Background: The association between hemoglobin (Hb) levels and mortality in patients with ST-segment elevation myocardial infarction (STEMI) remains controversial. The purpose of this study was to examine the mortality among STEMI patients with anemia or erythrocytosis, and further establish the relationship between mortality and the increment of Hb level.
Methods: Between 2006 and 2012, 951 consecutive patients with STEMI undergoing primary percutaneous coronary intervention in a medical center in Northern Taiwan were enrolled in our study, including 535 patients with normal Hb level, 148 with anemia (male Hb  13 g/dl, female  12) and 268 with erythrocytosis (male Hb  16, female  15).
Results: Patients in the anemia group were the oldest, and had higher morbidity than the normal Hb group, followed by the erythrocytosis group. In regression analyses, neither anemia nor erythrocytosis was associated with 30-day and 1-year mortality. Each 1-g/dl increment of Hb level was not associated with 30-day mortality both in patients with anemia or erythrocytosis. However, it was associated with a decreased risk of 1-year mortality in anemic patients [hazard ratio (HR): 0.756, 95% confidence interval (CI): 0.608-0.938, p = 0.011] and an increased risk of 1-year mortality in those with erythrocytosis (HR: 2.086, 95%CI: 1.106-3.937, p = 0.023). In multivariate analysis, each 1-g/dl increment of Hb level was associated with 1-year mortality both in anemic patients and those with erythrocytosis (HR: 0.788, 95%CI: 0.621-0.999, p = 0.049; HR: 2.302, 95%CI: 1.051-5.04, p = 0.037).
Conclusions: Higher hemoglobin levels in STEMI patients with anemia were associated with decreased risks of 1-year mortality, whereas higher hemoglobin levels in those with erythrocytosis were associated with increased risks of one-year mortality.