Anemia is a well-established contributor to unfavorable outcomes in acute myocardial infarction (MI) patients.1 Both acute and chronic anemia independently predict increased mortality in this population.2 In acute coronary syndrome (ACS), anemia, prevalent in 10 %-43 % of cases, is often intertwined with comorbidities such as advanced age, hypertension, heart failure, malignancy, malnutrition, and chronic kidney disease.3 Moreover, acute anemia poses challenges to ACS interventions like thrombolytics, anticoagulation, and percutaneous coronary intervention (PCI).

The pathophysiologic consequences of anemia primarily stem from reduced oxygen supply and carrying capacity, exacerbating the compromised coronary blood flow in acute MI.4 This mismatch between oxygen supply and demand amplifies myocardial damage.4 Additionally, anemia fosters an augmented inflammatory response, impairing vascular healing and myocardial remodeling, ultimately contributing to poor long-term outcomes.4

While transfusing packed red blood cells (RBCs) to enhance oxygen carrying capacity is a potential solution, blood transfusions come with inherent risks such as transfusion reactions, volume overload, infections, pro-inflammatory and prothrombotic effects, and cost burdens. Determining the appropriate hemoglobin cutoff value and target levels for blood transfusions in ACS has been a subject of debate.5 Although RCTs comparing liberal (triggered by Hb <8) and restrictive (triggered by Hb <8) transfusion approaches yielded varied results, a predominantly favorable outcome trend was observed with the more restrictive strategy.3 Current guidelines endorsed by the American Association of Blood Banks also recommend a restrictive approach.5

This meta-analysis consolidates data from four pivotal clinical trials comparing liberal and restrictive blood transfusion approaches. Our objective is to comprehensively evaluate overall outcomes, specifically recurrent MI and death or MI, associated with both transfusion strategies. Secondarily, we aim to evaluate rates stroke, revascularization, heart failure, and all-cause mortality in both groups.