485 research outputs found

    Recurring patterns of atrial fibrillation in surface ECG predict restoration of sinus rhythm by catheter ablation

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    Background Non-invasive tools to help identify patients likely to benefit from catheter ablation (CA) of atrial fibrillation (AF) would facilitate personalised treatment planning. Aim To investigate atrial waveform organisation through recurrence plot indices (RPI) and their ability to predict CA outcome. Methods One minute 12-lead ECG was recorded before CA from 62 patients with AF (32 paroxysmal AF; 45 men; age 57±10 years). Organisation of atrial waveforms from i) TQ intervals in V1 and ii) QRST suppressed continuous AF waveforms (CAFW), were quantified using RPI: percentage recurrence (PR), percentage determinism (PD), entropy of recurrence (ER). Ability to predict acute (terminating vs. non-terminating AF), 3-month and 6-month postoperative outcome (AF vs. AF free) were assessed. Results RPI either by TQ or CAFW analysis did not change significantly with acute outcome. Patients arrhythmia-free at 6-month follow-up had higher organisation in TQ intervals by PD (

    Catheter ablation in patients with atrial fibrillation : mapping refinements, outcome prediction and effect on quality of life

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    PhD ThesisChapter 1 presents a literature review, focused primarily on the pathophysiology and management of atrial fibrillation (AF). Chapter 2 examines correlations between the dominant frequency of AF - calculated using principal component analysis from a modified surface 12-lead ECG (which included posterior leads), a standard 12-lead ECG and intracardiac recordings from both atria. The inclusion of posterior leads did not improve correlation with left atrial activity because of the dominance of lead V1 in both ECG configurations. Chapter 3 explores whether acute and 12-month outcome following catheter ablation for AF can be predicted beforehand from clinical and surface AF waveform parameters. Multivariate risk scores combining these parameters can predict arrhythmia outcome following ablation, and could therefore be used to identify those most likely to benefit from this therapy. Chapter 4 examines the effect of catheter ablation on AF symptoms and quality of life (QoL). AF symptom and QoL scores improved significantly in patients who maintained sinus rhythm after ablation but did not change in those with recurrent AF. AF-specific QoL scales are more responsive to change and correlate better with ablation outcome. Chapter 5 examines inter-atrial frequency gradients in patients with persistent AF using multipolar contact mapping. A right-to-left atrial frequency gradient was found in a quarter of the patients studied, implying that their arrhythmia was being maintained by high frequency sources in the right rather than the left atrium. Chapter 6 examines whether targeting high frequency and highly repetitive complex fractionated atrial electrogram sites, identified using multipolar contact mapping during persistent AF, resulted in arrhythmia termination and maintenance of sinus rhythm long-term. The utility of administering flecainide to distinguish critical from bystander AF sites was also investigated. Flecainide did not help refine ablation targets and 12-month outcome after targeting these sites was not superior to other ablation strategies

    Development of new signal analysis methods as preoperative predictors of the Cox-Maze procedure outcome in atrial fibrillation

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    Atrial fibrilation (AF) is the most common cardiac arrhythmia, however, the knowledge about its causes and mechanisms is still uncompleted. Several studies suggest that atrial structural and electrophysiological remodeling are directly related to its development and perpetuation. To this respect, ECG and preoperative clinical data have been studied to analyze different aspects of atrial remodeling. Nonetheless, there is a lack of studies using ECG parameters to provide valuable clinical information in the study of AF aggressive treatments, such as the Cox-Maze surgery. In this work, ECG parameters such as fibrillatory (f) waves organization and amplitude are studied to predict patient's rhythm from the discharge after the Cox-Maze surgery until a twelve months follow up period. On the other hand, widely used clinical parameters such as age, AF duration and left atrial size (LA size) are studied to assess electrocardiographic results. In addition, clinical information known as a risk factor to develop AF such as weight and body mass index has also been analyze. After assess the individual indices, classification models were created in order to optimize the prediction capability. The results obtained reported that the ECG indices outperform the cinical indices. Nevertheless, the information contained in both types of indices is complementary as the generation of a classification model combining the indices shows. This model exceeded 90% accuracy in each period analyzed. In conclusion, studying the AF information contained in an ECG could provide new data to understand the AF and also could help to develop a reliable method to predict preoperatively the Cox-Maze outcome.La fibrilación auricular (FA) es la arritmia cardiaca más comúnmente encontrada en la práctica clínica diaria, sin embargo, todavía no se comprenden completamente los mecanismos fisiológicos que causan el inicio y la perpetuación de la FA. Diversos estudios sugieren que el remodelado estructural y electrofisiológico de la aurícula está relacionado directamente con el desarrollo y perpetuación de la FA. En este sentido, se ha estudiado el ECG e información clínica preoperatoria para analizar distintos aspectos del remodelado. Sin embargo, hay una falta de estudios usando parámetros electrocardiográficos para proporcionar información clínica valiosa en el estudio de tratamientos agresivos de la FA como la cirugía Cox-Maze. En este trabajo, se estudian parámetros electrocardiográficos como la organización de las ondas fibrilatorias y su amplitud para predecir el ritmo de los pacientes desde el momento del alta, tras la cirugía Cox-Maze hasta 12 meses después de la operación. Por otro lado, para evaluar la capacidad de dichos índices, se han utilizado parámetros clínicos ampliamente utilizados como la edad, el tamaño de la aurícula izquierda y el tiempo en FA. Además, se han estudiado también parámetros clínicos conocidos como factores de riesgo para desarrollar FA como son el peso y el índice de masa corporal. Tras analizar la capacidad predictiva de los índices individualmente, éstos se han combinado mediante la generación de modelos de predicción para optimizar la precisión de las predicciones. Los resultados obtenidos señalan que la información contenida en el ECG obtuvo resultados estadísticamente significativos y predicciones más precisas que los índices clínicos. No obstante, el desarrollo de modelos de predicción combinando ambos tipos de índices superó al uso de éstos por separado, con resultados por encima del 90% en todos los períodos estudiados. En conclusión, el análisis del ECG podría aportar nuevos enfoques a la hora de estudiar la FA, y su uso como herramienta de predicción podría ayudar a desarrollar tratamientos más eficientes y personalizados.La fibril·lació auricular (FA) és l'arítmia cardíaca més comunament trobada en la pràctica clínica diària, no obstant això, encara no es comprenen completament els mecanismes fisiològics que causen l'inici i la perpetuació de la FA. Diversos estudis suggerixen que el remodelat estructural i electrofisiològic de l'aurícula està relacionat directament amb el desenrotllament i perpetuació de la FA. En este sentit, s'ha estudiat l'ECG i informació clínica preoperatòria per a analitzar distints aspectes del remodelat. No obstant això, hi ha una falta d'estudis usant paràmetres electrocardiográficos per a proporcionar informació clínica valuosa en l'estudi de tractaments agressius de la FA com la cirurgia Cox-Maze. En este treball, s'estudien paràmetres electrocardiográficos com l'organització de les ones fibrilatorias i la seua amplitud per a predir el ritme dels pacients des del moment de l'alta, després de la cirurgia Cox-Maze fins a 12 mesos després de l'operació. Per un altre costat per a avaluar la capacitat dels dits índexs, s'han utilitzat paràmetres clínics àmpliament utilitzats com l'edat, la grandària de l'aurícula esquerra i el temps en FA. A més, s'han estudiat també paràmetres clínics coneguts com a factors de risc per a desenrotllar FA com són el pes i l'índex de massa corporal. Després d'analitzar la capacitat predictiva dels índexs individualment, estos s'han combinat per mitjà de la generació de models de predicció per a optimitzar la precisió de les prediccions. Els resultats obtinguts assenyalen que la informació continguda en l'ECG va obtindre resultats estadísticament significatius i prediccions més precises que els índexs clínics. No obstant això, el desenrotllament de models de predicció combinant ambdós tipus d'índexs va superar a l'ús d'estos per separat, amb resultats per damunt del 90% en tots els períodes estudiats. En conclusió, l'anàlisi de l'ECG podria aportar nous enfocaments a l'hora d'estudiar la FA, i el seu ús com a ferramenta de predicció podria ajudar a desenrotllar tractaments més eficients i personalitzats.Hernández Alonso, A. (2017). Development of new signal analysis methods as preoperative predictors of the Cox-Maze procedure outcome in atrial fibrillation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90491TESI

    Noninvasive Assessment of Atrial Fibrillation Complexity in Relation to Ablation Characteristics and Outcome

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    Background: The use of surface recordings to assess atrial fibrillation (AF) complexity is still limited in clinical practice. We propose a noninvasive tool to quantify AF complexity from body surface potential maps (BSPMs) that could be used to choose patients who are eligible for AF ablation and assess therapy impact.Methods: BSPMs (mean duration: 7 ± 4 s) were recorded with a 252-lead vest in 97 persistent AF patients (80 male, 64 ± 11 years, duration 9.6 ± 10.4 months) before undergoing catheter ablation. Baseline cycle length (CL) was measured in the left atrial appendage. The procedural endpoint was AF termination. The ablation strategy impact was defined in terms of number of regions ablated, radiofrequency delivery time to achieve AF termination, and acute outcome. The atrial fibrillatory wave signal extracted from BSPMs was divided in 0.5-s consecutive segments, each projected on a 3D subspace determined through principal component analysis (PCA) in the current frame. We introduced the nondipolar component index (NDI) that quantifies the fraction of energy retained after subtracting an equivalent PCA dipolar approximation of heart electrical activity. AF complexity was assessed by the NDI averaged over the entire recording and compared to ablation strategy.Results: AF terminated in 77 patients (79%), whose baseline AF CL was 177 ± 40 ms, whereas it was 157 ± 26 ms in patients with unsuccessful ablation outcome (p = 0.0586). Mean radiofrequency emission duration was 35 ± 21 min; 4 ± 2 regions were targeted. Long-lasting AF patients (≥12 months) exhibited higher complexity, with higher NDI values (≥12 months: 0.12 ± 0.04 vs. <12 months: 0.09 ± 0.03, p < 0.01) and short CLs (<160 ms: 0.12 ± 0.03 vs. between 160 and 180 ms: 0.10 ± 0.03 vs. >180 ms: 0.09 ± 0.03, p < 0.01). More organized AF as measured by lower NDI was associated with successful ablation outcome (termination: 0.10 ± 0.03 vs. no termination: 0.12 ± 0.04, p < 0.01), shorter procedures (<30 min: 0.09 ± 0.04 vs. ≥30 min: 0.11 ± 0.03, p < 0.001) and fewer ablation targets (<4: 0.09 ± 0.03 vs. ≥4: 0.11 ± 0.04, p < 0.01).Conclusions: AF complexity can be noninvasively quantified by PCA in BSPMs and correlates with ablation outcome and AF pathophysiology

    Wavelet entropy as a measure of ventricular beat suppression from the electrocardiogram in atrial fibrillation

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    A novel method of quantifying the effectiveness of the suppression of ventricular activity from electrocardiograms (ECGs) in atrial fibrillation is proposed. The temporal distribution of the energy of wavelet coefficients is quantified by wavelet entropy at each ventricular beat. More effective ventricular activity suppression yields increased entropies at scales dominated by the ventricular and atrial components of the ECG. Two studies are undertaken to demonstrate the efficacy of the method: first, using synthesised ECGs with controlled levels of residual ventricular activity, and second, using patient recordings with ventricular activity suppressed by an average beat template subtraction algorithm. In both cases wavelet entropy is shown to be a good measure of the effectiveness of ventricular beat suppression

    Novel ECG and Intracardiac Electrograms Signal Processing Schemes for Predicting the Outcome of Atrial Fibrillation Catheter Ablation

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    Atrial fibrillation (AF) is the most common encountered cardiac rhythm disorder (arrhythmia) in clinical practice. It is responsible for about one third of arrhythmia-related hospitalizations. This arrhythmia, which increases in prevalence with age, leads to severe complications and subsequently decreases the quality of life for the affected patients. Lifetime risks for developing AF are ~25% in subjects older than 40 years old. Currently, this arrhythmia is considered as a major public health concern. AF is a progressive disease, starting by short and rare episodes which further develop into longer and more frequent occurrences. When the arrhythmia becomes sustained for more than one year, it is labelled as long-standing persistent. AF advancement gives rise to an electrical of the atria (the upper chambers of the heart) resulting from abnormal high frequency atrial activations. The main goals of therapeutic management for patients with AF are to prevent severe complications associated with this arrhythmia, and ultimately to restore a normal rhythm. Currently, the cornerstone of non-pharmacological therapy is the radiofrequency catheter ablation of AF, which consists in delivering at strategic locations within the atria high-frequency electrical impulses. However, catheter ablation for patients with long-standing persistent AF involves extensive ablation of the atria and the success rate reported in various publications is associated with conflicting results. Over the last twenty years, an important effort has been made by the scientific community to develop signal processing algorithms to quantify the complexity of temporal or spectral characteristics of AF dynamics in terms of organization. As such, multiple approaches have been proposed to quantify AF organization either based on time-domain or frequency-domain analysis. All these methods shared one common goal: the development of organization indices which are interpretable from an electrophyisiological viewpoint. In the context of catheter ablation of patients with long-standing persistent AF, the success rate appears limited as the "classical" organization indices are not performant in assessing the amount of ablation required to achieve AF termination. Thus, there is a strong interest in predicting the procedural outcome from the surface electrocardiogram (ECG) recorded at baseline, i.e., prior to ablation. The main objective of this thesis was to derive novel organization indices from surface ECG and intracardiac signals acquired at baseline which could discriminate patients in whom AF was terminated from patients in whom AF persisted during catheter ablation within the left atrium. As the standard surface ECG is not appropriate for measuring the atrial activity, we aimed at adapting the placement of at least one ECG lead such that additional electrical information from the atria was provided. In our ECG signals study, we hypothesized that a quantification of the harmonic structure of AF signals brings more insight into AF complexity. Time-invariant and time-varying approaches were used to derive the ECG organization indices, and their performance for predicting the acute outcome of catheter ablation were compared. In the first scheme, the harmonic components of AF waves were extracted using linear time-invariant filters. In the second one, the components were extracted using an adaptive harmonic frequency tracking algorithm. [...

    Genetic Determinants of Atrial Fibrillation:converging genetic and clinical information

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    Atrial fibrillation is a common cardiac arrhythmia and is characterized by an irregular heart rate. Approximately one-third of the individuals above the age of 55 years will develop atrial fibrillation in their lifetime. The daily life of patients with atrial fibrillation may be limited by symptoms such as shortness of breath, dizziness or palpitations. Episodes of atrial fibrillation may increase over time. However, not all patients experience symptoms and atrial fibrillation may be unnoticed and not treated. This may be life-threatening since atrial fibrillation increases risk of heart failure, dementia, stroke and death. Therefore, it is important to identify individuals at risk of atrial fibrillation. Risk factors identified for atrial fibrillation are increasing age, hypertension, diabetes, high body mass index (BMI) and existing cardiovascular diseases. Moreover genetics are involved in the development of atrial fibrillation. International collaboration via the AFGen consortium resulted in the discovery of over 100 genetic variants associated with atrial fibrillation. Nonetheless, the translation from genetics to clinical practice is difficult, because underlying pathways are mostly unknown. This thesis studies the genetic and clinical information of atrial fibrillation. Genetic risk scores clarify the genetic risk profile and causal associations of atrial fibrillation. The results of this thesis may be used to search for new molecular targets, treatment outcomes and personalized therapies. Thus, in the long run personalized care of atrial fibrillation can be improved and benefit the wellbeing of individuals at risk or diagnosed with atrial fibrillation

    Statistiques de forme, de structure et de déformation à l'échelle d'une population pour l'étude de la fibrillation auriculaire

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    Atrial fibrillation (AF) is the most common cardiac arrhythmia, characterized by chaotic electrical activation and unsynchronized contraction of the atria. This epidemic and its life-threatening complications and fast progression call for diagnosis and effective treatment as early as possible. Catheter ablation, an invasive procedure that establishes lesions to block the trigger points of AF and creates a barrier to the propagation of the arrhythmia, is an effective treatment for patients refractory to anti-arrhythmic drugs. However, the success rate of the first-time ablation may range from 30% to 75%, such that multiple ablation procedures may be recommended, and atrial mechanical function may be adversely affected. With evolving imaging and digital technologies, the objective of the study is to understand the underlying physiology of AF better and to provide tools to assist clinical decision-making. We analyze the correlations between recurrent arrhythmia and patient characteristics before ablation, including the left atrial shape extracted from computed tomography images. Non-invasive extraction of the anatomical structures of the heart is a crucial prerequisite. We first developed semi-automatic methods to segment the left atrium and the left atrial wall from images. Next, we achieved good segmentation results with a neural network model. Then, we studied markers of shape related to both global and local remodeling, and the quantification of adipose tissue, deploying diffeomorphometry and statistical analysis tools. Finally, we extended the work to the statistical analysis of temporal deformation. We proposed a symmetric reformulation of the pole ladder, which improves the numerical consistency and stability.La fibrillation auriculaire (FA) est le type d'arythmie cardiaque la plus commun, caractérisée par une activation électrique chaotique et une contraction non synchronisée des oreillettes. Cette maladie et ses complications potentiellement mortelles ainsi que sa progression rapide exigent de diagnostiquer et de mettre en place un traitement efficace dès que possible. L'ablation par cathéter, une procédure invasive qui établit des lésions pour bloquer les points de déclenchement de la FA et la propagation de l'arythmie, est un traitement efficace pour les patients réfractaires aux médicaments. Cependant, pour 30% des patients, la FA se redéveloppe, entraînant des interventions d'ablation multiples et affectant la fonction mécanique auriculaire. Le but de cette étude est de combiner l'expertise mathématique et informatique à la médecine afin de mieux comprendre la physiologie sous-jacente à la FA et de fournir des outils d'aide à la décision aux cliniciens. Nous analysons des corrélations entre l'arythmie récurrente et les caractéristiques du patient avant l'ablation, y compris la forme de l’oreillette gauche extraite d'images tomodensitométriques. Nous développons pour ce faire des méthodes semi-automatiques pour segmenter l’oreillette gauche et sa paroi à partir d’images. Ensuite, nous avons obtenu de bons résultats de segmentation avec un modèle de réseau de neurones artificiels. En outre, nous étudions des marqueurs de forme liés au remodelage global et local, et la quantification du tissu adipeux, en combinant une approche morphométrique difféomorphe à une analyse statistique. Enfin, le travail s’étend à l’analyse statistique de la déformation temporelle. Nous proposons une reformulation symétrique de l'échelle de perroquet qui améliore la cohérence et la stabilité numérique
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