- "Asymptomatic patients" will be defined as patients without a history of cardiac arrest, a history of "arrhythmic syncope" or a history of "suspected arrhythmic syncope." Arrhythmic syncope" is a syncope occurring during documented ventricular tachyarrhythmias. "Suspected arrhythmic syncope" is syncope without documented arrhythmias believed to be caused by a tachyarrhythmia based on clinical judgment. In other words, patients with typical vagal syncope will be counted as "asymptomatic" and will be accepted to the registry whereas patients with a clinical history suggesting "syncope other than vagal syncope" will not be accepted to this Registry.