Wearable sensor network to study laterality of brain functions.

In the last decade researches on laterality of brain functions have been reinvigorated. New models of lateralization of brain functions were proposed and new methods for understanding mechanisms of asymmetry between right and left brain functions were described. We design a system to study laterality of motor and autonomic nervous system based on wearable sensors network. A mobile application was developed for analysis of upper and lower limbs movements, cardiac and respiratory function. The functionalities and experience gained with deployment of the system are described.

Comparative analysis of two systems for unobtrusive heart signal acquisition and characterization.

In this paper we describe and compared method of heart rate estimation from cardiac signal acquired with EMFIT, FMCW Doppler radar and Finapres based technology, in the same context, and briefly investigated their similarities and differences. Study of processing of acquired cardiac signal for accurate peak detection using Wavelet Transform is also described. The results suggest good reliability of the two implemented unobtrusive systems for heart rate estimation.

[Acute electrophysiological modulation of the atria and pulmonary veins: effects of sympathetic and parasympathetic interaction on atrial fibrillation inducibility]. / Modulação eletrofisiológica das auriculas e veias pulmonares: interação da estimulação simpática e parassimpática na inducibilidade de fibrilhação aguda auricular num modelo experimental in vivo.

UNLABELLED: Atrial fibrillation (AF) is a complex disease with multiple mechanisms, involving the interaction between the autonomic nervous system (ANS), electrophysiological properties of the atria and pulmonary veins (PVs), and vulnerability for AF. AIM: We assessed the effects of acute vagal (vagus_stim) and sympathetic stimulation (symp_stim) on atrial conduction, atrial and PV refractoriness and inducibility of AF in an in vivo rabbit model with preserved autonomic innervation. METHODS: An open-epicardial approach was used in 17 anesthetized and artificially ventilated New Zealand white rabbits. The ECG was recorded with bipolar subcutaneous electrodes placed in the four limbs. Electrograms were obtained with four monopolar electrodes placed epicardially along the atria, and a circular electrode adapted to the proximal PVs. The cervical vagus nerve and thoracic sympathetic trunk were stimulated with bipolar electrodes. Epicardial activation was recorded in sinus rhythm, and effective refractory periods (ERPs) and conduction times from the high-lateral right atrium (RA) to the high-lateral left atrium (LA) and PVs were quantified at baseline and during vagus_stim, symp_stim, or combined vagal and sympathetic stimulation (dual_stim). Burst pacing (50 Hz, 10 s), alone or combined with vagus_stim, symp_stim or dual_stim, was performed in the right (RAA) and left atrial appendage (LAA) and PVs to test for AF inducibility. RESULTS: At baseline, ERPs were higher in the LAA and there was a delay in the conduction time from RA to PV, compared to the mean activation time from RA to LA. During vagus_stim or dual_stim, ERP decreased significantly at all sites, and baseline interatrial activation times changed from 20 +/- 4 ms to 30 +/- 10 ms and 31 +/- 11 ms, respectively (p < 0.05). Symp_stim resulted in a significant decrease in ERPs only in the LAA, and a reduction of the interatrial interval to 16 +/- 11 ms (p < 0.05 vs baseline). AF inducibility ranged from 35% to 53% with baseline 50 Hz pacing, 65% to 76% during vagus_stim or symp_stim, and 75% to 100% with dual_stim (p < 0.05). AF duration increased significantly during ANS stimulation. In two-thirds of the animals with longer inducible AF, the arrhythmia ceased immediately after cessation of vagus_stim. CONCLUSIONS: In the fully innervated rabbit heart in vivo, acute ANS stimulation shortens atrial and PV refractoriness, and significantly changes atrial conduction times, promoting AF induction and prolonging the arrhythmia. This underscores the importance of acute variations in ANS tone and its interactions in the pathophysiology of AF.

Acute vagal modulation of electrophysiology of the atrial and pulmonary veins increases vulnerability to atrial fibrillation.

Vagal activity is thought to influence atrial electrophysiological properties and play a role in the initiation and maintenance of atrial fibrillation (AF). We evaluated the effects of acute vagal stimulation on atrial conduction, refractoriness of atrial and pulmonary veins (PVs) and inducibility of AF. An open-chest epicardial approach was performed in New Zealand White rabbits with preserved autonomic innervation. Atrial electrograms were obtained with four unipolar electrodes placed epicardially along the atria (n = 22) and an electrode adapted to the proximal left PV (n = 10). The cervical vagus nerve was stimulated with bipolar platinum electrodes (20 Hz). Epicardial activation was recorded in sinus rhythm, and effective refractory periods (ERPs), dispersion of refractoriness and conduction times from high-lateral right atrium (RA) to high-lateral left atrium (LA) and PVs assessed at baseline and during vagal stimulation. Burst pacing (50 Hz, 10 s), alone or combined with vagal stimulation, was applied to the right (RAA) and left atrial appendage (LAA) and PVs to induce AF. At baseline, ERPs were lower in PVs than in LA and LAA, but did not differ significantly from RA and RAA, and there was a significant delay in the conduction time from RA to PVs compared with the activation time from RA to LA (P < 0.01). During vagal stimulation, ERP decreased significantly at all sites, without significant differences in the dispersion of refractoriness, and the atrial conduction times changed from 39 ± 19 to 49 ± 9 ms (RA to PVs; n.s.) and from 14 ± 7 to 28 ± 12 ms (RA to LA; P = 0.01). Induction of AF was reproducible in 50% of cases with 50 Hz and in 82% with 50 Hz combined with vagal stimulation (P < 0.05). During vagal stimulation, AF cycle length decreased at all sites, and AF duration changed from 1.0 ± 0.9 to 14.0 ± 10.0 s (P < 0.01), with documentation of PV tachycardia in three cases. In 70% of the animals, AF ceased immediately after interruption of vagal stimulation. We conclude that in the intact rabbit heart, vagal activity prolongs interatrial conduction and shortens atrial and PV ERP, contributing to the vulnerability to the induction and maintenance of AF. This model may be useful in the assessment of the autonomic influence in the mechanisms underlying AF.

Cardio-respiratory and daily activity monitor based on FMCW Doppler radar embedded in a wheelchair.

Unobtrusive monitoring of the cardio-respiratory and daily activity for wheelchair users became nowadays an important challenge, considering population aging phenomena and the increasing of the elderly with chronic diseases that affect their motion capabilities. This work reports the utilization of FMCW (frequency modulated continuous wave) Doppler radar sensors embedded in a manual wheelchair to measure the cardiac and respiratory activities and the physical activity of the wheelchair user. Another radar sensor is included in the system in order to quantify the motor activity through the wheelchair traveled distance, when the user performs the manual operation of the wheelchair. A conditioning circuit including active filters and a microcontroller based primary processing module was designed and implemented to deliver the information through Bluetooth communication protocol to an Android OS tablet computer. The main capabilities of the software developed using Android SDK and Java were the signal processing of Doppler radar measurement channel signals, graphical user interface, data storage and Wi-Fi data synchronization with remote physiological and physical activity database.

New insight into arrhythmia onset using HRV and BPV analysis.

In this paper Heart Rate Variability (HRV) and Blood Pressure Variability (BPV) were analyzed before the onset of cardiac arrhythmia in order to derive markers for short-term forecasting. The (a) coherence between systolic blood pressure (SBP) and cardiac oscillations in low-frequency (LF) and high-frequency (HF) band; (b) fluctuations of phase; (c) HRV and BPV as a LF power and HF power in frequency and time-frequency domain; (d) transfer function analysis of cardiovascular signals were analyzed. Arrhythmia was preceded by: a) lower coherence; b) increase in fluctuations of phase between signals; c) higher spectral energy associated with respiratory frequency in blood pressure signal; d) raise of sympathetic outflow to the heart; e) decreased HRV. Cardiac arrhythmia was characterized mainly by an increase in LF power of blood pressure, cardiac signal and transfer function. During self-termination of arrhythmia a larger increased in total BPV and HRV was recorded. These results suggest that important information about both neuronal cardiovascular control and risk for spontaneous arrhythmia can be provided by combined analysis of frequency, phase, and time-frequency analysis of blood pressure and cardiac oscillation.

Effects of vagal stimulation on induction and termination of atrial fibrillation in an in vivo rabbit heart model.

INTRODUCTION: Vagal activity is thought to influence atrial electrophysiological properties and play a role in the initiation and maintenance of atrial fibrillation (AF). In this study, we assessed the effects of acute vagal stimulation (vagus_stim) on atrial conduction times, atrial and pulmonary vein (PV) refractoriness, and vulnerability to induction of AF in the rabbit heart with intact autonomic innervation. METHODS: An open-chest epicardial approach was performed in 11 rabbits (New Zealand; 3.9-5.0 kg), anesthetized and artificially ventilated after neuromuscular blockade. A 3-lead ECG was obtained. Atrial electrograms were recorded along the atria, from right to left (four monopolar electrodes), together with a circular electrode adapted for proximal left PV assessment. Acute vagus nerve stimulation was obtained with bipolar electrodes (20 Hz). Epicardial activation was recorded in sinus rhythm, and the conduction time from right (RA) to left atrium (LA), and from RA to PVs, was measured in basal conditions and during vagus_stim. The atrial effective refractory period (ERP) and dispersion of refractoriness (Disp_A) were analyzed. Vulnerability to AF induction was assessed at the right (RAA) and left (LAA) atrial appendages and the PVs. Atrial stimulation (50 Hz) was performed alone or combined with vagus_stim. Heart rate and blood pressure were monitored. RESULTS: In basal conditions, there was a significant delay in conduction from RA to PVs, not influenced by vagus_stim, and the PV ERPs were shorter than those measured in LA and LAA, but without significant differences compared to RA and RAA. During vagus_stim, conduction times between RA and LA increased from 16+8 ms to 27+6 ms (p < 0.05) and ERPs shortened significantly in RA, LAA and LA (p < 0.05), but not in RAA. There were no significant differences in Disp_A. AF induction was reproducible in 45% of cases at 50 Hz and in 100% at 50 Hz+vagus_stim (p < 0.05). The duration of inducible AF increased from 1.0 +/- 0.2 s to 12.0 +/- 4.5 s with 50 Hz+vagus_stim (p < 0.01). AF lasted >10 s in 45.4% of rabbits during vagus_stim, and ceased after vagus_stim in 4 out of these 5 cases. In 3 animals, PV tachycardia, with fibrillatory conduction, induced with 50 Hz PV pacing during vagus_stim. CONCLUSIONS: Vagus_stim reduces interatrial conduction velocity and significantly shortens atrial ERP, contributing to the induction and duration of AF episodes in the in vivo rabbit heart. This model may be useful for the assessment of autonomic influence on the pathophysiology of AF,