Phonocardiography in interventricular septal defects

Abstract

Physiologic studies in patients with interventricular septal defects have, in recent years, demonstrated a whole spectrum of abnormalities. 1,2 At one end, there are the small left-to-right shunts, with pressures and resistances in the pulmonary and systemic circuits remaining normal. The magnitude of the shunt is regulated in these cases by the size of the opening and the pressure gradient across it. In the larger defects, however, the anatomic communication presents less of an obstruction. Here the magnitude of the left-to-right shunt is controlled by the relative resistance of the pulmonary and systemic arterioles. 3 There may be very large shunts, several times the systemic flow, in cases in which pulmonary resistance is low. The pulmonary resistance, however, may reach such a magnitude that the left-to-right shunt will be much reduced in volume, and a right-to-left shunt may appear. The classic physical findings are altered with these modifications in flows and pressures. Recently, phonocardiographic studies have been utilized in the assessment of these patients who are now often under consideration for surgical repair of the defect. 4 The present study demonstrates the relationship between the phonocardiographic findings and the physiologic abnormalities as disclosed by cardiac catheterization.