[What studies should be done in syncope?].

Fainting (short loss of consciousness) is a frequent reason for a consultation in a general practitioner's or cardiologist's office. Four main causes are recognized commonly: cardial with auriculo-ventricular block and arrhythmias, vascular in particular vaso-vagal syncopes, neurologic and other causes. In 38 to 47% of the patients no etiology is found: these are syncopal attacks of unknown origin. The first diagnostic step comprises noninvasive investigations. A 24-hour recording of the ECG or a 'long strip' improve the diagnostic rate by 10%. They are particularly useful for sick sinus syndromes. The head-up tilt-test has been developed recently. It is very useful for detection of vagovasal syncope and permits to understand the pathophysiology and the therapeutic consequences of these disorders. This test plays a particular role for the diagnosis of syncopes of unknown causes and shows in 24 to 75% of the cases pathologic results. Patients at high risk for ventricular arrhythmia can be recognized by ECG with high amplification. Doppler investigation of the neck vessels, however, seems to be of low diagnostic value in syncopes. Invasive measures are the last line resort. Electrophysiologic studies provide criteria that are well defined. They are useful for detection of ventricular dysrhythmias and conduction disorders. This latter approach is reserved to patients with negative noninvasive tests and in particular with cardiopathy. The approach to syncope and the power of noninvasive and invasive tests is thus well established. However, in a certain number of patients the cause for fainting is not disclosed. Fortunately mortality is low in this particular group.