Background: Heart failure (HF) is associated with impaired maximal aerobic capacity as indicated by decreases in peak oxygen uptake (peak VO2). Considering that aging by itself has a negative effect on this variable, the evaluation of maximum capacity is often questioned because current predicted peak VO2 is based on subjects without heart disease or beta-blocker therapy. In contrast, if decline in predicted and attained peak VO2 were age-related, proportionally, loss of aerobic function (predicted peak VO2, %) would remain stable over time in these patients. The purpose of this investigation is to assess the effects of age on peak VO2 in HF patients taking beta-blockers.Methods: We retrospectively evaluated 483 (132 female) patients (aged 20-88 years, LVEF 31 +/- 11%) with non-ischemic (n = 362), ischemic (n = 74) and Chagas-related HF (n = 47) who had been submitted to an incremental cardiopulmonary exercise testing on a motorized treadmill. Linear regression was used to develop the equation to predict peak VO2, based on age.Results: Peak VO2 decreased 0.9 mL/min/kg per age-decade, maximum HR also decreased with aging and VE/VCO2 slope was similar among all decades. The predicted new beta-blocker equation to peak VO2bb was 20.934 - 0.092 x age.Conclusions: Clinical interpretation of aerobic capacity impairment is influenced by aging in HF patients. This evidence must be considered when using peak VO2 for prognostic stratification and clinical decision-making in patients with HF under beta-blocker therapy.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Sao Paulo State Univ, UNESP, Sch Sci, Exercise & Chron Dis Res Lab,Phys Educ Dept, Bauru, BrazilUniv Sao Paulo, Hosp Clin, Fac Med, Heart Inst InCor, Sao Paulo, BrazilSao Paulo State Univ, UNESP, Sch Sci, Exercise & Chron Dis Res Lab,Phys Educ Dept, Bauru, BrazilFAPESP: 10/08554-7FAPESP: 12/02409-0CNPq: 304733/2008-3