A numerical assessment of wall shear stress changes after endovascular stenting.

This theoretical/numerical study aims at assessing the haemodynamic changes induced by endovascular stenting. By using the classical one-dimensional linear pressure waves theory in elastic vessels, we first show that the modulus of the reflection coefficient induced by an endovascular prosthesis is most likely small since it is proportional to the stent-to-wavelength ratio. As a direct consequence, the wall motion of the elastic (stented) artery can be prescribed a priori and the coupled fluid-structure problem does not have to be solved for assessing the haemodynamic changes due to stenting. Several 2D axisymetric calculations are performed to solve the unsteady incompressible Navier-Stokes equations on moving meshes for different types of (stented) arteries. The numerical results suggest that endovascular stenting increases the systo-diastolic variations of the wall shear stress (by 35% at the middle of the stent, by almost 50% in the proximal transition region). Additional calculations show that over-dilated stents produce less haemodynamic perturbations. Indeed, the increase of the amplitude of the wall shear stress variations over the cardiac cycle is only 10% when the stent radius is equal to the radius of the elastic artery at systole (instead of being equal to the mean artery radius).