Sympatho-vagal activity described by the complex and deterministic behavior of heart rate variability

Presents new variables to improve the characterization of autonomic nervous system function by analyzing heart rate variability. These new variables are the effective energies (Efe), defined from the Hartley-Shannon theorem, in the three frequency bands Efe/sub VLF/ (0-0.04 Hz), Efe/sub LF/ (0.04-0.15 Hz) and Efe/sub HF/ (0.15-0.45 Hz). The effective energy is obtained using a complexity measure of the R-R signal (the Shannon entropy) and the instantaneous frequency, defined from the time-frequency representation. Two groups of subjects have been studied: 53 patients with idiopathic dilated cardiomyopathy (IDC) and 64 healthy people considered as the control group. The effective energies obtained in the VLF, LF and HF bands presented statistically significant differences (p<0.005) characterizing IDC patients. The instantaneous frequency contained in the VLF band was lower in IDC patients than in the control group. The main complexity differences given by the analyzed entropies were obtained in the LF and HF bands.