Abstract 3002: Development of a Cardiopulmonary Exercise Prognostic Score for Optimising Risk Stratification in Heart Failure: The (P)e(R)i(O)dic (B)reathing during (E)xercise (PROBE) Study
Aims: Cardiopulmonary exercise testing (CPET) provides powerful information on risk of death in HF. We sought to define the relative and additive contribution of the three landmark (CPET) prognostic markers: peak oxygen consumption (VO2); ventilation to CO2 (VE/VCO2) slope and exercise periodic breathing (EPB), to the overall risk of cardiac death and to develop a prognostic score for optimising risk stratification in heart failure (HF) patients.
Methods and Results: 695 stable HF patients (average LVEF: 25±8%) underwent a symptom-limited CPET maximum test after familiarisation and were propsectively tracked for cardiac mortality. At multivariable Cox analysis EPB emerged as the strongest prognosticator. Using a statistical bootstrap technique (5000 data resamplings), point estimates and 95% confidence intervals were obtained. A total of 32 configurations were adopted to classify patients into a given cell, according to EPB presence or absence and values of the two other covariates.
Results: Configurations without EPB and with VE/VCO2 slope ≤30 were not significantly different from 0 (reference value). Statistical power of configurations increased with higher VE/VCO2 slope and lower peak VO2. This prompted us to formulate a score including EPB as a discriminating variable, the (P)e(R)i(O)dic (B)reathing during (E)xercise (PROBE), which ranges between −1 to 1, with zero as reference configuration, that would help to optimize the prognostic accuracy of CPET-derived variables. The greatest PROBE score impact was provided by EPB, followed by VE/VCO2 slope, whereas peak VO2 added minimal prognostic power.
Conclusions: EPB with an elevated VE/VCO2 slope leads to the highest and most precise PROBE score, while no additional risk information emerges when EPB is present with a peak VO2 <10 mlO2. kg−1. min−1. PROBE score appears to provide a step forward for optimising CPET use in HF prognostic definition.