Cardiac channelopathies in pediatrics: a genetic update.

Cardiac channelopathies are a group of inherited syndromes that can cause malignant arrhythmias and sudden cardiac death, particularly in the pediatric population. Today, a 12-lead electrocardiogram is the most effective tool to diagnose these diseases. Incomplete penetrance and variable expressivity are hallmarks of these syndromes. Some of these malignant entities may remain hidden and only a trigger such as exercise, emotions or fever can unmask the electrical pattern to diagnose the disease. Sudden cardiac death may be the first manifestation of any of these syndromes. The use of complementary tests that allow early diagnosis is strongly recommended, among which we find: pharmacological provocations, exercise tests, and genetic analysis. Genetic testing makes it possible to unravel the origin of the disease, and also identify family members who carry the harmful genetic defect and are therefore at risk. One of the main challenges in this area is the large number of genetic variants of uncertain significance, which prevent effective translation into clinical practice. Early identification of the pediatric population at risk and adequate risk stratification are crucial to adopting personalized preventive measures that reduce the risk of lethal episodes in this population. What is Known: • In the pediatric population, malignant arrhythmias leading to sudden cardiac death are mainly caused by inherited syndromes. • A conclusive genetic diagnosis unravels the origin of the syndrome and allows cascade screening to identify relatives carrying the genetic alteration. What is New: • The use of sequencing technologies allows a broad genetic analysis, helping to unravel new genetic alterations causing inherited arrhythmogenic syndromes. • A periodic reanalysis of genetic variants that currently have an ambiguous role will help discern those that are truly pathogenic.

Role of miRNA-mRNA Interactome in Pathophysiology of Arrhythmogenic Cardiomyopathy.

Arrhythmogenic cardiomyopathy is an inherited entity characterized by irregular cell-cell adhesion, cardiomyocyte death and fibro-fatty replacement of ventricular myocytes, leading to malignant ventricular arrythmias, contractile dysfunction and sudden cardiac death. Pathogenic variants in genes that encode desmosome are the predominant cause of arrhythmogenic cardiomyopathy. Moreover, signalling pathways such as Wnt/ß-catenin and transforming growth factor-ß have been involved in the disease progression. However, still little is known about the molecular pathophysiological mechanisms that underlie arrhythmogenic cardiomyopathy pathogenesis. We used mRNA and small RNA sequencing to analyse the transcriptome of health and arrhythmogenic cardiomyopathy of autopsied human hearts. Our results showed 697 differentially expressed genes and eight differentially expressed miRNAs. Functional enrichment revealed mitochondrial respiratory-related pathways, impaired response to oxidative stress, apoptotic signalling pathways and inflammatory response-related and extracellular matrix response pathways. Furthermore, analysis of the miRNA-mRNA interactome identified eleven negatively correlated miRNA-target pairs for arrhythmogenic cardiomyopathy. Our finding revealed novel arrhythmogenic cardiomyopathy-related miRNAs with important regulatory function in disease pathogenesis, highlighting their value as potential key targets for therapeutic approaches.

A narrative review of inherited arrhythmogenic syndromes in young population: role of genetic diagnosis in exercise recommendations.

Sudden cardiac death is a rare but socially devastating event, especially if occurs in young people. Usually, this unexpected lethal event occurs during or just after exercise. One of the leading causes of sudden cardiac death is inherited arrhythmogenic syndromes, a group of genetic entities characterised by incomplete penetrance and variable expressivity. Exercise can be the trigger for malignant arrhythmias and even syncope in population with a genetic predisposition, being sudden cardiac death as the first symptom. Due to genetic origin, family members must be clinically assessed and genetically analysed after diagnosis or suspected diagnosis of a cardiac channelopathy. Early identification and adoption of personalised preventive measures is crucial to reduce risk of arrhythmias and avoid new lethal episodes. Despite exercise being recommended by the global population due to its beneficial effects on health, particular recommendations for these patients should be adopted considering the sport practised, level of demand, age, gender, arrhythmogenic syndrome diagnosed but also genetic diagnosis. Our review focuses on the role of genetic background in sudden cardiac death during exercise in child and young population.

Congenital LMNA-Related Muscular Dystrophy in Paediatrics: Cardiac Management in Monozygotic Twins.

Pathogenic variants in LMNA have been associated with a wide spectrum of muscular conditions: the laminopathies. LMNA-related congenital muscular dystrophy is a laminopathy characterised by the early onset of symptoms and often leads to a fatal outcome at young ages. Children face a heightened risk of malignant arrhythmias. No established paediatric protocols for managing this condition are available. We review published cases and provide insights into disease progression in two twin sisters with LMNA-related muscular dystrophy. Our objective is to propose a cardiac surveillance and management plan tailored specifically for paediatric patients. We present a family of five members, including two twin sisters with LMNA-related muscular dystrophy. A comprehensive neuromuscular and cardiac work-up was performed in all family members. Genetic analysis using massive sequencing technology was performed in both twins. Clinical assessment showed that only the twins showed diagnoses of LMNA-related muscular dystrophy. Follow-up showed an early onset of symptoms and life-threatening arrhythmias, with differing disease progressions despite both twins passing away. Genetic analysis identified a de novo rare missense deleterious variant in the LMNA gene. Other additional rare variants were identified in genes associated with myasthenic syndrome. Early-onset neuromuscular symptoms could be related to a prognosis of worse life-threatening arrhythmias in LMNA related muscular dystrophy. Being a carrier of other rare variants may be a modifying factor in the progression of the phenotype, although further studies are needed. There is a pressing need for specific cardiac recommendations tailored to the paediatric population to mitigate the risk of malignant arrhythmias.

Phacomatosis pigmentokeratotica: Exploring extracutaneous comorbidities and topical therapy.

Phacomatosis pigmentokeratotica (PPK) is a RASopathy characterized by the presence of a sebaceous nevus and a papular speckled lentiginous nevus. This case report highlights the associated extracutaneous comorbidities, including life-threatening arrhythmia, and introduces topical rapamycin as a potential therapeutic avenue for sebaceous nevus in PPK patients.

Implementing a New Algorithm for Reinterpretation of Ambiguous Variants in Genetic Dilated Cardiomyopathy.

Dilated cardiomyopathy is a heterogeneous entity that leads to heart failure and malignant arrhythmias. Nearly 50% of cases are inherited; therefore, genetic analysis is crucial to unravel the cause and for the early identification of carriers at risk. A large number of variants remain classified as ambiguous, impeding an actionable clinical translation. Our goal was to perform a comprehensive update of variants previously classified with an ambiguous role, applying a new algorithm of already available tools. In a cohort of 65 cases diagnosed with dilated cardiomyopathy, a total of 125 genetic variants were classified as ambiguous. Our reanalysis resulted in the reclassification of 12% of variants from an unknown to likely benign or likely pathogenic role, due to improved population frequencies. For all the remaining ambiguous variants, we used our algorithm; 60.9% showed a potential but not confirmed deleterious role, and 24.5% showed a potential benign role. Periodically updating the population frequencies is a cheap and fast action, making it possible to clarify the role of ambiguous variants. Here, we perform a comprehensive reanalysis to help to clarify the role of most of ambiguous variants. Our specific algorithms facilitate genetic interpretation in dilated cardiomyopathy.

Role of microRNAs in arrhythmogenic cardiomyopathy: translation as biomarkers into clinical practice.

Arrhythmogenic cardiomyopathy is a rare inherited entity, characterized by a progressive fibro-fatty replacement of the myocardium. It leads to malignant arrhythmias and a high risk of sudden cardiac death. Incomplete penetrance and variable expressivity are hallmarks of this arrhythmogenic cardiac disease, where the first manifestation may be syncope and sudden cardiac death, often triggered by physical exercise. Early identification of individuals at risk is crucial to adopt protective and ideally personalized measures to prevent lethal episodes. The genetic analysis identifies deleterious rare variants in nearly 70% of cases, mostly in genes encoding proteins of the desmosome. However, other factors may modulate the phenotype onset and outcome of disease, such as microRNAs. These small noncoding RNAs play a key role in gene expression regulation and the network of cellular processes. In recent years, data focused on the role of microRNAs as potential biomarkers in arrhythmogenic cardiomyopathy have progressively increased. A better understanding of the functions and interactions of microRNAs will likely have clinical implications. Herein, we propose an exhaustive review of the literature regarding these noncoding RNAs, their versatile mechanisms of gene regulation and present novel targets in arrhythmogenic cardiomyopathy.

Indications and management of implantable cardioverter-defibrillator therapy in childhood hypertrophic cardiomyopathy.

Sudden cardiac death is the most common mode of death during childhood and adolescence in hypertrophic cardiomyopathy, and identifying those individuals at highest risk is a major aspect of clinical care. The mainstay of preventative therapy is the implantable cardioverter-defibrillator, which has been shown to be effective at terminating malignant ventricular arrhythmias in children with hypertrophic cardiomyopathy but can be associated with substantial morbidity. Accurate identification of those children at highest risk who would benefit most from implantable cardioverter-defibrillator implantation while minimising the risk of complications is, therefore, essential. This position statement, on behalf of the Association for European Paediatric and Congenital Cardiology (AEPC), reviews the currently available data on established and proposed risk factors for sudden cardiac death in childhood-onset hypertrophic cardiomyopathy and current approaches for risk stratification in this population. It also provides guidance on identification of individuals at risk of sudden cardiac death and optimal management of implantable cardioverter-defibrillators in children and adolescents with hypertrophic cardiomyopathy.

Sex differences in long QT syndrome.

Long QT Syndrome (LQTS) is a rare, inherited channelopathy characterized by cardiac repolarization dysfunction, leading to a prolonged rate-corrected QT interval in patients who are at risk for malignant ventricular tachyarrhythmias, syncope, and even sudden cardiac death. A complex genetic origin, variable expressivity as well as incomplete penetrance make the diagnosis a clinical challenge. In the last 10 years, there has been a continuous improvement in diagnostic and personalized treatment options. Therefore, several factors such as sex, age diagnosis, QTc interval, and genetic background may contribute to risk stratification of patients, but it still currently remains as a main challenge in LQTS. It is widely accepted that sex is a risk factor itself for some arrhythmias. Female sex has been suggested as a risk factor in the development of malignant arrhythmias associated with LQTS. The existing differences between the sexes are only manifested after puberty, being the hormones the main inducers of arrhythmias. Despite the increased risk in females, no more than 10% of the available publications on LQTS include sex-related data concerning the risk of malignant arrhythmias in females. Therein, the relevance of our review data update concerning women and LQTS.

Characterization of cardiac involvement in children with LMNA-related muscular dystrophy.

Introduction: LMNA-related muscular dystrophy is a rare entity that produce "laminopathies" such as Emery-Dreifuss muscular dystrophy (EDMD), limb-girdle muscular dystrophy type 1B (LGMD1B), and LMNA-related congenital muscular dystrophy (L-CMD). Heart failure, malignant arrhythmias, and sudden death may occur. No consensus exists on cardiovascular management in pediatric laminopathies. The aim was to perform an exhaustive cardiologic follow-up in pediatric patients diagnosed with LMNA-related muscular dystrophy. Methods: Baseline cardiac work-up consisted of clinical assessment, transthoracic Doppler echocardiography, 12-lead electrocardiogram, electrophysiological study, and implantation of a long-term implantable cardiac loop recorder (ILR). Results: We enrolled twenty-eight pediatric patients diagnosed with EDMD (13 patients), L-CMD (11 patients), LGMD1B (2 patients), and LMNA-related mild weakness (2 patients). Follow-up showed dilated cardiomyopathy (DCM) in six patients and malignant arrhythmias in five (four concomitant with DCM) detected by the ILR that required implantable cardioverter defibrillator (ICD) implantation. Malignant arrhythmias were detected in 20% of our cohort and early-onset EDMD showed worse cardiac prognosis. Discussion: Patients diagnosed with early-onset EDMD are at higher risk of DCM, while potentially life-threatening arrhythmias without DCM appear earlier in L-CMD patients. Early onset neurologic symptoms could be related with worse cardiac prognosis. Specific clinical guidelines for children are needed to prevent sudden death.

Molecular autopsy in sudden cardiac death.

A post-mortem genetic analysis in the process of investigating a sudden death episode is known as 'molecular autopsy'. It is usually performed in cases without a conclusive cause of death and after a comprehensive medico-legal autopsy. In these sudden unexplained death cases, an underlying inherited arrhythmogenic cardiac disease is the main suspected cause of death. The objective is to unravel a genetic diagnosis of the victim, but it also enables cascade genetic screening of the victim's relatives. Early identification of a deleterious genetic alteration associated with an inherited arrhythmogenic disease may help to adopt preventive personalized measures to reduce risk of malignant arrhythmias and sudden death. It is important to remark that the first symptom of an inherited arrhythmogenic cardiac disease may the malignant arrhythmia and even sudden death. Next-generation sequencing allows a rapid and cost-effectives genetic analysis. Close interaction between the forensic scientist, pathologist, cardiologist, pediatric cardiologist and geneticist has allowed a progressive increase of genetic yield in recent years, identifying the pathogenic genetic alteration. However, large numbers of rare genetic alterations remain classified as having an ambiguous role, impeding a proper genetic interpretation and useful translation into both forensic and cardiological arena.

Molecular autopsy: Twenty years of post-mortem diagnosis in sudden cardiac death.

In the forensic medicine field, molecular autopsy is the post-mortem genetic analysis performed to attempt to unravel the cause of decease in cases remaining unexplained after a comprehensive forensic autopsy. This negative autopsy, classified as negative or non-conclusive, usually occurs in young population. In these cases, in which the cause of death is unascertained after a thorough autopsy, an underlying inherited arrhythmogenic syndrome is the main suspected cause of death. Next-generation sequencing allows a rapid and cost-effectives genetic analysis, identifying a rare variant classified as potentially pathogenic in up to 25% of sudden death cases in young population. The first symptom of an inherited arrhythmogenic disease may be a malignant arrhythmia, and even sudden death. Early identification of a pathogenic genetic alteration associated with an inherited arrhythmogenic syndrome may help to adopt preventive personalized measures to reduce risk of malignant arrhythmias and sudden death in the victim's relatives, at risk despite being asymptomatic. The current main challenge is a proper genetic interpretation of variants identified and useful clinical translation. The implications of this personalized translational medicine are multifaceted, requiring the dedication of a specialized team, including forensic scientists, pathologists, cardiologists, pediatric cardiologists, and geneticists.

Indications and utility of cardiac genetic testing in athletes.

Sports Cardiology practice commonly involves the evaluation of athletes for genetically determined cardiac conditions that may predispose to malignant arrhythmias, heart failure, and sudden cardiac death. High-level exercise can lead to electrical and structural cardiac remodelling which mimics inherited cardiac conditions (ICCs). Differentiation between 'athlete's heart' and pathology can be challenging and often requires the whole armamentarium of available investigations. Genetic studies over the last 30 years have identified many of the genetic variants that underpin ICCs and technological advances have transformed genetic testing to a more readily available and affordable clinical tool which may aid diagnosis, management, and prognosis. The role of genetic testing in the evaluation and management of athletes with suspected cardiac conditions is often unclear beyond the context of specialist cardio-genetics centres. This document is aimed at physicians, nurses, and allied health professionals involved in the athlete's care. With the expanding role and availability of genetic testing in mind, this document was created to address the needs of the broader sports cardiology community, most of whom work outside specialized cardio-genetics centres, when faced with the evaluation and management of athletes with suspected ICC. The first part of the document provides an overview of basic terminology and principles and offers guidance on the appropriate use of genetic testing in the assessment of such athletes. It outlines key considerations when contemplating genetic testing, highlighting the potential benefits and pitfalls, and offers a roadmap to genetic testing. The second part of the document presents common clinical scenarios in Sports Cardiology practice, outlining the diagnostic, prognostic, and therapeutic implications of genetic testing, including impact on exercise recommendations. The scope of this document does not extend to a comprehensive description of the genetic basis, investigation, or management of ICCs.

Structural Heart Alterations in Brugada Syndrome: Is it Really a Channelopathy? A Systematic Review.

Brugada syndrome (BrS) is classified as an inherited cardiac channelopathy attributed to dysfunctional ion channels and/or associated proteins in cardiomyocytes rather than to structural heart alterations. However, hearts of some BrS patients exhibit slight histologic abnormalities, suggesting that BrS could be a phenotypic variant of arrhythmogenic cardiomyopathy. We performed a systematic review of the literature following Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement (PRISMA) criteria. Our comprehensive analysis of structural findings did not reveal enough definitive evidence for reclassification of BrS as a cardiomyopathy. The collection and comprehensive analysis of new cases with a definitive BrS diagnosis are needed to clarify whether some of these structural features may have key roles in the pathophysiological pathways associated with malignant arrhythmogenic episodes.

Update on the Diagnostic Pitfalls of Autopsy and Post-Mortem Genetic Testing in Cardiomyopathies.

Inherited cardiomyopathies are frequent causes of sudden cardiac death (SCD), especially in young patients. Despite at the autopsy they usually have distinctive microscopic and/or macroscopic diagnostic features, their phenotypes may be mild or ambiguous, possibly leading to misdiagnoses or missed diagnoses. In this review, the main differential diagnoses of hypertrophic cardiomyopathy (e.g., athlete's heart, idiopathic left ventricular hypertrophy), arrhythmogenic cardiomyopathy (e.g., adipositas cordis, myocarditis) and dilated cardiomyopathy (e.g., acquired forms of dilated cardiomyopathy, left ventricular noncompaction) are discussed. Moreover, the diagnostic issues in SCD victims affected by phenotype-negative hypertrophic cardiomyopathy and the relationship between myocardial bridging and hypertrophic cardiomyopathy are analyzed. Finally, the applications/limits of virtopsy and post-mortem genetic testing in this field are discussed, with particular attention to the issues related to the assessment of the significance of the genetic variants.

Malignant Arrhythmogenic Role Associated with RBM20: A Comprehensive Interpretation Focused on a Personalized Approach.

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.

The role of clinical assessment and electrophysiology study in Brugada syndrome patients with syncope.

BACKGROUND: Cardiogenic syncope in Brugada syndrome (BrS) increases the risk of major events. Nevertheless, clinical differentiation between cardiogenic and vasovagal syncope can be challenging. We characterized the long-term incidence of major events in a large cohort of BrS patients who presented with syncope. METHODS: From a total of 474 patients, syncope was the initial manifestation in 135 (28.5%) individuals (43.9 ±â€¯13.9 years, 71.1% male). The syncope was classified prospectively as cardiogenic, vasovagal, or undefined if unclear characteristics were present. Clinical, electrocardiographic, genetic, and electrophysiologic features were analyzed. Cardiogenic syncope, sustained ventricular arrhythmias, and sudden death were considered major events in follow-up. RESULTS: In 66 patients (48.9%), the syncope was cardiogenic; in 51 (37.8%), vasovagal and in 18 (13.3%); undefined. The electrophysiology study (EPS) inducibility was more frequent in patients with cardiogenic syncope and absent in all patients with undefined syncope (28 [53.8%] vs 5 [12.2%] vs 0 [0%]; P < .01). During follow-up (7.7 ±â€¯5.6 years), only patients with cardiogenic syncope presented major events (16 [11.9%]). Among patients with inducible EPS, 7 (21.2%) presented major events (P = .04). The negative predictive value of the EPS for major events was 92.4%. The incidence rate of major events was 2.6% person-year. Parameters associated with major events included cardiogenic syncope (hazard ratio [HR] 6.3; 95% CI 1.1-10.4; P = .05), spontaneous type 1 electrocardiogram (HR 3.7; 95% CI 1.3-10.5; P = .01), and inducible EPS (HR 2.8; 95% CI 1.1-8.8; P = .05). CONCLUSIONS: An accurate syncope classification is crucial in BrS patients for risk stratification. In patients with syncope of unclear characteristics, the EPS may be helpful to prevent unnecessary implantable cardioverter defibrillators.

Pediatric Malignant Arrhythmias Caused by Rare Homozygous Genetic Variants in TRDN: A Comprehensive Interpretation.

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.

La autopsia molecular en la muerte súbita cardiaca / Molecular autopsy in sudden cardiac death

Resumen Actualmente hay un porcentaje importante de autopsias que quedan sin un diag nóstico concluyente del fallecimiento, especialmente cuando este evento letal se produce súbitamente. El análisis genético se ha ido incorporando recientemente al campo de la medicina forense, sobre todo en aquellos pacientes que han fallecido de forma repentina, y donde no se identifica causa concluyente del fallecimiento tras una autopsia médico-legal completa. En estos casos las enfermedades eléctricas primarias son las principales responsables del fallecimiento. Hasta la fecha se han descrito más de 40 genes asociados a afecciones arritmogénicas causantes de muerte súbita cardiaca. Las principales enfermedades arritmogénicas son el síndrome de QT largo y la taquicardia ventricular; estudios genéticos post-mortem no solo permiten llevar a cabo un diagnóstico de la causa del fallecimiento, sino que también permiten una traslación clínica hacia los familiares, focalizado en la identificación precoz de individuos en riesgo de síncope, así como adopción de medidas terapéuticas personalizadas para la prevención de un episodio arrítmico letal.

Abstract Currently, there are a significant percentage of autopsies left without a conclusive diagnosis of death, especially when this lethal event occurs suddenly. Genetic analysis has been recently incorporated into the field of forensic medicine, especially in patients with sudden death and where no conclusive cause of death is identified after a complete medical- legal autopsy. Inherited arrhythmogenic diseases are the main cause of death in these cases. To date, more than 40 genes have been associated with arrhythmogenic disease, and causing sudden cardiac death has been described. The main arrhythmogenic diseases are Long QT Syndrome, Catecholaminergic Polymorphic Ventricular Tachycardia, Brugada Syndrome, and Short QT Syndrome. These post-mortem genetic studies, not only allow a diagnosis of the cause of death, but also allow a clinical translation in relatives, focusing on the early identification of individuals at risk of syncope, as well as adopting personalised therapeutic measures for the prevention of a lethal arrhythmic episode.

Recent Advances in Short QT Syndrome.

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.