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Harvey A, Curnier D, Dodin P, Jacquemet V, Caru M. The Effects of Cycle Ergometer Versus Treadmill Exercise Stress Testing on QTc Interval Prolongation in Patients With Long QT Syndrome: A Systematic Review and Meta-analysis. Clin J Sport Med 2024:00042752-990000000-00218. [PMID: 39012267 DOI: 10.1097/jsm.0000000000001256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 01/16/2024] [Indexed: 07/17/2024]
Abstract
OBJECTIVE The safest and most effective exercise stress tests (EST) modalities for long QT syndrome (LQTS) are currently unknown. The main objective was to explore the effects of EST on the corrected QT interval (QTc) in patients with LQTS, and to compare the effects of different EST modalities (cycle ergometer vs treadmill). DATA SOURCES Systematic searches were performed in September 2022 in accordance with the PRISMA statement through PubMed, Medline, EBM Reviews, Embase, and Web of Science. MAIN RESULTS A total of 1728 patients with LQTS, whether congenital or acquired, without any age restrictions (pediatric age ≤18 years and adult age >19 years), and 2437 control subjects were included in the 49 studies. The QT interval data were available for 15 studies. Our analyses showed that the QT interval prolonged in a similar manner using either a cycle ergometer or a treadmill (standardized mean difference [SMD] = 1.89 [95% CI, 1.07-2.71] vs SMD = 1.46 [95% CI, 0.78-2.14], respectively). Therefore, it seems that either modality may be used to evaluate patients with LQTS. CONCLUSIONS The methodology for the measurement of the QT interval was very heterogeneous between studies, which inevitably influenced the quality of the analyses. Hence, researchers should proceed with caution when exploring and interpreting data in the field of exercise and LQTS.
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Affiliation(s)
- Audrey Harvey
- Laboratory of Pathophysiology of EXercise (LPEX), School of Kinesiology and Physical Activity Sciences, Faculty of Medicine, University of Montreal, Montreal, Canada
- Sainte-Justine University Health Center, Research Center, Montreal, Canada
| | - Daniel Curnier
- Laboratory of Pathophysiology of EXercise (LPEX), School of Kinesiology and Physical Activity Sciences, Faculty of Medicine, University of Montreal, Montreal, Canada
- Sainte-Justine University Health Center, Research Center, Montreal, Canada
| | - Philippe Dodin
- Sainte-Justine University Health Center, Research Center, Montreal, Canada
| | - Vincent Jacquemet
- Department of Pharmacology and Physiology, Faculty of Medicine, University of Montreal, Montreal, Canada; and
| | - Maxime Caru
- Department of Pediatrics and Department of Public Health Sciences, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
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Kashiwa A, Itoh H, Makiyama T, Wada Y, Ozawa J, Kato K, Fukuyama M, Nakajima T, Ohno S, Horie M. Clinical characterization of type 1 long QT syndrome caused by C-terminus Kv7.1 variants. Heart Rhythm 2024; 21:1113-1120. [PMID: 38367891 DOI: 10.1016/j.hrthm.2024.02.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 01/27/2024] [Accepted: 02/07/2024] [Indexed: 02/19/2024]
Abstract
BACKGROUND Variants in the KCNQ1 gene, encoding the α-subunit of the slow component of delayed rectifier K+ channel Kv7.1, cause long QT syndrome (LQTS) type 1. The location of variants may be one of the factors in determining prognosis. However, detailed genotype-phenotype relationships associated with C-terminus variants remain unelucidated. OBJECTIVE We investigated the clinical characteristics and variant-specific arrhythmic risks in patients with LQTS carrying Kv7.1 C-terminus variants. METHODS The study comprises 202 consecutive patients with LQTS (98 probands and 104 family members) who carry a rare heterozygous variant in the Kv7.1 C-terminus. Their clinical characteristics and arrhythmic events were investigated. RESULTS We identified 36 unique C-terminus variants (25 missense and 11 non-missense). The p.R366W variant was identified in 8 families, and p.T587M was identified in 21 families in large numbers from northwestern Japan. As for the location of the variant, we found that the variants in highly conserved regions and nonhelical domains were associated with longer QTc intervals compared with the variants in other regions. Both p.R366W and p.T587M variants are located in the highly conserved and functionally pivotal regions close to helices A and D, which are associated with calmodulin binding and channel assembly (tetramerization), respectively. The probands carrying p.T587M and p.R366W variants had worse arrhythmia outcomes compared with those with other C-terminus variants. The haplotype analysis of p.T587M families was suggestive of a founder effect. CONCLUSION The arrhythmic risk of C-terminus variants in Kv7.1 in LQTS is not homogeneous, and locations of variants can be a determining factor for prognosis.
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Affiliation(s)
- Asami Kashiwa
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan; Department of Cardiology, Niigata City General Hospital, Niigata, Japan.
| | - Hideki Itoh
- Division of Patient Safety, Hiroshima University Hospital, Minami-ku, Hiroshima, Japan
| | - Takeru Makiyama
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Yuko Wada
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Junichi Ozawa
- Department of Pediatrics, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Koichi Kato
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Megumi Fukuyama
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Tadashi Nakajima
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Seiko Ohno
- Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Minoru Horie
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan
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Younis A, Bos JM, Zareba W, Aktas MK, Wilde AAM, Tabaja C, Bodurian C, Tobert KE, McNitt S, Polonsky B, Shimizu W, Ackerman MJ, Goldenberg I. Association Between Syncope Trigger Type and Risk of Subsequent Life-Threatening Events in Patients With Long QT Syndrome. JAMA Cardiol 2023; 8:775-783. [PMID: 37436769 PMCID: PMC10339217 DOI: 10.1001/jamacardio.2023.1951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 05/13/2023] [Indexed: 07/13/2023]
Abstract
Importance Syncope is the most powerful predictor for subsequent life-threatening events (LTEs) in patients with congenital long QT syndrome (LQTS). Whether distinct syncope triggers are associated with differential subsequent risk of LTEs is unknown. Objective To evaluate the association between adrenergic (AD)- and nonadrenergic (non-AD)-triggered syncopal events and the risk of subsequent LTEs in patients with LQT types 1 to 3 (LQT1-3). Design, Setting, and Participants This retrospective cohort study included data from 5 international LQTS registries (Rochester, New York; the Mayo Clinic, Rochester, Minnesota; Israel, the Netherlands, and Japan). The study population comprised 2938 patients with genetically confirmed LQT1, LQT2, or LQT3 stemming from a single LQTS-causative variant. Patients were enrolled from July 1979 to July 2021. Exposures Syncope by AD and non-AD triggers. Main Outcomes and Measures The primary end point was the first occurrence of an LTE. Multivariate Cox regression was used to determine the association of AD- or non-AD-triggered syncope on the risk of subsequent LTE by genotype. Separate analysis was performed in patients with β-blockers. Results A total of 2938 patients were included (mean [SD] age at enrollment, 29 [7] years; 1645 [56%] female). In 1331 patients with LQT1, a first syncope occurred in 365 (27%) and was induced mostly with AD triggers (243 [67%]). Syncope preceded 43 subsequent LTEs (68%). Syncopal episodes associated with AD triggers were associated with the highest risk of subsequent LTE (hazard ratio [HR], 7.61; 95% CI, 4.18-14.20; P < .001), whereas the risk associated with syncopal events due to non-AD triggers was statistically nonsignificant (HR, 1.50; 95% CI, 0.21-4.77; P = .97). In 1106 patients with LQT2, a first syncope occurred in 283 (26%) and was associated with AD and non-AD triggers in 106 (37%) and 177 (63%), respectively. Syncope preceded 55 LTEs (56%). Both AD- and non-AD-triggered syncope were associated with a greater than 3-fold increased risk of subsequent LTE (HR, 3.07; 95% CI, 1.66-5.67; P ≤ .001 and HR, 3.45, 95% CI, 1.96-6.06; P ≤ .001, respectively). In contrast, in 501 patients with LQT3, LTE was preceded by a syncopal episode in 7 (12%). In patients with LQT1 and LQT2, treatment with β-blockers following a syncopal event was associated with a significant reduction in the risk of subsequent LTEs. The rate of breakthrough events during treatment with β-blockers was significantly higher among those treated with selective agents vs nonselective agents. Conclusion and Relevance In this study, trigger-specific syncope in LQTS patients was associated with differential risk of subsequent LTE and response to β-blocker therapy.
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Affiliation(s)
- Arwa Younis
- Cardiac Electrophysiology Section, Department of Cardiovascular Medicine, Cleveland Clinic, Cleveland, Ohio
- Clinical Cardiovascular Research Center, University of Rochester Medical Center, Rochester, New York
| | - J. Martijn Bos
- Divisions of Heart Rhythm Services and Pediatric Cardiology, Departments of Cardiovascular Medicine, Pediatric and Adolescent Medicine, and Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Genetic Heart Rhythm Clinic and Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Wojciech Zareba
- Clinical Cardiovascular Research Center, University of Rochester Medical Center, Rochester, New York
| | - Mehmet K. Aktas
- Clinical Cardiovascular Research Center, University of Rochester Medical Center, Rochester, New York
| | - Arthur A. M. Wilde
- Heart Center, Amsterdam Cardiovascular Sciences, Department of Clinical and Experimental Cardiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, the Netherlands
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart, Amsterdam, the Netherlands
| | - Chadi Tabaja
- Cardiac Electrophysiology Section, Department of Cardiovascular Medicine, Cleveland Clinic, Cleveland, Ohio
| | - Christopher Bodurian
- Clinical Cardiovascular Research Center, University of Rochester Medical Center, Rochester, New York
| | - Kathryn E. Tobert
- Divisions of Heart Rhythm Services and Pediatric Cardiology, Departments of Cardiovascular Medicine, Pediatric and Adolescent Medicine, and Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Genetic Heart Rhythm Clinic and Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Scott McNitt
- Clinical Cardiovascular Research Center, University of Rochester Medical Center, Rochester, New York
| | - Bronislava Polonsky
- Clinical Cardiovascular Research Center, University of Rochester Medical Center, Rochester, New York
| | - Wataru Shimizu
- Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan
| | - Michael J. Ackerman
- Divisions of Heart Rhythm Services and Pediatric Cardiology, Departments of Cardiovascular Medicine, Pediatric and Adolescent Medicine, and Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Genetic Heart Rhythm Clinic and Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Ilan Goldenberg
- Clinical Cardiovascular Research Center, University of Rochester Medical Center, Rochester, New York
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Nagata Y, Watanabe R, Eichhorn C, Ohno S, Aiba T, Ishikawa T, Nakano Y, Aizawa Y, Hayashi K, Murakoshi N, Nakajima T, Yagihara N, Mishima H, Sudo T, Higuchi C, Takahashi A, Sekine A, Makiyama T, Tanaka Y, Watanabe A, Tachibana M, Morita H, Yoshiura KI, Tsunoda T, Watanabe H, Kurabayashi M, Nogami A, Kihara Y, Horie M, Shimizu W, Makita N, Tanaka T. Targeted deep sequencing analyses of long QT syndrome in a Japanese population. PLoS One 2022; 17:e0277242. [PMID: 36480497 PMCID: PMC9731492 DOI: 10.1371/journal.pone.0277242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Accepted: 10/22/2022] [Indexed: 12/13/2022] Open
Abstract
Long QT syndrome (LQTS) is one of the most common inherited arrhythmias and multiple genes have been reported as causative. Presently, genetic diagnosis for LQTS patients is becoming widespread and contributing to implementation of therapies. However, causative genetic mutations cannot be detected in about 20% of patients. To elucidate additional genetic mutations in LQTS, we performed deep-sequencing of previously reported 15 causative and 85 candidate genes for this disorder in 556 Japanese LQTS patients. We performed in-silico filtering of the sequencing data and found 48 novel variants in 33 genes of 53 cases. These variants were predicted to be damaging to coding proteins or to alter the binding affinity of several transcription factors. Notably, we found that most of the LQTS-related variants in the RYR2 gene were in the large cytoplasmic domain of the N-terminus side. They might be useful for screening of LQTS patients who had no known genetic factors. In addition, when the mechanisms of these variants in the development of LQTS are revealed, it will be useful for early diagnosis, risk stratification, and selection of treatment.
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Affiliation(s)
- Yuki Nagata
- Bioresourse Research Center, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
- Department of Human Genetics and Disease Diversity, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Ryo Watanabe
- Department of Human Genetics and Disease Diversity, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Christian Eichhorn
- Department of Human Genetics and Disease Diversity, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
- Private University of the Principality of Liechtenstein, Triesen, Liechtenstein
| | - Seiko Ohno
- Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Takeshi Aiba
- Devision of Arrhythmia, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Taisuke Ishikawa
- Omics Research Center, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Yukiko Nakano
- Department of Cardiovascular Medicine, Hiroshima University, Hiroshima, Japan
| | - Yoshiyasu Aizawa
- Department of Cardiology, International University of Health and Welfare Narita Hospital, Narita, Japan
| | - Kenshi Hayashi
- Department of Cardiovascular Medicine, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan
| | - Nobuyuki Murakoshi
- Department of Cardiology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Tadashi Nakajima
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Nobue Yagihara
- Department of Cardiovascular Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Hiroyuki Mishima
- Department of Human Genetics, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan
| | - Takeaki Sudo
- Institute of Education, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Chihiro Higuchi
- Artificial Intelligence Center for Health and Biomedical Research, National Institutes of Biomedical Innovation, Health and Nutrition, Ibaraki, Japan
| | - Atsushi Takahashi
- Department of Genomic Medicine, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Akihiro Sekine
- Department of Infection and Host Defense, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Takeru Makiyama
- Department of Cardiovascular Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Yoshihiro Tanaka
- Center for Arrhythmia Research, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
| | - Atsuyuki Watanabe
- Department of Cardiology, National Hospital Organization Okayama Medical Center, Okayama, Japan
| | - Motomi Tachibana
- Department of Cardiology, Sakakibara heart institute of Okayama, Okayama, Japan
| | - Hiroshi Morita
- Department of Cardiovascular Therapeutics, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Koh-ichiro Yoshiura
- Department of Human Genetics, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan
- Division of Advanced Preventive Medical Sciences and Leading Medical Research Core Unit, Nagasaki Univerisity Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Tatsuhiko Tsunoda
- Laboratory for Medical Science Mathematics, Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
- Laboratory for Medical Science Mathematics, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
| | - Hiroshi Watanabe
- Department of Cardiovascular Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Masahiko Kurabayashi
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Akihiko Nogami
- Department of Cardiology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Yasuki Kihara
- Department of Cardiovascular Medicine, Hiroshima University, Hiroshima, Japan
| | - Minoru Horie
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Wataru Shimizu
- Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan
| | - Naomasa Makita
- Omics Research Center, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Toshihiro Tanaka
- Bioresourse Research Center, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
- Department of Human Genetics and Disease Diversity, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
- * E-mail:
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Lu H, Ding W, Xiao H, Dai M, Xue Y, Jia Z, Guo J, Wu M, Shen B, Zhao R. Association of the P441L KCNQ1 variant with severity of long QT syndrome and risk of cardiac events. Front Cardiovasc Med 2022; 9:922335. [PMID: 36386331 PMCID: PMC9659898 DOI: 10.3389/fcvm.2022.922335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Accepted: 09/12/2022] [Indexed: 11/27/2022] Open
Abstract
Dysfunction of potassium voltage-gated channel subfamily Q member 1 (KCNQ1) is a primary cause of long QT syndrome type 1 (LQT1). Here, we report a missense mutation P441L in KCNQ1 C-terminus of a 37-year-old woman with severe LQT1 phenotype. Variant P441L transporting to the plasma membrane and interacting with KCNE1 were both markedly decreased, leading to potassium efflux disorder and eventually LQT1. Mutations between the C-terminal helix A and helix B of KCNQ1 have linked with low cardiac event risk, however, we firstly find variant P441L causing a severe LQT1 phenotype with a high risk of cardiac events.
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Affiliation(s)
- Haoyang Lu
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Wen Ding
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Hui Xiao
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Manyu Dai
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Yangcheng Xue
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Zhuoran Jia
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Jie Guo
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Mengzuo Wu
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Bing Shen
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
- Bing Shen,
| | - Ren Zhao
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
- *Correspondence: Ren Zhao,
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Krahn AD, Laksman Z, Sy RW, Postema PG, Ackerman MJ, Wilde AAM, Han HC. Congenital Long QT Syndrome. JACC Clin Electrophysiol 2022; 8:687-706. [PMID: 35589186 DOI: 10.1016/j.jacep.2022.02.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 02/16/2022] [Accepted: 02/16/2022] [Indexed: 12/14/2022]
Abstract
Congenital long QT syndrome (LQTS) encompasses a group of heritable conditions that are associated with cardiac repolarization dysfunction. Since its initial description in 1957, our understanding of LQTS has increased dramatically. The prevalence of LQTS is estimated to be ∼1:2,000, with a slight female predominance. The diagnosis of LQTS is based on clinical, electrocardiogram, and genetic factors. Risk stratification of patients with LQTS aims to identify those who are at increased risk of cardiac arrest or sudden cardiac death. Factors including age, sex, QTc interval, and genetic background all contribute to current risk stratification paradigms. The management of LQTS involves conservative measures such as the avoidance of QT-prolonging drugs, pharmacologic measures with nonselective β-blockers, and interventional approaches such as device therapy or left cardiac sympathetic denervation. In general, most forms of exercise are considered safe in adequately treated patients, and implantable cardioverter-defibrillator therapy is reserved for those at the highest risk. This review summarizes our current understanding of LQTS and provides clinicians with a practical approach to diagnosis and management.
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Affiliation(s)
- Andrew D Krahn
- Center for Cardiovascular Innovation, Heart Rhythm Services, Division of Cardiology, University of British Columbia, Vancouver, BC, Canada.
| | - Zachary Laksman
- Center for Cardiovascular Innovation, Heart Rhythm Services, Division of Cardiology, University of British Columbia, Vancouver, BC, Canada
| | - Raymond W Sy
- Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Pieter G Postema
- Department of Clinical and Experimental Cardiology, Heart Center, Amsterdam University Medical Centers, Amsterdam, the Netherlands
| | - Michael J Ackerman
- Department of Cardiovascular Medicine, Division of Heart Rhythm Services, Windland Smith Rice Genetic Heart Rhythm Clinic, Mayo Clinic, Rochester, Minnesota, USA; Department of Pediatric and Adolescent Medicine, Division of Pediatric Cardiology, Mayo Clinic, Rochester, Minnesota, USA; Departments of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota, USA
| | - Arthur A M Wilde
- Department of Clinical and Experimental Cardiology, Heart Center, Amsterdam University Medical Centers, Amsterdam, the Netherlands; European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart (ERN GUARD-Heart), Academic University Medical Center, Amsterdam, the Netherlands
| | - Hui-Chen Han
- Center for Cardiovascular Innovation, Heart Rhythm Services, Division of Cardiology, University of British Columbia, Vancouver, BC, Canada; Victorian Heart Institute, Monash University, Clayton, VIC, Australia
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Harvey A, Curnier D, Dodin P, Abadir S, Jacquemet V, Caru M. OUP accepted manuscript. Eur J Prev Cardiol 2022; 29:1633-1677. [PMID: 35537006 DOI: 10.1093/eurjpc/zwac081] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 04/15/2022] [Accepted: 04/18/2022] [Indexed: 11/13/2022]
Abstract
Current exercise recommendations make it difficult for long QT syndrome (LQTS) patients to adopt a physically active and/or athletic lifestyle. The purpose of this review is to summarize the current evidence, identify knowledge gaps, and discuss research perspectives in the field of exercise and LQTS. The first aim is to document the influence of exercise training, exercise stress, and postural change interventions on ventricular repolarization in LQTS patients, while the second aim is to describe electrophysiological measurements used to study the above. Studies examining the effects of exercise on congenital or acquired LQTS in human subjects of all ages were included. Systematic searches were performed on 1 October 2021, through PubMed (NLM), Ovid Medline, Ovid All EBM Reviews, Ovid Embase, and ISI Web of Science, and limited to articles written in English or French. A total of 1986 LQTS patients and 2560 controls were included in the 49 studies. Studies were mainly case-control studies (n = 41) and examined exercise stress and/or postural change interventions (n = 48). One study used a 3-month exercise training program. Results suggest that LQTS patients have subtype-specific repolarization responses to sympathetic stress. Measurement methods and quality were found to be very heterogeneous, which makes inter-study comparisons difficult. In the absence of randomized controlled trials, the current recommendations may have long-term risks for LQTS patients who are discouraged from performing physical activity, rendering its associated health benefits out of range. Future research should focus on discovering the most appropriate levels of exercise training that promote ventricular repolarization normalization in LQTS.
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Affiliation(s)
- Audrey Harvey
- Laboratory of Pathophysiology of EXercise (LPEX), School of Kinesiology and Physical Activity Sciences, Faculty of Medicine, University of Montreal, Montreal, Canada
- Sainte-Justine University Health Center, Research Center, Montreal, Canada
| | - Daniel Curnier
- Laboratory of Pathophysiology of EXercise (LPEX), School of Kinesiology and Physical Activity Sciences, Faculty of Medicine, University of Montreal, Montreal, Canada
- Sainte-Justine University Health Center, Research Center, Montreal, Canada
| | - Philippe Dodin
- Sainte-Justine University Health Center, Research Center, Montreal, Canada
| | - Sylvia Abadir
- Department of Pediatric Cardiology, Sainte-Justine University Health Center, Montreal, Canada
| | - Vincent Jacquemet
- Department of Pharmacology and Physiology, Faculty of Medicine, University of Montreal, Montreal, Canada
| | - Maxime Caru
- Sainte-Justine University Health Center, Research Center, Montreal, Canada
- Department of Pediatrics, Pennsylvania State University College of Medicine, Hershey, PA, USA
- Department of Public Health Sciences, Pennsylvania State University College of Medicine, Hershey, PA, USA
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8
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Akgun-Dogan O, Ağaoğlu NB, K Demirkol Y, Doğanay L, Ergül Y, Karacan M. Mutational spectrum of congenital long QT syndrome in Turkey; identification of 12 novel mutations across KCNQ1, KCNH2, SCN5A, KCNJ2, CACNA1C, and CALM1. J Cardiovasc Electrophysiol 2021; 33:262-273. [PMID: 34860437 DOI: 10.1111/jce.15306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 10/10/2021] [Accepted: 11/08/2021] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Long QT syndrome (LQTS) is of great importance as it is the most common cause of sudden cardiac death in childhood. The diagnosis is made by the prolongation of the QTc interval on the electrocardiography. However, clinical heterogeneity and nondiagnostic QTc intervals may cause a delay in the diagnosis. In such cases, genetic tests such as next-generation sequencing (NGS) panel analysis enable a definitive diagnosis. We present the first study that aimed to expand the LQTS's mutational spectrum by NGS panel analysis from Turkey. METHODS Fifty-seven unrelated patients with clinically diagnosed LQTS were investigated using an NGS panel that includes six LQTS-related genes. Clinical aspects, outcome, and molecular analysis results were reviewed. RESULTS Pathogenic (53%)/likely pathogenic (23%)/variant of unknown significance (4%) variants were detected in any of the genes examined in 79% of the patients. Among all detected variants, KCNQ1(71%) was the most common gene, followed by SCN5A (11%), KCNH2 (10%), CALM1 (5%), and CACNA1C (3%). Twelve novel variants were detected. Among the variants in KCNQ1, the c.1097G>A variant was present in 42% of patients. This variant also composed 31% of the variants detected in all of the genes. CONCLUSION Our study expands the spectrum of the variations associated with LQTS with twelve novel variants in five genes. And also it draws attention to the frequency of the KCNQ1 c.1097G>A variant and forms the basis for new studies to determine the possible founder effect in the Turkish population. Furthermore, identifying new variants and clinical findings has importance in elaborating the roles of related genes in pathophysiology and determining the variable expression and incomplete penetration rates in this syndrome.
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Affiliation(s)
- Ozlem Akgun-Dogan
- Division of Pediatric Genetics, Umraniye Training and Research Hospital, Istanbul, Turkey
| | - Nihat B Ağaoğlu
- Department of Medical Genetics, Umraniye Training and Research Hospital, Istanbul, Turkey
| | - Yasemin K Demirkol
- Division of Pediatric Genetics, Umraniye Training and Research Hospital, Istanbul, Turkey
| | - Levent Doğanay
- Department of Internal Medicine, Genomic Laboratory (GLAB), Umraniye Training and Research Hospital, Istanbul, Turkey
| | - Yakup Ergül
- Department of Pediatric Cardiology, Mehmet Akif Ersoy Thoracic and Cardiovascular Research and Education Hospital, Istanbul, Turkey
| | - Mehmet Karacan
- Department of Pediatric Cardiology, Umraniye Training and Research Hospital, Istanbul, Turkey
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9
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Abstract
The physiological heart function is controlled by a well-orchestrated interplay of different ion channels conducting Na+, Ca2+ and K+. Cardiac K+ channels are key players of cardiac repolarization counteracting depolarizating Na+ and Ca2+ currents. In contrast to Na+ and Ca2+, K+ is conducted by many different channels that differ in activation/deactivation kinetics as well as in their contribution to different phases of the action potential. Together with modulatory subunits these K+ channel α-subunits provide a wide range of repolarizing currents with specific characteristics. Moreover, due to expression differences, K+ channels strongly influence the time course of the action potentials in different heart regions. On the other hand, the variety of different K+ channels increase the number of possible disease-causing mutations. Up to now, a plethora of gain- as well as loss-of-function mutations in K+ channel forming or modulating proteins are known that cause severe congenital cardiac diseases like the long-QT-syndrome, the short-QT-syndrome, the Brugada syndrome and/or different types of atrial tachyarrhythmias. In this chapter we provide a comprehensive overview of different K+ channels in cardiac physiology and pathophysiology.
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10
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Abstract
Long QT syndrome (LQTS) is a cardiovascular disorder characterized by an abnormality in cardiac repolarization leading to a prolonged QT interval and T-wave irregularities on the surface electrocardiogram. It is commonly associated with syncope, seizures, susceptibility to torsades de pointes, and risk for sudden death. LQTS is a rare genetic disorder and a major preventable cause of sudden cardiac death in the young. The availability of therapy for this lethal disease emphasizes the importance of early and accurate diagnosis. Additionally, understanding of the molecular mechanisms underlying LQTS could help to optimize genotype-specific treatments to prevent deaths in LQTS patients. In this review, we briefly summarize current knowledge regarding molecular underpinning of LQTS, in particular focusing on LQT1, LQT2, and LQT3, and discuss novel strategies to study ion channel dysfunction and drug-specific therapies in LQT1, LQT2, and LQT3 syndromes.
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Affiliation(s)
| | - Isabelle Deschênes
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio
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11
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Clinical Implications and Gender Differences of KCNQ1 p.Gly168Arg Pathogenic Variant in Long QT Syndrome. J Clin Med 2020; 9:jcm9123846. [PMID: 33256261 PMCID: PMC7760054 DOI: 10.3390/jcm9123846] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 11/19/2020] [Accepted: 11/24/2020] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Long QT syndrome (LQTS) is an inheritable arrhythmogenic disorder associated with life-threatening arrhythmic events (LAEs). In general, patients with LQTS2 (KCNH2) and LQTS3 (SCN5A) are considered to be a greater risk of LAEs than LQTS1 (KCNQ1) patients. Gender differences are also important. Series analyzing families with the same pathogenic variants may help in the progress of elaborating strong specific genotype-phenotype management strategies. In this manuscript, we describe the phenotype of seven unrelated families, carriers of the KCNQ1 G168R pathogenic variant. METHODS we identified all consecutive index cases referred for genetic testing with LQTS diagnosis carriers of KCNQ1 G168R variant. Genetic and clinical screening for all available relatives was performed. RESULTS we evaluated seven unrelated families, with a total 34 KCNQ1 G168R carriers (two obligated carriers died without available EKGs to evaluate the phenotype). All index cases but one were women and three of them presented with aborted sudden cardiac death (SCD) or syncope. The presence of sudden death in these families is notable, with a total of nine unexplained sudden deaths and four aborted SCD. Phenotype penetrance was 100% in women and 37.5% in men. CONCLUSIONS KCNQ1 G168R is a pathogenic variant, with a high penetrance among women and mild penetrance among men. Risk for LAEs in this variant seems not negligible, especially among woman, and risk stratification should always be carefully evaluated.
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Kashiwa A, Aiba T, Makimoto H, Shimamoto K, Yamagata K, Kamakura T, Wada M, Miyamoto K, Inoue-Yamada Y, Ishibashi K, Noda T, Nagase S, Miyazaki A, Sakaguchi H, Shiraishi I, Yagihara N, Watanabe H, Aizawa Y, Makiyama T, Itoh H, Hayashi K, Yamagishi M, Sumitomo N, Yoshinaga M, Morita H, Ohe T, Miyamoto Y, Makita N, Yasuda S, Kusano K, Ohno S, Horie M, Shimizu W. Systematic Evaluation of KCNQ1 Variant Using ACMG/AMP Guidelines and Risk Stratification in Long QT Syndrome Type 1. CIRCULATION. GENOMIC AND PRECISION MEDICINE 2020. [PMID: 32936022 DOI: 10.1161/circgen.120.002926] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background - Mutation/variant-site specific risk stratification in long-QT syndrome type 1 (LQT1) has been well investigated, but it is still challenging to adapt current enormous genomic information to clinical aspects caused by each mutation/variant. We assessed a novel variant-specific risk stratification in LQT1 patients. Methods - We classified a pathogenicity of 141 KCNQ1 variants among 927 LQT1 patients (536 probands) based on the American College of Medical Genetics and Genomics (ACMG) and Association for Molecular Pathology (AMP) guidelines and evaluated whether the ACMG/AMP-based classification was associated with arrhythmic risk in LQT1 patients. Results - Among 141 KCNQ1 variants, 61 (43.3%), 55 (39.0%), and 25 (17.7%) variants were classified into pathogenic (P), likely pathogenic (LP), and variant of unknown significance (VUS), respectively. Multivariable analysis showed that proband (HR = 2.53; 95%CI = 1.94-3.32; p <0.0001), longer QTc (≥500ms) (HR = 1.44; 95%CI = 1.13-1.83; p = 0.004), variants at membrane spanning (MS) (vs. those at N/C terminus) (HR = 1.42; 95%CI = 1.08-1.88; p = 0.01), C-loop (vs. N/C terminus) (HR = 1.52; 95%CI = 1.06-2.16; p = 0.02), and P variants [(vs. LP) (HR = 1.72; 95%CI = 1.32-2.26; p <0.0001), (vs. VUS) (HR = 1.81; 95%CI = 1.15-2.99; p = 0.009)] were significantly associated with syncopal events. The ACMG/AMP-based KCNQ1 evaluation was useful for risk stratification not only in family members but also in probands. A clinical score (0~4) based on proband, QTc (≥500ms), variant location (MS or C-loop) and P variant by ACMG/AMP guidelines allowed identification of patients more likely to have arrhythmic events. Conclusions - Comprehensive evaluation of clinical findings and pathogenicity of KCNQ1 variants based on the ACMG/AMP-based evaluation may stratify arrhythmic risk of congenital long-QT syndrome type 1.
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Affiliation(s)
- Asami Kashiwa
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita & Department of Cardiovascular & Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Takeshi Aiba
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Hisaki Makimoto
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Keiko Shimamoto
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Kenichiro Yamagata
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Tsukasa Kamakura
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Mitsuru Wada
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Koji Miyamoto
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Yuko Inoue-Yamada
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Kohei Ishibashi
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Takashi Noda
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Satoshi Nagase
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Aya Miyazaki
- Department of Pediatric Cardiology, Shizuoka Children's Hospital, Shizuoka, Japan
| | - Heima Sakaguchi
- Department of Pediatric Cardiology, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Isao Shiraishi
- Department of Pediatric Cardiology, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Nobue Yagihara
- Department of Cardiovascular Biology & Medicine, Niigata University Graduate School of Medical & Dental Sciences, Niigata, Japan
| | - Hiroshi Watanabe
- Department of Cardiovascular Biology & Medicine, Niigata University Graduate School of Medical & Dental Sciences, Niigata, Japan
| | - Yoshifusa Aizawa
- Department of Cardiology, Tachikawa General Hospital, Niigata, Japan
| | - Takeru Makiyama
- Department of Cardiovascular & Medicine Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Hideki Itoh
- Division of Patient Safety, Hiroshima University Hospital, Hiroshima, Japan
| | - Kenshi Hayashi
- Department of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine Science, Kanazawa, Japan
| | | | - Naotaka Sumitomo
- Department of Pediatric Cardiology, Saitama Medical University International Medical Center, Saitama, Japan
| | - Masao Yoshinaga
- Department of Pediatrics, Kagoshima Medical Center, Kagoshima, Japan
| | - Hiroshi Morita
- Department of Cardiovascular Therapeutics, Okayama University Graduate School of Medicine, Okayama, Japan
| | - Tohru Ohe
- Department of Cardiovascular Therapeutics, Okayama University Graduate School of Medicine, Okayama, Japan
| | - Yoshihiro Miyamoto
- Division of Preventive Cardiology, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Naomasa Makita
- Omics Research Center, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Satoshi Yasuda
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Kengo Kusano
- Department of Cardiovascular Medicine, National Cerebral & Cardiovascular Center, Suita, Japan
| | - Seiko Ohno
- Department of Bioscience & Genetics, National Cerebral & Cardiovascular Center Suita, Japan
| | - Minoru Horie
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Wataru Shimizu
- Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan
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13
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Popa-Fotea NM, Cojocaru C, Scafa-Udriste A, Micheu MM, Dorobantu M. The Multifaced Perspectives of Genetic Testing in Pediatric Cardiomyopathies and Channelopathies. J Clin Med 2020; 9:E2111. [PMID: 32635562 PMCID: PMC7408669 DOI: 10.3390/jcm9072111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 06/28/2020] [Accepted: 07/02/2020] [Indexed: 12/22/2022] Open
Abstract
Pediatric inherited cardiomyopathies (CMPs) and channelopathies (CNPs) remain important causes of death in this population, therefore, there is a need for prompt diagnosis and tailored treatment. Conventional evaluation fails to establish the diagnosis of pediatric CMPs and CNPs in a significant proportion, prompting further, more complex testing to make a diagnosis that could influence the implementation of lifesaving strategies. Genetic testing in CMPs and CNPs may help unveil the underlying cause, but needs to be carried out with caution given the lack of uniform recommendations in guidelines about the precise time to start the genetic evaluation or the type of targeted testing or whole-genome sequencing. A very diverse etiology and the scarce number of randomized studies of pediatric CMPs and CNPs make genetic testing of these maladies far more particular than their adult counterpart. The genetic diagnosis is even more puzzling if the psychological impact point of view is taken into account. This review aims to put together different perspectives, state-of-the art recommendations-synthetizing the major indications from European and American guidelines-and psychosocial outlooks to construct a comprehensive genetic assessment of pediatric CMPs and CNPs.
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Affiliation(s)
- Nicoleta-Monica Popa-Fotea
- Department of Cardiology, Clinical Emergency Hospital of Bucharest, Floreasca Street 8, 014461 Bucharest, Romania; (N.-M.P.-F.); (C.C.); (A.S.-U.); (M.D.)
- Department 4—Cardiothoracic Pathology, University of Medicine and Pharmacy Carol Davila, Eroii Sanitari Bvd. 8, 050474 Bucharest, Romania
| | - Cosmin Cojocaru
- Department of Cardiology, Clinical Emergency Hospital of Bucharest, Floreasca Street 8, 014461 Bucharest, Romania; (N.-M.P.-F.); (C.C.); (A.S.-U.); (M.D.)
| | - Alexandru Scafa-Udriste
- Department of Cardiology, Clinical Emergency Hospital of Bucharest, Floreasca Street 8, 014461 Bucharest, Romania; (N.-M.P.-F.); (C.C.); (A.S.-U.); (M.D.)
- Department 4—Cardiothoracic Pathology, University of Medicine and Pharmacy Carol Davila, Eroii Sanitari Bvd. 8, 050474 Bucharest, Romania
| | - Miruna Mihaela Micheu
- Department of Cardiology, Clinical Emergency Hospital of Bucharest, Floreasca Street 8, 014461 Bucharest, Romania; (N.-M.P.-F.); (C.C.); (A.S.-U.); (M.D.)
| | - Maria Dorobantu
- Department of Cardiology, Clinical Emergency Hospital of Bucharest, Floreasca Street 8, 014461 Bucharest, Romania; (N.-M.P.-F.); (C.C.); (A.S.-U.); (M.D.)
- Department 4—Cardiothoracic Pathology, University of Medicine and Pharmacy Carol Davila, Eroii Sanitari Bvd. 8, 050474 Bucharest, Romania
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14
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Brewer KR, Kuenze G, Vanoye CG, George AL, Meiler J, Sanders CR. Structures Illuminate Cardiac Ion Channel Functions in Health and in Long QT Syndrome. Front Pharmacol 2020; 11:550. [PMID: 32431610 PMCID: PMC7212895 DOI: 10.3389/fphar.2020.00550] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 04/09/2020] [Indexed: 12/13/2022] Open
Abstract
The cardiac action potential is critical to the production of a synchronized heartbeat. This electrical impulse is governed by the intricate activity of cardiac ion channels, among them the cardiac voltage-gated potassium (Kv) channels KCNQ1 and hERG as well as the voltage-gated sodium (Nav) channel encoded by SCN5A. Each channel performs a highly distinct function, despite sharing a common topology and structural components. These three channels are also the primary proteins mutated in congenital long QT syndrome (LQTS), a genetic condition that predisposes to cardiac arrhythmia and sudden cardiac death due to impaired repolarization of the action potential and has a particular proclivity for reentrant ventricular arrhythmias. Recent cryo-electron microscopy structures of human KCNQ1 and hERG, along with the rat homolog of SCN5A and other mammalian sodium channels, provide atomic-level insight into the structure and function of these proteins that advance our understanding of their distinct functions in the cardiac action potential, as well as the molecular basis of LQTS. In this review, the gating, regulation, LQTS mechanisms, and pharmacological properties of KCNQ1, hERG, and SCN5A are discussed in light of these recent structural findings.
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Affiliation(s)
- Kathryn R. Brewer
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
| | - Georg Kuenze
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
| | - Carlos G. Vanoye
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Alfred L. George
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
- Department of Pharmacology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany
| | - Charles R. Sanders
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
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15
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Wu J, Sakaguchi T, Takenaka K, Toyoda F, Tsuji K, Matsuura H, Horie M. A trafficking-deficient KCNQ1 mutation, T587M, causes a severe phenotype of long QT syndrome by interfering with intracellular hERG transport. J Cardiol 2019; 73:343-350. [DOI: 10.1016/j.jjcc.2018.10.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 09/11/2018] [Accepted: 10/24/2018] [Indexed: 11/29/2022]
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16
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17
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Wang T, Chen X, Yu J, Du Q, Zhu J, Yang M, Wu H, Wang M, Zhu Y. High-Throughput Electrophysiology Screen Revealed Cardiotoxicity of Strychnine by Selectively Targeting hERG Channel. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2018; 46:1825-1840. [PMID: 30545237 DOI: 10.1142/s0192415x1850091x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Although the efficacy and the health care advantages of Chinese herbal medicine (CHM) have become increasingly recognized worldwide, the potential side effects and toxicity still restrict its broader application. This study established and applied an integrated platform anchored on automatic patch clamp system to screen and evaluate a collection of CHM extracts, compositions and monomeric compounds for in vitro cardiac toxicity. Of 1036 CHM samples screened, 2.79% significantly inhibited hERG channel activity. Among them, Strychnine was identified for the first time as a potent hERG inhibitor with an IC 50 of 6.65±1.04μ M in comparison to that of Dofetilide at 1.80±0.24μ M and Quinidine at 7.42±0.54μ M. Langendorff-perfusion experiments confirmed that strychnine increased QT interphase from 71.69±5.34 ms to 98.61±5.54 ms and decreased heart rates from 227.65±5.40 bmp to 162.91±14.70 bmp in isolated rat hearts. The cardiac toxicity effect of strychnine appears to be specific to hERG channel since an in vitro multiplex imaging analysis showed that it did not affect cellular phenotypes such as cell vitality, nucleus area, mitochondria mass and function, nor intracellular calcium in rat primary myocytes. This integrated high-throughput hERG patch clamp and high-content multi-parameter imaging cardiac toxicity screen approach should be useful for large-scale preclinical evaluation of complex Chinese herbal medicine.
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Affiliation(s)
- Taiyi Wang
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Xiaonan Chen
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Jiahui Yu
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Qunqun Du
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Jie Zhu
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Mingzhu Yang
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Honghua Wu
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Meng Wang
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Yan Zhu
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
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18
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Chen XM, Guo K, Li H, Lu QF, Yang C, Yu Y, Hou JW, Fei YD, Sun J, Wang J, Li YX, Li YG. A novel mutation KCNQ1p.Thr312del is responsible for long QT syndrome type 1. Heart Vessels 2018; 34:177-188. [DOI: 10.1007/s00380-018-1223-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 07/06/2018] [Indexed: 11/29/2022]
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19
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A challenge for mutation specific risk stratification in long QT syndrome type 1. J Cardiol 2018; 72:56-65. [DOI: 10.1016/j.jjcc.2017.12.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 12/05/2017] [Accepted: 12/20/2017] [Indexed: 01/31/2023]
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20
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Kwok SY, Pflaumer A, Pantaleo SJ, Date E, Jadhav M, Davis AM. Ten-year experience in atenolol use and exercise evaluation in children with genetically proven long QT syndrome. J Arrhythm 2017; 33:624-629. [PMID: 29255512 PMCID: PMC5728996 DOI: 10.1016/j.joa.2017.08.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Revised: 07/19/2017] [Accepted: 08/15/2017] [Indexed: 11/13/2022] Open
Abstract
Background Due to its availability, atenolol is the primary beta-blocker used in Australia for children with long QT syndrome. There is limited data on long-term follow-up of its use. Methods A single-tertiary-center, retrospective, observational study investigating all children and adolescents who had genetically proven long QT syndrome type 1 (LQT1) and type 2 (LQT2) was conducted. Their pretreatment exercise tests were evaluated for QTc intervals into the recovery phase of exercise. Results Eighty six patients were identified (LQT1, 67, and LQT2, 19) from 2004 to 2014. The majority (86%) of patients were initially referred for family screening. Atenolol was administered at a mean dose of 1.58 ± 0.51 mg/kg/day. During the median follow-up period of 4.29 years, only one proband developed ventricular arrhythmia whilst taking atenolol, No patient had cardiac arrest or aborted cardiac arrest. With respect to side effects of atenolol, only two patients had intolerable side effects necessitating changes of medication. Evaluation of exercise tests (pretreatment) demonstrated that corrected QT (QTc) intervals at 2–3 min into the recovery phase of exercise were significantly prolonged for LQT1 patients. LQT1 patients with transmembrane mutation had longer QTc intervals than their C-terminus mutation counterparts, reaching statistical significance at 3 min into the recovery phase of exercise. Conclusions Atenolol is an effective treatment for genetically proven LQT1 and LQT2 children and adolescents, with good tolerability. In LQT1 patients, QTc intervals at 2–3 min into the recovery phase of exercise were significantly prolonged, particularly in patients with transmembrane mutations.
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Key Words
- Atenolol
- Beta-blocker
- ECG, Electrocardiogram
- Exercise
- ICD, Implantable cardioverter-defibrillator
- LCSD, Left cardiac sympathetic denervation
- LQT1, Long QT syndrome type 1
- LQT2, Long QT syndrome type 2
- LQTS, Long QT syndrome
- Long QT syndrome
- Pediatrics
- QTc, Corrected QT
- SD, Standard deviation
- SFM, Screened family members
- TdP, Torsade de pointes
- min, Minutes
- s, Seconds
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Affiliation(s)
- Sit-Yee Kwok
- Department of Cardiology, Royal Children's Hospital, Melbourne, Australia
| | - Andreas Pflaumer
- Department of Cardiology, Royal Children's Hospital, Melbourne, Australia.,Murdoch Children's Research Institute, Parkville, VIC 3052, Australia.,Department of Paediatrics, Melbourne University, Australia
| | | | - Erin Date
- Department of Cardiology, Royal Children's Hospital, Melbourne, Australia
| | - Mangesh Jadhav
- Department of Cardiology, Royal Children's Hospital, Melbourne, Australia
| | - Andrew Mark Davis
- Department of Cardiology, Royal Children's Hospital, Melbourne, Australia.,Murdoch Children's Research Institute, Parkville, VIC 3052, Australia.,Department of Paediatrics, Melbourne University, Australia
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21
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Uysal F, Turkgenc B, Toksoy G, Bostan OM, Evke E, Uyguner O, Yakicier C, Kayserili H, Cil E, Temel SG. "Homozygous, and compound heterozygous mutation in 3 Turkish family with Jervell and Lange-Nielsen syndrome: case reports". BMC MEDICAL GENETICS 2017; 18:114. [PMID: 29037160 PMCID: PMC5644177 DOI: 10.1186/s12881-017-0474-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 10/01/2017] [Indexed: 11/10/2022]
Abstract
BACKGROUND Jervell and Lange-Nielsen syndrome (JLNS) isa recessive model of long QT syndrome which might also be related to possible hearing loss. Although the syndrome has been demonstrated to be originated from homozygous or compound heterozygous mutations in either the KCNQ1 or KCNE1 genes, additional mutations in other genetic loci should be considered, particularly in malignant course patients. CASE PRESENTATIONS Three patients were admitted into hospital due to recurrent seizures/syncope, intrauterine and postnatal bradycardia respectively; moreover all three patients had congenital sensorineural hearing-loss. Their electrocardiograms showed markedly prolonged QT interval. Implantable defibrillator was implanted and left cardiac sympathetic denervation was performed due to the progressive disease in case 1. She had countless ventricular fibrillation and appropriate shock while using an implantable defibrillator. The DNA sequencing analysis of the KCNQ1 gene disclosed a homozygous c.728G > A (p.Arg243His) missense mutation in case1. Further targeted next generation sequencing of cardiac panel comprising 68 gene revealed a heterozygous c.1346 T > G (p.Ile449Arg) variant in RYR2 gene and a heterozygous c.809G > A (p.Cys270Tyr) variant in NKX2-5 gene in the same patient. Additional gene alterations in RYR2 and NKX2-5 genes were thought to be responsible for progressive and malignant course of the disease. As a result of DNA sequencing analysis of KCNQ1 and KCNE1 genes, a compound heterozygosity for two mutations had been detected in KCNQ1 gene in case 2: a maternally derived c.477 + 1G > A splice site mutation and a paternally derived c.520C > T (p.Arg174Cys) missense mutation. Sanger sequencing of KCNQ1 and KCNE1 genes displayed a homozygous c.1097G > A (p.Arg366Gln) mutation in KCNQ1 gene in case 3. β-blocker therapy was initiated to all the index subjects. CONCLUSIONS Three families of JLNS who presented with long QT and deafness and who carry homozygous, or compound heterozygous mutation in KCNQ1 gene were presented in this report. It was emphasized that broad targeted cardiac panels may be useful to predict the outcome especially in patients with unexplained phenotype-genotype correlation. Clinical presentations and molecular findings will be discussed further to clarify the phenotype genotype associations.
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Affiliation(s)
- Fahrettin Uysal
- Department of Pediatric Cardiology, University of Uludag, School of Medicine, Bursa, Turkey
| | | | - Guven Toksoy
- Department of Medical Genetics, Istanbul University, Faculty of Medicine, Istanbul, Turkey
| | - Ozlem M. Bostan
- Department of Pediatric, Cardiology, Uludag University, Faculty of Medicine, Bursa, Turkey
| | - Elif Evke
- Bursa Genetic Diagnostic Center, Bursa, Turkey
| | - Oya Uyguner
- Department of Medical Genetics, Istanbul University, Faculty of Medicine, Istanbul, Turkey
| | - Cengiz Yakicier
- Acibadem Genetic Diagnostic Center, Istanbul, Turkey
- Department of Molecular Biology and Genetic, Acibadem University, Faculty of Science, Istanbul, Turkey
| | - Hulya Kayserili
- Department of Medical Genetics, Istanbul University, Faculty of Medicine, Istanbul, Turkey
- Department of Medical Genetics, Koc University, Faculty of Medicine, Istanbul, Turkey
| | - Ergun Cil
- Department of Pediatric, Cardiology, Uludag University, Faculty of Medicine, Bursa, Turkey
| | - Sehime G. Temel
- Department of Histology& Embryology, Near East University, Faculty of Medicine, Nicosia, North Cyprus
- Department of Medical Genetics, Uludag University, Faculty of Medicine, Bursa, Turkey
- Department of Histology & Embryology, Uludag University, Faculty of Medicine, Bursa, Turkey
- Gorukle campuss, Uludag University, School of Medicine, 16059, Nilufer, Bursa, Turkey
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22
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Zafari Z, Dalili M, Zeinali S, Saber S, Fazeli Far AF, Akbari MT. Identification and characterization of a novel recessive KCNQ1 mutation associated with Romano-Ward Long-QT syndrome in two Iranian families. J Electrocardiol 2017; 50:912-918. [PMID: 29033053 DOI: 10.1016/j.jelectrocard.2017.07.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Indexed: 12/20/2022]
Abstract
BACKGROUND One of the foremost causes of sudden cardiac death in the young is an inherent cardiac arrhythmia known as Long-QT syndrome (LQTS). Whereas heterozygous mutations typically lead to the Romano-Ward type of LQTS, We have provided a further evidence for the recessive transmission of a novel KCNQ1 gene mutation in two consanguineous families for the first time in Iran. METHODS Next generation sequencing, DNA Sanger sequencing and haplotype analysis were performed for genotype determination. Twelve different in silico tools were used for predicting the variant pathogenecity along with the family and population study. RESULTS A novel recessive KCNQ1 variant (p.D564G) was revealed in none of the unrelated healthy individuals but four patients in two apparently unrelated families. The variant was classified as a likely pathogenic mutation by combining the resulted criteria for the changed amino acid. CONCLUSIONS Identification of the novel mutation not only supports the genetic testing as a definitive diagnostic tool for detection of at risk family members, but also emphasizes its screening in Iranian LQTS patients as this mutation is very likely a founder mutation in Iran.
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Affiliation(s)
- Zahra Zafari
- Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Mohammad Dalili
- Cardiac Electrophysiology Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Sirus Zeinali
- Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Siamak Saber
- Cardiac Electrophysiology Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Amir Farjam Fazeli Far
- Cardiac Electrophysiology Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Mohammad Taghi Akbari
- Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
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23
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Wu J, Ding WG, Horie M. Molecular pathogenesis of long QT syndrome type 1. J Arrhythm 2016; 32:381-388. [PMID: 27761162 PMCID: PMC5063268 DOI: 10.1016/j.joa.2015.12.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 11/16/2015] [Accepted: 12/17/2015] [Indexed: 01/08/2023] Open
Abstract
Long QT syndrome type 1 (LQT1) is a subtype of a congenital cardiac syndrome caused by mutation in the KCNQ1 gene, which encodes the α-subunit of the slow component of delayed rectifier K+ current (IKs) channel. Arrhythmias in LQT1 are characterized by prolongation of the QT interval on ECG, as well as the occurrence of life-threatening cardiac events, frequently triggered by adrenergic stimuli (e.g., physical or emotional stress). During the past two decades, much advancement has been made in understanding the molecular pathogenesis underlying LQT1. Uncovering the genotype-phenotype correlations in LQT1 is of clinical importance to better understand the gene-specific differences that may influence the propensity for developing life-threatening arrhythmias under specific conditions. Elucidation of these mechanisms will also help to improve the diagnosis and management of this cardiac disorder based on gene-specific considerations. This review describes the current medical consensus and recent developments regarding the molecular pathogenesis of LQT1 and provides a novel insight into the adrenergic regulation of this disease.
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Affiliation(s)
- Jie Wu
- Department of Pharmacology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, 710061, Xi׳an, China
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu 520-2192, Japan
- Department of Physiology, Shiga University of Medical Science, Otsu 520-2192, Japan
| | - Wei-Guang Ding
- Department of Physiology, Shiga University of Medical Science, Otsu 520-2192, Japan
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu 520-2192, Japan
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24
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Faragli A, Underwood K, Priori SG, Mazzanti A. Is There a Role for Genetics in the Prevention of Sudden Cardiac Death? J Cardiovasc Electrophysiol 2016; 27:1124-32. [PMID: 27279603 DOI: 10.1111/jce.13028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 04/27/2016] [Accepted: 05/24/2016] [Indexed: 12/16/2022]
Abstract
The identification of patients at risk for sudden cardiac death (SCD) is fundamental for both acquired cardiovascular diseases (such as coronary artery diseases, CAD) and inherited arrhythmia syndromes (such as the long-QT syndrome, LQTS). Genetics may play a role in both situations, although the potential to exploit this information to reduce the burden of SCD varies among these two groups. Concerning acquired cardiovascular diseases, which affect most of the general population, preliminary data suggest an association between genetics and the risk of dying suddenly. The maximal utility, instead, is reached in inherited arrhythmia syndromes, where the discovery of monogenic diseases such as LQTS tracked the way for the first genotype-phenotype correlations. The aim of this review is to provide a general overview focusing on the current genetic knowledge and on the present and future applicability for prevention in these two populations at risk for SCD.
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Affiliation(s)
| | | | - Silvia G Priori
- Molecular Cardiology, IRCCS Salvatore Maugeri Foundation, Pavia, Italy. .,Department of Molecular Medicine, University of Pavia, Pavia, Italy.
| | - Andrea Mazzanti
- Molecular Cardiology, IRCCS Salvatore Maugeri Foundation, Pavia, Italy
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25
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Izumi G, Hayama E, Yamazawa H, Inai K, Shimada M, Furutani M, Nishizawa T, Furutani Y, Matsuoka R, Nakanishi T. Compound Mutations Cause Increased Cardiac Events in Children with Long QT Syndrome: Can the Sequence Homology-Based Tools be Applied for Prediction of Phenotypic Severity? Pediatr Cardiol 2016; 37:962-70. [PMID: 27041096 DOI: 10.1007/s00246-016-1378-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 03/21/2016] [Indexed: 11/29/2022]
Abstract
Long QT syndrome (LQTS) can cause syncope, ventricular fibrillation, and death. Recently, several disease-causing mutations in ion channel genes have been identified, and compound mutations have also been detected. It is unclear whether children who are carriers of compound mutations exhibit a more severe phenotype than those with single mutations. Although predicting phenotypic severity is clinically important, the availability of prediction tools for LQTS is unknown. To determine whether the severity of the LQTS phenotype can be predicted by the presence of compound mutations in children is needed. We detected 97 single mutations (Group S) and 13 compound mutations (Group C) between 1998 and 2012, age at diagnosis ranging 0-19 years old (median age is 9.0) and 18.0 years of follow-up period. The phenotypes and Kaplan-Meier event-free rates of the two groups were compared for cardiac events. This study investigated phenotypic severity in relation to the location of mutations in the protein sequence, which was analyzed using two sequence homology-based tools. In results, compound mutations in children were associated with a high incidence of syncope within the first decade (Group S: 32 % vs. Group C: 61 %), requiring an ICD in the second decade (Group S: 3 % vs. Group C: 56 %). Mortality in these patients was high within 5 years of birth (23 %). Phenotypic prediction tools correctly predicted the phenotypic severity in both Groups S and C, especially by using their coupling method. The coupling prediction method is useful in the initial evaluation of phenotypes both with single and compound mutations of LQTS patients. However, it should be noted that the compound mutation makes more severe phenotype.
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Affiliation(s)
- Gaku Izumi
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan. .,Department of Pediatrics, Hokkaido University Graduate School of Medicine, North-15 West-7, Sapporo, 060-8638, Japan.
| | - Emiko Hayama
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Hirokuni Yamazawa
- Department of Pediatrics, Hokkaido University Graduate School of Medicine, North-15 West-7, Sapporo, 060-8638, Japan
| | - Kei Inai
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Mitsuyo Shimada
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Michiko Furutani
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Tsutomu Nishizawa
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Yoshiyuki Furutani
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Rumiko Matsuoka
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Toshio Nakanishi
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
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Abstract
Cardiac delayed rectifier potassium channels conduct outward potassium currents during the plateau phase of action potentials and play pivotal roles in cardiac repolarization. These include IKs, IKr and the atrial specific IKur channels. In this article, we will review their molecular identities and biophysical properties. Mutations in the genes encoding delayed rectifiers lead to loss- or gain-of-function phenotypes, disrupt normal cardiac repolarization and result in various cardiac rhythm disorders, including congenital Long QT Syndrome, Short QT Syndrome and familial atrial fibrillation. We will also discuss the prospect of using delayed rectifier channels as therapeutic targets to manage cardiac arrhythmia.
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Affiliation(s)
- Lei Chen
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | - Kevin J Sampson
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | - Robert S Kass
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA.
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27
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Phenotype guided characterization and molecular analysis of Indian patients with long QT syndromes. Indian Pacing Electrophysiol J 2016; 16:8-18. [PMID: 27485560 PMCID: PMC4936664 DOI: 10.1016/j.ipej.2016.03.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 03/27/2016] [Accepted: 03/28/2016] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND Long QT syndromes (LQTS) are characterized by prolonged QTc interval on electrocardiogram (ECG) and manifest with syncope, seizures or sudden cardiac death. Long QT 1-3 constitute about 75% of all inherited LQTS. We classified a cohort of Indian patients for the common LQTS based on T wave morphology and triggering factors to prioritize the gene to be tested. We sought to identify the causative mutations and mutation spectrum, perform genotype-phenotype correlation and screen family members. METHODS Thirty patients who fulfilled the criteria were enrolled. The most probable candidate gene among KCNQ1, KCNH2 and SCN5A were sequenced. RESULTS Of the 30 patients, 22 were classified at LQT1, two as LQT2 and six as LQT3. Mutations in KCNQ1 were identified in 17 (77%) of 22 LQT1 patients, KCNH2 mutation in one of two LQT2 and SCN5A mutations in two of six LQT3 patients. We correlated the presence of the specific ECG morphology in all mutation positive cases. Eight mutations in KCNQ1 and one in SCN5A were novel and predicted to be pathogenic by in-silico analysis. Of all parents with heterozygous mutations, 24 (92%) of 26 were asymptomatic. Ten available siblings of nine probands were screened and three were homozygous and symptomatic, five heterozygous and asymptomatic. CONCLUSIONS This study in a cohort of Asian Indian patients highlights the mutation spectrum of common Long QT syndromes. The clinical utility for prevention of unexplained sudden cardiac deaths is an important sequel to identification of the mutation in at-risk family members.
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28
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Cheung CC, Laksman ZWM, Mellor G, Sanatani S, Krahn AD. Exercise and Inherited Arrhythmias. Can J Cardiol 2016; 32:452-8. [PMID: 26927864 DOI: 10.1016/j.cjca.2016.01.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 12/29/2015] [Accepted: 01/06/2016] [Indexed: 01/11/2023] Open
Abstract
Sudden cardiac death (SCD) in an apparently healthy individual is a tragedy that prompts a series of investigations to identify the cause of death and to prevent SCD in potentially at-risk family members. Several inherited channelopathies and cardiomyopathies, including long QT syndrome (LQTS), catecholaminergic polymorphic ventricular cardiomyopathy (CPVT), hypertrophic cardiomyopathy (HCM), and arrhythmogenic right ventricular cardiomyopathy (ARVC) are associated with exercise-related SCD. Exercise restriction has been a historical mainstay of therapy for these conditions. Syncope and cardiac arrest occur during exercise in LQTS and CPVT because of ventricular arrhythmias, which are managed with β-blockade and exercise restriction. Exercise may provoke hemodynamic or ischemic changes in HCM, leading to ventricular arrhythmias. ARVC is a disease of the desmosome, whose underlying disease process is accelerated by exercise. On this basis, expert consensus has erred on the side of caution, recommending rigorous exercise restriction for all inherited arrhythmias. With time, as familiarity with inherited arrhythmia conditions has increased and patients with milder forms of disease are diagnosed, practitioners have questioned the historical rigorous restrictions advocated for all. This change has been driven by the fact that these are often children and young adults who wish to lead active lives. Recent evidence suggests a lower risk of exercise-related arrhythmias in treated patients than was previously assumed, including those with previous symptoms managed with an implantable cardioverter-defibrillator. In this review, we emphasize shared decision making, monitored medical therapy, individual and team awareness of precautions and emergency response measures, and a more permissive approach to recreational and competitive exercise.
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Affiliation(s)
- Christopher C Cheung
- Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Zachary W M Laksman
- Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Gregory Mellor
- Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Shubhayan Sanatani
- Children's Heart Centre, BC Children's Hospital, Vancouver, British Columbia, Canada
| | - Andrew D Krahn
- Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada.
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29
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Spears DA, Gollob MH. Genetics of inherited primary arrhythmia disorders. APPLICATION OF CLINICAL GENETICS 2015; 8:215-33. [PMID: 26425105 PMCID: PMC4583121 DOI: 10.2147/tacg.s55762] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A sudden unexplained death is felt to be due to a primary arrhythmic disorder when no structural heart disease is found on autopsy, and there is no preceding documentation of heart disease. In these cases, death is presumed to be secondary to a lethal and potentially heritable abnormality of cardiac ion channel function. These channelopathies include congenital long QT syndrome, catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, and short QT syndrome. In certain cases, genetic testing may have an important role in supporting a diagnosis of a primary arrhythmia disorder, and can also provide prognostic information, but by far the greatest strength of genetic testing lies in the screening of family members, who may be at risk. The purpose of this review is to describe the basic genetic and molecular pathophysiology of the primary inherited arrhythmia disorders, and to outline a rational approach to genetic testing, management, and family screening.
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Affiliation(s)
- Danna A Spears
- Division of Cardiology - Electrophysiology, University Health Network, Toronto General Hospital, Toronto, ON, Canada
| | - Michael H Gollob
- Division of Cardiology - Electrophysiology, University Health Network, Toronto General Hospital, Toronto, ON, Canada
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30
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Ruwald MH, Xu Parks X, Moss AJ, Zareba W, Baman J, McNitt S, Kanters JK, Shimizu W, Wilde AA, Jons C, Lopes CM. Stop-codon and C-terminal nonsense mutations are associated with a lower risk of cardiac events in patients with long QT syndrome type 1. Heart Rhythm 2015; 13:122-31. [PMID: 26318259 DOI: 10.1016/j.hrthm.2015.08.033] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND In long QT syndrome type 1 (LQT1), the location and type of mutations have been shown to affect the clinical outcome. Although haploinsufficiency, including stop-codon and frameshift mutations, has been associated with a lower risk of cardiac events in patients with LQT1, nonsense mutations have been presumed functionally equivalent. OBJECTIVE The purpose of this study was to evaluate clinical differences between patients with nonsense mutations. METHODS The study sample comprised 1090 patients with genetically confirmed mutations. Patients were categorized into 5 groups, depending on mutation type and location: missense not located in the high-risk cytoplasmic loop (c-loop) (n = 698), which is used as reference; missense c-loop (n = 192); stop-codon (n = 67); frameshift (n = 39); and others (n = 94). The primary outcome was a composite end point of syncope, aborted cardiac arrest, and long QT syndrome-related death (cardiac events). Outcomes were evaluated using the multivariate Cox proportional hazards regression analysis. Standard patch clamp techniques were used. RESULTS Compared to patients with missense non-c-loop mutations, the risk of cardiac events was reduced significantly in patients with stop-codon mutations (hazard ratio [HR] 0.57; 95% confidence interval [CI] 0.34-0.96; P = .035), but not in patients with frameshift mutations (HR 1.01; 95% CI 0.58-1.77; P = .97). Our data suggest that currents of the most common stop-codon mutant channel (Q530X) were larger than those of haploinsufficient channels (wild type: 42 ± 6 pA/pF, n = 20; Q530X+wild type: 79 ± 14 pA/pF, n = 20; P < .05) and voltage dependence of activation was altered. CONCLUSION Stop-codon mutations are associated with a lower risk of cardiac events in patients with LQT1, while frameshift mutations are associated with the same risk as the majority of the missense mutations. Our data indicate functional differences between these previously considered equivalent mutation subtypes.
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Affiliation(s)
- Martin H Ruwald
- Heart Research Follow-up Program, Division of Cardiology, University of Rochester Medical Center, Rochester, New York; Department of Cardiology, Gentofte Hospital, Hellerup, Denmark
| | - Xiaorong Xu Parks
- Cardiovascular Research Institute, Department of Medicine, University of Rochester, Rochester, New York
| | - Arthur J Moss
- Heart Research Follow-up Program, Division of Cardiology, University of Rochester Medical Center, Rochester, New York
| | - Wojciech Zareba
- Heart Research Follow-up Program, Division of Cardiology, University of Rochester Medical Center, Rochester, New York
| | - Jayson Baman
- Heart Research Follow-up Program, Division of Cardiology, University of Rochester Medical Center, Rochester, New York
| | - Scott McNitt
- Heart Research Follow-up Program, Division of Cardiology, University of Rochester Medical Center, Rochester, New York
| | - Jorgen K Kanters
- Department of Cardiology, Gentofte Hospital, Hellerup, Denmark; Laboratory of Experimental Cardiology, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Wataru Shimizu
- Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan
| | - Arthur A Wilde
- AMC Heart Centre, Department of Clinical and Experimental Cardiology, Academic Medical Centre, Amsterdam, The Netherlands
| | - Christian Jons
- Department of Cardiology, Gentofte Hospital, Hellerup, Denmark
| | - Coeli M Lopes
- Cardiovascular Research Institute, Department of Medicine, University of Rochester, Rochester, New York.
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Abstract
Sudden cardiac death (SCD) from cardiac arrest is a major international public health problem accounting for an estimated 15%-20% of all deaths. Although resuscitation rates are generally improving throughout the world, the majority of individuals who experience a sudden cardiac arrest will not survive. SCD most often develops in older adults with acquired structural heart disease, but it also rarely occurs in the young, where it is more commonly because of inherited disorders. Coronary heart disease is known to be the most common pathology underlying SCD, followed by cardiomyopathies, inherited arrhythmia syndromes, and valvular heart disease. During the past 3 decades, declines in SCD rates have not been as steep as for other causes of coronary heart disease deaths, and there is a growing fraction of SCDs not due to coronary heart disease and ventricular arrhythmias, particularly among certain subsets of the population. The growing heterogeneity of the pathologies and mechanisms underlying SCD present major challenges for SCD prevention, which are magnified further by a frequent lack of recognition of the underlying cardiac condition before death. Multifaceted preventative approaches, which address risk factors in seemingly low-risk and known high-risk populations, will be required to decrease the burden of SCD. In this Compendium, we review the wide-ranging spectrum of epidemiology underlying SCD within both the general population and in high-risk subsets with established cardiac disease placing an emphasis on recent global trends, remaining uncertainties, and potential targeted preventive strategies.
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Affiliation(s)
- Meiso Hayashi
- From the Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan (M.H., W.S.); and Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (C.M.A.)
| | - Wataru Shimizu
- From the Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan (M.H., W.S.); and Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (C.M.A.).
| | - Christine M Albert
- From the Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan (M.H., W.S.); and Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (C.M.A.).
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32
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Nakano Y, Shimizu W. Genetics of long-QT syndrome. J Hum Genet 2015; 61:51-5. [PMID: 26108145 DOI: 10.1038/jhg.2015.74] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 05/31/2015] [Accepted: 05/31/2015] [Indexed: 11/09/2022]
Abstract
Congenital long QT syndrome (LQTS) is an inherited arrhythmia syndrome characterized by a prolonged QT interval in the 12-lead ECG, torsades de pointes and not negligible prevalence of sudden cardiac death. The genetic testing plays an important role in the diagnosis of LQTS. A total of 15 genes have been reported for autosomal-dominant forms of Romano-Ward-type congenital LQTS and 2 genes for autosomal-recessive forms of the Jervell and Lange-Nielsen syndrome. In this review, we summarize the recent advances in genetics of LQTS and briefly describe forward perspectives of LQTS investigation.
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Affiliation(s)
- Yukiko Nakano
- Programs for Biomedical Research Graduate School of Biomedical Science, Division of Frontier Medical Science, Department of Cardiovascular Medicine, Hiroshima University, Hiroshima, Japan
| | - Wataru Shimizu
- Department of Cardiovascular Medicine, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
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33
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Abstract
Long QT syndrome (LQTS) is a potentially life-threatening cardiac arrhythmia characterized by delayed myocardial repolarization that produces QT prolongation and increased risk for torsades des pointes (TdP)-triggered syncope, seizures, and sudden cardiac death (SCD) in an otherwise healthy young individual with a structurally normal heart. Currently, there are three major LQTS genes (KCNQ1, KCNH2, and SCN5A) that account for approximately 75% of the disorder. For the major LQTS genotypes, genotype-phenotype correlations have yielded gene-specific arrhythmogenic triggers, electrocardiogram (ECG) patterns, response to therapies, and intragenic and increasingly mutation-specific risk stratification. The 10 minor LQTS-susceptibility genes collectively account for less than 5% of LQTS cases. In addition, three atypical LQTS or multisystem syndromic disorders that have been associated with QT prolongation have been described, including ankyrin-B syndrome, Anderson-Tawil syndrome (ATS), and Timothy syndrome (TS). Genetic testing for LQTS is recommended in patients with either a strong clinical index of suspicion or persistent QT prolongation despite their asymptomatic state. However, genetic test results must be interpreted carefully.
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34
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Itoh H, Dochi K, Shimizu W, Denjoy I, Ohno S, Aiba T, Kimura H, Kato K, Fukuyama M, Hasagawa K, Schulze-Bahr E, Guicheney P, Horie M. A Common Mutation of Long QT Syndrome Type 1 in Japan. Circ J 2015; 79:2026-30. [DOI: 10.1253/circj.cj-15-0342] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Hideki Itoh
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
- Sorbonne Universités, Institut de Recherche sur les Maladies Cardiovasculaires, du Métabolisme et de la Nutrition
- Institute of Cardiometabolism and Nutrition (ICAN)
| | - Kenichi Dochi
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Wataru Shimizu
- Division of Cardiology, Department of Internal Medicine, Nippon Medical School
- Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center
| | - Isabelle Denjoy
- AP-HP, Hôpital Bichat, Service de Cardiologie, Centre de Référence des Maladies Cardiaques Héréditaires, Université Denis Diderot
| | - Seiko Ohno
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Takeshi Aiba
- Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center
| | - Hiromi Kimura
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Koichi Kato
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Megumi Fukuyama
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Kanae Hasagawa
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Eric Schulze-Bahr
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster
- Interdisciplinary Centre for Clinical Research (IZKF) of the University of Münster
| | - Pascale Guicheney
- Sorbonne Universités, Institut de Recherche sur les Maladies Cardiovasculaires, du Métabolisme et de la Nutrition
- Institute of Cardiometabolism and Nutrition (ICAN)
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
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Mazzanti A, O'Rourke S, Ng K, Miceli C, Borio G, Curcio A, Esposito F, Napolitano C, Priori SG. The usual suspects in sudden cardiac death of the young: a focus on inherited arrhythmogenic diseases. Expert Rev Cardiovasc Ther 2014; 12:499-519. [PMID: 24650315 DOI: 10.1586/14779072.2014.894884] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Up to 14,500 young individuals die suddenly every year in Europe of cardiac pathologies. The majority of these tragic events are related to a group of genetic defects that predispose the development of malignant arrhythmias (inherited arrhythmogenic diseases [IADs]). IADs include both cardiomyopathies (hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, dilated cardiomyopathy) and channelopathies (long QT syndrome, short QT syndrome, Brugada syndrome and catecholaminergic polymorphic ventricular tachycardia). Every time an IAD is identified in a patient, other individuals in his/her family may be at risk of cardiac events. However; if a timely diagnosis is made, simple preventative measures may be applied. Genetic studies play a pivotal role in the diagnosis of IADs and may help in the management of patients and their relatives.
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Affiliation(s)
- Andrea Mazzanti
- Molecular Cardiology, IRCCS Salvatore Maugeri Foundation, Pavia, Italy
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Bennett MT, Gula LJ, Klein GJ, Skanes AC, Yee R, Leong-Sit P, Chattha I, Sy R, Jones DL, Krahn AD. Effect of beta-blockers on QT dynamics in the long QT syndrome: measuring the benefit. ACTA ACUST UNITED AC 2014; 16:1847-51. [DOI: 10.1093/europace/euu086] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Abstract
Over the past 2 decades, a number of inherited cardiac arrhythmias, including congenital long QT syndrome (LQTS) and Brugada syndrome (BrS), have been shown to have a link to mutations in genes encoding for ion channels or other membrane components. The recent HRS/EHRA/APHRS expert consensus statement on the diagnosis and management of patients with inherited arrhythmia syndromes has updated the clinical diagnosis of congenital LQTS and BrS. Genetic studies have identified 13 forms of congenital LQTS in 50-80% of clinically affected patients. Genotype-phenotype correlations have been investigated in the 3 major genotypes, LQT1, LQT2 and LQT3 syndromes, resulting in genotype-specific management and therapy. More detailed analyses of each genotype have suggested mutation location-, type-, or function-specific differences in clinical phenotype among the LQT1, LQT2, and possibly LQT3 genotypes. In BrS, only one-third of affected patients can be genotyped, mainly in the sodium channel gene, SCN5A; therefore, clinical studies of genotype-phenotype relationships have been limited. More recently, a genome-wide association study using a gene array explored the role of common genetic variants (polymorphisms) as the susceptible or modifier gene in both congenital LQTS and BrS.
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Affiliation(s)
- Wataru Shimizu
- Department of Cardiovascular Medicine, Nippon Medical School
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Vyas V, Lambiase PD. The investigation of sudden arrhythmic death syndrome (SADS)-the current approach to family screening and the future role of genomics and stem cell technology. Front Physiol 2013; 4:199. [PMID: 24062688 PMCID: PMC3771072 DOI: 10.3389/fphys.2013.00199] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 07/11/2013] [Indexed: 11/14/2022] Open
Abstract
SADS is defined as sudden death under the age of 40 years old in the absence of structural heart disease. Family screening studies are able to identify a cause in up to 50% of cases-most commonly long QT syndrome (LQTS), Brugada and early repolarization syndrome, and catecholaminergic polymorphic ventricular tachycardia (CPVT) using standard clinical screening investigations including pharmacological challenge testing. These diagnoses may be supported by genetic testing which can aid cascade screening and may help guide management. In the current era it is possible to undertake molecular autopsy provided suitable samples of DNA can be obtained from the proband. With the evolution of rapid sequencing techniques it is possible to sequence the whole exome for candidate genes. This major advance offers the opportunity to identify novel causes of lethal arrhythmia but also poses the challenge of managing the volume of data generated and evaluating variants of unknown significance (VUS). The emergence of induced pluripotent stem cell technology could enable evaluation of the electrophysiological relevance of specific ion channel mutations in the proband or their relatives and will potentially enable screening of idiopathic ventricular fibrillation survivors combining genetic and electrophysiological studies in derived myocytes. This also could facilitate the assessment of personalized preventative pharmacological therapies. This review will evaluate the current screening strategies in SADS families, the role of molecular autopsy and genetic testing and the potential applications of molecular and cellular diagnostic strategies on the horizon.
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Affiliation(s)
- Vishal Vyas
- Barnet and Chase Farm Hospitals NHS Trust, Medicine Enfield, UK
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LAKSMAN ZACHARYW, HAMILTON ROBERTM, CHOCKALINGAM PRIYA, BALLANTYNE EMILY, STEPHENSON ELIZABETHA, GROSS GILJ, GULA LORNEJ, KLEIN GEORGEJ, WILDE ARTHURA, KRAHN ANDREWD. Mutation Location Effect on Severity of Phenotype During Exercise Testing in Type 1 Long-QT Syndrome: Impact of Transmembrane and C-Loop Location. J Cardiovasc Electrophysiol 2013; 24:1015-20. [DOI: 10.1111/jce.12172] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2013] [Revised: 04/15/2013] [Accepted: 04/19/2013] [Indexed: 11/30/2022]
Affiliation(s)
| | | | | | | | | | - GIL J. GROSS
- The Hospital for Sick Children; Toronto Ontario Canada
| | - LORNE J. GULA
- University of Western Ontario; London Ontario Canada
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41
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Mahida S, Hogarth AJ, Cowan C, Tayebjee MH, Graham LN, Pepper CB. Genetics of congenital and drug-induced long QT syndromes: current evidence and future research perspectives. J Interv Card Electrophysiol 2013; 37:9-19. [PMID: 23515882 DOI: 10.1007/s10840-013-9779-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Accepted: 01/07/2013] [Indexed: 12/17/2022]
Abstract
The long QT syndrome (LQTS) is a condition characterized by abnormal prolongation of the QT interval with an associated risk of ventricular arrhythmias and sudden cardiac death. Congenital forms of LQTS arise due to rare and highly penetrant mutations that segregate in a Mendelian fashion. Over the years, multiple mutations in genes encoding ion channels and ion channel binding proteins have been reported to underlie congenital LQTS. Drugs are by far the most common cause of acquired forms of LQTS. Emerging evidence suggests that drug-induced LQTS also has a significant heritable component. However, the genetic substrate underlying drug-induced LQTS is presently largely unknown. In recent years, advances in next-generation sequencing technology and molecular biology techniques have significantly enhanced our ability to identify genetic variants underlying both monogenic diseases and more complex traits. In this review, we discuss the genetic basis of congenital and drug-induced LQTS and focus on future avenues of research in the field. Ultimately, a detailed characterization of the genetic substrate underlying congenital and drug-induced LQTS will enhance risk stratification and potentially result in the development of tailored genotype-based therapies.
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Affiliation(s)
- Saagar Mahida
- Leeds General Infirmary, Great George Street, Leeds, LS1 3EX, UK.
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Hsiao PY, Tien HC, Lo CP, Juang JMJ, Wang YH, Sung RJ. Gene mutations in cardiac arrhythmias: a review of recent evidence in ion channelopathies. APPLICATION OF CLINICAL GENETICS 2013; 6:1-13. [PMID: 23837003 PMCID: PMC3699290 DOI: 10.2147/tacg.s29676] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Over the past 15 years, molecular genetic studies have linked gene mutations to many inherited arrhythmogenic disorders, in particular, “ion channelopathies”, in which mutations in genes encode functional units of ion channels and/or their transporter-associated proteins in patients without primary cardiac structural abnormalities. These disorders are exemplified by congenital long QT syndrome (LQTS), short QT syndrome, Brugada syndrome (BrS) and catecholaminergic polymorphic ventricular tachycardia (CPVT). Functional and pathophysiological studies have led to better understanding of the clinical spectrum, ion channel structures and cellular electrophysiology involving dynamics of intracellular calcium cycling in many subtypes of these disorders and more importantly, development of potentially more effective pharmacological agents and even curative gene therapy. In this review, we have summarized (1) the significance of unveiling mutations in genes encoding transporter-associated proteins as the cause of congenital LQTS, (2) the technique of catheter ablation applied at the right ventricular outflow tract may be curative for severely symptomatic BrS, (3) mutations with channel function modulated by protein Kinase A-dependent phosphorylation can be the culprit of CPVT mimicry in Andersen-Tawil syndrome (LQT7), (4) ablation of the ion channel anchoring protein may prevent arrhythmogenesis in Timothy syndrome (LQT8), (5) altered intracellular Ca2+ cycling can be the basis of effective targeted pharmacotherapy in CPVT, and (6) the technology of induced pluripotent stem cells is a promising diagnostic and research tool as it has become a new paradigm for pathophysiological study of patient- and disease-specific cells aimed at screening new drugs and eventual clinical application of gene therapy. Lastly, we have discussed (7) genotype-phenotype correlation in relation to risk stratification of patients with congenital LQTS in clinical practice.
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Affiliation(s)
- Pi-Yin Hsiao
- Institute of Life Sciences, National Central University, Taoyuan, Taiwan
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Gillie DJ, Novick SJ, Donovan BT, Payne LA, Townsend C. Development of a high-throughput electrophysiological assay for the human ether-à-go-go related potassium channel hERG. J Pharmacol Toxicol Methods 2013; 67:33-44. [DOI: 10.1016/j.vascn.2012.10.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 10/02/2012] [Accepted: 10/18/2012] [Indexed: 01/03/2023]
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Aidery P, Kisselbach J, Schweizer PA, Becker R, Katus HA, Thomas D. Impaired ion channel function related to a common KCNQ1 mutation — Implications for risk stratification in long QT syndrome 1. Gene 2012; 511:26-33. [DOI: 10.1016/j.gene.2012.09.041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 09/05/2012] [Accepted: 09/11/2012] [Indexed: 11/28/2022]
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Mullally J, Goldenberg I, Moss AJ, Lopes CM, Ackerman MJ, Zareba W, McNitt S, Robinson JL, Benhorin J, Kaufman ES, Towbin JA, Barsheshet A. Risk of life-threatening cardiac events among patients with long QT syndrome and multiple mutations. Heart Rhythm 2012; 10:378-82. [PMID: 23174487 DOI: 10.1016/j.hrthm.2012.11.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Indexed: 11/17/2022]
Abstract
BACKGROUND Patients with long QT syndrome (LQTS) who harbor multiple mutations (i.e. ≥ 2 mutations in ≥ 1 LQTS-susceptibility gene) may experience increased risk for life-threatening cardiac events. OBJECTIVES The present study was designed to compare the clinical course of LQTS patients with multiple mutations to those with a single mutation. METHODS The risk for life-threatening cardiac events (comprising aborted cardiac arrest, implantable defibrillator shock, or sudden cardiac death) from birth through age 40 years, by the presence of multiple vs. single mutations, was assessed among 403 patients from the LQTS Registry. RESULTS Patients with multiple mutations (n=57) exhibited a longer QTc at enrollment compared with those with a single mutation (mean ± SD: 506 ± 72 vs. 480 ± 56 msec, respectively; P=0.003) and had a higher rate of life threatening cardiac events during follow-up (23% vs. 11%, respectively; p=0.031). Consistently, multivariate analysis demonstrated that patients with multiple mutations had a 2.3-fold (P=0.015) increased risk for life threatening cardiac events as compared to patients with a single mutation. The presence of multiple mutations in a single LQTS gene was associated with a 3.2-fold increased risk for life threatening cardiac events (P=0.010) whereas the risk associated with multiple mutation status involving >1 LQTS gene was not significantly different from the risk associated with a single mutation (HR 1.7, P=0.26). CONCLUSIONS LQTS patients with multiple mutations have a greater risk for life-threatening cardiac events as compared to patients with a single mutation.
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Affiliation(s)
- Jamie Mullally
- Cardiology Division, University of Rochester Medical Center, Rochester, New York 14642, USA
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Burgess DE, Bartos DC, Reloj AR, Campbell KS, Johnson JN, Tester DJ, Ackerman MJ, Fressart V, Denjoy I, Guicheney P, Moss AJ, Ohno S, Horie M, Delisle BP. High-risk long QT syndrome mutations in the Kv7.1 (KCNQ1) pore disrupt the molecular basis for rapid K(+) permeation. Biochemistry 2012; 51:9076-85. [PMID: 23092362 DOI: 10.1021/bi3009449] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Type 1 long QT syndrome (LQT1) is caused by loss-of-function mutations in the KCNQ1 gene, which encodes the K(+) channel (Kv7.1) that underlies the slowly activating delayed rectifier K(+) current in the heart. Intragenic risk stratification suggests LQT1 mutations that disrupt conserved amino acid residues in the pore are an independent risk factor for LQT1-related cardiac events. The purpose of this study is to determine possible molecular mechanisms that underlie the loss of function for these high-risk mutations. Extensive genotype-phenotype analyses of LQT1 patients showed that T322M-, T322A-, or G325R-Kv7.1 confers a high risk for LQT1-related cardiac events. Heterologous expression of these mutations with KCNE1 revealed they generated nonfunctional channels and caused dominant negative suppression of WT-Kv7.1 current. Molecular dynamics simulations of analogous mutations in KcsA (T85M-, T85A-, and G88R-KcsA) demonstrated that they disrupted the symmetrical distribution of the carbonyl oxygen atoms in the selectivity filter, which upset the balance between the strong attractive and K(+)-K(+) repulsive forces required for rapid K(+) permeation. We conclude high-risk LQT1 mutations in the pore likely disrupt the architectural and physical properties of the K(+) channel selectivity filter.
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Affiliation(s)
- Don E Burgess
- Center for Muscle Biology, Department of Physiology, University of Kentucky, 800 Rose Street, MS508, Lexington, Kentucky 40536, United States
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Lysophosphatidic acid increases the electrophysiological instability of adult rabbit ventricular myocardium by augmenting L-type calcium current. PLoS One 2012; 7:e45862. [PMID: 23029283 PMCID: PMC3448719 DOI: 10.1371/journal.pone.0045862] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Accepted: 08/22/2012] [Indexed: 01/17/2023] Open
Abstract
Lysophosphatidic acid (LPA) has diverse actions on the cardiovascular system and is widely reported to modulate multiple ion currents in some cell types. However, little is known about its electrophysiological effects on cardiac myocytes. This study investigated whether LPA has electrophysiological effects on isolated rabbit myocardial preparations. The results indicate that LPA prolongs action potential duration at 90% repolarization (APD90) in a concentration- and frequency-dependent manner in isolated rabbit ventricular myocytes. The application of extracellular LPA significantly increases the coefficient of APD90 variability. LPA increased L-type calcium current (ICa,L) density without altering its activation or deactivation properties. In contrast, LPA has no effect on two other ventricular repolarizing currents, the transient outward potassium current (Ito) and the delayed rectifier potassium current (IK). In arterially perfused rabbit left ventricular wedge preparations, the monophasic action potential duration, QT interval, and Tpeak-end are prolonged by LPA. LPA treatment also significantly increases the incidence of ventricular tachycardia induced by S1S2 stimulation. Notably, the effects of LPA on action potentials and ICa,L are PTX-sensitive, suggesting LPA action requires a Gi-type G protein. In conclusion, LPA prolongs APD and increases electrophysiological instability in isolated rabbit myocardial preparations by increasing ICa,L in a Gi protein-dependent manner.
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Barsheshet A, Goldenberg I, O-Uchi J, Moss AJ, Jons C, Shimizu W, Wilde AA, McNitt S, Peterson DR, Zareba W, Robinson JL, Ackerman MJ, Cypress M, Gray DA, Hofman N, Kanters JK, Kaufman ES, Platonov PG, Qi M, Towbin JA, Vincent GM, Lopes CM. Mutations in cytoplasmic loops of the KCNQ1 channel and the risk of life-threatening events: implications for mutation-specific response to β-blocker therapy in type 1 long-QT syndrome. Circulation 2012; 125:1988-96. [PMID: 22456477 DOI: 10.1161/circulationaha.111.048041] [Citation(s) in RCA: 153] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND β-Adrenergic stimulation is the main trigger for cardiac events in type 1 long-QT syndrome (LQT1). We evaluated a possible association between ion channel response to β-adrenergic stimulation and clinical response to β-blocker therapy according to mutation location. METHODS AND RESULTS The study sample comprised 860 patients with genetically confirmed mutations in the KCNQ1 channel. Patients were categorized into carriers of missense mutations located in the cytoplasmic loops (C loops), membrane-spanning domain, C/N terminus, and nonmissense mutations. There were 27 aborted cardiac arrest and 78 sudden cardiac death events from birth through 40 years of age. After multivariable adjustment for clinical factors, the presence of C-loop mutations was associated with the highest risk for aborted cardiac arrest or sudden cardiac death (hazard ratio versus nonmissense mutations=2.75; 95% confidence interval, 1.29-5.86; P=0.009). β-Blocker therapy was associated with a significantly greater reduction in the risk of aborted cardiac arrest or sudden cardiac death among patients with C-loop mutations than among all other patients (hazard ratio=0.12; 95% confidence interval, 0.02-0.73; P=0.02; and hazard ratio=0.82; 95% confidence interval, 0.31-2.13; P=0.68, respectively; P for interaction=0.04). Cellular expression studies showed that membrane spanning and C-loop mutations produced a similar decrease in current, but only C-loop mutations showed a pronounced reduction in channel activation in response to β-adrenergic stimulation. CONCLUSIONS Patients with C-loop missense mutations in the KCNQ1 channel exhibit a high risk for life-threatening events and derive a pronounced benefit from treatment with β-blockers. Reduced channel activation after sympathetic activation can explain the increased clinical risk and response to therapy in patients with C-loop mutations.
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Affiliation(s)
- Alon Barsheshet
- Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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Identification and functional characterization of the novel human ether-a-go-go-related gene (hERG) R744P mutant associated with hereditary long QT syndrome 2. Biochem Biophys Res Commun 2012; 418:830-5. [PMID: 22314138 DOI: 10.1016/j.bbrc.2012.01.118] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2012] [Accepted: 01/24/2012] [Indexed: 11/20/2022]
Abstract
Mutations of the cyclic nucleotide binding domain (CNBD) may disrupt human ether-a-go-go-related gene (hERG) K(+) channel function and lead to hereditary long QT syndrome (LQTS). We identified a novel missense mutation located in close proximity to the CNBD, hERG R744P, in a patient presenting with recurrent syncope and aborted cardiac death triggered by sudden auditory stimuli. Functional properties of wild type (WT) and mutant hERG R744P subunits were studied in Xenopus laevis oocytes using two-electrode voltage clamp electrophysiology and Western blot analysis. HERG R744P channels exhibited reduced activating currents compared to hERG WT (1.48±0.26 versus 3.40±0.29μA; n=40). These findings were confirmed by tail current analysis (hERG R744P, 0.53±0.07μA; hERG WT, 0.97±0.06μA; n=40). Cell surface trafficking of hERG R744P protein subunits was not impaired. To simulate the autosomal-dominant inheritance associated with LQTS, WT and R744P subunits were co-expressed in equimolar ratio. Mean activating and tail currents were reduced by 32% and 25% compared to hERG WT (n=40), indicating that R744P protein did not exert dominant-negative effects on WT channels. The half-maximal activation voltage was not significantly affected by the R744P mutation. This study highlights the significance of in vitro testing to provide mechanistic evidence for pathogenicity of mutations identified in LQTS. The functional defect associated with hERG R744P serves as molecular basis for LQTS in the index patient.
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Costa J, Lopes CM, Barsheshet A, Moss AJ, Migdalovich D, Ouellet G, McNitt S, Polonsky S, Robinson JL, Zareba W, Ackerman MJ, Benhorin J, Kaufman ES, Platonov PG, Shimizu W, Towbin JA, Vincent GM, Wilde AAM, Goldenberg I. Combined assessment of sex- and mutation-specific information for risk stratification in type 1 long QT syndrome. Heart Rhythm 2012; 9:892-8. [PMID: 22293141 DOI: 10.1016/j.hrthm.2012.01.020] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Indexed: 01/08/2023]
Abstract
BACKGROUND Men and women with type 1 long QT syndrome (LQT1) exhibit time-dependent differences in the risk for cardiac events. OBJECTIVE We hypothesized that sex-specific risk for LQT1 is related to the location and function of the disease-causing mutation in the KCNQ1 gene. METHODS The risk for life-threatening cardiac events (comprising aborted cardiac arrest [ACA] or sudden cardiac death [SCD]) from birth through age 40 years was assessed among 1051 individuals with LQT1 (450 men and 601 women) by the location and function of the LQT1-causing mutation (prespecified as mutations in the intracellular domains linking the membrane-spanning segments [ie, S2-S3 and S4-S5 cytoplasmic loops] involved in adrenergic channel regulation vs other mutations). RESULTS Multivariate analysis showed that during childhood (age group: 0-13 years) men had >2-fold (P < .003) increased risk for ACA/SCD than did women, whereas after the onset of adolescence the risk for ACA/SCD was similar between men and women (hazard ratio = 0.89 [P = .64]). The presence of cytoplasmic-loop mutations was associated with a 2.7-fold (P < .001) increased risk for ACA/SCD among women, but it did not affect the risk among men (hazard ratio 1.37; P = .26). Time-dependent syncope was associated with a more pronounced risk-increase among men than among women (hazard ratio 4.73 [P < .001] and 2.43 [P = .02], respectively), whereas a prolonged corrected QT interval (≥ 500 ms) was associated with a higher risk among women than among men. CONCLUSION Our findings suggest that the combined assessment of clinical and mutation location/functional data can be used to identify sex-specific risk factors for life-threatening events for patients with LQT1.
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Affiliation(s)
- Jason Costa
- Cardiology Division, University of Rochester Medical Center, Rochester, NY 14642, USA
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