Ventricular Septal Defect

Essentials of Diagnosis

• Adults asymptomatic if defect is small to moderate.
  
• Grade II-VI/VI pansystolic murmur maximal at the left sternal border; associated thrill common.
  
• ECG may show left ventricular hypertrophy - or right ventricular hypertrophy if shunt is reversed; x-ray shows increased pulmonary vascularity. Echo-Doppler is diagnostic.

General Considerations

In this lesion, a persistent opening in the upper interventricular septum resulting from failure of fusion with the aortic septum permits blood to pass from the high-pressure left ventricle into the low-pressure right ventricle. The subsequent natural history and pathophysiology depend on the size of the defect and the magnitude of left-to-right shunting. Large defects are associated with early left ventricular failure. Chronic but more moderate left-to-right shunts may lead to pulmonary vascular disease and right-sided failure.

Many ventricular defects close spontaneously in early childhood.

Clinical Findings

A. Symptoms and Signs
The clinical features are dependent upon the size of the defect and the presence or absence of a raised pulmonary vascular resistance. Large shunts are associated with loud, harsh holosystolic murmurs in the left third and fourth interspaces along the sternum and, in some cases, middiastolic flow murmurs and an S3 at the apex. Smaller shunts may produce only an early systolic murmur or a diamond-shaped murmur. A systolic thrill is common. Clinical evidence of pulmonary hypertension is often more informative than the murmur itself. High defects may be associated with aortic regurgitation owing to prolapse of a valve leaflet.

B. Electrocardiography and Chest X-Ray
The ECG may be normal or may show right, left, or biventricular hypertrophy, depending on the size of the defect and the pulmonary vascular resistance. With large shunts, the right or left ventricle (or both), the left atrium, and the pulmonary arteries are enlarged, and pulmonary vascularity is increased on chest radiographs. If pulmonary vascular disease evolves, an enlarged pulmonary artery with diminished distal vascularity is seen.

C. Diagnostic Studies
Echocardiography can demonstrate chamber size and may demonstrate the defect. Doppler ultrasound can qualitatively assess the magnitude of shunting and the pulmonary artery pressure. Magnetic resonance imaging can often visualize the defect, while radionuclide flow studies quantify pulmonary-to-systemic flow ratios. Cardiac catheterization permits definitive diagnosis in all but the most trivial defects; it is the only technique that can measure pulmonary vascular resistance.