Detection of atrial fibrillation after cryptogenic stroke

Patients with ischemic stroke and atrial fibrillation (AF) are treated with long-term oral anticoagulation (OAC) because it is considerably more effective than antiplatelet (AP) therapy for the prevention of subsequent strokes and systemic emboli. Therefore, detecting AF changes therapy and makes secondary prevention more effective. Technology for detection of rare episodes of paroxysmal AF (PAF) has improved recently. AF that is only detectable by prolonged monitoring (occult AF, or oAF) may underlie some strokes of unknown cause (cryptogenic stroke). However, the ideal method and duration of cardiac monitoring to detect oAF after stroke is unknown. Furthermore, new technologies allow the detection of brief, rare episodes of AF that would not have been detectable at the time classic studies establishing the benefit of OAC were conducted. Therefore, it is unknown what the minimum threshold of oAF burden or duration is that mandates OAC instead of AP therapy. Here we review the available technologies, and discuss the therapeutic implications and uncertainties when oAF is found after ischemic stroke. There is evidence that 3 weeks of outpatient cardiac telemetry has a high yield of detection of AF after cryptogenic stroke; however, ongoing studies may show that even longer monitoring periods have higher yield.