Clinical question: How does a restrictive transfusion strategy (transfusion threshold of 7 to 8 g/dL) compare to a liberal transfusion strategy (transfusion threshold of 10 g/dL) in patients with acute myocardial infarction (MI) and anemia?
Background: Management of anemia in patients with acute MI is an important topic with considerable variability in practice. Generally, there has been a push towards restrictive transfusion to conserve resources and prevent adverse effects, but these patients may be especially vulnerable to physiological strain from anemia. Current clinical guidelines indicate there is insufficient data to support a strong recommendation for hemoglobin thresholds in this patient population.
Study design: Meta-analysis; patient-level data pooled from multiple randomized controlled trials
Setting: Four randomized controlled trials in various clinical settings
Synopsis: Investigators pooled data from four recent randomized controlled trials that evaluated lower versus higher hemoglobin transfusion thresholds for anemia in patients with MI: MINT, CRIT, REALITY, and MINT Pilot. This included 4,311 patients (mean age 72 years, 55% men). The primary outcome of death or recurrent MI within 30 days was not significantly different between groups (15% in the restrictive transfusion group versus 14% in the liberal transfusion group). For secondary outcomes, there was an increase in cardiac mortality at 30 days and all-cause mortality at six months in the restrictive transfusion group compared with the liberal transfusion group (relative risk [RR], 1.47; 95% CI, 1.11 to 1.94; hazard ratio [HR], 1.08; 95% CI, 1.05 to 1.11, respectively). Limitations included that over 80% of the participants were from MINT, and that design differences in the trials limited analysis (e.g., not all trials characterized the type of MI as type 1 versus type 2).
Bottom line: For patients with acute MI and anemia, there was no demonstrable harm of a restrictive transfusion threshold for the major outcome of death or recurrent MI at 30 days. However, it was associated with an increased risk of 30-day cardiac mortality and six-month all-cause mortality. This suggests that restrictive strategies may not be the best option universally for patients with acute MI.
Citation: Carson JL, et al. Restrictive versus liberal transfusion in myocardial infarction—a patient-level meta-analysis. NEJM Evid. 2025;4(2): doi:10.1056/EVIDoa2400223.
Dr. Hebel is an internal medicine resident, PGY-2, at MaineHealth Maine Medical Center in Portland, Maine