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Kakaletsis S, Malinowski M, Snider JC, Mathur M, Sugerman GP, Luci JJ, Kostelnik CJ, Jazwiec T, Bersi MR, Timek TA, Rausch MK. Untangling the mechanisms of pulmonary arterial hypertension-induced right ventricular stiffening in a large animal model. Acta Biomater 2023; 171:155-165. [PMID: 37797706 PMCID: PMC11048731 DOI: 10.1016/j.actbio.2023.09.043] [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: 05/04/2023] [Revised: 09/20/2023] [Accepted: 09/26/2023] [Indexed: 10/07/2023]
Abstract
Pulmonary hypertension (PHT) is a devastating disease with low survival rates. In PHT, chronic pressure overload leads to right ventricle (RV) stiffening; thus, impeding diastolic filling. Multiple mechanisms may contribute to RV stiffening, including wall thickening, microstructural disorganization, and myocardial stiffening. The relative importance of each mechanism is unclear. Our objective is to use a large animal model to untangle these mechanisms. Thus, we induced pulmonary arterial hypertension (PAH) in sheep via pulmonary artery banding. After eight weeks, the hearts underwent anatomic and diffusion tensor MRI to characterize wall thickening and microstructural disorganization. Additionally, myocardial samples underwent histological and gene expression analyses to quantify compositional changes and mechanical testing to quantify myocardial stiffening. Finally, we used finite element modeling to disentangle the relative importance of each stiffening mechanism. We found that the RVs of PAH animals thickened most at the base and the free wall and that PAH induced excessive collagen synthesis, increased cardiomyocyte cross-sectional area, and led to microstructural disorganization, consistent with increased expression of fibrotic genes. We also found that the myocardium itself stiffened significantly. Importantly, myocardial stiffening correlated significantly with collagen synthesis. Finally, our computational models predicted that myocardial stiffness contributes to RV stiffening significantly more than other mechanisms. Thus, myocardial stiffening may be the most important predictor for PAH progression. Given the correlation between myocardial stiffness and collagen synthesis, collagen-sensitive imaging modalities may be useful for estimating myocardial stiffness and predicting PAH outcomes. STATEMENT OF SIGNIFICANCE: Ventricular stiffening is a significant contributor to pulmonary hypertension-induced right heart failure. However, the mechanisms that lead to ventricular stiffening are not fully understood. The novelty of our work lies in answering this question through the use of a large animal model in combination with spatially- and directionally sensitive experimental techniques. We find that myocardial stiffness is the primary mechanism that leads to ventricular stiffening. Clinically, this knowledge may be used to improve diagnostic, prognostic, and therapeutic strategies for patients with pulmonary hypertension.
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Affiliation(s)
- Sotirios Kakaletsis
- Department of Aerospace Engineering & Engineering Mechanics, The University of Texas at Austin, Austin, TX, USA
| | - Marcin Malinowski
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA; Department of Cardiac Surgery, Medical University of Silesia, Katowice, Poland
| | - J Caleb Snider
- Department of Mechanical Engineering & Materials Science, Washington University at St. Louis, St. Louis, MO, USA
| | - Mrudang Mathur
- Department of Mechanical Engineering, The University of Texas at Austin, TX, USA
| | - Gabriella P Sugerman
- Department of Biomedical Engineering, The University of Texas at Austin, TX, USA
| | - Jeffrey J Luci
- Center for Advanced Human Brain Imaging Research, Rutgers University, Piscataway, NJ, USA; Scully Neuroimaging Center, Princeton University, Princeton, NJ, USA
| | - Colton J Kostelnik
- Department of Mechanical Engineering, The University of Texas at Austin, TX, USA; Department of Biomedical Engineering, The University of Texas at Austin, TX, USA
| | - Tomasz Jazwiec
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA; Department of Cardiac, Vascular and Endovascular Surgery and Transplantology, Medical University of Silesia in Katowice, Silesian Centre for Heart Diseases, Zabrze, Poland
| | - Matthew R Bersi
- Department of Mechanical Engineering & Materials Science, Washington University at St. Louis, St. Louis, MO, USA
| | - Tomasz A Timek
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
| | - Manuel K Rausch
- Department of Aerospace Engineering & Engineering Mechanics, The University of Texas at Austin, Austin, TX, USA; Department of Mechanical Engineering, The University of Texas at Austin, TX, USA; Department of Biomedical Engineering, The University of Texas at Austin, TX, USA.
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Iwasieczko A, Malinowski M, Solarewicz M, Bush J, MacDougall B, Rausch M, Timek TA. Impact of reductive tricuspid ring annuloplasty on right ventricular size, geometry and strain in an ovine model of functional tricuspid regurgitation. Interact Cardiovasc Thorac Surg 2022; 35:6628589. [PMID: 35781336 PMCID: PMC9270866 DOI: 10.1093/icvts/ivac187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/18/2022] [Accepted: 06/01/2022] [Indexed: 11/14/2022] Open
Abstract
Abstract
OBJECTIVES
Reductive ring annuloplasty of the tricuspid annulus represents the contemporary surgical approach to functional tricuspid regurgitation (FTR). We set out to investigate the influence of moderate reductive tricuspid ring annuloplasty on tricuspid regurgitation and right ventricular (RV) size, geometry and strain in an ovine model of chronic FTR.
METHODS
Eight healthy Dorsett male sheep (62.8 + 2kg) underwent a left thoracotomy for placement and tightening of pulmonary artery band to at least double proximal pulmonary artery blood pressure. After 8 weeks of recovery, animals underwent sternotomy, epicardial echocardiography and sonomicrometry crystal implantation. Six crystals were placed around tricuspid annulus and 13 on RV free wall epicardium along 3 parallels defining 3 wall regions (basal, mid and lower) and 1 on the RV apex. All animals underwent beating heart implantation of 26 mm MC3 annuloplasty ring during a second cardiopulmonary bypass run after baseline data acquisition. Simultaneous haemodynamic, sonomicrometry and echocardiography data were acquired at Baseline and after reductive tricuspid ring annuloplasty.
RESULTS
Implantation of reductive ring annuloplasty resulted in 47 ± 7% annular area reduction (996 ± 152 mm vs 516 ± 52 mm2, P = 0.0002) and significantly decreased RV end-diastolic volume (185 ± 27 vs 165 ± 30 ml, P = 0.02). Tricuspid ring annuloplasty effectively reduced FTR grade (3.75 ± 0.6 vs 0.3 ± 0.5, P = 0.00004) and had little influence on RV function, cross-sectional area, radius of curvature or free wall regional strains.
CONCLUSIONS
In adult sheep with 8 weeks of pulmonary artery banding and FTR, tricuspid annulus reduction of 47% with prosthetic ring annuloplasty effectively abolished FTR while maintaining regional RV function and strain patterns.
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Affiliation(s)
- Artur Iwasieczko
- Division of Cardiothoracic Surgery, Spectrum Health , Michigan State College of Human Medicine, Grand Rapids, MI, USA
- Clinical Department of Cardiac Surgery, District Hospital No. 2, University of Rzeszow , Rzeszow, Poland
| | - Marcin Malinowski
- Department of Cardiac Surgery, Medical University of Silesia, School of Medicine in Katowice , Katowice, Poland
| | - Monica Solarewicz
- Division of Cardiothoracic Surgery, Spectrum Health , Michigan State College of Human Medicine, Grand Rapids, MI, USA
| | - Jared Bush
- Division of Cardiothoracic Surgery, Spectrum Health , Michigan State College of Human Medicine, Grand Rapids, MI, USA
| | - Brian MacDougall
- Division of Cardiothoracic Surgery, Spectrum Health , Michigan State College of Human Medicine, Grand Rapids, MI, USA
| | - Manuel Rausch
- Department of Aerospace Engineering & Engineering Mechanics, Department of Biomedical Engineering, Institute of Computational Engineering and Science, University of Texas at Austin , Austin, TX, USA
| | - Tomasz A Timek
- Division of Cardiothoracic Surgery, Spectrum Health , Michigan State College of Human Medicine, Grand Rapids, MI, USA
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Jazwiec T, Malinowski M, Ferguson H, Wodarek J, Quay N, Bush J, Goehler M, Parker J, Rausch M, Timek TA. Effect of variable annular reduction on functional tricuspid regurgitation and right ventricular dynamics in an ovine model of tachycardia-induced cardiomyopathy. J Thorac Cardiovasc Surg 2021; 161:e277-e286. [DOI: 10.1016/j.jtcvs.2019.10.194] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 10/11/2019] [Accepted: 10/27/2019] [Indexed: 11/30/2022]
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Kakaletsis S, Meador WD, Mathur M, Sugerman GP, Jazwiec T, Malinowski M, Lejeune E, Timek TA, Rausch MK. Right ventricular myocardial mechanics: Multi-modal deformation, microstructure, modeling, and comparison to the left ventricle. Acta Biomater 2021; 123:154-166. [PMID: 33338654 PMCID: PMC7946450 DOI: 10.1016/j.actbio.2020.12.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 11/30/2020] [Accepted: 12/02/2020] [Indexed: 01/03/2023]
Abstract
The right ventricular myocardium, much like the rest of the right side of the heart, has been consistently understudied. Presently, little is known about its mechanics, its microstructure, and its constitutive behavior. In this work, we set out to provide the first data on the mechanics of the mature right ventricular myocardium in both simple shear and uniaxial loading and to compare these data to the mechanics of the left ventricular myocardium. To this end, we tested ovine tissue samples of the right and left ventricle under a comprehensive mechanical testing protocol that consisted of six simple shear modes and three tension/compression modes. After mechanical testing, we conducted a histology-based microstructural analysis on each right ventricular sample that yielded high resolution fiber distribution maps across the entire samples. Equipped with this detailed mechanical and histological data, we employed an inverse finite element framework to determine the optimal form and parameters for microstructure-based constitutive models. The results of our study show that right ventricular myocardium is less stiff then the left ventricular myocardium in the fiber direction, but similarly exhibits non-linear, anisotropic, and tension/compression asymmetric behavior with direction-dependent Poynting effect. In addition, we found that right ventricular myocardial fibers change angles transmurally and are dispersed within the sheet plane and normal to it. Through our inverse finite element analysis, we found that the Holzapfel model successfully fits these data, even when selectively informed by rudimentary microstructural information. And, we found that the inclusion of higher-fidelity microstructural data improved the Holzapfel model's predictive ability. Looking forward, this investigation is a critical step towards understanding the fundamental mechanical behavior of right ventricular myocardium and lays the groundwork for future whole-organ mechanical simulations.
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Affiliation(s)
- Sotirios Kakaletsis
- Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, Austin, TX 78712, USA
| | - William D Meador
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
| | - Mrudang Mathur
- Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Gabriella P Sugerman
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
| | - Tomasz Jazwiec
- Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, 49503, USA; Department of Cardiac, Vascular, and Endovascular Surgery and Transplantology, Medical University of Silesia School of Medicine in Katowice, Silesian Centre for Heart Diseases, Zabrze, Poland
| | - Marcin Malinowski
- Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, 49503, USA; Department of Cardiac Surgery, Medical University of Silesia School of Medicine in Katowice, Katowice, Poland
| | - Emma Lejeune
- Department of Mechanical Engineering, Boston University, Boston, MA, 02215, USA
| | - Tomasz A Timek
- Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, 49503, USA
| | - Manuel K Rausch
- Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, Austin, TX 78712, USA; Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712, USA; Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX, 78712, USA.
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Mathur M, Meador WD, Jazwiec T, Malinowski M, Timek TA, Rausch MK. Tricuspid Valve Annuloplasty Alters Leaflet Mechanics. Ann Biomed Eng 2020; 48:2911-2923. [PMID: 32761558 PMCID: PMC8000450 DOI: 10.1007/s10439-020-02586-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Accepted: 07/27/2020] [Indexed: 10/23/2022]
Abstract
Tricuspid valve regurgitation is associated with significant morbidity and mortality. Its most common treatment option, tricuspid valve annuloplasty, is not optimally effective in the long-term. Toward identifying the causes for annuloplasty's ineffectiveness, we have previously investigated the technique's impact on the tricuspid annulus and the right ventricular epicardium. In our current work, we are extending our analysis to the anterior tricuspid valve leaflet. To this end, we adopted our previous strategy of performing DeVega suture annuloplasty as an experimental methodology that allows us to externally control the degree of cinching during annuloplasty. Thus, in ten sheep we successively cinched the annulus and quantified changes to leaflet motion, dynamics, and strain in the beating heart by combining sonomicrometry with our well-established mechanical framework. We found that successive cinching of the valve enforced earlier coaptation and thus reduced leaflet range of motion. Additionally, leaflet angular velocity during opening and closing decreased. Finally, we found that leaflet strains were also reduced. Specifically, radial and areal strains decreased as a function of annular cinching. Our findings are critical as they suggest that suture annuloplasty alters the mechanics of the tricuspid valve leaflets which may disrupt their resident cells' mechanobiological equilibrium. Long-term, such disruption may stimulate tissue maladaptation which could contribute to annuloplasty's sub-optimal effectiveness. Additionally, our data suggest that the extent to which annuloplasty alters leaflet mechanics can be controlled via degree of cinching. Hence, our data may provide direct surgical guidelines.
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Affiliation(s)
- Mrudang Mathur
- Department of Mechanical Engineering, University of Texas at Austin, 204 E Dean Keeton Street, Austin, TX, 78712, USA
| | - William D Meador
- Department of Biomedical Engineering, University of Texas at Austin, 107 W Dean Keeton Street, Austin, TX, 78712, USA
| | - Tomasz Jazwiec
- Department of Cardiac, Vascular and Endovascular Surgery and Transplantology, Silesian Centre for Heart Diseases, Medical University of Silesia in Katowice, Zabrze, Poland
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, 49503, USA
| | - Marcin Malinowski
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, 49503, USA
- Department of Cardiac Surgery, School of Medicine in Katowice, Medical University of Silesia, Katowice, Poland
| | - Tomasz A Timek
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, 49503, USA
| | - Manuel K Rausch
- Departments of Aerospace Engineering & Engineering Mechanics, Biomedical Engineering, University of Texas at Austin, 2617 Wichita Street, Austin, TX, 78712, USA.
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Mathur M, Meador WD, Jazwiec T, Malinowski M, Timek TA, Rausch MK. The Effect of Downsizing on the Normal Tricuspid Annulus. Ann Biomed Eng 2020; 48:655-668. [PMID: 31659604 PMCID: PMC8353055 DOI: 10.1007/s10439-019-02387-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 10/11/2019] [Indexed: 12/17/2022]
Abstract
Tricuspid annuloplasty is a surgical procedure that cinches the valve's annulus in order to reduce regurgitant blood flow. One of its critical parameters is the degree of downsizing. To provide insight into the effect of downsizing, we studied the annulus of healthy sheep during suture annuloplasty. To this end, we implanted fiduciary markers along the annulus of sheep and subsequently performed a DeVega suture annuloplasty. We performed five downsizing steps in each animal while recording hemodynamic and sonomicrometry data in beating hearts. Subsequently, we used splines to approximate the annulus at baseline and at each downsizing step. Based on these approximations we computed clinical metrics of annular shape and dynamics, and the continuous field metrics height, strain, and curvature. With these data, we demonstrated that annular area reduction during downsizing was primarily driven by compression of the anterior annulus. Similarly, reduction in annular dynamics was driven by reduced contractility in the anterior annulus. Finally, changes in global height and eccentricity of the annulus could be explained by focal changes in the continuous height profile and changes in annular curvature. Our findings are important as they provide insight into a regularly performed surgical procedure and may inform the design of transcatheter devices that mimic suture annuloplasty.
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Affiliation(s)
- Mrudang Mathur
- Department of Mechanical Engineering, University of Texas at Austin, 204 E Dean Keeton Street, Austin, TX, 78712, USA
| | - William D Meador
- Department of Biomedical Engineering, University of Texas at Austin, 107 W Dean Keeton Street, Austin, TX, 78712, USA
| | - Tomasz Jazwiec
- Silesian Centre for Heart Diseases, Department of Cardiac, Vascular and Endovascular Surgery and Transplantology, Medical University of Silesia in Katowice, Zabrze, Poland
| | - Marcin Malinowski
- Department of Cardiac Surgery, School of Medicine in Katowice, Medical University of Silesia, Katowice, Poland
| | - Tomasz A Timek
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, 49503, USA
| | - Manuel K Rausch
- Departments of Aerospace Engineering & Engineering Mechanics, Biomedical Engineering, University of Texas at Austin, 2617, Wichita Street, Austin, TX, 78712, USA.
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Rausch MK, Mathur M, Meador WD. Biomechanics of the Tricuspid Annulus: A Review of the Annulus' In Vivo Dynamics With Emphasis on Ovine Data. MITTEILUNGEN DER GESELLSCHAFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK 2019; 42:e201900012. [PMID: 38690196 PMCID: PMC11058966 DOI: 10.1002/gamm.201900012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 01/28/2019] [Indexed: 05/02/2024]
Abstract
The tricuspid annulus forms the boundary between the tricuspid valve leaflets and their surrounding perivalvular tissue of the right atrioventricular junction. Its shape changes throughout the cardiac cycle in response to the forces from the contracting right heart myocardium and the blood-valve interaction. Alterations to annular shape and dynamics in disease lead to valvular dysfunctions such as tricuspid regurgitation from which millions of patients suffer. Successful treatment of such dysfunction requires an in-depth understanding of the normal shape and dynamics of the tricuspid annulus and of the changes following disease and subsequent repair. In this manuscript we review what we know about the shape and dynamics of the normal tricuspid annulus and about the effects of both disease and repair based on non-invasive imaging studies and invasive fiduciary marker-based studies. We further show, by means of ovine data, that detailed engineering analyses of the tricuspid annulus provide regionally-resolved insight into the kinematics of the annulus which would remain hidden if limiting analyses to simple geometric metrics.
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Affiliation(s)
- Manuel K. Rausch
- Aerospace Engineering & Engineering Mechanics, Biomedical Engineering, Institute for Computational Engineering and Sciences, University of Texas at Austin, TX, USA
| | - Mrudang Mathur
- Aerospace Engineering & Engineering Mechanics, Biomedical Engineering, Institute for Computational Engineering and Sciences, University of Texas at Austin, TX, USA
| | - William D. Meador
- Aerospace Engineering & Engineering Mechanics, Biomedical Engineering, Institute for Computational Engineering and Sciences, University of Texas at Austin, TX, USA
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Liu ZQ, Zhang X, Wenk JF. Quantification of regional right ventricular strain in healthy rats using 3D spiral cine dense MRI. J Biomech 2019; 94:219-223. [PMID: 31421808 DOI: 10.1016/j.jbiomech.2019.07.026] [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: 04/11/2019] [Revised: 07/03/2019] [Accepted: 07/22/2019] [Indexed: 11/26/2022]
Abstract
Statistical data from clinical studies suggests that right ventricular (RV) circumferential strain (Ecc) and longitudinal strain (Ell) are significant biomarkers for many cardiovascular diseases. However, a detailed and regional characterization of these strains in the RV is very limited. In the current study, RV images were obtained with 3D spiral cine DENSE MRI in healthy rats. An algorithm for surface growing was proposed in order to fit irregular topology. Specifically, a new custom plugin for the DENSEanalysis program, called 3D DENSE Plugin for Crescent Organ, was developed for surface reconstruction and precise segmentation of organs with sharp curvature, such as the murine RV. The RV free wall (RVFW) was divided into three longitudinal thirds (i.e., basal, middle, and apical) with each one partitioned into circumferential fourths (i.e., anterior, anteriorlateral, inferiorlateral and inferior). Peak systolic strains were quantified for each segment and comparisons were performed statistically. The inclusion of a new plugin was able to generate global values for Ecc and Ell that are in good agreement with previous findings using MRI. Despite no regional variation found in the peak Ecc, the peak Ell exhibited regional variation at the anterior side of the RV, which is potentially due to differences in biventricular torsion at the RV insertion point and fiber architecture. These results provide fundamental insights into the regional contractile function of the RV in healthy rat and could act as a normative baseline for future studies on regional changes induced by disease or treatment.
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Affiliation(s)
- Zhan-Qiu Liu
- Department of Mechanical Engineering, University of Kentucky, Lexington, KY, United States
| | - Xiaoyan Zhang
- Department of Mechanical Engineering, University of Kentucky, Lexington, KY, United States; Department of Bioengineering, University of California, San Diego, CA, United States
| | - Jonathan F Wenk
- Department of Mechanical Engineering, University of Kentucky, Lexington, KY, United States; Department of Surgery, University of Kentucky, Lexington, KY, United States.
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Mathur M, Jazwiec T, Meador WD, Malinowski M, Goehler M, Ferguson H, Timek TA, Rausch MK. Tricuspid valve leaflet strains in the beating ovine heart. Biomech Model Mechanobiol 2019; 18:1351-1361. [PMID: 30980211 DOI: 10.1007/s10237-019-01148-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 04/03/2019] [Indexed: 12/25/2022]
Abstract
The tricuspid leaflets coapt during systole to facilitate proper valve function and, thus, ensure efficient transport of deoxygenated blood to the lungs. Between their open state and closed state, the leaflets undergo large deformations. Quantification of these deformations is important for our basic scientific understanding of tricuspid valve function and for diagnostic or prognostic purposes. To date, tricuspid valve leaflet strains have never been directly quantified in vivo. To fill this gap in our knowledge, we implanted four sonomicrometry crystals per tricuspid leaflet and six crystals along the tricuspid annulus in a total of five sheep. In the beating ovine hearts, we recorded crystal coordinates alongside hemodynamic data. Once recorded, we used a finite strain kinematic framework to compute the temporal evolutions of area strain, radial strain, and circumferential strain for each leaflet. We found that leaflet strains were larger in the anterior leaflet than the posterior and septal leaflets. Additionally, we found that radial strains were larger than circumferential strains. Area strains were as large as 97% in the anterior leaflet, 31% in the posterior leaflet, and 31% in the septal leaflet. These data suggest that tricuspid valve leaflet strains are significantly larger than those in the mitral valve. Should our findings be confirmed they could suggest either that the mechanobiological equilibrium of tricuspid valve resident cells is different than that of mitral valve resident cells or that the mechanotransductive apparatus between the two varies. Either phenomenon may have important implications for the development of tricuspid valve-specific surgical techniques and medical devices.
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Affiliation(s)
- M Mathur
- Department of Mechanical Engineering, University of Texas at Austin, Austin, TX, USA
| | - T Jazwiec
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
- Department of Cardiac, Vascular and Endovascular Surgery and Transplantology, Medical University of Silesia in Katowice, Silesian Centre for Heart Diseases, Zabrze, Poland
| | - W D Meador
- Department of Biomedical Engineering, University of Texas at Austin, 2501 Speedway, Room 7.620, Austin, TX, 78712, USA
| | - M Malinowski
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
- Department of Cardiac Surgery, School of Medicine in Katowice, Medical University of Silesia, Katowice, Poland
| | - M Goehler
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
| | - H Ferguson
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
| | - T A Timek
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
| | - M K Rausch
- Department of Biomedical Engineering, University of Texas at Austin, 2501 Speedway, Room 7.620, Austin, TX, 78712, USA.
- Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, Austin, TX, USA.
- The Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, TX, USA.
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Malinowski M, Jazwiec T, Goehler M, Bush J, Quay N, Ferguson H, Rausch MK, Timek TA. Impact of tricuspid annular size reduction on right ventricular function, geometry and strain. Eur J Cardiothorac Surg 2019; 56:5303950. [PMID: 30698674 DOI: 10.1093/ejcts/ezy484] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 12/21/2018] [Indexed: 02/28/2024] Open
Abstract
OBJECTIVES Restrictive tricuspid annuloplasty is a clinically accepted approach to treat functional tricuspid regurgitation. We set out to investigate the effect of varying degrees of tricuspid annular reduction on the right ventricular (RV) function, geometry and strain. METHODS Eight, healthy sheep (45 ± 4 kg) had 6 sonomicrometry crystals implanted around the tricuspid annulus and 20 onto the epicardium of the right ventricle defining 3 free wall regions: basal, mid and lower. A polypropylene annuloplasty suture was placed around the tricuspid annulus and externalized to an epicardial tourniquet. Simultaneous echocardiographic, haemodynamic and sonomicrometry data were acquired at baseline and during 5 consecutive annular reduction steps (TAR 1-5) with successive (5-7 mm) suture cinching. RV free wall circumferential, longitudinal and areal cardiac and interventional strains, RV radius of curvature (ROC), cross-sectional area and tricuspid annular dimensions were calculated from 3-dimensional crystal coordinates. RESULTS TAR 1-5 resulted in 19 ± 15%, 35 ± 15%, 51 ± 15%, 60 ± 15% and 68 ± 13% tricuspid annular area reduction, respectively. TAR 1 and 2 had minimal influence on the RV function, RV-ROC and strains. TAR 4 and 5 decreased RV-ROC in basal and mid-regions, but reduced the RV cross-sectional area change (from 19 ± 4% at baseline to 14 ± 3% and 13 ± 2%, respectively, P < 0.001) and circumferential and areal strains. TAR 3 significantly decreased free wall RV-ROC from 44.0 ± 1.5 to 42.6 ± 2.4 mm P < 0.001 at the RV base but maintained the regional ventricular function and strains. CONCLUSIONS In healthy ovine hearts, a tricuspid annular area reduction of ∼50% provides optimal conditions for reducing RV-ROC while maintaining regional RV function and strain patterns.
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Affiliation(s)
- Marcin Malinowski
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
- Department of Cardiac Surgery, Medical University of Silesia, School of Medicine in Katowice, Katowice, Poland
| | - Tomasz Jazwiec
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
- Department of Cardiac, Vascular and Endovascular Surgery and Transplantology, Medical University of Silesia in Katowice, Silesian Centre for Heart Disease, Zabrze, Poland
| | - Matthew Goehler
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
| | - Jared Bush
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
| | - Nathan Quay
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
| | - Haley Ferguson
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
| | - Manuel K Rausch
- Department of Aerospace Engineering and Engineering Mechanics, Institute for Computational Engineering and Science, University of Texas at Austin, Austin, TX, USA
- Department of Biomedical Engineering, Institute for Computational Engineering and Science, University of Texas at Austin, Austin, TX, USA
| | - Tomasz A Timek
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
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