[Cardiac syncopes]

Cardiac causes explain 5 to 30% of the syncopes and their incidence increases with age. Prognosis is poor in case of misdiagnosis. Mechanical causes are related principally to obstruction of left ventricular outflow, and responsible for exertional syncope. Diagnosis is easy through clinical examination and echocardiography. Arrhythmic causes are due either to brady-cardia (diagnosed by surface electrocardiogram, 24-hour holter monitoring and electrophysiologic study in patients with bundle branch block) or to supraventricular or ventricular tachycardia. Arrhythmic syncope is easily prevented by antiarrhythmic drugs or non medical treatments such as radiofrequency ablation of tachycardia, pace-maker or defibrillator implantation.