pós-infarto agudo do miocárdio (IAM) têm mostrado baixo valor preditivo positivo quando estudados isoladamente. A possibilidade da Eletrocardiografia Dinâmica de 24 horas (ECGD) fornecer dados referentes a isquemia silenciosa (IS), arritmias ventriculares e modulação autonômica do coração pelo estudo da variabilidade da freqüência cardíaca (VFC), levou o autor a empregar este método em pacientes acometidos de IAM com o objetivo de avaliar se estas três variáveis estariam relacionadas a presença de eventos desfavoráveis em evolução a médio prazo. Material e Métodos – Foram selecionados 91 pacientes acometidos de um primeiro IAM não-complicado e realizados exames de ECGD de 24 h por dois dias consecutivos, antes da alta hospitalar. Os parâmetros pesquisados nos exames foram: isquemia silenciosa, identificação e quantificação de arritmias ventriculares e determinação dos índices de VFC pelos métodos do domínio do tempo e do mapa de retorno tridimensional. Foram considerados como desfechos: re-infarto, angina instável, taquicardia ventricular sustentada e morte. Resultados – No seguimento médio de 27,7 meses (DP=15,45), 23 (25%) dos pacientes apresentaram eventos, sendo nove fatais. Os eventos foram mais freqüentes entre os pacientes que apresentaram extra-sístoles ventriculares ≥10/hora (p=0,01) e também naqueles com IS (p=0,02). Em modelo de análise multifatorial, a presença de dislipidemia elevou o valor preditivo positivo dessas variáveis. Nenhum dos índices de VFC esteve significativamente relacionado ao surgimento de eventos. Conclusões – Em pacientes pós-IAM de baixo risco, a presença de arritmias ventriculares freqüentes ou de isquemia silenciosa está relacionada a um prognóstico desfavorável. O estudo da VFC não mostrou utilidade na estratificação de risco destes pacientes. / Introduction and objective – The noninvasive methods used in post-acute myocardial infarction (AMI) risk stratification have been shown to have a low predictive value when studied in isolation. The possibility that ambulatory electrocardiographic monitoring (AEM) may provide data on silent ischemia (SI), ventricular arrhythmias (VA) and autonomic modulation of the heart through the study of heart rate variability (HRV) led the present author to use this method in AMI patients with the aim of assessing whether these three variables could be related to the presence of unfavorable events in the medium term follow-up. Methods – Ninety-one patients with a first, uncomplicated AMI were selected and submitted to AEM for two consecutive days prior to discharge from the hospital. The parameters studied in the examination were as follows: presence of SI, identification and quantification of VA and determination of the HRV indices by the time domain and three-dimensional return map methods. The following were regarded as outcomes: new AMI, unstable angina, sustained ventricular tachycardia and death. Results – In the mean follow-up of 27.7 months (SD=15.45), 23 (25%) of the patients presented events, nine of which were fatal. Events occurred most frequently in the patients who presented ventricular premature contractions >= (p=0.01) and also in those with SI (p=0.04). In the multifactorial analysis the presence of dislipidemia raised the positive predictive value of these variables. None of the HRV indices was significantly correlated with the occurrence of events. Conclusions – In low-risk post-AMI patients the presence of frequent ventricular arrhythmias or silent ischemia is associated with an unfavorable prognosis. The study of HRV was not shown to be useful in the risk stratification of these patients.

pós-infarto agudo do miocárdio (IAM) têm mostrado baixo valor preditivo positivo quando estudados isoladamente. A possibilidade da Eletrocardiografia Dinâmica de 24 horas (ECGD) fornecer dados referentes a isquemia silenciosa (IS), arritmias ventriculares e modulação autonômica do coração pelo estudo da variabilidade da freqüência cardíaca (VFC), levou o autor a empregar este método em pacientes acometidos de IAM com o objetivo de avaliar se estas três variáveis estariam relacionadas a presença de eventos desfavoráveis em evolução a médio prazo. Material e Métodos – Foram selecionados 91 pacientes acometidos de um primeiro IAM não-complicado e realizados exames de ECGD de 24 h por dois dias consecutivos, antes da alta hospitalar. Os parâmetros pesquisados nos exames foram: isquemia silenciosa, identificação e quantificação de arritmias ventriculares e determinação dos índices de VFC pelos métodos do domínio do tempo e do mapa de retorno tridimensional. Foram considerados como desfechos: re-infarto, angina instável, taquicardia ventricular sustentada e morte. Resultados – No seguimento médio de 27,7 meses (DP=15,45), 23 (25%) dos pacientes apresentaram eventos, sendo nove fatais. Os eventos foram mais freqüentes entre os pacientes que apresentaram extra-sístoles ventriculares ≥10/hora (p=0,01) e também naqueles com IS (p=0,02). Em modelo de análise multifatorial, a presença de dislipidemia elevou o valor preditivo positivo dessas variáveis. Nenhum dos índices de VFC esteve significativamente relacionado ao surgimento de eventos. Conclusões – Em pacientes pós-IAM de baixo risco, a presença de arritmias ventriculares freqüentes ou de isquemia silenciosa está relacionada a um prognóstico desfavorável. O estudo da VFC não mostrou utilidade na estratificação de risco destes pacientes. / Introduction and objective – The noninvasive methods used in post-acute myocardial infarction (AMI) risk stratification have been shown to have a low predictive value when studied in isolation. The possibility that ambulatory electrocardiographic monitoring (AEM) may provide data on silent ischemia (SI), ventricular arrhythmias (VA) and autonomic modulation of the heart through the study of heart rate variability (HRV) led the present author to use this method in AMI patients with the aim of assessing whether these three variables could be related to the presence of unfavorable events in the medium term follow-up. Methods – Ninety-one patients with a first, uncomplicated AMI were selected and submitted to AEM for two consecutive days prior to discharge from the hospital. The parameters studied in the examination were as follows: presence of SI, identification and quantification of VA and determination of the HRV indices by the time domain and three-dimensional return map methods. The following were regarded as outcomes: new AMI, unstable angina, sustained ventricular tachycardia and death. Results – In the mean follow-up of 27.7 months (SD=15.45), 23 (25%) of the patients presented events, nine of which were fatal. Events occurred most frequently in the patients who presented ventricular premature contractions >= (p=0.01) and also in those with SI (p=0.04). In the multifactorial analysis the presence of dislipidemia raised the positive predictive value of these variables. None of the HRV indices was significantly correlated with the occurrence of events. Conclusions – In low-risk post-AMI patients the presence of frequent ventricular arrhythmias or silent ischemia is associated with an unfavorable prognosis. The study of HRV was not shown to be useful in the risk stratification of these patients.

pós-infarto agudo do miocárdio (IAM) têm mostrado baixo valor preditivo positivo quando estudados isoladamente. A possibilidade da Eletrocardiografia Dinâmica de 24 horas (ECGD) fornecer dados referentes a isquemia silenciosa (IS), arritmias ventriculares e modulação autonômica do coração pelo estudo da variabilidade da freqüência cardíaca (VFC), levou o autor a empregar este método em pacientes acometidos de IAM com o objetivo de avaliar se estas três variáveis estariam relacionadas a presença de eventos desfavoráveis em evolução a médio prazo. Material e Métodos – Foram selecionados 91 pacientes acometidos de um primeiro IAM não-complicado e realizados exames de ECGD de 24 h por dois dias consecutivos, antes da alta hospitalar. Os parâmetros pesquisados nos exames foram: isquemia silenciosa, identificação e quantificação de arritmias ventriculares e determinação dos índices de VFC pelos métodos do domínio do tempo e do mapa de retorno tridimensional. Foram considerados como desfechos: re-infarto, angina instável, taquicardia ventricular sustentada e morte. Resultados – No seguimento médio de 27,7 meses (DP=15,45), 23 (25%) dos pacientes apresentaram eventos, sendo nove fatais. Os eventos foram mais freqüentes entre os pacientes que apresentaram extra-sístoles ventriculares ≥10/hora (p=0,01) e também naqueles com IS (p=0,02). Em modelo de análise multifatorial, a presença de dislipidemia elevou o valor preditivo positivo dessas variáveis. Nenhum dos índices de VFC esteve significativamente relacionado ao surgimento de eventos. Conclusões – Em pacientes pós-IAM de baixo risco, a presença de arritmias ventriculares freqüentes ou de isquemia silenciosa está relacionada a um prognóstico desfavorável. O estudo da VFC não mostrou utilidade na estratificação de risco destes pacientes. / Introduction and objective – The noninvasive methods used in post-acute myocardial infarction (AMI) risk stratification have been shown to have a low predictive value when studied in isolation. The possibility that ambulatory electrocardiographic monitoring (AEM) may provide data on silent ischemia (SI), ventricular arrhythmias (VA) and autonomic modulation of the heart through the study of heart rate variability (HRV) led the present author to use this method in AMI patients with the aim of assessing whether these three variables could be related to the presence of unfavorable events in the medium term follow-up. Methods – Ninety-one patients with a first, uncomplicated AMI were selected and submitted to AEM for two consecutive days prior to discharge from the hospital. The parameters studied in the examination were as follows: presence of SI, identification and quantification of VA and determination of the HRV indices by the time domain and three-dimensional return map methods. The following were regarded as outcomes: new AMI, unstable angina, sustained ventricular tachycardia and death. Results – In the mean follow-up of 27.7 months (SD=15.45), 23 (25%) of the patients presented events, nine of which were fatal. Events occurred most frequently in the patients who presented ventricular premature contractions >= (p=0.01) and also in those with SI (p=0.04). In the multifactorial analysis the presence of dislipidemia raised the positive predictive value of these variables. None of the HRV indices was significantly correlated with the occurrence of events. Conclusions – In low-risk post-AMI patients the presence of frequent ventricular arrhythmias or silent ischemia is associated with an unfavorable prognosis. The study of HRV was not shown to be useful in the risk stratification of these patients.

L'objectif de ce travail était de mieux appréhender les mécanismes impliqués dans la réponse à la resynchronisation biventriculaire (BIV) en insistant sur la caractérisation du substrat électrique éligible à la thérapie et l'intérêt de la resynchronisation électrique. Nous avons démontré qu'il existe une relation forte entre l'asynchronisme électrique de base défini tant par l'ECG de surface que par cartographie détaillée de l'activation ventriculaire (ECM) et la réponse hémodynamique à la stimulation BIV. Par rapport à l'ECG de surface, l'ECM permet une caractérisation plus fine de l'asynchronisme électrique ventriculaire avec une meilleure prédiction de la réponse clinique à la stimulation BIV. La présence d'un asynchronisme de base minimum, en particulier d'un retard d'activation ventriculaire gauche (VG) par rapport au ventricule droit (typiquement >SOms), est un prérequis à l'efficacité de la thérapie. Les patients avec bloc de branche gauche présentent un haut degré d'asynchronisme et la stimulation BIV agit sur ce substrat par resynchronisation de l'activation électrique. A contrario, la stimulation BIV dégrade la séquence d'activation ainsi que l'hémodynamique des patients à QRS fins (dyssynchronie iatrogène). Les patients présentant un trouble de conduction aspécifique présentent des degrés variables d'asynchronie électrique et en conséquence des réponses contrastées à la stimulation BIV. De même, l'analyse ECM de l'asynchronisme des patients chroniquement stimulés sur le ventricule droit a permis de mettre en évidence des degrés variables de retard d'activation du VG. Si la resynchronisation électrique est garante d'une amélioration de la fonction cardiaque, d'autres mécanismes sont impliqués telle la redistribution du travail segmentaire au sein du myocarde ventriculaire. L'efficacité de la stimulation mono-VG implique une participation accrue du ventricule droit au travail global (interaction ventriculaire). / We aimed to characterize the electrical substrate amenable to biventricular pacing (BVP) and to assess the actual value of electrical resynchronization. We showed, both with respect to surface ECG and detailed ventricular electrocardiographic mapping (ECM), a strong relationship between the baseline electrical dyssnchrony and the hemodynamic response to BIV pacing. Compared with standard ECG, ECM allows a more detailed analysis of the ventricular dyssynchrony and better predicts clinical outcomes after BVP. A minimal amount of electrical dyssynchrony, in particular a sufficient LV activation delay relative to right ventricular activation, is a prerequisite to the hemodynamic response to BVP. Due to their advanced electrical dyssynchrony, patients with left bundle branch block present potential for BVP positive response which acts by electrical resynchronization. Conversely, BVP worsens the electrical activation (iatrogenic dyssynchrony) and hemodynamics in patients with narrow QRS suffering from insufficient electrical dyssynchrony at baseline. Patients with unspecified conduction disorders show variable levels of electrical dyssynchrony and as a consequence mixed results to BVP. Similarly, ECM reveals a variable degree of left ventricular activation delay in patients chronically paced in the right ventricle. Beside the electrical resynchronization, other mechanisms are involved in the cardiac pump function improvement such as the redistribution of the mechanical work over the right and left ventricles. Through ventricular interaction, the RV myocardium importantly contributes to the improvement in LV pump function induced by single site LV pacing.

El presente trabajo propone un sistema electrónico de monitoreo continuo de las señales electrocardiográficas de pacientes para la detección de arritmias de tipo Fibrilación auricular y envío de resultados obtenidos para ofrecer una completa supervisión médica que agilice el diagnóstico y atención del paciente. El sistema está compuesto por dos partes, la primera de Hardware y la segunda de Software. En primer lugar, el Hardware del sistema está compuesto por equipos que permiten adquirir las señales electrocardiográficas, realizar el procesamiento y enviar las señales a una base de datos. En segundo lugar, el Software analiza dos parámetros de la señal electrocardiográfica para inferir si el paciente presenta fibrilación auricular y envía una alerta al especialista para la revisión de la señal involucrada. La validación del funcionamiento del sistema se realizó utilizando señales de la base de datos Physionet con una efectividad de 97.3% y señales extraídas de un conjunto de personas con una efectividad del 85.7%. / The present work proposes an electronic system for constant monitoring of the electrocardiographic signals of the patients for the detection of atrial fibrillation and sending the results in order to offer a complete medical supervision that expedites diagnosis and patient care. The system is composed of two parts, the first Hardware and the second Software. First, the system Hardware consists of equipment that allows electrocardiographic signals to be obtained, to process and send the signals to a database. Second, the system Software analyzes 02 parameters of the electrocardiographic signal to conclude if the patient has atrial fibrillation. The validation of the operation of the system is performed using signals from the Physionet database with 97.3% effectiveness and signals extracted from a sample of people with 85.7% effectiveness. / Tesis

[ES] La fibrilación auricular (FA) es una de las arritmias más comunes en la práctica clínica cuyos mecanismos, hasta ahora, no han sido comprendidos en su totalidad. El estudio de dichos mecanismos mediante el estudio de la información clínica, la metodología de estudios computacionales y los algoritmos de inteligencia artificial (IA) que permiten la identificación de nuevos patrones para la personalización de los tratamientos es clave para desvelar las características de la arritmia. Actualmente, el tratamiento de preferencia para los pacientes con FA que ha presentado mayores ratios de efectividad ha sido la ablación cardiaca. Este procedimiento invasivo utiliza un catéter para ablacionar o quemar el área del tejido cardiaco que es responsable del mantenimiento de la arritmia. Para poder identificar dicha área, es indispensable realizar un estudio electrofisiológico para evaluar las señales eléctricas intracavitarias. En el campo de las simulaciones por ordenador, varios estudios han presentado abordajes personalizados que intentan establecer una plataforma complementaria para la planificación de la ablación. En este ámbito, la electrocardiografía por imagen se ha utilizado para la estratificación y caracterización previa de pacientes antes del procedimiento de ablación. Finalmente, los estudios observacionales clínicos permiten la caracterización de la población de FA, ayudando a recoger, no solo datos electrofisiológicos, sino también biomarcadores clínicos directamente relacionados con la prognosis del paciente. Dada toda la información producida durante este tipo de estudios, la IA se ha introducido paulatinamente en este tipo de estudios con el objetivo de identificar patrones o biomarcadores que permitan caracterizar a estos pacientes incluyendo toda la información recogida. Además, los algoritmos de predicción, que permiten estimar el éxito del tratamiento y la prognosis del paciente, han sido desarrollados. Debido a todas estas razones, estos campos han sido estudiados durante el desarrollo de este trabajo. En primer lugar, se realizaron simulaciones por ordenador utilizan-do una población de modelos que permitía evaluar la inducibilidad y mantenimiento de la arritmia en diferentes escenarios. Teniendo en cuenta la gran cantidad de datos derivados de las simulaciones, que incluían la variabilidad introducida en la población y diferentes fármacos, se implementaron algoritmos de IA que extrajeron patrones de los perfiles más proarrítmicos. En segundo lugar, se realizaron simulaciones personalizadas en una cohorte de pacientes, incluyendo las anatomías de las aurículas y considerando diferentes escenarios arrítmicos. Estos experimentos se realizaron con una carga computacional menor comparado con otros estudios y permitieron identificar un biomarcador obtenido de dichos datos que caracterizaba la actividad en la zona de las venas pulmonares y la comparaba con la evolución del paciente 12 meses tras el procedimiento de ablación. Finalmente, se analizó el estudio observacional STRATIFY-AF utilizando la información obtenida del ECGi y combinándola con datos clínicos. Como resultado, se obtuvo un score electrofisiológico que per-mite predecir el tratamiento más exitoso para cada paciente. Los resultados presentados en esta tesis ilustran un claro ejemplo de combinación de diferentes tecnologías, como las simulaciones in silico, con datos clínicos y algoritmos de IA, que pueden ser de gran utilidad para investigar los mecanismos de la arritmia cardiaca. / [CA] La fibril·lació auricular (FA) és una de les arítmies més comunes. En la pràctica clínica els mecanismes de la qual, fins ara, no han sigut compresos en la seua totalitat. L'estudi dels dits mecanismes per mitjà de l'estudi de la informació clínica, la metodologia d'estudis computacionals i els algoritmes d'intel·ligència artificial (IA) que permeten la identificació de nous patrons per a la personalització dels tractaments és clau per a desvelar les característiques de l'arítmia. Actualment, el tractament de preferència per als pacients amb FA que ha presentat majors ràtios d'efectivitat ha sigut l'ablació cardíaca. Este procediment invasiu utilitza un catèter per a ablacionar o cremar l'àrea del teixit cardíac que és responsable del manteniment de l'arítmia. Per a poder identificar la dita àrea, és indispensable realitzar un estudi electrofisiologia per a avaluar els senyals elèctrics intracavitarias. En el camp de les simulacions per ordinador, diversos estudis han presentat abordatges personalitzats que intenten establir una plataforma complementària per a la planificació de l'ablació. En este àmbit, l'electrocardiografia per imatge s'ha utilitzat per a l'estratificació i caracterització prèvia de pacients abans del procediment d'ablació. Finalment, els estudis observacionals clínics permeten la caracterització de la població de FA, ajudant a arreplegar, no sols dades electrofisiològiques, sinó també biomarcadores clínics directament relacionats amb la prognosi del pacient. Donada tota la informació produïda durant este tipus d'estudis, la IA s'ha introduït gradualment en este tipus d'estudis amb l'objectiu d'identificar patrons o biomarcadores que permeten caracteritzar estos pacients incloent tota la informació arreplegada. A més, els algoritmes de predicció, que permeten estimar l'èxit del tractament i la prognosi del pacient, han sigut desenrotllats. A causa de totes estes raons, estos camps han sigut estudiats durant el desenrotllament d'este treball. En primer lloc, es van utilitzar simulacions per ordinador utilitzant una població de models que permetia avaluar la inducibilidad i manteniment de l'arítmia en diferents escenaris. Donada la variabilitat introduïda en la població, en combinació amb diferents fàrmacs, els algoritmes d'IA es van utilitzar per a extraure patrons que identificaven els perfils més proarítmics. En segon lloc, es van realitzar simulacions personalitzades en una cohort de pacients, incloent les anatomies de les aurícules i considerant diferents escenaris arítmics. Estos experiments es van realitzar amb una càrrega computacional menor comparat amb altres estudis i van permetre identificar un biomarcador obtingut de les dits dades que caracteritzava l'activitat en la zona de les venes pulmonars i la comparava amb l'evolució del pacient 12 mesos després del procediment d'ablació. Finalment, l'estudi observacional STRATIFY-AF es va analitzar utilitzant la informació obtinguda de l'ECGi i combinant-la amb dades clíniques. Com resultat, es va obtindre un score electrofisiològic que permet predir el tractament més reeixit per a cada pacient. Els resultats presentats en esta tesi il·lustren, per tant, que la combinació de les tecnologies in silico, junt amb les dades clíniques i el processament de dades disponibles gràcies als algoritmes d'IA poden ser de gran utilitzar per a investigar els mecanismes de l'arítmia cardíaca. / [EN] Atrial Fibrillation (AF) is one of the most common arrhythmias in clinical practice and thus far, the electrophysiological mechanisms underlying its initiation and maintenance are not fully understood. The study of such mechanism including clinical information, computational models and artificial intelligence (AI) algorithms that enable the identification of new patterns for the personalization of the treatments is key to unveil the characteristics of the arrhythmia. At the present, the treatment of choice for AF patients with higher effectiveness has proved to be cardiac ablation. This invasive procedure uses a catheter to ablate or burn the area of the cardiac tissue that is responsible for the maintenance of the arrhythmia. In order to find this specific area, it is indispensable to perform an electrophysiological study to evaluate the intracavitary electrical signals. In the computational field, several studies have presented personalized approaches that aim to stablish a complimentary platform for ablation planning. In this area, electrocardiographic imaging has also been used for the stratification and prior characterization of patients before the ablation procedure. Finally, observational studies enable the characterization of the AF population, enabling to collect, not only electrophysiological data but clinical biomarkers that can be related with the prognosis of the patients. Due to all the information produced during this type of studies, AI has been recently incorporated into these studies, with the main objective of identifying patterns or biomarkers that are able to characterize these patients including all the collected information. In addition, prediction algorithms, that allow to estimate the success of the treatment and prognosis of the patient have also been developed. For this purpose, these three fields of study were explored in this thesis. First, computational simulations using a population of models were performed to evaluate arrhythmia inducibility and maintenance under different scenarios. Due to the variability introduced in the population of models in combination with different drugs, AI algorithms were applied to extract patterns that identified the most proarrhythmic profiles. Secondly, personalized simulations were performed in a cohort of patients including their anatomical cardiac geometries and considering different arrhythmic scenarios. These experiments were achieved with a lowered computational costs and included the identification of a biomarker extracted from the simulation analysis that characterized the activity in the pulmonary vein area and evaluating it with the 12-month ablation outcome. Finally, the STRATIFY-AF observational study was analyzed, using the ECGi information from the patients combined with clinical infor-mation. As a results, a stratification score was obtained to predict the most successful treatment for each of the patients. The results presented in this thesis illustrate that the combination of in silico technologies with clinical data and processing algorithms can be of great utility to further investigate the arrhythmic mechanisms. / Sánchez De La Nava, AM. (2022). Definition of a Sensitivity Profile for Drug Treatment and Identification on Clinical Biomarkers in Atrial Fibrillation [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/184778

Les tachycardies ventriculaires (TV) et atriales (TA) sont les arythmies les plus fréquemment diagnostiquées en clinique. En vue d’ablater les tissus pathologiques, deux techniques de diagnostic sont utilisées : la cartographie électro-anatomique pour un diagnostic précis à l’aide d’électrogrammes (EGM) mesurés par cathéters intracardiaques et repérés sur la géométrie tridimensionnelle (3-D) de la cavité étudiée ; et l’imagerie électrocardiographique non-invasive (ECGi) pour une vision globale de l’arythmie, avec des EGM reconstruits mathématiquement à partir des électrocardiogrammes et des géométries cardio-thoraciques 3-D obtenues par CT-Scan. Les TV et TA sont alors diagnostiquées en étudiant les cartes d’activation qui sont des représentations des temps de passage locaux de l’onde d’activation sur la géométrie 3-D cardiaque. Cependant, les zones de ralentissement favorisant les TV et TA, et leurs motifs de propagation spécifiques n’y sont pas facilement identifiables. Ainsi, la caractérisation locale de la propagation de l’onde d’activation peut être utile pour améliorer le diagnostic. L’objet de cette thèse est le développement d’une méthode de caractérisation locale de la propagation de l’onde d’activation. Pour cela, un champ vectoriel de vitesse est estimé et analysé. La méthode a en premier lieu été validée sur des données simulées issues de modélisation, puis appliquée 1) à des données cliniques issues de l’ECGi pour la localisation des cicatrices d’infarctus et pour améliorer le diagnostic des TA; et 2) sur des données obtenues par cartographie électro-anatomique pour caractériser les zones pathogènes. / Ventricular (VT) and atrial (AT) tachycardias are some of the most common clinical cardiac arrhythmias. For ablation of tachycardia substrates, two clinical diagnosis methods are used : electro-anatomical mapping for an accurate diagnosis using electrograms (EGMs) acquired with intracardiac catheters and localized on the three-dimensional (3-D) mesh of the studied cavities ; and non-invasive electrocardiographic imaging (ECGi) for a global view of the arrhythmia, with EGMs mathematically reconstructed from body surface electrocardiograms and the 3-D cardio-thoracic meshes obtained with CT-scan. VT and AT are diagnosed studying activation time maps ; that are 3-D representations of the transit time of the activation wavefront on the cardiac mesh. Nevertheless, slow conduction areas, a well-known pro-arrhythmic feature for tachycardias, and the tachycardias specific propagation patterns are not easily identifiable with these maps. Hence, local characterization of the activation wavefront propagation can be helpful for improving VT and AT diagnosis. The purpose of this thesis is to develop a method to locally characterize the activation wavefront propagation. For that, a conduction velocity vector field is estimated and analyzed. The method was first validated on a simulated database from computer models, then applied to 1) a clinical database obtained from ECGi to localize infarct tissues and improve AT diagnosis ; and 2) a clinical database acquired with electro-anatomical mapping systems to define pathological areas.

Made available in DSpace on 2014-07-29T15:07:57Z (GMT). No. of bitstreams: 1 Andrea Cintra 1ff.pdf: 4196439 bytes, checksum: 84bfc46a22b5675802e1bda5e2d0f500 (MD5) Previous issue date: 2009-02-27 / The obesity is a morbid condition commonnly incident in veterinary practice, generally associate to the companion animals reduction of time and quality of life. This factor, added to the regularity that it is observed, makes from obesity, nowadays, the most important metabolism disease in dogs, being still able to promote serious health problems, including cardiovascular disorders. For this study, 14 medium-sized neutered mongrel adult female dogs were divided in two groups and submitted to a program of weight gain. Group I, presenting highest percentage of weight gain (average 21.4% above the initial weight, in average) and Group II, with shortest weight gain percentage (15% above the initial weight, in average). Afterwards, both groups were submitted to a obesity correction food program, to reach the initial weight. During the food programs, in the initial phase (T1), obesity phase (T2) and final phase of weight reduction (T3), examinations carried out were: electrocardiographic, radiographic and mensurations of the blood pressure. During the phases T2 and T3, ecodopplercardiographic examinations of all dogs were also performed. At the end of the experimental phase, every variables obtained were statistically evaluated, comparing the groups and the different phases within the same group. The results revealed no significant eletrocardiographic and ecodopplercardiographic alterations, considering up to 21% of increment on body weight; increase of cardiac silhouette on radiographic evaluation during the obesity phase and decrease after the weight loss, and increase of arterial systolic pressure after the weight increment. / A obesidade é uma condição mórbida de ocorrência comum na prática veterinária, estando geralmente associada à redução do tempo e da qualidade de vida dos animais de companhia. Esse fator, unido à regularidade com que é observada, faz da obesidade, atualmente, a forma mais importante de doença do metabolismo em cães, podendo provocar sérios problemas de saúde, dentre eles os distúrbios cardiovasculares. Neste trabalho, 14 cadelas de porte médio, sem raça definida, adultas e castradas foram divididas em dois grupos e submetidas a um programa de ganho de peso. O Grupo I com maior porcentagem de ganho de peso (em média 21,4% acima do peso inicial) e o Grupo II com menor porcentagem de ganho de peso (em média 15% acima do peso inicial). Posteriormente foram submetidas a um programa alimentar de correção da obesidade até atingirem o peso inicial. Durante os programas alimentares, na fase inicial (T1), fase de obesidade (T2) e fase final de redução de peso (T3) foram realizados exames eletrocardiográficos, radiográficos e mensurações da pressão arterial e nas fases T2 e T3 exames ecodopplercardiográficos em todas as cadelas. Ao final da fase experimental, todas as variáveis obtidas foram avaliadas estatisticamente, comparando os grupos e as diferentes fases dentro do mesmo grupo. Os resultados revelaram que não ocorreram alterações eletrocardiográficas e nem ecodopplercardiograficas significativas, considerando incremento de peso corporal de até 21%; aumento significativo da silhueta cardíaca à avaliação radiográfica, na fase de obesidade, e diminuição da mesma após perda de peso e a pressão arterial sistólica dos cães aumenta com o incremento do peso.