Thrombus histopathological composition in distal versus proximal vessel occlusions treated by mechanical thrombectomy.

Abstract

Intracranial thrombus composition plays a key role in determining the response to both intravenous thrombolysis (IVT) and mechanical thrombectomy (MT), and the likelihood of achieving successful recanalization. This study investigated the histopathological composition of thrombi retrieved from distal medium vessel occlusions (DMVO) versus proximal large vessel occlusions (PLVO) during MT. A retrospective analysis of acute ischemic stroke patients who underwent MT at a single institution between January 2019 and July 2024 was conducted. Thrombi retrieved from distal and proximal occlusions were histologically analyzed using hematoxylin-eosin and Martius Scarlet Blue staining. The primary outcome was the difference in thrombus composition between DMVO and PLVO. Among 637 MT procedures, 163 thrombi were successfully analyzed, including 21 and 142 from DMVO and PLVO patients, respectively. Clinical and angiographic outcomes were comparable between both types of occlusions. DMVO thrombi exhibited significantly higher median platelet content (45%, IQR: 30-55% vs 20%, IQR: 15-35%; p=0.007) and lower median red blood cell content (40%, IQR: 10-50% vs 60%, IQR: 37-70%; p=0.001) compared with PLVO thrombi. Thrombi from patients with non-successful reperfusion exhibited higher median white blood cell content (10%, IQR: 5-14%) than those of patients with final successful recanalization (5%, IQR: 0-10%; p=0.04), regardless of occlusion site. This study demonstrated significant compositional differences between thrombi retrieved from DMVO and PLVO, with thrombi from distal occlusions exhibiting higher platelet and lower RBC content compared with those from proximal occlusions. However, larger studies with more detailed immunohistopathological analyses are warranted to confirm these results.