title: Fractal fluctuations in cardiac time series.
abstract: Human heart rate, controlled by complex feedback mechanisms, is a vital index of systematic circulation. However, it has been shown that beat-to-beat values of heart rate fluctuate continually over a wide range of time scales. Herein we use the relative dispersion, the ratio of the standard deviation to the mean, to show, by systematically aggregating the data, that the correlation in the beat-to-beat cardiac time series is a modulated inverse power law. This scaling property indicates the existence of long-time memory in the underlying cardiac control process and supports the conclusion that heart rate variability is a temporal fractal. We argue that the cardiac control system has allometric properties that enable it to respond to a dynamical environment through scaling.
authors.affiliation: Army Research Office, Research Triangle, NC 27709-2211, USA. westb@aro-emh1.army.mil
authors.forename: B J
authors.initials: BJ
authors.lastname: West
authors.forename: R
authors.initials: R
authors.lastname: Zhang
authors.forename: A W
authors.initials: AW
authors.lastname: Sanders
authors.forename: S
authors.initials: S
authors.lastname: Miniyar
authors.forename: J H
authors.initials: JH
authors.lastname: Zuckerman
authors.forename: B D
authors.initials: BD
authors.lastname: Levine
mesh_terms: D000328:Adult; D002320:Cardiovascular Physiological Phenomena; D005246:Feedback; D005260:Female; D017709:Fractals; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008433:Mathematics; D008955:Models, Cardiovascular; D015233:Models, Statistical; D017711:Nonlinear Dynamics; D013997:Time Factors