The novel KCNQ1S338F mutation segregated with prolonged QT interval and torsade de pointes; the second variant, F339S, was associated with fetal bradycardia and prolonged QT interval, but no other clinical events.
KCNQ1 and KCNH2 are the two most common potassium channel genes causing long QT syndrome (LQTS), an inherited cardiac arrhythmia featured by QT prolongation and increased risks of developing torsade de pointes and sudden death.
High concentrations of intravenous nicorandil, a potassium channel opener, have been shown to be capable of decreasing QT and TDR, and preventing TdP in LQT1 and LQT2 but not in LQT3.
A decrease of IKr or IKs by mutations in either HERG, KvLQT1, or KCNE family results in inherited long QT syndrome (LQTS) with high risk for Torsades de pointes (TdP)-type polymorphic ventricular tachycardia and ventricular fibrillation.
Propranolol (1 micromol/L), a beta blocker, completely prevented the effect of isoproterenol to persistently or transiently increase TDR and to induce TdP in the LQT1 and LQT2 models, but facilitated TdP in the LQT3 model.