Abstract Body (Do not enter title and authors here): Background:
Although pulmonary vein isolation (PVI) is the cornerstone of atrial fibrillation (AF) management, recurrence of AF and atrial tachycardia (AT) remains a significant challenge. Concurrently, atrial antitachycardia pacing (A-ATP) delivered by cardiac implantable electronic devices (CIEDs) is clinically effective in suppressing atrial arrhythmias. This study aimed to investigate which ablation strategies in addition to PVI have more beneficial effect on the success of A-ATP in patients with refractory AF and AT.

Methods:
We retrospectively analyzed all AF/AT episodes detected via remote monitoring over a 9-month period, (4 to 12 months post-ablation) in 24 patients (mean age: 77.4 ± 9.1 years, male: 58.3%) who underwent catheter ablation and had CIEDs with A-ATP. Episodes in which A-ATP was delivered were extracted and divided into two groups based on termination outcome documented by the device. Linear ablation strategies in this study included the roof, bottom, lateral mitral, and anterior mitral lines. We stratified AF/AT episodes into two groups according to the number of linear ablation lines (low: 0–1, high: ≥2), and evaluated A-ATP success rates between the two groups.

Results:
Among the 24 patients, 14 received PVI alone either with defragmentation, or with a single additional line, such as a roof or lateral mitral line. The remaining 10 underwent PVI with posterior wall isolation (roof and bottom lines), with some also undergoing an additional line, including the lateral or anterior mitral line. A total of 2,577 AF/AT episodes were recorded in 24 patients. Of these, 1,287 episodes (49.9%) were treated with A-ATP, resulting in successful termination in 762 episodes (59.2%). Among the episodes treated with A-ATP, 425 were in the low group and 862 in the high group. A significant difference in A-ATP success rates was observed between the two groups: 43.5% in the low group versus 66.9% in the high group (P<0.001). Logistic regression analysis further confirmed that the high linear ablation group was significantly associated with A-ATP success (odds ratio: 2.63, P<0.001).

Conclusion:
The current study revealed that successful A-ATP in terminating atrial arrhythmias is significantly associated with more extensive linear ablation strategies, including posterior wall isolation and additional linear ablations. This finding highlights the potential benefit of combining catheter ablation and device-based A-ATP therapy in managing refractory AF and AT.