The ductus arteriosus is a vascular connection, which during fetal life directs blood flow from the pulmonary artery to the aorta, bypassing the lungs (Fig. 31-2). Functional closure of the ductus occurs within hours or days after birth, in some cases taking 6 months to several years to close. If the ductus remains patent, the direction of blood flow is reversed to left-to-right, because of high systemic pressure in the aorta. A patent ductus arteriosus (PDA), which can escape recognition until adulthood, accounts for about 10% of all cases of congenital heart disease and predominates in women. The incidence of PDA is higher at high altitude than at sea level. It is reported that the risk for PDA in individuals residing between 4,500 and 5,000 m is 30 times higher than in counterparts living at sea level.¹⁸ This increased risk is due to a postnatal persistence of pulmonary hypertension. There is reversal of pulmonary hypertension after prolonged residence at sea level.¹⁸

The hemodynamic changes and clinical manifestations depend on the magnitude of the pulmonary blood flow. The amount of left-to-right shunt is related to the size of the ductal lumen and the resistance in the pulmonary vascular bed. When the ductus is small, the pulmonary artery pressure remains normal; when larger, aortic pressure is transmitted into the pulmonary trunk.

A PDA functions as an arteriovenous fistula, increasing the work of the left ventricle. The major complications are ventricular failure
and presence of increased pulmonary vascular disease. Adults with small left-to-right shunts from a persistent ductus have no symptoms and life expectancy is normal. Patients with large shunts and relatively low pulmonary vascular resistance are at risk for developing left ventricular failure, pulmonary vascular disease, and reversed shunting. In such cases, operation is advised. Once pulmonary resistance exceeds systemic pressure, patients are rendered inoperable.

The clinical appearance characterizing a moderate or large PDA with normal pulmonary arterial pressure includes bounding peripheral pulses, a widened pulse pressure, with diastolic pressures as low as 30 to 50 mm Hg. The left ventricular impulse is hyperdynamic, and, if present, a systolic thrill may be palpated over the suprasternal notch area. A continuous loud “machinery” murmur accentuated in late systole is heard best in the first or second left intercostal space. In the setting of increased pulmonary vascular resistance, the diastolic component of the murmur disappears, leaving only the systolic component.

Patients with a moderate shunt may have no symptoms during infancy but may begin to develop fatigue, dyspnea, or palpitations during childhood or adulthood. Occasionally, the ductus arteriosus may become aneurismal, calcified, and rupture.¹³

In the absence of pulmonary vascular disease, it is recommended that all PDAs be closed either by surgical ligation or by interventional catheterization using percutaneous closure devices. Patients with moderate to large size PDAs who go unrepaired are at risk for endarteritis, heart failure, and pulmonary hypertension. One third of these patients die by the age of 40 years; two thirds of them die by the age of 60 year.¹³,¹⁹ Once closed, periodic long-term evaluation is recommended because residual problems such as pulmonary hypertension, atrial arrhythmias may develop particularly in those repaired later in life. Endocarditis prophylaxis in not required after surgical or device closure even if a residual shunt persists.²⁰

Atrial septal defects (ASDs) are abnormal communications between the left and right atria (Fig. 31-3). They constitute 10% of all congenital heart anomalies. There is a female predominance.¹⁴ They are differentiated by their occurrence within the septum. Ostium secundum ASD, the most common type, occurs in the central region of the fossa ovalis. Ostium primum ASD, which occurs low in the atrial septum, has an associated cleft anterior mitral valve with varying degree of mitral insufficiency. Sinus venosus ASD occurs in the upper part of the atrial septum near the entry of the superior vena cava and may be associated with the partial anomalous right pulmonary venous connection (Fig. 31-4). Owing to the trivial or absent physical signs, ASD may go undetected until the fourth or fifth decade.

The hemodynamic consequences of ASD are dependent on (1) the size and direction of the shunt; (2) the compliance of the left and right ventricles; and (3) the responsive behavior of the pulmonary vascular bed. In infancy, the persistence of increased pulmonary vascular resistance and the relatively equally compliant left and right ventricles limit the amount of left-to-right shunting. With increasing age, pulmonary vascular resistance decreases, and the right ventricle becomes thinner, offering less resistance to filling than the left. Consequently, the conditions are appropriate for left-to-right flow across the defect. Although left atrial pressure is only slightly higher than right atrial pressure, a left-to-right shunt is present, and the pulmonary blood flow may exceed systemic blood flow by three to four times.²¹

Major problems of adults with unrepaired ASD include the development of atrial arrhythmias, which increase in frequency with age; a persistent rise in pulmonary vascular resistance leading eventually to reversed shunting and cyanosis, or the Eisenmenger reaction; and heart failure. The latter is usually the result of associated diseases affecting left ventricular function, such as systemic hypertension or ischemic heart disease. Left ventricular failure reduces the distensibility of the left ventricle, increasing the volume of left atrial blood being shunted across the defect, thus adding to the burden of an already volume-overloaded right ventricle.

Characteristic of the increased pulmonary flow across the pulmonic valves is a soft mid-systolic pulmonic ejection murmur. If the shunt is large, a mild diastolic rumbling murmur is heard at the lower left sternal border, due to increased blood flow across the tricuspid valve. A second sound, which is widely split and does not vary with respiration, is consistent with a low pulmonary vascular resistance. Prominent right ventricle pulsations along the left sternal border and pulmonary artery are palpable. The presence of a systolic thrill reflects a large shunt or coexisting pulmonic stenosis. In ostium primum, there is the addition of the murmur of mitral regurgitation, a left ventricular impulse, and systolic thrill. In sinus venosus, the clinical findings are similar to the ostium secundum. Most patients with ASD remain asymptomatic but may complain of easy fatigability and exertional dyspnea.

Closure of ASD is recommended if the pulmonary-to-systemic blood flow ratio (Q_p/Q_s) is ≥1.5:1. Most surgical repairs are performed in infancy by simple suture closure; in larger defects a pericardial or prosthetic patch may be required to close the defect. For Ostium primum defects, repair of the mitral valve cleft is also undertaken. If mitral insufficiency persists, the patient must be followed closely to determine need for further valve repair or even replacement.

Today, transcatheter closure of ASD is the established method of closure for patients with secundum ASD with success rates of greater than 95% being reported.²²,²³ While occurring infrequently, the long-term concerns for these devices include incomplete closure of the shunt, acute embolization of the devices, and the potential for thromboembolic complications.

Adults with simple ASD repaired in infancy and no residual effects may be followed at the community level. Patients with residual lesions or patients in whom the ASD is diagnosed in adulthood should be evaluated at a regional ACHD center. Indications for specialty care include pre- or postoperative arrhythmias, valvular and/or ventricular dysfunction, and elevated pulmonary pressures. Endocarditis prophylaxis is only indicated within the first 6 months after percutaneous closure with a device or surgical closure using prosthetic material.²⁰

Interventricular defects result in shunting of blood between right and left ventricles (Fig. 31-5). Ventricular septal defects (VSDs) are the most common heart defects, representing about 35% of all congenital cardiac anomalies.⁴,¹⁴ There are three main categories of VSD, each classified according to its location: perimembranous VSD, muscular VSD, and subarterial VSD (Fig. 31-6). Perimembranous defects are the commonest type of defect accounting for 80% of all VSDs and occur in the membranous part of the ventricular septum and the surrounding muscular septum. A muscular VSD occurs in the muscular portion of the septum and accounts for approximately 15%. Subarterial VSDs occur in only 5% of cases and are located directly below the atrioventricular valves. VSDs are further categorized as either restrictive or unrestrictive. Restrictive VSDs are small defects resulting in a high-pressure gradient between right and left ventricle, while nonrestrictive VSDs are large defects in which the pressure between right and left ventricle is equalized. Unrestricted defects are typically repaired in childhood, but restrictive VSDs account for 7% of congenital heart defects found in adults. Isolated VSD occur with equal frequency in men and women. The 25 year follow-up indicates that the majority of patients managed medically or surgically, who do not develop Eisenmenger syndrom will fare well.²⁴,²⁵

Defects may be single or multiple, with the degree of shunting dependent on the size of the defect rather than the anatomic location. Defects vary in size from a millimeter or two in diameter to large openings with little or no septal wall, which behave physiologically like a single ventricle. Small isolated defects (<7 mm in diameter), and moderate-sized defects (7 mm to 1.25 cm) are considered to be restrictive. They have minimal hemodynamic changes and produce little or no symptomatology. But if moderate in size, it may be significant enough to produce some cardiac enlargement. If the defect is large (1.5 to 3 cm), systemic pressure in the right ventricle is equal or slightly lower than the left ventricle creating a left-to-right shunt and increased pulmonary blood flow (unrestricted VSD). This increase in blood flow is returned to the left heart, creating volume overload of both right and left ventricles. In addition, increased pulmonary blood flow may produce pulmonary hypertension. Because of the open communication between the two ventricles, systolic blood pressure in the pulmonary artery rises, equaling that in the aorta. If the pulmonary artery pressure continues to increase and pulmonary vascular resistance approaches or exceeds systemic pressure, shunt reversal (right to left) occurs, rendering the patient cyanotic and no longer a candidate for surgical correction. This syndrome is referred to as Eisenmenger reaction.

Clinical features depend on the volume of pulmonary blood flow, which in turn depends on the size of the defect and the pulmonary vascular resistance. A harsh holosystolic murmur and palpable thrill along the lower left sternal border may be the only findings
of a small or moderate defect. A normal splitting second sound indicates the pulmonary arterial pressure is below systemic pressure. In large shunts, the murmur is lower in intensity, a mid-diastolic “flow murmur” and third heart sound are heard at the apex, and a right ventricular impulse is palpable.

Patients with small VSD (<7 mm in diameter) have minimal hemodynamic changes and produce little or no symptoms. Therefore, they do not require surgical intervention. In the absence of high or fixed pulmonary vascular obstructive disease, surgical correction is indicated in patients with moderate to large left-to-right shunt. VSD closure will be considered if the Q_p/Q_s is higher than 2:1. According to the 2007 guidelines, endocarditis prophylaxis is no longer indicated, except for patients with prosthetic material (e.g. patch for VSD closure) with residua or within the first 6 months after an operation in which prosthetic material is placed.²⁰

Patients with isolated, small VSDs or those with successful surgical repair require periodic follow-up visits every 3 to 5 years²⁶ may be cared for in general medical community. On the other hand, patients with residual defects or those who develop clinical sequelae such as right or left ventricular outflow tract obstruction, atrial or ventricular arrhythmias, or aortic regurgitation, annual cardiac evaluation is recommended. Patients who had late repairs of moderate-sized or large defects should have follow-up every 1 to 2 years to assess for left ventricular dysfunction and elevated pulmonary pressures.²⁶ Endocarditis prophylaxis in VSD is only indicated within the first 6 months after percutaneous closure with a device or surgical closure using prosthetic material.²⁰

The incidence of congenital aortic stenosis is 0.4 per 1,000 live births.⁴ Congenital aortic stenosis is characterized by an obstruction to left ventricular outflow and can occur at three levels: valvular, supravalvular, or subvalvular (Fig. 31-7). The most common form is valvular aortic stenosis, which accounts for 3% to 6% of all cases of congenital heart disease. It is mostly the result of a bicuspid aortic valve. Congenital aortic stenosis occurs more frequently in men than in women.¹³ In about 20% of the cases, valvular aortic stenosis may be associated with coarctation of the aorta or PDA.¹³,²⁷ Long-term survival is good in patients who have undergone intervention in childhood or adolescence²⁸ and in patients who are symptom-free. Once symptoms such as angina pectoris, syncope or near-syncope, and heart failure occur, life expectancy dramatically decreases if untreated.¹³ In these patients, aortic valve replacement is required.

Aortic stenosis is characterized by thickening and rigidity of the valve tissue with a varying degree of commissure fusion in childhood and adolescence and calcification in adults. The adaptation response of chronic aortic stenosis is concentric hypertrophy, which can sustain large pressure gradients across the aortic valve without a drop in cardiac output, left ventricle dilatation, or development of symptoms. Peak systolic pressure gradients with a normal cardiac output reflect the severity of the obstruction. Mild obstruction produces a pressure gradient of <25 mm Hg (an aortic orifice of 0.8 cm²/m² of body surface area); a moderate obstruction produces a gradient of 25 to 50 mm Hg (0.5 to 0.8 cm²/m²); stenosis that produces gradients >75 mm Hg (a body surface area of less 0.5 cm²/m²) reflects severe obstruction to left ventricular outflow. While resting cardiac output and stroke volume are generally within normal limits, the cardiac output increases with exercise. The gradient across the area of obstruction also increases with exercise, causing the obstruction to become more severe.

In severe aortic stenosis, the hemodynamic abnormalities produced by the obstruction to the left ventricle outflow increase myocardial oxygen demand, and the abnormally elevated pressure compressing the coronary perfusion pressure exceeds the coronary perfusion pressure, thereby interfering with coronary blood flow. As a result, significant stenosis may result in reduced subendocardial perfusion, particularly during exercise, leading to ischemia. Subendocardial ischemia plays a key role in the angina, syncope, ventricular arrhythmias, and sudden death reported in patients with aortic stenosis.¹⁴ Exertional syncope, which can occur in patients with gradients exceeding 50 mm Hg, is related to the inability of the left ventricle to increase its output and to maintain cerebral flow during exercise. The onset of clinical symptoms in adults may not occur until the fourth or fifth decade and is usually the result of aortic valve calcification.

The symptoms of valvular aortic stenosis may be inconspicuous. When they occur, those most noted are fatigue, exertional dyspnea, angina, and syncope. With significant stenosis, a left ventricle lift may be palpable. A precordial systolic thrill is palpated over
the base of the heart and is transmitted to the suprasternal notch and over both carotid arteries. The typical murmur of valvular aortic stenosis is a harsh, loud systolic murmur that begins after the first heart sound, rising to a peak (crescendo) and declining (decrescendo) before the second heart sound. The murmur radiates to the suprasternal notch and carotid arteries. A systolic ejection sound, which may be heard at the cardiac apex, implies a mobile valve and is found in mild to moderate stenosis. As calcification impairs valve mobility, the ejection sound decreases or vanishes completely.

Asymptomatic patients with mild aortic stenosis and gradients <25 mm Hg may be treated medically. With higher gradients >50 mm Hg, balloon valvuloplasty may be successfully performed resulting in a 60% to 70% reduction in systolic gradient across the aortic valve. Balloon valvuloplasty is not recommended if aortic insufficiency is present, in patients with subvalvar stenosis or in adults with heavily calcified valves.²¹ Symptomatic or asymptomatic patients with gradients >50 mm Hg are usually treated with surgical resection of subaortic fibrous ring leaving the aortic valve intact. For patients with a narrowed left ventricle outflow tract and small aortic valve annulus, the Ross-Konno surgical procedure maybe performed to relieve left ventricular obstruction to outflow.

Patients with discrete subvalvar aortic stenosis and mild gradients (<30 mm Hg) must be evaluated regularly to detect signs of progressive valve disease. This may be done by local practitioners. Patients with significant residual effects, however, should be followed in an adult congenital heart disease center every 1 to 2 years.²⁶ Prophylaxis against endocarditis is not required, unless prosthetic cardiac valves have been placed.²⁰

Coarctation of the aorta is a deformity of the aortic isthmus, characterized by narrowing either proximal or distal to the left subclavian artery where the ductus arteriosus joins the descending aorta (Fig. 31-8). Occasionally, the coarctation occurs above the origin of the right subclavian. Coarctation of the aorta represents 5% to 10% of all congenital cardiac anomalies¹⁴ and occurs with greater frequency in men than in women.¹³,²⁷ It is strongly associated with bicuspid aortic valve, VSD, PDA, and initial valve abnormalities.¹³ A noncardiac anomaly associated with coarctation of the aorta is an aneurysm of the circle of Willis.