POWER SPECTRAL-ANALYSIS OF HEART-RATE-VARIABILITY REFLECTS THE LEVEL OF CARDIAC AUTONOMIC ACTIVITY IN RABBITS

Power spectral analysis of heart rate (HR) variability was tested in c onscious rabbits to assess the reliability of this method for assessin g cardiac autonomic function in normal rabbits under resting condition s. Evaluation of power spectrum was performed in 5 rabbits under norma l resting conditions and after sympathetic, parasympathetic and combin ed sympathetic plus parasympathetic blockade. Rabbits were randomly as signed to undergo sympathetic (propranolol) or parasympathetic (methsc opolamine) blockade at the initial step followed by combined blockade. The power spectrum of heart-rate variability in rabbits was presented as one broad spectral component at frequencies mainly between 0 and 0 .5 Hz. This component was considerably modulated by both sympathetic a nd parasympathetic influences with substantial overlap of sympathetic- and parasympathetic-related components of the spectrogram. Neverthele ss, it was clearly shown that power of heart-rare variability at frequ encies from 0.4373 Hz to 0.5625 Hz was determined only by parasympathe tic influences, and sympathetic modulation of HR was presented mainly at frequencies from 0.0625 Hz to 0.1875 Hz. Spectral subcomponent anal ysis of the power spectrum of HR variability may be useful to follow c hanges in cardiac autonomic function in rabbits.