Left Atrial Diameter and Atrial Ectopic Burden in Patients with Embolic Stroke of Undetermined Source: Risk Stratification of Atrial Fibrillation with Insertable Cardiac Monitor Analysis

Background and Purpose An insertable cardiac monitor (ICM) has been demonstrated to be a useful tool for detecting subclinical atrial fibrillation (AF) in patients with embolic stroke of undetermined source (ESUS). This study aimed to identify the clinical predictors of AF in ESUS patients with ICMs. Methods We retrospectively selected consecutive patients with an ICM implanted for AF detection following ESUS. The primary endpoint was defined as any AF episode lasting for longer than 5 min. The atrial ectopic burden (AEB) was calculated as the percentage of the number of conducted QRS from atrial ectopy on Holter monitoring. Results This study included 136 patients. AF lasting >= 5 min was detected in 20 patients (14.7%) during a median follow-up period of 6.6 months (interquartile range, 3.3-10.8 months). AF patients had a higher AEB (0.20% vs. 0.02%, p<0.001) and a larger left atrial diameter (LAD, 41.0 mm vs. 35.3 mm, p<0.001) than those without AF. The areas under the receiver operating characteristic curves were 0.795 and 0.816 for the LAD and log-transformed AEB, respectively, for the best cutoff values of 38.5 mm for LAD and 0.050% for AEB. AF lasting >= 5 min was detected in 34.6% (9/26) of patients with LAD >= 38.5 mm and AEB >= 0.050%, and in 0% (0/65) of those with LAD <38.5 mm and AEB <0.050%. Conclusions AF was detected in a significant proportion of ESUS patients during a 6.6-month follow-up. The LAD and AEB are good predictors of AF and might be useful for AF risk stratification in ESUS patients.