MINT Trial: Restrictive or Liberal Transfusion Strategy in Myocardial Infarction, Anemia

The question of the appropriate transfusion threshold for patients presenting with acute myocardial infarction (MI) has been studied in 3 previous randomized, controlled clinical trials. The initial trial, the CRIT randomized pilot study, consisted of 45 patients randomized to a restrictive or liberal transfusion level. It showed no statistically significant difference for in-hospital death, recurrent MI, or new/worsening heart failure but hinted toward harm with the liberal transfusion strategy.¹ This study was followed by the MINT pilot clinical trial, which randomized 110 patients to a restrictive or liberal transfusion strategy. No statistically significant difference was found in the primary outcome of death, MI, or unscheduled revascularization, but the liberal transfusion strategy trended toward better outcomes.² The third trial, the REALITY randomized clinical trial, randomized 668 patients to a restrictive or liberal transfusion threshold and demonstrated noninferiority of the restrictive strategy compared with the liberal strategy.³

However, these trials had low numbers of study participants (823 overall) and conflicting results. The MINT trial⁴ sought to address the question of the appropriate transfusion threshold in patients presenting with acute MI and anemia. A total of 3504 patients were randomly assigned to a restrictive transfusion strategy (target hemoglobin value, 7-8 g/dL) or a liberal transfusion strategy (target hemoglobin value, 10 g/dL). The baseline hemoglobin for participants prior to intervention was 8.6 g/dL; those in the restrictive group averaged 0.7 red-cell unit transfusions compared with the liberal group, which averaged 2.5 red-cell unit transfusions. The primary outcome of MI or death at 30 days was not statistically significant between the 2 transfusion thresholds, with a P value of 0.07; however, the trial did suggest a possible benefit with the liberal strategy. Prespecified subgroup analyses showed patients with type 1 MI randomized to the restrictive strategy had more primary outcome events, with a risk ratio of 1.32 (95% CI, 1.04-1.67); this difference was not seen in patients with type 2 MI.

While the MINT trial did not reach statistical significance, it did offer more data to help clinicians determine the appropriate transfusion threshold for individual patients presenting with acute MI and anemia. Further trials should be conducted to elucidate if the liberal transfusion strategy clearly leads to better clinical outcomes and, if so, which patient population is most likely to benefit.

Dr. Cali Clark is a PGY3 chief resident at Freeman Health Systems and served as a CardioNerds Conference Scholar for the American Heart Association 2023 Scientific Sessions.

References

1. Cooper HA, Rao SV, Greenberg MD, et al. Conservative versus liberal red cell transfusion in acute myocardial infarction (the CRIT randomized pilot study). Am J Cardiol. 2011;108(8):1108-1111. doi:10.1016/j.amjcard.2011.06.014
2. Carson JL, Brooks MM, Abbott JD, et al. Liberal versus restrictive transfusion thresholds for patients with symptomatic coronary artery disease. Am Heart J. 2013. doi:10.1016/j.ahj.2013.03.001
3. Ducrocq G, Gonzalez-Juanatey JR, Puymirat E, et al. Effect of a restrictive vs liberal blood transfusion strategy on major cardiovascular events among patients with acute myocardial infarction and anemia: the REALITY randomized clinical trial. 2021;325(6):552-560. doi:10.1001/jama.2021.0135
4. Carson JL, Brooks MM, Hébert PC, et al; MINT Investigators. Restrictive or liberal transfusion strategy in myocardial infarction and anemia. N Engl J Med. 2023. doi:10.1056/NEJMoa2307983