Activation of the epicardial surface of the left ventricle following left ventriculotomy and left bundle branch block

Abstract

By utilizing cardiopulmonary bypass and surface electrodes, the sequence of activation of the epicardial surface of the left ventricle was studied in dogs before and after left ventriculotomy and also before and after left bundle branch block. Following left ventriculotomy there is no delay or change in the sequence of activation of the left ventricular epicardium. Following left ventriculotomy and left bundle branch block, the pattern of epicardial activation is changed, the earliest points being adjacent to the interventricular grooves anteriorly and posteriorly. Epicardial activation becomes progressively delayed at points located nearer to the mid-portion of the ventricle. It thus would appear that, following left bundle branch block, the epicardial surface of the left ventricle adjacent to the interventricular grooves is activated by impulses spreading directly from the right ventricle, while the more centrally located portion of the left ventricular wall may still be activated by its Purkinje system.