Etiological myocardial injury classification versus binary myocardial infarction classification in the multi-ethnic study of atherosclerosis (MESA).

Background: Prospective cohorts almost exclusively classified acute myocardial injury as a binary entity-presence or absence of myocardial infarction (MI). Objective: To compare Binary Classification of MI used in the Multi-Ethnic Study of Atherosclerosis (MESA) to an Etiological Classification of myocardial injury. Methods: Comparison of two different MI adjudication systems in 6809 participants aged 45-84 years old from MESA, a community-dwelling cohort free of cardiovascular disease at enrollment (2000). The Binary Classification defined events as MI versus "No MI". The Etiological Classification, based on the Fourth Universal Definition of MI, categorized events as MI (types 1-5), acute non-ischemic myocardial injury, chronic myocardial injury, and no myocardial injury. Number and distribution of myocardial infarction/injury events identified by each classification system were compared. Results: Binary Classification identified 333 MI events, while Etiological Classification identified 406 MIs, of which 202 (49.8%) were type 1 MI and 182 (44.8%) were type 2 MI, 22 (5.4%) were other MI types. Notably, 147 events (33 type 1 MI, 105 type 2 MI, 9 other MI types) were newly captured as MI with the Etiological Classification that were classified as No-MI by the Binary Classification. Among the 333 MI identified by the Binary Classification, 51% were type 1 MI ( Conclusions: Etiological Classification identifies additional, etiologically distinct myocardial injury events. Almost half of the events identified as an MI by Binary Classification were identified as type 2 MI or acute non-ischemic myocardial injury by Etiological Classification.