Evaluation of the pulmonary and muscle oxygen kinetics in heart failure patients with reduced and preserved ejection fraction

Abstract Introduction Possible differences in the oxygen supply and the dynamics may impact the exercise's response between heart failure (HF) with reduced ejection fraction (HFrEF) and preserved (HFpEF), mainly due to body composition differences. Thus, our study was designed to determine whether pulmonary and muscle oxygen kinetics responses may be present in HFpEF, which may help understand the phenotype differences in muscle microvascular perfusion on exercise capacity and stimulate future investigations. Objective I) To assess the kinetics of pulmonary oxygen uptake (V'O2p), skeletal muscle deoxygenation (HHb), and O2 microvascular delivery (QO2mv) in HFrEF and HFpEF; and II) To assess the pulmonary and muscle kinetic association with exercise performance and body composition variables. Methods 10 HFpEF and 11 HFrEF underwent cardiopulmonary exercise tests to assess V′O2 kinetics and near-infrared spectroscopy (NIRS) for HHb. Microvascular O2 delivery (QO2mv) was calculated using the Fick principle, and body composition via dual-energy x-ray absorptiometry (DEXA). Results Regarding the V′O2 kinetics, time constant (t) was slower in HFrEF (63±10.8 vs. 45.4±7.9s; P0.05) while the HHb were faster (t = 12.4±9.9 vs. 25±11.6s, P0.05). In addition, QO2mv were greater in HFrEF (3.6±1.2 vs 1.7±0.8, P0.05) (Figure 1) while time to exercise intolerance shorter (281.6±84 vs. 405.3±96s, P0.05). Time to exercise tolerance correlated to QO2mv (rho= -0.51; P0.05) and tV′O2 (rho= -0.63, P0.05) in both groups. We found that body adiposity negatively correlates with HHb amplitude (rho =-0.78) and peak V’O2 (rho =-0.54) in both groups, while lean muscle percentage positively correlates with HHb amplitude and tau (rho= 0.74 and 0.57; P0.05). Conclusions Along with oxygen uptake (V'O2p) kinetics reduction, deoxy-hemoglobin kinetics, and microvascular O2 delivery are also more severely affected in HFrEF than HFpEF. We also demonstrated that greater adiposity and less lean mass are related to a reduced oxygen diffusion capacity and poor oxygen uptake kinetics.