The behavior of mitral valve tissue is very complex because of its material composition, geometric layout and loading environment. Due to recent advances in the constitutive modeling of mitral valve material, particularly in the area of incorporating the collagen fibers with the continuum tissue matrix, we are able to now simulate the behavior of the mitral valve under various loading and surgical conditions. Further, advance in FEM computational formulation also enables us to accurately simulate the nature of the incompressible material as representative of the mitral valve tissue which was a difficult proposition only a few years ago.
In this thesis, we first implemented a constitutive relation specifically developed for mitral valve tissue into a commercial finite element software LSDYNA. The geometry of the mitral valve and its chordae were modeled via previously published anatomical measurements and our observations during animal experiments. We first simulated the motion of a porcine mitral valve under normal conditions that enabled us to make inferences about the state of stress of the mitral valve, i.e. we indentified sites of high stress and consequently locations of high failure possibility. Having modeled a healthy mitral valve we then modeled a prolapsed leaflet by removing chordae attached to the anterior leaflet of the valve. Further we proceeded to simulate a novel surgical procedure used to repair prolapse. The effects of surgical repair in term of the stresses the valve were quantified in comparison to its natural state.In our constitutive equations we included the material fiber direction, i.e. the direction of the collagen fibers in the mitral valve tissue. In accordance with stress modulated growth laws, we assumed that the fiber direction will tend to align with the maximum principal direction of stress as the tissue remodels under the influence of new external forces after surgical alteration. This study shows the change in principal stress directions due to surgical alteration, and therefore is an indicator of remodeling to follow. Thus, the ability, as demonstrated by this study, to predict these alteration may be one way to devise a strategy for minimizing fiber reorientation and thereby prolong the effects of surgical intervention or even avoid future re-intervention.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-10212008-073253 |
| Date | 28 January 2009 |
| Creators | Urankar, Sandeep Abhay |
| Contributors | JEEN-SHANG LIN, MICHAEL LOVELL, TINKAN HUNG |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-10212008-073253/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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