[How I study syncope].

The diagnosis of the cause of a syncope is based, above all, on the basis of a careful clinical history obtained from the patient or from persons who attended one of the episodes of loss of consciousness. It should also include a careful clinical examination comprising an electrocardiogram and, most often, an echocardiogram. The selection of further investigations should be guided by the existence or absence of an underlying cardiac disease. In the presence of a patent cardiac disease, one should first try to detect a disorder of cardiac rhythm (Holter, mini-Holter, possibly invasive electrophysiology); a dysfunction of the autonomic regulation of the cardiovascular system should only be considered in a second step (Tilt table test). The sequence of investigation should be reversed when syncope occurs in a patient without underlying cardiac disorder.