In approximately 10-20% of all sudden deaths no structural cardiac abnormalities 
can be identified. Important potential causes of sudden cardiac deaths in the 
absence of heart disease are primary electrical diseases such as Brugada 
syndrome, long QT syndrome (LQTS), short QT syndrome and catecholaminergic 
polymorphic ventricular tachyarrhythmias. Each of these cardiac channelopathies 
is charaterized by unique genetic and clinical features. The resting ECG and the 
ECG under exercise are pivotal for the diagnosis of ion channel diseases. 
Molecular genetic screening can reveal underlying mutations in a variable degree 
among the cardiac ion channel diseases in up to 70% (LQTS) and may identify 
individuals with incomplete penetration of the disease. In patients with primary 
electrical diseases specific clinical triggers for arrhythmic events such as 
syncope or sudden cardiac death have been identified including exercise, 
strenuous activity, auditory stimuli or increased vagal tone. The significance 
of programmed ventricular stimulation is at present unclear concerning risk 
stratification in patients with Brugada syndrome and short QT syndrome and of no 
significance in long QT syndrome and catecholaminergic polymorphic ventricular 
tachycardias. The success of medical therapy remains modest for prevention of 
sudden cardiac death and may necessitate the insertion of an implantable 
cardioverter. However, side effects with inappropriate therapies in this patient 
group with often young and active individuals have to be encountered. More 
insights into the arrhythmogenesis is critical for future development of 
effective medical treatment strategies.