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Pérez JJ, González-Suárez A. How intramyocardial fat can alter the electric field distribution during Pulsed Field Ablation (PFA): Qualitative findings from computer modeling. PLoS One 2023; 18:e0287614. [PMID: 37917621 PMCID: PMC10621855 DOI: 10.1371/journal.pone.0287614] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 06/08/2023] [Indexed: 11/04/2023] Open
Abstract
Even though the preliminary experimental data suggests that cardiac Pulsed Field Ablation (PFA) could be superior to radiofrequency ablation (RFA) in terms of being able to ablate the viable myocardium separated from the catheter by collagen and fat, as yet there is no formal physical-based analysis that describes the process by which fat can affect the electric field distribution. Our objective was thus to determine the electrical impact of intramyocardial fat during PFA by means of computer modeling. Computer models were built considering a PFA 3.5-mm blunt-tip catheter in contact with a 7-mm ventricular wall (with and without a scar) and a 2-mm epicardial fat layer. High voltage was set to obtain delivered currents of 19, 22 and 25 A. An electric field value of 1000 V/cm was considered as the lethal threshold. We found that the presence of fibrotic tissue in the scar seems to have a similar impact on the electric field distribution and lesion size to that of healthy myocardium only. However, intramyocardial fat considerably alters the electrical field distribution and the resulting lesion shape. The electric field tends to peak in zones with fat, even away from the ablation electrode, so that 'cold points' (i.e. low electric fields) appear around the fat at the current entry and exit points, while 'hot points' (high electric fields) occur in the lateral areas of the fat zones. The results show that intramyocardial fat can alter the electric field distribution and lesion size during PFA due to its much lower electrical conductivity than that of myocardium and fibrotic tissue.
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Affiliation(s)
- Juan J. Pérez
- BioMIT, Department of Electronic Engineering, Universitat Politècnica de València, Valencia, Spain
| | - Ana González-Suárez
- Translational Medical Device Lab, School of Engineering, University of Galway, Galway, Ireland
- Universidad Internacional de Valencia—VIU, Valencia, Spain
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2
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Fadle Aziz MR, Wlodarek L, Alibhai F, Wu J, Li S, Sun Y, Santerre JP, Li RK. A Polypyrrole-Polycarbonate Polyurethane Elastomer Alleviates Cardiac Arrhythmias via Improving Bio-Conductivity. Adv Healthc Mater 2023:e2203168. [PMID: 36849128 DOI: 10.1002/adhm.202203168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 01/27/2023] [Indexed: 03/01/2023]
Abstract
Myocardial fibrosis, resulting from myocardial infarction (MI), significantly alters cardiac electrophysiological properties. As fibrotic scar tissue forms, its resistance to incoming action potentials increases, leading to cardiac arrhythmia, and eventually sudden cardiac death or heart failure. Biomaterials are gaining increasing attention as an approach for addressing post-MI arrhythmias. The current study investigates the hypothesis that a bio-conductive epicardial patch can electrically synchronize isolated cardiomyocytes in vitro and rescue arrhythmic hearts in vivo. A new conceived biocompatible, conductive, and elastic polyurethane composite bio-membrane, referred to as polypyrrole-polycarbonate polyurethane (PPy-PCNU), is developed, in which solid-state conductive PPy nanoparticles are distributed throughout an electrospun aliphatic PCNU nanofiber patch in a controlled manner. Compared to PCNU alone, the resulting biocompatible patch demonstrates up to six times less impedance, with no conductivity loss over time, as well as being able to influence cellular alignment. Furthermore, PPy-PCNU promotes synchronous contraction of isolated neonatal rat cardiomyocytes and alleviates atrial fibrillation in rat hearts upon epicardial implantation. Taken together, epicardially-implanted PPy-PCNU could potentially serve as a novel alternative approach for the treatment of cardiac arrhythmias.
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Affiliation(s)
- Monir Riasad Fadle Aziz
- Toronto General Hospital Research Institute, University Health Network, Toronto, ON, M5G 1L7, Canada.,Institute of Biomedical Engineering, University of Toronto, Toronto, ON, M5S 3G9, Canada.,Faculty of Dentistry, Translational Biology and Engineering Program at the Ted Rogers Centre for Heart Research, University of Toronto, Toronto, ON, M5G 1M1, Canada
| | - Lukasz Wlodarek
- Toronto General Hospital Research Institute, University Health Network, Toronto, ON, M5G 1L7, Canada
| | - Faisal Alibhai
- Toronto General Hospital Research Institute, University Health Network, Toronto, ON, M5G 1L7, Canada
| | - Jun Wu
- Toronto General Hospital Research Institute, University Health Network, Toronto, ON, M5G 1L7, Canada
| | - Shuhong Li
- Toronto General Hospital Research Institute, University Health Network, Toronto, ON, M5G 1L7, Canada
| | - Yu Sun
- Institute of Biomedical Engineering, University of Toronto, Toronto, ON, M5S 3G9, Canada.,Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, M5S 3G8, Canada
| | - J Paul Santerre
- Institute of Biomedical Engineering, University of Toronto, Toronto, ON, M5S 3G9, Canada.,Faculty of Dentistry, Translational Biology and Engineering Program at the Ted Rogers Centre for Heart Research, University of Toronto, Toronto, ON, M5G 1M1, Canada
| | - Ren-Ke Li
- Toronto General Hospital Research Institute, University Health Network, Toronto, ON, M5G 1L7, Canada.,Institute of Biomedical Engineering, University of Toronto, Toronto, ON, M5S 3G9, Canada.,Division of Cardiac Surgery, Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, ON, M5G 2C4, Canada
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3
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Queiroz SA, Gonzalez MC, da Silva AMB, Costa JKDA, de Oliveira CDR, de Sousa IM, Fayh APT. Is the standardized phase angle a predictor of short and long-term adverse cardiovascular events in acute myocardial infarction patients? A cohort study. Nutrition 2022; 103-104:111774. [DOI: 10.1016/j.nut.2022.111774] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 05/27/2022] [Accepted: 06/06/2022] [Indexed: 11/25/2022]
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4
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Sánchez-Muñoz EJ, Berjano E, González-Suárez A. Computer simulations of consecutive radiofrequency pulses applied at the same point during cardiac catheter ablation: Implications for lesion size and risk of overheating. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2022; 220:106817. [PMID: 35468542 DOI: 10.1016/j.cmpb.2022.106817] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 04/12/2022] [Accepted: 04/14/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND AND OBJECTIVES To study temperature distribution and lesion size during two repeated radiofrequency (RF) pulses applied at the same point in the context of RF cardiac ablation (RFCA). METHODS An in-silico RFCA model accounting for reversible and irreversible changes in myocardium electrical properties due to RF-induced heating. Arrhenius damage model to estimate lesion size during the application of two 20 W pulses at intervals (INT) of from 5 to 70 s. We considered two pulse durations: 20 s and 30 s. RESULTS INT has a significant effect on lesion size and maximum tissue temperature (TMAX). The shorter the INT the greater the increase in lesion size after the second pulse but also the greater the TMAX. If the second pulse is applied almost immediately (INT=5 s), depth increases 1.4 mm and 1.5 mm for pulses of 20 s and 30 s, respectively. If INT is longer than 30 s it increases 1.1 mm and 1.3 mm for pulses of 20 s and 30 s, respectively. While a single 20 s pulse causes TMAX=79 ºC, a second pulse produces values of from 92 to 96 ºC (the higher the temperature the shorter the INT). For 30 s pulses, TMAX=93 ºC for a single pulse, and varied from 98 to 104 ºC for a second pulse. CONCLUSIONS Applying a second RF pulse at the same ablation site increases lesion depth by 1 - 1.5 mm more than a single pulse and could lead to higher temperatures (up to 17 ºC). Both lesion depth and maximum tissue temperature increased at shorter inter-pulse intervals, which could cause clinical complications from overheating such as steam pops.
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Affiliation(s)
| | - Enrique Berjano
- BioMIT, Department of Electronic Engineering, Universitat Politècnica de València, Valencia, Spain
| | - Ana González-Suárez
- Electrical and Electronic Engineering, National University of Ireland Galway, Ireland; Translational Medical Device Lab, National University of Ireland Galway, Ireland.
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5
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Muñoz M, Eren Cimenci C, Goel K, Comtois-Bona M, Hossain M, McTiernan C, Zuñiga-Bustos M, Ross A, Truong B, Davis DR, Liang W, Rotstein B, Ruel M, Poblete H, Suuronen EJ, Alarcon EI. Nanoengineered Sprayable Therapy for Treating Myocardial Infarction. ACS NANO 2022; 16:3522-3537. [PMID: 35157804 DOI: 10.1021/acsnano.1c08890] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We report the development, as well as the in vitro and in vivo testing, of a sprayable nanotherapeutic that uses surface engineered custom-designed multiarmed peptide grafted nanogold for on-the-spot coating of an infarcted myocardial surface. When applied to mouse hearts, 1 week after infarction, the spray-on treatment resulted in an increase in cardiac function (2.4-fold), muscle contractility, and myocardial electrical conductivity. The applied nanogold remained at the treatment site 28 days postapplication with no off-target organ infiltration. Further, the infarct size in the mice that received treatment was found to be <10% of the total left ventricle area, while the number of blood vessels, prohealing macrophages, and cardiomyocytes increased to levels comparable to that of a healthy animal. Our cumulative data suggest that the therapeutic action of our spray-on nanotherapeutic is highly effective, and in practice, its application is simpler than other regenerative approaches for treating an infarcted heart.
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Affiliation(s)
- Marcelo Muñoz
- BEaTS Research, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
| | - Cagla Eren Cimenci
- BEaTS Research, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Keshav Goel
- BEaTS Research, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
| | - Maxime Comtois-Bona
- BEaTS Research, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
| | - Mahir Hossain
- BEaTS Research, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
| | - Christopher McTiernan
- BEaTS Research, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
| | - Matias Zuñiga-Bustos
- Departamento de Bioinformática, Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería, Universidad de Talca, Campus Talca, 2 Norte 685, 3460000, Talca, Chile
| | - Alex Ross
- BEaTS Research, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
| | - Brenda Truong
- BEaTS Research, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
| | - Darryl R Davis
- University of Ottawa Heart Institute, Division of Cardiology, Department of Medicine, University of Ottawa, Ottawa, Ontario K1Y 4W7, Canada
- Cardiac Electrophysiology Lab, University of Ottawa, Ottawa, Ontario K1Y 4W7, Canada
| | - Wenbin Liang
- University of Ottawa Heart Institute, Division of Cardiology, Department of Medicine, University of Ottawa, Ottawa, Ontario K1Y 4W7, Canada
- Cardiac Electrophysiology Lab, University of Ottawa, Ottawa, Ontario K1Y 4W7, Canada
| | - Benjamin Rotstein
- Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
- Molecular Imaging Probes and Radiochemistry Laboratory, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, Ontario K1Y 4W7, Canada
| | - Marc Ruel
- BEaTS Research, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Horacio Poblete
- Departamento de Bioinformática, Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería, Universidad de Talca, Campus Talca, 2 Norte 685, 3460000, Talca, Chile
- Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Talca, 2 Norte 685, 3460000 Talca, Chile
| | - Erik J Suuronen
- BEaTS Research, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Emilio I Alarcon
- BEaTS Research, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
- Molecular Imaging Probes and Radiochemistry Laboratory, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, Ontario K1Y 4W7, Canada
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6
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Fu A, Yang Y, Wu J, Li S, Fan Y, Yau TM, Li R. Bio-Conductive Polymers for Treating Myocardial Conductive Defects: Long-Term Efficacy Study. Adv Healthc Mater 2022; 11:e2101838. [PMID: 34704404 DOI: 10.1002/adhm.202101838] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 10/15/2021] [Indexed: 01/23/2023]
Abstract
Following myocardial infarction (MI), the resulting fibrotic scar is nonconductive and leads to ventricular dysfunction via electrical uncoupling of the remaining viable cardiomyocytes. The uneven conductive properties between normal myocardium and scar tissue result in arrhythmia, yielding sudden cardiac death/heart failure. A conductive biopolymer, poly-3-amino-4-methoxybenzoic acid-gelatin (PAMB-G), is able to resynchronize myocardial contractions in vivo. Intravenous PAMB-G injections into mice show that it does not cause any acute toxicity, up to the maximum tolerated dose (1.6 mL kg-1 ), which includes the determined therapeutic dose (0.4 mL kg-1 ). There is also no short- or long-term toxicity when PAMB-G is injected into the myocardium of MI rats, with no significant changes in body weight, organ-brain ratio, hematologic, and histological parameters for up to 12 months post-injection. At the therapeutic dose, PAMB-G restores electrical conduction in infarcted rat hearts, resulting in lowered arrhythmia susceptibility and improved cardiac function. PAMB-G is also durable, as mass spectrometry detected the biopolymer for up to 12 months post-injection. PAMB-G did not impact reproductive organ function or offspring characteristics when given intravenously into healthy adult rats. Thus, PAMB-G is a nontoxic, durable, and conductive biomaterial that is able to improve cardiac function for up to 1 year post-implantation.
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Affiliation(s)
- Anne Fu
- Toronto General Hospital Research Institute Division of Cardiovascular Surgery University Health Network TorontoM5G 1L7 Canada
- Department of Laboratory Medicine and Pathology University of Toronto TorontoM5G 1L7 Canada
| | - Yahan Yang
- Toronto General Hospital Research Institute Division of Cardiovascular Surgery University Health Network TorontoM5G 1L7 Canada
| | - Jun Wu
- Toronto General Hospital Research Institute Division of Cardiovascular Surgery University Health Network TorontoM5G 1L7 Canada
| | - Shu‐Hong Li
- Toronto General Hospital Research Institute Division of Cardiovascular Surgery University Health Network TorontoM5G 1L7 Canada
| | - Yunfei Fan
- Toronto General Hospital Research Institute Division of Cardiovascular Surgery University Health Network TorontoM5G 1L7 Canada
| | - Terrance M Yau
- Toronto General Hospital Research Institute Division of Cardiovascular Surgery University Health Network TorontoM5G 1L7 Canada
- Division of Cardiac Surgery Department of Surgery University of Toronto TorontoM5G 1L7 Canada
| | - Ren‐Ke Li
- Toronto General Hospital Research Institute Division of Cardiovascular Surgery University Health Network TorontoM5G 1L7 Canada
- Department of Laboratory Medicine and Pathology University of Toronto TorontoM5G 1L7 Canada
- Division of Cardiac Surgery Department of Surgery University of Toronto TorontoM5G 1L7 Canada
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7
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Choi YS, Yin RT, Pfenniger A, Koo J, Avila R, Benjamin Lee K, Chen SW, Lee G, Li G, Qiao Y, Murillo-Berlioz A, Kiss A, Han S, Lee SM, Li C, Xie Z, Chen YY, Burrell A, Geist B, Jeong H, Kim J, Yoon HJ, Banks A, Kang SK, Zhang ZJ, Haney CR, Sahakian AV, Johnson D, Efimova T, Huang Y, Trachiotis GD, Knight BP, Arora RK, Efimov IR, Rogers JA. Fully implantable and bioresorbable cardiac pacemakers without leads or batteries. Nat Biotechnol 2021; 39:1228-1238. [PMID: 34183859 PMCID: PMC9270064 DOI: 10.1038/s41587-021-00948-x] [Citation(s) in RCA: 105] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 05/06/2021] [Indexed: 12/22/2022]
Abstract
Temporary cardiac pacemakers used in periods of need during surgical recovery involve percutaneous leads and externalized hardware that carry risks of infection, constrain patient mobility and may damage the heart during lead removal. Here we report a leadless, battery-free, fully implantable cardiac pacemaker for postoperative control of cardiac rate and rhythm that undergoes complete dissolution and clearance by natural biological processes after a defined operating timeframe. We show that these devices provide effective pacing of hearts of various sizes in mouse, rat, rabbit, canine and human cardiac models, with tailored geometries and operation timescales, powered by wireless energy transfer. This approach overcomes key disadvantages of traditional temporary pacing devices and may serve as the basis for the next generation of postoperative temporary pacing technology.
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Affiliation(s)
- Yeon Sik Choi
- Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, USA
- Querrey Simpson Institute for Biotechnology, Northwestern University, Evanston, IL, USA
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA
| | - Rose T Yin
- Department of Biomedical Engineering, The George Washington University, Washington, DC, USA
| | - Anna Pfenniger
- Feinberg School of Medicine, Cardiology, Northwestern University, Chicago, IL, USA
| | - Jahyun Koo
- Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, USA
- Querrey Simpson Institute for Biotechnology, Northwestern University, Evanston, IL, USA
| | - Raudel Avila
- Department of Mechanical Engineering, Northwestern University, Evanston, IL, USA
| | - K Benjamin Lee
- Department of Surgery, The George Washington University, Washington, DC, USA
| | - Sheena W Chen
- Department of Surgery, The George Washington University, Washington, DC, USA
| | - Geumbee Lee
- Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, USA
- Querrey Simpson Institute for Biotechnology, Northwestern University, Evanston, IL, USA
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA
| | - Gang Li
- Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, MO, USA
| | - Yun Qiao
- Department of Biomedical Engineering, The George Washington University, Washington, DC, USA
| | | | - Alexi Kiss
- Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
- The George Washington Cancer Center, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
| | - Shuling Han
- Comprehensive Transplant Center, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Department of Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Seung Min Lee
- Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, USA
| | - Chenhang Li
- Department of Mechanical Engineering, Northwestern University, Evanston, IL, USA
| | - Zhaoqian Xie
- State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, International Research Center for Computational Mechanics, Dalian University of Technology, Dalian, China
| | - Yu-Yu Chen
- Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Amy Burrell
- Feinberg School of Medicine, Cardiology, Northwestern University, Chicago, IL, USA
| | - Beth Geist
- Feinberg School of Medicine, Cardiology, Northwestern University, Chicago, IL, USA
| | - Hyoyoung Jeong
- Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, USA
- Querrey Simpson Institute for Biotechnology, Northwestern University, Evanston, IL, USA
| | - Joohee Kim
- Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, USA
- Querrey Simpson Institute for Biotechnology, Northwestern University, Evanston, IL, USA
| | - Hong-Joon Yoon
- Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, USA
- Querrey Simpson Institute for Biotechnology, Northwestern University, Evanston, IL, USA
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Republic of Korea
| | - Anthony Banks
- Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, USA
- Querrey Simpson Institute for Biotechnology, Northwestern University, Evanston, IL, USA
| | - Seung-Kyun Kang
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Zheng Jenny Zhang
- Comprehensive Transplant Center, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Department of Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Chad R Haney
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
- Center for Advanced Molecular Imaging, Northwestern University, Evanston, IL, USA
| | - Alan Varteres Sahakian
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
- Department of Electrical and Computer Engineering, Northwestern University, Evanston, IL, USA
| | - David Johnson
- Feinberg School of Medicine, Cardiology, Northwestern University, Chicago, IL, USA
| | - Tatiana Efimova
- Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
- The George Washington Cancer Center, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
| | - Yonggang Huang
- Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, USA
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA
- Department of Mechanical Engineering, Northwestern University, Evanston, IL, USA
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL, USA
| | - Gregory D Trachiotis
- Department of Cardiothoracic Surgery, Veteran Affairs Medical Center, Washington, DC, USA
| | - Bradley P Knight
- Feinberg School of Medicine, Cardiology, Northwestern University, Chicago, IL, USA
| | - Rishi K Arora
- Feinberg School of Medicine, Cardiology, Northwestern University, Chicago, IL, USA.
| | - Igor R Efimov
- Department of Biomedical Engineering, The George Washington University, Washington, DC, USA.
| | - John A Rogers
- Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, USA.
- Querrey Simpson Institute for Biotechnology, Northwestern University, Evanston, IL, USA.
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA.
- Department of Mechanical Engineering, Northwestern University, Evanston, IL, USA.
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA.
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
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8
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Degache A, Poulletier de Gannes F, Garenne A, Renom R, Percherancier Y, Lagroye I, Bernus O, Lewis N. In vitrodifferentiation of human cardiac fibroblasts into myofibroblasts: characterization using electrical impedance. Biomed Phys Eng Express 2021; 8. [PMID: 34243179 DOI: 10.1088/2057-1976/ac12e1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 07/09/2021] [Indexed: 11/12/2022]
Abstract
Cardiac arrhythmias represent about 50% of the cardiovascular diseases which are the first cause of mortality in the world. Implantable medical devices play a major role for treating these arrhythmias. Nevertheless the leads induce an unwanted biological phenomenon called fibrosis. This phenomenon begins at a cellular level and is effective at a macroscopic scale causing tissue remodelling with a local modification of the active cardiac tissue. Fibrosis mechanism is complex but at the cellular level, it mainly consists in cardiac fibroblasts activation and differentiation into myofibroblasts. We developed a simplifiedin vitromodel of cardiac fibrosis, with human cardiac fibroblasts whom differentiation into myofibroblasts was promoted with TGF-β1. Our study addresses an unreported impedance-based method for real-time monitoring ofin vitrocardiac fibrosis. The objective was to study whether the differentiation of cardiac fibroblasts in myofibroblasts had a specific signature on the cell index, an impedance-based feature measured by the xCELLigence system. Primary human cardiac fibroblasts were cultured along 6 days, with or without laminin coating, to study the role of this adhesion protein in cultures long-term maintenance. The cultures were characterized in the presence or absence of TGF-β1 and we obtained a significant cell index signature specific to the human cardiac fibroblasts differentiation.
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Affiliation(s)
- Amelie Degache
- IMS Laboratory, CNRS UMR 5218, University of Bordeaux College of Science and Technology, 351 cours de la liberation, Talence, Aquitaine, 33400, FRANCE
| | - Florence Poulletier de Gannes
- IMS Laboratory, CNRS UMR 5218, University of Bordeaux College of Science and Technology, 351 cours de la liberation, Talence, Aquitaine, 33400, FRANCE
| | - André Garenne
- IMS Laboratory, CNRS UMR 5218, University of Bordeaux College of Science and Technology, 351 cours de la liberation, Talence, Aquitaine, 33400, FRANCE
| | - Rémy Renom
- IMS Laboratory, CNRS UMR 5218, University of Bordeaux College of Science and Technology, 351 cours de la liberation, Talence, Aquitaine, 33400, FRANCE
| | - Yann Percherancier
- IMS Laboratory, CNRS UMR 5218, University of Bordeaux College of Science and Technology, 351 cours de la liberation, Talence, Aquitaine, 33400, FRANCE
| | - Isabelle Lagroye
- IMS Laboratory, CNRS UMR 5218, University of Bordeaux College of Science and Technology, 351 cours de la liberation, Talence, Aquitaine, 33400, FRANCE
| | - Olivier Bernus
- IHU LIRYC, Electrophysiology and Heart Modelling Institute, U1045, University of Bordeaux, Avenue du haut leveque, Pessac, Aquitaine, 33600, FRANCE
| | - Noëlle Lewis
- IMS Laboratory, CNRS UMR 5218, University of Bordeaux College of Science and Technology, 351 cours de la liberation, Talence, Aquitaine, 33400, FRANCE
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9
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Schaefer M, Gross W, Gebhard MM. Hearts during ischemia with or without HTK-protection analysed by dielectric spectroscopy. Physiol Meas 2018; 39:025002. [PMID: 29303486 DOI: 10.1088/1361-6579/aaa575] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVE We investigated canine hearts during ischemia after aortic cross clamping (UI, n = 20) and after HTK-cardioplegia (HTK, n = 24) at 35 °C, 25 °C, 15 °C, and 5 °C with the aim to compare tissue changes caused by the activity of anaerobic metabolism(AAM), cell membrane destruction(CD), and gap junction uncoupling(GJU). APPROACH We measured continuously the complex dielectric spectrum(DS), ATP- and lactate content, extracellular pH, and rigor contracture. To identify changes in DS caused by AAM, CD, and GJU we performed additional experiments on the gap junction-free skeletal muscle. We used heart model simulations to calculate the effect of temperature. MAIN RESULTS AAM affected the DS at 10 MHz and we found a strong correlation between DS and the proton concentration with a maximum of DS at 10 mmol g-1 dry weight in ATP-concentration. The time of GJU was detected by a characteristic increase in DS and CD by a characteristic decrease at 13 kHz. In comparison to UI, GJU, AAM and CD were delayed by HTK and by hypothermia, indicating a minimization of energy consumption and an improved preservation of tissue structure. SIGNIFICANCE The novel findings were that in UI at 5 °C GJU occurred earlier and AAM remained constant, indicating a less effective preservation in UI by deep hypothermia in contrast to HTK.
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Affiliation(s)
- Michael Schaefer
- University Hospital Heidelberg, Section Surgical Research, INF 365, D-69120 Heidelberg, Germany
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10
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Determinants of Subcutaneous Implantable Cardioverter-Defibrillator Efficacy. JACC Clin Electrophysiol 2017; 3:405-414. [DOI: 10.1016/j.jacep.2016.10.016] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 10/11/2016] [Accepted: 10/21/2016] [Indexed: 01/28/2023]
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11
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Amorós-Figueras G, Jorge E, García-Sánchez T, Bragós R, Rosell-Ferrer J, Cinca J. Recognition of Fibrotic Infarct Density by the Pattern of Local Systolic-Diastolic Myocardial Electrical Impedance. Front Physiol 2016; 7:389. [PMID: 27630580 PMCID: PMC5006502 DOI: 10.3389/fphys.2016.00389] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 08/22/2016] [Indexed: 11/13/2022] Open
Abstract
Myocardial electrical impedance is a biophysical property of the heart that is influenced by the intrinsic structural characteristics of the tissue. Therefore, the structural derangements elicited in a chronic myocardial infarction should cause specific changes in the local systolic-diastolic myocardial impedance, but this is not known. This study aimed to characterize the local changes of systolic-diastolic myocardial impedance in a healed myocardial infarction model. Six pigs were successfully submitted to 150 min of left anterior descending (LAD) coronary artery occlusion followed by reperfusion. 4 weeks later, myocardial impedance spectroscopy (1–1000 kHz) was measured at different infarction sites. The electrocardiogram, left ventricular (LV) pressure, LV dP/dt, and aortic blood flow (ABF) were also recorded. A total of 59 LV tissue samples were obtained and histopathological studies were performed to quantify the percentage of fibrosis. Samples were categorized as normal myocardium (<10% fibrosis), heterogeneous scar (10–50%) and dense scar (>50%). Resistivity of normal myocardium depicted phasic changes during the cardiac cycle and its amplitude markedly decreased in dense scar (18 ± 2 Ω·cm vs. 10 ± 1 Ω·cm, at 41 kHz; P < 0.001, respectively). The mean phasic resistivity decreased progressively from normal to heterogeneous and dense scar regions (285 ± 10 Ω·cm, 225 ± 25 Ω·cm, and 162 ± 6 Ω·cm, at 41 kHz; P < 0.001 respectively). Moreover, myocardial resistivity and phase angle correlated significantly with the degree of local fibrosis (resistivity: r = 0.86 at 1 kHz, P < 0.001; phase angle: r = 0.84 at 41 kHz, P < 0.001). Myocardial infarcted regions with greater fibrotic content show lower mean impedance values and more depressed systolic-diastolic dynamic impedance changes. In conclusion, this study reveals that differences in the degree of myocardial fibrosis can be detected in vivo by local measurement of phasic systolic-diastolic bioimpedance spectrum. Once this new bioimpedance method could be used via a catheter-based device, it would be of potential clinical applicability for the recognition of fibrotic tissue to guide the ablation of atrial or ventricular arrhythmias.
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Affiliation(s)
- Gerard Amorós-Figueras
- Department of Cardiology, Hospital de la Santa Creu i Sant Pau, Institut d'Investigació Biomèdica - Sant Pau, Universitat Autònoma de Barcelona Barcelona, Spain
| | - Esther Jorge
- Department of Cardiology, Hospital de la Santa Creu i Sant Pau, Institut d'Investigació Biomèdica - Sant Pau, Universitat Autònoma de Barcelona Barcelona, Spain
| | - Tomás García-Sánchez
- Electronic and Biomedical Instrumentation Group, Department of Electronics Engineering, Universitat Politècnica de Catalunya Barcelona, Spain
| | - Ramón Bragós
- Electronic and Biomedical Instrumentation Group, Department of Electronics Engineering, Universitat Politècnica de Catalunya Barcelona, Spain
| | - Javier Rosell-Ferrer
- Electronic and Biomedical Instrumentation Group, Department of Electronics Engineering, Universitat Politècnica de Catalunya Barcelona, Spain
| | - Juan Cinca
- Department of Cardiology, Hospital de la Santa Creu i Sant Pau, Institut d'Investigació Biomèdica - Sant Pau, Universitat Autònoma de Barcelona Barcelona, Spain
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PÉREZ JUANJ, D'AVILA ANDRE, ARYANA ARASH, TRUJILLO MACARENA, BERJANO ENRIQUE. Can Fat Deposition After Myocardial Infarction Alter the Performance of RF Catheter Ablation of Scar-Related Ventricular Tachycardia?: Results from a Computer Modeling Study. J Cardiovasc Electrophysiol 2016; 27:947-52. [DOI: 10.1111/jce.13006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 04/18/2016] [Accepted: 04/26/2016] [Indexed: 01/20/2023]
Affiliation(s)
- JUAN J. PÉREZ
- Centro de Investigación e Innovación en Bioingeniería (Ci2B); Universitat Politècnica de València; Valencia Spain
| | - ANDRE D'AVILA
- IPAC-Instituto de Pesquisa em Arritmia Cardiaca-Hospital Cardiologico; Florianopolis SC Brazil
| | - ARASH ARYANA
- Dignity Health Heart and Vascular Institute; Sacramento California USA
| | - MACARENA TRUJILLO
- Instituto Universitario de Matemática Pura y Aplicada; Valencia Spain
| | - ENRIQUE BERJANO
- Biomedical Synergy, Electronic Engineering Department; Universitat Politècnica de València; Valencia Spain
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13
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Puig-Sanvicens VAC, Semino CE, Zur Nieden NI. Cardiac differentiation potential of human induced pluripotent stem cells in a 3D self-assembling peptide scaffold. Differentiation 2015; 90:101-10. [PMID: 26707885 DOI: 10.1016/j.diff.2015.11.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 11/19/2015] [Accepted: 11/20/2015] [Indexed: 01/01/2023]
Abstract
In the past decade, various strategies for cardiac reparative medicine involving stem cells from multiple sources have been investigated. However, the intra-cardiac implantation of cells with contractile ability may seriously disrupt the cardiac syncytium and de-synchronize cardiac rhythm. For this reason, bioactive cardiac implants, consisting of stem cells embedded in biomaterials that act like band aids, have been exploited to repair the cardiac wall after myocardial infarction. For such bioactive implants to function properly after transplantation, the choice of biomaterial is equally important as the selection of the stem cell source. While adult stem cells have shown promising results, they have various disadvantages including low proliferative potential in vitro, which make their successful usage in human transplants difficult. As a first step towards the development of a bioactive cardiac patch, we investigate here the cardiac differentiation properties of human induced pluripotent stem cells (hiPSCs) when cultured with and without ascorbic acid (AA) and when embedded in RAD16-I, a biomaterial commonly used to develop cardiac implants. In adherent cultures and in the absence of RAD16-I, AA promotes the cardiac differentiation of hiPSCs by enhancing the expression of specific cardiac genes and proteins and by increasing the number of contracting clusters. In turn, embedding in peptide hydrogel based on RAD16-I interferes with the normal cardiac differentiation progression. Embedded hiPSCs up-regulate genes associated with early cardiogenesis by up to 105 times independently of the presence of AA. However, neither connexin 43 nor troponin I proteins, which are related with mature cardiomyocytes, were detected and no contraction was noted in the constructs. Future experiments will need to focus on characterizing the mature cardiac phenotype of these cells when implanted into infarcted myocardia and assess their regenerative potential in vivo.
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Affiliation(s)
- Veronica A C Puig-Sanvicens
- Department of Cell Biology & Neuroscience and Stem Cell Center, College of Natural and Agricultural Sciences, University of California Riverside, United States; Laboratory of Tissue Engineering, Department of Bioengineering, Institut Químic de Sarrià, School of Engineering, Universitat Ramon Llull, Barcelona, Spain.
| | - Carlos E Semino
- Laboratory of Tissue Engineering, Department of Bioengineering, Institut Químic de Sarrià, School of Engineering, Universitat Ramon Llull, Barcelona, Spain.
| | - Nicole I Zur Nieden
- Department of Cell Biology & Neuroscience and Stem Cell Center, College of Natural and Agricultural Sciences, University of California Riverside, United States.
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Jorge E, Amorós-Figueras G, García-Sánchez T, Bragós R, Rosell-Ferrer J, Cinca J. Early detection of acute transmural myocardial ischemia by the phasic systolic-diastolic changes of local tissue electrical impedance. Am J Physiol Heart Circ Physiol 2015; 310:H436-43. [PMID: 26608340 DOI: 10.1152/ajpheart.00754.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 11/19/2015] [Indexed: 11/22/2022]
Abstract
Myocardial electrical impedance is influenced by the mechanical activity of the heart. Therefore, the ischemia-induced mechanical dysfunction may cause specific changes in the systolic-diastolic pattern of myocardial impedance, but this is not known. This study aimed to analyze the phasic changes of myocardial resistivity in normal and ischemic conditions. Myocardial resistivity was measured continuously during the cardiac cycle using 26 different simultaneous excitation frequencies (1 kHz-1 MHz) in 7 anesthetized open-chest pigs. Animals were submitted to 30 min regional ischemia by acute left anterior descending coronary artery occlusion. The electrocardiogram, left ventricular (LV) pressure, LV dP/dt, and aortic blood flow were recorded simultaneously. Baseline myocardial resistivity depicted a phasic pattern during the cardiac cycle with higher values at the preejection period (4.19 ± 1.09% increase above the mean, P < 0.001) and lower values during relaxation phase (5.01 ± 0.85% below the mean, P < 0.001). Acute coronary occlusion induced two effects on the phasic resistivity curve: 1) a prompt (5 min ischemia) holosystolic resistivity rise leading to a bell-shaped waveform and to a reduction of the area under the LV pressure-impedance curve (1,427 ± 335 vs. 757 ± 266 Ω·cm·mmHg, P < 0.01, 41 kHz) and 2) a subsequent (5-10 min ischemia) progressive mean resistivity rise (325 ± 23 vs. 438 ± 37 Ω·cm at 30 min, P < 0.01, 1 kHz). The structural and mechanical myocardial dysfunction induced by acute coronary occlusion can be recognized by specific changes in the systolic-diastolic myocardial resistivity curve. Therefore these changes may become a new indicator (surrogate) of evolving acute myocardial ischemia.
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Affiliation(s)
- Esther Jorge
- Department of Cardiology, Hospital de la Santa Creu i Sant Pau, Institute of Biomedical Research Sant Pau, Universitat Autonoma de Barcelona, Barcelona, Spain; and
| | - Gerard Amorós-Figueras
- Department of Cardiology, Hospital de la Santa Creu i Sant Pau, Institute of Biomedical Research Sant Pau, Universitat Autonoma de Barcelona, Barcelona, Spain; and
| | - Tomás García-Sánchez
- Electronic and Biomedical Instrumentation Group, Department of Electronics Engineering, Universitat Politecnica de Catalunya, Barcelona, Spain
| | - Ramón Bragós
- Electronic and Biomedical Instrumentation Group, Department of Electronics Engineering, Universitat Politecnica de Catalunya, Barcelona, Spain
| | - Javier Rosell-Ferrer
- Electronic and Biomedical Instrumentation Group, Department of Electronics Engineering, Universitat Politecnica de Catalunya, Barcelona, Spain
| | - Juan Cinca
- Department of Cardiology, Hospital de la Santa Creu i Sant Pau, Institute of Biomedical Research Sant Pau, Universitat Autonoma de Barcelona, Barcelona, Spain; and
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Farraha M, Nguyen DT, Barry MA, Lu J, McEwan AL, Pouliopoulos J. Investigating the utility of in vivo bio-impedance spectroscopy for the assessment of post-ischemic myocardial tissue. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:1111-4. [PMID: 25570157 DOI: 10.1109/embc.2014.6943789] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Increased myocardial structural heterogeneity in response to ischemic injury following myocardial infarction (MI) is purported as the mechanism of ventricular arrhythmogenesis. Current modalities for in vivo assessment of structural heterogeneity for identification of arrhythmogenic substrate are limited due to the complex nature of the structural microenvironment post-MI. We investigated the utility of in vivo bio-impedance spectroscopy (BIS) in a large post-infarct animal model for differentiation between normal and infarcted tissue. We also investigated the quantitative effects of adipose and collagen on BIS assessment of myocardium. The results indicate that the degree of myocardial injury following chronic post-infarction remodeling could be reliably quantified (performed in triplicates) using BIS. Furthermore, the presence of intramyocardial adipose tissue that develops in conjunction with collagen within the infarct zone had a greater and significant influence on BIS then collagen tissue alone. These preliminary results indicate a potential role of BIS for quantitative assessment and characterization of complex arrhythmogenic substrates in ischemic cardiomyopathy.
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16
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Prat-Vidal C, Gálvez-Montón C, Puig-Sanvicens V, Sanchez B, Díaz-Güemes I, Bogónez-Franco P, Perea-Gil I, Casas-Solà A, Roura S, Llucià-Valldeperas A, Soler-Botija C, Sánchez-Margallo FM, Semino CE, Bragos R, Bayes-Genis A. Online monitoring of myocardial bioprosthesis for cardiac repair. Int J Cardiol 2014; 174:654-61. [DOI: 10.1016/j.ijcard.2014.04.181] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 03/07/2014] [Accepted: 04/17/2014] [Indexed: 02/07/2023]
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17
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Do changes in electrical skin resistance of acupuncture points reflect menstrual pain? A comparative study in healthy volunteers and primary dysmenorrhea patients. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2014; 2014:836026. [PMID: 24876879 PMCID: PMC4020393 DOI: 10.1155/2014/836026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Revised: 03/20/2014] [Accepted: 03/31/2014] [Indexed: 11/29/2022]
Abstract
Electrical skin resistance (ESR) measurements were performed with a four-electrode impedance detector at 10 points bilaterally on the first day of and the third day after menstruation in 48 healthy volunteers and 46 primary dysmenorrhea (PD) patients, to assess whether ESR changes of acupuncture points can reflect menstrual pain or not. The results showed statistical reductions in ESR imbalance ratio between left and right side that were detected at SP8 (Diji) and GB39 (Xuanzhong) (P < 0.05), and a statistical increase was detected at SP6 (Sanyinjiao) (P = 0.05) on the first day of menstruation compared with those values on the third day after menstruation in dysmenorrhea group. No significant differences were detected at other points within and between two groups (P > 0.05). This study showed that the imbalance of ESR at uterine-relevant points in PD patients is not significantly different from those of healthy women on both the 1st day of and the 3rd day after menstruation. The ESR imbalance ratio of certain points can either be lower or higher during menstruation in PD patients. The ESR property of acupuncture points needs to be investigated in further clinical trials with appropriate points, diseases, larger sample sizes, and optimal device.
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18
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Chiu HW, Chuang JM, Lu CC, Lin WT, Lin CW, Lin ML. In situ measurement of tissue impedance using an inductive coupling interface circuit. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2013; 7:225-235. [PMID: 23853322 DOI: 10.1109/tbcas.2012.2199488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In this work, a method of an inductive coupling impedance measurement (ICIM) is proposed for measuring the nerve impedance of a dorsal root ganglion (DRG) under PRF stimulation. ICIM provides a contactless interface for measuring the reflected impedance by an impedance analyzer with a low excitation voltage of 7 mV. The paper develops a calibration procedure involving a 50-Ω reference resistor to calibrate the reflected resistance for measuring resistance of the nerve in the test. A de-embedding technique to build the equivalent transformer circuit model for the ICIM circuit is also presented. A batteryless PRF stimulator with ICIM circuit demonstrated good accuracy for the acute measurement of DRG impedance both in situ and in vivo. Besides, an in vivo animal experiment was conducted to show that the effectiveness of pulsed radiofrequency (PRF) stimulation in relieving pain gradually declined as the impedance of the stimulated nerve increased. The experiment also revealed that the excitation voltage for measuring impedance below 25 mV can prevent the excitation of a nonlinear response of DRG.
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Affiliation(s)
- Hung-Wei Chiu
- Department of Electronic Engineering and Graduate Institute of Computer and Communication Engineering, National Taipei University of Technology, Taipei 10608, Taiwan.
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19
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Pollard AE, Barr RC. A new approach for resolution of complex tissue impedance spectra in hearts. IEEE Trans Biomed Eng 2013; 60:2494-503. [PMID: 23625349 DOI: 10.1109/tbme.2013.2258917] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
This study was designed to test the feasibility of using sinusoidal approximation in combination with a new instrumentation approach to resolve complex impedance (uCI) spectra from heart preparations. To assess that feasibility, we applied stimuli in the 10-4000 Hz range and recorded potential differences (uPDs) in a four-electrode configuration that allowed identification of probe constants (Kp) during calibration that were in turn used to measure total tissue resistivity ρt from rabbit ventricular epicardium. Simultaneous acquisition of a signal proportional to the supplied current (Vstim) with uPD allowed identification of the V- I ratio needed for ρt measurement, as well as the phase shift from Vstim to uPD needed for uCI spectra resolution. Performance with components integrated to reduce noise in cardiac electrophysiologic experiments, in particular, and provide accurate electrometer-based measurements, in general, was first characterized in tests using passive loads. Load tests showed accurate uCI recovery with mean uPD SNRs between 10 (1) and 10 (3) measured with supplied currents as low as 10 nA. Comparable performance characteristics were identified during calibration of nine arrays built with 250 μm Ag/AgCl electrodes, with uCIs that matched analytic predictions and no apparent effect of frequency ( F = 0.12, P = 0.99). The potential ability of parasitic capacitance in the presence of the electrode-electrolyte interface associated with the small sensors to influence the uCI spectra was therefore limited by the instrumentation. Resolution of uCI spectra in rabbit ventricle allowed measurement of ρt = 134 ± 53 Ω· cm. The rapid identification available with this strategy provides an opportunity for new interpretations of the uCI spectra to improve quantification of disease-, region-, tissue-, and species-dependent intercellular uncoupling in hearts.
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20
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Sanchez B, Louarroudi E, Jorge E, Cinca J, Bragos R, Pintelon R. A new measuring and identification approach for time-varying bioimpedance using multisine electrical impedance spectroscopy. Physiol Meas 2013; 34:339-57. [PMID: 23442821 DOI: 10.1088/0967-3334/34/3/339] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The bioimpedance measurement/identification of time-varying biological systems Z(ω, t) by means of electrical impedance spectroscopy (EIS) is still a challenge today. This paper presents a novel measurement and identification approach, the so-called parametric-in-time approach, valid for time-varying (bio-)impedance systems with a (quasi) periodic character. The technique is based on multisine EIS. Contrary to the widely used nonparametric-in-time strategy, the (bio-)impedance Z(ω, t) is assumed to be time-variant during the measurement interval. Therefore, time-varying spectral analysis tools are required. This new parametric-in-time measuring/identification technique has experimentally been validated through three independent sets of in situ measurements of in vivo myocardial impedance. We show that the time-varying myocardial impedance Z(ω, t) is dominantly periodically time varying (PTV), denoted as ZPTV(ω, t). From the temporal analysis of ZPTV(ω, t), we demonstrate that it is possible to decompose ZPTV(ω, t) into a(n) (in)finite sum of fundamental (bio-)impedance spectra, the so-called harmonic impedance spectra (HIS) Zk(ω)s with [Formula: see text]. This is similar to the well-known Fourier series of a periodic signal, but now understood at the level of a periodic system's frequency response. The HIS Zk(ω)s for [Formula: see text] actually summarize in the bi-frequency (ω, k) domain all the temporal in-cycle information about the periodic changes of Z(ω, t). For the particular case k = 0 (i.e. on the ω-axis), Z0(ω) reflects the mean in-cycle behavior of the time-varying bioimpedance. Finally, the HIS Zk(ω)s are directly identified from noisy current and voltage myocardium measurements at the multisine measurement frequencies (i.e. nonparametric-in-frequency).
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Affiliation(s)
- B Sanchez
- Electronic and Biomedical Instrumentation Group, Department of Electrical Engineering, Universitat Politecnica de Catalunya (UPC), E-08034 Barcelona, Spain.
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21
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Sanchez B, Guasch A, Bogonez P, Galvez C, Puig V, Prat C, Semino CE, Bayes-Genis A, Bragos R. Towards on line monitoring the evolution of the myocardium infarction scar with an implantable electrical impedance spectrum monitoring system. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2012:3223-6. [PMID: 23366612 DOI: 10.1109/embc.2012.6346651] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The human heart tissue has a limited capacity for regeneration. Tissue and cellular therapies based on the use of stem cells may be useful alternatives to limit the size of myocardial infarction. In this paper, the preliminary results from an experimental campaign for on-line monitoring of myocardium scar infarction are presented. This study has been carried out under a research project that has as main objective the development and application of a bioactive patch implant for regeneration of myocardial infarction. Electrical Impedance Spectroscopy (EIS) has been chosen as a tissue state monitoring technique. What is presented in this communication is the first results of an implantable EIS measurement system which has been implanted in a subset of the animals corresponding to the control group, along one month. In all the animals, the myocardial infarction was induced by the ligation of the first circumflex marginal artery. In the animal group presented, the bioactive patch scaffold and the electrodes were implanted without the stem cells load. The scaffold is a piece of decellularized human pericardium, lyophilized and rehydrated with hydrogel RAD16-I. Nanogold particles were also placed near the electrodes to improve the electrode area conductivity. The results presented correspond to the subset of animals (n = 5), which had implanted the bioimpedance system monitoring the electrical impedance spectrum in vivo during 1 month. Two electrodes were connected to the bioactive patch implant. A total of 14 logarithmically spaced frequencies were measured every 5 minutes, from 100 Hz to 200 kHz. Results show a convergence of low-frequency and high frequency impedance magnitudes along the measurement period, which is coherent with the scar formation.
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Affiliation(s)
- B Sanchez
- ICREC Research Program, IGTP, Hospital Universitari Germans Trias i Pujol, Badalona, Spain
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22
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Sanchez B, Schoukens J, Bragos R, Vandersteen G. Novel estimation of the electrical bioimpedance using the local polynomial method. Application to in vivo real-time myocardium tissue impedance characterization during the cardiac cycle. IEEE Trans Biomed Eng 2011; 58:3376-85. [PMID: 21878408 DOI: 10.1109/tbme.2011.2166116] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Classical measurements of myocardium tissue electrical impedance for characterizing the morphology of myocardium cells, as well as cell membranes integrity and intra/extra cellular spaces, are based on the frequency-sweep electrical impedance spectroscopy (EIS) technique. In contrast to the frequency-sweep EIS approach, measuring with broadband signals, i.e., multisine excitations, enables to collect, simultaneously, multiple myocardium tissue impedance data in a short measuring time. However, reducing the measuring time makes the measurements to be prone to the influence of the transients introduced by noise and the dynamic time-varying properties of tissue. This paper presents a novel approach for the impedance-frequency-response estimation based on the local polynomial method (LPM). The fast LPM version presented rejects the leakage error's influence on the impedance frequency response when measuring electrical bioimpedance in a short time. The theory is supported by a set of validation measurements. Novel preliminary experimental results obtained from real-time in vivo healthy myocardium tissue impedance characterization within the cardiac cycle using multisine excitation are reported.
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Affiliation(s)
- Benjamin Sanchez
- Department of Electronic Engineering, Technical University of Catalonia, Barcelona 08034, Spain.
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23
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Giovinazzo G, Ribas N, Cinca J, Rosell-Ferrer J. The feasibility of transoesophageal bioimpedance measurements for the detection of heart graft rejection. Physiol Meas 2011; 32:867-76. [DOI: 10.1088/0967-3334/32/7/s10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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24
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Sanchez B, Vandersteen G, Rosell-Ferrer J, Cinca J, Bragos R. In-cycle myocardium tissue electrical impedance monitoring using broadband impedance spectroscopy. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2011; 2011:2518-2521. [PMID: 22254853 DOI: 10.1109/iembs.2011.6090697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Measurements of myocardium tissue impedance during the cardiac cycle have information about the morphology of myocardium cells as well as cell membranes and intra/extra cellular spaces. Although the variation with time of the impedance cardiac signal has information about the myocardium tissue activity during the cardiac cycle, this information has been usually underestimated in the studies based on frequency-sweep Electrical Impedance Spectroscopy (EIS) technique. In these cases, the dynamic behavior was removed from the impedance by means of averaging. The originality of this research is to show the time evolution of in-vivo healthy myocardium tissue impedance during the cardiac cycle, being measured with a multisine excitation at 26 frequencies (1 kHz-1 MHz). The obtained parameters from fitting data to a Cole model are valid indicators to explain the time relation of the systolic and diastolic function with respect to the myocardium impedance time variation. This paper presents a successful application of broadband Impedance Spectroscopy for time-varying impedance monitoring. Furthermore, it can be extended to understand various unsolved problems in a wide range of biomedical and electrochemical applications, where the system dynamics are intended to be studied.
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Affiliation(s)
- Benjamin Sanchez
- Department of Electrical Engineering, Technical University of Catalonia, Barcelona 08034, Spain.
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25
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JACOBSON JASONT, HUTCHINSON MATHEWD, COOPER JOSHUAM, WOO YJOSEPH, SHANDLER RICHARDS, CALLANS DAVIDJ. Tissue-Specific Variability in Human Epicardial Impedance. J Cardiovasc Electrophysiol 2010; 22:436-9. [DOI: 10.1111/j.1540-8167.2010.01929.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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26
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27
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Kalvøy H, Frich L, Grimnes S, Martinsen ØG, Hol PK, Stubhaug A. Impedance-based tissue discrimination for needle guidance. Physiol Meas 2009; 30:129-40. [DOI: 10.1088/0967-3334/30/2/002] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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28
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Bogónez-Franco P, Bragós R, Bayés-Genis A, Rosell-Ferrer J. Implantable bioimpedance monitor using ZigBee. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2009; 2009:4868-4871. [PMID: 19963630 DOI: 10.1109/iembs.2009.5332452] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In this paper, a novel implantable bioimpedance monitor using a free ZigBee protocol for the transmission of the measured data is described. The application field is the tissue and organ monitoring through electrical impedance spectroscopy in the 100 Hz - 200 kHz range. The specific application is the study of the viability and evolution of engineered tissue in cardiac regeneration. Additionally to the telemetric feature, the measured data are stored in a memory for backup purposes and can be downloaded at any time after an RF link break. In the debugging prototype, the system autonomy exceeds 1 month when a 14 frequencies impedance spectrum is acquired every 5 minutes. In the current implementation, the effective range of the RF link is reduced and needs for a range extender placed near the animal. Current work deals with improving this range.
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Affiliation(s)
- P Bogónez-Franco
- Instrumentation and Bioengineering Group (IEB) of the Universitat Politècnica de Catalunya (UPC), c/Jordi Girona 1-3, Barcelona, Spain.
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Dumas Iii JH, Himel Iv HD, Kiser AC, Quint SR, Knisley SB. Myocardial electrical impedance as a predictor of the quality of RF-induced linear lesions. Physiol Meas 2008; 29:1195-207. [PMID: 18799837 DOI: 10.1088/0967-3334/29/10/004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Production of complete (i.e. continuous and transmural) cardiac lesions by radiofrequency (RF) ablation can cure certain cardiac arrhythmias. However, a predictor of lesion completeness that is reliable and can be measured intraoperatively is needed in order to maximize effectiveness of ablation therapy. Predictors that require membrane excitation or response to stimulation are not always practical. This study tested whether changes of myocardial impedance across the lesion can predict completeness. RF energy was applied epicardially on perfused rabbit ventricles to produce linear lesions that were complete (n = 25) or incomplete (noncontinuous or nontransmural, n = 25). Before and after creation of each lesion, the magnitude and phase of impedance at 1 kHz were measured with a four-electrode epicardial array across the lesion. For 16 of the lesions, the translesion stimulus-excitation delay was also measured. Lesion completeness was evaluated with 2,3,5-triphenyltetrazolium chloride stain. Complete lesions increased resistivity by 26 Omega cm (21% of the preablation value, p = 0.0007, n = 17) when the inactive RF electrode remained on the epicardium during impedance measurements. When the RF electrode was removed during measurements, the rise of resistivity by complete lesions increased to 58 Omega cm (30% of the preablation value, p = 0.022, n = 8). For incomplete lesions, resistivity did not change significantly. Ablation did not significantly alter the phase of impedance. Accuracies of predictions of lesion completeness by the change in resistivity or the change in translesion stimulus-excitation delay were comparable (Youden's index 0.75 and 0.625, respectively, n = 16). Thus, RF ablation increases myocardial resistivity. The resistivity can predict lesion completeness and may provide an alternative to predictors based on excitation.
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Affiliation(s)
- John H Dumas Iii
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7575, USA
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Yang F, Patterson R. Optimal Transvenous Coil Position on Active-can Single-coil ICD Defibrillation Efficacy: A Simulation Study. Ann Biomed Eng 2008; 36:1659-67. [DOI: 10.1007/s10439-008-9548-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Accepted: 07/31/2008] [Indexed: 11/30/2022]
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Changes in myocardial electrical impedance in human heart graft rejection. Eur J Heart Fail 2008; 10:594-600. [PMID: 18501669 DOI: 10.1016/j.ejheart.2008.04.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2007] [Revised: 04/09/2008] [Accepted: 04/28/2008] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Monitoring of post-transplant heart rejection is currently based on endomyocardial biopsy analysis. This study aimed to assess the effects of heart graft rejection on myocardial electrical impedance. METHODS AND RESULTS Twenty-nine cardiac transplant patients and 9 controls underwent measurement of myocardial electrical impedance using a specifically designed amplifying system. The module and phase angle of myocardial impedance were measured. Histopathological rejection grading was performed according to ISHLT classification. Fifty impedance tests were performed in transplanted patients. Myocardial impedance (Z) was higher in controls than in transplanted patients (p<0.001) and followed a progressive decline at increasing current frequencies (p<0.001). Likewise, the phase angle of impedance in controls ranged from positive values at low frequencies to negative values at higher frequencies (from 2.5+/-0.9 degrees at 10 kHz to -3.8+/-2.1 degrees at 300 kHz, p<0.001). Rejection was associated with a significant decrease in myocardial impedance (Z) (15+/-6.6 Omega in grade 0, 13+/-6.0 Omega in grade 1A, and 3.3+/-0.9 Omega in grade 3A at 10 kHz, p<0.003). CONCLUSIONS Mild degrees of cardiac graft rejection are associated with significant changes in myocardial electrical impedance in transplant patients. Further clinical investigation is warranted to assess the potential of cardiac impedance to detect heart graft rejection.
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A Simulation Study on the Effect of Thoracic Conductivity Inhomogeneities on Sensitivity Distributions. Ann Biomed Eng 2008; 36:762-8. [DOI: 10.1007/s10439-008-9469-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Accepted: 02/08/2008] [Indexed: 10/22/2022]
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Del Rio CL, McConnell PI, Kukielka M, Dzwonczyk R, Clymer BD, Howie MB, Billman GE. Electrotonic remodeling following myocardial infarction in dogs susceptible and resistant to sudden cardiac death. J Appl Physiol (1985) 2007; 104:386-93. [PMID: 18048585 DOI: 10.1152/japplphysiol.01106.2007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Passive electrical remodeling following myocardial infarction (MI) is well established. These changes can alter electrotonic loading and trigger the remodeling of repolarization currents, a potential mechanism for ventricular fibrillation (VF). However, little is known about the role of passive electrical markers as tools to identify VF susceptibility post-MI. This study investigated electrotonic remodeling in the post-MI ventricle, as measured by myocardial electrical impedance (MEI), in animals prone to and resistant to VF. MI was induced in dogs by a two-stage left anterior descending (LAD) coronary artery ligation. Before infarction, MEI electrodes were placed in remote (left circumflex, LCX) and infarcted (LAD) myocardium. MEI was measured in awake animals 1, 2, 7, and 21 days post-MI. Subsequently, VF susceptibility was tested by a 2-min LCX occlusion during exercise; 12 animals developed VF (susceptible, S) and 12 did not (resistant, R). The healing infarct had lower MEI than the normal myocardium. This difference was stable by day 2 post-MI (287 +/- 32 Omega vs. 425 +/- 62 Omega, P < 0.05). Significant differences were observed between resistant and susceptible animals 7 days post-MI; susceptible dogs had a wider electrotonic gradient between remote and infarcted myocardium (R: 89 +/- 60 Omega vs. S: 180 +/- 37 Omega). This difference increased over time in susceptible animals (252 +/- 53 Omega at 21 days) due to post-MI impedance changes on the remote myocardium. These data suggest that early electrotonic changes post-MI could be used to assess later arrhythmia susceptibility. In addition, passive-electrical changes could be a mechanism driving active-electrical remodeling post-MI, thereby facilitating the induction of arrhythmias.
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Affiliation(s)
- Carlos L Del Rio
- Dept. of Physiology and Cell Biology, The Ohio State Univ., 1645 Neil Ave., 305 Hamilton Hall, Columbus, OH 43210, USA
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Potse M, LeBlanc AR, Cardinal R, Vinet A. ST elevation or depression in subendocardial ischemia? CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2006:3899-902. [PMID: 17945814 DOI: 10.1109/iembs.2006.259485] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
ST-segment depression in epicardial electrograms can be a "reciprocal" effect of remote myocardial ischemia (MI), and can also be due to local partial-thickness or "subendocardial" MI. Experimental studies have shown either ST elevation or depression in leads overlying a subendocardial ischemic region. Those reporting elevation have shown depression over the lateral borders of the ischemia. Simulation studies with anisotropic models have explained the ST-elevation results. Presently, while experimentalists may have difficulty understanding the ST elevation, most model studies fail to explain ST depression in overlying leads during partial-thickness ischemia. We have simulated partial-thickness ischemia in a 3-dimensional model of the human heart. Our results show that the conductivity of the intracavitary blood, geometry of the ischemic region, and bidomain anisotropy ratios can all have a decisive influence on the sign of the ST deviation. We hypothesize that ST depression in leads overlying an ischemic zone is due to subendocardial ischemia in tissue where a redistribution of gap junctions has taken place.
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Affiliation(s)
- Mark Potse
- Res. Center, Hosp. du Sacre-Coeur de Montreal, Que.
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Yang F, Patterson RP. The contribution of the lungs to thoracic impedance measurements: a simulation study based on a high resolution finite difference model. Physiol Meas 2007; 28:S153-61. [PMID: 17664633 DOI: 10.1088/0967-3334/28/7/s12] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A high resolution electrical finite difference model of the human thorax based on a 43 slice MRI data set along with lead field theory was used to examine the contribution of the lungs to the total impedance for a typical mid-thoracic 2D EIT eight and sixteen electrode configuration. Regional analysis of the thoracic sources of impedance revealed that the maximum contribution of lungs to the total impedance was approximately 22% for the eight electrode array and 25% for the sixteen electrode array. Analysis of impedance distribution of the lungs using a mid-thoracic application showed that the contribution of impedance of each slice followed closely the volume of the lungs in the given slice. This suggests that the mid-thoracic application gives results reflecting the entire lung. The contributions of the lung impedance for the various electrode positions showed that the eight electrode configuration had a more smooth change between adjacent electrodes compared to the 16 electrode arrangement.
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Affiliation(s)
- Fei Yang
- The Bakken Medical Instrumentation and Devices (MIND) Laboratory, Biomedical Engineering Institute, University of Minnesota, 420 Delaware St, MMC 297, Minneapolis, MN 55455, USA
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Potse M, Coronel R, Falcao S, LeBlanc AR, Vinet A. The effect of lesion size and tissue remodeling on ST deviation in partial-thickness ischemia. Heart Rhythm 2007; 4:200-6. [PMID: 17275757 DOI: 10.1016/j.hrthm.2006.10.022] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Accepted: 10/13/2006] [Indexed: 11/29/2022]
Abstract
BACKGROUND Myocardial ischemia causes ST segment elevation or depression in electrocardiograms and epicardial leads. ST depression in epicardium overlying the ischemic zone indicates that the ischemia is nontransmural. However, nontransmural ischemia does not always cause ST depression. Especially in animal models, ST depression is hard to reproduce. OBJECTIVE The purpose of this study was to determine the circumstances in which ST depression could be expected. METHODS We studied ischemia in a large-scale computer model of the human heart. A realistic representation of the ischemia-induced changes in resting membrane potential was used, which was based on diffusion of extracellular potassium. Ischemia diameter, transmural extent, and tissue conductivity were varied. RESULTS Our simulations confirm earlier work showing that partial-thickness ischemia, like full-thickness ischemia, typically causes ST elevation in an anisotropic model of the ventricles. However, we identified three situations in which ST depression can occur in overlying leads. The first is a reduced anisotropy ratio of the intracellular conductivity, which may result from hypertrophy and gap-junctional remodeling, circumstances that are likely to accompany ischemia. Second, an increase of the extracellular anisotropy has the same effect. Third, ST depression was found, independent of the anisotropy ratios, in very large and thin ischemic regions, resembling those that may occur in left-main or multivessel disease. CONCLUSION Both tissue remodeling and geometric factors can explain ST depression in overlying epicardial leads. We note at the same time that ST elevation is found in most circumstances, while depression occurs as a reciprocal effect, even in partial-thickness ischemia.
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Affiliation(s)
- Mark Potse
- Research Center, Sacré-Coeur Hospital, Montréal, Québec, Canada. mark.potse.nl
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Ahn AC, Wu J, Badger GJ, Hammerschlag R, Langevin HM. Electrical impedance along connective tissue planes associated with acupuncture meridians. Altern Ther Health Med 2005; 5:10. [PMID: 15882468 PMCID: PMC1142259 DOI: 10.1186/1472-6882-5-10] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2004] [Accepted: 05/09/2005] [Indexed: 12/23/2022]
Abstract
Background Acupuncture points and meridians are commonly believed to possess unique electrical properties. The experimental support for this claim is limited given the technical and methodological shortcomings of prior studies. Recent studies indicate a correspondence between acupuncture meridians and connective tissue planes. We hypothesized that segments of acupuncture meridians that are associated with loose connective tissue planes (between muscles or between muscle and bone) visible by ultrasound have greater electrical conductance (less electrical impedance) than non-meridian, parallel control segments. Methods We used a four-electrode method to measure the electrical impedance along segments of the Pericardium and Spleen meridians and corresponding parallel control segments in 23 human subjects. Meridian segments were determined by palpation and proportional measurements. Connective tissue planes underlying those segments were imaged with an ultrasound scanner. Along each meridian segment, four gold-plated needles were inserted along a straight line and used as electrodes. A parallel series of four control needles were placed 0.8 cm medial to the meridian needles. For each set of four needles, a 3.3 kHz alternating (AC) constant amplitude current was introduced at three different amplitudes (20, 40, and 80 μAmps) to the outer two needles, while the voltage was measured between the inner two needles. Tissue impedance between the two inner needles was calculated based on Ohm's law (ratio of voltage to current intensity). Results At the Pericardium location, mean tissue impedance was significantly lower at meridian segments (70.4 ± 5.7 Ω) compared with control segments (75.0 ± 5.9 Ω) (p = 0.0003). At the Spleen location, mean impedance for meridian (67.8 ± 6.8 Ω) and control segments (68.5 ± 7.5 Ω) were not significantly different (p = 0.70). Conclusion Tissue impedance was on average lower along the Pericardium meridian, but not along the Spleen meridian, compared with their respective controls. Ultrasound imaging of meridian and control segments suggested that contact of the needle with connective tissue may explain the decrease in electrical impedance noted at the Pericardium meridian. Further studies are needed to determine whether tissue impedance is lower in (1) connective tissue in general compared with muscle and (2) meridian-associated vs. non meridian-associated connective tissue.
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Affiliation(s)
- Andrew C Ahn
- Division for Research and Education in Complementary and Integrative Medical Therapies, Harvard Medical School, Boston, MA, USA
| | - Junru Wu
- Departments of Physics, University of Vermont, Burlington, VT, USA
| | - Gary J Badger
- Department of Medical Biostatistics, University of Vermont, Burlington, VT, USA
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