Assessment of cardiac autonomic modulation during graded head-up tilt by symbolic analysis of heart rate variability
Open Access
- 1 July 2007
- journal article
- Published by American Physiological Society in American Journal of Physiology-Heart and Circulatory Physiology
- Vol. 293 (1), H702-H708
- https://doi.org/10.1152/ajpheart.00006.2007
Abstract
Two symbolic indexes, the percentage of sequences characterized by three heart periods with no significant variations (0V%) and that with two significant unlike variations (2UV%), have been found to reflect changes in sympathetic and vagal modulations, respectively. We tested the hypothesis that symbolic indexes may track the gradual shift of the cardiac autonomic modulation during an incremental head-up tilt test. Symbolic analysis was carried out over heart period variability series (250 cardiac beats) derived from ECG recordings during a graded head-up tilt test (0, 15, 30, 45, 60, 75, and 90°) in 17 healthy subjects. The percentage of subjects showing a significant linear correlation (Spearman rank-order correlation) with tilt angles was utilized to evaluate the performance of symbolic analysis. Spectral analysis was carried out for comparison over the same series. 0V% progressively increased with tilt angles, whereas 2UV% gradually decreased. The decline of 2UV% was greater than the increase of 0V% at low tilt angles. Linear correlation with tilt angles was exhibited in a greater percentage of subjects for 0V% and 2UV% than for any spectral index. Our findings suggest that symbolic analysis performed better than spectral analysis and, thus, is a suitable methodology for assessment of the subtle changes of cardiac autonomic modulation induced by a graded head-up tilt test. Moreover, symbolic analysis indicates that the changes of cardiac sympathetic and vagal modulations observed during this protocol were reciprocal but characterized by different absolute magnitudes.Keywords
This publication has 19 references indexed in Scilit:
- Symbolic Dynamics of Heart Rate VariabilityCirculation, 2005
- Oscillatory patterns in sympathetic neural discharge and cardiovascular variables during orthostatic stimulus.Circulation, 2000
- Human responses to upright tilt: a window on central autonomic integrationThe Journal of Physiology, 1999
- Sympathovagal BalanceCirculation, 1998
- Sympathovagal BalanceCirculation, 1997
- Power spectrum analysis of heart rate variability to assess the changes in sympathovagal balance during graded orthostatic tilt.Circulation, 1994
- Important influence of respiration on human R-R interval power spectra is largely ignoredJournal of Applied Physiology, 1993
- Cardiovascular neural regulation explored in the frequency domain.Circulation, 1991
- Power Spectrum Analysis of Heart Rate Fluctuation: A Quantitative Probe of Beat-to-Beat Cardiovascular ControlScience, 1981
- Reciprocal and non-reciprocal action of the vagal and sympathetic nerves innervating the heartJournal of the Autonomic Nervous System, 1979