The incremental prognostic importance of body fat adjusted peak oxygen consumption in chronic heart failure

OBJECTIVES: We sought to assess whether the adjustment of peak oxygen consumption (PkVO2) to lean body mass would yield a more accurate discriminator of outcomes in the chronic heart failure population. BACKGROUND: Peak oxygen consumption is traditionally used to risk stratify patients with congestive heart failure (CHF) and to time cardiac transplantation. There is, however, considerable variability in body fat content, which represents metabolically inactive mass. METHODS: In 225 consecutive patients with CHF, the percentage of body fat was determined by the sum of skinfolds technique. All underwent CPX using a ramping treadmill protocol. Mean follow-up duration was 18.9+/-11.3 months. RESULTS: There were 14 cardiovascular deaths and 15 transplants. Peak oxygen consumption lean, both as a continuous variable and using a cutoff of < or =19 ml/kg/min, was a better predictor of outcome than unadjusted PkVO2 (p = 0.003 vs. 0.027 for the continuous variables and p = 0.0006 vs. 0.055 for < or =19 ml/kg/min and < or =14 ml/kg/min unadjusted body weight, respectively). Using partial correlation index R statistics, the Cox model using PkVO2 lean < or =19 ml/kg/min, in addition to age and etiology of CHF as covariates, yielded the strongest predictive relationship to the combined end point (chi-square value 24.32). Especially in the obese patients and in women, there was considerably better correlation of PkVO2 lean with outcome than the unadjusted PkVO2. CONCLUSIONS: The adjustment of PkVO2 to lean body mass increases the prognostic value of cardiopulmonary stress testing in the evaluation of patients with chronic heart failure. The use of <19 ml O2/kg of lean body mass/min as a cutoff in PkVO2 should be used for timing transplantation, particularly in women and the obese.