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

Abstract

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.

Keywords: acute coronary syndrome; anticoagulant; antiplatelet; myocardial infarction; non-ST-elevation myocardial infarction; revascularization; type 1 myocardial infarction; type 2 myocardial infarction.

Figure 1

Classification of myocardial infarction based on the fourth universal definition.5 CABG, coronary artery bypass grafting; CAD, coronary artery disease; ECG, electrocardiogram; MI, myocardial infarction; PCI, percutaneous coronary intervention

Figure 2

Algorithm for the management of non‐ST‐elevation myocardial infarction. Adapted with permission from Amsterdam et al1 ^aPatients treated with fondaparinux should also receive an anticoagulant that inhibits factor IIa at the time of PCI to reduce the risk of catheter thrombosis. ^bBivalirudin (class I, LOE B) is also recommended for patients undergoing an early invasive strategy but is only used in the catheterization laboratory. Fondaparinux (class I, LOE B) is not routinely recommended; patients treated with fondaparinux should also receive an anticoagulant that inhibits factor IIa at the time of PCI to reduce the risk of catheter thrombosis. ASA, aspirin; CABG, coronary artery bypass graft; cath, cardiac catheterization; d, days; DAPT, dual antiplatelet therapy; GPI, glycoprotein IIb/IIIa inhibitor; h, hours; LOE, level of evidence; mo, months; NSTEMI, non‐ST‐elevation myocardial infarction; PCI, percutaneous coronary intervention; pts, patients; UFH, unfractionated heparin

Figure 3

A proposed framework for management of type 2 myocardial infarction. Adapted with permission from Januzzi and Sandoval.50 CAD, coronary artery disease