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This study focuses on examining the hemodynamic profile in older people with symptoms of orthostatic intolerance (OI) undergoing an active stand and to investigate if their dynamic cardiovascular profile during six-minute walk distance would be different to those of controls. The database included a total of 65 participants, aged over 70 years of age (70.11±5.85), of whom 65% were females. The participants underwent a supine to stand orthostatic test with non-invasive beat to beat systolic (SBP) and diastolic blood pressure (DBP) and inter-beat interval (R-R) monitoring. Sample Entropy (SampEn) method was calculated at each phase. R-R SampEn values showed statistically significant differences during Phase 2 and Phase 4 between symptomatic and asymptomatic OI participants. This study empathizes the importance of entropy analysis to extract information of cardiovascular signals. SampEn based measures might provide useful indicators of pathological changes in cardiac activity and be suitable for the early detection of autonomic cardiovascular dysfunction.

Orthostatic hypotension (OH) is an excessive fall in blood pressure when an upright position is assumed. It is related symptoms associated with the occurrence of syncope. It presents as a heterogeneous group of diseases but commonly is manifested itself as symptoms of orthostatic intolerance (OI). Heart Rate (HR) variability is the output of multiple physiologic control mechanisms that operate over a wide range of time scales. This study is focused to quantify the regularity changes in the HR dynamics in different time scales by Multiscale entropy (MSE) measures in older people, with and without symptoms of OI. We analyzed 65 elderly people. There was no significant differences in age and gender between symptomatic and asymptomatic OI participants, 44.6% (n=29) had symptoms of OI and 55.4% (n=36) did not. The main differences were observed in the ascent phase and descent phase between symptomatic and asymptomatic OI patients. In both cases, the symptomatic OI group presents higher levels of entropy in all time scales. Moreover, it is possible to observe that male group showed higher differences between symptomatic and asymptomatic OI participants than female group. The main conclusion is that the MSE features capture differences in heart rate regularity providing hemodynamic changes that occur in symptomatic OI patients.

Electroencephalogram (EEG) recordings often experience interference by different kinds of noise, including white, muscle, and baseline, severely limiting its utility. The recent research has demonstrated that discrete-time Volterra models can be successfully applied to reduce the broadband and narrowband noise. Their usefulness is mainly because of their ability to approximate to an arbitrary precision any fading memory system and their property of linearity with respect to parameters, the kernels coefficients. The main drawback of these models is their parametric complexity implying the need to estimate a huge number of parameters. Numerical results show that the developed algorithm achieves performance improvement over the standard filtered algorithm. This paper presents a Volterra filter (VF) algorithm based on a multichannel structure for noise reduction. Several methods have been developed, but the VF appears to be the most effective for reducing muscle and baseline noise, especially when the contamination is greater in amplitude than the brain signal. The present study introduces a new method of reducing noise in EEG signals in one step with low EEG distortion and high noise reduction. Applications with different real and synthetic signals are discussed, showing the validity of the proposed method.

[EN] Orthostatic intolerance syndrome occurs when the autonomic nervous system is incapacitated and fails to respond to the demands associated with the upright position. Assessing this syndrome among the elderly population is important in order to prevent falls. However, this problem is still challenging. The goal of this work was to determine the relationship between orthostatic intolerance (OI) and the cardiovascular response to exercise from the analysis of heart rate and blood pressure. More specifically, the behavior of these cardiovascular variables was evaluated in terms of refined composite multiscale fuzzy entropy (RCMFE), measured at different scales. The dataset was composed by 65 older subjects, 44.6% (n = 29) were OI symptomatic and 55.4% (n = 36) were not. Insignificant differences were found in age and gender between symptomatic and asymptomatic OI participants. When heart rate was evaluated, higher differences between groups were observed during the recovery period immediately after exercise. With respect to the blood pressure and other hemodynamic parameters, most significant results were obtained in the post-exercise stage. In any case, the symptomatic OI group exhibited higher irregularity in the measured parameters, as higher RCMFE levels in all time scales were obtained. This information could be very helpful for a better understanding of cardiovascular instability, as well as to recognize risk factors for falls and impairment of functional status., This research was funded by the Ministerio de Economia y Competitividad from the Spanish Government, through its research program Programa Estatal de I+D+i Orientada a los Retos de la Sociedad, grant number DPI2015-70821-R.

Recent studies on atrial fibrillation (AF) have identified different activation patterns in paroxysmal and persistent AF. In this study, bipolar intra-atrial registers from 28 patients (14 paroxysmal AF and 14 persistent AF) were analyzed in order to find out regional differences in the organization in both types of arrhythmias. The organization of atrial electrical activity was assessed in terms of nonlinear parameters, such as entropy measurements. Results showed differences between the atrial chambers with a higher disorganization in the left atrium in paroxysmal AF patients and a more homogenous behavior along the atria in persistent AF patients.

Introduccion y objetivos La navegacion magnetica remota con sistema Stereotaxis® supone una nueva forma de ablacion que podria aumentar la estabilidad del cateter. Quisimos evaluar si la posible mejoria del contacto tisular obliga a modificar los parametros convencionales de radiofrecuencia. Metodos Se comparo a 19 pacientes sometidos a ablacion de taquicardia intranodal con cateter remoto de 4 mm con 18 pacientes con procedimiento convencional (4 mm, 60-65 °C, 50 W). Evaluamos la energia de radiofrecuencia necesaria para conseguir la no inducibilidad de mas de un eco nodal. Resultados El primer cateter remoto presento carbonizacion tras las primeras aplicaciones con parametros habituales. Asi, redujimos la energia (50 °C, 40 W) en el resto. No hubo diferencias en numero de aplicaciones entre grupo remoto y control (mediana, 6 [rango intercuartilico, 11] frente a 8,5 [9]). Aplicaciones ≤ 5 s suelen deberse a desplazamiento del cateter. Solo 4 pacientes del grupo remoto tuvieron aplicaciones ≤ 5 s frente a 11 controles (p = 0,041). La ablacion remota fue igual de efectiva, y se realizo con menores temperaturas y potencias medias (media ± DE, 46 ± 2 frente a 50 ± 4 °C; p Conclusiones En nuestra serie inicial, el uso de navegacion remota en la ablacion de taquicardia intranodal fue efectiva y segura. La mejoria del contacto tisular disminuye desplazamientos involuntarios del cateter y parece que se necesita disminuir la potencia de radiofrecuencia para evitar la carbonizacion del cateter.

Changes in patients' autonomic tone and specific pharmacologic interventions may modify the ventricular response (actual heart rate) during atrial fibrillation (AF). Hypnotic agents such as propofol may modify autonomic balance as they promote a sedative state. It has been shown that propofol slightly slows atrial fibrillatory activity, but the net global effect on the ventricular response remains unknown. We aimed to evaluate in patients in AF the effect of a propofol bolus on the ventricular rate and regularity at ECG. We analysed the possible relation with local atrial fibrillatory activities, as ratios between atrial and ventricular rates (AVRs), analysing atrial activity from intracardiac electrograms at the free wall of the right and left atria and at the interatrial septum. We compared data at the baseline and after complete hypnosis. Propofol was associated with a more homogeneous ventricular response and lower AVR values at the interatrial septum.

In a substantial number of patients atrial fibrillation (AF) recurs after successful electrical cardioversion. Recurrence of AF is insufficiently predictable by clinical and echocardiographic parameters used in the clinic procedure. In this study some parameters were extracted from the analysis of electrocardiograms (ECGs), in an effort to predict the maintenance of sinus rhythm after cardioversion in patients with persistent AF. The database under study includes some ECG registers undergoing cardioversion with some additional physiological and anatomical information of each patient. After 12 weeks following cardioversion, only 15 (41.6%) of 34 patients maintained sinus rhythm. The ECG recordings were processed using the continuous wavelet transform (CWT) and the discrete wavelet transform (DWT). The method estimated the predictive power with respect to defibrillation outcome of some parameters extracted with CWT and DWT analysis, such as the main frequency peak frequency and the energy of detail coefficients, respectively. A logistic regression model was constructed, determining the calibration with the Homer–Lemeshow test and the discrimination with the area under the receiver operation characteristic (ROC) curve. The proposed methodology demonstrated a diagnostic capability of 82.4% for the prediction of AF recurrence, contributing to an improved interpretation of AF arrhythmias and their relation with recurrence risk.

Radiofrequency catheter ablation is currently used widely and successfully to treat atrial fibrillation (AF), whose success is limited in part by uncertainty in the mechanisms that sustain AF. AF intracardiac recordings were registered from the right atrium (RA) and left atrial (LA) in 41 patients immediately before AF ablation procedure. They were divided in 2 groups according to AF recurrence outcome 3 months after ablation procedure: 26 of them remained in sinus rhythm and the other 15 turned back to AF. There was no statistically significant difference between clinical parameters from recurrent and non-recurrent AF patients in both groups. Atrial peaks were detected from the envelope obtained by Teager Energy operator. Results showed differences between maximum of atrial fibrillation cycle length in the RA in both groups, with shorter atrial intervals in the group without recurrences in AF (p=0,03). Moreover, differences between both atria were found in AF non-recurrent patients, higher atrial intervals in the LA (p=0.04), nevertheless not statistical significant differences were found recurrent AF group. High frequency values, especially without a gradient between both atria, predict AF recurrence. It suggests that when the atrial electrical activity is more irregular and similar in both atria, the reversion to sinus rhythm is more difficult.

The objective of this study was to determine the effect of aging on regularity of blood pressure and pulse interval in resting and active conditions. We studied two normotensive subjects groups: young (20 to 40 years, n=23) and elderly people (60 to 80 years, n=23). No differences of gender have been found between young and elderly groups. Beat-to-beat blood pressure was measured by Finapres system during the six-minutes walk distance test. Overall systolic and diastolic blood pressures and pulse intervals regularity were determined. Differences in blood pressure and heart rate regularity were found between age groups. These results show the efficiency of nonlinear methods to characterize cardiac dynamic.

Orthostatic hypotension (OH) is an excessive fall in blood pressure when an upright position is assumed and is related symptoms associated with the occurrence of syncope. It presents as a heterogeneous group of diseases but commonly manifest with symptoms of orthostatic intolerance (OI). This study is focused to quantify the regularity in hemodynamic profile by Shannon Entropy (SE) hemodynamic measures to in older people with symptoms of OI undergoing an active stand and to investigate if their dynamic cardiovascular profile during a six-minute walk would be different to those of controls. The database included a total of 65 participants, aged over 70 years of age, of whom 65% were female. There was no significant differences in age and gender between symptomatic and asymptomatic participants 44.6% (n=29) had symptomatic OI and 55.4% (n=36) did not. SE measurement of HR showed differences during phase 2 in both groups with statistical signification (p=0.03), with 1.73±0.56 in non-symptomatic OI and 2.05±0.62 in symptomatic OI. These differences did not arrive to the statistical signification for the average of diastolic and systolic blood pressure. Moreover, HR entropy measures showed statistical significant differences between phases in the control group with a regularity increase during the physically active phase. The main conclusion is that orthostatic HR regularity response appears impaired during the exercise, especially in the symptomatic OI patients, with more irregular time series during the active phase.

[EN] Atrial fibrillation (AF) recurrence rates after successful ablation procedures are still high and difficult to predict. This work studies the capability of entropy measured from intracardiac recordings as an indicator for recurrence outcome. Intra-atrial recordings from 31 AF patients were registered previously to an ablation procedure. Four electrodes were located at the right atrium (RA) and four more at the left atrium (LA). Sample entropy measurements were applied to these signals, in order to characterize different non-linear AF dynamics at the RA and LA independently. In a 3 months follow-up, 19 of them remained in sinus rhythm, whereas the other 12 turned back to AF. Entropy values can be associated to a proarrhythmic indicator as they were higher in patients with AF recurrence (1.11 +/- 0.15 vs. 0.91 +/- 0.13), in persistent patients (1.03 +/- 0.19 vs. 0.96 +/- 0.15), and at the LA with respect to the RA (1.03 +/- 0.23 vs. 0.89 +/- 0.15 for paroxysmal AF patients). Furthermore, entropy values at the RA arose as a more reliable predictor for recurrence outcome than at the LA. Results suggest that high entropy values, especially at the RA, are associated with high risk of AF recurrence. These findings show the potential of the proposed method to predict recurrences post-ablation, providing additional insights to the understanding of arrhythmia., This work was supported by the Castilla-La Mancha Research Scheme (PPII- 2014-024-P).

The dominant atrial frequency is a key parameter for the analysis of atrial fibrillation (AF) from intracardiac recordings. The preprocessing approach employed by Botteron et al. in an early work is able to retrieve this frequency. The preprocessing steps are: (1) 40-250-Hz band-pass filtering, (2) rectification, and (3) 20 Hz low-pass filtering.The theoretical aspects of this process are addressed. Moreover, its time-domain and frequency-domain properties are evaluated using both simulations and real electrogram (EGM) recordings. The fundamental frequency is emphasized, due to the rectification step. As the interval between consecutive activations becomes more irregular, fundamental frequency detection becomes less robust. In the case of fractionated EGM, this approach fails. In time-domain, the waveform of the atrial beats are dramatically modified, hence hindering any further analysis on the morphology of the activations.Botteron preprocessing succeeds in estimating the dominant atrial rate in most EGMs during AF. However, this approach presents some limitations and improved methods are required.

The mechanism underlying atrial fibrillation (AF) remains poorly understood. Multiple wandering propagation wavelets drifting through both atria under hierarchical models are not understood. Some pharmacological drugs, known as antiarrhythmics, modify the cardiac ionic currents supporting the fibrillation process within the atria and may modify the AF propagation dynamics terminating the fibrillation process. Other medications, theoretically non-antiarrhythmic, may slightly affect the fibrillation process in non-defined mechanisms. We evaluated whether the most commonly used anaesthetic agent, propofol, affects AF patterns. Partial least-squares (PLS) analysis was performed to reduce significant noise into the main latent variables to find the differences between groups. The final results showed an excellent discrimination between groups with slow atrial activity during the propofol infusion. © 2012 Institute of Physics and Engineering in Medicine. © 2012 Institute of Physics and Engineering in Medicine., This work was supported by the Ministry of Education and Science of Spain. (Ref: EASI TEC2009-13939).

During atrial fibrillation (AF), multiple wandering propagation wavelets at high rates drift around both atria under controversial hierarchical models. Antiarrhythmic drugs modify the cardiac ionic currents supporting the fibrillation process within the atria, and can alter AF propagation dynamics and even terminate the arrhythmia. However, some other drugs, theoretically nonantiarrhythmic, may slightly block particular cardiac ionic currents through uncertain mechanisms in such a subtle way at regular heart rates that may have been pharmacologically overlooked. These potential effects might be better exposed at much higher activation rates as in AF, where atrial cells depolarize over 400 times per second. In this review, we aimed to compile and discuss results from several studies evaluating the net effect of profound sedation with propofol on atrial cells and atrioventricular (AV) conduction. Propofol is a very commonly used anesthetic agent, and its possible effect on AF dynamics has systematically not been taken into account in the myriad of clinical studies dealing with AF intracardiac recordings. The possible effect of sedation with propofol on AF was evaluated through the analysis of AF propagation patterns before and after its infusion in a series of patients submitted to pulmonary vein ablation. Effect on AV conduction will be discussed as well.

La fibrilación auricular es la arritmia más frecuente en la práctica clínica, con una prevalencia que alcanza el 10% en la población mayor de 70 años, y unas perspectivas de incremento en consonancia con el aumento de la esperanza de vida. No obstante, a pesar de ser la arritmia más frecuente, los mecanismos causantes de su generación y persistencia no se conocen con exactitud. Por esta razón, los estudios cuyo objetivo sea profundizar en los mecanismos que envuelven la citada arritmia son de gran ayuda para el desarrollo de protocolos clínicos que mejoren el diagnóstico, y permitan seleccionar los tratamientos más apropiados.Numerosos estudios científicos han indagado en cuáles son los factores que afectan al estado electrofisiológico de las aurículas, responsables de la iniciación y mantenimiento de la fibrilación, así como en los que gobiernan la transmisión de los impulsos eléctricos entre la aurícula y el ventrículo, donde el sistema nervioso autónomo se ha apuntado como uno de los factores responsables.En esta tesis doctoral se ha estudiado el efecto sobre la actividad auricular y ventricular, del anestésico más comúnmente usado en terapias destinadas a restablecer el ritmo sinusal en pacientes con episodios de fibrilación auricular. Este anestésico es el propofol (2,6-diisopropylphenol), que es un rápido anestésico intravenoso.La rápida redistribución y metabolismo del propofol resultan en una rápida eliminación de aproximadamente 1 hora, haciéndolo útil para sedaciones de corta duración. La hipótesis de este estudio es si el propofol puede alterar la actividad auricular durante la fibrilación auricular.Simultáneamente a la realización de los procedimientos de ablación, se realizan registros electrocardiográficos y electrogramas auriculares. Los electrogramas permiten extraer información local de las aurículas, muy útil para reflejar los procesos electrofisiológicos que ocurren durante la fibrilación auricular. Habitualmente, los registros internos de epi, Cervigón Abad, R. (2009). Signal processing of intracardiac recordings for the evaluation of propofol effects during atrial fibrillation [Tesis doctoral no publicada]. Universitat Politècnica de València. doi:10.4995/Thesis/10251/5766.

Since the cardiac activity during atrial fibrillation (AF) may be influenced by autonomic modulations, in this study, a novel method to quantify the effects of the most common anesthetic agent (propofol) in AF ablation procedures is introduced. This study has two main objectives: first, to assess whether the sedation earlier to radio frequency ablation affects the arrhythmia itself, and second, to provide new information that contributes to a better understanding of the influence of the autonomic nervous system on AF. The methodology presented is based on the measurement of synchronization and delay indexes between two atrial activations at adjacent intracavitary electrodes. These parameters aim to estimate whether two activations at different sites may be caused by the same propagating wavefront, or otherwise, are the consequence of independent wavefronts. The results showed that the mentioned indexes have a different behavior at both atria: the right atrium becomes more synchronized with propofol administration, whereas the synchronization index decreases at the left atrium.

The Stereotaxis(R) remote magnetic navigation system provides a new approach to ablation that could increase catheter stability. The aim was to determine whether improved tissue contact necessitates a change in traditional radiofrequency ablation parameters.The study compared ablation of atrioventricular nodal reentrant tachycardia (AVNRT) using remote navigation (4-mm catheter) in 19 patients with conventional ablation in 18 patients (4-mm catheter, temperature 60-65 degrees C, power 50 W). The radiofrequency energy needed to ensure that no more than a single nodal echo beat could be induced was measured.Charring was observed with traditional parameters on the first applications of the remotely navigated catheter. Hence, the energy was subsequently reduced (to 50 degrees C and 40 W). There was no difference in the number of applications between remote navigation and conventional groups (median: 6 vs. 8.5; interquartile range [IQR]: 11 vs. 9). Applications lastingor=5 s were usually due to catheter dislodgment. Only four patients in the remote group had applicationsor=5 s compared with 11 in the conventional group (P=.041). Ablation using remote navigation was equally effective and required lower temperatures and powers (mean+/-SD temperature: 46+/-2 degrees C vs. 50+/-4 degrees C, P.001; median [IQR] power: 29 [14] W vs. 50 [7] W, P.001), with no difference in total energy delivered. With remote navigation, the range of impedance values between applications was less (mean+/-SD: 10.4+/-7.6 Omega vs. 19.3+/-15.4 Omega; P=.035) and the temperature variation tended to be less, suggesting greater stability between applications. There were no complications.In this initial series, remote magnetic navigation was safe and effective in AVNRT ablation. Improved tissue contact reduced catheter dislodgment and necessitated a reduction in radiofrequency energy to avoid charring.

In this study the effect of the most useful anaesthetic will be evaluated in patients with atrial fibrillation (AF). Principal component analysis (PCA) has been applied as a method to represent the electrogram recordings in a more efficient manner using fewer channels. Subsequently, PCA was applied to reduce the data set to a few representative activations, measured the average dissimilarity between consecutive activations of an intracardiac signal. The purpose of PCA is here to reduce the amount of data to be analyzed in order to analyze the differences in the waveforms morphology. The proposed indexes show different behavior patterns along the atrial area during the anaesthetic effects.

Since the cardiac activity during atrial fibrillation (AF) may be influenced by autonomic modulations. In this study a new method to quantify the effect of the most useful anaesthetic agent (propofol) on the fibrillation patterns will be introduced. This method is based in the measurement of the delay between two atrial activations. Experimental data were obtained using a bipolar catheter in the atria in 27 patients during AF. The single averaged delay index from adjacent pairs of bipolar recordings situated in left and right atrial areas was computed. The results showed that this index has a different behaviour in both atria during the anaesthetic infusion, what is congruence with a previous study and corroborate it as valid descriptors of the electrophysiological properties of atrial tissues.

Effect of anaesthetic agents in restoration rhythm procedures during atrial fibrillation (AF) has not been fully investigated. We evaluated the effects of a widely used anaesthetic agent (propofol) in the fibrillation patterns. Intra-atrial recordings belong to 18 patients diagnosed with AF were analyzed ldquobeforerdquo (baseline) and ldquoduringrdquo anaesthetic infusion. The goal of this study is to characterize the variation in atrial properties along the atria in both states. The wavelet variance decomposes the variance of a time series on a scale by scale basis and hence has considerable appeal when physical phenomena are analyzed in terms of variations operating over a range of different scales. Moreover, the variance estimates are more accurately determined with a maximal-overlap version of the wavelet transform (MODWT). As mother wavelet was used the Haar wavelet where the signal was partitioned over seven scales. Wavelet analysis highlights a significant lower changes during the anaesthetic infusion respect to the basal conditions in the right atrium, with an opposite effect and non significant values in the left atrium. The proposed methodology provides an additional approach to the understanding of the role of the anaesthetic, showing a decrease in the variance inter-scales during the anaesthetic infusion in the right atrium, with the opposite effect in the left atrium.

Power line interference may severely corrupt a biomedical recording. Notch Filters and adaptive cancellers have been suggested to suppress this interference. In this paper, an improved adaptive canceller for the reduction of the fundamental power line interference component in electrocardiogram (ECG) recordings is proposed. A comparison is made between the performance of our method and a narrow and a wide notch filter and notch adaptive filter in suppressing the fundamental power line interference component. For this purpose, a deal ECG signal is corrupted by an artificial power line interference signal. The cleaned signal after applying all methods is compared with the original ECG signal. Results indicate that power line interference of ECG are removed effectively by this new method. Interference elimination can be performed continuously and rapidly even if the situations of interference are changing with time or frequency. In the worst conditions 48.5 Hz and 51.5 Hz (BW 1.5 Hz), ANN obtained results show the efficiency (CCC=0.96plusmn0.02 SIR=17.3plusmn0.4) in comparison with the classical technique with the best performance (CCC=0.91plusmn0.03 SIR=13.2plusmn0.6). The method is easy to implement and it is applicable not only to ECG but also other biomedical signals.

The effect of conventional i.v. anaesthetic agents on atrial fibrillation (AF) dynamics has not been fully addressed. We aim to evaluate whether the most frequently used intravenous anaesthetic agent, propofol, modifies AF organization parameters. Multiple and simultaneous intraatrial bipolar recordings from 27 patients in AF were analyzed before and after infusing a propofol bolus. Signal organization parameters were determined using time and frequency domain analysis. Non-linear analysis was also performed to determine signal entropy. Linear analysis showed that AF becomes more organized in right atrial recordings after infusing propofol, increasing interelectrode correlation (difference of 0.017 +/- 0.005), with the contrary effect on the left atrial dipoles (difference of -0.015 +/- 0.009, p = 0.008). Entropy analysis showed similar findings, achieving a statistical significance of p = 0.001 with Shannon Entropy.

The mechanisms responsible for the maintenance of atrial fibrillation (AF) are not completely understood yet. It has been demonstrated that AF can be modulated by several cardiac diseases, the autonomic nervous system and even drugs with purportedly no antiarrhythmic properties. We evaluated the effects of a widely used anaesthetic agent (propofol) in the fibrillation patterns. Spectral analysis was performed over atrial electrograms at baseline and immediately after a propofol bolus. Only after performing principal component analysis (PCA), we were able to significantly detect that propofol slows AF.

In a substantial number of patients atrial fibrillation (AF) recurs after successful electrical cardioversion, but at present there are no reliable clinical markers for confidently identifying the patients in which recurrence will occur within a short period of time. This study evaluates the predictive classification performance of Sample Entropy (SampEn) in the discrimination between recurrent and non-recurrent AF episodes. A validated database of 35 ECG recordings acquired from AF subjects undergoing cardioversion was used throughout the study, together with their known recurrence status at one month. SampEn was applied to these QRST-reduced electrocardiograms, to atrial activity (AA), and also to heart rate (R-R intervals). The sample entropy of R–R intervals was significantly reduced (p=0.043) in the recurrent AF episodes compared with maintenance sinus rhythm episodes. SampEn applied to the AA signal showed a opposite results, it was reduced with a significant increasing trend in the maintenance sinus rhythm episodes (p=0.017). There is a need for welldefined studies with larger patient groups in order to assess the entropy changes further and to look for possible changes, which might predict AF recurrence.

Nowadays, there exist different approaches to cancel out noise effect and baseline drift in biomedical signals. However, none of them can be considered as completely satisfactory. In this work, an artificial neural network (ANN) based approach to cancel out baseline drift in electrocardiogram signals is presented. The system is based on a grown ANN allowing to optimize both the hidden layer number of nodes and the coefficient matrixes. These matrixes are optimized following the Window-Hoff Delta algorithm, offering much lower computational cost that the traditional back propagation algorithm. The proposed methodology has been compared with traditional baseline reduction methods (FIR, Wavelet and Adaptive LMS filtering) making use of cross correlation, signal to interference ratio and signal to noise ratio indexes. Obtained results show that the ANN-based approach performs better, with respect to baseline drift reduction and signal distortion at filter output, than traditional methods.

Effect of anaesthetic agents in restoration rhythm procedures during atrial fibrillation (AF) has not been fully investigated. Intra-atrial recordings belong to 27 patients diagnosed with AF were analyzed ldquobeforerdquo (baseline) and ldquoduringrdquo anaesthetic infusion. Organization measurements were evaluated in time-domain and frequency-domain, as well as approaches from non linear analysis. The frequency domain measurements showed that the average AF cycle length increased as an effect of anaesthesia. The results of time and frequency linear organization measurements showed a higher correlation during the anaesthetic infusion in the right atrium with an opposite effect in the left atrium. The same effects were corroborated with entropy analysis. The proposed methodology provide additional insights to the understanding of the role of the anaesthetic, by suggesting increased parasympathetic activation at atrial level.

The pathophysiological mechanisms of atrial fibrillation (AF) are not entirely clear yet, and there is no full explanation for the development and evolution of the arrhythmia. The goal of this study is to find inter-atrium differences in electrophysiological behavior between persistent and paroxysmal AF. The database analyzed contains intra-cardiac records from 14 patients with paroxysmal AF and 10 with persistent AF. Dominant frequency and sample entropy measurements showed that in the paroxysmal group there was a left-to-right gradient. These differences were enhanced after the extraction of the main components with principal component analysis. These findings may be interpreted as a possible evolutionary path from paroxysmal to persistent AF, with a higher irregularity in the left atrium in paroxysmal AF and non- significant differences in persistent AF.

Blind source separation (BSS) has been probed as one of the most effective techniques for the atrial activity (AA) extraction in supraventricular tachyarrhythmia episodes like atrial fibrillation (AF). In these situations, the registered episodes with only a few leads are noisy and time-varying and previous stages for sparse separation have been demonstrated as necessary. Including wavelet transform de-noising and natural gradient algorithm for the BSS system can improve the extraction quality with low computational load. Synthetic signals have been used to test the proposed technique in different noisy cases. The obtained cross-correlation coefficients with sparse sequential separation between the extracted signal and the original ones exceed the 94% in contrast with the obtained results using standalone BSS method. The easy and fast implementation and the minimum required reference recordings of the same ECG are some of the main advantages of this technique and make the application in real time systems possible

International audience

The effect of the most useful anaesthetic in cardiovascular therapy, called propofol, was evaluated in patients with atrial fibrillation (AF). In order to represent the electrogram recordings in a more efficient manner Principal component analysis (PCA) has been applied. Moreover, to reduce the data set to a few representative activations PCA was applied again to measure the average dissimilarity between consecutive activations of an intracardiac signal. In addition PCA was applied directly to the activations extracted from each dipole to analysis temporal varibility, and spatial variability with the comparation of the signals from different dipoles. The proposed indexes show different behaviour patterns along the atrial area during the anaesthetic effects.

The aim of our study was to analysed the proportion of both casual direction between inter-beat interval (R-R) and non-invasive beat to beat blood pressure (BP) during six minutes walking distance test between symptomatic and asymptomatic participants of orthostatic intolerance (OI). We analysed 65 older subjects, of whom 42 were women. The participants underwent a supine to stand orthostatic test with non-invasive beat-to-beat systolic blood pressure and diastolic blood pressure and R-R monitoring. Transfer Entropy (TE) method was applied to identify relationship between hemodynamical variables. The directionality index quantifies the preferred direction of information flow from difference between both directional couplings. Results show a higher symmetric bidirectional couplings in asymptomatic OI group. These results show that systolic blood pressure affects heart rate; nevertheless directional coupling between these cardiovascular signals is altered depending on changes in autonomic control introduced by the orthostatic test.