POWER SPECTRUM ANALYSIS OF HEART-RATE-VARIABILITY IN GUILLAIN-BARRE-SYNDROME - A LONGITUDINAL-STUDY

Power spectrum analysis of heart rate variability was repeatedly carri ed out on 13 patients with Guillain-Barre syndrome for up to I year by Fourier analysis of regular beat-to-beat (R-R) intervals which were r ecorded for 5 min, converted into a continous function by linear inter polation and resampled at 5 Hz. Low-frequency (LF) power (reflecting a mixture of parasympathetic and sympathetic activity) and high-frequen cy (HF) power (reflecting parasympathetic tone) were calculated by int egrating the spectra from 0.04 to 0.15 Hz and from 0.15 to 0.4 Hz, res pectively. At the height of the disease, the HF component was signific antly decreased. The LF : HF ratio, which has been suggested to be an indicator for sympathetic activity, was increased compared with the fo llow-up value after I year Both measures returned to normal gradually over time. Pooled-data analysis suggested that both HF and LF power we re significantly related to the responses of standardized parasympathe tic function tests, while the LF: HF ratio was inversely correlated wi th sympathetic vasomotor activity. In patients presenting with tachyca rdia, LF and HF power were strikingly decreased compared with patients with normal heart rates, while in patients showing vagal over-reactiv ity, the power of both spectral bands was significantly increased. The results suggest that spectral analysis of heart rate variability is u seful for investigating the cardiovascular neural regulation in patien ts with Guillain-Barre syndrome. In this disorder the sympathovagal ba lance is clearly shifted to sympathetic predominance at the height of the disease.