Atrial fibrosis, atrial volume and implantable loop recorder-detected atrial fibrillation in embolic stroke

Abstract Background Atrial fibrosis and increased volumes on cardiac magnetic resonance imaging (MRI) are seen in patients with atrial fibrillation (AF) and represent underlying atrial substrate changes. Similar changes are seen in patients with embolic stroke of undetermined source (ESUS); increasing fibrosis and left atrial volume have been associated with increased chance of recurrent stroke or incident atrial fibrillation. Purpose To characterise the degree of atrial fibrosis and left atrial volumes in a cohort with embolic stroke and correlate degree of fibrosis and left atrial volume with AF detection during follow-up with continuous cardiac monitoring. Methods This is a prospective, multicentre, observational study of patients aged 18-85 years enrolled after embolic stroke undergoing cardiac MRI at enrolment with dedicated atrial fibrosis imaging and receiving continuous cardiac monitoring via implantable loop recorder. Results Twenty patients, 13 (65%) female, mean age 72±6 years, were enrolled a mean of 137±58 days following stroke. Nineteen patients had embolic stroke of undetermined source (ESUS) and one patient had intracranial atherosclerotic disease (ICAD) as the cause of stroke. During a mean follow-up of 760±252 days, 6 patients (30%) were diagnosed with AF on implantable cardiac monitoring a mean of 234±91 days post-stroke. Mean left atrial fibrosis was 11±7% in patients who developed AF versus 7±4% in those who did not, though this did not reach statistical significance (p=0.1). Mean left atrial volume of 101±30mL vs 75±22mL (p=0.04) and mean left atrial surface area of 138±28cm2 vs 116±16cm2 (p=0.04) were significantly higher in patients who developed AF versus those who did not, respectively. In patients with AF, median burden was low at 1% (0.3-1.4), median longest episode was 251 minutes (113-1422), with 5 of 6 patients having AF episodes over 1 hour and 2 of 6 having episodes over 24 hours long. Conclusion Patients with embolic stroke and implantable cardiac monitor-detected AF in this series had increased left atrial volume and left atrial surface area on cardiac MRI when compared with those who did not. Moderate fibrosis was present, though not different between groups, and AF burden was low. Larger cohorts will be needed to refine incident AF and recurrent stroke predictors in this group, to ultimately guide tailored treatment approaches.