<unk>  is the third most common subtype of long QT syndrome, occurring in 5-10% of LQTS cases. It is most commonly associated with cardiac events that occur during sleep. It is also associated with Brugada syndrome and sudden infant death syndrome. This subtype is highly likely to show shortening of the QT interval in response to administration of mexilitine. This subtype is caused by a mutation in the SCN5A gene on chromosome 3, which affects the sodium channels. The slow leakage of sodium into the cells causes cell membrane instability, and a prolonged QT interval on EKG.
LQT3
LQT1
LQT2
LQT4
LQT5
LQT6
LQT10
LQT8