Patients with heart failure in the "intermediate Range" of peak oxygen uptake: Additive value of heart rate recovery and the minute ventilation/carbon dioxide output slope in predicting mortality

PURPOSE: While patients with heart failure who achieve a peak oxygen uptake (peak (Equation is included in full-text article.)VO ₂) of 10 mL•kg ^-1•min ^-1 or less are often considered for intensive surveillance or intervention, those achieving 14 mL•kg ^-1•min ^-1 or more are generally considered to be at lower risk. Among patients in the "intermediate" range of 10.1 to 13.9 mL•kg ^-1•min ^-1, optimally stratifying risk remains a challenge. METHODS: Patients with heart failure (N = 1167) referred for cardiopulmonary exercise testing were observed for 21 ± 13 months. Patients were classified into 3 groups of peak (Equation is included in full-text article.)Vo ₂ (≤10, 10.1-13.9, and ≥14 mL•kg ^-1•min ^-1). The ability of heart rate recovery at 1 minute (HRR1) and the minute ventilation/carbon dioxide output ((Equation is included in full-text article.)E/(Equation is included in full-text article.)co ₂) slope to complement peak (Equation is included in full-text article.)Vo ₂ in predicting cardiovascular mortality were determined. RESULTS: Peak (Equation is included in full-text article.)Vo ₂, HRR ₁ (2 slope (>34) were independent predictors of mortality (hazard ratio 1.6, 95% CI: 1.2-2.29, P = .006; hazard ratio 1.7, 95% CI: 1.1-2.5, P = .008; and hazard ratio 2.4, 95% CI: 1.6-3.4, P <.001, respectively). Compared with those achieving a peak (Equation is included in full-text article.)Vo ₂ ≥ 14 mL•kg ^-1•min ^-1, patients within the intermediate range with either an abnormal (Equation is included in full-text article.)E/(Equation is included in full-text article.)co ₂ slope or HRR1 had a nearly 2-fold higher risk of cardiac mortality. Those with both an abnormal HRR1 and (Equation is included in full-text article.)E/(Equation is included in full-text article.)co ₂ slope had a higher mortality risk than those with a peak (Equation is included in full-text article.)Vo ₂ ≤ 10 mL•kg ^-1•min ^-1. Survival was not different between those with a peak (Equation is included in full-text article.)Vo ₂ ≤ 10 mL•kg ^-1•min ^-1 and those in the intermediate range with either an abnormal HRR1 or (Equation is included in full-text article.)E/(Equation is included in full-text article.)co ₂ slope. CONCLUSIONS: HRR1 and the (Equation is included in full-text article.)E/(Equation is included in full-text article.)co ₂ slope effectively stratify patients with peak (Equation is included in full-text article.)Vo ₂ within the intermediate range into distinct groups at high and low risk.