Unraveling the Multitude of Etiologies in Myocardial Infarction With Nonobstructive Coronary Arteries.

Although recent studies revealed suboptimal outcomes in patients with myocardial infarction with nonobstructive coronary arteries (MINOCAs), the underlying etiology remains unknown in most patients. Therefore, adequate treatment modalities have not yet been established. We aimed to assess demographics, treatment strategies, and long-term clinical outcome in MINOCA subgroups. We retrospectively analyzed data from a large, prospective observational study of patients with acute coronary syndrome admitted to the Isala hospital in Zwolle, The Netherlands between 2006 and 2014. Patients with MINOCA were divided into subgroups based on the underlying cause of the event. From 7,693 patients, 402 patients (5%) concerned MINOCA. After the exclusion of missing cases (n = 47), 5 subgroups were distinguished: "true" acute myocardial infarction (10%), perimyocarditis (13%), cardiomyopathy (including Takotsubo cardiomyopathy) (19%), miscellaneous causes (21%), and an indeterminate group (38%). Patients with cardiomyopathy were predominantly women (78%) and showed the highest incidence of major adverse cardiovascular events at 30 days follow-up (7%; p = 0.012), 1 year (19%; p = 0.004), and mortality at long-term follow-up (27%; p = 0.010) compared with any other MINOCA subgroup. The cardiomyopathy group was followed by the indeterminate group, with major adverse cardiovascular events rates of 1% and 5%, respectively, and 17% long-term all-cause mortality. In conclusion, long-term prognosis in MINOCA depends on the underlying etiology. Prognosis is worst in the cardiomyopathy group followed by the indeterminate group. This underlines the importance of revealing the diagnosis to ultimately optimize treatment.