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RESEARCH PAPERS

Structural and Drug Diffusion Models of Conventional and Auxetic Drug-Eluting Stents

[+] Author and Article Information
William Jacob Dolla

 University of Missouri—Kansas City, Mechanical Engineering, 5100 Rockhill Road, Kansas City, MO 64110-2499wjdolla@umkc.edu

Brian A. Fricke

 University of Missouri—Kansas City, Mechanical Engineering, 5100 Rockhill Road, Kansas City, MO 64110-2499frickeb@umkc.edu

Bryan R. Becker

 University of Missouri—Kansas City, Mechanical Engineering, 5100 Rockhill Road, Kansas City, MO 64110-2499beckerb@umkc.edu

J. Med. Devices 1(1), 47-55 (Aug 09, 2006) (9 pages) doi:10.1115/1.2355691 History: Received April 07, 2006; Revised August 09, 2006

Most balloon angioplasty procedures include the insertion of tiny cylindrical wire mesh structures, called cardiovascular stents, into the artery to prevent the elastic recoil that follows arterial dilatation. The scaffolding characteristics of the stent provide strength to the artery wall. However, vascular injury during stent deployment and∕or recognition of the stent as a foreign material triggers neointimal hyperplasia, causing re-closure, or restenosis, of the artery. A recent advancement to counteract restenosis is to employ drug-eluting stents to locally deliver immunosuppressant and antiproliferative drugs. In this project, Fick’s law of diffusion was used to model drug diffusion from the stent matrix into the adjacent arterial tissue. An analytical procedure was also developed to estimate the circumferential and the flexural stiffnesses of stents. Furthermore, a unique auxetic (negative Poisson’s ratio) stent structure was proposed that exhibits high circumferential strength in its expanded configuration and low flexural rigidity in its crimped configuration. Results generated with the analytical diffusion model, developed in this project, compare favorably with previously published clinical and experimental data. The circumferential and flexural stiffnesses estimated using the analytical procedure developed in this project compare favorably with the results from rigorous finite element analyses and previously published experimental data.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 3

Percentage of the drug remaining in the microporous polymer matrix drug reservoir of the stent, (1−Q)×100%, versus time, for reservoir thicknesses: θ=0.02ro to θ=0.08ro

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Figure 1

Drug-eluting stent diffusion model

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Figure 2

Percentage of the drug remaining in the microporous polymer matrix drug reservoir of the stent, (1−Q)×100%, versus time

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Figure 9

Schematic of a sinusoidal ligament auxetic structure and its unit cell

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Figure 10

Schematic of a sinusoidal ligament auxetic stent

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Figure 11

Interluminal pressure versus radial deformation

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Figure 4

Percentage of the drug remaining in the microporous polymer matrix drug reservoir of the stent, (1−Q)×100%, at t=28days versus outer radius of the microporous polymer matrix drug reservoir, ro, for reservoir thicknesses: θ=0.02ro to θ=0.08ro

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Figure 5

Schematic diagram of a diamond cell stent flat pattern and its unit cell

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Figure 6

Schematic diagram of a diamond cell stent

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Figure 7

Schematic of a helically wound structure depicting the helical winding angle, β

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Figure 8

Apparent circumferential stiffness, Eθ, and flexural stiffness, Ez, of the diamond cell stent with winding angle, β, and unit-cell arm angle, α (w=0.1ro, ri=0.94ro)

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