Defining and managing patients with non-ST-elevation myocardial infarction: Sorting through type 1 vs other types

Advances in cardiovascular (CV) imaging, redefined electrocardiogram criteria, and high-sensitivity CV biomarker assays have enabled more differentiated etiological classification of myocardial infarction (MI). Type 1 MI has a different underlying pathophysiology than type 2 through type 5 MI; type 1 MI is characterized primarily by intracoronary atherothrombosis and the other types by a variety of mechanisms, which can occur with or without an atherosclerotic component. In type 2 MI, there is evidence of myocardial oxygen supply-demand imbalance unrelated to acute coronary atherothrombosis. Types 1 and 2 MI are spontaneous events, while type 4 and type 5 are procedure-related; type 3 MI is identified only after death. Most type 1 and type 2 MI present as non-ST-elevation MI (NSTEMI), although both types can also present as ST-elevation MI. Because of their different underlying etiologies, type 1 and type 2 NSTEMI have different presentation and prognosis and should be managed differently. In this article, we discuss the epidemiology, prognosis, and management of NSTEMI occurring in the setting of underlying type 1 or type 2 pathophysiology. Most NSTEMI (65%-90%) are type 1 MI. Patients with type 2 MI have multiple comorbidities and causes of in-hospital mortality among these patients are not always CV-related. It is important to distinguish between type 1 and type 2 NSTEMI early in the clinical course to allow for the use of the most appropriate treatments that will provide the greatest benefit for these patients.