实验性顿抑心肌微血管结构和功能改变

The changes of microvascular function and structure in experimental myocardial stunning

目的 探讨心肌顿抑时心肌微血管结构和功能改变。方法 制备冠状动脉左前降支(LAD)不同阻断时间 (1 5min和 60min)后再灌注犬心肌顿抑模型 ,在不同观察时间点静脉注射含全氟丙烷声振白蛋白微泡造影剂 ,采用二次谐波成像和间歇发射技术行心肌声学造影。由主动脉根部分别注射乙酰胆碱 (ACH)和硝酸甘油 (NG)后重复心肌声学造影 ,并计算用药后 /前二维超声上所示心肌灰阶峰值比值 (PVIR)和顿抑区与正常区心肌灰阶峰值比值的比值PVIRR。心肌标本行透射电镜检查。结果 ⑴LAD阻断 1 5min组再灌注早期NG PVIR和ACH PVIR明显减低 ,但分别在再灌注 60min和 1 2 0min时恢复至结扎前水平 ;⑵LAD阻断 60min组再灌注早期NG PVIR减低 ,至再灌注 1 2 0min时才恢复到结扎前水平 ,而再灌注期ACH PVIR明显减低 ,随着再灌注时间的延长虽有逐渐回升趋势 ,但至再灌注 1 2 0min仍未恢复至结扎前水平 ;⑶两组PVIRR的变化与PVIR一致 ,唯恢复稍慢 ;⑷LAD阻断 1 5min组心肌毛细血管和内皮细胞结构未见明显改变 ,而LAD阻断 60min组毛细血管内皮细胞肿胀 ,内皮细胞间连接间隙稍增宽。结论 顿抑心肌微血管舒张功能受损 ,缺血时间较长则还有微血管结构改变 。

Objective To observe the changes of microvascular function and structure in myocardial stunning Methods Twelve dogs underwent 15 or 60 min of left anterior descending coronary artery (LAD) occlusion, followed by 120 min of reperfusion Myocardial contrast echocardiography(MCE) was performed by intravenously using C 3F 8 exposed sonicated dextrose albumin at different time points After resting MCE at each time point, acetylcholine (ACH) and nitroglycerin (NG)were given from aortic root injections and MCE was repeated, respectively End systolic images in short axis were acquired in harmonic mode and digitized on line Background subtracted peak videointensity(PVI) in myocardium area was measured form MCE and the ratios of PVI and of PVI ratio between stunned and normal region, post and pre ACH or NG(ACH PVIR, NG PVIR, ACH PVIRR, NG PVIRR),were calculated Results NG PVIR were markedly declined in the early period of reperfusion in both 15 and 60 min LAD occlusion group However, significantly decreased ACH PVIR was only seen in the early period of reperfusion in the 15 min LAD occlusion group and lasted during reperfusion in the 60 min LAD occlusion group The changes in NG PVIRR and ACH PVIRR were similar to those in NG PVIR and ACH PVIR, respectively, but with slightly slow restoration No ultrastructural changes of microvessels were noted in stunned myocardium from the 15 min LAD occlusion group In the 60 min LAD occlusion group, endothelial cells of capillaries were swelling, and the intercellular linking gaps of endothelial cells slightly widened Conclusion There are microvascular endothelium damage and endothelium dependent dilatation impairments in stunned myocardium, and their severity and recovering speeds might be related to original ischemia duration