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Buchan S, Kar R, John M, Post A, Razavi M. Electrical Stimulation for Low-Energy Termination of Cardiac Arrhythmias: a Review. Cardiovasc Drugs Ther 2023; 37:323-340. [PMID: 34363570 DOI: 10.1007/s10557-021-07236-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/02/2021] [Indexed: 11/24/2022]
Abstract
Cardiac arrhythmias are a leading cause of morbidity and mortality in the developed world, estimated to be responsible for hundreds of thousands of deaths annually. Our understanding of the electrophysiological mechanisms of such arrhythmias has grown since they were formally characterized in the late nineteenth century, and this has led to the development of numerous devices and therapies that have markedly improved outcomes for patients affected by such conditions. Despite these advancements, the application of a single large shock remains the clinical standard for treating deadly tachyarrhythmias. Such defibrillating shocks are undoubtedly effective in terminating such arrhythmias; however, they are applied without forewarning, contributing to the patient's stress and anxiety; they can be intensely painful; and they can have adverse psychological and physiological effects on patients. In recent years, there has been interest in developing defibrillation protocols that can terminate arrhythmias without crossing the human pain threshold for energy delivery, generally estimated to be between 0.1 and 1 J. In this article, we review existing literature on the development of such low-energy defibrillation methods and their underlying mechanisms, in an attempt to broadly describe the current landscape of these technologies.
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Affiliation(s)
- Skylar Buchan
- Electrophysiology Clinical Research and Innovations, Texas Heart Institute, 6770 Bertner Avenue, Houston, TX, 77030, USA
| | - Ronit Kar
- Electrophysiology Clinical Research and Innovations, Texas Heart Institute, 6770 Bertner Avenue, Houston, TX, 77030, USA.,Department of Biomedical Engineering, The University of Texas At Austin, Austin, TX, 78712, USA
| | - Mathews John
- Electrophysiology Clinical Research and Innovations, Texas Heart Institute, 6770 Bertner Avenue, Houston, TX, 77030, USA
| | - Allison Post
- Electrophysiology Clinical Research and Innovations, Texas Heart Institute, 6770 Bertner Avenue, Houston, TX, 77030, USA
| | - Mehdi Razavi
- Electrophysiology Clinical Research and Innovations, Texas Heart Institute, 6770 Bertner Avenue, Houston, TX, 77030, USA. .,Division of Cardiology, Department of Medicine, Baylor College of Medicine, Houston, TX, 77030, USA.
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2
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Arevalo HJ, Boyle PM, Trayanova NA. Computational rabbit models to investigate the initiation, perpetuation, and termination of ventricular arrhythmia. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 121:185-94. [PMID: 27334789 DOI: 10.1016/j.pbiomolbio.2016.06.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 06/13/2016] [Indexed: 12/29/2022]
Abstract
Current understanding of cardiac electrophysiology has been greatly aided by computational work performed using rabbit ventricular models. This article reviews the contributions of multiscale models of rabbit ventricles in understanding cardiac arrhythmia mechanisms. This review will provide an overview of multiscale modeling of the rabbit ventricles. It will then highlight works that provide insights into the role of the conduction system, complex geometric structures, and heterogeneous cellular electrophysiology in diseased and healthy rabbit hearts to the initiation and maintenance of ventricular arrhythmia. Finally, it will provide an overview on the contributions of rabbit ventricular modeling on understanding the mechanisms underlying shock-induced defibrillation.
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Affiliation(s)
- Hermenegild J Arevalo
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA; Simula Research Laboratory, Oslo, Norway
| | - Patrick M Boyle
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Natalia A Trayanova
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA.
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3
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Optical Imaging of Cardiac Action Potential. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 859:299-311. [PMID: 26238058 DOI: 10.1007/978-3-319-17641-3_12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
This chapter reviews the major milestones and scientific achievements facilitated by optical imaging of the action potential in the heart over more than four decades since its introduction. We discuss the limitations of this technique, which sometimes are not fully recognized; the unresolved issues, such as motion artifacts, and the newest developments and future directions.
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4
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Burton RAB, Lee P, Casero R, Garny A, Siedlecka U, Schneider JE, Kohl P, Grau V. Three-dimensional histology: tools and application to quantitative assessment of cell-type distribution in rabbit heart. Europace 2015; 16 Suppl 4:iv86-iv95. [PMID: 25362175 PMCID: PMC4217519 DOI: 10.1093/europace/euu234] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Aims Cardiac histo-anatomical organization is a major determinant of function. Changes in tissue structure are a relevant factor in normal and disease development, and form targets of therapeutic interventions. The purpose of this study was to test tools aimed to allow quantitative assessment of cell-type distribution from large histology and magnetic resonance imaging- (MRI) based datasets. Methods and results Rabbit heart fixation during cardioplegic arrest and MRI were followed by serial sectioning of the whole heart and light-microscopic imaging of trichrome-stained tissue. Segmentation techniques developed specifically for this project were applied to segment myocardial tissue in the MRI and histology datasets. In addition, histology slices were segmented into myocytes, connective tissue, and undefined. A bounding surface, containing the whole heart, was established for both MRI and histology. Volumes contained in the bounding surface (called ‘anatomical volume’), as well as that identified as containing any of the above tissue categories (called ‘morphological volume’), were calculated. The anatomical volume was 7.8 cm3 in MRI, and this reduced to 4.9 cm3 after histological processing, representing an ‘anatomical’ shrinkage by 37.2%. The morphological volume decreased by 48% between MRI and histology, highlighting the presence of additional tissue-level shrinkage (e.g. an increase in interstitial cleft space). The ratio of pixels classified as containing myocytes to pixels identified as non-myocytes was roughly 6:1 (61.6 vs. 9.8%; the remaining fraction of 28.6% was ‘undefined’). Conclusion Qualitative and quantitative differentiation between myocytes and connective tissue, using state-of-the-art high-resolution serial histology techniques, allows identification of cell-type distribution in whole-heart datasets. Comparison with MRI illustrates a pronounced reduction in anatomical and morphological volumes during histology processing.
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Affiliation(s)
- Rebecca A B Burton
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK
| | - Peter Lee
- Department of Physics, University of Oxford, Oxford OX1 3RH, UK
| | - Ramón Casero
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford OX3 7DQ, UK
| | - Alan Garny
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK
| | - Urszula Siedlecka
- The Heart Science Centre, National Heart and Lung Institute, Imperial College London, Harefield UB9 6JH, UK
| | - Jürgen E Schneider
- British Heart Foundation Experimental MR Unit, Radcliffe Department of Medicine, Division of Cardiovascular Medicine, University of Oxford, Oxford OX3 7BN, UK
| | - Peter Kohl
- The Heart Science Centre, National Heart and Lung Institute, Imperial College London, Harefield UB9 6JH, UK
| | - Vicente Grau
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford OX3 7DQ, UK
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5
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Caldwell BJ, Trew ML, Pertsov AM. Cardiac response to low-energy field pacing challenges the standard theory of defibrillation. Circ Arrhythm Electrophysiol 2015; 8:685-93. [PMID: 25772543 DOI: 10.1161/circep.114.002661] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 02/25/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND The electric response of myocardial tissue to periodic field stimuli has attracted significant attention as the basis for low-energy antifibrillation pacing, potentially more effective than traditional single high-energy shocks. In conventional models, an electric field produces a highly nonuniform response of the myocardial wall, with discrete excitations, or hot spots (HS), occurring at cathodal tissue surfaces or large coronary vessels. We test this prediction using novel 3-dimensional tomographic optical imaging. METHODS AND RESULTS Experiments were performed in isolated coronary perfused pig ventricular wall preparations stained with near-infrared voltage-sensitive fluorescent dye DI-4-ANBDQBS. The 3-dimensional coordinates of HS were determined using alternating transillumination. To relate HS formation with myocardial structures, we used ultradeep confocal imaging (interrogation depths, >4 mm). The peak HS distribution is located deep inside the heart wall, and the depth is not significantly affected by field polarity. We did not observe the strong colocalization of HS with major coronary vessels anticipated from theory. Yet, we observed considerable lateral displacement of HS with field polarity reversal. Models that de-emphasized lateral intracellular coupling and accounted for resistive heterogeneity in the extracellular space showed similar HS distributions to the experimental observations. CONCLUSIONS The HS distributions within the myocardial wall and the significant lateral displacements with field polarity reversal are inconsistent with standard theories of defibrillation. Extended theories based on enhanced descriptions of cellular scale electric mechanisms may be necessary. The considerable lateral displacement of HS with field polarity reversal supports the hypothesis of biphasic stimuli in low-energy antifibrillation pacing being advantageous.
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Affiliation(s)
- Bryan J Caldwell
- From the Department of Pharmacology, State University of New York Upstate Medical University, Syracuse (B.J.C., A.M.P.); and Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand (M.L.T.)
| | - Mark L Trew
- From the Department of Pharmacology, State University of New York Upstate Medical University, Syracuse (B.J.C., A.M.P.); and Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand (M.L.T.).
| | - Arkady M Pertsov
- From the Department of Pharmacology, State University of New York Upstate Medical University, Syracuse (B.J.C., A.M.P.); and Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand (M.L.T.)
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6
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Costa CM, Campos FO, Prassl AJ, dos Santos RW, Sánchez-Quintana D, Ahammer H, Hofer E, Plank G. An efficient finite element approach for modeling fibrotic clefts in the heart. IEEE Trans Biomed Eng 2014; 61:900-10. [PMID: 24557691 DOI: 10.1109/tbme.2013.2292320] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Advanced medical imaging technologies provide a wealth of information on cardiac anatomy and structure at a paracellular resolution, allowing to identify microstructural discontinuities which disrupt the intracellular matrix. Current state-of-the-art computer models built upon such datasets account for increasingly finer anatomical details, however, structural discontinuities at the paracellular level are typically discarded in the model generation process, owing to the significant costs which incur when using high resolutions for explicit representation. In this study, a novel discontinuous finite element (dFE) approach for discretizing the bidomain equations is presented, which accounts for fine-scale structures in a computer model without the need to increase spatial resolution. In the dFE method, this is achieved by imposing infinitely thin lines of electrical insulation along edges of finite elements which approximate the geometry of discontinuities in the intracellular matrix. Simulation results demonstrate that the dFE approach accounts for effects induced by microscopic size scale discontinuities, such as the formation of microscopic virtual electrodes, with vast computational savings as compared to high resolution continuous finite element models. Moreover, the method can be implemented in any standard continuous finite element code with minor effort.
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7
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Trayanova NA, Rantner LJ. New insights into defibrillation of the heart from realistic simulation studies. Europace 2014; 16:705-13. [PMID: 24798960 PMCID: PMC4010179 DOI: 10.1093/europace/eut330] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 09/17/2013] [Indexed: 11/12/2022] Open
Abstract
Cardiac defibrillation, as accomplished nowadays by automatic, implantable devices, constitutes the most important means of combating sudden cardiac death. Advancing our understanding towards a full appreciation of the mechanisms by which a shock interacts with the heart, particularly under diseased conditions, is a promising approach to achieve an optimal therapy. The aim of this article is to assess the current state-of-the-art in whole-heart defibrillation modelling, focusing on major insights that have been obtained using defibrillation models, primarily those of realistic heart geometry and disease remodelling. The article showcases the contributions that modelling and simulation have made to our understanding of the defibrillation process. The review thus provides an example of biophysically based computational modelling of the heart (i.e. cardiac defibrillation) that has advanced the understanding of cardiac electrophysiological interaction at the organ level, and has the potential to contribute to the betterment of the clinical practice of defibrillation.
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Affiliation(s)
- Natalia A. Trayanova
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 3400 N Charles Street, 216 Hackerman Hall, Baltimore, MD 21218, USA
- Institute for Computational Medicine, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA
| | - Lukas J. Rantner
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 3400 N Charles Street, 216 Hackerman Hall, Baltimore, MD 21218, USA
- Institute for Computational Medicine, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA
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8
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Chamakuri N, Kunisch K, Plank G. On boundary stimulation and optimal boundary control of the bidomain equations. Math Biosci 2013; 245:206-15. [PMID: 23856647 DOI: 10.1016/j.mbs.2013.07.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 07/02/2013] [Accepted: 07/04/2013] [Indexed: 11/30/2022]
Abstract
The bidomain equations with Neumann boundary stimulation and optimal control of these stimuli are investigated. First an analytical framework for boundary control is provided. Then a parallel finite element based algorithm is devised and its efficiency is demonstrated not only for the direct problem but also for the optimal control problem. The computations realize a model configuration corresponding to optimal boundary defibrillation of a reentry phenomenon by applying current density stimuli.
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Affiliation(s)
- Nagaiah Chamakuri
- Radon Institute for Computational and Applied Mathematics, Altenbergerstr. 69, Linz A-4040, Austria.
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9
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Dössel O, Krueger MW, Weber FM, Wilhelms M, Seemann G. Computational modeling of the human atrial anatomy and electrophysiology. Med Biol Eng Comput 2012; 50:773-99. [PMID: 22718317 DOI: 10.1007/s11517-012-0924-6] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 05/21/2012] [Indexed: 01/08/2023]
Abstract
This review article gives a comprehensive survey of the progress made in computational modeling of the human atria during the last 10 years. Modeling the anatomy has emerged from simple "peanut"-like structures to very detailed models including atrial wall and fiber direction. Electrophysiological models started with just two cellular models in 1998. Today, five models exist considering e.g. details of intracellular compartments and atrial heterogeneity. On the pathological side, modeling atrial remodeling and fibrotic tissue are the other important aspects. The bridge to data that are measured in the catheter laboratory and on the body surface (ECG) is under construction. Every measurement can be used either for model personalization or for validation. Potential clinical applications are briefly outlined and future research perspectives are suggested.
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Affiliation(s)
- Olaf Dössel
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology, Karlsruhe, Germany.
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10
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Colli Franzone P, Pavarino L, Scacchi S. Cardiac excitation mechanisms, wavefront dynamics and strength–interval curves predicted by 3D orthotropic bidomain simulations. Math Biosci 2012; 235:66-84. [DOI: 10.1016/j.mbs.2011.10.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 10/12/2011] [Accepted: 10/21/2011] [Indexed: 11/15/2022]
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11
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Bishop MJ, Plank G. Representing cardiac bidomain bath-loading effects by an augmented monodomain approach: application to complex ventricular models. IEEE Trans Biomed Eng 2011; 58:1066-75. [PMID: 21292591 PMCID: PMC3075562 DOI: 10.1109/tbme.2010.2096425] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although the cardiac bidomain model has been widely used in the simulation of electrical activation, its relatively computationally expensive nature means that monodomain approaches are generally required for long-duration simulations (for example, investigations of arrhythmia mechanisms). However, the presence of a conducting bath surrounding the tissue is known to induce wavefront curvature (surface leading bulk), a phenomena absent in standard monodomain approaches. Here, we investigate the biophysical origin of the bidomain bath-loading induced wavefront curvature and present a novel augmented monodomain-equivalent bidomain approach faithfully replicating all aspects of bidomain wavefront morphology and conduction velocity, but with a fraction of the computational cost. Bath-loading effects are shown to be highly dependent upon specific conductivity parameters, but less dependent upon the thickness or conductivity of the surrounding bath, with even relatively thin surrounding fluid layers (~ 0.1 mm) producing significant wavefront curvature in bidomain simulations. We demonstrate that our augmented monodomain approach can be easily adapted for different conductivity sets and applied to anatomically complex models, thus facilitating fast and accurate simulation of cardiac wavefront dynamics during long-duration simulations, further aiding the faithful comparison of simulations with experiments.
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Affiliation(s)
- Martin J Bishop
- Computing Laboratory, University of Oxford, Oxford OX1 3QD, UK.
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12
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Colli-Franzone P, Pavarino L, Scacchi S. Exploring anodal and cathodal make and break cardiac excitation mechanisms in a 3D anisotropic bidomain model. Math Biosci 2011; 230:96-114. [DOI: 10.1016/j.mbs.2011.02.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 02/04/2011] [Accepted: 02/09/2011] [Indexed: 01/09/2023]
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13
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Caldwell BJ, Wellner M, Mitrea BG, Pertsov AM, Zemlin CW. Probing field-induced tissue polarization using transillumination fluorescent imaging. Biophys J 2011; 99:2058-66. [PMID: 20923639 DOI: 10.1016/j.bpj.2010.07.057] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Revised: 07/27/2010] [Accepted: 07/28/2010] [Indexed: 10/19/2022] Open
Abstract
Despite major successes of biophysical theories in predicting the effects of electrical shocks within the heart, recent optical mapping studies have revealed two major discrepancies between theory and experiment: 1), the presence of negative bulk polarization recorded during strong shocks; and 2), the unexpectedly small surface polarization under shock electrodes. There is little consensus as to whether these differences result from deficiencies of experimental techniques, artifacts of tissue damage, or deficiencies of existing theories. Here, we take advantage of recently developed near-infrared voltage-sensitive dyes and transillumination optical imaging to perform, for the first time that we know of, noninvasive probing of field effects deep inside the intact ventricular wall. This technique removes some of the limitations encountered in previous experimental studies. We explicitly demonstrate that deep inside intact myocardial tissue preparations, strong electrical shocks do produce considerable negative bulk polarization previously inferred from surface recordings. We also demonstrate that near-threshold diastolic field stimulation produces activation of deep myocardial layers 2-6 mm away from the cathodal surface, contrary to theory. Using bidomain simulations we explore factors that may improve the agreement between theory and experiment. We show that the inclusion of negative asymmetric current can qualitatively explain negative bulk polarization in a discontinuous bidomain model.
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Affiliation(s)
- Bryan J Caldwell
- Department of Pharmacology, State University of New York Upstate Medical University, Syracuse, New York, NY, USA.
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14
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Bishop MJ, Boyle PM, Plank G, Welsh DG, Vigmond EJ. Modeling the role of the coronary vasculature during external field stimulation. IEEE Trans Biomed Eng 2010; 57:2335-45. [PMID: 20542762 PMCID: PMC2976591 DOI: 10.1109/tbme.2010.2051227] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The exact mechanisms by which defibrillation shocks excite cardiac tissue far from both the electrodes and heart surfaces require elucidation. Bidomain theory explains this phenomena through the existence of intramural virtual electrodes (VEs), caused by discontinuities in myocardial tissue structure. In this study, we assess the modeling components essential in constructing a finite-element cardiac tissue model including blood vessels from high-resolution magnetic resonance data and investigate the specific role played by coronary vasculature in VE formation, which currently remains largely unknown. We use a novel method for assigning histologically based fiber architecture around intramural structures and include an experimentally derived vessel lumen wall conductance within the model. Shock-tissue interaction in the presence of vessels is assessed through comparison with a simplified model lacking intramural structures. Results indicate that VEs form around blood vessels for shocks > 8 V/cm. The magnitude of induced polarizations is attenuated by realistic representation of fiber negotiation around vessel cavities, as well as the insulating effects of the vessel lumen wall. Furthermore, VEs formed around large subepicardial vessels reduce epicardial polarization levels. In conclusion, we have found that coronary vasculature acts as an important substrate for VE formation, which may help interpretation of optical mapping data.
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Affiliation(s)
- Martin J Bishop
- Computing Laboratory, University of Oxford, Oxford, OX1 3QD, UK.
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15
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Abramson D, Bernabeu MO, Bethwaite B, Burrage K, Corrias A, Enticott C, Garic S, Gavaghan D, Peachey T, Pitt-Francis J, Pueyo E, Rodriguez B, Sher A, Tan J. High-throughput cardiac science on the Grid. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2010; 368:3907-3923. [PMID: 20643684 DOI: 10.1098/rsta.2010.0170] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Cardiac electrophysiology is a mature discipline, with the first model of a cardiac cell action potential having been developed in 1962. Current models range from single ion channels, through very complex models of individual cardiac cells, to geometrically and anatomically detailed models of the electrical activity in whole ventricles. A critical issue for model developers is how to choose parameters that allow the model to faithfully reproduce observed physiological effects without over-fitting. In this paper, we discuss the use of a parametric modelling toolkit, called Nimrod, that makes it possible both to explore model behaviour as parameters are changed and also to tune parameters by optimizing model output. Importantly, Nimrod leverages computers on the Grid, accelerating experiments by using available high-performance platforms. We illustrate the use of Nimrod with two case studies, one at the cardiac tissue level and one at the cellular level.
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Affiliation(s)
- David Abramson
- Faculty of Information Technology, Monash University, Caulfield East, Melbourne, Victoria 3145, Australia.
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16
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Bishop MJ, Plank G, Burton RAB, Schneider JE, Gavaghan DJ, Grau V, Kohl P. Development of an anatomically detailed MRI-derived rabbit ventricular model and assessment of its impact on simulations of electrophysiological function. Am J Physiol Heart Circ Physiol 2009; 298:H699-718. [PMID: 19933417 PMCID: PMC2822578 DOI: 10.1152/ajpheart.00606.2009] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent advances in magnetic resonance (MR) imaging technology have unveiled a wealth of information regarding cardiac histoanatomical complexity. However, methods to faithfully translate this level of fine-scale structural detail into computational whole ventricular models are still in their infancy, and, thus, the relevance of this additional complexity for simulations of cardiac function has yet to be elucidated. Here, we describe the development of a highly detailed finite-element computational model (resolution: approximately 125 microm) of rabbit ventricles constructed from high-resolution MR data (raw data resolution: 43 x 43 x 36 microm), including the processes of segmentation (using a combination of level-set approaches), identification of relevant anatomical features, mesh generation, and myocyte orientation representation (using a rule-based approach). Full access is provided to the completed model and MR data. Simulation results were compared with those from a simplified model built from the same images but excluding finer anatomical features (vessels/endocardial structures). Initial simulations showed that the presence of trabeculations can provide shortcut paths for excitation, causing regional differences in activation after pacing between models. Endocardial structures gave rise to small-scale virtual electrodes upon the application of external field stimulation, which appeared to protect parts of the endocardium in the complex model from strong polarizations, whereas intramural virtual electrodes caused by blood vessels and extracellular cleft spaces appeared to reduce polarization of the epicardium. Postshock, these differences resulted in the genesis of new excitation wavefronts that were not observed in more simplified models. Furthermore, global differences in the stimulus recovery rates of apex/base regions were observed, causing differences in the ensuing arrhythmogenic episodes. In conclusion, structurally simplified models are well suited for a large range of cardiac modeling applications. However, important differences are seen when behavior at microscales is relevant, particularly when examining the effects of external electrical stimulation on tissue electrophysiology and arrhythmia induction. This highlights the utility of histoanatomically detailed models for investigations of cardiac function, in particular for future patient-specific modeling.
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Affiliation(s)
- Martin J Bishop
- University of Oxford Computing Laboratory, Parks Road, Oxford OX1 3QD, UK.
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17
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Fenton FH, Luther S, Cherry EM, Otani NF, Krinsky V, Pumir A, Bodenschatz E, Gilmour RF. Termination of atrial fibrillation using pulsed low-energy far-field stimulation. Circulation 2009; 120:467-76. [PMID: 19635972 DOI: 10.1161/circulationaha.108.825091] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Electrically based therapies for terminating atrial fibrillation (AF) currently fall into 2 categories: antitachycardia pacing and cardioversion. Antitachycardia pacing uses low-intensity pacing stimuli delivered via a single electrode and is effective for terminating slower tachycardias but is less effective for treating AF. In contrast, cardioversion uses a single high-voltage shock to terminate AF reliably, but the voltages required produce undesirable side effects, including tissue damage and pain. We propose a new method to terminate AF called far-field antifibrillation pacing, which delivers a short train of low-intensity electric pulses at the frequency of antitachycardia pacing but from field electrodes. Prior theoretical work has suggested that this approach can create a large number of activation sites ("virtual" electrodes) that emit propagating waves within the tissue without implanting physical electrodes and thereby may be more effective than point-source stimulation. METHODS AND RESULTS Using optical mapping in isolated perfused canine atrial preparations, we show that a series of pulses at low field strength (0.9 to 1.4 V/cm) is sufficient to entrain and subsequently extinguish AF with a success rate of 93% (69 of 74 trials in 8 preparations). We further demonstrate that the mechanism behind far-field antifibrillation pacing success is the generation of wave emission sites within the tissue by the applied electric field, which entrains the tissue as the field is pulsed. CONCLUSIONS AF in our model can be terminated by far-field antifibrillation pacing with only 13% of the energy required for cardioversion. Further studies are needed to determine whether this marked reduction in energy can increase the effectiveness and safety of terminating atrial tachyarrhythmias clinically.
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Affiliation(s)
- Flavio H Fenton
- Department of Biomedical Sciences, T7 012C Veterinary Research Tower, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
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18
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Plank G, Burton RAB, Hales P, Bishop M, Mansoori T, Bernabeu MO, Garny A, Prassl AJ, Bollensdorff C, Mason F, Mahmood F, Rodriguez B, Grau V, Schneider JE, Gavaghan D, Kohl P. Generation of histo-anatomically representative models of the individual heart: tools and application. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:2257-92. [PMID: 19414455 PMCID: PMC2881535 DOI: 10.1098/rsta.2009.0056] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
This paper presents methods to build histo-anatomically detailed individualized cardiac models. The models are based on high-resolution three-dimensional anatomical and/or diffusion tensor magnetic resonance images, combined with serial histological sectioning data, and are used to investigate individualized cardiac function. The current state of the art is reviewed, and its limitations are discussed. We assess the challenges associated with the generation of histo-anatomically representative individualized in silico models of the heart. The entire processing pipeline including image acquisition, image processing, mesh generation, model set-up and execution of computer simulations, and the underlying methods are described. The multifaceted challenges associated with these goals are highlighted, suitable solutions are proposed, and an important application of developed high-resolution structure-function models in elucidating the effect of individual structural heterogeneity upon wavefront dynamics is demonstrated.
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Affiliation(s)
- Gernot Plank
- Computational Biology Group, University of Oxford, Oxford OX1 2JD, UK.
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19
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Plank G, Zhou L, Greenstein JL, Cortassa S, Winslow RL, O'Rourke B, Trayanova NA. From mitochondrial ion channels to arrhythmias in the heart: computational techniques to bridge the spatio-temporal scales. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2008; 366:3381-409. [PMID: 18603526 PMCID: PMC2778066 DOI: 10.1098/rsta.2008.0112] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Computer simulations of electrical behaviour in the whole ventricles have become commonplace during the last few years. The goals of this article are (i) to review the techniques that are currently employed to model cardiac electrical activity in the heart, discussing the strengths and weaknesses of the various approaches, and (ii) to implement a novel modelling approach, based on physiological reasoning, that lifts some of the restrictions imposed by current state-of-the-art ionic models. To illustrate the latter approach, the present study uses a recently developed ionic model of the ventricular myocyte that incorporates an excitation-contraction coupling and mitochondrial energetics model. A paradigm to bridge the vastly disparate spatial and temporal scales, from subcellular processes to the entire organ, and from sub-microseconds to minutes, is presented. Achieving sufficient computational efficiency is the key to success in the quest to develop multiscale realistic models that are expected to lead to better understanding of the mechanisms of arrhythmia induction following failure at the organelle level, and ultimately to the development of novel therapeutic applications.
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Affiliation(s)
- Gernot Plank
- Institute of Biophysics, Medical University Graz8010 Graz, Austria
- Institute for Computational Medicine, Johns Hopkins UniversityBaltimore, MD 21218, USA
| | - Lufang Zhou
- Institute of Molecular Cardiobiology, Johns Hopkins School of MedicineBaltimore, MD 21205, USA
- Department of Biomedical Engineering, Johns Hopkins UniversityBaltimore, MD 21205, USA
| | - Joseph L Greenstein
- Institute for Computational Medicine, Johns Hopkins UniversityBaltimore, MD 21218, USA
- Department of Biomedical Engineering, Johns Hopkins UniversityBaltimore, MD 21205, USA
| | - Sonia Cortassa
- Institute of Molecular Cardiobiology, Johns Hopkins School of MedicineBaltimore, MD 21205, USA
- Department of Biomedical Engineering, Johns Hopkins UniversityBaltimore, MD 21205, USA
| | - Raimond L Winslow
- Institute for Computational Medicine, Johns Hopkins UniversityBaltimore, MD 21218, USA
- Department of Biomedical Engineering, Johns Hopkins UniversityBaltimore, MD 21205, USA
| | - Brian O'Rourke
- Institute of Molecular Cardiobiology, Johns Hopkins School of MedicineBaltimore, MD 21205, USA
| | - Natalia A Trayanova
- Institute for Computational Medicine, Johns Hopkins UniversityBaltimore, MD 21218, USA
- Department of Biomedical Engineering, Johns Hopkins UniversityBaltimore, MD 21205, USA
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Maleckar MM, Woods MC, Sidorov VY, Holcomb MR, Mashburn DN, Wikswo JP, Trayanova NA. Polarity reversal lowers activation time during diastolic field stimulation of the rabbit ventricles: insights into mechanisms. Am J Physiol Heart Circ Physiol 2008; 295:H1626-33. [PMID: 18708441 DOI: 10.1152/ajpheart.00706.2008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To fully characterize the mechanisms of defibrillation, it is necessary to understand the response, within the three-dimensional (3D) volume of the ventricles, to shocks given in diastole. Studies that have examined diastolic responses conducted measurements on the epicardium or on a transmural surface of the left ventricular (LV) wall only. The goal of this study was to use optical imaging experiments and 3D bidomain simulations, including a model of optical mapping, to ascertain the shock-induced virtual electrode and activation patterns throughout the rabbit ventricles following diastolic shocks. We tested the hypothesis that the locations of shock-induced regions of hyperpolarization govern the different diastolic activation patterns for shocks of reversed polarity. In model and experiment, uniform-field monophasic shocks of reversed polarities (cathode over the right ventricle is RV-, reverse polarity is LV-) were applied to the ventricles in diastole. Experiments and simulations revealed that RV- shocks resulted in longer activation times compared with LV- shocks of the same strength. 3D simulations demonstrated that RV- shocks induced a greater volume of hyperpolarization at shock end compared with LV- shocks; most of these hyperpolarized regions were located in the LV. The results of this study indicate that ventricular geometry plays an important role in both the location and size of the shock-induced virtual anodes that determine activation delay during the shock and subsequently affect shock-induced propagation. If regions of hyperpolarization that develop during the shock are sufficiently large, activation delay may persist until shock end.
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Affiliation(s)
- M M Maleckar
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland 21218, USA
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