HEART DEFIBRILLATION EXPERIMENTAL AND THEORETICAL ASPECTS

It was shown on 12 anaesthetized dogs in 66 experiments that the myocardial contractile response to an impulse of the defibrillator at ventricular fibrillation was incomplete. The magnitude of the potential induced on myocytic membranes at the action of the defibrillating impulse was calculated. Different mechanisms of defibrillation can be realized depending on the magnitude of the charge used: a direct electrical break-down and a shift of the transmembranous potential in the "zone of silence". A common feature of these mechanisms consists in that the contractile function of myocytes ceases for the period sufficient for the occurrence of the state of adequate homogeneous repolarization of the myocardial cells. Thereafter, the first impulse of the pacemaker produces a coordinated contractile response of the heart.