Abstract Body (Do not enter title and authors here): Introduction
Patients undergoing atrial fibrillation (AF) ablation have historically been hospitalized overnight or longer post-procedure. We conducted this study to characterize national rates of same-day discharge, associated clinical factors, variation across hospitals and in-hospital outcomes.

Methods
The NCDR AF Ablation Registry was used to identify all index procedures from January 1^st, 2016, to June 30^th, 2023. Patients were stratified by post-procedure disposition into 3 cohorts: (1) same-day discharge, (2) overnight hospitalization (<1-day) or (3) >1-day hospitalization. Rates of same-day discharge, associated clinical factors, hospital-level variation and unadjusted post-procedural complication rates were analyzed.

Results
Among 139,391 patients who underwent index AF ablation across 197 hospitals in the US, 51622 (37.0%) were discharged the same-day, 78220 (56.1%) hospitalized overnight and 9549 (6.9%) hospitalized for >1-day post-procedure. Shown in Figure 1, the rate of same-day discharge increased from 0.99% (Quarter 1 of 2016) to 62.3% (Q2 2023), p<0.0001 for trend, with a sharp rise in Q1 of 2020 and corresponding decline in those hospitalized overnight (83.3% in Q1 2016 to 32.9% Q2 2023, p<0.0001 for trend). The quarter during which AF ablation procedure was conducted was associated with same-day discharge (OR 1.26, 95% CI 1.256-1.264, Figure 2). In contrast, Black race (OR 0.71, 95% CI 0.65-0.78), persistent AF classification (OR 0.85, 95% CI 0.82-0.88) and prior non-AF catheter ablation (OR 0.89, 95% CI 0.85-0.93) favored overnight hospitalization. Variation in same-day discharge across hospitals was significant (MOR 4.12, 95% CI 3.48-4.79). Aggregate major and overall in-hospital complication rates were 0.70% and 2.13%, respectively. In comparison, major and overall complication rates were 0.03% and 0.19% for same-day discharge and 0.24% and 0.98% for overnight hospitalization.

Conclusion
Rates of same-day discharge following AF ablation increased over time and surpassed overnight hospitalization by Q1 2021. Those with paroxysmal AF and fewer comorbid conditions were more likely to undergo same-day discharge with substantial variation across hospitals. Peri-procedural complication rates of those undergoing same day discharge were comparable to overnight hospitalization. With substantial growth in same-day discharge and development of outpatient or ambulatory procedural centers, our findings may assist future procedural policy development.