Oral anticoagulants in patients with atrial fibrillation at low stroke risk : a multicentre observational study

Background: There is currently no consensus on whether atrial fibrillation (AF) patients at low risk for stroke (1 non-sex-related CHA2DS2-VASc point) should be treated with an oral anticoagulant. Methods and results: We conducted a multi-country cohort study in Sweden, Denmark, Norway, and Scotland. In total, 59 076 patients diagnosed with AF at low stroke risk were included. We assessed the rates of stroke or major bleeding during treatment with a non-vitamin K antagonist oral anticoagulant (NOAC), a vitamin K antagonist (VKA), or no treatment, using inverse probability of treatment weighted (IPTW) Cox regression. In untreated patients, the rate for ischemic stroke was 0.70 per 100 person-years and the rate for a bleed also 0.70 per 100 person-years. Comparing NOAC to no treatment, the stroke rate was lower (hazard ratio [HR] 0.72; 95% confidence interval [CI] 0.56- 0.94), and the rate for intracranial haemorrhage (ICH) was not increased (HR 0.84; 95% CI 0.54-1.30). Comparing VKA to no treatment, the rate for stroke tended to be lower (HR 0.81; 95% CI 0.59-1.09), and the rate for ICH tended to be higher during VKA treatment (HR 1.37; 95% CI 0.88-2.14). Comparing NOAC to VKA treatment, the rate for stroke was similar (HR 0.92; 95% CI 0.70-1.22), but the rate for ICH was lower during NOAC treatment (HR 0.63; 5% CI 0.42-0.94). Conclusion: These observational data suggest that NOAC treatment may be associated with a positive net clinical benefit compared to no treatment or VKA treatment in patients at low stroke risk, a question that can be tested through a randomised controlled trial