The Effect of a Threshold Electrical Stimulus upon the Repolarization Process of the Left Ventricle of the Intact Dog Heart

A threshold stimulus applied either at apex or base of the intact dog ventricle at any depth of the myocardium produces a delay in repolarization during the following three to four normal beats, in an area equivalent to the size of the proximal zone of the precordial lead. This change in repolarization is not caused by postextrasystolic distension of the ventricle. The question is discussed whether a threshold stimulus initiates a propagated disturbance from the point of the electrodes or the larger area whose repolarization is altered.