MINOCA (myocardial infarction with non obstructed coronary arteries) has been known for quite some time but is greatly under appreciated. Such patients meet the universal definition of MI but have coronary arteriograms demonstrating no lesions causing greater than 50% obstruction. They may be deceptively labeled as having “insignificant coronary artery disease.” Some will be misdiagnosed as stress cardiomyopathy (formerly Takotsubo) or myocarditis. What’s really going on? It’s a complex and poorly understood interplay of multiple factors. Mild (less than 50% obstructive) plaques may ulcerate or rupture. This may cause thrombus with obstruction which spontaneously recanalizes. Inflammation, endothelial dysfunction, coronary spasm and procoagulant influences may interact. Other patients may have type 2 MI. These mechanisms are reviewed in a recent editorial.