SCN5A and familial long QT syndrome: The SCN5A gene, encoding the vital cardiac sodium channel, is responsible for multiple clinically diverse heart rhythm disorders [8,9]; in turn, LQTS type 3, caused by SCN5A-damaging variants, is difficult to manage [10] and is characterized by a wider spectrum of symptoms, including frequent bradycardia [11,12] and the higher lethality of arrhythmic events than in other LQTS subtypes [13].