Hybrid versus Endocardial Ablation for LSPAF. Introduction: Ablation of longstanding persistent atrial fibrillation (LSPAF) is the most challenging procedure in the treatment of AF, either by surgical or by percutaneous approach. Objective: We investigated the difference in success and complication rates between combined surgical epicardial and endocardial catheter ablation procedure and our standard endocardial ablation procedure. Methods and Results: Twenty-four consecutive patients (group 1) with LSPAF and enlarged left atrium (>4.5 cm) underwent a combined procedure, consisting of surgical, closed-chest, epicardial, radiofrequency ablation (nContact, NC, USA) via pericardial access, and concomitant endocardial ablation (hybrid procedure). Procedural complications and long-term outcomes were compared to those of 35 consecutive patients who refused the hybrid procedure and underwent standard endocardial only ablation (group 2). Baseline characteristics were comparable. In group 1, 1 patient (4.2%) developed post-procedural cardio-embolic stroke and 3 (12.5%) died (1 atrio-esophageal fistula, 1 fatal stroke, 1 of unknown cause in early follow-up), while no strokes or deaths occurred in group 2. Overall complication rates were higher for group 1 (P = 0.036). At 24-month follow-up, 4 (19%) patients in group 1 and 19 (54.3%) in group 2 were arrhythmia-free after a single procedure, on or off antiarrhythmic drugs (P<.001). Total procedural time (276.9 +/- 63.5 vs. 203.15 +/- 67.3 minutes) and length of hospital stay (5 [IQR 3-8] vs. 1 [IQR 1-3] days were significantly shorter for group 2 (P 0.001). Conclusion: In patients with LSPAF and enlarged left atrium, a concomitant combined surgical/endocardial ablation approach increases complication rate and does not improve outcomes when compared to extensive endocardial ablation only.