For more than 40 years, replacement of diseased natural heart valves with prosthetic devices has dramatically extended the quality and length of the lives of millions of patients worldwide. However, as in many medical therapies today, replacement valves are never as good as natural, healthy valves. Bioprosthetic heart valves (BHV) continue to fail due to structural failure, a result of both poor tissue durability and faulty design. Clearly, an in-depth understanding of the biomechanical behavior of the BHV at both the tissue- and functional prosthesis levels is essential to improving BHV design and the mechanisms of failure.
The goal of this research effort was to develop and evaluate a complete process for biomechanical simulations of heart valve biomaterials, with an emphasis on numerical stability and experimental validation. This process started from the collection of appropriate experimental data, formulating and validating a constitutive model, obtaining and refining material parameters, finite element implementation and validation of a constitutive model, and finally finite element simulation of valve deformation.
The results of this study indicated that explicit expression of shear behavior was required for proper computational implementation of the exponential Fung pseudo-elastic model and thus, biaxial testing with extension only did not provide sufficient information to constitute a strain energy function for computational implementation. This study also demonstrated that a set of model constraints imposed by the convexity of strain energy function and condition number of elasticity tensor were necessary for numerical stability. When applied to an intact valve, the finite element model demonstrated an overall discrepancy of only 0.0187 strain when compared to experimental validation data, which was within the experimental error. This result underscored the need for rigorous experimentation and constitutive modeling to allow a close match between FE and experiment output. The present study is, to our knowledge, the most rigorously developed and validated model available to date for characterizing valve deformation. It is hoped that the developed approaches will be a valuable tool for evaluating various valve design parameters and will greatly facilitate optimal BHV design.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-11262003-150806 |
| Date | 02 February 2004 |
| Creators | Sun, Wei |
| Contributors | James F. Antaki, Ph.D., Michael J. Scott, Ph.D., David A. Vorp, Ph.D., William S. Slaughter, Ph.D., Michael S. Sacks, Ph.D. |
| 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-11262003-150806/ |
| 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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