Influence of body mass on risk prediction during cardiopulmonary exercise testing in patients with chronic heart failure.

INTRODUCTION: Peak oxygen uptake (VO2) during a maximal exercise test is used to stratify patients with chronic heart failure (CHF) and is usually corrected for body mass.
OBJECTIVE: To explore the influence of body mass on risk prediction during treadmill cardiopulmonary exercise testing (CPET) in patients with CHF.
METHODS: A total of 411 patients with suspected CHF (mean [± SD] age 64±12 years; 81% male; mean left ventricular ejection fraction 39±6%) underwent symptom-limited, maximal CPET on a treadmill. Patients were categorized as normal weight, overweight or obese based on body mass index.
RESULTS: One hundred fifteen patients died during a median follow-up period of 8.7±2.3 years in survivors. In the univariable analysis, peak VO2 adjusted for body mass (χ(2)=41.4) and unadjusted (χ(2)=40.2) were similar for predicting all-cause mortality. Peak VO2 adjusted for body mass showed marginally higher χ(2) values in normal weight, overweight and obese categories than unadjusted values. Anaerobic threshold had similar prognostic power regardless of whether it was corrected for body mass (χ(2)=22.4 and χ(2)=24.4), with no difference between the two in any of the subgroups separately. In all patients, unadjusted ventilation (VE)/carbon dioxide production (VCO2) slope (χ(2)=40.6) was a stronger predictor of all-cause mortality than body mass adjusted values (χ(2)=32.8), and unadjusted values remained stronger in normal weight, overweight and obese subgroups.
CONCLUSION: Correcting peak VO2 for body mass slightly improves risk prediction, especially in obese patients with CHF. The adjustment of other CPET-derived variables including anaerobic threshold and VE/VCO2 slope for body mass appears to provide less prognostic value.