HISTOPATHOLOGICAL COMPOSITION OF THROMBUS MATERIAL IN A LARGE SERIES OF PATIENTS WITH ACUTE ISCHEMIC STROKE: THE STUDY OF ATYPICAL CLOT

Laura Rojas-Bartolomé ¹ María Payá Montes ¹ Rosa Barbella-Aponte ² Laura Restrepo Carvajal ¹ JORGE GARCÍA GARCÍA ¹ Oscar Ayo-Martin ¹ Juan David Molina-Nuevo ³ Gemma Serrano-Heras ⁴ Enrique Juliá-Molla ³ María José Pedrosa-Jiménez ³ Lorena López-Martínez ³ Ángela Fernández-López ³ Tomás Segura Martín ^1,5 Francisco Hernandez-Fernandez ^1,3,6*

• ¹ Department of Neurology, General University Hospital of Albacete, Albacete, Spain
• ² Department of Pathology, Albacete University Hospital Complex, Albacete, Spain
• ³ Department of Radiology, Albacete University Hospital Complex, Albacete, Spain
• ⁴ Research Unit, Albacete University Hospital Complex, Albacete, Spain
• ⁵ Institute for Research in Neurological Disabilities (IDINE), Faculty of Medicine, Albacete, Spain
• ⁶ Complejo Hospitalario Universitario de Albacete, Albacete, Spain

Clot composition appears to be related to outcomes in stroke recanalisation therapy. The aim of this study is to analyse the thrombus composition and to evaluate the relationship between atypical clot composition with clinical parameters, laboratory markers, and recanalization strategies in a series of patients with acute ischaemic stroke (AIS) undergoing endovascular treatment (EVT).Prospective single-centre registry from December 2014-July 2022. All the retrieved clots were studied under an established protocol and classified as follows: red blood cells-rich clots (RBC), fibrin/platelet-rich clots (FPC), Mixed (MC), septic emboli (SE), atheroma emboli (AE), fatty emboli (FE) and calcium emboli (CE). We considered two groups: atypical clot composition (ACC: SE, AE, FE, and CE) and usual clot composition (UCC: RBC, FPC, and MC). A subgroup of 10 ACC (4 SE, 3 AE, 2 FE, and 1 CE) and 9 UCC (3 RBC, 3 FPC, and 3 MC), matched by age and sex, were analyzed by immunohistochemistry to detect neutrophil extracellular traps (NETs). Results 606 patients were assessed for EVT of which 448 (73.92%) fulfilled the inclusion criteria. The clot categorization was: FPC 211 (47.1%), RBC 105 (23.4%), MC 104 (23.2%), SE 16(3.6%), AE 5 (1.1%), CE 4 (0.9%), FE 3 (0.7%). We therefore classified 420 (93.75%) patients in the UCC group and 28 (6.25%) in the ACC group. Bivariate analysis revealed that the ACC group had a significantly higher number of leukocytes (11.40 leukocytes/mm3 vs. 9.49, p=0.005), more frequent TICA occlusion (28.6% vs. 9.8%, p=0.006) and higher mortality at 3 months (28.6% vs. 12.4%, p=0.038). In multivariate analysis, atypical clot composition was significantly associated with higher prevalence of Diabetes Mellitus, smoking, occlusion of terminal internal carotid artery, and higher number of passes.Immunohistochemical studies showed the presence of neutrophil extracellular traps (NETs) in all 19 thrombi analyzed.