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

Abstract

Background-The cardiac output (CO) response to exercise and other invasively derived hemodynamic variables has been variably described to provide better prognostication than peak VO 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 VO 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, 53Ϯ14 years; 80% male; left ventricular ejection fraction, 24Ϯ12%; 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 337Ϯ252 days (median, 295 days). Univariate and multivariate analysis were performed. The variables analyzed included peak VO 2 , peak CO, peak cardiac power, VE/VCO 2 slope, and VO 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 VO 2 was 12.9Ϯ4.5 mL/kg per min, and peak cardiac power was 1.7Ϯ0.9 W. Peak VO 2 , peak CO, peak cardiac power, VE/VCO 2 slope, and VO 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 (Pϭ0.01). Conclusions-Peak cardiac power, measured noninvasively, is an independent predictor of outcome that can enhance the prognostic power of peak VO 2 in the evaluation of patients with heart failure. (Circ Heart Fail. 2009;2:33-38.)

Clinician’s Guide to Cardiopulmonary Exercise Testing in Adults

“…Advances in technology now permit measurement of cardiac output with inert gas-rebreathing techniques (Appendix 1), and recent studies suggest that cardiac power measurements (eg, peak cardiac outputϫmean arterial pressure) may offer enhanced prognostic information beyond peak V O 2 , but these results need to be confirmed. 108 Statistical models that include peak V O 2 have also been developed 109 but are not yet used clinically and remain a promising area for future research. One such model, the Heart Failure Survival Score, is a multivariable predictive index that was developed from data on 80 clinical characteristics of 268 ambulatory patients with advanced heart failure.…”

“…Other recent reports have demonstrated that peak cardiac output can be measured noninvasively and provides an independent predictor of outcome that can enhance the prognostic utility of peak V O 2 . 108,242 Other potential applications of exercise cardiac output measures include the identification of hyperdynamic states due to impaired peripheral oxygen extraction. The finding of abnormally high cardiac output relative to V O 2 in certain myopathic and autonomic abnormalities provides a rationale for the use of exercise cardiac output measures in the identification of these conditions (see CPX in Patients With Skeletal Muscle Fiber and Mitochondrial Myopathy).…”

2016 Focused Update: Clinical Recommendations for Cardiopulmonary Exercise Testing Data Assessment in Specific Patient Populations

“…Studies have demonstrated that noninvasively determined peak CO provides an independent predictor of outcomes that enhances the prognostic utility of peak V ⋅ o 2 . [86][87][88][89][90] More recent reports suggest that noninvasively determined peak cardiac index complements indexes of ventilatory inefficiency and peak V ⋅ o 2 and that combining these markers provides the most powerful stratification of risk. 91,92 Although the Fick and thermodilution methods remain the gold standards for the measurement of CO, 93 several rebreathing methods that use CPX are available.…”

Selection of Cardiac Transplantation Candidates in 2010

“…The ventilatory response to exercise has been demonstrated to yield strong prognostic data. 34 Timing of the anaerobic threshold, measurement of cardiac power now with the advent of noninvasive rebreathing technologies, 35 and percent predicted V O 2 36 are parameters that have been examined. Although additional prognostic information can be gleaned from the exercise test, a wealth of additional clinical and laboratory data collected at the time of transplant evaluation needs to be considered.…”