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

Objectives This study assessed the prognostic value of peak cardiac power o utput, measured non-invasively during maximal cardiopulmonary exercise test ing, against other exercise-derived haemodynamic variables in patients with chronic congestive heart failure. Method and Results Two hundred and nineteen unselected, consecutive patient s with congestive heart failure (166 men, mean (+/- SD) age of 56 +/- 13 ye ars) who underwent maximal symptom limited cardiopulmonary treadmill exerci se testing with non-invasive estimation of cardiac output using carbon diox ide 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 produc t of cardiac output and mean arterial blood pressure. All cause mortality w as 12.3% (27 deaths). Peak and resting cardiac power output, peak mean arte rial blood pressure. peak and resting cardiac output and peak VO2 were all predictive of outcome on univariate analyses. Peak cardiac power output, ei ther entered continuously or categorically with a cut-off value of 1.96 wat ts, 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 cardi ac power output < 1.96 watts. Conclusion Peak cardiac power output is an independent predictor of mortali ty that can be measured non-invasively using cardiopulmonary exercise testi ng. It can give further prognostic power to a peak VO2 in the assessment of patients with congestive heart failure.