Samijo S K, Willigers J M, Barkhuysen R, Kitslaar P J, Reneman R S, Brands P J, Hoeks A P
Department of Biophysics, Maastricht University, The Netherlands.
Cardiovasc Res. 1998 Aug;39(2):515-22. doi: 10.1016/s0008-6363(98)00074-1.
It has been postulated that in the arterial system mean wall shear stress is maintained at a constant value. The present study was performed to investigate the level of wall shear stress in the common carotid artery (CCA) as function of age and possible interactions between diameter and storage capacity, defined as the absolute area change per heart beat, with mean wall shear stress.
Wall shear stress (wall shear rate multiplied by whole blood viscosity) was assessed in the right CCA of 111 presumed healthy male (n = 56) and female (n = 55) volunteers, varying in age between 10 and 60 years. Wall shear rate was measured with a high resolution ultrasound system. Simultaneously, arterial diameter and storage capacity were determined. Whole blood viscosity was calculated from haematocrit, plasma viscosity and shear rate.
From the second to the sixth age decade peak wall shear stress was significantly higher in males than in females and decreased from 4.3 Pa to 2.6 Pa (r = -0.56, p < 0.001) in males and from 3.3 Pa to 2.5 Pa (r = -0.54, p < 0.001) in females. Mean wall shear stress tended to decrease from 1.5 Pa to 1.2 Pa (r = -0.26, p = 0.057) in males and decreased significantly from 1.3 Pa to 1.1 Pa (r = -0.30, p = 0.021) in females. No significant difference in mean wall shear stress was found between males and females in any age decade. The diameter of the CCA increased significantly in both males (r = 0.26, p < 0.05) and females (r = 0.40, p < 0.003). Storage capacity decreased significantly in both sexes (males: r = -0.63, p < 0.001; females: r = -0.68, p < 0.001).
These observations suggest that the reduction in mean wall shear stress with age results from the concomitant increase in diameter in an attempt of the arterial system to limit the reduction in storage capacity of the arterial system with increasing age.
据推测，在动脉系统中平均壁面剪应力维持在恒定值。本研究旨在调查颈总动脉（CCA）壁面剪应力水平随年龄的变化，以及直径与储存容量（定义为每次心跳时的绝对面积变化）之间可能的相互作用及其与平均壁面剪应力的关系。
在111名年龄在10至60岁之间的假定健康男性（n = 56）和女性（n = 55）志愿者的右侧CCA中评估壁面剪应力（壁面剪切速率乘以全血粘度）。使用高分辨率超声系统测量壁面剪切速率。同时，测定动脉直径和储存容量。根据血细胞比容、血浆粘度和剪切速率计算全血粘度。
从第二个十年到第六个十年，男性的峰值壁面剪应力显著高于女性，男性从4.3 Pa降至2.6 Pa（r = -0.56，p < 0.001），女性从3.3 Pa降至2.5 Pa（r = -0.54，p < 0.001）。男性的平均壁面剪应力趋于从1.5 Pa降至1.2 Pa（r = -0.26，p = 0.057），女性则从1.3 Pa显著降至1.1 Pa（r = -0.30，p = 0.021）。在任何年龄十年中，男性和女性的平均壁面剪应力均未发现显著差异。男性（r = 0.26，p < 0.05）和女性（r = 0.40，p < 0.003）的CCA直径均显著增加。两性的储存容量均显著下降（男性：r = -0.63，p < 0.001；女性：r = -0.68，p < 0.001）。
这些观察结果表明，平均壁面剪应力随年龄的降低是由于动脉系统直径随之增加，以试图限制动脉系统储存容量随年龄增长而减少。
