Peak Cardiac Power Output, Measured Noninvasively, Is a Powerful Predictor of Outcome in Chronic Heart Failure

BACKGROUND: The cardiac output (CO) response to exercise and other invasively derived hemodynamic variables has been variably described to provide better prognostication than peak V(O(2)) in patients with chronic heart failure. Using noninvasive measurements of CO during exercise, we compared the prognostic value of peak CO and cardiac power to peak V(O(2)) in chronic heart failure patients. METHOD AND RESULTS: One hundred seventy-one consecutive patients with chronic heart failure underwent symptom limited bicycle exercise with noninvasive estimation of CO using an inert gas rebreathing method. An accurate measure of peak CO was obtained in 148 patients (85% of patients; mean age, 53+/-14 years; 80% male; left ventricular ejection fraction, 24+/-12%; ischemic etiology, 34%). Peak cardiac power was derived from the product of the peak mean arterial blood pressure and CO divided by 451. End points consisted of death, urgent heart transplant, or left ventricular assist device implantation. Duration of follow-up averaged 337+/-252 days (median, 295 days). Univariate and multivariate analysis were performed. The variables analyzed included peak V(O(2)), peak CO, peak cardiac power, V(E)/V(CO(2)) slope, and V(O(2)) at anaerobic threshold. Event-free survival for the entire cohort was 83% with 5 deaths, 4 left ventricular assist device implants, and 16 urgent transplants. Peak V(O(2)) was 12.9+/-4.5 mL/kg per min, and peak cardiac power was 1.7+/-0.9 W. Peak V(O(2)), peak CO, peak cardiac power, V(E)/V(CO(2)) slope, and V(O(2)) at anaerobic threshold were predictive of outcome on univariate analysis. On multivariate analysis, peak cardiac power and peak CO were predictive of outcome with peak cardiac power being the most powerful independent predictor of outcome (P=0.01). CONCLUSIONS: Peak cardiac power, measured noninvasively, is an independent predictor of outcome that can enhance the prognostic power of peak V(O(2)) in the evaluation of patients with heart failure.