Long QT syndrome (LQTS) is a rare inherited or acquired heart condition in which delayed repolarization of the heart following a heartbeat increases the risk of episodes of torsades de pointes (TdP, a form of irregular heartbeat that originates from the ventricles).
These episodes may lead to palpitations, fainting, and sudden death due to ventricular fibrillation.
Episodes may be provoked by various stimuli, depending on the subtype of the condition.
rs10494366, a SNP in the NOS1AP gene encoding the nitric oxide synthase I adaptor protein, accounts for some of the variation seen in abnormal heart rhythms, in particular, the QT interval.
Based on studies totaling ~4,000 individuals of Caucasian ancestry, homozygotes for one allele have shorter QT intervals, while homozygotes for the other allele have a longer QT interval.