Direct Aspiration vs. Partial and Complete Stent Retriever Retraction in Stroke: Influence of Collateral Flow on Recanalization and Embolic Risk

Background Cerebral collateral status is considered an independent prognostic factor in stroke patients. We aimed to assess whether collateral extent also modifies first-pass recanalization (FPR) and distal emboli generation across different mechanical thrombectomy (MT) strategies. Methods Two in-vitro neurovascular models were created: good (GCM) and poor collaterals model (PCM). Both were identical up to the M2 segment of the middle cerebral artery (MCA), but only the GCM included primary and secondary anastomoses. Soft (stiffness = 53.72 ± 5.32kPa) and stiff (stiffness = 110.02 ± 10.59kPa) clot analogs embolized the M1-MCA. The study was randomized for thrombectomy technique: direct aspiration thrombectomy, partial stent retriever retraction and complete stent retriever retraction. Outcome measures were: complete (TICI2c-3), substantial (TICI2b-3) recanalization, and distal emboli parameters. Results A total of 240 MTs were performed (20 experiments per technique/model/clot type). Overall rates of complete and substantial recanalization were 23.8% and 68.8% respectively. Complete recanalization was higher in GCM (33.3%) than in PCM (14.2%; p < 0.01) regardless of clot type or technique. Across all clot types and collateral status, complete stent-retriever technique achieved highest rate of TICI 2b-3 and direct aspiration the highest rates of TICI 2c-3, particularly in PCM. Partial stent-retriever retraction technique was the least effective. There were no significant differences in distal embolization according to collaterals or clot types, however partial stent-retriever retraction technique generated the highest embolic load and direct aspiration the lowest. Conclusion The degree of collateral circulation may modify MT angiographic outcomes with different impacts according to techniques or clot composition and could be used to guide therapeutic decisions.