心肌声学造影评价实验性顿抑心肌的微血管功能改变

Observations on the changes of microvascular function in experimental myocardial stunning with intravenous myocardial contrast echocardiography

目的 探讨心肌顿抑时心肌微血管功能改变以及静脉心肌声学造影方法的价值。方法 制备左前降支冠脉 (LAD)不同阻断时间 ( 15min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 (MCE)。由主动脉根部分别注射乙酰胆碱 (ACH)和硝酸甘油 (NG)后重复MCE并计算用药后、前二维超声上所示心肌灰阶峰值 (PVI)和峰值比值 (PVIR)。结果 ①心肌顿抑早期心肌PVI显著增高 ,60min后恢复至结扎前水平 ;② 15minLAD阻断组再灌注早期NG PVIR和ACH PVIR明显减低 ,但分别在再灌注 60min和 12 0min时恢复至结扎前水平 ;③60minLAD阻断组再灌注早期NG PVIR减低 ,至再灌注 12 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 12 0min仍未恢复至结扎前水平。结论 ①心肌顿抑早期微血管扩张 ,血液灌注增加 ,此后较快恢复正常 ;②顿抑心肌微血管内皮受损 ,血管内皮依赖性舒张功能减弱 ,其恢复速度与原缺血时间长短有关。

Objective To observe the changes of microvascular function during myocardial stunning and the effect of assessing with myocardial contrast echocardiography(MCE). Methods Twelve dogs underwent 15 or 60 min of left anterior descending coronary artery (LAD)occlusion, followed by 120 min of reperfusion. MCE was performed intravenously using C 3F 8 exposed sonicated dextrose albumin at baseline, during coronary occlusion, and at 5,30,60,90,and 120 min after reperfusion. At baseline, 5,60,and 120 min after reperfusion, 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 stunned myocardium area was measured from MCE and the ratios of PVI post and pre ACH or NG (ACH PVIR, NG PVIR) were calculated. Results A marked increase in PVI occurred in all dogs with stunned myocardium in the early period of reperfusion and the PVI restored to the pre occlusion level after 60 min of reperfusion. NG PVIR were markedly declined in the early period of reperfusion, and restored to their pre occlusion levels at 60 and 120 min of reperfusion both in 15 and 60 min LAD occlusion groups. However, significantly decreased ACH PVIR was only seen in the early period of reperfusion in the 15 min LAD occlusion group and lasted for whole period of reperfusion in the 60 min LAD occlusion group.Conclusions Stunned myocardium is hyperemic in the early period of reperfusion and the blood perfusion restores to normal level in a short time after reperfusion. There are microvascular endothelium damage and endothelium dependent dilatation impairments in stunned myocardium, and their improving speeds might be related to original ischemia duration.