Blood transfusion linked to STEMI mortality, causality remains uncertain
MedWire News: Red blood cell transfusion is associated with increased mortality in patients with ST-segment elevation myocardial infarction (STEMI), researchers report.
Christopher Granger (Duke Clinical Research Center, Durham, North Carolina, USA) and team studied the association of transfusion with 90-day mortality in MI patients using data from the Assessment of Pexelizumab in Acute Myocardial Infarction (APEX) trial of 5532 STEMI patients who all underwent percutaneous coronary intervention (PCI).
“After adjusting for the propensity of receiving transfusion and other key mortality predictors and biases, patients who received transfusion were still about twice as likely to die after their MIs,” the researchers report in the European Heart Journal.
However, the team still cannot rule out effects of anemia and bleeding on the association, which “could be directly resulting in death and/or indirectly related to risk of death as markers of disease severity.”
Having initially determined baseline and in-hospital predictors of transfusion using two multivariable models, the researchers compared survival between the 213 patients who did and 5319 who did not undergo transfusion, using Cox hazards modeling, at the prespecified landmarks of 24, 48, 72, and 96 hours after randomization. From this the trend for association between transfusion and 90-day mortality could be derived. The authors note that they chose such a landmark analysis to minimize any survival bias, “whereby patients who die soon after their MIs are less likely to receive blood transfusion.”
After multivariable adjustment, blood transfusion was significantly associated with increased 90-day mortality (HR=2.21), and remained so after further adjustment for the propensity of receiving a blood transfusion (HR=2.16).
The association was not significant among patients who survived to discharge, although it was consistent in direction, and the authors note the number of events was very low in this subset.
Granger and colleagues write: “The association between transfusion and mortality is consistent and independent of measured confounding factors in a population in which all patients underwent invasive procedures.
However, they add that, although transfusion may be causally related to mortality, it is likely that at least part of the association is due to confounding.
They conclude: “This association illustrates the complex relationship between transfusion, bleeding, and mortality and underscores the need for further research to understand the relationship between transfusion and clinical outcomes.”
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By Caroline Price