Abstract 3103: A Cardiopulmonary Exercise Testing Score for Predicting Risk in Patients with Heart Failure
Background. Cardiopulmonary exercise test (CPX) responses, including markers of ventilatory inefficiency (eg. the VE/VCO2 slope and oxygen uptake efficiency slope [OUES]), and hemodynamic responses, such as heart rate recovery (HRR) and chronotropic incompetence (CRI) predict outcomes in patients with heart failure (HF). However, multivariate risk models integrating the full range of CPX variables have not been fully explored.
Methods: 710 HF patients (568 male/142 female, mean age 56±13 years, EF 33±14%) underwent CPX and were followed for major cardiac events (death, transplant, LVAD implantation) for a mean of 29± 25 months. The age-adjusted prognostic power of peak VO2, VE/VCO2 slope, OUES (VO2 = a log10VE + b), resting end-tidal CO2 pressure (PetCO2), HRR, and CRI were determined using Cox proportional hazards, optimal cutpoints were determined, the variables were weighted, and a multivariate score was derived.
Results. There were 111 composite outcomes. Multivariately, only CRI was not a significant predictor of risk. The VE/VCO2 slope (≥ 34) was the strongest predictor, and was attributed a relative weight of 7, with weighted scores for abnormal HRR (≤6 beats at 1 min), OUES (>1.4), PetCO2 (<33mmHg), and peak VO2 (≤14 ml/kg/min) having scores of 5, 3, 3, and 2, respectively. A Kaplan-Meier curve illustrating the incremental scores is presented in the figure⇓; a score >15 was associated with an annual mortality rate of 26% and a relative risk of 15.
Conclusion. A score using CPX responses provides a simple and integrated method that powerfully predicts outcomes in patients with HF.