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Neumann B, Vink AS, Hermans BJM, Lieve KVV, Cömert D, Beckmann BM, Clur SAB, Blom NA, Delhaas T, Wilde AAM, Kääb S, Postema PG, Sinner MF. Manual vs. automatic assessment of the QT-interval and corrected QT. Europace 2023; 25:euad213. [PMID: 37470430 PMCID: PMC10469369 DOI: 10.1093/europace/euad213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 05/29/2023] [Accepted: 06/29/2023] [Indexed: 07/21/2023] Open
Abstract
AIMS Sudden cardiac death (SCD) is challenging to predict. Electrocardiogram (ECG)-derived heart rate-corrected QT-interval (QTc) is used for SCD-risk assessment. QTc is preferably determined manually, but vendor-provided automatic results from ECG recorders are convenient. Agreement between manual and automatic assessments is unclear for populations with aberrant QTc. We aimed to systematically assess pairwise agreement of automatic and manual QT-intervals and QTc. METHODS AND RESULTS A multi-centre cohort enriching aberrant QTc comprised ECGs of healthy controls and long-QT syndrome (LQTS) patients. Manual QT-intervals and QTc were determined by the tangent and threshold methods and compared to automatically generated, vendor-provided values. We assessed agreement globally by intra-class correlation coefficients and pairwise by Bland-Altman analyses and 95% limits of agreement (LoA). Further, manual results were compared to a novel automatic QT-interval algorithm. ECGs of 1263 participants (720 LQTS patients; 543 controls) were available [median age 34 (inter-quartile range 35) years, 55% women]. Comparing cohort means, automatic and manual QT-intervals and QTc were similar. However, pairwise Bland-Altman-based agreement was highly discrepant. For QT-interval, LoAs spanned 95 (tangent) and 92 ms (threshold), respectively. For QTc, the spread was 108 and 105 ms, respectively. LQTS patients exhibited more pronounced differences. For automatic QTc results from 440-540 ms (tangent) and 430-530 ms (threshold), misassessment risk was highest. Novel automatic QT-interval algorithms may narrow this range. CONCLUSION Pairwise vendor-provided automatic and manual QT-interval and QTc results can be highly discrepant. Novel automatic algorithms may improve agreement. Within the above ranges, automatic QT-interval and QTc results require manual confirmation, particularly if T-wave morphology is challenging.
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Affiliation(s)
- Benjamin Neumann
- Department of Medicine I, LMU University Hospital, LMU Munich, Munich, Germany
- German Centre for Cardiovascular Research (DZHK), partner site: Munich Heart Alliance, Munich, Germany
| | - A Suzanne Vink
- Department of Clinical and Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Heart Center, Amsterdam, The Netherlands
- Department of Pediatric Cardiology, Emma Children’s Hospital, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Ben J M Hermans
- Department of Biomedical Engineering, Maastricht University, Maastricht, The Netherlands
- Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, The Netherlands
| | - Krystien V V Lieve
- Department of Clinical and Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Heart Center, Amsterdam, The Netherlands
| | - Didem Cömert
- Department of Clinical and Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Heart Center, Amsterdam, The Netherlands
| | - Britt-Maria Beckmann
- Department of Medicine I, LMU University Hospital, LMU Munich, Munich, Germany
- Department of Legal Medicine, Goethe Univeristy, University Hospital Frankfurt, Frankfurt am Main, Germany
| | - Sally-Ann B Clur
- Department of Pediatric Cardiology, Emma Children’s Hospital, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Nico A Blom
- Department of Pediatric Cardiology, Emma Children’s Hospital, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
- Department of Pediatric Cardiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Tammo Delhaas
- Department of Biomedical Engineering, Maastricht University, Maastricht, The Netherlands
- Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, The Netherlands
| | - Arthur A M Wilde
- Department of Clinical and Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Heart Center, Amsterdam, The Netherlands
- Department of Pediatric Cardiology, Leiden University Medical Center, Leiden, The Netherlands
- Princess Al-Jawhara Al-Brahim Center of Excellence in Research of Hereditary Disorders, Jeddah, Kingdom of Saudi Arabia
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart (ERN GUARD-Heart), Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - Stefan Kääb
- Department of Medicine I, LMU University Hospital, LMU Munich, Munich, Germany
- German Centre for Cardiovascular Research (DZHK), partner site: Munich Heart Alliance, Munich, Germany
| | - Pieter G Postema
- Department of Clinical and Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Heart Center, Amsterdam, The Netherlands
| | - Moritz F Sinner
- Department of Medicine I, LMU University Hospital, LMU Munich, Munich, Germany
- German Centre for Cardiovascular Research (DZHK), partner site: Munich Heart Alliance, Munich, Germany
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2
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de Vries TAC, Seelig J, Pisters R, Hemels MEW. Drug-induced notched T waves. Neth Heart J 2021; 29:473-474. [PMID: 33564958 PMCID: PMC8397812 DOI: 10.1007/s12471-021-01544-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/25/2021] [Indexed: 10/30/2022] Open
Affiliation(s)
- T A C de Vries
- Department of Cardiology, Rijnstate Hospital, Arnhem, The Netherlands. .,Department of Cardiology, Amsterdam UMC, University of Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, The Netherlands.
| | - J Seelig
- Department of Cardiology, Rijnstate Hospital, Arnhem, The Netherlands.,Cardiovascular Research Institute Maastricht (CARIM), Maastricht, The Netherlands.,Department of Cardiology, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - R Pisters
- Department of Cardiology, Rijnstate Hospital, Arnhem, The Netherlands
| | - M E W Hemels
- Department of Cardiology, Rijnstate Hospital, Arnhem, The Netherlands.,Department of Cardiology, Radboud University Medical Centre, Nijmegen, The Netherlands
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3
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Zhang Y, Dempsey CE, Hancox JC. Electrophysiological characterization of the modified hERG T potassium channel used to obtain the first cryo-EM hERG structure. Physiol Rep 2020; 8:e14568. [PMID: 33091232 PMCID: PMC7580876 DOI: 10.14814/phy2.14568] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 08/13/2020] [Accepted: 08/14/2020] [Indexed: 01/02/2023] Open
Abstract
The voltage-gated hERG (human-Ether-à-go-go Related Gene) K+ channel plays a fundamental role in cardiac action potential repolarization. Loss-of-function mutations or pharmacological inhibition of hERG leads to long QT syndrome, whilst gain-of-function mutations lead to short QT syndrome. A recent open channel cryo-EM structure of hERG represents a significant advance in the ability to interrogate hERG channel structure-function. In order to suppress protein aggregation, a truncated channel construct of hERG (hERGT ) was used to obtain this structure. In hERGT cytoplasmic domain residues 141 to 350 and 871 to 1,005 were removed from the full-length channel protein. There are limited data on the electrophysiological properties of hERGT channels. Therefore, this study was undertaken to determine how hERGT influences channel function at physiological temperature. Whole-cell measurements of hERG current (IhERG ) were made at 37°C from HEK 293 cells expressing wild-type (WT) or hERGT channels. With a standard +20 mV activating command protocol, neither end-pulse nor tail IhERG density significantly differed between WT and hERGT . However, the IhERG deactivation rate was significantly slower for hERGT . Half-maximal activation voltage (V0.5 ) was positively shifted for hERGT by ~+8 mV (p < .05 versus WT), without significant change to the activation relation slope factor. Neither the voltage dependence of inactivation, nor time course of development of inactivation significantly differed between WT and hERGT , but recovery of IhERG from inactivation was accelerated for hERGT (p < .05 versus WT). Steady-state "window" current was positively shifted for hERGT with a modest increase in the window current peak. Under action potential (AP) voltage clamp, hERGT IhERG showed modestly increased current throughout the AP plateau phase with a significant increase in current integral during the AP. The observed consequences for hERGT IhERG of deletion of the two cytoplasmic regions may reflect changes to electrostatic interactions influencing the voltage sensor domain.
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Affiliation(s)
- Yihong Zhang
- School of Physiology and Pharmacology and NeuroscienceBiomedical Sciences BuildingThe University of BristolUniversity WalkBristolUK
| | - Christopher E. Dempsey
- School of BiochemistryBiomedical Sciences BuildingThe University of BristolUniversity WalkBristolUK
| | - Jules C. Hancox
- School of Physiology and Pharmacology and NeuroscienceBiomedical Sciences BuildingThe University of BristolUniversity WalkBristolUK
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4
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Strand S, Strasburger JF, Cuneo BF, Wakai RT. Complex and Novel Arrhythmias Precede Stillbirth in Fetuses With De Novo Long QT Syndrome. Circ Arrhythm Electrophysiol 2020; 13:e008082. [PMID: 32421437 DOI: 10.1161/circep.119.008082] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
BACKGROUND Long QT syndrome (LQTS) is a leading cause of sudden cardiac death in early life and has been implicated in ≈10% of sudden infant deaths and unexplained stillbirths. The purpose of our study was to use fetal magnetocardiography to characterize the electrophysiology and rhythm phenotypes of fetuses with de novo and inherited LQTS variants and identify risk factors for sudden death before birth. METHODS We reviewed the fetal magnetocardiography database from the University of Wisconsin Biomagnetism Laboratory for fetuses with confirmed LQTS. We assessed waveform intervals, heart rate, and rhythm, including the signature LQTS rhythms: functional 2° atrioventricular block, T-wave alternans, and torsade de pointes (TdP). RESULTS Thirty-nine fetuses had pathogenic variants in LQTS genes: 27 carried the family variant, 11 had de novo variants, and 1 was indeterminate. De novo variants, especially de novo SCN5A variants, were strongly associated with a severe rhythm phenotype and perinatal death: 9 (82%) showed signature LQTS rhythms, 6 (55%) showed TdP, 5 (45%) were stillborn, and 1 (9%) died in infancy. Those that died exhibited novel fetal rhythms, including atrioventricular block with 3:1 conduction ratio, QRS alternans in 2:1 atrioventricular block, long-cycle length TdP, and slow monomorphic ventricular tachycardia. Premature ventricular contractions were also strongly associated with TdP and perinatal death. Fetuses with familial variants showed a lower incidence of signature LQTS rhythm (6/27=22%), including TdP (3/27=11%). All were live born. CONCLUSIONS The malignancy of de novo LQTS variants was remarkably high and demonstrate that these mutations are a significant cause of stillbirth. Their ability to manifest rhythms not known to be associated with LQTS increases the difficulty of echocardiographic diagnosis and decreases the likelihood that a resultant fetal loss is attributed to LQTS. Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT03047161.
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Affiliation(s)
- Sarah Strand
- Department of Medical Physics, University of Wisconsin-Madison (S.S. R.T.W.)
| | - Janette F Strasburger
- Division of Cardiology, Department of Pediatrics, Children's Hospital of Wisconsin, Medical College of Wisconsin, Milwaukee (J.F.S.)
| | - Bettina F Cuneo
- Division of Cardiology, Department of Pediatrics (B.F.C.), Children's Hospital Colorado & University of Colorado School of Medicine, Aurora.,The Colorado Fetal Care Center (B.F.C), Children's Hospital Colorado & University of Colorado School of Medicine, Aurora
| | - Ronald T Wakai
- Department of Medical Physics, University of Wisconsin-Madison (S.S. R.T.W.)
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5
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Vink AS, Neumann B, Lieve KVV, Sinner MF, Hofman N, El Kadi S, Schoenmaker MHA, Slaghekke HMJ, de Jong JSSG, Clur SAB, Blom NA, Kääb S, Wilde AAM, Postema PG. Determination and Interpretation of the QT Interval. Circulation 2019; 138:2345-2358. [PMID: 30571576 DOI: 10.1161/circulationaha.118.033943] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Long QT syndrome (LQTS) is associated with potentially fatal arrhythmias. Treatment is very effective, but its diagnosis may be challenging. Importantly, different methods are used to assess the QT interval, which makes its recognition difficult. QT experts advocate manual measurements with the tangent or threshold method. However, differences between these methods and their performance in LQTS diagnosis have not been established. We aimed to assess similarities and differences between these 2 methods for QT interval analysis to aid in accurate QT assessment for LQTS. METHODS Patients with a confirmed pathogenic variant in KCNQ1(LQT1), KCNH2(LQT2), or SCN5A(LQT3) genes and their family members were included. Genotype-positive patients were identified as LQTS cases and genotype-negative family members as controls. ECGs were analyzed with both methods, providing inter- and intrareader validity and diagnostic accuracy. Cutoff values based on control population's 95th and 99th percentiles, and LQTS-patients' 1st and 5th percentiles were established based on the method to correct for heart rate, age, and sex. RESULTS We included 1484 individuals from 265 families, aged 33±21 years and 55% females. In the total cohort, QTTangent was 10.4 ms shorter compared with QTThreshold (95% limits of agreement±20.5 ms, P<0.0001). For all genotypes, QTTangent was shorter than QTThreshold ( P<0.0001), but this was less pronounced in LQT2. Both methods yielded a high inter- and intrareader validity (intraclass correlation coefficient >0.96), and a high diagnostic accuracy (area under the curve >0.84). Using the current guideline cutoff (QTc interval 480 ms), both methods had similar specificity but yielded a different sensitivity. QTc interval cutoff values of QTTangent were lower compared with QTThreshold and different depending on the correction for heart rate, age, and sex. CONCLUSION The QT interval varies depending on the method used for its assessment, yet both methods have a high validity and can both be used in diagnosing LQTS. However, for diagnostic purposes current guideline cutoff values yield different results for these 2 methods and could result in inappropriate reassurance or treatment. Adjusted cutoff values are therefore specified for method, correction formula, age, and sex. In addition, a freely accessible online probability calculator for LQTS ( www.QTcalculator.org ) has been made available as an aid in the interpretation of the QT interval.
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Affiliation(s)
- Arja Suzanne Vink
- Heart Center, Department of Clinical and Experimental Cardiology (A.S.V., K.V.V.L., N.H., S.e.K., M.H.A.S., H.M.J.S., A.A.M.W., P.G.P.), Amsterdam UMC, University of Amsterdam, The Netherlands.,Department of Pediatric Cardiology, Emma Children's Hospital (A.S.V., S.-A.B.C., N.A.B.), Amsterdam UMC, University of Amsterdam, The Netherlands
| | - Benjamin Neumann
- Department of Medicine I, University Hospital Munich, Ludwig-Maximilians University, Germany (B.N., M.F.S., S.K.)
| | - Krystien V V Lieve
- Heart Center, Department of Clinical and Experimental Cardiology (A.S.V., K.V.V.L., N.H., S.e.K., M.H.A.S., H.M.J.S., A.A.M.W., P.G.P.), Amsterdam UMC, University of Amsterdam, The Netherlands
| | - Moritz F Sinner
- Department of Medicine I, University Hospital Munich, Ludwig-Maximilians University, Germany (B.N., M.F.S., S.K.).,Princess Al-Jawhara Al-Brahim Center of Excellence in Research of Hereditary Disorders, Jeddah, Kingdom of Saudi Arabia (M.F.S., A.A.M.W.)
| | - Nynke Hofman
- Heart Center, Department of Clinical and Experimental Cardiology (A.S.V., K.V.V.L., N.H., S.e.K., M.H.A.S., H.M.J.S., A.A.M.W., P.G.P.), Amsterdam UMC, University of Amsterdam, The Netherlands
| | - Soufiane El Kadi
- Heart Center, Department of Clinical and Experimental Cardiology (A.S.V., K.V.V.L., N.H., S.e.K., M.H.A.S., H.M.J.S., A.A.M.W., P.G.P.), Amsterdam UMC, University of Amsterdam, The Netherlands
| | - Melissa H A Schoenmaker
- Heart Center, Department of Clinical and Experimental Cardiology (A.S.V., K.V.V.L., N.H., S.e.K., M.H.A.S., H.M.J.S., A.A.M.W., P.G.P.), Amsterdam UMC, University of Amsterdam, The Netherlands
| | - Hanneke M J Slaghekke
- Heart Center, Department of Clinical and Experimental Cardiology (A.S.V., K.V.V.L., N.H., S.e.K., M.H.A.S., H.M.J.S., A.A.M.W., P.G.P.), Amsterdam UMC, University of Amsterdam, The Netherlands
| | | | - Sally-Ann B Clur
- Department of Pediatric Cardiology, Emma Children's Hospital (A.S.V., S.-A.B.C., N.A.B.), Amsterdam UMC, University of Amsterdam, The Netherlands
| | - Nico A Blom
- Department of Pediatric Cardiology, Emma Children's Hospital (A.S.V., S.-A.B.C., N.A.B.), Amsterdam UMC, University of Amsterdam, The Netherlands.,Department of Pediatric Cardiology, Leiden University Medical Center, The Netherlands (N.A.B.)
| | - Stefan Kääb
- Department of Medicine I, University Hospital Munich, Ludwig-Maximilians University, Germany (B.N., M.F.S., S.K.).,German Cardiovascular Research Center (DZHK), Munich Heart Alliance, Germany (S.K.)
| | - Arthur A M Wilde
- Heart Center, Department of Clinical and Experimental Cardiology (A.S.V., K.V.V.L., N.H., S.e.K., M.H.A.S., H.M.J.S., A.A.M.W., P.G.P.), Amsterdam UMC, University of Amsterdam, The Netherlands.,Princess Al-Jawhara Al-Brahim Center of Excellence in Research of Hereditary Disorders, Jeddah, Kingdom of Saudi Arabia (M.F.S., A.A.M.W.)
| | - Pieter G Postema
- Heart Center, Department of Clinical and Experimental Cardiology (A.S.V., K.V.V.L., N.H., S.e.K., M.H.A.S., H.M.J.S., A.A.M.W., P.G.P.), Amsterdam UMC, University of Amsterdam, The Netherlands
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6
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Kanner SA, Jain A, Colecraft HM. Development of a High-Throughput Flow Cytometry Assay to Monitor Defective Trafficking and Rescue of Long QT2 Mutant hERG Channels. Front Physiol 2018; 9:397. [PMID: 29725305 PMCID: PMC5917007 DOI: 10.3389/fphys.2018.00397] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 04/04/2018] [Indexed: 11/24/2022] Open
Abstract
Long QT Syndrome (LQTS) is an acquired or inherited disorder characterized by prolonged QT interval, exertion-triggered arrhythmias, and sudden cardiac death. One of the most prevalent hereditary LQTS subtypes, LQT2, results from loss-of-function mutations in the hERG channel, which conducts IKr, the rapid component of the delayed rectifier K+ current, critical for cardiac repolarization. The majority of LQT2 mutations result in Class 2 deficits characterized by impaired maturation and trafficking of hERG channels. Here, we have developed a high-throughput flow cytometric assay to analyze the surface and total expression of wild-type (WT) and mutant hERG channels with single-cell resolution. To test our method, we focused on 16 LQT2 mutations in the hERG Per-Arnt-Sim (PAS) domain that were previously studied via a widely used biochemical approach that compares levels of 135-kDa immature and 155-kDa fully glycosylated hERG protein to infer surface expression. We confirmed that LQT2 mutants expressed in HEK293 cells displayed a decreased surface density compared to WT hERG, and were differentially rescued by low temperature. However, we also uncovered some notable differences from the findings obtained via the biochemical approach. In particular, three mutations (N33T, R56Q, and A57P) with apparent WT-like hERG glycosylation patterns displayed up to 50% decreased surface expression. Furthermore, despite WT-like levels of complex glycosylation, these mutants have impaired forward trafficking, and exhibit varying half-lives at the cell surface. The results highlight utility of the surface labeling/flow cytometry approach to quantitatively assess trafficking deficiencies associated with LQT2 mutations, to discern underlying mechanisms, and to report on interventions that rescue deficits in hERG surface expression.
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Affiliation(s)
- Scott A Kanner
- Doctoral Program in Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York, NY, United States
| | - Ananya Jain
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, NY, United States
| | - Henry M Colecraft
- Doctoral Program in Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York, NY, United States.,Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, NY, United States.,Department of Pharmacology, Columbia University College of Physicians and Surgeons, New York, NY, United States
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7
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Steffensen AB, Andersen MN, Mutsaers N, Mujezinovic A, Schmitt N. SUMO co-expression modifies K V 11.1 channel activity. Acta Physiol (Oxf) 2018; 222. [PMID: 28888063 DOI: 10.1111/apha.12974] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 08/31/2017] [Accepted: 09/06/2017] [Indexed: 11/27/2022]
Abstract
AIM The voltage-gated potassium channel KV 11.1 is the molecular basis for the IKr current, which plays an important role in cardiac physiology. Its malfunction is associated with both inherited and acquired cardiac arrhythmias. Native currents differ from those in experimental models, suggesting additional regulatory mechanisms. We hypothesized that the post-translational modification sumoylation fine-tunes channel activity. METHODS The functional effects of sumoylation on KV 11.1 were addressed by employing two-electrode voltage-clamp (TEVC) experiments in Xenopus laevis oocytes. Site-directed mutagenesis enabled a further analysis of the SUMO-target amino acids. We assessed protein expression levels and used confocal imaging for localization studies. RESULTS Co-expression with Ubc9 and SUMO alters the electrophysiological properties of KV 11.1 leading to a decrease in steady-state current amplitude largely due to faster inactivation and alteration of deactivation kinetics. We identified three lysines (K21, K93 and K116) in the PAS domain as the putative SUMO-targets. CONCLUSION This study indicates KV 11.1 as a sumoylation target and offers three main targets: K21, K93, and K116. Furthermore, it proposes an underlying mechanism for the observed kinetic impact of the PAS domain.
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Affiliation(s)
- A. B. Steffensen
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; Danish National Research Foundation Centre for Cardiac Arrhythmia; University of Copenhagen; Copenhagen Denmark
| | - M. N. Andersen
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; Danish National Research Foundation Centre for Cardiac Arrhythmia; University of Copenhagen; Copenhagen Denmark
| | - N. Mutsaers
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; Danish National Research Foundation Centre for Cardiac Arrhythmia; University of Copenhagen; Copenhagen Denmark
| | - A. Mujezinovic
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; Danish National Research Foundation Centre for Cardiac Arrhythmia; University of Copenhagen; Copenhagen Denmark
| | - N. Schmitt
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; Danish National Research Foundation Centre for Cardiac Arrhythmia; University of Copenhagen; Copenhagen Denmark
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8
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Salem JE, Germain M, Hulot JS, Voiriot P, Lebourgeois B, Waldura J, Tregouet DA, Charbit B, Funck-Brentano C. GENomE wide analysis of sotalol-induced IKr inhibition during ventricular REPOLarization, "GENEREPOL study": Lack of common variants with large effect sizes. PLoS One 2017; 12:e0181875. [PMID: 28800628 PMCID: PMC5553738 DOI: 10.1371/journal.pone.0181875] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 07/07/2017] [Indexed: 12/19/2022] Open
Abstract
Many drugs used for non-cardiovascular and cardiovascular purposes, such as sotalol, have the side effect of prolonging cardiac repolarization, which can trigger life-threatening cardiac arrhythmias by inhibiting the potassium-channel IKr (KCNH2). On the electrocardiogram (ECG), IKr inhibition induces an increase in QTc and Tpeak-Tend (TpTe) interval and a decrease of T wave maximal amplitude (TAmp). These changes vary markedly between subjects, suggesting the existence of predisposing genetic factors. 990 healthy individuals, prospectively challenged with an oral 80mg sotalol dose, were monitored for changes in ventricular repolarization on ECG between baseline and 3 hours post dosing. QTc and TpTe increased by 5.5±3.5% and 15±19.6%, respectively, and TAmp decreased by 13.2±15.5%. A principal-component analysis derived from the latter ECG changes was performed. A random subsample of 489 individuals were subjected to a genome-wide-association analysis where 8,306,856 imputed single nucleotide polymorphisms (SNPs) were tested for association with QTc, TpTe and TAmp modulations, as well their derived principal-components, to search for common genetic variants associated with sotalol-induced IKr inhibition. None of the studied SNPs reached the statistical threshold for genome-wide significance. This study supports the lack of common variants with larger effect sizes than one would expect based on previous ECG genome-wide-association studies. CLINICAL TRIAL REGISTRATION ClinicalTrials.gov NCT00773201.
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Affiliation(s)
- Joe-Elie Salem
- Sorbonne-Universités, UPMC Univ Paris 06, INSERM, UMRS-1166, Institute of Cardio metabolism and Nutrition (ICAN), Paris, France
- AP-HP, CIC-1421-Paris-Est, Pitié-Salpêtrière Hospital, Paris, France
| | - Marine Germain
- AP-HP, CIC-1421-Paris-Est, Pitié-Salpêtrière Hospital, Paris, France
| | - Jean-Sébastien Hulot
- Sorbonne-Universités, UPMC Univ Paris 06, INSERM, UMRS-1166, Institute of Cardio metabolism and Nutrition (ICAN), Paris, France
- AP-HP, CIC-1421-Paris-Est, Pitié-Salpêtrière Hospital, Paris, France
| | | | - Bruno Lebourgeois
- Sorbonne-Universités, UPMC Univ Paris 06, INSERM, UMRS-1166, Institute of Cardio metabolism and Nutrition (ICAN), Paris, France
| | | | - David-Alexandre Tregouet
- Sorbonne-Universités, UPMC Univ Paris 06, INSERM, UMRS-1166, Institute of Cardio metabolism and Nutrition (ICAN), Paris, France
| | - Beny Charbit
- AP-HP, CIC-1421-Paris-Est, Pitié-Salpêtrière Hospital, Paris, France
| | - Christian Funck-Brentano
- Sorbonne-Universités, UPMC Univ Paris 06, INSERM, UMRS-1166, Institute of Cardio metabolism and Nutrition (ICAN), Paris, France
- AP-HP, CIC-1421-Paris-Est, Pitié-Salpêtrière Hospital, Paris, France
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9
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Shakibfar S, Graff C, Kanters JK, Nielsen J, Schmidt S, Struijk JJ. Minimal T-wave representation and its use in the assessment of drug arrhythmogenicity. Ann Noninvasive Electrocardiol 2017; 22. [DOI: 10.1111/anec.12413] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Affiliation(s)
- Saeed Shakibfar
- Center for Sensory Motor Interaction (SMI); Department of Health Science and Technology; Aalborg University; Aalborg Denmark
| | - Claus Graff
- Medical Informatics Group (MI); Department of Health Science and Technology; Aalborg University; Aalborg Denmark
| | - Jørgen K. Kanters
- Laboratory of Experimental Cardiology; Department of Biomedical Sciences; University of Copenhagen; Copenhagen Denmark
- Department of Cardiology; Herlev & Gentofte University Hospitals; Copenhagen Denmark
- Department of Cardiology; Aalborg University Hospital; Aalborg Denmark
| | - Jimmi Nielsen
- Center for Schizophrenia; Aalborg Psychiatric Hospital; Aalborg University Hospital; Aalborg Denmark
| | - Samuel Schmidt
- Medical Informatics Group (MI); Department of Health Science and Technology; Aalborg University; Aalborg Denmark
| | - Johannes J. Struijk
- Medical Informatics Group (MI); Department of Health Science and Technology; Aalborg University; Aalborg Denmark
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Benson M, Iñiguez-Lluhí JA, Martens J. Sumo Modification of Ion Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 963:127-141. [PMID: 28197910 DOI: 10.1007/978-3-319-50044-7_8] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recently, a role for SUMO modification outside of the nucleus has emerged. Although the number of extranuclear proteins known to be sumoylated is comparatively small, ion channels represent one important new class of these proteins. Ion channels are responsible for the control of membrane excitability and therefore are critical for fundamental physiological processes such as muscle contraction, neuronal firing, and cellular homeostasis. As such, these ion-conducting proteins are subject to precise regulation. Recently, several studies have identified sumoylation as a novel mechanism of modulating ion channel function. These studies expand the list of known functions of sumoylation and reveal that, in addition to its more established role in the regulation of nuclear proteins, this modification plays important roles at the cytoplasmic face of membranes.
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Affiliation(s)
- Mark Benson
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | | | - Jeffrey Martens
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA.
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11
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Vicente J, Johannesen L, Mason JW, Crumb WJ, Pueyo E, Stockbridge N, Strauss DG. Comprehensive T wave morphology assessment in a randomized clinical study of dofetilide, quinidine, ranolazine, and verapamil. J Am Heart Assoc 2015; 4:e001615. [PMID: 25870186 PMCID: PMC4579946 DOI: 10.1161/jaha.114.001615] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2015] [Accepted: 03/06/2015] [Indexed: 12/19/2022]
Abstract
BACKGROUND Congenital long QT syndrome type 2 (abnormal hERG potassium channel) patients can develop flat, asymmetric, and notched T waves. Similar observations have been made with a limited number of hERG-blocking drugs. However, it is not known how additional calcium or late sodium block, that can decrease torsade risk, affects T wave morphology. METHODS AND RESULTS Twenty-two healthy subjects received a single dose of a pure hERG blocker (dofetilide) and 3 drugs that also block calcium or sodium (quinidine, ranolazine, and verapamil) as part of a 5-period, placebo-controlled cross-over trial. At pre-dose and 15 time-points post-dose, ECGs and plasma drug concentration were assessed. Patch clamp experiments were performed to assess block of hERG, calcium (L-type) and late sodium currents for each drug. Pure hERG block (dofetilide) and strong hERG block with lesser calcium and late sodium block (quinidine) caused substantial T wave morphology changes (P<0.001). Strong late sodium current and hERG block (ranolazine) still caused T wave morphology changes (P<0.01). Strong calcium and hERG block (verapamil) did not cause T wave morphology changes. At equivalent QTc prolongation, multichannel blockers (quinidine and ranolazine) caused equal or greater T wave morphology changes compared with pure hERG block (dofetilide). CONCLUSIONS T wave morphology changes are directly related to amount of hERG block; however, with quinidine and ranolazine, multichannel block did not prevent T wave morphology changes. A combined approach of assessing multiple ion channels, along with ECG intervals and T wave morphology may provide the greatest insight into drug-ion channel interactions and torsade de pointes risk. CLINICAL TRIAL REGISTRATION URL: http://clinicaltrials.gov/ Unique identifier: NCT01873950.
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Affiliation(s)
- Jose Vicente
- Office of Science and Engineering Laboratories, CDRH, US FDA, Silver Spring, MD (J.V., L.J., E.P., D.G.S.)
- Division of Cardiovascular and Renal Products, Office of New Drugs, CDER, US FDA, Silver Spring, MD (J.V., N.S.)
- BSICoS Group, Aragón Institute for Engineering Research (I3A), IIS Aragón, University of Zaragoza, Zaragoza, Spain (J.V., E.P.)
| | - Lars Johannesen
- Office of Science and Engineering Laboratories, CDRH, US FDA, Silver Spring, MD (J.V., L.J., E.P., D.G.S.)
- Department of Clinical Physiology, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden (L.J., D.G.S.)
| | - Jay W. Mason
- Spaulding Clinical Research, West Bend, WI (J.W.M.)
| | | | - Esther Pueyo
- Office of Science and Engineering Laboratories, CDRH, US FDA, Silver Spring, MD (J.V., L.J., E.P., D.G.S.)
- BSICoS Group, Aragón Institute for Engineering Research (I3A), IIS Aragón, University of Zaragoza, Zaragoza, Spain (J.V., E.P.)
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER‐BBN), Zaragoza, Spain (E.P.)
| | - Norman Stockbridge
- Division of Cardiovascular and Renal Products, Office of New Drugs, CDER, US FDA, Silver Spring, MD (J.V., N.S.)
| | - David G. Strauss
- Office of Science and Engineering Laboratories, CDRH, US FDA, Silver Spring, MD (J.V., L.J., E.P., D.G.S.)
- Department of Clinical Physiology, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden (L.J., D.G.S.)
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12
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Sadrieh A, Domanski L, Pitt-Francis J, Mann SA, Hodkinson EC, Ng CA, Perry MD, Taylor JA, Gavaghan D, Subbiah RN, Vandenberg JI, Hill AP. Multiscale cardiac modelling reveals the origins of notched T waves in long QT syndrome type 2. Nat Commun 2014; 5:5069. [PMID: 25254353 DOI: 10.1038/ncomms6069] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 08/26/2014] [Indexed: 01/08/2023] Open
Abstract
The heart rhythm disorder long QT syndrome (LQTS) can result in sudden death in the young or remain asymptomatic into adulthood. The features of the surface electrocardiogram (ECG), a measure of the electrical activity of the heart, can be equally variable in LQTS patients, posing well-described diagnostic dilemmas. Here we report a correlation between QT interval prolongation and T-wave notching in LQTS2 patients and use a novel computational framework to investigate how individual ionic currents, as well as cellular and tissue level factors, contribute to notched T waves. Furthermore, we show that variable expressivity of ECG features observed in LQTS2 patients can be explained by as little as 20% variation in the levels of ionic conductances that contribute to repolarization reserve. This has significant implications for interpretation of whole-genome sequencing data and underlies the importance of interpreting the entire molecular signature of disease in any given individual.
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Affiliation(s)
- Arash Sadrieh
- 1] Division of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia [2] St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Luke Domanski
- CSIRO eResearch and Computational and Simulation Sciences, Canberra, Australian Capital Territory 2601, Australia
| | - Joe Pitt-Francis
- Department of Computer Science, University of Oxford, Oxford OX1 3QD, UK
| | - Stefan A Mann
- 1] Division of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia [2] St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Emily C Hodkinson
- 1] Division of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia [2] St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Chai-Ann Ng
- 1] Division of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia [2] St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Matthew D Perry
- 1] Division of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia [2] St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - John A Taylor
- CSIRO eResearch and Computational and Simulation Sciences, Canberra, Australian Capital Territory 2601, Australia
| | - David Gavaghan
- Department of Computer Science, University of Oxford, Oxford OX1 3QD, UK
| | - Rajesh N Subbiah
- 1] Division of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia [2] St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Jamie I Vandenberg
- 1] Division of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia [2] St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Adam P Hill
- 1] Division of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia [2] St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
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Christiansen M, Hedley PL, Theilade J, Stoevring B, Leren TP, Eschen O, Sørensen KM, Tybjærg-Hansen A, Ousager LB, Pedersen LN, Frikke-Schmidt R, Aidt FH, Hansen MG, Hansen J, Bloch Thomsen PE, Toft E, Henriksen FL, Bundgaard H, Jensen HK, Kanters JK. Mutations in Danish patients with long QT syndrome and the identification of a large founder family with p.F29L in KCNH2. BMC MEDICAL GENETICS 2014; 15:31. [PMID: 24606995 PMCID: PMC4007532 DOI: 10.1186/1471-2350-15-31] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 02/18/2014] [Indexed: 01/08/2023]
Abstract
Background Long QT syndrome (LQTS) is a cardiac ion channelopathy which presents clinically with palpitations, syncope or sudden death. More than 700 LQTS-causing mutations have been identified in 13 genes, all of which encode proteins involved in the execution of the cardiac action potential. The most frequently affected genes, covering > 90% of cases, are KCNQ1, KCNH2 and SCN5A. Methods We describe 64 different mutations in 70 unrelated Danish families using a routine five-gene screen, comprising KCNQ1, KCNH2 and SCN5A as well as KCNE1 and KCNE2. Results Twenty-two mutations were found in KCNQ1, 28 in KCNH2, 9 in SCN5A, 3 in KCNE1 and 2 in KCNE2. Twenty-six of these have only been described in the Danish population and 18 are novel. One double heterozygote (1.4% of families) was found. A founder mutation, p.F29L in KCNH2, was identified in 5 “unrelated” families. Disease association, in 31.2% of cases, was based on the type of mutation identified (nonsense, insertion/deletion, frameshift or splice-site). Functional data was available for 22.7% of the missense mutations. None of the mutations were found in 364 Danish alleles and only three, all functionally characterised, were recorded in the Exome Variation Server, albeit at a frequency of < 1:1000. Conclusion The genetic etiology of LQTS in Denmark is similar to that found in other populations. A large founder family with p.F29L in KCNH2 was identified. In 48.4% of the mutations disease causation was based on mutation type or functional analysis.
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Affiliation(s)
- Michael Christiansen
- Department of Clinical Biochemistry, Immunology and Genetics, Statens Serum Institut, Ørestads Boulevard 5, 2300S, Copenhagen, Denmark.
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Sensoy B, Ozeke O, Canpolat U, Cay S, Oksuz F, Topaloglu S, Aras D, Aydogdu S. Postexercise recovery phase T-wave notching in concealed long QT syndrome. Herz 2013; 40:153-6. [PMID: 24154883 DOI: 10.1007/s00059-013-3968-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 08/22/2013] [Accepted: 08/23/2013] [Indexed: 10/26/2022]
Affiliation(s)
- B Sensoy
- Department of Cardiology, Turkiye Yuksek Ihtisas Training and Research Hospital, Kardiyoloji Klinigi , 06100, Ankara, Turkey
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Denjoy I, Maltret A, Probst V. Syndrome du QT long congénital, tachycardie ventriculaire catécholergique, syndrome de Brugada et mort subite inexpliquée en pédiatrie. ARCHIVES OF CARDIOVASCULAR DISEASES SUPPLEMENTS 2012. [DOI: 10.1016/s1878-6480(12)70829-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Effect of Nalmefene 20 and 80 mg on the Corrected QT Interval and T-Wave Morphology. Clin Drug Investig 2012; 31:799-811. [DOI: 10.1007/bf03256919] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Graff C, Struijk JJ, Kanters JK, Andersen MP, Toft E, Tyl B. Effects of bilastine on T-wave morphology and the QTc interval: a randomized, double-blind, placebo-controlled, thorough QTc study. Clin Drug Investig 2012; 32:339-51. [PMID: 22393898 DOI: 10.2165/11599270-000000000-00000] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
BACKGROUND AND OBJECTIVES The International Conference of Harmonisation (ICH) E14 guideline for thorough QT studies requires assessing the propensity of new non-antiarrhythmic drugs to affect cardiac repolarization. The present study investigates whether a composite ECG measure of T-wave morphology (Morphology Combination Score [MCS]) can be used together with the heart rate corrected QT interval (QTc) in a fully ICH E14-compliant thorough QT study to exclude clinically relevant repolarization effects of bilastine, a novel antihistamine. METHODS Thirty participants in this crossover study were randomly assigned to receive placebo, moxifloxacin 400 mg, bilastine at therapeutic and supratherapeutic doses (20 and 100 mg) and bilastine 20 mg co-administered with ketoconazole 400 mg. Resting ECGs recorded at 12 nominal time points before and after treatments were used to determine Fridericia corrected QTc (QTcF) and MCS from the T-wave characteristics: asymmetry, flatness and notching. RESULTS There were no effects of bilastine monotherapy (20 and 100 mg) on MCS or QTcF at those study times where the bilastine plasma concentrations were highest. MCS changes for bilastine monotherapy did not exceed the normal intrasubject variance of T-wave shapes for triplicate ECG recordings. Maximum QTcF prolongation for bilastine monotherapy was 5 ms or less: 3.8 ms (90% CI 0.3, 7.3 ms) for bilastine 20 mg and 5.0 ms (90% CI 2.0, 8.0 ms) for bilastine 100 mg. There were no indications of bilastine inducing larger repolarization effects on T-wave morphology as compared with the QTcF interval, as evidenced by the similarity of z-score equivalents for placebo-corrected changes in MCS and QTcF values. CONCLUSION This study shows that bilastine, at therapeutic and supratherapeutic dosages, does not induce any effects on T-wave morphology or QTcF. These results confirm the absence of an effect for bilastine on cardiac repolarization.
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Affiliation(s)
- Claus Graff
- Medical Informatics Group, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
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18
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Gustina AS, Trudeau MC. HERG potassium channel regulation by the N-terminal eag domain. Cell Signal 2012; 24:1592-8. [PMID: 22522181 PMCID: PMC4793660 DOI: 10.1016/j.cellsig.2012.04.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 04/04/2012] [Indexed: 01/19/2023]
Abstract
Human ether-á-go-go related gene (hERG, K(v)11.1) potassium channels play a significant role in cardiac excitability. Like other K(v) channels, hERG is activated by membrane voltage; however, distinct from other K(v) channels, hERG channels have unusually slow kinetics of closing (deactivation). The mechanism for slow deactivation involves an N-terminal "eag domain" which comprises a PAS (Per-Arnt-Sim) domain and a short Cap domain. Here we review recent advances in understanding how the eag domain regulates deactivation, including several new Nuclear Magnetic Resonance (NMR) solution structures of the eag domain, and evidence showing that the eag domain makes a direct interaction with the C-terminal C-linker and Cyclic Nucleotide-Binding Homology Domain.
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Affiliation(s)
- Ahleah S. Gustina
- Program in Neuroscience, University of Maryland, School of Medicine, 660 W Redwood St, Baltimore, MD 21201
- Department of Physiology, University of Maryland, School of Medicine, 660 W Redwood St, Baltimore, MD 21201
| | - Matthew C. Trudeau
- Department of Physiology, University of Maryland, School of Medicine, 660 W Redwood St, Baltimore, MD 21201
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A presumably benign human ether-a-go-go-related gene mutation (R176W) with a malignant primary manifestation of long QT syndrome. Cardiol Young 2012; 22:360-3. [PMID: 22067087 DOI: 10.1017/s1047951111001831] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A 12-year-old girl presented with a first prolonged syncope. She was successfully resuscitated by external defibrillation after recording torsade de pointes tachycardia. Repeated electrocardiograms and a 12-channel Holter monitoring showed an intermittent prolongation of the QT interval. Genetic analysis identified a heterozygous point mutation in the KCNH2 gene, which is thought to be associated with a rather mild clinical phenotype of the long QT syndrome.
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Harley CA, Jesus CSH, Carvalho R, Brito RMM, Morais-Cabral JH. Changes in channel trafficking and protein stability caused by LQT2 mutations in the PAS domain of the HERG channel. PLoS One 2012; 7:e32654. [PMID: 22396785 PMCID: PMC3292575 DOI: 10.1371/journal.pone.0032654] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 01/30/2012] [Indexed: 11/25/2022] Open
Abstract
Inherited human long-QT2 syndrome (LQTS) results from mutations in the gene encoding the HERG channel. Several LQT2-associated mutations have been mapped to the amino terminal cytoplasmic Per-Arnt-Sim (PAS) domain of the HERG1a channel subunit. Here we have characterized the trafficking properties of some LQT2-associated PAS domain mutants and analyzed rescue of the trafficking mutants by low temperature (27°C) or by the pore blocker drug E4031. We show that the LQT2-associated mutations in the PAS domain of the HERG channel display molecular properties that are distinct from the properties of LQT2-associated mutations in the trans-membrane region. Unlike the latter, many of the tested PAS domain LQT2-associated mutations do not result in trafficking deficiency of the channel. Moreover, the majority of the PAS domain mutations that cause trafficking deficiencies are not rescued by a pore blocking drug. We have also explored the in vitro folding stability properties of isolated mutant PAS domain proteins using a thermal unfolding fluorescence assay and a chemical unfolding assay.
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Affiliation(s)
- Carol A Harley
- IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
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Keller DUJ, Weiss DL, Dossel O, Seemann G. Influence of ${I_{Ks}}$ Heterogeneities on the Genesis of the T-wave: A Computational Evaluation. IEEE Trans Biomed Eng 2012; 59:311-22. [DOI: 10.1109/tbme.2011.2168397] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
Acquired and hereditary long-QT syndromes are important causes of sudden cardiac death. Both categories are characterized by abnormally prolonged cardiac repolarization arising from a complex interaction between genetic and environmental factors. This produces a potentially dangerous substrate for polymorphic ventricular tachycardia and sudden cardiac death. In this review, the pathophysiologic, diagnostic, and prognostic features of long-QT syndromes, as well as recommendations regarding therapy, are reviewed.
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Matz J, Graff C, Vainio PJ, Kallio A, Højer AM, Struijk JJ, Kanters JK, Andersen MP, Toft E. Effect of nalmefene 20 and 80 mg on the corrected QT interval and T-wave morphology: a randomized, double-blind, parallel-group, placebo- and moxifloxacin-controlled, single-centre study. Clin Drug Investig 2011. [PMID: 21967071 DOI: 10.2165/11592950-000000000-00000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
BACKGROUND Nalmefene is an orally administered competitive opioid receptor antagonist targeted at reducing alcohol consumption in alcohol-dependent patients. As part of the regulatory requirements for drug approval, the potential of novel compounds for causing unwanted proarrhythmia should be studied in a thoroughly designed clinical QT/corrected QT (QTc) study (International Conference on Harmonisation [ICH] E14 guideline). OBJECTIVE This study was designed to evaluate whether nalmefene 20 and 80 mg/day induced changes in cardiac repolarization biomarkers indicative of proarrhythmia (the QTc interval and T-wave morphology). METHODS This was a prospective, randomized, double-blind, parallel-group, placebo- and moxifloxacin-controlled, single-centre study carried out in a clinical pharmacology unit. The study included 270 healthy male and female subjects (age 18-45 years). The subjects were randomized to a 7-day treatment period of placebo, nalmefene 20 mg/day or nalmefene 80 mg/day, or placebo for 6 days followed by a single dose of moxifloxacin 400 mg on day 7. Serial triplicate ECGs were obtained over a 24-hour period at protocol-defined time-points. The primary protocol-defined endpoint was the largest time-matched baseline- and placebo-adjusted mean difference in the individually heart rate-corrected QT interval (QTcNi) recorded at any of the 12 ECG time-points distributed over a 24-hour period on day 7 of treatment. Secondary endpoints included a similar analysis using the Fridericia- (QTcF) and Bazett-corrected (QTcB) intervals. An explorative analysis included quantitative assessment of T-wave morphology using the T-wave morphology composite score (MCS) to assess for differences between treatment groups and placebo on day 7 of treatment. The frequency of outliers in the QTc intervals, the pharmacokinetics of nalmefene and the tolerability of nalmefene were also assessed. RESULTS Nalmefene was rapidly absorbed with a time to reach maximum plasma concentration of 2.2 hours and a dose-proportionate relationship between dose administered and exposure. The largest baseline- and placebo-adjusted mean changes from baseline in the individualized QTcNi (primary endpoint) were 5.45 ms (90% CI 1.52, 9.37) and 5.57 ms (90% CI 1.62, 9.52) for nalmefene 20 and 80 mg/day, respectively, with study sensitivity confirmed by the expected largest increase in mean QTcNi of 10.15 ms (90% CI 5.67, 14.63) for moxifloxacin. Quantitative assessment using the T-wave MCS demonstrated the largest baseline- and placebo-adjusted increase in MCS to be non-significantly different from the intra-subject variability of triplicate recordings in the placebo group. No deaths or serious adverse events occurred in the study. CONCLUSION This thorough QT/QTc study was a negative study in accordance with the ICH E14 guideline, meaning that nalmefene has no clinically relevant effect on the QTc interval and T-wave morphology. The study predicts no concern over proarrhythmia or need for intensive QTc monitoring with the use of nalmefene in clinical practice.
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MAURIELLO DANIELA, JOHNSON JONATHANN, ACKERMAN MICHAELJ. Holter Monitoring in the Evaluation of Congenital Long QT Syndrome. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2011; 34:1100-4. [DOI: 10.1111/j.1540-8159.2011.03102.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Novel ECG markers for ventricular repolarization: Is the QT interval obsolete? Heart Rhythm 2011; 8:1044-5. [PMID: 21349350 DOI: 10.1016/j.hrthm.2011.02.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Indexed: 11/22/2022]
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Graff C, Struijk JJ, Matz J, Kanters JK, Andersen MP, Nielsen J, Toft E. Covariate analysis of QTc and T-wave morphology: new possibilities in the evaluation of drugs that affect cardiac repolarization. Clin Pharmacol Ther 2010; 88:88-94. [PMID: 20485337 DOI: 10.1038/clpt.2010.51] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This study adds the dimension of a T-wave morphology composite score (MCS) to the QTc interval-based evaluation of drugs that affect cardiac repolarization. Electrocardiographic recordings from 62 subjects on placebo and 400 mg moxifloxacin were compared with those from 21 subjects on 160 and 320 mg D,L-sotalol. T-wave morphology changes, as assessed by DeltaMCS, are larger after 320 mg D,L-sotalol than after 160 mg D,L-sotalol; and the changes associated with 160 mg D,L-sotalol are, in turn, larger than those associated with moxifloxacin and placebo. Covariate analyses of DeltaQTc and DeltaMCS showed that changes in T-wave morphology are a significant effect of D,L-sotalol. By contrast, moxifloxacin was found to have no significant effect on T-wave morphology (DeltaMCS) at any given change in QTc. This study offers new insights into the repolarization behavior of a drug associated with low cardiac risk vs. one associated with a high risk and describes the added benefits of a T-wave MCS as a covariate to the assessment of the QTc interval.
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Affiliation(s)
- C Graff
- Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
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Graff C, Matz J, Christensen EB, Andersen MP, Kanters JK, Toft E, Pehrson S, Hardahl TB, Nielsen J, Struijk JJ. Quantitative analysis of T-wave morphology increases confidence in drug-induced cardiac repolarization abnormalities: evidence from the investigational IKr inhibitor Lu 35-138. J Clin Pharmacol 2010; 49:1331-42. [PMID: 19843657 DOI: 10.1177/0091270009344853] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This study investigates repolarization changes induced by a new candidate drug to determine whether a composite electrocardiographic (ECG) measure of T-wave morphology could be used as a reliable marker to support the evidence of abnormal repolarization, which is indicated by QT interval prolongation. Seventy-nine healthy subjects were included in this parallel study. After a baseline day during which no drug was given, 40 subjects received an I(Kr)-blocking antipsychotic compound (Lu 35-138) on 7 consecutive days while 39 subjects received placebo. Resting ECGs were recorded and used to determine a combined measure of repolarization morphology (morphology combination score [MCS]), based on asymmetry, flatness, and notching. Replicate measurements were used to determine reliable change and study power for both measures. Lu 35-138 increased the QTc interval with corresponding changes in T-wave morphology as determined by MCS. For subjects taking Lu 35-138, T-wave morphology was a more reliable indicator of I(Kr) inhibition than QTcF (chi(2) = 20.3, P = .001). At 80% study power for identifying a 5-millisecond placebo-adjusted change from baseline for QTcF, the corresponding study power for MCS was 93%. As a covariate to the assessment of QT interval liability, MCS offered important additive information to the effect of Lu 35-138 on cardiac repolarization.
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Affiliation(s)
- Claus Graff
- Department of Health Science and Technology, Center for Sensory Motor Interaction, Aalborg University, Aalborg, Denmark.
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Extramiana F, Dubois R, Vaglio M, Roussel P, Dreyfus G, Badilini F, Leenhardt A, Maison-Blanche P. The time course of new T-wave ECG descriptors following single- and double-dose administration of sotalol in healthy subjects. Ann Noninvasive Electrocardiol 2010; 15:26-35. [PMID: 20146779 PMCID: PMC6932454 DOI: 10.1111/j.1542-474x.2009.00336.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
INTRODUCTION The aim of the study was to assess the time course effect of IKr blockade on ECG biomarkers of ventricular repolarization and to evaluate the accuracy of a fully automatic approach for QT duration evaluation. METHODS Twelve-lead digital ECG Holter was recorded in 38 healthy subjects (27 males, mean age = 27.4 + or - 8.0 years) on baseline conditions (day 0) and after administration of 160 mg (day 1) and 320 mg (day 2) of d-l sotalol. For each 24-hour period and each subject, ECGs were extracted every 10 minutes during the 4-hour period following drug dosage. Ventricular repolarization was characterized using three biomarker categories: conventional ECG time intervals, principal component analysis (PCA) analysis on the T wave, and fully automatic biomarkers computed from a mathematical model of the T wave. RESULTS QT interval was significantly prolonged starting 1 hour 20 minutes after drug dosing with 160 mg and 1 hour 10 minutes after drug dosing with 320 mg. PCA ventricular repolarization parameters sotalol-induced changes were delayed (>3 hours). After sotalol dosing, the early phase of the T wave changed earlier than the late phase prolongation. Globally, the modeled surrogate QT paralleled manual QT changes. The duration of manual QT and automatic surrogate QT were strongly correlated (R(2) = 0.92, P < 0.001). The Bland and Altman plot revealed a nonstationary systematic bias (bias = 26.5 ms + or - 1.96*SD = 16 ms). CONCLUSIONS Changes in different ECG biomarkers of ventricular repolarization display different kinetics after administration of a potent potassium channel blocker. These differences need to be taken into account when designing ventricular repolarization ECG studies.
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Affiliation(s)
- Fabrice Extramiana
- Lariboisière Hospital, APHP, Paris 7 University, INSERM U942, Paris, France.
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29
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Hedley PL, Jørgensen P, Schlamowitz S, Wangari R, Moolman-Smook J, Brink PA, Kanters JK, Corfield VA, Christiansen M. The genetic basis of long QT and short QT syndromes: A mutation update. Hum Mutat 2009; 30:1486-511. [DOI: 10.1002/humu.21106] [Citation(s) in RCA: 318] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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30
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Graff C, Andersen MP, Xue JQ, Hardahl TB, Kanters JK, Toft E, Christiansen M, Jensen HK, Struijk JJ. Identifying Drug-Induced Repolarization Abnormalities from Distinct ECG Patterns in Congenital Long QT Syndrome. Drug Saf 2009; 32:599-611. [DOI: 10.2165/00002018-200932070-00006] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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31
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Hanton G, Yvon A, Racaud A. Temporal variability of QT interval and changes in T wave morphology in dogs as markers of the clinical risk of drug-induced proarrhythmia. J Pharmacol Toxicol Methods 2008; 57:194-201. [DOI: 10.1016/j.vascn.2008.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2007] [Accepted: 03/10/2008] [Indexed: 01/10/2023]
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32
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The long QT syndrome. COR ET VASA 2007. [DOI: 10.33678/cor.2007.144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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33
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Abstract
The heart is a frequent site of toxicity of pharmaceutical compounds in humans, and when developing a new drug it is critical to conduct a thorough preclinical evaluation of its possible adverse effects on cardiac structure and function. Changes in cardiac morphology such as myocardial necrosis, hypertrophy or valvulopathy are assessed in regulatory toxicity studies in laboratory animals, although specific models may be needed for a more accurate detection of the risk. The potential proarrhythmic risk of new drugs is a major subject of concern and needs to be fully addressed before treatment of volunteers or patients takes place. In vitro assays are conducted to determine the effects on cardiac ion channels, in particular I(Kr) potassium channel antagonism. Prolongation of the QT interval is assessed in vivo, generally in telemetered dogs. Together, these two tests are considered to detect most arrhythmic drugs. The results of this core battery can be refined by additional studies, in particular assays on isolated cardiac tissues determining changes in cardiac action potential duration, shape and variability over time. Triggering of arrhythmia is assessed in hypokalaemic dogs with artificially created bradycardia, or in vitro in isolated whole hearts. The proarrhythmic risk of the new compound is then evaluated by integrating the results of these different tests. Drug adverse effects on cardiac electrophysiological function, in particular impulse formation and conduction, are evaluated through changes in ECG, generally recorded in dogs, pigs or monkeys. Changes in cardiac contractility occurring either as a primary effect of the drug on cardiac function or as a consequence of cardiac lesions should also be carefully assessed. In telemetered or anaesthetised animals, cardiac contractility is evaluated by measurement of left ventricular pressure and its first derivative over time. Echocardiography allows non-invasive measurement of drug-induced changes in ventricular wall movements and cardiac haemodynamics indicative of effects on contractility. In conclusion, a reliable and accurate evaluation of the cardiac safety of a new pharmaceutical agent is based on the results of in vitro tests, with overall moderate to high throughput, and in vivo experiments assessing the effects of the drug on the heart in its physiological environment. The specific sensitivities of the animals used in these assays to cardiac adverse effects should also be considered. The final evaluation of the cardiac risk is therefore based on an integrated analysis of the results from a battery of tests.
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Affiliation(s)
- Gilles Hanton
- Pfizer Global Research and Development, Amboise, France.
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34
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Chung SK, MacCormick JM, McCulley CH, Crawford J, Eddy CA, Mitchell EA, Shelling AN, French JK, Skinner JR, Rees MI. Long QT and Brugada syndrome gene mutations in New Zealand. Heart Rhythm 2007; 4:1306-14. [PMID: 17905336 DOI: 10.1016/j.hrthm.2007.06.022] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Accepted: 06/21/2007] [Indexed: 11/23/2022]
Abstract
BACKGROUND Genetic testing in long QT syndrome (LQTS) is moving from research into clinical practice. We have recently piloted a molecular genetics program in a New Zealand research laboratory with a view to establishing a clinical diagnostic service. OBJECTIVE This study sought to report the spectrum of LQTS and Brugada mutations identified by a pilot LQTS gene testing program in New Zealand. METHODS Eighty-four consecutive index cases referred for LQT gene testing, from New Zealand and Australia, were evaluated. The coding sequence and splice sites of 5 LQTS genes (KCNQ1, HERG, SCN5A, KCNE1, and KCNE2) were screened for genomic variants by transgenomics denaturing high-performance liquid chromatography (dHPLC) system and automated DNA sequencing. RESULTS Forty-five LQTS mutations were identified in 43 patients (52% of the cohort): 25 KCNQ1 mutations (9 novel), 13 HERG mutations (7 novel), and 7 SCN5A mutations (2 novel). Forty patients had LQTS, and 3 had Brugada syndrome. Mutations were identified in 14 patients with resuscitated sudden cardiac death: 4 KCNQ1, 5 HERG, 5 SCN5A. In 17 cases there was a family history of sudden cardiac death in a first-degree relative: 8 KCNQ1, 6 HERG, 2 SCN5A, and 1 case with mutations in both KCNQ1 and HERG. CONCLUSION The spectrum of New Zealand LQTS and Brugada mutations is similar to previous studies. The high proportion of novel mutations (40%) dictates a need to confirm pathogenicity for locally prevalent mutations. Careful screening selection criteria, cellular functional analysis of novel mutations, and development of locally relevant control sample cohorts will all be essential to establishing regional diagnostic services.
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MESH Headings
- Adolescent
- Adult
- Brugada Syndrome/diagnosis
- Brugada Syndrome/genetics
- Cardiopulmonary Resuscitation
- Child
- Child, Preschool
- Chromosome Deletion
- DNA Mutational Analysis
- Death, Sudden, Cardiac/etiology
- Death, Sudden, Cardiac/prevention & control
- ERG1 Potassium Channel
- Ether-A-Go-Go Potassium Channels/genetics
- Female
- Genetic Predisposition to Disease/genetics
- Genetic Variation/genetics
- Humans
- INDEL Mutation/genetics
- Infant
- KCNQ1 Potassium Channel/genetics
- Long QT Syndrome/diagnosis
- Long QT Syndrome/genetics
- Male
- Middle Aged
- Muscle Proteins/genetics
- Mutation, Missense/genetics
- NAV1.5 Voltage-Gated Sodium Channel
- New Zealand
- Open Reading Frames/genetics
- Pilot Projects
- Polymerase Chain Reaction
- Polymorphism, Single Nucleotide/genetics
- Potassium Channels, Voltage-Gated/genetics
- RNA Splice Sites/genetics
- Risk Factors
- Sequence Analysis, DNA
- Sequence Analysis, Protein
- Sodium Channels/genetics
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Affiliation(s)
- Seo-Kyung Chung
- Department of Molecular Medicine and Pathology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
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Chaves AA, Zingaro GJ, Yordy MA, Bustard KA, O'Sullivan S, Galijatovic-Idrizbegovic A, Schuck H, Christian DB, Hoe CM, Briscoe RJ. A highly sensitive canine telemetry model for detection of QT interval prolongation: Studies with moxifloxacin, haloperidol and MK-499. J Pharmacol Toxicol Methods 2007; 56:103-14. [PMID: 17643323 DOI: 10.1016/j.vascn.2007.04.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2007] [Accepted: 04/25/2007] [Indexed: 11/20/2022]
Abstract
INTRODUCTION Preclinical evaluation of delayed ventricular repolarization manifests electrocardiographically as QT interval prolongation and is routinely used as an indicator of potential risk for pro-arrhythmia (potential to cause Torsades de Pointes) of novel human pharmaceuticals. In accordance with ICH S7A and S7B guidelines we evaluated the sensitivity and validity of the beagle dog telemetry (Integrated Telemetry Services (ITS)) model as a preclinical predictor of QT interval prolongation in humans. METHODS Cardiovascular monitoring was conducted for 2 h pre-dose and 24 h post-dosing with moxifloxacin (MOX), haloperidol (HAL), and MK-499, with a toxicokinetic (TK) evaluation in a separate group of dogs. In both cardiovascular and TK studies, MOX (0, 10, 30 and 100 mg/kg), HAL (0, 0.3, 1, 3 mg/kg) and MK-499 (0, 0.03, 0.3 and 3 mg/kg) were administered orally by gavage in 0.5% methylcellulose. Each dog received all 4 doses using a dose-escalation paradigm. Inherent variability of the model was assessed with administration of vehicle (0.5% methylcellulose) alone for 4 days. RESULTS Significant increases in QT(c) were evident with 10, 30 and 100 mg/kg of MOX (C(max)< or =40 microM), 0.3, 1 and 3 mg/kg of HAL (C(max)< or =0.36 microM) and 0.3 and 3 mg/kg of MK-499 (C(max)< or =825 nM) with peak increases of 45 (20%), 31 (13%), and 45 (19%) ms, respectively (p< or =0.05). DISCUSSION In conclusion, we have demonstrated that the ITS-telemetry beagle dog exhibits low inherent intra-animal variability and high sensitivity to detect small but significant increases in QT/QT(c) interval ( approximately 3-6%) with MOX, HAL and MK-499 in the same range of therapeutic plasma concentrations attained in humans. Therefore, this dog telemetry model should be considered an important preclinical predictor of QT prolongation of novel human pharmaceuticals.
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Affiliation(s)
- A A Chaves
- Safety Assessment, Merck Research Laboratories, West Point, PA 19486, USA
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36
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Couderc JP, McNitt S, Xia J, Zareba W, Moss AJ. Repolarization morphology in adult LQT2 carriers with borderline prolonged QTc interval. Heart Rhythm 2006; 3:1460-6. [PMID: 17161789 DOI: 10.1016/j.hrthm.2006.08.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Accepted: 08/06/2006] [Indexed: 11/25/2022]
Abstract
BACKGROUND At least 50% of LQT2 carriers have borderline QTc (0.42-0.47 s), and they present a diagnostic difficulty to clinicians evaluating patients suspected of having long QT syndrome (LQTS). OBJECTIVES Because QTc in this borderline range is nondiagnostic, the purpose of this study was to investigate whether analysis of phenotypic features of T-wave morphology could help identify LQT2 carriers with normal or near-normal QTc-interval duration. METHODS Standard 12-lead ECGs recorded without beta-blockers from LQT2 carriers (n = 90, 33 +/- 14 years, 61% female) and noncarriers (n = 69, 38 +/- 17 years, 58% female) were digitized. The following parameters were automatically measured: RR interval, QT/QTc, QT apex, T-wave amplitude, ascending (alpha(L)) and descending slopes (alpha(R)) of the T wave, and T-wave symmetry. We used a linear logistic regression model to identify the most relevant parameters for separating LQT2 carriers from noncarriers, within the overall population and among patients without overt QTc prolongation (390 </= QTc </= 470). RESULTS Logistic regression selected three parameters: QT, RR interval, and alpha(L) in all models. In the overall population, the model provided 92.7% sensitivity and 90.0% specificity. In the group of patients without beta-blockers and near-normal QTc interval, 92.0% sensitivity (n = 46) and 81.4% specificity (n = 49) were achieved by the model including alpha(L.) CONCLUSION Abnormal T-wave morphology is a phenotypic expression of LQT2, and its quantification could be used to identify patients with suspected LQTS who do not have overt QTc prolongation (QTc >470).
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Affiliation(s)
- Jean-Philippe Couderc
- Heart Research Follow-up Program, University of Rochester Medical Center, Rochester, New York
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37
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Abstract
PURPOSE OF REVIEW Dramatic advances have been made in understanding of both the genetics and the phenotypic expression of congenital long QT syndrome. This paper reviews recent clinically relevant literature. RECENT FINDINGS Long QT syndrome is one of the leading causes of sudden cardiac death. This syndrome, once diagnosed by a clinical profile, has been more clearly defined by specific gene defects causing ion channel abnormalities in the beating heart. Genetic testing for long QT syndrome, once available only through research laboratories, is now commercially available. Diagnosis, risk assessment, and management are increasingly being guided by gene-specific diagnoses. In a family with suspected disease, the genetic test will determine the defect in as many as 75% of subjects. Once the diagnosis is made, the mainstay of therapy continues to be beta-blockers. Implantable cardioverter-defibrillators are indicated in patients at high risk for malignant arrhythmias. SUMMARY Long QT syndrome is one of the first cardiovascular diseases to see the dramatic changes that bench research can bring to the clinical arena. Future research is needed to determine the gene defect in the remaining 25% of patients with suspected long QT syndrome and in risk stratification.
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Affiliation(s)
- Kathryn K Collins
- University of California-San Francisco, 521 Parnassus, San Francisco, CA 94143, USA.
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38
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Ching CK, Tan EC. Congenital long QT syndromes: clinical features, molecular genetics and genetic testing. Expert Rev Mol Diagn 2006; 6:365-74. [PMID: 16706739 DOI: 10.1586/14737159.6.3.365] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Congenital long QT syndrome (LQTS) is a primary electrical disease characterized by a prolonged QT interval in the surface electrocardiogram and increased predisposition to a typical polymorphic ventricular tachycardia, termed Torsade de Pointes. Most patients with LQTS are asymptomatic and are diagnosed incidentally based on an electrocardiogram. Symptomatic patients may suffer from severe cardiac events, such as syncope and/or sudden cardiac death. Autosomal dominant forms are caused by heterozygous mutations in genes encoding the components of the ion channels. The autosomal recessive form with congenital deafness is also known as Jervell and Lang-Nielsen syndrome. It is caused by homozygous mutations or certain compound heterozygous mutations. Depending on the genetic defects, there are differences in the age of onset, severity of symptoms, and number of cardiac events and event triggers. With advances in gene technology, it is now feasible to perform genetic testing for LQTS, especially for those with family history. Identification of the mutation will lead to better management of symptoms and more targeted treatment, depending on the underlying genetic defect, resulting in a reduction of mortality and cardiac events.
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Affiliation(s)
- Chi-Keong Ching
- National Heart Centre, Department of Cardiology, National Heart Centre, Mistri Wing 17 Third Hospital Avenue, Singapore 168752, Republic of Singapore
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39
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Struijk JJ, Kanters JK, Andersen MP, Hardahl T, Graff C, Christiansen M, Toft E. Classification of the long-QT syndrome based on discriminant analysis of T-wave morphology. Med Biol Eng Comput 2006; 44:543-9. [PMID: 16937190 DOI: 10.1007/s11517-006-0061-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Accepted: 04/24/2006] [Indexed: 10/24/2022]
Abstract
The long QT syndrome (LQTS) is a genetic disorder, typically characterized by a prolonged QT interval in the ECG due to abnormal cardiac repolarization. LQTS may lead to syncopal episodes and sudden cardiac death. Various parameters based on T-wave morphology, as well as the QT interval itself have been shown to be useful discriminators, but no single ECG parameter has been sufficient to solve the diagnostic problem. In this study we present a method for discrimination among persons with a normal genotype and those with mutations in the KCNQ1 (KvLQT1 or LQT1) and KCNH2 (HERG or LQT2) genes on the basis of parameters describing T-wave morphology in terms of duration, asymmetry, flatness and amplitude. Discriminant analyses based on 4 or 5 parameters both resulted in perfect discrimination in a learning set of 36 subjects. In both cases cross-validation of the resulting classifiers showed no misclassifications either.
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Affiliation(s)
- J J Struijk
- Department of Health Science and Technology, Center for Sensory Motor Interaction, Fredrik Bajers Vej 7D3, 9220, Aalborg, Denmark.
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40
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Thomsen MB, Matz J, Volders PGA, Vos MA. Assessing the proarrhythmic potential of drugs: current status of models and surrogate parameters of torsades de pointes arrhythmias. Pharmacol Ther 2006; 112:150-70. [PMID: 16714061 DOI: 10.1016/j.pharmthera.2005.04.009] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Accepted: 04/06/2005] [Indexed: 02/08/2023]
Abstract
Torsades de pointes (TdP) is a potentially lethal cardiac arrhythmia that can occur as an unwanted adverse effect of various pharmacological therapies. Before a drug is approved for marketing, its effects on cardiac repolarisation are examined clinically and experimentally. This paper expresses the opinion that effects on repolarisation duration cannot directly be translated to risk of proarrhythmia. Current safety assessments of drugs only involve repolarisation assays, however the proarrhythmic profile can only be determined in the predisposed model. The availability of these proarrhythmic animal models is emphasised in the present paper. It is feasible for the pharmaceutical industry to establish one or more of these proarrhythmic animal models and large benefits are potentially available if pharmaceutical industries and patient-care authorities embraced these models. Furthermore, suggested surrogate parameters possessing predictive power of TdP arrhythmia are reviewed. As these parameters are not developed to finalisation, any meaningful study of the proarrhythmic potential of a new drug will include evaluation in an integrated model of TdP arrhythmia.
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Affiliation(s)
- Morten B Thomsen
- Department of Medical Physiology, Heart Lung Centre Utrecht, University Medical Centre Utrecht, Yalelaan 50, NL-3584 CM Utrecht, Netherlands.
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41
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Abstract
Long QT syndrome (LQTS) refers to a group of "channelopathies"-disorders that affect cardiac ion channels. The "family" concept of syndromes has been applied to the multiple LQTS genotypes, LQT1-8, which exhibit converging mechanisms leading to QT prolongation and slowed ventricular repolarization. The 470+ allelic mutations induce loss-of-function in the passage of mainly K+ ions, and gain-of-function in the passage of Na+ ions through their respective ion channels. Resultant early after depolarizations can lead to a polymorphic form of ventricular tachycardia known as torsade de pointes, resulting in syncope, sudden cardiac death, or near-death (i.e., cardiac arrest aborted either spontaneously or with external defibrillation). LQTS may be either congenital or acquired. The genetic epidemiology of both forms can vary with subpopulation depending on the allele, but as a whole, LQTS appears in every corner of the globe. Many polymorphisms, such as HERG P448R and A915V in Asians, and SCN5A S1102Y in African Americans, show racial-ethnic specificity. At least nine genetic polymorphisms may enhance susceptibility to drug-induced arrhythmia (an "acquired" form of LQTS). Studies have generally demonstrated greater QT prolongation and more severe outcomes among adult females. Gene-gene interactions, e.g., between SCN5A Q1077del mutations and the SCN5A H558B polymorphism, have been shown to seriously reduce ion channel current. While phenotypic ascertainment remains a mainstay in the clinical setting, SSCP and DHPLC-aided DNA sequencing are a standard part of mutational investigation, and direct sequencing on a limited basis is now commercially available for patient diagnosis.
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Affiliation(s)
- Stephen M Modell
- Department of Health Management and Policy, University of Michigan School of Public Health, University of Michigan Medical System, Ann Arbor, MI 48109-2029, USA.
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42
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Viitasalo M, Oikarinen L, Swan H, Glatter KA, Väänänen H, Fodstad H, Chiamvimonvat N, Kontula K, Toivonen L, Scheinman MM. Ratio of late to early T-wave peak amplitude in 24-h electrocardiographic recordings as indicator of symptom history in patients with long-QT Syndrome types 1 and 2. J Am Coll Cardiol 2005; 47:112-20. [PMID: 16386673 DOI: 10.1016/j.jacc.2005.07.068] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2005] [Revised: 07/14/2005] [Accepted: 07/25/2005] [Indexed: 10/25/2022]
Abstract
UNLABELLED We reviewed 24-h electrocardiographic recordings from 214 genotyped subjects--97 with long-QT syndrome type 1 (LQT1), 62 with LQT2, and 55 unaffected--to record maximal diurnal amplitude ratios between late and early T-wave peaks. Maximal amplitude ratios between late and early T-wave peaks were higher in symptomatic than in asymptomatic patients both in LQT1 (3.2 +/- 1.0 vs. 2.3 +/- 0.8; p < 0.001) and in LQT2 patients (2.6 +/- 1.0 vs. 1.7 +/- 0.5; p < 0.001). The maximal amplitude ratio between late and early T-wave peaks was independently associated with symptom history in both LQT1 and LQT2 patients. OBJECTIVES We tested the hypothesis that in long-QT syndrome types 1 (LQT1) and 2 (LQT2), the diurnal maximal ratio between late and early T-wave peak amplitudes correlates with a history of symptoms better than QT interval durations. BACKGROUND Genotype and phenotype studies have delineated clinical profiles of the most prevalent LQT1 and LQT2 subtypes of inherited LQT, but prediction of arrhythmia risk remains uncertain, the baseline QTc interval being the best predictor. In experimental long-QT syndrome models, the ratio between late and early T-wave peak amplitude predicts onset of torsade de pointes. METHODS We reviewed 24-h electrocardiographic recordings from 214 genotyped subjects--97 with LQT1, 62 with LQT2, and 55 unaffected-to record maximal amplitude ratios between late and early T-wave peaks by use of a computer-assisted program. RESULTS Maximal amplitude ratios between late and early T-wave peaks were higher in symptomatic than in asymptomatic patients both in LQT1 (3.2 +/- 1.0 vs. 2.3 +/- 0.8; p < 0.001) and LQT2 patients (2.6 +/- 1.0 vs. 1.7 +/- 0.5; p < 0.001). Although the QTc interval also was longer in symptomatic patients, only the maximal amplitude ratio between late and early T-wave peaks was independently associated with symptoms in both LQT1 and LQT2 patients. CONCLUSIONS Maximal diurnal ratio between late and early T-wave peak amplitude improves noninvasive risk assessment both in LQT1 and LQT2 syndromes. We propose this new indicator in clinical evaluation of arrhythmia risk in LQT1 and LQT2.
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Affiliation(s)
- Matti Viitasalo
- Department of Cardiology, Helsinki University Central Hospital, Helsinki, Finland.
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Shah RR, Hondeghem LM. Refining detection of drug-induced proarrhythmia: QT interval and TRIaD. Heart Rhythm 2005; 2:758-72. [PMID: 15992736 DOI: 10.1016/j.hrthm.2005.03.023] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2005] [Accepted: 03/27/2005] [Indexed: 01/10/2023]
Abstract
QT interval prolongation is so frequently associated with torsades de pointes (TdP) that it has come to be recognized as a surrogate marker of this unique tachyarrhythmia. However, not only does TdP not always follow QT interval prolongation, but TdP can occur even in the absence of a prolonged QT interval. Worse still, even shortening of the QT interval may be associated with serious arrhythmias (particularly ventricular tachycardia [VT] and ventricular fibrillation [VF]). It appears increasingly probable that the distinction between various ventricular tachyarrhythmias may be arbitrary, and drug-induced TdP, polymorphic VT, VT, catecholaminergic polymorphic VT, and VF may represent discrete entities within a spectrum of drug-induced proarrhythmia. Although they are differentiated by the coupling interval and the duration of QT interval, they appear to share a common substrate: a set of disturbances of repolarization characterized by Triangulation, Reverse use dependency, electrical Instability of the action potential, and Dispersion (TRIaD). It is becoming increasingly evident that augmentation of TRIaD, rather than changes in the duration of QT interval, provides the proarrhythmic substrate. In contrast, when not associated with an increase of TRIaD, QT interval prolongation can be an antiarrhythmic property. Electrophysiologically, augmentation of TRIaD can be explained by inhibition of hERG (human ether-a-go-go related gene) channel. Because drug-induced disturbances in repolarization commonly result from inhibition of hERG channels or I(Kr), hERG blockade and the resulting prolongation of QT interval are important properties of a drug to be studied. However, these need only be a concern if associated with TRIaD. More significantly, TRIaD so often precedes prolongation of action potential duration or QT interval and ventricular tachyarrhythmias that it should be considered a marker of proarrhythmia until proven otherwise, even in the absence of QT interval prolongation. Detecting drug-induced augmentation of TRIaD may offer an additional, more sensitive, and accurate indicator of the broader proarrhythmic potential of a drug than may QT interval prolongation alone.
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Affiliation(s)
- Rashmi R Shah
- Medicines and Healthcare Products Regulatory Agency, London, UK.
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44
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Shimizu W, Noda T, Takaki H, Nagaya N, Satomi K, Kurita T, Suyama K, Aihara N, Sunagawa K, Echigo S, Miyamoto Y, Yoshimasa Y, Nakamura K, Ohe T, Towbin JA, Priori SG, Kamakura S. Diagnostic value of epinephrine test for genotyping LQT1, LQT2, and LQT3 forms of congenital long QT syndrome. Heart Rhythm 2005; 1:276-83. [PMID: 15851169 DOI: 10.1016/j.hrthm.2004.04.021] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2004] [Accepted: 04/14/2004] [Indexed: 12/24/2022]
Abstract
OBJECTIVES The aim of this study was to test the hypothesis that epinephrine test may have diagnostic value for genotyping LQT1, LQT2, and LQT3 forms of congenital long QT syndrome (LQTS). BACKGROUND A differential response of dynamic QT interval to epinephrine infusion between LQT1, LQT2, and LQT3 syndromes has been reported, indicating the potential diagnostic value of the epinephrine test for genotyping the three forms. METHODS The responses of 12-lead ECG parameters to epinephrine were retrospectively examined in 15 LQT1, 10 LQT2, 8 LQT3, and 10 healthy volunteers to select the best ECG criteria for separating the four groups. The epinephrine test then was prospectively conducted in 42 probands clinically affected with LQTS, their 67 family members, and 10 new volunteers. The best criteria were applied in a blinded fashion to prospectively separate a different group of 31 LQT1, 23 LQT2, 6 LQT3, and 30 Control patients (10 genotype-negative LQT1, 10 genotype-negative LQT2 family members, and 10 volunteers). RESULTS The sensitivity (penetrance) by ECG diagnostic criteria was lower in LQT1 (68%) than in LQT2 (83%) or LQT3 (83%) before epinephrine and was improved with steady-state epinephrine in LQT1 (87%) and LQT2 (91%) but not in LQT3 (83%), without the expense of specificity (100%). The sensitivity and specificity to differentiate LQT1 from LQT2 were 97% and 96%, those from LQT3 were 97% and 100%, and those from Control were 97% and 100%, respectively, when Delta mean corrected Q-Tend >/=35 ms at steady state was used. The sensitivity and specificity to differentiate LQT2 from LQT3 or Control were 100% and 100%, respectively, when Delta mean corrected Q-Tend >/=80 ms at peak was used. CONCLUSIONS Epinephrine infusion is a powerful test to predict the genotype of LQT1, LQT2, and LQT3 syndromes as well as to improve the clinical diagnosis of genotype-positive patients, especially those with LQT1 syndrome.
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Affiliation(s)
- Wataru Shimizu
- Division of Cardiology, Department of Internal Medicine, National Cardiovascular Center, Suita, Japan.
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Antzelevitch C, Belardinelli L, Wu L, Fraser H, Zygmunt AC, Burashnikov A, Di Diego JM, Fish JM, Cordeiro JM, Goodrow RJ, Scornik F, Perez G. Electrophysiologic properties and antiarrhythmic actions of a novel antianginal agent. J Cardiovasc Pharmacol Ther 2005; 9 Suppl 1:S65-83. [PMID: 15378132 DOI: 10.1177/107424840400900106] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Ranolazine is a novel antianginal agent capable of producing anti-ischemic effects at plasma concentrations of 2 to 6 microM without a significant reduction of heart rate or blood pressure. This review summarizes the electrophysiologic properties of ranolazine. Ranolazine significantly blocks I(Kr) (IC(50) = 12 microM), late I(Na), late I(Ca), peak I(Ca), I(Na-Ca) (IC(50) = 5.9, 50, 296, and 91 microM, respectively) and I(Ks) (17% at 30 microM), but causes little or no inhibition of I(to) or I(K1). In left ventricular tissue and wedge preparations, ranolazine produces a concentration-dependent prolongation of action potential duration (APD) in epicardium, but abbreviation of APD of M cells, leading to either no change or a reduction in transmural dispersion of repolarization (TDR). The result is a modest prolongation of the QT interval. Prolongation of APD and QT by ranolazine is fundamentally different from that of other drugs that block I(Kr) and induce torsade de pointes in that APD prolongation is rate-independent (ie, does not display reverse rate-dependent prolongation of APD) and is not associated with early after depolarizations, triggered activity, increased spatial dispersion of repolarization, or polymorphic ventricular tachycardia. Torsade de pointes arrhythmias were not observed spontaneously nor could they be induced with programmed electrical stimulation in the presence of ranolazine at concentrations as high as 100 microM. Indeed, ranolazine was found to possess significant antiarrhythmic activity, acting to suppress the arrhythmogenic effects of other QT-prolonging drugs. Ranolazine produces ion channel effects similar to those observed after chronic exposure to amiodarone (reduced late I(Na), I(Kr), I(Ks), and I(Ca)). Ranolazine's actions to reduce TDR and suppress early after depolarization suggest that in addition to its anti-anginal actions, the drug possesses antiarrhythmic activity.
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Khositseth A, Hejlik J, Shen WK, Ackerman MJ. Epinephrine-induced T-wave notching in congenital long QT syndrome. Heart Rhythm 2005; 2:141-6. [PMID: 15851286 DOI: 10.1016/j.hrthm.2004.11.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2004] [Accepted: 11/05/2004] [Indexed: 11/18/2022]
Abstract
OBJECTIVES The purpose of this study was to characterize the effect of epinephrine on T-wave morphology in patients with congenital long QT syndrome (LQTS). BACKGROUND QT prolongation is a paradoxical, LQT1-specific response to low-dose epinephrine infusion. At rest, notched T waves are more common in LQT2. METHODS Thirty subjects with LQT1, 28 with LQT2, and 32 controls were studied using epinephrine provocation. Twelve-lead ECG was recorded continuously, and QT, QTc, and heart rate were obtained during each stage. Blinded to phenotype and genotype, T-wave morphology was classified as normal, biphasic, G1 (notch at or below the apex), or G2 (distinct protuberance above the apex). RESULTS At baseline, 97% LQT1, 71% LQT2, and 94% control had normal T-wave profiles. During epinephrine infusion, G1- and G2-T waves were more common in LQT2 than in LQT1 (75% vs 26%, P = .009). However, epinephrine-induced G1-T waves were present in 34% of control. Epinephrine-precipitated biphasic T waves were observed similarly in all groups: LQT1 (6/30), LQT2 (3/28), and control (4/32). During low-dose epinephrine infusion (< or =0.05 microg/kg/min), G1-T waves occurred more frequently in LQT2 (LQT1: 25% vs 3%; control 9%, P = .02). Low-dose epinephrine-induced G2-T waves were detected exclusively in LQT2 (18%). Low-dose epinephrine elicited G1/G2-T waves in 8 of 15 LQT2 patients with a nondiagnostic baseline QTc. CONCLUSIONS Biphasic and G1-T waves are nonspecific responses to high-dose epinephrine. Changes in T-wave morphology during low-dose epinephrine (<0.05 microg/kg/min) may yield diagnostic information. G2-notched T waves elicited during low-dose epinephrine may unmask some patients with concealed LQT2.
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Affiliation(s)
- Anant Khositseth
- Department of Pediatric and Adolescent Medicine, Division of Pediatric Cardiology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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Towbin JA, Friedman RA. Provocation testing in inherited arrhythmia disorders: Can we be more specific? Heart Rhythm 2005; 2:147-8. [PMID: 15851287 DOI: 10.1016/j.hrthm.2004.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Novotny T, Sisakova M, Kadlecova J, Florianova A, Semrad B, Gaillyova R, Vlasinova J, Chroust K, Toman O. Occurrence of notched T wave in healthy family members with the long QT interval syndrome. Am J Cardiol 2004; 94:808-11. [PMID: 15374797 DOI: 10.1016/j.amjcard.2004.05.070] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Revised: 05/26/2004] [Accepted: 05/26/2004] [Indexed: 11/15/2022]
Abstract
The notched T wave is considered 1 of the diagnostic signs of long QT interval syndrome (LQTIS). The investigators report observations of notched T waves in noncarrier members of families with LQTIS and compare the exercise-induced dynamic behavior of these complex T-wave patterns in mutation carriers and noncarriers of 3 families with LQTIS.
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Affiliation(s)
- Tomas Novotny
- Department of Cardiology, University Hospital Brno Bohunice, Jihlavska 20, 625-00 Brno, Czech Republic.
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Kanters JK, Fanoe S, Larsen LA, Bloch Thomsen PE, Toft E, Christiansen M. T wave morphology analysis distinguishes between KvLQT1 and HERG mutations in long QT syndrome. Heart Rhythm 2004; 1:285-92. [PMID: 15851171 DOI: 10.1016/j.hrthm.2004.05.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2004] [Accepted: 05/01/2004] [Indexed: 10/26/2022]
Abstract
OBJECTIVES The aim of this study was to develop an objective method to distinguish between HERG and KvLQT1 genotypes on the surface ECG. BACKGROUND The two most prevalent genes affected in long QT syndrome (LQTS) are KvLQT1 (KCNQ1) and HERG (KCNH2), which are mutated in >90% of patients with a reported LQTS genotype. It is known that T waves have lower amplitude and more notches in HERG patients than T waves in KvLQT1 patients, but this semiquantitative method lacks the discriminative power to be used in a clinical setting. We developed a simple mathematical method that allowed us to quantify T wave shape in LQTS mutations for clinical use. METHODS ECGs from 24 HERG patients, 13 KvLQT1 LQTS patients, and 13 healthy relatives were examined. The repolarizing integral (RI) was constructed from the T wave. The resulting RI is sigmoid and was modeled using the Hill equation as (RI(t) = V(max)*[t(n)/[K(m)(n) + t(n)]]). V(max) is equivalent to the total T wave area, K(m) is the time when 50% of the T wave area is reached, and n is a measure of the slope of the sigmoid RI. RESULTS The RI correlated nearly perfectly to the fitted sigmoid, r = 0.99. In lead V(2), V(max) was larger in KvLQT1 (0.148 +/- 0.021) (mean +/- SE) compared to HERG (0.080 +/- 0.012) and controls (0.067 +/- 0.021). The Hill coefficient n of the RI discriminated perfectly between HERG (2.00 +/- 0.11) and KvLQT1 (4.11 +/- 0.15). CONCLUSIONS RI allows distinguishing between HERG and KvLQT1 mutations based solely on the T wave morphology in the present LQTS population.
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Abstract
Congenital long QT syndrome (LQTS) is a rare but potentially lethal disease, characterized by prolongation of QT interval, recurrent syncope, and sudden death. In the pregenomic era (1959-1991), sympathetic imbalance was thought to be responsible for this disease. Since 1991 (postgenomic era), 7 LQTS genes have been discovered and more than 300 mutations have been identified to account for approximately 70% of patients affected. Despite the advancement in molecular genetic knowledge, diagnosis of congenital LQTS is still based on electrocardiographic and clinical characteristics. Beta-blockers remain the mainstay treatment. For high-risk patients, the implantable cardioverter-defibrillator (ICD) offer an effective therapeutic option to reduce mortality. Gene-based specific therapy is still preliminary. Further studies are required to investigate new strategies for targeting the defective genes or mutant channels. For acquired LQTS, it is generally believed that the main issue is the blockade of the slow component of the delayed rectifier K+ current (IKr). These IKr blockers have a "reverse frequency-dependent" effect on the QTc interval and increase the dispersion in repolarization. In the presence of risk factors such as female gender, slow heart rate, and hypokalemia, these IKr blockers have a high propensity to induce torsades de pointes. For patients with a history of drug-induced LQTS, care must be taken to avoid further exposure to QT-prolonging drugs or conditions. Molecular genetic analysis could be useful to unravel subclinical mutations or polymorphisms. Physicians not only need to be aware of the pharmacodynamic and pharmacokinetic interactions of various important drugs, but also need to update their knowledge.
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Affiliation(s)
- Chern-En Chiang
- Division of Cardiology, Taipei Veterans General Hospital, National Yang-Ming University, Taipei, Taiwan.
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