Mechanisms of atrial arrhythmia and outcomes from catheter ablation

Abstract

INTRODUCTION. Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia in humans. Persistent (pers)AF has worse outcomes from catheter ablation (CA) than paroxysmal AF, due to non-pulmonary vein substrate. Patients frequently have sinus node disease (SND, ~25%) and CA outcomes in this group are even worse. SND also frequently co-exists with cavotricuspid isthmus-dependent atrial flutter (CTI-AFL), but whether it is mechanistically implicated is unknown. METHODS. Three studies were carried out to investigate the relationships between SND, persAF and AFL, and CA outcomes for the latter using novel ablation technology. The first utilised ultra-high density (UHD) mapping of the right atrium (RA) in AFL and control patients, the second in persAF and control patients, and the third compared local impedance (LI)-guided ablation and UHD mapping to conventional and contact force (CF)-guided ablation for CTI-AFL. RESULTS. There was evidence of sinoatrial node (SAN) remodelling in patients with AFL and persAF. In the former group, the SAN contributes the superior portion of the posterior line of block (LOB) required for the CTI-AFL circuit, conduction velocities (CV) are reduced, and sinus node recovery times are prolonged, with positive correlation to the degree of block present. This LOB is more extensive in AFL than control patients. In the latter group, there is greater fractionation, slower CV, and presence of low voltage around the SAN. LI-guided ablation and UHD mapping is at least as effective as conventional and CF-guided ablation for CTI-AFL. CONCLUSIONS. SAN region-specific remodelling adds to the inferior LOB, which based on clinical and simulated data needs to be at least 50% of the intercaval distance in order to maintain CTI-AFL. This regional remodelling may act as a nidus for driver activity in triggering and perpetuating persAF, and correlates with previous observations that RA drivers may be important in persAF. LI-guided ablation and UHD mapping may reduce total ablation time due to shortening the duration of each lesion, and improving the time taken to detect breakthrough across the CTI. Further work is required to prove these findings due to the small sample sizes in our studies.

Date of Award	24 Nov 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Clifford Garratt (Co Supervisor) & Gwilym Morris (Main Supervisor)