Ischemia-reperfusion injury to coronary arteries: Comprehensive microscopic study after reperfused myocardial infarction.

Background: Coronary arteries supply oxygen and nutrients to the heart. We evaluated the dynamics of microscopic damage throughout the ischemia-reperfusion process in the wall of coronary arteries following myocardial infarction (MI).

Methods: In a swine model of reperfused MI, animals were divided into one control and four MI groups: 90-min ischemia without reperfusion, or followed by one minute, one week or one month reperfusion. Left anterior descending (LAD; infarct-related artery) and control right coronary arteries (RCA) were isolated. Taking the balloon inflation region as a reference, we isolated the proximal and distal LAD areas, performing histological staining and immunohistochemistry.

Results: Although mild changes in tunica intima were observed during ischemia, an almost complete absence of endothelium, and abnormal breaks in the internal elastic layer were found post-revascularization. In tunica media, increased thickness was observed soon after reperfusion, whereas larger thickness, disorganized muscle cell distribution and edema were found one week after reperfusion. This damage was more pronounced in distal rather than proximal LAD, whereas no changes were detected in RCA. In the tunica adventitia, vasa vasorum density decayed during ischemia in both LAD regions, but was restored after one month. Leukocyte adhesion to the artery was observed post-revascularization, developing into a massive presence in the three layers one week post-reperfusion.

Conclusions: Ischemia-reperfusion can itself induce damage in the wall of the epicardial coronary artery, becoming more pronounced in the region distal to balloon inflation. Exploring these abnormalities will provide insight into the pathophysiology of coronary circulation and MI.