Negative Autopsy in Infant and Juvenile Population: Role of Cardiac Arrhythmias

Negative autopsy is a post-mortem examination in which a comprehensive analysis does not provide a cause of death. These include situation of death, anatomical and histological analysis, toxicology and microbiological study. A low part of autopsies remain without a conclusive cause of death, but all these cases are usually seen in young population, apparently healthy who died suddenly and unexpectedly. In these situations a cardiac arrhythmia is suspected as cause of death and genetic testing is recommended despite not regularly performed. Sudden death is a natural and unexpected decease that occurs in apparently healthy people, or whose disease was not severe enough to expect a fatal outcome. It can be due to several pathologies, usually of cardiac cause and called sudden cardiac death. In infants and young people, both long QT syndrome and catecholaminergic polymorphic ventricular tachycardia are main causes in negative autopsies. These genetic diseases lead to ventricular fibrillation, syncope and sudden cardiac death in a normal heart. Unfortunately, sudden cardiac death could be the first manifestation of the diseases, being early identification and prevention a crucial point in current medical practice. This chapter focuses on sudden death and negative autopsy in young population, mainly due to cardiac arrhythmias

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

Personalized Genetic Diagnosis of Congenital Heart Defects in Newborns

Congenital heart disease is a group of pathologies characterized by structural malformations of the heart or great vessels. These alterations occur during the embryonic period and are the most frequently observed severe congenital malformations, the main cause of neonatal mortality due to malformation, and the second most frequent congenital malformations overall after malformations of the central nervous system. The severity of different types of congenital heart disease varies depending on the combination of associated anatomical defects. The causes of these malformations are usually considered multifactorial, but genetic variants play a key role. Currently, use of high-throughput genetic technologies allows identification of pathogenic aneuploidies, deletions/duplications of large segments, as well as rare single nucleotide variants. The high incidence of congenital heart disease as well as the associated complications makes it necessary to establish a diagnosis as early as possible to adopt the most appropriate measures in a personalized approach. In this review, we provide an exhaustive update of the genetic bases of the most frequent congenital heart diseases as well as other syndromes associated with congenital heart defects, and how genetic data can be translated to clinical practice in a personalized approach.This work was supported by Obra Social "La Caixa Foundation" (LCF/PR/GN16/50290001, and LCF/PR/GN19/50320002). Funders had no role in study design, data collection, data analysis, interpretation, or writing of the report

Update on Genes Associated with Arrhythmogenic Cardiomyopathy

Arrhythmogenic cardiomyopathy is a rare genetic entity characterized by progressive fibro-fatty replacement of myocardium leading to malignant arrhythmias, syncope, and sudden cardiac death. Mostly it affects the right ventricle, but cases have also been described with biventricular and even isolated left ventricular involvement. The disease affects mainly young males and arrhythmias are usually induced by exercise. Arrhythmogenic cardiomyopathy has a genetic origin and is basically caused by deleterious alterations in genes encoding desmosomal proteins, especially plakophilin-2. To date, more than 400 rare genetic alterations have been identified in 18 genes, mainly with autosomal dominant inheritance, but some recessive forms have also been reported (Naxos disease and Carvajal syndrome). A comprehensive genetic analysis identifies a rare variant as potential cause of the disease in around 60% of patients, suggesting the existence of unknown genes as well as other genome alterations not yet discovered. Genetic interpretation classifies some of these rare variants as ambiguous, playing an uncertain role in arrhythmogenic cardiomyopathy. This makes a proper translation of genetic data into clinical practice difficult. Moreover, incomplete penetrance and variable phenotypic expression makes it difficult to arrive at the correct diagnosis. In the present chapter, we focus on recent advances in the knowledge regarding the genetic basis of arrhythmogenic cardiomyopathy

Molecular autopsy in sudden cardiac death

Actualmente hay un porcentaje importante de autopsias que quedan sin un diagnóstico 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.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 medicallegal 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

Generation of four induced pluripotent stem cell lines from a family harboring a single nucleotide variant in SCN5A

Patient-derived induced pluripotent stem cells (iPSC) are a valuable approach to model cardiovascular diseases. We nucleofected non-integrating episomal vectors in skin fibroblasts of three family members carrying a single nucleotide variant (SNV) in SCN5A, which encodes the cardiac-type sodium channel, and of a related healthy control. The SNV SCN5A_c.4573G > A had been previously identified in a Brugada Syndrome patient. The resulting iPS cell lines differentiate into cells of the 3 germ layers, display normal karyotypes and express pluripotency surface markers and genes. Thus, they are a reliable source to study the effect of the identified mutation in a physiologically relevant environment

Short QT Syndrome: Update on Genetic Basis

Short QT syndrome (SQTS) is an extremely rare inherited arrhythmogenic entity. Nowadays, less than 200 families affected worldwide have been reported. This syndrome is characterized by the presence of a short QT interval leading to malignant ventricular tachyarrhythmias, syncope and sudden cardiac death. It is one of the most lethal heart diseases in children and young adults. Both incomplete penetrance and variable expressivity are hallmarks of this entity, making it difficult to diagnose and manage. Currently, rare variants in nine genes have been associated with SQTS (CACNA1C, CACNA2D1, CACNB2, KCNH2, KCNJ2, KCNQ1, SLC22A5, SLC4A3 and SCN5A). However, only pathogenic variants in four genes (KCNH2, KCNQ1, KCNJ2 and SLC4A3) have been found to definitively cause SQTS. The remaining genes lack a clear association with the disease, making clinical interpretation of the variants challenging. The diagnostic yield of genetic tests is currently less than 30%, leaving most families clinically diagnosed with SQTS without a conclusive genetic diagnosis. We reviewed and updated the main genetic features of SQTS, as well as recent evidence on increasingly targeted treatment

Personalized Interpretation and Clinical Translation of Genetic Variants Associated With Cardiomyopathies

Cardiomyopathies are a heterogeneous group of inherited cardiac diseases characterized by progressive myocardium abnormalities associated with mechanical and/or electrical dysfunction. Massive genetic sequencing technologies allow a comprehensive genetic analysis to unravel the cause of disease. However, most identified genetic variants remain of unknown clinical significance due to incomplete penetrance and variable expressivity. Therefore, genetic interpretation of variants and translation into clinical practice remain a current challenge. We performed retrospective comprehensive clinical assessment and genetic analysis in six families, four diagnosed with arrhythmogenic cardiomyopathy, and two diagnosed with hypertrophic cardiomyopathy (HCM). Genetic testing identified three rare variants (two non-sense and one small indel inducing a frameshift), each present in two families. Although each variant is currently classified as pathogenic and the cause of the diagnosed cardiomyopathy, the onset and/or clinical course differed in each patient. New genetic technology allows comprehensive yet cost-effective genetic analysis, although genetic interpretation, and clinical translation of identified variants should be carefully done in each family in a personalized manner

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

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.This work was supported by Obra Social "La Caixa Foundation" (LCF/PR/GN16/50290001 and LCF/PR/GN19/50320002), Fondo Investigacion Sanitaria (FIS PI16/01203 and FIS, PI17/01690) from Instituto Salud Carlos III (ISCIII), and "Fundacio Privada Daniel Bravo Andreu". CIBERCV is an initiative of the ISCIII, Spanish Ministry of Economy and Competitiveness