Temporal cardiovascular causality during orthostatic stress by extended partial directed coherence.

The aim of this study was to investigate the temporal dynamic behavior of cardiovascular interactions between heart period and systolic blood pressure during a 20-min head-up tilt test at 70° in young women with orthostatic intolerance compared to healthy women. Methods included the lagged and extended partial directed coherence applied to short-term windows shifted by 5 seconds, extracted from a multivariate set of cardiovascular and respiratory time series. Findings revealed significantly increased information flow (p <; 0.

Time-Frequency Analysis of Cardiovascular and Cardiorespiratory Interactions During Orthostatic Stress by Extended Partial Directed Coherence.

In this study, the linear method of extended partial directed coherence (ePDC) was applied to establish the temporal dynamic behavior of cardiovascular and cardiorespiratory interactions during orthostatic stress at a 70° head-up tilt (HUT) test on young age-matched healthy subjects and patients with orthostatic intolerance (OI), both male and female. Twenty 5-min windows were used to analyze the minute-wise progression of interactions from 5 min in a supine position (baseline, BL) until 18 min of the orthostatic phase (OP) without including pre-syncopal phases. Gender differences in controls were present in cardiorespiratory interactions during OP without compromised autonomic regulation.

Cardiovascular variability in young male and female subjects in health and orthostatic intolerance.

The aim of this study was to investigate the effect of head-up tilt (HUT) test on male and female young patients, diagnosed with orthostatic intolerance (OI), in comparison to male and female healthy subjects. Twenty seven OI patients (21 women, 6 men) and 26 age-matched healthy subjects (13 women, 13 men) were enrolled in a 70° HUT test. In addition to hemodynamic variables, cardiovascular and respiratory parameters were determined using linear and nonlinear methods to analyze heart rate (HRV) and blood pressure variability (BPV).

Study of impaired cardiovascular and respiratory coupling during orthostatic stress based on joint symbolic dynamics.

The present study investigates the instantaneous coupling among the cardiac, vascular, and respiratory systems, using the heart rate, respiration, and systolic and diastolic blood pressure variability in 12 healthy and 16 vasovagal syncope female subjects during a head-up tilt (HUT) testing protocol at 70° This study contributes to the coupling analysis by using a nonlinear joint symbolic dynamics (JSD) in a high-temporal resolution scheme, based on 5 min segments of the time series that are shifted every minute. For each segment, a bivariate JSD matrix was constructed to obtain global and local coupling indices in accordance to Shannon's entropy and the probability of occurrence of various bivariate words, respectively. The novel approach revealed important findings in the coupling dynamics of the systems, thus allowing the detection of group differences during the early orthostatic phase, and during the HUT test, before the occurrence of any pre-syncopal symptoms.

Cardiovascular and Cerebral Hemodynamics in Asymptomatic Healthy Subjects With/Without Abnormal Head-up Tilt Test Versus Recurrent Fainters.

Purpose: The aim of this study was to compare hemodynamic and autonomic responses during head-up tilt test (HUTT) between healthy volunteers and patients with a history of fainting and confirmed vasovagal syncope. We hypothesize that the autonomic and hemodynamic physiologic responses remain intact during orthostatic stress in people without previous fainting and negative HUTT, but deteriorate similarly in patients with recurrent vasovagal syncope and in asymptomatic healthy subjects who develop a vasovagal response during HUTT.

Methods: The study included 57 asymptomatic healthy volunteers (42% women, mean age 23.