Outcomes of mechanical thrombectomy in acute stroke due to primary embolic middle cerebral artery M2 occlusions: a comparison of late versus early windows

Background: Current guidelines consider mechanical thrombectomy (MT) reasonable for M2 segment middle cerebral artery (MCA) occlusions within 6 h of symptom onset, yet the impact of delayed intervention in this population remains unclear. Objectives: This study compared effectiveness and safety outcomes of MT performed in late (>6 h) versus early (⩽6 h) treatment windows in patients with acute primary embolic M2 occlusions. Design: We retrospectively analyzed patients with primary embolic M2 occlusions treated with MT within 24 h of onset from the ARTISTA (A Registry for Thrombectomy In Stroke Therapy from Andalusia) registry (2017–2024) in Seville-Huelva, Spain. Methods: Outcomes compared between late and early treatment groups included good outcome (90-day modified Rankin Scale (mRS) 0–2 or return to prestroke mRS), futile recanalization (FR; 90-day mRS >2 despite successful recanalization), successful recanalization (modified Thrombolysis in Cerebral Infarction ⩾2b), and symptomatic intracranial hemorrhage (sICH). Multivariable logistic regression and inverse probability of treatment weighting (IPTW) analyses were performed to evaluate associations between treatment window and MT outcomes. Results: Among 524 patients (median age 76, 48.3% women), 207 (39.5%) underwent MT in the late window. Late treatment showed numerically lower rates of good outcome (58.9% vs 64.4%) and higher rates of FR (37.8% vs 32.5%) and sICH (3.4% vs 3.2%), though none were statistically significant (all p ⩾0.211). Successful recanalization rates were nearly identical between the late and early windows (95.7% vs 95.6%; p = 0.970). IPTW-adjusted analyses also found no significant differences in good outcome (adjusted odds ratio (aOR), 0.82; 95% confidence interval (CI), 0.39–1.73; p = 0.600) or FR (aOR, 1.19; 95% CI, 0.56–2.50; p = 0.653) at 90 days. Conclusion: In this multicenter real-world cohort, MT performed beyond 6 h showed effectiveness and safety outcomes comparable to early-window intervention in patients with primary embolic MCA M2 occlusions.