Li H G, Jones D L, Yee R, Klein G J
Department of Physiology, University of Western Ontario, London, Canada.
Pacing Clin Electrophysiol. 1995 Jun;18(6):1225-35. doi: 10.1111/j.1540-8159.1995.tb06962.x.
The cellular electrophysiological effects of defibrillation shocks on the myocardium during ventricular fibrillation are not clear. The present study investigated the effects of high voltage shocks on membrane potentials of isolated guinea pig and pig papillary muscles during rapid activations simulating ventricular fibrillation. High voltage shocks induced an action potential with a prolonged duration, followed by a transient refractory state. Subsequent action potentials following this refractory state had shortened durations. The duration of the transient refractory state varied in proportion to shock intensity and stimulation rate, whether the shock was biphasic or monophasic. Shock induced prolonged depolarization was not a consistent finding and mainly observed with slow stimulation rates. In conclusion, high voltage shocks induce bimodal changes of the action potential duration associated with a transient refractory state during rapid activation. The rate dependency of this refractory state suggests that the duration of the shock induced refractory state may be longer in the fibrillating than the normal beating heart, and may contribute to successful defibrillation.
心室颤动期间除颤电击对心肌的细胞电生理效应尚不清楚。本研究调查了在模拟心室颤动的快速激活过程中，高压电击对分离的豚鼠和猪乳头肌膜电位的影响。高压电击诱发了持续时间延长的动作电位，随后是短暂的不应期。此不应期后的后续动作电位持续时间缩短。短暂不应期的持续时间与电击强度和刺激频率成比例变化，无论电击是双相还是单相。电击诱发的延长去极化并非一致发现，主要在慢刺激频率下观察到。总之，高压电击在快速激活期间诱发与短暂不应期相关的动作电位持续时间的双峰变化。这种不应期的频率依赖性表明，电击诱发的不应期持续时间在颤动的心脏中可能比正常跳动的心脏更长，并且可能有助于成功除颤。
