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

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.

Wingspan Stents for the Treatment of Symptomatic Atherosclerotic Stenosis in Small Intracranial Vessels: Safety and Efficacy Evaluation

“…Conversely, oversizing significantly increased intramural stress, which can cause acute vessel dissection and can chronically stimulate smooth muscle proliferation and initiate an inflammatory response. 28 Thus, both undersizing and oversizing can lead to ISR. In the course of treatment detailed in our study, the Wingspan stent was slightly oversized, measuring 0.5 to 1.0 mm larger than the diameter of the reference artery.…”

Incomplete Stent Apposition Causes High Shear Flow Disturbances and Delay in Neointimal Coverage as a Function of Strut to Wall Detachment Distance

“…Several investigators have described previously how protruding or detached struts can alter normal coronary flow and affect drug distribution and recirculation, 35,42,43 and the larger the strut, the more severe its impact on flow, 35 but the intrinsic dependence of shear rate on the detachment distance and its effect on coverage has not been shown previously hitherto. This information is relevant to understand the problem of acute ISA properly, that is, ISA that appears as a consequence of suboptimal stent implantation during the coronary intervention, therefore at the moment when optimization is still possible.…”

Sequential Structural and Fluid Dynamics Analysis of Balloon-Expandable Coronary Stents: A Multivariable Statistical Analysis

“…These computational methods of analysis employ sophisticated numerical techniques, such as the finite element and finite volume methods, to obtain approximate numerical solutions to complex physical problems. To date, a large number of studies have carried out computational structural (CS) analyses 1,4,5,14,15,19,[25][26][27][28][29]37,44,53,54,57,59,[62][63][64]72,73,78,80,85,87,[90][91][92] and computational fluid dynamics (CFD) analyses 3,8,9,12,30,31,33,42,[47][48][49][50][51]65,66,69,[74][75][76]83,89 ...…”