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Electrophysiologic Characteristics of Human Ventricular and Purkinje Fibers

We studied the electrophysiologic characteristics of ventricular muscle and Purkinje fibers from the hearts of five patients undergoing cardiac transplantation. All five patients had congestive failure and coronary artery disease before surgery and were receiving digitalis therapy. Ventricular muscle had a maximal diastolic potential (MDP) of −78 i 1 mV (mean + SEM), an action potential (AP) amplitude of 104 i 2 mV, a phase 0 upstroke velocity (Via) of 297 + 19 V/sec and an AP duration at 50% repolarization (APD.Q) of 190 + 4 msec. Purkinje fibers had an MDP of −80 2 mV, an AP amplitude of 107: + 2 mV, a VI1 of388 i 25 V/sec and an APD, S of 195 ± 9 msec. Fibers from infarcted sections of the heart had significantly longer APD than those from noninfarcted, which resulted in marked dispersion of APD in infarcted and adjacent zones. Both epinephrine and ouabain induced delayed afterdepolarizations in Purkinje fiber. This suggests that delayed afterdepolarizations and resultant triggered activity can occur in the human ventricle.