KCNH2 and familial long QT syndrome: Type 2 LQTS (LQT2) is the second most prevalent form of congenital LQTS and is due to mutations in KCNH2, which encodes the α subunit of the Kv11.1 (hERG) channel responsible for conducting the rapid delayed rectifier potassium current (IKr) in cardiomyocytes (Curran et al., 1995).