Assessment and Treatment of Patients with Type 2 Myocardial Infarction and Acute Non-Ischemic Myocardial Injury

While coronary thrombus overlying a disrupted atherosclerotic plaque has long been considered the hallmark and the primary therapeutic target for acute myocardial infarction (MI), multiple other mechanisms are now known to cause or contribute to MI. It is further recognized that a myocardial infarction (MI) is just one of many types of acute myocardial injury. The Fourth Universal Definition of Myocardial Infarction (UDMI) provides a taxonomy for acute myocardial injury, including five subtypes of MI and non-ischemic myocardial injury. The diagnosis of MI is reserved for patients with myocardial ischemia as the cause of myocardial injury, whether due to acute atherothrombosis (type 1 MI) or supply/demand mismatch without acute atherothrombosis (type 2 MI). Myocardial injury in the absence of ischemia is categorized as acute or chronic non-ischemic myocardial injury. However, optimal evaluation and treatment strategies for these etiologically distinct diagnoses have yet to be defined. Herein, we review the epidemiology, risk factor associations, and diagnostic tools that may assist in differentiating between non-ischemic myocardial injury, Type 1 MI, and Type 2 MI. We identify limitations, review new research, and propose a framework for the diagnostic and therapeutic approach for patients who have suspected MI or other causes of myocardial injury.