Differences in Cardiopulmonary Exercise Performance Between True Anemia and Hemodilution in Patients with Advanced Heart Failure

PurposeAnemia is a common coexisting condition in patients with heart failure (HF). In addition to true anemia from decreased red blood cell volume (RBCV), HF often results in congestion and increase in plasma volume (PV) which could lead to hemodilution as a cause of anemia. Anemia is associated with decreased cardiopulmonary exercise testing (CPET) performance in HF but the difference between true anemia and hemodilution in CPET performance is unknown.MethodsThis is a prospective two-center study enrolling patients with advanced HF who underwent invasive CPET and blood volume analysis (BVA). The BVA measures total blood volume (TBV), RBCV and PV using the indicator dilution technique with an I131-tagged albumin tracer. Anemia was defined using hematocrit cut-off of 41% in men and 36% in women. In anemia group, patients had true anemia if RBCV was < 95% of ideal RBCV. Patients with anemia and normal RBCV were categorized as hemodilution. One-way ANOVA was used to compare between 3 groups. If a significant difference was noted, pairwise comparison was subsequently performed.ResultsTotal of 43 patients were included. Of those, 42% were anemia (61% true anemia and 39% hemodilution). There was no significant difference in demographics or LVEF between groups. We observed a significant difference in the minute ventilation/carbon dioxide production (VE/VCO2) slope between groups (no anemia: 34.1 ± 7.8 vs. true anemia: 32.4 ± 7.6 vs. hemodilution: 43.4 ± 14.3, p=0.03). A pairwise comparison only showed a significant difference between true anemia and hemodilution (p=0.04). There were no between-group differences in mean peak oxygen consumption (VO2), % predicted maximal VO2 or respiratory exchange ratio (RER).ConclusionCompared to true anemia, hemodilution appears to have worse cardiopulmonary performance as evidenced by higher VE/VCO2. The underlying mechanisms of this finding as well as its clinical implications need to be further investigated. Anemia is a common coexisting condition in patients with heart failure (HF). In addition to true anemia from decreased red blood cell volume (RBCV), HF often results in congestion and increase in plasma volume (PV) which could lead to hemodilution as a cause of anemia. Anemia is associated with decreased cardiopulmonary exercise testing (CPET) performance in HF but the difference between true anemia and hemodilution in CPET performance is unknown. This is a prospective two-center study enrolling patients with advanced HF who underwent invasive CPET and blood volume analysis (BVA). The BVA measures total blood volume (TBV), RBCV and PV using the indicator dilution technique with an I131-tagged albumin tracer. Anemia was defined using hematocrit cut-off of 41% in men and 36% in women. In anemia group, patients had true anemia if RBCV was < 95% of ideal RBCV. Patients with anemia and normal RBCV were categorized as hemodilution. One-way ANOVA was used to compare between 3 groups. If a significant difference was noted, pairwise comparison was subsequently performed. Total of 43 patients were included. Of those, 42% were anemia (61% true anemia and 39% hemodilution). There was no significant difference in demographics or LVEF between groups. We observed a significant difference in the minute ventilation/carbon dioxide production (VE/VCO2) slope between groups (no anemia: 34.1 ± 7.8 vs. true anemia: 32.4 ± 7.6 vs. hemodilution: 43.4 ± 14.3, p=0.03). A pairwise comparison only showed a significant difference between true anemia and hemodilution (p=0.04). There were no between-group differences in mean peak oxygen consumption (VO2), % predicted maximal VO2 or respiratory exchange ratio (RER). Compared to true anemia, hemodilution appears to have worse cardiopulmonary performance as evidenced by higher VE/VCO2. The underlying mechanisms of this finding as well as its clinical implications need to be further investigated.