Apixaban, reduced the risk of stroke or systemic embolism in patients with atrial fibrillation who were at high risk of stroke but unsuitable for vitamin K antagonist therapy in the AVERROES study (n= 5599). In a report in the Lancet Neurolgy, researchers evaluated whether the subgroup of patients with previous stroke or transient ischaemic attack (TIA) would show a greater benefit from apixaban compared with aspirin than patients without previous cerebrovascular events.

Patients were randomised to apixaban 5mg BD or aspirin (81 to 324mg daily). The mean follow-up was 1.1 years. The primary efficacy outcome was stroke or systemic embolism; the primary safety outcome was major bleeding. This pre-specified subgroup analysis estimated compared 1-year event risk in patients with and without previous stroke or TIA.

The following findings were reported:

• In patients with previous stroke or TIA, 10 events of stroke or systemic embolism occurred in the apixaban group (n=390, cumulative hazard 2.39% per year) compared with 33 in the aspirin group (n=374, 9.16% per year; hazard ratio 0.29, 95% CI, 0.15 to 0.60).

• In those without previous stroke or TIA, 41 events occurred in the apixaban group (n=2417, 1.68% per year) compared with 80 in the aspirin group (n=2415, 3.06% per year; 0.51; 0.35 to 0.74).

• p values for interaction between history of previous stroke or TIA and treatment were not significant, indicating that the results in the subgroups were consistent with the overall result of the study.

• Major bleeding was more frequent in patients with history of stroke or TIA than in patients without (2.88; 1.77 to 4.55) but risk of this event did not differ between treatment groups.

The researchers suggest from this pre-specified analysis of the AVERROES study that apixaban is similarly effective in patients with atrial fibrillation, whether or not they have had a previous stroke or TIA. They suggest that the absolute benefits might be greater in this group as it has a higher risk of stroke.