SCN5A and progressive familial heart block, type 1A: Since the early 2000s, murine models with loss of function (LOF) of the cardiac isoform of the voltage-gated sodium channel (Nav1.5) have been studied in hopes of elucidating the mechanisms of arrhythmogenesis in diseases such as Brugada syndrome (BrS) and Lenegre disease (Lev’s disease; 1–5).