The Apical First Heart Sound as an Aid in the Diagnosis of Atrial Septal Defect

The phonocardiograms of 187 patients were reviewed. In 89 the apical first heart sound was soft or single; in 57 M1 was louder than T1 and in 23 the two components were equal. In only 18 cases was T1 louder than M1 at the mitral area, and of this group five were suspected of having atrial septal defect and 10 were proved cases. In three of the proved cases, this was the only significant finding, the other usual features being absent. Only two proved cases of atrial septal defect in this series did not have T1 louder than M1 at the apex; both had T1 equal to M1. One case suspected of having atrial septal defect also had T1 equal to M1 and in another suspected case the first heart sound was single. This unusual characteristic of the first heart sound may be useful as an indication favoring the diagnosis of uncomplicated atrial septal defect.