Abstract
In 80 cases of complete right bundle branch block and 21 cases of complete left bundle branch block, a parabolic relationship between QRS duration and the split interval of the second heart sound was established. However, the relationship was not so very close, and the exceptions mainly due to hemodynamic burdens co-exist were not infrequent. Clinical significance of the relationship was discussed and the mechanism of reversed splitting of the second heart sound in complete left bundle branch block was analyzed in a case of alternating QRS duration. At least in this case, the prolongation of isometric contraction had the most important significance to the occurrence of the reversed splitting.
