Abstract Number: Esoc2026a2458 Occlusion Site and Treatment Effect in Vertebrobasilar Artery Occlusion: A Pooled Analysis of Randomized Controlled Trials

Abstract Background and aims Vertebrobasilar artery occlusions (VBAO) are anatomically heterogeneous, and the occlusion site may influence both prognosis and response to endovascular therapy (EVT). We evaluated the association between occlusion location and outcomes and assessed whether EVT benefit varies by anatomical site. Methods We performed an individual patient data meta-analysis pooling randomized controlled trial data from BASICS, BEST, ATTENTION, and BAOCHE. Occlusion sites were classified as vertebral artery V4, proximal basilar artery (BA), mid-BA, and distal BA (reference). The primary outcome was a favorable functional outcome (modified Rankin Scale mRS 0–3) at 90 days. Multivariable logistic regression assessed associations between occlusion site and outcomes, with interaction testing between occlusion site and treatment. Results Among 832 patients with documented occlusion sites, 5.5% had V4, 33.8% proximal BA, 31.0% mid-BA, and 29.7% distal BA occlusions. Intracranial atherosclerosis was more frequent in proximal locations (V4: 67.4%; proximal BA: 65.6%) than distal BA (19.0%; P0.001). Favorable outcomes occurred in 41.3% of V4, 32.4% of proximal BA, 34.5% of mid-BA, and 48.2% of distal BA occlusions (P=0.001). Compared with distal BA, proximal BA (adjusted OR aOR 0.46, 95% CI 0.31–0.70) and mid-BA (aOR 0.45, 95% CI 0.30–0.69) were associated with worse outcomes (P0.001). However, a significant interaction between occlusion site and treatment was observed (P=0.004), with greater relative EVT benefit in proximal occlusions (interaction OR 2.77, 95% CI 1.38–5.58). Conclusions Occlusion site strongly influences prognosis in VBAO. Despite worse baseline outcomes, proximal occlusions appear to derive greater relative benefit from EVT compared with distal occlusions. Conflict of interest No relevant disclosures to this work.