Computational Haemodynamics—An Introduction - Computational Hemodynamics: Theory, Modelling and Applications - page 14

Fig. 1.12 Analysis of WSS on the arterial tissue in the stented arteries. Wall shear stress ( WSS )
analysis can be carried out based on various stent design parameters such as number, width, and
thickness of struts and stent-to-artery diameter ratio. (Image from LaDisa et al. 2004)
that are poorly matched to patient-specific vessels may pose vascular complications
and lead to restenosis after stenting (Gordon et al. 1994; Kuntz and Baim 1993;
Rogers and Edelman 1995). The in-stent restenosis rate is found to occur in as many
as 20-50 % of stented vessels. Fortunately, computational modelling can be used
to improve the stability of stent-vessel interaction to achieve a long term stenting
performance without restenosis from the engineering point of view.
Since stent geometry affects WSS distribution on the vessel wall, designing
an ideal stent structure that can minimize stent-induced low wall shear stress is
desired. Thinner struts and with more alignment to the blood flow direction mi-
nimises the occurrence of low WSS (LaDisa et al. 2004, 2005a). Moreover, CHD
can also be used to compare various commercial stent designs (Duraiswamy et al.
2009; Gundert et al. 2011; He et al. 2005; Murphy and Boyle 2010) as shown in
Figs. 1.12 , 1.13 , and 1.14 .
Sometimes, during stent implantation, fitting correctly to the geometry of the
vessel does not occur. The stent may be deployed and expanded uniformly with a
poor curvature fit along the wall of the curvilinear artery. In the case of asymmetric
distribution of the plaque along the arterial axis, the stent is forced to bend against
the artery wall, causing the sharp edge of the stent to cut through the artery wall.
Over time, this may lead to platelet activation and thrombosis, which can result in
restenosis of the artery. Fragments of the formed thrombus may travel downstream
of the carotid artery to block the blood flow in micro vessels, and thereby causing
stroke. Therefore, it is important to fully assess the need of stent implantation based
on medical expert opinion.