PURPOSE OF REVIEW: Sudden cardiac death in patients without structural heart 
disease remains a challenge in diagnostics and risk stratification. Genetically 
determined arrhythmias are a potential cause for a primary electrical disease. A 
recently discovered primary electrical disease is discussed.
RECENT FINDINGS: The inherited short QT syndrome is a recently recognized 
genetic condition, which is associated with atrial fibrillation, syncope and/or 
sudden cardiac death. Attention has been focused on diagnostic ECG features, the 
identification of underlying mutations and mechanisms of arrhythmogenesis.
SUMMARY: The short QT syndrome is clinically associated with atrial 
fibrillation, syncope and sudden cardiac death. A shortened QT interval (QTc 
<360 ms) and reduced ventricular refractory period together with an increased 
dispersion of repolarization constitute the potential substrate for reentry and 
life-threatening ventricular tachyarrhythmia. To date, gain-of-function 
mutations in KCNH2, KCNQ1, KCNJ2, encoding potassium channels and 
loss-of-function mutations in CACNA1C and CACNB2b, encoding L-type calcium 
channel subunits have been identified. The therapy of choice is the implantable 
cardioverter defibrillator in symptomatic patients. Quinidine has been shown to 
prolong the QT interval and to normalize the effective refractory periods of the 
atrium and ventricle in patients with short QT-1 syndrome.