The Nav1.5 sodium channel, encoded by the SCN5A gene, is the primary voltage-gated sodium channel in the heart. It is crucial for initiating and propagating cardiac action potentials by allowing rapid sodium ion influx. Its function is vital for normal heart rhythm, and mutations are linked to various arrhythmias and channelopathies, including Long QT Syndrome (LQT3) and Brugada Syndrome.