第58届ACC会议给临床医生带来了关于对STEMI患者施行后处理的精彩探讨。所谓后处理，即缺血后立即重复中断冠脉血流，可显著降低ST段抬高心肌梗死患者经皮冠状动脉介入治疗（PCI）后的心肌梗死面积和心衰发生。

    据调查表明，即使进行了成功的直接PCI，仍有高达20%的急性心肌梗死（AMI）患者死于大面积心肌梗死。原因之一为再灌注损伤，即突然再开通闭塞动脉。因此，逐步开通动脉可以缓和再灌注并保存更多心肌。

    来自丹麦Copenhagen的心血管专业的首席顾问Engstrom博士表示，“急性心肌梗死的死亡率很高，因此降低死亡率显得非常重要。后处理，即在开通动脉及植入支架前通过导丝和球囊再开通动脉30秒，然后再闭塞动脉，连续反复4次。通过缓慢再灌注可减少STEMI后的心肌梗死面积和心衰发生。”

    在该项研究中，118例ST段抬高心肌梗死患者12小时内随机为常规PCI组和PCI加后处理组。使用四个低压球囊扩张再灌注后立即进行后处理，每次再灌注30秒后接着闭塞30秒。主要终点是3个月时利用延迟增强心脏磁共振测量梗死面积。该研究发现，与对照组相比，后处理组增加了心肌挽救率（ 51±16% vs.63±17%，P=0.007），相当于心肌挽救率增加了32%。亚组分析表明，存在前降支（LAD）病变的36例患者后处理效果更为显着。与对照组比较，后处理使梗死面积从21.9%降低至15.5%，后处理对所有梗死面积和梗死部位的治疗均有效。与对照组相比，后处理组心力衰竭患者例数显着降低（27 vs. 16，P=0.048）。3个月时，后处理组中纽约心功能分级II 至IV级的患者占27%，而对照组为47%。

    目前研究人员正在研究后处理中的有效药物。2009年1月启动的一项研究显示，GLP-1的类似物—exenatide，产生于肠道，可以降低糖尿病患者的血糖。Engstrom教授认为，exenatide可能也有后处理作用，并且已经在动物模型上得到证实，现在他们正在进行临床研究，到目前为止已经招收28例患者。

（任芳 吕树铮  首都医科大学附属北京安贞医院）
 

英文原文：
POSTCONDITIONING REDUCES INFARCT SIZE AND HEART FAILURE AFTER PCI FOR STEMI
Opening and Closing the Target Vessel Four Times Before PCI Can Make Reperfusion More Gentle and Increase the Salvage Ratio of the Myocardium

Orlando，FL–Repetitive interruptions of coronary blood flow applied immediately after a period of ischemia–a process known as postconditioning–can significantly reduce infarct size and heart failure in patients with ST-elevation myocardial infarction undergoing percutaneous coronary intervention(PCI)，according to research presented during the i2 Summit at the American College of Cardiology’s 58th annual scientific session.

Up to 20 percent of patients with acute myocardial infarction(MI)who undergo a successful primary PCI still end up with very large infarctions.One reason for this is thought to be due to reperfusion injury，which occurs with abrupt reopening of the occluded artery.Gradually reopening the artery might make the reperfusion gentler and save more myocardium.
“In general，mortality after an acute MI is high.It is very important to reduce this mortality，”said Thomas Engstrom， Ph.D.， chief consultant in the department of cardiology， Rigshospitalet， Copenhagen，Denmark.“Postconditioning，which involves reopening the artery by means of a wire and a balloon for 30 seconds，and then occluding it again for four consecutive times before the artery is permanently reopened and stented，can reduce infarct size and heart failure after STEMI by slowing the reperfusion rate.”

In this study，118 patients with ST-elevation myocardial infarction referred within 12 hours of onset of symptoms were randomly assigned to receive conventional PCI or to PCI with postconditioning.Postconditioning was deployed immediately after generation of reperfusion with four low-pressure balloon inflations，with each occlusion lasting 30 seconds followed by 30 seconds of reperfusion.The primary endpoint was infarct size measured with delayed enhancement cardiac magnetic resonance at three months.

Overall，there was an increase in myocardial salvage in the postconditioning group compared with the control group(51±16 percent vs.63±17 percent;P=0.007)，which corresponded to a relative increase in salvage ratio of 32 percent.Subgroup analysis showed that the effect was more pronounced in a subgroup of 36 patients who had lesions in the left descending artery (LAD).

Postconditioning resulted in a reduction in infarct size from 21.9 percent of area at risk to 15.5 percent of area at risk when compared with the control group.The treatment was effective for all infarct sizes and all infarct locations.

The number of patients with heart failure was significantly decreased in the postconditioning group compared with the control group(16 vs.27;P=0.048).Twenty-seven percent of patients in the postconditioning group had New York Heart Association class II to IV heart failure at three months，compared with 47 percent of patients in the control group.
The investigators are now studying the efficacy of pharmacological substances in postconditioning.A study，begun in January 2009，is studying exenatide，an analoque of GLP 1， a hormone that is produced in the gut，which has been shown to lower blood sugar in patients with diabetes.

“We believe that it might also have a postconditioning effect.We have already shown this in animal models and now we are studying this in humans.To date we have enrolled 28 patients，” Engstrom said.