Restrictive versus liberal blood transfusion strategies in patients with myocardial infarction and anemia: individual patient data meta-analysis of randomized trials
Authors: Carson J , Fergusson D A , Noveck H , Mallick R , Rao S V , Simon T , Steg P G , Cooper H A , Goodman S G , Alexander J H , Stanworth S J , Brooks M M , Hebert P A 
Published: October 2024

Abstract

Background
There are insufficient data to guide the appropriate use of red blood cell transfusion in patients with anemia and acute myocardial infarction (MI).

Purpose
To combine individual patient data from randomized clinical trials evaluating restrictive versus liberal transfusion strategies in patients with acute MI and anemia to generate precise estimates of treatment effects.

Methods
We searched all major databases to identify trials comparing restrictive versus liberal transfusion strategies in patients with acute MI and anemia (Hgb &lt; 10 g/dl). We included studies that allocated participants to a liberal transfusion strategy that maintained hemoglobin greater than 10 g/dL or a restrictive transfusion strategy in which transfusion was administered if hemoglobin concentration was less than 8 g/dL. The primary outcome was a composite of 30-day death or MI. Secondary outcomes included 30-day death, 30-day cardiac death, and 6-month death. One-stage individual patient data meta-analyses were performed using a multilevel generalized linear model accounting for the clustering of patients within trials.

Results
We included 4311 participants from four trials. The primary outcome occurred in 334 patients (15.4%) in the restrictive and 296 patients (13.8%) in the liberal strategy (relative risk (RR) 1.13, 95% confidence interval (CI), 0.97 to 1.30) (figure 1). Death at 30-days occurred in 201 patients (9.3%) in the restrictive and 174 patients (8.1%) in the liberal strategy (RR 1.15; 95% CI, 0.95 to 1.39). Cardiac death at 30 days occurred in 5.5% in the restrictive strategy compared to 3.7% in the liberal strategy (RR 1.47; 95% CI, 1.11 to 1.94). Heart failure and thromboembolism occurred slightly more frequently in the liberal transfusion strategy group. Death at six months was higher in the restrictive (20.5%) compared to the liberal strategy (19.1%) (hazard ratio (HR) 1.08; 95% CI 1.05 to 1.11) (figure 2). The HR for cardiac death at 6 months was higher with a restrictive than liberal strategy (HR 1.38; 95% CI 1.08 to 1.76). In contrast, the HR for non-cardiac death at 6 months was lower with a restrictive than a liberal transfusion strategy (HR 0.89; 95% CI 0.84 to 0.94). Adjustment for baseline characteristics minimally changed the relative risk. Results for subgroups were similar except in patients without a history of renal failure whose risk of death or MI was increased with a restrictive strategy (RR 1.19; 95% CI, 1.01 to 1.39).

Conclusions
Pooled data from randomized trials found no significant differences for the primary outcome 30-day death or MI, but risk of cardiac death at 30 days and all cause death at 6 months was higher with a restrictive transfusion strategy. Given most outcomes favored liberal transfusion, and the risks from liberal transfusion were low, it may be prudent to use a liberal transfusion strategy in patients with acute MI and anemia.