Peak exercise cardiac power output; a direct indicator of cardiac function strongly predictive of prognosis in chronic heart failure

Abstract

Objectives This study assessed the prognostic value of peak cardiac power output, measured non-invasively during maximal cardiopulmonary exercise testing, against other exercise-derived haemodynamic variables in patients with chronic congestive heart failure.

Method and Results Two hundred and nineteen unselected, consecutive patients with congestive heart failure (166 men, mean (±SD) age of 56±13 years) who underwent maximal symptom limited cardiopulmonary treadmill exercise testing with non-invasive estimation of cardiac output using carbon dioxide re-breathing techniques, were followed-up for a mean period of 4·64 (4·47–4·82, 95% CI) years. Cardiac power output was calculated from the product of cardiac output and mean arterial blood pressure. All cause mortality was 12·3% (27 deaths). Peak and resting cardiac power output, peak mean arterial blood pressure, peak and resting cardiac output and peak VO₂were all predictive of outcome on univariate analyses. Peak cardiac power output, either entered continuously or categorically with a cut-off value of 1·96 watts, was the only independent predictor of mortality (P=0·0004 for values <>1·96 watts and P=0·001 for continuous values) using multivariate analysis. A relative risk ratio of 5·08 (1·94–13·3, 95% CI) was obtained for a cardiac power output <1·96 watts.

Conclusion Peak cardiac power output is an independent predictor of mortality that can be measured non-invasively using cardiopulmonary exercise testing. It can give further prognostic power to a peak VO₂in the assessment of patients with congestive heart failure.

Chronic heart failure, cardiac power output, prognosis, non-invasive cardiopulmonary exercise testing

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Correspondence: Dr Lip-Bun Tan, Consultant Cardiologist, Institute for Cardiovascular Research, Yorkshire Heart Centre, Leeds General Infirmary, Leeds LS1 3EX, U.K.