Impact of retrograde shear rate on brachial and superficial femoral artery flow-mediated dilation in older subjects

Purpose: The effect of exercise intensity on vasodilator function is poorly understood in children. The authors compared the acute effect of high-intensity interval exercise (HIIE) with moderate-intensity steady-state exercise (MISS) on postexercise vasodilation and shear patterns in 7- to 12- year-old children. Methods: Superficial femoral artery diameter, shear rates, and flow-mediated dilation were measured pre, immediately following (post), and 1 hour after (post60) HIIE (six 1-min sprints at 90% peak power [Wmax], with 1-min recovery) and MISS (15 min at 44% Wmax). Results: Baseline superficial femoral artery diameter increased similarly following both HIIE (pre 4.23 [0.41] mm, post 4.73 [0.56] mm) and MISS (pre 4.28 [0.56] mm, post 4.59 [0.64] mm), returning to preexercise values post60. Blood flow and antegrade shear rate were increased post HIIE and MISS, but to a greater extent, post HIIE (P < .05). Retrograde shear rate was attenuated post both exercise conditions and remained post60 (P < .001). There was a decline in flow-mediated dilation postexercise (HIIE Δ −2.9%; MISS Δ −2.4%), which was no longer apparent when corrected for baseline diameter. Conclusion: Acute bouts of external work-matched HIIE or MISS exert a similar impact on shear-mediated conduit artery vasodilation and flow-mediated dilation in children, and this is reversed 1 hour after exercise.

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Sitting cross-legged for 30 min alters lower limb shear stress pattern but not flow-mediated dilation or arterial stiffness

Applied Physiology Nutrition and Metabolism ◽

10.1139/apnm-2018-0339 ◽

2019 ◽

Vol 44 (2) ◽

pp. 221-224

Author(s):

Joshua C. Tremblay ◽

Taylor V. Stimpson ◽

Kristen M. Murray ◽

Kyra E. Pyke

Keyword(s):

Shear Stress ◽

Shear Rate ◽

Femoral Artery ◽

Superficial Femoral Artery ◽

Lower Limb ◽

Pulse Wave ◽

Stress Pattern ◽

Flow Mediated Dilation ◽

Sitting Position ◽

Prolonged Sitting

Prolonged sitting decreases lower limb endothelial function via sustained reductions in mean shear rate. We tested whether 30 min of sitting cross-legged differentially impacts superficial femoral artery shear rate pattern, flow-mediated dilation (FMD), and leg pulse-wave velocity (PWV) compared with sitting flat-footed. Sitting cross-legged attenuated the reduction in mean and antegrade shear rate and increased arterial pressure compared with sitting flat-footed. Superficial femoral artery FMD and leg PWV were unaltered following either sitting position.

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Vitamin C prevents the acute decline of flow-mediated dilation after altered shear rate patterns

Applied Physiology Nutrition and Metabolism ◽

10.1139/apnm-2012-0169 ◽

2013 ◽

Vol 38 (3) ◽

pp. 268-274 ◽

Cited By ~ 26

Author(s):

Blair D. Johnson ◽

Kieren J. Mather ◽

Sean C. Newcomer ◽

Timothy D. Mickleborough ◽

Janet P. Wallace

Keyword(s):

Oxidative Stress ◽

Shear Rate ◽

Vitamin C ◽

Flow Mediated Dilation ◽

Double Blind ◽

Vitamin C Supplementation ◽

Artery Flow ◽

Blind Crossover Study ◽

Double Blind Crossover Study ◽

Retrograde Shear

Oscillatory and retrograde shear rate (SR) impairs endothelial function, potentially through shear-induced oxidative stress. We tested the hypothesis that acute vitamin C supplementation would prevent the attenuation of brachial artery flow-mediated dilation (FMD) after a period of augmented oscillatory and retrograde SR. Twelve healthy men (aged 26 ± 3 years) participated in two 30-min study visits in which one arm was subjected to increased oscillatory and retrograde SR, using 60 mm Hg of forearm cuff compression, and the contralateral arm served as the control. Subjects ingested capsules containing either placebo (sucrose) or vitamin C at 90 and 120 min (1000 mg total vitamin C) prior to cuff compression periods in a randomized placebo-controlled double-blind crossover study. Oscillatory and retrograde SR in the cuffed arms increased during the compression periods in the placebo and vitamin C study visits (p < 0.01 for both), with no difference between studies (p > 0.05). Antegrade SR remained unchanged throughout the compression periods (p > 0.05), and mean SR was lower in the cuffed arm than in the control arm for both study visits (p < 0.05). FMD decreased after cuff compression in the placebo cuffed arm (precompression vs. postcompression, 5.2% ± 1.4% vs. 3.5% ± 1.4%; p < 0.05), but remained unchanged after vitamin C therapy in the cuffed arm (precompression vs. postcompression, 5.3% ± 2.4% vs. 5.7% ± 2.6%; p > 0.05). No FMD changes were observed in the control arm for either study visit (p > 0.05). These data demonstrate that acute vitamin C supplementation prevents the attenuation of FMD due to altered SR patterns, suggesting that oxidative stress contributes to the oscillatory and retrograde SR-induced impairment of FMD.

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Effects of posture on shear rates in human brachial and superficial femoral arteries

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01108.2007 ◽

2008 ◽

Vol 294 (4) ◽

pp. H1833-H1839 ◽

Cited By ~ 43

Author(s):

S. C. Newcomer ◽

C. L. Sauder ◽

N. T. Kuipers ◽

M. H. Laughlin ◽

C. A. Ray

Keyword(s):

Shear Rate ◽

Femoral Artery ◽

Brachial Artery ◽

Superficial Femoral Artery ◽

Upright Posture ◽

Brachial Artery Diameter ◽

Shear Rates ◽

Femoral Arteries ◽

Lower Shear ◽

Relative Shear

Shear rate is significantly lower in the superficial femoral compared with the brachial artery in the supine posture. The relative shear rates in these arteries of subjects in the upright posture (seated and/or standing) are unknown. The purpose of this investigation was to test the hypothesis that upright posture (seated and/or standing) would produce greater shear rates in the superficial femoral compared with the brachial artery. To test this hypothesis, Doppler ultrasound was used to measure mean blood velocity (MBV) and diameter in the brachial and superficial femoral arteries of 21 healthy subjects after being in the supine, seated, and standing postures for 10 min. MBV was significantly higher in the brachial compared with the superficial femoral artery during upright postures. Superficial femoral artery diameter was significantly larger than brachial artery diameter. However, posture had no significant effect on either brachial or superficial femoral artery diameter. The calculated shear rate was significantly greater in the brachial (73 ± 5, 91 ± 11, and 97 ± 13 s−1) compared with the superficial femoral (53 ± 4, 39 ± 77, and 44 ± 5 s−1) artery in the supine, seated, and standing postures, respectively. Contrary to our hypothesis, our current findings indicate that mean shear rate is lower in the superficial femoral compared with the brachial artery in the supine, seated, and standing postures. These findings of lower shear rates in the superficial femoral artery may be one mechanism for the higher propensity for atherosclerosis in the arteries of the leg than of the arm.

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Preserved flow-mediated dilation in the inactive legs of spinal cord-injured individuals

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00958.2003 ◽

2004 ◽

Vol 287 (1) ◽

pp. H374-H380 ◽

Cited By ~ 84

Author(s):

Patricia C. E. de Groot ◽

Fleur Poelkens ◽

Miriam Kooijman ◽

Maria T. E. Hopman

Keyword(s):

Spinal Cord ◽

Shear Rate ◽

Endothelial Function ◽

Femoral Artery ◽

Brachial Artery ◽

Rate Ratio ◽

Arterial Occlusion ◽

Flow Mediated Dilation ◽

Dilatory Response ◽

Spinal Cord Injured

The aim of the study was to assess endothelial function, measured by flow-mediated dilation (FMD), in an inactive extremity (leg) and chronically active extremity (arm) within one subject. Eleven male spinal cord-injured (SCI) individuals and eleven male controls (C) were included. Echo Doppler measurements were performed to measure FMD responses after 10 and 5 min of arterial occlusion of the leg (superficial femoral artery, SFA) and the arm (brachial artery, BA), respectively. A nitroglycerine spray was administered to determine the endothelium independent vasodilatation in the SFA. In the SFA, relative changes in FMD were significantly enhanced in SCI compared with C (SCI: 14.1 ± 1.3%; C: 9.2 ± 2.3%), whereas no differences were found in the BA (SCI: 12.5 ± 2.9%; C: 14.2 ± 3.3%). Because the FMD response is directly proportional to the magnitude of the stimulus, the FMD response was also expressed relative to the shear rate. No differences between the groups were found for the FMD-to-shear rate ratio in the SFA (SCI:0.061 ± 0.023%/s−1; C: 0.049 ± 0.024%/s−1), whereas the FMD-to-shear rate ratio was significantly decreased in the BA of SCI individuals (SCI: 0.037 ± 0.01%/s−1; C: 0.061 ± 0.027%/s−1). The relative dilatory response to nitroglycerine did not differ between the groups. (SCI: 15.6 ± 2.0%; C: 13.4 ± 2.3%). In conclusion, our results indicate that SCI individuals have a preserved endothelial function in the inactive legs and possibly an attenuated endothelial function in the active arms compared with controls.

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Sympathetic nervous system contributes to the age-related impairment of flow-mediated dilation of the superficial femoral artery

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00240.2006 ◽

2006 ◽

Vol 291 (6) ◽

pp. H3122-H3129 ◽

Cited By ~ 44

Author(s):

Dick H. J. Thijssen ◽

Patricia de Groot ◽

Miriam Kooijman ◽

Paul Smits ◽

Maria T. E. Hopman

Keyword(s):

Nervous System ◽

Sympathetic Nervous System ◽

Femoral Artery ◽

Superficial Femoral Artery ◽

Sympathetic Activity ◽

Cold Pressor Test ◽

Young Men ◽

Older Men ◽

Flow Mediated Dilation ◽

Sympathetic Nervous

The physiological aging process is associated with endothelial dysfunction, as assessed by flow-mediated dilation (FMD). Aging is also characterized by increased sympathetic tone. Therefore, the aim of the present study is to assess whether acute changes in sympathetic activity alter FMD in the leg. For this purpose, the FMD of the superficial femoral artery was determined in 10 healthy young (22 ± 1 yr) and 8 healthy older (69 ± 1 yr) men in three different conditions: 1) at baseline, 2) during reduction of sympathetic activity, and 3) during sympathetic stimulation. Reduction of sympathetic activity was achieved by performing a maximal cycling exercise, leading to postexercise attenuation of the sympathetic responsiveness in the exercised limb. A cold pressor test was used to increase sympathetic activity. Nitroglycerin (NTG) was used to assess endothelium-independent vasodilation in all three conditions. Our results showed that, in older men, the FMD and NTG responses were significantly lower compared with young men ( P = 0.001 and P = 0.02, respectively). In older men, sympathetic activity significantly affected the FMD response [repeated-measures (RM) ANOVA: P = 0.01], with a negative correlation between the level of sympathetic activity and FMD ( R = −0.41, P = 0.049). This was not the case for NTG responses (ANOVA; P = 0.48). FMD and NTG responses in young men did not differ among the three conditions (RM-ANOVA: P = 0.32 and P = 0.31, respectively). In conclusion, in older men, FMD of the femoral artery is impaired. Local attenuation of the sympathetic responsiveness partly restores the FMD in these subjects. In contrast, in young subjects, acute modulation of the sympathetic nervous system activity does not alter flow-mediated vasodilation in the leg.

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Acute Effects of Interrupting Prolonged Sitting on Vascular Function in Type 2 Diabetes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00422.2020 ◽

2020 ◽

Author(s):

Frances C. Taylor ◽

David W. Dunstan ◽

Ashleigh R Homer ◽

Paddy C. Dempsey ◽

Bronwyn A Kingwell ◽

...

Keyword(s):

Type 2 Diabetes ◽

Shear Rate ◽

Femoral Artery ◽

Vascular Function ◽

Acute Effects ◽

Obese Adults ◽

Endothelin 1 ◽

Prolonged Sitting ◽

Artery Flow

In healthy and overweight/obese adults, interrupting prolonged sitting with activity bouts mitigates impairment in vascular function. However, it is unknown whether these benefits extend to those with type 2 diabetes (T2D); nor, whether an optimal frequency of activity interruptions exist. We examined the acute effects on vascular function in T2D of interrupting prolonged sitting with simple resistance activities (SRA) at different frequencies. In a randomized crossover trial, 24 adults with T2D (35-70 years) completed three 7-hour conditions: 1) uninterrupted sitting (SIT); 2) sitting with 3 minute bouts of SRA every 30 min (SRA3); and, 3) sitting with 6 minute bouts of SRA every 60 min (SRA6). Femoral artery flow-mediated dilation (FMD), resting shear rate, blood flow and endothelin-1 were measured at 0h, 1h, 3.5h, 4.5h, and 6.5-7h. Mean femoral artery FMD over 7 hours was significantly higher in SRA3 (4.1 ± 0.3%) compared to SIT (3.7 ± 0.3%, p = 0.04), but not in SRA6. Mean resting femoral shear rate over 7 hours was increased significantly for SRA3 (45.3±4.1/s, p<0.001) and SRA6 (46.2±4.1/s, p<0.001) relative to SIT (33.1±4.1/s). Endothelin-1 concentrations were not statistically different between conditions. Interrupting sitting with activity breaks every 30 minutes, but not 60 minutes, significantly increased mean femoral artery FMD over 7 hours, relative to SIT. Our findings suggest that more-frequent and shorter breaks may be more beneficial than longer, less-frequent breaks for vascular health in those with T2D.

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