Abstract WP130: MRI-Detected Embolic Infarcts in Atrial Fibrillation Patients without History of Stroke: Prevalence, Characteristics, Predictors, and Potential Sources

Background: MRI-detected embolic infarcts are often observed in patients with atrial fibrillation (AF), even in the absence of clinical stroke. The prevalence, characteristics, and underlying risk factors of these lesions remain poorly understood. Methods: We conducted a retrospective analysis of 823 consecutive patients with AF who underwent brain MRI between 2015 and 2022. Patients with prior ischemic/hemorrhagic stroke, transient ischemic attack, or neurodegenerative disorders were excluded. Embolic infarcts were identified on brain MRIs, and comprehensive clinical, laboratory, and echocardiographic data were collected. To identify factors independently associated with MRI-detected embolic infarcts, we applied multivariable logistic regression models. Additionally, mediation analyses were performed to explore potential structural or functional cardiac features underlying the observed associations. Results: The study included 823 patients with a mean age of 72 ± 11 years; 303 (36.6%) were female; 557 (67.7%) were using anticoagulants. MRI-detected “covert” embolic infarcts were present in 44 patients (5.3%), with a median infarct volume of 0.36mL (interquartile range: 0.14 – 1.25). No significant difference in the presence of infarcts (p = 0.942) or infarct volume (p = 0.831) was observed between patients on anticoagulation and those not receiving anticoagulation. Independent predictors of MRI-detected embolic infarcts included the presence of heart failure (aOR 2.6, 95% CI 1.4-5.0, p = 0.003) and daily consumption of alcohol (aOR 2.5, 95% CI 1.1-5.9). In a secondary analysis of a subset with available echocardiographic data (n=458), larger left atrial diameter partially mediated the association between heart failure and MRI-detected embolic infarcts (bootstrapped 95% CI for indirect effect: 0.014-0.50). In contrast, left ventricular ejection fraction showed no mediation. Conclusions: MRI-detected embolic infarcts occur in 1 in 19 AF patients without prior clinical stroke. These lesions are small and occur irrespective of anticoagulation status. Heart failure and daily alcohol consumption were independently associated with the presence of these infarcts; both factors are closely linked to AF pathophysiology. The partial mediating role of left atrial enlargement further supports an AF-related embolic mechanism underlying these infarcts.