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Fitzpatrick DJ, Pham K, Ross CJ, Hudson LT, Laurence DW, Yu Y, Lee CH. Ex vivo experimental characterizations for understanding the interrelationship between tissue mechanics and collagen microstructure of porcine mitral valve leaflets. J Mech Behav Biomed Mater 2022; 134:105401. [DOI: 10.1016/j.jmbbm.2022.105401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 07/18/2022] [Accepted: 07/24/2022] [Indexed: 12/13/2022]
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2
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Jazwiec T, Malinowski MJ, Ferguson H, Parker J, Mathur M, Rausch MK, Timek TA. Tricuspid Valve Anterior Leaflet Strains in Ovine Functional Tricuspid Regurgitation. Semin Thorac Cardiovasc Surg 2020; 33:356-364. [PMID: 32977016 DOI: 10.1053/j.semtcvs.2020.09.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Accepted: 09/08/2020] [Indexed: 01/31/2023]
Abstract
Functional tricuspid regurgitation (FTR) is thought to arise due to annular dilation and alteration of right ventricular (RV) geometry in the presence of normal leaflets, yet mitral leaflets have been shown to remodel significantly in functional mitral regurgitation. We set out to evaluate tricuspid valve anterior leaflet deformations in ovine FTR. Eleven animals (FTR group) underwent implantation of a pacemaker with high rate pacing to induce biventricular dysfunction and at least moderate TR. Subsequently, both FTR (n = 11) and Control (n = 12) animals underwent implantation of 6 sonomicrometry crystals around the tricuspid annulus, 4 on the anterior leaflet, and 14 on RV epicardium. Tricuspid valve geometry and anterior leaflet strains were calculated from crystal coordinates. Left ventricular ejection fraction and RV fractional area change were significantly lower in FTR animals versus Control. Tricuspid annular area, septo-lateral diameter, RV pressures were all significantly greater in the FTR group. Mean TR grade (+0-3) was 0.7 ± 0.5 in Control and 2.4 ± 0.5 in FTR (P = < 0.001). The anterior leaflet area and length increased significantly. Global radial leaflet strain was significantly lower in FTR mostly driven by decreased free edge leaflet strain. Global circumferential anterior leaflet strain was also significantly lower in FTR with more remarkable reduction in the belly region. Rapid ventricular pacing in sheep resulted in a clinically pertinent model of RV and annular dilation with FTR and leaflet enlargement. Both circumferential and radial anterior leaflet strains were significantly reduced with FTR. Functional TR may be associated with alteration of leaflet mechanical properties.
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Affiliation(s)
- Tomasz Jazwiec
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, Michigan; Department of Cardiac, Vascular and Endovascular Surgery and Transplantology, Medical University of Silesia in Katowice, Silesian Centre for Heart Diseases, Zabrze, Poland
| | - Marcin J Malinowski
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, Michigan; Department of Cardiac Surgery, Medical University of Silesia, School of Medicine in Katowice, Katowice, Poland
| | - Haley Ferguson
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, Michigan
| | - Jessica Parker
- Research Department, Spectrum Health, Grand Rapids, Michigan
| | - Mrudang Mathur
- Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas
| | - Manuel K Rausch
- Department of Aerospace Engineering & Engineering Mechanics, Department of Biomedical Engineering, Oden Institute for Computational Engineering and Science, University of Texas at Austin, Austin, Texas
| | - Tomasz A Timek
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, Michigan.
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3
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Ross CJ, Laurence DW, Richardson J, Babu AR, Evans LE, Beyer EG, Childers RC, Wu Y, Towner RA, Fung KM, Mir A, Burkhart HM, Holzapfel GA, Lee CH. An investigation of the glycosaminoglycan contribution to biaxial mechanical behaviours of porcine atrioventricular heart valve leaflets. J R Soc Interface 2019; 16:20190069. [PMID: 31266416 PMCID: PMC6685018 DOI: 10.1098/rsif.2019.0069] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Accepted: 06/03/2019] [Indexed: 01/06/2023] Open
Abstract
The atrioventricular heart valve (AHV) leaflets have a complex microstructure composed of four distinct layers: atrialis, ventricularis, fibrosa and spongiosa. Specifically, the spongiosa layer is primarily proteoglycans and glycosaminoglycans (GAGs). Quantification of the GAGs' mechanical contribution to the overall leaflet function has been of recent focus for aortic valve leaflets, but this characterization has not been reported for the AHV leaflets. This study seeks to expand current GAG literature through novel mechanical characterizations of GAGs in AHV leaflets. For this characterization, mitral and tricuspid valve anterior leaflets (MVAL and TVAL, respectively) were: (i) tested by biaxial mechanical loading at varying loading ratios and by stress-relaxation procedures, (ii) enzymatically treated for removal of the GAGs and (iii) biaxially mechanically tested again under the same protocols as in step (i). Removal of the GAG contents from the leaflet was conducted using a 100 min enzyme treatment to achieve approximate 74.87% and 61.24% reductions of all GAGs from the MVAL and TVAL, respectively. Our main findings demonstrated that biaxial mechanical testing yielded a statistically significant difference in tissue extensibility after GAG removal and that stress-relaxation testing revealed a statistically significant smaller stress decay of the enzyme-treated tissue than untreated tissues. These novel findings illustrate the importance of GAGs in AHV leaflet behaviour, which can be employed to better inform heart valve therapeutics and computational models.
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Affiliation(s)
- Colton J. Ross
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, USA
| | - Devin W. Laurence
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, USA
| | - Jacob Richardson
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, USA
| | - Anju R. Babu
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, USA
| | - Lauren E. Evans
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, USA
| | - Ean G. Beyer
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, USA
| | - Rachel C. Childers
- Stephenson School of Biomedical Engineering, The University of Oklahoma, Norman, OK, USA
| | - Yi Wu
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, USA
| | - Rheal A. Towner
- Advanced Magnetic Resonance Center, MS 60, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Kar-Ming Fung
- Department of Pathology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Stephenson Cancer Center, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Arshid Mir
- Division of Pediatric Cardiology, Department of Pediatrics, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Harold M. Burkhart
- Division of Cardiothoracic Surgery, Department of Surgery, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Gerhard A. Holzapfel
- Institute of Biomechanics, Graz University of Technology, Graz, Austria
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Chung-Hao Lee
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, USA
- Institute for Biomedical Engineering, Science and Technology, The University of Oklahoma, Norman, OK, USA
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4
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Rego BV, Khalighi AH, Drach A, Lai EK, Pouch AM, Gorman RC, Gorman JH, Sacks MS. A noninvasive method for the determination of in vivo mitral valve leaflet strains. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2018; 34:e3142. [PMID: 30133180 DOI: 10.1002/cnm.3142] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 06/21/2018] [Accepted: 08/07/2018] [Indexed: 06/08/2023]
Abstract
Assessment of mitral valve (MV) function is important in many diagnostic, prognostic, and surgical planning applications for treatment of MV disease. Yet, to date, there are no accepted noninvasive methods for determination of MV leaflet deformation, which is a critical metric of MV function. In this study, we present a novel, completely noninvasive computational method to estimate MV leaflet in-plane strains from clinical-quality real-time three-dimensional echocardiography (rt-3DE) images. The images were first segmented to produce meshed medial-surface leaflet geometries of the open and closed states. To establish material point correspondence between the two states, an image-based morphing pipeline was implemented within a finite element (FE) modeling framework in which MV closure was simulated by pressurizing the open-state geometry, and local corrective loads were applied to enforce the actual MV closed shape. This resulted in a complete map of local systolic leaflet membrane strains, obtained from the final FE mesh configuration. To validate the method, we utilized an extant in vitro database of fiducially labeled MVs, imaged in conditions mimicking both the healthy and diseased states. Our method estimated local anisotropic in vivo strains with less than 10% error and proved to be robust to changes in boundary conditions similar to those observed in ischemic MV disease. Next, we applied our methodology to ovine MVs imaged in vivo with rt-3DE and compared our results to previously published findings of in vivo MV strains in the same type of animal as measured using surgically sutured fiducial marker arrays. In regions encompassed by fiducial markers, we found no significant differences in circumferential(P = 0.240) or radial (P = 0.808) strain estimates between the marker-based measurements and our novel noninvasive method. This method can thus be used for model validation as well as for studies of MV disease and repair.
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Affiliation(s)
- Bruno V Rego
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Amir H Khalighi
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Andrew Drach
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
| | - Eric K Lai
- Gorman Cardiovascular Research Group, Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Alison M Pouch
- Gorman Cardiovascular Research Group, Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Robert C Gorman
- Gorman Cardiovascular Research Group, Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Joseph H Gorman
- Gorman Cardiovascular Research Group, Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Michael S Sacks
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas
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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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6
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Bark DL, Dasi LP. The Impact of Fluid Inertia on In Vivo Estimation of Mitral Valve Leaflet Constitutive Properties and Mechanics. Ann Biomed Eng 2016; 44:1425-35. [PMID: 26416720 PMCID: PMC4809800 DOI: 10.1007/s10439-015-1463-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 09/15/2015] [Indexed: 11/24/2022]
Abstract
We examine the influence of the added mass effect (fluid inertia) on mitral valve leaflet stress during isovolumetric phases. To study this effect, oscillating flow is applied to a flexible membrane at various frequencies to control inertia. Resulting membrane strain is calculated through a three-dimensional reconstruction of markers from stereo images. To investigate the effect in vivo, the analysis is repeated on a published dataset for an ovine mitral valve (Journal of Biomechanics 42(16): 2697-2701). The membrane experiment demonstrates that the relationship between pressure and strain must be corrected with a fluid inertia term if the ratio of inertia to pressure differential approaches 1. In the mitral valve, this ratio reaches 0.7 during isovolumetric contraction for an acceleration of 6 m/s(2). Acceleration is reduced by 72% during isovolumetric relaxation. Fluid acceleration also varies along the leaflet during isovolumetric phases, resulting in spatial variations in stress. These results demonstrate that fluid inertia may be the source of the temporally and spatially varying stiffness measurements previously seen through inverse finite element analysis of in vivo data during isovolumetric phases. This study demonstrates that there is a need to account for added mass effects when analyzing in vivo constitutive relationships of heart valves.
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Affiliation(s)
- David L. Bark
- Colorado State University, School of Mechanical Engineering, Fort Collins, CO, United States
| | - Lakshmi P. Dasi
- Colorado State University, School of Mechanical Engineering, Fort Collins, CO, United States
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7
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Roberts N, Morticelli L, Jin Z, Ingham E, Korossis S. Regional biomechanical and histological characterization of the mitral valve apparatus: Implications for mitral repair strategies. J Biomech 2015; 49:2491-501. [PMID: 26787008 DOI: 10.1016/j.jbiomech.2015.12.042] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 12/18/2015] [Indexed: 11/15/2022]
Abstract
The aim of this study was to investigate the regional and directional differences in the biomechanics and histoarchitecture of the porcine mitral valve (MV) apparatus, with a view to tailoring tissue-engineered constructs for MV repair. The anterior leaflet displayed the largest directional anisotropy with significantly higher strength in the circumferential direction compared to the posterior leaflet. The histological results indicated that this was due to the circumferential alignment of the collagen fibers. The posterior leaflet demonstrated no significant directional anisotropy in the mechanical properties, and there was no significant directionality of the collagen fibers in the main body of the leaflet. The thinner commissural chordae were found to be significantly stiffer and less extensible than the strut chordae. Histological staining demonstrated a tighter knit of the collagen fibers in the commissural chordae than the strut chordae. By elucidating the inhomogeneity of the histoarchitecture and biomechanics of the MV apparatus, the results from this study will aid the regional differentiation of MV repair strategies, with tailored mitral-component-specific biomaterials or tissue-engineered constructs.
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Affiliation(s)
- Nicholas Roberts
- Institute of Medical and Biological Engineering, University of Leeds, LS2 9JT Leeds, UK
| | - Lucrezia Morticelli
- Institute of Medical and Biological Engineering, University of Leeds, LS2 9JT Leeds, UK; Department of Cardiothoracic, Transplantation and Vascular Surgery, Hannover Medical School, Carl-Neuberg-Strasse 1, Hannover 30625, Germany
| | - Zhongmin Jin
- Institute of Medical and Biological Engineering, University of Leeds, LS2 9JT Leeds, UK; State Key Laboratory for Manufacturing System Engineering, Xi׳an Jiaotong University, Xi׳an, China
| | - Eileen Ingham
- Institute of Medical and Biological Engineering, University of Leeds, LS2 9JT Leeds, UK
| | - Sotirios Korossis
- Institute of Medical and Biological Engineering, University of Leeds, LS2 9JT Leeds, UK; Department of Cardiothoracic, Transplantation and Vascular Surgery, Hannover Medical School, Carl-Neuberg-Strasse 1, Hannover 30625, Germany; Lower Saxony Centre for Biomedical Engineering Implant Research and Development, Hannover Medical School, Feodor-Lynen-Strasse 31, Hannover 30625, Germany.
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8
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Engelhardt S, Lichtenberg N, Al-Maisary S, De Simone R, Rauch H, Roggenbach J, Müller S, Karck M, Meinzer HP, Wolf I. Towards Automatic Assessment of the Mitral Valve Coaptation Zone from 4D Ultrasound. FUNCTIONAL IMAGING AND MODELING OF THE HEART 2015. [DOI: 10.1007/978-3-319-20309-6_16] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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9
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Kuan MY, Espino DM. Systolic fluid–structure interaction model of the congenitally bicuspid aortic valve: assessment of modelling requirements. Comput Methods Biomech Biomed Engin 2014; 18:1305-20. [DOI: 10.1080/10255842.2014.900663] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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10
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Wilcox A, Buchan K, Espino D. Frequency and diameter dependent viscoelastic properties of mitral valve chordae tendineae. J Mech Behav Biomed Mater 2014; 30:186-95. [DOI: 10.1016/j.jmbbm.2013.11.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 11/14/2013] [Accepted: 11/18/2013] [Indexed: 11/30/2022]
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11
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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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12
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Wells SM, Pierlot CM, Moeller AD. Physiological remodeling of the mitral valve during pregnancy. Am J Physiol Heart Circ Physiol 2012; 303:H878-92. [DOI: 10.1152/ajpheart.00845.2011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is growing evidence that heart valves are not passive structures but can remodel with left ventricular dysfunction. To determine if these tissues remodel under nonpathological conditions, we examined the mirtal valve anterior leaflet during the volume loading and cardiac expansion of pregnancy using a bovine model. We measured leaflet dimensions, chordal attachments, and biaxial mechanical properties of leaflets collected from never-pregnant heifers and pregnant cows (pregnancy duration estimated from fetal length). Hydrothermal isometric tension (HIT) tests were performed to assess the denaturation temperature (Td) associated with collagen molecular stability and the load decay half-time ( t1//2) associated with intermolecular cross-linking. Histological changes were examined using Verhoeff-van Gieson and picrosirius red staining with polarized light. We observed striking changes to the structure and material properties of the mitral anterior leaflet during pregnancy. Leaflet area was increased 33%, with a surprising increase (nearly 25%) in chordae tendinae attachments. There was a biphasic change in leaflet extensibility: it rapidly decreased by 30% and then reversed to prepregnant values by late pregnancy. The 2°C decrease in Td in pregnancy was indicative of collagen remodeling, whereas the 70% increase in HIT t1/2 indicated an increase in collagen cross-linking. Finally, histological results suggested transient increases in leaflet thickness and transient decreases in collagen crimp. This remodeling may compensate for the increased loading conditions associated with pregnancy by normalizing leaflet stress and maintaining coaptation. Understanding the mechanisms of mitral valve physiological remodeling in pregnancy could contribute to alternative treatments of pathological remodeling associated with left ventricular dysfunction.
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Affiliation(s)
- Sarah M. Wells
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; and
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Caitlin M. Pierlot
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; and
| | - Andrew D. Moeller
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; and
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13
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Espino DM, Shepherd DET, Hukins DWL. Evaluation of a transient, simultaneous, arbitrary Lagrange-Euler based multi-physics method for simulating the mitral heart valve. Comput Methods Biomech Biomed Engin 2012; 17:450-8. [PMID: 22640492 DOI: 10.1080/10255842.2012.688818] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
A transient multi-physics model of the mitral heart valve has been developed, which allows simultaneous calculation of fluid flow and structural deformation. A recently developed contact method has been applied to enable simulation of systole (the stage when blood pressure is elevated within the heart to pump blood to the body). The geometry was simplified to represent the mitral valve within the heart walls in two dimensions. Only the mitral valve undergoes deformation. A moving arbitrary Lagrange-Euler mesh is used to allow true fluid-structure interaction (FSI). The FSI model requires blood flow to induce valve closure by inducing strains in the region of 10-20%. Model predictions were found to be consistent with existing literature and will undergo further development.
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Affiliation(s)
- Daniel M Espino
- a School of Mechanical Engineering, University of Birmingham , Birmingham , B15 2TT , UK
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14
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Timek TA, Miller DC. Another multidisciplinary look at ischemic mitral regurgitation. Semin Thorac Cardiovasc Surg 2012; 23:220-31. [PMID: 22172360 DOI: 10.1053/j.semtcvs.2011.07.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/21/2011] [Indexed: 12/31/2022]
Abstract
Ischemic mitral regurgitation (IMR) continues to challenge surgeons and scientists alike. This vexing clinical entity frequently complicates myocardial infarction and carries a poor prognosis both in the setting of coronary disease and idiopathic dilated cardiomyopathy. Ischemic mitral regurgitation encompasses a difficult patient population that is characterized by high operative mortality, poor long term outcomes, and frequent recurrent insufficiency after standard surgical repair. Yet optimal surgical repair and improved clinical outcomes can only be achieved with better knowledge of the pathophysiology of IMR which is still incompletely understood. The causative mechanism of IMR appears to lie in the annular and subvalvular frame of the valve rather than leaflet or chordal structure leading to such labels as "ischemic," "functional," "non-organic," and "cardiomyopathy associated" being applied in the clinical literature. Although ischemic mitral regurgitation is a prevailing clinical entity, it has not been consistently defined in the literature, contributing to considerable confusion and contradictory results of clinical studies. As the mechanisms of pathophysiology have been better elucidated, novel surgical and interventional strategies have been developed recently to provide better treatment for this difficult patient population. In this review, we undertake a multidisciplinary update of the pathophysiology, classification, and surgical and interventional treatment of ischemic mitral regurgitation in today's clinical practice.
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Affiliation(s)
- Tomasz A Timek
- West Michigan Cardiothoracic Surgeons and Spectrum Health System, Grand Rapids, Michigan, USA
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15
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Influence of Chronic Tethering of the Mitral Valve on Mitral Leaflet Size and Coaptation in Functional Mitral Regurgitation. JACC Cardiovasc Imaging 2012; 5:337-45. [DOI: 10.1016/j.jcmg.2011.10.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 09/28/2011] [Accepted: 10/11/2011] [Indexed: 11/18/2022]
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16
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Richards JM, Farrar EJ, Kornreich BG, Moïse NS, Butcher JT. The mechanobiology of mitral valve function, degeneration, and repair. J Vet Cardiol 2012; 14:47-58. [PMID: 22366572 PMCID: PMC3586284 DOI: 10.1016/j.jvc.2012.01.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 12/24/2011] [Accepted: 01/17/2012] [Indexed: 12/28/2022]
Abstract
In degenerative valve disease, the highly organized mitral valve leaflet matrix stratification is progressively destroyed and replaced with proteoglycan rich, mechanically inadequate tissue. This is driven by the actions of originally quiescent valve interstitial cells that become active contractile and migratory myofibroblasts. While treatment for myxomatous mitral valve disease in humans ranges from repair to total replacement, therapies in dogs focus on treating the consequences of the resulting mitral regurgitation. The fundamental gap in our understanding is how the resident valve cells respond to altered mechanical signals to drive tissue remodeling. Despite the pathological similarities and high clinical occurrence, surprisingly little mechanistic insight has been gleaned from the dog. This review presents what is known about mitral valve mechanobiology from clinical, in vivo, and in vitro data. There are a number of experimental strategies already available to pursue this significant opportunity, but success requires the collaboration between veterinary clinicians, scientists, and engineers.
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Affiliation(s)
| | - Emily J. Farrar
- Department of Biomedical Engineering, Cornell University, Ithaca NY, USA
| | - Bruce G. Kornreich
- Department of Clinical Sciences, Section of Cardiology, College of Veterinary Medicine, Cornell University, Ithaca NY, USA
| | - N. Sydney Moïse
- Department of Clinical Sciences, Section of Cardiology, College of Veterinary Medicine, Cornell University, Ithaca NY, USA
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Grande-Allen KJ, Liao J. The heterogeneous biomechanics and mechanobiology of the mitral valve: implications for tissue engineering. Curr Cardiol Rep 2011; 13:113-20. [PMID: 21221857 PMCID: PMC4410006 DOI: 10.1007/s11886-010-0161-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
There are compelling reasons to develop a tissue-engineered mitral valve, but this endeavor has not received the same attention as tissue engineering strategies for the semilunar valves. Challenges in regenerating a mitral valve include recapitulating the complex heterogeneity in terms of anatomy (differently sized leaflets, numerous chordae), extracellular matrix composition, biomechanical behavior, valvular interstitial cell and endothelial cell phenotypes, and interior vasculature and innervation. It will also be essential to restore the functional relationships between the native mitral valve and left ventricle. A growing amount of information relevant to tissue engineering a mitral valve has been recently collected through investigations of cell mechanobiology and collagen organization. It is hoped that the development of tissue-engineered mitral valves can build on knowledge derived from engineering semilunar valves, but the mitral valve will present its own unique challenges as investigators move toward a first-generation prototype.
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May-Newman K, Enriquez-Almaguer L, Posuwattanakul P, Dembitsky W. Biomechanics of the Aortic Valve in the Continuous Flow VAD-Assisted Heart. ASAIO J 2010; 56:301-8. [DOI: 10.1097/mat.0b013e3181e321da] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Stress-strain behavior of mitral valve leaflets in the beating ovine heart. J Biomech 2009; 42:1909-16. [PMID: 19535081 DOI: 10.1016/j.jbiomech.2009.05.018] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 04/29/2009] [Accepted: 05/10/2009] [Indexed: 11/21/2022]
Abstract
Excised anterior mitral leaflets exhibit anisotropic, non-linear material behavior with pre-transitional stiffness ranging from 0.06 to 0.09 N/mm(2) and post-transitional stiffness from 2 to 9 N/mm(2). We used inverse finite element (FE) analysis to test, for the first time, whether the anterior mitral leaflet (AML), in vivo, exhibits similar non-linear behavior during isovolumic relaxation (IVR). Miniature radiopaque markers were sewn to the mitral annulus, AML, and papillary muscles in 8 sheep. Four-dimensional marker coordinates were obtained using biplane videofluoroscopic imaging during three consecutive cardiac cycles. A FE model of the AML was developed using marker coordinates at the end of isovolumic relaxation (when pressure difference across the valve is approximately zero), as the reference state. AML displacements were simulated during IVR using measured left ventricular and atrial pressures. AML elastic moduli in the radial and circumferential directions were obtained for each heartbeat by inverse FEA, minimizing the difference between simulated and measured displacements. Stress-strain curves for each beat were obtained from the FE model at incrementally increasing transmitral pressure intervals during IVR. Linear regression of 24 individual stress-strain curves (8 hearts, 3 beats each) yielded a mean (+/-SD) linear correlation coefficient (r(2)) of 0.994+/-0.003 for the circumferential direction and 0.995+/-0.003 for the radial direction. Thus, unlike isolated leaflets, the AML, in vivo, operates linearly over a physiologic range of pressures in the closed mitral valve.
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Real Time, Non-Invasive Assessment of Leaflet Deformation in Heart Valve Tissue Engineering. Ann Biomed Eng 2008; 37:532-41. [DOI: 10.1007/s10439-008-9621-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Accepted: 12/10/2008] [Indexed: 12/17/2022]
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Krishnamurthy G, Ennis DB, Itoh A, Bothe W, Swanson JC, Karlsson M, Kuhl E, Miller DC, Ingels NB. Material properties of the ovine mitral valve anterior leaflet in vivo from inverse finite element analysis. Am J Physiol Heart Circ Physiol 2008; 295:H1141-H1149. [PMID: 18621858 DOI: 10.1152/ajpheart.00284.2008] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We measured leaflet displacements and used inverse finite-element analysis to define, for the first time, the material properties of mitral valve (MV) leaflets in vivo. Sixteen miniature radiopaque markers were sewn to the MV annulus, 16 to the anterior MV leaflet, and 1 on each papillary muscle tip in 17 sheep. Four-dimensional coordinates were obtained from biplane videofluoroscopic marker images (60 frames/s) during three complete cardiac cycles. A finite-element model of the anterior MV leaflet was developed using marker coordinates at the end of isovolumic relaxation (IVR; when the pressure difference across the valve is approximately 0), as the minimum stress reference state. Leaflet displacements were simulated during IVR using measured left ventricular and atrial pressures. The leaflet shear modulus (G(circ-rad)) and elastic moduli in both the commisure-commisure (E(circ)) and radial (E(rad)) directions were obtained using the method of feasible directions to minimize the difference between simulated and measured displacements. Group mean (+/-SD) values (17 animals, 3 heartbeats each, i.e., 51 cardiac cycles) were as follows: G(circ-rad) = 121 +/- 22 N/mm2, E(circ) = 43 +/- 18 N/mm2, and E(rad) = 11 +/- 3 N/mm2 (E(circ) > E(rad), P < 0.01). These values, much greater than those previously reported from in vitro studies, may result from activated neurally controlled contractile tissue within the leaflet that is inactive in excised tissues. This could have important implications, not only to our understanding of mitral valve physiology in the beating heart but for providing additional information to aid the development of more durable tissue-engineered bioprosthetic valves.
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Affiliation(s)
- Gaurav Krishnamurthy
- Department of Cardiothoracic Surgery, Stanford University, Stanford, California, USA
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Jimenez JH, Liou SW, Padala M, He Z, Sacks M, Gorman RC, Gorman JH, Yoganathan AP. A saddle-shaped annulus reduces systolic strain on the central region of the mitral valve anterior leaflet. J Thorac Cardiovasc Surg 2007; 134:1562-8. [DOI: 10.1016/j.jtcvs.2007.08.037] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 08/01/2007] [Accepted: 08/14/2007] [Indexed: 11/28/2022]
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Timek TA, Lai DT, Dagum P, Liang D, Daughters GT, Ingels NB, Miller DC. Mitral leaflet remodeling in dilated cardiomyopathy. Circulation 2006; 114:I518-23. [PMID: 16820630 DOI: 10.1161/circulationaha.105.000554] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Normal mammalian mitral leaflets have regional heterogeneity of biochemical composition, collagen fiber orientation, and geometric deformation. How leaflet shape and regional geometry are affected in dilated cardiomyopathy is unknown. METHODS AND RESULTS Nine sheep had 8 radio-opaque markers affixed to the mitral annulus (MA), 4 markers sewn on the central meridian of the anterior mitral leaflet (AML) forming 4 distinct segments S1 to S4 and 2 on the posterior leaflet (PML) forming 2 distinct segments S5 and S6. Biplane videofluoroscopy and echocardiography were performed before and after rapid pacing (180 to 230 bpm for 15+/-6 days) sufficient to develop tachycardia-induced cardiomyopathy (TIC) and functional mitral regurgitation (FMR). Leaflet tethering was defined as change of displacement of AML and PML edge markers from the MA plane from baseline values while leaflet length was obtained by summing the segments between respective leaflet markers. With TIC, total AML and PML length increased significantly (2.11+/-0.16 versus 2.43+/-0.23 cm and 1.14+/-0.27 versus 1.33+/-0.25 cm before and after pacing for AML and PML, respectively; P<0.05 for both), but only segments near the edge of each leaflet (S4 lengthened by 23+/-17% and S5 by 24+/-18%; P<0.05 for both) had significant regional remodeling. AML shape did not change and no leaflet tethering was observed. CONCLUSIONS TIC was not associated with leaflet tethering or shape change, but both anterior and posterior leaflets lengthened because of significant remodeling localized near the leaflet edge. Leaflet remodeling accompanies mitral regurgitation in cardiomyopathy and casts doubt on FMR being purely "functional" in etiology.
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Affiliation(s)
- Tomasz A Timek
- Department of Cardiothoracic Surgery, Stanford University School of Medicine Stanford, California 94305-5247, USA
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Chen L, May-Newman K. Effect of Strut Chordae Transection on Mitral Valve Leaflet Biomechanics. Ann Biomed Eng 2006; 34:917-26. [PMID: 16783648 DOI: 10.1007/s10439-006-9095-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2005] [Accepted: 02/22/2006] [Indexed: 10/24/2022]
Abstract
Strut chordae transection (SCT) has been recommended as a surgical treatment for mitral regurgitation (MR) arising from ischemic heart disease. However, little is known about the contribution of anterior strut chordae to leaflet tissue mechanics. In this study, experimental measurements of mitral valve deformation under quasi-static pressure loading were performed on isolated pig hearts before and after transecting both strut chordae. Biplane video images of markers placed on the anterior leaflet surface were used to reconstruct the 3D position of the markers. The 2D nonhomogeneous deformations in the anterior leaflet were calculated by least squares fit to the 3D marker coordinates in successive pressure loading states. Results show that the anterior leaflet undergoes large, anisotropic and nonhomogeneous deformation, with a significant radial stretch gradient and smaller, uniform circumferential stretch. Following chordal transection, the radial deformation decreases. A gradient in the circumferential stretch is observed as an increase from the annulus toward the coaptation line. Without the support provided by the strut chordae, the center portion of the anterior leaflet experienced a substantial change in shape in response to the systolic pressure, altering the load-bearing mechanism in the valvular structure. The shift of the deformation distribution suggests that additional strain energy is absorbed by the circumferentially oriented collagen fibers following SCT and may result in long-term tissue remodeling. This study provides detailed biomechanical data for interpreting the results of previous investigations of SCT, as well as for exploring a greater understanding of how SCT affects MR through computational modeling.
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Affiliation(s)
- Ling Chen
- Department of Mechanical Engineering, San Diego State University, CA, 92182-1323, USA
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Mackerle J. Finite element modelling and simulations in cardiovascular mechanics and cardiology: A bibliography 1993–2004. Comput Methods Biomech Biomed Engin 2005; 8:59-81. [PMID: 16154871 DOI: 10.1080/10255840500141486] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The paper gives a bibliographical review of the finite element modelling and simulations in cardiovascular mechanics and cardiology from the theoretical as well as practical points of views. The bibliography lists references to papers, conference proceedings and theses/dissertations that were published between 1993 and 2004. At the end of this paper, more than 890 references are given dealing with subjects as: Cardiovascular soft tissue modelling; material properties; mechanisms of cardiovascular components; blood flow; artificial components; cardiac diseases examination; surgery; and other topics.
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Affiliation(s)
- Jaroslav Mackerle
- Department of Mechanical Engineering, Linköping Institute of Technology, Sweden.
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