Evaluation of Fractal Properties of Long Term Heartbeat Fluctuations of Spinal Cord Injury Patients

Abstract

It is known that very low frequency of R-R interval (RRI) is induced by the autonomic nervous system, and it is useful to evaluate the property of autonomic control of heart. Therefore, in this study, we analyze long term heartbeat fluctuations of spinal cord injury patients with fractal analysis to evaluate their fractal properties of autonomic nervous system. First, fractal property is obtained using Detrended Fluctuation Analysis. As a result, we find that spinal cord injury subjects have the same correlated volatility of healthy subjects. Second, we apply space-scale correlation using wavelet to their heart rate variability of RRI to quantify local fractal property including cascade structure. In the result, it is found that correlation of spinal cord injury patients is significantly higher than that of healthy subjects. These results present that the differences of circular dynamic state between spinal cord injury subjects and healthy subjects are not observed in the global fractal properties but in the heteroscedasticity.