ABSTRACT NUMBER: ESOC2026A2470 ASSOCIATION BETWEEN EARLY VENOUS FILLING AFTER MECHANICAL THROMBECTOMY AND HEMORRHAGIC TRANSFORMATION IN POSTERIOR CIRCULATION ISCHEMIC STROKE

Abstract Background and aims Early venous filling (EVF) is described as an early opacification of a cerebral vein during the arterial phase of angiography. Several studies have demonstrated its prognostic value after successful mechanical thrombectomy (MT) in anterior circulation stroke, namely as a risk factor for hemorrhagic transformation (HT), which may help inform acute-phase management. The aim of this study was to evaluate the association between EVF and post-thrombectomy HT in posterior circulation acute ischemic stroke (AIS). Methods We conducted a retrospective observational study including patients with vertebrobasilar AIS who underwent mechanical thrombectomy between 2020 and 2024. Demographic, clinical, and imaging variables were extracted from medical records, and all angiographic runs were reviewed to determine the presence of EVF. Results A total of 144 patients with posterior circulation AIS and successful post-thrombectomy recanalization (mTICI ≥ 2b) were included; 37 (25.7%) developed HT (ECASS-II). Ten patients presented EVF (inter-observer agreement: 0.81). Among these 10 EVF-positive patients, 7 developed HT during hospitalisation (70%). In multivariable logistic regression adjusting for hypertension and baseline NIHSS, EVF remained independently associated with hemorrhagic transformation (aOR 4.95, 95% CI 1.01–24.39). There were no significant differences in 90-day functional outcome or mortality. Conclusions These findings suggest that EVF may serve as a novel angiographic marker of hemorrhagic risk in the vertebrobasilar circulation stroke treated with MT. Larger, ideally prospective, cohorts are needed to validate this association and better define its prognostic value. Conflict of interest Nothing to disclose