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Aims Current long QT syndrome (LQTS) therapy, largely based on beta-blockade, does not prevent arrhythmias in all patients; therefore, novel therapies are warranted. Pharmacological inhibition of the serum/glucocorticoid-regulated kinase 1 (SGK1-Inh) has been shown to shorten action potential duration (APD) in LQTS type 3. We aimed to investigate whether SGK1-Inh could similarly shorten APD in LQTS types 1 and 2. Methods and results Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and hiPSC-cardiac cell sheets (CCS) were obtained from LQT1 and LQT2 patients; CMs were isolated from transgenic LQT1, LQT2, and wild-type (WT) rabbits. Serum/glucocorticoid-regulated kinase 1 inhibition effects (300 nM–10 µM) on field potential durations (FPD) were investigated in hiPSC-CMs with multielectrode arrays; optical mapping was performed in LQT2 CCS. Whole-cell and perforated patch clamp recordings were performed in isolated LQT1, LQT2, and WT rabbit CMs to investigate SGK1-Inh (3 µM) effects on APD. In all LQT2 models across different species (hiPSC-CMs, hiPSC-CCS, and rabbit CMs) and independent of the disease-causing variant (KCNH2-p.A561V/p.A614V/p.G628S/IVS9-28A/G), SGK1-Inh dose-dependently shortened FPD/APD at 0.3–10 µM (by 20–32%/25–30%/44–45%). Importantly, in LQT2 rabbit CMs, 3 µM SGK1-Inh normalized APD to its WT value. A significant FPD shortening was observed in KCNQ1-p.R594Q hiPSC-CMs at 1/3/10 µM (by 19/26/35%) and in KCNQ1-p.A341V hiPSC-CMs at 10 µM (by 29%). No SGK1-Inh-induced FPD/APD shortening effect was observed in LQT1 KCNQ1-p.A341V hiPSC-CMs or KCNQ1-p.Y315S rabbit CMs at 0.3–3 µM. Conclusion A robust SGK1-Inh-induced APD shortening was observed across different LQT2 models, species, and genetic variants but less consistently in LQT1 models. This suggests a genotype- and variant-specific beneficial effect of this novel therapeutic approach in LQTS.

Cardiac arrhythmias are a major cause of death and disability. A large number of experimental cell and animal models have been developed to study arrhythmogenic diseases. These models have provided important insights into the underlying arrhythmia mechanisms and translational options for their therapeutic management. This position paper from the ESC Working Group on Cardiac Cellular Electrophysiology provides an overview of (i) currently available in vitro, ex vivo, and in vivo electrophysiological research methodologies, (ii) the most commonly used experimental (cellular and animal) models for cardiac arrhythmias including relevant species differences, (iii) the use of human cardiac tissue, induced pluripotent stem cell (hiPSC)-derived and in silico models to study cardiac arrhythmias, and (iv) the availability, relevance, limitations, and opportunities of these cellular and animal models to recapitulate specific acquired and inherited arrhythmogenic diseases, including atrial fibrillation, heart failure, cardiomyopathy, myocarditis, sinus node, and conduction disorders and channelopathies. By promoting a better understanding of these models and their limitations, this position paper aims to improve the quality of basic research in cardiac electrophysiology, with the ultimate goal to facilitate the clinical translation and application of basic electrophysiological research findings on arrhythmia mechanisms and therapies.

Brugada syndrome (BrS) is a cardiac arrhythmia disorder associated with sudden death in young adults. With the exception of SCN5A, encoding the cardiac sodium channel Na(V)1.5, susceptibility genes remain largely unknown. Here we performed a genome-wide association meta-analysis comprising 2,820 unrelated cases with BrS and 10,001 controls, and identified 21 association signals at 12 loci (10 new). Single nucleotide polymorphism (SNP)-heritability estimates indicate a strong polygenic influence. Polygenic risk score analyses based on the 21 susceptibility variants demonstrate varying cumulative contribution of common risk alleles among different patient subgroups, as well as genetic associations with cardiac electrical traits and disorders in the general population. The predominance of cardiac transcription factor loci indicates that transcriptional regulation is a key feature of BrS pathogenesis. Furthermore, functional studies conducted on MAPRE2, encoding the microtubule plus-end binding protein EB2, point to microtubule-related trafficking effects on Na(V)1.5 expression as a new underlying molecular mechanism. Taken together, these findings broaden our understanding of the genetic architecture of BrS and provide new insights into its molecular underpinnings. Genome-wide association analyses identify new susceptibility loci for Brugada syndrome. Functional studies implicate microtubule-related trafficking effects on sodium channel expression as an underlying molecular mechanism., European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program [772376-EScORIAL]; Health~Holland; Top Sector Life Sciences Health; Wellcome Trust [076113, 085475, 090355]; Helmholtz Zentrum Munchen-German Research Center for Environmental Health - German Federal Ministry of Education and Research; State of Bavaria; Munich Center of Health Sciences (MC Health), Ludwig-Maximilians-Universitat, as part of LMUinnovativ; research program Etoiles montantes des Pays de la Loire [REGIOCARD RPH081-U1087-REG-PDL]; ANR JCJC LEARN [R21006NN, RPV21014NNA]; H2020-MSCA-IF-2014 Program of the European Commission [RISTRAD-661617]; Canadian Heart Rhythm Society's George Mines Award; European Society of Cardiology research award; Philippa and Marvin Carsley Cardiology Chair; Fondation Leducq; National Institutes of Health (NIH) NHGRI T32 [1T32HG010464-01]; IRP-VERACITIES-New Mechanisms for VEntricular ARrhythmia And CardIomeTabolic DIseasES an I-SITE NExT health and engineering initiative (Ecole Centrale); IRP-VERACITIES-New Mechanisms for VEntricular ARrhythmia And CardIomeTabolic DIseasES an I-SITE NExT health and engineering initiative (Nantes University); IRP-GAINES-Genetic Architecture IN cardiovascular disEaSes - INSERM; CNRS; Amsterdam Cardiovascular Sciences fellowship; NHLBI BioData Catalyst Fellows Program; Dutch Heart Foundation [CVON PREDICT2]; Innovational Research Incentives Scheme Vidi grant from the Netherlands Organisation for Health Research and Development (ZonMw) [91714371]; Robert Lancaster Memorial Fund; Cardiac Risk in the Young; Wetenschappelijk Fonds Willy Gepts VUB-UZ Brussel; VUB IRP project `IMAGica: an Integrative personalized Medical Approach for Genetic diseases, Inherited Cardia Arrhythmias as a model' and Innoviris BRIDGE 2017; project `IGenCare: Integrated Personalised Medical Genomics Care Solution for Patients with Rare Genetic Diseases'; Barts BRC; DZHK (German Centre for Cardiovascular Research); BMBF (German Ministry of Education and Research); Danish Heart Foundation; IWT [140935]; ALS Liga Belgie; National Lottery of Belgium; KU Leuven Opening the Future Fund; HYPERGENES [HEALTH-F4-2007]; Leducq Foundation for Cardiovascular Research grant [18CVD05]; Netherlands CardioVascular Research Initiative [CVON PREDICT2]; NIH [HL47678, HL138103, 1RO1HL092577, R01HL128914, K24HL105780]; W.W. Smith Charitable Trust; Wistar Morris Fund; GOA-Antigone [33933]; Senior Clinical Fellowship of the Flemish Science Foundation (FWO); British Heart Foundation; BHF Clinical Research Training Fellowship [FS/11/71/28918]; Cardiac Risk in the Young and Robert Lancaster Memorial fund - McColl's Ltd. Retail Group; European Union's Horizon 2020 research and innovation program under acronym ESCAPE-NET [733381]; Dutch Heart Foundation; Fondation Leducq [14CVD01, 17CVD02]; American Heart Association [18SFRN34110082, 18SFRN34250007]; Bayer AG; NIH grant [1R01HL139731]; Federation Francaise de Cardiologie (PREVENT project); Leducq Foundation; Burroughs Wellecome Fund; Fondation pour la Recherche Medicale [DEQ20140329545]; National Agency for Research [ANR-GENSUD-14-CE10-0001]; Netherlands Organization for Scientific Research (VICI fellowship) [016.150.610]; [K23HL127704]; [R01 HL149826]; [P50 GM115305]; [NIH-RO1 HL134328], We are greatly indebted to the patients included in the study. We thank V. Cotard, C. Goutsmedt, M.-F. Le Cunff and N. Bourgeais for assistance in patient recruitment and L. Beekman for his technical support. We thank the biological resource centre for biobanking (CHU Nantes, Nantes Universite, Centre de ressources biologiques (BB0033-00040), F-44000 Nantes, France) for applying the following guidelines68. We are most grateful to the Genomics and Bioinformatics Core Facility of Nantes (GenoBiRD, Biogenouest, IFB) for its technical support. This research has been conducted using the UK Biobank resource; we are grateful to UK Biobank participants. The MINE study (J.H.V.) has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement no. 772376-EScORIAL). The collaboration project is cofunded by the PPP Allowance made available by Health~Holland, Top Sector Life Sciences & Health, to stimulate public-private partnerships. This study makes use of data generated by the Wellcome Trust Case-Control Consortium. A full list of the investigators who contributed to the generation of the data is available from www.wtccc.org.uk.Funding for the project was provided by the Wellcome Trust under award 076113, 085475 and 090355. The KORA research platform (KORA, Cooperative Research in the Region of Augsburg) was initiated and financed by the Helmholtz Zentrum Munchen-German Research Center for Environmental Health, which is funded by the German Federal Ministry of Education and Research and by the State of Bavaria. Furthermore, KORA research was supported within the Munich Center of Health Sciences (MC Health), Ludwig-Maximilians-Universitat, as part of LMUinnovativ. J. Barc is supported by the research program Etoiles montantes des Pays de la Loire REGIOCARD RPH081-U1087-REG-PDL, ANR JCJC LEARN (R21006NN, RPV21014NNA) and by the H2020-MSCA-IF-2014 Program of the European Commission (RISTRAD-661617). R.T. is supported by the Canadian Heart Rhythm Society's George Mines Award, the European Society of Cardiology research award, and the Philippa and Marvin Carsley Cardiology Chair. D.Y.C. is supported by Fondation Leducq and National Institutes of Health (NIH) NHGRI T32 (no. 1T32HG010464-01). M. Baudic was supported by IRP-VERACITIES-New Mechanisms for VEntricular ARrhythmia And CardIomeTabolic DIseasES, an I-SITE NExT health and engineering initiative (Ecole Centrale and Nantes University) and by the IRP-GAINES-Genetic Architecture IN cardiovascular disEaSes funded by INSERM and CNRS. R.W. is supported by an Amsterdam Cardiovascular Sciences fellowship. S.C. is supported by the NHLBI BioData Catalyst Fellows Program. C.A.R. is supported by Fondation Leducq, the Dutch Heart Foundation (CVON PREDICT2) and the Innovational Research Incentives Scheme Vidi grant from the Netherlands Organisation for Health Research and Development (ZonMw; 91714371). Y.D.W. is supported by the Robert Lancaster Memorial Fund. M.P. is supported by Cardiac Risk in the Young. S.V.D. is supported by Wetenschappelijk Fonds Willy Gepts VUB-UZ Brussel, project `Unravelling the molecular genetic pathways of Brugada Syndrome by cardiomics research', VUB IRP project `IMAGica: an Integrative personalized Medical Approach for Genetic diseases, Inherited Cardia Arrhythmias as a model' and Innoviris BRIDGE 2017, project `IGenCare: Integrated Personalised Medical Genomics Care Solution for Patients with Rare Genetic Diseases'. S.H. is supported by the Barts BRC. B.R.; is supported by the DZHK (German Centre for Cardiovascular Research) and by the BMBF (German Ministry of Education and Research). B.G.W. is supported by the Danish Heart Foundation. M.B.S. is supported by K23HL127704. Project MinE Belgium was supported by a grant from IWT (no. 140935), the ALS Liga Belgie, the National Lottery of Belgium and the KU Leuven Opening the Future Fund. D.C. and C.L. are supported by HYPERGENES (HEALTH-F4-2007). D.R. is supported by R01 HL149826, P50 GM115305. P.J.S. acknowledges the support of Leducq Foundation for Cardiovascular Research grant 18CVD05. P.V.D. is supported by the Netherlands CardioVascular Research Initiative (CVON PREDICT2). C.A. is supported by NIH HL47678 and HL138103, W.W. Smith Charitable Trust and Wistar Morris Fund. M.B. is Supported by the DZHK (German Centre for Cardiovascular Research) and by the BMBF (German Ministry of Education and Research). P.D.L. is supported by UCL/UCLH Biomedicine NIHR and Barts BRC. B.L. is supported by GOA-Antigone 33933. J.B. is supported by a Senior Clinical Fellowship of the Flemish Science Foundation (FWO). E.B. is supported by the British Heart Foundation including BHF Clinical Research Training Fellowship (FS/11/71/28918: Future diagnostic role and new genetic loci in SADS), Cardiac Risk in the Young and Robert Lancaster Memorial fund sponsored by McColl's Ltd. Retail Group. H.L.T. is supported by the European Union's Horizon 2020 research and innovation program under acronym ESCAPE-NET, registered under grant agreement no. 733381, and the Dutch Heart Foundation (CVON RESCUED and PREDICT2 projects). M.D. is supported by NIH-RO1 HL134328. P.T.E. was supported by the Fondation Leducq (14CVD01), the NIH (1RO1HL092577, R01HL128914, K24HL105780), the American Heart Association (18SFRN34110082) and by a research grant from Bayer AG to the Broad Institute. S.A.L. is supported by NIH grant 1R01HL139731 and American Heart Association 18SFRN34250007. J.-B.G. received a grant from the Federation Francaise de Cardiologie (PREVENT project). A.L.G. is supported by the Fondation Leducq. C.A.M.R. is supported by the Leducq Foundation and Burroughs Wellecome Fund. A.A.W. is supported by the Dutch Heart Foundation (CVON PREDICT2 project). J.-J.S. is supported by the Fondation pour la Recherche Medicale (DEQ20140329545). R.R. and P.G. are supported by the National Agency for Research (ANR-GENSUD-14-CE10-0001). C.R.B. is supported by the Dutch Heart Foundation (CVON PREDICT2 project), the Netherlands Organization for Scientific Research (VICI fellowship, 016.150.610) and Fondation Leducq (17CVD02).

The aims of this centre-based survey, promoted and disseminated by the European Heart Rhythm Association (EHRA) was to investigate the current practice for the investigation of Sudden Unexplained Death in the Young (SUDY) amongst European countries. An online questionnaire composed of 21 questions was submitted to the EHRA Research Network, European Cardiac Arrhythmia Genetics (ECGen) Focus Group members, and European Reference Network GUARD-Heart healthcare partners. There were 81 respondents from 24 European countries. The majority (78%) worked in a dedicated clinic focusing on families with inherited cardiac conditions and/or SUDY or had easy access to a nearby one. On average, an autopsy was performed in 43% of SUDY cases. Macroscopic examination of the body and all organs were completed in 71% of cases undergoing autopsy, and expert cardiac examination in 32%. Post-mortem genetic testing was requested on average in 37% of Sudden Arrhythmic Death Syndrome (SADS) cases, but not at all by 20% of survey respondents. Psychological support and bereavement counselling for SADS/SUDY families were available for ≤50% of participants. Whilst electrocardiogram (ECG) and echocardiography were largely employed to investigate SADS relatives, there was an inconsistent approach to the use of provocative testing with exercise ECG, sodium channel blocking drugs, and/or epinephrine and genetic testing. The survey highlighted a significant heterogeneity of service provision and variable adherence to current recommendations for the investigation of SUDY, partly attributable to the availability of dedicated units and specialist tests, genetic evaluation, and post-mortem examination.

Sex-related differences in prevalence, clinical presentation, and outcome of cardiac channelopathies are increasingly recognized, despite their autosomal transmission and hence equal genetic predisposition among sexes. In congenital long-QT syndrome, adult women carry a greater risk for Torsades de pointes and sudden cardiac death than do men. In contrast, Brugada syndrome is observed predominantly in adult men, with a considerably higher risk of arrhythmic sudden cardiac death in adult men than in women. In both conditions, the risk for arrhythmias varies with age. Sex-associated differences appear less evident in other cardiac channelopathies, likely a reflection of their rare(r) occurrence and our limited knowledge. In several cardiac channelopathies, sex-specific predictors of outcome have been identified. Together with genetic and environmental factors, sex hormones contribute to the sex-related disparities in cardiac channelopathies through modulation of the expression and function of cardiac ion channels. Despite these insights, essential knowledge gaps exist in the mechanistic understanding of these differences, warranting further investigation. Precise application of the available knowledge may improve the individualized care of patients with cardiac channelopathies. Promoting the reporting of sex-related phenotype and outcome parameters in clinical and experimental studies and advancing research on cardiac channelopathy animal models should translate into improved patient outcomes. This review provides a critical digest of the current evidence for sex-related differences in cardiac channelopathies and emphasizes their clinical implications and remaining gaps requiring further research.

Brugada syndrome is a rare cardiac arrhythmia disorder, causally related to SCN5A mutations in around 20% of cases. Through a genome-wide association study of 312 individuals with Brugada syndrome and 1,115 controls, we detected 2 significant association signals at the SCN10A locus (rs10428132) and near the HEY2 gene (rs9388451). Independent replication confirmed both signals (meta-analyses: rs10428132, P = 1.0 × 10(-68); rs9388451, P = 5.1 × 10(-17)) and identified one additional signal in SCN5A (at 3p21; rs11708996, P = 1.0 × 10(-14)). The cumulative effect of the three loci on disease susceptibility was unexpectedly large (Ptrend = 6.1 × 10(-81)). The association signals at SCN5A-SCN10A demonstrate that genetic polymorphisms modulating cardiac conduction can also influence susceptibility to cardiac arrhythmia. The implication of association with HEY2, supported by new evidence that Hey2 regulates cardiac electrical activity, shows that Brugada syndrome may originate from altered transcriptional programming during cardiac development. Altogether, our findings indicate that common genetic variation can have a strong impact on the predisposition to rare diseases.