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Original Articles

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

Chim C. Lang, MD; Paula Karlin, BS; Jennifer Haythe, MD; Tiong K. Lim, MD and Donna M. Mancini, MD

From the Division of Cardiology (C.C.L., P.K., J.H., D.M.M.), Columbia University, New York, NY; and the Division of Medicine and Therapeutics (C.C.L., T.K.L.), Ninewells Hospital and Medical School, Dundee, United Kingdom.

Correspondence to Donna M. Mancini, MD, Columbia Presbyterian Medical Center, 622 West 168th St, New York, NY 10032. E-mail dmm31{at}columbia.edu

Received April 15, 2008; accepted November 18, 2008.

Background— The cardiac output (CO) response to exercise and other invasively derived hemodynamic variables has been variably described to provide better prognostication than peak VO₂ 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 VO₂ 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 VO₂, peak CO, peak cardiac power, VE/VCO₂ slope, and VO₂ 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 VO₂ was 12.9±4.5 mL/kg per min, and peak cardiac power was 1.7±0.9 W. Peak VO₂, peak CO, peak cardiac power, VE/VCO₂ slope, and VO₂ 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 VO₂ in the evaluation of patients with heart failure.

Key Words: chronic heart failure • cardiac transplantation • peak VO₂ • cardiac output • exercise