The Long QT and Brugada syndromes: causes of unexpected syncope and sudden cardiac death in children and young adults.

Inherited Long QT and Brugada syndromes cause syncope and sudden cardiac death due to ventricular tachyarrhythmias. Diagnosis may be difficult and the syncopal events are commonly misdiagnosed as neurally mediated (vaso-vagal) episodes or as "seizures". The details of the events (onset, offset, sequelae, precipitating factors) and knowledge of the ECG features are key to the correct diagnosis, and in assisting the neurologist in discriminating these two life-threatening disorders from neurally mediated (vaso-vagal) syncope and in discerning when a "seizure" might be due to a lethal cardiac arrhythmia. Very effective treatments are available and prompt, correct diagnosis and appropriate treatment are life-saving.