Transfusion in Anemic Patients with Acute Coronary Syndromes: A Population-Based Cohort Study.

Background: There is controversy surrounding the effectiveness of red blood cell (RBC) transfusion for treating anemia in patients hospitalized for acute coronary syndromes (ACS), particularly as hemoglobin levels (Hb) approach and drop below the range of moderate anemia.

Methods: This population-based cohort study followed all adults hospitalized for ACS who experienced an in-hospital nadir Hb between 6.0-8.9g/dL between April 1, 2012 to March 31, 2021 in Ontario, Canada. Patients were excluded if they underwent coronary artery bypass graft surgery or had history of dementia, palliative care, or long-term care. Transfused patients were compared to non-transfused patients. The primary outcome was a composite of all-cause death and hospitalization for myocardial infarction (MI) within 30-days of hospital discharge. Overlap propensity score weighting was used to account for confounding and to emphasize the comparison in patients for whom there is clinical equipoise.

Results: This study included 7,922 patients, of whom 3,498 were transfused and 4,424 were not transfused. In the propensity weighted cohort, the mean nadir Hb for each group was 7.75g/dL. The 30-day cumulative incidence rate for the primary outcome after application of propensity score weights was 28.6% in the transfusion group and 33.3% in the no-transfusion group (hazard ratio [HR]: 0.83, 95% confidence interval [CI] 0.75-0.91), which persisted at 1-year after hospital discharge and across sensitivity analyses.

Conclusions: In patients hospitalized for ACS who experience nadir Hb levels between 6.0-8.9g/dL, RBC transfusion was associated with a reduction in the composite event of all-cause death and hospitalization for MI within 30-days after hospital discharge.