The purpose of this study is to evaluate the prevalence and morphological features of coronary plaques by means of OCT in patients with acute myocardial infarction but without any significant coronary stenosis at coronary angiography. In addition, cardiac magnetic resonance imaging (CMR) will be performed to assess the prevalence, location, and pattern of myocardial injury as well as other concomitant findings. As a secondary analysis, the association between the distribution and characteristics of coronary plaques detected on OCT and myocardial injury shown by CMR will be evaluated. In addition, a post-hoc survey regarding the potential modification of the interventional treatment approach based on OCT analysis will be conducted.