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Piktel JS, Wan X, Kouk S, Laurita KR, Wilson LD. Beneficial Effect of Calcium Treatment for Hyperkalemia Is Not Due to "Membrane Stabilization". Crit Care Med 2024; 52:1499-1508. [PMID: 39312458 PMCID: PMC11410510 DOI: 10.1097/ccm.0000000000006376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/25/2024]
Abstract
OBJECTIVES Hyperkalemia is a common life-threatening condition causing severe electrophysiologic derangements and arrhythmias. The beneficial effects of calcium (Ca 2+ ) treatment for hyperkalemia have been attributed to "membrane stabilization," by restoration of resting membrane potential (RMP). However, the underlying mechanisms remain poorly understood. Our objective was to investigate the mechanisms underlying adverse electrophysiologic effects of hyperkalemia and the therapeutic effects of Ca 2+ treatment. DESIGN Controlled experimental trial. SETTING Laboratory investigation. SUBJECTS Canine myocytes and tissue preparations. INTERVENTIONS AND MEASUREMENTS Optical action potentials and volume averaged electrocardiograms were recorded from the transmural wall of ventricular wedge preparations ( n = 7) at baseline (4 mM potassium), hyperkalemia (8-12 mM), and hyperkalemia + Ca 2+ (3.6 mM). Isolated myocytes were studied during hyperkalemia (8 mM) and after Ca 2+ treatment (6 mM) to determine cellular RMP. MAIN RESULTS Hyperkalemia markedly slowed conduction velocity (CV, by 67% ± 7%; p < 0.001) and homogeneously shortened action potential duration (APD, by 20% ± 10%; p < 0.002). In all preparations, this resulted in QRS widening and the "sine wave" pattern observed in severe hyperkalemia. Ca 2+ treatment restored CV (increase by 44% ± 18%; p < 0.02), resulting in narrowing of the QRS and normalization of the electrocardiogram, but did not restore APD. RMP was significantly elevated by hyperkalemia; however, it was not restored with Ca 2+ treatment suggesting a mechanism unrelated to "membrane stabilization." In addition, the effect of Ca 2+ was attenuated during L-type Ca 2+ channel blockade, suggesting a mechanism related to Ca 2+ -dependent (rather than normally sodium-dependent) conduction. CONCLUSIONS These data suggest that Ca 2+ treatment for hyperkalemia restores conduction through Ca 2+ -dependent propagation, rather than restoration of membrane potential or "membrane stabilization." Our findings provide a mechanistic rationale for Ca 2+ treatment when hyperkalemia produces abnormalities of conduction (i.e., QRS prolongation).
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Affiliation(s)
- Joseph S Piktel
- Department of Emergency Medicine, Emergency Care and Research and Innovation, MetroHealth Campus, Case Western Reserve University, Cleveland, OH
| | - Xiaoping Wan
- Department of Physiology & Cell Biology, The Ohio State University, College of Medicine, Columbus, OH
| | - Shalen Kouk
- Orthopedic Surgery and Sports Medicine, Mercy Clinic, St. Louis, MO
| | - Kenneth R Laurita
- The Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, Cleveland, OH
| | - Lance D Wilson
- Department of Emergency Medicine, Emergency Care and Research and Innovation, MetroHealth Campus, Case Western Reserve University, Cleveland, OH
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2
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Amesz JH, Zhang L, Everts BR, De Groot NMS, Taverne YJHJ. Living myocardial slices: Advancing arrhythmia research. Front Physiol 2023; 14:1076261. [PMID: 36711023 PMCID: PMC9880234 DOI: 10.3389/fphys.2023.1076261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 01/04/2023] [Indexed: 01/15/2023] Open
Abstract
Living myocardial slices (LMS) are ultrathin (150-400 µm) sections of intact myocardium that can be used as a comprehensive model for cardiac arrhythmia research. The recent introduction of biomimetic electromechanical cultivation chambers enables long-term cultivation and easy control of living myocardial slices culture conditions. The aim of this review is to present the potential of this biomimetic interface using living myocardial slices in electrophysiological studies outlining advantages, disadvantages and future perspectives of the model. Furthermore, different electrophysiological techniques and their application on living myocardial slices will be discussed. The developments of living myocardial slices in electrophysiology research will hopefully lead to future breakthroughs in the understanding of cardiac arrhythmia mechanisms and the development of novel therapeutic options.
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Affiliation(s)
- Jorik H. Amesz
- Translational Cardiothoracic Surgery Research Lab, Lowlands Institute for Bioelectric Medicine, Department of Cardiothoracic Surgery, Erasmus University Medical Center, Rotterdam, Netherlands
- Translational Electrophysiology, Lowlands Institute for Bioelectric Medicine, Department of Cardiology, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Lu Zhang
- Translational Electrophysiology, Lowlands Institute for Bioelectric Medicine, Department of Cardiology, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Bian R. Everts
- Translational Cardiothoracic Surgery Research Lab, Lowlands Institute for Bioelectric Medicine, Department of Cardiothoracic Surgery, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Natasja M. S. De Groot
- Translational Electrophysiology, Lowlands Institute for Bioelectric Medicine, Department of Cardiology, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Yannick J. H. J. Taverne
- Translational Cardiothoracic Surgery Research Lab, Lowlands Institute for Bioelectric Medicine, Department of Cardiothoracic Surgery, Erasmus University Medical Center, Rotterdam, Netherlands
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3
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Ripplinger CM, Glukhov AV, Kay MW, Boukens BJ, Chiamvimonvat N, Delisle BP, Fabritz L, Hund TJ, Knollmann BC, Li N, Murray KT, Poelzing S, Quinn TA, Remme CA, Rentschler SL, Rose RA, Posnack NG. Guidelines for assessment of cardiac electrophysiology and arrhythmias in small animals. Am J Physiol Heart Circ Physiol 2022; 323:H1137-H1166. [PMID: 36269644 PMCID: PMC9678409 DOI: 10.1152/ajpheart.00439.2022] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 10/11/2022] [Accepted: 10/17/2022] [Indexed: 01/09/2023]
Abstract
Cardiac arrhythmias are a major cause of morbidity and mortality worldwide. Although recent advances in cell-based models, including human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM), are contributing to our understanding of electrophysiology and arrhythmia mechanisms, preclinical animal studies of cardiovascular disease remain a mainstay. Over the past several decades, animal models of cardiovascular disease have advanced our understanding of pathological remodeling, arrhythmia mechanisms, and drug effects and have led to major improvements in pacing and defibrillation therapies. There exist a variety of methodological approaches for the assessment of cardiac electrophysiology and a plethora of parameters may be assessed with each approach. This guidelines article will provide an overview of the strengths and limitations of several common techniques used to assess electrophysiology and arrhythmia mechanisms at the whole animal, whole heart, and tissue level with a focus on small animal models. We also define key electrophysiological parameters that should be assessed, along with their physiological underpinnings, and the best methods with which to assess these parameters.
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Affiliation(s)
- Crystal M Ripplinger
- Department of Pharmacology, University of California Davis School of Medicine, Davis, California
| | - Alexey V Glukhov
- Department of Medicine, Cardiovascular Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University, Washington, District of Columbia
| | - Bastiaan J Boukens
- Department Physiology, University Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Medical Biology, University of Amsterdam, Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - Nipavan Chiamvimonvat
- Department of Pharmacology, University of California Davis School of Medicine, Davis, California
- Department of Internal Medicine, University of California Davis School of Medicine, Davis, California
- Veterans Affairs Northern California Healthcare System, Mather, California
| | - Brian P Delisle
- Department of Physiology, University of Kentucky, Lexington, Kentucky
| | - Larissa Fabritz
- University Center of Cardiovascular Science, University Heart and Vascular Center, University Hospital Hamburg-Eppendorf with DZHK Hamburg/Kiel/Luebeck, Germany
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Thomas J Hund
- Department of Internal Medicine, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio
- Department of Biomedical Engineering, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio
| | - Bjorn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Na Li
- Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Katherine T Murray
- Departments of Medicine and Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Steven Poelzing
- Virginia Tech Carilon School of Medicine, Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech, Roanoke, Virginia
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - T Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Carol Ann Remme
- Department of Experimental Cardiology, Heart Centre, Amsterdam Cardiovascular Sciences, Heart Failure and Arrhythmias Amsterdam UMC Location University of Amsterdam, Amsterdam, The Netherlands
| | - Stacey L Rentschler
- Cardiovascular Division, Department of Medicine, Washington University in Saint Louis, School of Medicine, Saint Louis, Missouri
| | - Robert A Rose
- Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Nikki G Posnack
- Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Hospital, Washington, District of Columbia
- Department of Pediatrics, George Washington University School of Medicine, Washington, District of Columbia
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4
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Chakraborty P, Massé S, Azam MA, Thollon C, Niri A, Lai PFH, Bouly M, Riazi S, Nanthakumar K. Effects of azumolene on arrhythmia substrate in a model of recurrent long-duration ventricular fibrillation. Biochem Biophys Res Commun 2022; 600:123-129. [PMID: 35219100 DOI: 10.1016/j.bbrc.2022.02.031] [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: 01/25/2022] [Accepted: 02/09/2022] [Indexed: 11/17/2022]
Abstract
BACKGROUND Proarrhythmic risk of conventional anti-arrhythmic agents is linked to unintended modulation of membrane voltage dynamics. We have demonstrated that the anti-fibrillatory effect of azumolene is mediated via stabilization of the hyperphosphorylated ryanodine receptor (RyR2), leading to attenuation of diastolic calcium leak. However, the concomitant effects on membrane voltage dynamics have not been evaluated yet. METHODS After baseline optical mapping, Langendorff-perfused rabbit hearts treated with azumolene, or vehicle, were subjected to global ischemia-reperfusion (I/R) followed by two episodes of long-duration ventricular fibrillation (LDVF). Simultaneous dual epicardial calcium transient (CaT) and voltage dynamics were studied optically. RESULTS Pre-treatment with azumolene was associated with higher CaT amplitude alternans ratios (0.94 ± 0.02 vs. 0.78 ± 0.03 in control hearts, at 6 Hz; p = 0.005; and action potential amplitude alternans ratio (0.95 ± 0.02 vs. 0.78 ± 0.04 at 6.0 Hz; p = 0.02), and reduction of action potential duration (APD80) dispersion (9.0 ± 4.8 msec vs. 19.3 ± 6.6 msec at 6.0 Hz p = 0.02) and optical action potential upstroke rise time (26.3 ± 2.6 msec in control vs. 13.8 ± 0.6 msec at 6.0 Hz, p = 0.02) after LDVF. No change in action potential duration (APD) was noted with azumolene treatment. CONCLUSION In a model of ischemic recurrent LDVF, treatment with azumolene led to reduction of cardiac alternans, i.e., calcium and voltage alternans. Unlike conventional anti-arrhythmic agents, reduction of action potential upstroke rise time and preservation of action potential duration following azumolene treatment may reduce the proarrhythmia risk.
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Affiliation(s)
- Praloy Chakraborty
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada
| | - Stéphane Massé
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada
| | - Mohammed Ali Azam
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada
| | | | - Ahmed Niri
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada
| | - Patrick F H Lai
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada
| | - Muriel Bouly
- Institut de Recherches Internationales Servier (IRIS), Suresnes, France
| | - Sheila Riazi
- Malignant Hyperthermia Investigation Unit, Department of Anesthesia and Pain Management, University Health Network, Toronto, Ontario, Canada
| | - Kumaraswamy Nanthakumar
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada.
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Roth BJ. Bidomain modeling of electrical and mechanical properties of cardiac tissue. BIOPHYSICS REVIEWS 2021; 2:041301. [PMID: 38504719 PMCID: PMC10903405 DOI: 10.1063/5.0059358] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 10/15/2021] [Indexed: 03/21/2024]
Abstract
Throughout the history of cardiac research, there has been a clear need to establish mathematical models to complement experimental studies. In an effort to create a more complete picture of cardiac phenomena, the bidomain model was established in the late 1970s to better understand pacing and defibrillation in the heart. This mathematical model has seen ongoing use in cardiac research, offering mechanistic insight that could not be obtained from experimental pursuits. Introduced from a historical perspective, the origins of the bidomain model are reviewed to provide a foundation for researchers new to the field and those conducting interdisciplinary research. The interplay of theory and experiment with the bidomain model is explored, and the contributions of this model to cardiac biophysics are critically evaluated. Also discussed is the mechanical bidomain model, which is employed to describe mechanotransduction. Current challenges and outstanding questions in the use of the bidomain model are addressed to give a forward-facing perspective of the model in future studies.
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Affiliation(s)
- Bradley J. Roth
- Department of Physics, Oakland University, Rochester, Michigan 48309, USA
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6
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Müllenbroich MC, Kelly A, Acker C, Bub G, Bruegmann T, Di Bona A, Entcheva E, Ferrantini C, Kohl P, Lehnart SE, Mongillo M, Parmeggiani C, Richter C, Sasse P, Zaglia T, Sacconi L, Smith GL. Novel Optics-Based Approaches for Cardiac Electrophysiology: A Review. Front Physiol 2021; 12:769586. [PMID: 34867476 PMCID: PMC8637189 DOI: 10.3389/fphys.2021.769586] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 10/18/2021] [Indexed: 12/31/2022] Open
Abstract
Optical techniques for recording and manipulating cellular electrophysiology have advanced rapidly in just a few decades. These developments allow for the analysis of cardiac cellular dynamics at multiple scales while largely overcoming the drawbacks associated with the use of electrodes. The recent advent of optogenetics opens up new possibilities for regional and tissue-level electrophysiological control and hold promise for future novel clinical applications. This article, which emerged from the international NOTICE workshop in 2018, reviews the state-of-the-art optical techniques used for cardiac electrophysiological research and the underlying biophysics. The design and performance of optical reporters and optogenetic actuators are reviewed along with limitations of current probes. The physics of light interaction with cardiac tissue is detailed and associated challenges with the use of optical sensors and actuators are presented. Case studies include the use of fluorescence recovery after photobleaching and super-resolution microscopy to explore the micro-structure of cardiac cells and a review of two photon and light sheet technologies applied to cardiac tissue. The emergence of cardiac optogenetics is reviewed and the current work exploring the potential clinical use of optogenetics is also described. Approaches which combine optogenetic manipulation and optical voltage measurement are discussed, in terms of platforms that allow real-time manipulation of whole heart electrophysiology in open and closed-loop systems to study optimal ways to terminate spiral arrhythmias. The design and operation of optics-based approaches that allow high-throughput cardiac electrophysiological assays is presented. Finally, emerging techniques of photo-acoustic imaging and stress sensors are described along with strategies for future development and establishment of these techniques in mainstream electrophysiological research.
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Affiliation(s)
| | - Allen Kelly
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Corey Acker
- Center for Cell Analysis and Modeling, UConn Health, Farmington, CT, United States
| | - Gil Bub
- Department of Physiology, McGill University, Montréal, QC, Canada
| | - Tobias Bruegmann
- Institute for Cardiovascular Physiology, University Medical Center Goettingen, Goettingen, Germany
| | - Anna Di Bona
- Department of Cardiac, Thoracic, Vascular Sciences and Public Health, University of Padova, Padova, Italy
| | - Emilia Entcheva
- Department of Biomedical Engineering, The George Washington University, Washington, DC, United States
| | | | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center and Medical Faculty, University of Freiburg, Freiburg, Germany
| | - Stephan E. Lehnart
- Heart Research Center Göttingen, University Medical Center Göttingen, Göttingen, Germany
- Department of Cardiology and Pneumology, Georg-August University Göttingen, Göttingen, Germany
- Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), University of Göttingen, Göttingen, Germany
| | - Marco Mongillo
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- Veneto Institute of Molecular Medicine, Padova, Italy
| | | | - Claudia Richter
- German Primate Center - Leibniz Institute for Primate Research, Göttingen, Germany
| | - Philipp Sasse
- Institute of Physiology I, Medical Faculty, University of Bonn, Bonn, Germany
| | - Tania Zaglia
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- Veneto Institute of Molecular Medicine, Padova, Italy
| | - Leonardo Sacconi
- European Laboratory for Nonlinear Spectroscopy, Sesto Fiorentino, Italy
- Institute for Experimental Cardiovascular Medicine, University Heart Center and Medical Faculty, University of Freiburg, Freiburg, Germany
- National Institute of Optics, National Research Council, Florence, Italy
| | - Godfrey L. Smith
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
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Piktel JS, Suen Y, Kouk S, Maleski D, Pawlowski G, Laurita KR, Wilson LD. Effect of Amiodarone and Hypothermia on Arrhythmia Substrates During Resuscitation. J Am Heart Assoc 2021; 10:e016676. [PMID: 33938226 PMCID: PMC8200710 DOI: 10.1161/jaha.120.016676] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Background Amiodarone is administered during resuscitation, but its antiarrhythmic effects during targeted temperature management are unknown. The purpose of this study was to determine the effect of both therapeutic hypothermia and amiodarone on arrhythmia substrates during resuscitation from cardiac arrest. Methods and Results We utilized 2 complementary models: (1) In vitro no‐flow global ischemia canine left ventricular transmural wedge preparation. Wedges at different temperatures (36°C or 32°C) were given 5 µmol/L amiodarone (36‐Amio or 32‐Amio, each n=8) and subsequently underwent ischemia and reperfusion. Results were compared with previous controls. Optical mapping was used to measure action potential duration, dispersion of repolarization (DOR), and conduction velocity (CV). (2) In vivo pig model of resuscitation. Pigs (control or targeted temperature management, 32–34°C) underwent ischemic cardiac arrest and were administered amiodarone (or not) after 8 minutes of ventricular fibrillation. In vitro: therapeutic hypothermia but not amiodarone prolonged action potential duration. During ischemia, DOR increased in the 32‐Amio group versus 32‐Alone (84±7 ms versus 40±7 ms, P<0.05) while CV slowed in the 32‐Amio group. Amiodarone did not affect CV, DOR, or action potential duration during ischemia at 36°C. Conduction block was only observed at 36°C (5/8 36‐Amio versus 6/7 36‐Alone, 0/8 32‐Amio, versus 0/7 32‐Alone). In vivo: QTc decreased upon reperfusion from ischemia that was ameliorated by targeted temperature management. Amiodarone did not worsen DOR or CV. Amiodarone suppressed rearrest caused by ventricular fibrillation (7/8 without amiodarone, 2/7 with amiodarone, P=0.041), but not pulseless electrical activity (2/8 without amiodarone, 5/7 with amiodarone, P=0.13). Conclusions Although amiodarone abolishes a beneficial effect of therapeutic hypothermia on ischemia‐induced DOR and CV, it did not worsen susceptibility to ventricular tachycardia/ventricular fibrillation during resuscitation.
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Affiliation(s)
- Joseph S Piktel
- Department of Emergency Medicine and The Heart and Vascular Research Center MetroHealth Campus Case Western Reserve University Cleveland OH
| | - Yi Suen
- Department of Emergency Medicine and The Heart and Vascular Research Center MetroHealth Campus Case Western Reserve University Cleveland OH
| | - Shalen Kouk
- Department of Emergency Medicine and The Heart and Vascular Research Center MetroHealth Campus Case Western Reserve University Cleveland OH
| | - Danielle Maleski
- Department of Emergency Medicine and The Heart and Vascular Research Center MetroHealth Campus Case Western Reserve University Cleveland OH
| | - Gary Pawlowski
- Department of Emergency Medicine and The Heart and Vascular Research Center MetroHealth Campus Case Western Reserve University Cleveland OH
| | - Kenneth R Laurita
- Department of Emergency Medicine and The Heart and Vascular Research Center MetroHealth Campus Case Western Reserve University Cleveland OH
| | - Lance D Wilson
- Department of Emergency Medicine and The Heart and Vascular Research Center MetroHealth Campus Case Western Reserve University Cleveland OH
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8
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Mezache L, Struckman HL, Greer-Short A, Baine S, Györke S, Radwański PB, Hund TJ, Veeraraghavan R. Vascular endothelial growth factor promotes atrial arrhythmias by inducing acute intercalated disk remodeling. Sci Rep 2020; 10:20463. [PMID: 33235263 PMCID: PMC7687901 DOI: 10.1038/s41598-020-77562-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 11/09/2020] [Indexed: 12/30/2022] Open
Abstract
Atrial fibrillation (AF) is the most common arrhythmia and is associated with inflammation. AF patients have elevated levels of inflammatory cytokines known to promote vascular leak, such as vascular endothelial growth factor A (VEGF). However, the contribution of vascular leak and consequent cardiac edema to the genesis of atrial arrhythmias remains unknown. Previous work suggests that interstitial edema in the heart can acutely promote ventricular arrhythmias by disrupting ventricular myocyte intercalated disk (ID) nanodomains rich in cardiac sodium channels (NaV1.5) and slowing cardiac conduction. Interestingly, similar disruption of ID nanodomains has been identified in atrial samples from AF patients. Therefore, we tested the hypothesis that VEGF-induced vascular leak can acutely increase atrial arrhythmia susceptibility by disrupting ID nanodomains and slowing atrial conduction. Treatment of murine hearts with VEGF (30–60 min, at clinically relevant levels) prolonged the electrocardiographic P wave and increased susceptibility to burst pacing-induced atrial arrhythmias. Optical voltage mapping revealed slower atrial conduction following VEGF treatment (10 ± 0.4 cm/s vs. 21 ± 1 cm/s at baseline, p < 0.05). Transmission electron microscopy revealed increased intermembrane spacing at ID sites adjacent to gap junctions (GJs; 64 ± 9 nm versus 17 ± 1 nm in controls, p < 0.05), as well as sites next to mechanical junctions (MJs; 63 ± 4 nm versus 27 ± 2 nm in controls, p < 0.05) in VEGF–treated hearts relative to controls. Importantly, super-resolution microscopy and quantitative image analysis revealed reorganization of NaV1.5 away from dense clusters localized near GJs and MJs to a more diffuse distribution throughout the ID. Taken together, these data suggest that VEGF can acutely predispose otherwise normal hearts to atrial arrhythmias by dynamically disrupting NaV1.5-rich ID nanodomains and slowing atrial conduction. These data highlight inflammation-induced vascular leak as a potential factor in the development and progression of AF.
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Affiliation(s)
- Louisa Mezache
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, 460 Medical Center Dr., Rm 415A, IBMR, Columbus, OH, 43210, USA
| | - Heather L Struckman
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, 460 Medical Center Dr., Rm 415A, IBMR, Columbus, OH, 43210, USA
| | - Amara Greer-Short
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Stephen Baine
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Sándor Györke
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Przemysław B Radwański
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA.,Division of Pharmacy Practice and Sciences, College of Pharmacy, The Ohio State University, Columbus, OH, USA
| | - Thomas J Hund
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, 460 Medical Center Dr., Rm 415A, IBMR, Columbus, OH, 43210, USA.,The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Rengasayee Veeraraghavan
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, 460 Medical Center Dr., Rm 415A, IBMR, Columbus, OH, 43210, USA. .,The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA. .,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA.
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9
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Yang R, Liao H, Ma W, Li J, Wang S. A Compact High-Speed Image-Based Method for Measuring the Longitudinal Motion of Living Tissues. SENSORS 2020; 20:s20164573. [PMID: 32824066 PMCID: PMC7472052 DOI: 10.3390/s20164573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 08/06/2020] [Accepted: 08/13/2020] [Indexed: 11/16/2022]
Abstract
Intraoperative imaging of living tissue at the cell level by endomicroscopy might help surgeons optimize surgical procedures and provide individualized treatments. However, the resolution of the microscopic image is limited by the motion of living tissue caused by heartbeat and respiration. An active motion compensation (AMC) strategy has been recognized as an effective way to reduce, or even eliminate, the influence of tissue movement for intravital fluorescence microscopy (IVM). To realize the AMC system, a high-speed sensor for measuring the motion of tissues is needed. At present, state-of-the-art commercialized displacement sensors are not suitable to apply in minimally invasive imaging instruments to measure the motion of living tissues because of the size problem, range of measurement or the update rate. In this study, a compact high-speed image-based method for measuring the longitudinal motion of living tissues is proposed. The complexity of the proposed method is the same as that of the traditional wide-field fluorescent microscopy (WFFM) system, which makes it easy to be miniaturized and integrated into a minimally invasive imaging instrument. Experimental results reveal that the maximum indication error, range of measurement and the sensitivity of the laboratory-built experimental prototype is 150 μm, 6 mm and −211.46 mm−1 respectively. Experimental results indicate that the proposed optical method is expected to be used in minimally invasive imaging instruments to build an AMC system.
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Affiliation(s)
- Ruilin Yang
- Key Laboratory for Mechanism Theory and Equipment Design of Ministry of Education, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China; (R.Y.); (W.M.); (J.L.)
| | - Heqin Liao
- National Ocean Technology Center, Tianjin 300112, China;
| | - Weng Ma
- Key Laboratory for Mechanism Theory and Equipment Design of Ministry of Education, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China; (R.Y.); (W.M.); (J.L.)
| | - Jinhua Li
- Key Laboratory for Mechanism Theory and Equipment Design of Ministry of Education, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China; (R.Y.); (W.M.); (J.L.)
| | - Shuxin Wang
- Key Laboratory for Mechanism Theory and Equipment Design of Ministry of Education, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China; (R.Y.); (W.M.); (J.L.)
- Correspondence:
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10
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Hoeker GS, James CC, Tegge AN, Gourdie RG, Smyth JW, Poelzing S. Attenuating loss of cardiac conduction during no-flow ischemia through changes in perfusate sodium and calcium. Am J Physiol Heart Circ Physiol 2020; 319:H396-H409. [PMID: 32678707 DOI: 10.1152/ajpheart.00112.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Myocardial ischemia leads to conduction slowing, cell-to-cell uncoupling, and arrhythmias. We previously demonstrated that varying perfusate sodium (Na+) and calcium (Ca2+) attenuates conduction slowing and arrhythmias during simulated ischemia with continuous perfusion. Cardioprotection was selectively associated with widening of the perinexus, a gap junction adjacent nanodomain important to ephaptic coupling. It is unknown whether perfusate composition affects the perinexus or ischemic conduction during nonsimulated ischemia, when coronary flow is reduced or halted. We hypothesized that altering preischemic perfusate composition could facilitate perinexal expansion and attenuate conduction slowing during global ischemia. To test this hypothesis, ex vivo guinea pig hearts (n = 49) were Langendorff perfused with 145 or 153 mM Na+ and 1.25 or 2.0 mM Ca2+ and optically mapped during 30 min of no-flow ischemia. Altering Na+ and Ca2+ did not substantially affect baseline conduction. Increasing Na+ and decreasing Ca2+ both lowered pacing thresholds, whereas increasing Ca2+ narrowed perinexal width (Wp). A least squares mean estimate revealed that reduced perfusate Na+ and Ca2+ resulted in the most severe conduction slowing during ischemia. Increasing Na+ alone modestly attenuated conduction slowing, yet significantly delayed the median time to conduction block (10 to 16 min). Increasing both Na+ and Ca2+ selectively widened Wp during ischemia (22.7 vs. 15.7 nm) and attenuated conduction slowing to the greatest extent. Neither repolarization nor levels of total or phosphorylated connexin43 correlated with conduction slowing or block. Thus, perfusate-dependent widening of the perinexus preserved ischemic conduction and may be an adaptive response to ischemic stress.NEW & NOTEWORTHY Conduction slowing during acute ischemia creates an arrhythmogenic substrate. We have shown that extracellular ionic concentrations can alter conduction by modulating ephaptic coupling. Here, we demonstrate increased extracellular sodium and calcium significantly attenuate conduction slowing during no-flow ischemia. This effect was associated with selective widening of the perinexus, an intercalated disc nanodomain and putative cardiac ephapse. These findings suggest that acute changes in ephaptic coupling may serve as an adaptive response to ischemic stress.
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Affiliation(s)
- Gregory S Hoeker
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - Carissa C James
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia
| | - Allison N Tegge
- Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Statistics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Robert G Gourdie
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - James W Smyth
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Steven Poelzing
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
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11
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Lee P, Quintanilla JG, Alfonso-Almazán JM, Galán-Arriola C, Yan P, Sánchez-González J, Pérez-Castellano N, Pérez-Villacastín J, Ibañez B, Loew LM, Filgueiras-Rama D. In vivo ratiometric optical mapping enables high-resolution cardiac electrophysiology in pig models. Cardiovasc Res 2020; 115:1659-1671. [PMID: 30753358 PMCID: PMC6704389 DOI: 10.1093/cvr/cvz039] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 01/31/2019] [Accepted: 02/06/2019] [Indexed: 11/28/2022] Open
Abstract
Aims Cardiac optical mapping is the gold standard for measuring complex electrophysiology in ex vivo heart preparations. However, new methods for optical mapping in vivo have been elusive. We aimed at developing and validating an experimental method for performing in vivo cardiac optical mapping in pig models. Methods and results First, we characterized ex vivo the excitation-ratiometric properties during pacing and ventricular fibrillation (VF) of two near-infrared voltage-sensitive dyes (di-4-ANBDQBS/di-4-ANEQ(F)PTEA) optimized for imaging blood-perfused tissue (n = 7). Then, optical-fibre recordings in Langendorff-perfused hearts demonstrated that ratiometry permits the recording of optical action potentials (APs) with minimal motion artefacts during contraction (n = 7). Ratiometric optical mapping ex vivo also showed that optical AP duration (APD) and conduction velocity (CV) measurements can be accurately obtained to test drug effects. Secondly, we developed a percutaneous dye-loading protocol in vivo to perform high-resolution ratiometric optical mapping of VF dynamics (motion minimal) using a high-speed camera system positioned above the epicardial surface of the exposed heart (n = 11). During pacing (motion substantial) we recorded ratiometric optical signals and activation via a 2D fibre array in contact with the epicardial surface (n = 7). Optical APs in vivo under general anaesthesia showed significantly faster CV [120 (63–138) cm/s vs. 51 (41–64) cm/s; P = 0.032] and a statistical trend to longer APD90 [242 (217–254) ms vs. 192 (182–233) ms; P = 0.095] compared with ex vivo measurements in the contracting heart. The average rate of signal-to-noise ratio (SNR) decay of di-4-ANEQ(F)PTEA in vivo was 0.0671 ± 0.0090 min−1. However, reloading with di-4-ANEQ(F)PTEA fully recovered the initial SNR. Finally, toxicity studies (n = 12) showed that coronary dye injection did not generate systemic nor cardiac damage, although di-4-ANBDQBS injection induced transient hypotension, which was not observed with di-4-ANEQ(F)PTEA. Conclusions In vivo optical mapping using voltage ratiometry of near-infrared dyes enables high-resolution cardiac electrophysiology in translational pig models.
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Affiliation(s)
- Peter Lee
- Essel Research and Development Inc., Toronto, 337 Sheppard Ave East, Toronto, Ontario M2N 3B3, Canada
| | - Jorge G Quintanilla
- Spanish National Cardiovascular Research Center, Carlos III (CNIC), Myocardial Pathophysiology Area, Melchor Fernández Almagro, 3, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Av. Monforte de Lemos 3-5, Madrid, Spain.,Arrhythmia Unit, Cardiovascular Institute, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Prof. Martín Lagos s/n, Madrid, Spain
| | - José M Alfonso-Almazán
- Spanish National Cardiovascular Research Center, Carlos III (CNIC), Myocardial Pathophysiology Area, Melchor Fernández Almagro, 3, Madrid, Spain
| | - Carlos Galán-Arriola
- Spanish National Cardiovascular Research Center, Carlos III (CNIC), Myocardial Pathophysiology Area, Melchor Fernández Almagro, 3, Madrid, Spain
| | - Ping Yan
- Richard D. Berlin Center for Cell Analysis and Modeling, University of Connecticut School of Medicine, 263 Farmington Avenue, Farmington, CT, USA
| | | | - Nicasio Pérez-Castellano
- Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Av. Monforte de Lemos 3-5, Madrid, Spain.,Arrhythmia Unit, Cardiovascular Institute, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Prof. Martín Lagos s/n, Madrid, Spain
| | - Julián Pérez-Villacastín
- Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Av. Monforte de Lemos 3-5, Madrid, Spain.,Arrhythmia Unit, Cardiovascular Institute, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Prof. Martín Lagos s/n, Madrid, Spain.,Fundación Interhospitalaria para la Investigación Cardiovascular (FIC), Paseo de San Francisco de Sales 3, Madrid, Spain
| | - Borja Ibañez
- Spanish National Cardiovascular Research Center, Carlos III (CNIC), Myocardial Pathophysiology Area, Melchor Fernández Almagro, 3, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Av. Monforte de Lemos 3-5, Madrid, Spain.,IIS-University Hospital Fundación Jiménez Díaz, Department of Cardiology, Av. Reyes Católicos 2, Madrid, Spain
| | - Leslie M Loew
- Richard D. Berlin Center for Cell Analysis and Modeling, University of Connecticut School of Medicine, 263 Farmington Avenue, Farmington, CT, USA
| | - David Filgueiras-Rama
- Spanish National Cardiovascular Research Center, Carlos III (CNIC), Myocardial Pathophysiology Area, Melchor Fernández Almagro, 3, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Av. Monforte de Lemos 3-5, Madrid, Spain.,Arrhythmia Unit, Cardiovascular Institute, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Prof. Martín Lagos s/n, Madrid, Spain
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12
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Morrissette-McAlmon J, Ginn B, Somers S, Fukunishi T, Thanitcul C, Rindone A, Hibino N, Tung L, Mao HQ, Grayson W. Biomimetic Model of Contractile Cardiac Tissue with Endothelial Networks Stabilized by Adipose-Derived Stromal/Stem Cells. Sci Rep 2020; 10:8387. [PMID: 32433563 PMCID: PMC7239907 DOI: 10.1038/s41598-020-65064-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 04/23/2020] [Indexed: 11/15/2022] Open
Abstract
Cardiac tissue engineering strategies have the potential to regenerate functional myocardium following myocardial infarction. In this study, we utilized novel electrospun fibrin microfiber sheets of different stiffnesses (50.0 ± 11.2 kPa and 90.0 ± 16.4 kPa) to engineer biomimetic models of vascularized cardiac tissues. We characterized tissue assembly, electrophysiology, and contractility of neonatal rat ventricular cardiomyocytes (NRVCMs) cultured on these sheets. NRVCMs cultured on the softer substrates displayed higher conduction velocities (CVs) and improved electrophysiological properties. Human umbilical vein endothelial cells (HUVECs) formed dense networks on the sheets when co-cultured with human adipose-derived stem/stromal cells (hASCs). To achieve vascularized cardiac tissues, we tested various tri-culture protocols of NRVCM:hASC:HUVEC and found that a ratio of 1,500,000:37,500:150,000 cells/cm2 enabled the formation of robust endothelial networks while retaining statistically identical electrophysiological characteristics to NRVCM-only cultures. Tri-cultures at this ratio on 90 kPa substrates exhibited average CVs of 14 ± 0.6 cm/s, Action Potential Duration (APD)80 and APD30 of 152 ± 11 ms and 71 ± 6 ms, respectively, and maximum capture rate (MCR) of 3.9 ± 0.7 Hz. These data indicate the significant potential of generating densely packed endothelial networks together with electrically integrated cardiac cells in vitro as a physiologic 3D cardiac model.
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Affiliation(s)
- Justin Morrissette-McAlmon
- Translational Tissue Engineering Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Brian Ginn
- Translational Tissue Engineering Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Material Sciences & Engineering, Johns Hopkins University, School of Engineering, Baltimore, MD, USA
| | - Sarah Somers
- Translational Tissue Engineering Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Takuma Fukunishi
- Department of Surgery & Cardiac Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Chanon Thanitcul
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Alexandra Rindone
- Translational Tissue Engineering Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Narutoshi Hibino
- Department of Surgery & Cardiac Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Leslie Tung
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Hai-Quan Mao
- Translational Tissue Engineering Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Material Sciences & Engineering, Johns Hopkins University, School of Engineering, Baltimore, MD, USA
- Institute for NanoBioTechnology (INBT), Johns Hopkins University School of Engineering, Baltimore, MD, USA
| | - Warren Grayson
- Translational Tissue Engineering Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Department of Material Sciences & Engineering, Johns Hopkins University, School of Engineering, Baltimore, MD, USA.
- Institute for NanoBioTechnology (INBT), Johns Hopkins University School of Engineering, Baltimore, MD, USA.
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13
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Effect of Carvacrol, TRP Channels Modulator, on Cardiac Electrical Activity. BIOMED RESEARCH INTERNATIONAL 2020; 2020:6456805. [PMID: 32337263 PMCID: PMC7166271 DOI: 10.1155/2020/6456805] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 02/14/2020] [Accepted: 03/11/2020] [Indexed: 01/18/2023]
Abstract
Despite the wide application of carvacrol (CAR) in medicines, dietary supplements, and foods, there is still insufficient electrophysiological data on the mechanisms of action of CAR, particularly with regard to heart function. Therefore, in this study, we attempted to elucidate whether CAR, whose inhibitory effect on both cardiac and vascular TRPM7 and L-type Ca2+ currents has been demonstrated previously, could modify cardiac electrical activity. We used a combination of optical mapping and microelectrode techniques to track the action potentials (APs) and the spread of electrical activity in a Langendorff-perfused rabbit heart model during atrial/endo/epicardial pacing. Simultaneously, ECG recordings were acquired. Because human trials on CAR are still lacking, we tested the action of CAR on human ventricular preparations obtained from explanted hearts. Activation time (AT), AP duration (APD), and conduction velocity maps were constructed. We demonstrated that at a low concentration (10 μM) of CAR, only marginal changes in the AP parameters were observed. At higher concentrations (≥100 μM), a decrease in AP upstroke velocity (dV/dtmax), suggesting inhibition of Na+ current, and APD (at 50 and 90% repolarization) was detected; also slowing in the spread of electrical signals via the atrioventricular node was observed, suggesting impaired functioning of Ca2+ channels. In addition, a decrease in the T-wave amplitude was seen on the ECG, suggesting an impaired repolarization process. Nevertheless, those changes occurred without a significant impact on the resting membrane potential and were reversible. We suggest that CAR might play a role in modulating cardiac electrical activity at high concentrations.
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14
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O'Shea C, Pavlovic D, Rajpoot K, Winter J. Examination of the Effects of Conduction Slowing on the Upstroke of Optically Recorded Action Potentials. Front Physiol 2019; 10:1295. [PMID: 31681008 PMCID: PMC6798176 DOI: 10.3389/fphys.2019.01295] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 09/26/2019] [Indexed: 01/27/2023] Open
Abstract
Introduction The upstroke of optical action potentials (APs) recorded from intact hearts are generally recognized to be slower than those recorded with microelectrodes. This is thought to reflect spatial signal averaging within the volume of tissue that makes up the optical signal. However, to date, there has been no direct experimental study on the relationship between conduction velocity (CV) and optical AP upstroke morphology in the intact heart. Notably, it is known that sodium channel block and gap junction inhibition, which both slow CV, exert differential effects on the upstroke velocity of microelectrode-recorded APs. Whether such differences are evident in optical APs is not known. The present study sought to determine the relationship between tissue CV and optical AP upstroke velocity in intact mouse hearts. Materials and Methods Isolated, perfused mouse hearts were stained with the potentiometric dye Rh-237. Fluorescent signals were recorded from across the anterior surface of the left and right ventricles during constant pacing. Maximum rate of change in fluorescence (dF/dtmax) and tissue CV were assessed in control conditions, during an acute period of low-flow ischemia, and following perfusion of flecainide (1–3 μmol/L), a sodium channel blocker, or carbenoxolone (10–50 μmol/L), a gap junction inhibitor. Results During epicardial pacing, an anisotropic pattern was observed in both activation and dF/dtmax maps, with more rapid optical AP upstroke velocities orientated along the fastest conduction paths (and vice versa). Low-flow ischemia resulted in a time-dependent slowing of ventricular CV, which was accompanied by a concomitant reduction in optical AP upstroke velocity. All values returned to baseline on tissue reperfusion. Both flecainide and carbenoxolone were associated with a concentration-dependent reduction in CV and decrease in optical AP upstroke velocity, despite distinct mechanisms of action. Similar responses to carbenoxolone were observed for low- (156 μm pixel with) and high- (20 μm pixel width) magnification recordings. Comparison of data from all interventions revealed a linear relationship between CV and upstroke dF/dt. Conclusion In intact mouse hearts, slowing of optical AP upstroke velocity is directly proportional to the change in CV associated with low-flow ischemia, sodium channel block, and gap junction inhibition.
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Affiliation(s)
- Christopher O'Shea
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom.,EPSRC Centre for Doctoral Training in Physical Sciences for Health, University of Birmingham, Birmingham, United Kingdom
| | - Davor Pavlovic
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Kashif Rajpoot
- School of Computer Science, University of Birmingham, Birmingham, United Kingdom
| | - James Winter
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
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15
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Piktel JS, Wilson LD. Translational Models of Arrhythmia Mechanisms and Susceptibility: Success and Challenges of Modeling Human Disease. Front Cardiovasc Med 2019; 6:135. [PMID: 31552276 PMCID: PMC6748164 DOI: 10.3389/fcvm.2019.00135] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 08/27/2019] [Indexed: 01/10/2023] Open
Abstract
We discuss large animal translational models of arrhythmia susceptibility and sudden cardiac death, focusing on important considerations when interpreting the data derived before applying them to human trials. The utility of large animal models of arrhythmia and the pros and cons of specific translational large animals used will be discussed, including the necessary tradeoffs between models designed to derive mechanisms vs. those to test therapies. Recent technical advancements which can be applied to large animal models of arrhythmias to better elucidate mechanistic insights will be introduced. Finally, some specific examples of past successes and challenges in translating the results of large animal models of arrhythmias to clinical trials and practice will be examined, and common themes regarding the success and failure of translating studies to therapy in man will be discussed.
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Affiliation(s)
| | - Lance D. Wilson
- Department of Emergency Medicine, Emergency Care Research Institute and Heart and Vascular Research Center, MetroHealth Campus of Case Western Reserve University, Cleveland, OH, United States
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16
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Veeraraghavan R, Hoeker GS, Alvarez-Laviada A, Hoagland D, Wan X, King DR, Sanchez-Alonso J, Chen C, Jourdan J, Isom LL, Deschenes I, Smyth JW, Gorelik J, Poelzing S, Gourdie RG. The adhesion function of the sodium channel beta subunit (β1) contributes to cardiac action potential propagation. eLife 2018; 7:37610. [PMID: 30106376 PMCID: PMC6122953 DOI: 10.7554/elife.37610] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 08/06/2018] [Indexed: 12/22/2022] Open
Abstract
Computational modeling indicates that cardiac conduction may involve ephaptic coupling – intercellular communication involving electrochemical signaling across narrow extracellular clefts between cardiomyocytes. We hypothesized that β1(SCN1B) –mediated adhesion scaffolds trans-activating NaV1.5 (SCN5A) channels within narrow (<30 nm) perinexal clefts adjacent to gap junctions (GJs), facilitating ephaptic coupling. Super-resolution imaging indicated preferential β1 localization at the perinexus, where it co-locates with NaV1.5. Smart patch clamp (SPC) indicated greater sodium current density (INa) at perinexi, relative to non-junctional sites. A novel, rationally designed peptide, βadp1, potently and selectively inhibited β1-mediated adhesion, in electric cell-substrate impedance sensing studies. βadp1 significantly widened perinexi in guinea pig ventricles, and selectively reduced perinexal INa, but not whole cell INa, in myocyte monolayers. In optical mapping studies, βadp1 precipitated arrhythmogenic conduction slowing. In summary, β1-mediated adhesion at the perinexus facilitates action potential propagation between cardiomyocytes, and may represent a novel target for anti-arrhythmic therapies.
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Affiliation(s)
- Rengasayee Veeraraghavan
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States
| | - Gregory S Hoeker
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States
| | | | - Daniel Hoagland
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States
| | - Xiaoping Wan
- Heart and Vascular Research Center, MetroHealth Medical Center, Department of Medicine, Case Western Reserve University, Cleveland, United States
| | - D Ryan King
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States.,Graduate Program in Translational Biology, Medicine and Health, Virginia Tech, Virginia, United States
| | - Jose Sanchez-Alonso
- Department of Myocardial Function, Imperial College London, London, United Kingdom
| | - Chunling Chen
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, United States
| | - Jane Jourdan
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States
| | - Lori L Isom
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, United States
| | - Isabelle Deschenes
- Heart and Vascular Research Center, MetroHealth Medical Center, Department of Medicine, Case Western Reserve University, Cleveland, United States.,Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Unites States
| | - James W Smyth
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States.,Department of Biological Sciences, College of Science, Blacksburg, United States
| | - Julia Gorelik
- Department of Myocardial Function, Imperial College London, London, United Kingdom
| | - Steven Poelzing
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic University, Blacksburg, United States
| | - Robert G Gourdie
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic University, Blacksburg, United States
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17
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Fukaya H, Piktel JS, Wan X, Plummer BN, Laurita KR, Wilson LD. Arrhythmogenic Delayed Afterdepolarizations Are Promoted by Severe Hypothermia But Not Therapeutic Hypothermia. Circ J 2018; 82:62-70. [DOI: 10.1253/circj.cj-17-0145] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Hidehira Fukaya
- The Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University
- Department of Cardiovascular Medicine, Kitasato University School of Medicine
| | - Joseph S. Piktel
- The Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University
- Department of Emergency Medicine, MetroHealth Campus, Case Western Reserve University
| | - Xiaoping Wan
- The Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University
| | - Bradley N. Plummer
- The Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University
| | - Kenneth R. Laurita
- The Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University
| | - Lance D. Wilson
- The Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University
- Department of Emergency Medicine, MetroHealth Campus, Case Western Reserve University
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18
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Barbic M, Moreno A, Harris TD, Kay MW. Detachable glass microelectrodes for recording action potentials in active moving organs. Am J Physiol Heart Circ Physiol 2017; 312:H1248-H1259. [PMID: 28476925 DOI: 10.1152/ajpheart.00741.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 04/11/2017] [Accepted: 04/27/2017] [Indexed: 12/17/2022]
Abstract
Here, we describe new detachable floating glass micropipette electrode devices that provide targeted action potential recordings in active moving organs without requiring constant mechanical constraint or pharmacological inhibition of tissue motion. The technology is based on the concept of a glass micropipette electrode that is held firmly during cell targeting and intracellular insertion, after which a 100-µg glass microelectrode, a "microdevice," is gently released to remain within the moving organ. The microdevices provide long-term recordings of action potentials, even during millimeter-scale movement of tissue in which the device is embedded. We demonstrate two different glass micropipette electrode holding and detachment designs appropriate for the heart (sharp glass microdevices for cardiac myocytes in rats, guinea pigs, and humans) and the brain (patch glass microdevices for neurons in rats). We explain how microdevices enable measurements of multiple cells within a moving organ that are typically difficult with other technologies. Using sharp microdevices, action potential duration was monitored continuously for 15 min in unconstrained perfused hearts during global ischemia-reperfusion, providing beat-to-beat measurements of changes in action potential duration. Action potentials from neurons in the hippocampus of anesthetized rats were measured with patch microdevices, which provided stable base potentials during long-term recordings. Our results demonstrate that detachable microdevices are an elegant and robust tool to record electrical activity with high temporal resolution and cellular level localization without disturbing the physiological working conditions of the organ.NEW & NOTEWORTHY Cellular action potential measurements within tissue using glass micropipette electrodes usually require tissue immobilization, potentially influencing the physiological relevance of the measurement. Here, we addressed this limitation with novel 100-µg detachable glass microelectrodes that can be precisely positioned to provide long-term measurements of action potential duration during unconstrained tissue movement.
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Affiliation(s)
- Mladen Barbic
- Applied Physics and Instrumentation Group, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia; and
| | - Angel Moreno
- Department of Biomedical Engineering, The George Washington University, Washington, District of Columbia
| | - Tim D Harris
- Applied Physics and Instrumentation Group, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia; and
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University, Washington, District of Columbia
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19
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Nassal MMJ, Wan X, Dale Z, Deschênes I, Wilson LD, Piktel JS. Mild hypothermia preserves myocardial conduction during ischemia by maintaining gap junction intracellular communication and Na + channel function. Am J Physiol Heart Circ Physiol 2017; 312:H886-H895. [PMID: 28283549 DOI: 10.1152/ajpheart.00298.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 03/03/2017] [Accepted: 03/03/2017] [Indexed: 11/22/2022]
Abstract
Acute cardiac ischemia induces conduction velocity (CV) slowing and conduction block, promoting reentrant arrhythmias leading to sudden cardiac arrest. Previously, we found that mild hypothermia (MH; 32°C) attenuates ischemia-induced conduction block and CV slowing in a canine model of early global ischemia. Acute ischemia impairs cellular excitability and the gap junction (GJ) protein connexin (Cx)43. We hypothesized that MH prevented ischemia-induced conduction block and CV slowing by preserving GJ expression and localization. Canine left ventricular preparations at control (36°C) or MH (32°C) were subjected to no-flow prolonged (30 min) ischemia. Optical action potentials were recorded from the transmural left ventricular wall, and CV was measured throughout ischemia. Cx43 and Na+ channel (NaCh) remodeling was assessed using both confocal immunofluorescence (IF) and/or Western blot analysis. Cellular excitability was determined by microelectrode recordings of action potential upstroke velocity (dV/dtmax) and resting membrane potential (RMP). NaCh current was measured in isolated canine myocytes at 36 and 32°C. As expected, MH prevented conduction block and mitigated ischemia-induced CV slowing during 30 min of ischemia. MH maintained Cx43 at the intercalated disk (ID) and attenuated ischemia-induced Cx43 degradation by both IF and Western blot analysis. MH also preserved dV/dtmax and NaCh function without affecting RMP. No difference in NaCh expression was seen at the ID by IF or Western blot analysis. In conclusion, MH preserves myocardial conduction during prolonged ischemia by maintaining Cx43 expression at the ID and maintaining NaCh function. Hypothermic preservation of GJ coupling and NaCh may be novel antiarrhythmic strategies during resuscitation.NEW & NOTEWORTHY Therapeutic hypothermia is now a class I recommendation for resuscitation from cardiac arrest. This study determined that hypothermia preserves gap junction coupling as well as Na+ channel function during acute cardiac ischemia, attenuating conduction slowing and preventing conduction block, suggesting that induced hypothermia may be a novel antiarrhythmic strategy in resuscitation.
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Affiliation(s)
- Michelle M J Nassal
- The Heart and Vascular Research Center and Department of Physiology, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio; and
| | - Xiaoping Wan
- The Heart and Vascular Research Center and Department of Physiology, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio; and
| | - Zack Dale
- The Heart and Vascular Research Center and Department of Emergency Medicine, MetroHealth Campus, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Isabelle Deschênes
- The Heart and Vascular Research Center and Department of Physiology, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio; and
| | - Lance D Wilson
- The Heart and Vascular Research Center and Department of Emergency Medicine, MetroHealth Campus, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Joseph S Piktel
- The Heart and Vascular Research Center and Department of Emergency Medicine, MetroHealth Campus, Case Western Reserve University School of Medicine, Cleveland, Ohio
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Hoeker GS, Skarsfeldt MA, Jespersen T, Poelzing S. Electrophysiologic effects of the IK1 inhibitor PA-6 are modulated by extracellular potassium in isolated guinea pig hearts. Physiol Rep 2017; 5:e13120. [PMID: 28087819 PMCID: PMC5256165 DOI: 10.14814/phy2.13120] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 12/14/2016] [Indexed: 12/02/2022] Open
Abstract
The pentamidine analog PA-6 was developed as a specific inward rectifier potassium current (IK1) antagonist, because established inhibitors either lack specificity or have side effects that prohibit their use in vivo. We previously demonstrated that BaCl2, an established IK1 inhibitor, could prolong action potential duration (APD) and increase cardiac conduction velocity (CV). However, few studies have addressed whether targeted IK1 inhibition similarly affects ventricular electrophysiology. The aim of this study was to determine the effects of PA-6 on cardiac repolarization and conduction in Langendorff-perfused guinea pig hearts. PA-6 (200 nm) or vehicle was perfused into ex-vivo guinea pig hearts for 60 min. Hearts were optically mapped with di-4-ANEPPS to quantify CV and APD at 90% repolarization (APD90). Ventricular APD90 was significantly prolonged in hearts treated with PA-6 (115 ± 2% of baseline; P < 0.05), but not vehicle (105 ± 2% of baseline). PA-6 slightly, but significantly, increased transverse CV by 7%. PA-6 significantly prolonged APD90 during hypokalemia (2 mmol/L [K+]o), although to a lesser degree than observed at 4.56 mmol/L [K+]o In contrast, the effect of PA-6 on CV was more pronounced during hypokalemia, where transverse CV with PA-6 (24 ± 2 cm/sec) was significantly faster than with vehicle (13 ± 3 cm/sec, P < 0.05). These results show that under normokalemic conditions, PA-6 significantly prolonged APD90, whereas its effect on CV was modest. During hypokalemia, PA-6 prolonged APD90 to a lesser degree, but profoundly increased CV Thus, in intact guinea pig hearts, the electrophysiologic effects of the IK1 inhibitor, PA-6, are [K+]o-dependent.
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Affiliation(s)
- Gregory S Hoeker
- Biomedical Engineering and Mechanics, Center for Heart and Regenerative Medicine, Virginia Tech Virginia Tech Carilion Research Institute, Roanoke, Virginia
| | - Mark A Skarsfeldt
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Steven Poelzing
- Biomedical Engineering and Mechanics, Center for Heart and Regenerative Medicine, Virginia Tech Virginia Tech Carilion Research Institute, Roanoke, Virginia
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Veeraraghavan R, Lin J, Keener JP, Gourdie R, Poelzing S. Potassium channels in the Cx43 gap junction perinexus modulate ephaptic coupling: an experimental and modeling study. Pflugers Arch 2016; 468:1651-61. [PMID: 27510622 DOI: 10.1007/s00424-016-1861-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 06/27/2016] [Accepted: 07/25/2016] [Indexed: 12/01/2022]
Abstract
It was recently demonstrated that cardiac sodium channels (Nav1.5) localized at the perinexus, an intercalated disc (ID) nanodomain associated with gap junctions (GJ), may contribute to electrical coupling between cardiac myocytes via an ephaptic mechanism. Impairment of ephaptic coupling by acute interstitial edema (AIE)-induced swelling of the perinexus was associated with arrhythmogenic, anisotropic conduction slowing. Given that Kir2.1 has also recently been reported to localize at intercalated discs, we hypothesized that Kir2.1 channels may reside within the perinexus and that inhibiting them may mitigate arrhythmogenic conduction slowing observed during AIE. Using gated stimulated emission depletion (gSTED) and stochastic optical reconstruction microscopy (STORM) super-resolution microscopy, we indeed find that a significant proportion of Kir2.1 channels resides within the perinexus. Moreover, whereas Nav1.5 inhibition during AIE exacerbated arrhythmogenic conduction slowing, inhibiting Kir2.1 channels during AIE preferentially increased transverse conduction velocity-decreasing anisotropy and ameliorating arrhythmia risk compared to AIE alone. Comparison of our results with a nanodomain computer model identified enrichment of both Nav1.5 and Kir2.1 at intercalated discs as key factors underlying the experimental observations. We demonstrate that Kir2.1 channels are localized within the perinexus alongside Nav1.5 channels. Further, targeting Kir2.1 modulates intercellular coupling between cardiac myocytes, anisotropy of conduction, and arrhythmia propensity in a manner consistent with a role for ephaptic coupling in cardiac conduction. For over half a century, electrical excitation in the heart has been thought to occur exclusively via gap junction-mediated ionic current flow between cells. Further, excitation was thought to depend almost exclusively on sodium channels with potassium channels being involved mainly in returning the cell to rest. Here, we demonstrate that sodium and potassium channels co-reside within nanoscale domains at cell-to-cell contact sites. Experimental and computer modeling results suggest a role for these channels in electrical coupling between cardiac muscle cells via an ephaptic mechanism working in tandem with gap junctions. This new insight into the mechanism of cardiac electrical excitation could pave the way for novel therapies against cardiac rhythm disturbances.
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Affiliation(s)
- Rengasayee Veeraraghavan
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, 2 Riverside Circle, Roanoke, VA, 24016, USA.
| | - Joyce Lin
- Department of Mathematics, California Polytechnic State University, San Luis Obispo, CA, USA
| | - James P Keener
- Department of Mathematics, University of Utah, 155 South 1400 East, Salt Lake City, UT, 84112, USA
| | - Robert Gourdie
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, 2 Riverside Circle, Roanoke, VA, 24016, USA.
- School of Biomedical Engineering and Sciences, Virginia Polytechnic University, Blacksburg, VA, USA.
| | - Steven Poelzing
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, 2 Riverside Circle, Roanoke, VA, 24016, USA.
- School of Biomedical Engineering and Sciences, Virginia Polytechnic University, Blacksburg, VA, USA.
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Majumder R, Engels MC, de Vries AAF, Panfilov AV, Pijnappels DA. Islands of spatially discordant APD alternans underlie arrhythmogenesis by promoting electrotonic dyssynchrony in models of fibrotic rat ventricular myocardium. Sci Rep 2016; 6:24334. [PMID: 27072041 PMCID: PMC4829862 DOI: 10.1038/srep24334] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 02/25/2016] [Indexed: 12/11/2022] Open
Abstract
Fibrosis and altered gap junctional coupling are key features of ventricular remodelling and are associated with abnormal electrical impulse generation and propagation. Such abnormalities predispose to reentrant electrical activity in the heart. In the absence of tissue heterogeneity, high-frequency impulse generation can also induce dynamic electrical instabilities leading to reentrant arrhythmias. However, because of the complexity and stochastic nature of such arrhythmias, the combined effects of tissue heterogeneity and dynamical instabilities in these arrhythmias have not been explored in detail. Here, arrhythmogenesis was studied using in vitro and in silico monolayer models of neonatal rat ventricular tissue with 30% randomly distributed cardiac myofibroblasts and systematically lowered intercellular coupling achieved in vitro through graded knockdown of connexin43 expression. Arrhythmia incidence and complexity increased with decreasing intercellular coupling efficiency. This coincided with the onset of a specialized type of spatially discordant action potential duration alternans characterized by island-like areas of opposite alternans phase, which positively correlated with the degree of connexinx43 knockdown and arrhythmia complexity. At higher myofibroblast densities, more of these islands were formed and reentrant arrhythmias were more easily induced. This is the first study exploring the combinatorial effects of myocardial fibrosis and dynamic electrical instabilities on reentrant arrhythmia initiation and complexity.
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Affiliation(s)
- Rupamanjari Majumder
- Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Centre Leiden, Leiden University Medical Enter, Leiden, the Netherlands
| | - Marc C. Engels
- Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Centre Leiden, Leiden University Medical Enter, Leiden, the Netherlands
| | - Antoine A. F. de Vries
- Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Centre Leiden, Leiden University Medical Enter, Leiden, the Netherlands
| | | | - Daniël A. Pijnappels
- Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Centre Leiden, Leiden University Medical Enter, Leiden, the Netherlands
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Variability of Action Potentials Within and Among Cardiac Cell Clusters Derived from Human Embryonic Stem Cells. Sci Rep 2016; 6:18544. [PMID: 26729331 PMCID: PMC4700458 DOI: 10.1038/srep18544] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 11/19/2015] [Indexed: 12/12/2022] Open
Abstract
Electrophysiological variability in cardiomyocytes derived from pluripotent stem cells continues to be an impediment for their scientific and translational applications. We studied the variability of action potentials (APs) recorded from clusters of human embryonic stem cell-derived cardiomyocytes (hESC-CMs) using high-resolution optical mapping. Over 23,000 APs were analyzed through four parameters: APD30, APD80, triangulation and fractional repolarization. Although measures were taken to reduce variability due to cell culture conditions and rate-dependency of APs, we still observed significant variability in APs among and within the clusters. However, similar APs were found in spatial locations with close proximity, and in some clusters formed distinct regions having different AP characteristics that were reflected as separate peaks in the AP parameter distributions, suggesting multiple electrophysiological phenotypes. Using a recently developed automated method to group cells based on their entire AP shape, we identified distinct regions of different phenotypes within single clusters and common phenotypes across different clusters when separating APs into 2 or 3 subpopulations. The systematic analysis of the heterogeneity and potential phenotypes of large populations of hESC-CMs can be used to evaluate strategies to improve the quality of pluripotent stem cell-derived cardiomyocytes for use in diagnostic and therapeutic applications and in drug screening.
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Abstract
BACKGROUND Optical mapping technology is an important tool to study cardiac electrophysiology. Transmembrane fluorescence signals from voltage-dependent dyes need to be preprocessed before analysis to improve the signal-to-noise ratio. Fourier analysis, based on spectral properties of stationary signals, cannot directly provide information on the spectrum changes with respect to time. Fourier filtering has the disadvantage of causing degradation of abrupt waveform changes such as those in action potential signals. Wavelet analysis has the ability to offer simultaneous localization in time and frequency domains, suitable for the analysis and reconstruction of irregular, non-stationary signals like the fast action-potential upstroke, and better than conventional filters for denoising. METHODS We applied discrete wavelet transformation for temporal processing of optical mapping signals and wavelet packet analysis approaches to process activation maps from simulated and experimental optical mapping data from canine right atrium. We compared the results obtained with the wavelet approach to a variety of other methods (Fast Fourier Transformation (FFT) with finite or infinite response filtering, and Gaussian filters). RESULTS Temporal wavelet analysis improved signal-to-noise ratio (SNR) better than FFT filtering for 5-10dB SNR, and caused less distortion of the action potential waveform over the full range of simulated noise (5-20dB). Spatial wavelet filtering produced more efficient denoising and/or more accurate conduction velocity estimates than Gaussian filtering. Propagation patterns were also best revealed by wavelet filtering. CONCLUSIONS Wavelet analysis is a promising tool, facilitating accurate action potential characterization, activation map formation, and conduction velocity estimation.
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Affiliation(s)
- Feng Xiong
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Que., Canada; Research Center, Montreal Heart Institute and Université de Montréal, 5000 Belanger Street East, Montreal, Que., Canada H1T 1C8
| | - Xiaoyan Qi
- Research Center, Montreal Heart Institute and Université de Montréal, 5000 Belanger Street East, Montreal, Que., Canada H1T 1C8
| | - Stanley Nattel
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Que., Canada; Research Center, Montreal Heart Institute and Université de Montréal, 5000 Belanger Street East, Montreal, Que., Canada H1T 1C8; Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Que., Canada
| | - Philippe Comtois
- Research Center, Montreal Heart Institute and Université de Montréal, 5000 Belanger Street East, Montreal, Que., Canada H1T 1C8; Department of Molecular and Integrative Physiology/Institute of Biomedical Engineering, Université de Montréal, Montreal, Que., Canada.
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25
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Mačianskienė R, Martišienė I, Navalinskas A, Vosyliūtė R, Treinys R, Vaidelytė B, Benetis R, Jurevičius J. Evaluation of excitation propagation in the rabbit heart: optical mapping and transmural microelectrode recordings. PLoS One 2015; 10:e0123050. [PMID: 25881157 PMCID: PMC4400155 DOI: 10.1371/journal.pone.0123050] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 02/18/2015] [Indexed: 11/18/2022] Open
Abstract
Background Because of the optical features of heart tissue, optical and electrical action potentials are only moderately associated, especially when near-infrared dyes are used in optical mapping (OM) studies. Objective By simultaneously recording transmural electrical action potentials (APs) and optical action potentials (OAPs), we aimed to evaluate the contributions of both electrical and optical influences to the shape of the OAP upstroke. Methods and Results A standard glass microelectrode and OM, using an near-infrared fluorescent dye (di-4-ANBDQBS), were used to simultaneously record transmural APs and OAPs in a Langendorff-perfused rabbit heart during atrial, endocardial, and epicardial pacing. The actual profile of the transmural AP upstroke across the LV wall, together with the OAP upstroke, allowed for calculations of the probing-depth constant (k ~2.1 mm, n = 24) of the fluorescence measurements. In addition, the transmural AP recordings aided the quantitative evaluation of the influences of depth-weighted and lateral-scattering components on the OAP upstroke. These components correspond to the components of the propagating electrical wave that are transmural and parallel to the epicardium. The calculated mean values for the depth-weighted and lateral-scattering components, whose sum comprises the OAP upstroke, were (in ms) 10.18 ± 0.62 and 0.0 ± 0.56 for atrial stimulation, 9.37 ± 1.12 and 3.01 ± 1.30 for endocardial stimulation, and 6.09 ± 0.79 and 8.16 ± 0.98 for epicardial stimulation; (n = 8 for each). For this dye, 90% of the collected fluorescence originated up to 4.83 ± 0.18 mm (n = 24) from the epicardium. Conclusions The co-registration of OM and transmural microelectrode APs enabled the probing depth of fluorescence measurements to be calculated and the OAP upstroke to be divided into two components (depth-weighted and lateral-scattering), and it also allowed the relative strengths of their effects on the shape of the OAP upstroke to be evaluated.
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Affiliation(s)
- Regina Mačianskienė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Irma Martišienė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Antanas Navalinskas
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Rūta Vosyliūtė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Rimantas Treinys
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Birutė Vaidelytė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Rimantas Benetis
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Jonas Jurevičius
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
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26
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Veeraraghavan R, Lin J, Hoeker GS, Keener JP, Gourdie RG, Poelzing S. Sodium channels in the Cx43 gap junction perinexus may constitute a cardiac ephapse: an experimental and modeling study. Pflugers Arch 2015; 467:2093-105. [PMID: 25578859 PMCID: PMC4500747 DOI: 10.1007/s00424-014-1675-z] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Revised: 11/26/2014] [Accepted: 12/15/2014] [Indexed: 11/30/2022]
Abstract
It has long been held that electrical excitation spreads from cell-to-cell in the heart via low resistance gap junctions (GJ). However, it has also been proposed that myocytes could interact by non-GJ-mediated “ephaptic” mechanisms, facilitating propagation of action potentials in tandem with direct GJ-mediated coupling. We sought evidence that such mechanisms contribute to cardiac conduction. Using super-resolution microscopy, we demonstrate that Nav1.5 is localized within 200 nm of the GJ plaque (a region termed the perinexus). Electron microscopy revealed close apposition of adjacent cell membranes within perinexi suggesting that perinexal sodium channels could function as an ephapse, enabling ephaptic cell-to-cell transfer of electrical excitation. Acute interstitial edema (AIE) increased intermembrane distance at the perinexus and was associated with preferential transverse conduction slowing and increased spontaneous arrhythmia incidence. Inhibiting sodium channels with 0.5 μM flecainide uniformly slowed conduction, but sodium channel inhibition during AIE slowed conduction anisotropically and increased arrhythmia incidence more than AIE alone. Sodium channel inhibition during GJ uncoupling with 25 μM carbenoxolone slowed conduction anisotropically and was also highly proarrhythmic. A computational model of discretized extracellular microdomains (including ephaptic coupling) revealed that conduction trends associated with altered perinexal width, sodium channel conductance, and GJ coupling can be predicted when sodium channel density in the intercalated disk is relatively high. We provide evidence that cardiac conduction depends on a mathematically predicted ephaptic mode of coupling as well as GJ coupling. These data suggest opportunities for novel anti-arrhythmic therapies targeting noncanonical conduction pathways in the heart.
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Affiliation(s)
- Rengasayee Veeraraghavan
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, Roanoke, VA, 24016, USA
| | - Joyce Lin
- Department of Mathematics, California Polytechnic State University, San Luis Obispo, CA, USA
| | - Gregory S Hoeker
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, Roanoke, VA, 24016, USA
| | - James P Keener
- Department of Mathematics, University of Utah, 155 South 1400 East, Salt Lake City, UT, 84112, USA.
| | - Robert G Gourdie
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, Roanoke, VA, 24016, USA. .,School of Biomedical Engineering and Sciences, Virginia Polytechnic University, Blacksburg, VA, USA.
| | - Steven Poelzing
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, Roanoke, VA, 24016, USA. .,School of Biomedical Engineering and Sciences, Virginia Polytechnic University, Blacksburg, VA, USA.
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Walton RD, Bernus O. Towards Depth-Resolved Optical Imaging of Cardiac Electrical Activity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 859:405-23. [DOI: 10.1007/978-3-319-17641-3_16] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Biophotonic Modelling of Cardiac Optical Imaging. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 859:367-404. [DOI: 10.1007/978-3-319-17641-3_15] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Bishop MJ, Plank G. Simulating photon scattering effects in structurally detailed ventricular models using a Monte Carlo approach. Front Physiol 2014; 5:338. [PMID: 25309442 PMCID: PMC4164003 DOI: 10.3389/fphys.2014.00338] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 08/19/2014] [Indexed: 11/17/2022] Open
Abstract
Light scattering during optical imaging of electrical activation within the heart is known to significantly distort the optically-recorded action potential (AP) upstroke, as well as affecting the magnitude of the measured response of ventricular tissue to strong electric shocks. Modeling approaches based on the photon diffusion equation have recently been instrumental in quantifying and helping to understand the origin of the resulting distortion. However, they are unable to faithfully represent regions of non-scattering media, such as small cavities within the myocardium which are filled with perfusate during experiments. Stochastic Monte Carlo (MC) approaches allow simulation and tracking of individual photon “packets” as they propagate through tissue with differing scattering properties. Here, we present a novel application of the MC method of photon scattering simulation, applied for the first time to the simulation of cardiac optical mapping signals within unstructured, tetrahedral, finite element computational ventricular models. The method faithfully allows simulation of optical signals over highly-detailed, anatomically-complex MR-based models, including representations of fine-scale anatomy and intramural cavities. We show that optical action potential upstroke is prolonged close to large subepicardial vessels than further away from vessels, at times having a distinct “humped” morphology. Furthermore, we uncover a novel mechanism by which photon scattering effects around vessels cavities interact with “virtual-electrode” regions of strong de-/hyper-polarized tissue surrounding cavities during shocks, significantly reducing the apparent optically-measured epicardial polarization. We therefore demonstrate the importance of this novel optical mapping simulation approach along with highly anatomically-detailed models to fully investigate electrophysiological phenomena driven by fine-scale structural heterogeneity.
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Affiliation(s)
- Martin J Bishop
- Division of Imaging Sciences & Biomedical Engineering, Department of Biomedical Engineering, King's College London London, UK
| | - Gernot Plank
- Institute of Biophysics, Medical University of Graz Graz, Austria ; Oxford eResearch Centre, University of Oxford Oxford, UK
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Walton RD, Bernus O, Dubois R. A novel approach for deriving global activation maps from non-averaged cardiac optical signals. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2013:1772-5. [PMID: 24110051 DOI: 10.1109/embc.2013.6609864] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Cardiac arrhythmias are often characterized by non-repetitive complex activation sequences. The properties of electrical activity in cardiac tissue, such as activation time (AT), can be accurately determined using optical imaging of electrical signals using voltage-sensitive dyes. The electrical AT of optical action potentials is known to accurately correlate with the time of the maximal derivative (dF/dt(max)) of the upstroke of ensemble averaged optical signals. The sensitivity of dF/dt(max) to noise is therefore problematic for mapping AT from nonrepetitive activity. Here we experimentally evaluated a novel method to determine activation times (AT) from non-averaged epicardial optical signals. The method depends upon the time delays of activation between adjacent pixels developing a global AT map, as opposed to measuring local AT from each pixel independently based on dF/dt(max). ATs from dF/dt(max) and global AT maps of non-ensemble averaged signals were correlated with averaged signals. Global ATs improved linear correlation coefficients and accuracy of AT patterns. Furthermore, global AT maps were significantly more robust at reproducing AT maps between consecutive stable beats. The proposed method of global AT mapping will potentially enable accurate mapping of non-repetitive propagation during arrhythmias.
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Gray RA, Mashburn DN, Sidorov VY, Roth BJ, Pathmanathan P, Wikswo JP. Transmembrane current imaging in the heart during pacing and fibrillation. Biophys J 2013; 105:1710-9. [PMID: 24094412 PMCID: PMC3791310 DOI: 10.1016/j.bpj.2013.08.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 06/28/2013] [Accepted: 08/07/2013] [Indexed: 11/20/2022] Open
Abstract
Recently, we described a method to quantify the time course of total transmembrane current (Im) and the relative role of its two components, a capacitive current (Ic) and a resistive current (Iion), corresponding to the cardiac action potential during stable propagation. That approach involved recording high-fidelity (200 kHz) transmembrane potential (Vm) signals with glass microelectrodes at one site using a spatiotemporal coordinate transformation via measured conduction velocity. Here we extend our method to compute these transmembrane currents during stable and unstable propagation from fluorescence signals of Vm at thousands of sites (3 kHz), thereby introducing transmembrane current imaging. In contrast to commonly used linear Laplacians of extracellular potential (Ve) to compute Im, we utilized nonlinear image processing to compute the required second spatial derivatives of Vm. We quantified the dynamic spatial patterns of current density of Im and Iion for both depolarization and repolarization during pacing (including nonplanar patterns) by calibrating data with the microelectrode signals. Compared to planar propagation, we found that the magnitude of Iion was significantly reduced at sites of wave collision during depolarization but not repolarization. Finally, we present uncalibrated dynamic patterns of Im during ventricular fibrillation and show that Im at singularity sites was monophasic and positive with a significant nonzero charge (Im integrated over 10 ms) in contrast with nonsingularity sites. Our approach should greatly enhance the understanding of the relative roles of functional (e.g., rate-dependent membrane dynamics and propagation patterns) and static spatial heterogeneities (e.g., spatial differences in tissue resistance) via recordings during normal and compromised propagation, including arrhythmias.
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Affiliation(s)
- Richard A Gray
- Division of Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland; Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama; Vanderbilt Institute for Integrative Biosystems Research and Education, Vanderbilt University, Nashville, Tennessee.
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JANOUŠEK O, KOLÁŘOVÁ J, RONZHINA M, NOVÁKOVÁ M, PROVAZNÍK I. Motion Artefact in Voltage-Sensitive Fluorescent Dye Emission During Repeated Ischemia of Isolated Heart. Physiol Res 2013; 62:371-8. [DOI: 10.33549/physiolres.932309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Motion artefact (MA) in voltage-sensitive fluorescent signals causes significant debasement of action potential. During ischemia and reperfusion in isolated rabbit heart, this artefact develops in a manner which may be described by the time of its onset, level, and shape. The MA during ischemia: (a) may become substantial with approximately two minutes delay after establishing global ischemia; (b) may be almost twice as high as the physiological action potential and decreases both with time and repetition of ischemia; (c) the MA shape is unpredictable and depends on individual rabbit.
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Affiliation(s)
- O. JANOUŠEK
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, University of Technology, Brno, Czech Republic
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Quinn TA, Kohl P. Combining wet and dry research: experience with model development for cardiac mechano-electric structure-function studies. Cardiovasc Res 2013; 97:601-11. [PMID: 23334215 PMCID: PMC3583260 DOI: 10.1093/cvr/cvt003] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 01/08/2013] [Accepted: 01/15/2013] [Indexed: 11/17/2022] Open
Abstract
Since the development of the first mathematical cardiac cell model 50 years ago, computational modelling has become an increasingly powerful tool for the analysis of data and for the integration of information related to complex cardiac behaviour. Current models build on decades of iteration between experiment and theory, representing a collective understanding of cardiac function. All models, whether computational, experimental, or conceptual, are simplified representations of reality and, like tools in a toolbox, suitable for specific applications. Their range of applicability can be explored (and expanded) by iterative combination of 'wet' and 'dry' investigation, where experimental or clinical data are used to first build and then validate computational models (allowing integration of previous findings, quantitative assessment of conceptual models, and projection across relevant spatial and temporal scales), while computational simulations are utilized for plausibility assessment, hypotheses-generation, and prediction (thereby defining further experimental research targets). When implemented effectively, this combined wet/dry research approach can support the development of a more complete and cohesive understanding of integrated biological function. This review illustrates the utility of such an approach, based on recent examples of multi-scale studies of cardiac structure and mechano-electric function.
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Affiliation(s)
- T Alexander Quinn
- National Heart and Lung Institute, Imperial College London, Heart Science Centre, Harefield UB9 6JH, UK.
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Veeraraghavan R, Larsen AP, Torres NS, Grunnet M, Poelzing S. Potassium channel activators differentially modulate the effect of sodium channel blockade on cardiac conduction. Acta Physiol (Oxf) 2013; 207:280-9. [PMID: 22913299 DOI: 10.1111/j.1748-1716.2012.02481.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Revised: 02/02/2012] [Accepted: 07/30/2012] [Indexed: 11/29/2022]
Abstract
AIMS Diminished repolarization reserve contributes to the arrhythmogenic substrate in many disease states. Pharmacological activation of K(+) channels has been suggested as a potential antiarrhythmic therapy in such conditions. Having previously demonstrated that I(K1) and I(Kr) can modulate cardiac conduction, we tested here the effects of pharmacological I(KATP) and I(Ks) activation on cardiac conduction and its dependence on the sodium current (I(Na)). METHODS AND RESULTS Bath electrocardiograms (ECGs) recorded from Langendorff-perfused guinea pig ventricles revealed QRS prolongation during I(KATP) activation by pinacidil but not during I(Ks) activation by R-L3 relative to control. In contrast, when I(Na) was partially blocked by flecainide, R-L3 but not pinacidil prolonged the QRS relative to flecainide alone. Conduction velocity (θ) was quantified by optical mapping during epicardial pacing. Both longitudinal (θ(L)) and transverse (θ(T)) θ were reduced by pinacidil (by 10 ± 1 and 9 ± 3%, respectively) and R-L3 (by 11 ± 2% and 15 ± 4%, respectively). Flecainide decreased θ(L) by 33 ± 4% and θ(T) by 36 ± 5%. Whereas pinacidil did not further slow θ relative to flecainide alone, R-L3 decreased both θ(L) and θ(T). CONCLUSION Pharmacological activation of I(KATP) and I(Ks) slows cardiac conduction; however, they demonstrate diverse effects on θ dependence on I(Na) blockade. These findings may have significant implications for the use of K(+) channel activators as antiarrhythmic drugs and for patients with Na(+) channel abnormalities or being treated with Na(+) channel blockers.
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Affiliation(s)
- R. Veeraraghavan
- Nora Eccles Harrison Cardiovascular Research and Training Institute; University of Utah; Salt Lake City; UT; USA
| | - A. P. Larsen
- Nora Eccles Harrison Cardiovascular Research and Training Institute; University of Utah; Salt Lake City; UT; USA
| | - N. S. Torres
- Nora Eccles Harrison Cardiovascular Research and Training Institute; University of Utah; Salt Lake City; UT; USA
| | | | - S. Poelzing
- Nora Eccles Harrison Cardiovascular Research and Training Institute; University of Utah; Salt Lake City; UT; USA
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Piktel JS, Rosenbaum DS, Wilson LD. Mild hypothermia decreases arrhythmia susceptibility in a canine model of global myocardial ischemia*. Crit Care Med 2013; 40:2954-9. [PMID: 22890250 DOI: 10.1097/ccm.0b013e31825fd39d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES Although the majority of sudden cardiac arrests occur in patients with ischemic heart disease, the effect of therapeutic hypothermia on arrhythmia susceptibility during acute global ischemia is not well understood. While both ischemia and severe hypothermia are arrhythmogenic, patients undergoing therapeutic hypothermia do not have an increase in arrhythmias, despite the fact that most sudden cardiac arrest occur in the setting of ischemia. We hypothesized that mild hypothermia induced prior to myocardial ischemia and reperfusion will have a beneficial effect on ischemia-related arrhythmia substrates. DESIGN We developed a model of global ischemia and reperfusion in the canine wedge preparation to study the transmural electrophysiologic effects of ischemia at different temperatures. SETTING Animal study. SUBJECTS Male mongrel dogs. INTERVENTIONS Canine left ventricle wedge preparations at 1) control (36°C) or 2) mild hypothermia, to simulate temperatures used in therapeutic hypothermia (32°C), were subjected to 15 mins of no-flow ischemia and subsequently reperfused. MEASUREMENTS AND MAIN RESULTS Optical action potentials were recorded spanning the transmural wall of left ventricle. Action potential duration for epicardial, mid-myocardial, and epicardial cells was measured. Transmural dispersion of repolarization and conduction velocity were measured at baseline, during ischemia, and during reperfusion. No difference was seen at baseline for conduction velocity or dispersion of repolarization between groups. Conduction velocity decreased from 0.46 ± 0.02 m/sec to 0.23 ± 0.07 m/sec, and dispersion of repolarization increased from 30 ± 5 msecs to 57 ± 4 msecs in the control group at 15 mins of ischemia. Mild hypothermia attenuated both the ischemia-induced conduction velocity slowing (decreasing from 0.44 ± 0.02 m/sec to 0.35 ± 0.03 m/sec; p = .019) and the ischemia-induced increase in dispersion of repolarization (25 ± 3 msecs to 37 ± 7 msecs; p = .037). Epicardial conduction block was observed in six of seven preparations of the control group, but no preparations in the mild hypothermia group developed conduction block (0/6). CONCLUSIONS Mild hypothermia attenuated ischemia-induced increase in dispersion of repolarization, conduction slowing, and block, which are known mechanisms of arrhythmogenesis in ischemia. These data suggest that therapeutic hypothermia may decrease arrhythmogenesis during myocardial ischemia.
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Affiliation(s)
- Joseph S Piktel
- The Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University School of Medicine, Cleveland, OH, USA.
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Di Diego JM, Sicouri S, Myles RC, Burton FL, Smith GL, Antzelevitch C. Optical and electrical recordings from isolated coronary-perfused ventricular wedge preparations. J Mol Cell Cardiol 2012; 54:53-64. [PMID: 23142540 DOI: 10.1016/j.yjmcc.2012.10.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 10/22/2012] [Accepted: 10/29/2012] [Indexed: 01/06/2023]
Abstract
The electrophysiological heterogeneity that exists across the ventricular wall in the mammalian heart has long been recognized, but remains an area that is incompletely understood. Experimental studies of the mechanisms of arrhythmogenesis in the whole heart often examine the epicardial surface in isolation and thereby disregard transmural electrophysiology. Significant heterogeneity exists in the electrophysiological properties of cardiomyocytes isolated from different layers of the ventricular wall, and given that regional heterogeneities of membrane repolarization properties can influence the electrophysiological substrate for re-entry, the diversity of cell types and characteristics spanning the ventricular wall is important in the study of arrhythmogenesis. For these reasons, coronary-perfused left ventricular wedge preparations have been developed to permit the study of transmural electrophysiology in the intact ventricle. Since the first report by Yan and Antzelevitch in 1996, electrical recordings from the transmural surface of canine wedge preparations have provided a wealth of data regarding the cellular basis for the electrocardiogram, the role of transmural heterogeneity in arrhythmogenesis, and differences in the response of the different ventricular layers to drugs and neurohormones. Use of the wedge preparation has since been expanded to other species and more recently it has also been widely used in optical mapping studies. The isolated perfused wedge preparation has become an important tool in cardiac electrophysiology. In this review, we detail the methodology involved in recording both electrical and optical signals from the coronary-perfused wedge preparation and review the advances in cardiac electrophysiology achieved through study of the wedge.
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Affiliation(s)
- José M Di Diego
- Masonic Medical Research Laboratory, 2150 Bleecker St., Utica, NY 13501, USA
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37
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Brines L, Such-Miquel L, Gallego D, Trapero I, del Canto I, Zarzoso M, Soler C, Pelechano F, Cánoves J, Alberola A, Such L, Chorro FJ. Modifications of mechanoelectric feedback induced by 2,3-butanedione monoxime and Blebbistatin in Langendorff-perfused rabbit hearts. Acta Physiol (Oxf) 2012; 206:29-41. [PMID: 22497862 DOI: 10.1111/j.1748-1716.2012.02441.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 11/16/2011] [Accepted: 03/26/2012] [Indexed: 11/30/2022]
Abstract
AIM Myocardial stretching is an arrhythmogenic factor. Optical techniques and mechanical uncouplers are used to study the mechanoelectric feedback. The aim of this study is to determine whether the mechanical uncouplers 2,3-butanedione monoxime and Blebbistatin hinder or modify the electrophysiological effects of acute mechanical stretch. METHODS The ventricular fibrillation (VF) modifications induced by acute mechanical stretch were studied in 27 Langendorff-perfused rabbit hearts using epicardial multiple electrodes and mapping techniques under control conditions (n = 9) and during the perfusion of 2,3-butanedione monoxime (15 mM) (n = 9) or Blebbistatin (10 μm) (n = 9). RESULTS In the control series, myocardial stretch increased the complexity of the activation maps and the dominant frequency (DF) of VF from 13.1 ± 2.0 Hz to 19.1 ± 3.1 Hz (P < 0.001, 46% increment). At baseline, the activation maps showed less complexity in both the 2,3-butanedione monoxime and Blebbistatin series, and the DF was lower in the 2,3-butanedione monoxime series (11.4 ± 1.2 Hz; P < 0.05). The accelerating effect of mechanical stretch was abolished under 2,3-butanedione monoxime (maximum DF = 11.7 ± 2.4 Hz, 5% increment, ns vs baseline, P < 0.0001 vs. control series) and reduced under Blebbistatin (maximum DF = 12.9 ± 0.7 Hz, 8% increment, P < 0.01 vs. baseline, P < 0.0001 vs. control series). The variations in complexity of the activation maps under stretch were not significant in the 2,3-butanedione monoxime series and were significantly attenuated under Blebbistatin. CONCLUSION The accelerating effect and increased complexity of myocardial activation during VF induced by acute mechanical stretch are abolished under the action of 2,3-butanedione monoxime and reduced under the action of Blebbistatin.
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Affiliation(s)
- L. Brines
- Department of Medicine; Valencia University, Estudi General; Valencia; Spain
| | - L. Such-Miquel
- Department of Physiotherapy; Valencia University, Estudi General; Valencia; Spain
| | - D. Gallego
- Department of Physiology; Valencia University, Estudi General; Valencia; Spain
| | - I. Trapero
- Department of Infirmary; Valencia University, Estudi General; Valencia; Spain
| | - I. del Canto
- Department of Medicine; Valencia University, Estudi General; Valencia; Spain
| | - M. Zarzoso
- Department of Physiology; Valencia University, Estudi General; Valencia; Spain
| | - C. Soler
- Department of Physiology; Valencia University, Estudi General; Valencia; Spain
| | - F. Pelechano
- Department of Medicine; Valencia University, Estudi General; Valencia; Spain
| | - J. Cánoves
- Service of Cardiology; Valencia University Clinic Hospital; INCLIVA, Valencia; Spain
| | - A. Alberola
- Department of Physiology; Valencia University, Estudi General; Valencia; Spain
| | - L. Such
- Department of Physiology; Valencia University, Estudi General; Valencia; Spain
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Cheng YJ, Lang D, Caruthers SD, Efimov IR, Chen J, Wickline SA. Focal but reversible diastolic sheet dysfunction reflects regional calcium mishandling in dystrophic mdx mouse hearts. Am J Physiol Heart Circ Physiol 2012; 303:H559-68. [PMID: 22777417 DOI: 10.1152/ajpheart.00321.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Cardiac dysfunction is a primary cause of patient mortality in Duchenne muscular dystrophy, potentially related to elevated cytosolic calcium. However, the regional versus global functional consequences of cellular calcium mishandling have not been defined in the whole heart. Here we sought for the first time to elucidate potential regional dependencies between calcium mishandling and myocardial fiber/sheet function as a manifestation of dystrophin-deficient (mdx) cardiomyopathy. Isolated-perfused hearts from 16-mo-old mdx (N = 10) and wild-type (WT; N = 10) were arrested sequentially in diastole and systole for diffusion tensor MRI quantification of myocardial sheet architecture and function. When compared with WT hearts, mdx hearts exhibited normal systolic sheet architecture but a lower diastolic sheet angle magnitude (|β|) in the basal region. The regional diastolic sheet dysfunction was normalized by reducing perfusate calcium concentrations. Optical mapping of calcium transients in isolated hearts (3 mdx and 4 WT) revealed a stretch-inducible regional defect of intracellular calcium reuptake, reflected by a 25% increase of decay times (T(50)) and decay constants, at the base of mdx hearts. The basal region of mdx hearts also exhibited greater fibrosis than did the apex, which matched the regional sheet dysfunction. We conclude that myocardial diastolic sheet dysfunction is observed initially in basal segments along with calcium mishandling, ultimately culminating in increased fibrosis. The preservation of relatively normal calcium reuptake and diastolic/systolic sheet mechanics throughout the rest of the heart, together with the rapid reversibility of functional defects by reducing cytosolic calcium, points to the significance of regional mechanical factors in the progression of the disease.
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Affiliation(s)
- Ya-Jian Cheng
- Cardiovascular Division, Washington University School of Medicine, Saint Louis, Missouri 63110, USA
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Asfour H, Swift L, Sarvazyan N, Doroslovački M, Kay M. Preprocessing of fluoresced transmembrane potential signals for cardiac optical mapping. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:227-30. [PMID: 22254291 DOI: 10.1109/iembs.2011.6090042] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Fluorescence imaging of transmembrane voltage-sensitive dyes is used to study electrical activation in cardiac tissue. However, fluorescence signals typically have a low signal to noise ratio that can be contaminated with motion artifacts. We describe an alternative processing approach for fluoresced transmembrane potentials (fTmps) using the wavelet multiresolution analysis. We show that fTmp signals can be decomposed and reconstructed to form three sub-signals that contain signal noise (noise signal), the early depolarization phase of the action potential (rTmp signal), and motion artifact (rMA signal). Discrete wavelet transform is used with coiflet 4 scaling and wavelet functions for fTmp decomposition and reconstruction of these sub-signals. Our results show that this type of analysis can be used to remove baseline drift, reduce noise, and reveal wavefronts. It streamlines the preprocessing of fTmps for subsequent measurement of activation times and conduction velocities. The approach is promising for studying wave fronts without aggressive mechanical tissue constraint or electromechanical uncoupling agents, and it is particularly useful for single camera systems that do not provide for ratiometric imaging.
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Affiliation(s)
- Huda Asfour
- The George Washington University, Washington, DC 20052, USA
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40
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Walton RD, Smith RM, Mitrea BG, White E, Bernus O, Pertsov AM. Extracting surface activation time from the optically recorded action potential in three-dimensional myocardium. Biophys J 2012; 102:30-8. [PMID: 22225795 DOI: 10.1016/j.bpj.2011.10.036] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 10/15/2011] [Accepted: 10/18/2011] [Indexed: 10/14/2022] Open
Abstract
Optical mapping has become an indispensible tool for studying cardiac electrical activity. However, due to the three-dimensional nature of the optical signal, the optical upstroke is significantly longer than the electrical upstroke. This raises the issue of how to accurately determine the activation time on the epicardial surface. The purpose of this study was to establish a link between the optical upstroke and exact surface activation time using computer simulations, with subsequent validation by a combination of microelectrode recordings and optical mapping experiments. To simulate wave propagation and associated optical signals, we used a hybrid electro-optical model. We found that the time of the surface electrical activation (t(E)) within the accuracy of our simulations coincided with the maximal slope of the optical upstroke (t(F)*) for a broad range of optical attenuation lengths. This was not the case when the activation time was determined at 50% amplitude (t(F50)) of the optical upstroke. The validation experiments were conducted in isolated Langendorff-perfused rat hearts and coronary-perfused pig left ventricles stained with either di-4-ANEPPS or the near-infrared dye di-4-ANBDQBS. We found that t(F)* was a more accurate measure of t(E) than was t(F50) in all experimental settings tested (P = 0.0002). Using t(F)* instead of t(F50) produced the most significant improvement in measurements of the conduction anisotropy and the transmural conduction time in pig ventricles.
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Affiliation(s)
- Richard D Walton
- Institute of Membrane and Systems Biology, Faculty of Biological Sciences, Multidisciplinary Cardiovascular Research Center, University of Leeds, Leeds, United Kingdom
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Bishop MJ, Rowley A, Rodriguez B, Plank G, Gavaghan DJ, Bub G. The role of photon scattering in voltage-calcium fluorescent recordings of ventricular fibrillation. Biophys J 2011; 101:307-18. [PMID: 21767482 DOI: 10.1016/j.bpj.2011.06.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 06/07/2011] [Accepted: 06/13/2011] [Indexed: 11/25/2022] Open
Abstract
Recent optical mapping studies of cardiac tissue suggest that membrane voltage (V(m)) and intracellular calcium concentrations (Ca) become dissociated during ventricular fibrillation (VF), generating a proarrhythmic substrate. However, experimental methods used in these studies may accentuate measured dissociation due to differences in fluorescent emission wavelengths of optical voltage/calcium (V(opt)/Ca(opt)) signals. Here, we simulate dual voltage-calcium optical mapping experiments using a monodomain-Luo-Rudy ventricular-tissue model coupled to a photon-diffusion model. Dissociation of both electrical, V(m)/Ca, and optical, V(opt)/Ca(opt), signals is quantified by calculating mutual information (MI) for VF and rapid pacing protocols. We find that photon scattering decreases MI of V(opt)/Ca(opt) signals by 23% compared to unscattered V(m)/Ca signals during VF. Scattering effects are amplified by increasing wavelength separation between fluorescent voltage/calcium signals and respective measurement-location misalignment. In contrast, photon scattering does not affect MI during rapid pacing, but high calcium dye affinity can decrease MI by attenuating alternans in Ca(opt) but not in V(opt). We conclude that some dissociation exists between voltage and calcium at the cellular level during VF, but MI differences are amplified by current optical mapping methods.
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Affiliation(s)
- Martin J Bishop
- Computing Laboratory, University of Oxford, Oxford, United Kingdom.
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Wall ST, Guccione JM, Ratcliffe MB, Sundnes JS. Electromechanical feedback with reduced cellular connectivity alters electrical activity in an infarct injured left ventricle: a finite element model study. Am J Physiol Heart Circ Physiol 2011; 302:H206-14. [PMID: 22058157 DOI: 10.1152/ajpheart.00272.2011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Myocardial infarction (MI) significantly alters the structure and function of the heart. As abnormal strain may drive heart failure and the generation of arrhythmias, we used computational methods to simulate a left ventricle with an MI over the course of a heartbeat to investigate strains and their potential implications to electrophysiology. We created a fully coupled finite element model of myocardial electromechanics consisting of a cellular physiological model, a bidomain electrical diffusion solver, and a nonlinear mechanics solver. A geometric mesh built from magnetic resonance imaging (MRI) measurements of an ovine left ventricle suffering from a surgically induced anteroapical infarct was used in the model, cycled through the cardiac loop of inflation, isovolumic contraction, ejection, and isovolumic relaxation. Stretch-activated currents were added as a mechanism of mechanoelectric feedback. Elevated fiber and cross fiber strains were observed in the area immediately adjacent to the aneurysm throughout the cardiac cycle, with a more dramatic increase in cross fiber strain than fiber strain. Stretch-activated channels decreased action potential (AP) dispersion in the remote myocardium while increasing it in the border zone. Decreases in electrical connectivity dramatically increased the changes in AP dispersion. The role of cross fiber strain in MI-injured hearts should be investigated more closely, since results indicate that these are more highly elevated than fiber strain in the border of the infarct. Decreases in connectivity may play an important role in the development of altered electrophysiology in the high-stretch regions of the heart.
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Affiliation(s)
- Samuel T Wall
- Center for Biomedical Computing, Simula Research Laboratory, Oslo, Norway.
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43
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Costa AR, Panda NC, Yong S, Mayorga ME, Pawlowski GP, Fan K, Penn MS, Laurita KR. Optical mapping of cryoinjured rat myocardium grafted with mesenchymal stem cells. Am J Physiol Heart Circ Physiol 2011; 302:H270-7. [PMID: 22037193 DOI: 10.1152/ajpheart.00019.2011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Mesenchymal stem cells (MSCs) have been shown to improve cardiac electrophysiology when administered in the setting of acute myocardial infarction. However, the electrophysiological phenotype of MSCs in situ is not clear. We hypothesize that MSCs delivered intramyocardially to cryoinjured myocardium can engraft, but will not actively generate, action potentials. Cryoinjury-induced scar was created on the left ventricular epicardial surface of adult rat hearts. Within 30 min, hearts were injected with saline (sham, n = 11) or bone marrow-derived MSCs (2 × 10(6)) labeled with 1,1'-dioctadecyl-3,3,3,3'-tetramethylindocarbocyanine percholate (DiI; n = 16). At 3 wk, optical mapping and cell isolation were used to measure optical action potentials and calcium transients, respectively. Histological analysis confirmed subepicardial scar thickness and the presence of DiI-positive cells that express connexin-43. Optical action potential amplitude within the scar at MSC-positive sites (53.8 ± 14.3%) was larger compared with sites devoid of MSCs (35.3 ± 14.2%, P < 0.05) and sites within the scar of shams (33.5 ± 6.9%, P < 0.05). Evidence of simultaneous action potential upstroke, the loss of action potential activity following ablation of adjacent viable myocardium, and no rapid calcium transient response in isolated DiI+ cells suggest that the electrophysiological influence of engrafted MSCs is electrotonic. MSCs can engraft when directly injected into a cryoinjury and are associated with evidence of action potential activity. However, our results suggest that this activity is not due to generation of action potentials, but rather passive influence coupled from neighboring viable myocardium.
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Affiliation(s)
- Andrea R Costa
- MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio, USA
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Veeraraghavan R, Salama ME, Poelzing S. Interstitial volume modulates the conduction velocity-gap junction relationship. Am J Physiol Heart Circ Physiol 2011; 302:H278-86. [PMID: 22021331 DOI: 10.1152/ajpheart.00868.2011] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiac conduction through gap junctions is an important determinant of arrhythmia susceptibility. Yet, the relationship between degrees of G(j) uncoupling and conduction velocity (θ) remains controversial. Conflicting results in similar experiments are normally attributed to experimental differences. We hypothesized that interstitial volume modulates conduction velocity and its dependence on G(j). Interstitial volume (V(IS)) was quantified histologically from guinea pig right ventricle. Optical mapping was used to quantify conduction velocity and anisotropy (AR(θ)). Albumin (4 g/l) decreased histologically assessed V(IS), increased transverse θ by 71 ± 10%, and lowered AR(θ). Furthermore, albumin did not change isolated cell size. Conversely, mannitol increased V(IS), decreased transverse θ by 24 ± 4%, and increased AR(θ). Mannitol also decreased cell width by 12%. Furthermore, mannitol was associated with spontaneous ventricular tachycardias in three of eight animals relative to zero of 15 during control. The θ-G(j) relationship was assessed using the G(j) uncoupler carbenoxolone (CBX). Whereas 13 μM CBX did not significantly affect θ during control, it slowed transverse θ by 38 ± 9% during mannitol (edema). These data suggest changes in V(IS) modulate θ, AR(θ), and the θ-G(j) relationship and thereby alter arrhythmia susceptibility. Therefore, V(IS) may underlie arrhythmia susceptibility, particularly in diseases associated with gap junction remodeling.
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Affiliation(s)
- Rengasayee Veeraraghavan
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, 84112-5000, USA
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45
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Biary N, Xie C, Kauffman J, Akar FG. Biophysical properties and functional consequences of reactive oxygen species (ROS)-induced ROS release in intact myocardium. J Physiol 2011; 589:5167-79. [PMID: 21825030 DOI: 10.1113/jphysiol.2011.214239] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Reactive oxygen species (ROS)-induced ROS release (RIRR) is a fundamental mechanism by which cardiac mitochondria respond to elevated ROS levels by stimulating endogenous ROS production in a regenerative, autocatalytic process that ultimately results in global oxidative stress (OS), cellular dysfunction and death. Despite elegant studies describing the phenomenon of RIRR under artificial conditions such as photo-induced oxidation of discrete regions within cardiomyocytes, the existence, biophysical properties and functional consequences of RIRR in intact myocardium remain unclear. Here, we used a semi-quantitative approach of optical superoxide (O(2)(-)) mapping using dihydroethidium (DHE) fluorescence to explore RIRR, its arrhythmic consequences and underlying mechanisms in intact myocardium. Initially, perfusion of rat hearts with 200 μM H(2)O(2) for 40 min (n = 4) elicited two distinct O(2)(-) peaks that were readily distinguished by their timing and amplitude. The first peak (P1), which was generated rapidly (within 5-8 min of H(2)O(2) perfusion) was associated with a relatively limited (10 ± 2%) rise in normalized O(2)(-) levels relative to baseline. In contrast, the second peak (P2) occurred 19-26 min following onset of H(2)O(2) perfusion and was associated with a significantly greater amplitude compared to P1. Spatio-temporal ROS mapping during P2 revealed active O(2)(-) propagation across the myocardium at a velocity of ~20 μm s(-1). Exposure of hearts (n = 18) to a short (10 min) episode of H(2)O(2) perfusion revealed consistent generation of P2 by high (≥200 μM, 8/8) but not lower (≤100 μM, 3/8) H(2)O(2) concentrations (P < 0.03). In these hearts, onset of P2 occurred following, not during, the 10 min OS protocol, consistent with RIRR. Importantly, P2 (+) hearts exhibited a markedly greater (by 3.8-fold, P < 0.001) arrhythmia score compared to P2 (-) hearts. To explore the mechanism underlying RIRR in intact myocardium, hearts were perfused with either cyclosporin A (CsA) or 4-chlorodiazepam (4-Cl-DZP) to inhibit the mitochondrial permeability transition pore (mPTP) or the inner membrane anion channel (IMAC), respectively. Surprisingly, perfusion with CsA failed to suppress (P = 0.75, n.s.) or even delay H(2)O(2)-induced P2 or the incidence of arrhythmias compared to untreated hearts. In sharp contrast, perfusion with 4-Cl-DZP markedly blunted O(2)(-) levels during P2, and suppressed the incidence of sustained ventricular tachycardia or ventricular fibrillation (VT/VF). Finally, perfusion of hearts with the synthetic superoxide dismutase/catalase mimetic EUK-134 completely abolished the H(2)O(2)-mediated RIRR response as well as the incidence of arrhythmias. These findings extend the concept of RIRR to the level of the intact heart, establish regenerative O(2)(-) production as the mediator of RIRR-related arrhythmias and reveal their strong dependence on IMAC and not the mPTP in this acute model of OS.
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Affiliation(s)
- Nora Biary
- Cardiovascular Institute, Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA
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Asfour H, Swift LM, Sarvazyan N, Doroslovački M, Kay MW. Signal decomposition of transmembrane voltage-sensitive dye fluorescence using a multiresolution wavelet analysis. IEEE Trans Biomed Eng 2011; 58:2083-93. [PMID: 21511560 DOI: 10.1109/tbme.2011.2143713] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Fluorescence imaging of transmembrane voltage-sensitive dyes is used to study electrical activation in cardiac tissue. However, the fluorescence signals, typically, have low SNRs and may be contaminated with motion artifact. In this report, we introduce a new processing approach for fluoresced transmembrane potentials (fTmps) that is based upon a discrete wavelet transform. We show how fTmp signals can be decomposed and reconstructed to form three subsignals that contain signal noise (noise signal), the early depolarization phase of the action potential (rTmp signal), and motion artifact (rMA signal). A coiflet4 wavelet is used for fTmp decomposition and reconstruction of these subsignals. Results using fTmp signals that are contaminated with motion artifact indicate that the approach is a useful processing step to remove baseline drift, reduce noise, and reveal wavefronts. It streamlines the preprocessing of fTmps for the subsequent measurement of activation times and conduction velocities. It is a promising approach for studying wavefronts without aggressive mechanical tissue constraint or electromechanical uncoupling agents and is, useful for single-camera systems that do not provide for ratiometric imaging.
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Affiliation(s)
- Huda Asfour
- Department of Electrical and Computer Engineering, The George Washington University, Washington, DC 20052, USA.
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Plummer BN, Cutler MJ, Wan X, Laurita KR. Spontaneous calcium oscillations during diastole in the whole heart: the influence of ryanodine reception function and gap junction coupling. Am J Physiol Heart Circ Physiol 2011; 300:H1822-8. [PMID: 21378143 DOI: 10.1152/ajpheart.00766.2010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Triggered arrhythmias due to spontaneous cytoplasmic calcium oscillations occur in a variety of disease conditions; however, their cellular mechanisms in tissue are not clear. We hypothesize that spontaneous calcium oscillations in the whole heart are due to calcium release from the sarcoplasmic reticulum and are facilitated by calcium diffusion through gap junctions. Optical mapping of cytoplasmic calcium from Langendorff perfused guinea pig hearts (n = 10) was performed using oxygenated Tyrode's solution (in mM): 140 NaCl, 0.7 MgCl, 4.5 KCl, 5.5 dextrose, 5 HEPES, and 5.5 CaCl₂ (pH 7.45, 34°C). Rapid pacing was used to induce diastolic calcium oscillations. In all preparations, pacing-induced multicellular diastolic calcium oscillations (m-SCR) occurred across most of the mapping field, at all pacing rates tested. Ryanodine (1 μM) eliminated all m-SCR activity. Low-dose caffeine (1 mM) increased m-SCR amplitude (+10.4 ± 4.4%, P < 0.05) and decreased m-SCR time-to-peak (-17.4 ± 6.7%, P < 0.05) and its temporal synchronization (i.e., range) across the mapping field (-26.9 ± 17.1%, P < 0.05). Surprisingly, carbenoxolone increased the amplitude of m-SCR activity (+14.8 ± 4.1%, P < 0.05) and decreased m-SCR time-to-peak (-11.3 ± 9.6%, P < 0.01) and its synchronization (-37.0 ± 19.1%, P < 0.05), similar to caffeine. In isolated myocytes, carbenoxolone (50 μM) had no effect on the frequency of aftercontractions, suggesting the effect of cell-to-cell uncoupling on m-SCR activity is tissue specific. Therefore, in the whole heart, overt m-SCR activity caused by calcium release from the SR can be induced over a broad range of pacing rates. Enhanced ryanodine receptor open probability and, surprisingly, decreased cell-to-cell coupling increased the amplitude and temporal synchronization of spontaneous calcium release in tissue.
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Affiliation(s)
- Bradley N Plummer
- Heart and Vascular Research Center, Department of Medicine, MetroHealth Campus, Case Western Reserve Univ, Cleveland, OH 44109-1997, USA
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Mitrea BG, Caldwell BJ, Pertsov AM. Imaging electrical excitation inside the myocardial wall. BIOMEDICAL OPTICS EXPRESS 2011; 2:620-633. [PMID: 21412467 PMCID: PMC3047367 DOI: 10.1364/boe.2.000620] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 02/11/2011] [Accepted: 02/13/2011] [Indexed: 05/26/2023]
Abstract
Cardiac arrhythmias are often triggered by ectopic membrane depolarization originating deep inside the myocardial wall. Here we propose a new method utilizing a novel near-infrared voltage-sensitive fluorescent dye DI-4-ANBDQBS to determine the three-dimensional (3D) coordinates of the sources of such depolarization. We tested the method in live preparations of pig left and right ventricular myocardium (thickness 8-18 mm) and phantoms imitating the optical properties of myocardial tissue. The method utilizes an alternating transillumination approach that involves comparing pairs of simultaneously recorded broad-field epifluorescence and transillumination images produced at two alternating directions of illumination. Recordings were taken simultaneously by two CCD cameras facing the endocardial and epicardial surfaces of the heart at a frame rate up to 3 KHz. In live preparations, we were able to localize the origin of the depolarization wave with a precision of ±1.3mm in the transmural direction and 3 mm in the image plane. The accuracy of detection was independent of the depth of the source inside ventricular wall.
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Piktel JS, Jeyaraj D, Said TH, Rosenbaum DS, Wilson LD. Enhanced dispersion of repolarization explains increased arrhythmogenesis in severe versus therapeutic hypothermia. Circ Arrhythm Electrophysiol 2010; 4:79-86. [PMID: 21163888 DOI: 10.1161/circep.110.958355] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
BACKGROUND Hypothermia is proarrhythmic, and, as the use of therapeutic hypothermia (TH) increases, it is critically important to understand the electrophysiological effects of hypothermia on cardiac myocytes and arrhythmia substrates. We tested the hypothesis that hypothermia-enhanced transmural dispersion of repolarization (DOR) is a mechanism of arrhythmogenesis in hypothermia. In addition, we investigated whether the degree of hypothermia, the rate of temperature change, and cooling versus rewarming would alter hypothermia-induced arrhythmia substrates. METHODS AND RESULTS Optical action potentials were recorded from cells spanning the transmural wall of canine left ventricular wedge preparations at baseline (36°C), during cooling and during rewarming. Electrophysiological parameters were examined while varying the depth of hypothermia. On cooling to 26°C, DOR increased from 26±4 ms to 93±18 ms (P=0.021); conduction velocity decreased from 35±5 cm/s to 22±5 cm/s (P=0.010). On rewarming to 36°C, DOR remained prolonged, whereas conduction velocity returned to baseline. Conduction block and reentry was observed in all severe hypothermia preparations. Ventricular fibrillation/ventricular tachycardia was seen more during rewarming (4/5) versus cooling (2/6). In TH (n=7), cooling to 32°C mildly increased DOR (31±6 to 50±9, P=0.012), with return to baseline on rewarming and was associated with decreased arrhythmia susceptibility. Increased rate of cooling did not further enhance DOR or arrhythmogenesis. CONCLUSIONS Hypothermia amplifies DOR and is a mechanism for arrhythmogenesis. DOR is directly dependent on the depth of cooling and rewarming. This provides insight into the clinical observation of a low incidence of arrhythmias in TH and has implications for protocols for the clinical application of TH.
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Affiliation(s)
- Joseph S Piktel
- The Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, Cleveland, OH, USA.
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Benson AP, Bernus O, Dierckx H, Gilbert SH, Greenwood JP, Holden AV, Mohee K, Plein S, Radjenovic A, Ries ME, Smith GL, Sourbron S, Walton RD. Construction and validation of anisotropic and orthotropic ventricular geometries for quantitative predictive cardiac electrophysiology. Interface Focus 2010; 1:101-16. [PMID: 22419977 DOI: 10.1098/rsfs.2010.0005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 11/08/2010] [Indexed: 11/12/2022] Open
Abstract
Reaction-diffusion computational models of cardiac electrophysiology require both dynamic excitation models that reconstruct the action potentials of myocytes as well as datasets of cardiac geometry and architecture that provide the electrical diffusion tensor D, which determines how excitation spreads through the tissue. We illustrate an experimental pipeline we have developed in our laboratories for constructing and validating such datasets. The tensor D changes with location in the myocardium, and is determined by tissue architecture. Diffusion tensor magnetic resonance imaging (DT-MRI) provides three eigenvectors e(i) and eigenvalues λ(i) at each voxel throughout the tissue that can be used to reconstruct this architecture. The primary eigenvector e(1) is a histologically validated measure of myocyte orientation (responsible for anisotropic propagation). The secondary and tertiary eigenvectors (e(2) and e(3)) specify the directions of any orthotropic structure if λ(2) is significantly greater than λ(3)-this orthotropy has been identified with sheets or cleavage planes. For simulations, the components of D are scaled in the fibre and cross-fibre directions for anisotropic simulations (or fibre, sheet and sheet normal directions for orthotropic tissues) so that simulated conduction velocities match values from optical imaging or plunge electrode experiments. The simulated pattern of propagation of action potentials in the models is partially validated by optical recordings of spatio-temporal activity on the surfaces of hearts. We also describe several techniques that enhance components of the pipeline, or that allow the pipeline to be applied to different areas of research: Q ball imaging provides evidence for multi-modal orientation distributions within a fraction of voxels, infarcts can be identified by changes in the anisotropic structure-irregularity in myocyte orientation and a decrease in fractional anisotropy, clinical imaging provides human ventricular geometry and can identify ischaemic and infarcted regions, and simulations in human geometries examine the roles of anisotropic and orthotropic architecture in the initiation of arrhythmias.
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Affiliation(s)
- Alan P Benson
- Institute of Membrane and Systems Biology , University of Leeds , Leeds LS2 9JT , UK
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