Validation of a new CPET multivariable score to predict cardiovascular events in heart failure patients

Abstract

Abstract Introduction Cardiopulmonary exercise testing (CPET) is recommended in patients with heart failure (HF) to optimize exercise prescription and as part of the evaluation for heart transplantation. Recently, a new multivariable score (MVS) was proposed as a powerful method to predict HF events with an optimal cut-off value of 120. Purpose We aimed to evaluate the prognostic value of this tool in patients with HF. Methods We conducted a single-centre study assessing consecutive patients with HF who underwent CPET from 2013 to 2017. Classic and recently proposed variables were collected, including peak O2 uptake (pVO2), minute ventilation–CO2 production (VE/VCO2 slope), partial pressure of end-tidal CO2 at the anaerobic threshold (PETCO2L), circulatory power (CP=pVO2 x peak SBP), and ventilatory power (VP=peak SBP/(VE/VCO2) slope). The score was calculated as follows: (pVO2 × 2.194) + (PETCO2L × 1.545) + (LVEF × 1.134) + (HR × 1.055; 0 if AF, 1 if sinus rhythm). The primary outcome was a composite of HF hospitalization, heart transplant, and all-cause mortality. Results We included 212 patients 76.9% male and with a mean age of 55.4±10.9 years-old. The most frequent aetiology was dilated cardiomyopathy (43.9%) followed by ischaemic heart disease (38.7%). Accordingly, the mean left ventricle ejection fraction was 29±13%. Additionally, 39.8% had atrial fibrillation. The most used exercise protocol was the modified Naughton (76.6%). Mean pVO2 was 16.7±5.9mL O2·kg−1·min−1, median VE/VCO2 slope was 37.5 [32.7-44.3], and PETCO2L 33.5±5.2mmHg. Mean VP was 3.46±1.31mmHg while the median CP was 1927 [1427-2697]mmHg·min/mL/kg. The mean MVS was 116.2±23.1. Despite weak, there were significant positive correlations between the MVS and both VP (r=0.59, p<0.01) and CP (rs=0.64, p<0.01). After a median follow-up of 71 [49-81] months, the primary outcome occurred in 66.0% of patients (rehospitalization, heart transplant, and all-cause death occurred in 56.1%, 25.9%, and 32.5%, respectively). The new CPET MVS was associated with the primary outcome (p<0.01). Additionally, patients with MVS <120 had a higher rate of the primary outcome (83.2% vs. 39.1%, p<0.01). Kaplan-Meier estimates of tthe primary outcome according to the optimal cut-off value of 120 are shown in Figure 1A. Receiver operating characteristic curve revealed that the MVS has higher discriminative power for the primary endpoint (AUC 0.80, p<0.01) compared to pVVO2, VP, and CP (Figure 1B). Conclusion The novel multivariable score is associated with the composite of HF hospitalization, heart transplant, and all-cause mortality in patients with heart failure, enhancing the role of CPET in risk stratification.