Design Innovation Paper

A Deployable Transseptal Brace for Stabilizing Cardiac Catheters

[+] Author and Article Information
Leah P. Gaffney

Paulson School of Engineering and Applied Sciences,
Harvard University,
Cambridge, MA 02138
e-mail: leahgaffney@post.harvard.edu

Paul M. Loschak

Paulson School of Engineering and Applied Sciences,
Harvard University,
Cambridge, MA 02138
e-mail: loschak@seas.harvard.edu

Robert D. Howe

Paulson School of Engineering and Applied Sciences,
Harvard University,
Cambridge, MA 02138
e-mail: howe@seas.harvard.edu

1Corresponding author.

Contributed by the Design Innovation and Devices of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received October 28, 2017; final manuscript received February 24, 2018; published online May 11, 2018. Assoc. Editor: David Myszka.

J. Mech. Des 140(7), 075003 (May 11, 2018) (12 pages) Paper No: MD-17-1722; doi: 10.1115/1.4039495 History: Received October 28, 2017; Revised February 24, 2018

A bracing device for stabilizing cardiac catheters inside the heart was developed to provide surgical-level dexterity to minimally invasive catheter-based procedures for cardiac valve disease. The brace was designed to have a folding structure, which lies flat along a catheter during navigation through vasculature and then unfolds into a rigid bracing configuration after deployment across the interatrial septum. The brace was designed to be easily deployable, provide bracing support for a transseptal catheter, and also be compliant enough to be delivered to the heart via tortuous vasculature. This aims to improve dexterity in catheter-based mitral valve repair and enable other complex surgical procedures to be done with minimally invasive instruments.

Copyright © 2018 by ASME
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Fig. 1

The transseptal catheter applies force to the mitral valve annulus. RA = right atrium, LA = left atrium, IVC = inferior vena cava.

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Fig. 2

Computer assisted design model of rigid foldable brace

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Fig. 3

Brace deployment steps: (a) insert catheter sheath transeptally, (b) deploy distal brace and pull back to atrial septum, (c) deploy proximal brace and advance to atrial septum, and (d) insert catheter through inner lumen

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Fig. 4

Brace linkage geometry

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Fig. 5

Cross-sectional catheter brace geometry

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Fig. 6

Diagram of the bracing device during insertion through vasculature. Joints 1 and 3 (denoted by circles) must rotate about a single living hinge axis. Joint 2 (denoted by squares) must bend in multiple axes without failing.

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Fig. 7

Bending dimensions of a living hinge [20]

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Fig. 8

Joint 1 shown deploying and then braced

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Fig. 9

Joint 2 dual layer design

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Fig. 10

Joint 3 shown deploying and then braced

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Fig. 11

Layers are aligned and then compressed under heat

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Fig. 13

IVC analog for insertion testing

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Fig. 14

Braced catheter turning through the IVC analog

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Fig. 15

Deployment testing setup

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Fig. 16

Experimental deployment force

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Fig. 17

Friction between catheter tubes

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Fig. 18

Bracing testing setup

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Fig. 19

Example bracing data

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Fig. 20

Bracing results histogram from 40 loadings

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Fig. 21

Rotational orientation of the brace

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Fig. 22

Catheter tip stiffness derivation

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Fig. 23

Calculated range of catheter tip stiffness

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Fig. 24

Bracing test setup with rubber septum analog

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Fig. 25

Brace deflections for various septum analogs

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Fig. 26

Defining IVC geometry

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Fig. 28

Catheter brace turning through IVC and corresponding geometric model

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Fig. 30

Defining the bend angle between joints during insertion

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Fig. 31

Defining the largest possible brace. (a) Small size brace can easily curve through the IVC, (b) medium size brace can curve through the IVC with a small margin of error, and (c) large size brace cannot curve through the IVC.

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Fig. 35

Clinical decision matrix for choosing H and L values given patient parameters Datria = 30 mm and DIVC = 15 mm

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Fig. 34

Defining lengths L and H

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Fig. 33

Brace dimension options as a function of DIVC. Datria = 30 mm, R = 44.75 mm, and DIVC = 10–20 mm

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Fig. 32

Defining IVC geometry with respect to the long rigid brace segment




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