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Research Papers

Shape Optimization of a Self-deployable Anchor Designed for Percutaneous Mitral Valve Repair

[+] Author and Article Information
Farhad Javid1

Centre for Intelligent Machines (CIM) andDepartment of Mechanical Engineering,  McGill University, Montreal, Quebec, H3A 0C3farhad@cim.mcgill.ca

Jorge Angeles

Centre for Intelligent Machines (CIM) andDepartment of Mechanical Engineering,  McGill University, Montreal, Quebec, H3A 0C3angeles@cim.mcgill.ca

Damiano Pasini

Department of Mechanical Engineering,  McGill University, Montreal, Quebec, H3A 0C3damiano.pasini@mcgill.ca

Renzo Cecere

Biosurgery and Design Unit,Department of Surgery,  McGill University Health Centre, Montreal, Quebec, H3A 1A1renzo.cecere@muhc.mcgill.ca

This is a geometric concept, not to be confused with the neutral axis of beams.

Because of symmetry, only one half of the anchor, part A to B of Fig. 2, is considered.

To model the anchor in ANSYS, its mid-curve Γ is rotated −90° around the x axis. The XZ plane is, therefore, the plane of Γ in Figs. 6, 8, and 9.

The critical point is that with maximum von Mises stress and strain.

1

Address all correspondence to this author.

J. Med. Devices 6(1), 011003 (Mar 13, 2012) (7 pages) doi:10.1115/1.4005780 History: Received February 18, 2011; Revised November 08, 2011; Published March 12, 2012; Online March 13, 2012

A new percutaneous annuloplasty technique for mitral regurgitation is proposed here. In this technique, inter-related anchors are first inserted around the annulus via a trans-septal catheter. The tethered wire passed through the anchors is then pulled to shrink the annulus and stop regurgitation. The anchors should withstand large deformation, applied during the delivery process, and should recover their original shape after being released inside the tissue. The shape of the anchors is, thus, optimized in an iterative process, to avoid stress concentration by minimizing the weighted rms value of the curvature along the anchor. The weight coefficients in each iteration are defined based on the stress distribution of the anchor obtained in the previous iteration. The procedure finally results in a structurally optimum anchor with a minimum in the maximum von Mises stress. This anchor is fabricated from Nitinol and tested in a cadaveric swine heart.

FIGURES IN THIS ARTICLE
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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

The percutaneous technique suggested by our research team: (a) schematic illustration; and (b) its implementation on a cadaveric veal heart

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Figure 2

Schematic shape of the designed anchor: (a) outside the needle; (b) and (c) inside the needle

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Figure 3

Super-elastic stress-strain behavior of Nitinol

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Figure 4

(a) Schematic G2 -continuous curve segment, and (b) boundary and dimension constraints

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Figure 5

Maximum von Mises stress of the simple shape anchor versus the number of elements

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Figure 6

Applied displacements to the finite element model: (a) in-plane displacement, and (b) out-of-plane displacement

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Figure 7

Evolution of maximum von Mises (a) stress, and (b) strain versus number of iterations

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Figure 8

(a) von Mises stress, and (b) strain distributions of the geometrically optimum anchor

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Figure 9

(a) von Mises stress, and (b) strain distributions of the structurally optimum anchor

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Figure 10

Geometric and structural optimum mid-curves in comparison with simple shape anchor

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Figure 11

The anchor (a) fabricated with Nitinol wire to experimentally verify the concept, (b) as inserted into the catheterlike tube, and (c) as released into the mitral annulus

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