VENTRICULAR FIBRILLATION DUE TO SINGLE, LOCALIZED INDUCTION AND CONDENSER SHOCKS APPLIED DURING THE VULNERABLE PHASE OF VENTRICULAR SYSTOLE

Abstract

A brief induction or condenser shock applied to normal hearts of old or young dogs by stigmatic electrodes induces fibrillation only when the shock falls during the vulnerable period of late systole. Since the effect is obtained by use of stigmatic electrodes, passage of the current through the whole or large parts of the myocardium is not necessary to initiate fibrillation. Fibrillation following use of prolonged electrical currents, drugs, chemicals and ischemia may likewise be induced by some effective stimulus[long dash]possibly a fortuitous one[long dash]falling during the vulnerable period. One reason why an alternating current at critical voltages is more dangerous than the direct current seems to lie in the fact that effective variations of current strength obviously fall during the vulnerable phase in the former and only during closing and opening of the direct current. Exptl. results indicate that the effectiveness of currents or the variations of myocardial sensitivity to fibrillation cannot be tested experimentally by noting variations in the duration of current flow, a criterion frequently employed by previous investigators.