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Vigmond EJ, Bouyssier J, Bayer J, Haïssaguerre M, Ashikaga H. On the nature of delays allowing anatomical re-entry involving the Purkinje network: a simulation study. Europace 2021; 23:i71-i79. [PMID: 33463686 DOI: 10.1093/europace/euaa395] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Accepted: 12/03/2020] [Indexed: 12/31/2022] Open
Abstract
AIMS Clinical observations suggest that the Purkinje network can be part of anatomical re-entry circuits in monomorphic or polymorphic ventricular arrhythmias. However, significant conduction delay is needed to support anatomical re-entry given the high conduction velocity within the Purkinje network. METHODS AND RESULTS We investigated, in computer models, whether damage rendering the Purkinje network as either an active lesion with slow conduction or a passive lesion with no excitable ionic channel, could explain clinical observations. Active lesions had compromised sodium current and a severe reduction in gap junction coupling, while passive lesions remained coupled by gap junctions, but modelled the membrane as a fixed resistance. Both types of tissue could provide significant delays of over 100 ms. Electrograms consistent with those obtained clinically were reproduced. However, passive tissue could not support re-entry as electrotonic coupling across the delay effectively increased the proximal refractory period to an extremely long interval. Active tissue, conversely, could robustly maintain re-entry. CONCLUSION Formation of anatomical re-entry using the Purkinje network is possible through highly reduced gap junctional coupling leading to slowed conduction.
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Affiliation(s)
- Edward J Vigmond
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, F-33600 Pessac-Bordeaux, France.,Univ. Bordeaux, IMB, UMR 5251, F-33400 Talence, France
| | - Julien Bouyssier
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, F-33600 Pessac-Bordeaux, France.,Univ. Bordeaux, IMB, UMR 5251, F-33400 Talence, France
| | - Jason Bayer
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, F-33600 Pessac-Bordeaux, France.,Univ. Bordeaux, IMB, UMR 5251, F-33400 Talence, France
| | - Michel Haïssaguerre
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, F-33600 Pessac-Bordeaux, France.,Univ. Bordeaux, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, F-33000 Bordeaux, France.,Bordeaux University Hospital (CHU), Electrophysiology and Ablation Unit, F-33600 Pessac, France
| | - Hiroshi Ashikaga
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, F-33600 Pessac-Bordeaux, France.,Cardiac Arrhythmia Service, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Csepe TA, Zhao J, Hansen BJ, Li N, Sul LV, Lim P, Wang Y, Simonetti OP, Kilic A, Mohler PJ, Janssen PML, Fedorov VV. Human sinoatrial node structure: 3D microanatomy of sinoatrial conduction pathways. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2015; 120:164-78. [PMID: 26743207 DOI: 10.1016/j.pbiomolbio.2015.12.011] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 12/10/2015] [Accepted: 12/18/2015] [Indexed: 01/09/2023]
Abstract
INTRODUCTION Despite a century of extensive study on the human sinoatrial node (SAN), the structure-to-function features of specialized SAN conduction pathways (SACP) are still unknown and debated. We report a new method for direct analysis of the SAN microstructure in optically-mapped human hearts with and without clinical history of SAN dysfunction. METHODS Two explanted donor human hearts were coronary-perfused and optically-mapped. Structural analyses of histological sections parallel to epicardium (∼13-21 μm intervals) were integrated with optical maps to create 3D computational reconstructions of the SAN complex. High-resolution fiber fields were obtained using 3D Eigen-analysis of the structure tensor, and used to analyze SACP microstructure with a fiber-tracking approach. RESULTS Optical mapping revealed normal SAN activation of the atria through a lateral SACP proximal to the crista terminalis in Heart #1 but persistent SAN exit block in diseased Heart #2. 3D structural analysis displayed a functionally-observed SAN border composed of fibrosis, fat, and/or discontinuous fibers between SAN and atria, which was only crossed by several branching myofiber tracts in SACP regions. Computational 3D fiber-tracking revealed that myofiber tracts of SACPs created continuous connections between SAN #1 and atria, but in SAN #2, SACP region myofiber tracts were discontinuous due to fibrosis and fat. CONCLUSIONS We developed a new integrative functional, structural and computational approach that allowed for the resolution of the specialized 3D microstructure of human SACPs for the first time. Application of this integrated approach will shed new light on the role of the specialized SAN microanatomy in maintaining sinus rhythm.
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Affiliation(s)
- Thomas A Csepe
- Department of Physiology & Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Jichao Zhao
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Brian J Hansen
- Department of Physiology & Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Ning Li
- Department of Physiology & Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Lidiya V Sul
- Department of Physiology & Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Praise Lim
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Yufeng Wang
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Orlando P Simonetti
- Department of Biomedical Informatics, College of Medicine, The Ohio State University, Columbus, OH, USA; Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Ahmet Kilic
- Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Peter J Mohler
- Department of Physiology & Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Paul M L Janssen
- Department of Physiology & Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Vadim V Fedorov
- Department of Physiology & Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA.
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McCain ML, Desplantez T, Kléber AG. Engineering Cardiac Cell JunctionsIn Vitroto Study the Intercalated Disc. ACTA ACUST UNITED AC 2014; 21:181-91. [DOI: 10.3109/15419061.2014.905931] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Akar FG, Hajjar RJ. Gene therapies for arrhythmias in heart failure. Pflugers Arch 2014; 466:1211-7. [PMID: 24566976 DOI: 10.1007/s00424-014-1485-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 02/14/2014] [Indexed: 01/16/2023]
Abstract
In this article, we review recent advances in our understanding of arrhythmia mechanisms in the failing heart. We focus on changes in repolarization, conduction, and intracellular calcium cycling because of their importance to the vast majority of clinical arrhythmias in heart failure. We highlight recent efforts to combat arrhythmias using gene-based approaches that target ion channel, gap junction, and calcium cycling proteins. We further discuss the advantages and limitations associated with individual approaches.
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Affiliation(s)
- Fadi G Akar
- The Cardiovascular Research Center, Mount Sinai School of Medicine, New York, NY, USA,
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Veeraraghavan R, Gourdie RG, Poelzing S. Mechanisms of cardiac conduction: a history of revisions. Am J Physiol Heart Circ Physiol 2014; 306:H619-27. [PMID: 24414064 DOI: 10.1152/ajpheart.00760.2013] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiac conduction is the process by which electrical excitation spreads through the heart, triggering individual myocytes to contract in synchrony. Defects in conduction disrupt synchronous activation and are associated with life-threatening arrhythmias in many pathologies. Therefore, it is scarcely surprising that this phenomenon continues to be the subject of active scientific inquiry. Here we provide a brief review of how the conceptual understanding of conduction has evolved over the last century and highlight recent, potentially paradigm-shifting developments.
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Affiliation(s)
- Rengasayee Veeraraghavan
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, Roanoke, Virginia; and
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Jin H, Lyon AR, Akar FG. Arrhythmia mechanisms in the failing heart. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2008; 31:1048-56. [PMID: 18684263 DOI: 10.1111/j.1540-8159.2008.01134.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND Heart failure (HF) claims over 200,000 lives annually in the United States alone. Approximately 50% of these deaths are sudden and unexpected, and presumably the consequence of lethal ventricular tachyarrhythmias. Electrical remodeling that occurs at the cellular and tissue network levels predisposes patients with HF to malignant arrhythmias. Our limited understanding of fundamental arrhythmia mechanisms has hampered the development of effective treatment strategies for these patients. METHODS AND CONCLUSIONS In this review, we outline recent advances in our understanding of arrhythmia mechanisms in the failing heart, highlighting various aspects of remodeling of ion channels, calcium handling proteins, and gap junction-related molecules. As will be discussed, these changes promote the prolongation of the action potential, the enhancement of spatio-temporal gradients of repolarization, the formation of calcium-mediated triggers and conduction abnormalities, all of which combine to form an electrophysiological substrate that is ripe for the genesis of lethal arrhythmias and sudden cardiac death.
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Affiliation(s)
- Hongwei Jin
- Division of Cardiology, Cardiovascular Research Center, Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, New York, USA
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Agladze K, Kay MW, Krinsky V, Sarvazyan N. Interaction between spiral and paced waves in cardiac tissue. Am J Physiol Heart Circ Physiol 2007; 293:H503-13. [PMID: 17384124 PMCID: PMC3019092 DOI: 10.1152/ajpheart.01060.2006] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
For prevention of lethal arrhythmias, patients at risk receive implantable cardioverter-defibrillators, which use high-frequency antitachycardia pacing (ATP) to convert tachycardias to a normal rhythm. One of the suggested ATP mechanisms involves paced-induced drift of rotating waves followed by their collision with the boundary of excitable tissue. This study provides direct experimental evidence of this mechanism. In monolayers of neonatal rat cardiomyocytes in which rotating waves of activity were initiated by premature stimuli, we used the Ca(2+)-sensitive indicator fluo 4 to observe propagating wave patterns. The interaction of the spiral tip with a paced wave was then monitored at a high spatial resolution. In the course of the experiments, we observed spiral wave pinning to local heterogeneities within the myocyte layer. High-frequency pacing led, in a majority of cases, to successful termination of spiral activity. Our data show that 1) stable spiral waves in cardiac monolayers tend to be pinned to local heterogeneities or areas of altered conduction, 2) overdrive pacing can shift a rotating wave from its original site, and 3) the wave break, formed as a result of interaction between the spiral tip and a paced wave front, moves by a paced-induced drift mechanism to an area where it may become unstable or collide with a boundary. The data were complemented by numerical simulations, which was used to further analyze experimentally observed behavior.
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Affiliation(s)
- Konstantin Agladze
- Pharmacology and Physiology Department, The George Washington University, 2300 Eye Street, Washington, DC 20037.
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Akar JG, Akar FG. Mapping arrhythmias in the failing heart: from Langendorff to patient. J Electrocardiol 2006; 39:S19-23. [PMID: 16920143 DOI: 10.1016/j.jelectrocard.2006.03.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2006] [Accepted: 03/30/2006] [Indexed: 11/17/2022]
Abstract
Sudden cardiac death due to ventricular arrhythmias is a major cause of mortality in patients with heart failure (HF). As HF develops, a host of changes occur at multiple levels, spanning the spectrum from subcellular/molecular to organ-system levels. These changes, collectively referred to as "cardiac remodeling," predispose to electrical disturbances via multiple mechanisms. In humans, most arrhythmias are reentrant by nature, involving circulatory wavefront(s) that excite the heart in rapid, irregular succession. Hence, by definition, reentrant excitation occurs at the multicellular intact tissue level, and therefore, a complete understanding of its dynamics and underlying mechanisms requires investigation of electrophysiological properties (such as action potentials and calcium transients) in intact tissue preparations where cells are electrically coupled to one another. While molecular and cellular studies are critical for identifying changes in individual myocytes, only recently have we begun to understand how these complex changes can create an environment ripe for arrhythmias. In particular, the integrative technique of optical action potential mapping was used in recent years to address key questions regarding changes in network electrical properties of the failing myocardium. In the present manuscript, we review recent findings from mapping studies in the experimental laboratory as they relate to the characterization of the arrhythmic substrate of the failing heart, followed by a discussion of clinical mapping approaches used to identify key characteristics of atrial and ventricular arrhythmias in patients with HF.
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Affiliation(s)
- Joseph G Akar
- Division of Cardiology and the Institute of Computational Medicine, John Hopkins University, Baltimore, MD 21205, USA
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Jiao Z, De Jesús VR, Iravanian S, Campbell DP, Xu J, Vitali JA, Banach K, Fahrenbach J, Dudley SC. A possible mechanism of halocarbon-induced cardiac sensitization arrhythmias. J Mol Cell Cardiol 2006; 41:698-705. [PMID: 16919292 PMCID: PMC3169205 DOI: 10.1016/j.yjmcc.2006.07.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2006] [Revised: 07/03/2006] [Accepted: 07/06/2006] [Indexed: 11/16/2022]
Abstract
Cardiac sensitization is the term used for malignant ventricular arrhythmias associated with exposure to inhaled halocarbons in the presence of catecholamines. We investigated the electrophysiological changes associated with cardiomyocyte exposure to epinephrine and a halocarbon known to be associated with cardiac sensitization (halon 1301, CF3Br). Cardiomyocytes (CMs) were isolated from neonatal rats and grown on multielectrode arrays (MEAs). Upon exposure to epinephrine, the CM inter-spike interval (ISI) was decreased 14% at 10 microg/L (P<0.05) and 27% at 100 microg/L (P<0.05) as compared to baseline. Halon alone (50 mg/L) mildly prolonged the field potential (FP) duration (7%). CMs exposed to combinations of epinephrine (100 microg/L) and halon (50 mg/L) for 15 min showed a blunted increase in the ISI (35+/-12%) and a 38% decrease in conduction velocity (P<0.05) when compared to epinephrine alone. There was no change in field potential properties, but dephosphorylated connexin 43 (Cx43) was increased 60+/-16% with the combination as compared to epinephrine alone (P<0.05). Treatment with okadaic acid, a phosphatase inhibitor, prevented the Cx43 dephosphorylation and the reduction in conduction velocity upon exposure to halon and epinephrine. Moreover, the electrophysiological changes induced by epinephrine and halon were indistinguishable from those seen with the gap junction inhibitor heptanol. In conclusion, the combination of a halocarbon and epinephrine results in a unique electrophysiological signature including slow conduction that may explain, in part, the basis for cardiac sensitization. The slowing of conduction is most likely related to changes in the phosphorylation state of Cx43.
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Affiliation(s)
- Zhe Jiao
- Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
- Atlanta Veterans Affairs Medical Center, Decatur, GA 30033, USA
| | - Víctor R. De Jesús
- Health and Environmental Systems Laboratory, Georgia Tech Research Institute, Atlanta, GA 30332, USA
| | - Shahriar Iravanian
- Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
- Atlanta Veterans Affairs Medical Center, Decatur, GA 30033, USA
| | - Daniel P. Campbell
- Health and Environmental Systems Laboratory, Georgia Tech Research Institute, Atlanta, GA 30332, USA
| | - Jie Xu
- Health and Environmental Systems Laboratory, Georgia Tech Research Institute, Atlanta, GA 30332, USA
| | - Juan A. Vitali
- Army Test and Evaluation Command, Army Evaluation Center, Alexandria, VA 22302, USA
| | - Kathrin Banach
- Department of Physiology, Loyola University Chicago, Maywood, IL 60153, USA
| | - John Fahrenbach
- Department of Physiology, Loyola University Chicago, Maywood, IL 60153, USA
| | - Samuel C. Dudley
- Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
- Atlanta Veterans Affairs Medical Center, Decatur, GA 30033, USA
- Corresponding author. Division of Cardiology, Emory University/VAMC, 1670 Clairmont Rd. (111B), Decatur, GA 30033, USA. Tel.: +1 404 329 4626; fax: +1 404 329 2211. (S.C. Dudley)
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Akar FG, Tomaselli GF. Conduction Abnormalities in Nonischemic Dilated Cardiomyopathy: Basic Mechanisms and Arrhythmic Consequences. Trends Cardiovasc Med 2005; 15:259-64. [PMID: 16226681 DOI: 10.1016/j.tcm.2005.08.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Revised: 08/01/2005] [Accepted: 08/04/2005] [Indexed: 10/25/2022]
Abstract
Heart failure is associated with an increased risk of sudden death caused by ventricular tachyarrhythmias. The role of altered repolarization in the formation of arrhythmogenic substrates and triggers has been studied at multiple levels of integration, including molecular, cellular, tissue, and organ levels. Numerous studies have focused on conduction abnormalities in the context of ischemic heart disease and left ventricular dysfunction after myocardial infarction. However, ischemia alone, independent of left ventricular dysfunction, alters conduction by depressing membrane excitability and increasing tissue resistivity. In this review, we focus on the role of conduction abnormalities in the genesis of arrhythmias in nonischemic dilated cardiomyopathy and discuss their underlying cellular and molecular mechanisms, including changes in myocyte excitability, the extracellular matrix, and cell-to-cell coupling. We compare the nature of conduction slowing in ischemic and nonischemic heart failure and highlight the mechanistic differences between the two disease etiologies.
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Affiliation(s)
- Fadi G Akar
- Division of Cardiology, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA
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Kaji H, Takii Y, Nishizawa M, Matsue T. Pharmacological characterization of micropatterned cardiac myocytes. Biomaterials 2003; 24:4239-44. [PMID: 12853255 DOI: 10.1016/s0142-9612(03)00275-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The cardiac myocytes patterned on a single cell level were prepared by microcontact printing, and the response to chemical stimuli was studied using confocal fluorescent Ca(2+) imaging. The patterned myocytes were found to conjugate by forming gap junction. It was confirmed for the patterned myocytes that gap junction communication was reversibly inhibited by 1-octanol, but activated by caffeine. Localized stimulation with chemicals was also attempted using a microinjection system for the myocyte patterns formed by single cell alignment. This research was carried out with the objective of developing a bioassay system based on a cellular network.
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Affiliation(s)
- Hirokazu Kaji
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
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