Table 1.

Clinical Characteristics in Common Genotypes of Congenital Long QT Syndrome

Characteristic	LQT1	LQT2	LQT3
Gene muted	KCNQ1 (=KvLQT1)	KCNH2 (=HERG)	SCN5A
Current affected	I_Ks	I_Kr	I_Na
Events occurring with emotional stress	Strong association	Moderate association	Weak association
Events occurring with exercise	Strong association	Weak association	Weak association
Other triggers	Diving	Loud noise	Sleep
		Rest	Rest
Events before the age of 10 (%)	40	16	2
Events before the age of 40 (%)	63	46	18
Median age at first event (years)	9	12	16
Efficacy of β-blockade to prevent events	Strong association	Moderate association	Weak association

LQT, long QT subtype; I_Ks, slowly activating potassium-delayed rectifier; I_Kr, rapidly activating potassium-delayed rectifier; I_Na, cardiac voltage-dependent sodium channel.