The past 2 decades have witnessed the emergence of many disease states related 
to ion-channel disorders, the so-called "channelopathies," usually associated 
with structurally normal hearts. The initial emphasis was directed toward the 
congenital long QT syndrome and the Brugada syndrome. Recently, the hereditary 
short QT syndrome has emerged as yet another rare channelopathy. This autosomal 
dominant syndrome can afflict infants, children, or young adults; often a 
remarkable family background of sudden cardiac death is elucidated. The 
electrocardiogram is characterized by a strikingly short QT interval (typically 
<320 milliseconds); virtual absence of the ST segment; and tall, peaked, 
narrow-based T waves. There is a marked propensity for paroxysmal atrial 
fibrillation, and increased risk for sudden cardiac death from ventricular 
tachyarrhythmias. At electrophysiology study, short atrial and ventricular 
refractory periods are found, with easily inducible atrial fibrillation and 
polymorphic ventricular tachycardia with programmed electrical stimulation. 
Gain-of-function mutations in 3 genes encoding potassium channels have been 
identified, which explain the abbreviated repolarization seen in this condition. 
The suggested treatment is an implantable cardioverter-defibrillator, though the 
possibilities of inappropriate shocks have caused some concern, especially in 
younger patients. The ability of quinidine and disopyramide to prolong the QT 
interval has the potential to be effective pharmacological therapy for patients 
with short QT syndrome, but awaits additional confirmatory clinical data.