Clinical features and outcomes of patients with type 2 myocardial infarction: Insights from the Thrombin Receptor Antagonist for Clinical Event Reduction in Acute Coronary Syndrome (TRACER) trial.

Background: Type 2 myocardial infarction (MI) is characterized by an imbalance between myocardial blood supply and demand, leading to myocardial ischemia without coronary plaque rupture, but its diagnosis is challenging.
Methods: In the TRACER trial, patients with non-ST-segment elevation acute coronary syndromes were included. We aimed to describe provoking factors, cardiac biomarker profiles, treatment patterns, and clinical outcomes of patients with type 2 MIs. MI events during trial follow-up were adjudicated by an independent clinical events classification committee (CEC) and were classified according to the Third Universal Definition of MI. Using available source documents retrieved as part of the CEC process, we performed a retrospective chart abstraction to collect details on the type 2 MIs. Cox regression models were used to explore the association between MI type (type 1 or type 2) and cardiovascular death.
Results: Overall, 10.3% (n=1327) of TRACER participants had a total of 1579 adjudicated MIs during a median follow-up of 502 days (25th and 75th percentiles [IQR] 349-667). Of all MIs, 5.2% (n=82) were CEC-adjudicated type 2 MIs, occurring in 76 patients. The incidence of type 2 MI was higher in the first month following randomization, after which the distribution became more scattered. The most frequent potential provoking factors for type 2 MIs were tachyarrhythmias (38.2%), anemia/bleeding (21.1%), hypotension/shock (14.5%), and hypertensive emergencies (11.8%). Overall, 36.3% had a troponin increase >10× the upper limit of normal. Coronary angiography was performed in 22.4% (n=17) of patients during hospitalizations due to type 2 MIs. The hazard of cardiovascular death was numerically higher following type 2 MI (vs. no MI, adj. HR 11.82, 95% CI 5.71-24.46; P<.0001) than that of type 1 MI (vs. no MI, adj. HR 8.90, 95% CI 6.93-11.43; P<.0001).
Conclusions: Type 2 MIs were more prevalent in the first month after ACS, were characterized by the presence of triggers and infrequent use of an invasive strategy, and were associated with a high risk of death. Further efforts are needed to better define the role and implications of type 2 MI in both clinical practice and research.
(Copyright © 2017 Elsevier Inc. All rights reserved.)