Prospective comparison of ventilatory equivalent versus peak oxygen consumption in predicting outcomes of patients...

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 beta 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 < or =0.0002); VE did not independently predict outcomes. Other independent predictors were higher heart rate at rest (p < or =0.02) and presence of an implantable cardioverter-defibrillator (p < or =0.04). In conclusion, peak VO2, but not VE, predicts clinical outcomes of patients with HF who are treated with contemporary medical therapies.