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.

Radial artery wall shear stress evaluation in patients with arteriovenous fistula for hemodialysis access.

It has been extensively documented that changes in blood flow induce vascular remodeling and this phenomenon seems to be correlated to the shear forces imposed on the vessel wall by motion of blood. Wall shear stress, the tractive force that acts on the endothelium, has been shown to influence endothelial cell function. To study changes in wall shear stress that develop on the vessel wall upon changes of blood flow, we set up a technique that allows estimation of shear stress in the radial artery of patients on chronic hemodialysis therapy. The technique is based on color-flow Doppler examination of the radial artery before and after surgical creation of radiocephalic fistula for hemodialysis. Calculation of time function wall shear stress and blood flow rate in the radial artery is performed on the basis of arterial diameter, center-line velocity waveform and blood viscosity, using a numerical method developed according to Womersley's theory for pulsatile flow in tubes. The results presented confirm that the model developed is suitable for calculation of the wall shear stress that develops in the radial artery of patients before and after surgical creation of an arteriovenous fistula for hemodialysis. This methodology was developed for characterization of wall shear stress in the radial artery but may be well applied to other vessels that can be examined by echo-Doppler technique.