Red blood cell transfusion among patients with coronary artery disease has become an increasingly controversial practice over the years, with a growing body of evidence suggesting that the procedure in the setting of acute coronary syndromes and in hospitalized patients with a history of coronary artery disease may be associated with a greater risk of myocardial infarction (MI) and death. Given anemia is a commonly known risk factor for exacerbating myocardial ischemia, and that increasing hemoglobin through red blood cell transfusion is a guaranteed way of increasing oxygen to the heart and mitigating an ischemic outcome, this clashing of real-world practice and pathophysiological rationale has left many in the medical community treading a cautious line.

In a new investigation published Feb. 25 in the Journal of the American Medical Association, Matthew Sherwood, MD, Duke Clinical Research Institute, and his team of researchers sought to provide a more comprehensive, evidence-based set of guidelines for transfusion in patients with coronary artery disease, and found that blood transfusion for patients undergoing percutaneous coronary intervention (PCI) is associated with an increased risk of in-hospital cardiac events.

Using data from the CathPCI Registry — examining the variation in transfusion practice patterns of 2,258,711 patient visits across 1,431 U.S. hospitals from July 2009 to March 2013 —Sherwood and his colleagues successfully determined the current patterns of blood transfusions among patients undergoing PCI and the association of transfusion with adverse cardiac outcomes across hospitals in the U.S.

Compared to no transfusion, patients who underwent the procedure were more likely to experience in-hospital MI (42,803 events; 4.5 percent vs 1.8 percent; odds ratio [OR], 2.60; 95 percent CI, 2.57-2.63), stroke (5,011 events; 2.0 percent vs 0.2 percent; OR, 7.72; 95 percent CI, 7.47-7.98), and death (31,885 events; 12.5 percent vs 1.2 percent; OR, 4.63; 95 percent CI, 4.57-4.69), with these associations remaining significant in patients with and without bleeding events at nearly all hemoglobin levels.

Sherwood and his team conclude that their resulting data highlights the need for randomized trials of transfusion strategies to guide better practice in patients undergoing PCI. However, until such trials are initiated clinicians should continue to use strategies that reduce the risk of bleeding and subsequent need for transfusion.

"The findings of this study are not surprising because the majority of studies that evaluated the impact of blood transfusion on outcome after PCI or after coronary artery bypass graft surgery (CABG) reached the same conclusion (i.e., blood transfusion is associated with worse outcome)," said Issam D. Moussa, MD, FACC, chair of the CathPCI Registry. "What remains unclear, however, is whether blood transfusion per se is the reason for the worse outcome or its the fact that patients who require blood transfusion are sicker patients with higher frequency of co-morbidities and bleeding events. At any rate, in clinical practice it seems that blood transfusion is being used more often than it should. There need to be more robust evidence and guidelines to reduce unnecessary transfusions. It goes without saying that avoiding bleeding complications after PCI and CABG is critically important."

Keywords: Registries, Erythrocyte Transfusion, Coronary Disease, Risk Factors, Coronary Artery Bypass, Percutaneous Coronary Intervention, National Cardiovascular Data Registries, CathPCI Registry

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