双相电震诱发的心脏易损区与其高效除颤的关系

Myocardial Vulnerability to Biphasic Shocks: the Rightward Shift of ULV vs. LLV Might Be Responsible for Its High Defibrillation Efficacy

兔离体心脏用Ｌａｎｇｅｎｄｏｒｆ方法灌流，５００ｍｓ周长起搏。通过两只方形钢板电极对每只心脏平均施加（８４±１１）个电震强度（ＳＳ）和偶联间期（ＣＩ）随机组合的双相电震。心脏对电震的反应用单相动作电位（ＭＡＰ）来记录。易损区（ＡＯＶ）由诱发室性纤颤（ＶＦ）的数据点组成，为ＳＳ和ＣＩ的二维函数。由易损性上下限（ＵＬＶ，ＬＬＶ）和易损区左右边界（ＬＢＶ，ＲＢＶ）４个点所限定的ＡＯＶ是均一的。ＵＬＶ和ＬＬＶ发生的ＳＳ分别为（３７３±６２）和（２１３±３９）Ｖ；发生时间分别为（１８７±９）和（１７５±１２）ｍｓ，ｐ＜０．０１，这导致ＵＬＶ的复极水平（８４％±９％）比ＬＬＶ（７３％±７％）更完全（ｐ＜０．０１）。易损区左右边界分别为（１７０±１３）和（１９４±５）ｍｓ；且右边界的ＳＳ比左边界抬高了（６４±５１）Ｖ（ｐ＜０．０１）。ＵＬＶ发生时间较ＬＬＶ的右移以及右边界比左边界ＳＳ的抬高导致双相电震ＡＯＶ呈现向右倾斜。

Biphasic shocks defibrillate more effectively than monophasic shocks, however, the mechanisms are still unknown. Isolated Langendorff perfused rabbit hearts were paced at a cycle length of 500 ms and the myocardial responses to shocks wererecorded by MAP technique. A total of (84±11) biphasic T wave shocks were administered to each heart through two large shock plate electrodes flanking the bath to describe the “area of vulnerability”(AOV). The AOV was characterized by theinduction of VF and was defined two dimensionally by shock strength and coupling interval. ULV and LLV, which represent the upper and lower coner of AOV, respetively, occurred at shock strength of (373±62)V and (213±39)V, respectively.The coupling interval for ULV and LLV were (187±9) vs. (175±12)ms, p <0 01, which resulted in a more complete repolarization level for ULV (84±9)% compare to that for LLV ((73±7)%, p <0 01). The left and right borders of AOV (LBV,RBV) were (170±13) ms and (194±5) ms. The shock strength for RBV had a vertical upshift of (64±51) V ( p <0 01) compare to that for LBV. The rightward shift of the ULV timing compare to the LLV and the shock strength upshift ofRBVvs. LBV resulted in a right tilt of the AOV for biphasic shocks. This rightward shift of ULV timing vs. LLV might be responsible for its high defibrillation efficacy.