超速起搏预适应对缺血再灌注心室肌有效不应期及其离散度的影响

目的　观察超速起搏预适应对缺血再灌注 (I/ R)心室肌有效不应期 (ERP)及不应期离散度的影响。　方法　 4 8只健康家兔分为对照组 (C组 )、缺血再灌注组 (IR组 )、起搏预适应早期保护作用组 (EP组 )和延迟保护作用组 (DP组 )。观察 3个试验组 I/ R心肌超微结构、心室肌 ERP及 ERP离散度变化。　结果　 (1 )电镜下 EP组和 DP组心肌细胞超微结构损伤较 IR组明显减轻。 (2 ) EP及 DP组 ERP缺血早期 (I5min)较缺血前 (I前)延长 ,缺血晚期 (I30 min)和再灌注早期 (R5 min,R1 5 min)较缺血前明显缩短。与 IR组相比 ,EP及 DP组 I5 min和 I1 5 min的心室肌 ERP明显缩短 ,I30 min明显延长 (P<0 .0 5 )。(3)缺血期各时点和 R5min的心室肌 ERP离散度较 IR组明显减少 (P<0 .0 5 )。　结论　超速起搏预适应可明显减轻兔 I/ R时心肌细胞超微结构损伤 ,其抗 I/ R心律失常的重要机制可能是明显减轻缺血期和再灌注早期心室肌 ERP离散度

Changes of Overdriving Pacing Preconditioning on Effective Refractory Period and Dispersion of Refractoriness in Ventricular Myocardium of Ischemia-reperfusion

Objective To investigate the effects of overdriving pacing preconditioning on effective refractory period(ERP) and dispersion of ERP in ventricular myocardium of ischemia|reperfusion. Methods 48 rabbits were divided into 4 groups at random:control(C) group, ischemia|reperfusion(IR) group, early protection of overdriving pacing preconditioning(EP) group and delayed protection(DP) group; the changes of myocardial ultrastructure were examined. ERP and dispersion of ERP in IR, EP and DP group were observed, respectively. Results (1) Compared with IR group, injury of myocardial ultrastructure were reduced significantly by EP and DP. (2)The ERP in ventricular myocardium of EP/DP group were longer in ischemia at 5 min(I 5 min) than before ischemia, late phase of ischemia at 30 min(I 30 min) and early phase of reperfusion(R 5 min and R 15 min) were longer than I 5 min. The ERP in ventricular myocardiium of EP/DP group were shorter remarkably at I 5 min and I 15 min, and increased remarkably at {I 30 min} when compared with IR group(P<0 05 or P<0 01, respectively). (3)The dispersion of ERP in EP/DP group were lower remarkably than that in the IR group(P<0 05). Conclusion EP and DP induced by overdriving pacing preconditioning could reduce the myocardial ultrastructive injury, and lessen the effective refractory period and dispersion of ERP during ischemia and the early phase of reperfusion.