Oxygen uptake (VO2) work rate (WR) flattening in heart failure patients with reduced EF : insights from exercise-echocardiography

Background: Cardiopulmonary exercise test (CPET) allows functional assessment by assessing VO2 and its kinetic. The flattening of VO2/WR slope during incremental maximal exercise has been described in some cardiovascular disorders, mainly in heart failure (HF) patients with reduced EF (HFrEF) and in the presence of exercise-induced myocardial ischemia. In a HFrEF population we explored the cardiac determinants of VO2/WR looking at both systolic and diastolic HF. Methods and Results: 39 HFrEF patients (mean age 63±9; male 70%; NYHA II 47%, III 45%, IV 8%) underwent a maximal cardiopulmonary exercise testing evaluation (bike, personalized incremental ramp protocol) combined with Echo-Doppler assessment. We considered 2 subgroups according to the occurrence of VO2/WR slope flattening, defined as a change >20% of the slope during exercise (mean LVEF at rest 33±7%, at peak exercise 35±10%; mean RV Area Fraction at rest 40±13%, at peak exercise 30±13%; without significant difference between the 2 subgroups). The table shows the main clinical characteristics and test results. Conclusions: In this HFrEF population VO2/WR slope flattening is significantly associated with higher NTproBNP serum levels, more severe dilatation of both ventricles and left atrium at rest and peak exercise, a more severe mitral regurgitation at rest and peak exercise and a lower peak O2 pulse. These results highlight the relevance of detecting a VO2/WR flattening as a marker for identifying a subset of HFrEF patients with a more compromised global cardiac function during exercise.