I read with interest this month’s Yonder article,1 which highlighted a recent study by Murphy et al on loop-recorder screening for atrial fibrillation (AF).2 They anticoagulated all patients found to have AF, but only followed them up for 2 weeks, prompting the question, ‘Does diagnosing and anticoagulating asymptomatic patients truly provide a meaningful clinical benefit?’
A recent Circulation meta-analysis3 combined data from two randomised controlled trials (NOAH-AFNET 64 and ARTESiA5). The results showed that direct oral anticoagulants (DOACs) modestly reduced stroke risk in asymptomatic, device-detected AF, yet increased bleeding rates. In these trials, AF was detected via pacemakers, implanted cardioverter defibrillators, or implantable cardiac monitors, and the patients were otherwise asymptomatic. The median CHA2DS2-VASc score in NOAH-AFNET 6 was 4 (IQR 3–5), while ARTESiA reported a mean of 3.9 (±1.1 SD).
By pooling more than 6500 participants, the meta-analysis found that DOACs lowered the annual ischaemic stroke risk from 1.0% (aspirin or placebo) to 0.7%, translating to an absolute risk reduction [ARR] of 0.3% and a number needed to treat [NNT] of 333 per year. However, the annual major bleeding rate, defined according to ISTH criteria,6 increased from 1.0% to 1.7%, amounting to an absolute risk increase [ARI] of 0.7% (number needed to harm [NNH] of 143 per year).
As the use of smartwatches grows, I believe we will see more asymptomatic AF diagnoses. A robust primary care RCT designed to assess the risks and benefits of anticoagulating this population would be invaluable. Until then, I consider the aforementioned trials the best evidence available for guiding shared decision making.
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