HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 293/1/H702    most recent 00006.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Porta, A. Articles by Gnecchi-Ruscone, T. Search for Related Content PubMed PubMed Citation Articles by Porta, A. Articles by Gnecchi-Ruscone, T.

Assessment of cardiac autonomic modulation during graded head-up tilt by symbolic analysis of heart rate variability

¹Department of Technologies for Health, Galeazzi Orthopaedic Institute, ²Department of Clinical Sciences L. Sacco, Internal Medicine II, L. Sacco Hospital, University of Milan, Milan; and ³Department of Cardiology, S. L. Mandic Hospital, Merate, Lecco, Italy

Submitted 3 January 2007 ; accepted in final form 12 February 2007

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.

autonomic nervous system; power spectral density

This article has been cited by other articles:

				A. Porta, K. R. Casali, A. G. Casali, T. Gnecchi-Ruscone, E. Tobaldini, N. Montano, S. Lange, D. Geue, D. Cysarz, and P. Van Leeuwen Temporal asymmetries of short-term heart period variability are linked to autonomic regulation Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2008; 295(2): R550 - R557. [Abstract] [Full Text] [PDF]

				A. Porta, T. Gnecchi-Ruscone, E. Tobaldini, S. Guzzetti, R. Furlan, and N. Montano Progressive decrease of heart period variability entropy-based complexity during graded head-up tilt J Appl Physiol, October 1, 2007; 103(4): 1143 - 1149. [Abstract] [Full Text] [PDF]