The
short QT syndrome is a new congenital entity associated with
familial atrial fibrillation and/or
sudden death or
syncope. Three different gain-of-function mutations in genes encoding for cardiac
potassium channels (KCNH2, KCNQ1, and KCNJ2) have been identified up to now to cause
short QT syndrome. The syndrome is characterized electrocardiographically by a shortened QTc interval less than 300 to 320 milliseconds and a lack of adaptation during increasing heart rates. During programmed electrical stimulation, atrial and ventricular effective refractory periods are shortened, and in a high percentage,
ventricular tachyarrhythmias are inducible.
Sudden cardiac death occurs in all age groups and even in newborns.
Therapy for choice seems to be the
implantable cardioverter-defibrillator because of the high incidence of
sudden death. However, ICD
therapy may be associated with an increased risk of inappropriate
therapies for T wave oversensing, which, however, can be resolved by reprogramming ICD detection algorithms. The impact of
sotalol,
ibutilide,
flecainide, and
quinidine on QT prolongation has been evaluated. But only
quinidine effectively suppressed gain-of-function in IKr, along with prolongation of the QT interval. Furthermore, in patients with a mutation in HERG (SQT1),
quinidine rendered
ventricular tachyarrhythmias noninducible and restored the QT interval/heart rate relationship toward a reference range. It may serve as an adjunct to ICD
therapy or as possible alternative treatment especially for children and newborns.