Manipulation of arterial stiffness, wave reflections, and retrograde shear rate in the femoral artery using lower limb external compression

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.

Sympathetic nervous system activation, arterial shear rate, and flow-mediated dilation

“…Despite the accommodation of the shear pattern, changes in central hemodynamics to 30-min LBNP were comparable to those observed after 10 min. At least this suggests that the regulation of retrograde shear rate is not simply explained through changes in peripheral vascular tone alone, but may also relate to other mechanisms, such as pressure from wave reflections (9). An effect of shear, as against direct effects of SNS activation per se, is supported by our observation that heating attenuated retrograde shear and increased FMD, whereas cuff inflation increased retrograde shear and decreased FMD.…”

Hemodynamic Correlates of Late Systolic Flow Velocity Augmentation in the Carotid Artery

“…Waves in the systemic circulation with a pulling effect have been known to exist for quite some time [ 42 ]. This suction wave has been shown to be an important correlate/moderator of late systolic/early diastolic flow in the coronary [ 12 , 43 ], aorta [ 8 , 10 ], and femoral arteries [ 14 ]. Most notably, this suction wave has been implicated as a factor contributing to aortic flow reversal and valve closure [ 8 , 9 ].…”

“…This results in propagation of a forward travelling expansion wave (also known as a decompression wave or rarefaction wave) [ 9 ] which creates a suction effect that applies a “braking” action to the column of blood from behind and actively decelerates flow [ 10 , 11 ]. Suction waves contribute to late systolic/early diastolic flow in the coronary circulation [ 12 ], the aorta/aortic valve closure [ 8 , 13 ], and the femoral artery [ 14 ]. Previous studies have identified the existence of a late systolic forward travelling expansion wave in the carotid artery as well [ 15 , 16 ].…”

Functional aortic stiffness: role of CD4+ T lymphocytes

“…Reflected flow waves have the same shape as the pressure waves but are 180° out of phase (Westerhof et al, 1972 ). We measured the distance from the EKG R-wave to the initial beginning of the innominate lower extremity flow wave (Heffernan et al, 2013 ) and presented it as the transit time of the reflective wave (ms).…”