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Fringand T, Mace L, Cheylan I, Lenoir M, Favier J. Analysis of Fluid-Structure Interaction Mechanisms for a Native Aortic Valve, Patient-Specific Ozaki Procedure, and a Bioprosthetic Valve. Ann Biomed Eng 2024:10.1007/s10439-024-03566-1. [PMID: 39225853 DOI: 10.1007/s10439-024-03566-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 06/08/2024] [Indexed: 09/04/2024]
Abstract
The Ozaki procedure is a surgical technique which avoids to implant foreign aortic valve prostheses in human heart, using the patient's own pericardium. Although this approach has well-identified benefits, it is still a topic of debate in the cardiac surgical community, which prevents its larger use to treat valve pathologies. This is linked to the actual lack of knowledge regarding the dynamics of tissue deformations and surrounding blood flow for this autograft pericardial valve. So far, there is no numerical study examining the coupling between the blood flow characteristics and the Ozaki leaflets dynamics. To fill this gap, we propose here a comprehensive comparison of various performance criteria between a healthy native valve, its pericardium-based counterpart, and a bioprosthetic solution, this is done using a three-dimensional fluid-structure interaction solver. Our findings reveal similar physiological dynamics between the valves but with the emergence of fluttering for the Ozaki leaflets and higher velocity and wall shear stress for the bioprosthetic heart valve.
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Affiliation(s)
- Tom Fringand
- Aix Marseille Univ, CNRS, Centrale Med, M2P2, Marseille, France.
| | - Loic Mace
- Aix Marseille Univ, CNRS, Centrale Med, M2P2, Marseille, France
- Department of Cardiac Surgery, La Timone Hospital, APHM, Aix Marseille Univ, Marseille, France
| | | | - Marien Lenoir
- Aix Marseille Univ, CNRS, Centrale Med, M2P2, Marseille, France
- Department of Cardiac Surgery, La Timone Hospital, APHM, Aix Marseille Univ, Marseille, France
| | - Julien Favier
- Aix Marseille Univ, CNRS, Centrale Med, M2P2, Marseille, France
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2
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Wang X, Carpenter HJ, Ghayesh MH, Kotousov A, Zander AC, Amabili M, Psaltis PJ. A review on the biomechanical behaviour of the aorta. J Mech Behav Biomed Mater 2023; 144:105922. [PMID: 37320894 DOI: 10.1016/j.jmbbm.2023.105922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 05/14/2023] [Accepted: 05/20/2023] [Indexed: 06/17/2023]
Abstract
Large aortic aneurysm and acute and chronic aortic dissection are pathologies of the aorta requiring surgery. Recent advances in medical intervention have improved patient outcomes; however, a clear understanding of the mechanisms leading to aortic failure and, hence, a better understanding of failure risk, is still missing. Biomechanical analysis of the aorta could provide insights into the development and progression of aortic abnormalities, giving clinicians a powerful tool in risk stratification. The complexity of the aortic system presents significant challenges for a biomechanical study and requires various approaches to analyse the aorta. To address this, here we present a holistic review of the biomechanical studies of the aorta by categorising articles into four broad approaches, namely theoretical, in vivo, experimental and combined investigations. Experimental studies that focus on identifying mechanical properties of the aortic tissue are also included. By reviewing the literature and discussing drawbacks, limitations and future challenges in each area, we hope to present a more complete picture of the state-of-the-art of aortic biomechanics to stimulate research on critical topics. Combining experimental modalities and computational approaches could lead to more comprehensive results in risk prediction for the aortic system.
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Affiliation(s)
- Xiaochen Wang
- School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia.
| | - Harry J Carpenter
- School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Mergen H Ghayesh
- School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia.
| | - Andrei Kotousov
- School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Anthony C Zander
- School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Marco Amabili
- Department of Mechanical Engineering, McGill University, Montreal H3A 0C3, Canada
| | - Peter J Psaltis
- Adelaide Medical School, The University of Adelaide, Adelaide, South Australia 5005, Australia; Department of Cardiology, Central Adelaide Local Health Network, Adelaide, South Australia 5000, Australia; Vascular Research Centre, Heart Health Theme, South Australian Health & Medical Research Institute (SAHMRI), Adelaide, South Australia 5000, Australia
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3
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Li M, Zheng C, Wu B, Ding K, Zhang S, Huang X, Lei Y, Wang Y. Glycidyl methacrylate-crosslinked fish swim bladder as a novel cardiovascular biomaterial with improved antithrombotic and anticalcification properties. J Biomater Appl 2021; 36:1188-1200. [PMID: 34719293 DOI: 10.1177/08853282211054205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
At present, commercial artificial biological valves are mostly prepared by crosslinking bovine or porcine pericardia with glutaraldehyde. Swim bladder has similar components and lower immunogenicity compared to bovine or porcine pericardium. In this study, we used a glycidyl methacrylate (GMA)-based radical polymerization method to crosslink decellularized swim bladders. Amino and carboxyl groups in the swim bladder were reacted with epoxy groups on GMA to introduce carbon-carbon double bonds to the swim bladder. The results showed that the platelet adhesion of GMA-crosslinked swim bladders (GMA-SBs) decreased by 35%, as compared to that of glutaraldehyde-crosslinked swim bladders (GLUT-SBs). Moreover, the superior anticoagulant property was further verified by the ex vivo arteriovenous shunt assay. Meanwhile, the subcutaneous implantation in rats showed that GMA-SBs were able to effectively inhibit the calcification compared with GLUT-SBs. In conclusion, GMA-SBs showed improved antithrombotic and anticalcification properties compared to GLUT-SBs.
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Affiliation(s)
| | | | | | | | | | | | - Yang Lei
- 12530Sichuan University, Chengdu, China
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4
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Porcine and bovine aortic valve comparison for surgical optimization: A fluid-structure interaction modeling study. Int J Cardiol 2021; 334:88-95. [PMID: 33932427 DOI: 10.1016/j.ijcard.2021.04.051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 03/28/2021] [Accepted: 04/26/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND Porcine aortic valve (PAV) and bovine aortic valve (BAV) are commonly used in aortic valve replacement (AVR) surgeries. A detailed comparison for their hemodynamic and structural stress/strain performances would help to better understand valve cardiac function and select valve type and size for AVR outcome optimizations. METHODS Eight fluid-structure interaction models were constructed to compare hemodynamic and stress/strain behaviors of PAV and BAV with 4 sizes (19, 21, 23, and 25 mm). Blood flow velocity, systolic cross-valve pressure gradient (SCVPG), geometric orifice area (GOA), flow shear stresses (FSS), and stress/strain were obtained for comparison. RESULTS Compared with PAV, BAV has better hemodynamic performance, with lower maximum flow velocity (7.17%) and pressure (9.82%), smaller pressure gradient (mean and peak SCVPG: 8.92% and 9.28%), larger GOA (9.56%) and lower FSS (6.61%). The averages of the mean and peak net pressure gradient values from 4 BAV models were 8.10% and 8.35% lower than that from PAV models. Larger valve sizes for both PAV and BAV had improved hemodynamic performance. Maximum flow velocity, pressure, mean SCVPG and maximum FSS from 25 mm BAV were 36.80%, 15.81%, 39.05% and 38.83% lower than those from 19 mm BAV. The GOA of PAV and BAV 25 mm Valve were 43.75% and 33.07% larger than 19 mm valves, respectively. BAV has lower stress on the leaflets than PAV. CONCLUSIONS BAV had better hemodynamic performance and lower leaflets stress than PAV. More patient studies are needed to validate our findings.
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Xu F, Johnson EL, Wang C, Jafari A, Yang CH, Sacks MS, Krishnamurthy A, Hsu MC. Computational investigation of left ventricular hemodynamics following bioprosthetic aortic and mitral valve replacement. MECHANICS RESEARCH COMMUNICATIONS 2021; 112:103604. [PMID: 34305195 PMCID: PMC8301225 DOI: 10.1016/j.mechrescom.2020.103604] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The left ventricle of the heart is a fundamental structure in the human cardiac system that pumps oxygenated blood into the systemic circulation. Several valvular conditions can cause the aortic and mitral valves associated with the left ventricle to become severely diseased and require replacement. However, the clinical outcomes of such operations, specifically the postoperative ventricular hemodynamics of replacing both valves, are not well understood. This work uses computational fluid-structure interaction (FSI) to develop an improved understanding of this effect by modeling a left ventricle with the aortic and mitral valves replaced with bioprostheses. We use a hybrid Arbitrary Lagrangian-Eulerian/immersogeometric framework to accommodate the analysis of cardiac hemodynamics and heart valve structural mechanics in a moving fluid domain. The motion of the endocardium is obtained from a cardiac biomechanics simulation and provided as an input to the proposed numerical framework. The results from the simulations in this work indicate that the replacement of the native mitral valve with a tri-radially symmetric bioprosthesis dramatically changes the ventricular hemodynamics. Most significantly, the vortical motion in the left ventricle is found to reverse direction after mitral valve replacement. This study demonstrates that the proposed computational FSI framework is capable of simulating complex multiphysics problems and can provide an in-depth understanding of the cardiac mechanics.
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Affiliation(s)
- Fei Xu
- Ansys Inc., Austin, TX 78746, USA
| | - Emily L. Johnson
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA
| | | | - Arian Jafari
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA
| | - Cheng-Hau Yang
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA
| | - Michael S. Sacks
- Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX 78712, USA
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
| | - Adarsh Krishnamurthy
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA
| | - Ming-Chen Hsu
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA
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Subramaniam DR, Gutmark E, Andersen N, Nielsen D, Mortensen K, Gravholt C, Backeljauw P, Gutmark-Little I. Influence of Material Model and Aortic Root Motion in Finite Element Analysis of Two Exemplary Cases of Proximal Aortic Dissection. J Biomech Eng 2021; 143:014504. [PMID: 32793953 DOI: 10.1115/1.4048084] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Indexed: 01/25/2023]
Abstract
The risk of type-A dissection is increased in subjects with connective tissue disorders and dilatation of the proximal aorta. The location and extents of vessel wall tears in these patients could be potentially missed during prospective imaging studies. The objective of this study is to estimate the distribution of systolic wall stress in two exemplary cases of proximal dissection using finite element analysis (FEA) and evaluate the sensitivity of the distribution to the choice of anisotropic material model and root motion. FEA was performed for predissection aortas, without prior knowledge of the origin and extents of vessel wall tear. The stress distribution was evaluated along the wall tear in the postdissection aortas. The stress distribution was compared for the Fung and Holzapfel models with and without root motion. For the subject with spiral dissection, peak stress coincided with the origin of the tear in the sinotubular junction. For the case with root dissection, maximum stress was obtained at the distal end of the tear. The FEA predicted tear pressure was 20% higher for the subject with root dissection as compared to the case with spiral dissection. The predicted tear pressure was higher (9-11%) for root motions up to 10 mm. The Holzapfel model predicted a tear pressure that was lower (8-15%) than the Fung model. The FEA results showed that both material response and root motion could potentially influence the predicted dissection pressure of the proximal aorta at least for conditions tested in this study.
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Affiliation(s)
| | - Ephraim Gutmark
- Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati, Cincinnati, OH 45221-0070
| | - Niels Andersen
- Department of Cardiology, Aalborg University Hospital, Aalborg 9100, Denmark
| | - Dorte Nielsen
- Department of Cardiology, Aarhus University Hospital, Aarhus 8200, Denmark
| | - Kristian Mortensen
- Cardiorespiratory Unit, Great Ormond Street Hospital for Children, London WC1N 3JH, UK
| | - Claus Gravholt
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus 8200, Denmark
| | - Philippe Backeljauw
- Division of Endocrinology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
| | - Iris Gutmark-Little
- Division of Endocrinology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
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Liu M, Liang L, Sun W. A generic physics-informed neural network-based constitutive model for soft biological tissues. COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2020; 372:113402. [PMID: 34012180 PMCID: PMC8130895 DOI: 10.1016/j.cma.2020.113402] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Constitutive modeling is a cornerstone for stress analysis of mechanical behaviors of biological soft tissues. Recently, it has been shown that machine learning (ML) techniques, trained by supervised learning, are powerful in building a direct linkage between input and output, which can be the strain and stress relation in constitutive modeling. In this study, we developed a novel generic physics-informed neural network material (NNMat) model which employs a hierarchical learning strategy by following the steps: (1) establishing constitutive laws to describe general characteristic behaviors of a class of materials; (2) determining constitutive parameters for an individual subject. A novel neural network structure was proposed which has two sets of parameters: (1) a class parameter set for characterizing the general elastic properties; and (2) a subject parameter set (three parameters) for describing individual material response. The trained NNMat model may be directly adopted for a different subject without re-training the class parameters, and only the subject parameters are considered as constitutive parameters. Skip connections are utilized in the neural network to facilitate hierarchical learning. A convexity constraint was imposed to the NNMat model to ensure that the constitutive model is physically relevant. The NNMat model was trained, cross-validated and tested using biaxial testing data of 63 ascending thoracic aortic aneurysm tissue samples, which was compared to expert-constructed models (Holzapfel-Gasser-Ogden, Gasser-Ogden-Holzapfel, and four-fiber families) using the same fitting and testing procedure. Our results demonstrated that the NNMat model has a significantly better performance in both fitting (R2 value of 0.9632 vs 0.9019, p=0.0053) and testing (R2 value of 0.9471 vs 0.8556, p=0.0203) than the Holzapfel-Gasser-Ogden model. The proposed NNMat model provides a convenient and general methodology for constitutive modeling.
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Affiliation(s)
- Minliang Liu
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States of America
| | - Liang Liang
- Department of Computer Science, University of Miami, Coral Gables, FL, United States of America
| | - Wei Sun
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States of America
- Correspondence to: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Technology Enterprise Park, Room 206 387 Technology Circle, Atlanta GA 30313-2412, United States of America. (W. Sun)
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8
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He Q, Laurence DW, Lee CH, Chen JS. Manifold learning based data-driven modeling for soft biological tissues. J Biomech 2020; 117:110124. [PMID: 33515902 DOI: 10.1016/j.jbiomech.2020.110124] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 07/16/2020] [Accepted: 11/03/2020] [Indexed: 02/08/2023]
Abstract
Data-driven modeling directly utilizes experimental data with machine learning techniques to predict a material's response without the necessity of using phenomenological constitutive models. Although data-driven modeling presents a promising new approach, it has yet to be extended to the modeling of large-deformation biological tissues. Herein, we extend our recent local convexity data-driven (LCDD) framework (He and Chen, 2020) to model the mechanical response of a porcine heart mitral valve posterior leaflet. The predictability of the LCDD framework by using various combinations of biaxial and pure shear training protocols are investigated, and its effectiveness is compared with a full structural, phenomenological model modified from Zhang et al. (2016) and a continuum phenomenological Fung-type model (Tong and Fung, 1976). We show that the predictivity of the proposed LCDD nonlinear solver is generally less sensitive to the type of loading protocols (biaxial and pure shear) used in the data set, while more sensitive to the insufficient coverage of the experimental data when compared to the predictivity of the two selected phenomenological models. While no pre-defined functional form in the material model is necessary in LCDD, this study reinstates the importance of having sufficiently rich data coverage in the date-driven and machine learning type of approaches. It is also shown that the proposed LCDD method is an enhancement over the earlier distance-minimization data-driven (DMDD) against noisy data. This study demonstrates that when sufficient data is available, data-driven computing can be an alternative method for modeling complex biological materials.
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Affiliation(s)
- Qizhi He
- Department of Structural Engineering, University of California, San Diego, La Jolla, CA 92093, USA; Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99354, USA
| | - Devin W Laurence
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA
| | - Chung-Hao Lee
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA; Institute for Biomedical Engineering, Science and Technology, The University of Oklahoma, Norman, OK 73019, USA
| | - Jiun-Shyan Chen
- Department of Structural Engineering, University of California, San Diego, La Jolla, CA 92093, USA.
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Liang L, Sun B. A Proof of Concept Study of Using Machine-Learning in Artificial Aortic Valve Design: From Leaflet Design to Stress Analysis. Bioengineering (Basel) 2019; 6:bioengineering6040104. [PMID: 31717333 PMCID: PMC6955850 DOI: 10.3390/bioengineering6040104] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 10/31/2019] [Accepted: 11/04/2019] [Indexed: 12/02/2022] Open
Abstract
Artificial heart valves, used to replace diseased human heart valves, are life-saving medical devices. Currently, at the device development stage, new artificial valves are primarily assessed through time-consuming and expensive benchtop tests or animal implantation studies. Computational stress analysis using the finite element (FE) method presents an attractive alternative to physical testing. However, FE computational analysis requires a complex process of numeric modeling and simulation, as well as in-depth engineering expertise. In this proof of concept study, our objective was to develop machine learning (ML) techniques that can estimate the stress and deformation of a transcatheter aortic valve (TAV) from a given set of TAV leaflet design parameters. Two deep neural networks were developed and compared: the autoencoder-based ML-models and the direct ML-models. The ML-models were evaluated through Monte Carlo cross validation. From the results, both proposed deep neural networks could accurately estimate the deformed geometry of the TAV leaflets and the associated stress distributions within a second, with the direct ML-models (ML-model-d) having slightly larger errors. In conclusion, although this is a proof-of-concept study, the proposed ML approaches have demonstrated great potential to serve as a fast and reliable tool for future TAV design.
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Affiliation(s)
- Liang Liang
- Department of Computer Science, University of Miami, Coral Gables, FL 33146, USA
- Correspondence:
| | - Bill Sun
- Walton High School, Marietta, GA 30062, USA;
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10
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Morales-Bonilla S, Martines-Arano H, Torres-Torres D, Ochoa-Ortega G, Carrillo-Delgado C, Trejo-Valdez M, Torres-Torres C. Dynamic and plasmonic response exhibited by Au nanoparticles suspended in blood plasma and cerebrospinal fluids. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.02.073] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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11
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Ross C, Laurence D, Wu Y, Lee CH. Biaxial Mechanical Characterizations of Atrioventricular Heart Valves. J Vis Exp 2019. [PMID: 31033941 PMCID: PMC8008701 DOI: 10.3791/59170] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Extensive biaxial mechanical testing of the atrioventricular heart valve leaflets can be utilized to derive optimal parameters used in constitutive models, which provide a mathematical representation of the mechanical function of those structures. This presented biaxial mechanical testing protocol involves (i) tissue acquisition, (ii) the preparation of tissue specimens, (iii) biaxial mechanical testing, and (iv) postprocessing of the acquired data. First, tissue acquisition requires obtaining porcine or ovine hearts from a local Food and Drug Administration-approved abattoir for later dissection to retrieve the valve leaflets. Second, tissue preparation requires using tissue specimen cutters on the leaflet tissue to extract a clear zone for testing. Third, biaxial mechanical testing of the leaflet specimen requires the use of a commercial biaxial mechanical tester, which consists of force-controlled, displacement-controlled, and stress-relaxation testing protocols to characterize the leaflet tissue's mechanical properties. Finally, post-processing requires the use of data image correlation techniques and force and displacement readings to summarize the tissue's mechanical behaviors in response to external loading. In general, results from biaxial testing demonstrate that the leaflet tissues yield a nonlinear, anisotropic mechanical response. The presented biaxial testing procedure is advantageous to other methods since the method presented here allows for a more comprehensive characterization of the valve leaflet tissue under one unified testing scheme, as opposed to separate testing protocols on different tissue specimens. The proposed testing method has its limitations in that shear stress is potentially present in the tissue sample. However, any potential shear is presumed negligible.
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Affiliation(s)
- Colton Ross
- Biomechanics and Biomaterials Design Laboratory (BBDL), School of Aerospace and Mechanical Engineering, The University of Oklahoma
| | - Devin Laurence
- Biomechanics and Biomaterials Design Laboratory (BBDL), School of Aerospace and Mechanical Engineering, The University of Oklahoma
| | - Yi Wu
- Biomechanics and Biomaterials Design Laboratory (BBDL), School of Aerospace and Mechanical Engineering, The University of Oklahoma
| | - Chung-Hao Lee
- Biomechanics and Biomaterials Design Laboratory (BBDL), School of Aerospace and Mechanical Engineering, The University of Oklahoma; Institute for Biomedical Engineering, Science and Technology (IBEST), The University of Oklahoma;
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12
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Noble C, Choe J, Uthamaraj S, Deherrera M, Lerman A, Young M. In Silico Performance of a Recellularized Tissue Engineered Transcatheter Aortic Valve. J Biomech Eng 2019; 141:61004-6100412. [PMID: 30874717 DOI: 10.1115/1.4043209] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Indexed: 01/04/2023]
Abstract
Commercially available heart valves have many limitations, such as a lack of re-modeling, risk of calcification and thromboembolic problems. Many state-of-the-art tissue engineered heart valves rely on recellularization. Current in vitro testing is insufficient in characterizing a soon to be living valve. It is imperative to understand the performance of an in situ valve, but due to the complex in vivo environment this is difficult to accomplish. Finite element analysis has become a standard tool for modeling mechanical behavior of heart valves; yet, research to date has mostly focused on commercial valves. The purpose of this study has been to develop finite element models of a decellularized and recellularized tissue engineered heart valve. Mechanical properties from porcine aortic valves were utilized to develop finite element models, which were run through a full physiological cardiac cycle. Maximum principal stresses and strains from the leaflets and commissures were analyzed. The results of this study demonstrate that the explanted tissues had reduced mechanical strength compared to the implants but were similar to the native tissues. For the finite element models the explanted recellularized leaflets showed lower stress but increased compliance in the leaflet belly compared to native tissues and higher compliance than implant tissues. Histology demonstrated recellularization and remodeling although remodeled collagen had no clear directionality. In conclusion, we observed successful recellularization and remodeling of the tissue, however, the mechanical response indicates the further remodeling is required following implantation in the aortic/pulmonary position.
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Affiliation(s)
- Christopher Noble
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Joshua Choe
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | | | - Milton Deherrera
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Amir Lerman
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Melissa Young
- Department of Cardiovascular Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN, USA 55905, phone: +1 (507)-266-5120
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13
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Jin L, Guo G, Jin W, Lei Y, Wang Y. Cross-Linking Methacrylated Porcine Pericardium by Radical Polymerization Confers Enhanced Extracellular Matrix Stability, Reduced Calcification, and Mitigated Immune Response to Bioprosthetic Heart Valves. ACS Biomater Sci Eng 2019; 5:1822-1832. [DOI: 10.1021/acsbiomaterials.9b00091] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Linhe Jin
- National Engineering Research Center for Biomaterials, Sichuan University, No. 24 South Section 1 Yihuan Road, Chengdu 610064, P. R. China
| | - Gaoyang Guo
- National Engineering Research Center for Biomaterials, Sichuan University, No. 24 South Section 1 Yihuan Road, Chengdu 610064, P. R. China
| | - Wanyu Jin
- National Engineering Research Center for Biomaterials, Sichuan University, No. 24 South Section 1 Yihuan Road, Chengdu 610064, P. R. China
| | - Yang Lei
- National Engineering Research Center for Biomaterials, Sichuan University, No. 24 South Section 1 Yihuan Road, Chengdu 610064, P. R. China
| | - Yunbing Wang
- National Engineering Research Center for Biomaterials, Sichuan University, No. 24 South Section 1 Yihuan Road, Chengdu 610064, P. R. China
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14
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Comparative mechanical, morphological, and microstructural characterization of porcine mitral and tricuspid leaflets and chordae tendineae. Acta Biomater 2019; 85:241-252. [PMID: 30579963 DOI: 10.1016/j.actbio.2018.12.029] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 11/30/2018] [Accepted: 12/19/2018] [Indexed: 11/23/2022]
Abstract
BACKGROUND Healthy function of tricuspid valve (TV) structures is essential to avoid tricuspid regurgitation (TR) and may significantly improve disease prognosis. Mitral valve (MV) structures have been extensively studied, but little is known about the TV and right-sided heart diseases. Therefore, clinical decisions and finite element (FE) simulations often rely heavily on MV data for TV applications, despite fundamentally different mechanical and physiological environments. METHOD/RESULTS To bridge this gap, we performed a rigorous mechanical, morphological, and microstructural characterization of the MV and TV leaflets and chordae in a porcine model. Planar biaxial testing, uniaxial testing, second harmonic generation imaging and Verhoeff Van Gieson staining were performed. Morphological parameters, tissue moduli, extensibility, and anisotropy were quantified and compared. No major differences in leaflet mechanics or structure were found between TV and MV; chordal mechanics, morphology, and structure were found to compensate for anatomical and physiological loading differences between the valves. No differences in chordal mechanics were observed by insertion point within a leaflet; the septal tricuspid leaflet (STL) and posterior mitral leaflet (PML) did not have distinguishable strut chords, and the STL had the shortest chords. Within a valve, chords from septally-located leaflets were more extensible. MV chords were stiffer. CONCLUSIONS This study presents the first rigorous comparative mechanical and structural dataset of MV and TV structures. Valve type and anatomical location may be stronger predictors of chordal mechanics. Chords from septally-located leaflets differ from each other and from their intravalvular counterparts; they merit special consideration in surgical and computational applications. STATEMENT OF SIGNIFICANCE A better understanding of the tricuspid valve (TV) and its associated structures is important for making advancements towards the repair of tricuspid regurgitation. Mitral valve structures have been extensively studied, but little is known about the TV and right-sided heart diseases. Clinical decisions and computational simulations often rely heavily on MV data for TV applications, despite fundamentally different environments. We therefore performed a rigorous mechanical, morphological, and microstructural characterization of atrioventricular leaflets and chordae tendineae in a porcine model. Finding that valve type and anatomical location may be strong predictors of chordal mechanics, chords from septally-located leaflets differ from each other and from their intravalvular counterparts; they merit special consideration in surgical and computational applications.
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15
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A material modeling approach for the effective response of planar soft tissues for efficient computational simulations. J Mech Behav Biomed Mater 2019; 89:168-198. [DOI: 10.1016/j.jmbbm.2018.09.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 08/22/2018] [Accepted: 09/14/2018] [Indexed: 11/23/2022]
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16
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Shaheen R, Doumit M. Modelling a soft composite accumulator for human mobility assist devices. J Mech Behav Biomed Mater 2018; 80:81-87. [PMID: 29414479 DOI: 10.1016/j.jmbbm.2018.01.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 01/25/2018] [Accepted: 01/28/2018] [Indexed: 11/16/2022]
Abstract
Research in the field of human mobility assist devices, aiming to reduce the metabolic cost of daily activities, is seeing the benefits of the exclusive use of accumulators to store and release energy during the gait cycle. The Pneumatic Artificial Muscle, used in a passive state, has proven to be a superior choice for these devices when compared to its alternatives, however, challenges regarding muscle pressure dissipation and a limited elongation potential have been identified. A recently developed, novel Soft Composite material has been shown to experimentally replicate the distinctive mechanical behaviour of the Pneumatic Artificial Muscle, without the need for internal pressurization. This paper presents two separate constitutive models to provide a closer insight into the behaviour of these Soft Composite accumulators. Both models were derived from methods involving finite elasticity theory and employed either a structural strain energy function of Holzapfel, Gasser, and Ogden's type or a phenomenological strain energy function of Fung's type. Both models were in good agreement with the experimental data that were collected through a modified extension-inflation test and, therefore, provide a basis for further examination as a Soft Composite design model.
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Affiliation(s)
- Robert Shaheen
- Department of Mechanical Engineering, University of Ottawa, Ottawa, Ontario, Canada.
| | - Marc Doumit
- Department of Mechanical Engineering, University of Ottawa, Ottawa, Ontario, Canada.
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17
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Caballero A, Sulejmani F, Martin C, Pham T, Sun W. Evaluation of transcatheter heart valve biomaterials: Biomechanical characterization of bovine and porcine pericardium. J Mech Behav Biomed Mater 2017; 75:486-494. [PMID: 28826102 PMCID: PMC5614867 DOI: 10.1016/j.jmbbm.2017.08.013] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/03/2017] [Accepted: 08/08/2017] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Bovine pericardium (BP) has been identified as a choice biomaterial for the development of surgical bioprosthetic heart valves (BHV) and transcatheter aortic valves (TAV). Porcine pericardium (PP) and younger BP have been suggested as candidates TAV leaflet biomaterials for smaller-profile devices due to their reduced thickness; however, their mechanical and structural properties remain to be fully characterized. This study characterized the material properties of chemically treated thick (PPK) and thin (PPN) PP, as well as fetal (FBP), calf (CBP) and adult (ABP) BP tissues in order to better understand their mechanical behavior. METHODS Planar biaxial testing and uniaxial failure testing methods were employed to quantify tissue mechanical responses and failure properties. Fiber characteristics were examined using histological analysis. RESULTS ABP and CBP tissues were significantly stiffer and stronger than the younger FBP tissues. Histological analysis revealed a significantly larger concentration of thin immature collagen fibers in the FBP tissues than in the ABP and CBP tissues. While PP tissues were thinnest, they were stiffer and less extensible than the BP tissues. CONCLUSIONS Due to comparable mechanical properties but significantly reduced thickness, CBP tissue may be a more suitable material for TAV manufacturing than ABP tissue. FBP tissue, despite its reduced thickness and higher flexibility, was weaker and should be studied in more detail. Although PP tissues are the thinnest, they were least extensible and failed at earlier strain than BP tissues. The differences between PP and BP tissues should be further investigated and suggest that they should not be used interchangeably in the manufacturing of TAV.
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Affiliation(s)
- Andrés Caballero
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Fatiesa Sulejmani
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Caitlin Martin
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Thuy Pham
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Wei Sun
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States.
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18
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Zakerzadeh R, Hsu MC, Sacks MS. Computational methods for the aortic heart valve and its replacements. Expert Rev Med Devices 2017; 14:849-866. [PMID: 28980492 PMCID: PMC6542368 DOI: 10.1080/17434440.2017.1389274] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 10/04/2017] [Indexed: 01/19/2023]
Abstract
INTRODUCTION Replacement with a prosthetic device remains a major treatment option for the patients suffering from heart valve disease, with prevalence growing resulting from an ageing population. While the most popular replacement heart valve continues to be the bioprosthetic heart valve (BHV), its durability remains limited. There is thus a continued need to develop a general understanding of the underlying mechanisms limiting BHV durability to facilitate development of a more durable prosthesis. In this regard, computational models can play a pivotal role as they can evaluate our understanding of the underlying mechanisms and be used to optimize designs that may not always be intuitive. Areas covered: This review covers recent progress in computational models for the simulation of BHV, with a focus on aortic valve (AV) replacement. Recent contributions in valve geometry, leaflet material models, novel methods for numerical simulation, and applications to BHV optimization are discussed. This information should serve not only to infer reliable and dependable BHV function, but also to establish guidelines and insight for the design of future prosthetic valves by analyzing the influence of design, hemodynamics and tissue mechanics. Expert commentary: The paradigm of predictive modeling of heart valve prosthesis are becoming a reality which can simultaneously improve clinical outcomes and reduce costs. It can also lead to patient-specific valve design.
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Affiliation(s)
- Rana Zakerzadeh
- Center for Cardiovascular Simulation Institute for Computational Engineering & Sciences Department of Biomedical Engineering The University of Texas at Austin, Austin, TX
| | - Ming-Chen Hsu
- Department of Mechanical Engineering Iowa State University, Ames, IA
| | - Michael S. Sacks
- Center for Cardiovascular Simulation Institute for Computational Engineering & Sciences Department of Biomedical Engineering The University of Texas at Austin, Austin, TX
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Soares JS, Feaver KR, Zhang W, Kamensky D, Aggarwal A, Sacks MS. Biomechanical Behavior of Bioprosthetic Heart Valve Heterograft Tissues: Characterization, Simulation, and Performance. Cardiovasc Eng Technol 2016; 7:309-351. [PMID: 27507280 DOI: 10.1007/s13239-016-0276-8] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 07/13/2016] [Indexed: 12/11/2022]
Abstract
The use of replacement heart valves continues to grow due to the increased prevalence of valvular heart disease resulting from an ageing population. Since bioprosthetic heart valves (BHVs) continue to be the preferred replacement valve, there continues to be a strong need to develop better and more reliable BHVs through and improved the general understanding of BHV failure mechanisms. The major technological hurdle for the lifespan of the BHV implant continues to be the durability of the constituent leaflet biomaterials, which if improved can lead to substantial clinical impact. In order to develop improved solutions for BHV biomaterials, it is critical to have a better understanding of the inherent biomechanical behaviors of the leaflet biomaterials, including chemical treatment technologies, the impact of repetitive mechanical loading, and the inherent failure modes. This review seeks to provide a comprehensive overview of these issues, with a focus on developing insight on the mechanisms of BHV function and failure. Additionally, this review provides a detailed summary of the computational biomechanical simulations that have been used to inform and develop a higher level of understanding of BHV tissues and their failure modes. Collectively, this information should serve as a tool not only to infer reliable and dependable prosthesis function, but also to instigate and facilitate the design of future bioprosthetic valves and clinically impact cardiology.
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Affiliation(s)
- Joao S Soares
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA
| | - Kristen R Feaver
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA
| | - Will Zhang
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA
| | - David Kamensky
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA
| | - Ankush Aggarwal
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA
- College of Engineering, Swansea University, Bay Campus, Fabian Way, Swansea, SA1 8EN, UK
| | - Michael S Sacks
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA.
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Multiphysics simulation of the effect of leaflet thickness inhomogeneity and material anisotropy on the stress-strain distribution on the aortic valve. J Biomech 2016; 49:2502-12. [PMID: 26961798 DOI: 10.1016/j.jbiomech.2016.02.041] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Accepted: 02/21/2016] [Indexed: 11/23/2022]
Abstract
This study developed a realistic 3D FSI computational model of the aortic valve using the fixed-grid method, which was eventually employed to investigate the effect of the leaflet thickness inhomogeneity and leaflet mechanical nonlinearity and anisotropy on the simulation results. The leaflet anisotropy and thickness inhomogeneity were found to significantly affect the valve stress-strain distribution. However, their effect on valve dynamics and fluid flow through the valve were minor. Comparison of the simulation results against in-vivo and in-vitro data indicated good agreement between the computational models and experimental data. The study highlighted the importance of simulating multi-physics phenomena (such as fluid flow and structural deformation), regional leaflet thickness inhomogeneity and anisotropic nonlinear mechanical properties, to accurately predict the stress-strain distribution on the natural aortic valve.
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21
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Sacks MS, Zhang W, Wognum S. A novel fibre-ensemble level constitutive model for exogenous cross-linked collagenous tissues. Interface Focus 2016; 6:20150090. [PMID: 26855761 DOI: 10.1098/rsfs.2015.0090] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Exogenous cross-linking of soft collagenous tissues is a common method for biomaterial development and medical therapies. To enable improved applications through computational methods, physically realistic constitutive models are required. Yet, despite decades of research, development and clinical use, no such model exists. In this study, we develop the first rigorous full structural model (i.e. explicitly incorporating various features of the collagen fibre architecture) for exogenously cross-linked soft tissues. This was made possible, in-part, with the use of native to cross-linked matched experimental datasets and an extension to the collagenous structural constitutive model so that the uncross-linked collagen fibre responses could be mapped to the cross-linked configuration. This allowed us to separate the effects of cross-linking from kinematic changes induced in the cross-linking process, which in turn allowed the non-fibrous tissue matrix component and the interaction effects to be identified. It was determined that the matrix could be modelled as an isotropic material using a modified Yeoh model. The most novel findings of this study were that: (i) the effective collagen fibre modulus was unaffected by cross-linking and (ii) fibre-ensemble interactions played a large role in stress development, often dominating the total tissue response (depending on the stress component and loading path considered). An important utility of the present model is its ability to separate the effects of exogenous cross-linking on the fibres from changes due to the matrix. Applications of this approach include the utilization in the design of novel chemical treatments to produce specific mechanical responses and the study of fatigue damage in bioprosthetic heart valve biomaterials.
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Affiliation(s)
- Michael S Sacks
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering , The University of Texas at Austin , 201 East 24th Street, PO Box 5.236, Stop C0200, Austin, TX 78712 , USA
| | - Will Zhang
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering , The University of Texas at Austin , 201 East 24th Street, PO Box 5.236, Stop C0200, Austin, TX 78712 , USA
| | - Silvia Wognum
- Department of Biomedical Engineering , Eindhoven University of Technology , PO Box 513, 5600 MB Eindhoven , The Netherlands
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22
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Liu H, Sun W. Computational efficiency of numerical approximations of tangent moduli for finite element implementation of a fiber-reinforced hyperelastic material model. Comput Methods Biomech Biomed Engin 2015; 19:1171-80. [PMID: 26692168 DOI: 10.1080/10255842.2015.1118467] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
In this study, we evaluated computational efficiency of finite element (FE) simulations when a numerical approximation method was used to obtain the tangent moduli. A fiber-reinforced hyperelastic material model for nearly incompressible soft tissues was implemented for 3D solid elements using both the approximation method and the closed-form analytical method, and validated by comparing the components of the tangent modulus tensor (also referred to as the material Jacobian) between the two methods. The computational efficiency of the approximation method was evaluated with different perturbation parameters and approximation schemes, and quantified by the number of iteration steps and CPU time required to complete these simulations. From the simulation results, it can be seen that the overall accuracy of the approximation method is improved by adopting the central difference approximation scheme compared to the forward Euler approximation scheme. For small-scale simulations with about 10,000 DOFs, the approximation schemes could reduce the CPU time substantially compared to the closed-form solution, due to the fact that fewer calculation steps are needed at each integration point. However, for a large-scale simulation with about 300,000 DOFs, the advantages of the approximation schemes diminish because the factorization of the stiffness matrix will dominate the solution time. Overall, as it is material model independent, the approximation method simplifies the FE implementation of a complex constitutive model with comparable accuracy and computational efficiency to the closed-form solution, which makes it attractive in FE simulations with complex material models.
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Affiliation(s)
- Haofei Liu
- a Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering , Georgia Institute of Technology, Atlanta , GA , USA
| | - Wei Sun
- a Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering , Georgia Institute of Technology, Atlanta , GA , USA
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23
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Mega M, Marom G, Halevi R, Hamdan A, Bluestein D, Haj-Ali R. Imaging analysis of collagen fiber networks in cusps of porcine aortic valves: effect of their local distribution and alignment on valve functionality. Comput Methods Biomech Biomed Engin 2015; 19:1002-8. [PMID: 26406926 DOI: 10.1080/10255842.2015.1088009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The cusps of native aortic valve (AV) are composed of collagen bundles embedded in soft tissue, creating a heterogenic tissue with asymmetric alignment in each cusp. This study compares native collagen fiber networks (CFNs) with a goal to better understand their influence on stress distribution and valve kinematics. Images of CFNs from five porcine tricuspid AVs are analyzed and fluid-structure interaction models are generated based on them. Although the valves had similar overall kinematics, the CFNs had distinctive influence on local mechanics. The regions with dilute CFN are more prone to damage since they are subjected to higher stress magnitudes.
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Affiliation(s)
- Mor Mega
- a School of Mechanical Engineering , Tel Aviv University , Tel Aviv , Israel
| | - Gil Marom
- b Department of Biomedical Engineering , Stony Brook University , Stony Brook , NY , USA
| | - Rotem Halevi
- a School of Mechanical Engineering , Tel Aviv University , Tel Aviv , Israel
| | - Ashraf Hamdan
- c Heart Institute, Chaim Sheba Medical Center , Tel Hashomer , Israel
| | - Danny Bluestein
- b Department of Biomedical Engineering , Stony Brook University , Stony Brook , NY , USA
| | - Rami Haj-Ali
- a School of Mechanical Engineering , Tel Aviv University , Tel Aviv , Israel
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24
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Sacks MS. Simulation of Fatigue in Bioprosthetic Heart Valve Biomaterials1. J Med Device 2015. [DOI: 10.1115/1.4030581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Michael S. Sacks
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229
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25
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Tepole AB, Kabaria H, Bletzinger KU, Kuhl E. Isogeometric Kirchhoff-Love shell formulations for biological membranes. COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2015. [PMID: 26251556 DOI: 10.1016/j.cma.2015.03.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Computational modeling of thin biological membranes can aid the design of better medical devices. Remarkable biological membranes include skin, alveoli, blood vessels, and heart valves. Isogeometric analysis is ideally suited for biological membranes since it inherently satisfies the C1-requirement for Kirchhoff-Love kinematics. Yet, current isogeometric shell formulations are mainly focused on linear isotropic materials, while biological tissues are characterized by a nonlinear anisotropic stress-strain response. Here we present a thin shell formulation for thin biological membranes. We derive the equilibrium equations using curvilinear convective coordinates on NURBS tensor product surface patches. We linearize the weak form of the generic linear momentum balance without a particular choice of a constitutive law. We then incorporate the constitutive equations that have been designed specifically for collagenous tissues. We explore three common anisotropic material models: Mooney-Rivlin, May Newmann-Yin, and Gasser-Ogden-Holzapfel. Our work will allow scientists in biomechanics and mechanobiology to adopt the constitutive equations that have been developed for solid three-dimensional soft tissues within the framework of isogeometric thin shell analysis.
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Affiliation(s)
- Adrián Buganza Tepole
- Department of Mechanical Engineering, Stanford University, 496 Lomita Mall, Stanford, CA 94305, USA
| | - Hardik Kabaria
- Department of Mechanical Engineering, Stanford University, 496 Lomita Mall, Stanford, CA 94305, USA
| | - Kai-Uwe Bletzinger
- Lehrstuhl für Statik, Technische Universität München, Arcisstr. 21, München 80333, Germany
| | - Ellen Kuhl
- Department of Mechanical Engineering, Stanford University, 496 Lomita Mall, Stanford, CA 94305, USA
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26
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LI LIN, HUA LIN, ZHANG HAIXIA, LIU ZHICHENG. DIFFERENCES BETWEEN PULMONARY ARTERIAL AND AORTIC MATERIAL PROPERTIES. J MECH MED BIOL 2015. [DOI: 10.1142/s0219519415500190] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
To investigate the differences of mechanical responses between pulmonary artery and aorta to different biaxial loading conditions, we simulated the process of human pulmonary artery and aorta subjected to biaxial loading based on four-family fiber strain density function model determined from uniaxial extension data of arterial walls. It was shown that different stress–strain curves of pulmonary artery and aorta under biaxial loading conditions: different loading ratios between the loads in two perpendicular directions and displacement-controlled equibiaxial stretch. Tissue stiffness, defined as the first derivative of the stress–strain response at a strain point, of human pulmonary artery and aorta were obtained when they were subjected to biaxial loads (systemic pressure). The two-dimensional mechanical response of artery can be acquired by determination of the four-family fiber strain density function model of the tissue based on uniaxial extensile data. There are differences between material properties of pulmonary artery and aorta: aorta is stiffer circumferentially than longitudinally, and pulmonary artery is more compliant circumferentially than longitudinally.
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Affiliation(s)
- LIN LI
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing 100069, P. R. China
| | - LIN HUA
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing 100069, P. R. China
| | - HAIXIA ZHANG
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing 100069, P. R. China
| | - ZHICHENG LIU
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing 100069, P. R. China
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27
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Hsu MC, Kamensky D, Xu F, Kiendl J, Wang C, Wu MCH, Mineroff J, Reali A, Bazilevs Y, Sacks MS. Dynamic and fluid-structure interaction simulations of bioprosthetic heart valves using parametric design with T-splines and Fung-type material models. COMPUTATIONAL MECHANICS 2015; 55:1211-1225. [PMID: 26392645 PMCID: PMC4574293 DOI: 10.1007/s00466-015-1166-x] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
This paper builds on a recently developed immersogeometric fluid-structure interaction (FSI) methodology for bioprosthetic heart valve (BHV) modeling and simulation. It enhances the proposed framework in the areas of geometry design and constitutive modeling. With these enhancements, BHV FSI simulations may be performed with greater levels of automation, robustness and physical realism. In addition, the paper presents a comparison between FSI analysis and standalone structural dynamics simulation driven by prescribed transvalvular pressure, the latter being a more common modeling choice for this class of problems. The FSI computation achieved better physiological realism in predicting the valve leaflet deformation than its standalone structural dynamics counterpart.
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Affiliation(s)
- Ming-Chen Hsu
- Department of Mechanical Engineering, Iowa State University, 2025 Black Engineering, Ames, IA 50011, USA
| | - David Kamensky
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712, USA
| | - Fei Xu
- Department of Mechanical Engineering, Iowa State University, 2025 Black Engineering, Ames, IA 50011, USA
| | - Josef Kiendl
- Department of Civil Engineering and Architecture, University of Pavia, via Ferrata 3, 27100 Pavia, Italy
| | - Chenglong Wang
- Department of Mechanical Engineering, Iowa State University, 2025 Black Engineering, Ames, IA 50011, USA
| | - Michael C. H. Wu
- Department of Mechanical Engineering, Iowa State University, 2025 Black Engineering, Ames, IA 50011, USA
| | - Joshua Mineroff
- Department of Mechanical Engineering, Iowa State University, 2025 Black Engineering, Ames, IA 50011, USA
| | - Alessandro Reali
- Department of Civil Engineering and Architecture, University of Pavia, via Ferrata 3, 27100 Pavia, Italy
| | - Yuri Bazilevs
- Department of Structural Engineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0085, La Jolla, CA 92093, USA
| | - Michael S. Sacks
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712, USA
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Zhang W, Feng Y, Lee CH, Billiar KL, Sacks MS. A generalized method for the analysis of planar biaxial mechanical data using tethered testing configurations. J Biomech Eng 2015; 137:064501. [PMID: 25429606 DOI: 10.1115/1.4029266] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2013] [Indexed: 11/08/2022]
Abstract
Simulation of the mechanical behavior of soft tissues is critical for many physiological and medical device applications. Accurate mechanical test data is crucial for both obtaining the form and robust parameter determination of the constitutive model. For incompressible soft tissues that are either membranes or thin sections, planar biaxial mechanical testing configurations can provide much information about the anisotropic stress-strain behavior. However, the analysis of soft biological tissue planar biaxial mechanical test data can be complicated by in-plane shear, tissue heterogeneities, and inelastic changes in specimen geometry that commonly occur during testing. These inelastic effects, without appropriate corrections, alter the stress-traction mapping and violates equilibrium so that the stress tensor is incorrectly determined. To overcome these problems, we presented an analytical method to determine the Cauchy stress tensor from the experimentally derived tractions for tethered testing configurations. We accounted for the measured testing geometry and compensate for run-time inelastic effects by enforcing equilibrium using small rigid body rotations. To evaluate the effectiveness of our method, we simulated complete planar biaxial test configurations that incorporated actual device mechanisms, specimen geometry, and heterogeneous tissue fibrous structure using a finite element (FE) model. We determined that our method corrected the errors in the equilibrium of momentum and correctly estimated the Cauchy stress tensor. We also noted that since stress is applied primarily over a subregion bounded by the tethers, an adjustment to the effective specimen dimensions is required to correct the magnitude of the stresses. Simulations of various tether placements demonstrated that typical tether placements used in the current experimental setups will produce accurate stress tensor estimates. Overall, our method provides an improved and relatively straightforward method of calculating the resulting stresses for planar biaxial experiments for tethered configurations, which is especially useful for specimens that undergo large shear and exhibit substantial inelastic effects.
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A review of: Application of synthetic scaffold in tissue engineering heart valves. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2015; 48:556-65. [DOI: 10.1016/j.msec.2014.12.016] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 08/26/2014] [Accepted: 12/05/2014] [Indexed: 01/28/2023]
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Huang S, Huang HYS. Prediction of matrix-to-cell stress transfer in heart valve tissues. J Biol Phys 2014; 41:9-22. [PMID: 25298285 DOI: 10.1007/s10867-014-9362-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 08/12/2014] [Indexed: 11/27/2022] Open
Abstract
Non-linear and anisotropic heart valve leaflet tissue mechanics manifest principally from the stratification, orientation, and inhomogeneity of their collagenous microstructures. Disturbance of the native collagen fiber network has clear consequences for valve and leaflet tissue mechanics and presumably, by virtue of their intimate embedment, on the valvular interstitial cell stress-strain state and concomitant phenotype. In the current study, a set of virtual biaxial stretch experiments were conducted on porcine pulmonary valve leaflet tissue photomicrographs via an image-based finite element approach. Stress distribution evolution during diastolic valve closure was predicted at both the tissue and cellular levels. Orthotropic material properties consistent with distinct stages of diastolic loading were applied. Virtual experiments predicted tissue- and cellular-level stress fields, providing insight into how matrix-to-cell stress transfer may be influenced by the inhomogeneous collagen fiber architecture, tissue anisotropic material properties, and the cellular distribution within the leaflet tissue. To the best of the authors' knowledge, this is the first study reporting on the evolution of stress fields at both the tissue and cellular levels in valvular tissue and thus contributes toward refining our collective understanding of valvular tissue micromechanics while providing a computational tool enabling the further study of valvular cell-matrix interactions.
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Affiliation(s)
- Siyao Huang
- Mechanical and Aerospace Engineering Department, North Carolina State University, R3158 Engineering Building 3, Campus Box 7910, 911 Oval Drive, Raleigh, NC, 27695, USA
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31
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Hill MR, Simon MA, Valdez-Jasso D, Zhang W, Champion HC, Sacks MS. Structural and mechanical adaptations of right ventricle free wall myocardium to pressure overload. Ann Biomed Eng 2014. [PMID: 25164124 DOI: 10.1007/s10439‐014‐1096‐3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Right ventricular (RV) failure in response to pulmonary hypertension (PH) is a severe disease that remains poorly understood. PH-induced pressure overload leads to changes in the RV free wall (RVFW) that eventually results in RV failure. While the development of computational models can benefit our understanding of the onset and progression of PH-induced pressure overload, detailed knowledge of the underlying structural and biomechanical events remains limited. The goal of the present study was to elucidate the structural and biomechanical adaptations of RV myocardium subjected to sustained pressure overload in a rat model. Hemodynamically confirmed severe chronic RV pressure overload was induced in Sprague-Dawley rats via pulmonary artery banding. Extensive tissue-level biaxial mechanical and histomorphological analyses were conducted to assess the remodeling response in the RV free wall. Simultaneous myofiber hypertrophy and longitudinal re-orientation of myo- and collagen fibers were observed, with both fiber types becoming more highly aligned. Transmural myo- and collagen fiber orientations were co-aligned in both the normal and diseased state. The overall tissue stiffness increased, with larger increases in longitudinal vs. circumferential stiffness. The latter was attributed to longitudinal fiber re-orientation, which increased the degree of anisotropy. Increased mechanical coupling between the two axes was attributed to the increased fiber alignment. Interestingly, estimated myofiber stiffness increased while the collagen fiber stiffness remained unchanged. The increased myofiber stiffness was consistent with clinical results showing titin-associated increased sarcomeric stiffening observed in PH patients. These results further our understanding of the underlying adaptive and maladaptive remodeling mechanisms and may lead to improved techniques for prognosis, diagnosis, and treatment for PH.
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Affiliation(s)
- Michael R Hill
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, University Station, C0200, POB 5.236, Austin, TX, 78712-0027, USA
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Hill MR, Simon MA, Valdez-Jasso D, Zhang W, Champion HC, Sacks MS. Structural and mechanical adaptations of right ventricle free wall myocardium to pressure overload. Ann Biomed Eng 2014; 42:2451-65. [PMID: 25164124 DOI: 10.1007/s10439-014-1096-3] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 08/13/2014] [Indexed: 01/08/2023]
Abstract
Right ventricular (RV) failure in response to pulmonary hypertension (PH) is a severe disease that remains poorly understood. PH-induced pressure overload leads to changes in the RV free wall (RVFW) that eventually results in RV failure. While the development of computational models can benefit our understanding of the onset and progression of PH-induced pressure overload, detailed knowledge of the underlying structural and biomechanical events remains limited. The goal of the present study was to elucidate the structural and biomechanical adaptations of RV myocardium subjected to sustained pressure overload in a rat model. Hemodynamically confirmed severe chronic RV pressure overload was induced in Sprague-Dawley rats via pulmonary artery banding. Extensive tissue-level biaxial mechanical and histomorphological analyses were conducted to assess the remodeling response in the RV free wall. Simultaneous myofiber hypertrophy and longitudinal re-orientation of myo- and collagen fibers were observed, with both fiber types becoming more highly aligned. Transmural myo- and collagen fiber orientations were co-aligned in both the normal and diseased state. The overall tissue stiffness increased, with larger increases in longitudinal vs. circumferential stiffness. The latter was attributed to longitudinal fiber re-orientation, which increased the degree of anisotropy. Increased mechanical coupling between the two axes was attributed to the increased fiber alignment. Interestingly, estimated myofiber stiffness increased while the collagen fiber stiffness remained unchanged. The increased myofiber stiffness was consistent with clinical results showing titin-associated increased sarcomeric stiffening observed in PH patients. These results further our understanding of the underlying adaptive and maladaptive remodeling mechanisms and may lead to improved techniques for prognosis, diagnosis, and treatment for PH.
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Affiliation(s)
- Michael R Hill
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, University Station, C0200, POB 5.236, Austin, TX, 78712-0027, USA
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33
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Biomechanical properties of native and tissue engineered heart valve constructs. J Biomech 2014; 47:1949-63. [DOI: 10.1016/j.jbiomech.2013.09.023] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 09/09/2013] [Accepted: 09/10/2013] [Indexed: 11/18/2022]
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34
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Marom G, Peleg M, Halevi R, Rosenfeld M, Raanani E, Hamdan A, Haj-Ali R. Fluid-structure interaction model of aortic valve with porcine-specific collagen fiber alignment in the cusps. J Biomech Eng 2014; 135:101001-6. [PMID: 23775457 DOI: 10.1115/1.4024824] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 06/05/2013] [Indexed: 11/08/2022]
Abstract
Native aortic valve cusps are composed of collagen fibers embedded in their layers. Each valve cusp has its own distinctive fiber alignment with varying orientations and sizes of its fiber bundles. However, prior mechanical behavior models have not been able to account for the valve-specific collagen fiber networks (CFN) or for their differences between the cusps. This study investigates the influence of this asymmetry on the hemodynamics by employing two fully coupled fluid-structure interaction (FSI) models, one with asymmetric-mapped CFN from measurements of porcine valve and the other with simplified-symmetric CFN. The FSI models are based on coupled structural and fluid dynamic solvers. The partitioned solver has nonconformal meshes and the flow is modeled by employing the Eulerian approach. The collagen in the CFNs, the surrounding elastin matrix, and the aortic sinus tissues have hyperelastic mechanical behavior. The coaptation is modeled with a master-slave contact algorithm. A full cardiac cycle is simulated by imposing the same physiological blood pressure at the upstream and downstream boundaries for both models. The mapped case showed highly asymmetric valve kinematics and hemodynamics even though there were only small differences between the opening areas and cardiac outputs of the two cases. The regions with a less dense fiber network are more prone to damage since they are subjected to higher principal stress in the tissues and a higher level of flow shear stress. This asymmetric flow leeward of the valve might damage not only the valve itself but also the ascending aorta.
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35
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Fan R, Sacks MS. Simulation of planar soft tissues using a structural constitutive model: Finite element implementation and validation. J Biomech 2014; 47:2043-54. [PMID: 24746842 DOI: 10.1016/j.jbiomech.2014.03.014] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 03/11/2014] [Accepted: 03/11/2014] [Indexed: 10/25/2022]
Abstract
Computational implementation of physical and physiologically realistic constitutive models is critical for numerical simulation of soft biological tissues in a variety of biomedical applications. It is well established that the highly nonlinear and anisotropic mechanical behaviors of soft tissues are an emergent behavior of the underlying tissue microstructure. In the present study, we have implemented a structural constitutive model into a finite element framework specialized for membrane tissues. We noted that starting with a single element subjected to uniaxial tension, the non-fibrous tissue matrix must be present to prevent unrealistic tissue deformations. Flexural simulations were used to set the non-fibrous matrix modulus because fibers have little effects on tissue deformation under three-point bending. Multiple deformation modes were simulated, including strip biaxial, planar biaxial with two attachment methods, and membrane inflation. Detailed comparisons with experimental data were undertaken to insure faithful simulations of both the macro-level stress-strain insights into adaptations of the fiber architecture under stress, such as fiber reorientation and fiber recruitment. Results indicated a high degree of fidelity and demonstrated interesting microstructural adaptions to stress and the important role of the underlying tissue matrix. Moreover, we apparently resolve a discrepancy in our 1997 study (Billiar and Sacks, 1997. J. Biomech. 30 (7), 753-756) where we observed that under strip biaxial stretch the simulated fiber splay responses were not in good agreement with the experimental results, suggesting non-affine deformations may have occurred. However, by correctly accounting for the isotropic phase of the measured fiber splay, good agreement was obtained. While not the final word, these simulations suggest that affine fiber kinematics for planar collagenous tissues is a reasonable assumption at the macro level. Simulation tools such as these are imperative in the design and simulation of native and engineered tissues.
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Affiliation(s)
- Rong Fan
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Michael S Sacks
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA.
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36
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Pham T, Sun W. Material properties of aged human mitral valve leaflets. J Biomed Mater Res A 2013; 102:2692-703. [PMID: 24039052 DOI: 10.1002/jbm.a.34939] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 08/01/2013] [Accepted: 08/26/2013] [Indexed: 11/08/2022]
Abstract
This study aimed to characterize the mechanical properties of aged human anterior mitral leaflets (AML) and posterior mitral leaflets (PML). The AML and PML samples from explanted human hearts (n = 21, mean age of 82.62 ± 8.77-years-old) were subjected to planar biaxial mechanical tests. The material stiffness, extensibility, and degree of anisotropy of the leaflet samples were quantified. The microstructure of the samples was assessed through histology. Both the AML and PML samples exhibited a nonlinear and anisotropic behavior with the circumferential direction being stiffer than the radial direction. The AML samples were significantly stiffer than the PML samples in both directions, suggesting that they should be modeled with separate sets of material properties in computational studies. Histological analysis indicated the changes in the tissue elastic constituents, including the fragmented and disorganized elastin network, the presence of fibrosis and proteoglycan/glycosaminoglycan infiltration and calcification, suggesting possible valvular degenerative characteristics in the aged human leaflet samples. Overall, stiffness increased and areal strain decreased with calcification severity. In addition, leaflet tissues from hypertensive individuals also exhibited a higher stiffness and low areal strain than normotensive individuals. There are significant differences in the mechanical properties of the two human mitral valve leaflets from this advanced age group. The morphologic changes in the tissue composition and structure also infer the structural and functional difference between aged human valves and those of animals.
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Affiliation(s)
- Thuy Pham
- Tissue Mechanics Laboratory, Department of Mechanical Engineering, Biomedical Engineering Program, University of Connecticut, Storrs, Connecticut, 06269
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37
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Li L, Qian X, Wang H, Hua L, Zhang H, Liu Z. Power type strain energy function model and prediction of the anisotropic mechanical properties of skin using uniaxial extension data. Med Biol Eng Comput 2013; 51:1147-56. [PMID: 23864550 DOI: 10.1007/s11517-013-1098-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Accepted: 07/03/2013] [Indexed: 11/24/2022]
Abstract
Many successful models to describe the biomechanical characteristics of planar biological soft tissues are based on strain energy function. However, the parameters in these models are determined by biaxial extension test, which might be difficult to exercise for certain types of soft tissue. This study presents a new constitutive model, the power type strain energy density function model (PTM), and a method to identify its material parameters for rabbit skin using uniaxial extension test of 4-direction strip samples. The abdominal skins from eight rabbits were taken to perform uniaxial tension tests in 7 different directions. The material parameters were identified for each subject based on any 4 out of 7 directions by applying some definite conditions of this issue. For each rabbit, the 35 groups of material parameters were consistent. The 7 material parameters in PTM were identified with root mean square errors <0.061. The results indicate that the material parameters of rabbit skin can be identified from uniaxial extension test data.
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Affiliation(s)
- Lin Li
- School of Biomedical Engineering, Capital Medical University, Beijing, 100069, China
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38
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Eckert CE, Fan R, Mikulis B, Barron M, Carruthers CA, Friebe VM, Vyavahare NR, Sacks MS. On the biomechanical role of glycosaminoglycans in the aortic heart valve leaflet. Acta Biomater 2013; 9:4653-60. [PMID: 23036945 PMCID: PMC3508081 DOI: 10.1016/j.actbio.2012.09.031] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2012] [Revised: 09/09/2012] [Accepted: 09/25/2012] [Indexed: 12/14/2022]
Abstract
While the role of collagen and elastin fibrous components in heart valve valvular biomechanics has been extensively investigated, the biomechanical role of the glycosaminoglycan (GAG) gelatinous-like material phase remains unclear. In the present study, we investigated the biomechanical role of GAGs in porcine aortic valve (AV) leaflets under tension utilizing enzymatic removal. Tissue specimens were removed from the belly region of porcine AVs and subsequently treated with either an enzyme solution for GAG removal or a control (buffer with no enzyme) solution. A dual stress level test methodology was used to determine the effects at low and high (physiological) stress levels. In addition, planar biaxial tests were conducted both on-axis (i.e. aligned to the circumferential and radial axes) and at 45° off-axis to induce maximum shear, to explore the effects of augmented fiber rotations on the fiber-fiber interactions. Changes in hysteresis were used as the primary metric of GAG functional assessment. A simulation of the low-force experimental setup was also conducted to clarify the internal stress system and provide viscoelastic model parameters for this loading range. Results indicated that under planar tension the removal of GAGs had no measureable affect extensional mechanical properties (either on- or 45° off-axis), including peak stretch, hysteresis and creep. Interestingly, in the low-force range, hysteresis was markedly reduced, from 35.96±2.65% in control group to 25.00±1.64% (p<0.001) as a result of GAG removal. Collectively, these results suggest that GAGs do not play a direct role in modulating the time-dependent tensile properties of valvular tissues. Rather, they appear to be strongly connected with fiber-fiber and fiber-matrix interactions at low force levels. Thus, we speculate that GAGs may be important in providing a damping mechanism to reduce leaflet flutter when the leaflet is not under high tensile stress.
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Affiliation(s)
- Chad E Eckert
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA
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39
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Bellini C, Glass P, Sitti M, Di Martino ES. Biaxial mechanical modeling of the small intestine. J Mech Behav Biomed Mater 2011; 4:1727-40. [DOI: 10.1016/j.jmbbm.2011.05.030] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2011] [Revised: 05/03/2011] [Accepted: 05/23/2011] [Indexed: 12/22/2022]
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40
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Ciarletta P, Izzo I, Micera S, Tendick F. Stiffening by fiber reinforcement in soft materials: A hyperelastic theory at large strains and its application. J Mech Behav Biomed Mater 2011; 4:1359-68. [DOI: 10.1016/j.jmbbm.2011.05.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 04/23/2011] [Accepted: 05/03/2011] [Indexed: 11/26/2022]
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41
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Comparison of biaxial mechanical properties of coronary sinus tissues from porcine, ovine and aged human species. J Mech Behav Biomed Mater 2011; 6:21-9. [PMID: 22301170 DOI: 10.1016/j.jmbbm.2011.09.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 08/31/2011] [Accepted: 09/02/2011] [Indexed: 11/22/2022]
Abstract
Due to its proximity to the mitral valve, the coronary sinus (CS) vessel serves as a conduit for the deployment and implantation of the percutaneous transvenous mitral annuloplasty (PTMA) devices that can potentially reduce the mitral regurgitation. Because CS vessel is a venous tissue and seldom diseased, its mechanical properties have not been well studied. In this study, we performed a multi-axial mechanical test and histological analysis to characterize the mechanical and structural properties of the aged human, porcine and ovine CS tissues. The results showed that the aged human CS tissues exhibited much stiffer and highly anisotropic behaviors compared to the porcine and ovine. Both of the porcine and ovine CS vessel walls were thicker and mainly composed of striated muscle fibers (SMF), whereas the thinner aged human CS had higher collagen, less SMF, and more fragmented elastin fibers, which are possibly due to aging effects. We also observed that the anatomical features of porcine CS vessel might be not suitable for PTMA deployment. These differences between animal and human models raise questions for the validity of using animal models to investigate the biomechanics involved in the PTMA intervention. Therefore, caution must be taken in future studies of PTMA stents using animal models.
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Simulated Thin Pericardial Bioprosthetic Valve Leaflet Deformation Under Static Pressure-Only Loading Conditions: Implications for Percutaneous Valves. Ann Biomed Eng 2010; 38:2690-701. [DOI: 10.1007/s10439-010-0009-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2009] [Accepted: 03/10/2010] [Indexed: 10/19/2022]
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Abstract
Computational simulations are playing an increasingly important role in enhancing our understanding of the normal human physiological function, etiology of diseased states, surgical and interventional planning, and in the design and evaluation of artificial implants. Researchers are taking advantage of computational simulations to speed up the initial design of implantable devices before a prototype is developed and hence able to reduce animal experimentation for the functional evaluation of the devices under development. A review of the reported studies to date relevant to the simulation of the native and prosthetic heart valve dynamics is the subject of the present paper. Potential future directions toward multi-scale simulation studies for our further understanding of the physiology and pathophysiology of heart valve dynamics and valvular implants are also discussed.
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44
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Sun W, Chaikof EL, Levenston ME. Numerical approximation of tangent moduli for finite element implementations of nonlinear hyperelastic material models. J Biomech Eng 2009; 130:061003. [PMID: 19045532 DOI: 10.1115/1.2979872] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Finite element (FE) implementations of nearly incompressible material models often employ decoupled numerical treatments of the dilatational and deviatoric parts of the deformation gradient. This treatment allows the dilatational stiffness to be handled separately to alleviate ill conditioning of the tangent stiffness matrix. However, this can lead to complex formulations of the material tangent moduli that can be difficult to implement or may require custom FE codes, thus limiting their general use. Here we present an approach, based on work by Miehe (Miehe, 1996, "Numerical Computation of Algorithmic (Consistent) Tangent Moduli in Large Strain Computational Inelasticity," Comput. Methods Appl. Mech. Eng., 134, pp. 223-240), for an efficient numerical approximation of the tangent moduli that can be easily implemented within commercial FE codes. By perturbing the deformation gradient, the material tangent moduli from the Jaumann rate of the Kirchhoff stress are accurately approximated by a forward difference of the associated Kirchhoff stresses. The merit of this approach is that it produces a concise mathematical formulation that is not dependent on any particular material model. Consequently, once the approximation method is coded in a subroutine, it can be used for other hyperelastic material models with no modification. The implementation and accuracy of this approach is first demonstrated with a simple neo-Hookean material. Subsequently, a fiber-reinforced structural model is applied to analyze the pressure-diameter curve during blood vessel inflation. Implementation of this approach will facilitate the incorporation of novel hyperelastic material models for a soft tissue behavior into commercial FE software.
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Affiliation(s)
- Wei Sun
- Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269, USA.
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45
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Gilbert TW, Wognum S, Joyce EM, Freytes DO, Sacks MS, Badylak SF. Collagen fiber alignment and biaxial mechanical behavior of porcine urinary bladder derived extracellular matrix. Biomaterials 2008; 29:4775-82. [PMID: 18801572 DOI: 10.1016/j.biomaterials.2008.08.022] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Accepted: 08/22/2008] [Indexed: 12/27/2022]
Abstract
The collagen fiber alignment and biomechanical behavior of naturally occurring extracellular matrix (ECM) scaffolds are important considerations for the design of medical devices from these materials. Both should be considered in order to produce a device to meet tissue specific mechanical requirements (e.g., tendon vs. urinary bladder), and could ultimately affect the remodeling response in vivo. The present study evaluated the collagen fiber alignment and biaxial mechanical behavior of ECM scaffold material harvested from porcine urinary bladder tunica mucosa and basement membrane (together referred to as urinary bladder matrix (UBM)) and ECM harvested from urinary bladder submucosa (UBS). Since the preparation of UBM allows for control of the direction of delamination, the effect of the delamination method on the mechanical behavior of UBM was determined by delaminating the submucosa and other abluminal layers by scraping along the longitudinal axis of the bladder (apex to neck) (UBML) or along the circumferential direction (UBMC). The processing of UBS does not allow for similar directional control. UBML and UBS had similar collagen fiber distributions, with a preferred collagen fiber alignment along the longitudinal direction. UBMC showed a more homogenous collagen fiber orientation. All samples showed a stiffer mechanical behavior in the longitudinal direction. Despite similar collagen fiber distributions, UBML and UBS showed quite different mechanical behavior for the applied loading patterns with UBS showing a much more pronounced toe region. The mechanical behavior for UBMC in both directions was similar to the mechanical behavior of UBML. There are distinct differences in the mechanical behavior of different layers of ECM from the porcine urinary bladder, and the processing methods can substantially alter the mechanical behavior observed.
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Affiliation(s)
- Thomas W Gilbert
- McGowan Institute for Regenerative Medicine, Department of Surgery, University of Pittsburgh, Pittsburgh, PA 15219, USA
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46
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Toosi KK, Nagatomi J, Chancellor MB, Sacks MS. The effects of long-term spinal cord injury on mechanical properties of the rat urinary bladder. Ann Biomed Eng 2008; 36:1470-80. [PMID: 18622703 DOI: 10.1007/s10439-008-9525-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2007] [Accepted: 06/16/2008] [Indexed: 10/21/2022]
Abstract
We have demonstrated that bladder wall tissue in spinal cord injury (SCI) rats at 10 days post-injury is more compliant and accompanied by changes in material class from orthotropic to isotropic as compared to normal tissue. The present study examined the long-term effects (3-, 6-, and 10-weeks) post-SCI on the mechanical properties of bladder wall tissues, along with quantitative changes in smooth muscle orientation and collagen and elastin content. Bladder wall compliance (defined as det(F) - 1 under an equi-biaxial stress state of 100 kPa, where F is the deformation gradient tensor) was found to be significantly greater at 3- and 6-weeks (0.873 +/- 0.092 and 0.864 +/- 0.112, respectively) when compared to the normal bladders (0.260 +/- 0.028), but at 10 weeks the compliance reduced (0.389 +/- 0.061) to near that of normal bladders. This trend in mechanical compliance closely paralleled the collagen/elastin ratio. Moreover, changes in material class, assessed using a graphical technique, correlated closely with quantitative changes in smooth muscle fiber orientation. The results of the present study provide the first evidence that, while similarities exist between acute and chronic responses of the urinary bladder wall tissue to SCI, the overall alterations are distinct, result in profound and complex time dependent changes in bladder wall structure, and will lay the basis for simulations of the bladder wall disease process.
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Affiliation(s)
- Kevin K Toosi
- Engineered Tissue Mechanics and Mechanobiology Laboratory, Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15219, USA
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47
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Structural simulations of prosthetic tri-leaflet aortic heart valves. J Biomech 2008; 41:1510-9. [PMID: 18395212 DOI: 10.1016/j.jbiomech.2008.02.026] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2007] [Revised: 02/05/2008] [Accepted: 02/18/2008] [Indexed: 11/22/2022]
Abstract
This study presents a combined computational and experimental approach for the nonlinear structural simulations of polymeric tri-leaflet aortic valves (PAVs). Nonlinear shell-based and quasi-static finite-element (FE) structural models are generated for a prosthetic valve geometry that includes the leaflets, stents and root materials, such as the bottom base and outside walls. The PAV structural model is subject to an ensemble averaged transvalvular pressure waveform measured from repeated in vitro tests conducted with a left heart simulator. High-resolution optical measurements are used to measure the in vitro kinematics of the leaflets and the stents. Qualitative and quantitative deformation measures are defined in order to compare the predicted kinematics from the PAV models with the in vitro measurements. Six new quantitative deformation metrics are introduced. They include three distances measuring the current PAV geometric center to the leaflet edges while additional three distances define the stent post-to-stent post (SPTSP) distances. The structural model is able to predict the kinematic deformation metrics with maximum errors around 10% especially in systole where the displacements are larger in magnitude. The combined structural modeling with experimental simulations along with the new proposed deformation metrics provide an effective way to study the PAV structural behavior and a path for improving the structural design of prosthetic valves.
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Jernigan SR, Buckner GD, Eischen JW, Cormier DR. Finite element modeling of the left atrium to facilitate the design of an endoscopic atrial retractor. J Biomech Eng 2008; 129:825-37. [PMID: 18067386 DOI: 10.1115/1.2801650] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
With the worldwide prevalence of cardiovascular diseases, much attention has been focused on simulating the characteristics of the human heart to better understand and treat cardiac disorders. The purpose of this study is to build a finite element model of the left atrium (LA) that incorporates detailed anatomical features and realistic material characteristics to investigate the interaction of heart tissue and surgical instruments. This model is used to facilitate the design of an endoscopically deployable atrial retractor for use in minimally invasive, robotically assisted mitral valve repair. Magnetic resonance imaging (MRI) scans of a pressurized explanted porcine heart were taken to provide a 3D solid model of the heart geometry, while uniaxial tensile tests of porcine left atrial tissue were conducted to obtain realistic material properties for noncontractile cardiac tissue. A finite element model of the LA was constructed using ANSYS Release 9.0 software and the MRI data. The Mooney-Rivlin hyperelastic material model was chosen to characterize the passive left atrial tissue; material constants were derived from tensile test data. Finite element analysis (FEA) models of a CardioVations Port Access retractor and a prototype endoscopic retractor were constructed to simulate interaction between each instrument and the LA. These contact simulations were used to compare the quality of retraction between the two instruments and to optimize the design of the prototype retractor. Model accuracy was verified by comparing simulated cardiac wall deflections to those measured by MRI. FEA simulations revealed that peak forces of approximately 2.85 N and 2.46 N were required to retract the LA using the Port Access and prototype retractors, respectively. These forces varied nonlinearly with retractor blade displacement. Dilation of the atrial walls and rigid body motion of the chamber were approximately the same for both retractors. Finite element analysis is shown to be an effective tool for analyzing instrument/tissue interactions and for designing surgical instruments. The benefits of this approach to medical device design are significant when compared to the alternatives: constructing prototypes and evaluating them via animal or clinical trials.
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Affiliation(s)
- S R Jernigan
- Department of Mechanical and Aerospace Engineering, North Carolina State University, NCSU Box 7910, Raleigh, NC 27695, USA.
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Shah SR, Vyavahare NR. The effect of glycosaminoglycan stabilization on tissue buckling in bioprosthetic heart valves. Biomaterials 2008; 29:1645-53. [PMID: 18199477 DOI: 10.1016/j.biomaterials.2007.12.009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Accepted: 12/09/2007] [Indexed: 11/24/2022]
Abstract
Bioprosthetic valves are used in thousands of heart valve replacement surgeries. Existing glutaraldehyde-crosslinked bioprosthetic valves fail due to either calcification or degeneration. Glutaraldehyde crosslinking does not stabilize valvular glycosaminoglycans (GAGs). GAGs, predominantly present in the medial spongiosa layer of native heart valve cusps, play an important role in regulating physico-mechanical behavior of the native cuspal tissue during dynamic motion. The primary objective of this study was to identify the role of cuspal GAGs in valve tissue buckling. Glutaraldehyde-crosslinked cusps showed extensive buckling compared to fresh, native cusps. Removal of GAGs by treatment with GAG-degrading enzymes led to a marked increase in buckling behavior in glutaraldehyde-crosslinked cusps. We demonstrate that the retention of valvular GAGs by carbodiimide crosslinking together with chemical attachment of neomycin trisulfate (a hyaluronidase inhibitor), prior to glutaraldehyde crosslinking, reduces the extent of buckling in bioprosthetic heart valves. Furthermore, following exposure to GAG-digestive enzymes, neomycin-trisulfate-bound cusps experienced no alterations in buckling behavior. Such moderate buckling patterns mimicked that of fresh, untreated cusps subjected to similar bending curvatures. Thus, GAG stabilization may subsequently improve the durability of these bioprostheses.
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Affiliation(s)
- Sagar R Shah
- Cardiovascular Implant Research Laboratory, Department of Bioengineering, Clemson University, 401 Rhodes Engineering Research Center, Clemson, SC 29634, USA
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Kim H, Lu J, Sacks MS, Chandran KB. Dynamic Simulation of Bioprosthetic Heart Valves Using a Stress Resultant Shell Model. Ann Biomed Eng 2007; 36:262-75. [DOI: 10.1007/s10439-007-9409-4] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Accepted: 11/16/2007] [Indexed: 11/30/2022]
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