Impact of Insertable Cardiac Monitor-Detected Atrial Fibrillation on Future Ischemic Events Following Cryptogenic Stroke

Background: Insertable cardiac monitors (ICMs) are often implanted after cryptogenic stroke (CS) to detect atrial fibrillation (AF) and guide anticoagulation. However, the impact of this practice on stroke recurrence remains unclear. Objectives: This study sought to compare stroke recurrence between CS patients with and without ICM-detected AF and identify predictors of recurrent stroke. Methods: A retrospective analysis was conducted of consecutive patients admitted to a stroke center with no history of AF who received an ICM for CS or transient ischemic attack. Results: Among 840 patients (median follow-up 990 days), AF was detected in 235. Recurrent strokes occurred in 112 patients, of which 70.5% occurred in patients without AF ever being detected. Patients with AF were observed to have increased stroke recurrence when analyzing AF as a time-varying exposure (adjusted HR: 2.73; 95% CI: 1.33-5.59), despite most patients with AF being started on anticoagulation (97.9%). Other covariates associated with increased risk of recurrent stroke in multivariable analyses included an elevated CHA₂DS₂-VASc (Congestive heart failure, Hypertension, Age ≥75 years, Diabetes, history of Stroke or transient ischemic attack, VAscular disease, Age 65-74 years, and Sex category [female]) score ≥4 and male sex. In exploratory subgroup analysis of patients with a CHA₂DS₂-VASc score <4 and age of <65 years (n = 107), only 1 patient with a recurrent stroke had AF detected (<1%). Conclusions: Despite the high rate of detection of AF following CS by ICMs, most strokes occurring in this population may not be due to AF. Further randomized trials are needed to verify these observations and clarify the benefit of routine ICM implantation for secondary CS prevention.