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We propose a new band-phase-randomized surrogate data method to evaluate the chaotic dynamics in the high (HF) and low frequency (LF) bands of heart rate variability (HRV) in healthy subjects. The chaotic strength of normal HRV as assessed by a noise titration assay completely vanished when its power spectrum was phase-randomized over the entire frequency band or the HF band alone, but not the LF...
A wide variety of methods based on fractal, entropic or chaotic approaches have been applied to the analysis of complex physiological time series. In this paper, we show that fractal and entropy measures are poor indicators of nonlinearity for gait data and heart rate variability data. In contrast, the noise titration method based on Volterra autoregressive modeling represents the most reliable currently...
Transient hyper-chaos with extraordinary high strength was observed in HRV of CHF patients by means of numerical titration method based on Volterra-Wiener series. In comparison with healthy subjects, RR series of CHF patients present sporadic impulses composed of normal, rather then premature beats. To illustrate such impulses and its relation to hyper-chaos, a sinoatrial node (SAN) model was developed...
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