O2 max after reinfusion. At a given submaximal VO2, HR and blood lactates were increased at lowered Hb concentration and decreased at increased Hb concentration over control levels. Correlation coefficient for the change in Q in relation to the acute change in Hb concentration at a given submaximal VO2 was -0.49 (P less than 0.05).47:T62d,Previous studies have shown that patients with heart failure with reduced ejection fraction (HFrEF) and anemia have reduced peak oxygen consumption (VO2). Black or African American (B-AA) patients have a higher prevalence of anemia and are underrepresented in clinical studies of HFrEF. The aim of this study was to determine the contribution of hemoglobin to peak VO2 in B-AA patients recently hospitalized for acute decompensated HFrEF.We analyzed cardiopulmonary exercise testing (CPX) data measured within two weeks of discharge for acute decompensated HF in B-AA patients with HFrEF (left ventricular ejection fraction [LVEF] ≤40%) without severe anemia (Hb<8 g/dL). Blood samples were collected prior to CPX. Data are reported as median [interquartile range] and compared between groups with the Mann-Whitney, Chi-Square, and Spearman's rank tests.We included 81 patients; 27 (33%) women, 57 [27-79] years of age, Body Mass Index of 33 [15-55] kg/m^{2} and LVEF of 30 [23-36] %. Hemoglobin ranged between 9.1 to 18.1 g/dL (median= 13.3 [11.9-14.5] g/dL); 26 (32%) were considered to have anemia based on a Hb concentration of males <13 g/dL and females <12 g/dL. Peak VO2 was lower in patients with anemia (11.8 [10.0-14.2] vs. 14.1 [10.6-17.0] mL·kg^{-1}·min^{-1}; P=0.010) with a significant correlation between peak VO2 and hemoglobin concentration (R=+0.455; P<0.001).Anemia is prevalent among B-AA patients with recently decompensated HFrEF and appears to be a significant contributor to reductions in peak VO2.48:T4bc,Anemia is frequent in chronic heart failure (HF). To calculate what change in peak oxygen uptake ( VO(2)) should be ex