Abstract 2947: Differentiating Antegrade Flow Across Intravascular Thrombus from Retrograde Collateral Flow in Occluded Cerebral Arteries: Initial Experience Using Time-Resolved CT Angiography

Abstract

Introduction: In acute stroke patients with occluded cerebral arteries, angiographic demonstration of antegrade opacification distal to an occlusion has been associated with higher rates of vessel recanalization. We sought to determine whether antegrade flow can be demonstrated on near-whole-brain time-resolved four-dimensional CT angiography (4D-CTA) and whether it can be differentiated from retrograde collateral flow. Methods: Among 123 consecutive patients with angiographically proven acute intracranial anterior circulation vessel occlusion, thin-section 4D-CTA data obtained as part of a diagnostic multi-modal CT exam were available in 48 cases, 47 of which met inclusion criteria. Pre-treatment thrombolysis in cerebral infarction (TICI) grade, presence of the outline sign (defined as antegrade contrast opacification distal to the thrombus) and presence of retrograde collateral flow extending to the distal thrombus end were assessed on 4D-CTA. Digital subtraction angiograms were reviewed for pre-treatment TICI grade, presence of the outline sign as well as post-intervention TICI grade. Results: On 4D-CTA, evidence of antegrade flow was present in 5 of 47 cases (10.6%). Compared to angiography, 4D-CTA correctly classified antegrade flow in 4 cases (80.0%), there was 1 false positive and no false negatives. Recanalization (TICI ≥2a) was achieved in all 5 cases with evidence of antegrade flow on 4D-CTA versus 34 out of the 42 cases (81.0%) without evidence of antegrade flow. Conclusion: Using 4D-CTA, it is possible to differentiate antegrade flow across a cerebral artery occlusion from retrograde collateral flow. Further studies, preferably with a larger sample size are needed to confirm our findings and assess whether 4D-CTA can be used to predict success of recanalization procedures in select cases.