Abstract 3189: The Relationship Between Body Mass Index and Cardiopulmonary Exercise Testing in Chronic Systolic Heart Failure
Background: Cardiopulmonary exercise testing (CPX) in patients with systolic heart failure (HF) is important for determining HF prognosis and helping guide timing of heart transplantation. Although approximately 20 –30% of patients with HF are obese (body mass index [BMI]>30kg/m2), the impact of BMI on CPX results is not well established. The objective of the present study was to assess the relationship between BMI and CPX variables, including peak oxygen uptake, anaerobic threshold, O2 pulse, and ventilation/carbon dioxide production ratio.
Methods: Consecutive systolic HF patients (n=2324) enrolled in the Heart Failure and A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION) trial who had baseline BMI recorded were included in the present study. Subjects were divided into strata based on BMI: underweight (BMI< 18.5 kg/m2), normal weight (BMI 18.5–24.9 kg/m2), overweight (BMI 25.0 –29.9 kg/m2), obese I (BMI 30 –34.9 kg/m2), obese II (BMI 35–39.9 kg/m2), and obese III (BMI ≥40 kg/m2).
Results: Absolute peak oxygen uptake (PKVO2, mL/min) increased with increasing BMI category. However, relative PKVO2 (mL/kg/min) was lowest in the Obese III category and not qualitatively different among the normal weight, overweight, and Obese I categories. Ventilatory-derived anaerobic threshold, O2 pulse, ventilation carbon dioxide production ratio (VE/VCO2 slope), and exercise time all decreased with increasing BMI category. Distance on six-minute walk test also decreased with increasing BMI category (Table⇓). In multivariate linear regression analysis for prediction of PKVO2 (mL/kg/min) as a continuous variable, BMI was a strong predictor of PKVO2, second only to age (partial R2=0.07, p< 0.0001 in patients with chronic systolic HF.
Conclusions: BMI is significantly associated with key CPX fitness variables in HF patients. The influence of BMI on the prognostic value of CPX in HF requires further evaluation in longitudinal studies.