD is present, a pulmonary artery band may be considered. Complete repair through a midline approach can be performed if the VSD is large.

IAA Types B and C should undergo early complete repair through a midline sternotomy with deep hypothermia and circulatory arrest. The coarcted segment is repaired, and a primary end-to-end anastomosis is performed. Associated VSDs are repaired through a right atriotomy incision. When severe LVOT obstruction also is present, the subvalvular obstruction can be corrected with septal myotomy and myectomy. Augmentation of the ascending aorta and arch can be considered for those with multiple levels of obstruction.

Aortic Stenosis (Valvular/Subvalvular/Supravalvular)

Categories Congenital Aortic Stenosis This represents 8–10 percent of patients with CHD. Stenosis may be discrete or can encompass diffuse parts of the LVOT. Critical neonatal aortic stenosis can have diffuse endocardial fibroelastosis within the left ventricle, which, if severe, can become a hypoplastic left heart syndrome. It often is associated with coarctation of the aorta, pulmonary stenosis, mitral valve abnormalities, PDA, and VSD.

It is three to four times more prevalent in males. Supravalvular stenosis is associated with peripheral pulmonary stenosis and Williams' syndrome. It is rare and usually found secondary to VSD, Marfan syndrome and other connective tissue disease, congential stenosis with secondary insufficiency, or rheumatic disease.

Valvular Stenosis This occurs in about 2 percent of the population; 75 percent have a bicuspid aortic valve with varying degrees of annular hypoplasia. A common finding is fusion of the right and left cusps with the undeveloped commissure represented by a median raphe that can extend to the ventricular wall. Thickening of the wall cusp and mild poststenotic dilatation of the ascending aorta occur.

With severe valvular stenosis, more severe deformities such as single-cuspid valve, a small annulus with annular hypoplasia, and diffuse ventricular fibroelastosis are common. The left ventricle can be so underdeveloped as to be unsalvageable. Subvalvular stenosis is rare; pathology ranges from a discrete fibrous ring with localized obstruction to diffuse fibromuscular obstruction. Diffuse fibromuscular subvalvular stenosis or tunnel-like subaortic obstruction results from diffuse fibromuscular narrowing of the subvalvular left ventricular outflow tract. The obstruction usually is concentric and severe.

Idiopathic hypertropic subaortic stenosis (IHSS) is an inherited hypotrophic cardiomyopathy that results in asymmetric septal hypertrophy, systolic anterior motion (SAM) of the anterior leaflet of the mitral valve, and dynamic LVOT obstruction. Symptoms are angina, dyspnea, and syncope. With progressive disease, atrial fibrillation, systemic emboli, and sudden death are significant events.

Supravalvular Stenosis Peripheral pulmonary stenosis should be ruled out; focal stenosis may be present. Thirty percent of patients have associated involvement of the aortic valve cusps; coronary abnormalities are common.

Pathophysiology Physiologic abnormality is directly related to the severity of the obstruction. Some neonates present with severe heart failure and metabolic acidosis requiring intensive therapy and urgent intervention with balloon angioplasty or operative correction. Milder forms may remain asymptomatic for years and slowly develop findings of left ventricular hypertrophy and cardiomegaly, which can lead to significant concentric ventricular hypertrophy or congestive heart failure. Correction should be performed for patients whose gradient is greater than 50–60 mmHg and the cross-sectional area is less than 0.5 cm/m2 and for patients with deteriorating left ventricular systolic function.

Decreased exercise capacity, an abnormal drop in ejection fraction in response to exercise, arrhythmias, and pulmonary congestion on exercise are indications for operation. Operation is indicated when symptoms develop before the onset of irreversible cardiac damage.

Clinical Manifestations Neonates present with congestive heart failure, acidosis, and low-output syndrome. Older children may be asymptomatic or present with fatigue, dyspnea, angina, arrhythmias, and syncope. Physical findings include a systolic ejection murmur, a forceful left ventricular impulse, and a narrow pulse pressure. Pulse pressure can be decreased. Diastolic murmur may indicate concomitant aortic insufficiency.

ECG may indicate the degree of stenosis; echocardiogram accurately determines the transvalvular gradient and annular size and the subvalvular LVOT. MRI delineates anatomy and assesses the aortic arch and peripheral pulmonary arteries. It is indicated in patients with supravalvular stenosis.

Treatment Valvular Aortic Stenosis Neonates require balloon valvuloplasty and surgical valvotomy using cardiopulmonary bypass. Surgical valvotomy is performed with cardiopulmonary bypass and cardioplegic arrest, cutting the fused stenotic area up to the commissure. Overcorrection can result in tearing of the valve and aortic insufficiency.

With valvular stenosis, the fused commissures are incised along the center of the fibrous raphe, leaving a thick margin on each of the two cusps, which are separated. Primitive, thickened hypoplastic leaflet tissue is partially excised. In older children with isolated stenosis from a bicuspid valve, balloon valvuloplasty is the treatment of choice.

Valve replacement is reserved for patients with significant annular hypoplasia or those with recurrent stenosis. Most are treated with the Ross procedure (pulmonary autotransplant). Those with significant annular hypoplasia are treated with extended aortic root replacement using human homograft or the Ross procedure and root enlargement.

Operative mortality for neonates is 10–30 percent; for older children there is a less than 1 percent risk.

Subvalvular Stenosis For patients with a discrete subvalvular ring, the valve cups are retracted and the fibrotic ring excised. Excellent visualization is required to prevent injury to the base of the aortic valve, the mitral valve, or the conduction bundle in the ventricular septum. The fibrous ring usually involves 270 degrees of the circumference of the LVOT; complete excision is required.

To avoid late recurrence and restenosis, if fibromuscular obstruction is found, a block of muscle from the septum is resected.

Tunnel-like or diffuse subvalvular obstruction requires extensive resection of fibromuscular tissue from the LVOT. Patients with severe LVOT obstruction may require aortoventriculoplasty with extended root replacement using homograft or with a combination of the Ross procedure and patch enlargement of the LVOT. These procedures obviate the need for anticoagulation therapy.

IHSS Surgical myotomy and myectomy are indicated in symptomatic patients with an outflow gradient of greater than 50 mmHg despite medications. Using a transaortic approach, a rectangular block of ventricular muscle is excised from the septum, stopping at the level of the anterior leaflet of the mitral valve. Relief of the gradient should be confirmed.

Supravalvular Stenosis With the hourglass type of stenosis, widening the stenotic area by adding a patch of Dacron or pericardium produces excellent results. Before the patch is placed, the fibrous ridge above the sinotubular junction should be excised completely. An alternative is to excise totally the supravalvular ridge of stenosis and perform an end-to-end anastomosis between the distal aorta and the aortic root. Incidence of reoperation is low.

Congenital Mitral Valve Disease

Rheumatic heart disease, endocarditis, and cardiomyopathy can produce mitral valve pathology during childhood; it represents 1 percent of all cases.

Pathology Four types of congenital mitral valve abnormalities are (1) typical congenital mitral stenosis with varying degrees of obliteration and fusion of the chordae tendineae and subvalvular apparatus and mild to moderate deficiency of leaflet tissue (50 percent), (2) “parachute mitral valve,” which is rare and refers to insertion of all the chordae tendineae into a single, shortened papillary muscle, resulting in restricted leaflet mobility with valvular obstruction, (3) mitral stenosis with hypoplasia as part of diffuse LVOT obstruction, representing the most extreme form of this condition (40 percent), and (4) supraannular mitral stenosis, which is rare and results from a supraannular ring of connective tissue in the left atrium.

Associated cardiac malformations occur in 75 percent of patients and include VSD (30 percent), valvular aortic stenosis (29 percent), aortic atresia and hypoplastic left heart syndrome (29 percent), and less severe subvalvular LVOT obstruction (30–60 percent). Abnormal left ventricular muscle with endocardial fibroelastosis occurs in most patients with mitral stenosis and diffuse LVOT obstruction and in nearly 50 percent of patients with mitral valve stenosis.

Clinical Manifestations Symptoms appear in infancy and include dyspnea, orthopnea, and pulmonary edema. Chest x-ray and ECG will demonstrate an enlarged left atrium, pulmonary congestion, and P mitrale of stenotic lesions. Transesophageal echocardiography will identify lesions in the left atrium and the degree of stenosis.

Treatment Operation should be timed to avoid further deterioration of left ventricular function. Repair might not be feasible, and valve replacement might be required.

Cor Triatriatum

This is a variant of total anomalous pulmonary venous drainage, but the unreabsorbed common pulmonary venous sinus empties into the left atrium through a restricted aperture. The common venous chamber is superior and posterior to the left atrium with a diaphragm separating this from the true left atrium. A small opening in the thick muscular diaphragm is the only communication between the upper pulmonary venous chamber and the lower true atrial chamber. This severely obstructs pulmonary venous return and produces supraannular mitral obstruction with left-to-right shunting across any defect in the atrial septum (present in about 70 percent).

Clinical Manifestations This produces severe pulmonary congestion with pulmonary artery hypertension. Congestive heart failure usually is severe. Gradients can be as high as 20 mmHg. If not corrected, 70–75 percent of patients die in the first year of life.

Chest x-ray demonstrates pulmonary congestion and an enlarged right ventricle. ECG shows right ventricular hypertrophy and some pulmonary hypertension.

Treatment Operation should be performed promptly in patients with severe obstruction; less severely obstructed patients with significant left-to-right shunting may be operated on later in childhood.

At operation, the defect is approached through the right atrium, enlarging the septal defect and excising the left atrial membrane to create a common unobstructed left atrial chamber. The atrial defect is closed with a patch of pericardium.

INCREASED PULMONARY BLOOD FLOW (LEFT-TO-RIGHT SHUNTS)

Patent Ductus Arteriosus (PDA)

This is a common form of congential heart disease (10 percent) and is a normal physiologic state in severely premature infants. It is two to three times more common in females than in males. In premature infants, the prostaglandin effect is pronounced, resulting in increased ductal patency. Closure of a PDA can be hastened by administration of indomethacin.

Associated anomalies occur in 15 percent of patients; the most common are VSD and coarctation of the aorta. Depending on the diameter of the ductus, a varying amount of blood is shunted from the aorta to the pulmonary artery. If pulmonary resistance has been elevated for a long period, only partial regression may occur at closure of the ductus; otherwise, resistance decreases immediately to normal.

Clinical Manifestations In premature infants, a large patent ductus can cause serious heart failure; most full-term infants and older children are asymptomatic. When symptoms are present, the most common are palpitations, dyspnea, and decreased exercise tolerance. Symptoms of congestive heart failure may present in adults.

The hallmark of PDA is the continuous “machinery” murmur. With a large ductus, wide pulse pressure usually is evident, produced by a decrease in diastolic pressure. In an extremely large ductus, low-level diastolic pressure may be associated with peripheral vascular findings. Signs of pulmonary congestion may be present. There is an increased risk of bacterial endocarditis.

Diagnosis may be made in premature infants from the widened pulse pressure detected through an umbilical arterial catheter and confirmed by echocardiography. Chest x-ray shows increased pulmonary blood flow. In children, the diagnosis is made from the characteristic murmur and echocardiography. In adults, catheterization measures the pulmonary vascular resistance to assess ductal length and calcification.

Treatment In premature infants, PDA closure can be achieved with indomethacin therapy. Operation is indicated when there is severe respiratory insufficiency. In full-term infants without congestive heart failure, PDA closure can be performed at 6 months to 2 years. Insertion of a specially designed coil results in successful occlusion in most older children. Surgical division is indicated for those with a large-diameter ductus or extremely short length.

For operative closure, the patent ductus is exposed through a short, posterolateral incision in the fourth intercostal space; in premature infants, the patent ductus is doubly ligated. Surgical division is performed in older children by placing a partial occlusion clamp on the aorta adjacent to the ductus, and an angled vascular clamp is placed on the pulmonary artery side of the ductus. The ductus is divided sharply, and each side is oversewn, being careful that the suture line is flush with the aorta to avoid late aneurysm formation because of an unobliterated ductus diverticulum.

Aortopulmonary Window

This is a rare anomaly that results from the incomplete development of the spiral septum dividing the primitive truncus arteriosus into the aorta and pulmonary artery. It usually is located proximally near the ostium of the coronary arteries. The disease progresses rapidly because of the tremendous amount of shunting, resulting in early development of severe congestive heart failure.

Diagnosis is made readily by echocardiography and confirmed by MRI. Operation should be performed on diagnosis. A transaortic approach is used, and large defects are closed with a prosthetic patch.

Ventricular Septal Defects

Ventricular septal defect (VSD) is a common form of congential heart disease (20–30 percent) with no known etiologic factors. Associated anomalies are PDA, coarctation of the aorta, ASD, right ventricular outflow tract obstruction, tetralogy of Fallot, double-outlet right ventricle, TGA, truncus arteriosus, and aortic insufficiency from prolapse of an aortic valve cusp into the VSD.

Pathophysiology The defects are classified according to position: perimembranous, posterior inlet or atrioventricular canal type, outlet or supracristal, and muscular. Perimembranous defects are the most common (80 percent) requiring surgery. These involve the membranous septum. The bundle of His is located along the posterior, rightward rim of the septum, where it bifurcates into left and right conduction bundles. It may extend superiorly into the outlet septum next to the aortic valve annulus.

Inlet or atrioventricular canal type defects are perimembranous defects that extend posteriorly beneath the conal papillary muscle and the tricuspid valve involving the inlet septum. The conduction tissue runs adjacent to the rim of the septum.

Outlet or supracristal defects are in the infundibular septum adjacent of the pulmonary and aortic valves. Aortic insufficiency is common. These defects are away from the conduction bundle.

Muscular VSDs are the most common but may close spontaneously before age 2–3 years and do not require surgery. They are located inferiorly in the muscular septum and often are multiple. VSDs may be classified as restrictive or nonrestrictive depending on whether the right ventricular pressure is elevated to systemic levels. The nonrestrictive defect is equal in diameter to the aortic annulus. With a large, nonrestrictive defect, the right ventricular pressure is equal to systemic pressure, and the left-to-right shunt may be 4:1 or greater. With long-standing defect, the pulmonary resistance may increase significantly, leading to irreversible pulmonary vascular changes, and a right-to-left shunt may develop, which leads to cyanosis (Eisenmenger's syndrome). Small restrictive defects have increased risk of bacterial endocarditis.

Clinical Manifestations Patients with small defects usually are asymptomatic but may have a loud murmur and thrill. With large defects, severe heart failure, dyspnea, and pulmonary congestion are common. Patients may have frequent respiratory symptoms, pneumonia, and lag in growth and development. Severe cardiac failure can occur in the first few months of life or much later in adulthood. Patients may be asymptomatic until cyanosis and hemoptysis develop. Chest x-rays appear normal. ECG usually shows left ventricular or biventricular hypertrophy.

Treatment Small defects should be observed (60–70 percent will close early, 90 percent by 8 years). Large defects depend on cardiac failure and increased pulmonary vascular resistance. Infants with severe cardiac failure require immediate operation; children with large left-to-right shunts require operation at 3–6 months. Criteria for nonoperability vary but include a nonreactive, fixed pulmonary vascular resistance of greater than 10 Woods units.

Operation is performed through a median sternotomy with extracorporeal circulation. The VSD is closed through a right atrial approach, which minimizes the risk of ventricular dysfunction and arrhythmias, or through a short transverse ventriculotomy. It is critical to avoid heart block.

Atrial Septal Defect (ASD)

Malformations involve the atrial septum or the pulmonary veins and include ostium secundum defects, sinus venosus defects with partial anomalous pulmonary venous return, and ostium primum defects. They are common (10–15 percent) and twice as frequent in females as in males.

Pathophysiology ASDs vary in size and location, but the majority are located in the middle part of the atrial septum in the area of the ostium secundum. A high subcaval defect near the orifice of the superior vena cava is referred to as a sinus venosus defect. It is associated with anomalous entry of one or more right pulmonary veins into the superior vena cava with drainage of the upper and middle lobe veins, which enter below the entry site of the azygos vein. Unusual defects include the common atrium, “unroofing” of the coronary sinus, and low ostium secundum defects that extend toward the inferior vena cava. Right pulmonary veins may have a common atrium or be associated with a large posterior ostium secundum defect. Part of the septum may be fenestrated.

Partial anomalous pulmonary veins entering the inferior vena cava is a “scimitar” syndrome and is associated with hypoplasia of the right lung and left-to-right shunt.

A rare variant is ostium secundum defect combined with mitral stenosis (Lutembacher's syndrome). Mitral stenosis retards blood flow from the left atrium to the left ventricle and produces a large left-to-right shunt through the septal defect with massive dilation of the pulmonary arteries.

Clinical Manifestations Children may have symptoms of fatigue, palpitations, and exertional dyspnea. Adults may have congestive heart failure or arrhythmias. Chest x-ray may show mild to moderate cardiac enlargement, as well as an enlarged right atrium and pulmonary artery. ECG will show a right-axis deviation.

Treatment Most children are asymptomatic; operation is recommend on the basis of a large echocardiographic defect with significant left-to-right shunting. Contraindication is increased pulmonary vascular resistance and Eisenmenger's syndrome.

At operation, the patient is placed on cardiopulmonary bypass; the heart is electrically fibrillated or arrested with cardioplegia. The right atrium is opened and the defect closed. Large ostium secundum defects may require patch closure; those with partial anomalous venous drainage are corrected by placement of a pericardial patch so as to recreate the atrial septum, redirecting the anomalous veins into the newly created left atrial chamber. Sinus venosus defects are closed by rerouting the anomalous pulmonary venous blood from the right upper and middle lobe veins across the high sinus venosus defect.

Incomplete Atrioventricular Septal Defect

The terms incomplete atrioventricular septal defect, incomplete atrioventricular canal defect, and ostium primum atrial septal defect are interchangable and account for 4–5 percent of ASDs. Associated abnormalities are an unroofed coronary sinus, PDA, persistent left superior vena cava, coarctation of the aorta, and LVOT obstruction. Twenty percent of patients have Down syndrome.

Pathophysiology There are two anatomic defects. One is a partial cleft in the anterior leaflet of the mitral valve. The other is a complete defect, which separates the entire anterior leaflet in halves. Physiologic abnormalities are a left-to-right shunt and mitral insufficiency.

Clinical Manifestations With significant mitral insufficiency, cardiac failure with pulmonary congestion and dyspnea may be fatal in the first year of life unless corrected. Chest x-ray shows moderate cardiac enlargement; increased pulmonary vascularity is common. ECG will show a left-axis deviation with counterclockwise rotation.

Treatment Operative correction often is performed when the patient is between 1 and 4 years of age. Operation is through a median sternotomy or a small right anterior thoracotomy incision with the patient on extracorporeal circulation. The cleft in the anterior mitral valve leaflet is closed, and the ASD is repaired. To avoid heart block, the sutures are inserted superficially and leftward along the annulus of the mitral valve or rightward in relation to the coronary sinus.

Complete Atrioventricular Septal Defects

Pathophysiology This also is referred to as complete atrioventricular canal defect or complete endocardial cushion defect, and it results from failure of fusion of the endocardial cushions in the central portion of the heart, which causes a large defect involving the atrial and ventricular septum. The central portion of the annulus between the mitral and tricuspid valves also does not form. Eighty percent of patients have Down syndrome.

Rastelli's classification divides the deformity into types A, B, and C based on the presence of clefts or septal attachments in the bridging superior common leaflet. The common atrioventricular valve is a six-leaflet structure that overlies a large septal defect involving the ventricular and the atrial septum. Intermediate or transitional atrioventricular septal defect occurs when all components are present but the VSD is restricted. When a single atrioventricular valve overrides one ventricle by more than 50 percent and the other ventricle is underdeveloped, it is termed unbalanced.

Diagnosis is by echocardiography; catheterization should be done for evaluation of pulmonary hypertension and elevated pulmonary vascular resistance, particularly if the child is more than 6 months old or other lesions are suspected. Catheterization shows a typical “gooseneck” deformity in the LVOT.

Treatment Early complete repair is recommended for most patients before 6 months of age or at 2–3 months if significant congestive heart failure is present. Operation consists of placement of a prosthetic patch to correct the underlying VSD, reattachment of the atrioventricular valve leaflets, and closure of the ostium primum ASD component. Repair may be performed using a single-or double-patch technique; the two-patch approach is preferred because it is more precise and has less late leaflet dehiscence.

CYANOTIC LESIONS

Cyanosis results from any intracardiac defect producing right-to-left shunting of unoxygenated venous blood resulting in systemic oxygen desaturation. Conditions include tetralogy of Fallot, pulmonary atresia, and tricuspid atresia. Conditions evidencing moderate cyanosis and increased pulmonary blood are TGA, double-outlet right ventricle, and truncus arteriosus.

Palliative Shunts The modified Blalock-Taussig (BT) shunt involves placement of an interposition between the subclavian and pulmonary arteries with a 4–5-mm expanded polytetrafluoroethylene (Gore-Tex) graft. It can be performed in neonates and lasts 1–2 years. Another option is a central systemic-to-pulmonary shunt performed through a sternotomy using a 3.4–4-mm Gore-Tex graft from the ascending aorta or the innominate artery to the pulmonary artery. It is technically easy to perform and produces minimal distortion of the pulmonary arteries.

A venous-to-pulmonary shunt is the bidirectional Glenn shunt or hemi-Fontan procedure, which is an end-to-side anastomosis between the divided superior vena cava and the pulmonary artery. This is performed using cardiopulmonary bypass or passive temporary cavoatrial shunt. This shunt improves oxygenation without overperfusion of the lungs and is used in patients with tricuspid atresia, single-ventricle complex, or hypoplastic left heart syndrome.

Currently, transcatheter balloon dilation of the pulmonary valve and arteries combined with coil occlusion of large systemic-to-pulmonary collateral vessels is used for patients with tetralogy of Fallot and small pulmonary arteries.

Tetralogy of Fallot

The four features are (1) malalignment of the ventricular septal defect, (2) dextroposition of the aorta, (3) right ventricular outflow tract obstruction, and (4) right ventricular hypertrophy. All are a result of underdevelopment and anterior malalignment of the infundibular septum, which deviates anteriorly and cephalad, creating a large ventricular defect at the point of nonunion.

The anterocephalad deviation narrows the right ventricular outflow tract and allows the aortic root to “override” the ventricular septum in a rightward direction, producing the malalignment VSD, which is a large, perimembranous defect. This results in systemic pressures in the right ventricle, while concentric right ventricular hypertrophy results from obstruction of the right ventricular outflow tract.

Patients have decreased pulmonary blood flow, cyanosis secondary to right-to-left shunting, and systemic right ventricular pressures with right ventricular hypertrophy.

Clinical Manifestations Most patients with untreated tetralogy of Fallot die from progressive hypoxia with repeated cyanotic “spells” resulting in cardiac arrest, cerebral injury, pulmonary thrombosis, or infection. Brain abscess is a fatal late complication. Patients are symptomatic with exertional dyspnea and cyanosis. Squatting and clubbing of digits are classic manifestations. A systolic murmur of grade II to III is common along the left sternal border; 50 percent have a thrill.

Chest x-ray shows a normal-sized heart with an unusual boot-shaped contour (coeur en sabot). ECG shows right ventricular hypertrophy with right-axis deviation.

Treatment Early correction is the treatment of choice. Infants with early cyanotic spells, hypoplastic or discontinuous pulmonary arteries, and pulmonary atresia require emergent systemic-to-pulmonary shunt for palliation. Patients with underdeveloped pulmonary arteries are treated with balloon dilation of the pulmonary valve or pulmonary vessels.

Repair is performed through a median sternotomy with extracorporeal perfusion and cardioplegic arrest. The VSD is approached through the right atrium or through a right ventriculotomy, and the patch is placed through the tricuspid valve. All areas of potential obstruction are reexamined during operation. After repair, the infundibular outflow tract is inspected, and the main pulmonary artery is opened just above the valve. The main pulmonary artery, pulmonary bifurcation, left and right pulmonary arteries, the pulmonary valve, and the pulmonary annulus are calibrated with Hegar dilators. A transannular incision is made only if the pulmonary annulus is hypoplastic.

If the annular size is adequate and leaflet mobility can be restored, the valve is preserved; a small ventriculotomy is made below the valve to correct any infundibular stenosis, or a resection of the infundibular obstruction is performed through the tricuspid valve. If the annulus is hypoplastic, the incision is extended across the annulus far enough to correct the infundibular stenosis while preserving as much right ventricular function as possible. The transannular incision is closed, tailoring the patch to prevent late aneurysmal formation in the patch.

When the distal pulmonary arteries are severely stenosed or hypoplastic, a valved pulmonary artery homograft may be required to reconstruct the outflow tract; the valve minimizes regurgitation of blood into the right ventricle and lowers the risk of long-term dysfunction.

After cardiopulmonary bypass is discontinued, intracardiac pressure is measured to confirm correction of right ventricular outflow. Right ventricular outflow should be 60–70 percent less than left ventricular pressure; if still elevated, additional correction should be considered. The ratio of right to left ventricular pressure is less than 0.50–0.60 after successful repair, with a pulmonary artery systolic pressure of 20–25 mmHg.

Pulmonary Stenosis/Pulmonary Atresia with Intact Ventricular Septum

This is a common defect (10 percent of congenital cardiac lesions); 50 percent have only valvular pulmonary stenosis. Pulmonary atresia with intact septum results in total obstruction of the outflow tract with atresia of the valve, hypoplasia of the annulus, and degrees of hypoplasia and maldevelopment of the right ventricle (1–3 percent).

Pathophysiology Pathologic findings range from isolated valvular stenosis to total valvular atresia with hypoplasia of the inlet, body, and outflow tract of the right ventricle. Pulmonary stenosis may be mild or critical with a pinhole opening. The valve usually is bicuspid or tricuspid and domed with fused commissures; the annulus may be normal or hypoplastic.

Approximately 40 percent of children with pulmonary stenosis have infundibular obstruction; 10 percent are severe. Pulmonary atresia with intact ventricular septum (PAIVS) presents in newborns with an atretic valve and no forward blood flow; the right ventricle is underdeveloped. The right ventricle is classified according to its degree of development: unipartite, bipartite, and tripartite depending on the adequacy of the inlet, body, and outlet portions. A minimum of bipartite ventricle is necessary if the right heart is to be used in circulation. The ventricle is extremely small, thickened, and hypertensive with myocardial muscular disarray. In 10 percent of patients, sinusoids connect the right ventricle with the coronary circulation, resulting in right ventricular-dependent coronary circulation. The tricuspid valve often is regurgitant; if severely hypoplastic or totally atretic, the patient is treated as having single-ventricle physiology.

With moderate pulmonary stenosis, the obstruction produces an elevation in right ventricular pressure with subsequent ventricular hypertrophy. A gradient of less than 50 mmHg is mild; a gradient of 80–100 mmHg is more severe. With severe stenosis, suprasystemic right ventricular pressures can develop. In patients with critical pulmonary stenosis or PAIVS, most forward blood flow may be absent.

Clinical Manifestations Hypoxia, cyanosis, and acidosis develop shortly after birth. Ductal patency is maintained with prostaglandins until the diagnosis is made. Chest x-ray shows decreased pulmonary blood flow, a flat or concave pulmonary artery segment, and a normal or enlarged heart.

Diagnosis is made by echocardiography. Cardiac catheterization is used for intervention (e.g., balloon dilation). In PAIVS it is used to determine the presence or absence of sinusoids feeding the coronary circulation.

Treatment Treatment of choice for infants with critical pulmonary stenosis and adolescents with moderate to severe isolate pulmonary stenosis is balloon dilation. Patients with hypoplastic outflow tract obstruction or with PAIVS require surgical correction, but operative risk is high. Correction requires cardiopulmonary bypass, a valvotomy and systemic-to-pulmonary shunt, or a transannular patch to relieve outflow tract obstruction plus a systemic-to-pulmonary shunt.

Tricuspid Atresia

This affects 2–5 percent of children with cyanotic heart disease and consists of total atresia of the tricuspid valve and ventricular inlet, hypoplasia of the body and outlet portion of the right ventricle, and an ASD or VSD. Pulmonary atresia or severe pulmonary stenosis is seen in 85 percent. Most patients have total ductus-dependent pulmonary blood flow. TGA occurs in 30 percent. When the aorta and pulmonary artery are transposed, 70 percent have unrestricted pulmonary blood flow with overperfusion of the lungs (single-ventricle complex). Hypoxia is severe because of the absence of blood flow through the atretic tricuspid valve combined with restricted or absent flow across the septal defect and through the rudimentary right ventricle into the pulmonary artery.

Clinical Manifestations Most patients are markedly hypoxic and dyspneic shortly after birth; most die without palliative shunting. Diagnosis is made during days 1–2 of life. Chest x-ray shows decreased vascularity. ECG shows a left-axis deviation. Echocardiogram can establish the diagnosis with certainty.

Treatment Emergency systemic-to-pulmonary shunt usually is required in the first few days or weeks to prevent death from hypoxia. A modified Blalock-Taussig shunt is satisfactory. In some patients, a balloon septostomy is necessary to increase the right-to-left shunt.

After palliative shunting, a modification of the Fontan procedure is performed in which a direct connection between the systemic venous circulation and the pulmonary arteries is constructed. A bidirectional Glenn shunt procedure often is performed at 3–8 months. This is coupled with a takedown of a previously performed systemic-to-pulmonary shunt, which minimizes volume overload and is the first step to a final corrective modified Fontan procedure. This is performed by connecting the superior vena cava to the pulmonary artery with a bidirectional Glenn shunt and connecting the inferior vena cava to the pulmonary artery; this is a total cavopulmonary connection. The inferior caval connection can be done with an intraatrial lateral Dacron tunnel or with an extracardiac conduit. Flow dynamics and clinical outcomes are better than with the direct atriopulmonary connection method. Modified Fontan procedures are delayed until 8–12 months.

Single-Ventricle Complex

This includes patients with a single atrioventricular connection and differing ventricular morphology, mitral atresia with unrestricted aortic outlet, unbalanced atrioventricular septal defects, and a variety of other anatomic configurations with a single functioning ventricular chamber.

Clinical Manifestations Some patients have unrestricted pulmonary blood flow and cyanosis. Others have severe hypoxia, cyanosis, and restricted pulmonary blood flow shortly after birth and require an emergency palliative shunt. With moderate degrees of restriction, patients do reasonably well in the first few years of life.

Treatment Unrestricted pulmonary blood flow with severe pulmonary congestion requires urgent pulmonary artery banding; severe cyanosis and hypoxia require emergency placement of a palliative shunt. After palliative treatment, the final planned surgical correction is some modification of the Fontan procedure (total cavopulmonary procedure). For most patients with single-ventricle complex, placement of a bidirectional Glenn shunt is performed at 3–6 months while taking down the pulmonary artery band or the palliative shunt. At 12–18 months, a bidirectional Glenn shunt is converted to a modified Fontan total cavopulmonary connection, which often is fenestrated.

Ebstein's Anomaly

This is uncommon (0.5 percent). It is a malformation of the septal and posterior leaflets of the tricuspid valve. The origin of the leaflets is displaced downward, creating a third chamber on the right side of the heart. Leaflet tissue and chordae are abnormal. The anterior tricuspid leaflet may be unusually large and prominent (sail-like). The segment of right ventricular wall between the true annulus becomes functionally part of the right atrium with hypoplasia. The atrialized segment has some muscle fibers with little paradoxical motion. The distal functioning right ventricle is small. A patent foramen ovale or ostium secundum defect usually is present with right-to-left shunting. The right atrium usually is dilated.

Malformation varies from minor valvular abnormalities to atresia of the valve leaflets with severe regurgitation. Disturbances include restricted pulmonary blood flow, inadequate cardiac output from right ventricular dysfunction, tricuspid insufficiency, and right-to-left shunting at the atrial level. Arrhythmias commonly occur, with frequent supraventricular tachycardias and Wolff-Parkinson-White syndrome and accessory pathways and preexcitation occurring in 5 percent. Moderate cyanosis occurs in 50 percent.

Clinical Manifestations Patients present in the first month of life with tachypnea and cyanosis. Fifty percent are severely symptomatic and die. After the first month, symptoms decrease, and disability becomes minimal. Onset of symptoms after surviving childhood is gradual; average age at diagnosis is the midteens.

Systolic and diastolic murmurs are present; chest x-ray shows cardiac enlargement. Echocardiogram is diagnostic. Cardiac catheterization may be considered.

Treatment Depending on the degree of anatomic abnormality, valve reconstruction may be considered; valve replacement is necessary in patients with severe valvular deformity.

TRANSPOSITION OF THE GREAT ARTERIES (TGA)

TGA is common (5–8 percent) and is responsible for 25 percent of neonatal deaths. It results from abnormal division of the bulbar trunk. The aorta originates from the right ventricle and the pulmonary artery from the left ventricle. This circulatory arrangement is incompatible with life. A PDA, a patent foramen ovale, or a VSD must be present for the patient to survive. LVOT obstruction resulting in pulmonic stenosis occurs frequently. Coarctation of the aorta, pulmonary atresia, and dextrocardia also may occur.

Hypoxia and progressive pulmonary congestion occur, leading to severe, progressive cardiac failure. Patients with TGA and intact ventricular septum and patients with TGA, VDS, and LVOT obstruction develop severe cyanosis. TGA is lethal if untreated. TGA and VDS patients develop rapid pulmonary vascular changes.

Clinical Manifestations Many infants are cyanotic at birth. Pulmonary congestion with cardiac failure is frequent. Cyanosis often is severe. Chest x-ray shows a heart that may be egg-shaped, the base of the cardiac shadow may be unusually narrow, and pulmonary congestion often is marked. ECG shows severe right ventricle hypertrophy. Echocardiogram is diagnostic.

Treatment The most critically ill are those neonates with TGA and an intact ventricular septum. A Rashkind balloon septostomy often is necessary shortly after birth. The atrial switch operation should be performed at 7–14 days. After 2 weeks of age, infants may require preliminary banding of the pulmonary artery to induce hypertrophy in the left ventricle before it is feasible to perform the arterial switch operation. With TGA and VSD, the arterial switch is done within the first 2 weeks of life.

Repair often is done with the patient in deep hypothermia and circulatory arrest. After cardiopulmonary bypass and cardioplegia, the great vessels are transected distal to the sinotubular ridge. A small button of aorta that includes the ostium of the coronary artery is resected from the posterior sinus of the anterior great vessel and transferred to the corresponding sinus of the posterior great vessel. A similar transfer is made with a button of the anterior right coronary artery. The anterior aorta is relocated posteriorly and sutured end-to-end to the posterior great vessel distal to the coronary artery reimplantation site. The pulmonary artery is brought anteriorly and connected to the anterior great vessel, which exits from the right ventricle.

Patients with TGA, VSD, and LVOT obstruction may require palliation with a systemic-to-pulmonary shunt followed by a Rastelli operation at 4–5 years. This procedure uses a prosthetic patch to reroute the anterior aorta to connect internally to the posterior left ventricle across the VSD. The systemic venous ventricle is connected extraanatomically into the pulmonary artery with a valved homograft conduit or a prosthetic valve and graft.

Double-Outlet Right Ventricle (DORV)

This is a congenital malformation in which both great arteries arise from the morphologic right ventricle (5 percent of CHD patients). Patients are classified by location: (1) subaortic, (2) subpulmonic, (3) doubly committed, and (4) uncommitted. The aorta rotates anteriorly, arising from the right ventricle, and the great vessels usually are side by side; in extreme cases, the aorta is completely anterior.

When the aorta rotates to a greater degree anteriorly and the pulmonary artery begins to rotate posteriorly, a condition of DORV and subpulmonic VSD occurs (Taussig-Bing syndrome). The aorta and the pulmonary artery arise from the right ventricle, allowing some mixing of venous and arterial blood with some bidirectional shunting. The amount of cyanosis varies.

Clinical Manifestations In patients with DORV and a large subaortic VSD or doubly committed VSD, there is a large, isolated VSD with markedly increased pulmonary blood flow. Patients develop congestive heart failure early with pulmonary hypertension, early pulmonary vascular resistance changes, and cyanosis.

DORV and subaortic VSD with pulmonary stenosis patients have hypoxia and cyanosis. Patients with DORV and subpulmonic VSD (Taussig-Bing syndrome) have increased pulmonary blood flow with pulmonary congestion and moderate hypoxia with cyanosis. Echocardiography can determine diagnosis.

Treatment Most forms of DORV can be corrected with an intracardiac tunnel to channel blood from the left ventricle across the VSD to the aorta. The right ventricular outflow tract is enlarged with a patch or homograft valved conduit. Mortality is 2–5 percent. In patients with Taussig-Bing syndrome, some have used the arterial switch procedure along with VSD closure to redirect blood through the neoaorta. Mortality is 5–10 percent.

Truncus Arteriosus

This is a rare malformation (3 percent) that results from a failure of the fetal truncus to separate into the pulmonary arteries, resulting in a single arterial trunk. The entire circulation (the aortic valve, the aorta, the pulmonary arteries, the coronary arteries) arises from a common arterial trunk. A single truncal semilunar valve is present that may be bicuspid (30 percent), tricuspid (50 percent), or quadricuspid (20 percent). There is an underlying VSD.

Pathophysiology In Type I truncus arteriosus there is a single main pulmonary trunk off the aorta, in Type II the right and left pulmonary arteries originate from the dorsal wall of the truncus arteriosus from separate orifices, in Type III the pulmonary arteries arise as separate ostia, and in Type IV the pulmonary blood supply is provided by systemic aorta-to-pulmonary collateral vessels arising from the descending aorta. In most, the ductus arteriosus is absent.

Physiologic abnormality is severe; 50 percent die in the first month of life, 90 percent in first year. Death is from unrestricted pulmonary blood flow with severe pulmonary congestion, congestive heart failure, and progressive pulmonary vascular changes. Patients develop early dyspnea and respiratory distress.

Shunting is bidirectional, and arterial oxygen desaturation is always present with cyanosis. Severe pulmonary vascular disease develops rapidly.

Clinical Manifestations Chest x-ray shows cardiomegaly and pulmonary congestion. Right and left hypertrophy are evident on ECG. Echocardiogram is diagnostic.

Treatment Operation should be performed when the diagnosis is made. The pulmonary arteries are detached from the truncus, the right ventricle is opened, the VSD is closed with a patch, and a homograft valve conduit is used to reconstruct flow into the pulmonary vascular bed.

OTHER COMPLEX MALFORMATIONS

Hypoplastic Left Heart Syndrome (HLHS)

HLHS is made up of a group of malformations that include aortic hypoplasia or atresia and poorly developed or absent left ventricle (2–4 percent).

Pathophysiology The pathology produces severe LVOT obstruction with almost no forward blood flow. The ascending aorta and proximal aortic arch are diminutive, providing retrograde flow to the coronary arteries. The left ventricle is severely hypoplastic or absent, and the myocardial muscle fibers are in disarray with severe endocardial fibroelastosis. The mitral valve is hypoplastic or totally atretic (85 percent); some have a severely malaligned common atrioventricular valve (15 percent).

Clinical Manifestations Infants become symptomatic 24–48 h after birth; they develop cyanosis, tachypnea, respiratory distress, severe acidosis, and ashen color. Death occurs if the ductus arteriosus is not reopened with prostaglandin infusion.

Examination reveals congestive heart failure (e.g., rales), hepatomegaly, diminished peripheral pulses, and poor perfusion. Chest x-ray shows significant pulmonary congestion, and ECG shows an absence of left-sided forces, right-axis deviation, and right ventricular hypertrophy. Echocardiogram is diagnostic.

Treatment Initial treatment is with prostaglandin E1. Acidosis is corrected with sodium bicarbonate. Best results are obtained with staged palliative treatment. The initial operation is in first week of life with the patient in deep hypothermia and circulatory arrest; a stage I Norwood procedure establishes unobstructed flow from the right ventricle to the systemic circulation by anastomosis of the pulmonary artery to the aortic arch. Controlled pulmonary blood flow is established by a systemic-to-pulmonary modified Blalock-Taussig shunt. At 4–6 months, a stage 2 bidirectional Glenn shunt is performed. Cardiac catheterization is performed beforehand to evaluate the aortic arch and aortic outflow tract, the pulmonary arteries, and pulmonary vascular resistance. The Blalock-Taussig shunt is taken down, and the pulmonary arteries are augmented as necessary. At l year, the stage 3 Fontan procedure is performed.

Total Anomalous Pulmonary Venous Return (TAPVR)

Pathophysiology This is classified according to the path of the anomalous venous drainage: supracardiac—the common venous channel usually is a vertical vein that enters the innominate vein (40–50 percent); intracardiac—the anomalous venous channel typically enters the coronary sinus (25 percent); infracardiac—the common venous channel traverses the diaphragm and enters the portal system (25 percent); and mixed (5 percent). Pulmonary venous obstruction producing severe pulmonary congestion and respiratory distress is common. Untreated, 50 percent of patients die in first month, 80 percent in first year.

Clinical Manifestations Severe tachypnea is the dominant symptom. Infants with severe obstruction have severe pulmonary congestion and hypoxemia and diminished peripheral perfusion. Chest x-ray may show a double contour (snowman). Echocardiography can be diagnostic, but cardiac catheterization and angiography are necessary.

Treatment Operation is urgent; total repair is done using hypothermia and circulatory arrest. Correction includes construction of large (2.5–3.0 cm) side-to-side anastomosis between the common venous trunk and left atrium followed by closure of the ASD and ligation of the left vertical vein.

Corrected Transposition

In this situation the anatomic right ventricle and the anatomic left ventricle are switched or inverted (ventricular inversion). The most common associated defects are VSD (80 percent), conduction abnormalities, pulmonic stenosis, and left-sided (tricuspid) atrioventricular valvular insufficiency.

Clinical Manifestations Heart block is present at birth (5–10 percent). Left-to-right shunting and pulmonary congestion are common. Hypoxia and cyanosis are present in 30 percent. ECG is abnormal, echocardiogram is diagnostic, and cardiac catheterization may be necessary.

Treatment Closure of the VSD is technically difficult. A standard transatrial approach through the right atrium and tricuspid valve is preferred. Heart block is common after operation (10–20 percent). Patients with severe pulmonic stenosis require placement of an extracardiac valve homograft to the pulmonary artery. Valve repair or replacement may be necessary.

OTHER ANOMALIES

Anomalous Origin of the Left Coronary Artery

This occurs in 1 in 300,000 births. The flow of blood in the anomalous left coronary artery is retrograde into the low-pressure pulmonary artery. Patients are symptomatic early, with myocardial infarction and left ventricular failure within 3 months of birth. Other symptoms include tachypnea, sweating, poor feeding, respiratory distress, and heart failure.

Chest x-ray shows extensive enlargement of the left ventricle with pulmonary congestion. ECG is diagnostic. Transesophageal echocardiography is confirmatory. Cardiac catheterization and angiography are done before repair.

Treatment Operative repair is early. Coronary transfer is performed with the patient on cardiopulmonary bypass and cardioplegic arrest. The left main pulmonary artery is transected distal to the sinotubular junction. The ostium is excised from the sinus and reimplanted on the appropriate point of the lower medial ascending aorta. The posterior pulmonary sinus may be augmented; the pulmonary artery is closed. If significant mitral insufficiency is present, mitral valve annuloplasty is performed.

Vascular Rings

These are congenital defects in which an anomalous arterial formation can result in compression of the esophagus or trachea. The five types of anomalies include double aortic arch, right aortic arch with left ligamentum arteriosum, retroesophageal subclavian artery, anomalous origin of innominate artery, and anomalus origin of left common carotid artery.

Clinical Manifestations Most symptoms result from compression of the trachea. Dyspnea, stridor, and periodic episodes of serious respiratory distress are common. Feeding often precipitates respiratory crisis. Recurrent pneumonia is common. Some patients with mild symptoms may recover spontaneously.

Examination of the esophagus with a barium swallow is diagnostic. MRI and MR angiography establish diagnosis. Bronchoscopy usually is performed.

Treatment No treatment is necessary without symptoms. Mild symptoms require observation. Clear symptoms require prompt operation. At operation, the aorta and aortic arch are completely dissected. With a double aortic arch, the smaller of the two arches should be divided. With a left descending aorta, the anterior arch is smaller and can be divided between the left common carotid and left subclavian arteries. If the posterior arch is smaller, it can be divided behind the esophagus. With a right descending thoracic aorta, the posterior arch usually is smaller, and it is divided. With a right aortic arch and retroesophageal ligamentum or ductus arteriosus, division of the ligamentum or ductus is all that is necessary.

Pulmonary Artery Sling

The left pulmonary artery arises from the right pulmonary artery, coursing to the left between the trachea and the esophagus to reach the left pulmonary hilus and forming a sling or ring around the trachea. The trachea often is segmentally narrowed at the site of compression. Fifty percent have severe tracheal stenosis with complete cartilaginous rings.

Clinical Manifestations Most infants develop symptoms in the first months of life with feeding difficulty, wheezing, stridor, and severe respiratory distress. Chest x-ray shows a density separating the trachea from the esophagus on the lateral view. An esophageal barium swallow is diagnostic. MRI is the examination of choice; if uncertain, catheterization and angiography are performed. Bronchoscopy is routine.

Treatment Older patients with minimal or no symptoms require no specific treatment. In the absence of severe tracheal stenosis, the repair is performed through a left lateral thoracotomy, dividing the anomalous pulmonary artery at its origin and reanastomosing it to the main pulmonary artery anteriorly. The ligamentum arteriosum is divided. With significant tracheal stenosis, the segmental tracheal stenosis should be resected at the time of sling repair, reanastomosing the trachea end to end.

For a more detailed discussion, see Galloway AC, Artman M, and Colvin SB: Congenital Heart Disease, chap. 17 in Principles of Surgery, 7th ed.

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Copyright © 1998 McGraw-Hill
Seymour I. Schwartz
Principles of Surgery Companion Handbook