Head-up tilt test with clomipramine challenge in vasovagal syndrome--a new tilt testing protocol.

PURPOSE The aim of the study was to randomly compare clomipramine, used as a challenge-agent during head-up tilt test, with isoproterenol, used in the conventional test, in patients with vasovagal syndrome. SUBJECTS AND METHODS The serotonergic re-uptake inhibitor clomipramine was infused (5mg in 5min) at the start of head-up tilt test (Clom-HUT) in 126 patients (mean age 41+/-16 years) with positive history of recurrent neurocardiogenic syncope, and in 54 healthy control subjects (mean age 46+/-15 years). All subjects had also been tested with a conventional 60 degrees head-up tilt test (Con-HUT) for 30 min and, if negative, isoproterenol infusion was performed at the end of the test. The two tests were performed in a random order with a 24-h interval between them. RESULTS Fifty-two of the 126 patients (41%) and two of the 54 controls had a positive response to Con-HUT. In the Clom-HUT the proportion of patients who experienced a positive response increased to 83% (105 subjects), while this happened only to four control subjects. The predictive accuracy of Clom-HUT increased compared to Con-HUT from 58 to 86%, respectively. CONCLUSION The results indicate an increased responsiveness of central serotonergic neural system in subjects with vasovagal syndrome, the activation of which leads to sympathetic withdrawal. The use of clomipramine infusion during tilt test seems to improve considerably its diagnostic value.