Background: Head-up tilt testing (HUT) plays a pivotal role in the management of vasovagal
syncope (VVS). Heart rate variability (HRV) is a well-known method used for noninvasive
evaluation of autonomic nervous system activity. However, different results have been obtained
in studies that have evaluated the HRV response to HUT in patients with VVS.
Methods: One hundred fourteen patients with recurrent VVS were enrolled in the study.
According to the results of HUT, patients were divided into five groups: positive (n = 30) and
negative (n = 23) Westminster; positive (n = 44) and negative (n = 11) Italian. Fourteen
healthy volunteers with no history of syncope comprised the control group. Spectral indices of
HRV variability were analyzed for three short-term intervals.
Results: Both protocols showed similar distribution of responses to tilt-testing. In the supine
position, significant differences were observed between patients from groups 1, 2 and 3 in
comparison with the control and Italian negative groups. They had significantly lower initial
results of LF1 [nu] and LF1/HF1 ratio, and higher HF1 [nu] values. The onset of HUT in
patients with positive Westminster protocol was characterized by an almost two-fold increase
in LF [nu] and decrease in HF [nu] compared to all other patients. LF2/HF2 ratio in the
Westminster positive group had increased more than five times since the baseline level, while
during the last period, LF3/HF3 ratio had increased more than six times.
Conclusions: Patients with VVS have disturbed sympathovagal balance at rest. Our data
suggests that the results of HUT could be predicted by analyzing the spectral parameters of
HRV during the first five minutes of the test. The reaction to orthostasis in patients with
syncope during the Westminster protocol was more severe compared to the Italian protocol
group and the control group. Vasovagal response during the Italian protocol may be triggered
by drug-induced vasodilatation. (Cardiol J 2011; 18, 5: 521–526
