[Basal autonomic tone in patients with vasovagal syncope]

Autonomic nervous mechanisms play an important part in the pathogenesis of vasovagal syncope. The objective of the submitted work was investigation of the autonomic tone in patients with vasovagal syncope. The authors examined a group of 39 patients with vasovagal syncope (patients with a positive head-up tilt test (HUT) from a group of patients with syncopes of unknown origin--12 men, 27 women, mean age 34 years), a control group of 21 patients with negative HUT from the group of patients with syncope of unknown etiology (11 men, 10 women, mean age 32 years) and a control group of 14 healthy subjects without history of syncope (14 men, mean age 26 years). The autonomic tone was evaluated on the basis of statistical and spectral analysis of heart rate variability. The basal autonomic tone in patients with vasovagal syncope does not differ from that in normal subjects. The increased vagal tonus probably is not a predisposing moment for the development of vasovagal syncope. Assessment of the basal autonomic tone does not make prediction of the results of the head-up tilt test possible.