Gutron treatment of patients suffering from essential orthostatic hypotony. Part Two--Autonomic system investigation.

Neurovegative control of circulatory system in essential orthostatic hypotony (EOH) is not well recognized. Therefore, in group of 9 patients (pts) with EOH treated with midodrine (Gutron, Gu) 5 mg i.v. we performed a study of sympathovagal balance, based on heart rate variability (HRV) analysis. From computer-assisted tachograms we calculated standard deviation of 512 sinus cycles length (SD-SCL) and from power spectral analysis by fast Fourier transformation we derived: amplitudes of high frequency (HF, 0.15-0.35 Hz) and low frequency (LF, 0.05-0.15 Hz) spectra, percentage of power of HF and LF spectra and their ratio, named vegetative control coefficient (VCC, %LF:%HF). Results were compared to that received from control group (11 volunteers). We found that EOH-pts presented lower amplitude of HF, especially after Gu, a lack of increment of %LF irrespective to treatment and higher VCC, which normalized to control value after Gu. We stated that: 1) both branches of autonomic system are disturbed in EOH-patients; 2) Gutron shifts sympatho-vagal balance from initial resting sympathicotomy into parasympathetic predominance.