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Khaledian N, Villard PF, Hammer PE, Perrin DP, Berger MO. Image-based simulation of mitral valve dynamic closure including anisotropy. Med Image Anal 2024; 99:103323. [PMID: 39243597 DOI: 10.1016/j.media.2024.103323] [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: 01/31/2024] [Revised: 07/10/2024] [Accepted: 08/20/2024] [Indexed: 09/09/2024]
Abstract
Simulation of the dynamic behavior of mitral valve closure could improve clinical treatment by predicting surgical procedures outcome. We propose here a method to achieve this goal by using the immersed boundary method. In order to go towards patient-based simulation, we tailor our method to be adapted to a valve extracted from medical image data. It includes investigating segmentation process, smoothness of geometry, case setup and the shape of the left ventricle. We also study the influence of leaflet tissue anisotropy on the quality of the valve closure by comparing with an isotropic model. As part of the anisotropy analysis, we study the influence of the principal material direction by comparing methods to obtain them without dissection. Results show that our method can be scaled to various image-based data. We evaluate the mitral valve closure quality based on measuring bulging area, contact map, and flow rate. The results show also that the anisotropic material model more precisely represents the physiological characteristics of the valve tissue. Furthermore, results indicate that the orientation of the principal material direction plays a role in the effectiveness of the valve seal.
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Affiliation(s)
| | | | - Peter E Hammer
- Department of Cardiac Surgery, Boston Children's Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA
| | - Douglas P Perrin
- Department of Cardiac Surgery, Boston Children's Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA
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2
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Arminio M, Carbonaro D, Morbiducci U, Gallo D, Chiastra C. Fluid-structure interaction simulation of mechanical aortic valves: a narrative review exploring its role in total product life cycle. FRONTIERS IN MEDICAL TECHNOLOGY 2024; 6:1399729. [PMID: 39011523 PMCID: PMC11247014 DOI: 10.3389/fmedt.2024.1399729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Accepted: 06/07/2024] [Indexed: 07/17/2024] Open
Abstract
Over the last years computer modelling and simulation has emerged as an effective tool to support the total product life cycle of cardiovascular devices, particularly in the device preclinical evaluation and post-market assessment. Computational modelling is particularly relevant for heart valve prostheses, which require an extensive assessment of their hydrodynamic performance and of risks of hemolysis and thromboembolic complications associated with mechanically-induced blood damage. These biomechanical aspects are typically evaluated through a fluid-structure interaction (FSI) approach, which enables valve fluid dynamics evaluation accounting for leaflets movement. In this context, the present narrative review focuses on the computational modelling of bileaflet mechanical aortic valves through FSI approach, aiming to foster and guide the use of simulations in device total product life cycle. The state of the art of FSI simulation of heart valve prostheses is reviewed to highlight the variety of modelling strategies adopted in the literature. Furthermore, the integration of FSI simulations in the total product life cycle of bileaflet aortic valves is discussed, with particular emphasis on the role of simulations in complementing and potentially replacing the experimental tests suggested by international standards. Simulations credibility assessment is also discussed in the light of recently published guidelines, thus paving the way for a broader inclusion of in silico evidence in regulatory submissions. The present narrative review highlights that FSI simulations can be successfully framed within the total product life cycle of bileaflet mechanical aortic valves, emphasizing that credible in silico models evaluating the performance of implantable devices can (at least) partially replace preclinical in vitro experimentation and support post-market biomechanical evaluation, leading to a reduction in both time and cost required for device development.
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Affiliation(s)
| | | | | | | | - Claudio Chiastra
- PoliToMed Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
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3
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Christierson L, Frieberg P, Lala T, Töger J, Liuba P, Revstedt J, Isaksson H, Hakacova N. Validation of fluid-structure interaction simulations of the opening phase of phantom mitral heart valves under physiologically inspired conditions. Comput Biol Med 2024; 171:108033. [PMID: 38430739 DOI: 10.1016/j.compbiomed.2024.108033] [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: 10/23/2023] [Revised: 12/22/2023] [Accepted: 01/26/2024] [Indexed: 03/05/2024]
Abstract
BACKGROUND AND OBJECTIVE Atrioventricular valve disease is a common cause of heart failure, and successful surgical or interventional outcomes are crucial. Patient-specific fluid-structure interaction (FSI) modeling may provide valuable insights into valve dynamics and guidance of valve repair strategies. However, lack of validation has kept FSI modeling from clinical implementation. Therefore, this study aims to validate FSI simulations against in vitro benchmarking data, based on clinically relevant parameters for evaluating heart valve disease. METHODS An FSI model that mimics the left heart was developed. The domain included a deformable mitral valve of different stiffnesses run with different inlet velocities. Five different cases were simulated and compared to in vitro data based on the pressure difference across the valve, the valve opening, and the velocity in the flow domain. RESULTS The simulations underestimate the pressure difference across the valve by 6.8-14 % compared to catheter measurements. Evaluation of the valve opening showed an underprediction of 5.4-7.3 % when compared to cine MRI, 2D Echo, and 3D Echo data. Additionally, the simulated velocity through the valve showed a 7.9-8.4 % underprediction in relation to Doppler Echo measurements. Qualitative assessment of the velocity profile in the ventricle and the streamlines of the flow in the domain showed good agreement of the flow behavior. CONCLUSIONS Parameters relevant to the diagnosis of heart valve disease estimated by FSI simulations showed good agreement when compared to in vitro benchmarking data, with differences small enough not to affect the grading of heart valve disease. The FSI model is thus deemed good enough for further development toward patient-specific cases.
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Affiliation(s)
- Lea Christierson
- Department of Clinical Sciences Lund, Pediatric Heart Center, Skåne University Hospital, Lund University, Lund, Sweden. Address: Barnhjärtcentrum mottagning, Skånes universitetssjukhus, Lasarettsgatan 48, 221 85, Lund, Sweden; Department of Biomedical Engineering, Lund University, Lund, Sweden. Address: Box 118, 221 00, Lund, Sweden.
| | - Petter Frieberg
- Department of Clinical Sciences Lund, Clinical Physiology, Skåne University Hospital, Lund University, Lund, Sweden. Address: Box 177, 221 00, Lund, Sweden
| | - Tania Lala
- Department of Biomedical Engineering, Lund University, Lund, Sweden. Address: Box 118, 221 00, Lund, Sweden; Department of Clinical Sciences Lund, Clinical Physiology, Skåne University Hospital, Lund University, Lund, Sweden. Address: Box 177, 221 00, Lund, Sweden
| | - Johannes Töger
- Department of Clinical Sciences Lund, Clinical Physiology, Skåne University Hospital, Lund University, Lund, Sweden. Address: Box 177, 221 00, Lund, Sweden
| | - Petru Liuba
- Department of Clinical Sciences Lund, Pediatric Heart Center, Skåne University Hospital, Lund University, Lund, Sweden. Address: Barnhjärtcentrum mottagning, Skånes universitetssjukhus, Lasarettsgatan 48, 221 85, Lund, Sweden
| | - Johan Revstedt
- Department of Energy Science, Lund University, Lund, Sweden. Address: Box 118, 221 00, Lund, Sweden
| | - Hanna Isaksson
- Department of Biomedical Engineering, Lund University, Lund, Sweden. Address: Box 118, 221 00, Lund, Sweden
| | - Nina Hakacova
- Department of Clinical Sciences Lund, Pediatric Heart Center, Skåne University Hospital, Lund University, Lund, Sweden. Address: Barnhjärtcentrum mottagning, Skånes universitetssjukhus, Lasarettsgatan 48, 221 85, Lund, Sweden
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4
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Weissmann J, Charles CJ, Richards AM, Yap CH, Marom G. Material property alterations for phenotypes of heart failure with preserved ejection fraction: A numerical study of subject-specific porcine models. Front Bioeng Biotechnol 2022; 10:1032034. [PMID: 36312535 PMCID: PMC9614036 DOI: 10.3389/fbioe.2022.1032034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 09/26/2022] [Indexed: 11/19/2022] Open
Abstract
A substantial proportion of heart failure patients have a preserved left ventricular (LV) ejection fraction (HFpEF). This condition carries a high burden of morbidity and mortality and has limited therapeutic options. left ventricular pressure overload leads to an increase in myocardial collagen content, causing left ventricular stiffening that contributes to the development of heart failure patients have a preserved left ventricular ejection fraction. Although several heart failure patients have a preserved left ventricular ejection fraction models have been developed in recent years to aid the investigation of mechanical alterations, none has investigated different phenotypes of the disease and evaluated the alterations in material properties. In this study, two similar healthy swine were subjected to progressive and prolonged pressure overload to induce diastolic heart failure characteristics, providing a preclinical model of heart failure patients have a preserved left ventricular ejection fraction. Cardiac magnetic resonance imaging (cMRI) scans and intracardiac pressures were recorded before and after induction. In both healthy and disease states, a corresponding finite element (FE) cardiac model was developed via mesh morphing of the Living Heart Porcine model. The material properties were derived by calibrating to its passive and active behavior. The change in the passive behavior was predominantly isotropic when comparing the geometries before and after induction. Myocardial thickening allowed for a steady transition in the passive properties while maintaining tissue incompressibility. This study highlights the importance of hypertrophy as an initial compensatory response and might also pave the way for assessing disease severity.
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Affiliation(s)
- Jonathan Weissmann
- Department of Biomedical Engineering, Tel Aviv University, Tel Aviv, Israel
| | - Christopher J. Charles
- Department of Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Cardiovascular Research Institute, National University of Singapore, Singapore, Singapore
- Christchurch Heart Institute, Department of Medicine, University of Otago, Christchurch, New Zealand
| | - A. Mark Richards
- Cardiovascular Research Institute, National University of Singapore, Singapore, Singapore
- Christchurch Heart Institute, Department of Medicine, University of Otago, Christchurch, New Zealand
| | - Choon Hwai Yap
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Gil Marom
- School of Mechanical Engineering, Tel Aviv University, Tel Aviv, Israel
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5
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Ansari M, Gandhi HA, Foster DG, White AD. Iterative Symbolic Regression for Learning Transport Equations. AIChE J 2022. [DOI: 10.1002/aic.17695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Mehrad Ansari
- Department of Chemical Engineering University of Rochester Rochester New York USA
| | - Heta A. Gandhi
- Department of Chemical Engineering University of Rochester Rochester New York USA
| | - David G. Foster
- Department of Chemical Engineering University of Rochester Rochester New York USA
| | - Andrew D. White
- Department of Chemical Engineering University of Rochester Rochester New York USA
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6
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Adventures in Heart Valve Function A Personal Thank You to Dr. Ajit P. Yoganathan. Cardiovasc Eng Technol 2021; 12:651-653. [PMID: 34145557 DOI: 10.1007/s13239-021-00555-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 06/07/2021] [Indexed: 01/19/2023]
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7
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Lantz J, Bäck S, Carlhäll CJ, Bolger A, Persson A, Karlsson M, Ebbers T. Impact of prosthetic mitral valve orientation on the ventricular flow field: Comparison using patient-specific computational fluid dynamics. J Biomech 2020; 116:110209. [PMID: 33422725 DOI: 10.1016/j.jbiomech.2020.110209] [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: 05/27/2020] [Revised: 12/10/2020] [Accepted: 12/14/2020] [Indexed: 11/29/2022]
Abstract
Significant mitral valve regurgitation creates progressive adverse remodeling of the left ventricle (LV). Replacement of the failing valve with a prosthesis generally improves patient outcomes but leaves the patient with non-physiological intracardiac flow patterns that might contribute to their future risk of thrombus formation and embolism. It has been suggested that the angular orientation of the implanted valve might modify the postoperative distortion of the intraventricular flow field. In this study, we investigated the effect of prosthetic valve orientation on LV flow patterns by using heart geometry from a patient with LV dysfunction and a competent native mitral valve to calculate intracardiac flow fields with computational fluid dynamics (CFD). Results were validated using in vivo 4D Flow MRI. The computed flow fields were compared to calculations following virtual implantation of a mechanical heart valve oriented in four different angles to assess the effect of leaflet position. Flow patterns were visualized in long- and short-axes and quantified with flow component analysis. In comparison to a native valve, valve implantation increased the proportion of the mitral inflow remaining in the basal region and further increased the residual volume in the apical area. Only slight changes due to valve orientation were observed. Using our numerical framework, we demonstrated quantitative changes in left ventricular blood flow due to prosthetic mitral replacement. This framework may be used to improve design of prosthetic heart valves and implantation procedures to minimize the potential for apical flow stasis, and potentially assist personalized treatment planning.
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Affiliation(s)
- Jonas Lantz
- Division of Cardiovascular Medicine, Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
| | - Sophia Bäck
- Division of Cardiovascular Medicine, Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
| | - Carl-Johan Carlhäll
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden; Department of Clinical Physiology in Linköping, and Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden
| | - Ann Bolger
- Department of Clinical Physiology in Linköping, and Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden; Department of Medicine, University of California, San Francisco, United States
| | - Anders Persson
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden; Division of Radiology, Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden
| | - Matts Karlsson
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden; Division of Applied Thermodynamics and Fluid Mechanics, Department of Management and Engineering, Linköping University, Sweden
| | - Tino Ebbers
- Division of Cardiovascular Medicine, Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.
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8
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Kerr MM, Gourlay T. Design and numerical simulation for the development of an expandable paediatric heart valve. Int J Artif Organs 2020; 44:518-524. [PMID: 33300423 PMCID: PMC8366171 DOI: 10.1177/0391398820977509] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Current paediatric valve replacement options cannot compensate for somatic growth, leading to an obstruction of flow as the child outgrows the prosthesis. This often necessitates an increase in revision surgeries, leading to legacy issues into adulthood. An expandable valve concept was modelled with an inverse relationship between annulus size and height, to retain the leaflet geometry without requiring additional intervention. Parametric design modelling was used to define certain valve parameter aspect ratios in relation to the base radius, Rb, including commissural radius, Rc, valve height, H and coaptation height, x. Fluid-structure simulations were subsequently carried out using the Immersed Boundary method to radially compress down the fully expanded aortic valve whilst subjecting it to diastolic and systolic loading cycles. Leaflet radial displacements were analysed to determine if valve performance is likely to be compromised following compression. Work is ongoing to optimise valvular parameter design for the paediatric patient cohort.
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Affiliation(s)
- Monica M Kerr
- Department of Biomedical Engineering, University of Strathclyde, Glasgow, UK
| | - Terence Gourlay
- Department of Biomedical Engineering, University of Strathclyde, Glasgow, UK
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9
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Pre-Operative Modeling of Transcatheter Mitral Valve Replacement in a Surgical Heart Valve Bioprosthesis. PROSTHESIS 2020. [DOI: 10.3390/prosthesis2010004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Obstruction of the left ventricular outflow tract (LVOT) is a common complication of transcatheter mitral valve replacement (TMVR). This procedure can determine an elongation of an LVOT (namely, the neo-LVOT), ultimately portending hemodynamic impairment and patient death. This study aimed to understand the biomechanical implications of LVOT obstruction in a patient who underwent TMVR using a transcatheter heart valve (THV) to repair a failed bioprosthetic heart valve. We first reconstructed the heart anatomy and the bioprosthetic heart valve to virtually implant a computer-aided-design (CAD) model of THV and evaluate the neo-LVOT area. A numerical simulation of THV deployment was then developed to assess the anchorage of the THV to the bioprosthetic heart valve as well as the resulting Von Mises stress at the mitral annulus and the contract pressure among implanted bioprostheses. Quantification of neo-LVOT and THV deployment may facilitate more accurate predictions of the LVOT obstruction in TMVR and help clinicians in the optimal choice of the THV size.
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10
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Madhurapantula RS, Krell G, Morfin B, Roy R, Lister K, Orgel JP. Advanced Methodology and Preliminary Measurements of Molecular and Mechanical Properties of Heart Valves under Dynamic Strain. Int J Mol Sci 2020; 21:E763. [PMID: 31991583 PMCID: PMC7037596 DOI: 10.3390/ijms21030763] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 01/15/2020] [Accepted: 01/21/2020] [Indexed: 11/16/2022] Open
Abstract
Mammalian heart valves are soft tissue assemblies with multi-scale material properties. This is because they are constructs comprising both muscle and non-contractile extracellular matrix proteins (such as collagens and proteoglycans) and transition regions where one form of tissue structure becomes another, significantly different form. The leaflets of the mitral and tricuspid valves are connected to chordae tendinae which, in turn, bind through papillary muscles to the cardiac wall of the ventricle. The transition regions between these tissue subsets are complex and diffuse. Their material composition and mechanical properties have not been previously described with both micro and nanoscopic data recorded simultaneously, as reported here. Annotating the mechanical characteristics of these tissue transitions will be of great value in developing novel implants, improving the state of the surgical simulators and advancing robot-assisted surgery. We present here developments in multi-scale methodology that produce data that can relate mechanical properties to molecular structure using scanning X-ray diffraction. We correlate these data to corresponding tissue level (macro and microscopic) stress and strain, with particular emphasis on the transition regions and present analyses to indicate points of possible failure in these tissues.
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Affiliation(s)
- Rama S. Madhurapantula
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA;
- Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, IL 60616, USA;
| | - Gabriel Krell
- Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, IL 60616, USA;
| | - Berenice Morfin
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA;
| | - Rajarshi Roy
- Corvid Technologies, Mooresville, NC 28117, USA; (R.R.); (K.L.)
| | - Kevin Lister
- Corvid Technologies, Mooresville, NC 28117, USA; (R.R.); (K.L.)
| | - Joseph P.R.O. Orgel
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA;
- Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, IL 60616, USA;
- Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, IL 60616, USA
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11
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Balu A, Nallagonda S, Xu F, Krishnamurthy A, Hsu MC, Sarkar S. A Deep Learning Framework for Design and Analysis of Surgical Bioprosthetic Heart Valves. Sci Rep 2019; 9:18560. [PMID: 31811244 PMCID: PMC6898064 DOI: 10.1038/s41598-019-54707-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 11/15/2019] [Indexed: 12/17/2022] Open
Abstract
Bioprosthetic heart valves (BHVs) are commonly used as heart valve replacements but they are prone to fatigue failure; estimating their remaining life directly from medical images is difficult. Analyzing the valve performance can provide better guidance for personalized valve design. However, such analyses are often computationally intensive. In this work, we introduce the concept of deep learning (DL) based finite element analysis (DLFEA) to learn the deformation biomechanics of bioprosthetic aortic valves directly from simulations. The proposed DL framework can eliminate the time-consuming biomechanics simulations, while predicting valve deformations with the same fidelity. We present statistical results that demonstrate the high performance of the DLFEA framework and the applicability of the framework to predict bioprosthetic aortic valve deformations. With further development, such a tool can provide fast decision support for designing surgical bioprosthetic aortic valves. Ultimately, this framework could be extended to other BHVs and improve patient care.
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Affiliation(s)
- Aditya Balu
- Iowa State University, Department of Mechanical Engineering, Ames, Iowa, 50011, USA
| | - Sahiti Nallagonda
- Iowa State University, Department of Mechanical Engineering, Ames, Iowa, 50011, USA
| | - Fei Xu
- Iowa State University, Department of Mechanical Engineering, Ames, Iowa, 50011, USA
| | - Adarsh Krishnamurthy
- Iowa State University, Department of Mechanical Engineering, Ames, Iowa, 50011, USA.
| | - Ming-Chen Hsu
- Iowa State University, Department of Mechanical Engineering, Ames, Iowa, 50011, USA
| | - Soumik Sarkar
- Iowa State University, Department of Mechanical Engineering, Ames, Iowa, 50011, USA
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12
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Benim AC, Frank T, Assmann A, Lichtenberg A, Akhyari P. Computational investigation of hemodynamics in hardshell venous reservoirs: A comparative study. Artif Organs 2019; 44:411-418. [PMID: 31660617 DOI: 10.1111/aor.13593] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 10/05/2019] [Accepted: 10/07/2019] [Indexed: 11/28/2022]
Abstract
Extracorporeal circulation using heart-lung-machines is associated with a profound activation of corpuscular and plasmatic components of circulating blood, which can also lead to deleterious events such as systemic inflammatory response and hemolysis. Individual components used to install the extracorporeal circulation have an impact on the level of activation, most predominantly membrane oxygenators and hardshell venous reservoirs as used in extracorporeal systems. The blood flows in two different hardshell reservoirs are computationally investigated. A special emphasis is placed on the prediction of an onset of transition and turbulence generation. Reynolds-averaged numerical simulations (RANS) based on a transitional turbulence model, as well as large eddy simulations (LES) are applied to achieve an accurate prediction. In the LES analysis, the non-Newtonian behavior of the blood is considered via the Carreau model. Blood damage potential is quantified applying the Modified Index of Hemolysis (MIH) based on the predicted flow fields. The results indicate that the flows in both reservoirs remain predominantly laminar. For one of the reservoirs, considerable turbulence generation is observed near the exit site, caused by the specific design for the connection with the drainage tube. This difference causes the MIH of this reservoir to be nearly twice as large as compared to the alternative design. However, a substantial improvement of these performance criteria can be expected by a local geometry modification.
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Affiliation(s)
- Ali Cemal Benim
- Department of Mechanical and Process Engineering, Duesseldorf University of Applied Sciences-Center of Flow Simulation (CFS), Duesseldorf, Germany
| | - Thiemo Frank
- Department of Cardiovascular Surgery, Heinrich Heine University, Duesseldorf, Germany
| | - Alexander Assmann
- Department of Cardiovascular Surgery, Heinrich Heine University, Duesseldorf, Germany
| | - Artur Lichtenberg
- Department of Cardiovascular Surgery, Heinrich Heine University, Duesseldorf, Germany
| | - Payam Akhyari
- Department of Cardiovascular Surgery, Heinrich Heine University, Duesseldorf, Germany
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13
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Biomechanical modeling of transcatheter aortic valve replacement in a stenotic bicuspid aortic valve: deployments and paravalvular leakage. Med Biol Eng Comput 2019; 57:2129-2143. [PMID: 31372826 DOI: 10.1007/s11517-019-02012-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 07/08/2019] [Indexed: 12/17/2022]
Abstract
Calcific aortic valve disease (CAVD) is characterized by stiffened aortic valve leaflets. Bicuspid aortic valve (BAV) is the most common congenital heart disease. Transcatheter aortic valve replacement (TAVR) is a treatment approach for CAVD where a stent with mounted bioprosthetic valve is deployed on the stenotic valve. Performing TAVR in calcified BAV patients may be associated with post-procedural complications due to the BAV asymmetrical structure. This study aims to develop refined computational models simulating the deployments of Evolut R and PRO TAVR devices in a representative calcified BAV. The paravalvular leakage (PVL) was also calculated by computational fluid dynamics simulations. Computed tomography scan of severely stenotic BAV patient was acquired. The 3D calcium deposits were generated and embedded inside a parametric model of the BAV. Deployments of the Evolut R and PRO inside the calcified BAV were simulated in five bioprosthesis leaflet orientations. The hypothesis of asymmetric and elliptic stent deployment was confirmed. Positioning the bioprosthesis commissures aligned with the native commissures yielded the lowest PVL (15.7 vs. 29.5 mL/beat). The Evolut PRO reduced the PVL in half compared with the Evolut R (15.7 vs. 28.7 mL/beat). The proposed biomechanical computational model could optimize future TAVR treatment in BAV patients. Graphical abstract.
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14
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Sacks M, Drach A, Lee CH, Khalighi A, Rego B, Zhang W, Ayoub S, Yoganathan A, Gorman RC, Gorman Iii JH. On the simulation of mitral valve function in health, disease, and treatment. J Biomech Eng 2019; 141:2731932. [PMID: 31004145 PMCID: PMC6611349 DOI: 10.1115/1.4043552] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 03/26/2019] [Indexed: 12/19/2022]
Abstract
The mitral valve (MV) is the heart valve that regulates blood ?ow between the left atrium and left ventricle (LV). In situations where the MV fails to fully cover the left atrioventricular ori?ce during systole, the resulting regurgitation causes pulmonary congestion, leading to heart failure and/or stroke. The causes of MV insuf?ciency can be either primary (e.g. myxomatous degeneration) where the valvular tissue is organically diseased, or secondary (typically inducded by ischemic cardiomyopathy) termed ischemic mitral regurgitation (IMR), is brought on by adverse LV remodeling. IMR is present in up to 40% of patients and more than doubles the probability of cardiovascular morbidity after 3.5 years. There is now agreement that adjunctive procedures are required to treat IMR caused by lea?et tethering. However, there is no consensus regarding the best procedure. Multicenter registries and randomized trials would be necessary to prove which procedure is superior. Given the number of proposed procedures and the complexity and duration of such studies, it is highly unlikely that IMR procedure optimization will be achieved by prospective clinical trials. There is thus an urgent need for cell and tissue physiologically based quantitative assessments of MV function to better design surgical solutions and associated therapies. Novel computational approaches directed towards optimized surgical repair procedures can substantially reduce the need for such trial-and-error approaches. We present the details of our MV modeling techniques, with an emphasis on what is known and investigated at various length scales.
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Affiliation(s)
- Michael Sacks
- aWillerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX
| | - Andrew Drach
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX
| | - Chung-Hao Lee
- Department of Mechanical and Aerospace Engineering, University of Oklahoma, Norman, OK
| | - Amir Khalighi
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX
| | - Bruno Rego
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX
| | - Will Zhang
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX
| | - Salma Ayoub
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX
| | - Ajit Yoganathan
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA
| | - Robert C Gorman
- Gorman Cardiovascular Research Group, Department of Surgery, University of Pennsylvania, Philadelphia, PA
| | - Joseph H Gorman Iii
- Gorman Cardiovascular Research Group, Department of Surgery, University of Pennsylvania, Philadelphia, PA
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15
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Joda A, Jin Z, Summers J, Korossis S. Comparison of a fixed-grid and arbitrary Lagrangian–Eulerian methods on modelling fluid–structure interaction of the aortic valve. Proc Inst Mech Eng H 2019; 233:544-553. [DOI: 10.1177/0954411919837568] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This study was aimed at assessing the robustness of a fixed-grid fluid–structure interaction method (Multi-Material Arbitrary Lagrangian–Eulerian) to modelling the two-dimensional native aortic valve dynamics and comparing it to the Arbitrary Lagrangian–Eulerian method. For the fixed-grid method, the explicit finite element solver LS-DYNA was utilized, where two independent meshes for the fluid and structure were generated and the penalty method was used to handle the coupling between the fluid and structure domains. For the Arbitrary Lagrangian–Eulerian method, the implicit finite element solver ADINA was used where two separate conforming meshes were used for the valve structure and the fluid domains. The comparison demonstrated that both fluid–structure interaction methods predicted accurately the valve dynamics, fluid flow, and stress distribution, implying that fixed-grid methods can be used in situations where the Arbitrary Lagrangian–Eulerian method fails.
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Affiliation(s)
- Akram Joda
- Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
- Cardiopulmonary Regenerative Engineering (CARE) Group, The Centre for Biological Engineering (CBE), Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, UK
| | - Zhongmin Jin
- Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
- State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, China
| | - Jon Summers
- Institute of Engineering Thermofluids, Surface and Interfaces, University of Leeds, Leeds, UK
| | - Sotirios Korossis
- Cardiopulmonary Regenerative Engineering (CARE) Group, The Centre for Biological Engineering (CBE), Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, UK
- Department of Cardiothoracic, Transplantation and Vascular Surgery, Hannover Medical School, Hannover, Germany
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16
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Assessing the Thrombogenic Potential of Heart Valve Prostheses: An Approach for a Standardized In-Vitro Method. Cardiovasc Eng Technol 2019; 10:216-224. [DOI: 10.1007/s13239-019-00408-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 02/23/2019] [Indexed: 10/27/2022]
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17
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Adverse Hemodynamic Conditions Associated with Mechanical Heart Valve Leaflet Immobility. Bioengineering (Basel) 2018; 5:bioengineering5030074. [PMID: 30223603 PMCID: PMC6165326 DOI: 10.3390/bioengineering5030074] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 09/08/2018] [Accepted: 09/10/2018] [Indexed: 11/16/2022] Open
Abstract
Artificial heart valves may dysfunction, leading to thrombus and/or pannus formations. Computational fluid dynamics is a promising tool for improved understanding of heart valve hemodynamics that quantify detailed flow velocities and turbulent stresses to complement Doppler measurements. This combined information can assist in choosing optimal prosthesis for individual patients, aiding in the development of improved valve designs, and illuminating subtle changes to help guide more timely early intervention of valve dysfunction. In this computational study, flow characteristics around a bileaflet mechanical heart valve were investigated. The study focused on the hemodynamic effects of leaflet immobility, specifically, where one leaflet does not fully open. Results showed that leaflet immobility increased the principal turbulent stresses (up to 400%), and increased forces and moments on both leaflets (up to 600% and 4000%, respectively). These unfavorable conditions elevate the risk of blood cell damage and platelet activation, which are known to cascade to more severe leaflet dysfunction. Leaflet immobility appeared to cause maximal velocity within the lateral orifices. This points to the possible importance of measuring maximal velocity at the lateral orifices by Doppler ultrasound (in addition to the central orifice, which is current practice) to determine accurate pressure gradients as markers of valve dysfunction.
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18
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Study on the Accuracy of Structural and FSI Heart Valves Simulations. Cardiovasc Eng Technol 2018; 9:723-738. [DOI: 10.1007/s13239-018-00373-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 08/11/2018] [Indexed: 12/29/2022]
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19
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Defining the breaking point: Benefits and pitfalls of modeling long-term durability of a third-generation transcatheter valve in an era of short-term data. J Thorac Cardiovasc Surg 2018; 157:538-539. [PMID: 29941163 DOI: 10.1016/j.jtcvs.2018.05.051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Revised: 05/12/2018] [Accepted: 05/14/2018] [Indexed: 11/24/2022]
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20
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Cardiovascular tissue engineering: From basic science to clinical application. Exp Gerontol 2018; 117:1-12. [PMID: 29604404 DOI: 10.1016/j.exger.2018.03.022] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 03/26/2018] [Indexed: 12/20/2022]
Abstract
Valvular heart disease is an increasing population health problem and, especially in the elderly, a significant cause of morbidity and mortality. The current treatment options, such as mechanical and bioprosthetic heart valve replacements, have significant restrictions and limitations. Considering the increased life expectancy of our aging population, there is an urgent need for novel heart valve concepts that remain functional throughout life to prevent the need for reoperation. Heart valve tissue engineering aims to overcome these constraints by creating regenerative, self-repairing valve substitutes with life-long durability. In this review, we give an overview of advances in the development of tissue engineered heart valves, and describe the steps required to design and validate a novel valve prosthesis before reaching first-in-men clinical trials. In-silico and in-vitro models are proposed as tools for the assessment of valve design, functionality and compatibility, while in-vivo preclinical models are required to confirm the remodeling and growth potential of the tissue engineered heart valves. An overview of the tissue engineered heart valve studies that have reached clinical translation is also presented. Final remarks highlight the possibilities as well as the obstacles to overcome in translating heart valve prostheses into clinical application.
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21
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Kamensky D, Xu F, Lee CH, Yan J, Bazilevs Y, Hsu MC. A contact formulation based on a volumetric potential: Application to isogeometric simulations of atrioventricular valves. COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2018; 330:522-546. [PMID: 29736092 PMCID: PMC5935269 DOI: 10.1016/j.cma.2017.11.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
This work formulates frictionless contact between solid bodies in terms of a repulsive potential energy term and illustrates how numerical integration of the resulting forces is computationally similar to the "pinball algorithm" proposed and studied by Belytschko and collaborators in the 1990s. We thereby arrive at a numerical approach that has both the theoretical advantages of a potential-based formulation and the algorithmic simplicity, computational efficiency, and geometrical versatility of pinball contact. The singular nature of the contact potential requires a specialized nonlinear solver and an adaptive time stepping scheme to ensure reliable convergence of implicit dynamic calculations. We illustrate the effectiveness of this numerical method by simulating several benchmark problems and the structural mechanics of the right atrioventricular (tricuspid) heart valve. Atrioventricular valve closure involves contact between every combination of shell surfaces, edges of shells, and cables, but our formulation handles all contact scenarios in a unified manner. We take advantage of this versatility to demonstrate the effects of chordal rupture on tricuspid valve coaptation behavior.
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Affiliation(s)
- David Kamensky
- Department of Structural Engineering, University of California, San Diego, La Jolla, CA 92093, USA
- Corresponding author: (David Kamensky)
| | - Fei Xu
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA
| | - Chung-Hao Lee
- School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA
| | - Jinhui Yan
- Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Yuri Bazilevs
- Department of Structural Engineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Ming-Chen Hsu
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA
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22
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Drach A, Khalighi AH, Sacks MS. A comprehensive pipeline for multi-resolution modeling of the mitral valve: Validation, computational efficiency, and predictive capability. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2018; 34:10.1002/cnm.2921. [PMID: 28776326 PMCID: PMC5797517 DOI: 10.1002/cnm.2921] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/26/2017] [Accepted: 07/28/2017] [Indexed: 05/18/2023]
Abstract
Multiple studies have demonstrated that the pathological geometries unique to each patient can affect the durability of mitral valve (MV) repairs. While computational modeling of the MV is a promising approach to improve the surgical outcomes, the complex MV geometry precludes use of simplified models. Moreover, the lack of complete in vivo geometric information presents significant challenges in the development of patient-specific computational models. There is thus a need to determine the level of detail necessary for predictive MV models. To address this issue, we have developed a novel pipeline for building attribute-rich computational models of MV with varying fidelity directly from the in vitro imaging data. The approach combines high-resolution geometric information from loaded and unloaded states to achieve a high level of anatomic detail, followed by mapping and parametric embedding of tissue attributes to build a high-resolution, attribute-rich computational models. Subsequent lower resolution models were then developed and evaluated by comparing the displacements and surface strains to those extracted from the imaging data. We then identified the critical levels of fidelity for building predictive MV models in the dilated and repaired states. We demonstrated that a model with a feature size of about 5 mm and mesh size of about 1 mm was sufficient to predict the overall MV shape, stress, and strain distributions with high accuracy. However, we also noted that more detailed models were found to be needed to simulate microstructural events. We conclude that the developed pipeline enables sufficiently complex models for biomechanical simulations of MV in normal, dilated, repaired states.
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Affiliation(s)
- Andrew Drach
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Amir H Khalighi
- 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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23
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Khalighi AH, Drach A, Gorman RC, Gorman JH, Sacks MS. Multi-resolution geometric modeling of the mitral heart valve leaflets. Biomech Model Mechanobiol 2017; 17:351-366. [PMID: 28983742 DOI: 10.1007/s10237-017-0965-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 09/18/2017] [Indexed: 10/18/2022]
Abstract
An essential element of cardiac function, the mitral valve (MV) ensures proper directional blood flow between the left heart chambers. Over the past two decades, computational simulations have made marked advancements toward providing powerful predictive tools to better understand valvular function and improve treatments for MV disease. However, challenges remain in the development of robust means for the quantification and representation of MV leaflet geometry. In this study, we present a novel modeling pipeline to quantitatively characterize and represent MV leaflet surface geometry. Our methodology utilized a two-part additive decomposition of the MV geometric features to decouple the macro-level general leaflet shape descriptors from the leaflet fine-scale features. First, the general shapes of five ovine MV leaflets were modeled using superquadric surfaces. Second, the finer-scale geometric details were captured, quantified, and reconstructed via a 2D Fourier analysis with an additional sparsity constraint. This spectral approach allowed us to easily control the level of geometric details in the reconstructed geometry. The results revealed that our methodology provided a robust and accurate approach to develop MV-specific models with an adjustable level of spatial resolution and geometric detail. Such fully customizable models provide the necessary means to perform computational simulations of the MV at a range of geometric accuracies in order to identify the level of complexity required to achieve predictive MV simulations.
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Affiliation(s)
- Amir H Khalighi
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Andrew Drach
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Robert C Gorman
- Gorman Cardiovascular Research Group, Department of Surgery, University of Pennsylvania, Philadelphia, PA, USA
| | - Joseph H Gorman
- Gorman Cardiovascular Research Group, Department of Surgery, University of Pennsylvania, Philadelphia, PA, 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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24
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Gao H, Qi N, Feng L, Ma X, Danton M, Berry C, Luo X. Modelling mitral valvular dynamics-current trend and future directions. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33:e2858. [PMID: 27935265 PMCID: PMC5697636 DOI: 10.1002/cnm.2858] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 09/30/2016] [Accepted: 11/26/2016] [Indexed: 05/19/2023]
Abstract
Dysfunction of mitral valve causes morbidity and premature mortality and remains a leading medical problem worldwide. Computational modelling aims to understand the biomechanics of human mitral valve and could lead to the development of new treatment, prevention and diagnosis of mitral valve diseases. Compared with the aortic valve, the mitral valve has been much less studied owing to its highly complex structure and strong interaction with the blood flow and the ventricles. However, the interest in mitral valve modelling is growing, and the sophistication level is increasing with the advanced development of computational technology and imaging tools. This review summarises the state-of-the-art modelling of the mitral valve, including static and dynamics models, models with fluid-structure interaction, and models with the left ventricle interaction. Challenges and future directions are also discussed.
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Affiliation(s)
- Hao Gao
- School of Mathematics and StatisticsUniversity of GlasgowUK
| | - Nan Qi
- School of Mathematics and StatisticsUniversity of GlasgowUK
| | - Liuyang Feng
- School of Mathematics and StatisticsUniversity of GlasgowUK
| | | | - Mark Danton
- Department of Cardiac SurgeryRoyal Hospital for ChildrenGlasgowUK
| | - Colin Berry
- Institute of Cardiovascular and Medical SciencesUniversity of GlasgowUK
| | - Xiaoyu Luo
- School of Mathematics and StatisticsUniversity of GlasgowUK
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25
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Vukicevic M, Vekilov DP, Grande-Allen JK, Little SH. Patient-specific 3D Valve Modeling for Structural Intervention. STRUCTURAL HEART-THE JOURNAL OF THE HEART TEAM 2017. [DOI: 10.1080/24748706.2017.1377363] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Marija Vukicevic
- Department of Cardiology, Methodist DeBakey Heart & Vascular Center, Houston Methodist Hospital, Houston, Texas, USA
| | | | | | - Stephen H. Little
- Department of Cardiology, Methodist DeBakey Heart & Vascular Center, Houston Methodist Hospital, Houston, Texas, USA
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26
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Subhash NN, Rajeev A, Sujesh S, Muraleedharan CV. TTK Chitra tilting disc heart valve model TC2: An assessment of fatigue life and durability. Proc Inst Mech Eng H 2017; 231:758-765. [DOI: 10.1177/0954411917703676] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Average age group of heart valve replacement in India and most of the Third World countries is below 30 years. Hence, the valve for such patients need to be designed to have a service life of 50 years or more which corresponds to 2000 million cycles of operation. The purpose of this study was to assess the structural performance of the TTK Chitra tilting disc heart valve model TC2 and thereby address its durability. The TC2 model tilting disc heart valves were assessed to evaluate the risks connected with potential structural failure modes. To be more specific, the studies covered the finite element analysis–based fatigue life prediction and accelerated durability testing of the tilting disc heart valves for nine different valve sizes. First, finite element analysis–based fatigue life prediction showed that all nine valve sizes were in the infinite life region. Second, accelerated durability test showed that all nine valve sizes remained functional for 400 million cycles under experimental conditions. The study ensures the continued function of TC2 model tilting disc heart valves over duration in excess of 50 years. The results imply that the TC2 model valve designs are structurally safe, reliable and durable.
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Affiliation(s)
- NN Subhash
- Department of Medical Devices Engineering, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - Adathala Rajeev
- Department of Medical Devices Engineering, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - Sreedharan Sujesh
- Department of Medical Devices Engineering, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - CV Muraleedharan
- Department of Medical Devices Engineering, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
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27
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Review of numerical methods for simulation of mechanical heart valves and the potential for blood clotting. Med Biol Eng Comput 2017; 55:1519-1548. [DOI: 10.1007/s11517-017-1688-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 07/10/2017] [Indexed: 11/26/2022]
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28
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Cao K, Sucosky P. Computational comparison of regional stress and deformation characteristics in tricuspid and bicuspid aortic valve leaflets. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33:e02798. [PMID: 27138991 DOI: 10.1002/cnm.2798] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 03/22/2016] [Accepted: 04/20/2016] [Indexed: 06/05/2023]
Abstract
The bicuspid aortic valve (BAV) is the most common congenital valvular defect and a major risk factor for secondary calcific aortic valve disease. While hemodynamics is presumed to be a potential contributor to this complication, the validation of this theory has been hampered by the limited knowledge of the mechanical stress abnormalities experienced by BAV leaflets and their dependence on the heterogeneous BAV fusion patterns. The objective of this study was to compare computationally the regional and temporal fluid wall shear stress (WSS) and structural deformation characteristics in tricuspid aortic valve (TAV), type-0, and type-I BAV leaflets. Arbitrary Lagrangian-Eulerian fluid-structure interaction models were designed to simulate the flow and leaflet dynamics in idealized TAV, type-0, and type-I BAV geometries subjected to physiologic transvalvular pressure. The regional leaflet mechanics was quantified in terms of temporal shear magnitude (TSM), oscillatory shear index (OSI), temporal shear gradient (TSG), and stretch. The simulations identified regions of WSS overloads and increased WSS bidirectionality (174% increase in temporal shear magnitude, 0.10 increase in OSI on type-0 leaflets) in BAV leaflets relative to TAV leaflets. BAV leaflets also experienced larger radial deformations than TAV leaflets (4% increase in type-0 BAV leaflets). Type-I BAV leaflets exhibited contrasted WSS environments marked by WSS overloads on the non-coronary leaflet and sub-physiologic WSS levels on the fused leaflet. This study provides important insights into the mechanical characteristics of BAV leaflets, which may further our understanding of the role played by hemodynamic forces in BAV disease. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- K Cao
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, 365 Fitzpatrick Hall, Notre Dame, IN, 46556, USA
| | - P Sucosky
- Department of Mechanical and Materials Engineering, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH, 45435, USA
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29
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Hanafizadeh P, Mirkhani N, Davoudi MR, Masouminia M, Sadeghy K. Non-Newtonian Blood Flow Simulation of Diastolic Phase in Bileaflet Mechanical Heart Valve Implanted in a Realistic Aortic Root Containing Coronary Arteries. Artif Organs 2017; 40:E179-E191. [PMID: 27739601 DOI: 10.1111/aor.12787] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Revised: 04/22/2016] [Accepted: 05/17/2016] [Indexed: 11/28/2022]
Abstract
Coronary arteries, which are branched from the sinuses, have tangible effects on the hemodynamic performance of the bileaflet mechanical heart valve (BMHV), especially in the diastolic phase. To better understand this issue, a computer model of ascending aorta including realistic sinus shapes and coronary arteries has been generated in this study in order to investigate the BMHV performance during diastole. Three-dimensional transient numerical analysis is conducted to simulate the diastolic blood flow through the hinges and in coronary arteries under the assumption of non-Newtonian behavior. Results indicate that as blood flows to the coronary arteries mainly during diastole, leakage flow from the hinge and other gaps will change considering the influence of coronary arteries. In addition, BMHV in the case of aortic replacement will increase blood flow rate into the coronary arteries about 100% as the mechanical valve resistance is higher than a native heart valve. Also, it will change the wall shear stress (WSS) distribution and increase coronary artery disease (CAD) potential. It is found out that although less leakage flow reduces the velocity magnitudes through the gaps, the shear stress acting on blood elements with non-Newtonian assumption will be detrimental in the hinge corner at the ventricular side. High WSS of 1800 Pa is observed at beginning of diastole at this region.
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Affiliation(s)
- Pedram Hanafizadeh
- Center of Excellence in Design and Optimization of Energy Systems, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
| | - Nima Mirkhani
- Center of Excellence in Design and Optimization of Energy Systems, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
| | | | - Mahtab Masouminia
- Center of Excellence in Design and Optimization of Energy Systems, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
| | - Keyvan Sadeghy
- Center of Excellence in Design and Optimization of Energy Systems, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
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30
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Gilmanov A, Stolarski H, Sotiropoulos F. Non-linear rotation-free shell finite-element models for aortic heart valves. J Biomech 2016; 50:56-62. [PMID: 27876370 DOI: 10.1016/j.jbiomech.2016.11.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 11/02/2016] [Indexed: 10/20/2022]
Abstract
Hyperelastic material models have been incorporated in the rotation-free, large deformation, shell finite element (FE) formulation of (Stolarski et al., 2013) and applied to dynamic simulations of aortic heart valve. Two models used in the past in analysis of such problem i.e. the Saint-Venant and May-Newmann-Yin (MNY) material models have been considered and compared. Uniaxial tests for those constitutive equations were performed to verify the formulation and implementation of the models. The issue of leaflets interactions during the closing of the heart valve at the end of systole is considered. The critical role of using non-linear anisotropic model for proper dynamic response of the heart valve especially during the closing phase is demonstrated quantitatively. This work contributes an efficient FE framework for simulating biological tissues and paves the way for high-fidelity flow structure interaction simulations of native and bioprosthetic aortic heart valves.
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Affiliation(s)
- Anvar Gilmanov
- Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414, United States
| | - Henryk Stolarski
- Department of Civil, Environment and Geo-Engineering, University of Minnesota, Minneapolis, MN 55414, United States
| | - Fotis Sotiropoulos
- College of Engineering and Applied Sciences, Stony Brook University, Stony Brook, NY 11794-2200, United States.
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31
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Gunning PS, Saikrishnan N, Yoganathan AP, McNamara LM. Total ellipse of the heart valve: the impact of eccentric stent distortion on the regional dynamic deformation of pericardial tissue leaflets of a transcatheter aortic valve replacement. J R Soc Interface 2016; 12:20150737. [PMID: 26674192 DOI: 10.1098/rsif.2015.0737] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Transcatheter aortic valve replacements (TAVRs) are a percutaneous alternative to surgical aortic valve replacements and are used to treat patients with aortic valve stenosis. This minimally invasive procedure relies on expansion of the TAVR stent to radially displace calcified aortic valve leaflets against the aortic root wall. However, these calcium deposits can impede the expansion of the device causing distortion of the valve stent and pericardial tissue leaflets. The objective of this study was to elucidate the impact of eccentric TAVR stent distortion on the dynamic deformation of the tissue leaflets of the prosthesis in vitro. Dual-camera stereophotogrammetry was used to measure the regional variation in strain in a leaflet of a TAVR deployed in nominal circular and eccentric (eccentricity index = 28%) orifices, representative of deployed TAVRs in vivo. It was observed that (i) eccentric stent distortion caused incorrect coaptation of the leaflets at peak diastole resulting in a 'peel-back' leaflet geometry that was not present in the circular valve and (ii) adverse bending of the leaflet, arising in the eccentric valve at peak diastole, caused significantly higher commissure strains compared with the circular valve in both normotensive and hypertensive pressure conditions (normotension: eccentric = 13.76 ± 2.04% versus circular = 11.77 ± 1.61%, p = 0.0014, hypertension: eccentric = 15.07 ± 1.13% versus circular = 13.56 ± 0.87%, p = 0.0042). This study reveals that eccentric distortion of a TAVR stent can have a considerable impact on dynamic leaflet deformation, inducing deleterious bending of the leaflet and increasing commissures strains, which might expedite leaflet structural failure compared to leaflets in a circular deployed valve.
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Affiliation(s)
- Paul S Gunning
- Biomechanics Research Centre, Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Republic of Ireland
| | - Neelakantan Saikrishnan
- Cardiovascular Fluid Mechanics Laboratory, Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Ajit P Yoganathan
- Cardiovascular Fluid Mechanics Laboratory, Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Laoise M McNamara
- Biomechanics Research Centre, Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Republic of Ireland
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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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On-X Heart Valve Prosthesis: Numerical Simulation of Hemodynamic Performance in Accelerating Systole. Cardiovasc Eng Technol 2016; 7:223-37. [PMID: 27164902 DOI: 10.1007/s13239-016-0265-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 04/26/2016] [Indexed: 10/21/2022]
Abstract
Numerical simulation of the bileaflet mechanical heart valves (BMHVs) has been of interest for many researchers due to its capability of predicting hemodynamic performance. A lot of studies have tried to simulate this three-dimensional complex flow in order to analyze the effect of different valve designs on the blood flow pattern. However, simplified models and prescribed motion for the leaflets were utilized. In this paper, transient complex blood flow in the location of ascending aorta has been investigated in a realistic model by fully coupled simulation. Geometry model for the aorta and the replaced valve is constructed based on the medical images and extracted point clouds. A 23-mm On-X Medical BMHV as the new generation design has been selected for the flow field analysis. The two-way coupling simulation is conducted throughout the accelerating phase in order to obtain valve dynamics in the opening process. The complex flow field in the hinge recess is captured precisely for all leaflet positions and recirculating zones and elevated shear stress areas have been observed. Results indicate that On-X valve yields relatively less transvalvular pressure gradient which would lower cardiac external work. Furthermore, converging inlet leads to a more uniform flow and consequently less turbulent eddies. However, the leaflets cannot open fully due to middle diffuser-shaped orifice. In addition, asymmetric butterfly-shaped hinge design and converging orifice leads to better hemodynamic performance. With the help of two-way fluid solid interaction simulation, leaflet angle follows the experimental trends more precisely rather than the prescribed motion in previous 3D simulations.
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Rim Y, McPherson DD, Kim H. Effect of Congenital Anomalies of the Papillary Muscles on Mitral Valve Function. J Med Biol Eng 2015; 35:104-112. [PMID: 25750606 PMCID: PMC4342526 DOI: 10.1007/s40846-015-0011-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 04/24/2014] [Indexed: 11/29/2022]
Abstract
Parachute mitral valves (PMVs) and parachute-like asymmetric mitral valves (PLAMVs) are associated with congenital anomalies of the papillary muscles. Current imaging modalities cannot provide detailed biomechanical information. This study describes computational evaluation techniques based on three-dimensional (3D) echocardiographic data to determine the biomechanical and physiologic characteristics of PMVs and PLAMVs. The closing and opening mechanics of a normal mitral valve (MV), two types of PLAMV with different degrees of asymmetry, and a true PMV were investigated. MV geometric data in a patient with a normal MV was acquired from 3D echocardiography. The pathologic MVs were modeled by altering the configuration of the papillary muscles in the normal MV model. Dynamic finite element simulations of the normal MV, PLAMVs, and true PMV were performed. There was a strong correlation between the reduction of mitral orifice size and the degree of asymmetry of the papillary muscle location. The PLAMVs demonstrated decreased leaflet coaptation and tenting height. The true PMV revealed severely wrinkled leaflet deformation and narrowed interchordal spaces, leading to uneven leaflet coaptation. There were considerable decreases in leaflet coaptation and abnormal leaflet deformation corresponding to the anomalous location of the papillary muscle tips. This computational MV evaluation strategy provides a powerful tool to better understand biomechanical and pathophysiologic MV abnormalities.
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Affiliation(s)
- Yonghoon Rim
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, 6431 Fannin St, MSB 1.246, Houston, TX 77030 USA
| | - David D McPherson
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, 6431 Fannin St, MSB 1.246, Houston, TX 77030 USA
| | - Hyunggun Kim
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, 6431 Fannin St, MSB 1.246, Houston, TX 77030 USA
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Abstract
In the past two decades, major advances have been made in the clinical evaluation and treatment of valvular heart disease owing to the advent of noninvasive cardiac imaging modalities. In clinical practice, valvular disease evaluation is typically performed on two-dimensional (2D) images, even though most imaging modalities offer three-dimensional (3D) volumetric, time-resolved data. Such 3D data offer researchers the possibility to reconstruct the 3D geometry of heart valves at a patient-specific level. When these data are integrated with computational models, native heart valve biomechanical function can be investigated, and preoperative planning tools can be developed. In this review, we outline the advances in valve geometry reconstruction, tissue property modeling, and loading and boundary definitions for the purpose of realistic computational structural analysis of cardiac valve function and intervention.
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Affiliation(s)
- Wei Sun
- Tissue Mechanics Lab, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30313;
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Rim Y, McPherson DD, Kim H. Effect of leaflet-to-chordae contact interaction on computational mitral valve evaluation. Biomed Eng Online 2014; 13:31. [PMID: 24649999 PMCID: PMC3976553 DOI: 10.1186/1475-925x-13-31] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 03/17/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Computational simulation using numerical analysis methods can help to assess the complex biomechanical and functional characteristics of the mitral valve (MV) apparatus. It is important to correctly determine physical contact interaction between the MV apparatus components during computational MV evaluation. We hypothesize that leaflet-to-chordae contact interaction plays an important role in computational MV evaluation, specifically in quantitating the degree of leaflet coaptation directly related to the severity of mitral regurgitation (MR). In this study, we have performed dynamic finite element simulations of MV function with and without leaflet-to-chordae contact interaction, and determined the effect of leaflet-to-chordae contact interaction on the computational MV evaluation. METHODS Computational virtual MV models were created using the MV geometric data in a patient with normal MV without MR and another with pathologic MV with MR obtained from 3D echocardiography. Computational MV simulation with full contact interaction was specified to incorporate entire physically available contact interactions between the leaflets and chordae tendineae. Computational MV simulation without leaflet-to-chordae contact interaction was specified by defining the anterior and posterior leaflets as the only contact inclusion. RESULTS Without leaflet-to-chordae contact interaction, the computational MV simulations demonstrated physically unrealistic contact interactions between the leaflets and chordae. With leaflet-to-chordae contact interaction, the anterior marginal chordae retained the proper contact with the posterior leaflet during the entire systole. The size of the non-contact region in the simulation with leaflet-to-chordae contact interaction was much larger than for the simulation with only leaflet-to-leaflet contact. CONCLUSIONS We have successfully demonstrated the effect of leaflet-to-chordae contact interaction on determining leaflet coaptation in computational dynamic MV evaluation. We found that physically realistic contact interactions between the leaflets and chordae should be considered to accurately quantitate leaflet coaptation for MV simulation. Computational evaluation of MV function that allows precise quantitation of leaflet coaptation has great potential to better quantitate the severity of MR.
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Affiliation(s)
| | | | - Hyunggun Kim
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA.
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Nobari S, Mongrain R, Leask R, Cartier R. The effect of aortic wall and aortic leaflet stiffening on coronary hemodynamic: a fluid-structure interaction study. Med Biol Eng Comput 2013; 51:923-36. [PMID: 23549924 DOI: 10.1007/s11517-013-1066-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 03/16/2013] [Indexed: 12/22/2022]
Abstract
Pathologies of the aortic valve such as aortic sclerosis are thought to impact coronary blood flow. Recent clinical investigations have observed simultaneous structural and hemodynamic variations in the aortic valve and coronary arteries due to regional pathologies of the aortic valve. The goal of the present study is to elucidate this observed and yet unexplained phenomenon, in which a local pathology in the aortic valve region could potentially lead to the initiation or progression of coronary artery disease. Results revealed a considerable impact on the coronary flow, velocity profile, and consequently shear stress due to an increase in the aortic wall or aortic leaflet stiffness and thickness which concur with clinical observations. The cutoff value of 0.75 for fractional flow reserve was reached when the values of leaflet thickness and aortic wall stiffness were approximately twice and three times their normal value, respectively. Variations observed in coronary velocity profiles as well as wall shear stress suggest a possible link for the initiation of coronary artery disease.
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Affiliation(s)
- S Nobari
- Department of Biomedical Engineering, McGill University, Montreal, QC, Canada.
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Marom G, Haj-Ali R, Raanani E, Schäfers HJ, Rosenfeld M. A fluid-structure interaction model of the aortic valve with coaptation and compliant aortic root. Med Biol Eng Comput 2011; 50:173-82. [PMID: 22170305 DOI: 10.1007/s11517-011-0849-5] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 12/03/2011] [Indexed: 11/30/2022]
Abstract
While aortic valve root compliance and leaflet coaptation have significant influence on valve closure, their implications have not yet been fully evaluated. The present study developed a full fluid-structure interaction (FSI) model that is able to cope with arbitrary coaptation between the leaflets of the aortic valve during the closing phase. Two simplifications were also evaluated for the simulation of the closing phase only. One employs an FSI model with a rigid root and the other uses a "dry" (without flow) model. Numerical tests were performed to verify the model. New metrics were defined to process the results in terms of leaflet coaptation area and contact pressure. The axial displacement of the leaflets, closure time and coaptation parameters were similar in the two FSI models, whereas the dry model, with imposed uniform load on the leaflets, produced larger coaptation area and contact pressure, larger axial displacement and faster closure time compared with the FSI model. The differences were up to 30% in the coaptation area, 55% in the contact pressure and 170% in the closure time. Consequently, an FSI model should be used to accurately resolve the kinematics of the aortic valve and leaflet coaptation details during the end-closing stage.
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Affiliation(s)
- Gil Marom
- The Fleischman Faculty of Engineering, School of Mechanical Engineering, Tel Aviv University, Ramat Aviv, 69978 Tel Aviv, Israel.
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Effect of Geometry on the Leaflet Stresses in Simulated Models of Congenital Bicuspid Aortic Valves. Cardiovasc Eng Technol 2011; 2:48-56. [PMID: 21980326 DOI: 10.1007/s13239-011-0035-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The aim of the study was to assess the effect of geometric variations on the stresses developed in the leaflets of congenital bicuspid aortic valves (CBAV). We developed a model for the human tri-leaflet aortic valve based on the geometry and dimensions published in the literature. We also developed simulated CBAV geometry based on the most common geometry present in patients with CBAV that is published in the literature. We employed a constitutive relationship for the leaflet material from the previously published experimental data of fresh porcine aortic valve leaflet specimens for the analysis. We performed dynamic finite element (FE) structural analysis of the valves in the aortic position in order to compute the strain and stress distribution on the leaflets of the tri-leaflet valve and the CBAV models. Our results showed that large changes in the computed in-plane leaflet strain and stress occurred with variations in the geometry of the simulated CBAV whereas changes due to alterations in material constants were correspondingly less. The valve orifice area in the fully open position was significantly reduced in CBAV compared to that for the tri-leaflet valve. The changes in geometry of CBAV resulted in large changes in in-plane strain and stress and our results suggest that geometrical variations may be a potential risk factor inducing calcific aortic stenosis frequently present in patients with CBAV.
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