Body surface potential distribution following the production of right bundle branch block in dogs. Effects of breakthrough and right ventricular excitation on the body surface potentials.

Right bundle branch block (RBBB) was produced in five dogs by incising the main right bundle branch. Body surface isopotential maps of each of these dogs were obtained from 85 thoracic electrocardiograms using a mini-computer technique. In addition, the epicardial activaton process was obtained from the same dog, and were correlated with the map pattern. Following the incision, the following characteristic changes in the map pattern occurred: The ventricular activation was prolonged in RBBB as compared with normal. During the early stage of ventricular excitation, the maximum was shifted leftward due to the activation wavefronts in the left ventricle in contrast to the double septal activation in the control. A localized lower potential area (a concavity) which appears in the middle stage of activation within the anterior positivity as an initial representation of breakthrough was also shifted left-and-downward and delayed in appearance. The sudden change in the potential distribution subsequently observed occurred quite differently. The terminal excitation was characterized by the maximum occurring over the right chest in RBBB in contrast to the left chest in control. These changes in the pattern of the potential distribution were compatible with the changes in the ventricular excitation process. This result may be applied to human RBBB map interpretation.