Purpose: Peak oxygen uptake (peak VO₂) and ventilatory inefficiency (VE/VCO₂ slope) have proven to be strong prognostic markers in patients with chronic heart failure (CHF). Recently increased red cell distribution width (RDW) has emerged as an additional predictor of poor outcome in CHF. We sought to evaluate the relationship between RDW and cardiopulmonary exercise test (CPET) parameters in CHF patients and healthy controls.
Materials and methods: 85 ambulatory CHF patients (68 men, 54±10 years) and 107 healthy controls, who underwent a symptom-limited CPET on a treadmill according to the modified Bruce ramp protocol, were enrolled. CHF patients and healthy controls were divided into RDW tertile groups and laboratory, echocardiographic, and CPET results were analyzed.
Results: For patients with CHF, compared with patients in the lowest RDW tertile, those in the highest tertile had lower peak VO₂ (22 mL/kg/min vs. 28 mL/kg/min, p<0.001) and higher VE/VCO₂ slope (31 vs. 25, p=0.004). Multivariate regression analysis revealed RDW to be an independent predictor for peak VO₂ (β=-0.247, p=0.035) and VE/VCO₂ slope (β=0.366, p=0.004). The optimal cutoff value of RDW for predicting peak VO₂ ≤20 mL/kg/min and VE/VCO₂ slope ≥34 was 13.6% (sensitivity 53%, specificity 89%) and 13.4% (sensitivity 75%, specificity 82%), respectively. In contrast, for healthy controls, RDW was not related to both peak VO₂ and VE/VCO₂ slope.
Conclusion: Higher RDW is independently related to peak VO₂ and VE/VCO₂ slope only in patients with CHF. RDW assessment, an inexpensive and simple method, might help predict functional capacity and ventilatory efficiency in these patients.
Keywords: Cardiopulmonary exercise test; heart failure; red cell distribution width.