The pathway of ventricular depolarization in the dog.

Studies of ventricular depolarization with multichannel recording technics permit detailed three dimensional analysis of the process. Activity commences on the mid left septal surface, followed by activity on the right septum. Rapid endocardial excitation follows and leads to endoepicardial activation of the walls. The latest areas activated are in the basal septum. These findings are related to the genesis of the normal QRS. Theories of simultaneous activation and eleetrocardiographic silent areas are discussed.