Short-term complexity indexes of heart period and systolic arterial pressure variabilities provide complementary information

Abstract

It is unclear whether the complexity of the variability of the systolic arterial pressure (SAP) provides complementary information to that of the heart period (HP). The complexity of HP and SAP variabilities was assessed from short beat-to-beat recordings (i.e., 256 cardiac beats). The evaluation was made during a pharmacological protocol that induced vagal blockade with atropine or a sympathetic blockade (beta-adrenergic blockade with propranolol or central sympathetic blockade with clonidine) alone or in combination, during a graded head-up tilt, and in patients with Parkinson's disease (PD) without orthostatic hypotension undergoing orthostatic challenge. Complexity was quantified according to the mean square prediction error (MSPE) derived from univariate autoregressive (AR) and multivariate AR (MAR) models. We found that: 1) MSPE(MAR) did not provide additional information to that of MSPE(AR); 2) SAP variability was less complex than that of HP; 3) because HP complexity was reduced by either vagal blockade or vagal withdrawal induced by head-up tilt and was unaffected by beta-adrenergic blockade, HP was under vagal control; 4) because SAP complexity was increased by central sympathetic blockade and was unmodified by either vagal blockade or vagal withdrawal induced by head-up tilt, SAP was under sympathetic control; 5) SAP complexity was increased in patients with PD; and 6) during orthostatic challenge, the complexity of both HP and SAP variabilities in patients with PD remained high, thus indicating both vagal and sympathetic impairments. Complexity indexes derived from short HP and SAP beat-to-beat series provide complementary information and are helpful in detecting early autonomic dysfunction in patients with PD well before circulatory symptoms become noticeable.

Conditional symbolic analysis detects nonlinear influences of respiration on cardiovascular control in humans

“…Given that in the HP variability an increased presence of 0V patterns and a decreased incidence of more variable ones, such that observed during graded head-up tilt [21], is associated with a loss of complexity of the cardiac control [35], we suggest that the evoked syncope is characterized by a dramatic reduction of complexity of the cardiac control. This relevant reduction of complexity might be again a consequence of the exaggerated sympathetic activation limiting considerably the possibility to respond to stimulatory inputs and the range of temporal scales involved in cardiovascular regulation [35].…”

“…This relevant reduction of complexity might be again a consequence of the exaggerated sympathetic activation limiting considerably the possibility to respond to stimulatory inputs and the range of temporal scales involved in cardiovascular regulation [35]. When the univariate symbolic analysis was applied to SAP variability, 0V% remained stable during TILT and PRESY, thus suggesting a steady complexity of the vascular control.…”

Assessment of spontaneous cardiovascular oscillations in Parkinson's disease

“…To the best of our knowledge, prior studies have focused on group comparisons ,ofter reaching contradictory results [1,3,16,20,21,25,28,29,32,33,35]. It should be noted that, even if a significant statistical difference associated to a certain feature is consistently revealed across several studies, this is not sufficient to demonstrate its potential application to the clinical necessity of single-subject characterization.…”

“…However, other authors documented an increase in complexity of systolic arterial pressure in PD patients when compared to controls [32]. In addition, while the physiology underlying complexity-related measures of heartbeat dynamics is still unknown, it is well known that their quantification can provide meaningful information on psychophysiological as well as pathological states [8,10,14,24,39].…”

Complex and Nonlinear Analysis of Heart Rate Variability in the Assessment of Fetal and Neonatal Wellbeing

“…Indices derived from symbolic dynamics might provide a reliable alternative to markers of complexity and causality that can be derived from model-based multiple linear regression approaches in time and frequency domains [117][118][119][120]. In the medical field, it can be expected that symbolic dynamics will have a powerful impact in the coming years by playing a significant role in tailoring individual treatments, improving diagnostics and therapy, managing patient data and reducing the cost of healthcare systems via a more precise risk stratification [15].…”