Heart Rate Variability in the Prognosis of Tilt-Testing Results

Study aim was assessment of dynamics of spectral parameters of heart rate variability (HRV) during the Westminster and Italian protocols of tilt-test (TT). We included in this study 114 patients with recurrent vasovagal syncope (VVS). Basing on TT results we distinguished 4 groups of patients: with positive result of the Westminster protocol (WPTT) (group 1, n=30); with negative result of WPTT (group 2, n=23); with positive result of the Italian protocol (IPTT) (group 3, n=44); with negative result of IPTT (group 4, n=11). Control group comprised 14 healthy persons without history of syncope. Spectral parameters of HRV were analyzed in 3 five minutes intervals (before TT in horizontal position, during first and last 5 minutes of orthostasis). Structure of vasovagal responses was similar for all TT protocols used. In lying position in patients of groups 1-3 lower values of LF1 and LF1/HF1were registered, as well as high values of HF1 compared with the control group and patients with negative results of IPTT. Initial stage of TT in patients with positive result of WPTT (group 1) was characterized by almost twofold increase of LF values (n.u.) and decrease of HF parameters (n.u.) compared with other patients. In the group 1 during the second period LF2/HF2 ratio increased more than 5 times, and in the third period value of LF3/HF3 increased more than 6 times compared with baseline data. Thus even in baseline state before TT patients with VVS had disturbances of the sympatho-vagal balance. Positive response during WPTT was characterized by most pronounced HRV dynamics compared with IPTT and the control group. It is suggested that vasovagal reactions during IPTT can be initiated by drug induced vasodilation.