Autonomic heart rate control by multifractal tools

Heart rate variability of people suffering from the left ventrical systolic dysfunction and healthy ones is considered in terms of multifractal analysis in order to investigate the scaling properties in the low, very low and ultra low frequency bands of standard power spectral analysis. Two methods: Wavelet Transform Modulus Maxima and Multifractal Detrended Fluctuation Analysis, are used to assess multifractal properties. They are applied to two types of signals: a sequence of RR intervals and a sequence of moments in time when subsequent heart beats occur (integrated RR-intervals). The increased activation of the sympathetic nervous system caused by left ventricle systolic dysfunction is detected directly in both signals in the low frequency band. In the ultra low frequency band a monofractal-type of dependences is found suggesting that driving process of autonomic control is close to a monofractal one.