The underlying genetic defects of long QT syndrome were first described in the 1990s, identifying three genes (KCNQ1, KCNH2, and SCN5A) that encoded ion channel proteins (KvLQT1, hERG, and NaV 1.5) responsible for transmembrane ion currents critical to cardiac depolarization and repolarization. The gene discussed is SCN5A; the disease is Prolonged QT interval.