The influence of body mass index on the oxygen uptake efficiency slope in patients with heart failure

There does not appear to be a relationship between peak oxygen consumption (VO₂) and body mass index (BMI) in patients with heart failure (HF). We assessed the hypothesis that BMI and the oxygen uptake efficiency slope (OUES) would be related. Three hundred and thirty-seven HF patients (280 male/57 female, mean age: 56.5 ± 14.1 years, resting left ventricular ejection fraction: 35.1 ± 14.2%, BMI: 29.3 ± 6.2 kg/m²) underwent cardiopulmonary exercise testing where peak VO₂ and the OUES (VO₂ = a log₁₀VE + b, units: L/min) were determined. Pearson product moment correlation analysis revealed that the correlation between BMI and the OUES was significant (r = 0.32, p <0.001). Furthermore, the OUES was prognostically significant in normal weight (optimal threshold: ≤/> 1.2, hazard ratio: 3.7, 95% confidence interval: 1.4-9.9, p = 0.01), overweight (optimal threshold: ≤/> 1.5, hazard ratio: 3.9, 95% confidence interval: 1.3-11.1, p = 0.01) and obese (optimal threshold: ≤/> 1.7, hazard ratio: 4.1, 95% confidence interval: 1.4-12.8, p = 0.01) subgroups. The OUES appears to improve with body weight in patients with HF. Furthermore, the OUES appears to be a significant prognostic marker irrespective of BMI although the optimal threshold value may differ according to body weight.