Effect of Red Blood Cell Transfusion Strategy on Clinical Outcomes Among Patients with Acute Myocardial Infarction Undergoing Revascularization: A Prespecified Analysis of the MINT Trial.

Background: The Myocardial Ischemia and Transfusion (MINT) Trial (N=3504) randomized patients with acute MI and a hemoglobin ≤ 10 g/dL to liberal (maintain Hgb ≥ 10 g/dL) or restrictive (maintain Hgb ≥ 8 g/dL) red blood cell transfusion. The results suggested a benefit on 30-day death or MI with a liberal transfusion strategy. The effect of transfusion in acute MI patients undergoing revascularization is unclear. Methods: In this pre-specified analysis of the MINT trial, patients who underwent revascularization (N=1002) before randomization but during index hospitalization were compared with those who did not (N=2442). The primary outcome was 30-day death or MI; secondary outcomes included 30-day death, recurrent MI, the composite of death, recurrent MI, ischemia driven unscheduled revascularization, or readmission for ischemic cardiac diagnosis, heart failure, and cardiac death. Multivariable log binomial regression was used to determine the relative risks of the primary and secondary outcomes by transfusion strategy for revascularized and non-revascularized patients with interaction terms. Results: Patients undergoing revascularization were younger, more often female, and had fewer comorbidities than those who did not. There was no significant interaction between revascularization and assigned transfusion strategy for any outcome except cardiac death. Compared with liberal transfusion, restrictive transfusion increased the risk of 30-day cardiac death among non-revascularized patients [RR 2.45 (1.58, 3.81)] but not among revascularized patients [(RR 0.97 (0.59, 1.60), interaction p 0.006]. Conclusions: In this analysis of the MINT trial, revascularization did not alter the effect of randomized transfusion strategy on 30-day death or MI. The hypothesis-generating finding that a restrictive transfusion strategy was associated with an increased risk of cardiac death among anemic patients with acute MI who do not undergo revascularization requires confirmation.