The vectorcardiogram in chronic chagas myocarditis: An analysis of the intraventricular conduction delays associated with a superiorly oriented ÂQRS ∗

Abstract

Fourteen patients with chronic Chagas myocarditis showing intraventricular conduction disturbance in the electrocardiogram were studied vectorcardiographically. According to the appearance of the QRS loop in the horizontal plane the vectorcardiograms were classified into three groups. In ten patients (groups I and II) the electrocardiographic diagnosis of a complete right bundle branch block was confirmed by the vectorcardiogram. In group I the QRS loop in the horizontal plane characteristically followed the pattern described by Grishman et al. for right bundle branch block. In group II the QRS loop followed the pattern described by Cabrera et al. for right bundle branch block in coronary sclerosis. In both groups, however, the vectorcardiograms brought out some peculiarities that were not given by electrocardiographic analysis, namely: (1) intraventricular conduction disturbance, probably located at the level of the connections of the Purkinje fibers with the myocardium, and (2) loss of electrical forces due to myocardial fibrosis probably located in the inferior two-thirds of the interventricular septum and free wall of the left ventricle. The third group did not present electrical characteristics of right bundle branch block. There were signs of left ventricular hypertrophy in all four patients of this group, of whom two had been diagnosed electrocardiographically as having left bundle branch block. The vectorcardiographic study of these patients revealed very important facts not shown by the electrocardiogram: (1) the left bundle branch block was not confirmed since the horizontal plane inscription of the QRS loop was counterclockwise in all patients and the delay was predominantly located in the terminal portion of the loop; (2) intraventricular conduction disturbances with delay in one or more portions of the loop were present in all patients; and (3) the QRS loop suggested that some electrical forces had been subtracted probably because of destruction of the myocardial tissue mainly located in the inferior two-thirds of the septum and adjacent ventricular wall.