缺血预适应促发心肌毛细血管床功能性开放

目的:探讨反复短暂缺血剌激导致缺血预适应(IP)对心肌毛细血管床功能的影响。方法:复制套扎前降支冠状动脉犬模型。IP组给予缺血5min,灌注5min,反复4次;假手术组不予缺血与灌注剌激,观察40min。分别于实验前、第1次缺血与再灌注及第4次缺血与再灌注末行心肌声学造影,最后对心肌毛细血管进行超微结构观察,并定量分析,做组内及组间比较。结果:第4次缺血较第1次缺血其声学显影最小缺损面积百分比(ADmin%)由32.6%±5.7%降至21.8%±5.2%(P＜0.05),定量分析指标峰值(PI)、曲线下面积(AUC)、峰减半时间(HT)均增高;心肌毛细血管数、管腔内径、内皮细胞厚度及内皮细胞超微结构均无明显差别。结论:反复短暂缺血增加心肌微循环血液灌注但无毛细血管超微结构改变,提示IP促发心肌毛细血管床功能性开放。

Ischemic preconditioning induced functional opening of myocardial capillary beds

AIM:To explore the protective effect of ischemic preconditioning on myocardial capillary bed.METHODS:Anesthetized open-chest dogs in ischemic preconditioning (IP) group (n=6) were subjected to 5 min ischemia and 5 min reperfusion for 4 times in left descending coronary artery (LDA) while the dogs in sham-operated (SO) group (n=6) were observed for 40 min without any stimulating. Myocardial contrast echocardiography (MCE) was performed before the surgery, at the end of the first and the fourth ischemia and reperfusion period, respectively. Myocardial samples in ischemic area were obtained for capillaries ultrastructure examination and their quantitative analysis was conducted by corresponding imagine analyzing system, then compared within group and between control group.RESULTS:(1) Comparing fourth 5 min ischemia with first one, the percents of area defect in minimum (AD min%) by MCE decreased from 32.6%±5.7% to 21.8%±5.2%(P＜0.05), meanwhile, the peak intensity (PI), area under curve (AUC) and half time of peak intensity attenuation (HT) in intensity-time curve all increased significantly. (2) The number, diameter, thickness and ultrastructure of endothelial cells of myocardial capillaries didnt change in IP group compared with SO group.CONCLUSION:Repeated brief ischemia stimulus can obviously enhance myocardial perfusion without any ultrastructure changes of the capillaries, which suggests IP stimulus may promote the functional opening of myocardial capillary beds.