Association between the number of thrombectomy passes and clinical outcomes after mechanical thrombectomy for medium vessel occlusion

Background First-pass reperfusion is associated with favorable outcomes after mechanical thrombectomy (MT) for medium vessel occlusion (MeVO), but the impact of increasing pass number remains unclear. We investigated the association between thrombectomy pass number and outcomes in MeVO. Methods Patients undergoing MT for MeVO between January 2016 and December 2025 were retrospectively analyzed in a multicenter registry. The primary outcome was the 90-day modified Rankin Scale (mRS) distribution. Multivariable models evaluated associations between pass number and outcomes, adjusting for first-line thrombectomy procedure and subsequently for treatment timing, procedure duration, excellent reperfusion, and symptomatic intracranial hemorrhage (sICH). Exploratory threshold and marginal effects analyses were performed. Results Among 234 patients, 111, 58, 31, and 34 underwent 1, 2, 3, and ≥4 passes, respectively. Increasing pass number was associated with a less favorable 90-day mRS distribution (adjusted common OR 0.70 (95% CI 0.58 to 0.85)) and a higher risk of sICH (adjusted OR 1.64 (95% CI 1.07 to 2.54)). The association with 90-day mRS remained significant after additional adjustment for onset-to-puncture time, puncture-to-procedure end time, and excellent reperfusion (adjusted common OR 0.73 (95% CI 0.58 to 0.94)). In exploratory threshold analyses, ≥3 passes was the first prespecified cut-off associated with both lower functional independence and increased sICH, while adjusted functional independence declined progressively with increasing pass number. Conclusions Increasing pass number was associated with less favorable functional outcomes and a higher sICH risk after MT for MeVO. These findings do not establish a stopping rule but support caution with additional passes.