ABSTRACT NUMBER: ESOC2026A2253 CAROTID STENOSIS: DIFFERENT HISTOLOGICAL FEATURES IN CONVENTIONAL STENOSIS AND NEAR-OCCLUSION

Abstract Background and aims Symptomatic carotid near-occlusion (CNO) has an unclear stroke mechanism, it might be similar as conventional stenosis, i.e. embolic. The only existing histological analysis of CNO had 13 cases with long delay to surgery (>2 months). This study aimed to compare histological features between symptomatic CNO and conventional stenoses. Methods This study included patients with ≥50% symptomatic carotid stenosis that underwent carotid surgery. Expert-assessed computed tomography was used to assess degree of stenosis (CNO or conventional stenosis). All plaques were stained with relevant stainings and interpreted. All histological outcomes suggested in Oxford plaque study and/or the Athero-express study were used, which includes lipid core size, cap thickness, thrombus, intraplaque hemorrhage and inflammation assessments. Results We included 86 patients, 38 with CNO and 44 with conventional stenosis. Median delay from last event to surgery was 8 (IQR 6-13) days. Compared to conventional stenosis, CNO had more often moderate/severe plaque lymphocytes (100% vs 83%, p=0.008) and plaque macrophages (65% vs 33%, p=0.004). CNO also tended to more often have an atheromatous plaque type (45% vs 33%, p=0.08), no/minor fibrosis (89% Vs 71%, p=0.06), moderate/severe cap lymphocytes (100% Vs 90%, p=0.07), and intraplaque hemorrhage (84% vs 65%, p=0.051). Remaining assessments were non-significant (p>0.1). Conclusions Symptomatic CNO plaques have overall a similar histological appearance as symptomatic conventional stenosis plaques. If anything, all differences (significant and tendencies) pointed towards more unstable findings in CNO than conventional stenosis. These findings support an embolic mechanism in symptomatic CNO. Conflict of interest Isabell Hedberg: Nothing to disclose. Elias Johansson: Nothing to disclose