Cancellation of the Maternal and Extraction of the Fetal ECG in Noninvasive Recordings

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Susceptibility to Paroxysmal Atrial Fibrillation: A Study using Sinus Rhythm P Wave Parameters

International audienceEarly recognition of patients at high risk for atrial fibrillation may help to minimize potential health risks. The detection of susceptibility to develop atrial fibrillation is thus a real clinical challenge. Whereas many studies have used the signal-averaged P wave, the aim of this work is to determine whether electrocardiographic parameters resulting from the analysis of the P wave in ECG recorded during sinus rhythm could be markers for paroxysmal atrial fibrillation susceptibility. Our idea was to compare the ECG in sinus rhythm from two populations: healthy people and patients subject to paroxysmal atrial fibrillation. In addition to standard P wave parameters (P width, P-R interval,...), the Euclidean distance between beat-to-beat P waves, which has been rarely addressed in this context, was studied on lead V1. Significant differences between the healthy and the paroxysmal atrial fibrillation groups were obtained for various parameters. Moreover, a classification of the two groups based on the joint analysis of P width and P-R interval was suggested. This proposed classification could lead to an effective identification of patients at risk to develop atrial fibrillation

Digital DC-Reconstruction of AC-Coupled Electrophysiological Signals with a Single Inverting Filter

Since the introduction of digital electrocardiographs, high-pass filters have been necessary for successful analog-to-digital conversion with a reasonable amplitude resolution. On the other hand, such high-pass filters may distort the diagnostically significant ST-segment of the ECG, which can result in a misleading diagnosis. We present an inverting filter that successfully undoes the effects of a 0.05 Hz single pole high-pass filter. The inverting filter has been tested on more than 1600 clinical ECGs with one-minute durations and produces a negligible mean RMS-error of 3.1*10(-8) LSB. Alternative, less strong inverting filters have also been tested, as have different applications of the filters with respect to rounding of the signals after filtering. A design scheme for the alternative inverting filters has been suggested, based on the maximum strength of the filter. With the use of the suggested filters, it is possible to recover the original DC-coupled ECGs from AC-coupled ECGs, at least when a 0.05 Hz first order digital single pole high-pass filter is used for the AC-coupling

Debatable issues in automated ECG reporting

Although automated ECG analysis has been available for many years, there are some aspects which require to be re-assessed with respect to their value while newer techniques which are worthy of review are beginning to find their way into routine use. At the annual International Society of Computerized Electrocardiology conference held in April 2017, four areas in particular were debated. These were a) automated 12 lead resting ECG analysis; b) real time out of hospital ECG monitoring; c) ECG imaging; and d) single channel ECG rhythm interpretation. One speaker presented the positive aspects of each technique and another outlined the more negative aspects. Debate ensued. There were many positives set out for each technique but equally, more negative features were not in short supply, particularly for out of hospital ECG monitoring

Diagnostic and prognostic value of QRS duration and QTc interval in patients with suspected myocardial infarction

Background: While prolongation of QRS duration and QTc interval during acute myocardial infarction (AMI) has been reported in animals, limited data is available for these readily available electrocardiography (ECG) markers in humans. Methods: Diagnostic and prognostic value of QRS duration and QTc interval in patients with suspected AMI in a prospective diagnostic multicentre study were prospectively assessed. Digital 12-lead ECGs were recorded at presentation. QRS duration and QTc interval were automatically calculated in a blinded fashion. Final diagnosis was adjudicated by two independent cardiologists. The prognostic endpoint was all-cause mortality during 24 months of follow-up. Results: Among 4042 patients, AMI was the final diagnosis in 19% of patients. Median QRS duration and median QTc interval were significantly greater in patients with AMI compared to those with other final diagnoses (98 ms [IQR 88–108] vs. 94 ms [IQR 86–102] and 436 ms [IQR 414–462] vs. 425 ms [IQR 407–445], p < 0.001 for both comparisons). The diagnostic value of both ECG signatures however was only modest (AUC 0.56 and 0.60). Cumulative mortality rates after 2 years were 15.9% vs. 5.6% in patients with a QRS > 120 ms compared to a QRS duration ≤ 120 ms (p < 0.001), and 11.4% vs. 4.3% in patients with a QTc > 440 ms compared to a QRS duration ≤ 440 ms (p < 0.001). After adjustment for age and important ECG and clinical parameters, the QTc interval but not QRS duration remained an independent predictor of mortality. Conclusions: Prolongation of QRS duration > 120 ms and QTc interval > 440 ms predict mortality in patients with suspected AMI, but do not add diagnostic value

Automatically computed ECG algorithm for the quantification of myocardial scar and the prediction of mortality

Myocardial scar is associated with adverse cardiac outcomes. The Selvester QRS-score was developed to estimate myocardial scar from the 12-lead ECG, but its manual calculation is difficult. An automatically computed QRS-score would allow identification of patients with myocardial scar and an increased risk of mortality.; To assess the diagnostic and prognostic value of the automatically computed QRS-score.; The diagnostic value of the QRS-score computed automatically from a standard digital 12-lead was prospectively assessed in 2742 patients with suspected myocardial ischemia referred for myocardial perfusion imaging (MPI). The prognostic value of the QRS-score was then prospectively tested in 1151 consecutive patients presenting to the emergency department (ED) with suspected acute heart failure (AHF).; Overall, the QRS-score was significantly higher in patients with more extensive myocardial scar: the median QRS-score was 3 (IQR 2-5), 4 (IQR 2-6), and 7 (IQR 4-10) for patients with 0, 5-20 and > 20% myocardial scar as quantified by MPI (p < 0.001 for all pairwise comparisons). A QRS-score ≥ 9 (n = 284, 10%) predicted a large scar defined as > 20% of the LV with a specificity of 91% (95% CI 90-92%). Regarding clinical outcomes in patients presenting to the ED with symptoms suggestive of AHF, mortality after 1 year was 28% in patients with a QRS-score ≥ 3 as opposed to 20% in patients with a QRS-score < 3 (p = 0.001).; The QRS-score can be computed automatically from the 12-lead ECG for simple, non-invasive and inexpensive detection and quantification of myocardial scar and for the prediction of mortality. TRIAL-REGISTRATION: http://www.clinicaltrials.gov . Identifier, NCT01838148 and NCT01831115

Restauration et analyse de l'électrocardiogramme acquis pendant les examens d'imagerie par résonance magnétique :

The electrocardiogram (ECG) is used in magnetic resonance imaging (MRI) for patient monitoring and for synchronization of the MR images. The environment of MRI (magnetic field, magnetic field gradients and radiofrequency waves) complicates the acquisition of the ECG and needs specific developments. In the first part, the thesis analyses the interferences of the MRI on the ECG and vice versa. This part concludes with a physical model of the interferences between MRI and ECG. Thanks to this model an ECG sensor that is better adapted to the MRI environment has been constructed. In the second part, artefact suppression superposing the ECG signal by software is discussed. A mathematical model is proposed as base for the artefact suppression. The linear and time invariant model (LTI) of the gradient artefact generation is verified and validated. The test methods for the verification of restoration algorithms of the ECG are defined. For offline restoration, the method by FFT, by cross-power spectrum, Wiener filtering and least squares are studied. In the third part, a second category of algorithms is tested in case of online restoration. The LMS and RLS filters and their subtypes are analysed. In the summary, the Wiener filter is used for easier manual annotation of artefacted ECG. The LMS filter as well as a QRS detection and beat classification module are applied to a annotated ECG database in order to show the real-time suppression efficiency of the artefacts due to magnetic field gradient artefactsL'électrocardiogramme (ECG) est utilisé en imagerie par résonance magnétique (IRM) pour le monitorage du patient et pour la synchronisation des séquences d'images. L'environnement de l'IRM (champ magnétique, gradients du champ magnétique temporels et ondes radiofréquence) complique la mesure de l'ECG et nécessite des développements spécifiques pour l'exploitation de ce signal. Dans la première partie, la thèse analyse les aspects de l'interférence de l'IRM sur l'ECG et réciproquement. Cette partie conclut par un modèle physique des interférences entre l'IRM et l'ECG. Grâce à ce modèle, on a pu construire un capteur ECG mieux adapté à l'environnement IRM. Dans la deuxième partie, la suppression des artefacts se superposant à l'ECG par logiciel est discutée. Un modèle mathématique est proposé qui servira de base à la suppression de ces artefacts. Le modèle linéaire et invariant dans le temps pour la génération des artefacts dus aux gradients IRM est vérifié et validé. Des méthodes de test pour la vérification des algorithmes de restauration de l'ECG sont définies. Des méthodes par FFT, par spectre de puissance croisé, par filtrage de Wiener et par la méthode des moindres carrés sont étudiées pour la restauration en temps différé du signal ECG. Le filtrage par Wiener s'est avéré optimal. Dans la troisième partie, une deuxième catégorie d'algorithmes est ensuite testée dans le cas de la restauration en temps réel. Les filtres adaptatifs LMS, RLS et leurs variantes sont analysés. Dans la synthèse de la thèse, le filtrage de Wiener est utilisé pour l'annotation manuel plus facile des ECG artefactés. Le filtre LMS ainsi qu'une module de détection QRS et classification des battements sont appliqués à une base de donnée d'ECG annoté pour montrer l'efficacité de la suppression en temps réel des artefacts dus aux gradients de champ magnétiqu

Restauration et analyse de l'électrocardiogramme acquis pendant les examens d'imagerie par résonance magnétique

L'électrocardiogramme (ECG) est utilisé en imagerie par résonance magnétique (IRM) pour le monitorage du patient et pour la synchronisation des séquences d'images. L'environnement de l'IRM (champ magnétique, gradients du champ magnétique temporels et ondes radiofréquence) complique la mesure de l'ECG et nécessite des développements spécifiques pour l'exploitation de ce signal. Dans la première partie, la thèse analyse les aspects de l'interférence de l'IRM sur l'ECG et réciproquement. Cette partie conclut par un modèle physique des interférences entre l'IRM et l'ECG. Grâce à ce modèle, on a pu construire un capteur ECG mieux adapté à l'environnement IRM. Dans la deuxième partie, la suppression des artefacts se superposant à l'ECG par logiciel est discutée. Un modèle mathématique est proposé qui servira de base à la suppression de ces artefacts. Le modèle linéaire et invariant dans le temps pour la génération des artefacts dus aux gradients IRM est vérifié et validé. Des méthodes de test pour la vérification des algorithmes de restauration de l'ECG sont définies. Des méthodes par FFT, par spectre de puissance croisé, par filtrage de Wiener et par la méthode des moindres carrés sont étudiées pour la restauration en temps différé du signal ECG. Le filtrage par Wiener s'est avéré optimal. Dans la troisième partie, une deuxième catégorie d'algorithmes est ensuite testée dans le cas de la restauration en temps réel. Les filtres adaptatifs LMS, RLS et leurs variantes sont analysés. Dans la synthèse de la thèse, le filtrage de Wiener est utilisé pour l'annotation manuel plus facile des ECG artefactés. Le filtre LMS ainsi qu'une module de détection QRS et classification des battements sont appliqués à une base de donnée d'ECG annoté pour montrer l'efficacité de la suppression en temps réel des artefacts dus aux gradients de champ magnétique.The electrocardiogram (ECG) is used in magnetic resonance imaging (MRI) for patient monitoring and for synchronization of the MR images. The environment of MRI (magnetic field, magnetic field gradients and radiofrequency waves) complicates the acquisition of the ECG and needs specific developments. In the first part, the thesis analyses the interferences of the MRI on the ECG and vice versa. This part concludes with a physical model of the interferences between MRI and ECG. Thanks to this model an ECG sensor that is better adapted to the MRI environment has been constructed. In the second part, artefact suppression superposing the ECG signal by software is discussed. A mathematical model is proposed as base for the artefact suppression. The linear and time invariant model (LTI) of the gradient artefact generation is verified and validated. The test methods for the verification of restoration algorithms of the ECG are defined. For offline restoration, the method by FFT, by cross-power spectrum, Wiener filtering and least squares are studied. In the third part, a second category of algorithms is tested in case of online restoration. The LMS and RLS filters and their subtypes are analysed. In the summary, the Wiener filter is used for easier manual annotation of artefacted ECG. The LMS filter as well as a QRS detection and beat classification module are applied to a annotated ECG database in order to show the real-time suppression efficiency of the artefacts due to magnetic field gradient artefacts.NANCY/VANDOEUVRE-INPL (545472102) / SudocSudocFranceF

Independent component analysis-based artefact reduction: application to the electrocardiogram for improved magnetic resonance imaging triggering.

International audienceElectrocardiogram (ECG) is required during magnetic resonance (MR) examination for monitoring patients under anaesthesia or with heart diseases and for synchronizing image acquisition with heart activity (triggering). Accurate and fast QRS detection is therefore desirable, but this task is complicated by artefacts related to the complex MR environment (high magnetic field, radio-frequency pulses and fast switching magnetic gradients). Specific signal processing has been proposed, whether using specific MR QRS detectors or ECG denoising methods. Most state-of-the-art techniques use a connection to the MR system for achieving their task, which is a major drawback since access to the MR system is often restricted. This paper introduces a new method for on-line ECG signal enhancement, called ICARE, which takes advantage of using multi-lead ECG and does not require any connection to the MR system. It is based on independent component analysis (ICA) and applied in real time. This algorithm yields accurate QRS detection for efficient triggering