Abstract Body (Do not enter title and authors here): Background: Atrial fibrillation (AF) causes significantly increased risk of stroke and patients often need to be on lifelong anticoagulation. Left atrial appendage occlusion (LAAO) device is an alternative approach to prevent strokes in patients who cannot tolerate anticoagulation. Patients undergoing LAA electrical isolation (LAAEI) as part of their ablation strategy are at increased risk of stroke due to the loss of LAA contractility. In patients with prior LAAEI, the optimum timing of LAAO is unknown.

Objective: The aim of this study is to investigate whether early versus delayed LAAO impacts risk of stroke in patients with prior LAAEI adherent to anticoagulation.

Methods: Patients who received both LAAEI and LAAO were included in this analysis. Demographics, co-morbidities, anticoagulation adherence, timing between LAAEI and LAAO, and occurrence of stroke between LAAEI and LAAO were summarized. Patients who received LAAO ≤6 month of LAAEI were designated as the early group, and those >6 month the late group.

Results: A total of 171 patients were included in this study with 135 in the early group and 36 in the late group and all patients were adherent to oral anticoagulation. Patients in the early vs late group had similar age (69.8 vs 70.7 yr), BMI (28.8 vs 27.3 kg/m²), CHA₂DS₂-VAS_C score (2.19 vs 1.83), left ventricular ejection fraction (57.9% vs 57.9%), diabetes (88.9% vs 87.4%), LAA maximum orifice width (18.1 vs 18.5 mm) and percentage of paroxysmal AF (25.0% vs 25.9%). Patients in the early group were more likely to be male but did not reach statistical significance (83.3% vs 71.8%, p=0.161). During a mean follow up duration of 18.6 ± 5.5 months after LAAEI, no stroke events occurred in either group between the date of LAAEI and date of LAAO.

Conclusion: Delayed LAAO after >6 month of LAAEI is not associated with increased risk of stroke compared to early LAAO (≤6 month) in patients adherent with oral anticoagulation. Delayed occlusion allows for the opportunity to confirm LAAEI and reisolate if needed as the effectiveness and technical difficulty of LAA ablation significantly increases after LAAO.