SCN5A and familial long QT syndrome: NaV1.5 channel variants have been associated with several congenital cardiac disorders such as atrial standstill, atrial fibrillation (AF), Burgada syndrome (BrS), cardiac conduction disease (CCD), dilated cardiomyopathy (DCM), LQTS and sudden infant death syndrome (SIDS).25, 26 Gain‐of‐function mutations in NaV1.5 result in increased persistent current which may lead to long‐QT syndrome type 3 (LQTS‐3), while loss‐of‐function mutations result in decreased peak INa and are implicated in BrS and sick sinus syndrome (SSD).