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Impact of repeated increases in shear stress via reactive hyperemia and handgrip exercise: no evidence of systematic changes in brachial artery FMD

Impact of repeated increases in shear stress via reactive hyperemia and handgrip exercise: no... Abstract Reactive hyperemia (RH) creates an uncontrolled, transient increase in brachial artery (BA) shear stress (SS) for flow-mediated dilation (FMD) assessment. In contrast, handgrip exercise (HGEX) can create similar, sustained SS increases over repeated trials. The purpose of this study was to examine the impact of repeated SS elevation via RH or HGEX and the relationship between RH and HGEX %FMD. BA diameter and blood velocity were assessed with echo and Doppler ultrasound in 20 healthy subjects. Visit A consisted of four 6-min HGEX trials (HGEX trials 1–4 ) at the intensity required to achieve a shear rate (SR = mean blood velocity/BA diameter; an estimate of SS) of 65 s −1 . Visit B consisted of four RH trials (RH trials 1–4 ). The RH SR area under the curve (AUC) was higher in trial 1 versus trial 3 and trial 4 ( P = 0.019 and 0.047). The HGEX mean SR was similar across trials (mean SR = 66.1 ± 5.8 s −1 , P = 0.152). There were no differences in %FMD across trials or tests (RH trial 1 : 6.9 ± 3.5%, trial 2 : 6.9 ± 2.3%, trial 3 : 7.1 ± 3.5%, and trial 4 : 7.0 ± 2.8%; HGEX trial 1 : 7.3 ± 3.6%, trial 2 : 7.0 ± 3.6%, trial 3 : 6.5 ± 3.5%, and trial 4 : 6.8 ± 2.9%, P = 0.913). No relationship between subject's RH %FMD and HGEX %FMD was detected ( r 2 = 0.12, P = 0.137). However, with response normalization, a relationship emerged (RH %FMD/SR AUC vs. HGEX %FMD/mean SR, r 2 = 0.44, P = 0.002). In conclusion, with repeat trials, there were no systematic changes in RH or HGEX %FMD. The relationship between normalized RH and HGEX %FMD suggests that endothelial responses to different SS profiles provide related information regarding endothelial function. endothelial function Doppler ultrasound shear stress profile flow-mediated dilation Copyright © 2011 the American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Heart and Circulatory Physiology The American Physiological Society

Impact of repeated increases in shear stress via reactive hyperemia and handgrip exercise: no evidence of systematic changes in brachial artery FMD

AJP - Heart and Circulatory Physiology , Volume 300 (3): H1078 – Mar 1, 2011

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Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
0363-6135
eISSN
1522-1539
DOI
10.1152/ajpheart.00736.2010
pmid
21186268
Publisher site
See Article on Publisher Site

Abstract

Abstract Reactive hyperemia (RH) creates an uncontrolled, transient increase in brachial artery (BA) shear stress (SS) for flow-mediated dilation (FMD) assessment. In contrast, handgrip exercise (HGEX) can create similar, sustained SS increases over repeated trials. The purpose of this study was to examine the impact of repeated SS elevation via RH or HGEX and the relationship between RH and HGEX %FMD. BA diameter and blood velocity were assessed with echo and Doppler ultrasound in 20 healthy subjects. Visit A consisted of four 6-min HGEX trials (HGEX trials 1–4 ) at the intensity required to achieve a shear rate (SR = mean blood velocity/BA diameter; an estimate of SS) of 65 s −1 . Visit B consisted of four RH trials (RH trials 1–4 ). The RH SR area under the curve (AUC) was higher in trial 1 versus trial 3 and trial 4 ( P = 0.019 and 0.047). The HGEX mean SR was similar across trials (mean SR = 66.1 ± 5.8 s −1 , P = 0.152). There were no differences in %FMD across trials or tests (RH trial 1 : 6.9 ± 3.5%, trial 2 : 6.9 ± 2.3%, trial 3 : 7.1 ± 3.5%, and trial 4 : 7.0 ± 2.8%; HGEX trial 1 : 7.3 ± 3.6%, trial 2 : 7.0 ± 3.6%, trial 3 : 6.5 ± 3.5%, and trial 4 : 6.8 ± 2.9%, P = 0.913). No relationship between subject's RH %FMD and HGEX %FMD was detected ( r 2 = 0.12, P = 0.137). However, with response normalization, a relationship emerged (RH %FMD/SR AUC vs. HGEX %FMD/mean SR, r 2 = 0.44, P = 0.002). In conclusion, with repeat trials, there were no systematic changes in RH or HGEX %FMD. The relationship between normalized RH and HGEX %FMD suggests that endothelial responses to different SS profiles provide related information regarding endothelial function. endothelial function Doppler ultrasound shear stress profile flow-mediated dilation Copyright © 2011 the American Physiological Society

Journal

AJP - Heart and Circulatory PhysiologyThe American Physiological Society

Published: Mar 1, 2011

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