Endovascular thrombectomy for acute ischemic stroke due to medium or distal vessel occlusion: A systematic review and meta-analysis

INTRODUCTION: Acute ischemic stroke (AIS) due to medium-vessel occlusion (MeVO) accounts for up to 40 % of ischemic strokes. While traditionally assumed to have better outcomes than large-vessel occlusion (LVO) strokes, recent evidence suggests that MeVO often results in poor functional outcomes despite optimal medical management. The role of endovascular thrombectomy (EVT) in MeVO remains uncertain despite recent trials, due to limited high-quality evidence when considering observational studies. This systematic review and meta-analysis evaluated the efficacy and safety of EVT compared to standard medical therapy (SMT) in patients with AIS due to MeVO. METHODS: We systematically searched PubMed, Embase, and Cochrane Central for studies comparing EVT and SMT in patients after AIS secondary to MeVO that reported at least one clinical outcome of interest, such as functional outcome, mortality, and hemorrhagic complications. We used risk ratio (RR) with 95 % confidence intervals (CIs) as the effect size measure for binary outcomes, employing a random-effects model, and RoB-2 and ROBINS-I tools for risk of bias assessment. RESULTS: We included 23 studies (2 RCTs and 21 observational studies) encompassing 7100 patients. There was not significant difference between groups regarding excellent (RR 1.08; 95 % CI 0.96-1.22; p = 0.2204; I² = 65.2 %) and functional independence outcome (RR 1.04; 95 % CI 0.93-1.15; p = 0.4924; I² = 75.1 %), and mortality (RR 1.18; 95 % CI 0.97-1.43; p = 0.0937; I² = 16.6 %). Subgroup analyses showed a benefit of EVT over SMT in PCA occlusions regarding excellent functional outcome. However, EVT was associated with a significantly higher likelihood of hemorrhagic complication than SMT, such as sICH (RR 1.69; 95 % CI 1.18-2.43; p = 0.0042; I² = 39.7 %), and its subtype, SAH (RR 7.97, 95 % CI 4.78-13.30, p < 0.0001; I² = 0.0 %). CONCLUSION: The combined therapy of EVT and SMT on MeVO AIS showed similar functional status and mortality results as SMT alone. However, the use of EVT increased the risk of hemorrhagic complications (sICH and SAH). While most subgroup analyses showed no potential benefits for M2, ACA and PCA occlusions, overall randomized data remain limited. Future trials should stratify their patient population by occlusion site.