1
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Zaytseva AK, Kulichik OE, Kostareva AA, Zhorov BS. Biophysical mechanisms of myocardium sodium channelopathies. Pflugers Arch 2024; 476:735-753. [PMID: 38424322 DOI: 10.1007/s00424-024-02930-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 02/15/2024] [Accepted: 02/16/2024] [Indexed: 03/02/2024]
Abstract
Genetic variants of gene SCN5A encoding the alpha-subunit of cardiac voltage-gated sodium channel Nav1.5 are associated with various diseases, including long QT syndrome (LQT3), Brugada syndrome (BrS1), and progressive cardiac conduction disease (PCCD). In the last decades, the great progress in understanding molecular and biophysical mechanisms of these diseases has been achieved. The LQT3 syndrome is associated with gain-of-function of sodium channels Nav1.5 due to impaired inactivation, enhanced activation, accelerated recovery from inactivation or the late current appearance. In contrast, BrS1 and PCCD are associated with the Nav1.5 loss-of-function, which in electrophysiological experiments can be manifested as reduced current density, enhanced fast or slow inactivation, impaired activation, or decelerated recovery from inactivation. Genetic variants associated with congenital arrhythmias can also disturb interactions of the Nav1.5 channel with different proteins or drugs and cause unexpected reactions to drug administration. Furthermore, mutations can affect post-translational modifications of the channels and their sensitivity to pH and temperature. Here we briefly review the current knowledge on biophysical mechanisms of LQT3, BrS1 and PCCD. We focus on limitations of studies that use heterologous expression systems and induced pluripotent stem cells (iPSC) derived cardiac myocytes and summarize our understanding of genotype-phenotype relations of SCN5A mutations.
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Affiliation(s)
- Anastasia K Zaytseva
- Almazov National Medical Research Centre, St. Petersburg, Russia.
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia.
| | - Olga E Kulichik
- Almazov National Medical Research Centre, St. Petersburg, Russia
| | | | - Boris S Zhorov
- Almazov National Medical Research Centre, St. Petersburg, Russia
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
- McMaster University, Hamilton, Canada
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2
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Sommerfeld LC, Holmes AP, Yu TY, O'Shea C, Kavanagh DM, Pike JM, Wright T, Syeda F, Aljehani A, Kew T, Cardoso VR, Kabir SN, Hepburn C, Menon PR, Broadway-Stringer S, O'Reilly M, Witten A, Fortmueller L, Lutz S, Kulle A, Gkoutos GV, Pavlovic D, Arlt W, Lavery GG, Steeds R, Gehmlich K, Stoll M, Kirchhof P, Fabritz L. Reduced plakoglobin increases the risk of sodium current defects and atrial conduction abnormalities in response to androgenic anabolic steroid abuse. J Physiol 2024. [PMID: 38345865 DOI: 10.1113/jp284597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 01/16/2024] [Indexed: 03/07/2024] Open
Abstract
Androgenic anabolic steroids (AAS) are commonly abused by young men. Male sex and increased AAS levels are associated with earlier and more severe manifestation of common cardiac conditions, such as atrial fibrillation, and rare ones, such as arrhythmogenic right ventricular cardiomyopathy (ARVC). Clinical observations suggest a potential atrial involvement in ARVC. Arrhythmogenic right ventricular cardiomyopathy is caused by desmosomal gene defects, including reduced plakoglobin expression. Here, we analysed clinical records from 146 ARVC patients to identify that ARVC is more common in males than females. Patients with ARVC also had an increased incidence of atrial arrhythmias and P wave changes. To study desmosomal vulnerability and the effects of AAS on the atria, young adult male mice, heterozygously deficient for plakoglobin (Plako+/- ), and wild type (WT) littermates were chronically exposed to 5α-dihydrotestosterone (DHT) or placebo. The DHT increased atrial expression of pro-hypertrophic, fibrotic and inflammatory transcripts. In mice with reduced plakoglobin, DHT exaggerated P wave abnormalities, atrial conduction slowing, sodium current depletion, action potential amplitude reduction and the fall in action potential depolarization rate. Super-resolution microscopy revealed a decrease in NaV 1.5 membrane clustering in Plako+/- atrial cardiomyocytes after DHT exposure. In summary, AAS combined with plakoglobin deficiency cause pathological atrial electrical remodelling in young male hearts. Male sex is likely to increase the risk of atrial arrhythmia, particularly in those with desmosomal gene variants. This risk is likely to be exaggerated further by AAS use. KEY POINTS: Androgenic male sex hormones, such as testosterone, might increase the risk of atrial fibrillation in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC), which is often caused by desmosomal gene defects (e.g. reduced plakoglobin expression). In this study, we observed a significantly higher proportion of males who had ARVC compared with females, and atrial arrhythmias and P wave changes represented a common observation in advanced ARVC stages. In mice with reduced plakoglobin expression, chronic administration of 5α-dihydrotestosterone led to P wave abnormalities, atrial conduction slowing, sodium current depletion and a decrease in membrane-localized NaV 1.5 clusters. 5α-Dihydrotestosterone, therefore, represents a stimulus aggravating the pro-arrhythmic phenotype in carriers of desmosomal mutations and can affect atrial electrical function.
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Affiliation(s)
- Laura C Sommerfeld
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
- University Center of Cardiovascular Science, University Heart and Vascular Center, UKE Hamburg, Hamburg, Germany
- German Center for Cardiovascular Research (DZHK), Standort Hamburg/Kiel/Lübeck, Germany
| | - Andrew P Holmes
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
- School of Biomedical Sciences, Institute of Clinical Sciences, University of Birmingham, Birmingham, UK
| | - Ting Y Yu
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
- Research and Training Centre in Physical Sciences for Health, Birmingham, UK
| | - Christopher O'Shea
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
- Research and Training Centre in Physical Sciences for Health, Birmingham, UK
| | - Deirdre M Kavanagh
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
- Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, UK
| | - Jeremy M Pike
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
- Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, UK
| | - Thomas Wright
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
| | - Fahima Syeda
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
| | - Areej Aljehani
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
| | - Tania Kew
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
| | - Victor R Cardoso
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
- Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, UK
| | - S Nashitha Kabir
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
| | - Claire Hepburn
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
| | - Priyanka R Menon
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
| | | | - Molly O'Reilly
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
| | - Anika Witten
- Genetic Epidemiology, Institute for Human Genetics, University of Münster, Münster, Germany
- Core Facility Genomics of the Medical Faculty, University of Münster, Münster, Germany
| | - Lisa Fortmueller
- University Center of Cardiovascular Science, University Heart and Vascular Center, UKE Hamburg, Hamburg, Germany
- German Center for Cardiovascular Research (DZHK), Standort Hamburg/Kiel/Lübeck, Germany
- Genetic Epidemiology, Institute for Human Genetics, University of Münster, Münster, Germany
| | - Susanne Lutz
- Institute of Pharmacology and Toxicology, University Medical Center Göttingen, Göttingen, Germany
| | - Alexandra Kulle
- Division of Paediatric Endocrinology and Diabetes, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | - Georgios V Gkoutos
- University Center of Cardiovascular Science, University Heart and Vascular Center, UKE Hamburg, Hamburg, Germany
- Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, UK
- Institute of Translational Medicine, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
- MRC Health Data Research UK (HDR), Midlands Site, UK
| | - Davor Pavlovic
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
| | - Wiebke Arlt
- Institute of Metabolism and Systems Research (IMSR), University of Birmingham, Birmingham, UK
- Centre for Endocrinology, Diabetes and Metabolism (CEDAM), Birmingham Health Partners, Birmingham, UK
- Medical Research Council London Institute of Medical Sciences, London UK & Institute of Clinical Sciences, Faculty of Medicine, Imperial College, London, UK
| | - Gareth G Lavery
- Institute of Metabolism and Systems Research (IMSR), University of Birmingham, Birmingham, UK
- Centre for Endocrinology, Diabetes and Metabolism (CEDAM), Birmingham Health Partners, Birmingham, UK
| | - Richard Steeds
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
- Department of Cardiology, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
| | - Katja Gehmlich
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
| | - Monika Stoll
- Genetic Epidemiology, Institute for Human Genetics, University of Münster, Münster, Germany
- Core Facility Genomics of the Medical Faculty, University of Münster, Münster, Germany
- Cardiovascular Research Institute Maastricht, Department of Biochemistry, Maastricht University, Maastricht, The Netherlands
| | - Paulus Kirchhof
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
- German Center for Cardiovascular Research (DZHK), Standort Hamburg/Kiel/Lübeck, Germany
- Department of Cardiology, University Heart & Vascular Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Larissa Fabritz
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, UK
- University Center of Cardiovascular Science, University Heart and Vascular Center, UKE Hamburg, Hamburg, Germany
- German Center for Cardiovascular Research (DZHK), Standort Hamburg/Kiel/Lübeck, Germany
- Department of Cardiology, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
- Department of Cardiology, University Heart & Vascular Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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Popa IP, Șerban DN, Mărănducă MA, Șerban IL, Tamba BI, Tudorancea I. Brugada Syndrome: From Molecular Mechanisms and Genetics to Risk Stratification. Int J Mol Sci 2023; 24:ijms24043328. [PMID: 36834739 PMCID: PMC9967917 DOI: 10.3390/ijms24043328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 01/13/2023] [Accepted: 02/06/2023] [Indexed: 02/11/2023] Open
Abstract
Brugada syndrome (BrS) is a rare hereditary arrhythmia disorder, with a distinctive ECG pattern, correlated with an increased risk of ventricular arrhythmias and sudden cardiac death (SCD) in young adults. BrS is a complex entity in terms of mechanisms, genetics, diagnosis, arrhythmia risk stratification, and management. The main electrophysiological mechanism of BrS requires further research, with prevailing theories centered on aberrant repolarization, depolarization, and current-load match. Computational modelling, pre-clinical, and clinical research show that BrS molecular anomalies result in excitation wavelength (k) modifications, which eventually increase the risk of arrhythmia. Although a mutation in the SCN5A (Sodium Voltage-Gated Channel Alpha Subunit 5) gene was first reported almost two decades ago, BrS is still currently regarded as a Mendelian condition inherited in an autosomal dominant manner with incomplete penetrance, despite the recent developments in the field of genetics and the latest hypothesis of additional inheritance pathways proposing a more complex mode of inheritance. In spite of the extensive use of the next-generation sequencing (NGS) technique with high coverage, genetics remains unexplained in a number of clinically confirmed cases. Except for the SCN5A which encodes the cardiac sodium channel NaV1.5, susceptibility genes remain mostly unidentified. The predominance of cardiac transcription factor loci suggests that transcriptional regulation is essential to the Brugada syndrome's pathogenesis. It appears that BrS is a multifactorial disease, which is influenced by several loci, each of which is affected by the environment. The primary challenge in individuals with a BrS type 1 ECG is to identify those who are at risk for sudden death, researchers propose the use of a multiparametric clinical and instrumental strategy for risk stratification. The aim of this review is to summarize the latest findings addressing the genetic architecture of BrS and to provide novel perspectives into its molecular underpinnings and novel models of risk stratification.
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Affiliation(s)
- Irene Paula Popa
- Cardiology Clinic, “St. Spiridon” County Clinical Emergency Hospital, 700111 Iași, Romania
| | - Dragomir N. Șerban
- Department of Physiology, “Grigore T. Popa” University of Medicine and Pharmacy, 700115 Iași, Romania
| | - Minela Aida Mărănducă
- Department of Physiology, “Grigore T. Popa” University of Medicine and Pharmacy, 700115 Iași, Romania
| | - Ionela Lăcrămioara Șerban
- Department of Physiology, “Grigore T. Popa” University of Medicine and Pharmacy, 700115 Iași, Romania
| | - Bogdan Ionel Tamba
- Department of Pharmacology, “Grigore T. Popa” University of Medicine and Pharmacy, 700115 Iași, Romania
- Correspondence:
| | - Ionuț Tudorancea
- Cardiology Clinic, “St. Spiridon” County Clinical Emergency Hospital, 700111 Iași, Romania
- Department of Physiology, “Grigore T. Popa” University of Medicine and Pharmacy, 700115 Iași, Romania
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4
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SCN5A Overlap Syndromes: an open-minded approach. Heart Rhythm 2022; 19:1363-1368. [DOI: 10.1016/j.hrthm.2022.03.1223] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 03/07/2022] [Accepted: 03/22/2022] [Indexed: 12/19/2022]
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Daimi H, Lozano-Velasco E, Aranega A, Franco D. Genomic and Non-Genomic Regulatory Mechanisms of the Cardiac Sodium Channel in Cardiac Arrhythmias. Int J Mol Sci 2022; 23:1381. [PMID: 35163304 PMCID: PMC8835759 DOI: 10.3390/ijms23031381] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 12/30/2021] [Accepted: 01/06/2022] [Indexed: 12/19/2022] Open
Abstract
Nav1.5 is the predominant cardiac sodium channel subtype, encoded by the SCN5A gene, which is involved in the initiation and conduction of action potentials throughout the heart. Along its biosynthesis process, Nav1.5 undergoes strict genomic and non-genomic regulatory and quality control steps that allow only newly synthesized channels to reach their final membrane destination and carry out their electrophysiological role. These regulatory pathways are ensured by distinct interacting proteins that accompany the nascent Nav1.5 protein along with different subcellular organelles. Defects on a large number of these pathways have a tremendous impact on Nav1.5 functionality and are thus intimately linked to cardiac arrhythmias. In the present review, we provide current state-of-the-art information on the molecular events that regulate SCN5A/Nav1.5 and the cardiac channelopathies associated with defects in these pathways.
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Affiliation(s)
- Houria Daimi
- Biochemistry and Molecular Biology Laboratory, Faculty of Pharmacy, University of Monastir, Monastir 5000, Tunisia
| | - Estefanía Lozano-Velasco
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
| | - Amelia Aranega
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
| | - Diego Franco
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
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6
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Glazer AM, Wada Y, Li B, Muhammad A, Kalash OR, O'Neill MJ, Shields T, Hall L, Short L, Blair MA, Kroncke BM, Capra JA, Roden DM. High-Throughput Reclassification of SCN5A Variants. Am J Hum Genet 2020; 107:111-123. [PMID: 32533946 PMCID: PMC7332654 DOI: 10.1016/j.ajhg.2020.05.015] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 05/19/2020] [Indexed: 12/19/2022] Open
Abstract
Partial or complete loss-of-function variants in SCN5A are the most common genetic cause of the arrhythmia disorder Brugada syndrome (BrS1). However, the pathogenicity of SCN5A variants is often unknown or disputed; 80% of the 1,390 SCN5A missense variants observed in at least one individual to date are variants of uncertain significance (VUSs). The designation of VUS is a barrier to the use of sequence data in clinical care. We selected 83 variants: 10 previously studied control variants, 10 suspected benign variants, and 63 suspected Brugada syndrome-associated variants, selected on the basis of their frequency in the general population and in individuals with Brugada syndrome. We used high-throughput automated patch clamping to study the function of the 83 variants, with the goal of reclassifying variants with functional data. The ten previously studied controls had functional properties concordant with published manual patch clamp data. All 10 suspected benign variants had wild-type-like function. 22 suspected BrS variants had loss of channel function (<10% normalized peak current) and 22 variants had partial loss of function (10%-50% normalized peak current). The previously unstudied variants were initially classified as likely benign (n = 2), likely pathogenic (n = 10), or VUSs (n = 61). After the patch clamp studies, 16 variants were benign/likely benign, 45 were pathogenic/likely pathogenic, and only 12 were still VUSs. Structural modeling identified likely mechanisms for loss of function including altered thermostability and disruptions to alpha helices, disulfide bonds, or the permeation pore. High-throughput patch clamping enabled reclassification of the majority of tested VUSs in SCN5A.
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Affiliation(s)
- Andrew M Glazer
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Yuko Wada
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Bian Li
- Department of Biological Sciences, Center for Structural Biology, and Vanderbilt Genetics Institute, Vanderbilt University, Nashville, TN 37235, USA
| | - Ayesha Muhammad
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Olivia R Kalash
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Matthew J O'Neill
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Tiffany Shields
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Lynn Hall
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Laura Short
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Marcia A Blair
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Brett M Kroncke
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - John A Capra
- Department of Biological Sciences, Center for Structural Biology, and Vanderbilt Genetics Institute, Vanderbilt University, Nashville, TN 37235, USA
| | - Dan M Roden
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
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7
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Li W, Yin L, Shen C, Hu K, Ge J, Sun A. SCN5A Variants: Association With Cardiac Disorders. Front Physiol 2018; 9:1372. [PMID: 30364184 PMCID: PMC6191725 DOI: 10.3389/fphys.2018.01372] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Accepted: 09/10/2018] [Indexed: 12/19/2022] Open
Abstract
The SCN5A gene encodes the alpha subunit of the main cardiac sodium channel Nav1.5. This channel predominates inward sodium current (INa) and plays a critical role in regulation of cardiac electrophysiological function. Since 1995, SCN5A variants have been found to be causatively associated with Brugada syndrome, long QT syndrome, cardiac conduction system dysfunction, dilated cardiomyopathy, etc. Previous genetic, electrophysiological, and molecular studies have identified the arrhythmic and cardiac structural characteristics induced by SCN5A variants. However, due to the variation of disease manifestations and genetic background, impact of environmental factors, as well as the presence of mixed phenotypes, the detailed and individualized physiological mechanisms in various SCN5A-related syndromes are not fully elucidated. This review summarizes the current knowledge of SCN5A genetic variations in different SCN5A-related cardiac disorders and the newly developed therapy strategies potentially useful to prevent and treat these disorders in clinical setting.
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Affiliation(s)
- Wenjia Li
- Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Lei Yin
- Department of Urology, Shanghai Tenth People's Hospital, Tongji University, Shanghai, China
| | - Cheng Shen
- Department of Cardiology, The Affiliated Hospital of Jining Medical University, Jining, China
| | - Kai Hu
- Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Junbo Ge
- Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai, China.,Department of Cardiology, Institute of Biomedical Science, Fudan University, Shanghai, China
| | - Aijun Sun
- Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai, China.,Department of Cardiology, Institute of Biomedical Science, Fudan University, Shanghai, China
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Lehmann HI, Meltendorf U, Klein HU. Long-term follow-up of permanent atrial standstill in a German family with mutation in the SCN5A gene. HeartRhythm Case Rep 2018; 4:356-358. [PMID: 30116708 PMCID: PMC6092983 DOI: 10.1016/j.hrcr.2018.04.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 04/15/2018] [Accepted: 04/30/2018] [Indexed: 11/28/2022] Open
Affiliation(s)
- H Immo Lehmann
- Department of Internal Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.,Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
| | - Ulf Meltendorf
- Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
| | - Helmut U Klein
- Otto-von-Guericke-University Magdeburg, Magdeburg, Germany.,Heart Research Follow-up Program, University of Rochester Medical Center, Rochester, New York
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9
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Hayashi H, Sumiyoshi M, Nakazato Y, Daida H. Brugada syndrome and sinus node dysfunction. J Arrhythm 2018; 34:216-221. [PMID: 29951135 PMCID: PMC6009769 DOI: 10.1002/joa3.12046] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 02/12/2018] [Indexed: 12/19/2022] Open
Abstract
Brugada syndrome (BrS) is a well-known catastrophic disease first reported in 1992 by the Brugada brothers. Ventricular fibrillation (VF) is an essential arrhythmia in BrS. An association between BrS and atrial tachyarrhythmias is not uncommon. However, sinus node dysfunction (SND) associated with BrS has not been well discussed. In this review, we focus on the association between BrS and SND. Based on previous reports describing clinical, epidemiological, and genetic evidence, SND is not a rare concomitant disorder in BrS. BrS may be a multiple conduction or arrhythmogenic disorder including not only the His-Purkinje system and right ventricle, but also the sinus node and atrium, derived from ion channel mutations.
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Affiliation(s)
- Hidemori Hayashi
- Department of Cardiovascular MedicineJuntendo University School of MedicineTokyoJapan
| | | | - Yuji Nakazato
- Department of CardiologyJuntendo University Urayasu HospitalUrayasuJapan
| | - Hiroyuki Daida
- Department of Cardiovascular MedicineJuntendo University School of MedicineTokyoJapan
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10
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Selga E, Sendfeld F, Martinez-Moreno R, Medine CN, Tura-Ceide O, Wilmut SI, Pérez GJ, Scornik FS, Brugada R, Mills NL. Sodium channel current loss of function in induced pluripotent stem cell-derived cardiomyocytes from a Brugada syndrome patient. J Mol Cell Cardiol 2018; 114:10-19. [PMID: 29024690 PMCID: PMC5807028 DOI: 10.1016/j.yjmcc.2017.10.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 09/15/2017] [Accepted: 10/04/2017] [Indexed: 12/24/2022]
Abstract
Brugada syndrome predisposes to sudden death due to disruption of normal cardiac ion channel function, yet our understanding of the underlying cellular mechanisms is incomplete. Commonly used heterologous expression models lack many characteristics of native cardiomyocytes and, in particular, the individual genetic background of a patient. Patient-specific induced pluripotent stem (iPS) cell-derived cardiomyocytes (iPS-CM) may uncover cellular phenotypical characteristics not observed in heterologous models. Our objective was to determine the properties of the sodium current in iPS-CM with a mutation in SCN5A associated with Brugada syndrome. Dermal fibroblasts from a Brugada syndrome patient with a mutation in SCN5A (c.1100G>A, leading to Nav1.5_p.R367H) were reprogrammed to iPS cells. Clones were characterized and differentiated to form beating clusters and sheets. Patient and control iPS-CM were structurally indistinguishable. Sodium current properties of patient and control iPS-CM were compared. These results were contrasted with those obtained in tsA201 cells heterologously expressing sodium channels with the same mutation. Patient-derived iPS-CM showed a 33.1-45.5% reduction in INa density, a shift in both activation and inactivation voltage-dependence curves, and faster recovery from inactivation. Co-expression of wild-type and mutant channels in tsA201 cells did not compromise channel trafficking to the membrane, but resulted in a reduction of 49.8% in sodium current density without affecting any other parameters. Cardiomyocytes derived from iPS cells from a Brugada syndrome patient with a mutation in SCN5A recapitulate the loss of function of sodium channel current associated with this syndrome; including pro-arrhythmic changes in channel function not detected using conventional heterologous expression systems.
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Affiliation(s)
- Elisabet Selga
- Cardiovascular Genetics Centre, Department of Medical Sciences, University of Girona, Girona, Spain; Institut d'Investigació Biomèdica de Girona (IDIBGI), Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain
| | - Franziska Sendfeld
- Scottish Centre for Regenerative Medicine, University of Edinburgh, United Kingdom; BHF/University Centre for Cardiovascular Sciences, University of Edinburgh, United Kingdom
| | - Rebecca Martinez-Moreno
- Cardiovascular Genetics Centre, Department of Medical Sciences, University of Girona, Girona, Spain; Institut d'Investigació Biomèdica de Girona (IDIBGI), Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain
| | - Claire N Medine
- Scottish Centre for Regenerative Medicine, University of Edinburgh, United Kingdom; BHF/University Centre for Cardiovascular Sciences, University of Edinburgh, United Kingdom
| | - Olga Tura-Ceide
- Department of Pulmonary Medicine, Hospital Clinic-Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, University of Barcelona, Spain
| | - Sir Ian Wilmut
- Scottish Centre for Regenerative Medicine, University of Edinburgh, United Kingdom
| | - Guillermo J Pérez
- Cardiovascular Genetics Centre, Department of Medical Sciences, University of Girona, Girona, Spain; Institut d'Investigació Biomèdica de Girona (IDIBGI), Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain
| | - Fabiana S Scornik
- Cardiovascular Genetics Centre, Department of Medical Sciences, University of Girona, Girona, Spain; Institut d'Investigació Biomèdica de Girona (IDIBGI), Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain
| | - Ramon Brugada
- Cardiovascular Genetics Centre, Department of Medical Sciences, University of Girona, Girona, Spain; Institut d'Investigació Biomèdica de Girona (IDIBGI), Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain; Hospital Josep Trueta, Girona, Spain
| | - Nicholas L Mills
- BHF/University Centre for Cardiovascular Sciences, University of Edinburgh, United Kingdom.
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11
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Gal DB, Wojciak J, Perera J, Tanel RE, Patel AR. Atrial standstill in a pediatric patient with associated caveolin-3 mutation. HeartRhythm Case Rep 2017; 3:513-516. [PMID: 29387541 PMCID: PMC5778098 DOI: 10.1016/j.hrcr.2017.07.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Affiliation(s)
- Dana B Gal
- Department of Pediatrics, University of California, San Francisco, San Francisco, California
| | - Julianne Wojciak
- Department of Pediatric Cardiology, University of California, San Francisco, San Francisco, California
| | - Jennifer Perera
- Department of Pediatric Cardiology, University of California, San Francisco, San Francisco, California
| | - Ronn E Tanel
- Department of Pediatric Cardiology, University of California, San Francisco, San Francisco, California
| | - Akash R Patel
- Department of Pediatric Cardiology, University of California, San Francisco, San Francisco, California
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12
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Tse G, Liu T, Li KHC, Laxton V, Chan YWF, Keung W, Li RA, Yan BP. Electrophysiological Mechanisms of Brugada Syndrome: Insights from Pre-clinical and Clinical Studies. Front Physiol 2016; 7:467. [PMID: 27803673 PMCID: PMC5067537 DOI: 10.3389/fphys.2016.00467] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 09/27/2016] [Indexed: 12/19/2022] Open
Abstract
Brugada syndrome (BrS), is a primary electrical disorder predisposing affected individuals to sudden cardiac death via the development of ventricular tachycardia and fibrillation (VT/VF). Originally, BrS was linked to mutations in the SCN5A, which encodes for the cardiac Na+ channel. To date, variants in 19 genes have been implicated in this condition, with 11, 5, 3, and 1 genes affecting the Na+, K+, Ca2+, and funny currents, respectively. Diagnosis of BrS is based on ECG criteria of coved- or saddle-shaped ST segment elevation and/or T-wave inversion with or without drug challenge. Three hypotheses based on abnormal depolarization, abnormal repolarization, and current-load-mismatch have been put forward to explain the electrophysiological mechanisms responsible for BrS. Evidence from computational modeling, pre-clinical, and clinical studies illustrates that molecular abnormalities found in BrS lead to alterations in excitation wavelength (λ), which ultimately elevates arrhythmic risk. A major challenge for clinicians in managing this condition is the difficulty in predicting the subset of patients who will suffer from life-threatening VT/VF. Several repolarization risk markers have been used thus far, but these neglect the contributions of conduction abnormalities in the form of slowing and dispersion. Indices incorporating both repolarization and conduction and based on the concept of λ have recently been proposed. These may have better predictive values than the existing markers.
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Affiliation(s)
- Gary Tse
- Department of Medicine and Therapeutics, Chinese University of Hong KongHong Kong, Hong Kong
- Li Ka Shing Institute of Health Sciences, Chinese University of Hong KongHong Kong, Hong Kong
| | - Tong Liu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical UniversityTianjin, China
| | - Ka H. C. Li
- Faculty of Medicine, Newcastle UniversityNewcastle, UK
| | - Victoria Laxton
- Intensive Care Department, Royal Brompton and Harefield NHS TrustLondon, UK
| | - Yin W. F. Chan
- School of Biological Sciences, University of CambridgeCambridge, UK
| | - Wendy Keung
- Stem Cell and Regenerative Medicine Consortium, Li Ka Shing Faculty of Medicine, The University of Hong KongPokfulam, Hong Kong
| | - Ronald A. Li
- Ming Wai Lau Centre for Reparative Medicine, Karolinska InstitutetSolna, Sweden
| | - Bryan P. Yan
- Department of Medicine and Therapeutics, Chinese University of Hong KongHong Kong, Hong Kong
- Department of Epidemiology and Preventive Medicine, Monash UniversityMelbourne, VIC, Australia
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Loussouarn G, Sternberg D, Nicole S, Marionneau C, Le Bouffant F, Toumaniantz G, Barc J, Malak OA, Fressart V, Péréon Y, Baró I, Charpentier F. Physiological and Pathophysiological Insights of Nav1.4 and Nav1.5 Comparison. Front Pharmacol 2016; 6:314. [PMID: 26834636 PMCID: PMC4712308 DOI: 10.3389/fphar.2015.00314] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 12/21/2015] [Indexed: 12/19/2022] Open
Abstract
Mutations in Nav1.4 and Nav1.5 α-subunits have been associated with muscular and cardiac channelopathies, respectively. Despite intense research on the structure and function of these channels, a lot of information is still missing to delineate the various physiological and pathophysiological processes underlying their activity at the molecular level. Nav1.4 and Nav1.5 sequences are similar, suggesting structural and functional homologies between the two orthologous channels. This also suggests that any characteristics described for one channel subunit may shed light on the properties of the counterpart channel subunit. In this review article, after a brief clinical description of the muscular and cardiac channelopathies related to Nav1.4 and Nav1.5 mutations, respectively, we compare the knowledge accumulated in different aspects of the expression and function of Nav1.4 and Nav1.5 α-subunits: the regulation of the two encoding genes (SCN4A and SCN5A), the associated/regulatory proteins and at last, the functional effect of the same missense mutations detected in Nav1.4 and Nav1.5. First, it appears that more is known on Nav1.5 expression and accessory proteins. Because of the high homologies of Nav1.5 binding sites and equivalent Nav1.4 sites, Nav1.5-related results may guide future investigations on Nav1.4. Second, the analysis of the same missense mutations in Nav1.4 and Nav1.5 revealed intriguing similarities regarding their effects on membrane excitability and alteration in channel biophysics. We believe that such comparison may bring new cues to the physiopathology of cardiac and muscular diseases.
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Affiliation(s)
- Gildas Loussouarn
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Damien Sternberg
- Institut National de la Santé et de la Recherche Médicale, U1127Paris, France; Sorbonne Universités, Université Pierre-et-Marie-Curie, UMR S1127Paris, France; Centre National de la Recherche Scientifique, UMR 7225Paris, France; Institut du Cerveau et de la Moelle Épinière, ICMParis, France; Assistance Publique - Hôpitaux de Paris (AP-HP), Centres de Référence des Canalopathies Musculaires et des Maladies Neuro-musculaires Paris-EstParis, France; Assistance Publique - Hôpitaux de Paris (AP-HP), Hôpital de la Pitié Salpêtrière, Service de Biochimie Métabolique, Unité de Cardiogénétique et MyogénétiqueParis, France
| | - Sophie Nicole
- Institut National de la Santé et de la Recherche Médicale, U1127Paris, France; Sorbonne Universités, Université Pierre-et-Marie-Curie, UMR S1127Paris, France; Centre National de la Recherche Scientifique, UMR 7225Paris, France; Institut du Cerveau et de la Moelle Épinière, ICMParis, France
| | - Céline Marionneau
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Francoise Le Bouffant
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Gilles Toumaniantz
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Julien Barc
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Olfat A Malak
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Véronique Fressart
- Assistance Publique - Hôpitaux de Paris (AP-HP), Hôpital de la Pitié Salpêtrière, Service de Biochimie Métabolique, Unité de Cardiogénétique et Myogénétique Paris, France
| | - Yann Péréon
- Centre Hospitalier Universitaire de Nantes, Centre de Référence Maladies Neuromusculaires Nantes-AngersNantes, France; Atlantic Gene Therapies - Biotherapy Institute for Rare DiseasesNantes, France
| | - Isabelle Baró
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Flavien Charpentier
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France; Centre Hospitalier Universitaire de Nantes, l'Institut du ThoraxNantes, France
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14
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Antzelevitch C, Patocskai B. Brugada Syndrome: Clinical, Genetic, Molecular, Cellular, and Ionic Aspects. Curr Probl Cardiol 2016; 41:7-57. [PMID: 26671757 PMCID: PMC4737702 DOI: 10.1016/j.cpcardiol.2015.06.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Brugada syndrome (BrS) is an inherited cardiac arrhythmia syndrome first described as a new clinical entity in 1992. Electrocardiographically characterized by distinct coved type ST segment elevation in the right-precordial leads, the syndrome is associated with a high risk for sudden cardiac death in young adults, and less frequently in infants and children. The electrocardiographic manifestations of BrS are often concealed and may be unmasked or aggravated by sodium channel blockers, a febrile state, vagotonic agents, as well as by tricyclic and tetracyclic antidepressants. An implantable cardioverter defibrillator is the most widely accepted approach to therapy. Pharmacologic therapy is designed to produce an inward shift in the balance of currents active during the early phases of the right ventricular action potential (AP) and can be used to abort electrical storms or as an adjunct or alternative to device therapy when use of an implantable cardioverter defibrillator is not possible. Isoproterenol, cilostazol, and milrinone boost calcium channel current and drugs like quinidine, bepridil, and the Chinese herb extract Wenxin Keli inhibit the transient outward current, acting to diminish the AP notch and thus to suppress the substrate and trigger for ventricular tachycardia or fibrillation. Radiofrequency ablation of the right ventricular outflow tract epicardium of patients with BrS has recently been shown to reduce arrhythmia vulnerability and the electrocardiographic manifestation of the disease, presumably by destroying the cells with more prominent AP notch. This review provides an overview of the clinical, genetic, molecular, and cellular aspects of BrS as well as the approach to therapy.
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Affiliation(s)
| | - Bence Patocskai
- Masonic Medical Research Laboratory, Utica, NY 13501
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Szeged, Hungary
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Abstract
OBJECTIVE The objective was to provide a brief history of J wave syndromes and to summarize our current understanding of their molecular, ionic, cellular mechanisms, and clinical features. We will also discuss the existing debates and further direction in basic and clinical research for J wave syndromes. DATA SOURCES The publications on key words of "J wave syndromes", "early repolarization syndrome (ERS)", "Brugada syndrome (BrS)" and "ST-segment elevation myocardial infarction (STEMI)" were comprehensively reviewed through search of the PubMed literatures without restriction on the publication date. STUDY SELECTION Original articles, reviews and other literatures concerning J wave syndromes, ERS, BrS and STEMI were selected. RESULTS J wave syndromes were firstly defined by Yan et al. in a Chinese journal a decade ago, which represent a spectrum of variable phenotypes characterized by appearance of prominent electrocardiographic J wave including ERS, BrS and ventricular fibrillation (VF) associated with hypothermia and acute STEMI. J wave syndromes can be inherited or acquired and are mechanistically linked to amplification of the transient outward current (I to )-mediated J waves that can lead to phase 2 reentry capable of initiating VF. CONCLUSIONS J wave syndromes are a group of newly highlighted clinical entities that share similar molecular, ionic and cellular mechanism and marked by amplified J wave on the electrocardiogram and a risk of VF. The clinical challenge ahead is to identify the patients with J wave syndromes who are at risk for sudden cardiac death and determine the alternative therapeutic strategies to reduce mortality.
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Affiliation(s)
- Guo-Liang Li
- Department of Cardiovascular Medicine, The First Affiliated Hospital, Xi’an Jiaotong University College of Medicine, Xi’an, Shaanxi 710061, China
| | - Lin Yang
- Department of Cardiovascular Medicine, The First Affiliated Hospital, Xi’an Jiaotong University College of Medicine, Xi’an, Shaanxi 710061, China
| | - Chang-Cong Cui
- Department of Cardiovascular Medicine, The First Affiliated Hospital, Xi’an Jiaotong University College of Medicine, Xi’an, Shaanxi 710061, China
| | - Chao-Feng Sun
- Department of Cardiovascular Medicine, The First Affiliated Hospital, Xi’an Jiaotong University College of Medicine, Xi’an, Shaanxi 710061, China
| | - Gan-Xin Yan
- Department of Cardiovascular Medicine, The First Affiliated Hospital, Xi’an Jiaotong University College of Medicine, Xi’an, Shaanxi 710061, China
- Department of Cardiovascular Medicine, Lankenau Medical Center and Lankenau Institute of Medical Research, PA, USA
- Department of Cardiovascular Medicine, Jefferson Medical College of Thomas Jefferson University, PA, USA
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16
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Compound heterozygous mutations in the SCN5A-encoded Nav1.5 cardiac sodium channel resulting in atrial standstill and His-Purkinje system disease. J Pediatr 2014; 165:1050-2. [PMID: 25171853 DOI: 10.1016/j.jpeds.2014.07.036] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 06/02/2014] [Accepted: 07/18/2014] [Indexed: 11/21/2022]
Abstract
An 11-year-old girl on evaluation for syncope was found to have progressive sinus node dysfunction and His-Purkinje system disease with atrial standstill. Genetic analysis revealed compound heterozygous mutations of the SCN5A gene in a novel combination.
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17
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Zhang J, Chen Y, Yang J, Xu B, Wen Y, Xiang G, Wei G, Zhu C, Xing Y, Li Y. Electrophysiological and trafficking defects of the SCN5A T353I mutation in Brugada syndrome are rescued by alpha-allocryptopine. Eur J Pharmacol 2014; 746:333-43. [PMID: 25261036 DOI: 10.1016/j.ejphar.2014.09.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 09/04/2014] [Accepted: 09/08/2014] [Indexed: 10/24/2022]
Abstract
Brugada syndrome (BrS), which causes arrhythmias that lead to sudden cardiac death, is linked to loss-of-function mutations that affect sodium channels. Here, we investigate the rescue effect of alpha-allocryptopine (All) from Chinese herbal medicine in a T353I mutation of SCN5A, which combines trafficking abnormalities with Brugada syndrome. SCN5A-T353I expressed in HEK293 cells showed a small peak current (I(peak)) of only 59.6% of WT and an observably sustained current (I(sus)). We found that All strongly enhanced the I(peak) of the T353I channel by enhancing the plasma membrane (PM) expression of Nav1.5 and rescued defective trafficking after co-incubation with HEK293 cells that carry mutation channel 24 h. It is also beneficial to increase the I(peak) of the T353I mutation by All by prolonging the closed-state inactivation (CSI) process and shortening the recovery from inactivation of the T353I mutation. Interestingly, the I(sus) of T353I was significantly inhibited by All, which reduces the occurrence of LQT syndrome 3 (LQT3). We provide evidence that All can rescue the trafficking deficiencies and restore the cellular electrophysiological characteristics of SCN5A-T353I. This feature of All may benefit patients with the BrS-associated Nav1.5 channel and might have other potential therapeutic effects.
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Affiliation(s)
- Jiancheng Zhang
- Provincial Clinical Medicine College of Fujian Medical University, Fuzhou 350001, Fujian, PR China
| | - Yu Chen
- Guang׳anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, PR China
| | - Jie Yang
- Department of Cardiology, General Hospital of People׳s Liberation Army, Beijing 100853, PR China
| | - Bin Xu
- Department of Cardiology, General Hospital of People׳s Liberation Army, Beijing 100853, PR China
| | - Yi Wen
- Department of Cardiology, General Hospital of People׳s Liberation Army, Beijing 100853, PR China
| | - Guojian Xiang
- Provincial Clinical Medicine College of Fujian Medical University, Fuzhou 350001, Fujian, PR China
| | - Guoliang Wei
- Provincial Clinical Medicine College of Fujian Medical University, Fuzhou 350001, Fujian, PR China
| | - Chao Zhu
- Department of Cardiology, General Hospital of People׳s Liberation Army, Beijing 100853, PR China
| | - Yanwei Xing
- Guang׳anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, PR China.
| | - Yang Li
- Department of Cardiology, General Hospital of People׳s Liberation Army, Beijing 100853, PR China.
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18
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Liu C, Tester DJ, Hou Y, Wang W, Lv G, Ackerman MJ, Makielski JC, Cheng J. Is sudden unexplained nocturnal death syndrome in Southern China a cardiac sodium channel dysfunction disorder? Forensic Sci Int 2014; 236:38-45. [PMID: 24529773 DOI: 10.1016/j.forsciint.2013.12.033] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Revised: 11/27/2013] [Accepted: 12/27/2013] [Indexed: 11/15/2022]
Abstract
Sudden unexplained nocturnal death syndrome (SUNDS) remains an enigma to both forensic pathologists and physicians. Previous epidemiological, clinical, and pilot genetic studies have implicated that SUNDS is most likely a disease allelic to Brugada syndrome (BrS). We have performed postmortem genetic testing to address the spectrum and role of genetic abnormalities in the SCN5A-encoded cardiac sodium channel and its several associated proteins in SUNDS victims from Southern China. Genomic DNA extracted from the blood samples of 123 medico-legal autopsy-negative SUNDS cases and 104 sex-, age- and ethnic-matched controls from Southern China underwent comprehensive amino acid coding region mutational analysis for the BrS associated genes SCN5A, SCN1B, SCN2B, SCN3B, SCN4B, MOG1, and GPD1-L using PCR and direct sequencing. We identified a total of 7 unique (4 novel) putative pathogenic mutations (all in SCN5A; V95I, R121Q [2 cases], R367H, R513H, D870H, V1764D, and S1937F) in 8/123 (6.5%) SUNDS cases. Three SCN5A mutations (V95I, R121Q, and R367H) have been previously implicated in BrS. An additional 8 cases hosted rare variants of uncertain clinical significance (SCN5A: V1098L, V1202M, R1512W; SCN1B: V138I [3 cases], T189M [2 cases]; SCN3B: A195T). There were no non-synonymous mutations found in SCN2B, SCN4B, MOG1, or GPD1-L. This first comprehensive genotyping for SCN5A and related genes in the Chinese Han population with SUNDS discovered 13 mutations, 4 of them novel, in 16 cases, which suggests cardiac sodium channel dysfunction might account for the pathogenesis of 7-13% of SUNDS in Southern China.
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Affiliation(s)
- Chao Liu
- Guangzhou Institute of Forensic Science, Guangzhou 510030, China
| | - David J Tester
- Departments of Medicine, Pediatrics, and Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, United States
| | - Yiding Hou
- Department of Forensic Pathology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Wen Wang
- Department of Forensic Pathology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Guoli Lv
- Guangzhou Institute of Forensic Science, Guangzhou 510030, China
| | - Michael J Ackerman
- Departments of Medicine, Pediatrics, and Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, United States
| | - Jonathan C Makielski
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI 53792, United States
| | - Jianding Cheng
- Department of Forensic Pathology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China.
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Three cases of corticosteroid therapy triggering ventricular fibrillation in J-wave syndromes. Heart Vessels 2013; 29:867-72. [PMID: 24281399 PMCID: PMC4226925 DOI: 10.1007/s00380-013-0443-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 11/08/2013] [Indexed: 12/20/2022]
Abstract
We describe three cases of J-wave syndrome in which ventricular fibrillation (VF) was probably induced by corticosteroid therapy. The patients involved were being treated with prednisolone for concomitant bronchial asthma. One of the three patients had only one episode of VF during her long follow-up period (14 years). Two patients had hypokalemia during their VF episodes. Corticosteroids have been shown to induce various types of arrhythmia and to modify cardiac potassium channels. We discuss the possible association between corticosteroid therapy and VF in J-wave syndrome based on the cases we have encountered.
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20
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Remme CA. Cardiac sodium channelopathy associated with SCN5A mutations: electrophysiological, molecular and genetic aspects. J Physiol 2013; 591:4099-116. [PMID: 23818691 DOI: 10.1113/jphysiol.2013.256461] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Over the last two decades, an increasing number of SCN5A mutations have been described in patients with long QT syndrome type 3 (LQT3), Brugada syndrome, (progressive) conduction disease, sick sinus syndrome, atrial standstill, atrial fibrillation, dilated cardiomyopathy, and sudden infant death syndrome (SIDS). Combined genetic, electrophysiological and molecular studies have provided insight into the dysfunction and dysregulation of the cardiac sodium channel in the setting of SCN5A mutations identified in patients with these inherited arrhythmia syndromes. However, risk stratification and patient management is hindered by the reduced penetrance and variable disease expressivity in sodium channelopathies. Furthermore, various SCN5A-related arrhythmia syndromes are known to display mixed phenotypes known as cardiac sodium channel overlap syndromes. Determinants of variable disease expressivity, including genetic background and environmental factors, are suspected but still largely unknown. Moreover, it has become increasingly clear that sodium channel function and regulation is more complicated than previously assumed, and the sodium channel may play additional, as of yet unrecognized, roles in cardiac structure and function. Development of cardiac structural abnormalities secondary to SCN5A mutations has been reported, but the clinical relevance and underlying mechanisms are unclear. Increased insight into these issues would enable a major next step in research related to cardiac sodium channel disease, ultimately enabling improved diagnosis, risk stratification and treatment strategies.
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Affiliation(s)
- Carol Ann Remme
- C. A. Remme: Department of Experimental Cardiology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
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Zumhagen S, Veldkamp MW, Stallmeyer B, Baartscheer A, Eckardt L, Paul M, Remme CA, Bhuiyan ZA, Bezzina CR, Schulze-Bahr E. A heterozygous deletion mutation in the cardiac sodium channel gene SCN5A with loss- and gain-of-function characteristics manifests as isolated conduction disease, without signs of Brugada or long QT syndrome. PLoS One 2013; 8:e67963. [PMID: 23840796 PMCID: PMC3695936 DOI: 10.1371/journal.pone.0067963] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 05/23/2013] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND The SCN5A gene encodes for the α-subunit of the cardiac sodium channel NaV1.5, which is responsible for the rapid upstroke of the cardiac action potential. Mutations in this gene may lead to multiple life-threatening disorders of cardiac rhythm or are linked to structural cardiac defects. Here, we characterized a large family with a mutation in SCN5A presenting with an atrioventricular conduction disease and absence of Brugada syndrome. METHOD AND RESULTS In a large family with a high incidence of sudden cardiac deaths, a heterozygous SCN5A mutation (p.1493delK) with an autosomal dominant inheritance has been identified. Mutation carriers were devoid of any cardiac structural changes. Typical ECG findings were an increased P-wave duration, an AV-block I° and a prolonged QRS duration with an intraventricular conduction delay and no signs for Brugada syndrome. HEK293 cells transfected with 1493delK showed strongly (5-fold) reduced Na(+) currents with altered inactivation kinetics compared to wild-type channels. Immunocytochemical staining demonstrated strongly decreased expression of SCN5A 1493delK in the sarcolemma consistent with an intracellular trafficking defect and thereby a loss-of-function. In addition, SCN5A 1493delK channels that reached cell membrane showed gain-of-function aspects (slowing of the fast inactivation, reduction in the relative fraction of channels that fast inactivate, hastening of the recovery from inactivation). CONCLUSION In a large family, congregation of a heterozygous SCN5A gene mutation (p.1493delK) predisposes for conduction slowing without evidence for Brugada syndrome due to a predominantly trafficking defect that reduces Na(+) current and depolarization force.
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Affiliation(s)
- Sven Zumhagen
- Institute for Genetics of Heart Diseases, Department of Cardiovascular Medicine, University Hospital Münster, Münster, Germany.
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23
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Disertori M, Quintarelli S, Grasso M, Pilotto A, Narula N, Favalli V, Canclini C, Diegoli M, Mazzola S, Marini M, Del Greco M, Bonmassari R, Masè M, Ravelli F, Specchia C, Arbustini E. Autosomal recessive atrial dilated cardiomyopathy with standstill evolution associated with mutation of Natriuretic Peptide Precursor A. ACTA ACUST UNITED AC 2012; 6:27-36. [PMID: 23275345 DOI: 10.1161/circgenetics.112.963520] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Atrial dilatation and atrial standstill are etiologically heterogeneous phenotypes with poorly defined nosology. In 1983, we described 8-years follow-up of atrial dilatation with standstill evolution in 8 patients from 3 families. We later identified 5 additional patients with identical phenotypes: 1 member of the largest original family and 4 unrelated to the 3 original families. All families are from the same geographic area in Northeast Italy. METHODS AND RESULTS We followed up the 13 patients for up to 37 years, extended the clinical investigation and monitoring to living relatives, and investigated the genetic basis of the disease. The disease was characterized by: (1) clinical onset in adulthood; (2) biatrial dilatation up to giant size; (3) early supraventricular arrhythmias with progressive loss of atrial electric activity to atrial standstill; (4) thromboembolic complications; and (5) stable, normal left ventricular function and New York Heart Association functional class during the long-term course of the disease. By linkage analysis, we mapped a locus at 1p36.22 containing the Natriuretic Peptide Precursor A gene. By sequencing Natriuretic Peptide Precursor A, we identified a homozygous missense mutation (p.Arg150Gln) in all living affected individuals of the 6 families. All patients showed low serum levels of atrial natriuretic peptide. Heterozygous mutation carriers were healthy and demonstrated normal levels of atrial natriuretic peptide. CONCLUSIONS Autosomal recessive atrial dilated cardiomyopathy is a rare disease associated with homozygous mutation of the Natriuretic Peptide Precursor A gene and characterized by extreme atrial dilatation with standstill evolution, thromboembolic risk, preserved left ventricular function, and severely decreased levels of atrial natriuretic peptide.
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Vouliotis AI, Gatzoulis KA, Dilaveris P, Stefanadis C. Multiple syncope mechanisms coexisting in a Brugada syndrome patient requiring a single therapeutic approach. Herz 2012; 38:309-12. [PMID: 23052904 DOI: 10.1007/s00059-012-3693-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Revised: 08/27/2012] [Accepted: 09/04/2012] [Indexed: 11/29/2022]
Abstract
We report the case of a Brugada syndrome patient with a history of syncopal and presyncopal episodes and evidence of sinus node and atrioventricular (AV) conduction abnormalities. The patient developed sinus bradycardia, sinoatrial conduction abnormalities, prolonged HV interval, early appearance of AV block, AV nodal reentrant tachycardia and polymorphic ventricular tachycardia in the electrophysiological study. He was treated with a dual-chamber pacemaker defibrillator. At the 9-year follow-up, the patient remained asymptomatic with several episodes of 1:1 AV-relationship tachycardia, interrupted with antitachycardia pacing, while the predominant pacing states of the device were AP-VS and AS-VP for most of the time.
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Affiliation(s)
- A I Vouliotis
- 1st Department of Cardiology, National and Kapodistrian University of Athens, Athens, Greece.
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Affiliation(s)
- Yuka Mizusawa
- Heart Failure Research Centre, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands
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Characteristics of electrocardiographic repolarization in acute myocardial infarction complicated by ventricular fibrillation. J Electrocardiol 2012; 45:252-9. [DOI: 10.1016/j.jelectrocard.2011.11.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Indexed: 11/22/2022]
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Concomitant Brugada-like and short QT electrocardiogram linked to SCN5A mutation. Eur J Hum Genet 2012; 20:1189-92. [PMID: 22490985 DOI: 10.1038/ejhg.2012.63] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mutations in the α-subunit of cardiac sodium channel gene SCN5A can lead to the overlapping phenotypes of both the Brugada and type 3 long QT syndromes. However, the combination of Brugada and a short QT phenotype resulting from mutation in SCN5A has not previously been described. A man with concomitant Brugada-like and short QT electrocardiogram (ECG) was identified and the SCN5A gene was sequenced. Whole-cell patch clamp analysis of human embryo kidney (HEK) 293 cells expressing a SCN5A channel with the patient's sequence was used to investigate the biophysical properties of the channel. The patient with the family history of sudden death showed Brugada-like and short QT interval ECG. Sequence analysis of the coding region of the SCN5A gene, identified a G to A heterozygous missense mutation at nucleotide site 2066 that resulted in a amino-acid substitution of arginine to histidine at amino-acid site 689 (R689H). Patch clamp analysis showed that the R689H failed to generate current when heterologously expressed in HEK293 cells, indicating it was a loss-of-function mutation. Our finding firstly shows that a heterozygous missense mutation R689H in SCN5A gene results in the loss of protein function and the coexistents of the Brugada-like and short QT interval ECG phenotypes.
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Watanabe H, Nogami A, Ohkubo K, Kawata H, Hayashi Y, Ishikawa T, Makiyama T, Nagao S, Yagihara N, Takehara N, Kawamura Y, Sato A, Okamura K, Hosaka Y, Sato M, Fukae S, Chinushi M, Oda H, Okabe M, Kimura A, Maemura K, Watanabe I, Kamakura S, Horie M, Aizawa Y, Shimizu W, Makita N. Electrocardiographic characteristics and SCN5A mutations in idiopathic ventricular fibrillation associated with early repolarization. Circ Arrhythm Electrophysiol 2011; 4:874-81. [PMID: 22028457 DOI: 10.1161/circep.111.963983] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Recently, we and others reported that early repolarization (J wave) is associated with idiopathic ventricular fibrillation. However, its clinical and genetic characteristics are unclear. METHODS AND RESULTS This study included 50 patients (44 men; age, 45 ± 17 years) with idiopathic ventricular fibrillation associated with early repolarization, and 250 age- and sex-matched healthy controls. All of the patients had experienced arrhythmia events, and 8 (16%) had a family history of sudden death. Ventricular fibrillation was inducible by programmed electric stimulation in 15 of 29 patients (52%). The heart rate was slower and the PR interval and QRS duration were longer in patients with idiopathic ventricular fibrillation than in controls. We identified nonsynonymous variants in SCN5A (resulting in A226D, L846R, and R367H) in 3 unrelated patients. These variants occur at residues that are highly conserved across mammals. His-ventricular interval was prolonged in all of the patients carrying an SCN5A mutation. Sodium channel blocker challenge resulted in an augmentation of early repolarization or development of ventricular fibrillation in all of 3 patients, but none was diagnosed with Brugada syndrome. In heterologous expression studies, all of the mutant channels failed to generate any currents. Immunostaining revealed a trafficking defect in A226D channels and normal trafficking in R367H and L846R channels. CONCLUSIONS We found reductions in heart rate and cardiac conduction and loss-of-function mutations in SCN5A in patients with idiopathic ventricular fibrillation associated with early repolarization. These findings support the hypothesis that decreased sodium current enhances ventricular fibrillation susceptibility.
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Affiliation(s)
- Hiroshi Watanabe
- Division of Cardiology, Niigata University School of Medicine, Niigata, Japan.
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Hasdemir H, Alper AT, Güvenç TS, Arslan Y, Aksu H, Poyraz E, Nurkalem Z, Orhan AL, Cakmak N. Coexistent Brugada syndrome and Wolff-Parkinson-White syndrome: what is the first clinical presentation? PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2011; 34:760-3. [PMID: 21208236 DOI: 10.1111/j.1540-8159.2010.02997.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The coexistence of Brugada syndrome and Wolff-Parkinson-White (WPW) syndrome is a very rare phenomenon. We describe a 31-year-old patient without any previous cardiac disorder admitted to our hospital due to palpitations and concomitantly diagnosed as WPW syndrome and treated with radiofrequency catheter ablation. He was later diagnosed with Brugada syndrome and followed-up 2 years without any symptoms. We discuss other previously reported cases in literature, in which these two conditions exist simultaneously.
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Affiliation(s)
- Hakan Hasdemir
- Department of Cardiology, Siyami Ersek Thoracic and Cardiovascular Surgery Center, Training and Research Hospital, Istanbul, Turkey.
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Berne P, Brugada J. Brugada Syndrome 2010. Card Electrophysiol Clin 2010; 2:533-549. [PMID: 28770717 DOI: 10.1016/j.ccep.2010.09.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The Brugada syndrome is a genetically determined cardiac disorder, presenting with characteristic electrocardiogram features and high risk of sudden cardiac death from polymorphic ventricular tachycardia/ventricular fibrillation in young individuals with a structurally normal heart. Scientific knowledge about the disease has grown exponentially in recent years. Two consensus reports on the disease were published (in 2002 and 2005) in an effort to state diagnostic criteria, risk stratification, and treatment indications. However, substantial controversies remain, especially considering risk stratification of asymptomatic patients. Given the enormous amount of valuable information collected by many groups since the consensus reports, current diagnostic criteria, recommended prognostic tools, and treatment must be reviewed. This article briefly reviews recent advances in understanding of Brugada syndrome and its genetic and molecular basis, arrhythmogenic mechanisms, and clinical course. An update of tools for risk stratification and treatment of the condition is also included.
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Affiliation(s)
- Paola Berne
- Arrhythmia Section, Cardiology Department, Thorax Institute, Hospital Clínic, Institut de Investigació Biomèdica August Pi i Sunyer (IDIBAPS), University of Barcelona, C/Villarroel, 170, 08036 Barcelona, Catalonia, Spain
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Abstract
The J wave, also referred to as an Osborn wave, is a deflection immediately following the QRS complex of the surface ECG. When partially buried in the R wave, the J wave appears as J-point elevation or ST-segment elevation. Several lines of evidence have suggested that arrhythmias associated with an early repolarization pattern in the inferior or mid to lateral precordial leads, Brugada syndrome, or arrhythmias associated with hypothermia and the acute phase of ST-segment elevation myocardial infarction are mechanistically linked to abnormalities in the manifestation of the transient outward current (I(to))-mediated J wave. Although Brugada syndrome and early repolarization syndrome differ with respect to the magnitude and lead location of abnormal J-wave manifestation, they can be considered to represent a continuous spectrum of phenotypic expression that we propose be termed J-wave syndromes. This review summarizes our current state of knowledge concerning J-wave syndromes, bridging basic and clinical aspects. We propose to divide early repolarization syndrome into three subtypes: type 1, which displays an early repolarization pattern predominantly in the lateral precordial leads, is prevalent among healthy male athletes and is rarely seen in ventricular fibrillation survivors; type 2, which displays an early repolarization pattern predominantly in the inferior or inferolateral leads, is associated with a higher level of risk; and type 3, which displays an early repolarization pattern globally in the inferior, lateral, and right precordial leads, is associated with the highest level of risk for development of malignant arrhythmias and is often associated with ventricular fibrillation storms.
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Hedley PL, Jørgensen P, Schlamowitz S, Moolman-Smook J, Kanters JK, Corfield VA, Christiansen M. The genetic basis of Brugada syndrome: a mutation update. Hum Mutat 2009; 30:1256-66. [PMID: 19606473 DOI: 10.1002/humu.21066] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Brugada syndrome (BrS) is a condition characterized by a distinct ST-segment elevation in the right precordial leads of the electrocardiogram and, clinically, by an increased risk of cardiac arrhythmia and sudden death. The condition predominantly exhibits an autosomal dominant pattern of inheritance with an average prevalence of 5:10,000 worldwide. Currently, more than 100 mutations in seven genes have been associated with BrS. Loss-of-function mutations in SCN5A, which encodes the alpha-subunit of the Na(v)1.5 sodium ion channel conducting the depolarizing I(Na) current, causes 15-20% of BrS cases. A few mutations have been described in GPD1L, which encodes glycerol-3-phosphate dehydrogenase-1 like protein; CACNA1C, which encodes the alpha-subunit of the Ca(v)1.2 ion channel conducting the depolarizing I(L,Ca) current; CACNB2, which encodes the stimulating beta2-subunit of the Ca(v)1.2 ion channel; SCN1B and SCN3B, which, in the heart, encodes beta-subunits of the Na(v)1.5 sodium ion channel, and KCNE3, which encodes the ancillary inhibitory beta-subunit of several potassium channels including the Kv4.3 ion channel conducting the repolarizing potassium I(to) current. BrS exhibits variable expressivity, reduced penetrance, and "mixed phenotypes," where families contain members with BrS as well as long QT syndrome, atrial fibrillation, short QT syndrome, conduction disease, or structural heart disease, have also been described.
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Affiliation(s)
- Paula L Hedley
- Department of Clinical Biochemistry and Immunology, Statens Serum Institut, Copenhagen, Denmark
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Abstract
Since the identification of the first SCN5A mutation associated with long QT syndrome in 1995, several mutations in this gene for the alpha subunit of the cardiac sodium channel have been identified in a heterogeneous subset of cardiac rhythm syndromes, including Brugada syndrome, progressive cardiac conduction defect, sick sinus node syndrome, atrial fibrillation and dilated cardiomyopathy. Robust clinical evidence has been accompanied by bench studies performed in different models spanning from in vitro expression systems to transgenic mice. Together, these studies have helped establish genotype-phenotype correlations and have shaped our understanding of the role of the cardiac sodium channel in health and in disease. Remarkably, these advances in understanding have impacted on clinical management by allowing us to start developing gene-specific risk stratification schemes and mutation-specific management strategies. In this Review, we summarize the current understanding of the molecular mechanism of SCN5A-associated inherited arrhythmias, focusing on the most recent development of mutation-specific management in SCN5A-associated long QT syndrome type 3. We also briefly discuss arrhythmia-causing mutations in the genes encoding the beta subunit of the cardiac sodium channel and in those encoding proteins in the associated macromolecular complex.
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Abstract
Mutations in the cardiac sodium channel gene SCN5A are responsible for a spectrum of hereditary arrhythmias, including type-3 long QT syndrome (LQT3), Brugada syndrome (BrS), conduction disturbance and sinus node dysfunction. These syndromes were originally regarded as independent entities with distinct clinical manifestations and biophysical properties, but recent evidence shows considerable clinical overlap, implying a new disease entity known as an overlap syndrome of cardiac sodium channelopathy. Class IC sodium-channel blockers often induced the BrS phenotype in some patients with LQT3, confirming the clinical overlap of LQT3 and BrS. It also raises a concern about the safety of the class IC drug and questions about the determinants of overlap. Here, an overview is given of current knowledge on the clinical features, prevalence, and molecular and biophysical mechanisms underlying overlap syndrome to gain more insight into this complex issue and generate better therapeutic strategies for patient management.
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Affiliation(s)
- Naomasa Makita
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
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Meregalli PG, Tan HL, Probst V, Koopmann TT, Tanck MW, Bhuiyan ZA, Sacher F, Kyndt F, Schott JJ, Albuisson J, Mabo P, Bezzina CR, Le Marec H, Wilde AAM. Type of SCN5A mutation determines clinical severity and degree of conduction slowing in loss-of-function sodium channelopathies. Heart Rhythm 2008; 6:341-8. [PMID: 19251209 DOI: 10.1016/j.hrthm.2008.11.009] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2008] [Accepted: 11/07/2008] [Indexed: 11/25/2022]
Abstract
BACKGROUND Patients carrying loss-of-function SCN5A mutations linked to Brugada syndrome (BrS) or progressive cardiac conduction disease (PCCD) are at risk of sudden cardiac death at a young age. The penetrance and expressivity of the disease are highly variable, and new tools for risk stratification are needed. OBJECTIVES We aimed to establish whether the type of SCN5A mutation correlates with the clinical and electrocardiographic phenotype. METHODS We studied BrS or PCCD probands and their relatives who carried a SCN5A mutation. Mutations were divided into 2 main groups: missense mutations (M) or mutations leading to premature truncation of the protein (T). The M group was subdivided according to available biophysical properties: M mutations with <or=90% (M(active)) or >90% (M(inactive)) peak I(Na) reduction were analyzed separately. RESULTS The study group was composed of 147 individuals with 32 different mutations. No differences in age and sex distribution were found between the groups. Subjects carrying a T mutation had significantly more syncopes than those with an M(active) mutation (19 of 75 versus 2 of 35, P = .03). Also, mutations associated with drastic peak I(Na) reduction (T and M(inactive) mutants) had a significantly longer PR interval, compared with M(active) mutations. All other electrocardiographic parameters were comparable. After drug provocation testing, both PR and QRS intervals were significantly longer in the T and M(inactive) groups than in the M(active) group. CONCLUSION In loss-of-function SCN5A channelopathies, patients carrying T and M(inactive) mutations develop a more severe phenotype than those with M(active) mutations. This is associated with more severe conduction disorders. This is the first time that genetic data are proposed for risk stratification in BrS.
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Affiliation(s)
- Paola G Meregalli
- Department of Cardiology, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands
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Genetic Na+ channelopathies and sinus node dysfunction. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 98:171-8. [PMID: 19027778 DOI: 10.1016/j.pbiomolbio.2008.10.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Voltage-gated Na+ channels are transmembrane proteins that produce the fast inward Na+ current responsible for the depolarization phase of the cardiac action potential. They play fundamental roles in the initiation, propagation, and maintenance of normal cardiac rhythm. Inherited mutations in SCN5A, the gene encoding the pore-forming alpha-subunit of the cardiac-type Na+ channel, result in a spectrum of disease entities termed Na+ channelopathies. These include multiple arrhythmic syndromes, such as the long QT syndrome type 3 (LQT3), Brugada syndrome (BrS), an inherited cardiac conduction defect (CCD), sudden infant death syndrome (SIDS) and sick sinus syndrome (SSS). To date, mutational analyses have revealed more than 200 distinct mutations in SCN5A, of which at least 20 mutations are associated with sinus node dysfunction including SSS. This review summarizes recent findings bearing upon: (i) the functional role of distinct voltage-gated Na+ currents in sino-atrial node pacemaker function; (ii) genetic Na+ channelopathy and its relationship to sinus node dysfunction.
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Cardiac sodium channel overlap syndromes: different faces of SCN5A mutations. Trends Cardiovasc Med 2008; 18:78-87. [PMID: 18436145 DOI: 10.1016/j.tcm.2008.01.002] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2007] [Revised: 12/29/2007] [Accepted: 01/07/2008] [Indexed: 12/19/2022]
Abstract
Cardiac sodium channel dysfunction caused by mutations in the SCN5A gene is associated with a number of relatively uncommon arrhythmia syndromes, including long-QT syndrome type 3 (LQT3), Brugada syndrome, conduction disease, sinus node dysfunction, and atrial standstill, which potentially lead to fatal arrhythmias in relatively young individuals. Although these various arrhythmia syndromes were originally considered separate entities, recent evidence indicates more overlap in clinical presentation and biophysical defects of associated mutant channels than previously appreciated. Various SCN5A mutations are now known to present with mixed phenotypes, a presentation that has become known as "overlap syndrome of cardiac sodium channelopathy." In many cases, multiple biophysical defects of single SCN5A mutations are suspected to underlie the overlapping clinical manifestations. Here, we provide an overview of current knowledge on SCN5A mutations associated with sodium channel overlap syndromes and discuss a possible role for modifiers in determining disease expressivity in the individual patient.
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Hosokawa Y, Morita N, Ogano M, Yokoyama H. Brugada Syndrome Subject to Depolarization Abnormality of the Conduction System. Ann Noninvasive Electrocardiol 2007; 12:383-7. [DOI: 10.1111/j.1542-474x.2007.00188.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Abstract
First introduced as a new clinical entity in 1992, the Brugada syndrome is associated with a relatively high risk of sudden death in young adults, and occasionally in children and infants. Recent years have witnessed a striking proliferation of papers dealing with the clinical and basic aspects of the disease. Characterized by a coved-type ST-segment elevation in the right precordial leads of the electrocardiogram (ECG), the Brugada syndrome has a genetic basis that thus far has been linked only to mutations in SCN5A, the gene that encodes the alpha-subunit of the sodium channel. The Brugada ECG is often concealed, but can be unmasked or modulated by a number of drugs and pathophysiological states including sodium channel blockers, a febrile state, vagotonic agents, tricyclic antidepressants, as well as cocaine and propranolol intoxication. Average age at the time of initial diagnosis or sudden death is 40 +/- 22, with the youngest patient diagnosed at 2 days of age and the oldest at 84 years. This review provides an overview of the clinical, genetic, molecular, and cellular aspects of the Brugada syndrome, incorporating the results of two recent consensus conferences. Controversies with regard to risk stratification and newly proposed pharmacologic strategies are discussed.
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Fazelifar AF, Haghjoo M, Arya A, Kazemi B, Bagherzadeh A, Nikoo MH, Sadr-Ameli MA. Spontaneous alternans in Brugada ECG morphology. J Interv Card Electrophysiol 2007; 15:131-4. [PMID: 16755343 DOI: 10.1007/s10840-006-8263-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Accepted: 03/11/2006] [Indexed: 10/24/2022]
Abstract
A 23-year-old man presented with sick sinus syndrome and Brugada-like ECG pattern. Coved type ECG (type 1) converted to saddleback configuration (type 2) when R-R interval decreased and it changed to coved type pattern with increasing R-R cycle length. During stable heart rate, there was no change in Brugada ECG pattern. The R-R interval effect on these patterns can be explained by intensity or kinetics of ion currents and autonomic tone.
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Affiliation(s)
- Amir Farjam Fazelifar
- Department of Pacemaker and Electrophysiology, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran.
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41
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Bezzina CR, Wilde AAM. Genetic Basis for Cardiac Arrhythmias. CARDIOVASCULAR MEDICINE 2007. [DOI: 10.1007/978-1-84628-715-2_126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Abstract
The incidence of Brugada syndrome (BS) is relatively high in Japan compared with the rest of the world, ranging between 0.1% and 0.2% in the general population. BS in Japan, as in other countries, is most prevalent in middle-aged men, and has characteristics ECG changes, a high recurrence rate in symptomatic patients, and relatively low incidence of SCN5A mutations. In contrast, both the incidence of a family history of BS and/or sudden cardiac death and the rate of developing cardiac events in asymptomatic patients are less in Japan than in other countries. Increased vagal tone and/or decreased sympathetic activity are suggested as provoking cardiac events. Several factors should be evaluated in risk stratification for recurrence of life-threatening arrhythmias, because there appears to be no single determinant for risk stratification: spontaneous ST elevation of coved-type (Type 1), family history of sudden cardiac death, inducible ventricular tachycardia/ventricular fibrillation and positive late potentials. An implantable cardioverter defibrillator is recommended for patients with aborted sudden cardiac death.
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Affiliation(s)
- Masayasu Hiraoka
- Department of Cardiovascular Diseases, Tokyo Medical and Dental University, Minato-ku, Tokyo 105-0011, Japan.
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Pfahnl AE, Viswanathan PC, Weiss R, Shang LL, Sanyal S, Shusterman V, Kornblit C, London B, Dudley SC. A sodium channel pore mutation causing Brugada syndrome. Heart Rhythm 2006; 4:46-53. [PMID: 17198989 PMCID: PMC1779366 DOI: 10.1016/j.hrthm.2006.09.031] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2006] [Accepted: 09/27/2006] [Indexed: 01/08/2023]
Abstract
BACKGROUND Brugada and long QT type 3 syndromes are linked to sodium channel mutations and clinically cause arrhythmias that lead to sudden death. We have identified a novel threonine-to-isoleucine missense mutation at position 353 (T353I) adjacent to the pore-lining region of domain I of the cardiac sodium channel (SCN5A) in a family with Brugada syndrome. Both male and female carriers are symptomatic at young ages, have typical Brugada-type electrocardiogram changes, and have relatively normal corrected QT intervals. OBJECTIVES To characterize the properties of the newly identified cardiac sodium channel (SCN5A) mutation at the cellular level. RESULTS Using whole-cell voltage clamp, we found that heterologous expression of SCN5A containing the T353I mutation resulted in 74% +/- 6% less peak macroscopic sodium current when compared with wild-type channels. A construct of the T353I mutant channel fused with green fluorescent protein failed to traffic properly to the sarcolemma, with a large proportion of channels sequestered intracellularly. Overnight exposure to 0.1 mM mexiletine, a Na(+) channel blocking agent, increased T353I channel trafficking to the membrane to near normal levels, but the mutant channels showed a significant late current that was 1.6% +/- 0.2% of peak sodium current at 200 ms, a finding seen with long QT mutations. CONCLUSIONS The clinical presentation of patients carrying the T353I mutation is that of Brugada syndrome and could be explained by a cardiac Na(+) channel trafficking defect. However, when the defect was ameliorated, the mutated channels had biophysical properties consistent with long QT syndrome. The lack of phenotypic changes associated with the long QT syndrome could be explained by a T353I-induced trafficking defect reducing the number of mutant channels with persistent currents present at the sarcolemma.
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Affiliation(s)
- Arnold E. Pfahnl
- Division of Cardiology, Atlanta Veterans Affairs Medical Center and Emory University, Atlanta, GA, 30033
| | | | | | - Lijuan L. Shang
- Division of Cardiology, Atlanta Veterans Affairs Medical Center and Emory University, Atlanta, GA, 30033
| | - Shamrendra Sanyal
- Division of Cardiology, Atlanta Veterans Affairs Medical Center and Emory University, Atlanta, GA, 30033
| | | | - Cari Kornblit
- Cardiovascular Institute, University of Pittsburgh, Pittsburgh, PA 15213
| | - Barry London
- Cardiovascular Institute, University of Pittsburgh, Pittsburgh, PA 15213
| | - Samuel C. Dudley
- Division of Cardiology, Atlanta Veterans Affairs Medical Center and Emory University, Atlanta, GA, 30033
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Poelzing S, Forleo C, Samodell M, Dudash L, Sorrentino S, Anaclerio M, Troccoli R, Iacoviello M, Romito R, Guida P, Chahine M, Pitzalis M, Deschênes I. SCN5A
Polymorphism Restores Trafficking of a Brugada Syndrome Mutation on a Separate Gene. Circulation 2006; 114:368-76. [PMID: 16864729 DOI: 10.1161/circulationaha.105.601294] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Brugada syndrome is associated with a high risk of sudden cardiac death and is caused by mutations in the cardiac voltage-gated sodium channel gene. Previously, the R282H-SCN5A mutation in the sodium channel gene was identified in patients with Brugada syndrome. In a family carrying the R282H-SCN5A mutation, an asymptomatic individual had a common H558R-SCN5A polymorphism and the mutation on separate chromosomes. Therefore, we hypothesized that the polymorphism could rescue the mutation. METHODS AND RESULTS In heterologous cells, expression of the mutation alone did not produce sodium current. However, coexpressing the mutation with the polymorphism produced significantly greater current than coexpressing the mutant with the wild-type gene, demonstrating that the polymorphism rescues the mutation. Using immunocytochemistry, we demonstrated that the R282H-SCN5A construct can traffic to the cell membrane only in the presence of the H558R-SCN5A polymorphism. Using fluorescence resonance energy transfer and protein fragments centered on H558R-SCN5A, we demonstrated that cardiac sodium channels preferentially interact when the polymorphism is expressed on one protein but not the other. CONCLUSIONS This study suggests a mechanism whereby the Brugada syndrome has incomplete penetrance. More importantly, this study suggests that genetic polymorphisms may be a potential target for future therapies aimed at rescuing specific dysfunctional protein channels.
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Affiliation(s)
- Steven Poelzing
- Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, 2500 MetroHealth Dr, Rammelkamp 658, Cleveland, OH 44109-1998, USA
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Shu J, Zhu T, Yang L, Cui C, Yan GX. ST-segment elevation in the early repolarization syndrome, idiopathic ventricular fibrillation, and the Brugada syndrome: cellular and clinical linkage. J Electrocardiol 2006; 38:26-32. [PMID: 16226071 DOI: 10.1016/j.jelectrocard.2005.06.006] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2005] [Accepted: 06/10/2005] [Indexed: 11/17/2022]
Abstract
ST-segment elevation in a structurally normal heart is associated with an electrocardiographic (ECG) J wave, which can be observed in the early repolarization syndrome (ERS), idiopathic ventricular fibrillation (VF), and the Brugada syndrome. Animal studies have demonstrated that the J wave is the consequence of a transmural voltage gradient resulting from an Ito-mediated action potential notch (spike and dome) in epicardium but not endocardium. Ito-mediated spike and dome morphology predisposes loss or depression of the dome in epicardium, leading to ST-segment elevation. Despite the fact that 3 clinical syndromes share many common ECG features, their clinical consequences are remarkably different. The ERS is a benign ECG finding characterized by a distinct J wave and ST segment in left precordial leads V4 through V6. In contrast, idiopathic VF and the Brugada syndrome, characterized by a J wave and ST-segment elevation in the inferior and right precordial leads, respectively, are the leading causes for sudden cardiac death in young Southeast Asian males. The underlying mechanism for such a difference in clinical consequences among these syndromes is due to a difference in Ito density and Ito-mediated epicardial spike and dome. When Ito is prominent, complete loss of the dome may occur due to either a decrease in inward currents or an increase in outward currents, leading to phase 2 reentry capable of initiating VF as in idiopathic VF and the Brugada syndrome. When Ito is relatively small as in the ERS, partial depression of the dome occurs without the development of phase 2 reentry.
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Affiliation(s)
- Juan Shu
- Cardiology Department, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China
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Fazelifar AF, Haghjoo M, Emkanjoo Z, Alizadeh A, Alasti M, Peighambari M, Sadr-Ameli MA. Brugada-Type ECG Association with Unexpected Sick Sinus Syndrome. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2006; 29:204-6. [PMID: 16492310 DOI: 10.1111/j.1540-8159.2006.00319.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A 23-year-old man was referred to our center for atrial flutter ablation. After arrhythmia termination sinus node dysfunction unmasked and persisted after 2 months drug-free follow-up. Secondary causes such as antiarrhythmic drug consumption, organic heart disease, or electrolyte disturbance could be excluded. Standard 12-lead ECG showed a coved-type ST elevation in V1-V3, which increased after flecainide provocative test. Following an unexpected sick sinus syndrome, a Brugada-type ECG should be noted.
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Affiliation(s)
- Amir Farjam Fazelifar
- Department of Pacemaker and Electrophysiology, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran.
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Abstract
The Brugada syndrome is a congenital syndrome of sudden cardiac death first described as a new clinical entity in 1992. Electrocardiographically characterized by a distinct coved-type ST segment elevation in the right precordial leads, the syndrome is associated with a high risk for sudden cardiac death in young and otherwise healthy adults, and less frequently in infants and children. The ECG manifestations of the Brugada syndrome are often dynamic or concealed and may be revealed or modulated by sodium channel blockers. The syndrome may also be unmasked or precipitated by a febrile state, vagotonic agents, alpha-adrenergic agonists, beta-adrenergic blockers, tricyclic or tetracyclic antidepressants, a combination of glucose and insulin, and hypokalemia, as well as by alcohol and cocaine toxicity. An implantable cardioverter-defibrillator (ICD) is the most widely accepted approach to therapy. Pharmacological therapy aimed at rebalancing the currents active during phase 1 of the right ventricular action potential is used to abort electrical storms, as an adjunct to device therapy, and as an alternative to device therapy when use of an ICD is not possible. Isoproterenol and cilostazol boost calcium channel current, and drugs like quinidine inhibit the transient outward current, acting to diminish the action potential notch and thus suppress the substrate and trigger for ventricular tachycardia/fibrillation (VT/VF).
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Affiliation(s)
- C Antzelevitch
- Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY 13501, USA.
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Makiyama T, Akao M, Tsuji K, Doi T, Ohno S, Takenaka K, Kobori A, Ninomiya T, Yoshida H, Takano M, Makita N, Yanagisawa F, Higashi Y, Takeyama Y, Kita T, Horie M. High Risk for Bradyarrhythmic Complications in Patients With Brugada Syndrome Caused by SCN5AGene Mutations. J Am Coll Cardiol 2005; 46:2100-6. [PMID: 16325048 DOI: 10.1016/j.jacc.2005.08.043] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Revised: 07/29/2005] [Accepted: 08/01/2005] [Indexed: 11/24/2022]
Abstract
OBJECTIVES We carried out a complete screening of the SCN5A gene in 38 Japanese patients with Brugada syndrome to investigate the genotype-phenotype relationship. BACKGROUND The gene SCN5A encodes the pore-forming alpha-subunit of voltage-gated cardiac sodium (Na) channel, which plays an important role in heart excitation/contraction. Mutations of SCN5A have been identified in 15% of patients with Brugada syndrome. METHODS In 38 unrelated patients with clinically diagnosed Brugada syndrome, we screened for SCN5A gene mutations using denaturing high-performance liquid chromatography and direct sequencing, and conducted a functional assay for identified mutations using whole-cell patch-clamp in heterologous expression system. RESULTS Four heterozygous mutations were identified (T187I, D356N, K1578fs/52, and R1623X) in 4 of the 38 patients. All of them had bradyarrhythmic complications: three with sick sinus syndrome (SSS) and the other (D356N) with paroxysmal complete atrioventricular block. SCN5A-linked Brugada patients were associated with a higher incidence of bradyarrhythmia (4 of 4) than non-SCN5A-linked Brugada patients (2 of 34). Families with T187I and K1578fs/52 had widespread penetrance of SSS. Notably, the patient with K1578fs/52, who had been diagnosed as having familial SSS without any clinical signs of Brugada syndrome, showed a Brugada-type ST-segment elevation after intravenous administration of pilsicainide and programmed electrical stimulation-induced ventricular tachycardia. All of the mutations encoded non-functional Na channels, and thus were suggested to cause impulse propagation defect underlying bradyarrhythmias. CONCLUSIONS Our findings suggest that loss-of-function SCN5A mutations resulting in Brugada syndrome are distinguished by profound bradyarrhythmias.
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Affiliation(s)
- Takeru Makiyama
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan
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Pérez Riera AR, Ferreira C, Dubner SJ, Schapachnik E, Soares JD, Francis J. Brief review of the recently described short QT syndrome and other cardiac channelopathies. Ann Noninvasive Electrocardiol 2005; 10:371-7. [PMID: 16029390 PMCID: PMC6932401 DOI: 10.1111/j.1542-474x.2005.00632.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
There are many diseases related to ion-channel disorders, so-called "channelopathies." Hereditary short QT syndrome is a clinical-electrocardiographic entity with autosomal-dominant mode of transmission and it is the most recently described channelopathy. The syndrome may affect infants, children, or young adults with strong positive family background of sudden cardiac death. Short QT syndrome is characterized by short QT and heart-rate-corrected QTc intervals. It is frequently associated with tall-, peaked-, and narrow-based T waves that are reminiscent of the typical "desert tent" T waves of hyperkalemia. There is a high tendency for paroxysmal atrial fibrillation due to the heterogeneous abbreviation of action potential duration and refractoriness of atrial myocytes. The arrhythmia can also be induced by programmed electrical stimulation. The safest treatment suggested is an implantable cardioverter defibrillator, though the possibilities of inappropriate shocks have caused some concern, especially in teenagers. The ability of quinidine to prolong the QT interval has the potential to be an effective therapy for patients with short QT syndrome. This is particularly important in developing countries, where the implantable cardioverter-defibrillator therapy is not always available. Since these patients are at risk of sudden cardiac death from birth, and implantable cardioverter-defibrillator implantation has a lot of limitations in very young children, the utility of quinidine has to be evaluated further. Clinicians need to be aware of this deadly electrocardiographic (ECG) pattern as it portends a high risk of sudden cardiac death in otherwise healthy subjects with structurally normal hearts.
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Makita N, Sasaki K, Groenewegen WA, Yokota T, Yokoshiki H, Murakami T, Tsutsui H. Congenital atrial standstill associated with coinheritance of a novel SCN5A mutation and connexin 40 polymorphisms. Heart Rhythm 2005; 2:1128-34. [PMID: 16188595 DOI: 10.1016/j.hrthm.2005.06.032] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Accepted: 06/30/2005] [Indexed: 12/31/2022]
Abstract
BACKGROUND Congenital atrial standstill has been linked to SCN5A. Incomplete penetrance observed in atrial standstill has been attributed in part to the digenic inheritance of polymorphisms in the atrial-specific gap junction connexin 40 (Cx40) in conjunction with an SCN5A mutation. OBJECTIVES The purpose of this study was to determine the clinical and biophysical characteristics of a novel SCN5A mutation identified in a family with atrial standstill. METHODS Family members of an apparently sporadic case of atrial standstill underwent genetic screening of SCN5A and atrial-specific genes including Cx40. Biophysical properties of the wild-type (WT) and mutant SCN5A channels in a heterologous expression system were studied using the whole-cell patch clamp technique. RESULTS The novel SCN5A mutation L212P was identified in the proband (age 11 years) and his father. The father was in normal sinus rhythm. The proband had no P waves on surface ECG, and his right atrium could not be captured by pacing. The recombinant L212P Na channel showed a large hyperpolarizing shift in both the voltage dependence of activation (WT: -48.1 +/- 0.9 mV; L212P: -63.5 +/- 1.5 mV; P < .001) and inactivation (WT: -86.6 +/- 0.9 mV; L212P: -95.6 +/- 0.8 mV; P < .001) and delayed recovery from inactivation. Further screenings for genetic variations that might mitigate L212P dysfunction revealed that the proband, but not his father, carries Cx40 polymorphisms inherited from his asymptomatic mother. CONCLUSION These results suggest that genetic defects in SCN5A most likely underlie atrial standstill. Coinheritance of Cx40 polymorphisms is a possible genetic factor that modifies the clinical manifestation of this inherited arrhythmia.
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Affiliation(s)
- Naomasa Makita
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
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