Analysis of the relation between complexity and multifractality in cardiac inter-beat intervals time series

摘要

Multifractal spectrum has been used as indicative of complexity of time series, the broader the spectrum, the richer and more complex is the structure with a higher degree of multifractality. There is a loss of multifractality of physiological time series when the subject to which these time series belong is not healthy. So time series from subjects with a pathological condition show a clear loss of complexity. In this work we discuss how to characterize the complexity of time series by using the degree of multifractality, in particular, heartbeat interval time series. We observe a loss of multifractality in patients with congestive heart failure, mainly in the sleep phase; we try to explain this loss of multifractality as a loss of complexity produced by the appearance of periodicities in heartbeat interval time series. These periodicities were detected by using the Higuchi's fractal dimension method.