SCN5A encodes Nav1.5, the pore-forming subunit of the cardiac voltage-gated sodium channel responsible for the depolarizing phase of action potentials in cardiomyocytes 1. Nav1.5 mediates sodium ion influx across the cell membrane, initiating the fast upstroke of the cardiac action potential and enabling electrical signal propagation throughout the heart 1. This channel is predominantly expressed in myocardial cells and is essential for normal cardiac electrical conduction, including formation of the infranodal ventricular conduction system 1. SCN5A mutations cause multiple inherited cardiac arrhythmia syndromes characterized by altered channel function. Loss-of-function mutations are associated with Brugada syndrome and conduction disease, while gain-of-function mutations cause Long QT syndrome type 3 2. SCN5A variants are found in approximately 20-25% of Brugada syndrome patients, and their presence is associated with increased arrhythmic risk (odds ratio 2.14) compared to mutation-negative patients 3. Beyond arrhythmias, recent studies reveal Nav1.5 possesses non-electrogenic functions affecting cardiac structural integrity and cardiomyopathy development 4. Additionally, SCN5A expression extends to extracardiac tissues, where it influences epilepsy, gastrointestinal motility, and innate immune responses 4. Alternative promoter usage and splicing generate transcript diversity, providing additional regulatory mechanisms for Nav1.5 expression 5.