From gene-discovery to gene-tailored clinical management: 25 years of research in channelopathies and cardiomyopathies

Epicardial ablation in high-risk Brugada syndrome to prevent ventricular fibrillation: results from a randomized clinical trial

AIMS

Epicardial ablation for Brugada syndrome (BrS) has shown promise in reducing ventricular fibrillation (VF), but its role remains controversial due to the lack of randomized trials. This study evaluates the efficacy of catheter ablation in high-risk BrS patients.

METHODS AND RESULTS

This prospective, single-centre, randomized (2:1) study enrolled BrS patients with cardiac arrest (CA) or appropriate ICD therapies. All patients had an ICD and were randomized to undergo epicardial ablation (ablation group) or no ablation (control group). Enrolment began in September 2017 and prematurely terminated in February 2024. The primary endpoint was freedom from VF recurrences. Secondary endpoints included procedure safety, ICD-related complications, and quality-of-life assessment. Forty patients (83% male, mean age 43.7 ± 12.1) were randomized: 26 in the ablation group and 14 in the control group. Thirty-six patients received appropriate ICD therapies before enrolment: 24 (92%) in the ablation group and 12 (86%) in the control group. One patient in the ablation group experienced a post-procedural pericardial effusion requiring pericardiocentesis. Thirteen patients (33%) had major ICD-related complications. After a mean follow-up of 4.0 ± 1.7 years, freedom from VF recurrence was 96% (25/26) in the ablation group and 50% (7/14) in the control group (P < 0.001). No unexplained or arrhythmic deaths occurred during follow-up.

CONCLUSION

Epicardial catheter ablation was associated with a reduction in VF recurrence compared with ICD therapy alone. These findings support the use of epicardial ablation in high-risk BrS patients.

CLINICALTRIALS.GOV

ID NCT03294278.

Countywide burden, pathology, and genetics of lethal hypertrophic cardiomyopathy: from the POST SCD study

AIMS

Incidence of sudden cardiac death (SCD) is 1%/year in cohorts with hypertrophic cardiomyopathy (HCM), but this estimate presumes arrhythmic cause and misses occult cases dying before diagnosis.

METHODS AND RESULTS

POST SCD (POstmortem Systematic InvesTigation of Sudden Cardiac Death) is a prospective cohort study using autopsy, clinical records, and toxicology to adjudicate arrhythmic or non-arrhythmic causes among presumed SCDs (pSCDs) meeting WHO criteria aged 0-90 years in San Francisco County. We included all incident cases 2/1/2011-3/1/2014 (n = 525) and approximately every third day 3/1/2014-9/1/2022 (n = 497) based on medical examiner call schedule. We identified HCM victims via three approaches: (i) pathology; (ii) echocardiogram [transthoracic echocardiogram (TTE)]; (iii) genetic criteria. Incidence calculations used county data and estimated HCM prevalence of 1:500 from studies of persons aged 23-35 years old. Of 1022 pSCDs [558 (54.6%) arrhythmic deaths] during the study period, 13 had HCM: 10 met pathology criteria; 2 via review of 203 TTEs (missed on initial report); 1 via genetic testing. Of these, 11 were arrhythmic deaths, yielding 1.3% burden of sudden death (pSCD) and 2% of arrhythmic death. Only 2 of 13 (15%) pSCDs with HCM had pre-mortem diagnosis. Incidence for persons with HCM 18-35 years old was 0.2% pSCDs/year and 0.1% SADs/year. pSCDs with HCM had a higher proportion of arrhythmic cause [11/13 (85%) vs. 547/1009 (54%), P = 0.03] than those without. pSCD burden due to HCM decreased with age (P = 0.003), highest among victims <35 years old, for whom HCM accounted for 7.1% of pSCD and 9.4% of arrhythmic death. Genetic testing of 317 consented pSCDs yielded pathogenic or likely pathogenic variants in 40% (2/5) and identified one additional case without clinical phenotype.

CONCLUSION

In this 11-year countywide post-mortem study, HCM meeting pathologic, clinical, or genetic criteria was associated with autopsy-confirmed arrhythmic cause of sudden death, accounting for 2% of SADs up to age 90, highest in cases <35 years old. Since 85% of cases were undiagnosed before pSCD, the true burden of HCM-related sudden death may be substantially underestimated.

Multiparametric models for predicting major arrhythmic events in Brugada syndrome: a systematic review and critical appraisal

AIMS

Despite several risk models to predict major arrhythmic events (MAE) in Brugada syndrome (BrS) having been developed, reproducibility and methodology remain a concern. Our aim was to assess the quality of model development and validation, and determine the discriminative performance of available models.

METHODS AND RESULTS

Electronic databases (Medline, Embase, and Central) were searched through September/2024 for studies developing or validating multivariable prediction models for MAE in BrS. Methodological quality and risk of bias (RoB) were assessed using the Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies (CHARMS) checklist and the Prediction Model Risk of Bias Assessment (PROBAST) Tool. Pooled random-effects c-statistics were obtained for each model. A total of 16 studies, including 11 unique multivariable scores, were included. All models had domains classified as high RoB. Common sources of bias were inappropriate inclusion/exclusion criteria, predictor selection, low number of events and underreporting of performance measures. Pooled c-statistics among patients without previous MAE showed good performance for Brugada-Risk [AUC 0.81, 95% confidence interval (CI) 0.71-0.91; I2 64%; three studies], fair for PAT (AUC 0.79, 95% CI 0.45-1.12; I2 95%; two studies), Delise (AUC 0.77, 95% CI 0.72-0.81, I2 39%, three studies), and Sieira (AUC 0.73, 95% CI 0.64-0.82; I2 64%; five studies), and moderate for Shanghai (AUC 0.69, 95% CI 0.61-0,76; I2 13%; three studies).

CONCLUSION

Currently available multiparametric models for prediction of MAE in BrS have important shortcomings in model development and inadequate evaluation. Further validation of current models in external cohorts is required before safe transition to clinical practice.

Cardiac Conduction Disorders Due to Acquired or Genetic Causes in Young Adults: A Review of the Current Literature

Cardiac conduction disorders can manifest in young adults in isolated forms, associated with myocardial diseases or as part of a multiorgan disorder. Underlying causes of cardiac conduction disorders may be genetically determined or acquired. Cardiac conduction disorder in young adults is a complex and often underestimated and underrecognized disease that may need of a multidisciplinary team for the diagnosis, treatment, and long-term management of these patients. Therefore, it is crucial to raise clinicians' awareness of this condition. In this review, we provide a comprehensive update on the cause, diagnosis, and treatment of young adults with cardiac conduction disorders, also suggesting potential strategies to improve the current clinical management of these patients.

The diagnostic role of pharmacological provocation testing in cardiac electrophysiology: a clinical consensus statement of the European Heart Rhythm Association and the European Association of Percutaneous Cardiovascular Interventions (EAPCI) of the ESC, the ESC Working Group on Cardiovascular Pharmacotherapy, the Association of European Paediatric and Congenital Cardiology (AEPC), the Paediatric & Congenital Electrophysiology Society (PACES), the Heart Rhythm Society (HRS), the Asia Pacific Heart Rhythm Society (APHRS), and the Latin American Heart Rhythm Society (LAHRS)

The pharmacological provocation test is a pivotal tool in cardiac electrophysiology for the diagnosis of potential causes of sudden cardiac death, sudden cardiac arrest (SCA), arrhythmias, symptoms, or ECG abnormalities. The 2022 European Society of Cardiology Guidelines for the Treatment of Ventricular Arrhythmias and Prevention of Sudden Cardiac Death offered guidance on provocation testing but did not describe the indications and requirements in depth. This clinical consensus statement, led by the European Heart Rhythm Association and approved by major international stakeholders, aims to advise the general cardiologist and the arrhythmia expert who to test and when, where, and how to do it. The statement focuses on current practice for the diagnosis of subclinical arrhythmia syndromes and the causes of SCA, building upon the recommendations of the Guidelines. We address the sodium channel blocker provocation test for patients suspected of Brugada syndrome as well as the use of epinephrine, isoproterenol, adenosine, ergonovine, and acetylcholine.

Identification of a new genetic locus associated with atrial fibrillation in the Taiwanese population by genome-wide and transcriptome-wide association studies

AIMS

Genome-wide association studies (GWASs) identified common single-nucleotide polymorphisms (SNPs) in more than 100 genomic regions associated with atrial fibrillation (AF). We aimed to identify novel AF genes in Taiwanese population by multi-stage GWAS.

METHODS AND RESULTS

In exploratory stage, we did GWAS with whole-genome genotypes (4 512 191 SNPs) in 516 patients with AF from the National Taiwan University AF Registry and 5160 normal sinus rhythm controls from the Taiwan Biobank. Significant loci were replicated in 1002 independent patients and 2003 controls and in the UK Biobank. Expression quantitative trait locus (eQTL) mapping and transcriptome-wide association study (TWAS) were performed to implicate functional significance. Stage I GWAS revealed three loci associated with AF with a genome-wide significance level, including one close to PITX2 gene (chromosome 4q25, rs2723329, minor allele frequency [MAF] 0.50 vs. 0.41, P = 1.53 × 10-10), another close to RAP1A gene (also to previous KCND3; chromosome 1p13.2, rs7525578, MAF 0.17 vs. 0.07, P = 1.24 × 10-26), and one novel locus close to HNF4G gene (chromosome 8q21.13, rs2980218, MAF 0.44 vs. 0.35, P = 2.19 × 10-9). They were validated in Stage II population. The eQTL analyses showed significant colocalization of 1p13.2 locus with RAP1A gene expression in fibroblasts and 8q21.13 locus with HNF4G expression in lymphocytes. There is a significant association of RAP1A gene expression in fibroblasts and HNF4G in lymphocytes and brain with AF in TWAS.

CONCLUSION

Genome-wide association study in Taiwan revealed PITX2 and RAP1A/KCND3 loci and novel AF locus (HNF4G) with the most significant locus in the RAP1A locus. RAP1A and HNF4G genes may implicate fibrosis, metabolic, and neurogenic pathways in pathogenesis of AF.

SCN5A variant type-dependent risk prediction in Brugada syndrome

AIMS

The variant in SCN5A with the loss of function (LOF) effect in the cardiac Na+ channel (Nav1.5) is the definitive cause for Brugada syndrome (BrS), and the functional analysis data revealed that LOF variants are associated with poor prognosis. However, which variant types (e.g. missense or non-missense) affect the prognoses of those variant carriers remain unelucidated.

METHODS AND RESULTS

We defined SCN5A LOF variants as all non-missense and missense variants that produce peak INa < 65% of wild-type previously confirmed by patch-clamp studies. The study population consisted of 76 Japanese BrS patients (74% patients were male and the median age [IQR] at diagnosis was 28 [14-45] years) with LOF type of SCN5A variants: 40 with missense and 36 with non-missense variants. Non-missense variant carriers presented significantly more severe cardiac conduction disorder compared to the missense variant carriers. During follow-up periods of 9.0 [5.0-14.0] years, compared to missense variants, non-missense variants were significant risk factors of lifetime lethal arrhythmia events (LAEs) (P = 0.023). When focusing only on the missense variants that produce no peak INa, these missense variant carriers exhibited the same clinical outcomes as those with non-missense (log-rank P = 0.325). After diagnosis, however, both variant types were comparable in risk of LAEs (P = 0.155).

CONCLUSION

We identified, for the first time, that SCN5A non-missense variants were associated with higher probability of LAE than missense variants in BrS patients though it did not change significantly after diagnosis.

Genetic Background and Clinical Phenotype in an Italian Cohort with Inherited Arrhythmia Syndromes and Arrhythmogenic Cardiomyopathy (ACM): A Whole-Exome Sequencing Study

Inherited arrhythmia syndromes include several different diseases, as well as Brugada syndrome (BrS), long QT syndrome (LQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT), and short QT syndrome (SQTS). They represent, together with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C), an important cause of sudden cardiac death in the young. Most arrhythmia syndromes are inherited in an autosomal dominant manner, and genetic studies are suggested.: to report the spectrum of genetic variations and clinical phenotype in an Italian cohort with confirmed inherited arrhythmia syndromes and arrhythmogenic cardiomyopathy using whole-exome sequencing (WES). Patients with confirmed inherited arrhythmia syndromes and hereditary cardiomyopathy were recruited at the Cardiology Unit, University Polyclinic Hospital of Foggia, Italy and were included in this study. Genomic DNA samples were extracted from peripheral blood and conducted for WES. The variants were annotated using BaseSpace Variant Interpreter Annotation Engine 3.15.0.0 (Illumina). Reported variants were investigated using ClinVar, VarSome Franklin and a literature review. They were categorised agreeing to the criteria of the American College of Medical Genetics and Genomics. Overall, 62 patients were enrolled. Most of them had a clinical diagnosis of BrS (n 48, 77%). The remaining patients included in the present study had diagnosis of confirmed LQT (n 7, 11%), AR-DCM (n 4, 6.5%), ARVD (n 2, 3%), and SQT (n 1, 1.6%). Using the WES technique, 22 variants in 15 genes associated with Brugada syndrome were identified in 21 patients (34%). Among these, the SCN5A gene had the highest number of variants (6 variants, 27%), followed by KCNJ5 and CASQ2 (2 variants). Only one variant was identified in the remaining genes. In 27 patients with a clinical diagnosis of BrS, no gene variant was detected. In patients with confirmed LQT, SQT, 10 variants in 9 genes were identified. Among patients with ARVD and AR-DCM, 6 variants in 5 genes were found. Variants found in our cohort were classified as pathogenic (6), likely pathogenic (3), of uncertain significance (26), and benign (1). Two additional gene variants were classified as risk factors. In this study, 13 novel genetic variations were recognized to be associated with inherited arrhythmogenic cardiomyopathies. Our understanding of inherited arrhythmia syndromes continues to progress. The era of next-generation sequencing has advanced quickly, given new genetic evidence including pathogenicity, background genetic noise, and increased discovery of variants of uncertain significance. Although NGS study has some limits in finding the full genetic data of probands, large-scale gene sequencing can promptly be applied in real clinical practices, especially in inherited and possibly fatal arrhythmia syndromes.

Nernst equilibrium, rectification, and saturation: Insights into ion channel behavior

The dissipation of electrochemical gradients through ion channels plays a central role in biology. Herein we use voltage-responsive kinetic models of ion channels to explore how electrical and chemical potentials differentially influence ion transport properties. These models demonstrate how electrically driven flux is greater than the Nernstian equivalent chemically driven flux yet still perfectly cancels when the two gradients oppose each other. We find that the location and relative stability of ion-binding sites dictates rectification properties by shifting the location of the most voltage-sensitive transitions. However, these rectification properties invert when bulk concentrations increase relative to the binding-site stabilities, moving the rate-limiting steps from uptake into a relatively empty channel to release from an ion-blocked full channel. Additionally, the origin of channel saturation is shown to depend on the free energy of uptake relative to bulk concentrations. Collectively these insights provide a framework for interpreting and predicting how channel properties manifest in electrochemical transport behavior.

Familial risk of sinus node dysfunction indicating pacemaker implantation: a nationwide cohort study

AIMS

We aimed to investigate the risk of sinus node dysfunction (SND) indicating cardiac pacing and mortality in first-degree relatives to patients with a pacemaker implanted on this indication and assess the effect of onset-age on disease risk.

METHODS AND RESULTS

In this nationwide register-based study, we used the Danish Civil Registration Registry to establish family structures and merged data with the Danish National Patient Registry and the Danish Pacemaker and ICD Registry containing information on all pacemakers implanted due to SND in Denmark. We followed 6 027 090 individuals born after 1954 in the period between 1982 and 2022 (180 775 041 person-years) among whom 2.477 pacemakers were implanted due to SND. The adjusted rate ratio (RR) of pacemaker-treated SND was 2.9 (2.4-3.6) for individuals having any father, mother, or sibling with a pacemaker implanted on this indication compared with the general population (derived cumulative incidence at the age of 68 years: 0.79 and 0.27%, respectively). This risk was inversely proportional to implantation age in the index person [≤60 years: RR = 5.5 (3.4-9.0)]. Overall, mortality was similar between individuals having a father, mother, or sibling with SND and the general population, but higher for relatives to index persons with an early onset [≤60 years: RR = 1.22 (1.05-1.41)].

CONCLUSION

First-degree relatives to SND patients are at increased risk of SND with risk being inversely associated with pacemaker implantation age in the index person. Mortality in first-degree relatives was comparable with the general population, although subgroup findings suggest an increased mortality among individuals with a family history of early-onset SND.

aTrial arrhythmias in inhEriTed aRrhythmIa Syndromes: results from the TETRIS study

AIMS

Little is known about the distribution and clinical course of patients with inherited arrhythmia syndrome (IAS) and concomitant atrial arrhythmias (AAs). The aim of the study is (i) to characterize the distribution of AAs in patients with IAS and (ii) evaluate the long-term clinical course of these patients.

METHODS AND RESULTS

An international multicentre study was performed and involved 28 centres in 16 countries. Inclusion criteria were (i) IAS and (ii) electrocardiographic documentation of AAs. The primary endpoint was a composite of sudden cardiac death, sustained ventricular arrhythmias (VAs), or appropriate implantable cardioverter defibrillator (ICD) interventions. Strokes, inappropriate ICD shocks due to AAs, and the occurrence of sinus node dysfunction were assessed. A total of 522 patients with IAS and AAs were included. Most patients were diagnosed with Brugada syndrome (n = 355, 68%) and long QT syndrome (n = 93, 18%). The remaining patients (n = 71, 14%) presented with short QT syndrome, early repolarization syndrome, catecholaminergic polymorphic ventricular tachycardia, progressive cardiac conduction diseases, or idiopathic ventricular fibrillation. Atrial fibrillation was the most prevalent AA (82%), followed by atrial flutter (9%) and atrial tachycardia (9%). Atrial arrhythmia was the first clinical manifestation of IAS in 52% of patients. More than one type of AA was documented in 23% of patients. Nine patients (3%) experienced VA before the diagnosis of IAS due the use of anti-arrhythmic medications taken for the AA. The incidence of the primary endpoint was 1.4% per year, with a two-fold increase in patients who experienced their first AA before the age of 20 (odds ratio 2.2, P = 0.043). This was consistent across the different forms of IAS. Inappropriate ICD shock due to AAs was reported in 2.8% of patients, strokes in 4.4%, and sinus node dysfunction in 9.6%.

CONCLUSION

Among patients with IAS and AAs, AA is the first clinical manifestation in about half of the cases, with more than one form of AAs present in one-fourth of the patients. The occurrence of AA earlier in life may be associated with a higher risk of VAs. The occurrence of stroke and sinus node dysfunction is not infrequently in this cohort.

2024 updated European Heart Rhythm Association core curriculum for physicians and allied professionals: a statement of the European Heart Rhythm Association of the European Society of Cardiology

Heart rhythm management is a continuously evolving sub-speciality of cardiology. Every year, many physicians and allied professionals (APs) start and complete their training in cardiac implantable electronic devices (CIEDs) or electrophysiology (EP) across the European Heart Rhythm Association (EHRA) member countries. While this training ideally ends with an EHRA certification, the description of the learning pathway (what, how, when, and where) through an EHRA core curriculum is also a prerequisite for a successful training. The first EHRA core curriculum for physicians was published in 2009. Due to the huge developments in the field of EP and device therapy, this document needed updating. In addition, a certification process for APs has been introduced, as well as a recertification process and accreditation of EHRA recognized training centres. Learning pathways are more individualized now, with Objective Structured Assessment of Technical Skills (OSATS) to monitor learning progression of trainees. The 2024 updated EHRA core curriculum for physicians and APs describes, for both CIED and EP, the syllabus, OSATS, training programme and certification, and recertification for physicians and APs and stresses the importance of continued medical education after certification. In addition, requirements for accreditation of training centres and trainers are given. Finally, suggested reading lists for CIED and EP are attached as online supplements.

Continuous Rhythm Monitoring With Implanted Loop Recorders in Children and Adolescents With Brugada Syndrome

BACKGROUND

Young (<18 years of age) patients with Brugada syndrome (BrS) are often under-represented in BrS studies and their management, especially related to syncopal episodes, remains unclear.

OBJECTIVES

This study sought to describe the arrhythmia prevalence among young patients with BrS undergoing continuous rhythm monitoring by implantable loop recorder (ILR) and to assess the etiology behind syncope of undetermined origin.

METHODS

A total of 147 patients with BrS with ILR were enrolled in 12 international centers and divided into pediatric (age <12 years; n = 77, 52%) and adolescents (age 13-18 years; n = 70, 48%).

RESULTS

Mean age was 11.3 years, 53 patients (36.1%) were female, and 31 (21.1%) had spontaneous type 1 electrocardiograms. Over a median follow-up of 3.6 years (Q1-Q3: 1.6-4.8 years), an arrhythmic event was recorded in 33 patients (22.4%), mainly of nonventricular origin: 15 atrial (10.2%) and 16 bradyarrhythmic events (10.9%). Ventricular arrhythmias occurred in 4 patients, all with spontaneous BrS, and were fever-related in one-half. Among all patients with recurrence of syncope during follow-up, true arrhythmic syncope was documented in 5 (17.8%), and it was due to bradyarrhythmias or atrial arrhythmias in 3 cases (60%).

CONCLUSIONS

Continuous rhythm monitoring with ILRs in young patients with BrS detects a broad range of arrhythmias. Ventricular arrhythmias occur predominantly in patients with spontaneous type 1 electrocardiograms and during fever. Despite the young age, bradyarrhythmias and atrial arrhythmias are frequent and represent the cause of arrhythmic syncope in 60% of patients. Young patients with BrS with syncope of undetermined origin may benefit from ILR implant.

Genetic testing for inherited arrhythmia syndromes and cardiomyopathies: results of the European Heart Rhythm Association survey

AIMS

Indications and clinical impact of genetic testing for cardiac diseases have increased significantly over the past years. The aim of this physician-based European Heart Rhythm Association (EHRA) survey was to assess current clinical practice and access to genetic testing for cardiac diseases across European Society of Cardiology countries and to evaluate adherence to the 2022 EHRA/HRS/APHRS/LAHRS Expert Consensus Statement on genetic testing.

METHODS AND RESULTS

An online questionnaire composed of 28 questions was submitted to the EHRA Research Network and European Reference Network GUARD-Heart healthcare partners and promoted via dedicated social media channels. There were 357 respondents from 69 countries, 40% working in a hospital setting with a cardiac genetic service and/or a dedicated clinic focusing on inherited cardiac diseases and 27% with an onsite genetic laboratory. No genetic testing or low annual rate (<10/year) was declared by 39% of respondents. The majority of respondents (78%) declared issues or limitations to genetic testing access in their clinical practice. The main reasons for not providing or limited access to genetic testing were no availability of dedicated unit or genetic laboratory (35%) or reimbursement issues (25%). The most frequently reported indication for genetic testing was diagnostic purpose (55%). Most respondents (92%) declared offering genetic testing preceded by genetic counselling and 42% regular multidisciplinary evaluations for patients with cardiac genetic diseases. The perceived value of genetic testing in the diagnostic, prognostic, and therapeutic assessment was variable (67, 39, and 29%, respectively) and primarily based on the specific inherited disease. The majority of respondents recommended cascade genetic testing for the first-degree family members in case of pathogenic/likely pathogenic variant in the proband.

CONCLUSION

This survey highlights a significant heterogeneity of genetic testing access and provision and issues attributable to the availability of dedicated unit/genetic laboratory and reimbursement. However, adequate adherence to indications in the current recommendations for genetic testing in patients with cardiac diseases was observed.

Nernst Equilibrium, Rectification, and Saturation: Insights into Ion Channel Behavior

The dissipation of electrochemical gradients through ion channels plays a central role in biology. Herein we use voltage responsive kinetic models of ion channels to explore how electrical and chemical potentials differentially influence ion transport properties. These models demonstrate how electrically driven flux is greater than the Nernstian equivalent chemically driven flux, yet still perfectly cancels when the two gradients oppose each other. We find that the location and relative stability of ion binding sites dictates rectification properties by shifting the location of the most voltage sensitive transitions. However, these rectification properties invert when bulk concentrations increase relative to the binding site stabilities, moving the rate limiting steps from uptake into a relatively empty channel to release from an ion-blocked full channel. Additionally, the origin of channel saturation is shown to depend on the free energy of uptake relative to bulk concentrations. Collectively these insights provide framework for interpreting and predicting how channel properties manifest in electrochemical transport behavior.

Autopsy of all young sudden death cases is important to increase survival in family members left behind

Sudden cardiac death (SCD) is an important public health problem worldwide, accounting for an estimated 6-20% of total mortality. A significant proportion of SCD is caused by inherited heart disease, especially among the young. An autopsy is crucial to establish a diagnosis of inherited heart disease, allowing for subsequent identification of family members who require cardiac evaluation. Autopsy of cases of unexplained sudden death in the young is recommended by both the European Society of Cardiology and the American Heart Association. Overall autopsy rates, however, have been declining in many countries across the globe, and there is a lack of skilled trained pathologists able to carry out full autopsies. Recent studies show that not all cases of sudden death in the young are autopsied, likely due to financial, administrative, and organizational limitations as well as awareness among police, legal authorities, and physicians. Consequently, diagnoses of inherited heart disease are likely missed, along with the opportunity for treatment and prevention among surviving relatives. This article reviews the evidence for the role of autopsy in sudden death, how the cardiologist should interpret the autopsy-record, and how this can be integrated and implemented in clinical practice. Finally, we identify areas for future research along with potential for healthcare reform aimed at increasing autopsy awareness and ultimately reducing mortality from SCD.

Genetic background determines the severity of age-dependent cardiac structural abnormalities and arrhythmia susceptibility in Scn5a-1798insD mice

AIMS

Patients with mutations in SCN5A encoding NaV1.5 often display variable severity of electrical and structural alterations, but the underlying mechanisms are not fully elucidated. We here investigate the combined modulatory effect of genetic background and age on disease severity in the Scn5a1798insD/+ mouse model.

METHODS AND RESULTS

In vivo electrocardiogram and echocardiograms, ex vivo electrical and optical mapping, and histological analyses were performed in adult (2-7 months) and aged (8-28 months) wild-type (WT) and Scn5a1798insD/+ (mutant, MUT) mice from the FVB/N and 129P2 inbred strains. Atrio-ventricular (AV) conduction, ventricular conduction, and ventricular repolarization are modulated by strain, genotype, and age. An aging effect was present in MUT mice, with aged MUT mice of both strains showing prolonged QRS interval and right ventricular (RV) conduction slowing. 129P2-MUT mice were severely affected, with adult and aged 129P2-MUT mice displaying AV and ventricular conduction slowing, prolonged repolarization, and spontaneous arrhythmias. In addition, the 129P2 strain appeared particularly susceptible to age-dependent electrical, functional, and structural alterations including RV conduction slowing, reduced left ventricular (LV) ejection fraction, RV dilatation, and myocardial fibrosis as compared to FVB/N mice. Overall, aged 129P2-MUT mice displayed the most severe conduction defects, RV dilatation, and myocardial fibrosis, in addition to the highest frequency of spontaneous arrhythmia and inducible arrhythmias.

CONCLUSION

Genetic background and age both modulate disease severity in Scn5a1798insD/+ mice and hence may explain, at least in part, the variable disease expressivity observed in patients with SCN5A mutations. Age- and genetic background-dependent development of cardiac structural alterations furthermore impacts arrhythmia risk. Our findings therefore emphasize the importance of continued assessment of cardiac structure and function in patients carrying SCN5A mutations.

Genetic characterization of KCNQ1 variants improves risk stratification in type 1 long QT syndrome patients

AIMS

KCNQ1 mutations cause QTc prolongation increasing life-threatening arrhythmias risks. Heterozygous mutations [type 1 long QT syndrome (LQT1)] are common. Homozygous KCNQ1 mutations cause type 1 Jervell and Lange-Nielsen syndrome (JLNS) with deafness and higher sudden cardiac death risk. KCNQ1 variants causing JLNS or LQT1 might have distinct phenotypic expressions in heterozygous patients. The aim of this study is to evaluate QTc duration and incidence of long QT syndrome-related cardiac events according to genetic presentation.

METHODS AND RESULTS

We enrolled LQT1 or JLNS patients with class IV/V KCNQ1 variants from our inherited arrhythmia clinic (September 1993 to January 2023). Medical history, ECG, and follow-up were collected. Additionally, we conducted a thorough literature review for JLNS variants. Survival curves were compared between groups, and multivariate Cox regression models identified genetic and clinical risk factors. Among the 789 KCNQ1 variant carriers, 3 groups were identified: 30 JLNS, 161 heterozygous carriers of JLNS variants (HTZ-JLNS), and 550 LQT1 heterozygous carriers of non-JLNS variants (HTZ-Non-JLNS). At diagnosis, mean age was 3.4 ± 4.7 years for JLNS, 26.7 ± 21 years for HTZ-JLNS, and 26 ± 21 years for HTZ-non-JLNS; 55.3% were female; and the mean QTc was 551 ± 54 ms for JLNS, 441 ± 32 ms for HTZ-JLNS, and 467 ± 36 ms for HTZ-Non-JLNS. Patients with heterozygous JLNS mutations (HTZ-JLNS) represented 22% of heterozygous KCNQ1 variant carriers and had a lower risk of cardiac events than heterozygous non-JLNS variant carriers (HTZ-Non-JLNS) [hazard ratio (HR) = 0.34 (0.22-0.54); P < 0.01]. After multivariate analysis, four genetic parameters were independently associated with events: haploinsufficiency [HR = 0.60 (0.37-0.97); P = 0.04], pore localization [HR = 1.61 (1.14-1.2.26); P < 0.01], C-terminal localization [HR = 0.67 (0.46-0.98); P = 0.04], and group [HR = 0.43 (0.27-0.69); P < 0.01].

CONCLUSION

Heterozygous carriers of JLNS variants have a lower risk of cardiac arrhythmic events than other LQT1 patients.

Prioritize Variant Reclassification in Pediatric Long QT Syndrome-Time to Revisit

Congenital long QT syndrome (LQTS) is an inherited arrhythmia syndrome associated with sudden cardiac death. Accurate interpretation and classification of genetic variants in LQTS patients are crucial for effective management. All patients with LQTS with a positive genetic test over the past 18 years (2002-2020) in our single tertiary pediatric cardiac center were identified. Reevaluation of the reported variants in LQTS genes was conducted using the American College of Genetics and Genomics (ACMG) guideline after refinement by the US ClinGen SVI working group and guideline by Walsh et al. on genetic variant reclassification, under multidisciplinary input. Among the 59 variants identified. 18 variants (30.5%) were reclassified. A significant larger portion of variants of unknown significance (VUS) were reclassified compared to likely pathogenic (LP)/pathogenic (P) variants (57.7% vs 9.1%, p < 0.001). The rate of reclassification was significantly higher in the limited/disputed evidence group compared to the definite/moderate evidence group (p = 0.0006). All LP/P variants were downgraded in the limited/disputed evidence group (p = 0.0057). VUS upgrades are associated with VUS located in genes within the definite/moderate evidence group (p = 0.0403) and with VUS present in patients exhibiting higher corrected QT intervals (QTc) (p = 0.0445). A significant number of pediatric LQTS variants were reclassified, particularly for VUS. The strength of the gene-disease association of the genes influences the reclassification performance. The study provides important insights and guidance for pediatricians to seek for reclassification of "outdated variants" in order to facilitate contemporary precision medicine.

The role for ambulatory electrocardiogram monitoring in the diagnosis and prognostication of Brugada syndrome: a sub-study of the Rare Arrhythmia Syndrome Evaluation (RASE) Brugada study

AIMS

Brugada syndrome (BrS) diagnosis and risk stratification rely on the presence of a spontaneous type 1 (spT1) electrocardiogram (ECG) pattern; however, its spontaneous fluctuations may lead to misdiagnosis and risk underestimation. This study aims to assess the role for repeat high precordial lead (HPL) resting and ambulatory ECG monitoring in identifying a spT1, and evaluate its prognostic role.

METHODS AND RESULTS

HPL resting and ambulatory monitoring ECGs of BrS subjects were reviewed retrospectively, and the presence of a spT1 associated with ventricular dysrhythmias and sudden cardiac death (SCD). Three-hundred and fifty-eight subjects (77 with spT1 pattern at presentation, Group 1, and 281 without, Group 2) were included. In total, 1651 resting HPL resting and 621 ambulatory monitoring ECGs were available for review, or adequately described. Over a median follow-up of 72 months (interquartile range - IQR - 75), 42/77 (55%) subjects in Group 1 showed a spT1 in at least one ECG. In Group 2, 36/281 subjects (13%) had a newly detected spT1 (1.9 per 100 person-year) and 23 on an HPL ambulatory recording (8%). Seven previously asymptomatic subjects, five of whom had a spT1 (four at presentation and one at follow-up), experienced arrhythmic events; survival analysis indicated that a spT1, either at presentation or during lifetime, was associated with events. Univariate models showed that a spT1 was consistently associated with increased risk [spT1 at presentation: hazard ratio (HR) 6.3, 95% confidence interval (CI) 1.4-28, P = 0.016; spT1 at follow-up: HR 3.1, 95% CI 1.3-7.2, P = 0.008].

CONCLUSION

Repeated ECG evaluation and HPL ambulatory monitoring are vital in identifying transient spT1 Brugada pattern and its associated risk.

Yield of molecular autopsy in sudden cardiac death in athletes: data from a large registry in the UK

AIMS

Sudden cardiac death (SCD) may occur in apparently healthy individuals, including athletes. The aim was to investigate the diagnostic role of post-mortem genetic testing, molecular autopsy (MA), in elucidating the cause of SCD in athletes.

METHODS AND RESULTS

We reviewed a database of 6860 consecutive cases of SCD referred to our specialist cardiac pathology centre. All cases underwent detailed cardiac autopsy, and 748 were deemed to be athletes. Of these, 42 (6%) were investigated with MA (28 using a targeted sequencing, 14 exome sequencing). Variants were classified as pathogenic, likely pathogenic, or variant of unknown significance using international guidelines. Clinical information was obtained from referring coroners who completed a detailed health questionnaire. Out of the 42 decedents (average age 35 years old, 98% males) who were investigated with MA, the autopsy was in keeping with a structurally normal heart [sudden arrhythmic death syndrome (SADS)] in n = 33 (78%) cases, followed by arrhythmogenic cardiomyopathy (ACM) in eight (19%) individuals and idiopathic left ventricular fibrosis in one (2%). Death occurred during exercise and at rest in 26 (62%) and 16 (38%) individuals, respectively. Variants that were adjudicated clinically actionable were present in seven cases (17%). There was concordance between the genetic and phenotypic findings in two cases of ACM (in FLNC and TMEM43 genes). None of the variants identified in SADS cases were previously linked to channelopathies. Clinically actionable variants in cardiomyopathy-associated genes were found in five cases of SADS.

CONCLUSION

The yield of MA in athletes who died suddenly is 17%. In SADS cases, clinically actionable variants were found in cardiomyopathy-associated genes and not in channelopathy-associated genes. Arrhythmogenic cardiomyopathy is a common cause of SCD in athletes, and one in four decedents with this condition had a clinically actionable variant in FLNC and TMEM43 genes.

Insights into adherence to medication and lifestyle recommendations in an international cohort of patients with catecholaminergic polymorphic ventricular tachycardia

AIMS

In patients with catecholaminergic polymorphic ventricular tachycardia (CPVT), a rare inherited arrhythmia syndrome, arrhythmic events can be prevented by medication and lifestyle recommendations. In patients who experience breakthrough arrhythmic events, non-adherence plays an essential role. We aimed to investigate the incidence and potential reasons for non-adherence to medication and lifestyle recommendations in a large, international cohort of patients with CPVT.

METHODS AND RESULTS

An online multilingual survey was shared with CPVT patients worldwide by their cardiologists, through peer-recruitment, and on social media from November 2022 until July 2023. Self-reported non-adherence was measured using the validated Medication Adherence Rating Scale (MARS) and a newly developed questionnaire about lifestyle. Additionally, validated questionnaires were used to assess potential reasons for medication non-adherence. Two-hundred-and-eighteen patients completed the survey, of whom 200 (92%) were prescribed medication [122 (61%) female; median age 33.5 years (interquartile range: 22-50)]. One-hundred-and-three (52%) were prescribed beta-blocker and flecainide, 85 (43%) beta-blocker, and 11 (6%) flecainide. Thirty-four (17%) patients experienced a syncope, aborted cardiac arrest or appropriate implantable cardioverter defibrillator shock after diagnosis. Nineteen (13.4%) patients were exercising more than recommended. Thirty (15%) patients were non-adherent to medication. Female sex [odds ratio (OR) 3.7, 95% confidence interval (CI) 1.3-12.0, P = 0.019], flecainide monotherapy compared to combination therapy (OR 6.8, 95% CI 1.6-31.0, P = 0.010), and a higher agreement with statements regarding concerns about CPVT medication (OR 1.2, 95% CI 1.1-1.3, P < 0.001) were independently associated with non-adherence.

CONCLUSION

The significant rate of non-adherence associated with concerns regarding CPVT-related medication, emphasizes the potential for improving therapy adherence by targeted patient education.

Effects of cohort, genotype, variant, and maternal β-blocker treatment on foetal heart rate predictors of inherited long QT syndrome

AIMS

In long QT syndrome (LQTS), primary prevention improves outcome; thus, early identification is key. The most common LQTS phenotype is a foetal heart rate (FHR) < 3rd percentile for gestational age (GA) but the effects of cohort, genotype, variant, and maternal β-blocker therapy on FHR are unknown. We assessed the influence of these factors on FHR in pregnancies with familial LQTS and developed a FHR/GA threshold for LQTS.

METHODS AND RESULTS

In an international cohort of pregnancies in which one parent had LQTS, LQTS genotype, familial variant, and maternal β-blocker effects on FHR were assessed. We developed a testing algorithm for LQTS using FHR and GA as continuous predictors. Data included 1966 FHRs at 7-42 weeks' GA from 267 pregnancies/164 LQTS families [220 LQTS type 1 (LQT1), 35 LQTS type 2 (LQT2), and 12 LQTS type 3 (LQT3)]. The FHRs were significantly lower in LQT1 and LQT2 but not LQT3 or LQTS negative. The LQT1 variants with non-nonsense and severe function loss (current density or β-adrenergic response) had lower FHR. Maternal β-blockers potentiated bradycardia in LQT1 and LQT2 but did not affect FHR in LQTS negative. A FHR/GA threshold predicted LQT1 and LQT2 with 74.9% accuracy, 71% sensitivity, and 81% specificity.

CONCLUSION

Genotype, LQT1 variant, and maternal β-blocker therapy affect FHR. A predictive threshold of FHR/GA significantly improves the accuracy, sensitivity, and specificity for LQT1 and LQT2, above the infant's a priori 50% probability. We speculate this model may be useful in screening for LQTS in perinatal subjects without a known LQTS family history.

The genetic basis of apparently idiopathic ventricular fibrillation: a retrospective overview

AIMS

During the diagnostic work-up of patients with idiopathic ventricular fibrillation (VF), next-generation sequencing panels can be considered to identify genotypes associated with arrhythmias. However, consensus for gene panel testing is still lacking, and variants of uncertain significance (VUS) are often identified. The aim of this study was to evaluate genetic testing and its results in idiopathic VF patients.

METHODS AND RESULTS

We investigated 419 patients with available medical records from the Dutch Idiopathic VF Registry. Genetic testing was performed in 379 (91%) patients [median age at event 39 years (27-51), 60% male]. Single-gene testing was performed in 87 patients (23%) and was initiated more often in patients with idiopathic VF before 2010. Panel testing was performed in 292 patients (77%). The majority of causal (likely) pathogenic variants (LP/P, n = 56, 15%) entailed the DPP6 risk haplotype (n = 39, 70%). Moreover, 10 LP/P variants were found in cardiomyopathy genes (FLNC, MYL2, MYH7, PLN (two), TTN (four), RBM20), and 7 LP/P variants were identified in genes associated with cardiac arrhythmias (KCNQ1, SCN5A (2), RYR2 (four)). For eight patients (2%), identification of an LP/P variant resulted in a change of diagnosis. In 113 patients (30%), a VUS was identified. Broad panel testing resulted in a higher incidence of VUS in comparison to single-gene testing (38% vs. 3%, P < 0.001).

CONCLUSION

Almost all patients from the registry underwent, albeit not broad, genetic testing. The genetic yield of causal LP/P variants in idiopathic VF patients is 5%, increasing to 15% when including DPP6. In specific cases, the LP/P variant is the underlying diagnosis. A gene panel specifically for idiopathic VF patients is proposed.