The role of first pass effect in mechanical thrombectomy for vertebrobasilar artery occlusion: a comprehensive meta-analysis of prevalence, outcomes, and predictive factors

Background First-pass effect (FPE) is crucial for better outcomes in mechanical thrombectomy (MT) for acute large vessel occlusions. However, its frequency and predictors in vertebrobasilar artery occlusion (VBAO) remain unclear.Objective To conduct a comprehensive systematic review and meta-analysis to assess the incidence of FPE in MT for VBAO and its impact on key clinical outcomes. Additionally, to explore potential predictors of achieving FPE, addressing critical knowledge gaps and providing evidence to optimize treatment strategies for patients with VBAO.Methods A systematic literature search was performed in PubMed, EMBASE, Web of Science, and the Cochrane Library up to November 1, 2024. Studies evaluating FPE in patients with acute VBAO undergoing MT were included. The prevalence of FPE was estimated using a meta-analysis of proportions, and associations with clinical outcomes and predictive factors were assessed using pooled ORs with random-effects models.Results Twenty studies involving 4315 patients met inclusion criteria. The overall prevalence of FPE in patients with VBAO was 41% (95% CI 33% to 50%). FPE was significantly associated with improved 90-day outcomes (modified Rankin Scale (mRS) score 0-2: OR=2.00, 95% CI 1.45 to 2.75; mRS score 0-3: OR=2.33, 95% CI 1.78 to 3.04), reduced risk of symptomatic intracranial hemorrhage (OR=0.49, 95% CI 0.27 to 0.87), and lower mortality (OR=0.43, 95% CI 0.32 to 0.57). The results showed that significant positive predictors of FPE included female sex, atrial fibrillation, cardioembolic or unknown stroke etiology, mid- or distal basilar artery occlusion, contact aspiration techniques, and the use of larger catheters. Conversely, negative predictors were identified as a history of hypertension, hyperlipidemia, prior stroke or transient ischemic attack, higher baseline NIHSS scores, prolonged procedure time, and the use of general anesthesia.Conclusion Achieving FPE in acute VBAO is strongly associated with improved clinical outcomes. Important clinical, procedural, and anatomical factors related to FPE were identified, aiding clinical decisions and thrombectomy techniques.