The head-up tilt table test in patients with syncope of unknown origin.

Forty patients with recurrent syncopal episodes of uncertain etiology were evaluated with a 60-degree head-up tilt table test for 60 minutes. There were 21 men and 19 women, with a mean age of 36 +/- 19 years, a mean of 7.6 syncopal episodes per patient, and a mean duration of symptoms of 4.2 +/- 6 years. Twelve patients had evidence of organic heart disease. Ten control subjects with no history of syncope were studied similarly. Syncope did not occur in any of these controls. Syncope occurred in 15 patients (37.5%) after a mean standing time of 42 +/- 12 minutes. Syncope was due to a typical vasovagal reaction in 11 patients and to hyperventilation in three patients. One last patient fainted without changes in heart rate or blood pressure. In each case, symptoms during the test resembled those previously experienced.