Normal Intraventricular Conduction and Intraventricular Block Occurring in Adjoining Complexes.

Abstract

The comparative permanence of electrocardiographic abnormalities, especially bundle branch block, once established is an admitted maxim. The more promising possibility of the transient nature of such disturbances is usually not considered. In experimental work on conduction in the heart of the dog, Wilson and I 1 were impressed by the fact that relatively light pressure exerted over one of the main branches of the His'bundle would produce bundle branch block from which there was complete recovery within a few minutes and a return to an absolutely normal intraventricular conduction time which was recorded.

Lewis had observed a patient with transient bundle branch block as early as 1913. There have been 9 other instances recorded in the literature which at one examination presented defective conduction while at another later examination the normal intraventricular conduction was recorded and vice versa. In none of these instances, however, was there any record of a transition of a sudden nature. In fact, in most of them there is a suggestion of a gradual transition. This condition is not so uncommon since 5 similar cases have come under my observation.

Three additional cases of unusual interest and importance were encountered. These were extraordinarily unique in that the sudden transitions were recorded electrocardiographically. In each one of these instances the transition was within one beat and was from complete bundle branch block to absolutely normal intraventricular conduction. These observations constitute clinical corroboration of our experimental findings and of the pathological findings of Cohn and Lewis. 2 There seems to be evidence sufficient that temporary mechanisms and functional changes in the conductive system in the diseased human heart as well as in the normal dog heart may induce bundle branch block.