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Type: Journal article
Title: Characterization of the asymmetry of the cardiac and sympathetic arms of the baroreflex from spontaneous variability during incremental head-up tilt
Author: De Maria, B.
Bari, V.
Cairo, B.
Vaini, E.
Esler, M.
Lambert, E.
Baumert, M.
Cerutti, S.
Dalla Vecchia, L.
Porta, A.
Citation: Frontiers in Physiology, 2019; 10(1):342-1-342-14
Publisher: Frontiers Media SA
Issue Date: 2019
ISSN: 1664-042X
Statement of
Beatrice De Maria, Vlasta Bari, Beatrice Cairo, Emanuele Vaini, Murray Esler, Elisabeth Lambert, Mathias Baumert, Sergio Cerutti, Laura Dalla Vecchia, and Alberto Porta
Abstract: Hysteresis of the baroreflex (BR) is the result of the different BR sensitivity (BRS) when arterial pressure (AP) rises or falls. This phenomenon has been poorly studied and almost exclusively examined by applying pharmacological challenges and static approaches disregarding causal relations. This study inspects the asymmetry of the cardiac BR (cBR) and vascular sympathetic BR (sBR) in physiological closed loop conditions from spontaneous fluctuations of physiological variables, namely heart period (HP) and systolic AP (SAP) leading to the estimation of cardiac BRS (cBRS) and muscle sympathetic nerve activity (MSNA) and diastolic AP (DAP) leading to the estimation of vascular sympathetic BRS (sBRS). The assessment was carried out in 12 young healthy subjects undergoing incremental head-up tilt with table inclination gradually increased from 0 to 60°. Two analytical methods were exploited and compared, namely the sequence (SEQ) and phase-rectified signal averaging (PRSA) methods. SEQ analysis is based on the detection of joint causal schemes representing the HP and MSNA burst rate delayed responses to spontaneous SAP and DAP modifications, respectively. PRSA analysis averages HP and MSNA burst rate patterns after aligning them according to the direction of SAP and DAP changes, respectively. Since cBRSs were similar when SAP went up or down, hysteresis of cBR was not detected. Conversely, hysteresis of sBR was evident with sBRS more negative when DAP was falling than rising. sBR hysteresis was no longer visible during sympathetic activation induced by the orthostatic challenge. These results were obtained via the SEQ method, while the PRSA technique appeared to be less powerful in describing the BR asymmetry due to the strong association between BRS estimates computed over positive and negative AP variations. This study suggests that cBR and sBR provide different information about the BR control, sBR exhibits more relevant non-linear features that are evident even during physiological changes of AP, and the SEQ method can be fruitfully exploited to characterize the BR hysteresis with promising applications to BR branches different from cBR and sBR.
Keywords: Hysteresis; muscle sympathetic nerve activity; MSNA; baroreflex sequence analysis; phase-rectified signal averaging; heart rate variability; autonomic nervous system; cardiovascular control
Rights: Copyright © 2019 De Maria, Bari, Cairo, Vaini, Esler, Lambert, Baumert, Cerutti, Dalla Vecchia and Porta. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
DOI: 10.3389/fphys.2019.00342
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