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To investigate the prognostic value of oxygen uptake (V̇O2) kinetics during low-intensity exercise in patients with congestive heart failure.Prospective cohort study.Tertiary care center.One hundred forty-six consecutive patients (128 men) with chronic heart failure, followed up for a mean (± SD) duration of 25 ± 15 months.A treadmill exercise test was performed with "breath by breath" gas-exchange monitoring. V̇O2kinetics were defined as the O2 deficit (ie, ΔV̇O2 × time [rest to steady state] − ΣV̇O2[rest to steady state]) and mean response time (MRT) [ie, O2 deficit/ΔV̇O2]. Cardiac death, urgent cardiac transplantation, and hospitalization due to worsening heart failure were considered as the end points.Thirty patients (21%) died, 11 patients (8%) underwent urgent transplantation, and 32 patients (22%) were hospitalized. In univariate analysis, MRT was the most powerful predictor of survival, survival free of urgent transplantation, and survival free of hospitalization (hazard ratios [HRs] per 10 s, 1.65, 1.72, and 1.61, respectively; all p < 0.0001). The predictive value of MRT exceeded that of peak V̇O2 (HR per mL/kg/min, 0.90; p = 0.02, 0.91; p = 0.007, and 0.95; p = 0.08, respectively). In multivariate analysis, MRT (HR per 10 s, 1.73; p = 0.0002), resting systolic BP (HR per 10 mm Hg, 0.65; p = 0.003), and the slope of the ventilatory response to exercise (HR per 10 U, 1.68; p = 0.02) were independent predictors of survival.Our results suggest that V̇O2 kinetics are strongly related to outcome in heart failure patients. Since it has several additional advantages over peak exercise testing (eg, less time-consuming, less demanding for the patients, less dependent on motivation, and applicable in patients with limitations other than cardiopulmonary disease), it has the potential to become a prognostic test for the assessment of heart failure patients.