Impact of red blood cell transfusion on acute coronary syndrome: a meta-analysis.

The impact of red blood cell transfusion on outcomes in patients with acute coronary syndrome is controversial. Pubmed, EMBASE, and Cochrane Library were searched for studies of red blood cell transfusion and acute coronary syndrome that were published in any language, from January 1, 1966, to April 1, 2016. We analyzed 17 observational studies, of 2,525,550 subjects. We conducted a systematic review with meta-analysis of studies assessing the association between blood transfusion and the risk for all-cause mortality and reinfarction. The search yielded 17 observational studies, of 2,525,550 subjects, during a study follow-up period, ranging from 30 days to 5 years. Red blood cell transfusion compared with no blood transfusion is associated with higher short- and long-term all-cause mortality as well as reinfarction rates (adjusted RR 2.23; 95% CI 1.47-3.39; HR 1.93; 95% CI 1.12-3.34; RR 2.61; 95% CI 2.17-3.14, respectively). In hemoglobin-stratified analyses, a graded association between red blood cell transfusion and mortality was observed, transfusion and risk of all-cause mortality was borderline significant at hemoglobin levels below 8.0 g/dL (RR 0.52; 95% CI 0.25-1.06), and was associated with an increased risk of mortality at a hemoglobin above 10 g/dL (RR 3.34; 95% CI 2.25-4.97). Red blood cell transfusion was associated with an increased risk of short- and long-term mortality as well as myocardial reinfarction. However, transfusion appeared to have beneficial or neutral effects on mortality at hemoglobin levels below 8.0 g/dL, and harmful effects above 10 g/dL. A large definitive randomized controlled trial addressing this issue is urgently required.