Causal relationship between heart rate and arterial blood pressure variability signals

A method is described which allows the determination of the causal relationship existing between two biological signals (heart rate and arterial blood pressure variability signals) which carry information about the role of control elicited by the autonomic nervous system. This method assumes an autoregressive (AR) model for the two signals to check the cross-correlation of the two residuals after AR identification. This information, together with the classical parameters of the spectral analysis (mean, variance, frequency and power in two typical bands, gain, phase and coherence) may provide a more precise evaluation of the complex mechanisms involved in the control of heart rate and blood pressure in numerous physiopathological situations.