Atrial fibrillation detected after stroke: Recent advances and future directions

Prolonged cardiac monitoring has made atrial fibrillation (AF) an increasingly common diagnosis after ischemic stroke. Applied to all patients with ischemic stroke, prolonged cardiac monitoring would result in over a million new AF diagnoses per year worldwide. Almost 10 years after the conceptual inception of AF detected after stroke (AFDAS), several patterns are now consistent across studies. AFDAS is a distinct, mechanistically heterogeneous entity that differs from AF known before stroke in its risk-factor profile, cardiac comorbidity, and its lower rate of ischemic stroke recurrence. Its detection is determined primarily by the monitoring method and increases with earlier and longer-duration monitoring. AF identified on a standard electrocardiogram behaves as a high-burden arrhythmia, resembling AF known before stroke, and should be distinguished from the low-burden AF detected by prolonged monitoring. Important questions remain unresolved. It is unproven that detecting more AF, or detecting it earlier, reduces recurrent ischemic stroke. The low-burden arrhythmia that monitoring increasingly identifies appears to carry a lower embolic risk than the high-burden AF for which anticoagulation was established. Whether patients with low-burden, monitor-detected AFDAS derive net benefit from anticoagulation, the contribution of neurogenic mechanisms, and the thresholds of AF burden that should guide treatment are undefined. Future trials should be powered for recurrent stroke as the primary endpoint.