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Type: Journal article
Title: Entropy analysis of RR and QT interval variability during orthostatic and mental stress in healthy subjects
Author: Baumert, M.
Czippelova, B.
Ganesan, A.
Schmidt, M.
Zaunseder, S.
Javorka, M.
Citation: Entropy: international and interdisciplinary journal of entropy and information studies, 2014; 16(12):6384-6393
Publisher: MDPI AG
Issue Date: 2014
ISSN: 1099-4300
Statement of
Mathias Baumert, Barbora Czippelova, Anand Ganesan, Martin Schmidt, Sebastian Zaunseder, and Michal Javorka
Abstract: Autonomic activity affects beat-to-beat variability of heart rate and QT interval. The aim of this study was to explore whether entropy measures are suitable to detect changes in neural outflow to the heart elicited by two different stress paradigms. We recorded short-term ECG in 11 normal subjects during an experimental protocol that involved head-up tilt and mental arithmetic stress and computed sample entropy, cross-sample entropy and causal interactions based on conditional entropy from RR and QT interval time series. Head-up tilt resulted in a significant reduction in sample entropy of RR intervals and cross-sample entropy, while mental arithmetic stress resulted in a significant reduction in coupling directed from RR to QT. In conclusion, measures of entropy are suitable to detect changes in neural outflow to the heart and decoupling of repolarisation variability from heart rate variability elicited by orthostatic or mental arithmetic stress.
Keywords: QT variability; heart rate variability; stress; sympathetic; complexity
Rights: © 2014 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (
DOI: 10.3390/e16126384
Grant ID:
VEGA 1/0059/13
VEGA 1/0087/14
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