Structural analysis of the natural aortic valve in dynamics: From unpressurized to physiologically loaded |
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| Authors: | Michel R Labrosse Keegan Lobo Carsten J Beller |
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| Institution: | 1. University of Ottawa, Department of Mechanical Engineering, Ottawa, Ontario, Canada K1N 6N5;2. Department of Cardiac Surgery, University Hospital Heidelberg, Heidelberg, Germany;1. Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414, United States;2. Department of Civil, Environmental and Geo-Engineering, University of Minnesota, Minneapolis, MN 55414, United States;1. University of Chicago Medical Center, Chicago, Illinois;2. Department of Electronics, Computer Science and Systems, University of Bologna, Bologna, Italy;3. Yale University, New Haven, Connecticut;1. University of Pavia, Department of Industrial Eng. and Informatics, Via Ferrata 3, 27100, Pavia, Italy;2. University of Pavia, Department of Civil Eng. and Architecture, Via Ferrata 3, 27100, Pavia, Italy;3. Department of Structural Engineering, University of California, 9500 Gilman Drive, La Jolla, CA 92093, USA;4. Cardiology Unit, S. Pio X Hospital, Opera S. Camillo Foundation, via Nava 31, 20159 Milano, Italy;5. Dynamore GmbH, Industriestr. 2, D-70565 Stuttgart, Germany;6. The Institute of Computational Engineering and Sciences (ICES), University of Texas at Austin, 201 East 24th Street, 1 University Station C0200, Austin, TX 78712, USA;1. Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414, United States;2. Department of Civil, Environment and Geo-Engineering, University of Minnesota, Minneapolis, MN 55414, United States;3. College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, NY 11794-2200, United States |
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| Abstract: | A novel finite element model of the natural aortic valve was developed implementing anisotropic hyperelastic material properties for the leaflets and aortic tissues, and starting from the unpressurized geometry. Static pressurization of the aortic root, silicone rubber moulds and published data helped to establish the model parameters, while high-speed video recording of the leaflet motion in a left-heart simulator allowed for comparisons with simulations. The model was discretized with brick elements and loaded with time-varying pressure using an explicit commercial solver. The aortic valve model produced a competent valve whose dynamic behavior (geometric orifice area vs. time) closely matched that observed in the experiment. In both cases, the aortic valve took approximately 30 ms to open to an 800 mm2 orifice and remained completely or more than half open for almost 200 ms, after which it closed within 30–50 ms. The highest values of stress were along the leaflet attachment line and near the commissure during diastole. Von Mises stress in the leaflet belly reached 600–750 kPa from early to mid-diastole. While the model using the unpressurized geometry as initial configuration was specially designed to satisfy the requirements of continuum mechanics for large deformations of hyperelastic materials, it also clearly demonstrated that dry models can be adequate to analyze valve dynamics. Although improvements are still needed, the advanced modeling and validation techniques used herein contribute toward improved and quantified accuracy over earlier simplified models. |
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