Does peak oxygen pulse complement peak oxygen uptake in risk stratifying patients with heart failure?

There is scarce information regarding the prognostic utility of peak exercise oxygen pulse (peak O2 pulse), a surrogate for stroke volume, in patients with heart failure (HF). From May 1994 to November 2007, 998 patients with HF underwent cardiopulmonary exercise testing. The ability of peak oxygen uptake (VO2) and peak O2 pulse to predict cardiac events was examined. Peak O2 pulse was calculated by dividing peak VO2 by heart rate at the time peak VO2 was achieved and was expressed in both milliliters per beat and as a percentage achieved of the age-predicted value. There were 212 cardiac events (176 deaths, 26 transplantations, and 10 left ventricular assist device implantations) over a mean of 28 ± 26 months of follow-up. Peak VO2 and age-predicted peak O2 pulse were demonstrated by univariate and multivariate Cox regression analyses to be independent predictors of mortality (p <0.001). The optimal cut points for peak VO2 and age-predicted peak O2 pulse (<14.3 and ≥14.3 [mL/kg-1/min-1] and <85% and ≥85%, respectively) were established by areas under the receiver-operating characteristic curves. Patients exhibiting abnormalities for both responses had 4.8-fold (95% confidence interval 2.7 to 8.5) and 6.7-fold (95% confidence interval 4.1 to 11.1) higher risks for mortality and cardiac events, respectively, than those whose responses were normal. Age-predicted peak O2 pulse also predicted mortality in patients in the intermediate range of peak VO2 (10 to 14 (mL/kg-1/min-1)). The 3-year mortality rate for patients in this range who had age-predicted peak O2 pulse values <85% was even slightly higher than those with peak VO2 <10.1 (mL/kg-1/min-1). In conclusion, age-predicted peak O2 pulse was a strong and independent predictor of cardiac mortality and complemented peak VO2 in predicting risk in patients with HF.