Characterization of autonomic states by complex sympathetic and parasympathetic dynamics

Author: Mimma Nardelli1, Luca Citi2, Riccardo Barbieri3, Gaetano Valenza1
Affiliation: <sup>1</sup> University of Pisa, Largo Lucio Lazzarino 1, Pisa, 56122, ITALY. <sup>2</sup> Laboratory of Brain Computer Interfaces, University of Essex, Wivenhoe Park, Colchester, Essex, CO4 3SQ, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND. <sup>3</sup> Department of Electronic, Informatics and Bioengineering, Politecnico di Milano, Milan, Milano, 20133, ITALY.
Conference/Journal: Physiol Meas
Date published: 2023 Feb 14
Other: Special Notes: doi: 10.1088/1361-6579/acbc07. , Word Count: 251

Assessment of heartbeat dynamics provides a promising framework for non-invasive monitoring of cardiovascular and autonomic states. Nevertheless, the non-specificity of such measurements among clinical populations and healthy conditions associated with different autonomic states severely limits their applicability and exploitation in naturalistic conditions. This limitation arises specially when pathological or postural change-related sympathetic hyperactivity is compared to autonomic changes across age and experimental conditions. In this frame, we investigate the intrinsic irregularity and complexity of cardiac sympathetic and vagal activity series in different populations, which are associated with different cardiac autonomic dynamics. Sample entropy, fuzzy entropy, and distribution entropy are calculated on the recently proposed sympathetic and parasympathetic activity indices (SAI and PAI) series, which are derived from publicly available heartbeat series of congestive heart failure patients, elderly and young subjects watching a movie in the supine position, and healthy subjects undergoing slow postural changes. Results show statistically significant differences between pathological/old subjects and young subjects in the resting state and during slow tilt, with interesting trends in SAI- and PAI-related entropy values. Moreover, while CHF patients and healthy subjects in upright position show the higher cardiac sympathetic activity, elderly and young subjects in resting state showed higher vagal activity. We conclude that quantification of intrinsic cardiac complexity from sympathetic and vagal dynamics may provide new physiology insights and improve on the non-specificity of heartbeat-derived biomarkers.

Keywords: autonomic nervous system; congestive heart failure (CHF); entropy; heart rate variability (HRV); parasympathetic activity index; sympathetic activity index; sympathovagal balance.

PMID: 36787644 DOI: 10.1088/1361-6579/acbc07