Abstract T P44: Relative Cerebral Blood Volume as a Marker of Durable Tissue-at-risk Viability in Hyperacute Ischemic Stroke

Background: Selection of best responders to endovascular reperfusion could be aided by predicting the expected duration of tissue-at-risk viability, which may be dependant on collateral circulation status. We aimed to identify the best predictor of good collateral circulation among perfusion computed tomography (PCT) parameters in middle cerebral artery (MCA) ischemic stroke, and to analyze how early MCA response to intravenous thrombolysis and PCT-derived markers of good collaterals interact to determine stroke outcome. Methods: We prospectively studied acute MCA ischemic stroke patients treated with intravenous thrombolysis who underwent PCT prior to treatment showing a target-mismatch profile. Collateral status was assessed using a PCT source-images based score. PCT maps were quantitatively analyzed. Cerebral blood volume (CBV), cerebral blood flow (CBF) and Tmax were calculated within the hypoperfused volume and in the equivalent region of unaffected hemisphere. Occluded MCAs were monitored by transcranial Duplex to assess early recanalization. Main outcome variables were final infarct volume and modified Rankin score at day 90. Results: One hundred MCA ischemic stroke patients imaged by PCT received intravenous thrombolysis, and 68 met all inclusion criteria. A relative CBV > 0.93 emerged as the most robust predictor of good collaterals [OR 12.6 (95% CI 2.9-55.9), p=0.001]. Early MCA recanalization was strongly associated with better long-term outcome and lower infarct volume in patients with rCBV <0.93, but not in patients with high rCBV. None of the patients with rCBV < 0.93 achieved good outcome in absence of early recanalization. Conclusion: rCBV was the strongest marker of collateral status and may help predict the duration of tissue-at-risk viability in hyperacute MCA ischemic stroke