KCNH2 and long QT syndrome 1: In the case of LQT type 1 (LQT1), the mutations are present in the KCNQ1 gene which encodes the α-subunit of the slow component of the delayed rectifier potassium current (Kv7.1) (Wang et al. 1996), whereas LQT2 is caused by mutations of the KCNH2 gene which encodes the α-subunit of the rapid component of the delayed rectifier potassium current (Kv11.1) (Sanguinetti et al. 1995).