Responsable d’un quart des accidents vasculaires cérébraux, la fibrillation auriculaire (FA) est l’arythmie cardiaque la plus répandue. La thérapie d’ablation par cathéter (CA) est de plus en plus utilisée pour traiter la FA, mais ses effets sur le substrat cardiaque ne sont pas suffisamment compris, d’où un taux de réussite très variable. L’électrocardiogramme (ECG) à 12 voies représente un outil non invasif peu coûteux pour caractériser la FA à partir de l’activité électrique du cœur. Cependant, les prédicteurs classiques de l’issue de la CA présentent plusieurs inconvénients, notamment leur calcul manuel sur une seule voie de l’ECG. Cette thèse exploite explicitement le caractère multi-capteur de l’ECG au moyen de techniques de décomposition multivariées, démontrant qu’elles peuvent améliorer la puissance prédictive de certaines propriétés de l’ECG dans le cadre de la CA. L’amplitude des ondes fibrillatoires est corrélée avec le résultat de la CA, et traitée par une méthode multi-capteur basée sur l’analyse en composantes principales (PCA). Des variantes comme la PCA pondérée (WPCA) et la factorisation en matrices non négatives (NMF) peuvent aussi quantifier la variabilité spatio-temporelle de la FA sur l’ECG. La théorie de l’information permet également d’estimer le niveau de corrélation entre les voies de l’ECG, mis en relation avec le résultat de la CA grâce à des approches multi-capteurs. Enfin, une dernière ligne de recherche concerne la réponse ventriculaire manifestée sur la variabilité cardiaque. L’approche paramétrique de processus ponctuel est capable de souligner certaines propriétés de cette variabilité, améliorant ainsi la caractérisation de la FA. / Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice, and one of the main causes of stroke. Yet its thorough characterization and treatment remain an open issue. Despite the increasing popularity of the radiofrequency catheter ablation (CA) therapy, very little is known about its impact on heart substrate, leading to rather uncertain success rates. This calls for advanced signal processing tools for quantitatively assessing CA outcome. The surface 12-lead electrocardiogram (ECG), a noninvasive and cost-effective cardiac activity recording modality, provides valuable information about AF. However, some issues affect most of the standard CA outcome predictors, e.g., manual computation and limited single-lead perspective. This thesis aims at explicitly exploiting the ECG’s multilead character through multivariate decomposition tools, so as to enhance the role of some ECG features as CA outcome predictors. Fibrillatory wave amplitude is correlated with CA success in a multilead framework through principal component analysis (PCA). Multivariate approaches also enhance AF spatiotemporal variability measured on the ECG (e.g., weighted PCA, nonnegative matrix factorization), evidencing that the less repetitive the AF pattern, the less likely CA success. Information theory also quantifies interlead similarity between AF patterns, and is linked with CA outcome in a multilead framework. Another perspective focuses on the ventricular response as reflected on heart rate variability (HRV). Point process modeling can highlight certain HRV properties typical of AF in a parametric probabilistic context, helping AF pattern recognition.

To circumvent some inherent problems in the conventional ECG, this research reinvestigates an ‘unassisted’ approach which enables ECG measurement without the placement of leads on the body. Employed in this research is a widely accepted assumption that the electrical activity of the heart may be represented, largely, by a 3-D time-varying current dipole (3D-CD). From the PhysioBank database, mECG and fECG data were obtained, and Singular Value Decomposition (SVD) was performed to estimate the time-varying Vector ECG dipole. To determine the sensing matrix responsible for transforming the activity of the 3D-CD into the potential distribution on the surface of the medium, the ECG vector dipole signals are used to excite a 3D-CD in water medium of a specific shape-containing-ellipsoid model(s) in COMSOL tool. The sensing matrix thereby estimated is then utilized to reconstruct the 3D-CD signals from the signals measured by the probes on the surface of the medium. Fairly low NRMSEs (Normalized Root-Mean-Squared Errors) are attained. The approach is also successfully extended to the case of two ellipsoids, one inside the other, representing a pregnant female subject. Low NRMSEs (Normalized Root-Mean-Squared Errors) are again observed.

La fibrillation atriale est la plus fréquente des arythmies cardiaques et sa physiopathologie reste mal comprise. Il n’existe pas actuellement de modèle animal dans lequel cette arythmie survienne de manière spontanée. Comme l’âge et l’hypertension artérielle sont deux facteurs de risque majeurs dela fibrillation atriale chez l’Homme, nous avons recherché si le rat spontanément hypertendu (SHR)vieillissant (11-13 mois d’âge) développe cette pathologie. Des enregistrements télémétriques de 24 h de l’électrocardiogramme (ECG) ont été réalisés dans 4 groupes de rats vigils. Ils ont révélé chez le rat SHR vieillissant la présence de nombreux épisodes de tachyarythmie atriale non soutenus, épisodes qui ne sont pas observés chez le rat SHR jeune ni chez lerat normotendu Wistar Kyoto jeune ou vieillissant. Les résultats rapportés ci-dessus ont été obtenus grâce à l’analyse visuelle de l’intégralité de chaque enregistrement ECG, ce qui représente une durée d’analyse incompatible avec des expérimentations de routine. Nous avons donc choisi de développer une méthode automatique de reconnaissance des arythmies atriales chez le rat vigil. Cette méthode utilise exclusivement les intervalles RR car les ondes P ne peuvent pas toujours être identifiées avec fiabilité dans les enregistrements télémétriques de l’ECG. Elle repère les motifs caractéristiques de tachyarythmie grâce à une structure d’automate, et présente une bonne performance sur les enregistrements télémétriques déjà réalisés. Le nouveau modèle animal, conjointement à la nouvelle méthode automatique d’analyse de l’ECG, devrait permettre de réaliser les analyses phénotypiques de qualité indispensables aux hypothèses physiopathologiques moléculaires actuellement avancées dans la fibrillation atriale. / Atrial fibrillation is the most common cardiac arrhythmia and its pathophysiology is still poorly understood. To date, there is no animal model in which the arrhythmia occurs spontaneously. As ageand hypertension are major risk factors of atrial fibrillation in humans, we examined whether the aging (11-13 months of age) spontaneously hypertensive rat (SHR) develops this pathology. Telemetric recordings of electrocardiogram (ECG) were obtained in four groups of conscious rats. They revealed the presence in the aging SHR of many non-sustained atrial tachyarrhythmic episodes that were observed neither in the young SHR nor in the young or aging normotensive Wistar Kyotorat. These results were obtained by visual examination of the whole ECG recordings, which is extremely time consuming and thus, not compatible with routine experiments. Therefore, we chose to develop an automated method to detect atrial arrhythmias in the conscious rat. This method only uses RR intervalsbecause P waves cannot always be accurately identified in telemetric recordings. It recognizes characteristicpatterns of tachyarrhythmia by using an automaton structure, and shows a good performance when applied to previously collected telemetric data. The new animal model, together with the new, automated method of ECG analysis, are expected to be extremely useful for producing high quality phenotypic data, which are necessary to test present molecular hypotheses of atrial fibrillation pathophysiology.

Made available in DSpace on 2016-01-26T18:55:31Z (GMT). No. of bitstreams: 1 Dissertacao.pdf: 489642 bytes, checksum: 095c84cd0f391c63e5fde8b3263ef666 (MD5) Previous issue date: 2011-08-01 / The lack or absence of physical activity in dogs, combined with a diet high in energy has seriously affected the health of dogs, taking them to the development of various problems associated with the heart. This study aimed to study the activity of serum enzymes creatine kinase (CK), creatine kinase MB fraction (CK-MB), lactate dehydrogenase (LDH) and glutathione peroxidase (GSH-Px), before and after short duration exercise, evaluating them with electrocardiographic findings such as heart rate (beats / minute), duration of P-R interval (seconds), heart rate and variation of the T wave in 8 healthy dogs. Heart rate, P-R segment size, heart rates and percentage of T wave, did not change during exercise. It can be concluded that exercise of short duration conducted with prior training of animals modified values of CK, CK-MB and LDH, probably caused by muscle injury due to physical exertion and increased GSH-Px was caused by increased production of free radicals due to the higher oxygen consumption by the body during physical effort. / A falta ou ausência de atividade física de cães, aliada a uma alimentação de alto valor energético, têm afetado seriamente a saúde destes, levando-os ao desenvolvimento de vários problemas associados ao coração. O presente estudo teve como objetivo estudar a atividade das enzimas séricas creatino quinase (CK), creatino quinase fração MB (CK-MB), lactato desidrogenase (LDH) e glutationa peroxidase (GSH-Px), antes e após a realização de exercício de curta duração, avaliando-os com os achados eletrocardiográficos tais como frequência cardíaca (batimentos/minuto), duração do intervalo PR (segundos), ritmo cardíaco e variação da amplitude de onda T em 8 cadelas hígidas. A freqüência cardíaca, tamanho do segmento PR, ritmos cardíacos e percentuais de onda T, não se alteraram durante o exercício. Pode-se concluir que o exercício físico de curta duração realizado com treinamento prévio dos animais modificou os valores das enzimas CK, CK-MB e LDH, provavelmente pela lesão causada no músculo devido ao esforço físico intenso e o aumento da GSH-Px foi ocasionado pela maior produção de radicais livres em virtude do maior consumo de oxigênio pelo organismo durante o esforço físico.

Made available in DSpace on 2016-07-18T17:53:08Z (GMT). No. of bitstreams: 1 Dissertacao.pdf: 489642 bytes, checksum: 095c84cd0f391c63e5fde8b3263ef666 (MD5) Previous issue date: 2011-08-01 / The lack or absence of physical activity in dogs, combined with a diet high in energy has seriously affected the health of dogs, taking them to the development of various problems associated with the heart. This study aimed to study the activity of serum enzymes creatine kinase (CK), creatine kinase MB fraction (CK-MB), lactate dehydrogenase (LDH) and glutathione peroxidase (GSH-Px), before and after short duration exercise, evaluating them with electrocardiographic findings such as heart rate (beats / minute), duration of P-R interval (seconds), heart rate and variation of the T wave in 8 healthy dogs. Heart rate, P-R segment size, heart rates and percentage of T wave, did not change during exercise. It can be concluded that exercise of short duration conducted with prior training of animals modified values of CK, CK-MB and LDH, probably caused by muscle injury due to physical exertion and increased GSH-Px was caused by increased production of free radicals due to the higher oxygen consumption by the body during physical effort. / A falta ou ausência de atividade física de cães, aliada a uma alimentação de alto valor energético, têm afetado seriamente a saúde destes, levando-os ao desenvolvimento de vários problemas associados ao coração. O presente estudo teve como objetivo estudar a atividade das enzimas séricas creatino quinase (CK), creatino quinase fração MB (CK-MB), lactato desidrogenase (LDH) e glutationa peroxidase (GSH-Px), antes e após a realização de exercício de curta duração, avaliando-os com os achados eletrocardiográficos tais como frequência cardíaca (batimentos/minuto), duração do intervalo PR (segundos), ritmo cardíaco e variação da amplitude de onda T em 8 cadelas hígidas. A freqüência cardíaca, tamanho do segmento PR, ritmos cardíacos e percentuais de onda T, não se alteraram durante o exercício. Pode-se concluir que o exercício físico de curta duração realizado com treinamento prévio dos animais modificou os valores das enzimas CK, CK-MB e LDH, provavelmente pela lesão causada no músculo devido ao esforço físico intenso e o aumento da GSH-Px foi ocasionado pela maior produção de radicais livres em virtude do maior consumo de oxigênio pelo organismo durante o esforço físico.

The aim of this thesis is to analyse high-frequency ECG to detect some heart diseases. This is performed with averaging of selected QRS complexes for each lead of the signal; these are thenfilteredin range 500-1 000 Hz. After that the envelope of the signal is done and here the peaks are detected. Based on mutual positions of this peaks, it is possible to detectwhat kind od signal we treat.

The aim of this thesis is to analyse high-frequency ECG to detect some heart diseases. This is performed with averaging of selected QRS complexes for each lead of the signal; these are then filtered in range 500-1 000 Hz. After that the envelope of the signal is done and here the peaks are detected. Based on mutual positions of this peaks, it is possible to detect what kind od signal we treat.

Main objective of this thesis was to learn about possibility of suppression of narrow band disturbances. We focused on use of Lynn’s filters. The objective was to realize these filters with respect to a fast algorithm of filtering. Concretely, for suppression of drift we realized the fast high pass filter with flexible cut off frequency. Then we realized filter for suppression of electrical network disturbance. We have realized these filters for sampling frequencies 250 and 500 Hz and we tested them with real ECG signals. Then we have evaluated their efficiency.

Objective of this diploma work was to study methods of adaptive filtering and their use in suppression of noise in biological signals. Adaptive filtering represents effective means of suppression of parasitic nonstationary disturbances in a useful signal. The task was to design various types of adaptive filters and implement an adaptation algorithm in Matlab programming environment. It namely included suppression of powerline noise at 50 Hz and 100 Hz in ECG signals with minimization useful components disturbing. The realized filters were verified on real ECH signals and their efficiency was evaluated.

The aim of this diploma work is the suggestion and realization of a cardiostimulator of „On Demand“ type operated by microcontroller. The work is structured on four thematic parts. For the correct suggestion of the whole system, firstly is necessary to understand correctly the cell’s electrophysiology and heart’s anatomy, inclusive the cardiology arrhytmia, which are adherent to cardiostimulators. The cardiostimulator is inhibited by the R-wave and is adaptive on a pulse rate of a source signal. The whole system is supplied by batteries and this supplying is taken into consideration. The network’s functionality is realized on the ECG simulator. There are suggested the suitable enhancements in discussion.