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MICROMECHANICAL MODELING OF HEART VALVE MATERIALS
by
Murat Surucu
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(BIOMEDICAL ENGINEERING)
May 2007
Copyright 2007 Murat Surucu
Object Description
| Title | Micromechanical modeling of heart valves |
| Author | Surucu, Murat |
| Author email | surucu@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Biomedical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2007-03-08 |
| Date submitted | 2007 |
| Restricted until | Unrestricted |
| Date published | 2007-04-24 |
| Advisor (committee chair) |
Khoo, Michael C.K. Kalia, Rajiv |
| Advisor (committee member) | Vesely, Ivan |
| Abstract | Load bearing soft tissues, such as mitral valve chordae, tendon, pericardium and heart valves, have stiff fibers embedded in a soft matrix. Mechanical interactions between these material constituents are poorly understood. To analyze the effect of the microstructure on the mechanical behavior of specific tissues, we used a high-fidelity micromechanics model for the viscoelastic response of periodic materials characterized by a repeating unit cell with an arbitrary microstructure.; The objective of this study is to model the micromechanical behavior of heart valve materials by using their microstructure. We modeled the microstructural differences in mitral valve chordae tendinae by using their differences in collagen crimp period and fibril distribution. Our results demonstrated that the crimp period is more important than the fibril distribution for duplicating the stress/strain behavior of mitral valve chordae. We also looked at the effect of microstructure on the viscoelastic properties of the chordae. The microstructural differences, such as collagen crimp period and fibril distribution, were not sufficient to explain the difference in the stress relaxation behavior of the different chordal types.; We used crossectional TEM images of tissue-engineered chordae and native chordae to analyze the effects of its microstructural differences on its mechanical behavior. Our model successfully retrieved the stress/strain behavior of tissue-engineered chordae. We used the material parameters that are optimized for the native chordae and microstructure representation for the tissue-engineered chordae. The resultant stress/strain behavior matched the mechanical behavior of tissue-engineered chordae quite well.; One of the purposes of this project is to study the elastin degradation and loss as a failure mechanism in porcine aortic bioprosthetic heart valves to better understand the microstructural interaction of the constituents of soft tissues. We calculated elastin degradation and loss by measuring the amount of desmosine and isodesmosine -- which are cross-linking amino acids specific to elastin. Our results suggested a significant loss of elastin with implant duration at a rate of 3.20 %/year which is higher than the rate of degradation of the total protein content (0.74 %/year). There was no significant effect of implantation position and gender on the rate of elastin degradation. |
| Keyword | micromechanical modeling; heart valve; soft tissue modeling; elastin; mitral valve chordae; micromechanics; desmosine; collagen; crimp |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Type | texts |
| Legacy record ID | usctheses-m456 |
| Rights | Surucu, Murat |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Surucu-20070424 |
| Archival file | uscthesesreloadpub_Volume26/etd-Surucu-20070424.pdf |
Description
| Title | Page 1 |
| Full text | MICROMECHANICAL MODELING OF HEART VALVE MATERIALS by Murat Surucu A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (BIOMEDICAL ENGINEERING) May 2007 Copyright 2007 Murat Surucu |
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