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A conclusive and early diagnosis of cardiomyopathy is essential for implementing preventive therapeutic measures and, therefore, reducing the risk of malignant arrhythmias and even sudden cardiac death. Occasionally, this lethal event can be the first manifestation of cardiomyopathy, with or without a clear structural defect. In cases of sudden death, especially in young patients, the autopsy may be ambiguous and therefore lack a definitive diagnosis of cardiomyopathy, although it can sometimes identify signs that lead us to suspect it. This is one of the current challenges of forensic science, where occult cardiomyopathies often remain unidentified without additional testing that is not routinely included in current forensic protocols. In this protocol, it is crucial to perform a molecular autopsy but also to include additional data, especially family history, that will help conclude or at least suspect this entity. Obtaining this diagnosis or suspicion of concealed cardiomyopathy not only provides an answer to the unexpected death but also helps the relatives determine the cause of death. In addition, physicians should initiate a family assessment to identify other family members who may be at risk early and adopt personalized preventive measures.

The GPD1L gene encodes a small cytoplasmic protein that is involved in the regulation of sodium currents. Alterations in this gene have been associated with Brugada syndrome. This rare arrhythmogenic syndrome is characterized by a typical electrocardiographic pattern, incomplete penetrance, variable expressivity, and risk of sudden cardiac death. To date, few families with a clinical diagnosis of Brugada syndrome caused by a rare alteration in the GPD1L gene have been reported worldwide. The increase in data focused on genetic variants allows us to improve the interpretation of their role in Brugada syndrome. In our study, we have compiled the GPD1L variants reported so far in patients with a definitive clinical diagnosis or suspected Brugada syndrome. We performed an exhaustive update and interpretation of each variant following the guidelines of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Our results showed that none of the variants described to date can be classified as truly harmful in Brugada syndrome. Despite this fact, more clinical and genetic data are needed to definitively rule out the GPD1L gene as a cause of Brugada syndrome. In summary, to date, there is insufficient evidence to conclude a definitive association between GPD1L and Brugada syndrome.

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.

Background/Objectives: Inherited arrhythmogenic syndromes comprise a heterogenic group of genetic entities that lead to malignant arrhythmias and sudden cardiac death. Genetic testing has become crucial to understand the disease etiology and allow for the early identification of relatives at risk; however, it requires an accurate interpretation of the data to achieve a clinically actionable outcome. This is particularly challenging for the large number of rare variants obtained by current high-throughput techniques, which are mostly classified as of unknown significance. Methods: In this work, we present a new algorithm for the genetic interpretation of the remaining rare variants in order to shed light on their potential clinical implications and reduce the burden of unknown significance. Results: Our study illustrates the potential utility of our individualized comprehensive stepwise analyses focused on the rare variants associated with IAS, which are currently classified as ambiguous, to further determine their trends towards pathogenicity or benign traits. Conclusions: We advocate for personalized disease-focused population frequency data and family segregation analyses for all rare variants that remain ambiguous to further clarify their role. The current ambiguity should not influence medical decisions, but a potential deleterious role would suggest a closer clinical follow-up and frequent genetic data review for a more personalized clinical approach.

Genetic testing is recommended in the diagnosis of short QT syndrome. This rare inherited lethal entity is characterized by structural normal hearts with short QT intervals in the electrocardiogram. Few families diagnosed with this arrhythmogenic disease have been reported worldwide so far, impeding a comprehensive understanding of this syndrome. Unraveling the origin of the disease helps to the early identification of genetic carriers at risk. However, only rare variants with a definite deleterious role should be actionable in clinical practice. Our aim was to perform a comprehensive update and reinterpretation, according to the American College of Medical Genetics and Genomics recommendations of all rare variants currently associated with short QT syndrome. We identified 34 rare variants. Reanalysis showed that only nine variants played a deleterious role associated with a definite short QT syndrome phenotype. These variants were located in the four main genes: KCNQ1, KCNH2, KCNJ2 or SLC4A3. Additional rare variants located in other genes were associated with other conditions with phenotypic shortened QT intervals, but not definite diagnosis of short QT syndrome. Periodically updating of rare variants, especially those previously classified as unknown, helps to clarify the role of rare variants and translate genetic data into clinical practice.

Brugada syndrome is a rare arrhythmogenic syndrome associated mainly with pathogenic variants in the SCN5A gene. Right ventricle outflow tract fibrosis has been reported in some cases of patients diagnosed with Brugada syndrome. Pulmonary atresia with an intact ventricular septum is characterized by the lack of a functional pulmonary valve, due to the underdevelopment of the right ventricle outflow tract. We report, for the first time, a 4-year-old boy with pulmonary atresia with an intact ventricular septum who harbored a pathogenic de novo variant in SCN5A, and the ajmaline test unmasked a type-1 Brugada pattern. We suggest that deleterious variants in the SCN5A gene could be implicated in pulmonary atresia with an intact ventricular septum embryogenesis, leading to overlapping phenotypes.