Relationship of resting hemoglobin concentration to peak oxygen uptake in heart failure patients

Anemia is frequent in chronic heart failure (HF). To calculate what change in peak oxygen uptake (V̇O2) should be expected in the event of changes in hemoglobin concentration, we studied the correlation between peak V̇O2 and hemoglobin concentration in a large HF population. We carried out retrospective analysis of all cardiopulmonary exercise tests (CPET) performed in our HF Clinic between June 2001 and March 2009 in HF patients who had a resting hemoglobin concentration measurement taken within 7 days of the CPET. We collected 967 CPETs, 704 tests were considered maximal and analyzed. We identified 181 patients (26%) as anemic. Peak V̇O2 was lower (P < 0.001) in anemic patients (971 ± 23 ml/min) compared with nonanemic (1243 ± 18 ml/min). The slope of the V̇O2 vs. hemoglobin ratio was 109 ml/min/g/dl at peak exercise. This correlation remained significant also when several confounding variables were analyzed by multivariate analysis. As an average, each gram of hemoglobin accounts, at peak exercise, for 109 ml/min change in V̇O2 which is equivalent to 0.97 ml/min/kg. Therefore, in HF patients anemia treatment should increase V̇O2 by 109 ml/min for each g/dl of hemoglobin increase.