Restrictive Versus Liberal Transfusion in Patients with Type 1 or Type 2 Myocardial Infarction: A Prespecified Analysis of the Myocardial Ischemia and Transfusion (MINT) Trial

BACKGROUND: The MINT trial (Myocardial Ischemia and Transfusion) raised concern for harm from a restrictive versus liberal transfusion strategy in patients with acute myocardial infarction (MI) and anemia. Type 1 and type 2 MI are distinct pathophysiologic entities that may respond differently to blood transfusion. This analysis sought to determine whether the effects of transfusion varied among patients with a type 1 or a type 2 MI and anemia. The authors hypothesized that the liberal transfusion strategy would be of greater benefit in type 2 than in type 1 MI. METHODS: The authors compared rates of death or MI at 30 days in patients with type 1 (n=1460) and type 2 (n=1955) MI and anemia who were randomly allocated to a restrictive (threshold, 7–8 g/dL) or a liberal (threshold, 10 g/dL) transfusion strategy. RESULTS: The primary outcome of death or MI was observed in 16% of type 1 MI and 15.4% of type 2 MI patients. The rate of death or MI was higher in patients with type 1 MI randomized to a restrictive (18.2%) versus liberal (13.8%) transfusion strategy (relative risk RR, 1.32 95% CI, 1.04–1.67) with no difference observed between the restrictive (15.8%) and liberal (15.1%) transfusion strategies in patients with type 2 MI (RR, 1.05 95% CI, 0.85–1.29). The test for a differential effect of transfusion strategy by MI type was not statistically significant ( P interaction = 0.16). CONCLUSIONS: The concern for harm with a restrictive transfusion strategy in patients with acute MI and anemia raised in the MINT primary outcome manuscript may be more apparent in patients with type 1 than type 2 MI. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02981407.