Intraventricular dissociation due to complete intraventricular block.

Intraventricular dissociation due to intraventricular block occurred in a patient with cardiac arrest due to massive cerebral hemorrhage. The electrocardiogram showed complete atrioventricular block with three different types of accelerated ventricular rhythm. The ectopic beats did not interfere with each other because of the existence of an area of complete block surrounding the areas in which impulse formation occurred. Hence, the corresponding QRS complexes did not result from depolarization of all the ventricular muscle mass but only of certain regions. The latter were large enough to produce ventricular complexes of enough size to be recorded at the body surface. This phenomenon is the clinical counterpart of the multiple isolated focal contractions which may be seen directly in the ventricules of dying hearts.