C ontemporary management strategies of acute ST-segment-elevation myocardial infarction (STEMI) are based on the pioneering early angiographic studies of DeWood and colleagues, 1 who demonstrated an occluded coronary artery in almost 90% of these patients. Accordingly, the 'open artery' management strategy was used, initially with the use of thrombolytic therapy and subsequently with percutaneous coronary interventions. In contrast, early angiography in patients with non-ST-segment-elevation myocardial infarction (NSTEMI) showed an occluded vessel in fewer than a third of these patients, 2 so that strategies focusing on maintaining arterial patency were developed. However, both of these acute myocardial infarction (MI) angiographic studies 1,2 demonstrated the presence of significant obstructive coronary artery disease in >97% of these MI patients, thus underscoring the importance of obstructive coronary atherosclerotic disease in this condition. Clinical Perspective on p 870With the widespread use of coronary angiography in the early clinical management of MI, multicenter MI registries have evolved and reported that as many as 10% of MI patients Background-Myocardial infarction with nonobstructive coronary arteries (MINOCA) is a puzzling clinical entity with no previous evaluation of the literature. This systematic review aims to (1) quantify the prevalence, risk factors, and 12-month prognosis in patients with MINOCA, and (2) evaluate potential pathophysiological mechanisms underlying this disorder. Methods and Results-Quantitative assessment of 28 publications using a meta-analytic approach evaluated the prevalence, clinical features, and prognosis of MINOCA. The prevalence of MINOCA was 6% [95% confidence interval, 5%-7%] with a median patient age of 55 years (95% confidence interval, 51-59 years) and 40% women. However, in comparison with those with myocardial infarction associated with obstructive coronary artery disease, the patients with MINOCA were more likely to be younger and female but less likely to have hyperlipidemia, although other cardiovascular risk factors were similar. All-cause mortality at 12 months was lower in MINOCA (4.7%; 95% confidence interval, 2.6%-6.9%) compared with myocardial infarction associated with obstructive coronary artery disease (6.7%, 95% confidence interval, 4.3%-9.0%). Qualitative assessment of 46 publications evaluating the underlying pathophysiology responsible for MINOCA revealed the presence of a typical myocardial infarct on cardiac magnetic resonance imaging in only 24% of patients, with myocarditis occurring in 33% and no significant abnormality in 26%. Coronary artery spasm was inducible in 27% of MINOCA patients, and thrombophilia disorders were detected in 14%. Conclusions-MINOCA should be considered as a working diagnosis with multiple potential causes that require evaluation so that directed therapies may improve its guarded prognosis. These patients with MI with nonobstructive coronary arteries (MINOCA) 4 represent a conundrum because the underlying cause ...

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