For selected older patients with an acute, non-lacunar, embolic stroke of undetermined source for which AF is suspected but unproven, we suggest additional ambulatory monitoring (beyond 24 hrs) for AF detection, where available, if it is likely that OAC therapy would be prescribed if prolonged* AF is detected. (Conditional Recommendation, Moderate Quality Evidence) [*There are currently insufficient data to indicate what the minimum AF duration should be for OAC to be instituted, and expert opinion varies widely.]

Practical tip: The yield of monitoring for AF detection depends on many factors including the type and duration of monitoring, patient adherence to monitoring, patient age38 and other characteristics. The presence of frequent atrial premature beats during a 24-hour Holter recording is a strong independent predictor of AF in this population.