反复正加速度暴露致兔缺血心肌动作电位变化的研究

Changes in myocardial action potential of rabbit with myocardial ischemia exposed to repeated positive acceleration(+Gz)

目的对比研究正常和缺血心肌在正加速度(+Gz)暴露下动作电位的变化,探讨心肌在冠脉病变所致缺血基础上发生心律失常的可能机制。方法新西兰大白兔60只,随机分为对照组(A组)、加速度组(B组)、缺血组(C组)、缺血+加速度组(D组),每组15只。采用单向动作电位法,记录并对比分析各组动物心肌缺血、+Gz暴露后单相动作电位振幅(MAPA)、0相最大上升速率(Vmax)、复极达50%振幅的单相动作电位时程(MAPD50)、复极达90%振幅的单相动作电位时程(MAPD90)的变化;记录完动作电位后再行S1S1程序刺激,观察心律失常诱发率。结果各组间MAPA和Vmax均无明显变化(P>0.05);与A组比较,B、C、D组MAPD50和MAPD90均明显缩短(P<0.05),其中D组较B、C组缩短程度大(P<0.05)。B、C、D组心律失常诱发率均明显高于A组(P<0.05),且D组明显高于B、C组(P<0.05)。结论 +Gz或缺血暴露后心肌细胞动作电位时程缩短,心律失常诱发率增加,且两因素之间有叠加效应,提示复极过程中存在相关离子通道功能异常。

Objective To explore the possible mechanism of arrhythmia caused by ischemic coronary vessel lesion through parallel analysis of the monophasic action potential （MAP） changes in normal and ischemic myocardium under positive acceleration （＋Gz） exposure. Methods Sixty New Zealand white rabbits were randomly divided into 4 groups （15 each）： control group （group A）, acceleration group （group B）, ischemia group （group C） and myocardial ischemia undergoing positive acceleration group （group D）. The changes in each group were recorded and analyzed, including MAP amplitude （MAPA, mV）, maximum rate of 0 phase （Vmax, mV/s）, 50% MAP repolarization （MAPDs0） and 90% MAP repolarization （MAPD90） by using monophasic action potential method after ＋Gz exposure and myocardial ischemia. The incidence of arrhythmia was then observed by S1S1 programmed stimulation. Results No significant changes were found in MAPA and Vmax among the 4 groups （P〉0.0S）. Compared with group A, MAPD50 and MAPD90 were shortened evidently in group B, C and D （P〈0.05）, most marked in group D, as it was significantly shortened than that of group B and C （P〈0.05）. The incidence of arrhythmia by S1S1 programmed stimulation was higher in groups B, C and D （P〈0.05） than in group A, and it was highest in group D （P〈0.05）. Conclusions The duration of action potential will be shortened in myocardial cell after exposure to ＋Gz or ischemia, and the probability of occurrence of tachyarrhythmias will be increased significantly. ＋Gz and ischemia are found to have cumulative effect, implying that the functional abnormality of related ion channels existed in the course ofrepolarization.