Characterization of the Substrate Modification in Patients Undergoing Catheter Ablation of Atrial Fibrillation.

Abstract

Atrial fibrillation (AF) continues to be the most common cardiac arrhythmia, affecting nowadays 2 − 4% of global adult population. Considering the current trend for longevity, prognostics for AF prevalence in the forthcoming years are disheartening, while quality of life of AF individuals is often negatively affected. Despite the high popularity of catheter ablation (CA) as the major AF treatment, there is still room and need for improvement, especially in persistent AF patients. Time spent in AF has a significant impact on AF confrontation and evolution, with 1 − 15% of paroxysmal AF patients progressing to persistent AF annually, hence facing higher complications regarding the AF therapy. Therefore, from early diagnosis to late follow-up therapy, every aspect of AF study that can contribute to the AF confrontation is of utmost importance.CA of pulmonary veins (PVs) is based on the declaration of PVs as the primary AF foci. However, multiple atrial sites can contribute to the AF propagation, either by triggering or by sustaining the AF activity. AF or atrial substrate is the term used to describe all these sites that are involved with the AF activity due to anatomical alterations causing further electrical and functional disturbance. Precise mapping of the atrial substrate and reliable recording of the atrial substrate modification, as a positive marker after CA sessions, are critical in the combat against AF. Electrocardiograms (ECGs) and electrograms (EGMs) are vastly recruited to map the atrial substrate or evaluate the atrial substrate modification.EGMs are mainly recruited for AF substrate mapping in order to detect any areas that provoke or perpetuate AF and indicate them as candidate CA targets after CA of PVs. This is especially important for persistent AF patients, where additional CA is often necessary in order to increase the CA efficiency. Hence, AF mapping via EGMs is an indispensable part of the CA procedure. On the other hand, with the ability to observe the atria universally, ECGs' main application is found in predicting the CA outcome by either assessing the atrial substrate modification or by analyzing electrical characteristics of the atrial component of the ECG from recordings acquired prior to CA. For recordings during AF, these are the f -waves, while for recordings in sinus rhythm (SR), these are the P-waves.Despite the extensive analysis on either recording types, some significant gaps exist. Additional CA out of PVs increases significantly the time spent in operation room, provoking higher health risks and increasing the healthcare costs. Furthermore, whether additional CA is actually beneficial regarding the CA outcome is under dispute. Regarding the atrial substrate modification analysis, various thresholds have been adopted in order to define a prolonged P-wave, which is directly connected with the atrial substrate and poor CA prognostics. Additionally, data acquired from P-wave analysis are quite generic, refering to the entire atria, while analysis could be improved by providing mor...