Abstract Body (Do not enter title and authors here): Background: In developed countries, valvular atrial fibrillation (vAF) in the setting of rheumatic heart disease (RHD) disproportionately impacts minority groups. In Australia, Indigenous Australians account for 92% of cases despite only representing 3.8% of the population. Studies to date, such as the INVICTUS trial, support the use of Vitamin K antagonists (VKAs) over direct oral anticoagulants (DOACs) in vAF. However, this assumes consistent adherence and regular clinic follow up. Reduced access to monitoring and dispensing clinics in Central Australia remains a challenge in the provision of VKAs and the use of DOACs may address this.

Hypothesis: DOACs may be comparably effective with VKAs in preventing major adverse cardiac and cerebrovascular events (MACCE) in a real-world vAF population.

Aim: To conduct a real-world retrospective observational study examining rates of MACCE for patients on VKAs or DOACs for vAF in Central Australia over a five-year period.

Methods: The Northern Territory RHD Register was accessed to identify patients with RHD and vAF in January 2019. Demographic and five-year outcome data (until January 2024) were collected. The primary outcome was MACCE, a composite of ischaemic stroke, systemic embolism, non-fatal myocardial infarction, cardiovascular death and all-cause mortality. The primary safety endpoint was major bleeding. Statistical analyses were conducted as both intention-to-treat (ITT) based on initial anticoagulation and as-treated (AT) based on anticoagulation prior to MACCE or trial endpoint, each excluding patients without anticoagulation.

Results: 61 patients were included. The mean age was 61.9 ± 13.9 years and 68.9% were female. At baseline, 65.6% received VKA, 14.8% DOAC and 19.7% were not anticoagulated. 30.6% of patients crossed over from the ITT analysis, with a non-significant trend favouring switch to DOAC (11 vs 0, p=0.09). In the ITT analysis (n=49), there was no significant difference in MACCE (25.0% vs 22.2%, p=0.86) or major bleeding (20.0% vs 11.1%, p=0.53) between VKA and DOAC groups. In the AT analysis (n=51), there was no significant difference in MACCE (27.3% vs 16.7%, p=0.39) or major bleeding (18.2% vs 22.2%, p=0.73) between VKA and DOAC groups.

Conclusion: Over a five-year period, there was a trend towards use of DOACs over VKAs in vAF. This study demonstrates that DOACs may be as effective as VKAs for reducing MACCE in a real-world vAF population however further investigation is required.