Hemodynamic changes induced by stenting in elastic arteries

Angioplasty, with or without endovascular stenting, is a promising, minimally-invasive technique that can be used as treatment of occlusive disease in medium to large arteries. It has been applied extensively in the coronary, renal, and peripheral vascular systems. The use of intravascular stents tends to lower the complication rate. Although re-stenosis rates as high as 15-30 % after six months for human coronary arteries have been observed; see e.g. Rau et al. (1998). One possible explanation for this observation relies on the hemodynamic modifications induced by the prosthesis. Changes in wall shear stress are believed to induce endothelial dysfunction, ultimately leading to intimal hyperplasia and re-stenosis. Davies et al. (2001) suggest that magnitude of the shear stress is of secondary importance to the spatial and temporal fluctuations of this quantity. In vivo testing performed by Vernhet et al. (2001), Vernhet et al. (2000), Rolland, Charifi & Verrier (1999) show that endovascular stenting induces a large modification of the arterial compliance and thus may drastically modify the propagation of arterial waves by introducing artificial reflexions. The first objective of this study is therefore to assess the amount of pressure-wave reflexion related to the endovascular stenting of an elastic artery. For this purpose, the stented section of the vessel is modeled as an elastic duct, whose compliance is less than the non-stented artery. We intent to clarify the extent of reflexion that can be expected, depending on the characteristics of both the stent and the host vessel. Another expected effect of the compliance mismatch induced by stenting is to modify the details of the blood motion in the stented area. Specifically, the wall shear stress (averaged over the cardiac cycle) might be changed, as well as the level of its systodiastolic variations. For high enough Reynolds numbers, one also expects recirculation zones to appear with larger residence times. The second objective of this paper is thus to clarify the changes in the blood motion that can be expected in relation to endovascular stenting. Note that this study deals with the global effect of the compliance mismatch, neglecting the details of the prosthesis structure (struts). Consistently, the prosthesis is modeled as a uniform (elastic) tube with its own compliance.