Cardiorespiratory Fitness as a Prognostic Factor in Heart Failure Needs to be Standardized for Body Composition

Abstract

We read the recently published study by Clark et al 1 Clark A.L. Fonarow G.C. Horwich T.B. Impact of cardiorespiratory fitness on the obesity paradox in patients with systolic heart failure. Am J Cardiol. 2015; 115: 209-213 Abstract Full Text Full Text PDF PubMed Scopus (63) Google Scholar of obesity as a positive prognostic factor in patients with advanced systolic heart failure (obesity paradox). The investigators observed the obesity paradox only in patients with lower cardiorespiratory fitness. Cardiorespiratory fitness was assessed as peak oxygen uptake (PKVO2) divided by total body weight (ml/min/kg). This measure has been shown to systematically underestimate cardiorespiratory fitness in not only healthy populations 2 Savonen K. Krachler B. Hassinen M. Komulainen P. Kiviniemi V. Lakka T.A. Rauramaa R. The current standard measure of cardiorespiratory fitness introduces confounding by body mass: the DR's EXTRA study. Int J Obes (Lond). 2012; 36: 1135-1140 Crossref PubMed Scopus (34) Google Scholar , 3 Batterham A.M. Vanderburgh P.M. Mahar M.T. Jackson A.S. Modeling the influence of body size on V(O2) peak: effects of model choice and body composition. J Appl Physiol. 1999; 87: 1317-1325 PubMed Google Scholar but also subjects with heart failure. 4 Osman A.F. Mehra M.R. Lavie C.J. Nunez E. Milani R.V. The incremental prognostic importance of body fat adjusted peak oxygen consumption in chronic heart failure. J Am Coll Cardiol. 2000; 36: 2126-2131 Abstract Full Text Full Text PDF PubMed Scopus (134) Google Scholar The bias can be avoided by expressing PKVO2 as a function of lean mass. 3 Batterham A.M. Vanderburgh P.M. Mahar M.T. Jackson A.S. Modeling the influence of body size on V(O2) peak: effects of model choice and body composition. J Appl Physiol. 1999; 87: 1317-1325 PubMed Google Scholar , 4 Osman A.F. Mehra M.R. Lavie C.J. Nunez E. Milani R.V. The incremental prognostic importance of body fat adjusted peak oxygen consumption in chronic heart failure. J Am Coll Cardiol. 2000; 36: 2126-2131 Abstract Full Text Full Text PDF PubMed Scopus (134) Google Scholar , 5 Krachler B. Savonen K. Komulainen P. Hassinen M. Lakka T.A. Rauramaa R. Cardiopulmonary fitness is a function of lean mass, not total body weight: the DR's EXTRA study. Euro J Prev Cardiol. 2014; (in press) PubMed Google Scholar Impact of Cardiorespiratory Fitness on the Obesity Paradox in Patients With Systolic Heart FailureAmerican Journal of CardiologyVol. 115Issue 2PreviewAlthough high body mass index (BMI) is associated with improved outcomes in established heart failure (HF), the impact of cardiorespiratory fitness on this obesity paradox is less clear. We studied 1,675 patients with systolic HF who underwent cardiopulmonary exercise testing at a single university center (77.4% men, mean age 52.2 ± 11.6 years, mean left ventricular ejection fraction 23.2 ± 7.1% and New York Heart Association class III or IV in 79.1%). We evaluated 2-year survival in patients stratified by both BMI (normal 18.5 to 24.9 kg/m2[reference], overweight 25 to 29.9 kg/m2, obese ≥30.0 kg/m2) and by peak oxygen uptake (PKVO2; high >14 ml/kg/minute, low ≤14 ml/kg/minute). Full-Text PDF ReplyAmerican Journal of CardiologyVol. 116Issue 1PreviewWe would like to thank Krachler et al for their letter regarding our study “The Impact of Cardiorespiratory Fitness on the Obesity Paradox in Heart Failure.”1 Our original study demonstrated that the “obesity paradox” in heart failure was significant only in patients with poor cardiorespiratory fitness, as defined by peak oxygen consumption on cardiopulmonary exercise testing of ≤14.0 mg/kg/m2. Krachler et al astutely point out that our measure of fitness relies on adjustment by total body weight, which may underestimate fitness levels; adjustment for lean body mass rather than total body weight has been shown to be a better predictor of outcomes in heart failure. Full-Text PDF