Background: Wall shear rate (WSR) is considered an important stimulus for flow-mediated dilatation (FMD). However, its estimation by conventional ul-trasound is challenging due to inherent difficulties of velocity estimation near the arterial wall. To evaluate how WSR influences brachial artery FMD, we used a prototype Doppler ultrasound system which provides simul-taneous estimates of WSR at near and far walls and continuous arterial diam-eter tracking. Methods: Data from 33 young healthy individuals (27.54.9yrs, 19F) were analysed. FMD was assessed with a conventional reactive hyperaemia tech-nique using Ultrasound Advanced Open Platform (ULA-OP). All acquired raw data were post-processed using custom-designed software to obtain WSR and diameter parameters. Results: Baseline diameter and FMD were 3.290.45 mm and 6.543.54 %, respectively. During hyperaemia, we observed two distinct patterns of increased WSR: monophasic (MOP, nZ15 fast increase reaching peak WSR at once) and biphasic (BIP, nZ18 fast followed by slow increase before reaching peak WSR). In BIP, peak WSR (657153 sec-1 vs 522132 sec-1) and WSR area under the curve until peak dilation (203986265 au vs 135305592 au) were significantly greater than in MOP (both p<0.05). Absolute diameter increase was significantly greater in BIP (0.240.10 mm) than in MOP (0.150.09 mm, p<0.05). Percentage diameter increase tended to be greater in BIP (7.63.3 %) than MOP (5.33.5 %, pZ0.08). Conclusions: These results demonstrate that there are distinct WSR increase patterns during hyperaemia, and that these patterns are associated with dif-ferences in the magnitude of hyperaemic WSR. Our observations suggest that these WSR increase patterns may be associated with the subsequent brachial artery FMD response.

Brachial artery flow-mediated dilatation: different patterns of wall shear rate increase during reactive hyperaemia

Carmela Morizzo;Carlo Palombo
2016

Abstract

Background: Wall shear rate (WSR) is considered an important stimulus for flow-mediated dilatation (FMD). However, its estimation by conventional ul-trasound is challenging due to inherent difficulties of velocity estimation near the arterial wall. To evaluate how WSR influences brachial artery FMD, we used a prototype Doppler ultrasound system which provides simul-taneous estimates of WSR at near and far walls and continuous arterial diam-eter tracking. Methods: Data from 33 young healthy individuals (27.54.9yrs, 19F) were analysed. FMD was assessed with a conventional reactive hyperaemia tech-nique using Ultrasound Advanced Open Platform (ULA-OP). All acquired raw data were post-processed using custom-designed software to obtain WSR and diameter parameters. Results: Baseline diameter and FMD were 3.290.45 mm and 6.543.54 %, respectively. During hyperaemia, we observed two distinct patterns of increased WSR: monophasic (MOP, nZ15 fast increase reaching peak WSR at once) and biphasic (BIP, nZ18 fast followed by slow increase before reaching peak WSR). In BIP, peak WSR (657153 sec-1 vs 522132 sec-1) and WSR area under the curve until peak dilation (203986265 au vs 135305592 au) were significantly greater than in MOP (both p<0.05). Absolute diameter increase was significantly greater in BIP (0.240.10 mm) than in MOP (0.150.09 mm, p<0.05). Percentage diameter increase tended to be greater in BIP (7.63.3 %) than MOP (5.33.5 %, pZ0.08). Conclusions: These results demonstrate that there are distinct WSR increase patterns during hyperaemia, and that these patterns are associated with dif-ferences in the magnitude of hyperaemic WSR. Our observations suggest that these WSR increase patterns may be associated with the subsequent brachial artery FMD response.
https://www.sciencedirect.com/science/article/abs/pii/S1872931216301636
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/884062
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