BACKGROUND:Accumulating evidence suggests that hematopoiesis, especially erythropoiesis, is disturbed in heart failure (HF) for many reasons. Low hemoglobin and red blood cell distribution width have emerged as prognostic indicators of HF independent of classic predictors. The prognostic implication of mean corpuscular volume (MCV) in HF, however, is unknown. In this context, we investigated the relationship between MCV and prognosis of acute decompensated HF (ADHF). METHODS AND RESULTS:This retrospective cohort study consisted of 458 consecutive patients with ADHF who had emergency admission to hospital. Patients were divided into 2 groups: MCV ≤100fl (non-macrocytic group, n=400); and MCV >100fl (macrocytic group, n=58). The relationship between MCV and all-cause death was tested using Cox proportional hazard models, adjusting for other predictors. Mean patient age was 72.4 years and mean MCV was 93.0±7.1fl. Hemoglobin was significantly lower in the macrocytic group than the non-macrocytic group. During the mean follow-up of 20.8 months, a total of 173 deaths (37.9%) occurred. Kaplan-Meier analysis showed that all-cause death was significantly higher in the macrocytic group (log-rank P<0.0001). Cox proportional hazards analysis indicated that macrocytosis was an independent predictor of all-cause death (hazard ratio, 2.288; 95% confidence interval: 1.390-3.643; P=0.0015) after adjustment in the multivariate model. CONCLUSIONS:It is proposed for the first time that MCV is an independent predictor of all-cause death in patients with ADHF.