Harmonic Analysis of Electrical Activity of the Autonomic Nervous System in Dorsal Perirenal Lumbar Regions in Healthy Volunteers and Patients with Arterial Hypertension.

To non-invasively assess the activity of the autonomic nervous system (ANS) and the pulsatile activity of arteries in the perirenal dorsal lumbar regions, electrical bioimpedance (BI) and biopotentials (BP) were recorded in healthy volunteers and patients with arterial hypertension (AH). Signals were processed using harmonic (Fourier) analysis to determine the effective values (rms) of spectral peaks for BI (MR, THR) and BP (MV, THV) in the Mayer (M) frequency range (0.03-0.2 Hz) and the Traube-Hering (TH) frequency band of a controlled respiration rate (0.3-0.4 Hz), which presumably reflect sympathetic and parasympathetic activity, respectively. The pulsatile activity of arteries was determined by the total effective value (TPrms) of four pulsatile harmonics. The indices of the sympathetic-parasympathetic balance were calculated as the ratios of MR/THR (for BI) and MV/THV (for BP). In healthy participants, the active orthostatic test significantly increased THR, MR, TPrms-1, and MV, which reflected increased activity of sympathetic (MR, TPrms-1, MV) and parasympathetic (THR) systems while maintaining overall autonomic balance. The spectral parameters of BI and BP were presented with normalized radar charts (RC). In patients with controlled AH, the median RCs were located within the interquartile range of RC of the healthy group indicating adequate drug therapy. In contrast, individual RCs of some patients with uncontrolled or refractory AH were outside this range, indicating the need to correct drug therapy or feasibility of renal denervation if pharmacotherapy fails. The advanced method enables the assessment of ANS activity in patients with AH of varying severity. It is concluded that harmonic analysis of electrical signals in human perirenal regions is a valuable non-invasive tool for evaluating local activity of ANS under physiological conditions and in AH patients.