Sims J J, Miller A W, Ujhelyi M R
University of Georgia College of Pharmacy, Medical College of Georgia, and Augusta Veterans Affairs Medical Center, Augusta, Georgia 30912, USA.
Am J Physiol. 1998 Jun;274(6):H1943-9. doi: 10.1152/ajpheart.1998.274.6.H1943.
The magnitude by which a defibrillation shock extends the refractory period immediately postshock (refractory period extension, RPE) does not explain why biphasic shocks defibrillate with greater efficacy than monophasic shocks. It may be that spatial heterogeneity of RPE is a more important regulator of defibrillation efficacy. We measured RPE in 15 pentobarbital-anesthetized swine using 400-V biphasic and monophasic shocks of equal pulse duration at three discrete myocardial sites. Spatial heterogeneity of RPE was calculated as the difference between the maximum and minimum values of the three recording sites. Monophasic shocks produced greater magnitude of RPE than biphasic shocks at all sites tested (82 +/- 6 to 99 +/- 13 and 64 +/- 6 to 68 +/- 5 ms, respectively; P < 0.05). However, RPE dispersion was significantly less with biphasic shocks versus monophasic shocks (29 +/- 4 and 48 +/- 7 ms, respectively; P < 0.05). This suggests that one potential mechanism by which biphasic shocks defibrillate with greater efficacy is limiting postshock spatial heterogeneity of refractoriness. Thus these data support our hypothesis that RPE heterogeneity is a more likely predictor of defibrillation efficacy than magnitude of RPE.
除颤电击后立即延长不应期的程度（不应期延长，RPE）并不能解释为什么双相电击比单相电击具有更高的除颤效率。可能RPE的空间异质性是除颤效率更重要的调节因素。我们使用400V、脉冲持续时间相等的双相和单相电击，在15只戊巴比妥麻醉猪的三个离散心肌部位测量了RPE。RPE的空间异质性计算为三个记录部位的最大值与最小值之差。在所有测试部位，单相电击产生的RPE幅度均大于双相电击（分别为82±6至99±13和64±6至68±5毫秒；P<0.05）。然而，与单相电击相比，双相电击的RPE离散度明显更小（分别为29±4和48±7毫秒；P<0.05）。这表明双相电击更有效地进行除颤的一种潜在机制是限制电击后不应期的空间异质性。因此，这些数据支持了我们的假设，即RPE异质性比RPE幅度更有可能是除颤效率的预测指标。
