Abstract Body (Do not enter title and authors here): Background: New onset post-operative atrial fibrillation is common after valvular heart surgery yet optimal oral anticoagulation (OAC) management in these patients is not known. Herein, we describe trends in the use of vitamin K antagonists (VKA), direct oral anti-coagulants (DOACs), versus no OAC and their outcomes in patients that develop new onset POAF after valve surgery.

Methods: Provincial-wide clinical registry with linkage to discharge abstracts was queried to obtain all patients ≥65 years-old undergoing isolated aortic and/or mitral valve bioprosthesis replacement or repair from 2008-2022. Patients undergoing replacement with mechanical prosthesis, history of prior atrial fibrillation or those who died within 90-days were excluded. Trends in utilization of OAC versus none were assessed over the study period in patients that developed POAF within 90-days of surgery. The primary outcome was the composite of death, stroke, myocardial infarction, thromboembolism, or major bleeding at 2-years compared in a cause-specific hazard model in propensity score matched cohort.

Results: In 7,774 patients undergoing valve surgery without a history of atrial fibrillation or OAC use, 3,075 patients (40%) developed POAF (mean age 74 years, 58% male, median CHADS2-Vasc score 4.0 [IQR: 3.0-4.0]). In 1,851 (60%) patients, OAC was started within 90-days of discharge with VKA (68%, n=1,263) or DOAC (32%, n=588) while no OAC was initiated in 1,224 patients (40%). There was decreasing use of VKA (2008: 68% 2022: 23%) and increasing use of DOAC after introduction in 2012 (2012:7%, 2022: 40%) without an overall increase in OAC use with time (2008: 68% 2022: 63%). Propensity matching on 20 demographics yielded 1,187 well matched pairs (96% match). The cumulative incidence of the primary outcome did not differ between OAC and no OAC patients at 2-years (Figure, 8.2% vs 7.2%, HR: 1.17, 95%CI: 0.87-1.57, p=0.3). The incidence of stroke at 2-years was similar between OAC and no OAC (1.7% vs 1.1%, p=0.22). There was no increased risk of major bleed at two years with OAC (3.5% vs 2.9%, p=0.41).

Conclusions: The use of OAC in patients with new onset atrial fibrillation after bioprosthetic valvular heart surgery was 60%. The use of OAC did not reduce the incidence of stroke nor was it associated with increased major bleeding in this population. Routine oral anticoagulation in patients with POAF after valve surgery may not be necessary.