THE INFLUENCE OF VARYING As-Vs INTERVALS ON SPLIT FIRST HEART SOUNDS: ITS BEARING ON THE CAUSE OF SPLIT SOUNDS AND THE MECHANISM OF THE FIRST SOUND 1

Abstract

Cases exhibiting both splitting of the first heart sound and varying auriculoventricular time relations were studied by simultaneously recording heart sounds and electrocardiogram. It was found that both components of the split sounds showed variations in amplitude of recorded vibrations depending on the P-R relation comparable to those observed in single first heart sounds. Furthermore during certain ranges of the P-R relation the variations in the 2 components appeared to be independent of each other. It was also noted that in a case of complete heart block with a prolonged but not split first sound, the early and late vibrations of the first sound showed similarly independent variations. Analysis of the time relations associated with the changes in the sounds indicates that the independent variations in the 2 components of split sounds are due to asynchronism in contraction on the 2 sides of the heart and that each ventricle contributes 1 component. The chief importance of this evidence is its bearing on the wider problem concerning the nature of the duality of first heart sounds in general. It now seems probable that this duality is due to contributions to the first sound from both the right and left ventricles.