[Non invasive evaluation of endothelial shearing phenomena in human arteries. Application to essential hypertension].

Pulsatile wall shear conditions close to the brachial artery were evaluated in 11 normotensive and in 19 hypertensive patients of similar age by determining arterial diameter and centerline blood velocity with a pulsed Doppler and blood viscosity at 96 sec-1 with a coaxial cylinder viscometer. A Womersley model of intraluminal distribution of blood velocities enabled to determine from unsteadiness parameter alpha of Womersley, arterial diameter and maximal minimal and pulse (maximal-minimal) values of centerline velocity, the maximal minimal and pulse shear rate and shear stress (product between shear rate and viscosity) close to the endothelium. Compared to normotensives hypertenvises had higher arterial diameter (p less than 0.001), lower maximal minimal and pulse centerline velocities (p less than 0.001, p less than 0.01, p less than 0.001) higher blood viscosity (p less than 0.001), lower maximal, minimal and pulse wall shear rate (p less than 0.001, p less than 0.05, p less than 0.001) and lower maximal minimal and pulse shear stress (p less than 0.01). In the overall normotensive and hypertensive group, mean blood pressure negatively correlated to maximal minimal and pulse shear rates (r = -0.65; r = -0.45, r = -0.63) and to maximal, minimal and pulse shear stress (r = -0.46; r = -0.37, r = -0.48). Thus, hypertension is associated with a reduction of oscillating shear conditions in the viscosity of the brachial artery wall which might in long term influence structural and/or functional response to the endothelium.