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Fluid-Structure Interaction Analysis of Papillary Muscle Forces Using a comprehensive Mitral Valve model with 3D Chordal Structure

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ANNALS OF BIOMEDICAL ENGINEERING 2016年第4期44卷 942-953页

作者： Toma, Milan Jensen, Morten O. Einstein, Daniel R. Yoganathan, Ajit P. Cochran, Richard P. Kunzelman, Karyn S. Georgia Inst Technol Dept Biomed Engn Technol Enterprise PkSuite 200387 Technol Circl Atlanta GA 30313 USA Pacific NW Natl Lab Computat Biol & Bioinformat Richland WA 99352 USA Univ Maine Dept Mech Engn 219 Boardman Hall Orono ME 04469 USA

Numerical models of native heart valves are being used to study valve biomechanics to aid design and development of repair procedures and replacement devices. These models have evolved from simple two-dimensional approximations to complex three-dimensional, fully coupled fluid-structure interaction (FSI) systems. Such simulations are useful for predicting the mechanical and hemodynamic loading on implanted valve devices. A current challenge for improving the accuracy of these predictions is choosing and implementing modeling boundary conditions. In order to address this challenge, we are utilizing an advanced in vitro system to validate FSI conditions for the mitral valve system. Explanted ovine mitral valves were mounted in an in vitro setup, and structural data for the mitral valve was acquired with CT. Experimental data from the in vitro ovine mitral valve system were used to validate the computational model. As the valve closes, the hemodynamic data, high speed leaflet dynamics, and force vectors from the in vitro system were compared to the results of the FSI simulation computational model. The total force of 2.6 N per papillary muscle is matched by the computational model. In vitro and in vivo force measurements enable validating and adjusting material parameters to improve the accuracy of computational models. The simulations can then be used to answer questions that are otherwise not possible to investigate experimentally. This work is important to maximize the validity of computational models of not just the mitral valve, but any biomechanical aspect using computational simulation in designing medical devices.

关键词： Fluid-structure interaction Mitral valve Forces comprehensive computational model Papillary muscle Chordal structure

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High-resolution subject-specific mitral valve imaging and modeling: experimental and computational methods

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BIOMECHANICS AND modelING IN MECHANOBIOLOGY 2016年第6期15卷 1619-1630页

作者： Toma, Milan Bloodworth, Charles H. Einstein, Daniel R. Pierce, Eric L. Cochran, Richard P. Yoganathan, Ajit P. Kunzelman, Karyn S. Georgia Inst Technol Wallace H Coulter Dept Biomed Engn Technol Enterprise PkSuite 200387 Technol Circl Atlanta GA 30313 USA Pacific Northwest Natl Lab Computat Biol & Bioinformat Richland WA 99352 USA Univ Maine Dept Mech Engn 219 Boardman Hall Orono ME 04469 USA

The diversity of mitral valve (MV) geometries and multitude of surgical options for correction of MV diseases necessitates the use of computational modeling. Numerical simulations of the MV would allow surgeons and engineers to evaluate repairs, devices, procedures, and concepts before performing them and before moving on to more costly testing modalities. Constructing, tuning, and validating these models rely upon extensive in vitro characterization of valve structure, function, and response to change due to diseases. Micro-computed tomography (mu CT) allows for unmatched spatial resolution for soft tissue imaging. However, it is still technically challenging to obtain an accurate geometry of the diastolic MV. We discuss here the development of a novel technique for treating MV specimens with glutaraldehyde fixative in order to minimize geometric distortions in preparation for mu CT scanning. The technique provides a resulting MV geometry which is significantly more detailed in chordal structure, accurate in leaflet shape, and closer to its physiological diastolic geometry. In this paper, computational fluid-structure interaction (FSI) simulations are used to show the importance of more detailed subject-specific MV geometry with 3D chordal structure to simulate a proper closure validated against mu CT images of the closed valve. Two computational models, before and after use of the aforementioned technique, are used to simulate closure of the MV.

关键词： Fluid-structure interaction Mitral valve comprehensive computational model Smooth particle hydrodynamics Chordal structure Chordae tendineae Fixation Glutaraldehyde

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Fluid-structure interaction and structural analyses using a comprehensive mitral valve model with 3D chordal structure

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017年第4期33卷 n/a-N.PAG页

作者： Toma, Milan Einstein, Daniel R. Bloodworth, Charles H. Cochran, Richard P. Yoganathan, Ajit P. Kunzelman, Karyn S. Georgia Inst Technol Wallace H Coulter Dept Biomed Engn Technol Enterprise PkSuite 200387 Technol Atlanta GA 30313 USA Emory Univ Technol Enterprise PkSuite 200387 Technol Atlanta GA 30313 USA St Martins Univ Dept Mech Engn 5000 Abbey Way SE Lacey WA 98503 USA Univ Maine Dept Mech Engn 219 Boardman Hall Orono ME 04469 USA

Over the years, three-dimensional models of the mitral valve have generally been organized around a simplified anatomy. Leaflets have been typically modeled as membranes, tethered to discrete chordae typically modeled as one-dimensional, non-linear cables. Yet, recent, high-resolution medical images have revealed that there is no clear boundary between the chordae and the leaflets. In fact, the mitral valve has been revealed to be more of a webbed structure whose architecture is continuous with the chordae and their extensions into the leaflets. Such detailed images can serve as the basis of anatomically accurate, subject-specific models, wherein the entire valve is modeled with solid elements that more faithfully represent the chordae, the leaflets, and the transition between the two. These models have the potential to enhance our understanding of mitral valve mechanics and to re-examine the role of the mitral valve chordae, which heretofore have been considered to be invisible' to the fluid and to be of secondary importance to the leaflets. However, these new models also require a rethinking of modeling assumptions. In this study, we examine the conventional practice of loading the leaflets only and not the chordae in order to study the structural response of the mitral valve apparatus. Specifically, we demonstrate that fully resolved 3D models of the mitral valve require a fluid-structure interaction analysis to correctly load the valve even in the case of quasi-static mechanics. While a fluid-structure interaction mode is still more computationally expensive than a structural-only model, we also show that advances in GPU computing have made such models tractable. Copyright (c) 2016 John Wiley & Sons, Ltd.

关键词： fluid-structure interaction mitral valve forces comprehensive computational model papillary muscle chordal structure chordae tendineae

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