Myocardial infarction without angiographic moderate to severe stenosis (> 50%) and any other related diagnosis on clinical presentation is defined as myocardial infarction with nonobstructive coronary arteries (MINOCA). Common causes of MINOCA working diagnosis includes plaque disruption, spontaneous coronary artery dissection, coronary artery spasm, coronary thromboembolism, Takotsubo cardiomyopathy, and myocarditis. Clinical history, assay of myocardial enzymes, electrocardiogram, echocardiography, coronary angiography, and left ventriculography facilitate the initial diagnosis of MINOCA and reveal the underlying causes, while cardiovascular magnetic resonance and optical coherence tomography (OCT) are used to confirm the diagnosis. Although cardiovascular magnetic resonance is the gold standard noninvasive diagnostic tool for MINOCA, its ability to diagnose the cause and mechanism underlying this condition in the coronary arteries is limited because of its image resolution. Observational studies have demonstrated that OCT can be used to determine the underlying cause of MINOCA by investigating the characteristics of the culprit lesions and to predict the prognosis of the patients. In this article, we review the current diagnostic approach for MINOCA focusing on each imaging tool. Furthermore, we reevaluate the role of OCT in the clinical management of MINOCA. Identifying the cause of MINOCA through OCT might help select optimal and effective drug treatments and improve prognosis.

Objective To evaluate the short-and long-term prevalence of persistent uncovered struts and in-stent thrombus after sirolimus-eluting stent(SES)implantation by optical coherence tomography (OCT).Methods OCT was performed for 31 SES in 21 patients at 3 months and for 30 SES in 21 patients at 2 years post SES implantation.Thickness of new intima inside each strut was measured and thickness equal to 0 μm was defined as an uncovered strut.Existence of in-stent thrombus was also evaluated.Results A total of 4545 struts and 3707 struts were evaluated at 3 months and at 2 years post SES implantation,respectively.New intima at 2 years was significantly thicker than that at 3 months[(71±93)μm vs.(29±41)μm,P＜0.01].Percent of uncovered struts at 2 years was significantly lower than that at 3 months(5%vs.15%,P＜0.01).Prevalence of uncovered struts was similar at 2 years and at 3 months(81%vs.95%,P＞0.05).subclinical thrombus was recognized in 14%patients at 3 months and 2 years post SES implantation.Conclusions Neointimal coverage inside the SES is a continuous process and the number of uncovered struts decreased from 3 months to 2 years after SES implantation.Few uncovered struts could still be visualized in the majority of patients at 2 years post SES implantation.