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Lerman BB, Markowitz SM, Cheung JW, Thomas G, Ip JE. Ventricular Tachycardia Due to Triggered Activity: Role of Early and Delayed Afterdepolarizations. JACC Clin Electrophysiol 2024; 10:379-401. [PMID: 38127010 DOI: 10.1016/j.jacep.2023.10.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 10/24/2023] [Accepted: 10/28/2023] [Indexed: 12/23/2023]
Abstract
Most forms of sustained ventricular tachycardia (VT) are caused by re-entry, resulting from altered myocardial conduction and refractoriness secondary to underlying structural heart disease. In contrast, VT caused by triggered activity (TA) is unrelated to an abnormal structural substrate and is often caused by molecular defects affecting ion channel function or regulation of intracellular calcium cycling. This review summarizes the cellular and molecular bases underlying TA and exemplifies their clinical relevance with selective representative scenarios. The underlying basis of TA caused by delayed afterdepolarizations is related to sarcoplasmic reticulum calcium overload, calcium waves, and diastolic sarcoplasmic reticulum calcium leak. Clinical examples of TA caused by delayed afterdepolarizations include sustained right and left ventricular outflow tract tachycardia and catecholaminergic polymorphic VT. The other form of afterpotentials, early afterdepolarizations, are systolic events and inscribe early afterdepolarizations during phase 2 or phase 3 of the action potential. The fundamental defect is a decrease in repolarization reserve with associated increases in late plateau inward currents. Malignant ventricular arrhythmias in the long QT syndromes are initiated by early afterdepolarization-mediated TA. An understanding of the molecular and cellular bases of these arrhythmias has resulted in generally effective pharmacologic-based therapies, but these are nonspecific agents that have off-target effects. Therapeutic efficacy may need to be augmented with an implantable defibrillator. Next-generation therapies will include novel agents that rescue arrhythmogenic abnormalities in cellular signaling pathways and gene therapy approaches that transfer or edit pathogenic gene variants or silence mutant messenger ribonucleic acid.
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Affiliation(s)
- Bruce B Lerman
- Department of Medicine, Division of Cardiology and the Greenberg Institute for Cardiac Electrophysiology, Department of Medicine, Cornell University Medical Center, New York, New York, USA.
| | - Steven M Markowitz
- Department of Medicine, Division of Cardiology and the Greenberg Institute for Cardiac Electrophysiology, Department of Medicine, Cornell University Medical Center, New York, New York, USA
| | - Jim W Cheung
- Department of Medicine, Division of Cardiology and the Greenberg Institute for Cardiac Electrophysiology, Department of Medicine, Cornell University Medical Center, New York, New York, USA
| | - George Thomas
- Department of Medicine, Division of Cardiology and the Greenberg Institute for Cardiac Electrophysiology, Department of Medicine, Cornell University Medical Center, New York, New York, USA
| | - James E Ip
- Department of Medicine, Division of Cardiology and the Greenberg Institute for Cardiac Electrophysiology, Department of Medicine, Cornell University Medical Center, New York, New York, USA
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2
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Wang R, Qu Z, Huang X. Dissecting the roles of calcium cycling and its coupling with voltage in the genesis of early afterdepolarizations in cardiac myocyte models. PLoS Comput Biol 2024; 20:e1011930. [PMID: 38416778 PMCID: PMC10927084 DOI: 10.1371/journal.pcbi.1011930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Revised: 03/11/2024] [Accepted: 02/19/2024] [Indexed: 03/01/2024] Open
Abstract
Early afterdepolarizations (EADs) are abnormal depolarizations during the plateau phase of the action potential, which are known to be associated with lethal arrhythmias in the heart. There are two major hypotheses for EAD genesis based on experimental observations, i.e., the voltage (Vm)-driven and intracellular calcium (Ca)-driven mechanisms. In ventricular myocytes, Ca and Vm are bidirectionally coupled, which can affect each other's dynamics and result in new dynamics, however, the roles of Ca cycling and its coupling with Vm in the genesis of EADs have not been well understood. In this study, we use an action potential model that is capable of independent Vm and Ca oscillations to investigate the roles of Vm and Ca coupling in EAD genesis. Four different mechanisms of EADs are identified, which are either driven by Vm oscillations or Ca oscillations alone, or oscillations caused by their interactions. We also use 5 other ventricular action potential models to assess these EAD mechanisms and show that EADs in these models are mainly Vm-driven. These mechanistic insights from our simulations provide a theoretical base for understanding experimentally observed EADs and EAD-related arrhythmogenesis.
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Affiliation(s)
- Rui Wang
- Department of Physics, South China University of Technology, Guangzhou, China
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Xiaodong Huang
- Department of Physics, South China University of Technology, Guangzhou, China
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3
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Kikel-Coury NL, Brandt JP, Correia IA, O’Dea MR, DeSantis DF, Sterling F, Vaughan K, Ozcebe G, Zorlutuna P, Smith CJ. Identification of astroglia-like cardiac nexus glia that are critical regulators of cardiac development and function. PLoS Biol 2021; 19:e3001444. [PMID: 34793438 PMCID: PMC8601506 DOI: 10.1371/journal.pbio.3001444] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 10/18/2021] [Indexed: 01/09/2023] Open
Abstract
Glial cells are essential for functionality of the nervous system. Growing evidence underscores the importance of astrocytes; however, analogous astroglia in peripheral organs are poorly understood. Using confocal time-lapse imaging, fate mapping, and mutant genesis in a zebrafish model, we identify a neural crest-derived glial cell, termed nexus glia, which utilizes Meteorin signaling via Jak/Stat3 to drive differentiation and regulate heart rate and rhythm. Nexus glia are labeled with gfap, glast, and glutamine synthetase, markers that typically denote astroglia cells. Further, analysis of single-cell sequencing datasets of human and murine hearts across ages reveals astrocyte-like cells, which we confirm through a multispecies approach. We show that cardiac nexus glia at the outflow tract are critical regulators of both the sympathetic and parasympathetic system. These data establish the crucial role of glia on cardiac homeostasis and provide a description of nexus glia in the PNS.
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Affiliation(s)
- Nina L. Kikel-Coury
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
- Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Jacob P. Brandt
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
- Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Isabel A. Correia
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Michael R. O’Dea
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Dana F. DeSantis
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
- Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Felicity Sterling
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Kevin Vaughan
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Gulberk Ozcebe
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Pinar Zorlutuna
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Cody J. Smith
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
- Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, Indiana, United States of America
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Ip JE, Xu L, Dai J, Steegborn C, Jaffré F, Evans T, Cheung JW, Basson CT, Panaghie G, Krogh-Madsen T, Abbott GW, Lerman BB. Constitutively Activating GNAS Somatic Mutation in Right Ventricular Outflow Tract Tachycardia. Circ Arrhythm Electrophysiol 2021; 14:e010082. [PMID: 34587755 PMCID: PMC8569928 DOI: 10.1161/circep.121.010082] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- James E. Ip
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Linna Xu
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Jie Dai
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Clemens Steegborn
- Department of Biochemistry, Weill-Cornell Medical College, New York, NY
- Present Address: Department of Biochemistry, University of Bayreuth, Germany
| | - Fabrice Jaffré
- Department of Surgery, Weill-Cornell Medical College, New York, NY
| | - Todd Evans
- Department of Surgery, Weill-Cornell Medical College, New York, NY
| | - Jim W. Cheung
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Craig T. Basson
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
- Present Address: Boston Pharmaceuticals, Cambridge, MA
| | - Gianina Panaghie
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Trine Krogh-Madsen
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Geoffrey W. Abbott
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
- Present Address: Department of Physiology & Biophysics, University of California, Irvine, CA
| | - Bruce B. Lerman
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
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5
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Magyar T, Árpádffy-Lovas T, Pászti B, Tóth N, Szlovák J, Gazdag P, Kohajda Z, Gyökeres A, Györe B, Gurabi Z, Jost N, Virág L, Papp JG, Nagy N, Koncz I. Muscarinic agonists inhibit the ATP-dependent potassium current and suppress the ventricle-Purkinje action potential dispersion. Can J Physiol Pharmacol 2021; 99:247-253. [PMID: 33242286 DOI: 10.1139/cjpp-2020-0408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Activation of the parasympathetic nervous system has been reported to have an antiarrhythmic role during ischemia-reperfusion injury by decreasing the arrhythmia triggers. Furthermore, it was reported that the parasympathetic neurotransmitter acetylcholine is able to modulate the ATP-dependent potassium current (I K-ATP), a crucial current activated during hypoxia. However, the possible significance of this current modulation in the antiarrhythmic mechanism is not fully clarified. Action potentials were measured using the conventional microelectrode technique from canine left ventricular papillary muscle and free-running Purkinje fibers, under normal and hypoxic conditions. Ionic currents were measured using the whole-cell configuration of the patch-clamp method. Acetylcholine at 5 μmol/L did not influence the action potential duration (APD) either in Purkinje fibers or in papillary muscle preparations. In contrast, it significantly lengthened the APD and suppressed the Purkinje-ventricle APD dispersion when it was administered after 5 μmol/L pinacidil application. Carbachol at 3 μmol/L reduced the pinacidil-activated I K-ATP under voltage-clamp conditions. Acetylcholine lengthened the ventricular action potential under simulated ischemia condition. In this study, we found that acetylcholine inhibits the I K-ATP and thus suppresses the ventricle-Purkinje APD dispersion. We conclude that parasympathetic tone may reduce the arrhythmogenic substrate exerting a complex antiarrhythmic mechanism during hypoxic conditions.
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Affiliation(s)
- Tibor Magyar
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Tamás Árpádffy-Lovas
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Bence Pászti
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Noémi Tóth
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Jozefina Szlovák
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Péter Gazdag
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Zsófia Kohajda
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - András Gyökeres
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Balázs Györe
- Faculty of Dentistry, University of Szeged, Hungary
| | - Zsolt Gurabi
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Norbert Jost
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Julius Gy Papp
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - István Koncz
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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6
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Adenosine and the Cardiovascular System: The Good and the Bad. J Clin Med 2020; 9:jcm9051366. [PMID: 32384746 PMCID: PMC7290927 DOI: 10.3390/jcm9051366] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 04/27/2020] [Accepted: 04/29/2020] [Indexed: 12/18/2022] Open
Abstract
Adenosine is a nucleoside that impacts the cardiovascular system via the activation of its membrane receptors, named A1R, A2AR, A2BR and A3R. Adenosine is released during hypoxia, ischemia, beta-adrenergic stimulation or inflammation and impacts heart rhythm and produces strong vasodilation in the systemic, coronary or pulmonary vascular system. This review summarizes the main role of adenosine on the cardiovascular system in several diseases and conditions. Adenosine release participates directly in the pathophysiology of atrial fibrillation and neurohumoral syncope. Adenosine has a key role in the adaptive response in pulmonary hypertension and heart failure, with the most relevant effects being slowing of heart rhythm, coronary vasodilation and decreasing blood pressure. In other conditions, such as altitude or apnea-induced hypoxia, obstructive sleep apnea, or systemic hypertension, the adenosinergic system activation appears in a context of an adaptive response. Due to its short half-life, adenosine allows very rapid adaptation of the cardiovascular system. Finally, the effects of adenosine on the cardiovascular system are sometimes beneficial and other times harmful. Future research should aim to develop modulating agents of adenosine receptors to slow down or conversely amplify the adenosinergic response according to the occurrence of different pathologic conditions.
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7
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Matthews GDK, Grace AA. Unmasking Adenosine: The Purinergic Signalling Molecule Critical to Arrhythmia Pathophysiology and Management. Arrhythm Electrophysiol Rev 2020; 8:240-248. [PMID: 32685154 PMCID: PMC7358948 DOI: 10.15420/aer.2019.05] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Adenosine was identified in 1929 and immediately recognised as having a potential role in therapy for arrhythmia because of its negative chronotropic and dromotropic effects. Adenosine entered mainstream use in the 1980s as a highly effective agent for the termination of supraventricular tachycardia (SVT) involving the atrioventricular node, as well as for its ability to unmask the underlying rhythm in other SVTs. Adenosine has subsequently been found to have applications in interventional electrophysiology. While considered a safe agent because of its short half-life, adenosine may provoke arrhythmias in the form of AF, bradyarrhythmia and ventricular tachyarrhythmia. Adenosine is also associated with bronchospasm, although this may reflect irritant-induced dyspnoea rather than true obstruction. Adenosine is linked to numerous pathologies relevant to arrhythmia predisposition, including heart failure, obesity, ischaemia and the ageing process itself. This article examines 90 years of experience with adenosine in the light of new European Society of Cardiology guidelines for the management of SVT.
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Affiliation(s)
- Gareth DK Matthews
- Cambridge University NHS Foundation Trust, Cambridge, UK; Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK
| | - Andrew A Grace
- Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK; Department of Biochemistry, University of Cambridge, Cambridge, UK
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Huang X, Song Z, Qu Z. Determinants of early afterdepolarization properties in ventricular myocyte models. PLoS Comput Biol 2018; 14:e1006382. [PMID: 30475801 PMCID: PMC6283611 DOI: 10.1371/journal.pcbi.1006382] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 12/06/2018] [Accepted: 09/17/2018] [Indexed: 12/20/2022] Open
Abstract
Early afterdepolarizations (EADs) are spontaneous depolarizations during the repolarization phase of an action potential in cardiac myocytes. It is widely known that EADs are promoted by increasing inward currents and/or decreasing outward currents, a condition called reduced repolarization reserve. Recent studies based on bifurcation theories show that EADs are caused by a dual Hopf-homoclinic bifurcation, bringing in further mechanistic insights into the genesis and dynamics of EADs. In this study, we investigated the EAD properties, such as the EAD amplitude, the inter-EAD interval, and the latency of the first EAD, and their major determinants. We first made predictions based on the bifurcation theory and then validated them in physiologically more detailed action potential models. These properties were investigated by varying one parameter at a time or using parameter sets randomly drawn from assigned intervals. The theoretical and simulation results were compared with experimental data from the literature. Our major findings are that the EAD amplitude and takeoff potential exhibit a negative linear correlation; the inter-EAD interval is insensitive to the maximum ionic current conductance but mainly determined by the kinetics of ICa,L and the dual Hopf-homoclinic bifurcation; and both inter-EAD interval and latency vary largely from model to model. Most of the model results generally agree with experimental observations in isolated ventricular myocytes. However, a major discrepancy between modeling results and experimental observations is that the inter-EAD intervals observed in experiments are mainly between 200 and 500 ms, irrespective of species, while those of the mathematical models exhibit a much wider range with some models exhibiting inter-EAD intervals less than 100 ms. Our simulations show that the cause of this discrepancy is likely due to the difference in ICa,L recovery properties in different mathematical models, which needs to be addressed in future action potential model development. Early afterdepolarizations (EADs) are abnormal depolarizations during the plateau phase of action potential in cardiac myocytes, arising from a dual Hopf-homoclinic bifurcation. The same bifurcations are also responsible for certain types of bursting behaviors in other cell types, such as beta cells and neuronal cells. EADs are known to play important role in the genesis of lethal arrhythmias and have been widely studied in both experiments and computer models. However, a detailed comparison between the properties of EADs observed in experiments and those from mathematical models have not been carried out. In this study, we performed theoretical analyses and computer simulations of different ventricular action potential models as well as different species to investigate the properties of EADs and compared these properties to those observed in experiments. While the EAD properties in the action potential models capture many of the EAD properties seen in experiments, the inter-EAD intervals in the computer models differ a lot from model to model, and some of them show very large discrepancy with those observed in experiments. This discrepancy needs to be addressed in future cardiac action potential model development.
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Affiliation(s)
- Xiaodong Huang
- Department of Physics, South China University of Technology, Guangzhou, China
| | - Zhen Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- * E-mail:
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Sohinki DA, Mathew ST. Ventricular Arrhythmias in the Patient with a Structurally Normal Heart. J Innov Card Rhythm Manag 2018; 9:3338-3353. [PMID: 32477784 PMCID: PMC7252725 DOI: 10.19102/icrm.2018.091004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 02/04/2018] [Indexed: 11/24/2022] Open
Abstract
Ventricular arrhythmias (VAs) are among the most common cardiac rhythm disturbances encountered in clinical practice. Patients presenting with frequent ventricular ectopy or sustained ventricular tachycardia represent a challenging and worrisome clinical scenario for many practitioners because of concerning symptoms, frequent associated acute hemodynamic compromise, and the adverse prognostic implications inherent to these cases. While an underlying structural or functional cardiac abnormality, metabolic derangement, or medication toxicity is often readily apparent, many patients have no obvious underlying condition, despite a comprehensive diagnostic evaluation. Such patients are diagnosed as having an idiopathic VA, which is a label with specific implications regarding arrhythmia origin, prognosis, and potential for pharmacologic and invasive management. Further, a subset of patients with otherwise benign idiopathic ventricular ectopy can present with polymorphic ventricular tachycardia and ventricular fibrillation, adding a layer of complexity to a clinical syndrome previously felt to have a benign clinical course. Thus, this review seeks to highlight the most common types of idiopathic VAs with a focus on their prognostic implications, underlying electrophysiologic mechanisms, unique electrocardiographic signatures, and considerations for invasive electrophysiologic study and catheter ablation. We further address some of the data regarding idiopathic ventricular fibrillation with respect to the heterogeneous nature of this diagnosis.
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Affiliation(s)
- Daniel A Sohinki
- Department of Cardiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Sunil T Mathew
- Department of Cardiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.,Heart Rhythm Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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10
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Lerman BB, Cheung JW, Ip JE, Liu CF, Thomas G, Markowitz SM. Mechanistic subtypes of focal right ventricular tachycardia. J Cardiovasc Electrophysiol 2018; 29:1181-1188. [DOI: 10.1111/jce.13505] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Accepted: 03/19/2018] [Indexed: 11/28/2022]
Affiliation(s)
- Bruce B. Lerman
- Division of Cardiology, Department of Medicine; Cornell University Medical Center, New York Presbyterian Hospital; New York NY USA
| | - Jim W. Cheung
- Division of Cardiology, Department of Medicine; Cornell University Medical Center, New York Presbyterian Hospital; New York NY USA
| | - James E. Ip
- Division of Cardiology, Department of Medicine; Cornell University Medical Center, New York Presbyterian Hospital; New York NY USA
| | - Christopher F. Liu
- Division of Cardiology, Department of Medicine; Cornell University Medical Center, New York Presbyterian Hospital; New York NY USA
| | - George Thomas
- Division of Cardiology, Department of Medicine; Cornell University Medical Center, New York Presbyterian Hospital; New York NY USA
| | - Steven M. Markowitz
- Division of Cardiology, Department of Medicine; Cornell University Medical Center, New York Presbyterian Hospital; New York NY USA
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11
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Wang Y, Wilson C, Cartwright EJ, Lei M. Plasma membrane Ca 2+ -ATPase 1 is required for maintaining atrial Ca 2+ homeostasis and electrophysiological stability in the mouse. J Physiol 2017; 595:7383-7398. [PMID: 29023784 PMCID: PMC5730856 DOI: 10.1113/jp274110] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 10/06/2017] [Indexed: 11/22/2022] Open
Abstract
Key points The role of plasma membrane Ca2+‐ATPase 1 (PMCA1) in Ca2+ homeostasis and electrical stability in atrial tissue has been investigated at both organ and cellular levels in mice with cardiomyocyte‐specific deletion of PMCA1 (PMCA1cko) The PMCA1cko hearts became more susceptible to atrial arrhythmic stress conditions than PMCA1loxP/loxP hearts. PMCA1 deficiency alters cellular Ca2+ homeostasis under both baseline and stress conditions. PMCA1 is required for maintaining cellular Ca2+ homeostasis and electrical stability in murine atria under stress conditions.
Abstract To determine the role of plasma membrane Ca2+‐ATPase 1 (PMCA1) in maintaining Ca2+ homeostasis and electrical stability in the atrium under physiological and stress conditions, mice with a cardiomyocyte‐specific deletion of PMCA1 (PMCA1cko) and their control littermates (PMCA1loxP/loxP) were studied at the organ and cellular levels. At the organ level, the PMCA1cko hearts became more susceptible to atrial arrhythmias under rapid programmed electrical stimulation compared with the PMCA1loxP/loxP hearts, and such arrhythmic events became more severe under Ca2+ overload conditions. At the cellular level, the occurrence of irregular‐type action potentials of PMCA1cko atrial myocytes increased significantly under Ca2+ overload conditions and/or at higher frequency of stimulation. The decay of Na+/Ca2+ exchanger current that followed a stimulation protocol was significantly prolonged in PMCA1cko atrial myocytes under basal conditions, with Ca2+ overload leading to even greater prolongation. In conclusion, PMCA1 is required for maintaining Ca2+ homeostasis and electrical stability in the atrium. This is particularly critical during fast removal of Ca2+ from the cytosol, which is required under stress conditions. The role of plasma membrane Ca2+‐ATPase 1 (PMCA1) in Ca2+ homeostasis and electrical stability in atrial tissue has been investigated at both organ and cellular levels in mice with cardiomyocyte‐specific deletion of PMCA1 (PMCA1cko) The PMCA1cko hearts became more susceptible to atrial arrhythmic stress conditions than PMCA1loxP/loxP hearts. PMCA1 deficiency alters cellular Ca2+ homeostasis under both baseline and stress conditions. PMCA1 is required for maintaining cellular Ca2+ homeostasis and electrical stability in murine atria under stress conditions.
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Affiliation(s)
- Yanwen Wang
- Department of Pharmacology, University of Oxford, Oxford, UK.,Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Claire Wilson
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Elizabeth J Cartwright
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Ming Lei
- Department of Pharmacology, University of Oxford, Oxford, UK
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12
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13
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Burnstock G, Pelleg A. Cardiac purinergic signalling in health and disease. Purinergic Signal 2015; 11:1-46. [PMID: 25527177 PMCID: PMC4336308 DOI: 10.1007/s11302-014-9436-1] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 11/25/2014] [Indexed: 01/09/2023] Open
Abstract
This review is a historical account about purinergic signalling in the heart, for readers to see how ideas and understanding have changed as new experimental results were published. Initially, the focus is on the nervous control of the heart by ATP as a cotransmitter in sympathetic, parasympathetic, and sensory nerves, as well as in intracardiac neurons. Control of the heart by centers in the brain and vagal cardiovascular reflexes involving purines are also discussed. The actions of adenine nucleotides and nucleosides on cardiomyocytes, atrioventricular and sinoatrial nodes, cardiac fibroblasts, and coronary blood vessels are described. Cardiac release and degradation of ATP are also described. Finally, the involvement of purinergic signalling and its therapeutic potential in cardiac pathophysiology is reviewed, including acute and chronic heart failure, ischemia, infarction, arrhythmias, cardiomyopathy, syncope, hypertrophy, coronary artery disease, angina, diabetic cardiomyopathy, as well as heart transplantation and coronary bypass grafts.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF, UK,
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Lerman BB. Outflow tract ventricular arrhythmias: An update. Trends Cardiovasc Med 2015; 25:550-8. [PMID: 25846938 DOI: 10.1016/j.tcm.2015.01.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 01/22/2015] [Accepted: 01/22/2015] [Indexed: 11/25/2022]
Abstract
During the last 20 years, the molecular etiology for many ventricular tachyarrhythmias once referred to as "idiopathic," has been elucidated. These arrhythmias are due to mutations in ion channels or structural proteins and include ventricular tachyarrhythmias due to long and short QT syndromes, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia (VT). However, the basis for the most common form of idiopathic ventricular arrhythmia, which originates from right or left ventricular outflow tracts, has remained elusive. Although traditionally considered a benign ventricular arrhythmia, it is now appreciated that some outflow tract arrhythmias also trigger polymorphic VT or sudden cardiac death or result in cardiomyopathy. The current understanding of outflow tract arrhythmias will be examined.
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Affiliation(s)
- Bruce B Lerman
- Department of Medicine, Cornell University Medical Center, New York, NY.
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LERMAN BRUCEB, IP JAMESE, SHAH BINDIK, THOMAS GEORGE, LIU CHRISTOPHERF, CIACCIO EDWARDJ, WIT ANDREWL, CHEUNG JIMW, MARKOWITZ STEVENM. Mechanism-Specific Effects of Adenosine on Ventricular Tachycardia. J Cardiovasc Electrophysiol 2014; 25:1350-8. [DOI: 10.1111/jce.12510] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 07/07/2014] [Accepted: 07/25/2014] [Indexed: 11/30/2022]
Affiliation(s)
- BRUCE B. LERMAN
- Division of Cardiology; Department of Medicine; Cornell University Medical Center; New York USA
| | - JAMES E. IP
- Division of Cardiology; Department of Medicine; Cornell University Medical Center; New York USA
| | - BINDI K. SHAH
- Division of Cardiology; Department of Medicine; Cornell University Medical Center; New York USA
| | - GEORGE THOMAS
- Division of Cardiology; Department of Medicine; Cornell University Medical Center; New York USA
| | - CHRISTOPHER F. LIU
- Division of Cardiology; Department of Medicine; Cornell University Medical Center; New York USA
| | - EDWARD J. CIACCIO
- Department of Pharmacology; College of Physicians and Surgeons; Columbia University; New York USA
| | - ANDREW L. WIT
- Department of Pharmacology; College of Physicians and Surgeons; Columbia University; New York USA
| | - JIM W. CHEUNG
- Division of Cardiology; Department of Medicine; Cornell University Medical Center; New York USA
| | - STEVEN M. MARKOWITZ
- Division of Cardiology; Department of Medicine; Cornell University Medical Center; New York USA
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Xie Y, Grandi E, Puglisi JL, Sato D, Bers DM. β-adrenergic stimulation activates early afterdepolarizations transiently via kinetic mismatch of PKA targets. J Mol Cell Cardiol 2013; 58:153-61. [PMID: 23481579 DOI: 10.1016/j.yjmcc.2013.02.009] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 01/25/2013] [Accepted: 02/11/2013] [Indexed: 02/04/2023]
Abstract
Sympathetic stimulation regulates cardiac excitation-contraction coupling in hearts but can also trigger ventricular arrhythmias caused by early afterdepolarizations (EADs) in pathological conditions. Isoproterenol (ISO) stimulation can transiently cause EADs which could result from differential kinetics of L-type Ca current (ICaL) vs. delayed rectifier potassium current (IKs) effects, but multiple PKA targets complicate mechanistic analysis. Utilizing a biophysically detailed model integrating Ca and β-adrenergic signaling, we investigate how different phosphorylation kinetics and targets influence β-adrenergic-induced transient EADs. We found that: 1) The faster time course of ICaL vs. IKs increases recapitulates experimentally observed ISO-induced transient EADs (which are due to ICaL reactivation). These EADs disappear at steady state ISO and do not occur during more gradual ISO application. 2) This ICaL vs. IKs kinetic mismatch with ISO can also induce transient EADs due to spontaneous sarcoplasmic reticulum (SR) Ca release and Na/Ca exchange current. The increased ICaL, SR Ca uptake and action potential duration (APD) raise SR Ca to cause spontaneous SR Ca release, but eventual IKs activation and APD shortening abolish these EADs. 3) Phospholemman (PLM) phosphorylation decreases both types of EADs by increasing outward Na/K-ATPase current (INaK) for ICaL-mediated EADs, and reducing intracellular Na and Ca loading for SR Ca-release-mediated EADs. Slowing PLM phosphorylation kinetics abolishes this protective effect. 4) Blocking phospholamban (PLB) phosphorylation has little effect on ICaL-mediated transient EADs, but abolishes SR Ca-release-mediated transient EADs by limiting SR Ca loading. 5) RyR phosphorylation has little effect on either transient EAD type. Our study emphasizes the importance of understanding non-steady state kinetics of several systems in mediating β-adrenergic-induced EADs and arrhythmias.
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Affiliation(s)
- Yuanfang Xie
- Department of Pharmacology, University of California Davis, Davis, CA, USA
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17
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Jakobsen Ø, Næsheim T, Aas KN, Sørlie D, Steensrud T. Adenosine instead of supranormal potassium in cardioplegia: it is safe, efficient, and reduces the incidence of postoperative atrial fibrillation. A randomized clinical trial. J Thorac Cardiovasc Surg 2012; 145:812-8. [PMID: 22964356 DOI: 10.1016/j.jtcvs.2012.07.058] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 07/08/2012] [Accepted: 07/26/2012] [Indexed: 10/27/2022]
Abstract
OBJECTIVE We aimed to evaluate the efficacy and safety of a cold crystalloid cardioplegic solution with adenosine (1.2 mmol/L) instead of supranormal potassium. METHODS Sixty low-risk patients scheduled for elective coronary artery bypass grafting (CABG) were randomized to receive standard cold crystalloid hyperkalemic cardioplegia (hyperkalemic group) or normokalemic cardioplegia in which supranormal potassium was replaced with 1.2 mmol/L adenosine (adenosine group). End points were postoperative release of troponin T and creatine kinase MB, hemodynamics measured by PiCCO arterial thermodilution catheters, perioperative release of markers of endothelial activation and injury, and clinical course. RESULTS The adenosine group had a significantly shorter time to arrest than did the hyperkalemic group (mean ± standard deviation, 11 ± 5 vs 44 ± 18 seconds; P < .001). Three hearts in the adenosine group were probably not adequately drained and received additional hyperkalemic cardioplegia to maintain satisfactory cardioplegic arrest. There were no differences between groups with respect to perioperative release of markers of endothelial activation or injury and no differences between groups in postoperative release of troponin T or creatine kinase MB. Postoperative hemodynamics including cardiac index were similar between groups. The incidence of postoperative atrial fibrillation was significantly lower in the adenosine group than in the hyperkalemic group (4 vs 15; P = .01). CONCLUSIONS Adenosine instead of hyperkalemia in cold crystalloid cardioplegia is safe, gives more rapid cardiac arrest, and affords similar cardioprotection and maintenance of hemodynamic parameters, together with a marked reduction in the incidence of postoperative atrial fibrillation.
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Affiliation(s)
- Øyvind Jakobsen
- Department of Cardiothoracic and Vascular Surgery, University Hospital of North Norway and Institute of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway.
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de Lange E, Xie Y, Qu Z. Synchronization of early afterdepolarizations and arrhythmogenesis in heterogeneous cardiac tissue models. Biophys J 2012; 103:365-73. [PMID: 22853915 DOI: 10.1016/j.bpj.2012.06.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 06/05/2012] [Accepted: 06/07/2012] [Indexed: 02/05/2023] Open
Abstract
Early afterdepolarizations (EADs) are linked to both triggered arrhythmias and reentrant arrhythmias by causing premature ventricular complexes (PVCs), focal excitations, or heterogeneous tissue substrates for reentry formation. However, a critical number of cells that synchronously exhibit EADs are needed to result in arrhythmia triggers and substrates in tissue. In this study, we use mathematical modeling and computer simulations to investigate EAD synchronization and arrhythmia induction in tissue models with random cell-to-cell variations. Our major observations are as follows. Random cell-to-cell variations in action potential duration without EAD presence do not cause large dispersion of refractoriness in well-coupled tissue. In the presence of phase-2 EADs, the cells may synchronously exhibit the same number of EADs or no EADs with a very small dispersion of refractoriness, or synchronize regionally to result in large dispersion of refractoriness. In the presence of phase-3 EADs, regional synchronization leads to propagating EADs, forming PVCs in tissue. Interestingly, even though the uncoupled cells exhibit either no EAD or only a single EAD, when these cells are coupled to form a tissue, more than one PVC can occur. When the PVCs occur at different locations and time, multifocal arrhythmias are triggered, with the foci shifting in space and time in an irregular manner. The focal arrhythmias either spontaneously terminate or degenerate into reentrant arrhythmias due to heterogeneities and spatiotemporal chaotic dynamics of the foci.
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Affiliation(s)
- Enno de Lange
- Cardiovascular Research Laboratory, Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California, USA.
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Qu Z. Chaos in the genesis and maintenance of cardiac arrhythmias. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2010; 105:247-57. [PMID: 21078337 DOI: 10.1016/j.pbiomolbio.2010.11.001] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Revised: 07/04/2010] [Accepted: 11/05/2010] [Indexed: 11/18/2022]
Abstract
Dynamical chaos, an irregular behavior of deterministic systems, has been widely shown in nature. It also has been demonstrated in cardiac myocytes in many studies, including rapid pacing-induced irregular beat-to-beat action potential alterations and slow pacing-induced irregular early afterdepolarizations, etc. Here we review the roles of chaos in the genesis of cardiac arrhythmias, the transition to ventricular fibrillation, and the spontaneous termination of fibrillation, based on evidence from computer simulation of mathematical models and experiments of animal models.
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Affiliation(s)
- Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, 650 Charles E. Young Drive South, Los Angeles, CA 90095, USA.
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Sato D, Xie LH, Nguyen TP, Weiss JN, Qu Z. Irregularly appearing early afterdepolarizations in cardiac myocytes: random fluctuations or dynamical chaos? Biophys J 2010; 99:765-73. [PMID: 20682253 DOI: 10.1016/j.bpj.2010.05.019] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Revised: 04/30/2010] [Accepted: 05/07/2010] [Indexed: 01/08/2023] Open
Abstract
Irregularly occurring early afterdepolarizations (EADs) in cardiac myocytes are traditionally hypothesized to be caused by random ion channel fluctuations. In this study, we combined 1), patch-clamp experiments in which action potentials were recorded at different pacing cycle lengths from isolated rabbit ventricular myocytes under several experimental conditions inducing EADs, including oxidative stress with hydrogen peroxide, calcium overload with BayK8644, and ionic stress with hypokalemia; 2), computer simulations using a physiologically detailed rabbit ventricular action potential model, in which repolarization reserve was reduced to generate EADs and random ion channel or path cycle length fluctuations were implemented; and 3), iterated maps with or without noise. By comparing experimental, modeling, and bifurcation analyses, we present evidence that noise-induced transitions between bistable states (i.e., between an action potential with and without an EAD) is not sufficient to account for the large variation in action potential duration fluctuations observed in experimental studies. We conclude that the irregular dynamics of EADs is intrinsically chaotic, with random fluctuations playing a nonessential, auxiliary role potentiating the complex dynamics.
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Affiliation(s)
- Daisuke Sato
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California, USA
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21
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Tran DX, Sato D, Yochelis A, Weiss JN, Garfinkel A, Qu Z. Bifurcation and chaos in a model of cardiac early afterdepolarizations. PHYSICAL REVIEW LETTERS 2009; 102:258103. [PMID: 19659123 PMCID: PMC2726623 DOI: 10.1103/physrevlett.102.258103] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Indexed: 05/03/2023]
Abstract
Excitable cells can exhibit complex patterns of oscillations, such as spiking and bursting. In cardiac cells, pathological voltage oscillations, called early afterdepolarizations (EADs), have been widely observed under disease conditions, yet their dynamical mechanisms remain unknown. Here, we show that EADs are caused by Hopf and homoclinic bifurcations. During period pacing, chaos always occurs at the transition from no EAD to EADs as the stimulation frequency decreases, providing a distinct explanation for the irregular EAD behavior frequently observed in experiments.
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Affiliation(s)
- Diana X. Tran
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
- Molecular, Cellular, and Integrative Physiology Program, University of California, Los Angeles, California 90095, USA
| | - Daisuke Sato
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
| | - Arik Yochelis
- Department of Chemical Engineering, Technion—Israel Institute of Technology, Haifa 32000, Israel
| | - James N. Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
| | - Alan Garfinkel
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
- Department of Physiological Science, University of California, Los Angeles, California 90095, USA
| | - Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
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22
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Synchronization of chaotic early afterdepolarizations in the genesis of cardiac arrhythmias. Proc Natl Acad Sci U S A 2009; 106:2983-8. [PMID: 19218447 DOI: 10.1073/pnas.0809148106] [Citation(s) in RCA: 174] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The synchronization of coupled oscillators plays an important role in many biological systems, including the heart. In heart diseases, cardiac myocytes can exhibit abnormal electrical oscillations, such as early afterdepolarizations (EADs), which are associated with lethal arrhythmias. A key unanswered question is how cellular EADs partially synchronize in tissue, as is required for them to propagate. Here, we present evidence, from computational simulations and experiments in isolated myocytes, that irregular EAD behavior is dynamical chaos. We then show in electrically homogeneous tissue models that chaotic EADs synchronize globally when the tissue is smaller than a critical size. However, when the tissue exceeds the critical size, electrotonic coupling can no longer globally synchronize EADs, resulting in regions of partial synchronization that shift in time and space. These regional partially synchronized EADs then form premature ventricular complexes that propagate into recovered tissue without EADs. This process creates multiple premature ventricular complexes that propagate as [corrected] "shifting" foci resembling polymorphic ventricular tachycardia. Shifting foci encountering shifting repolarization gradients can also develop localized wave breaks leading to reentry and fibrillation. As predicted by the theory, rabbit hearts exposed to oxidative stress (H(2)O(2)) exhibited multiple shifting foci causing polymorphic tachycardia and fibrillation. This mechanism explains how collective cellular behavior integrates at the tissue scale to generate lethal cardiac arrhythmias over a wide range of heart rates.
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Mustafa SJ, Morrison RR, Teng B, Pelleg A. Adenosine receptors and the heart: role in regulation of coronary blood flow and cardiac electrophysiology. Handb Exp Pharmacol 2009:161-88. [PMID: 19639282 PMCID: PMC2913612 DOI: 10.1007/978-3-540-89615-9_6] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2023]
Abstract
Adenosine is an autacoid that plays a critical role in regulating cardiac function, including heart rate, contractility, and coronary flow. In this chapter, current knowledge of the functions and mechanisms of action of coronary flow regulation and electrophysiology will be discussed. Currently, there are four known adenosine receptor (AR) subtypes, namely A(1), A(2A), A(2B), and A(3). All four subtypes are known to regulate coronary flow. In general, A(2A)AR is the predominant receptor subtype responsible for coronary blood flow regulation, which dilates coronary arteries in both an endothelial-dependent and -independent manner. The roles of other ARs and their mechanisms of action will also be discussed. The increasing popularity of gene-modified models with targeted deletion or overexpression of a single AR subtype has helped to elucidate the roles of each receptor subtype. Combining pharmacologic tools with targeted gene deletion of individual AR subtypes has proven invaluable for discriminating the vascular effects unique to the activation of each AR subtype. Adenosine exerts its cardiac electrophysiologic effects mainly through the activation of A(1)AR. This receptor mediates direct as well as indirect effects of adenosine (i.e., anti-beta-adrenergic effects). In supraventricular tissues (atrial myocytes, sinuatrial node and atriovetricular node), adenosine exerts both direct and indirect effects, while it exerts only indirect effects in the ventricle. Adenosine exerts a negative chronotropic effect by suppressing the automaticity of cardiac pacemakers, and a negative dromotropic effect through inhibition of AV-nodal conduction. These effects of adenosine constitute the rationale for its use as a diagnostic and therapeutic agent. In recent years, efforts have been made to develop A(1)R-selective agonists as drug candidates that do not induce vasodilation, which is considered an undesirable effect in the clinical setting.
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Affiliation(s)
- S Jamal Mustafa
- Department of Physiology and Pharmacology, School of Medicine, West Virginia University, Morgantown, WV 26505-9229, USA.
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25
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Affiliation(s)
- Bruce B Lerman
- Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, NY 10021, USA.
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Kim RJ, Iwai S, Markowitz SM, Shah BK, Stein KM, Lerman BB. Clinical and Electrophysiological Spectrum of Idiopathic Ventricular Outflow Tract Arrhythmias. J Am Coll Cardiol 2007; 49:2035-43. [PMID: 17512360 DOI: 10.1016/j.jacc.2007.01.085] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2006] [Revised: 01/17/2007] [Accepted: 01/28/2007] [Indexed: 11/17/2022]
Abstract
OBJECTIVES This study sought to compare and contrast the clinical and electrophysiological characteristics of outflow tract arrhythmias. BACKGROUND Idiopathic ventricular outflow tract arrhythmias manifest clinically in 3 forms: 1) paroxysmal sustained monomorphic ventricular tachycardia (SMVT), 2) repetitive nonsustained ventricular tachycardia (NSVT), or 3) premature ventricular contractions (PVCs). Although these arrhythmias have a similar site of origin, it is unknown whether they share a common mechanism or similar clinical features. METHODS A total of 127 patients (63 female [50%], mean age 51 +/- 15 years) were evaluated for outflow tract arrhythmias. RESULTS A total of 36 (28%) presented with the index clinical arrhythmia of SMVT, 46 (36%) with NSVT, and 45 (35%) with PVCs. The sites of origin of the arrhythmias were similar among the 3 groups, occurring in the right ventricular outflow tract in 82%. Sustained ventricular tachycardia was more likely to be induced during exercise in the SMVT (10 of 15 patients [67%]) than NSVT or PVCs groups (p < 0.01). Sustained outflow tract ventricular tachycardia was induced at electrophysiology study in 78% of SMVT patients, 48% of NSVT patients, and 4% of PVCs patients. Adenosine was similarly effective in all 3 groups (p = NS). CONCLUSIONS Patients with outflow tract arrhythmias can be differentiated based on the subtype of arrhythmia. However, the observation that approximately 50% of patients with NSVT and approximately 5% of patients with PVCs have inducible sustained ventricular tachycardia that behaves in an identically unique manner to those who present with sustained ventricular tachycardia (e.g., adenosine-sensitive) suggests that rather than representing distinct entities, outflow arrhythmias may be considered a continuum of a single mechanism.
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Affiliation(s)
- Robert J Kim
- Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, New York 10021, USA
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Hirose M, Laurita KR. Calcium-mediated triggered activity is an underlying cellular mechanism of ectopy originating from the pulmonary vein in dogs. Am J Physiol Heart Circ Physiol 2007; 292:H1861-7. [PMID: 17158650 DOI: 10.1152/ajpheart.00826.2006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Paroxysmal atrial fibrillation associated with focal ectopy originating from the pulmonary vein (PV) can be preceded by variations in autonomic tone; however, the underlying cellular mechanisms are not clear. To determine the mechanisms of autonomically mediated PV ectopy, high-resolution optical mapping techniques were used to measure action potentials and Ca2+ transients from the PV and the ligament of Marshall area in the arterially perfused canine left atrium. Rapid pacing was used to initiate ectopic activity during pituitary adenylate cyclase-activating polypeptide (PACAP) injection (1 nmol), as a surrogate for autonomic imbalance, before ( n = 9) and after ( n = 6) verapamil (10 nmol) administration. In all preparations, spontaneous activity was absent before rapid pacing. During PACAP injection, rapid pacing induced ectopic activity in eight of nine preparations. In contrast, before PACAP injection, rapid pacing did not induce ectopic activity. Activation maps of each episode of ectopic activity indicated that the site of origin occurred more frequently in the PV (70%) than in the ligament of Marshall (30%) area. As rapid pacing cycle length increased, so did the ectopic beat coupling interval. In addition, PACAP-induced ectopic activity was associated with large Ca2+ transient amplitudes and was always suppressed by verapamil, a Ca2+ channel blocker ( P < 0.05). Finally, during PACAP injection in the absence of an ectopic beat, spontaneous Ca2+ release and delayed afterdepolarizations were observed simultaneously after termination of rapid pacing. In conclusion, these data suggest that autonomically mediated PV ectopy may be due to Ca2+-mediated triggered activity arising from delayed afterdepolarizations.
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Affiliation(s)
- Masamichi Hirose
- Department of Molecular Pharmacology, Shinshu University School of Medicine, Nagano, Japan
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Bunch TJ, Day JD. Right Meets Left: A Common Mechanism Underlying Right and Left Ventricular Outflow Tract Tachycardias. J Cardiovasc Electrophysiol 2006; 17:1059-61. [PMID: 16989647 DOI: 10.1111/j.1540-8167.2006.00577.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Iwai S, Cantillon DJ, Kim RJ, Markowitz SM, Mittal S, Stein KM, Shah BK, Yarlagadda RK, Cheung JW, Tan VR, Lerman BB. Right and Left Ventricular Outflow Tract Tachycardias: Evidence for a Common Electrophysiologic Mechanism. J Cardiovasc Electrophysiol 2006; 17:1052-8. [PMID: 16800855 DOI: 10.1111/j.1540-8167.2006.00539.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
INTRODUCTION "Idiopathic" ventricular arrhythmias most often arise from the right ventricular outflow tract (RVOT), although arrhythmias from the left ventricular outflow tract (LVOT) are also observed. While previous work has elucidated the mechanism and electropharmacologic profile of RVOT arrhythmias, it is unclear whether those from the LVOT share these properties. The purpose of this study was to characterize the electropharmacologic properties of RVOT and LVOT arrhythmias. METHODS AND RESULTS One hundred twenty-two consecutive patients (61 male; 50.9 +/- 15.2 years) with outflow tract arrhythmias comprise this series, 100 (82%) with an RVOT origin, and 22 (18%) with an LVOT origin. The index arrhythmia was similar: sustained ventricular tachycardia (VT) (RVOT = 28%, LVOT = 36%), nonsustained VT (RVOT = 40%, LVOT = 23%), and premature ventricular complexes (RVOT = 32%, LVOT = 41%) (P = 0.32). Cardiac magnetic resonance imaging and microvolt T-wave alternans results (normal/indeterminate) were also comparable. In addition, 41% with RVOT foci and 50% with LVOT foci were inducible for sustained VT (P = 0.48), and induction of VT was catecholamine dependent in a majority of patients in both groups (66% and 73%; RVOT and LVOT, respectively; P = 1.0). VT was sensitive to adenosine (88% and 78% in the RVOT and LVOT groups, respectively, P = 0.59) as well as blockade of the slow-inward calcium current (RVOT = 70%, LVOT = 80%; P = 1.00) in both groups. CONCLUSIONS Electrophysiologic and pharmacologic properties, including sensitivity to adenosine, are similar for RVOT and LVOT arrhythmias. Despite disparate sites of origin, these data suggest a common arrhythmogenic mechanism, consistent with cyclic AMP-mediated triggered activity. Based on these similarities, these arrhythmias should be considered as a single entity, and classified together as "outflow tract arrhythmias."
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Affiliation(s)
- Sei Iwai
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY 10021, USA
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Marumoto A, Hasegawa J, Zhang F, Moritani H, Harada T, Sano A, Miura N, Kishimoto Y, Ohgi S. Trapidil enhances the slowly activating delayed rectifier potassium current and suppresses the transient inward current induced by catecholamine in Guinea pig ventricular myocytes. J Cardiovasc Pharmacol 2005; 46:167-76. [PMID: 16044028 DOI: 10.1097/01.fjc.0000167011.75306.ca] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We examined the electrophysiological effects of trapidil on the ionic currents influencing the repolarization and on the transient inward current (ITi) that can cause triggered arrhythmia using the whole-cell patch-clamp technique in guinea pig ventricular myocytes. Trapidil shortened the action potential duration (APD) and increased the delayed rectifier potassium current (IK) in a concentration-dependent manner. The effect of trapidil on the rapidly and slowly activating components of IK (IKr and IKs, respectively) was studied by the envelope of tails test. Trapidil failed to affect IKr and selectively enhanced IKs. Trapidil increased the amplitude of the L-type Ca2+ current (ICa,L), with an acceleration of its inactivation, whereas isoproterenol, a beta-adrenoceptor agonist, increased the amplitude of the ICa,L in a different manner. Isoproterenol activated ITi; however, trapidil not only failed to facilitate ITi but also suppressed isoproterenol-induced ITi. The inhibitory effect of trapidil on isoproterenol-induced ITi is at least partly via a reduction of Ca2+ overload through an acceleration of ICa,L inactivation and/or a sarcoplasmic reticulum (SR) Ca channel modulation. These results suggest that trapidil does not prolong the QT interval and has an antiarrhythmic effect on arrhythmias elicited by triggered activity secondary to Ca2+ overload at much higher concentrations than clinical concentration.
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Affiliation(s)
- Akira Marumoto
- Division of Pharmacotherapeutics, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Tottori University, Yonago, Japan
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Tan BH, Shimizu H, Furukawa Y, Kanemori T, Ohyanagi M. Sinus slowing caused by adenosine-5'-triphosphate in patients with and without sick sinus syndrome under various autonomic states. J Electrocardiol 2005; 37:305-9. [PMID: 15484159 DOI: 10.1016/j.jelectrocard.2004.07.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Adenosine infusion can potentially be used as a diagnostic test for sick sinus syndrome (SSS) based on its negative chronotropic effects. Whether autonomic tone underlies adenosine's negative chronotropic effects remains unknown. This study was to investigate the bradycardiac response of sinus node to ATP in patients with and without clinical SSS by measuring atrial cycle length (ACL) before and after bolus of ATP in different states of autonomic tone. The negative chronotropic effect of ATP was assessed by comparing the mean ACL before ATP administration with the longest ACL after a bolus of ATP infusion (Delta ACL). Our results showed that Delta ACL in patients with SSS were significantly greater than that without SSS (P<.001) in all 4 states, and IHR in patients with SSS were significantly lower than calculated IHR (P<.0001). Moreover, there was no significant difference in Delta ACL between the 4 states in patients with SSS (P = .99). However, Delta ACL was significantly greater during isoproterenol infusion and after propranolol administration in patients without sinus node dysfunction, comparing with baseline state (P<.01), but not after combination of atropine (P = .33). Our results indicate that the negative chronotropic effect of ATP on sinus node is much more dramatic in patients with SSS, in which the intrinsic disease of sinus node is responsible for the abnormal adenosine-mediated sinus arrest, and this effect is influenced by autonomic tone in patients without sinus node dysfunction but not in patients with SSS.
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Affiliation(s)
- Bi-Hua Tan
- Cardiovascular Division, Department of Internal Medicine, Hyogo College of Medicine, Nishinomiya, Japan.
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Abstract
Although the pathogenesis of ventricular outflow tract tachycardia has not been fully elucidated, recent findings suggest that defects in cAMP signalling may be involved.
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Stambler BS, Fenelon G, Shepard RK, Clemo HF, Guiraudon CM. Characterization of sustained atrial tachycardia in dogs with rapid ventricular pacing-induced heart failure. J Cardiovasc Electrophysiol 2003; 14:499-507. [PMID: 12776867 DOI: 10.1046/j.1540-8167.2003.02519.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
INTRODUCTION Atrial arrhythmias often complicate congestive heart failure (CHF). We characterized inducible atrial tachyarrhythmias and electrophysiologic alterations in dogs with CHF and atrial enlargement produced by rapid ventricular pacing. METHODS AND RESULTS Endocardial pacing leads were implanted in the right ventricle, right atrium, and coronary sinus in 18 dogs. The right ventricular lead was connected to an implanted pacemaker capable of rapid ventricular pacing. The atrial leads were used to perform electrophysiologic studies in conscious animals at baseline in all dogs, during CHF induced by rapid ventricular pacing at 235 beats/min in 15 dogs, and during recovery from CHF in 6 dogs. After 20 +/- 7 days of rapid ventricular pacing, inducibility of sustained atrial tachycardia (cycle length 120 +/- 12 msec) was enhanced in dogs with CHF. Atrial tachycardia required a critical decrease in atrial burst pacing cycle length (< or = 130 msec) for induction and often could be terminated by overdrive pacing. Calcium antagonists (verapamil, flunarizine, ryanodine) terminated atrial tachycardia and suppressed inducibility. Effective refractory periods at 400- and 300-msec cycle lengths in the right atrium and coronary sinus were prolonged in dogs with CHF. Atrial cells from dogs with CHF had prolonged action potential durations and reduced resting potentials and delayed afterdepolarizations (DADs). Mitochondria from atrial tissue from dogs with CHF were enlarged and had internal cristae disorganization. CONCLUSIONS CHF promotes inducibility of sustained atrial tachycardia. Based on the mode of tachycardia induction, responses to pacing and calcium antagonists, and presence of DADs, atrial tachycardia in this CHF model has a mechanism most consistent with DAD-induced triggered activity resulting from intracellular calcium overload.
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Affiliation(s)
- Bruce S Stambler
- Department of Medicine/Cardiology, West Roxbury Veterans Affairs Medical Center, Harvard Medical School, West Roxbury, Massachusetts, USA.
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Slotwiner DJ, Christini DJ, Stein KM, Markowitz SM, Mittal S, Iwai S, Das MK, Lerman BB. Muscle sympathetic nerve traffic during spontaneous- versus adenosine-mediated termination of idiopathic right ventricular outflow tract tachycardia. Am J Cardiol 2003; 91:86-8. [PMID: 12505580 DOI: 10.1016/s0002-9149(02)03006-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- David J Slotwiner
- Department of Medicine, Division of Cardiology, The New York Hospital-Cornell Medical Center, New York, New York 10021, USA
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Song Y, Shryock JC, Knot HJ, Belardinelli L. Selective attenuation by adenosine of arrhythmogenic action of isoproterenol on ventricular myocytes. Am J Physiol Heart Circ Physiol 2001; 280:H2789-95. [PMID: 11356637 DOI: 10.1152/ajpheart.2001.280.6.h2789] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examined whether adenosine equally attenuated the stimulatory effects of isoproterenol on arrhythmic activity and twitch shortening of guinea pig isolated ventricular myocytes. Transmembrane voltages and whole cell currents were recorded with patch electrodes, and cell twitch shortening was measured using a video-motion detector. Isoproterenol increased the action potential duration at 50% repolarization (APD50), L-type Ca2+ current [ I Ca(L)], and cell twitch shortening and induced delayed afterdepolarizations (DAD), transient inward current ( I Ti), and aftercontractions. Adenosine attenuated the arrhythmogenic actions of isoproterenol more than it attenuated the effects of isoproterenol on APD50, I Ca(L), or twitch shortening. Adenosine (0.1–100 μmol/l) decreased the amplitude of DADs by 30 ± 6% to 92 ± 5% but attenuated isoproterenol-induced prolongation of the APD50 by only 14 ± 4% to 59 ± 4% and had no effect on the voltage of action potential plateau. Adenosine (30 μmol/l) inhibited I Ti by 91 ± 4% but decreased isoproterenol-stimulated I Ca(L) by only 30 ± 12%. Isoproterenol-induced aftercontractions were abolished by adenosine (10 μmol/l), whereas the amplitude of twitch shortening was not reduced. The effects of adenosine on twitch shortenings and aftercontractions were mimicked by the A1-adenosine receptor agonist CPA ( N 6-cyclopentyladenosine) and by ryanodine. In conclusion, adenosine antagonized the proarrhythmic effect of β-adrenergic stimulation on ventricular myocytes without reducing cell twitch shortening.
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Affiliation(s)
- Y Song
- Department of Medicine, University of Florida, Gainesville, Florida 32610, USA
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Zhang YH, Hinde AK, Hancox JC. Anti-adrenergic effect of adenosine on Na(+)-Ca(2+) exchange current recorded from guinea-pig ventricular myocytes. Cell Calcium 2001; 29:347-58. [PMID: 11292391 DOI: 10.1054/ceca.2001.0197] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Na(+)-Ca(2+) exchanger is a protein present in the cell membrane of many cell types. In heart it plays important roles in Ca homeostasis and ionic current generation. Recently, it has been reported that the beta-adrenergic agonist isoprenaline (ISO) can increase directly Na(+)-Ca(2+) exchanger activity in guinea-pig ventricular myocytes. Adenosine (ADO) exerts anti-adrenergic properties that make it effective against some arrhythmias and the aim of the present study was to determine whether or not ADO can antagonize the direct modulatory effect of ISO on the exchanger.Whole-cell patch clamp measurements of Na(+)-Ca(2+) exchanger current (I(NaCa)) were made from guinea-pig ventricular myocytes, with major interfering currents inhibited. I(NaCa) was measured at 378 degrees C as current sensitive to external nickel (Ni(2+), 10 mM) during an applied descending voltage ramp. ISO (1 microM) significantly increased both inward and outward I(NaCa). This effect was abolished in the presence of ADO (200 microM). ADO alone did not significantly alter the amplitude of I(NaCa). The effect of ADO on the response of I(NaCa) to ISO was mimicked by the A(1)ADO receptor agonist N(6)-cyclopentyladenosine (CPA, 10 microM), whereas the effect of ADO on the response of I(NaCa) to ISO was inhibited by the A(1)ADO receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 2 microM). These data suggest that the A(1)ADO receptor mediated the response. The anti-adrenergic effects on I(NaCa) of ADO were not affected by the protein kinase C (PKC) inhibitor, chelerythrine (CLT, 1 microM), nor by the nitric oxide (NO) synthase inhibitor, N (G)-nitro-L-arginine methyl ester((L)-NAME, 0.5 mM). Moreover, in the presence of PKC activator phorbol 12-myristate 13-acetate (PMA, 1 microM) or exogenous NO donor sodium nitroprusside (SNP, 100 microM), ISO preserved its stimulatory effect on I(NaCa). However, prior incubation of myocytes with pertussis toxin (PTX, 5 microg ml(-1) did prevent the effect of ADO. The anti-adrenergic effect of ADO on I(NaCa) was mimicked by externally applied carbachol (CCh, 10 microM), a muscarinic receptor agonist. We conclude that ADO antagonized the effect of beta-adrenergic stimulation of I(NaCa) by directly activating inhibitory G-protein (G(i))-linked A(1) receptors in guinea-pig ventricular myocytes. These findings may suggest a novel mechanism by which adenosine exerts some of its antiarrhythmic effects.
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Affiliation(s)
- Y H Zhang
- Department of Physiology and Cardiovascular Research Laboratories, School of Medical Sciences, Bristol, UK
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Abstract
Idiopathic ventricular tachycardia (VT) is characterized by two predominant forms. The most common form originates from the right ventricular outflow tract and presents as repetitive monomorphic VT or exercise-induced VT. The tachycardia is adenosine sensitive and is thought to be because of cAMP-mediated triggered activity. The other major form of idiopathic VT is owing to verapamil-sensitive intrafascicular re-entrant tachycardia, which most often originates in the region of the left posterior fascicle. Both forms of idiopathic VT can be readily treated with radiofrequency catheter ablation.
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Affiliation(s)
- B B Lerman
- Department of Medicine, New York Hospital-Cornell University Medical Center, New York, USA.
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40
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Abstract
The aim of this review is to provide basic information on the electrophysiological changes during acute ischemia and reperfusion from the level of ion channels up to the level of multicellular preparations. After an introduction, section II provides a general description of the ion channels and electrogenic transporters present in the heart, more specifically in the plasma membrane, in intracellular organelles of the sarcoplasmic reticulum and mitochondria, and in the gap junctions. The description is restricted to activation and permeation characterisitics, while modulation is incorporated in section III. This section (ischemic syndromes) describes the biochemical (lipids, radicals, hormones, neurotransmitters, metabolites) and ion concentration changes, the mechanisms involved, and the effect on channels and cells. Section IV (electrical changes and arrhythmias) is subdivided in two parts, with first a description of the electrical changes at the cellular and multicellular level, followed by an analysis of arrhythmias during ischemia and reperfusion. The last short section suggests possible developments in the study of ischemia-related phenomena.
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Affiliation(s)
- E Carmeliet
- Centre for Experimental Surgery and Anesthesiology, University of Leuven, Leuven, Belgium
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Lerman BB, Stein KM, Markowitz SM, Mittal S, Slotwiner D. Catecholamine facilitated reentrant ventricular tachycardia: uncoupling of adenosine's antiadrenergic effects. J Cardiovasc Electrophysiol 1999; 10:17-26. [PMID: 9930905 DOI: 10.1111/j.1540-8167.1999.tb00637.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
INTRODUCTION Adenosine has no direct electrophysiologic function in ventricular tissue, but in the presence of cyclic adenosine monophosphate (cAMP), stimulation exerts a potent antiadrenergic effect. This effect has been exploited in the recognition and treatment of ventricular tachycardia (VT) due to cAMP-mediated triggered activity and automaticity, which are respectively terminated and suppressed by adenosine. However, the effects of adenosine on catecholamine-facilitated reentrant VT are unknown. A pivotal issue is whether termination of VT with adenosine is mechanism specific, or whether it represents a nonspecific antiadrenergic effect. The purpose of this study, therefore, was to define the effects of adenosine in a well-characterized group of patients with catecholamine-facilitated reentrant VT. METHODS AND RESULTS Fourteen patients with catecholamine-facilitated reentry were studied. In the 12 patients with structural heart disease (including two with arrhythmogenic right ventricular dysplasia), adenosine (260 to 550 microg/kg) failed to slow or terminate VT. Two patients without structural heart disease had intrafascicular tachycardia confined to the left posterior fascicle, a calcium-dependent, verapamil-sensitive arrhythmia. In the absence of isoproterenol, verapamil terminated VT but adenosine did not. However, when isoproterenol was subsequently required for facilitation of tachycardia, adenosine terminated VT in both patients. CONCLUSION Adenosine has no antiadrenergic (antiarrhythmic) effect in patients with catecholamine-facilitated VT due to structural heart disease. Patients with verapamil-sensitive, left posterior intrafascicular reentry have an unusual dual response to adenosine. In the unstimulated state, adenosine has no effect on basal inward calcium current and, therefore, no effect on VT. However, when induction of VT requires amplification of the inward calcium current through stimulation of cAMP, adenosine sensitivity of VT becomes manifest. These results indicate that with few exceptions, termination of VT with adenosine is strongly suggestive of a cAMP-mediated triggered mechanism rather than reentry.
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Affiliation(s)
- B B Lerman
- Department of Medicine, New York Hospital--Cornell University Medical Center, New York 10021, USA.
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Song Y, Shryock JC, Belardinelli L. Potentiating effect of acetylcholine on stimulation by isoproterenol of L-type Ca2+ current and arrhythmogenic triggered activity in guinea pig ventricular myocytes. J Cardiovasc Electrophysiol 1998; 9:718-26. [PMID: 9684720 DOI: 10.1111/j.1540-8167.1998.tb00959.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
INTRODUCTION The objective of this study was to determine whether the effect of isoproterenol (Iso) to increase L-type Ca2+ current [I(Ca(L))] and action potential duration (APD) was potentiated in ventricular myocytes following termination of an exposure of these cells to acetylcholine (ACh), and whether this potentiating effect of ACh could be arrhythmogenic. METHODS AND RESULTS Transmembrane currents and potentials of guinea pig isolated ventricular myocytes were measured using the whole cell, patch clamp technique. Stimulation of I(Ca(L)) and prolongation of APD caused by Iso (10 nmol/L) were attenuated in the presence of ACh (10 micromol/L), but were transiently enhanced by 111% +/- 20% and 214% +/- 44%, respectively, following termination of a 2- to 4-minute exposure of myocytes to ACh. No changes were observed in the absence of Iso. Both the amplitude and incidence of Iso-induced transient inward current, afterdepolarizations, and sustained triggered activity were greater immediately after termination of exposure to ACh than before application of ACh. CONCLUSION Stimulation by Iso of I(Ca(L)) is transiently enhanced in guinea pig ventricular myocytes following termination of exposure of these cells to ACh. The rebound increase of Iso-stimulated I(Ca(L)) is associated with an increase of APD and induction of arrhythmogenic triggered activity.
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Affiliation(s)
- Y Song
- Department of Medicine, University of Florida Medical School, Gainesville 32610-0277, USA
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Lerman BB, Dong B, Stein KM, Markowitz SM, Linden J, Catanzaro DF. Right ventricular outflow tract tachycardia due to a somatic cell mutation in G protein subunitalphai2. J Clin Invest 1998; 101:2862-8. [PMID: 9637720 PMCID: PMC508877 DOI: 10.1172/jci1582] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Idiopathic ventricular tachycardia is a generic term that describes the various forms of ventricular arrhythmias that occur in patients without structural heart disease and in the absence of the long QT syndrome. Many of these tachycardias are focal in origin, localize to the right ventricular outflow tract (RVOT), terminate in response to beta blockers, verapamil, vagal maneuvers, and adenosine, and are thought to result from cAMP-mediated triggered activity. DNA was prepared from biopsy samples obtained from myocardial tissue from a patient with adenosine-insensitive idiopathic ventricular tachycardia arising from the RVOT. Genomic sequences of the inhibitory G protein Galphai2 were determined after amplification by PCR and subcloning. A point mutation (F200L) in the GTP binding domain of the inhibitory G protein Galphai2 was identified in a biopsy sample from the arrhythmogenic focus. This mutation was shown to increase intracellular cAMP concentration and inhibit suppression of cAMP by adenosine. No mutations were detected in Galphai2 sequences from myocardial tissue sampled from regions remote from the origin of tachycardia, or from peripheral lymphocytes. These findings suggest that somatic cell mutations in the cAMP-dependent signal transduction pathway occurring during myocardial development may be responsible for some forms of idiopathic ventricular tachycardia.
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Affiliation(s)
- B B Lerman
- Department of Medicine, Division of Cardiology, The New York Hospital-Cornell Medical Center, New York, 10021, USA.
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Stephenson RS, Cai JJ, Drews TA, Lee HC. Effect of alpha2-adrenoceptor stimulation on isolated canine Purkinje fiber contraction. Eur J Pharmacol 1998; 345:261-7. [PMID: 9592025 DOI: 10.1016/s0014-2999(98)00006-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We have recently identified the presence of postjunctional alpha2-adrenoceptors in canine Purkinje fibers. In this study, we examined the effects of alpha2-adrenoceptor stimulation on the contraction strength of isolated Purkinje fibers. Exposure to the alpha2-adrenoceptor specific agonist and antagonist, UK 14,304 (5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine) and yohimbine (17-hydroxyyohimban-16-carboxylic acid methyl ester hydrochloride) alone at 0.1 microM respectively, did not produce any significant effect on Purkinje contraction strength. Purkinje contraction strength was augmented by isoproterenol (0.1 microM), forskolin (0.1 microM), or 8-bromo-adenosine cyclic 2',3'-monophosphate (8-bromo-cAMP, 10 microM). UK 14,304 significantly reversed the effects of isoproterenol and forskolin but not those of 8-bromo-cAMP on Purkinje contraction strength. After incubation with pertussis toxin, the positive inotropic effect of forskolin on Purkinje contraction strength remained intact, but the forskolin effect could no longer be reversed by UK 14,304. These results suggest that the postjunctional alpha2-adrenoceptors in canine Purkinje fibers are coupled to a pertussis toxin-sensitive G protein, probably Gi. Stimulation of the alpha2-adrenoceptor antagonizes the effect of beta-adrenoceptor stimulation on Purkinje contraction strength in an accentuated antagonism manner.
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Affiliation(s)
- R S Stephenson
- Department of Pediatrics, College of Medicine, the University of Iowa, Iowa City 52242, USA
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Friedrichs GS, Chi L, Park JL, Lucchesi BR. Adrenergic-dependent Effect of Adenosine-induced Ventricular Fibrillation in the Isolated Rabbit Heart. J Cardiovasc Pharmacol Ther 1997; 2:299-308. [PMID: 10684471 DOI: 10.1177/107424849700200408] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND: The present study examined the contributory role of endogenous catecholamines in adenosine-induced ventricular fibrillation in isolation rabbit hearts. METHODS AND RESULTS: Cardiac catecholamine depletion was induced in eleven rabbits by the administration of 6-hydroxydopamine (2 x 30 mg/kg, every 12 hours intramuscularly). Hearts were removed 24 hours later, and subjected to 12 minutes of hypoxic perfusion followed by 40 minutes of reoxygenation while heart rate was maintained with atrial pacing. One of six, and one of five hearts from 6-hydroxydopamine treated rabbits developed ventricular fibrillation during hypoxia-reoxygenation when exposed to 3,7-dimethyl-1-propargylzanthine (DMPX) (10 µM) + adenosine (ADO) (1 µM) and DMPX (10 µM) + ADO (10 µM), respectively. In hearts from a control group, not exposed to 6-hydroxydopamine, ventricular fibrillation developed in each of five (100% incidence) hearts when perfused in the presence of DMPX (10 µM) + ADO (10 µM) (P <.05). Nadolol (1 µM), a beta-adrenoceptor DMPX (10 µM) + ADO (10 µM) treated hearts (n = 6, P <.05 vs DMPX + ADO treated hearts). To ensure catecholamine depletion, spontaneously beating isolated hearts from vehicle and 6-hydroxydopamine treated rabbits were perfused under normoxic conditions while exposed to increasing concentrations of tyramine (1, 3, 10 mM) and the change in heart rate was determined. A concentration-related, positive chronotorpic response to tyramine was obtained in hearts from the vehicle treated group that was absent in hearts from 6-hydroxy-dopamine treated rabbits or hearts perfused in the presence of nadolol. CONCLUSIONS: The results demonstrate that inhibition of the cardiac adenosine A(2) receptor, unmasks an adenosine A(1) receptor profibrillatory effect that is dependent upon endogenous cardiac catecholamines and beta-adrenoreceptor activation during myocardial hypoxia-reoxygenation.
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Affiliation(s)
- GS Friedrichs
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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Abstract
Idiopathic left ventricular tachycardia (ILVT) differs from idiopathic right ventricular outflow tract (RVOT) tachycardia with respect to mechanism and pharmacologic sensitivity. ILVT can be categorized into three subgroups. The most prevalent form, verapamil-sensitive intrafascicular tachycardia, originates in the region of left posterior fascicle of the left bundle. This tachycardia is adenosine insensitive, demonstrates entrainment, and is thought to be due to reentry. The tachycardia is most often ablated in the region of the posteroinferior interventricular septum. A second type of ILVT is a form analogous to adenosine-sensitive RVOT tachycardia. This tachycardia appears to originate from deep within the interventricular septum and exits from the left side of the septum. This form of VT also responds to verapamil and is thought to be due to cAMP-mediated triggered activity. A third form of ILVT is propranolol sensitive. It is neither or initiated or terminated by programmed stimulation, does not terminate with verapamil, and is transiently suppressed by adenosine, responses consistent with an automatic mechanism. Recognition of the heterogeneity of ILVT and its unique characteristics should facilitate appropriate diagnosis and therapy in this group of patients.
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Affiliation(s)
- B B Lerman
- Department of Medicine, New York Hospital-Cornell University Medical Center, New York 10021, USA.
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Simons GR, Klein GJ, Natale A. Ventricular tachycardia: pathophysiology and radiofrequency catheter ablation. Pacing Clin Electrophysiol 1997; 20:534-51. [PMID: 9058854 DOI: 10.1111/j.1540-8159.1997.tb06209.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Limitations of pharmacological therapy for VT have led to great interest in alternative nonpharmacological therapies. The appeal of a curative therapy for VT initially led to the search for operative techniques to identify and destroy the underlying substrate, and more recently, has resulted in the development of catheter techniques to achieve the same goal in the electrophysiology laboratory. Investigations into the pathophysiology of VT have resulted in the recognition that this arrhythmia reflects a mechanistically and anatomically heterogeneous set of disorders. Recent growth in our understanding of these distinctions has both led to, and resulted from, simultaneous advances in catheter ablation techniques. The clinical electrophysiology laboratory has served as a testing ground for theories derived from in vitro and animal experiments while also providing its own set of human experimental data regarding the pathophysiology and treatment of VT. As a result of this process, several distinct forms of VT that are amenable to catheter ablation have been characterized. This article will summarize current knowledge of the pathophysiology of various VT subtypes and of techniques for catheter mapping and ablation.
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Affiliation(s)
- G R Simons
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27705, USA
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Abstract
INTRODUCTION Bundle branch reentry is an uncommon mechanism for ventricular tachycardia. More infrequently, both fascicles of the left bundle may provide the substrate for such macroreentrant bundle branch circuits, so-called interfascicular reentry. The effect of adenosine on bundle branch reentrant mechanisms of tachycardia is unknown. METHODS AND RESULTS A 59-year-old man with no apparent structural heart disease and history of frequent symptomatic wide complex tachycardias was referred to our center for further electrophysiologic evaluation. During electrophysiologic study, a similar tachycardia was reproducibly initiated only during isoproterenol infusion, which had the characteristics of bundle branch reentry, possibly using a left interfascicular mechanism. Intravenous adenosine reproducibly terminated the tachycardia. Application of radiofrequency energy to the breakout site from the left posterior fascicle prevented subsequent tachycardia induction and rendered the patient free of spontaneous tachycardia during long-term follow-up. CONCLUSIONS Patients with ventricular tachycardia involving a bundle branch reentrant circuit may be sensitive to adenosine. These results suggest that adenosine may not only inhibit catecholamine-mediated triggered activity but also some catecholamine-mediated reentrant ventricular arrhythmias.
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Affiliation(s)
- D S Rubenstein
- Electrophysiology Laboratory, University of Chicago Hospitals, IL 60637, USA
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