Vascular injury and occurrence of microthrombi after endovascular therapy for acute ischaemic stroke in a thromboembolic model

Background: Endovascular catheters and devices used for thrombectomy in patients who had a stroke can damage the vessel lumen leading to microthrombi. During stroke recanalisation, microthrombi could migrate distally and occlude cerebral microvasculature, potentially limiting the benefit of recanalisation therapy. Objectives: To describe vascular injury occurring after endovascular therapy (EVT), with stent retrievers (SR) and direct aspiration (DA), to open up avenues for further improvement of EVT technique. Methods: SR and DA were performed according to clinical procedures in extracranial vessels in a swine model of thromboembolic arterial occlusion. Treated vessels were collected at 2 hours or 3 days post-EVT to assess respectively acute injury and early healing (remnant vascular injury) as assessed by Evans-Blue (EB) dye exclusion. The presence of microthrombi was quantified using scanning electron microscopy. Markers of coagulation activation were measured periprocedurally in plasma. Results: Both SR and DA induced vascular injury. SR tended to result in larger EB positive areas than DA at 2 hours (99.5 vs 84.5; p=0.072) which reached statistical significance at day 3 (78.6 vs 48.6; p=0.040) post-EVT. Both EVT methods similarly yielded microthrombi in treated areas which were still observed at 3 days post-EVT. In addition, both EVT methods immediately increased systemic plasma levels of complexes of intrinsic-pathway coagulation activation: thrombin, Factor IX and Factor Xa:Antithrombin. Conclusions: In this preclinical thromboembolic model, SR thrombectomy and DA lead to acute vascular injury, yield microthrombi and trigger contact activation of the coagulation system. At 3 days after intervention, healing remains incomplete, showing remnant vascular injury in the treated arteries, especially in SR thrombectomy.