Diabetes and Vascular Medicine Research Centre, NIHR Exeter Clinical Research Facility, University of Exeter College of Medicine and Health, Exeter, UK.
Department of Information Engineering, University of Florence, Florence, Italy.
J Physiol. 2019 Aug;597(16):4151-4163. doi: 10.1113/JP278310. Epub 2019 Jul 15.
The vasodilatory response to reactive hyperaemia is impaired with advancing age, but it is unclear whether this is because of an altered wall shear rate (WSR) stimulus or an altered flow-mediated dilatation (FMD) response. Using new technology that allows detailed WSR measurement, we assessed the WSR-FMD response in healthy older people. Our data show that older people have a markedly altered and diminished WSR response to reactive hyperaemia compared to young people, but reduced WSR alone does not fully explain reduced FMD. In young people, WSR appears to be coupled to FMD but, by age ∼65 years, the arterial vasodilatory response has begun to uncouple from the WSR stimulus. These findings point to the importance and utility of comprehensively characterizing the WSR-FMD response when using reactive hyperaemia to assess vascular function, as well as giving new insight into the age-related alteration in vascular function.
The vasodilatory response to reactive hyperaemia is impaired with age, but it is unknown whether this is because of an altered wall shear rate (WSR) stimulus or an altered flow-mediated dilatation (FMD) response to the WSR stimulus. Inherent difficulties in measuring blood flow velocity close to the arterial wall have prevented detailed assessment of the WSR-FMD response. Using an enhanced multigate spectral Doppler ultrasound system (ultrasound advanced open platform), we aimed to produce new data on the WSR-FMD relationship in healthy older adults. Sixty healthy people, comprising 28 young (27.5 ± 5.5 years) and 32 older (64.9 ± 3.7 years) individuals, underwent FMD assessment. Raw data were post-processed using custom-designed software to obtain WSR and diameter parameters. The data revealed that older people have a much altered and diminished WSR response to reactive hyperaemia compared to younger people [e.g. WSR peak: 622 (571-673) vs. 443 (396-491) 1/s in young and older respectively; P < 0.05]. However, reduced WSR alone does not appear to fully explain the reduced FMD response in older people because associations between WSR and FMD were few and weak. This was in contrast to young adults, where associations were strong. We conclude that WSR during FMD is much altered and diminished in older people, and there appears to be an 'uncoupling' of WSR from FMD in older people that may reflect a loss of precision in the reactive hyperaemia stimulus-response relationship. These findings also point to the importance and utility of comprehensively characterizing the WSR-FMD response when using reactive hyperaemia to assess vascular function.
随着年龄的增长，对反应性充血的血管舒张反应受损，但尚不清楚这是由于壁切变率（WSR）刺激改变还是对 WSR 刺激的血流介导的扩张（FMD）反应改变所致。使用允许详细测量 WSR 的新技术，我们评估了健康老年人的 WSR-FMD 反应。我们的数据表明，与年轻人相比，老年人对反应性充血的 WSR 反应明显改变且减弱，但仅降低 WSR 并不能完全解释 FMD 的降低。在年轻人中，WSR 似乎与 FMD 相关，但到年龄约 65 岁时，动脉血管舒张反应已开始与 WSR 刺激脱耦。这些发现表明，在使用反应性充血评估血管功能时，全面描述 WSR-FMD 反应非常重要且有用，并为血管功能的年龄相关改变提供了新的见解。
随着年龄的增长，对反应性充血的血管舒张反应受损，但尚不清楚这是由于壁切变率（WSR）刺激改变还是对 WSR 刺激的血流介导的扩张（FMD）反应改变所致。在靠近动脉壁测量血流速度的固有困难，阻止了对 WSR-FMD 反应的详细评估。我们使用增强型多门频谱多普勒超声系统（超声高级开放平台），旨在为健康老年人的 WSR-FMD 关系提供新数据。60 名健康人，包括 28 名年轻人（27.5±5.5 岁）和 32 名老年人（64.9±3.7 岁），接受了 FMD 评估。原始数据使用定制设计的软件进行后处理，以获得 WSR 和直径参数。数据显示，与年轻人相比，老年人对反应性充血的 WSR 反应改变更大且减弱[例如，WSR 峰值：年轻人分别为 622（571-673）和 443（396-491）1/s；P<0.05]。然而，仅降低 WSR 似乎并不能完全解释老年人 FMD 反应的降低，因为 WSR 和 FMD 之间的关联很少且很弱。这与年轻人形成鲜明对比，年轻人之间的关联很强。我们的结论是，老年人的 FMD 期间的 WSR 改变很大且减弱，并且在老年人中似乎存在 WSR 与 FMD 的“脱耦”，这可能反映了反应性充血刺激-反应关系的精度损失。这些发现还表明，在使用反应性充血评估血管功能时，全面描述 WSR-FMD 反应非常重要且有用。
