title: Chronographic Imprint of Age-Induced Alterations in Heart Rate Dynamical Organization.
abstract: Beat-to-beat changes in the heart period are transformed into a network of increments between subsequent RR-intervals, which enables graphical descriptions of short-term heart period variability. Three types of such descriptions are considered: (1) network graphs arising from a set of vertices and directed edges, (2) contour plots of adjacency matrices A, representing the networks and transition matrices T, resulting from A, and (3) vector plots of gradients of the matrices A and T. Two indices are considered which summarize properties of A and T: the approximate deceleration capacity and the entropy rate. The method, applied to time series of nocturnal RR-intervals recorded from healthy subjects of different ages, reveals important aspect of changes in the autonomic activity caused by biological aging. Independent of the subject's age, following accelerations, a pendulum-like dynamics appears. With decelerations, this dynamics develops in line with the subject's age. This aging transition can be graphically visualized by vectors connecting the maxima of the transition probabilities of T, which, metaphorically, resemble a chronometer or the hands of a clock.
authors.affiliation: Institute of Theoretical Physics and Astrophysics, University of Gdańsk , Gdańsk , Poland.
authors.forename: Danuta
authors.initials: D
authors.lastname: Makowiec
authors.affiliation: Institute of Theoretical Physics and Astrophysics, University of Gdańsk , Gdańsk , Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Wejer
authors.affiliation: Faculty of Applied Physics and Mathematics, Gdańsk University of Technology , Gdańsk , Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Kaczkowska
authors.affiliation: 1st Chair & Clinic of Cardiology, Medical University of Gdańsk , Gdańsk , Poland.
authors.forename: Marta
authors.initials: M
authors.lastname: Żarczyńska-Buchowiecka
authors.affiliation: Institute of Theoretical Physics and Astrophysics, University of Gdańsk , Gdańsk , Poland ; RIKEN Brain Science Institute , Wako-shi , Japan ; Graduate School of Education, The University of Tokyo , Tokyo , Japan.
authors.forename: Zbigniew R
authors.initials: ZR
authors.lastname: Struzik
keywords: aging; deceleration capacity; entropy rate; short-term heart rate variability