Factors associated with increased atrial fibrillation detection in patients with embolic stroke of undetermined source

BACKGROUND: Studies suggest that longer duration of cardiac monitoring after embolic stroke of undetermined source (ESUS) yields higher detection rates for atrial fibrillation (AF). A common strategy for cardiac monitoring after ESUS starts with a 14-day surface monitor, which is easier to administer, and lower cost compared to implantable monitoring. We tested whether cardiac markers associated with higher likelihood of AF detection can be used to identify patients with ESUS who are more likely to benefit from initial short-term monitoring. METHODS: We adjudicated stroke etiology from patients with acute ischemic stroke discharged from a tertiary care medical center with 14-day surface cardiac monitor (ZioPatch®) between January 2019 and September 2023. The primary outcome was ≥30 seconds of AF on surface monitoring. Predictors included ECG and echocardiographic markers associated with AF in a general population identified during hospitalization. Associations were analyzed using Chi-squared or Fisher's exact tests and age-adjusted logistic regression. RESULTS: We identified 415 patients with ESUS (mean age 67.2 years, 49.9% female). 4.3% (n=18/415) developed AF after a median of 13.8 days (IQR 13-15.8) of monitoring. 9.6% (n=8/83) of patients with enlarged left atrial dimension >4cm and 8.0% (n=9/113) of patients with mitral valve regurgitation developed AF. Significantly more patients with AF had a combination of enlarged left atrial dimension and/or mitral valve regurgitation (36.8% with AF vs 61.1% without AF, p=0.037). Adjusting for age, enlarged left atrial dimension remained significantly associated with increased odds of detection of AF (OR 3.17, 95% CI 1.20-8.36). CONCLUSIONS: In patients with ESUS, the rate of AF detection using a surface 14-day cardiac monitor was low. However, the likelihood of detecting AF was higher among patients with enlarged left atrial dimension and mitral valve regurgitation, suggesting this group may benefit most from an initial short-term monitoring strategy.