Background Although mechanical thrombectomy (MT) is an effective treatment for large vessel occlusion (LVO) with a high successful recanalization rate, MT failure (MTF) occurs in 10–15% of cases and is associated with unfavorable outcomes. However, little is known about the clinical, technical, and radiological reasons for MTF. We investigated the technical factors associated with MTF.

Methods We conducted a retrospective analysis of consecutive patients with anterior LVO prospectively included in the ongoing observational multicenter ROSSETTI registry. Patients were categorized according to the success (≥mTICI 2b) or failure (<mTICI 2b) of the MT procedure. Baseline clinical and demographic characteristics, endovascular MT techniques, and angiographic and clinical outcomes were compared. Multivariate analysis for prediction of MTF was performed.

Results We analyzed 4135 patients, including 325 patients (7.9%) with MTF. Patients in the MTF group had a significantly lower Alberta Stroke Program Early CT Score (ASPECTS) at baseline (8 (7–10) vs 9 (8–10)), longer time since last time seen well (279 min vs 262 min), increased MT procedure time (76 min vs 31 min), higher rate of complications (23% vs 4%), higher symptomatic intracerebral hemorrhage (21% vs 7.9%), higher 24 hour National Institutes of Health Stroke Scale score (19 vs 6), worse functional outcome at 3 months (modified Rankin Scale score 0–2, 15.6% vs 53%), and higher mortality (45% vs 20%). Four or more passes were an independent predictor of MTF (OR 3.46, 95% CI 2.58 to 4.63; P<0.001). None of the endovascular techniques demonstrated a higher likelihood of MTF.

Conclusion In this study, MTF in anterior circulation LVO was associated with a high complication rate and worse outcomes.