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Technical Brief

The Localized Hemodynamics of Drug-Eluting Stents Are Not Improved by the Presence of Magnetic Struts

[+] Author and Article Information
P. R. S. Vijayaratnam

School of Mechanical and Manufacturing Engineering,
University of New South Wales,
Sydney 2052, Australia
e-mail: p.vijayaratnam@unsw.edu.au

T. J. Barber

School of Mechanical and Manufacturing Engineering,
University of New South Wales,
Sydney 2052, Australia
e-mail: t.barber@unsw.edu.au

J. A. Reizes

School of Mechanical and Manufacturing Engineering,
University of New South Wales,
Sydney 2052, Australia
e-mail: j.reizes@unsw.edu.au

Manuscript received April 17, 2016; final manuscript received November 4, 2016; published online November 30, 2016. Assoc. Editor: Ram Devireddy.

J Biomech Eng 139(1), 014502 (Nov 30, 2016) (6 pages) Paper No: BIO-16-1150; doi: 10.1115/1.4035263 History: Received April 17, 2016; Revised November 04, 2016

The feasibility of implementing magnetic struts into drug-eluting stents (DESs) to mitigate the adverse hemodynamics which precipitate stent thrombosis is examined. These adverse hemodynamics include platelet-activating high wall shear stresses (WSS) and endothelial dysfunction-inducing low wall shear stresses. By magnetizing the stent struts, two forces are induced on the surrounding blood: (1) magnetization forces which reorient red blood cells to align with the magnetic field and (2) Lorentz forces which oppose the motion of the conducting fluid. The aim of this study was to investigate whether these forces can be used to locally alter blood flow in a manner that alleviates the thrombogenicity of stented vessels. Two-dimensional steady-state computational fluid dynamics (CFD) simulations were used to numerically model blood flow over a single magnetic drug-eluting stent strut with a square cross section. The effects of magnet orientation and magnetic flux density on the hemodynamics of the stented vessel were elucidated in vessels transporting oxygenated and deoxygenated blood. The simulations are compared in terms of the size of separated flow regions. The results indicate that unrealistically strong magnets would be required to achieve even modest hemodynamic improvements and that the magnetic strut concept is ill-suited to mitigate stent thrombosis.

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Figures

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Fig. 1

The prothrombotic effects of nonphysiological wall shear stresses

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Fig. 2

Geometry and boundary conditions. A single 0.1-mm square cross section DES strut was positioned halfway between the inlet and outlet with one side of the strut in direct contact with the vessel wall.

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Fig. 3

Magnetic flux density contours of the magnetic DES strut used in this study. The magnet has been modeled as an infinitely long permanent rectangular magnet with height 2h = 70 μm and width 2w = 70 μm. The cases in which Bmax = 1 T are depicted for the configurations in which the poles are (a) on the top and bottom strut faces and (b) on the fore and aft strut faces. Note that the positions of the north and south poles are interchangeable in each case and do not affect the results.

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Fig. 4

The magnetically altered hemodynamics of oxygenated blood in a vessel with a well-apposed DES strut: (a) top–bottom and (b) fore–aft

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Fig. 5

The magnetically altered hemodynamics of deoxygenated blood in a vessel with a well-apposed DES strut: (a) top–bottom and (b) fore–aft

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