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

Abstract

Aims: There is currently no consensus on whether atrial fibrillation (AF) patients at low risk for stroke (one 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 ischaemic stroke was 0.70 per 100 person-years and the rate for a bleed was also 0.70 per 100 person-years. Comparing NOAC with 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 with 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 with 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; 95% CI 0.42-0.94).

Conclusion: These observational data suggest that NOAC treatment may be associated with a positive net clinical benefit compared with no treatment or VKA treatment in patients at low stroke risk, a question that can be tested through a randomized controlled trial.

Keywords: Atrial fibrillation; Non-vitamin K antagonist oral anticoagulants; Stroke risk; Vitamin K antagonists.

Structured Graphical Abstract

In patients with atrial fibrillation at low stroke-risk from Sweden, Denmark, Scotland, and Norway, treatment with a NOAC was associated with a lower stroke rate compared to no treatment and a lower intracranial haemorrhage rate compared to VKA treatment. NOAC, non-vitamin K antagonist oral anticoagulant; VKA, vitamin K antagonist; HR, hazard ratio; VS, versus.

Figure 1

Graphical representation of patient inclusion; starting on top and going down the boxes mean the following. Patients enter the cohort at 14 days after their atrial fibrillation diagnosis. The baseline exposure window is 90 days prior to the cohort entry date. Patients are excluded if (i) they have claimed a non-vitamin K antagonist oral anticoagulant or vitamin K antagonist in the 365 to 90 days prior to cohort entry; (ii) they have claimed an antiplatelet prescription in the 90 days prior to cohort entry; (iii) they suffered from a major bleed in the 182 days prior to cohort entry; (iv) they have a diagnosis or procedure code for mechanical valves or mitral stenosis in the 5 years prior to cohort entry; and (v) they immigrated in the 5 years prior to cohort entry. Baseline comorbidities were assessed in the 5 years prior to cohort entry. Baseline comedication was assessed in the 182 days prior to cohort entry. Patients were followed from cohort entry until censored.