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Noninvasive Frequency-Phase Mapping of Atrial Fibrillation
Acknowledgments
This work is supported in part by the Instituto de Salud Carlos III FEDER (Fondo Europeo de Desarrollo Regional; DTS16/00160; PI14/00857, PI16/01123; PI17/01059; PI17/01106); the Agencia Estatal de Investigación RYC2018-024346-I, Generalitat Valenciana grants (APOSTD/2017 and APOSTD/2018) and projects (GVA/2018/267); EITHealth 19600 AFFINE; and CIBERCV, Centro de Investigacion Biomedica en Red de Enfermedades Cardiovasculares.
Introduction
Translation of knowledge derived from animal experiments using high-resolution optical mapping demonstrated that the turbulent electrical activity seen in the electrogram recordings during atrial fibrillation (AF) in patients was the manifestation of a spatial hierarchical organization in the rate of atrial activation. Several studies have demonstrated that ablating AF-driving sources or “rotors,” which generate high-frequency reentrant activity, were able to effectively terminate AF and were associated with a favorable long-term outcome. AF-driving source detection was performed using different multipolar catheter types and signal processing methods. However, the location of sources was made difficult by the sequential nature of mapping, which hindered global atrial activation mapping and multipolar analyses limitations (i.e., far-field sources, interpolation) reduced the specificity of mapping. , Thus we aimed to personalize AF treatment that enabled us to target extrapulmonary vein sources and identify patients most suitable for ablation. This chapter presents the results of our endeavors to develop a noninvasive mapping system that reliably identified AF-driving mechanisms for effective treatment.
Body Surface Potential Mapping And Electrocardiographic Imaging Methodology
Noninvasive evaluation of the electrical status of the heart is based on the standard electrocardiogram (ECG), which records signals on the body surface, far away from the heart. Body surface potential mapping (BSPM) is an extension of the body surface ECG using a large number of electrodes in contact with the torso surface and recording the cardiac potentials on the body surface, not on the heart. In contrast, electrocardiographic imaging (ECGI) provides maps of cardiac electrical excitation in relation to the anatomy of the heart. ECGI computes potentials on the epicardial surface of the heart from recorded body surface potentials, solving the inverse problem of electrocardiography. This constitutes an inverse solution to Laplace’s equation, which describes the electric potential field in the volume between the heart surface and the body surface. Then, the recorded torso potential and geometrical information from the heart provide the input data for the ECGI algorithm. Patient-specific three-dimensional (3D) atrial geometry and exact locations of all the body surface electrodes on the patient’s torso are usually obtained using a computed tomography (CT) scan. From the time sequence of computed epicardial potentials, ECGI constructs electrograms on the epicardium to obtain the epicardial activation sequence and repolarization pattern. However, comparing ECGI reconstructions to epicardial electroanatomic mapping reveals the presence of inaccuracies in ECGI maps.
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