When to set anticoagulant therapy in asymptomatic AF? looking for a cut-off duration

The incidence of atrial fibrillation (AF) is progressively increasing, in line with the aging of the population and with the increase in chronic diseases. The care burden of the disease and above all to its consequences (i.e. ischaemic stroke and heart failure) significantly impacts the various health systems with forecasts of exponential increase in the near future. Clinical forms of AF, i.e. those diagnosed with electrocardiogram, have a clear correlation with systemic embolic events and also with a reduction in survival. Thromboembolic prophylaxis in these patients, with anticoagulant drugs, has in fact been shown to greatly reduce the incidence of ischaemic stroke and improve survival. In recent decades, the widespread use of therapeutic intra-cardiac devices, which allow constant and continuous monitoring of myocardial electrical activity, is bringing to light a large number of atrial high rate episodes (AHREs), which are not associated with clinical manifestation. The incidence of these findings grows linearly with the duration of the observation. More independent studies have shown that AHREs are associated with a risk of stroke that is higher (about double) than controls but significantly lower than in patients with manifest AF. However, taking into consideration patients with ischaemic stroke and wearers of implantable devices, no temporal correlation emerged between the incidence of the ischaemic episode and arrhythmia. The presence of AHRE is associated with an approximately six-fold increase in the incidence of clinical AF but only a minority of these patients meet the criteria for prescribing anticoagulation. Pending the publication of the studies still in progress, the European Society of Cardiology guidelines for the treatment of AF recommend considering the initiation of anticoagulant therapy in patients with long-lasting AHRE (> 24 h) associated with a high embolic risk. In patients with episodes of shorter duration (1–24 h), especially if with high burden, anticoagulant therapy can be considered in case of very high embolic risk (e.g. secondary prevention, CHADVASc ≥ 3).