Heart sounds and murmurs in pregnancy

Abstract

Fifty primigravidas were examined monthly through pregnancy, and phonocardiograms were taken. During pregnancy, a loud, widely split first sound due to early closure of the mitral valve developed in 88 per cent. No changes in the second sound occurred, other than poor movement of the two elements in late pregnancy. A loud third sound developed in 84 per cent. An occasional fourth sound was recorded (16 per cent). Ninety-two per cent of the patients developed a systolic murmur of the ejection type. In 9 cases an “early” diastolic murmur developed; this murmur was thought to be a flow murmur from the atrioventricular valve. These findings are summarized in Fig. 5. Systolic murmurs (4 per cent) and continuous murmurs (10 per cent) arising in breast vasculature were also found. The changes in heart sounds and murmurs started between 12 and 20 weeks of gestation, and mostly disappeared about a week after delivery. These time intervals do not correlate well with reported changes in cardiac output, but fit better with established alterations in blood volume. It is suggested that variations in blood viscosity and in the physical state of the walls of the great vessels may play a part in the formation of murmurs in pregnancy.