Objective Cardiopulmonary exercise testing (CPET) is used to predict outcome in patients with mild-to-moderate heart failure (HF). Single CPET-derived variables are often used, but we wanted to see if a composite score achieved better predictive power.

Methods Retrospective analysis of patient records at the department of cardiology, Castle Hill Hospital, Kingston-upon-Hull. 387 patients (median (25th–75th percentile)) (age 65 (56–72) years; 79% men; LVEF 34 (31–37) %) were included. Patients underwent a symptom-limited, maximal CPET on a treadmill. During a median follow-up of 8.6±2.1 years in survivors, 107 patients died. Survival models were built and validated using a hybrid approach between the bootstrap and Cox regression. Nine CPET-derived variables were included. Z-score defined each variable’s predictive strength. Model coefficients were converted to a risk score.

Results Four CPET-related variables were independent predictors of all-cause mortality in the survival model: the presence of exertional oscillatory ventilation (EOV), increasing slope of the relation between ventilation and carbon dioxide production (VE/VCO₂ slope), decreasing oxygen uptake efficiency slope (OUES), and an increase in the lowest ventilatory equivalent for carbon dioxide (VEqCO₂ nadir). Individual predictors of mortality ranged from 0.60 to 0.71 using Harrell's C-statistic, but the optimal combination of EOV+VE/VCO₂ slope+OUES+VEqCO₂ nadir reached 0.75. The Hull CPET risk score had a significantly higher area under the curve (0.78) when compared to the HF Survival Score (AUC=0.70; p<0.001).

Conclusions A composite risk score using variables from CPET out-performs the traditional single variable approach in predicting outcome in patients with mild-to-moderate HF.