KCNH2 and familial long QT syndrome: The second most common subtype of LQTS involves a loss of function mutation in the gene KCNH2 (LQT2), located at 7q35-36, present in around 20% of patients with LQTS.9 This gene encodes the subunit Kv11.1 of the voltage-gated inward rectifying potassium channel, another critical component in cardiac repolarization.9 Mutations in KCNH2 similarly disrupts the normal repolarization process, resulting on a T wave that appears asymmetrical and notched, often with a low amplitude.