Net Synergy/Redundancy Balance of Cardiovascular Interactions Allows the Stratification of the Risk in Patients with Asymptomatic Carotid Stenosis

Vlasta Bari1, Beatrice Cairo1, Nicoletta Curcio2, Michele Conti3, Rosanna Cardani4, Laura Valentina Renna4, Giacomo Dell'Antonio4, Giulia Matrone5, Paolo Righini6, Giovanni Nano1, Daniela Mazzaccaro6, Alberto Porta1
1Department of Biomedical Sciences for Health, University of Milan, 23D and Computer Simulation Laboratory, IRCCS Policlinico San Donato, 3Department of Civil Engineering and Architecture, University of Pavia, 4Biobank BioCor, IRCCS Policlinico San Donato, 5Department of Electrical, Computer and Biomedical Engineering, University of Pavia, 6Operative Unit of Vascular Surgery, IRCCS Policlinico San Donato

Abstract

Cardiovascular control could be impaired in patients with asymptomatic carotid stenosis (ACS) with such impairment being associated with the histological characteristics of the carotid plaque, as the presence of a thick fibrous cap. The net balance between redundancy and synergy can be exploited to characterize cardiovascular control from spontaneous variability of systolic arterial pressure (SAP) and heart period (HP) and can be proven helpful to early discriminate pathological conditions. We exploited a predictive information decomposition approach based on bivariate linear autoregressive model of HP with an exogenous SAP input. The method assesses the net synergy/redundancy balance of the past of HP and SAP in reducing the uncertainty of the current state of HP. Sixty-seven patients with ACS scheduled for carotid endarterectomy (age 74.9±7.6 yrs, 44 males) were enrolled and divided in two groups according to the presence of a plaque fibrous cap thicker than 200 µm (CAP>200, n=40) or not (CAP<200, n=27) as detected from postoperative histological analysis. HP and SAP time series were acquired preoperatively in supine position and during active standing (STAND). Traditional time and frequency domain markers of HP and SAP variability were derived as well as net synergy/redundancy. A prevalence of redundancy was observed in both populations and conditions. However, during STAND a more negative net balance between synergy and redundancy was observed in CAP>200 compared to CAP<200 (‒0.036±0.092 vs ‒0.001±0.046). Remarkably, none of the traditional time and frequency domain markers could separate the two groups. Findings suggest that in patients with thicker fibrous cap the independent contribution of the baroreflex in controlling HP could be reduced with respect to that of different regulatory mechanisms contributing to cardiac regulation, hence leading to a more important relative impact of redundancy on HP regulation. Advanced information domain markers can be exploited for risk stratification in patients with ACS.