Normal first heart sounds with nonfunctional tricuspid valve or right ventricle. Clinical and experimental evidence.

A case of Ebstein's malformation of the tricuspid valve with persistent foramen secundum and right bundle-branch block is presented. Preoperative tracings revealed three distinct components of the first sound with normal intervals between them. After resection of a single floating tricuspid leaflet, closure of the septal defect, and insertion of a Starr-Edwards valve, the phonocardiogram again showed three normal components of the first heart sound, followed by a loud closing snap of the prosthetic tricuspid valve. This case demonstrates the occurrence of the three normal components of the first heart sound independently of right ventricular contraction and of tricuspid closure or tensing. In five dogs left ventricular phonocardiograms, made after right heart bypass and destruction of the free ventricular wall, revealed three normal components of the first heart sounds in three animals, and of the first two components, separated by normal intervals in two others. These experiments exclude any participation of the right ventricle or tricuspid valve in the mechanism of origin of the first heart sound. The authors conclude that the three normal components of the first heart sound are of leftsided origin and that the designation "tricuspid" for the second component should be abandoned.