心肌梗死前后心室肌细胞单相动作电位的变化及其意义

Changes of Monophasic Action Potential of Ventricular Myocardium in a Porcine Model of Healed Myocardial Infarction and Its Significance

目的:运用单相动作电位(monophasicactionpotential,MAP)记录方法,探讨心肌梗死后数周发生单形性室性心动过速(ventriculartachycardia,VT)的电生理机制。方法:运用非开胸球囊堵闭猪的左前降支造成心肌梗死,通过MAP记录电极记录猪左心室心内膜多个部位MAP,比较心肌梗死前和梗死后数周出现VT猪的MAP各电生理参数的变化。这些参数包括动作电位时程(actionpotentialduration,APD)从激动开始至复极50%的时间APD50,复极90%的时间APD90;激动时间(activationtime,AT)、复极时间(repolarizationtime,RT)和AT、APD50、APD90、复极时间(RT)的离散度(dispersion),即ATd、APDd1、APDd2、RTd。结果:在心肌梗死前后分别记录了各40个部位MAP,测量各参数结果显示,猪心肌梗死后左心室肌细胞复极时间APD50和APD90虽略有延长,但与心肌梗死前比较无明显差异(P>0.05)。分析各参数的离散度,无论是APDd,还是心室激动时间及复极时间离散度均明显增加犤APDd1:(26±7)ms比(39±9)ms;APDd2:(34±11)ms比(48±13)ms;ATd:(32±9)ms比(52±17)ms,RTd:(29±10)ms比(50±15)ms,P<0.01犦。结论:心肌梗死数周后心室复极离散度增大,激动传导差异性增加是心肌梗死后产生室性心动过速的重要电生理机制之一。

Objective: To investigate the electrophysiologic mechanism of sustain ed monomorphic ventricular tachycardia in a porcine model of healed myocardial i nfarction using monophasic action potential(MAP)recording technique. Methods:Af ter having been developed a closed chest pig model of healed myocardial infarcti on,MAPs were recorded before and after infarction from left ventricular endocar dium. Observed electrophysiologic parameters of MAP include:action potential du ration of 50%repolarization(APD50),action potential duration of 90%repolariza tion(APD90)?dispersion of activation time (ATd)?dispersion of repolarization t ime(RTd)and dispersion of APD50(APDd1)and APD90(APDd2).Results:Although APD50 a nd APD90 prolonged after infarction,there were no significant differences compa red with those of normal state(P >0.05).APDd?ATd and RTd increased significantl y[APDd1:(26±7)ms vs (39±9)ms;APDd2:(34±11)ms vs (48±13)ms;ATd:(32±9)ms vs (52±17)ms;RTd:(29±10)ms vs(50±15)ms,P< 0.01]. Conclusion:Increases of repolarization dispersion and activation conduction after several weeks of infa rction are one of the major electrophysiologic mechanism which may induce ventri cular arrhythmias.