Spatiotemporal Behaviour of AF Drivers in Patients with Persistent Atrial Fibrillation Using Non-Contacting Intracardiac Atrial Electrograms

Atrial fibrillation (AF) is the most common cardiac arrhythmia and a major cause of hospitalisation and morbidity, impacting over 40 million people worldwide. Moreover, it increases the risk of stroke up to five-fold. Catheter ablation is recognised as an excellent percutaneous therapy used for drug-refractory AF with persistent AF (PersAF). Nevertheless, the success of ablation therapy for AF is between 40-70% due to the interaction between relevant atrial substrate and the initiation and maintenance of AF. Various methods are being developed in relation to employing intracardiac AF electrograms to identify critical substrate sites for catheter ablation. These approaches comprise dominant frequency mapping, phase mapping, spatiotemporal dispersion assessment, and so forth. Up until now, these approaches have attained completely different success rates. Therefore, this thesis aimed to analyse the spatiotemporal behaviour of AF drivers using phase mapping and dominant frequency mapping for identifying potential substrate targets during AF ablation for PersAF patients.

Phase mapping is useful for analysing the spatiotemporal characteristics of intracardiac AF electrograms. Therefore, the current work investigates the minimal acceptable recording duration for summarising the spatiotemporal behaviour of long lifespan of persistent phase singularity points (PSs), also known as ‘rotors’, during PersAF in humans. PersAF is believed to be maintained by means of localised sources, ‘drivers’, high-dominant frequency (HDF), rotors, etc. Yet, identifying these putative AF drivers in PersAF patients is a considerable challenge on account of the spatiotemporal instability of such sources. Accordingly, in this current work, we investigate the spatiotemporal stability of potential AF drivers within long-duration recordings of Virtual Intracardiac Electrograms (VEGMs) during PersAF in humans.

The pathogenesis of AF involves interactions occurring at cellular, tissue and organ levels and PersAF is not a single entity, but rather it is a moving and active target. The correlation between HDF and rotors has been evaluated in intracardiac contact recordings. Nonetheless, the association between frequency and phase on non-contact mapping (NCM) has not been completely characterised. Hence, it is essential to consider the spatial interactions between AF drivers. Therefore, this thesis studied the spatial disparities of rotor sites and HDF regions during catheter ablation for PersAF.