Radial Artery Remodeling in Response to Shear Stress Increase Within Arteriovenous Fistula for Hemodialysis Access

It is known that changes in blood flow induce vascular remodeling and that shear stress, the tractive force acting on the vessel wall due to blood flowing, influences endothelial cell function. The aim of the present study was to investigate the relation between changes in pulsatile shear forces and arterial remodeling in response to chronic elevation in blood flow within the radial artery. The authors studied vessel diameter, flow rate, and shear stress in the radial artery of uremic patients before and after surgical creation of a native arteriovenous fistula for hemodialysis access. For this purpose, the authors used echo-color-Doppler ultrasound to perform diameter and blood velocity measurements. Time-function blood flow rate and wall shear stress were calculated based on arterial diameter, center-line velocity wave-form, and blood viscosity, using a numerical method developed according to Womersley's theory for unsteady flow in tubes. The results confirmed that the radial artery diameter increases in response to a chronic increase in blood flow in uremic patients. Moreover, it seems that the radial artery dilates in such a way as to maintain the peak wall shear stress constant, suggesting that endothelial cells sense the maximum rather than the time-averaged wall shear stress. This finding may lead to further understanding of the mechanisms responsible for endothelial response to physical stimulation by flowing blood.