[The bundle of his electrogram in ebstein-s anomaly of the tricuspid valve]

His-bundle electrograms were recorded in four patients with Ebstein's anomaly of the tricuspid valve. In two of the patients His potentials could only be demonstrated in the atrialized portion of the right ventricle while in the other two patients they were recorded in the right ventricle proper. The demonstration of His-potentials only in the atrialized portion of the right ventricle suggests that the origin of the free portion of the septal tricuspid valve leaflet is significantly displaced downward into the right ventricular cavity. The prolonged atrioventricular conduction time in two patients is due to conduction delay proximal to the bundle of His.