Loss-of-function (LOF) variants in SCN1B (19q13.11), encoding the voltage-gated sodium channel (VGSC) β1/β1B subunits, are linked to human diseases that predispose patients to sudden death, including developmental and epileptic encephalopathy type 52 (DEE52; OMIM 617350), Genetic Epilepsy with Febrile Seizures plus (OMIM 617350), Brugada Syndrome 5 (OMIM 612838), cardiac conduction defects (OMIM 612838), and Atrial Fibrillation (AF) Familial 13 (OMIM 615377) (1, 2). Here, SCN1B is linked to atrial fibrillation.