Human ether-a-go-go-related gene (HERG) encodes the HERG ion channel, which is a member of the voltage-dependent potassium channel (Kv) family. HERG mutations reduce the outward flow of potassium during repolarization and elongate the QT interval leading to polymorphic ventricular tachycardia, cardiac syncope, and sudden death. This evidence concerns the gene KCNH2 and polymorphic ventricular tachycardia.