First heart sound in Ebstein's anomaly: observations on the cause of wide splitting by echophonocardiographic studies before and after operative repair.

Preoperative echophonocardiographic study of a 31 year old woman with Ebstein's anomaly and an atrial septal defect showed wide splitting of the first heart sound with an interval of 0.08 second between mitral valve and tricuspid valve closure. After application of the anterior tricuspid leaflet and anuloplasty, the mitral and tricuspid valves closed at the same time and there was a single first heart sound. These findings suggest that delayed tricuspid valve closure in Ebstein's anomaly is due to the abnormally large size and increased excursion of the anterior tricuspid leaflet rather than associated right bundle branch block or sluggish right ventricular contraction.