422.1 Pulmonary Valvular Insufficiency and Congenital Absence of the Pulmonary Valve

Pulmonary valvular insufficiency most often accompanies other cardiovascular diseases or may be secondary to severe pulmonary hypertension. Incompetence of the valve is an expected result after surgery for right ventricular outflow tract obstruction, for example, pulmonary valvotomy in patients with valvular pulmonic stenosis or valvotomy with infundibular resection in patients with tetralogy of Fallot. Isolated congenital insufficiency of the pulmonary valve is rare. These patients are usually asymptomatic because the insufficiency is generally mild.

The prominent physical sign is a decrescendo diastolic murmur at the upper and midleft sternal border, which has a lower pitch than the murmur of aortic insufficiency because of the lower pressure involved. Roentgenograms of the chest show prominence of the main pulmonary artery and, if the insufficiency is severe, right ventricular enlargement. The electrocardiogram is normal or shows minimal right ventricular hypertrophy. Pulsed and color Doppler studies demonstrate retrograde flow from the pulmonary artery to the right ventricle during diastole. Cardiac magnetic resonance angiography (MRA) is useful for quantifying both right ventricular volume and the regurgitant fraction. Isolated pulmonary valvular insufficiency is generally well tolerated and does not require surgical treatment. When pulmonary insufficiency is severe, especially if significant tricuspid insufficiency has begun to develop, replacement with a homograft valve may become necessary to preserve right ventricular function.

Congenital absence of the pulmonary valve is usually associated with a ventricular septal defect, often in the context of tetralogy of Fallot (Chapter 424.1). In many of these neonates, the pulmonary arteries become widely dilated and compress the bronchi, with subsequent recurrent episodes of wheezing, pulmonary collapse, and pneumonitis. The presence and degree of cyanosis are variable. Florid pulmonary valvular incompetence may not be well tolerated, and death may occur from a combination of bronchial compression, hypoxemia, and heart failure. Correction involves plication of the massively dilated pulmonary arteries, closure of the ventricular septal defect, and placement of a homograft across the right ventricular outflow tract.

422.3 Mitral Valve Prolapse

Mitral valve prolapse results from an abnormal mitral valve mechanism that causes billowing of one or both mitral leaflets, especially the posterior cusp, into the left atrium toward the end of systole. The abnormality is predominantly congenital but may not be recognized until adolescence or adulthood. Mitral valve prolapse is usually sporadic, is more common in girls, and may be inherited as an autosomal dominant trait with variable expression. It is common in patients with Marfan syndrome, straight back syndrome, pectus excavatum, scoliosis, Ehlers-Danlos syndrome, osteogenesis imperfecta, and pseudoxanthoma elasticum. The dominant abnormal signs are auscultatory, although occasional patients may have chest pain or palpitations. The apical murmur is late systolic and may be preceded by a click, but these signs may vary in the same patient and, at times, only the click is audible. In the standing or sitting position, the click may occur earlier in systole, and the murmur may be more prominent in late systole. Arrhythmias may occur and are primarily unifocal or multifocal premature ventricular contractions.

The electrocardiogram is usually normal but may show biphasic T waves, especially in leads II, III, aVF, and V₆; the T-wave abnormalities may vary at different times in the same patient. The chest roentgenogram is normal. The echocardiogram shows a characteristic posterior movement of the posterior mitral leaflet during mid- or late systole or demonstrates pansystolic prolapse of both the anterior and posterior mitral leaflets. These echocardiographic findings must be interpreted cautiously because the appearance of minimal mitral prolapse may be a normal variant. Prolapse is more precisely defined by single or bileaflet prolapse of >2 mm beyond the long axis annular plane with or without leaflet thickening. Prolapse with valve thickening >5 mm is “classic,” a lesser degree is “non-classic.” Two-dimensional real-time echocardiography shows that both the free edge and the body of the mitral leaflets move posteriorly in systole toward the left atrium. Doppler can assess the presence and severity of mitral regurgitation.

This lesion is not progressive in childhood, and specific therapy is not indicated. Antibiotic prophylaxis is no longer recommended during surgery and dental procedures (Chapter 431).

Adults (men more often than women) with mitral valve prolapse are at increased risk for cardiovascular complications (sudden death, arrhythmia, cerebrovascular accidents, progressive valve dilatation, heart failure, and endocarditis) in the presence of thickened (>5 mm) and redundant mitral valve leaflets. Risk factors for morbidity also include poor left ventricular function, moderate to severe mitral regurgitation, and left atrial enlargement.

Often, confusion exists concerning the diagnosis of mitral valve prolapse. The high frequency of mild prolapse on the echocardiogram in the absence of clinical findings suggests that, in these cases, true mitral valve prolapse syndrome is not present. These patients and their parents should be reassured of this fact, and no special recommendations should be made regarding management or frequent laboratory studies.

422.4 Tricuspid Regurgitation

Isolated tricuspid regurgitation is generally associated with Ebstein anomaly of the tricuspid valve. Ebstein anomaly may occur either without cyanosis or with varying degrees of cyanosis, depending on the severity of the tricuspid regurgitation and the presence of an atrial-level communication (patent foramen ovale or atrial septal defect). Older children tend to have the acyanotic form, whereas if detected in the newborn period, Ebstein anomaly is usually associated with severe cyanosis (Chapter 424.7).

Tricuspid regurgitation often accompanies right ventricular dysfunction. When the right ventricle becomes dilated because of volume overload or intrinsic myocardial disease, or both, the tricuspid annulus also enlarges, with resultant valve insufficiency. This form of regurgitation may improve if the cause of the right ventricular dilatation is corrected, or it may require surgical plication of the valve annulus. Tricuspid regurgitation is also encountered in newborns with perinatal asphyxia. The cause may be related to an increased susceptibility of the papillary muscles to ischemic damage and subsequent transient papillary muscle dysfunction. Finally, tricuspid regurgitation is seen in up to 30% of children after heart transplantation, which can be a risk factor for graft dysfunction but is also seen as a consequence of valve injury due to endomyocardial biopsy.