The Effects of the Firing Characteristics on the Power Density Spectrum of Electrocardiographic Signal

The effects of the firing characteristics, especially of the heart rate variability (HRV) which is characterized by the standard deviation of R-R intervals, on the power density spectrum (PDS) of electrocardiographic (ECG) signal are investigated based on a point process model. The theoretical analysis supported by experiments and simulations shows that the interaction between the R-R interval statistics and the ECG complex results in distinct peak and dip at the first and second harmonics of mean heart rate, respectively, in the PDS of the ECG signal. Furthermore, the HRV greatly affects the sharpness and the number of distinct peaks in the ECG power spectrum. In addition, different point processes of ECG signals would cause variations in the PDS, however, common characteristics can be extracted and quantified by using a newly proposed parameter, summedpeak-distinction (SPD), of the spectrum. It is observed that the SPD is highly related to the HRV and can reflect the relationship among HRV, mean heart rate and the ECG complex. More experiments should be carried out combined with an appropriate theoretical framework for better understanding of the possible interaction between cardiac dynamics and autonomic nervous system (ANS) for clinical applications.