Association of hemoglobin levels with clinical outcomes in acute coronary syndromes

Background - In the setting of an acute coronary syndrome (ACS), anemia has the potential to worsen myocardial ischemia; however, data relating anemia to clinical outcomes in ACS remain limited. Methods and Results - We examined the association between baseline hemoglobin values and major adverse cardiovascular events through 30 days in 39 922 patients enrolled in clinical trials of ACS. After adjustment for differences in baseline characteristics and index hospitalization treatments, a reverse J-shaped relationship between baseline hemoglobin values and major adverse cardiovascular events was observed. In patients with ST-elevation myocardial infarction, when those with hemoglobin values between 14 and 15 g/dL were used as the reference, cardiovascular mortality increased as hemoglobin levels fell below 14 g/dL, with an adjusted OR of 1.21 ( 95% CI 1.12 to 1.30, P < 0.001) for each 1-g/dL decrement in hemoglobin. At the other end of the range of hemoglobin, patients with hemoglobin values > 17 g/dL also had excess mortality ( OR 1.79, 95% CI 1.18 to 2.71, P = 0.007). In patients with non - ST-elevation ACS, with those with hemoglobin 15 to 16 g/dL used as the reference, the likelihood of cardiovascular death, myocardial infarction, or recurrent ischemia increased as the hemoglobin fell below 11 g/dL, with an adjusted OR of 1.45 ( 95% CI 1.33 to 1.58, P < 0.001) for each 1 g/dL decrement in hemoglobin. Patients with hemoglobin values > 16 g/dL also had an increased rate of death or ischemic events ( OR 1.31, 95% CI 1.03 to 1.66, P = 0.027). Conclusions - Anemia is a powerful and independent predictor of major adverse cardiovascular events in patients across the spectrum of ACS.