Morphologie de l'onde P du signal électrocardiographique. Analyse de forme des signaux bidimensionnels: mesure d'effets pharmacologiques sur les ondes P, QRS et T en représentation temps-fréquence

The aim of this work is to develop a signal processing methodology in order to improve fine studies of the cardiac signal, and specially of P wave, particularly focusing the measurement of shape variations. After a review of cardiac signal characteristics, a description of its physiological and pathological variability and of the different recording techniques, a critical study of cardiac signal processing methods is performed: noise reduction, specific filtering, signal averaging and jitter estimation. An interactive and practical software for ECO, particularly devoted to P wave studies, has been developed, with special algorithms of preprocessing and processing, concerning signal averaging procedure and shape comparison. In fact, the most important part of this work is devoted to a new and personal approach of measuring shape differences of bidimensional signaIs. This method is an extension to two dimensions of the distribution function method (DFM), called DFM-2D. The method is described and it is demonstrated that it can be applied to time-frequency representations of monodimensional signaIs. Through simulations applied on gaussian curves, it is clearly showed that DFM-2D performances are better than DFM-ID ones, on noisy as weIl as non-noisy signals. DFM-2D can also be applied to image processing, as it is proved by examples of histologic sections processing. Precise and early detection of electrophysiological action of drugs (such as Cibenzoline or Quinidine) on ECO waves (P, QRS, T) is an interesting application ofDFM-2D in pharmacology. The presented results demonstrate the abililty of this method to measure shape variations and to distinguish them from wave duration fluctuations.Cette thèse a pour objet la recherche d'une méthodologie de traitement du signal pour améliorer l'étude fine du signal cardiaque (électrocardiogramme ou ECG), en particulier de l'onde P (d'origine auriculaire), avec pour intérêt privilégié la mesure des variations de forme. Après le rappel des propriétés du signal cardiaque, de sa grande variabilité physiologique et pathologique, ainsi que de ses différentes techniques de recueil, une étude critique des méthodes existantes de traitement de ce signal est effectuée: réduction du bruit, filtrages spécifiques, sommation synchrone et estimation du "jitter". Un logiciel convivial et interactif de prétraitement et traitement (sommation-moyennage, comparaison de forme) de l'ECG, et de l'onde P en particulier, a été développé. Mais la partie principale de ce travail concerne une nouvelle approche de mesure des écarts de forme des signaux bidimensionnels. Cette méthode est une extension à deux dimensions de la méthode des fonctions de répartition (MFR), notée MFR-2D. La théorie de la méthode est exposée, et, en particulier, la possibilité de l'appliquer aux représentations temps-fréquence des signaux monodimensionnels est démontrée. Au travers de simulations sur des gaussiennes, sa supériorité par rapport à la MFR-1D est soulignée, que le signal soit ou non bruité. Elle s'avère aussi capable, sur des exemples de coupes histologiques, d'être employée au traitement d'images. Appliquée aux spectrogrammes des ondes ECG (P, QRS et T), elle est utilisable pour la détection précoce des actions électrophysiologiques de médicaments (Cibenzoline, Quinidine). Les résultats obtenus montrent l'efficacité de la méthode à mesurer des variations de forme en les distinguant des fluctuations de durée des ondes

Measuring shape variations of ECG waves through Time-Frequency Representations

International audienceThe Distribution Function Method in two dimensions (DFM-2D) is briefly presented as an extension of the previous Distribution Function Method in one dimension (DFM-1D). This novel method is applied to the estimation of shape difference between ECG waves through time-frequency representations (spectrograms). Shape variations due to drug action were followed along one day: for T-waves with Quinidine, for P-waves and QRS complexes with Cibenzoloine. Clustering in two and three classes according to the shape distance was made too. The both methods, DFM-2D and DFM-1D, were compared using a "pure shape distance", i.e. independently of scale changes, and a distance including width variations of the waves. The results concerning shape variations are coherent for the both methods, but in any case they are enhanced by using DFM-2D. In conclusion this novel method will be interesting for early detection and fine measurements of electrophysiological effects of cardiac drugs