Abstract WP257: Dynamic changes in collateral status during transfer for thrombectomy are predictive of outcome in large vessel occlusion stroke

Background and Aim: Collateral circulation that determines the pace of infarct progression in large vessel occlusion (LVO) is implicitly regarded as stationary. Whether changes in collateral status occur during a stroke event and influence outcomes remains unknown. We assessed changes in collateral circulation during transfer for thrombectomy and their effect on functional outcome in anterior LVO strokes. Methods: We analyzed 70 consecutive middle cerebral artery occlusion stroke patients transferred from nine primary stroke centres to our centre for thrombectomy between January 2017 and December 2018, who underwent repeated CTA upon arrival enabling longitudinal assessment of vessel and collateral status. Patient demographics, initial NIHSS, use of intravenous thrombolysis, blood pressure before thrombectomy, stroke-to-reperfusion time, recanalization status (TICI) after thrombectomy, and 90-day functional outcome (mRS) were collected. Collateral circulation (Tan score, collateral percentage) was analyzed using artificial intelligence-assisted imaging software. Ordinal logistic regression was used to identify predictors of functional outcome. Results: Collateral status was dynamic rather than stationary, generally worsening during transfer (M = -6.7%, SD = 27.64%). Collateral change emerged as a significant independent predictor of 90-day functional outcome (OR = 0.98, p = 0.008), with patients showing improvement in collaterals having better outcomes. Additionally, older age (OR = 1.04, p = 0.030), higher baseline NIHSS (OR = 1.20, p = 0.001), and longer stroke-to-reperfusion time (OR = 1.01, p = 0.014) were each significantly associated with worse 90-day functional outcomes. Collateral change remained significantly associated with 90-day functional outcomes (OR 0.97, p = 0.004) after adjusting for blood pressure. Patients with improved/stable collaterals had significantly better 90-day functional outcomes compared to decliners (median mRS 2 [IQR 0–4] vs. 4 [1.25–6], p = 0.008). Conclusion: Collateral status is not stationary during a stroke event and its improvement independently predicts good functional outcome highlighting the importance of therapeutic efforts to improve collateral circulation in LVO strokes.