In a large trial, differences in key outcomes favoring a liberal transfusion strategy just missed statistical significance.

A restrictive transfusion strategy (hemoglobin [Hb] cutoff, <7 g/dL) is accepted widely as the standard of care for most hospitalized patients. However, some controversy remains for patients with acute myocardial infarction (MI) and anemia (NEJM JW Gen Med May 1 2021 and JAMA 2021; 325:552). In this international study, researchers randomized 3500 adult patients with MI and anemia (Hb level, ≤10 g/dL) to either a restrictive transfusion strategy (Hb cutoff, <7 or <8 g/dL, per clinician judgment) or a liberal transfusion strategy (Hb cutoff, <10 g/dL).

At 30 days after randomization, the incidence of key outcomes for patients in the restrictive- and liberal-transfusion groups, respectively, were as follows:

• Primary outcome (recurrent MI or death at 30 days): 16.9% vs. 14.5%
• Death: 9.9% vs. 8.3%
• Recurrent MI: 8.5% vs. 7.2%

For each of the above endpoints, the numerical difference that suggested better outcomes with liberal transfusion just missed statistical significance. As expected, the total number of transfused units was much higher in the liberal-strategy group (4300 vs 1200 units), and patients in the liberal-strategy group were almost three times more likely to receive at least 1 transfused unit (95% vs. 34%). However, the incidence of new or worsening heart failure was only slightly (and not significantly) higher with the liberal strategy (6.3% vs. 5.8%).

Comment

This is the largest study to date of transfusion cutoffs among patients with acute MI and anemia. The borderline statistical differences in major adverse outcomes, slightly favoring the liberal strategy, suggest that clinicians should have some latitude in picking a transfusion threshold (i.e., somewhere between 7 and 10 g/dL). Nevertheless, a tendency toward a restrictive strategy also remains reasonable, given the lower consumption of blood resources, fewer transfusion reactions, and cost savings.