Abstract WP244: Complex Aortic Plaque on Computed Tomography Angiography in Embolic Stroke of Undetermined Source: Association with Multiple Strokes

Purpose: Complex aortic plaque (CAP), an underrecognized source of embolic stroke, lacks standardized CT criteria. We evaluated the prevalence of CAP on routine CTA at different thresholds of maximal plaque thickness (MPT) and additionally capturing low attenuation plaque and ulceration in patients with embolic stroke of undetermined source (ESUS). We assessed the association between CAP and history of prior strokes before the index ESUS. Materials and Methods: This retrospective single-center study reviewed consecutive patients with unilateral anterior circulation ESUS who underwent neck CTA including the aortic arch (ascending/arch/descending). The aortic arch was inspected for hypoattenuating plaques on axial and reformatted images by a radiologist. MPT was measured orthogonal to plaque. Plaques were manually segmented using 3D Slicer to record median attenuation in Hounsfield units (HU). CAP definitions included MPT ≥3 mm, ≥4 mm, HU ≤80, and combined criteria (MPT ≥4 mm or HU ≤80, with or without ulceration ≥2 mm). Attenuation of ≥4 vs. <4 mm plaques was compared by Welch’s t-test. Age, sex and vascular risk factors (hypertension, diabetes, hyperlipidemia, smoking) were compared between CAP and non-CAP groups using Chi-square or Fisher’s exact test. Primary outcome was multiple strokes, defined as a history of prior stroke and current index ESUS. Results: Of 143 ESUS patients, 133 (mean age 65±13 years; 70 women; baseline NIHSS 8±7) met inclusion. CAP prevalence was 15.7% with a ≥3 mm threshold, 6.0% by ≥4 mm, 7.5% by ≤80 HU, and 6.0% by ulceration; combined criteria (≥4 mm, ulceration, or ≤80 HU) yielded 10.5%. CAP ≥4 mm was significantly associated with multiple strokes (4/8 vs. 14/125; OR 7.9, p=0.012). With combined criteria, the association also remained significant (5/14 vs. 13/119; OR 4.5, p=0.024), capturing additional high-risk patients beyond the ≥4 mm cutoff. Plaques ≥4 mm had lower attenuation than smaller plaques (53±26 vs. 107±54 HU; p=0.006). Patients with ≥4 mm CAP were older (79 vs. 64 years; p=0.001) and did not differ by sex or other risk factors. Conclusion: CTA-detected CAP was present in 6–16% of ESUS patients. Plaque ≥4 mm and broader high-risk definition (≥4 mm, ≤80 HU, or ulceration) was significantly associated with multiple strokes. Aortic arch assessment on routine neck CTA may enhance detection of potential aortic embolic sources.