Mechanical Thrombectomy for Medium and Distal Vessel Occlusion: A Systematic Review and Meta-Analysis

ABSTRACT Objective We aimed to do an updated meta- analysis comparing outcomes of mechanical thrombectomy (MT) associated with standard medical treatment (SMT), compared to SMT alone, in adult patients with acute ischemic stroke (AIS) due to medium or distal vessel occlusion (MDVO). Methodology We systematically searched PubMed, LILACS, Scielo, Cochrane, and ClinicalTrials.gov databases. Randomized controlled trials (RCTs), retrospective cohort studies, and systematic reviews with meta-analysis comparing MT+SMT with SMT alone in adults with AIS due to MDVO, evaluating at least one of the outcomes of interest, were included. The evaluated outcomes were functional recovery (modified Rankin Scale [mRS] 0-1 and mRS 0-2) at 90 days, all-cause mortality at 90 days, and the occurrence of intracranial hemorrhage (ICH). Risk of bias was assessed using RoB 2, Newcastle-Ottawa, and AMSTAR 2 tools. Heterogeneity was assessed with Chi² and I², and publication bias with funnel plots and Egger/Begg tests. Results Twelve studies (4 RCTs, 7 cohorts, 1 systematic review) were included. Meta-analyses showed no significant difference between MT+SMT and SMT alone for: mRS 0-1 (Excellent Recovery), mRS 0-2 (Good Recovery), mortality at 90 days, and Symptomatic Intracranial Hemorrhage. Conclusion Current evidence, combining RCTs and observational studies, does not support the routine use of MT over SMT alone for MDVO in terms of functional improvement at 90 days (mRS 0-1 or 0-2). Non-significant trends towards increased mortality and sICH risk with MT were observed, with considerable heterogeneity for sICH. KEY MESSAGE Several randomized controlled trials (RCTs) have demonstrated the benefit of mechanical thrombectomy associated with standard medical treatment (SMT), in patients with IS caused by large vessel occlusion (LVO). There for the boundaries of MT began to be questioned, raising the possibility of performing it for medium and distal vessel occlusions (MDVO). As a result of this study, there was no evidence to support the use of MT over SMT alone for MDVO, therefore the therapeutic decisions should remain individualized and further research is crucial to define the exact role of the MT.