Auscultatory and Phonocardiographic Signs of Ventricular Septal Defect with Left-to-Right Shunt

Abstract

Ventricular septal defect with low pulmonary vascular resistance and left-to-right shunt is well known to be closely associated with a pansystolic murmur caused by the regurgitant shunt of blood at high velocity across the defect. With very high flows a pulmonary ejection murmur is superimposed on the pansystolic murmur and is occasionally the only systolic murmur if the ventricular septal defect is so large that the velocity of the shunt is small. In two patients thought to have small ventricular septal defects the shunt murmur was confined to early systole, probably because the defect was in the muscular septum and was closed by systolic contraction of the ventricle. The second heart sound is abnormally widely split in the majority of patients, even with small defects. The mechanism is difficult to elucidate but there appears to be slight shortening of the left ventricular isometric time (early A₂) and delay in contraction of the right ventricle (late P₂). The splitting of the second sound is a useful way of differentiating the large defects with left-to-right shunt from the Eisenmenger group of large defects with equal pulmonary and systemic vascular resistances and a loud single second sound. The auscultatory differential diagnosis of ventricular septal defect is discussed.