低温缺血再灌注后不同程度心律失常大鼠的心肌电生理特征:离体实验

Electrophysiological characteristics of myocardium after hypothermic ischemia-reperfusion in rats with different degrees of arrhythmia:an in vitro experiment

目的采用离体实验探讨低温缺血再灌注后不同程度心律失常大鼠的心肌电生理特征.方法清洁级健康雄性SD大鼠,2~3月龄,体重300~400 g,成功制备Langendroff离体心脏灌注模型16个,采用随机数字表法分为2组(n=8):对照组(C组)和低温缺血再灌注组(I/R组).采用全心低温(4℃)停灌60 min再灌注30 min的方法制备离体心脏低温缺血再灌注损伤模型.记录再灌注期间心律失常的发生情况、持续时间和心脏复跳时间.根据心律失常评分将I/R组大鼠分为低危组(I/R-L组,室性心律失常评分≤3分)和高危组(I/R-H组,室性心律失常评分>3分).分别于平衡灌注30 min(To)、再灌注15 min(T1)和再灌注30 min(T2)时,记录左心室前壁内膜层、中膜层、外膜层单相动作电位振幅(MAPA)、50%和90%单相动作电位时程(MAPD5o和MAPDgo)和0相最大上升速率(Vmax);采用程控电刺激技术测定左心室有效不应期(ERP)和室颤阈值(VFT),并计算ERP/MAPD9o比值.结果与To时比较,I/R-L组和I/R-H组3层心肌T12时MAPA降低,MAPD5o和MAPD90延长,I/R-H组3层心肌T1,2时Wmax降低(P<0.05);与T1时比较,I/R-L组和I/R-H组3层心肌T2时MAPD50和MAPD90缩短(P<0.05).与C组比较,I/R-L组和I/R-H组3层心肌T1,2时MAPD5o、MAPDgo和ERP延长,ERP/MAPDgo比值减小,VFT增大(P<0.05);与I/R-L组比较,I/R-H组心律失常持续时间、3层心肌T2时MAPD90和ERP延长,ERP/MAPD90比值减小,VFT增大(P<0.05).结论低温缺血再灌注后心律失常大鼠心肌去极化受抑制,复极时间延长,电生理稳定性降低,其中高危心律失常大鼠心肌复极时间延长和电生理稳定性降低更为明显.

Objective To investigate the electrophysiological characteristics of myocardium after hypothermic ischemia-reperfusion(I/R)in rats with different degrees of arrhythmia using an in vitro experiment.Methods Healthy clean-grade male Sprague-Dawley rats,aged 2-3 months,weighing 300-400 g,were used in this study.The rats were sacrificed after anesthesia,and their hearts were rapidly excised.Sixteen Langendorff-perfused hearts were prepared and divided into 2 groups(n=8 each)by a random number table method:control group(group C)and hypothermic I/R group(group I/R).The hearts were made globally ischemic for 60 min followed by 30-min hypothermic(4℃)reperfusion to establish the model of hypothermic I/R injury.The occurrence and duration of arrhythmia and time of recovery of spontaneous heartbeat were recorded during reperfusion.The rats in group I/R were further divided into low-risk group(I/R-L group,ventricular arrhythmia score≤3 points)and high-risk group(I/R-H group,ventricular arrhythmia score>3 points)according to the arrhythmia score.Monophasic action potential amplitude(MAPA),monophasic action potential(MAP)duration at 50%and 90%repolarization(MAPD50 and MAPD90)and maximum ascending velocity(Vmax)of phase 0 in the endocardium,myocardium and epicardium of the left ventricular anterior wall were recorded at 30 min of equilibration(T0)and 15 and 30 min of reperfusion(T1,2).The effective refractory period(ERP)and ventricular fibrillation threshold(VFT)of the left ventricle were measured by programmed electrical stimulation,and the ERP/MAPD90 ratio was calculated.Results Compared with the baseline at T0,MAPA in the three layers was significantly decreased,and MAPD50 and MAPD90 were prolonged at T1,2 in I/R-L and I/R-H groups,and Vmax in the three layers was decreased at T1,2 in I/R-H group(P<0.05).MAPD50 and MAPD90 in the three layers were significantly shorter at T2 than at T1 in I/R-L and I/R-H groups(P<0.05).Compared with group C,MAPD50,MAPD90 and ERP in the three layers were significantly prolonged at T1,2,the ERP/MAPD90 ratio was decreased,and VFT was increased in I/R-L and I/R-H groups(P<0.05).Compared with I/R-L group,the duration of arrhythmia and MAPD90 and ERP in the three layers were significantly prolonged at T2,the ERP/MAPD90 ratio was decreased,and VFT was increased in group I/R-H(P<0.05).Conclusion Myocardial depolarization is inhibited,repolarization duration is prolonged,and electrophysiological stability is decreased after hypothermic I/R in the rats with arrhythmia,and the prolongation of myocardial repolarization and decrease in electrophysiological stability are more obvious in the rats at high risk of arrhythmia.