title: Information domain analysis of the spontaneous baroreflex during pharmacological challenges.
abstract: The information carried by heart period (HP) given systolic arterial pressure (SAP) changes was assessed to characterize spontaneous baroreflex (i.e. the relation linking SAP variability to HP variability): the larger the information carried by HP given SAP changes, the greater the unpredictability of HP given SAP variations, the smaller the strength of the causal coupling from SAP series to HP series. It was typified according to two parameters: i) the information carried by HP given SAP changes within the same heart cycle (i.e. 0-step-ahead information) describing immediate effects of SAP variations on HP; ii) the rate of increase of the information carried by HP given SAP changes as a function of the temporal distance, k, between the conditioning SAP pattern and future HP value (i.e. the rate of increase of k-step-ahead information with k) describing short-term effects of SAP modifications on HP. Both parameters were found under vagal control. Indeed, i) 0-step-ahead information suggested that HP and SAP variabilities were significantly coupled from SAP to HP at baseline and after the reduction of the inhibitory effect of sympathetic control on vagal influences performed through the administration of propranolol or clonidine; and ii) during vagal blockade induced by atropine or combined vagal and sympathetic blockade induced by the administration of propranolol after atropine k-step-ahead information reached a level incompatible with coupled HP and SAP dynamics regardless of k. In addition, it was found that the 0-step-ahead information at baseline and after propranolol and the rate of increase of k-step-ahead information with k at baseline could be exclusively explained in terms of linear HP-SAP interactions. Conversely, the same parameters after clonidine suggested the raise of nonlinear mechanisms probably unveiled by the central sympathetic blockade. Comparison with more traditional parameters describing the HP-SAP variability relation such as baroreflex sensitivity and squared HP-SAP coherence confirmed the complementary value of the proposed information domain analysis.
authors.affiliation: Department of Biomedical Sciences for Health, Galeazzi Orthopedic Institute, University of Milan, Milan, Italy. Electronic address: alberto.porta@unimi.it.
authors.forename: Alberto
authors.initials: A
authors.lastname: Porta
authors.forename: Paolo
authors.initials: P
authors.lastname: Castiglioni
authors.forename: Marco
authors.initials: M
authors.lastname: Di Rienzo
authors.forename: Vlasta
authors.initials: V
authors.lastname: Bari
authors.forename: Tito
authors.initials: T
authors.lastname: Bassani
authors.forename: Andrea
authors.initials: A
authors.lastname: Marchi
authors.forename: Maddalena Alesssandra
authors.initials: MA
authors.lastname: Wu
authors.forename: Andrei
authors.initials: A
authors.lastname: Cividjian
authors.forename: Luc
authors.initials: L
authors.lastname: Quintin
mesh_terms: D000328:Adult; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001341:Autonomic Nervous System / Q000187:drug effects; D017704:Baroreflex / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology*; D004562:Electrocardiography; D019277:Entropy; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D011433:Propranolol / Q000494:pharmacology*; D012815:Signal Processing, Computer-Assisted
chemical_list: D000959:Antihypertensive Agents; D011433:Propranolol; D003000:Clonidine
keywords: Autonomic nervous system; Baroreflex; Cardiovascular control; Cross-conditional entropy; Heart rate variability; Information domain
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