Examinando por Autor "Goya Esteban, R"

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A Review on Recent Patents in Digital Processing for Cardiac Electric Signals (I): From Basic Systems to Arrhythmia Analysis
(2009-07-14T11:06:21Z) Goya Esteban, R; Barquero Pérez, Óscar; Alonso Atienza, Felipe; Everss, E; Requena Carrión, Jesús; García Alberola, Arcadi; Rojo-Álvarez, José Luis
Cardiac electric signals are currently the most informative source about the heart rhythm and its disorders, and hence, the use of adequate digital signal processing techniques is necessary to yield reliable diagnostic parameters, either to the clinician or to automatic monitoring systems. A number of systems have been patented during the last years, which are grouped in this review according to their application scope. In this first part, techniques for electrocardiogram and intracardiac electrogram filtering, and for feature extraction, are first examined, then patents on arrhythmia analysis are then summarized. The wide number of basic systems for cardiac signal processing analysis that have been disclosed indicates that this field represents a main scenario in the near and middle future of cardiac health.
A Review on Recent Patents in Digital Processing for Cardiac Electric Signals (II): Advanced Systems and Applications
(2009-07-14T11:13:08Z) Barquero Pérez, Óscar; Goya Esteban, R; Alonso Atienza, Felipe; Requena Carrión, Jesús; Everss, E; García Alberola, Arcadi; Rojo-Álvarez, José Luis
Digital signal processing algorithms for cardiac recordings have been paid much attention in recently disclosed patents. In this second part of our review of the state-of-art patents, systems for sudden cardiac death prediction, as well as for apnea analysis, are summarized. Advanced digital signal processing algorithms for cardiac electric signals are specifically reviewed, including independent component decompositions, and nonlinear methods (chaos, fractals, and entropies). Finally, systems aiming to solve the inverse problem in electrocardiography are presented. Concluding remarks on these systems and on the whole review are discussed.
Analysis of Physiological Meaning of Detrended Fluctuation Analysis in Heart Rate Variability Using a Lumped Parameter Model
(2009-06-15T10:04:05Z) Rojo-Álvarez, José Luis; Sánchez Sánchez, A; Barquero Pérez, Óscar; Goya Esteban, R; Everss, E; Mora Jimenez, I; García Alberola, A
Chaos and fractal based measurements, such as Detrended Fluctuation Analysis (DFA), have been widely used for quantifying the Heart Rate Variability (HRV) for cardiac risk stratification purposes. However, the physiological meaning of these measurements is not clear. Given that existing lumped parameter models contain a detailed physiological description of several of the circulatory system regulation processes, we hypothesize that controlled changes in these processes will highlight the physiological basis in DFA indices. We used a detailed lumped parameter model of HRV, introduced earlier [6]. Ten signals were generated in different physiological conditions. DFA coefficients 1, 2, and the Hurst exponent, were calculated. A clear disruption point was always observed. Modifications in sympatho-vagal activity yielded significant changes in 1 when compared to basal, but not in 2 or Hurst exponent. Modifications in non-nervous system mediated changes yielded significant differences only for peripheral resistance and heart period, only in 1. In conclusion, the analysis of the effect of changes in the regulatory system on the HRV chaotic/fractal indices can be analyzed using detailed lumped parameter models
Changes in Detrended Fluctuation Indices with Aging in Healthy and Congestive Heart Failure Subjects
(2009-06-15T09:01:00Z) Barquero Pérez, Óscar; Marqués de Sa, J; Rojo-Álvarez, José Luis; Goya Esteban, R
Detrended Fluctuation Analysis (DFA) aims to quantify the fractal correlation properties in nonstationary time series, and it has successfully been applied in the assessment of the Heart Rate Variability (HRV) for cardiac risk stratification purposes. However the physiological meaning of DFA indices and its relation with aging have not yet been completely established. Given that a loss of complexity in the physiological regulation of elderly subjects has been reported in the literature, we hypothesized that DFA indices could be modified by aging. In this work we computed the Hurst exponent (estimated using DFA method) and DFA indices alfa1 and alfa2 to assess the HRV in healthy and Congestive Heart Failure (CHF) subjects, and we studied the dependence of these indices on aging for both healthy and CHF subjects. We found that only alfa2 and Hurst exponent, and only in the case of healthy subjects, have significant discrimination capability to distinguish between young and elderly groups, and also that these indices have a steady increase with aging. Therefore, we can conclude that the loss of complexity due to aging can be quantified by changes in the values of alfa2 and Hurst exponent.
Characterization of Heart Rate Variability Loss with Aging and Heart Failure Using Sample Entropy
(2009-06-15T08:14:22Z) Goya Esteban, R; Marques de Sa, JP; Rojo-Álvarez, José Luis; Barquero Pérez, Óscar
Entropy based measures, such as Sample Entropy (SampEn), have been widely used for quantifying the Heart Rate Variability (HRV) for cardiac risk stratification purposes, with the hypothesis that decreasing entropy points to a perturbation of the complex physiological mechanisms or disease. However, in the literature, higher entropy values have been reported for some pathologies than for healthy subjects, which could be due to the use of a threshold value r tuned relative to the signal standard deviation. In the present paper we apply SampEn to assess the variability of the RR time series from healthy subjects and subjects with Congestive Heart Failure (CHF) in order to discriminate between both groups, as well as to characterize the variability loss due to aging. We conclude that the use of a fixed threshold value r in the SampEn algorithm instead of its conventional setting (as a percentage of the standard deviation of each data series), improves the discrimination capabilities between healthy and CHF subjects, and it allows to quantify the loss of HRV due to aging in healthy subjects.
Detection and Estimation of T Wave Alternans with Matched Filter and Nonparametric Bootstrap Test
(2009-06-15T09:07:17Z) Rojo-Álvarez, José Luis; Barquero Pérez, Óscar; Mora Jimenez, I; Goya Esteban, R; Gimeno Blanes, J; García Alberola, A
Though alternans phenomena in the cardiac repolarization phase has been shown to be related to arrhythmgenesis, a definitive estimation method from the T wave of ECG recordings is not yet available. We propose a statistical signal processing scheme which compares the T-wave morphology of even and odd beats by using a running matched filter, in order to increase the signal to noise ratio of the estimation. Given that previously proposed hypothesis tests for alternans detection rely on the knowledge of noise statistical distribution, we also analyzed the usefulness of a nonparametric bootstrap test. Data set composed of 100 ECG recordings included in the Challenge Database were used. Principal Component Analysis was previously made for multilead recordings. Subsequent preprocessing for each available lead consisted of conventional baseline removing, filtering, R-wave detection, exclusion of too noisy segments, T-wave segmentation, and template generation for even and odd beats. The difference between the template and a given beat was obtained by minimizing the absolute error of their comparison with a windowed circular shift. A paired bootstrap resampling test was made for deciding whether the averaged differences between the template and the T-waves were significant compared to the noise level.
Efectos de la Edad Sobre la Estructura Fractal de la Variabilidad de Frecuencia Cardíaca
(2009-07-28T09:54:38Z) Barquero Pérez, Óscar; Marqués de Sa, J; Rojo-Álvarez, José Luis; Goya Esteban, R
Estudio del Efecto del Umbral en la Entropía Muestral: Aplicación a la Variabilidad de Frecuencia Cardíaca
(2009-07-28T10:02:36Z) Goya Esteban, R; Marqués de Sa, J; Rojo-Álvarez, José Luis; Barquero Pérez, Óscar