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The atrial activity (AA) of surface ECGs in atrial fibrillation (AF) has been studied to evaluate and compare the ability of several nonlinear metrics in the discrimination of AF events by estimating their regularity. The AA signals were extracted by applying an adaptive QRST can-celation method. Next, the study of surrogate data was performed and revealed the nonlinear behavior of AA. The following...
Electrical cardioversion (ECV) is a well-established therapy for atrial fibrillation (AF), which is the most common cardiac arrhythmia in clinical practice. However, conventional ECV protocols cannot manage whether to stop or to continue delivering shocks to the patient after an unsuccessful tentative. To this respect, the present contribution analyzes the ability of the fibrillatory waves amplitude...
Ectopic beats are early heart beats notably different to the normal beat morphology. These beats are very common in atrial fibrillation (AF) being the source of important residua when ventricular activity is intended to be removed. Recently, their detection and clustering to build an efficient cancellation template, via principal component analysis (PCA), allowed us to obtain ECG signals with notably...
The estimation of atrial activation times in atrial fibrillation (AF) has become an established way to evaluate AF through several indices like organization of the arrhythmia, atrial cycle length, etc. Classic fibrillatory (f) waves delineation uses atrial electrograms because larger f waves are present in these recordings. This work introduces a new f waves delineator based on mathematical morphology...
Cox-Maze surgery is an effective procedure to terminate atrial fibrillation (AF) in patients requiring open-heart surgery associated to another heart disease. After the intervention, AF spontaneous reversion occurs immediately in some patients, but not in others. This work analyzes 23 twelve-lead preoperative ECGs from patients in AF to predict immediate termination of the arrythmia. To carry out...
The problem of classifying short atrial fibrillatory segments in ambulatory ECG recordings as being either paroxysmal or persistent is addressed by investigating a robust approach to signal characterization. The method comprises preprocessing estimation of the dominant atrial frequency for the purpose of controlling the subbands of a filter bank, computation of the relative subband (harmonics) energy,...
Sample Entropy (SampEn) is a nonlinear regularity index that requires the a priori selection of three parameters: the length of the sequences to be compared, m, the patterns similarity tolerance, r, and the number of samples under analysis, N. Appropriate values for m, r and N have been recommended in some cases, such as heart rate, hormonal data, etc., but no guidelines exist for the selection of...
The present work introduces a new ECG delineator, based on the Phasor Transform, which is characterized by its robustness, low computational cost and mathematical simplicity. The method converts each instantaneous ECG sample into a phasor, thus being able to deal very precisely with P and T waves, which are of notably lower amplitude than the QRS complex. Initially, the method relies on the detection...
The development of non-invasive tools able to provide valuable information about the effectiveness of a shock in external electrical cardioversion (ECV) is clinically relevant to enhance these protocols in the treatment of atrial fibrillation (AF). The present contribution analyzes the ability of a non-linear regularity index, such as sample entropy (SampEn), to follow-up noninvasively AF organization...
The analysis of the surface electrocardiogram (ECG) is the most extended noninvasive technique in medical diagnosis of atrial fibrillation (AF). In order to use the ECG as a tool for the analysis of AF, we need to separate the atrial activity (AA) from other cardioelectric signals. In this matter, statistical signal processing techniques, like independent component analysis (ICA) algorithms, are able...
The present work introduces a new ECG delineator, based on the Phasor Transform, which is able to operate in single lead recordings. The method converts each instantaneous ECG sample into a phasor, thus being able to deal very precisely with P and T waves, which are of notably lower amplitude than the QRS complex. Initially, the method relies on the detection of R peaks and, next, onset and offset...
In this work, a new method for ectopics removal from ECG recordings is proposed. The method distinguish between normal and ectopic beats through a forward/backward level windowing strategy. Next, by using an adaptive correlation index, the 15 most similar ectopic beats to the one under cancellation are clustered, thus serving to get their eigenvector matrix by singular value decomposition. Finally,...
Predicting non-invasively the effectiveness of a shock in external electrical cardioversion (ECV) is clinically relevant to enhance these protocols in the treatment of atrial fibrillation (AF). The present contribution analyzes the ability of a non-linear regularity index, such as sample entropy (SampEn), to follow-up noninvasively AF organization under successive attempts of ECV and to predict the...
Sample Entropy (SampEn) is a nonlinear regularity index that requires the a priori selection of three parameters: the length of the sequences to be compared, m, the patterns similarity tolerance, r, and the number of samples under analysis, N. Appropriate values for m, r and N have been recommended in some cases, such as heart rate, hormonal data, etc., but no guidelines exist for the selection of...
In order to use the ECG as a tool for the characterization of atrial fibrillation (AF), we need to dissociate atrial activity (AA) from ventricular activity. On the other hand, the reduced number of leads recorded from a Holter system limits the necessary spatial diversity required by Blind Source Separation (BSS) techniques to accurately extract the AA. In this work, we propose a new method, the...
In recent studies, Sample Entropy (SampEn) has demonstrated that can be a very promising non-linear index to assess atrial fibrillation (AF) organization from surface ECG recordings. However, non-linear regularity metrics are notably sensitive to noise. Thereby, in the present work, the effect that noise provokes in the SampEn-based organization estimation is analyzed. Given that AF organization was...
Wavelet Sample Entropy (WSE) has been previously introduced as a successful methodology to predict electrical cardioversion (ECV) outcome of persistent atrial fibrillation (AF). The method estimates AF organization based on the combination of Wavelet decomposition and a nonlinear regularity metric, such as Sample Entropy (SampEn). However, WSE has been only computed by applying a specific wavelet...
In this work, a method for non-invasive assessment of AF organization has been applied to discriminating between paroxysmal and long-term persistent AF episodes. Following extraction of the atrial activity (AA) signal, the dominant atrial frequency (DAF) of the AA was computed based on a hidden Markov model. Finally, the main atrial wave (MAW) was obtained by bandpass filtering centered on the DAF,...
In the present work, three methods based on the Sample Entropy (SampEn) non-invasive organization estimation of atrial fibrillation (AF) to predict its spontaneous termination are compared making use of the same patient's database. In the first strategy, the atrial activity (AA) is obtained through QRST cancellation. Next, the main atrial wave (MAW) of the AA is obtained by selective filtering centered...
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