Ventricular Excitation in Experimental Bundle-Branch Block

Multipolar recording apparatus has been used to study the pattern of ventricular excitation in experimental bundle-branch block. After block, the wave of activation spreads uniformly from the contralateral ventricle across the septum to the free wall of the homolateral ventricle. Septal activation consumes more time than in the normal. Changes occur in the site and extent of early endocardial activity in the blocked ventricle. Alterations in both septal and mural depolarization contribute to QRS changes. Endocardial depolarization is described during recovery from transient bundle-branch block.