Optimal Catheter Size for Medium Vessel Occlusion in Aspiration Thrombectomy

The efficacy of mechanical thrombectomy for medium vessel occlusion remains controversial, and optimal recanalization strategies are lacking. We investigated factors associated with successful recanalization using aspiration thrombectomy in patients with medium vessel occlusion. We conducted a retrospective study on patients with acute ischemic stroke who underwent aspiration thrombectomy for M2 occlusion between July 2021 and November 2025. We examined the factors associated with successful recanalization by focusing on the ratio of the catheter outer diameter to the target vessel inner diameter (Catheter-to-vessel ratio). Overall, 64 patients were included. First-pass successful recanalization (modified Thrombolysis in Cerebral Infarction ≥ 2c) was achieved in 24 patients. In patients with successful recanalization, the ratio of the catheter outer diameter to the target vessel inner diameter (Catheter-to-vessel ratio) was significantly higher than in those without successful recanalization (p = 0.029). In multivariate analysis, the Catheter-to-vessel ratio was independently associated with successful recanalization after adjustment for catheter position and thrombus size (odds ratio per 0.1 increase, 3.688; 95% confidence interval, 1.478-9.202; p = 0.0007). In the receiver operating characteristic analysis, the threshold for the Catheter-to-vessel ratio distinguishing successful recanalization was 0.70, with a sensitivity of 79% and a specificity of 63%.In aspiration thrombectomy for medium vessel occlusion, a Catheter-to-vessel ratio ≥ 0.70 may be an exploratory indicator associated with first-pass successful reperfusion.