Tilt-induced pseudosyncope.

Using the head-up tilt test (HUTT) we evaluated 986 consecutive patients affected by unexplained syncope. In 266 patients the test induced bradycardia and/or hypotension resulting in syncope or presyncope, thus allowing a diagnosis of neurally mediated syncope. In three other patients (0.3% of the entire population and 1% of the all positive tests) HUTT provoked loss of consciousness despite no significant change in heart rate and/or blood pressure. In all three cases unconsciousness was prolonged and no pathological finding was present except lack of response. This phenomenon has been defined as 'pseudosyncope' and related to psychiatric illness. Pseudosyncope induced by HUTT reproduced the clinical events, so the test outcome was considered a true positive response. Our experience suggests that HUTT may contribute to the recognition of psychiatric disorder in some patients affected by unexplained syncope.