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Liu H, Sacks MS, Simonian NT, Gorman JH, Gorman RC. Simulated Effects of Acute Left Ventricular Myocardial Infarction on Mitral Regurgitation in an Ovine Model. J Biomech Eng 2024; 146:101009. [PMID: 38652602 PMCID: PMC11225881 DOI: 10.1115/1.4065376] [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: 04/30/2023] [Revised: 04/12/2024] [Accepted: 04/18/2024] [Indexed: 04/25/2024]
Abstract
Ischemic mitral regurgitation (IMR) occurs from incomplete coaptation of the mitral valve (MV) after myocardial infarction (MI), typically worsened by continued remodeling of the left ventricular (LV). The importance of LV remodeling is clear as IMR is induced by the post-MI dual mechanisms of mitral annular dilation and leaflet tethering from papillary muscle (PM) distension via the MV chordae tendineae (MVCT). However, the detailed etiology of IMR remains poorly understood, in large part due to the complex interactions of the MV and the post-MI LV remodeling processes. Given the patient-specific anatomical complexities of the IMR disease processes, simulation-based approaches represent an ideal approach to improve our understanding of this deadly disease. However, development of patient-specific models of left ventricle-mitral valve (LV-MV) interactions in IMR are complicated by the substantial variability and complexity of the MR etiology itself, making it difficult to extract underlying mechanisms from clinical data alone. To address these shortcomings, we developed a detailed ovine LV-MV finite element (FE) model based on extant comprehensive ovine experimental data. First, an extant ovine LV FE model (Sci. Rep. 2021 Jun 29;11(1):13466) was extended to incorporate the MV using a high fidelity ovine in vivo derived MV leaflet geometry. As it is not currently possible to image the MVCT in vivo, a functionally equivalent MVCT network was developed to create the final LV-MV model. Interestingly, in pilot studies, the MV leaflet strains did not agree well with known in vivo MV leaflet strain fields. We then incorporated previously reported MV leaflet prestrains (J. Biomech. Eng. 2023 Nov 1;145(11):111002) in the simulations. The resulting LV-MV model produced excellent agreement with the known in vivo ovine MV leaflet strains and deformed shapes in the normal state. We then simulated the effects of regional acute infarctions of varying sizes and anatomical locations by shutting down the local myocardial contractility. The remaining healthy (noninfarcted) myocardium mechanical behaviors were maintained, but allowed to adjust their active contractile patterns to maintain the prescribed pressure-volume loop behaviors in the acute post-MI state. For all cases studied, the LV-MV simulation demonstrated excellent agreement with known LV and MV in vivo strains and MV regurgitation orifice areas. Infarct location was shown to play a critical role in resultant MV leaflet strain fields. Specifically, extensional deformations of the posterior leaflets occurred in the posterobasal and laterobasal infarcts, while compressive deformations of the anterior leaflet were observed in the anterobasal infarct. Moreover, the simulated posterobasal infarct induced the largest MV regurgitation orifice area, consistent with experimental observations. The present study is the first detailed LV-MV simulation that reveals the important role of MV leaflet prestrain and functionally equivalent MVCT for accurate predictions of LV-MV interactions. Importantly, the current study further underscored simulation-based methods in understanding MV function as an integral part of the LV.
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Affiliation(s)
- Hao Liu
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences, The Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Michael S. Sacks
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences, The Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Natalie T. Simonian
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences, The Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Joseph H. Gorman
- Gorman Cardiovascular Research Group, Smilow Center for Translational Research, University of Pennsylvania, Philadelphia, PA 19146-2701
| | - Robert C. Gorman
- Gorman Cardiovascular Research Group, Smilow Center for Translational Research, University of Pennsylvania, Philadelphia, PA 19146-2701
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Liu H, Simonian NT, Pouch AM, Iaizzo PA, Gorman JH, Gorman RC, Sacks MS. A Computational Pipeline for Patient-Specific Prediction of the Postoperative Mitral Valve Functional State. J Biomech Eng 2023; 145:111002. [PMID: 37382900 PMCID: PMC10405284 DOI: 10.1115/1.4062849] [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: 02/24/2023] [Revised: 06/08/2023] [Accepted: 06/13/2023] [Indexed: 06/30/2023]
Abstract
While mitral valve (MV) repair remains the preferred clinical option for mitral regurgitation (MR) treatment, long-term outcomes remain suboptimal and difficult to predict. Furthermore, pre-operative optimization is complicated by the heterogeneity of MR presentations and the multiplicity of potential repair configurations. In the present work, we established a patient-specific MV computational pipeline based strictly on standard-of-care pre-operative imaging data to quantitatively predict the post-repair MV functional state. First, we established human mitral valve chordae tendinae (MVCT) geometric characteristics obtained from five CT-imaged excised human hearts. From these data, we developed a finite-element model of the full patient-specific MV apparatus that included MVCT papillary muscle origins obtained from both the in vitro study and the pre-operative three-dimensional echocardiography images. To functionally tune the patient-specific MV mechanical behavior, we simulated pre-operative MV closure and iteratively updated the leaflet and MVCT prestrains to minimize the mismatch between the simulated and target end-systolic geometries. Using the resultant fully calibrated MV model, we simulated undersized ring annuloplasty (URA) by defining the annular geometry directly from the ring geometry. In three human cases, the postoperative geometries were predicted to 1 mm of the target, and the MV leaflet strain fields demonstrated close agreement with noninvasive strain estimation technique targets. Interestingly, our model predicted increased posterior leaflet tethering after URA in two recurrent patients, which is the likely driver of long-term MV repair failure. In summary, the present pipeline was able to predict postoperative outcomes from pre-operative clinical data alone. This approach can thus lay the foundation for optimal tailored surgical planning for more durable repair, as well as development of mitral valve digital twins.
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Affiliation(s)
- Hao Liu
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712-1229
| | - Natalie T. Simonian
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712-1229
| | - Alison M. Pouch
- Departments of Radiology and Bioengineering, University of Pennsylvania, Philadelphia, PA 19104
| | - Paul A. Iaizzo
- Visible Heart Laboratories, Department of Surgery, University of Minnesota, Minneapolis, MN 55455
| | - Joseph H. Gorman
- Gorman Cardiovascular Research Group, Department of Surgery, Smilow Center for Translational Research, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Robert C. Gorman
- Gorman Cardiovascular Research Group, Department of Surgery, Smilow Center for Translational Research, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Michael S. Sacks
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712-1229
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Gaidulis G, Padala M. Computational Modeling of the Subject-Specific Effects of Annuloplasty Ring Sizing on the Mitral Valve to Repair Functional Mitral Regurgitation. Ann Biomed Eng 2023; 51:1984-2000. [PMID: 37344691 PMCID: PMC10826925 DOI: 10.1007/s10439-023-03219-9] [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: 12/21/2022] [Accepted: 04/21/2023] [Indexed: 06/23/2023]
Abstract
Surgical repair of functional mitral regurgitation (FMR) that occurs in nearly 60% of heart failure (HF) patients is currently performed with undersizing mitral annuloplasty (UMA), which lacks short- and long-term durability. Heterogeneity in valve geometry makes tailoring this repair to each patient challenging, and predictive models that can help with planning this surgery are lacking. In this study, we present a 3D echo-derived computational model, to enable subject-specific, pre-surgical planning of the repair. Three computational models of the mitral valve were created from 3D echo data obtained in three pigs with HF and FMR. An annuloplasty ring model in seven sizes was created, each ring was deployed, and post-repair valve closure was simulated. The results indicate that large annuloplasty rings (> 32 mm) were not effective in eliminating regurgitant gaps nor in restoring leaflet coaptation or reducing leaflet stresses and chordal tension. Smaller rings (≤ 32 mm) restored better systolic valve closure in all investigated cases,but excessive valve tethering and restricted motion of the leaflets were still present. This computational study demonstrates that for effective correction of FMR, the extent of annular reduction differs between subjects, and overly reducing the annulus has deleterious effects on the valve.
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Affiliation(s)
- Gediminas Gaidulis
- Structural Heart Research and Innovation Laboratory, Carlyle Fraser Heart Center at Emory University Hospital Midtown, Atlanta, USA
- Division of Cardiothoracic Surgery, Emory University School of Medicine, Atlanta, USA
| | - Muralidhar Padala
- Structural Heart Research and Innovation Laboratory, Carlyle Fraser Heart Center at Emory University Hospital Midtown, Atlanta, USA.
- Division of Cardiothoracic Surgery, Emory University School of Medicine, Atlanta, USA.
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van Kampen A, Morningstar JE, Goudot G, Ingels N, Wenk JF, Nagata Y, Yaghoubian KM, Norris RA, Borger MA, Melnitchouk S, Levine RA, Jensen MO. Utilization of Engineering Advances for Detailed Biomechanical Characterization of the Mitral-Ventricular Relationship to Optimize Repair Strategies: A Comprehensive Review. Bioengineering (Basel) 2023; 10:601. [PMID: 37237671 PMCID: PMC10215167 DOI: 10.3390/bioengineering10050601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 05/10/2023] [Accepted: 05/12/2023] [Indexed: 05/28/2023] Open
Abstract
The geometrical details and biomechanical relationships of the mitral valve-left ventricular apparatus are very complex and have posed as an area of research interest for decades. These characteristics play a major role in identifying and perfecting the optimal approaches to treat diseases of this system when the restoration of biomechanical and mechano-biological conditions becomes the main target. Over the years, engineering approaches have helped to revolutionize the field in this regard. Furthermore, advanced modelling modalities have contributed greatly to the development of novel devices and less invasive strategies. This article provides an overview and narrative of the evolution of mitral valve therapy with special focus on two diseases frequently encountered by cardiac surgeons and interventional cardiologists: ischemic and degenerative mitral regurgitation.
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Affiliation(s)
- Antonia van Kampen
- Division of Cardiac Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
- Leipzig Heart Centre, University Clinic of Cardiac Surgery, 02189 Leipzig, Germany
| | - Jordan E. Morningstar
- Department of Regenerative Medicine and Cell Biology, University of South Carolina, Charleston, SC 29425, USA
| | - Guillaume Goudot
- Cardiac Ultrasound Laboratory, Department of Cardiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Neil Ingels
- Department of Biomedical Engineering, University of Arkansas, Fayetteville, AR 72701, USA
| | - Jonathan F. Wenk
- Department of Mechanical Engineering, University of Kentucky, Lexington, KY 40508, USA;
| | - Yasufumi Nagata
- Cardiac Ultrasound Laboratory, Department of Cardiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Koushiar M. Yaghoubian
- Division of Cardiac Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Russell A. Norris
- Department of Regenerative Medicine and Cell Biology, University of South Carolina, Charleston, SC 29425, USA
| | - Michael A. Borger
- Leipzig Heart Centre, University Clinic of Cardiac Surgery, 02189 Leipzig, Germany
| | - Serguei Melnitchouk
- Division of Cardiac Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Robert A. Levine
- Cardiac Ultrasound Laboratory, Department of Cardiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Morten O. Jensen
- Department of Biomedical Engineering, University of Arkansas, Fayetteville, AR 72701, USA
- Department of Surgery, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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Galili L, Weissmann J, White Zeira A, Marom G. Numerical modeling for efficiency and endurance assessment of an indirect mitral annuloplasty device. J Mech Behav Biomed Mater 2022; 136:105516. [PMID: 36215769 DOI: 10.1016/j.jmbbm.2022.105516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 10/02/2022] [Accepted: 10/03/2022] [Indexed: 11/06/2022]
Abstract
In recent years, several transcatheter systems have been introduced for treatment of common mitral regurgitation (MR). Such a system that is based on indirect mitral annuloplasty (IMA) is currently indicated for functional MR. Very few clinical studies have been performed to assess the efficiency and durability of such devices, despite their high risk of fracture resulting from ongoing exposure to large cyclic deformations. In this study, numerical models of moderate primary MR were created to test the implantation procedure of a customized IMA device and its sealing efficiency. The ability of the implanted device to reduce systolic leakage was evaluated and affirmed with a model of a more generic device. The long-term durability of the device was tested using a range of Nickel Titanium material properties. Our results demonstrated a considerable reduction in leakage for both the simplified generic device and the more detailed customized device models. The device met different fatigue criteria, confirming its resiliency and safety even after 10 years, even under the harsher conditions of primary MR. This is the first study to assess the performance and fatigue risk of IMA devices for the treatment of more complicated MR conditions. These findings may pave the way for further research to ultimately consider the device in selective cases of PMR.
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Affiliation(s)
- Lee Galili
- School of Mechanical Engineering, Tel Aviv University, Tel Aviv, Israel
| | - Jonathan Weissmann
- Department of Biomedical Engineering, Tel Aviv University, Tel Aviv, Israel
| | - Adi White Zeira
- School of Mechanical Engineering, Tel Aviv University, Tel Aviv, Israel
| | - Gil Marom
- School of Mechanical Engineering, Tel Aviv University, Tel Aviv, Israel.
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Galili L, White Zeira A, Marom G. Numerical biomechanics modelling of indirect mitral annuloplasty treatments for functional mitral regurgitation. ROYAL SOCIETY OPEN SCIENCE 2022; 9:211464. [PMID: 35242347 PMCID: PMC8753151 DOI: 10.1098/rsos.211464] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 12/14/2021] [Indexed: 05/03/2023]
Abstract
Mitral valve regurgitation (MR) is a common valvular heart disease where an improper closure leads to leakage from the left ventricle into the left atrium. There is a need for less-invasive treatments such as percutaneous repairs for a large inoperable patient population. The aim of this study is to compare several indirect mitral annuloplasty (IMA) percutaneous repair techniques by finite-element analyses. Two types of generic IMA devices were considered, based on coronary sinus vein shortening (IMA-CS) to reduce the annulus perimeter and based on shortening of the anterior-posterior diameter (IMA-AP). The disease, its treatments, and the heart function post-repair were modelled by modifying the living heart human model (Dassault Systèmes). A functional MR pathology that represents ischaemic MR was generated and the IMA treatments were simulated in it, followed by heart function simulations with the devices and leakage quantification from blood flow simulations. All treatments were able to reduce leakage, the IMA-AP device achieved better sealing, and there was a correlation between the IMA-CS device length and the reduction in leakage. The results of this study can help in bringing IMA-AP to market, expanding the use of IMA devices, and optimizing future designs of such devices.
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Affiliation(s)
- Lee Galili
- School of Mechanical Engineering, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Adi White Zeira
- School of Mechanical Engineering, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Gil Marom
- School of Mechanical Engineering, Tel Aviv University, Tel Aviv 6997801, Israel
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Marom G, Plitman Mayo R, Again N, Raanani E. Numerical Biomechanics Models of the Interaction Between a Novel Transcatheter Mitral Valve Device and the Subvalvular Apparatus. INNOVATIONS-TECHNOLOGY AND TECHNIQUES IN CARDIOTHORACIC AND VASCULAR SURGERY 2021; 16:327-333. [PMID: 33818178 PMCID: PMC8414811 DOI: 10.1177/1556984521999362] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Objective Mitral valve regurgitation (MR) is a common valvular heart disease where
improper closing causes leakage. Currently, no transcatheter mitral valve
device is commercially available. Raanani (co-author) and colleagues have
previously proposed a unique rotational implantation, ensuring anchoring by
metallic arms that pull the chordae tendineae. This technique is now being
implemented in a novel device design. The aim of this study is to quantify
the rotational implantation effect on the mitral annulus kinematics and on
the stresses in the chordae and papillary muscles. Methods Finite element analysis of the rotational step of the implantation in a whole
heart model is employed to compare 5 arm designs with varying diameters
(25.9 mm to 32.4 mm) and rotation angles (up to 140°). The arm rotation that
grabs the chordae was modeled when the valve was in systolic
configuration. Results An increase in the rotation angle results in reduced mitral annulus
perimeters. Larger rotation angles led to higher chordae stresses with the
29.8 mm experiencing the maximum stresses. The calculated chordae stresses
suggest that arm diameter should be <27.8 mm and the rotation angle
<120°. Conclusions The upper limit of this diameter range is preferred in order to reduce the
stresses in the papillary muscles while grabbing more chords. The findings
of this study can help improving the design and performance of this unique
device and procedural technique.
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Affiliation(s)
- Gil Marom
- 26745 School of Mechanical Engineering, Tel Aviv University, Israel
| | | | - Nadav Again
- The Sheba Fund for Health Services and Research, Tel Hashomer, Israel
| | - Ehud Raanani
- 26744 Leviev Cardiothoracic and Vascular Center, Chaim Sheba Medical Center, Tel Hashomer, Israel
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Abstract
Heart valve diseases are common disorders with five million annual diagnoses being made in the United States alone. All heart valve disorders alter cardiac hemodynamic performance; therefore, treatments aim to restore normal flow. This paper reviews the state-of-the-art clinical and engineering advancements in heart valve treatments with a focus on hemodynamics. We review engineering studies and clinical literature on the experience with devices for aortic valve treatment, as well as the latest advancements in mitral valve treatments and the pulmonic and tricuspid valves on the right side of the heart. Upcoming innovations will potentially revolutionize treatment of heart valve disorders. These advancements, and more gradual enhancements in the procedural techniques and imaging modalities, could improve the quality of life of patients suffering from valvular disease who currently cannot be treated.
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Affiliation(s)
- Gil Marom
- School of Mechanical Engineering, Tel Aviv University, Tel Aviv Israel
- To whom correspondence should be addressed. E-mail:
| | - Shmuel Einav
- Department of Biomedical Engineering, Tel Aviv University, Tel Aviv, Israel
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Baxter RD, Fann JI, DiMaio JM, Lobdell K. Digital Health Primer for Cardiothoracic Surgeons. Ann Thorac Surg 2020; 110:364-372. [PMID: 32268139 DOI: 10.1016/j.athoracsur.2020.02.072] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 01/03/2020] [Accepted: 02/23/2020] [Indexed: 12/12/2022]
Abstract
The burgeoning demands for quality, safety, and value in cardiothoracic surgery, in combination with the advancement and acceleration of digital health solutions and information technology, provide a unique opportunity to improve efficiency and effectiveness simultaneously in cardiothoracic surgery. This primer on digital health explores and reviews data integration, data processing, complex modeling, telehealth with remote monitoring, and cybersecurity as they shape the future of cardiothoracic surgery.
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Affiliation(s)
- Ronald D Baxter
- Department of Cardiothoracic Surgery, Baylor Scott and White, The Heart Hospital, Plano, Texas
| | - James I Fann
- Department of Cardiothoracic Surgery, Stanford University Medical Center, Stanford, California
| | - J Michael DiMaio
- Department of Cardiothoracic Surgery, Baylor Scott and White, The Heart Hospital, Plano, Texas
| | - Kevin Lobdell
- Sanger Heart and Vascular Institute, Atrium Health, Charlotte, North Carolina.
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Zhang Y, Wang VY, Morgan AE, Kim J, Handschumacher MD, Moskowitz CS, Levine RA, Ge L, Guccione JM, Weinsaft JW, Ratcliffe MB. Mechanical effects of MitraClip on leaflet stress and myocardial strain in functional mitral regurgitation - A finite element modeling study. PLoS One 2019; 14:e0223472. [PMID: 31600276 PMCID: PMC6786765 DOI: 10.1371/journal.pone.0223472] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Accepted: 09/23/2019] [Indexed: 11/18/2022] Open
Abstract
Purpose MitraClip is the sole percutaneous device approved for functional mitral regurgitation (MR; FMR) but MR recurs in over one third of patients. As device-induced mechanical effects are a potential cause for MR recurrence, we tested the hypothesis that MitraClip increases leaflet stress and procedure-related strain in sub-valvular left ventricular (LV) myocardium in FMR associated with coronary disease (FMR-CAD). Methods Simulations were performed using finite element models of the LV + mitral valve based on MRI of 5 sheep with FMR-CAD. Models were modified to have a 20% increase in LV volume (↑LV_VOLUME) and MitraClip was simulated with contracting beam elements (virtual sutures) placed between nodes in the center edge of the anterior (AL) and posterior (PL) mitral leaflets. Effects of MitraClip on leaflet stress in the peri-MitraClip region of AL and PL, septo-lateral annular diameter (SLAD), and procedure-related radial strain (Err) in the sub-valvular myocardium were calculated. Results MitraClip increased peri-MitraClip leaflet stress at end-diastole (ED) by 22.3±7.1 kPa (p<0.0001) in AL and 14.8±1.2 kPa (p<0.0001) in PL. MitraClip decreased SLAD by 6.1±2.2 mm (p<0.0001) and increased Err in the sub-valvular lateral LV myocardium at ED by 0.09±0.04 (p<0.0001)). Furthermore, MitraClip in ↑LV_VOLUME was associated with persistent effects at ED but also at end-systole where peri-MitraClip leaflet stress was increased in AL by 31.9±14.4 kPa (p = 0.0268) and in PL by 22.5±23.7 kPa (p = 0.0101). Conclusions MitraClip for FMR-CAD increases mitral leaflet stress and radial strain in LV sub-valvular myocardium. Mechanical effects of MitraClip are augmented by LV enlargement.
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Affiliation(s)
- Yue Zhang
- San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States of America
- Department of Surgery, University of California, San Francisco, CA, United States of America
| | - Vicky Y. Wang
- San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States of America
- Department of Surgery, University of California, San Francisco, CA, United States of America
| | - Ashley E. Morgan
- Department of Surgery, University of California, San Francisco, CA, United States of America
| | - Jiwon Kim
- Department of Medicine, Weill Cornell Medicine, New York, NY, United States of America
| | - Mark D. Handschumacher
- Division of Cardiology, Department of Medicine, Massachusetts General Hospital, Boston, MA, United States of America
| | - Chaya S. Moskowitz
- Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, NY, United States of America
| | - Robert A. Levine
- Division of Cardiology, Department of Medicine, Massachusetts General Hospital, Boston, MA, United States of America
| | - Liang Ge
- San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States of America
- Department of Surgery, University of California, San Francisco, CA, United States of America
| | - Julius M. Guccione
- San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States of America
- Department of Surgery, University of California, San Francisco, CA, United States of America
| | - Jonathan W. Weinsaft
- Department of Medicine, Weill Cornell Medicine, New York, NY, United States of America
| | - Mark B. Ratcliffe
- San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States of America
- Department of Surgery, University of California, San Francisco, CA, United States of America
- * E-mail:
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Neugebauer M, Tautz L, Hüllebrand M, Sündermann S, Degener F, Goubergrits L, Kühne T, Falk V, Hennemuth A. Virtual downsizing for decision support in mitral valve repair. Int J Comput Assist Radiol Surg 2018; 14:357-371. [PMID: 30293173 DOI: 10.1007/s11548-018-1868-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 09/28/2018] [Indexed: 12/30/2022]
Abstract
PURPOSE Various options are available for the treatment of mitral valve insufficiency, including reconstructive approaches such as annulus correction through ring implants. The correct choice of general therapy and implant is relevant for an optimal outcome. Additional to guidelines, decision support systems (DSS) can provide decision aid by means of virtual intervention planning and predictive simulations. Our approach on virtual downsizing is one of the virtual intervention tools that are part of the DSS workflow. It allows for emulating a ring implantation based on patient-specific lumen geometry and vendor-specific implants. METHODS Our approach is fully automatic and relies on a lumen mask and an annulus contour as inputs. Both are acquired from previous DSS workflow steps. A virtual surface- and contour-based model of a vendor-specific ring design (26-40 mm) is generated. For each case, the ring geometry is positioned with respect to the original, patient-specific annulus and additional anatomical landmarks. The lumen mesh is parameterized to allow for a vertex-based deformation with respect to the user-defined annulus. Derived from post-interventional observations, specific deformation schemes are applied to atrium and ventricle and the lumen mesh is altered with respect to the ring location. RESULTS For quantitative evaluation, the surface distance between the deformed lumen mesh and segmented post-operative echo lumen close to the annulus was computed for 11 datasets. The results indicate a good agreement. An arbitrary subset of six datasets was used for a qualitative evaluation of the complete lumen. Two domain experts compared the deformed lumen mesh with post-interventional echo images. All deformations were deemed plausible. CONCLUSION Our approach on virtual downsizing allows for an automatic creation of plausible lumen deformations. As it takes only a few seconds to generate results, it can be added to a virtual intervention toolset without unnecessarily increasing the pipeline complexity.
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Affiliation(s)
- Mathias Neugebauer
- Fraunhofer Institute for Medical Image Computing - MEVIS, Am Fallturm 1, 28359, Bremen, Germany.
| | - Lennart Tautz
- Fraunhofer Institute for Medical Image Computing - MEVIS, Am Fallturm 1, 28359, Bremen, Germany
- Charité - University Medicine Berlin, Berlin, Germany
| | - Markus Hüllebrand
- Fraunhofer Institute for Medical Image Computing - MEVIS, Am Fallturm 1, 28359, Bremen, Germany
| | | | - Franziska Degener
- German Heart Institute Berlin - DHZB, Berlin, Germany
- Charité - University Medicine Berlin, Berlin, Germany
| | | | - Titus Kühne
- German Heart Institute Berlin - DHZB, Berlin, Germany
- Charité - University Medicine Berlin, Berlin, Germany
| | - Volkmar Falk
- German Heart Institute Berlin - DHZB, Berlin, Germany
- Charité - University Medicine Berlin, Berlin, Germany
| | - Anja Hennemuth
- Fraunhofer Institute for Medical Image Computing - MEVIS, Am Fallturm 1, 28359, Bremen, Germany
- Charité - University Medicine Berlin, Berlin, Germany
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12
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Transcatheter Mitral Valve Intervention for Chronic Mitral Regurgitation: A Plethora of Different Technologies. Can J Cardiol 2018; 34:1200-1209. [DOI: 10.1016/j.cjca.2018.04.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 03/15/2018] [Accepted: 04/05/2018] [Indexed: 01/01/2023] Open
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13
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Ferrero Guadagnoli A, De Carlo C, Maisano F, Ho E, Saccocci M, Cuevas O, Luciani M, Kuwata S, Nietlispach F, Taramasso M. Cardioband system as a treatment for functional mitral regurgitation. Expert Rev Med Devices 2018; 15:415-421. [PMID: 29877743 DOI: 10.1080/17434440.2018.1485487] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
INTRODUCTION Are the current data on the Cardioband in the clinical area enough to consider it a tool for mitral regurgitation treatment? Severe secondary mitral valve insufficiency frequently affects high-risk surgical patients. The Cardioband system is a novel percutaneous surgical-like device for direct annuloplasty. It is implanted into the beating heart by transvenous femoral access, with minimal impact on hemodynamic and cardiac function during implantation. So far, it has demonstrated safety and feasibility in high-risk patients with functional mitral regurgitation; it has imparted significant annular reduction and regurgitation improvements. In well-selected patients, it could be an option for mitral valve repair. AREAS COVERED This is a bibliographic review based on scientific publications and medical congress reports. It includes the most current information related to Cardioband in mitral regurgitation. EXPERT COMMENTARY This novel, less-invasive and effective tool is an option for the open repair or replacement of the mitral valve in high-risk surgical patients. Although the current results of Cardioband are promising, more data and longer follow-up times are necessary to confirm its safety and efficacy and to evaluate the durability of the results.
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Affiliation(s)
| | - Carlotta De Carlo
- a University Heart Center , University Hospital , Zurich , Switzerland
| | - Francesco Maisano
- a University Heart Center , University Hospital , Zurich , Switzerland
| | - Edwin Ho
- a University Heart Center , University Hospital , Zurich , Switzerland
| | - Matteo Saccocci
- a University Heart Center , University Hospital , Zurich , Switzerland
| | - Oscar Cuevas
- a University Heart Center , University Hospital , Zurich , Switzerland
| | - Marco Luciani
- a University Heart Center , University Hospital , Zurich , Switzerland
| | - Shingo Kuwata
- a University Heart Center , University Hospital , Zurich , Switzerland
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Mitral annuloplasty ring flexibility preferentially reduces posterior suture forces. J Biomech 2018; 75:58-66. [PMID: 29747965 DOI: 10.1016/j.jbiomech.2018.04.043] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 04/23/2018] [Accepted: 04/25/2018] [Indexed: 11/20/2022]
Abstract
Annuloplasty ring repair is a common procedure for the correction of mitral valve regurgitation. Commercially available rings vary in dimensions and material properties. Annuloplasty ring suture dehiscence from the native annulus is a catastrophic yet poorly understood phenomenon that has been reported across ring types. Recognizing that sutures typically dehisce from the structurally weaker posterior annulus, our group is conducting a multi-part study in search of ring design parameters that influence forces acting on posterior annular sutures in the beating heart. Herein, we report the effect of ring rigidity on suture forces. Measurements utilized custom force sensors, attached to annuloplasty rings and implanted in normal ovine subjects via standard surgical procedure. Tested rings included the semi-rigid Physio (Edwards Lifesciences) and rigid and flexible prototypes of matching geometry. While no significant differences due to ring stiffness existed for sutures in the anterior region, posterior forces were significantly reduced with use of the flexible ring (rigid: 1.95 ± 0.96 N, semi-rigid: 1.76 ± 1.19 N, flexible: 1.04 ± 0.63 N; p < 0.001). The ratio of anterior to posterior FC scaled positively with increasing flexibility (p < 0.001), and posterior forces took more time to reach their peak load when a flexible ring was used (p < 0.001). This suggests a more rigid ring enables more rapid/complete force equilibration around the suture network, transferring higher anterior forces to the weaker posterior tissue. For mitral annuloplasties requiring ring rigidity, we propose a ring design concept to potentially disrupt this force transfer and improve suture retention.
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Ferrero Guadagnoli A, Taramasso M, Saccocci M, Cuevas O, Ho E, Luciani M, Kuwata S, Nietlispach F, Maisano F. Cardioband system: a novel percutaneous solution for atrioventricular valve insufficiency. Indian J Thorac Cardiovasc Surg 2018. [DOI: 10.1007/s12055-018-0667-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Sack KL, Davies NH, Guccione JM, Franz T. Personalised computational cardiology: Patient-specific modelling in cardiac mechanics and biomaterial injection therapies for myocardial infarction. Heart Fail Rev 2018; 21:815-826. [PMID: 26833320 PMCID: PMC4969231 DOI: 10.1007/s10741-016-9528-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Predictive computational modelling in biomedical research offers the potential to integrate diverse data, uncover biological mechanisms that are not easily accessible through experimental methods and expose gaps in knowledge requiring further research. Recent developments in computing and diagnostic technologies have initiated the advancement of computational models in terms of complexity and specificity. Consequently, computational modelling can increasingly be utilised as enabling and complementing modality in the clinic—with medical decisions and interventions being personalised. Myocardial infarction and heart failure are amongst the leading causes of death globally despite optimal modern treatment. The development of novel MI therapies is challenging and may be greatly facilitated through predictive modelling. Here, we review the advances in patient-specific modelling of cardiac mechanics, distinguishing specificity in cardiac geometry, myofibre architecture and mechanical tissue properties. Thereafter, the focus narrows to the mechanics of the infarcted heart and treatment of myocardial infarction with particular attention on intramyocardial biomaterial delivery.
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Affiliation(s)
- Kevin L Sack
- Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Private Bag X3, 7935, Observatory, South Africa
| | - Neil H Davies
- Cardiovascular Research Unit, MRC IUCHRU, Chris Barnard Division of Cardiothoracic Surgery, University of Cape Town, Observatory, South Africa
| | - Julius M Guccione
- Department of Surgery, University of California at San Francisco, San Francisco, CA, USA
| | - Thomas Franz
- Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Private Bag X3, 7935, Observatory, South Africa.
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17
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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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18
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Pappalardo O, Sturla F, Onorati F, Puppini G, Selmi M, Luciani G, Faggian G, Redaelli A, Votta E. Mass-spring models for the simulation of mitral valve function: Looking for a trade-off between reliability and time-efficiency. Med Eng Phys 2017; 47:93-104. [DOI: 10.1016/j.medengphy.2017.07.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 06/23/2017] [Accepted: 07/03/2017] [Indexed: 11/27/2022]
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Gao H, Feng L, Qi N, Berry C, Griffith BE, Luo X. A coupled mitral valve-left ventricle model with fluid-structure interaction. Med Eng Phys 2017; 47:128-136. [PMID: 28751011 PMCID: PMC6779302 DOI: 10.1016/j.medengphy.2017.06.042] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 06/13/2017] [Accepted: 06/24/2017] [Indexed: 12/16/2022]
Abstract
Understanding the interaction between the valves and walls of the heart is important in assessing and subsequently treating heart dysfunction. This study presents an integrated model of the mitral valve (MV) coupled to the left ventricle (LV), with the geometry derived from in vivo clinical magnetic resonance images. Numerical simulations using this coupled MV-LV model are developed using an immersed boundary/finite element method. The model incorporates detailed valvular features, left ventricular contraction, nonlinear soft tissue mechanics, and fluid-mediated interactions between the MV and LV wall. We use the model to simulate cardiac function from diastole to systole. Numerically predicted LV pump function agrees well with in vivo data of the imaged healthy volunteer, including the peak aortic flow rate, the systolic ejection duration, and the LV ejection fraction. In vivo MV dynamics are qualitatively captured. We further demonstrate that the diastolic filling pressure increases significantly with impaired myocardial active relaxation to maintain a normal cardiac output. This is consistent with clinical observations. The coupled model has the potential to advance our fundamental knowledge of mechanisms underlying MV-LV interaction, and help in risk stratification and optimisation of therapies for heart diseases.
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Affiliation(s)
- Hao Gao
- School of Mathematics and Statistics, University of Glasgow, Glasgow, UK.
| | - Liuyang Feng
- School of Mathematics and Statistics, University of Glasgow, Glasgow, UK
| | - Nan Qi
- School of Mathematics and Statistics, University of Glasgow, Glasgow, UK
| | - Colin Berry
- Institute of Cardiovascular and Medical Science, University of Glasgow, Glasgow, UK
| | - Boyce E Griffith
- Departments of Mathematics and Biomedical Engineering and McAllister Heart Institute, University of North Carolina, Chapel Hill, NC, USA
| | - Xiaoyu Luo
- School of Mathematics and Statistics, University of Glasgow, Glasgow, UK
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20
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Pierce EL, Bloodworth CH, Siefert AW, Easley TF, Takayama T, Kawamura T, Gorman RC, Gorman JH, Yoganathan AP. Mitral annuloplasty ring suture forces: Impact of surgeon, ring, and use conditions. J Thorac Cardiovasc Surg 2017; 155:131-139.e3. [PMID: 28728784 DOI: 10.1016/j.jtcvs.2017.06.036] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 05/30/2017] [Accepted: 06/15/2017] [Indexed: 10/19/2022]
Abstract
OBJECTIVE The study objective was to quantify the effect of ring type, ring-annulus sizing, suture position, and surgeon on the forces required to tie down and constrain a mitral annuloplasty ring to a beating heart. METHODS Physio (Edwards Lifesciences, Irvine, Calif) or Profile 3D (Medtronic, Dublin, Ireland) annuloplasty rings were instrumented with suture force transducers and implanted in ovine subjects (N = 23). Tie-down forces and cyclic contractile forces were recorded and analyzed at 10 suture positions and at 3 levels of increasing peak left ventricular pressure. RESULTS Across all conditions, tie-down force was 2.7 ± 1.4 N and cyclic contractile force was 2.0 ± 1.2 N. Tie-down force was not meaningfully affected by any factor except surgeon. Significant differences in overall and individual tie-down forces were observed between the 2 primary implanting surgeons. No other factors were observed to significantly affect tie-down force. Contractile suture forces were significantly reduced by ring-annulus true sizing. This was driven almost exclusively by Physio cases and by reduction along the anterior aspect, where dehiscence is less common clinically. Contractile suture forces did not differ significantly between ring types. However, when undersizing, Profile 3D forces were significantly more uniform around the annular circumference. A suture's tie-down force did not correlate to its eventual contractile force. CONCLUSIONS Mitral annuloplasty suture loading is influenced by ring type, ring-annulus sizing, suture position, and surgeon, suggesting that reports of dehiscence may not be merely a series of isolated errors. When compared with forces known to cause suture dehiscence, these in vivo suture loading data aid in establishing potential targets for reducing the occurrence of ring dehiscence.
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Affiliation(s)
- Eric L Pierce
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Ga
| | - Charles H Bloodworth
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Ga
| | - Andrew W Siefert
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Ga; Momentum PMV, Inc, Alpharetta, Ga
| | - Thomas F Easley
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Ga
| | - Tetsushi Takayama
- Gorman Cardiovascular Research Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pa
| | - Tomonori Kawamura
- Gorman Cardiovascular Research Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pa
| | - Robert C Gorman
- Gorman Cardiovascular Research Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pa
| | - Joseph H Gorman
- Gorman Cardiovascular Research Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pa
| | - Ajit P Yoganathan
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Ga.
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21
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Choi A, McPherson DD, Kim H. Computational virtual evaluation of the effect of annuloplasty ring shape. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33:10.1002/cnm.2831. [PMID: 27603720 PMCID: PMC5340636 DOI: 10.1002/cnm.2831] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 05/31/2016] [Accepted: 09/01/2016] [Indexed: 06/06/2023]
Abstract
Mitral regurgitation (MR) is a result of mitral valve (MV) pathology. Its etiology can be categorized as degenerative or functional MR. Ring annuloplasty aims to reconfigure a dilated mitral annulus to its normal size and shape. We investigated the effect of annuloplasty ring shape on MR outcome using our established 3-dimensional (3-D) echocardiography-based computational MV evaluation protocols. Virtual patient MV models were created from 3-D transesophageal echocardiographic data in patients with MR because of mitral annular dilation. Two distinct annuloplasty rings (Physio II and GeoForm) were designed and virtually implanted to the patient MVs. Dynamic finite element simulations of MV function were performed for each MV after virtual ring annuloplasty of either ring, and physiologic and biomechanical characteristics of MV function were compared. Excessive stress values appeared primarily in the midanterior and midposterior regions, and lack of leaflet coaptation was found in pre-annuloplasty patient MVs. Both rings demonstrated marked reduction of stresses and efficient leaflet coaptation. The Physio II ring demonstrated more evenly distributed stress reduction across the leaflets and annulus compared with the GeoForm ring. Conversely, the highly nonplanar curvature of the GeoForm ring more effectively increased leaflet coaptation compared with the Physio II ring. This indicates that the shape of annuloplasty ring affects post-annuloplasty physiologic and biomechanical conditions, which can lead to tissue alteration over a longer period after ring annuloplasty. This virtual ring annuloplasty simulation strategy provides detailed physiologic and biomechanical information and may help better plan the optimal ring selection and improved patient-specific MV repairs.
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Affiliation(s)
- Ahnryul Choi
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - David D. McPherson
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Hyunggun Kim
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, Texas, USA
- Department of Bio-Mechatronic Engineering, Sungkyunkwan University, Suwon, Gyeonggi, Republic of Korea
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22
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Kuwata S, Taramasso M, Guidotti A, Nietlispach F, Maisano F. Evaluation of Valtech’s transcatheter mitral valve repair device. Expert Rev Med Devices 2017; 14:189-195. [DOI: 10.1080/17434440.2017.1292122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
| | | | | | - Fabian Nietlispach
- University Heart Center Zurich, Zurich University Hospital, Zurich, Switzerland
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23
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Pham T, Kong F, Martin C, Wang Q, Primiano C, McKay R, Elefteriades J, Sun W. Finite Element Analysis of Patient-Specific Mitral Valve with Mitral Regurgitation. Cardiovasc Eng Technol 2017; 8:3-16. [PMID: 28070866 DOI: 10.1007/s13239-016-0291-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 12/29/2016] [Indexed: 12/30/2022]
Abstract
Functional mitral regurgitation (FMR) is a significant complication of left ventricular dysfunction and strongly associated with a poor prognosis. In this study, we developed a patient-specific finite element (FE) model of the mitral apparatus in a FMR patient which included: both leaflets with thickness, annulus, chordae tendineae, and chordae insertions on the leaflets and origins on the papillary muscles. The FE model incorporated human age- and gender-matched anisotropic hyperelastic material properties, and MV closure at systole was simulated. The model was validated by comparing the FE results from valve closure simulation with the in vivo geometry of the MV at systole. It was found that the FE model could not replicate the in vivo MV geometry without the application of tethering pre-tension force in the chordae at diastole. Upon applying the pre-tension force and performing model optimization by adjusting the chordal length, position, and leaflet length, a good agreement between the FE model and the in vivo model was established. Not only were the chordal forces high at both diastole and systole, but the tethering force on the anterior papillary muscle was higher than that of the posterior papillary muscle, which resulted in an asymmetrical gap with a larger orifice area at the anterolateral commissure resulting in MR. The analyses further show that high peak stress and strain were found at the chordal insertions where large chordal tethering forces were found. This study shows that the pre-tension tethering force plays an important role in accurately simulating the MV dynamics in this FMR patient, particularly in quantifying the degree of leaflet coaptation and stress distribution. Due to the complexity of the disease, the patient-specific computational modeling procedure of FMR patients presented should be further evaluated using a large patient cohort. However, this study provides useful insights into the MV biomechanics of a FMR patient, and could serve as a tool to assist in pre-operative planning for MV repair or replacement surgical or interventional procedures.
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Affiliation(s)
- Thuy Pham
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Technology Enterprise Park, Room 206, 387 Technology Circle, Atlanta, GA, 30313-2412, USA
| | - Fanwei Kong
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Technology Enterprise Park, Room 206, 387 Technology Circle, Atlanta, GA, 30313-2412, USA
| | - Caitlin Martin
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Technology Enterprise Park, Room 206, 387 Technology Circle, Atlanta, GA, 30313-2412, USA
| | - Qian Wang
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Technology Enterprise Park, Room 206, 387 Technology Circle, Atlanta, GA, 30313-2412, USA
| | | | - Raymond McKay
- Cardiology Department of Hartford Hospital, Hartford, CT, USA
| | | | - Wei Sun
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Technology Enterprise Park, Room 206, 387 Technology Circle, Atlanta, GA, 30313-2412, USA.
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Pantoja JL, Morgan AE, Grossi EA, Jensen MO, Weinsaft JW, Levine RA, Ge L, Ratcliffe MB. Undersized Mitral Annuloplasty Increases Strain in the Proximal Lateral Left Ventricular Wall. Ann Thorac Surg 2016; 103:820-827. [PMID: 27720201 DOI: 10.1016/j.athoracsur.2016.07.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 06/10/2016] [Accepted: 07/05/2016] [Indexed: 10/20/2022]
Abstract
BACKGROUND Recurrence of mitral regurgitation (MR) after undersized mitral annuloplasty (MA) for ischemic MR is as high as 60%, with the recurrence rate likely due to continued dilation of the left ventricle (LV). To better understand the causes of recurrent MR, we studied the effect of undersized MA on strain in the LV wall. We hypothesize that the acute change in ventricular shape induced by MA will cause increased strain in regions nearest the mitral valve. METHODS Finite element models were previously reported, based on cardiac magnetic resonance images of 5 sheep with mild to moderate ischemic MR. A 24-mm saddle-shaped rigid annuloplasty ring was modeled and used to simulate virtual MA. Longitudinal and myofiber strains were calculated at end-diastole and end-systole, with preoperative early diastolic geometry as the reference state. RESULTS The undersized MA significantly increased longitudinal strain at end-diastole in the lateral LV wall. The effect was greatest in the proximal-lateral endocardial surface, where longitudinal strain after MA was approximately triple the preoperative strain (11.17% ± 2.15% vs 3.45% ± 0.92%, p = 0.0057). In contrast, postoperative end-diastolic fiber strain decreased in this same region (2.53% ± 2.14% vs 7.72% ± 1.79%, p = 0.0060). There were no significant changes in either strain type at end-systole. CONCLUSIONS Undersized MA increased longitudinal strain in the proximal lateral LV wall at end-diastole. This procedure-related strain at the proximal-lateral LV wall may foster continued LV enlargement and subsequent recurrence of mitral regurgitation.
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Affiliation(s)
- Joe Luis Pantoja
- University of California, San Francisco, San Francisco, California
| | - Ashley E Morgan
- East Bay Surgical Residency, University of California, San Francisco, San Francisco, California
| | - Eugene A Grossi
- Department of Cardiothoracic Surgery, New York University, New York, New York; New York Harbor Veterans Affairs Medical Center, New York, New York
| | - Morten O Jensen
- Department of Biomedical Engineering, University of Arkansas, Fayetteville, Arkansas
| | - Jonathan W Weinsaft
- Departments of Medicine (Cardiology) and Radiology, Weill Cornell Medicine, New York, New York
| | - Robert A Levine
- Division of Cardiology, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts
| | - Liang Ge
- Department of Surgery, University of California, San Francisco, San Francisco, California; Department of Bioengineering, University of California, San Francisco, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California
| | - Mark B Ratcliffe
- Department of Surgery, University of California, San Francisco, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California.
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25
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Morgan AE, Pantoja JL, Grossi EA, Ge L, Weinsaft JW, Ratcliffe MB. Neochord placement versus triangular resection in mitral valve repair: A finite element model. J Surg Res 2016; 206:98-105. [PMID: 27916382 DOI: 10.1016/j.jss.2016.07.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 05/23/2016] [Accepted: 07/07/2016] [Indexed: 01/27/2023]
Abstract
BACKGROUND Recurrent mitral regurgitation after mitral valve repair is common, occurring in nearly 50% of patients within 10 years of surgery. Durability of repair is partly related to stress distribution over the mitral leaflets. We hypothesized that repair with neochords (NCs) results in lower stress than leaflet resection (LR). MATERIALS AND METHODS Magnetic resonance imaging and 3D echocardiography were performed before surgical repair of P2 prolapse in a single patient. A finite element model of the left ventricle and mitral valve was created previously, and the modeling program LS-DYNA was used to calculate leaflet stress for the following repairs: Triangular LR; LR with ring annuloplasty (LR + RA); One NC; Two NCs; and 2NC + RA. RESULTS (1) NC placement resulted in stable posterior leaflet stress: Baseline versus 2 NC at end diastole (ED), 12.1 versus 12.0 kPa, at end systole (ES) 20.3 versus 21.7 kPa. (2) In contrast, LR increased posterior leaflet stress: Baseline versus LR at ED 12.1 versus 40.8 kPa, at ES 20.3 versus 46.1 kPa. (3) All repair types reduced anterior leaflet stress: Baseline versus 2 NC versus LR 34.2 versus 25.8 versus 20.6 kPa at ED and 80.8 versus 76.8 versus 67.8 kPa at ES. (4) The addition of RA reduced leaflet stress relative to repair without RA. CONCLUSIONS Neochord repair restored normal leaflet coaptation without creating excessive leaflet stress, whereas leaflet resection more than doubled stress across the posterior leaflet. The excess stress created by leaflet resection was partially, but not completely, mitigated by ring annuloplasty.
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Affiliation(s)
- Ashley E Morgan
- East Bay Surgical Residency, University of California, San Francisco, California
| | - Joe L Pantoja
- College of Medicine, University of California, San Francisco, California
| | - Eugene A Grossi
- Department of Cardiothoracic Surgery, New York University, New York, New York; Department of Cardiothoracic Surgery, New York Harbor Veterans Affairs Medical Center, New York, New York
| | - Liang Ge
- Department of Surgery, University of California, San Francisco, California; Department of Bioengineering, University of California, San Francisco, California; Department of Surgery, Veterans Affairs Medical Center, San Francisco, California
| | - Jonathan W Weinsaft
- Department of Medicine (Cardiology), Weill Cornell Medical College, New York, New York; Department of Radiology, Weill Cornell Medical College, New York, New York
| | - Mark B Ratcliffe
- Department of Surgery, University of California, San Francisco, California; Department of Bioengineering, University of California, San Francisco, California; Department of Surgery, Veterans Affairs Medical Center, San Francisco, California.
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26
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Ge L. A Characteristic-Based Constitutive Law for Dispersed Fibers. J Biomech Eng 2016; 138:2520869. [PMID: 27138358 DOI: 10.1115/1.4033517] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Indexed: 11/08/2022]
Abstract
Biological tissues are typically constituted of dispersed fibers. Modeling the constitutive laws of such tissues remains a challenge. Direct integration over all fibers is considered to be accurate but requires very expensive numerical integration. A general structure tensor (GST) model was previously developed to bypass this costly numerical integration step, but there are concerns about the model's accuracy. Here we estimate the approximation error of the GST model. We further reveal that the GST model ignores strain energy induced by shearing motions. Subsequently, we propose a new characteristic-based constitutive law to better approximate the direct integration model. The new model is very cost-effective and closely approximates the "true" strain energy as calculated by the direct integration when stress-strain nonlinearity or fiber dispersion angle is small.
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27
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Ge L, Haraldsson H, Hope MD, Saloner D, Guccione JM, Ratcliffe M, Tseng EE. Suture Forces for Closure of Transapical Transcatheter Aortic Valve Replacement: A Mathematical Model. THE JOURNAL OF HEART VALVE DISEASE 2016; 25:424-429. [PMID: 28009944 PMCID: PMC8593802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
BACKGROUND Transcatheter aortic valve replacement (TAVR) has revolutionized the treatment of severe aortic stenosis in intermediate, high-risk, and inoperable patients. TAVR has multiple access routes, including transfemoral (TF), transapical (TA), direct aortic (DA), axillary, transcarotid, and transcaval. The most commonly applied algorithm is a TF-first approach, where only when patients are unsuitable for TF are alternatives such as TA considered. An infrequent - but dreaded - risk is left ventricular (LV) apical bleeding from tearing or rupture with the TA approach. With burgeoning transcatheter mitral technology that requires a TA approach, the study aim was to develop a mathematical model to determine suture forces for TA closure. METHODS Preoperative cine-cardiac magnetic resonance imaging (MRI) was used to acquire three-dimensional (3D) LV geometry at end-systole and end-diastole. Endocardial and epicardial boundaries were manually contoured using MeVisLab, a surface reconstruction software. 3D surfaces of endocardium and epicardium were reconstructed, and surfaces at end-systole were used to create a 3D LV finite element (FE) mesh. TA access was mimicked by developing a 10-mm defect within the LV FE model. The LV apex was closed using a virtual suture technique in FE analysis with the application of two virtual sutures. After virtual closure, a FE analysis was performed of LV model diastolic filling and systolic contraction. RESULTS Proof of concept was achieved to develop an LV transapical access site and perform FE analysis to achieve closure. The FE method of virtual suture technique successfully approximated the LV apical defect. The peak axial forces on virtual sutures at end-diastole and end-systole were 0.445N and 0.736N, respectively. CONCLUSIONS A LV TA access model was mathematically developed that could be used to evaluate the suture tension of the TA closure process. Further development of this approach may be useful to risk-stratify patients in the future for LV apical tearing. Video 1: Cine cardiac magnetic resonance imaging of the left ventricle. Video 2: Slow motion animation of left ventricular baseline simulation. Video 3: Animation of the virtual suturing process.
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Affiliation(s)
- Liang Ge
- Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, CA
| | - Henrik Haraldsson
- Department of Radiology, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, CA
| | - Michael D. Hope
- Department of Radiology, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, CA
| | - David Saloner
- Department of Radiology, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, CA
| | - Julius M. Guccione
- Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, CA
| | - Mark Ratcliffe
- Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, CA
| | - Elaine E. Tseng
- Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, CA
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Taramasso M, Inderbitzin DT, Guidotti A, Nietlispach F, Gaemperli O, Zuber M, Maisano F. Transcatheter direct mitral valve annuloplasty with the Cardioband system for the treatment of functional mitral regurgitation. Multimed Man Cardiothorac Surg 2016; 2016:mmw004. [PMID: 27247326 DOI: 10.1093/mmcts/mmw004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 01/28/2016] [Indexed: 06/05/2023]
Abstract
Direct mitral valve annuloplasty is a transcatheter mitral valve repair approach that mimics the conventional surgical approach to treat functional mitral regurgitation. The Cardioband system (Valtech Cardio, Inc., Or-Yehuda, Israel) is delivered by a trans-septal approach and the implant is performed on the atrial side of the mitral annulus, under live echo and fluoroscopic guidance using multiple anchor elements. The Cardioband system obtained CE mark approval in October 2015, and initial clinical experiences are promising with regard to feasibility, safety and efficacy.
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Affiliation(s)
- Maurizio Taramasso
- Cardiovascular Surgery Department, University Hospital of Zurich, University of Zurich, Zurich, Switzerland
| | - Devdas T Inderbitzin
- Cardiovascular Surgery Department, University Hospital of Zurich, University of Zurich, Zurich, Switzerland
| | - Andrea Guidotti
- Cardiovascular Surgery Department, University Hospital of Zurich, University of Zurich, Zurich, Switzerland
| | - Fabian Nietlispach
- Cardiology Department, University Hospital of Zurich, University of Zurich, Zurich, Switzerland
| | - Oliver Gaemperli
- Cardiology Department, University Hospital of Zurich, University of Zurich, Zurich, Switzerland
| | - Michel Zuber
- Cardiology Department, University Hospital of Zurich, University of Zurich, Zurich, Switzerland
| | - Francesco Maisano
- Cardiovascular Surgery Department, University Hospital of Zurich, University of Zurich, Zurich, Switzerland
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Morgan AE, Pantoja JL, Weinsaft J, Grossi E, Guccione JM, Ge L, Ratcliffe M. Finite Element Modeling of Mitral Valve Repair. J Biomech Eng 2016; 138:021009. [PMID: 26632260 PMCID: PMC5101040 DOI: 10.1115/1.4032125] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Revised: 11/18/2015] [Indexed: 11/08/2022]
Abstract
The mitral valve is a complex structure regulating forward flow of blood between the left atrium and left ventricle (LV). Multiple disease processes can affect its proper function, and when these diseases cause severe mitral regurgitation (MR), optimal treatment is repair of the native valve. The mitral valve (MV) is a dynamic structure with multiple components that have complex interactions. Computational modeling through finite element (FE) analysis is a valuable tool to delineate the biomechanical properties of the mitral valve and understand its diseases and their repairs. In this review, we present an overview of relevant mitral valve diseases, and describe the evolution of FE models of surgical valve repair techniques.
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Affiliation(s)
- Ashley E. Morgan
- University of California,
San Francisco—East Bay Surgical Residency,
Oakland, CA 94602
e-mail:
| | - Joe Luis Pantoja
- School of Medicine,
University of California, San Francisco,
San Francisco, CA 94143
e-mail:
| | - Jonathan Weinsaft
- Department of Cardiology,
Cornell University School of Medicine,
New York, NY 10065
e-mail:
| | - Eugene Grossi
- Department of Cardiothoracic Surgery,
NYU School of Medicine,
New York, NY 10016
e-mail:
| | - Julius M. Guccione
- Department of Surgery and Bioengineering,
University of California, San Francisco,
San Francisco, CA 94143
e-mail:
| | - Liang Ge
- Department of Surgery and Bioengineering,
Veterans Affairs Medical Center,
University of California, San Francisco,
San Francisco, CA 94121
e-mail:
| | - Mark Ratcliffe
- Surgical Service (112)
Departments of Surgery and Bioengineering,
Veterans Affairs Medical Center,
University of California, San Francisco,
4150 Clement Street,
San Francisco, CA 94121
e-mail:
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30
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Maisano F, Taramasso M, Nickenig G, Hammerstingl C, Vahanian A, Messika-Zeitoun D, Baldus S, Huntgeburth M, Alfieri O, Colombo A, La Canna G, Agricola E, Zuber M, Tanner FC, Topilsky Y, Kreidel F, Kuck KH. Cardioband, a transcatheter surgical-like direct mitral valve annuloplasty system: early results of the feasibility trial. Eur Heart J 2015; 37:817-25. [DOI: 10.1093/eurheartj/ehv603] [Citation(s) in RCA: 140] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 10/13/2015] [Indexed: 11/14/2022] Open
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Pantoja JL, Zhang Z, Tartibi M, Sun K, Macmillan W, Guccione JM, Ge L, Ratcliffe MB. Residual Stress Impairs Pump Function After Surgical Ventricular Remodeling: A Finite Element Analysis. Ann Thorac Surg 2015; 100:2198-205. [PMID: 26341601 DOI: 10.1016/j.athoracsur.2015.05.119] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 05/11/2015] [Accepted: 05/15/2015] [Indexed: 11/30/2022]
Abstract
BACKGROUND Surgical ventricular restoration (Dor procedure) is generally thought to reduce left ventricular (LV) myofiber stress (FS) but to adversely affect pump function. However, the underlying mechanism is unclear. The goal of this study was to determine the effect of residual stress (RS) on LV FS and pump function after the Dor procedure. METHODS Previously described finite element models of the LV based on magnetic resonance imaging data obtained in 5 sheep 16 weeks after anteroapical myocardial infarction were used. Simulated polyethylene terephthalate fiber (Dacron) patches that were elliptical and 25% of the infarct opening area were implanted using a virtual suture technique (VIRTUAL-DOR). In each case, diastole and systole were simulated, and RS, FS, LV volumes, systolic and diastolic function, and pump (Starling) function were calculated. RESULTS VIRTUAL-DOR was associated with significant RS that was tensile (2.89 ± 1.31 kPa) in the remote myocardium and compressive (234.15 ± 65.53 kPa) in the border zone. VIRTUAL-DOR+RS (compared with VIRTUAL-DOR-NO-RS) was associated with further reduction in regional diastolic and systolic FS, with the greatest change in the border zone (43.5-fold and 7.1-fold, respectively; p < 0.0001). VIRTUAL-DOR+RS was also associated with further reduction in systolic and diastolic volumes (7.9%; p = 0.0606, and 10.6%; p = 0.0630, respectively). The resultant effect was a further reduction in pump function after VIRTUAL-DOR+RS. CONCLUSIONS Residual stress that occurs after the Dor procedure is positive (tensile) in the remote myocardium and negative (compressive) in the border zone and associated with reductions in FS and LV volumes. The resultant effect is a further reduction in LV pump (Starling) function.
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Affiliation(s)
| | - Zhihong Zhang
- Veterans Affairs Medical Center, San Francisco, California
| | | | - Kay Sun
- Veterans Affairs Medical Center, San Francisco, California
| | | | - Julius M Guccione
- Department of Surgery, University of California, San Francisco, California; Department of Bioengineering, University of California, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California
| | - Liang Ge
- Department of Surgery, University of California, San Francisco, California; Department of Bioengineering, University of California, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California
| | - Mark B Ratcliffe
- Department of Surgery, University of California, San Francisco, California; Department of Bioengineering, University of California, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California.
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Human Cardiac Function Simulator for the Optimal Design of a Novel Annuloplasty Ring with a Sub-valvular Element for Correction of Ischemic Mitral Regurgitation. Cardiovasc Eng Technol 2015; 6:105-16. [PMID: 25984248 PMCID: PMC4427655 DOI: 10.1007/s13239-015-0216-z] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 01/27/2015] [Indexed: 12/14/2022]
Abstract
Ischemic mitral regurgitation is associated with substantial risk of death. We sought to: (1)
detail significant recent improvements to the Dassault Systèmes human cardiac function simulator (HCFS); (2) use the HCFS to simulate normal cardiac function as well as pathologic function in the setting of posterior left ventricular (LV) papillary muscle infarction; and (3) debut our novel device for correction of ischemic mitral regurgitation. We synthesized two recent studies of human myocardial mechanics. The first study presented the robust and integrative finite element HCFS. Its primary limitation was its poor diastolic performance with an LV ejection fraction below 20% caused by overly stiff ex vivo porcine tissue parameters. The second study derived improved diastolic myocardial material parameters using in vivo MRI data from five normal human subjects. We combined these models to simulate ischemic mitral regurgitation by computationally infarcting an LV region including the posterior papillary muscle. Contact between our novel device and the mitral valve apparatus was simulated using Dassault Systèmes SIMULIA software. Incorporating improved cardiac geometry and diastolic myocardial material properties in the HCFS resulted in a realistic LV ejection fraction of 55%. Simulating infarction of posterior papillary muscle caused regurgitant mitral valve mechanics. Implementation of our novel device corrected valve dysfunction. Improvements in the current study to the HCFS permit increasingly accurate study of myocardial mechanics. The first application of this simulator to abnormal human cardiac function suggests that our novel annuloplasty ring with a sub-valvular element will correct ischemic mitral regurgitation.
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Morrel WG, Ge L, Ward A, Zhang Z, Grossi EA, Guccione JM, Ratcliffe MB. Effect of mitral annuloplasty device shape and size on leaflet and myofiber stress following repair of posterior leaflet prolapse: a patient-specific finite element simulation. THE JOURNAL OF HEART VALVE DISEASE 2014; 23:727-734. [PMID: 25790620 PMCID: PMC6040586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
BACKGROUND AND AIM OF THE STUDY Mitral annuloplasty (MA) devices are available in different shapes and sizes, but the preferred shape and size are unclear. METHODS A previously described and validated finite element (FE) model of the left ventricle (LV) with mitral valve (MV) based on magnetic resonance imaging and three-dimensional echocardiography images from a patient with posterior leaflet (PL; P2) prolapse was used in this study. FE models of MA devices with different shapes (flat partial, shallow saddle, pronounced saddle) and sizes (36-30) were created. Virtual leaflet resection + MA with each shape and size were simulated. Leaflet geometry, stresses in the leaflets and base of the LV, and forces in the chordae and MA sutures were calculated. RESULTS All MA shapes increased the mitral coaptation length, reduced the elevated PL stress at end-diastole (ED) and end-systole (ES) that occurred after leaflet resection, and reduced anterior leaflet (AL) stress at ES. MA devices of all shapes and sizes modestly reduced myofiber stress at the LV base in ED and ES. In general, saddle-shaped devices had the greatest effect. CONCLUSION All MA shapes increased coaptation length and reduced mitral leaflet stress and myofiber stress in the base of the LV. an additional reduction in MA size further increased coaptation length and reduced leaflet and myofiber stress. In general, saddle-shaped devices had the greatest effect.
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Affiliation(s)
- William G. Morrel
- School of Medicine, University of California, San Francisco, California
| | - Liang Ge
- Department of Surgery, University of California, San Francisco, California
- Veterans Affairs Medical Center, San Francisco, California
| | - Alison Ward
- Department of Cardiothoracic Surgery, New York University
| | - Zhihong Zhang
- Veterans Affairs Medical Center, San Francisco, California
| | | | - Julius M. Guccione
- School of Medicine, University of California, San Francisco, California
- Department of Surgery, University of California, San Francisco, California
- Veterans Affairs Medical Center, San Francisco, California
| | - Mark B. Ratcliffe
- Department of Surgery, University of California, San Francisco, California
- Department of Bioengineering, University of California, San Francisco, California
- Veterans Affairs Medical Center, San Francisco, California
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34
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Pantoja JL, Ge L, Zhang Z, Morrel WG, Guccione JM, Grossi EA, Ratcliffe MB. Posterior papillary muscle anchoring affects remote myofiber stress and pump function: finite element analysis. Ann Thorac Surg 2014; 98:1355-62. [PMID: 25130075 PMCID: PMC6051352 DOI: 10.1016/j.athoracsur.2014.04.077] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 04/14/2014] [Accepted: 04/15/2014] [Indexed: 11/17/2022]
Abstract
BACKGROUND The role of posterior papillary muscle anchoring (PPMA) in the management of chronic ischemic mitral regurgitation (CIMR) is controversial. We studied the effect of anchoring point direction and relocation displacement on left ventricular (LV) regional myofiber stress and pump function. METHODS Previously described finite element models of sheep 16 weeks after posterolateral myocardial infarction (MI) were used. True-sized mitral annuloplasty (MA) ring insertion plus different PPM anchoring techniques were simulated. Anchoring points tested included both commissures and the central anterior mitral annulus; relocation displacement varied from 10% to 40% of baseline diastolic distance from the PPM to the anchor points on the annulus. For each reconstruction scenario, myofiber stress in the MI, border zone, and remote myocardium as well as pump function were calculated. RESULTS PPMA caused reductions in myofiber stress at end-diastole and end-systole in all regions of the left ventricle that were proportional to the relocation displacement. Although stress reduction was greatest in the MI region, it also occurred in the remote region. The maximum 40% displacement caused a slight reduction in LV pump function. However, with the correction of regurgitation by MA plus PPMA, there was an overall increase in forward stroke volume. Finally, anchoring point direction had no effect on myofiber stress or pump function. CONCLUSIONS PPMA reduces remote myofiber stress, which is proportional to the absolute distance of relocation and independent of anchoring point. Aggressive use of PPMA techniques to reduce remote myofiber stress may accelerate reverse LV remodeling without impairing LV function.
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Affiliation(s)
- Joe Luis Pantoja
- School of Medicine, University of California, San Francisco, San Francisco, California
| | - Liang Ge
- Department of Surgery, University of California, San Francisco, San Francisco, California; Department of Bioengineering, University of California, San Francisco, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California
| | - Zhihong Zhang
- Veterans Affairs Medical Center, San Francisco, California
| | - William G Morrel
- School of Medicine, University of California, San Francisco, San Francisco, California
| | - Julius M Guccione
- Department of Surgery, University of California, San Francisco, San Francisco, California; Department of Bioengineering, University of California, San Francisco, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California
| | - Eugene A Grossi
- Department of Cardiothoracic Surgery, New York University, New York, New York; New York Harbor Veterans Affairs Medical Center, New York, New York
| | - Mark B Ratcliffe
- Department of Surgery, University of California, San Francisco, San Francisco, California; Department of Bioengineering, University of California, San Francisco, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California.
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Chandran KB, Kim H. Computational mitral valve evaluation and potential clinical applications. Ann Biomed Eng 2014; 43:1348-62. [PMID: 25134487 DOI: 10.1007/s10439-014-1094-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 08/09/2014] [Indexed: 01/15/2023]
Abstract
The mitral valve (MV) apparatus consists of the two asymmetric leaflets, the saddle-shaped annulus, the chordae tendineae, and the papillary muscles. MV function over the cardiac cycle involves complex interaction between the MV apparatus components for efficient blood circulation. Common diseases of the MV include valvular stenosis, regurgitation, and prolapse. MV repair is the most popular and most reliable surgical treatment for early MV pathology. One of the unsolved problems in MV repair is to predict the optimal repair strategy for each patient. Although experimental studies have provided valuable information to improve repair techniques, computational simulations are increasingly playing an important role in understanding the complex MV dynamics, particularly with the availability of patient-specific real-time imaging modalities. This work presents a review of computational simulation studies of MV function employing finite element structural analysis and fluid-structure interaction approach reported in the literature to date. More recent studies towards potential applications of computational simulation approaches in the assessment of valvular repair techniques and potential pre-surgical planning of repair strategies are also discussed. It is anticipated that further advancements in computational techniques combined with the next generations of clinical imaging modalities will enable physiologically more realistic simulations. Such advancement in imaging and computation will allow for patient-specific, disease-specific, and case-specific MV evaluation and virtual prediction of MV repair.
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Affiliation(s)
- Krishnan B Chandran
- Department of Biomedical Engineering, The University of Iowa, Iowa City, IA, 52242, USA
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36
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Jensen MO, Honge JL, Benediktsson JA, Siefert AW, Jensen H, Yoganathan AP, Snow TK, Hasenkam JM, Nygaard H, Nielsen SL. Mitral valve annular downsizing forces: Implications for annuloplasty device development. J Thorac Cardiovasc Surg 2014; 148:83-9. [DOI: 10.1016/j.jtcvs.2013.07.045] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 06/26/2013] [Accepted: 07/12/2013] [Indexed: 11/30/2022]
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Choi A, Rim Y, Mun JS, Kim H. A novel finite element-based patient-specific mitral valve repair: virtual ring annuloplasty. Biomed Mater Eng 2014; 24:341-7. [PMID: 24211915 DOI: 10.3233/bme-130816] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Alterations of normal mitral valve (MV) function lead to mitral insufficiency, i.e., mitral regurgitation (MR). Mitral repair is the most popular and most efficient surgical intervention for MR treatment. An annuloplasty ring is implanted following complex reconstructive MV repairs to prevent potential reoccurrence of MR. We have developed a novel finite element (FE)-based simulation protocol to perform patient-specific virtual ring annuloplasty following the standard clinical guideline procedure. A virtual MV was created using 3D echocardiographic data in a patient with mitral annular dilation. Proper type and size of the ring were determined in consideration of the MV apparatus geometry. The ring was positioned over the patient MV model and annuloplasty was simulated. Dynamic simulation of MV function across the complete cardiac cycle was performed. Virtual patient-specific annuloplasty simulation well demonstrated morphologic information of the MV apparatus before and after ring implantation. Dynamic simulation of MV function following ring annuloplasty demonstrated markedly reduced stress distribution across the MV leaflets and annulus as well as restored leaflet coaptation compared to pre-annuloplasty. This novel FE-based patient-specific MV repair simulation technique provides quantitative information of functional improvement following ring annuloplasty. Virtual MV repair strategy may effectively evaluate and predict interventional treatment for MV pathology.
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Affiliation(s)
- Ahnryul Choi
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, 6431 Fannin St. MSB 1.246, Houston, Texas, USA
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Genet M, Lee LC, Nguyen R, Haraldsson H, Acevedo-Bolton G, Zhang Z, Ge L, Ordovas K, Kozerke S, Guccione JM. Distribution of normal human left ventricular myofiber stress at end diastole and end systole: a target for in silico design of heart failure treatments. J Appl Physiol (1985) 2014; 117:142-52. [PMID: 24876359 DOI: 10.1152/japplphysiol.00255.2014] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Ventricular wall stress is believed to be responsible for many physical mechanisms taking place in the human heart, including ventricular remodeling, which is frequently associated with heart failure. Therefore, normalization of ventricular wall stress is the cornerstone of many existing and new treatments for heart failure. In this paper, we sought to construct reference maps of normal ventricular wall stress in humans that could be used as a target for in silico optimization studies of existing and potential new treatments for heart failure. To do so, we constructed personalized computational models of the left ventricles of five normal human subjects using magnetic resonance images and the finite-element method. These models were calibrated using left ventricular volume data extracted from magnetic resonance imaging (MRI) and validated through comparison with strain measurements from tagged MRI (950 ± 170 strain comparisons/subject). The calibrated passive material parameter values were C0 = 0.115 ± 0.008 kPa and B0 = 14.4 ± 3.18; the active material parameter value was Tmax = 143 ± 11.1 kPa. These values could serve as a reference for future construction of normal human left ventricular computational models. The differences between the predicted and the measured circumferential and longitudinal strains in each subject were 3.4 ± 6.3 and 0.5 ± 5.9%, respectively. The predicted end-diastolic and end-systolic myofiber stress fields for the five subjects were 2.21 ± 0.58 and 16.54 ± 4.73 kPa, respectively. Thus these stresses could serve as targets for in silico design of heart failure treatments.
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Affiliation(s)
- Martin Genet
- Surgery Department, University of California at San Francisco, San Francisco, California; Marie-Curie International Outgoing Fellow, Brussels, Belgium
| | - Lik Chuan Lee
- Surgery Department, University of California at San Francisco, San Francisco, California
| | - Rebecca Nguyen
- Surgery Department, University of California at San Francisco, San Francisco, California
| | - Henrik Haraldsson
- Radiology and Biomedical Imaging Department, School of Medicine, University of California at San Francisco, San Francisco, California
| | - Gabriel Acevedo-Bolton
- Radiology and Biomedical Imaging Department, School of Medicine, University of California at San Francisco, San Francisco, California
| | - Zhihong Zhang
- Veterans Affairs Medical Center, San Francisco, California; and
| | - Liang Ge
- Veterans Affairs Medical Center, San Francisco, California; and
| | - Karen Ordovas
- Radiology and Biomedical Imaging Department, School of Medicine, University of California at San Francisco, San Francisco, California
| | - Sebastian Kozerke
- Institute for Biomedical Engineering, University and ETH, Zürich, Switzerland
| | - Julius M Guccione
- Surgery Department, University of California at San Francisco, San Francisco, California;
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Abstract
In the past two decades, major advances have been made in the clinical evaluation and treatment of valvular heart disease owing to the advent of noninvasive cardiac imaging modalities. In clinical practice, valvular disease evaluation is typically performed on two-dimensional (2D) images, even though most imaging modalities offer three-dimensional (3D) volumetric, time-resolved data. Such 3D data offer researchers the possibility to reconstruct the 3D geometry of heart valves at a patient-specific level. When these data are integrated with computational models, native heart valve biomechanical function can be investigated, and preoperative planning tools can be developed. In this review, we outline the advances in valve geometry reconstruction, tissue property modeling, and loading and boundary definitions for the purpose of realistic computational structural analysis of cardiac valve function and intervention.
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Affiliation(s)
- Wei Sun
- Tissue Mechanics Lab, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30313;
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40
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Lee LC, Genet M, Dang AB, Ge L, Guccione JM, Ratcliffe MB. Applications of computational modeling in cardiac surgery. J Card Surg 2014; 29:293-302. [PMID: 24708036 DOI: 10.1111/jocs.12332] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although computational modeling is common in many areas of science and engineering, only recently have advances in experimental techniques and medical imaging allowed this tool to be applied in cardiac surgery. Despite its infancy in cardiac surgery, computational modeling has been useful in calculating the effects of clinical devices and surgical procedures. In this review, we present several examples that demonstrate the capabilities of computational cardiac modeling in cardiac surgery. Specifically, we demonstrate its ability to simulate surgery, predict myofiber stress and pump function, and quantify changes to regional myocardial material properties. In addition, issues that would need to be resolved in order for computational modeling to play a greater role in cardiac surgery are discussed.
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Affiliation(s)
- Lik Chuan Lee
- Department of Surgery, University of California, San Francisco, California; Department of Bioengineering, University of California, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California
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Ge L, Morrel WG, Ward A, Mishra R, Zhang Z, Guccione JM, Grossi EA, Ratcliffe MB. Measurement of mitral leaflet and annular geometry and stress after repair of posterior leaflet prolapse: virtual repair using a patient-specific finite element simulation. Ann Thorac Surg 2014; 97:1496-503. [PMID: 24630767 DOI: 10.1016/j.athoracsur.2013.12.036] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Revised: 12/09/2013] [Accepted: 12/18/2013] [Indexed: 11/16/2022]
Abstract
BACKGROUND Recurrent mitral regurgitation after mitral valve (MV) repair for degenerative disease occurs at a rate of 2.6% per year and reoperation rate progressively reaches 20% at 19.5 years. We believe that MV repair durability is related to initial postoperative leaflet and annular geometry with subsequent leaflet remodeling due to stress. We tested the hypothesis that MV leaflet and annular stress is increased after MV repair. METHODS Magnetic resonance imaging was performed before and intraoperative three-dimensional (3D) transesophageal echocardiography was performed before and after repair of posterior leaflet prolapse in a single patient. The repair consisted of triangular resection and annuloplasty band placement. Images of the heart were manually co-registered. The left ventricle and MV were contoured, surfaced, and a 3D finite element (FE) model was created. Elements of the posterior leaflet region were removed to model leaflet resection and virtual sutures were used to repair the leaflet defect and attach the annuloplasty ring. RESULTS The principal findings of the current study are the following: (1) FE simulation of MV repair is able to accurately predict changes in MV geometry including changes in annular dimensions and leaflet coaptation; (2) average posterior leaflet stress is increased; and (3) average anterior leaflet and annular stress are reduced after triangular resection and mitral annuloplasty. CONCLUSIONS We successfully conducted virtual mitral valve prolapse repair using FE modeling methods. Future studies will examine the effects of leaflet resection type as well as annuloplasty ring size and shape.
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Affiliation(s)
- Liang Ge
- Department of Surgery, University of California, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California
| | - William G Morrel
- School of Medicine, University of California, San Francisco, California
| | - Alison Ward
- Department of Cardiothoracic Surgery, New York School of Medicine, New York, New York
| | - Rakesh Mishra
- Department of Medicine, University of California, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California
| | - Zhihong Zhang
- Veterans Affairs Medical Center, San Francisco, California
| | - Julius M Guccione
- Department of Surgery, University of California, San Francisco, California; Department of Bioengineering, University of California, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California
| | - Eugene A Grossi
- Department of Cardiothoracic Surgery, New York School of Medicine, New York, New York
| | - Mark B Ratcliffe
- Department of Surgery, University of California, San Francisco, California; Department of Bioengineering, University of California, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California.
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Siefert AW, Rabbah JPM, Pierce EL, Kunzelman KS, Yoganathan AP. Quantitative Evaluation of Annuloplasty on Mitral Valve Chordae Tendineae Forces to Supplement Surgical Planning Model Development. Cardiovasc Eng Technol 2014; 5:35-43. [PMID: 24634699 DOI: 10.1007/s13239-014-0175-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE Computational models of the heart's mitral valve (MV) exhibit potential for preoperative surgical planning in ischemic mitral regurgitation (IMR). However challenges exist in defining boundary conditions to accurately model the function and response of the chordae tendineae to both IMR and surgical annuloplasty repair. Towards this goal, a ground-truth data set was generated by quantifying the isolated effects of IMR and mitral annuloplasty on leaflet coaptation, regurgitation, and tethering forces of the anterior strut and posterior intermediary chordae tendineae. METHODS MVs were excised from ovine hearts (N=15) and mounted in a pulsatile heart simulator which has been demonstrated to mimic the systolic MV geometry and coaptation of healthy and chronic IMR sheep. Strut and intermediary chordae from both MV leaflets (N=4) were instrumented with force transducers. Tested conditions included a healthy control, IMR, oversized annuloplasty, true-sized annuloplasty, and undersized mitral annuloplasty. A2-P2 leaflet coaptation length, regurgitation, and chordal tethering were quantified and statistically compared across experimental conditions. RESULTS IMR was successfully simulated with significant increases in MR, tethering forces for each of the chordae, and decrease in leaflet coaptation (p<.05). Compared to the IMR condition, increasing levels of downsized annuloplasty significantly reduced regurgitation, increased coaptation, reduced posteromedial papillary muscle strut chordal forces, and reduced intermediary chordal forces from the anterolateral papillary muscle (p<.05). CONCLUSIONS These results provide for the first time a novel comprehensive data set for refining the ability of computational MV models to simulate IMR and varying sizes of complete rigid ring annuloplasty.
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Affiliation(s)
- Andrew W Siefert
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia
| | - Jean-Pierre M Rabbah
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia
| | - Eric L Pierce
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia
| | - Karyn S Kunzelman
- Department of Mechanical Engineering, University of Maine, Orono, Maine
| | - Ajit P Yoganathan
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia
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Rabbah JPM, Saikrishnan N, Siefert AW, Santhanakrishnan A, Yoganathan AP. Mechanics of healthy and functionally diseased mitral valves: a critical review. J Biomech Eng 2013; 135:021007. [PMID: 23445052 DOI: 10.1115/1.4023238] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The mitral valve is a complex apparatus with multiple constituents that work cohesively to ensure unidirectional flow between the left atrium and ventricle. Disruption to any or all of the components-the annulus, leaflets, chordae, and papillary muscles-can lead to backflow of blood, or regurgitation, into the left atrium, which deleteriously effects patient health. Through the years, a myriad of surgical repairs have been proposed; however, a careful appreciation for the underlying structural mechanics can help optimize long-term repair durability and inform medical device design. In this review, we aim to present the experimental methods and significant results that have shaped the current understanding of mitral valve mechanics. Data will be presented for all components of the mitral valve apparatus in control, pathological, and repaired conditions from human, animal, and in vitro studies. Finally, current strategies of patient specific and noninvasive surgical planning will be critically outlined.
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Affiliation(s)
- Jean-Pierre M Rabbah
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30332, USA
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Rausch MK, Tibayan FA, Ingels NB, Miller DC, Kuhl E. Mechanics of the mitral annulus in chronic ischemic cardiomyopathy. Ann Biomed Eng 2013; 41:2171-80. [PMID: 23636575 DOI: 10.1007/s10439-013-0813-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 04/16/2013] [Indexed: 10/26/2022]
Abstract
Approximately one third of all patients undergoing open-heart surgery for repair of ischemic mitral regurgitation present with residual and recurrent mitral valve leakage upon follow up. A fundamental quantitative understanding of mitral valve remodeling following myocardial infarction may hold the key to improved medical devices and better treatment outcomes. Here we quantify mitral annular strains and curvature in nine sheep 5 ± 1 weeks after controlled inferior myocardial infarction of the left ventricle. We complement our marker-based mechanical analysis of the remodeling mitral valve by common clinical measures of annular geometry before and after the infarct. After 5 ± 1 weeks, the mitral annulus dilated in septal-lateral direction by 15.2% (p = 0.003) and in commissure-commissure direction by 14.2% (p < 0.001). The septal annulus dilated by 10.4% (p = 0.013) and the lateral annulus dilated by 18.4% (p < 0.001). Remarkably, in animals with large degree of mitral regurgitation and annular remodeling, the annulus dilated asymmetrically with larger distortions toward the lateral-posterior segment. Strain analysis revealed average tensile strains of 25% over most of the annulus with exception for the lateral-posterior segment, where tensile strains were 50% and higher. Annular dilation and peak strains were closely correlated to the degree of mitral regurgitation. A complementary relative curvature analysis revealed a homogenous curvature decrease associated with significant annular circularization. All curvature profiles displayed distinct points of peak curvature disturbing the overall homogenous pattern. These hinge points may be the mechanistic origin for the asymmetric annular deformation following inferior myocardial infarction. In the future, this new insight into the mechanism of asymmetric annular dilation may support improved device designs and possibly aid surgeons in reconstructing healthy annular geometry during mitral valve repair.
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Affiliation(s)
- Manuel K Rausch
- Department of Mechanical Engineering, Stanford University, 496 Lomita Mall, Stanford, CA 94305, USA.
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A novel left heart simulator for the multi-modality characterization of native mitral valve geometry and fluid mechanics. Ann Biomed Eng 2012; 41:305-15. [PMID: 22965640 DOI: 10.1007/s10439-012-0651-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2012] [Accepted: 08/27/2012] [Indexed: 01/02/2023]
Abstract
Numerical models of the mitral valve have been used to elucidate mitral valve function and mechanics. These models have evolved from simple two-dimensional approximations to complex three-dimensional fully coupled fluid structure interaction models. However, to date these models lack direct one-to-one experimental validation. As computational solvers vary considerably, experimental benchmark data are critically important to ensure model accuracy. In this study, a novel left heart simulator was designed specifically for the validation of numerical mitral valve models. Several distinct experimental techniques were collectively performed to resolve mitral valve geometry and hemodynamics. In particular, micro-computed tomography was used to obtain accurate and high-resolution (39 μm voxel) native valvular anatomy, which included the mitral leaflets, chordae tendinae, and papillary muscles. Three-dimensional echocardiography was used to obtain systolic leaflet geometry. Stereoscopic digital particle image velocimetry provided all three components of fluid velocity through the mitral valve, resolved every 25 ms in the cardiac cycle. A strong central filling jet (V ~ 0.6 m/s) was observed during peak systole with minimal out-of-plane velocities. In addition, physiologic hemodynamic boundary conditions were defined and all data were synchronously acquired through a central trigger. Finally, the simulator is a precisely controlled environment, in which flow conditions and geometry can be systematically prescribed and resultant valvular function and hemodynamics assessed. Thus, this work represents the first comprehensive database of high fidelity experimental data, critical for extensive validation of mitral valve fluid structure interaction simulations.
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