Date of Award

August 2013

Degree Type

Thesis

Degree Name

Master of Science

Department

Engineering

First Advisor

Changsoo Kim

Committee Members

Ben Church, Kurt Beschorner

Keywords

Coating, Deformation, Delamination, Des, Finite Element, Stent

Abstract

The development of coronary stent medical devices was originally considered as a major advance in the treatment of obstructive cardiovascular disease. The implantation of stent, however, involves clinical adverse effects such as re-narrowing of arterial wall after stenting. Drug-eluting stents (DES) have been developed to prevent such adverse effects by slowly delivering anti-proliferative and/or anti-inflammatory drugs from coating composites of drug-containing polymers. One of the major issues in DES implantation is, however, that the coatings comprised of drug and polymer composite phases are often fractured or delaminated during the deployment of stent, which can lead to more serious clinical complications. In this study, we developed a computational model employing the finite element analysis (FEA) technique to predict the stress distributions of various components in DES medical devices including coating composites. This work is considered as one of the first attempts to address the stress concentrations of DES medical devices upon implantation using 2D/3D computational approaches. The ABAQUS commercial package (Hibbit Karlsson & Sorences Inc., Pawtucket, RI, USA) was used to perform computational analyses for systems with large elastic/plastic deformations. Designs of three commercial products (SYNERGY, TAXUS Express, and FLEX stents) available in the market have been modeled in this thesis. The displacement control method has been adopted in developing our model for the deployment of DES. Throughout the present thesis, the impacts of geometry and material variables such as stent strut/coating thicknesses and material contents in composites on the mechanical performance of the DES were quantitatively examined. Moreover, to predict the rate of in-stent restenosis (ISR), we developed a model to include the physiological environments, i.e., arterial wall and atherosclerotic plaque, in the system. From the results, it has been monitored that the strut thickness and coating thickness of DES are one of the major factors determining the amount of stress concentration on the inner surfaces of arterial wall and atherosclerotic plaque. The higher von-Mises stress accumulation was observed with thicker strut and coating. The findings indicate that the optimizing geometry of stent and coating is a critical variable to manipulate its mechanical performance and the rate of ISR. The computation results also demonstrate that the stress concentrations in the SYNERGY and FLEX DES are much lower than those observed in the TAXUS Express stents.

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