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TECHNICAL PAPERS: Fluids/Heat/Transport

Effects of Diffusion Coefficients and Struts Apposition Using Numerical Simulations for Drug Eluting Coronary Stents

[+] Author and Article Information
Rosaire Mongrain1

Department of Mechanical Engineering, McGill University, Montreal, Quebec H3A 2K6, Canada; Montreal Heart Institute, Montreal, Quebec H1T 1C8, Canadarosaire.mongrain@mcgill.ca

Isam Faik

Department of Mechanical Engineering, McGill University, Montreal, Quebec, H3A 2K6, Canada

Richard L. Leask

Department of Chemical Engineering, McGill University, Montreal, Quebec, H3A 2K6, Canada; Montreal Heart Institute, Montreal, Quebec, H1T 1C8, Canada

Josep Rodés-Cabau, Éric Larose, Olivier F. Bertrand

 Quebec Heart-Lung Institute, Laval Hospital, Quebec, Quebac G1V 4G5, Canada

1

Corresponding author.

J Biomech Eng 129(5), 733-742 (Feb 22, 2007) (10 pages) doi:10.1115/1.2768381 History: Received December 10, 2006; Revised February 22, 2007

In the context of drug eluting stent, we present two-dimensional numerical models of mass transport of the drug in the wall and in the lumen to study the effect of the drug diffusion coefficients in the three principal media (blood, vascular wall, and polymer coating treated as a three-compartment problem) and the impact of different strut apposition configurations (fully embedded, half embedded, and not embedded). The different conditions were analyzed in terms of their consequence on the drug concentration distribution in the arterial wall. We apply the concept of the therapeutic window to the targeted vascular wall region and derive simple metrics to assess the efficiency of the various stent configurations. Although most of the drug is dispersed in the lumen, variations in the blood flow rate within the physiological range of coronary blood flow and the diffusivity of the drug molecule in the blood were shown to have a negligible effect on the amount of drug in the wall. Our results reveal that the amount of drug cumulated in the wall depends essentially on the relative values of the diffusion coefficients in the polymer coating and in the wall. Concerning the strut apposition, it is shown that the fully embedded strut configuration would provide a better concentration distribution.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Helix stent and (b) corresponding 3D geometry to 2D axisymmetric model with same pitch

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Figure 2

(a) Geometric 2D model and boundary conditions (dimensions in mm) and (b) strut embedment configurations

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Figure 3

Global mesh and zoomed mesh resulting from the map scheme between two struts

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Figure 4

Normalized concentration as a function of DL with Dw=Dp=10−13m2∕s

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Figure 5

Normalized mean concentration remaining in the polymer coating as a function of Dp with (a) Dw=10−12m2∕s, (b) Dw=10−13m2∕s, and (c) Dw=10−14m2∕s

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Figure 6

Concentration as a function of time with Dw=Dp=10−13m2∕s with (a) half-embedded strut configuration, (b) fully embedded strut configuration, and (c) not-embedded strut configuration

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Figure 7

Concentration contours for Dw=Dp=10−13m2∕s after eight days

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