Congenital heart disease occurs in 8 per 1000 births. The spectrum of lesions ranges from asymptomatic to fatal. Although most cases of congenital heart disease are multifactorial, some lesions are associated with chromosomal disorders, single gene defects, teratogens, or maternal metabolic disease (see Table 139-2).
Congenital heart defects can be divided into three pathophysiologic groups (Table 143-1).
1.
2.
3.
Obstructive, stenotic lesions Acyanotic congenital heart disease includes left-to-right shunts resulting in an increase in pulmonary blood flow (patent ductus arteriosus [PDA], ventricular septal defect [VSD], atrial septal defect [ASD]) and obstructive lesions (aortic stenosis, pulmonary stenosis, coarctation of the aorta), which usually have normal pulmonary blood flow.
The ventricular septum is a complex structure that can be divided into four components. The largest component is the muscular septum. The inlet or posterior septum comprises endocardial cushion tissue. The subarterial or supracristal septum comprises conotruncal tissue. The membranous septum is below the aortic valve and is relatively small. VSDs occur when any of these components fails to develop normally (Fig. 143-1). VSD, the most common congenital heart defect, accounts for 25% of all congenital heart disease. Perimembranous VSDs are the most common of all VSDs (67%).
Although the location of the VSD is important prognostically and in approach to repair, the amount of flow crossing a VSD depends on the size of the defect and the pulmonary vascular resistance. Large VSDs are not symptomatic at birth because the pulmonary vascular resistance is normally elevated at this time. As the pulmonary vascular resistance decreases over the first 6 to 8 weeks of life, the amount of shunt increases, and symptoms may develop.
Small VSDs with little shunt are often asymptomatic but have a loud murmur. Moderate to large VSDs result in pulmonary
Coarctation of Tricuspid Atrial septal HLH the aorta atresia defect
HLH, Hypoplastic left heart syndrome; TAPVR, total anomalous pulmonary venous return.
Figure 143-1 Ventricular septal defect. AO, Aorta; LA, left atrium; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RV, right ventricle.
overcirculation and heart failure. The typical physical finding with a VSD is a pansystolic murmur, usually heard best at the lower left sternal border. There may be a thrill. Large shunts increase flow across the mitral valve causing a middiastolic murmur at the apex. The splitting of S2 and intensity of P2 depend on the pulmonary artery pressure.
Electrocardiogram (ECG) and chest x-ray findings depend on the size of the VSD. Small VSDs usually have normal studies. Larger VSDs cause volume overload to the left side of the heart, resulting in ECG findings of left atrial and ventricular enlargement and hypertrophy. A chest x-ray may reveal cardiomegaly, enlargement of the left ventricle, an increase in the pulmonary artery silhouette, and increased pulmonary blood flow. Pulmonary hypertension due to either increased flow or increased pulmonary vascular resistance may lead to right ventricular enlargement and hypertrophy.
Approximately one third of all VSDs close spontaneously. Small VSDs usually close spontaneously and, if they do not close, surgical closure may not be required. Initial treatment for moderate to large VSDs includes diuretics (± digoxin) and afterload reduction. Continued poor growth or pulmonary hypertension despite therapy requires closure of the defect. Most VSDs are closed surgically, but some VSDs, especially muscular defects, can be closed with devices placed at cardiac catheterization.