The exercise pressor reflex and active O ₂ transport in peripheral arterial disease

Abstract

It is unclear if the exaggerated exercise pressor reflex observed in peripheral arterial disease (PAD) patients facilitates Oxygen (O2) transport during presymptomatic exercise. Accordingly, this study compared O2 transport between PAD patients and healthy controls during graded presymptomatic work. Seven PAD patients and seven healthy controls performed dynamic plantar flexion in the bore of a 3T MRI scanner. Perfusion, T2* (an index of relative tissue oxygenation), and SvO2 (a measure of venous oxygen saturation) were collected from the medial gastrocnemius (MG) during the final 10 seconds of each stage. Blood pressure was also collected during the final minute of each stage. As expected, the pressor response to presymptomatic work (4 kg) was exaggerated in PAD patients compared to controls (+14 mmHg ± 4 and +7 mmHg ± 2, P ≤ 0.034). When normalized to changes in free water content (S0), T2* was lower at 2 kg in PAD patients compared to controls (−0.91 Δms/ΔAU ± 0.3 and 0.57 Δms/ΔAU ± 0.3, P ≤ 0.008); followed by a greater increase in perfusion at 4 kg in the PAD group (+18.8 mL/min/100g ± 6.2 vs. −0.21 mL/min/100g ± 3.2 in PAD and controls, P ≤ 0.026). Lastly, SvO2 decreased at 4 kg in both groups (−13% ± 4 and −2% ± 4 in PAD and controls, P ≤ 0.049), suggesting an increase in O2 extraction in the PAD group. Based on these findings, O2 transport appears to be augmented during graded presymptomatic work in PAD patients, and this may be partially mediated by an exaggerated pressor response.

Diagnosing Sport-Related Flow Limitations in the Iliac Arteries Using Near-Infrared Spectroscopy

“…This is consistent with blood flow limitation at the conduit iliac artery. It is well established that NIRS reoxygenation is faster in fitter subjects [48,49] and delayed in clinical conditions, such as peripheral vascular disease [14][15][16][17]50]. The present study demonstrates that NIRS kinetic parameters may be valuable in the diagnosis of FLIA.…”

Central and peripheral modulation of exercise pressor reflex sensitivity after nonfatiguing work

“…More research is needed to confirm and expand on these findings. Moreover, it would be important to know if this same response is observed in patient populations that are known to have an exaggerated blood pressure response to exercise, such as in peripheral arterial disease (25,30,38) or hypertension (13,15). This may provide insight into the mechanisms of blood pressure dysregulation in these patient populations.…”