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Technical Briefs

A Study on the Effects of Covered Stents on Tissue Prolapse

[+] Author and Article Information
Jason D. Weaver

Wallace H. Coulter Department of Biomedical Engineering,  Georgia Institute of Technology and Emory University, 315 Ferst Dr., Room 2119, Atlanta, GA 30332jason.weaver@gatech.edu

D. N. Ku1

George W. Woodruff School of Mechanical Engineering,  Georgia Institute of Technology, 315 Ferst Dr., Room 2307, Atlanta, GA 30332david.ku@me.gatech.edu

1

Corresponding author.

J Biomech Eng 134(2), 024505 (Mar 19, 2012) (6 pages) doi:10.1115/1.4006199 History: Received October 31, 2011; Revised February 14, 2012; Posted February 24, 2012; Published March 14, 2012; Online March 19, 2012

Polyvinyl alcohol (PVA) cryogel covered stents may reduce complications from thrombosis and restenosis by decreasing tissue prolapse. Finite element analysis was employed to evaluate the effects of PVA cryogel layers of varying thickness on tissue prolapse and artery wall stress for two common stent geometries and two vessel diameters. Additionally, several PVA cryogel covered stents were fabricated and imaged with an environmental scanning electron microscope. Finite element results showed that covered stents reduced tissue prolapse up to 13% and artery wall stress up to 29% with the size of the reduction depending on the stent geometry, vessel diameter, and PVA cryogel layer thickness. Environmental scanning electron microscope images of expanded covered stents showed the PVA cryogel to completely cover the area between struts without gaps or tears. Overall, this work provides both computational and experimental evidence for the use of PVA cryogels in covered stents.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Model geometry of stent repeating unit with arterial tissue (light gray) and PVA cryogel layer (dark gray). Due to symmetry, only a quarter model (upper-right portion) of the diamond-shape (a) is shown and only a half model (upper portion) of the w-shape (b) is shown. For both models, the arterial tissue thickness is 0.5 mm and the PVA cryogel layer thickness is 100 μm. The mesh has been made denser at areas of high stress. The black line marks the path along which the midline perimeter stress was taken for mesh convergence. The “L” illustrates the location of the luminal side.

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Figure 2

Displacement shown with undeformed edge line (a) and midline von Mises stress (b) for diamond-shape. The 3.5 mm diameter vessel is shown with no PVA cryogel layer (top) and with a 200 μm thick PVA cryogel layer (bottom). Displacement is shown in millimeters and stress is shown in kilopascals.

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Figure 3

Displacement shown with undeformed edge line (a) and midline von Mises stress (b) for w-shape. The 3.5 mm diameter vessel is shown with no PVA cryogel layer (top) and with a 200 μm thick PVA cryogel layer (bottom). Displacement is shown in millimeters and stress is shown in kilopascals.

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Figure 4

ESEM images of expanded PVA cryogel covered stents. The top left quadrant shows the smooth luminal side of a PVA cryogel covered stent. The top right quadrant shows complete coverage of a stent strut with the PVA cryogel material. The bottom quadrants show two points along the edge of the covered stent where it was cut in order to fit inside the ESEM chamber.

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