Acute myocardial infarction and blood transfusion: lessons learned from animal models and clinical studies.

In this issue of Blood Transfusion, Bulle et al. analyze the incidence of adverse cardiopulmonary events in an animal model of acute myocardial infarction (MI) and transfusion 1 .Blood transfusion in patients with acute MI may be indicated to improve oxygen delivery or reduce the risk of bleeding in the setting of anti-platelet agents or therapeutic anticoagulation 2,3 .Specifically, the management of acute MI may include concurrent administration of thrombolytic, antithrombotic, or antiplatelet therapies around the time of percutaneous coronary revascularization procedures, increasing the risk of bleeding and acute anemia.In addition, chronic anemia is often present in older patients with acute MI, especially in those with chronic kidney disease, congestive heart failure, or a history of coronary artery disease 4 .Several observational studies have associated acute and chronic anemia with adverse outcomes in patients with acute MI 5,6 .While most individuals are able to increase oxygen delivery and extraction of oxygen from RBCs over a range of hemoglobin concentrations, some patients with acute MI have reduced end-organ oxygen utilization and do not tolerate reductions in oxygen delivery with anemia 7 .In the setting of acute or chronic anemia, red blood cell (RBC) transfusion may be beneficial by sustaining oxygen delivery to myocardial cells and decreasing myocardial oxygen demand in patients with acute coronary occlusions or mitigate oxygen supply/demand mismatches in patients with non-occlusive MI.Concurrently, plasma components are at times transfused to patients with acute MI to reverse anticoagulation prior to coronary revascularization procedures or to treat coagulopathy in the setting of bleeding.Despite their potential benefits, blood transfusions include biologically active products that may induce immune responses and expand vascular volume.With advances in transfusion medicine, complications related to transfusion-transmitted infections, transfusion-related acute lung injury (TRALI), and severe hemolytic reactions have become rare 8,9 .However, transfusion may induce circulatory overload resulting in pulmonary edema (transfusion associated circulatory overload, TACO) and associated adverse patient outcomes.TACO remains the leading cause of transfusion-associated morbidity and mortality, and many of the risk factors for TACO, such as ischemic cardiomyopathy or chronic kidney disease, parallel those for acute MI 10,11 .Pulmonary edema is a recognized adverse outcome in clinical trials of acute MI and RBC transfusion.In the CRIT and REALITY trials, there was an increased number of cases of pulmonary edema in the liberally compared to restrictively transfused group 12,13 .