Purpose: To examine the contemporary burden and surgical treatment of Atrial Fibrillation (AF) in patients undergoing cardiac surgery in Australia and New Zealand. Method: A 10-year retrospective of the ANZsCTS database was performed(2011-2021). Treatment trends were compared to the 2017 AATS guidelines for surgical management of AF (1). Results: 140,680 patients were examined, and the incidence of AF was higher than previously reported (14%, vs 5-11%)(1). Patients with AF were more likely to be older, had lower LVEF, and higher NYHA classification of dyspnoea. AF was intimately associated with mitral valve disease, and the incidence varied between 25-36% depending on the presence of concomitant coronary and/or other valvular disease. 47% of patients with RHD had AF. Despite changes in treatment recommendations, both surgical ablation (Class IIB) and left atrial appendage ligation (LAAL) (IA-IB) were severely underperformed. In the 21077 patients with AF, 77% (16,363) did not have their appendage addressed and 83% (17,532) received no ablative surgery. Only 1.95% of patients with AF, received a combined ablation and LAAL since the AATS guidelines changed. In the last decade only 2,509 patients with AF of 21,077 had complete AF surgery. Conclusion: AF is more common in the Australasian cardiac surgery cohort than previously appreciated. Despite strong recommendations to surgically treat AF during concomitant cardiac surgery, both ablative techniques and LAAL are severely underperformed in Australia/New Zealand. References: 1. Bahdwar V, et al. The Society of Thoracic Surgeons 2017 Clinical guidelines for surgical treatment of atrial fibrillation, Ann Thoracic Surg. 2017;103(1):329-41.