Prognostic Value of Body Surface Area-Adjusted Oxygen Uptake Efficiency Slope in Heart Failure Patients

COVID-19 has been associated with a higher risk of developing heart failure (HF). Among the parameters derived from cardiopulmonary exercise testing (CPET), oxygen uptake efficiency slope (OUES) has become one of the most important parameters for predicting the prognosis of HF patients. However, the clinical utilization of OUES is limited owing to its variation with patient height and weight. This study aimed to evaluate the prognostic value of body surface area-adjusted OUES (OUES/BSA) in adults with HF.

Thirty-six HF patients (mean age, 57 ± 12 years; 30 men) undergoing CPET between July 2019 and May 2020 who were followed up for 12 months were enrolled. The endpoints were major cardiovascular (CV) events, including hospitalization due to acute decompensated HF, left ventricular assist device implantation, heart transplantation, and cardiovascular-related death. We analyzed the correlations between clinical/CPET variables and major CV events.

Among the analyzed CPET variables, OUES/BSA had better correlation with maximal oxygen uptake (VO_2max) than other variables. In univariate Cox proportional analysis, OUES/BSA and peak VO₂ were both significant independent prognostic factors. The cutoff value of OUES/BSA was 595 ml/min/m² with an area under the curve of 0.929. The patients with OUES/BSA < 595 ml/min/m² had a lower CV event-free survival rate at 12 months of follow-up compared with the other group (33.3% and 100%, respectively; log-rank test, p < 0.001).

BSA-adjusted OUES is an effective independent predictor for prognosis in HF patients and can be an alternative to peak VO₂ for risk stratification in HF patients, regardless of exercise intensity. However, further large-scale studies are required to validate our findings.