Characterization of Arrhythmia Substrate to Ablate Persistent Atrial Fibrillation

The optimal CA strategy for persistent AF remains unknown. Current data highlight the need for a better understanding of the substrate and mechanisms of arrhythmia maintenance in this population. Atrial scar-based catheter ablation has recently emerged as a promising strategy for ablation of AF. However, the available data has limitations that preclude definitive conclusions regarding the utility of this strategy (no data from multicenter, randomized studies available). Further research is needed to assess the role of scar-based ablation for persistent AF.

The Investigators hypothesize that catheter ablation of persistent AF (PeAF) tailored to abolish abnormal atrial substrate identified by intracardiac atrial scar mapping in addition to pulmonary vein isolation (PVI) will result in higher procedural success rates when compared to PVI alone.

The study will recruit 502 patients with PeAF (251 per treatment arm) who are candidates for CA ablation of AF according to the treating physician (and in agreement with current practice guidelines). Subjects will be recruited over a 42 month period. The total duration of the study is 60 months.

Prior to undergoing catheter ablation subjects will be seen by the investigator/ research assistant and the following data will be collected:

i. Age and sex ii. Structural heart disease if present iii. CHADS2VASc score iv. DR-FLASH score v. NYHA class vi. Current medications vii. Duration of uninterrupted AF viii. Height and weight ix. Echocardiogram and other cardiac imaging results (within previous 12 months, including assessment of left ventricular ejection fraction, left atrial volume and valve function) x. ECG, Holter or loop monitor recording (within past 36 months) documenting AF.

Subjects will be randomly assigned in a 1:1 ratio to undergo wide area circumferential ablation for pulmonary vein isolation (PVI- control arm) or wide area circumferential ablation PVI and scar ablation (experimental arm). Randomization will be stratified by centre and by sex. Subjects will be randomized prior to the procedure.

Enrolled subjects will have a clinical follow-up visit at 3, 6, 12 and 18 months after the ablation procedure. A 14-day continuous ambulatory ECG monitor will be completed at each visit. The results of monitoring will be interpreted at a centralized core lab, and the results will be adjudicated by an arrhythmia specialist blinded to treatment group. A total of three questionnaires will be administered throughout the study, each at a specific time point. The Quality of Life (EQ-5D), CCS-Severity of AF scale, and Atrial Fibrillation Effect on Quality of life (AFEQT) will be completed at baseline, and at the 12-month and 18 month visit.

Concomitant medical therapy will be selected according to the treating physician. All subjects will be maintained on systemic oral anticoagulation for at least 2 months following catheter ablation.