SCN5A and long QT syndrome 3: Among the 15 current forms of LQTS, long QT syndrome type 3 (LQT3) is caused by inherited variants of SCN5A accompanied with an increasing risk to sudden death during rest or sleep and electrocardiographically characterized by prolonged QT/QTc interval, accentuated QT dispersion, late onset of T wave and frequent prominent U wave.