Practical Aspects in Genetic Testing for Cardiomyopathies and Channelopathies

Sudden Cardiac Death and Channelopathies: What Lies behind the Clinical Significance of Rare Splice-Site Alterations in the Genes Involved?

Background and objectives: Sudden cardiac death (SCD) is a natural and unexpected death of cardiac origin that occurs within 1 h from the onset of acute symptoms. The major leading causes of SCD are cardiomyopathies and channelopathies. In this review, we focus on channelopathies, inherited diseases caused by mutations affecting genes encoding membrane ion channels (sodium, potassium or calcium channels) or cellular structures that affect Ca2+ availability. The diagnosis of diseases such as long QT, Brugada syndrome, short QT and catecholaminergic polymorphic ventricular tachycardia (CPVT) is still challenging. Currently, genetic testing and next-generation sequencing allow us to identify many rare alterations. However, some non-coding variants, e.g., splice-site variants, are usually difficult to interpret and to classify. Methods: In our review, we searched for splice-site variants of genes involved in channelopathies, focusing on variants of unknown significance (VUSs) registered on ClinVar up to now. Results: The research led to a high number of splice-site VUSs of genes involved in channelopathies, suggesting the performance of deeper studies. Conclusions: In order to interpret the correlation between variants and pathologies, we discuss experimental studies, such as RNA sequencing and functional analysis of proteins. Unfortunately, as these in vitro analyses cannot always be performed, we draw attention to in silico studies as future perspectives in genetics. This review has the aim of discussing the potential methods of detection and interpretation of VUSs, bringing out the need for a future reclassification of variants with currently unknown significance.

Genotype-Phenotype Insights of Inherited Cardiomyopathies-A Review

Background: Cardiomyopathies (CMs) represent a heterogeneous group of primary myocardial diseases characterized by structural and functional abnormalities. They represent one of the leading causes of cardiac transplantations and cardiac death in young individuals. Clinically they vary from asymptomatic to symptomatic heart failure, with a high risk of sudden cardiac death due to malignant arrhythmias. With the increasing availability of genetic testing, a significant number of affected people are found to have an underlying genetic etiology. However, the awareness of the benefits of incorporating genetic test results into the care of these patients is relatively low. Aim: The focus of this review is to summarize the current basis of genetic CMs, including the most encountered genes associated with the main types of cardiomyopathies: hypertrophic, dilated, restrictive arrhythmogenic, and non-compaction. Materials and Methods: For this narrative review, we performed a search of multiple electronic databases, to select and evaluate relevant manuscripts. Results: Advances in genetic diagnosis led to better diagnosis precision and prognosis prediction, especially with regard to the risk of developing arrhythmias in certain subtypes of cardiomyopathies. Conclusions: Implementing the genomic information to benefit future patient care, better risk stratification and management, promises a better future for genotype-based treatment.

Precision Medicine and Cardiac Channelopathies: Human iPSCs Take the Lead

Sudden cardiac death (SCD) is one of the leading causes of death worldwide, usually involving young people. SCD remains a critical public health problem accounting for 185,000-450,000 deaths annually, representing around 7%-18% of all deaths globally. As per evidence, ∼2%-54% of sudden unexpected deaths in people under the age of 35 years fail to show evidence of structural cardiac abnormalities at autopsy, making ion channelopathies the probable causes in such cases. The most generally recognized cardiac ion channelopathies with genetic testing are long QT syndrome (LQTS), Brugada syndrome (BrS), short QT syndrome (SQTS), and catecholaminergic polymorphic ventricular tachycardia (CPVT). The substantial progress in understanding the genetics of ion channelopathies in the last 2 decades has obliged the early diagnosis and prevention of SCD to a certain extent. In this review, we analyze the critical challenges and recent advancements in the identification, risk stratification, and clinical management of potentially fatal cardiac ion channel disorders. We also emphasize the application of precision medicine (PM) and artificial intelligence (AI) for comprehending the underlying genetic mechanisms, especially the role of human induced pluripotent stem cell (iPSC) based platforms to unravel the primary refractory clinical problems associated with channelopathies.

Next-Generation Sequencing Gene Panels in Inheritable Cardiomyopathies and Channelopathies: Prevalence of Pathogenic Variants and Variants of Unknown Significance in Uncommon Genes

The diffusion of next-generation sequencing (NGS)-based approaches allows for the identification of pathogenic mutations of cardiomyopathies and channelopathies in more than 200 different genes. Since genes considered uncommon for a clinical phenotype are also now included in molecular testing, the detection rate of disease-causing variants has increased. Here, we report the prevalence of genetic variants detected by using a NGS custom panel in a cohort of 133 patients with inherited cardiomyopathies (n = 77) or channelopathies (n = 56). We identified 82 variants, of which 50 (61%) were identified in genes without a strong or definitive evidence of disease association according to the NIH-funded Clinical Genome Resource (ClinGen; "uncommon genes"). Among these, 35 (70%) were variants of unknown significance (VUSs), 13 (26%) were pathogenic (P) or likely pathogenic (LP) mutations, and 2 (4%) benign (B) or likely benign (LB) variants according to American College of Medical Genetics (ACMG) classifications. These data reinforce the need for the screening of uncommon genes in order to increase the diagnostic sensitivity of the genetic testing of inherited cardiomyopathies and channelopathies by allowing for the identification of mutations in genes that are not usually explored due to a currently poor association with the clinical phenotype.

Role of genetic testing in cardiomyopathies: Α primer for cardiologists

Recent advances in cardiovascular genetics have transformed genetic testing into a valuable part of management of families with inherited cardiomyopathies. As novel mutations have been identified, understanding when to consider genetic testing has emerged as an important consideration in the management of these cases. Specific genetic testing has a paramount importance in the risk stratification of family members, in the prognosis of probands at higher risk of a serious phenotype expression, and finally in the identification of new mutations, all of which are discussed in this review. The indications for each type of cardiomyopathy are described, along with the limitations of genetic testing. Finally, the importance of public sharing of variants in large data sets is emphasized. The ultimate aim of this review is to present key messages about the genetic testing process in order to minimize potential harms and provide suggestions to specialized clinicians who act as a part of a multidisciplinary team in order to offer the best care to families with inherited cardiomyopathies.