Hemoglobin (Hb) threshold for red cell transfusion in myocardial infarction (MI) with anemia has been a matter of debate. Previous randomized trials have not consistently shown a benefit of liberal transfusion strategy. Mechanistically, liberal strategy could decrease ischemic injury by increasing oxygen delivery to the myocardium. However, this could be associated with an increased risk of heart failure (HF) from volume overload, thrombosis, and infection. The Myocardial Ischemia and Transfusion (MINT) trial randomized 3,504 patients diagnosed with acute MI and concomitant anemia (Hb <10 g/dL) who were randomized to a liberal transfusion strategy to maintain a Hb level ≥10 g/dL, or a restrictive strategy where transfusion was permitted but not required for Hb <8 g/dL but strongly recommended in Hb <7 g/dL or angina refractory to antianginals.¹ The primary endpoint was a composite of all-cause death or recurrent nonfatal MI at 30 days.

The primary composite endpoint of all-cause death or recurrent nonfatal MI for restrictive versus liberal strategies was 16.9% versus 14.5% (risk ratio [RR] 1.15, 95% confidence interval [CI] 0.99-1.34, p = 0.07), secondary outcomes were all-cause death (9.9% vs. 8.3%, RR 1.19 [95% CI 0.96-1.47]), recurrent nonfatal MI (8.5% vs. 7.2%, RR 1.19 [95% CI 0.94-1.49]), HF (5.8% vs. 6.3%, RR 0.92 [95% CI 0.71-1.20]), and no significant difference in the risk of infection or thrombotic events.

In contrast to previous evidence which did not show a difference in 30-day all-cause mortality with liberal versus restrictive transfusion,² the MINT trial although not statistically significant, numerically demonstrated a trend toward benefit of a liberal transfusion strategy as compared to a restrictive strategy with 2.4% lower risk of recurrent MI or death and 2.3% lower risk of cardiac death at 30 days, without increasing concerns for safety for liberal strategy.

References

1. Carson JL, Brooks MM, Hébert PC, et al., on behalf of the MINT Investigators. Restrictive or liberal transfusion strategy in myocardial infarction and anemia. N Engl J Med 2023;389:2446-56.
2. Carson JL, Stanworth SJ, Dennis JA, et al. Transfusion thresholds for guiding red blood cell transfusion. Cochrane Database Syst Rev 2021;12:CD002042.