Occult Atrial Fibrillation in Cryptogenic Stroke: Detection by 7-Day Electrocardiogram Versus Implantable Cardiac Monitors

Background and Purpose— A significant number of patients with cryptogenic stroke suffer from intermittent atrial fibrillation (iAF) which was not detected during the standard diagnostic procedures. We investigated whether implantation of an insertable cardiac monitor (ICM) is feasible in patients with cryptogenic stroke, and compared the iAF detection rate of the ICM with 7-day Holter monitoring. Methods— Sixty patients (median age 63; interquartile range, 48.5–72 years) with acute cryptogenic stroke were included. ICM was implanted 13 days (interquartile range; 10–65 days) after the qualifying event. Seven-day Holter was performed after the ICM was implanted. Results— The iAF was detected by the ICM in 10 patients (17%; 95% CI, 7% to 26%). Only 1 patient (1.7%; 95% CI, 0% to 5%) had iAF during 7-day Holter monitoring as well (P=0.0077). Episodes of iAF lasting 2 minutes or more were detected 64 (range, 1–556) days after implantation. There were no recurrent strokes during the observation period. The implantation procedure was well tolerated with no adverse events; the daily data transmission protocol was easy to handle by the patients. Conclusions— ICM implantation for the detection of iAF during outpatient follow-up is feasible in patients with cryptogenic stroke. ICMs offer a much higher diagnostic yield than 7-day Holter monitoring.