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TRANSLATIONAL PHYSIOLOGY

Effects of stent sizing on endothelial and vessel wall stress: potential mechanisms for in-stent restenosis

¹Weldon School of Biomedical Engineering, Purdue University, West Lafayette; ²Department of Cardiovascular Surgery, St. Vincent Hospital, Indianapolis; and Departments of ³Medicine (Cardiology), ⁴Mathematical Sciences, ⁵Surgery, ⁶Cellular and Integrative Physiology, and ⁷Biomedical Engineering, Indiana University Purdue University Indianapolis, Indianapolis, Indiana

Submitted 21 November 2008 ; accepted in final form 13 March 2009

ABSTRACT

Stent sizing and apposition have been shown to be important determinants of clinical outcome. This study evaluates the mechanical effects of undersizing and oversizing of stents on endothelial wall shear stress (WSS) and vessel wall stress to determine a possible biomechanical mechanism of in-stent restenosis and thrombosis. Three-dimensional computational models of stents, artery, and internal fluid were created in a computer-assisted design package, meshed, and solved in finite element and computational fluid dynamic packages. The simulation results show that the effects of various degrees of undersizing on WSS, WSS gradient, and oscillatory shear index were highly nonlinear. As the degree of undersizing increased, the heterogeneity of WSS became smaller. The WSS distribution for the 20% undersizing was smooth and uniform, whereas the 5% case was very heterogeneous. The combination of lower WSS and higher WSS gradient and oscillatory shear index in the 5% undersized case may induce neointimal hyperplasia or thrombosis. Additionally, the oversizing simulation results show that the maximum intramural wall stress of the 20% oversizing case is significantly larger than the maximum stress for the 10% and zero oversizing cases. Edge stress concentration was observed, consistent with the restenosis typically observed in this region. This study demonstrates that proper sizing of stent is important for reducing the hemodynamic and mechanical disturbances to the vessel wall. Furthermore, the present findings may be used to improve stent design to reduce endothelial flow disturbances and intramural wall stress concentrations.

undersizing; oversizing; intimial hyperplasia; shear stress