title: Evaluation of Arrhythmia Recurrence and Electrical Reconnection of The Pulmonary Veins following Ablation Index Guided Pulmonary Vein Isolation for Persistent Atrial Fibrillation
Creators: name: Hussein, Ahmed
Publisher: name: University of Liverpool Repository
Year: 2020

description: Introduction Ablation Index is a novel ablation quality marker that incorporates contact force (CF), power and application time (Force-Power-Time Index Formula). We hypothesised that the prospective use of Ablation Index previously published targets would result in better AF ablation outcomes compared to the commonly used contact-force guided ablation. Methods and Results Our research on Ablation Index was the first to investigate the prospective use of Ablation Index targets, 550 for anterior and 400 for posterior left atrial (LA) regions, to guide AF ablation. We investigated that in two studies; the first was a retrospective analysis and compared the acute procedural and long-term clinical outcomes with those of a propensity matched group in which AF ablation was contact force-guided. The study showed significant improvements in the incidence of acute pulmonary vein (PV) reconnection and in the freedom from recurrence atrial tachyarrhythmia (ATA), defined as atrial fibrillation, atrial flutter or atrial tachycardia, at 12 months compared to CF -guided ablation. The second study, the PRAISE (Pulmonary vein Reconnection following Ablation Index-guided ablation: Success Evaluation) study, was a multicenter prospective study of 40 patients with persistent AF of less than 12-month duration, and no significant structural heart disease who underwent a protocol-mandated repeat procedure after 2 months. Patients were monitored for atrial tachyarrhythmia recurrence using daily ECG recordings for 12 months. In that study Ablation Index-guided ablation resulted in a low rate of PV reconnection at repeat electrophysiology study, with 93% of PVs found to remain durably isolated. We then compared the AF ablation outcomes form the 40 patients who form the PRAISE study cohort with those of the 40 paroxysmal AF patients of the PRESSURE (Pulmonary vein RE-isolation as a routine Strategy: a SUccess Rate Evaluation) study who were also randomised to a repeat procedure 2-months following the initial CF-guided PVI. Acute and late reconnections were significantly lower in the PRAISE cohort when compared to CF-guided ablation in the PRESSURE cohort, despite significantly shorter ablation times, lower average CF values, and significantly larger left atria in the former cohort compared to the later cohort. No major complications occurred with Ablation Index-guided ablation in our research studies. We then studied the potential occurrence of LA structural and electrical reverse remodelling following Ablation Index-guided PVI, and found that both structural and electrical remodelling became evident two months following Ablation-Index guided PVI. We also found that factors known to be associated with less likelihood for development of left atrial fibrosis in persistent AF patients, rather than durable PVI alone, were associated with LA structural reverse remodelling. We then studied the relation between LA reverse remodelling and Ablation Index-guided AF ablation outcomes, and found that the occurrence of all three types of LA reverse remodelling together; structural, conduction velocity and LA voltage, was associated with a low likelihood for ATA recurrence. Finally, we studied the factors associated with late PV reconnection at repeat electrophysiology study and found that the occurrence of either absent first pass isolation or acute reconnection in a wide area circumferential ablation (WACA) circle predict late reconnection in the same WACA circle. A larger WACA circle transverse diameter was also found to be associated with a higher incidence of late PV reconnection. Late PV reconnection was also found to correlate with lower temperature and lower CF in the thicker anterior LA segments, and with lower impedance drop in the thinner posterior segments. Conclusion Ablation Index-guided ablation is associated with significant improvements in AF ablation outcomes with significant reduction of late reconnection and more freedom from atrial tachyarrhythmia at 12 months compared to CF-guided ablation, potentially due to the creation of more durable lesions as evidenced by higher impedance drop. LA structural and electrical reverse remodelling becomes evident two months following Ablation Index guided-PVI. Factors known to be associated with less likelihood for development of left atrial fibrosis in persistent AF patients, rather than durable PVI alone, are associated with LA structural reverse remodelling. The occurrence of both structural and electrical reverse remodelling together is associated with a low likelihood for ATA recurrence. The use of Ablation Index-guided ablation allowed the identification of factors associated with late PV reconnection in general as well as in the various LA regions. Late PV reconnection correlates with lower temperature and lower CF in the thicker anterior LA segments, and with lower impedance drop in the thinner posterior segments.