Mutations in the cardiac potassium channel HERG (KCNH2) cause chromosome 7-linked long QT syndrome (LQT2) characterized by a prolonged QT interval, recurrent syncope and sudden cardiac death.
KCNE2 encodes MinK-related peptide 1 (MiRP1), a subunit of the cardiac potassium channel I(Kr) that has been associated previously with inherited LQTS.
An exercise stress test was performed in 23 patients with a pore region mutation and in 22 patients with a C-terminal end mutation of the cardiac potassium channel gene causing LQT1 type of long QT syndrome (KVLQT1 gene), as well as in 20 patients with mutations of the cardiac potassium channel gene causing LQT2 type of long QT syndrome (HERG gene) and in 33 healthy relatives.
KVLQT1, the gene encoding the alpha-subunit of a cardiac potassium channel, is the most common cause of the dominant form of long-QT syndrome (LQT1-type), the Romano-Ward syndrome (RWS).