Objective: Atrial fibrillation (AF) may be present within a subset of patients with presumed cryptogenic TIA or stroke and remains undetected by standard diagnostic methods. We hypothesized that AF may be an under-recognized mechanism for cryptogenic TIA/stroke.

Methods: A consecutive series of 56 patients with cryptogenic TIA/stroke was analyzed after diagnostic evaluation and Mobile Cardiac Outpatient Telemetry (MCOT) for up to 21 days. Demographic, radiographic, echocardiographic, and MCOT results were reviewed. Predictors of AF detection by MCOT were determined by univariate analysis including Student t test and Fisher exact tests and multivariate analysis.

Results: The median MCOT monitoring duration was 21 (range 5–21) days resulting in an AF detection rate of 23% (13/56). AF was first detected after a median of 7 (range 2–19) days of monitoring. Twenty-seven asymptomatic AF episodes were detected in the 13 patients, of which 85% (23/27) were <30 seconds and the remaining 15% (4/27) were 4–24 hours in duration. Diabetes was predictive of AF detection by both univariate (p = 0.024) and multivariate analysis (OR 6.15; 95% CI 1.16 to 32.73; p = 0.033).

Conclusions: There is a high rate of atrial fibrillation (AF) detection by Mobile Cardiac Outpatient Telemetry (21 days) in patients with cryptogenic TIA/stroke that may be related to extended monitoring duration, patient selection, and inclusion of all new onset AF episodes. Brief AF episodes (<30 seconds) may be biomarkers of more prolonged and clinically significant AF.