Oxygen uptake recovery and impaired cardiac reserve capacity: interaction with tau parameter
G Crisci, V Serrantoni, M Losito, G Federico, M GuazziAbstract
Background
It is unknown how is the oxygen (O2) kinetics trajectories during the recovery phase in heart failure (HF) patients, according to different phenotypes.
Aim
to investigate the relationship between the kinetics of recovery of O2 consumption by assessment of peak exercise decay "τau" evaluation and gas exchange performance, peak exercise VO2, and VE/VCO2 slope.
Methods
All consecutive subjects referred to a tertiary dyspnea clinic in the period January 2024-January 2025 were enrolled and underwent combined cardiopulmonary exercise testing and imaging (CPET imaging). We measured to characterize VO2 recovery kinetics using a novel metric "τ", VO2 recovery delay, defined by the formula VO2(t)= VO2(b) + A [1 - e -(t- TD) τ ], which is the recovery of normal breathing after exercise.
Results
A total of 172 subjects have been enrolled (129 patients with HF -55 HFrEF and 74 HFpEF, and 43 healthy controls).
HFpEF patients (mean age 74.5 ± 6.4, 60% female) and HFrEF patients (mean age 65.6 ± 11.3, 30% female) showed a lower VO2 peak than the control population (16.1 ± 3.2 ml/min/kg vs 14.9 ± 4.6 ml/min/kg vs 22,8 ± 5,6 ml/min/kg, respectively; Table 1). Regarding Tau decay HF displayed a higher value compared to the control population (τ mean= 232.2 in HFpEF; 157.9 in HFrEF; 100 in controls). In HF, τ value is strongly correlated with impairment of exercise performance in terms of VO2 peak (respectively, r=0.75, r=0.60 p<0.001) and VE/VCO2 slope in both phenotypes (respectively, r=0.53 p<0.001; r=0.54 p<0.001) (Figure 1).
Conclusions
Recovery O2 uptake, expressed as τau is a simple, noninvasively derived parameter for assessing impaired circulatory response to exercise in HF. The τau value may complement established exercise-derived measurements detecting impaired cardiovascular response.Figure 1For image description, please refer to the figure legend and surrounding text.Table 1For image description, please refer to the figure legend and surrounding text.