Studies on the Mechanism of Ventricular Activity

Abstract

Controlled studies of ventricular excitation were performed in dogs exhibiting various Degreess of right and left bundle-branch block. Increases in the intraventricular conduction time during complete bundle-branch block are attributed to free wall as well as septal factors. Incomplete bundle-branch block may be either segmental or diffuse. In the segmental type, delayed excitation is present in only a portion of the involved ventricle. In the diffuse type, delayed excitation of the entire homolateral ventricle occurs, but some portions of the ventricle tend to be delayed to a greater extent than others. Certain segements of the ventricular myocardium appear to be supplied by fixed portions of the conducting system, without cross connections operating physiologically. The clinical implications of these observations are briefly discussed.