Retrospective Genetic Analysis of 200 Cases of Sudden Infant Death Syndrome and Its Relationship with Long QT Syndrome in Korea

Intersegment Contacts of Potentially Damaging Variants of Cardiac Sodium Channel

Over 1,500 missense variants of sodium channel hNav1.5, which are reported in the ClinVar database, are associated with cardiac diseases. For most of the variants, the clinical significance is uncertain (VUS), not provided (NP), or has conflicting interpretations of pathogenicity (CIP). Reclassifying these variants as pathogenic/likely pathogenic (P/LP) variants is important for diagnosing genotyped patients. In our earlier work, several bioinformatics tools and paralogue annotation method consensually predicted that 74 VUS/NP/CIP variants of 54 wild type residues (set w54) are potentially damaging variants (PDVs). Atomic mechanisms underlying dysfunction of the PDVs are unknown. Here we employed a recent cryo-EM structure of the hNav1.5 channel with likely inactivated pore domain (PD) and activated voltage-sensing domains (VSDs), and ad hoc models of the closed and open PD and resting VSDs to explore intersegment contacts of w54 residues. We found that 44 residues from set w54 contact 84 residues with 118 disease missense variants. These include 104 VUS/NP/CIP variants, most of which are associated with the loss-of-function Brugada syndrome (BrS1) or gain-of-function long QT syndrome (LQT3). Matrix representation of the PDVs and their contact variants facilitated recognition of coupled mutations associated with the same disease. In particular, BrS1-associated coupled mutations, which disturb the P-loops region with the selectivity filter slow inactivation gate, would cause the channel dysfunction. Other likely causes of the channel dysfunction include coupled BrS1-associated variants within VSDs that would destabilize their activated states and coupled LQT3-associated variants, which would stabilize the open PD or activated VSDs. Our study proposes mechanisms of channel dysfunction for scores of BrS1- and LQT3-associated variants, confirms status for 82% of PDVs, and suggests damaging status for their contact variants, which are currently categorized as VUS/NP/CIP variants.

Sudden cardiac death in children with congenital heart disease: a critical review of the literature

Sudden cardiac death is an uncommon but yet catastrophic event, which can occur in neonates and young children. Although extensive research has been carried out assessing the underlying causes, there still remains a degree of uncertainty around this area. Congenital heart disease (CHD) is one known cause of sudden cardiac death in children, the aetiology of which embraces virally induced mechanisms, genetic susceptibility, drug-induced, and maternal factors. Screening tools and investigations including electrocardiograms and echocardiograms alongside a concise history taking and physical examination can be used to identify the potential cardiovascular risk factors of sudden death. This review has comprehensively studied the causes and risk factors for sudden cardiac death in children with CHD and provides a collation and summary of the evidence available so far underpinning the complex link between the two. Moreover, current screening and prevention methods are discussed in detail in order to increase awareness and understanding of how we can improve patient outcomes.