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Aim: To perform a comprehensive phenotype-genotype correlation of all rare variants in Triadin leading to malignant arrhythmias in pediatrics. Methods: Triadin knockout syndrome is a rare entity reported in pediatric population. This syndrome is caused by rare variants in the TRDN gene. Malignant ventricular arrhythmias and sudden cardiac death can be a primary manifestation of disease. Although pharmacological measures are effective, some patients require an implantable defibrillator due to high risk of arrhythmogenic episodes. Main Results: Fourteen rare genetic alterations in TRDN have been reported to date. All of these potentially pathogenic alterations are located in a specific area of TRDN, highlighting this hot spot as an arrhythmogenic gene region. Conclusions: Early recognition and comprehensive interpretation of alterations in Triadin are crucial to adopt preventive measures and avoid malignant arrhythmogenic episodes in pediatric population.

Brugada syndrome is a rare inherited arrhythmogenic disease leading to ventricular fibrillation and high risk of sudden death. In 1998, this syndrome was linked with a genetic variant with an autosomal dominant pattern of inheritance. To date, rare variants identified in more than 40 genes have been potentially associated with this disease. Variants in regulatory regions, combinations of common variants and other genetic alterations are also proposed as potential origins of Brugada syndrome, suggesting a polygenic or oligogenic inheritance pattern. However, most of these genetic alterations remain of questionable causality; indeed, rare pathogenic variants in the SCN5A gene are the only established cause of Brugada syndrome. Comprehensive analysis of all reported genetic alterations identified the origin of disease in no more than 40% of diagnosed cases. Therefore, identifying the cause of this rare arrhythmogenic disease in the many families without a genetic diagnosis is a major current challenge in Brugada syndrome. Additional challenges are interpretation/classification of variants and translation of genetic data into clinical practice. Further studies focused on unraveling the pathophysiological mechanisms underlying the disease are needed. Here we provide an update on the genetic basis of Brugada syndrome.

Short QT syndrome, one of the most lethal entities associated with sudden cardiac death, is a rare genetic disease characterized by short QT intervals detected by electrocardiogram. Several genetic variants are causally linked to the disease, but there has yet to be a comprehensive analysis of variants among patients with short QT syndrome. To fill this gap, we performed an exhaustive study of variants currently catalogued as deleterious in short QT syndrome according to the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Analysis of the 32 variants described in the literature determined that only nine (28.12%) have a conclusive pathogenic role. All definitively pathogenic variants are located in KCNQ1, KCNH2, or KCNJ2; three genes encoding potassium channels. Other variants located in genes encoding calcium or sodium channels are associated with electrical alterations concomitant with shortened QT intervals but do not guarantee a diagnosis of short QT syndrome. We recommend caution regarding previously reported variants classified as pathogenic. An exhaustive re-analysis is necessary to clarify the role of each variant before routinely translating genetic findings to the clinical setting.

The Brugada syndrome is an inherited disorder associated with risk of ventricular fibrillation and sudden cardiac death in a structurally normal heart. Diagnosis is based on a characteristic electrocardiographic pattern (coved type ST-segment elevation =2 mm followed by a negative T-wave in =1 of the right precordial leads V(1) to V(2)), observed either spontaneously or during a sodium-channel blocker test. The prevalence varies among regions and ethnicities, affecting mostly males. The risk stratification and management of patients, principally asymptomatic, still remains challenging. The current main therapy is an implantable cardioverter-defibrillator, but radiofrequency catheter ablation has been recently reported as an effective new treatment. Since its first description in 1992, continuous achievements have expanded our understanding of the genetics basis and electrophysiological mechanisms underlying the disease. Currently, despite several genes identified, SCN5A has attracted most attention, and in approximately 30% of patients, a genetic variant may be implicated in causation after a comprehensive analysis.

Short QT syndrome is a highly malignant inherited cardiac disease characterized by ventricular tachyarrhythmias leading to syncope and sudden cardiac death. It is responsible of lethal episodes in young people, mainly infants. International guidelines establish diagnostic criteria with the presence of a QTc = 340 ms in the electrocardiogram despite clinical diagnostic values remain controversial. In last years, clinical diagnosis, risk stratification as well as preventive therapies have been improved due to identification of pathophysiological mechanisms. The only effective option is implantation of a defibrillator despite Quinidine may be at times an effective option. Currently, a limited number of rare variants have been identified in seven genes, which account for nearly 20-30% of families. However, some of these variants are associated with phenotypes showing a shorter QT interval but no conclusive diagnosis of Short QT syndrome. Therefore, an exhaustive interpretation of each variant and a close genotype-phenotype correlation is necessary before clinical translation. Here, we review the main clinical and genetic hallmarks of this rare entity.

Sudden cardiac death poses a unique challenge to clinicians because it may be the only symptom of an inherited heart condition. Indeed, inherited heart diseases can cause sudden cardiac death in older and younger individuals. Two groups of familial diseases are responsible for sudden cardiac death: cardiomyopathies (mainly hypertrophic cardiomyopathy, dilated cardiomyopathy, and arrhythmogenic cardiomyopathy) and channelopathies (mainly long QT syndrome, Brugada syndrome, short QT syndrome, and catecholaminergic polymorphic ventricular tachycardia). This review focuses on cardiac channelopathies, which are characterized by lethal arrhythmias in the structurally normal heart, incomplete penetrance, and variable expressivity. Arrhythmias in these diseases result from pathogenic variants in genes encoding cardiac ion channels or associated proteins. Due to a lack of gross structural changes in the heart, channelopathies are often considered as potential causes of death in otherwise unexplained forensic autopsies. The asymptomatic nature of channelopathies is cause for concern in family members who may be carrying genetic risk factors, making the identification of these genetic factors of significant clinical importance.

Catecholaminergic polymorphic ventricular tachycardia is a rare familial arrhythmogenic disease. It usually occurs in juvenile patients with a structurally normal heart and causes exercise-emotion triggered syncope and sudden cardiac death. The main gene associated with catecholaminergic polymorphic ventricular tachycardia is RyR2, encoding the cardiac ryanodine receptor protein which is involved in calcium homeostasis. After the identification of a 16 year-old man presenting with exercise-induced sudden cardiac death, clinically diagnosed as catecholaminergic polymorphic ventricular tachycardia, we collected the family information and performed a comprehensive genetic analysis using Next Generation Sequencing technology. The initial electrocardiogram in the emergency department revealed ventricular fibrillation. On electrocardiogram monitoring, sinus tachycardia degenerated into bidirectional ventricular and into ventricular fibrillation. Catecholaminergic polymorphic ventricular tachycardia was clinically diagnosed in 5 of the 14 family members evaluated. There were no additional reports of seizures, pregnancy loss, neonatal death, or sudden cardiac death in family members. Genetic analysis of the index case identified only one rare novel variant p.Ile11Ser (c.32T>G) in the RyR2 gene. Subsequent familial analysis identified segregation of the genetic variant with the disease. All current evidence supports that novel p.Ile11Ser variant in the RyR2 gene is a potential disease-causing variant in catecholaminergic polymorphic ventricular tachycardia. To our knowledge, there has been no previous case report of catecholaminergic polymorphic ventricular tachycardia associated to this missense variant.

Idiopathic dilated cardiomyopathy has become one of the most prevalent inherited cardiomyopathies over the past decades. Genetic screening of first-degree relatives has revealed that 30-50% of the cases have a familial origin. Similar to other heart diseases, familial dilated cardiomyopathy is characterized by a high genetic heterogeneity that complicates family studies. Cli'nical screening, 12-lead electrocardiogram and transthoracic echocardiogram are recommended for patients and first-degree family members. Magnetic resonance also needs to be considered. Genetic technologies have become fundamental for the clinical management of this disease. Newgeneration sequencing methods havemade genetic testing feasible for extensive panels of genes related to the disease. Recently, new imaging modalities such as speckle-tracking, strain and strain rate or magnetic resonance, and circulating biomarkers such as non-coding RNAs, have emerged as potential strategies to help cardiologists in their clinical practice. Imaging, genetic and blood-based techniques should be considered together in the evaluation and testing of familial dilated cardiomyopathy. Here, we discuss the current procedures and novel approaches for the clinical management of familial dilated cardiomyopathy. (C) 2016 Elsevier Ireland Ltd. All rights reserved.

Sudden cardiac arrest is a leading cause of death worldwide. Most cardiac arrests happen in patients who have previously suffered a myocardial infarct. The risk of sudden death after infarction may increase in people who carry a pathogenic genetic alteration in cardiac ion channels. We hypothesized that micro-ischemia could trigger lethal arrhythmogenesis, thus we sought to identify genetic alterations in cardiac ion channels in patients with micro-ischemic disease. We studied a cohort of 56 post-mortem samples. Autopsy studies identified myocardial infarction as the cause of death in each case. We used both Sanger sequencing and next-generation sequencing to screen candidate genes associated with sudden cardiac death. We identified six rare missense genetic variations in five unrelated patients. Two variants have been previously reported; one is associated with atrial fibrillation (SCN5A_p.H445D), and the other is predicted to be benign (ANK2_p.T2059M). The novel variants were predicted in silico as benign, except for one (RyR2_p.M4019T), which was classified as deleterious. Our post-mortem, micro-infarction cohort displayed a rate of nearly 10% non-common genetic variants. However, the clinical significance of most of the identified variants remains unknown due to lack of family assessment. Further analyses should be performed in large cohorts to clarify the role of ion-channel gene analysis in samples showing microscopic ischemic alterations.

Short QT syndrome is a malignant cardiac disease characterized by the presence of ventricular tachyarrhythmias leading to syncope and sudden cardiac death. Currently, international guidelines establish diagnostic criteria when QTc is below 340 ms. This entity is one of the main diseases responsible for sudden cardiac death in the pediatric population. In recent years, clinical, genetic and molecular advances in pathophysiological mechanisms related to short QT syndrome have improved diagnosis, risk stratification, and preventive measures. Despite these advances, automatic implantable cardiac defibrillator remains the most effective measure. Currently, six genes have been associated with short QT syndrome, which account for nearly 60% of clinically diagnosed families. Here, we review the main clinical hallmarks of the disease, focusing on the pediatric population.

Dilated cardiomyopathy is a rare cardiac disease characterized by left ventricular dilatation and systolic dysfunction leading to heart failure and sudden cardiac death. Currently, despite several conditions have been reported as aetiologies of the disease, a large number of cases remain classified as idiopathic. Recent studies determine that nearly 60% of cases are inherited, therefore due to a genetic cause. Progressive technological advances in genetic analysis have identified over 60 genes associated with this entity, being TTN the main gene, so far. All these genes encode a wide variety of myocyte proteins, mainly sarcomeric and desmosomal, but physiopathologic pathways are not yet completely unraveled. We review the recent published data about genetics of familial dilated cardiomyopathy. (C) 2016 Elsevier Ireland Ltd. All rights reserved.

The RBM20 gene encodes the muscle-specific splicing factor RNA-binding motif 20, a regulator of heart-specific alternative splicing. Nearly 40 potentially deleterious variants in RBM20 have been reported in the last ten years, being found to be associated with highly arrhythmogenic events in familial dilated cardiomyopathy. Frequently, malignant arrhythmias can be a primary manifestation of disease. The early recognition of arrhythmic genotypes is crucial in avoiding lethal episodes, as it may have an impact on the adoption of personalized preventive measures. Our study performs a comprehensive update of data concerning rare variants in RBM20 that are associated with malignant arrhythmogenic phenotypes with a focus on personalized medicine. Yes

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).

Purpose: Stringent variant interpretation guidelines can lead to high rates of variants of uncertain significance (VUS) for genetically heterogeneous disease like long QT syndrome (LQTS) and Brugada syndrome (BrS). Quantitative and disease-specific customization of American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines can address this false negative rate. Methods: We compared rare variant frequencies from 1847 LQTS (KCNQ1/KCNH2/SCN5A) and 3335 BrS (SCN5A) cases from the International LQTS/BrS Genetics Consortia to population-specific gnomAD data and developed disease-specific criteria for ACMG/AMP evidence classes-rarity (PM2/BS1 rules) and case enrichment of individual (PS4) and domain-specific (PM1) variants. Results: Rare SCN5A variant prevalence differed between European (20.8%) and Japanese (8.9%) BrS patients (p = 5.7 x 10(-18)) and diagnosis with spontaneous (28.7%) versus induced (15.8%) Brugada type 1 electrocardiogram (ECG) (p = 1.3 x 10(-13)). Ion channel transmembrane regions and specific N-terminus (KCNH2) and C-terminus (KCNQ1/KCNH2) domains were characterized by high enrichment of case variants and >95% probability of pathogenicity. Applying the customized rules, 17.4% of European BrS and 74.8% of European LQTS cases had (likely) pathogenic variants, compared with estimated diagnostic yields (case excess over gnomAD) of 19.2%/82.1%, reducing VUS prevalence to close to background rare variant frequency. Conclusion: Large case-control data sets enable quantitative implementation of ACMG/AMP guidelines and increased sensitivity for inherited arrhythmia genetic testing., Amsterdam Cardiovascular Sciences fellowship; Dutch Heart Foundation (CVON Predict-2/Concor-genes); Netherlands Organization for Scientific ResearchNetherlands Organization for Scientific Research (NWO) [VICI 016.150.610]; Fondation LeducqLeducq Foundation, R.W. is supported by an Amsterdam Cardiovascular Sciences fellowship. C.R.B. is supported by the Dutch Heart Foundation (CVON Predict-2/Concor-genes), Netherlands Organization for Scientific Research (VICI 016.150.610), and Fondation Leducq. See Supplement for all Acknowledgements.

BACKGROUND Andersen-Tawil Syndrome type 1 (ATS1) is a rare arrhythmogenic disorder, caused by loss-of-function mutations in the KCNJ2 gene. We present here the largest cohort of patients with ATS1 with outcome data reported. OBJECTIVES This study sought to define the risk of life-threatening arrhythmic events (LAE), identify predictors of such events, and define the efficacy of antiarrhythmic therapy in patients with ATS1. METHODS Clinical and genetic data from consecutive patients with ATS1 from 23 centers were entered in a database implemented at ICS Maugeri in Pavia, Italy, and pooled for analysis. RESULTS We enrolled 118 patients with ATS1 from 57 families (age 23 +/- 17 years at enrollment). Over a median follow-up of 6.2 years (interquartile range: 2.7 to 16.5 years), 17 patients experienced a first LAE, with a cumulative probability of 7.9% at 5 years. An increased risk of LAE was associated with a history of syncope (hazard ratio [HR]: 4.54; p = 0.02), with the documentation of sustained ventricular tachycardia (HR 9.34; p = 0.001) and with the administration of amiodarone (HR: 268; p < 0.001). The rate of LAE without therapy (1.24 per 100 person-years [py]) was not reduced by beta-blockers alone (1.37 per 100 py; p = 1.00), or in combination with Class Ic antiarrhythmic drugs (1.46 per 100 py, p = 1.00). CONCLUSIONS Our data demonstrate that the clinical course of patients with ATS1 is characterized by a high rate of LAE. A history of unexplained syncope or of documented sustained ventricular tachycardia is associated with a higher risk of LAE. Amiodarone is proarrhythmic and should be avoided in patients with ATS1. (C) 2020 Published by Elsevier on behalf of the American College of Cardiology Foundation.