1. Numerical Modeling of Geometric and Material Properties of Tricuspid Valves Chen Shen, Manuel Rausch  University of Texas at Austin/Department of Aerospace and Engineering Mechanics, 210 East 24th Street, W. R. Woolrich Laboratories, Austin, Texas, ,United States
Abstract
In the present research, we created a finite element computer model of the tricuspid valve. We digitized the geometric properties of an excised human tricuspid valve and fit cubic splines to create a surface for a finite element model. Subsequently, we identified the annular nodes and fit them into a spline which represents the same annulus before excision from the heart. Finally we ‘closed’ the valve numerically and inserted chordae tendineae in our model. Our simulations will provide a virtual test-bed to test and optimize
current and novel surgical approaches to tricuspid regurgitation.
1. Introduction
Leakage or regurgitation of the right atrioventricular heart valve, the tricuspid valve, is a significant source of morbidity and mortality. The gold standard treatment for tricuspid regurgitation is tricuspid annuloplasty, a surgery in which
implantation of a “ring” around the circumference of the annulus cinches the valve and is believed to reduce leakage (Fig. 1). Unfortunately, this surgery fails in about 30% of patients after five years. Toward developing a better understanding why these surgeries fail and how to improve annuloplasty rings, it is our goal to develop computer models of the tricuspid valve that are based on actual human valve
geometries and material properties.
2. Geometric modeling of the open tricuspid valve
We received excised human tricuspid valves from our collaborators(Fig. 2). We isolated the valve’s three leaflets and digitized their geometry via an image-based, custom Matlab code. Subsequently, we exported point clouds representing the leaflet’s circumference to a geometric modeling tool, where we fit cubic splines to these points. Based on the spline representation of the geometric boundaries, we discretized the surface via quadrilateral finite elements (Fig. 3). Additionally, we identified the annular nodes of this mesh and mathematically transformed them to conform with a spline representation of the same annulus measured before excision from the heart.
3. Numeric modeling of the closed tricuspid valve and chordae tendineae insertion
Once imported into the finite element software, Abaqus, we ran a preliminary implicit non-linear simulation in which we closed the currently open geometry of the tricuspid valve via Abaqus’ “wire” function (Fig. 4). Additionally, we identified chordal insertion points along the free edge of the three leaflets. We adjusted the length of the chordae to provide an optimal coaptation surface in an iterative identification algorithm. The constitutive properties for leaflets and chordae will be informed through material tests on the same tissue. This should complete our modeling process and provides us with a testing bed to the intrigue properties of tricuspid valves.
Fig. 1 Typical commercial annuloplasty rings
Fig. 3 Finite element model of the open tricuspid valve
Fig. 4 Finite element model of the tricuspid valve with chordae tendineae
Fig. 2 Excised Human Tricuspid Valve
Proceedings of the 2018 ASEE Gulf-Southwest Section Annual Conference The University of Texas at Austin
April 4-6, 2018