Acute Anemia Raises Risk After Heart Attack but Does Not Affect Transfusion Strategy Outcomes

A new analysis of the Myocardial Ischemia and Transfusion (MINT) trial has found that acute anemia in patients with myocardial infarction (MI) is associated with a higher risk of death or recurrent heart attack within 30 days. However, the study also concluded that the severity and timing of anemia do not change the effectiveness of different red blood cell (RBC) transfusion strategies.

The study, published as a secondary analysis of the MINT trial, examined data from 3144 patients across 126 hospitals in six countries. For this analysis, researchers classified anemia as either acute or chronic. Acute anemia was defined as an initial hemoglobin level above 13 g/dL in men or 12 g/dL in women, followed by a drop below 10 g/dL before randomization, or as a decrease of at least 2 g/dL before randomization. All other cases were classified as chronic anemia. The study assessed the impact of anemia acuity on patient outcomes and whether it influenced the effects of transfusion strategy.

The results showed that acute anemia was linked to a 25% higher risk of death or recurrent MI at 30 days compared with chronic anemia. The study also found that patients with acute anemia had a 47% higher risk of death and a 36% higher risk of pulmonary complications. However, the risks of recurrent MI, heart failure, cardiac death, and major bleeding were similar between the two anemia groups. Despite these differences in clinical outcomes, the effect of a restrictive transfusion strategy compared with a liberal one remained consistent, regardless of anemia acuity. There was no significant interaction between anemia acuity and transfusion strategy in the primary outcome analysis.

Patients with acute anemia were more likely to have experienced blood loss, hemodynamic instability, and critical care interventions prior to randomization. However, the study did not find evidence that these patients benefit more from a liberal transfusion strategy compared with those with chronic anemia.

The study had several limitations, including the classification of acute anemia based on available hemoglobin measurements, which may not have captured all cases accurately. Sensitivity analyses using an alternative definition of acute anemia yielded different results, highlighting the potential impact of classification criteria. Additionally, while the study adjusted for multiple clinical factors, the more severe illness seen in patients with acute anemia could have influenced the observed differences in outcomes.

“Anemia acuity did not appear to explain the potential harm of a restrictive RBC transfusion strategy observed in the MINT trial,” the study authors concluded. “In patients with anemia and MI, clinicians should not be guided by the acuity of the anemia in selecting a transfusion strategy.”

Reference
Carrier FM, Cooper HA, Portela GT, et al. Anemia acuity effect on transfusion strategies in acute myocardial infarction: a secondary analysis of the MINT trial. JAMA Netw Open. 2024;7(11):e2442361. Published 2024 Nov 4. doi:10.1001/jamanetworkopen.2024.42361