Is there a significant transmural gradient in repolarization time in the intact heart?: Repolarization Gradients in the Intact Heart.

In 1880, Burdon-Sanderson and Page recorded the ECG of the frog simultaneously with monophasic action potentials from the base and the apex of the left ventricle (LV).1 Part of the ventricular muscle was injured with a hot wire, and monophasic action potentials were recorded as the potential difference between the injured region and an uninjured area. The ECG was recorded with a capillary electrometer, a slow, but reliable instrument. They noted that repolarization occurred earlier at the base than at the apex.1 Warming the base resulted in a shortening of the basal action potential, leading to a deeper, more negative, and longer T wave in the ECG. Comparable findings were reported by Bayliss and Starling2 and by Mines.3 Noble and Cohen4 have reviewed the early literature on the T wave.