Angioscopy, which shows gross pathological findings in vivo, has the potential to clarify the differences in the pathogenic mechanisms between an erosion and rupture. Hayashi et al. examined the relationship between the morphologies of culprit lesions and the clinical features of the patients with acute myocardial infarction using coronary angioscopy and intravascular ultrasound [7]. These studies were performed immediately before percutaneous coronary intervention was undertaken. They found that the patients with eroded plaque lesions had smaller infarctions than those with ruptured plaque lesions. Furthermore, distal embolization was less frequent in the erosion group compared with the rupture group (rupture group 37.0 % vs. erosion group 0.0 %; P = 0.0026). These results also suggest that the morphology of the intimal injury may help to determine the optimal management of ACS. The mechanical stress caused by coronary spasm is suspected to contribute to the formation of erosion. The angioscopic findings of coronary spasm are discussed in detail in the next section.

There have been few angioscopic investigations of plaque erosion. Because a thrombus attaches to the injured intima, the morphology of the intima is often overlooked by angioscopy. The combination of angioscopy and an intravascular imaging device visualizing the cross-sectional images of the artery is thought to be helpful in identifying a plaque erosion. Identifying the morphology of the intimal injury may help to determine the optimal management of ACS.