ASSESSMENT OF AUTONOMIC NERVOUS FUNCTION BY POWER SPECTRAL-ANALYSIS OF HEART-RATE-VARIABILITY IN THE HORSE

We studied power spectral analysis of heart rate (HR) variability in t he horse, with the hypothesis that the quantitative information provid ed by the spectral analysis of HR variability reflects the interaction between sympathetic and parasympathetic regulatory activities. For th is purpose, electrocardiogram, blood pressure (BP) and respiratory (Re sp) waveform were simultaneously recorded from Thoroughbred horses (3- 5 years old) and analyzed by power spectrum. There were two major spec tral components at low-frequency (LF) and high-frequency (HF) bands fo r HR variability. The peak of Resp variability clearly occurred at the HF range. in contrast to Resp variability, the power spectra of BP va riability occurred at lower frequencies, The maximum coherence between HR and Resp variabilities and HR and BP variabilities occurred at sim ilar to 0.15 and similar to 0.03 Hz, respectively. These relationships were similar to the ensemble spectra, On the basis of these data, we have defined two frequency bands of interest: LF (0.01-0.07 Hz) and HF (0.07-0.6 Hz). Therefore, we believe that power spectral analysis of HR variability provides a very powerful technique for assessing autono mic nervous activity in the horse.