Direct oral anticoagulants helped in atrial fibrillation at intermediate stroke risk

Design

Multicentre, open-label, adjudicator-masked randomised superiority trial

Population

1,803 patients in South Korea with atrial fibrillation and CHA2DS2-VASc 1 (men) or 2 (women)

Primary outcome

Stroke, systemic embolism, major bleeding or CV death at 24 months

Effect

0.5% vs 1.5%; HR 0.31 (95% CI 0.10-0.94)

SINGLE-AF was an open-label, adjudicator-masked trial in South Korea. It randomised 1,803 patients with atrial fibrillation and a CHA2DS2-VASc score of 1 (men) or 2 (women) to a direct oral anticoagulant or no anticoagulation. Mean age was 60, and 24% were women.

At 24 months, the composite of stroke, systemic embolism, major bleeding or cardiovascular death occurred in 4 patients (0.5%) on anticoagulation and 13 (1.5%) without (difference 1.0 percentage point, 95% CI 0.1 to 2.0; HR 0.31, 0.10 to 0.94). Strokes were 3 and 10. Major bleeding and systemic embolism appeared similar, and there were no cardiovascular deaths.

Guidelines already give anticoagulation a class IIa recommendation at this risk level, and this is the first randomised evidence behind it. Event numbers are small and the population was younger than many Indian patients with atrial fibrillation, but the direction supports considering treatment.

• Consider offering a direct oral anticoagulant to patients with atrial fibrillation and one non-sex risk factor, after discussing bleeding risk.
• Recalculate the stroke risk score at every review; age alone moves many patients up a category.
• Assess and correct modifiable bleeding risks, such as uncontrolled blood pressure and unnecessary antiplatelet drugs.
• Explain that the absolute benefit over two years is about one event prevented per 100 patients.

Why it matters

It gives randomised support to a recommendation that until now rested on observational data.

Don't overread it

With 17 events and an open-label design, the size of the benefit is uncertain even if its direction is not.

The statistics, in plain English

The absolute difference was 1 percentage point over two years, so about 100 patients would need treatment to prevent one event. The hazard ratio's interval (0.10 to 0.94) is wide because there were only 17 events in total, so the true size of the benefit is uncertain.

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