双相电震致心律失常性的降低及其与高效除颤的关系

Reduced Arrhythmogenicity of Biphasic Shocks and Its Implicationsfor Defibrillation Efficacy

双相电震比单相电震除颤更有效，但其机制未明。除颤的易损性上限（ＵＬＶ）假说认为一个无效电震是由于它再次诱发了心室颤动（ＶＦ），因此研究ＶＦ诱发的机制可能有助于理解除颤的机制。单、双相电震以电震强度（ＳＳ）与偶联间期（ＣＩ）及波形随机结合的方式施加于Ｌａｎｇｅｎｄｏｒｆ灌流的兔离体心脏上，比较心脏对单、双相电震的ＶＦ易损性。结果心脏对双相电震的反应有如下几点不同于其对单相电震的反应：①易损区（ＡＯＶ）小（８．９±４．２个区域单位ｖｓ１３．９±６．０个区域单位，Ｐ＜０．０５）。②易损区与非心律失常反应区之间的过渡区窄（１４．７±４．８个区域单位ｖｓ２９．９±６．４个区域单位，Ｐ＜０．００１）。③双相电震将整个ＡＯＶ向更长的ＣＩ移动（左边界右移了１１．０±８．８ｍｓ，右边界右移了６．０±５．２ｍｓ，Ｐ均＜０．０１）。这种双相电震致心律失常性的降低可有助进一步解释双相电震除颤阈值降低的现象。

Biphasic waveforms defibrillate more effectively than monophasic waveforms,however,the mechanism remains unknown.The upper limit of vulnerability hypothesis of defibrillation suggests that unsuccessful defibrillation is due to reinduction of ventricular fibrillation (VF).Thus,VF induction mechanisms may be important for the understanding of defibrillation mechanisms.In 10 Langendorffperfused rabbit hearts,monophasic and biphasic T wave shocks were randomly administered over a wide range of shock coupling intervals and shock strengths to compare myocardial VF vulnerability to monophasic versus biphasic shocks.Results:The arrhythmic response to biphasic shocks differed from that to monophasic shocks in three distinct ways:①The area of vulnerability (AOV) was smaller (8.9±4.2 vs 13.9±6.0 area units,P<0.05).②The transition zone between VFinducing and nonarrhythmogenic shocks narrower (14.7±4.8 vs 29.9±6.4 area units,P<0.001).③The entire AOV shifted towards longer coupling intervals(by 11.0±8.8 ms at the left border and 6.0±5.2 ms at the right border of the AOV,both P<0.01).This reduced arrhythmogenicity of biphasic shocks might help explain the lower defibrillation threshold for biphasic shocks.