Spectral Analysis of Arterial Blood Pressure in the Rat During Atrial Fibrillation

This paper describes the development of a systems identification protocol in the rat for use in studies of the dynamics of blood pressure control The method is based on Taylor's canine random heart model and employs electrically induced atrial fibrillation to generate random fluctuations in arterial blood pressure. In order to evaluate the utility of the protocol, recordings of pulsatile blood pressure were obtained from the femoral arteries of anesthetized rats during atrial fibrillation. The data were reduced to spectral density function estimates using standard techniques of discrete spectral analysis. The results indicate that during atrial fibrillation, the time course of arterial blood pressure constitutes a white noise source in the frequency band from 0.01 to 10 Hz, in sharp contrast to the concentration of energy from the normal cardiac cycle into narrow frequency bands within this range. Thus, the protocol should be useful in the analysis of the dynamics of most physiological processes which respond to changes in blood pressure.