Prospective Comparison of Ventilatory Equivalent Versus Peak Oxygen Consumption in Predicting Outcomes of Patients With Heart Failure

In patients with heart failure (HF), peak exercise oxygen consumption (VO₂) is an important prognostic tool on which critical clinical decisions are made. However, recent retrospective data have suggested that ventilatory equivalent (VE = ventilation [liters per minute]/VO₂ [liters per minute]) may be a stronger predictor of outcomes than VO₂ in patients with HF on modern medical therapies. We prospectively collected baseline demographics, cardiovascular history, hemodynamics, and exercise ventilatory data from 221 consecutive patients with HF who underwent treadmill exercise VO₂ testing. The composite primary end point was death or heart transplantation. Mean follow-up was 508 days, during which 27 events occurred (13 deaths and 14 transplantations). One-year event-free survival was 88% (n = 104 with 1-year follow-up). Mean age was 49 years, 68% were men, 84% were taking β blockers, 82% were taking angiotensin-converting enzyme inhibitors, and 21% had an implantable cardioverter-defibrillator. Mean VO₂ was 16 ± 5 ml/kg/min. Mean VE was 47.4 ± 15.2. Univariate predictors of events included lower VO₂ (p <0.0001), higher heart rate at rest (p = 0.05), and presence of an implantable cardioverter-defibrillator (p = 0.024). Higher VE (p = 0.10) and lower maximum systolic blood pressure (p = 0.09) were of borderline significance. Age, gender, HF etiology or severity, and other ventilatory parameters were not significant predictors. Multivariate models that incorporated VE, VO₂, or their combination confirmed VO₂ as an independent predictor of event-free survival (p ≤0.0002); VE did not independently predict outcomes. Other independent predictors were higher heart rate at rest (p ≤0.02) and presence of an implantable cardioverter-defibrillator (p ≤0.04). In conclusion, peak VO₂, but not VE, predicts clinical outcomes of patients with HF who are treated with contemporary medical therapies.