Subclinical Atrial Fibrillation: Detection, Stroke Risk, and Treatment

Clinically evident atrial fibrillation is estimated to affect more than 1.8 million people in Germany. Atrial arrhythmias are increasingly being detected by cardiac devices and wearables in asymptomatic persons without any history of atrial fibrillation. Such cases are usually designated as "subclinical atrial fibrillation." With the limited and, in part, inconsistent evidence now available, it remains unclear whether this condition is medically relevant and an indication for oral anticoagulation.

This review is based on pertinent publications (2005-2025) retrieved by a selective search in the PubMed, Embase, and Cochrane Library databases on subclinical atrial fibrillation, atrial high-rate episodes (AHRE), and device- or wearable-detected atrial fibrillation.

Subclinical atrial fibrillation is associated with an elevated risk of stroke that increases with episode duration and arrhythmia burden. Observational studies have shown that device-detected episodes lasting 6 minutes or longer elevate the stroke risk by a factor of 2 to 2.5, yielding an absolute risk that is still lower than that of patients with clinically evident atrial fibrillation. No direct causal or temporal relationship has been shown between the detected episodes and thromboembolic events. Screening increases the detection rate without improving outcomes. Randomized trials (LOOP, NOAH-AFNET 6, ARTESiA) have not revealed any consistent clinical benefit from routine oral anticoagulation. In the ARTESiA trial, patients taking apixaban had fewer strokes (hazard ratio 0.63, 95% confidence interval [0.45; 0.88]), but also significantly more clinically relevant hemorrhages (HR 1.80 [1.26; 2.7]). In the NOAH-AFNET 6 trial, edoxaban was not found to have any benefit, but it did elevate the risk of bleeding.

Routine oral anticoagulation cannot currently be recommended for patients with subclinical atrial fibrillation. Important considerations for treatment decisions include the individual thromboembolic risk profile, the duration and burden of subclinical atrial fibrillation, and the reliability of the diagnosis. Current evidence suggests that subclinical atrial fibrillation is more likely to be a marker for underlying atrial cardiomyopathy than a direct precipitant of thromboembolic events.