Circadian aspects of apparent correlation dimension in human heart
rate dynamics.
Leeuwen, P. Van, H. Bettermann, U. An Der Heiden, H. C. Kmmell2.
EFMT, Research and Development Center for Microtherapy, 44799
Bochum, FRG, Department of Clinical Research,
Gemeinschaftskrankenhaus Herdecke, 58313 Herdecke, FRG, Center for
Nonlinear Dynamics, University of Witten/Herdecke, 58453 Witten,
FRG
APStracts 2:0020H, 1995.
Purpose of this study was to examine changes in complexity of cardiac
dynamics over 24 hours. Using Holter monitoring 27 24-hour ecg
recordings were obtained from 15 healthy subjects. For each recording
the apparent dimension DA was calculated for consecutive sections of
500 heart beats. These were used to determine nighttime and daytime
dimension, DAn and DAd, as well as their difference DDA. Mean 24h DA,
DAn and DAd were 5.9 0.3, 6.3 0.5 and 5.6 0.6, respectively. The
nighttime values were significantly higher than the daytime (p<0.001)
with a mean DDA of 0.6 0.7. Furthermore, 67% of the DDA values were
significantly different from zero at the 0.05 level. The results show
that dimension analysis may be applied to heart rate dynamics to
reveal circadian differences of heart rate complexity. We suggest
that the decreased complexity during daytime may result from the
synchronization of physiological functions. The increase in
complexity at night would then correspond to an uncoupling of these
functions during the regenerative period.
Received 2 August 1994; accepted in final form 27 January 1995.
APS Manuscript Number H0692.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 February 1995.