We study the long-range correlations of heartbeat fluctuations with the method of diffusion entropy. We show that this method of analysis yields a scaling parameter δ that apparently conflicts with the direct evaluation of the distribution of times of sojourn in states with a given heartbeat frequency. The strength of the memory responsible for this discrepancy is given by a parameter ϵ2, which is derived from real data. The distribution of patients in the (δ, ϵ2)-plane yields a neat separation of the healthy from the congestive heart failure subjects.
@article{arxiv.cond-mat/0107597,
title = {Memory beyond memory in heart beating: an efficient way to detect pathological conditions},
author = {P. Allegrini and P. Grigolini and P. Hamilton and L. Palatella and G. Raffaelli},
journal= {arXiv preprint arXiv:cond-mat/0107597},
year = {2009}
}