Diagnosis and Prognosis of Type 2 Myocardial Infarction Using Objective Evidence of Acute Myocardial Ischemia: A Validation Study.

BACKGROUND: Differentiating type 2 myocardial infarction from myocardial injury can be difficult. In addition, the presence of objective evidence of myocardial ischemia may facilitate identification of high-risk type 2 myocardial infarction patients. METHODS: This was an observational cohort study of adult emergency department patients undergoing high-sensitivity cardiac troponin T (hs-cTnT) measurement. Patients with ≥1 hs-cTnT >99th percentile were adjudicated following the Fourth Universal Definition of Myocardial Infarction. Patients were categorized as "subjective type 2 myocardial infarction" when ischemic symptoms were the lone criteria supporting type 2 myocardial infarction, or "objective type 2 myocardial infarction" when there was ≥1 objective clinical feature (electrocardiography, imaging, angiography) of acute myocardial ischemia. The primary outcome was mortality. RESULTS: A total of 857 patients were included, among which 55 (6.4%) were classified as subjective type 2 myocardial infarction, 36 (4.2%) as objective type 2 myocardial infarction, and 702 (82%) as myocardial injury. Those with objective type 2 myocardial infarction had a higher risk of mortality during the index presentation (17% vs 1.7%, P < .0001; hazard ratio 11.1; 95% confidence interval, 3.7-33.4) and at 2-year follow-up (47% vs 31%, P = .04; hazard ratio 1.92; 95% confidence interval, 1.17-3.14) than those with myocardial injury. Objective type 2 myocardial infarction had a higher mortality than subjective type 2 myocardial infarction at index presentation (17% vs 2.0%, P = .01) and at 1 (25% vs 9.1%, P = .04) and 3 months (31% vs 13%, P = .04) follow-up. There were no mortality differences between subjective type 2 myocardial infarction and myocardial injury. CONCLUSION: In patients diagnosed with type 2 myocardial infarction, those with objective evidence of myocardial ischemia have significantly worse outcomes compared with those with myocardial injury and subjective type 2 myocardial infarction. A more rigorous type 2 myocardial infarction definition that emphasizes these criteria may facilitate diagnosis and risk-stratification.