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Sadeghinia MJ, Persson RM, Ellensen VS, Haaverstad R, Holzapfel GA, Skallerud B, Prot V, Urheim S. Quantified planar collagen distribution in healthy and degenerative mitral valve: biomechanical and clinical implications. Sci Rep 2024; 14:15670. [PMID: 38977735 PMCID: PMC11231298 DOI: 10.1038/s41598-024-65598-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 06/21/2024] [Indexed: 07/10/2024] Open
Abstract
Degenerative mitral valve disease is a common valvular disease with two arguably distinct phenotypes: fibroelastic deficiency and Barlow's disease. These phenotypes significantly alter the microstructures of the leaflets, particularly the collagen fibers, which are the main mechanical load carriers. The predominant method of investigation is histological sections. However, the sections are cut transmurally and provide a lateral view of the microstructure of the leaflet, while the mechanics and function are determined by the planar arrangement of the collagen fibers. This study, for the first time, quantitatively examined planar collagen distribution quantitatively in health and disease using second harmonic generation microscopy throughout the thickness of the mitral valve leaflets. Twenty diseased samples from eighteen patients and six control samples were included in this study. Healthy tissue had highly aligned collagen fibers. In fibroelastic deficiency they are less aligned and in Barlow's disease they are completely dispersed. In both diseases, collagen fibers have two preferred orientations, which, in contrast to the almost constant one orientation in healthy tissues, also vary across the thickness. The results indicate altered in vivo mechanical stresses and strains on the mitral valve leaflets as a result of disease-related collagen remodeling, which in turn triggers further remodeling.
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Affiliation(s)
- Mohammad Javad Sadeghinia
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands Vei 1A, 7034, Trondheim, Norway
| | - Robert Matongo Persson
- Department of Heart Disease, Haukeland University Hospital, Bergen, Norway
- Institute of Clinical Science, Medical Faculty, University of Bergen, Bergen, Norway
| | | | - Rune Haaverstad
- Department of Heart Disease, Haukeland University Hospital, Bergen, Norway
- Institute of Clinical Science, Medical Faculty, University of Bergen, Bergen, Norway
| | - Gerhard A Holzapfel
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands Vei 1A, 7034, Trondheim, Norway
- Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | - Bjørn Skallerud
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands Vei 1A, 7034, Trondheim, Norway
| | - Victorien Prot
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands Vei 1A, 7034, Trondheim, Norway.
| | - Stig Urheim
- Department of Heart Disease, Haukeland University Hospital, Bergen, Norway
- Institute of Clinical Science, Medical Faculty, University of Bergen, Bergen, Norway
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Wu W, Ching S, Sabin P, Laurence DW, Maas SA, Lasso A, Weiss JA, Jolley MA. The effects of leaflet material properties on the simulated function of regurgitant mitral valves. J Mech Behav Biomed Mater 2023; 142:105858. [PMID: 37099920 PMCID: PMC10199327 DOI: 10.1016/j.jmbbm.2023.105858] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 03/30/2023] [Accepted: 04/12/2023] [Indexed: 04/28/2023]
Abstract
Advances in three-dimensional imaging provide the ability to construct and analyze finite element (FE) models to evaluate the biomechanical behavior and function of atrioventricular valves. However, while obtaining patient-specific valve geometry is now possible, non-invasive measurement of patient-specific leaflet material properties remains nearly impossible. Both valve geometry and tissue properties play a significant role in governing valve dynamics, leading to the central question of whether clinically relevant insights can be attained from FE analysis of atrioventricular valves without precise knowledge of tissue properties. As such we investigated (1) the influence of tissue extensibility and (2) the effects of constitutive model parameters and leaflet thickness on simulated valve function and mechanics. We compared metrics of valve function (e.g., leaflet coaptation and regurgitant orifice area) and mechanics (e.g., stress and strain) across one normal and three regurgitant mitral valve (MV) models with common mechanisms of regurgitation (annular dilation, leaflet prolapse, leaflet tethering) of both moderate and severe degree. We developed a novel fully-automated approach to accurately quantify regurgitant orifice areas of complex valve geometries. We found that the relative ordering of the mechanical and functional metrics was maintained across a group of valves using material properties up to 15% softer than the representative adult mitral constitutive model. Our findings suggest that FE simulations can be used to qualitatively compare how differences and alterations in valve structure affect relative atrioventricular valve function even in populations where material properties are not precisely known.
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Affiliation(s)
- Wensi Wu
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, 19104, PA, USA; Division of Pediatric Cardiology, Children's Hospital of Philadelphia, Philadelphia, 19104, PA, USA
| | - Stephen Ching
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, 19104, PA, USA
| | - Patricia Sabin
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, 19104, PA, USA
| | - Devin W Laurence
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, 19104, PA, USA; Division of Pediatric Cardiology, Children's Hospital of Philadelphia, Philadelphia, 19104, PA, USA
| | - Steve A Maas
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112, UT, USA; Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT 84112, UT, USA
| | - Andras Lasso
- Laboratory for Percutaneous Surgery, Queen's University, Kingston, ON, Canada
| | - Jeffrey A Weiss
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112, UT, USA; Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT 84112, UT, USA
| | - Matthew A Jolley
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, 19104, PA, USA; Division of Pediatric Cardiology, Children's Hospital of Philadelphia, Philadelphia, 19104, PA, USA.
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Sadeghinia MJ, Aguilera HM, Holzapfel GA, Urheim S, Persson RM, Ellensen VS, Haaverstad R, Skallerud B, Prot V. Mechanical Behavior and Collagen Structure of Degenerative Mitral Valve Leaflets and a Finite Element Model of Primary Mitral Regurgitation. Acta Biomater 2023; 164:269-281. [PMID: 37003496 DOI: 10.1016/j.actbio.2023.03.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 03/03/2023] [Accepted: 03/20/2023] [Indexed: 04/03/2023]
Abstract
Degenerative mitral valve disease is the main cause of primary mitral regurgitation with two phenotypes: fibroelastic deficiency (FED) often with localized myxomatous degeneration and diffuse myxomatous degeneration or Barlow's disease. Myxomatous degeneration disrupts the microstructure of the mitral valve leaflets, particularly the collagen fibers, which affects the mechanical behavior of the leaflets. The present study uses biaxial mechanical tests and second harmonic generation microscopy to examine the mechanical behavior of Barlow and FED tissue. Three tissue samples were harvested from a FED patient and one sample is from a Barlow patient. Then we use an appropriate constitutive model by excluding the collagen fibers under compression. Finally, we built an FE model based on the echocardiography of patients diagnosed with FED and Barlow and the characterized material model and collagen fiber orientation. The Barlow sample and the FED sample from the most affected segment showed different mechanical behavior and collagen structure compared to the other two FED samples. The FE model showed very good agreement with echocardiography with 2.02±1.8 mm and 1.05±0.79 mm point-to-mesh distance errors for Barlow and FED patients, respectively. It has also been shown that the exclusion of collagen fibers under compression provides versatility for the material model; it behaves stiff in the belly region, preventing excessive bulging, while it behaves very softly in the commissures to facilitate folding. STATEMENT OF SIGNIFICANCE: None.
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Affiliation(s)
- Mohammad Javad Sadeghinia
- Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, Norway.
| | - Hans Martin Aguilera
- Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, Norway
| | - Gerhard A Holzapfel
- Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, Norway; Institute of Biomechanics, Graz University of Technology, Austria
| | - Stig Urheim
- Haukeland University Hospital, Department of Heart Disease, Bergen, Norway; Institute of Clinical Science, University of Bergen, Bergen, Norway
| | - Robert Matongo Persson
- Haukeland University Hospital, Department of Heart Disease, Bergen, Norway; Institute of Clinical Science, University of Bergen, Bergen, Norway
| | | | - Rune Haaverstad
- Haukeland University Hospital, Department of Heart Disease, Bergen, Norway; Institute of Clinical Science, University of Bergen, Bergen, Norway
| | - Bjørn Skallerud
- Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, Norway
| | - Victorien Prot
- Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, Norway
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Benchtop characterization of the tricuspid valve leaflet pre-strains. Acta Biomater 2022; 152:321-334. [PMID: 36041649 DOI: 10.1016/j.actbio.2022.08.046] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 08/01/2022] [Accepted: 08/22/2022] [Indexed: 11/21/2022]
Abstract
The pre-strains of biological soft tissues are important when relating their in vitro and in vivo mechanical behaviors. In this study, we present the first-of-its-kind experimental characterization of the tricuspid valve leaflet pre-strains. We use 3D photogrammetry and the reproducing kernel method to calculate the pre-strains within the central 10×10 mm region of the tricuspid valve leaflets from n=8 porcine hearts. In agreement with previous pre-strain studies for heart valve leaflets, our results show that all the three tricuspid valve leaflets shrink after explant from the ex vivo heart. These calculated strains are leaflet-specific and the septal leaflet experiences the most compressive changes. Furthermore, the strains observed after dissection of the central 10×10 mm region of the leaflet are smaller than when the valve is explanted, suggesting that our computed pre-strains are mainly due to the release of in situ annulus and chordae connections. The leaflets are then mounted on a biaxial testing device and preconditioned using force-controlled equibiaxial loading. We show that the employed preconditioning protocol does not 100% restore the leaflet pre-strains as removed during tissue dissection, and future studies are warranted to explore alternative preconditioning methods. Finally, we compare the calculated biomechanically oriented metrics considering five stress-free reference configurations. Interestingly, the radial tissue stretches and material anisotropies are significantly smaller compared to the post-preconditioning configuration. Extensions of this work can further explore the role of this unique leaflet-specific leaflet pre-strains on in vivo valve behavior via high-fidelity in-silico models.
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