心肌缺血对心室颤动的诱发和除颤效率的影响

近来埋藏式心律转复除颤器（ＩＣＤ）已成为抗心律失常药物治疗无效的高危病人的优先选择。由于大多数需要ＩＣＤ治疗的病人常伴有缺血性心脏病，因此急性心肌缺血对ＩＣＤ病人的除颤失败和心脏猝死可能起一定作用。本文在离体灌流兔心脏标本上测定了急性心肌缺血对单相动作电位（ＭＡＰ）各参数以及心室颤动（ＶＦ）诱发和除颤的影响。结果表明，心肌缺血１５ｍｉｎ缩短ＭＡＰ时程（复极达９０％，ＡＰＤ９０）（１５４±８ｍｓｖｓ１０２±１８ｍｓ，Ｐ＜０．００１）和复极时间（ＲＴ９０）（１８５±６ｍｓｖｓ１３８±１３ｍｓ，Ｐ＜０．００１）；使激活时间（ＡＴ）增加（３１±５ｍｓｖｓ３６±８ｍｓ，Ｐ＜０．０１）；同时使ＲＴ９０弥散明显增加（３７±１６ｍｓｖｓ６９±２９ｍｓ，Ｐ＜０．０１）。心肌缺血对易损性上限（ＵＬＶ）和除颤阈值（ＤＦＴ）稍有影响，但无统计学意义（ＵＬＶ：２７４±５３Ｖｖｓ２９４±４４Ｖ，Ｐ＝ＮＳ；ＤＦＴ２６８±４２Ｖｖｓ２７１±３３Ｖ，Ｐ＝ＮＳ）；却使易损窗（ＶＷ）的宽度增加三倍（对照２５±２２ｍｓ，缺血１５ｍｉｎ时７５±２６ｍｓ，Ｐ＜０．００１）。复极时间与ＶＷ边界的相关分析表明，ＶＷ左边界和１０个ＭＡＰ中最短的ＲＴ９０高度?

Effects of Myocardial Ischemia on Ventricular Fibrillation Inducibility and Defibrillation Efficacy

Recently the implantable cardioverter defibrillator (ICD) has become the treatment of choice in patients at high risk for sudden cardiac death.Because most patients requiring treatment with an ICD have concomitant ischemic heart disease,acute ischemia may play a role in defibrillation failure and sudden cardiac death.This study determined the effects of acute ischemia on the monophasic action potentials (MAP),ventricular fibrillation inducibility and defibrillation.The results showed that fifteen minutes of ischemia as compared to baseline caused a decrease in MAP duration (APD90) (1548 vs 10218ms,P<0.001) and repolarization time (RT90) (1856vs 13813ms,P<0.001),and an increase in activation time (AT) (315vs 368ms,P<0.01) and RT90 dispersion (3716 vs 6929ms,P<0.01).The width of the vulnerable window (VW) increased from 2522ms during baseline to 7526ms during ischemia (P<0.001).Both the upper limit of vulnerability (ULV) and defibrillation threshold (DFT) remained unchanged (ischemia vs baseline: ULV 27453 vs 29444V,P=NS;DFT 26842 vs 27133V,P=NS).The left border of VW was significantly correlated with the shortest RT90.Conclusions: Severe ischemia caused a threefold increase in the width of the VW.However,the ULV and DFT are not affected by ischemia in this model.