Abstract
Exposure of the arterial wall to retrograde shear acutely leads to endothelial dysfunction and chronically contributes to a proatherogenic vascular phenotype. Arterial stiffness and increased pressure from wave reflections are known arbiters of blood flow in the systemic circulation and each related to atherosclerosis. Using distal external compression of the calf to increase upstream retrograde shear in the superficial femoral artery (SFA), we examined the hypothesis that changes in retrograde shear are correlated with changes in SFA stiffness and pressure from wave reflections. For this purpose, a pneumatic cuff was applied to the calf and inflated to 0, 35, and 70 mmHg (5 min compression, randomized order, separated by 5 min) in 16 healthy young men (23 ± 1 years of age). Doppler ultrasound and wave intensity analysis was used to measure SFA retrograde shear rate, reflected pressure wave intensity (negative area [NA]), elastic modulus (Ep), and a single-point pulse wave velocity (PWV) during acute cuff inflation. Cuff inflation resulted in stepwise increases in retrograde shear rate (P < 0.05 for main effect). There were also significant cuff pressure-dependent increases in NA, Ep, and PWV across conditions (P < 0.05 for main effects). Change in NA, but not Ep or PWV, was associated with change in retrograde shear rate across conditions (P < 0.05). In conclusion, external compression of the calf increases retrograde shear, arterial stiffness, and pressure from wave reflection in the upstream SFA in a dose-dependent manner. Wave reflection intensity, but not arterial stiffness, is correlated with changes in peripheral retrograde shear with this hemodynamic manipulation.
Highlights
The peripheral blood flow waveform in human conduit arteries is triphasic, exhibiting characteristic antegrade flow during systole and a combination of retrograde and secondary antegrade flow during early and late diastole, respectively (Mahler et al 1977; Marquis et al 1984; Hashimoto and Ito 2010)
Day-to-day repeatability of hemodynamic measures calculated from a subset of subjects (n = 6) on two separate days was fair and resting values did not differ between testing days (P > 0.05)
Inflation of a blood pressure cuff around the calf successfully induced a stepwise increase in upstream superficial femoral artery (SFA) retrograde shear, which confirms previous observations witnessed in the brachial artery (Thijssen et al 2009; Tinken et al 2009; Birk et al 2012)
Summary
The peripheral blood flow waveform in human conduit arteries is triphasic, exhibiting characteristic antegrade (forward) flow during systole and a combination of retrograde (backward) and secondary antegrade flow during early and late diastole, respectively (Mahler et al 1977; Marquis et al 1984; Hashimoto and Ito 2010). Highly investigated of late (Padilla et al 2010, 2011; Young et al 2010; Casey et al 2012), the vascular and hemodynamic correlates of retrograde shear in peripheral conduit vessels remain poorly understood (Halliwill and Minson 2010). Bifurcations and changes in peripheral vascular/arteriolar tone result in reflection of the pressure wave. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society
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