Collateral status evaluation coupled with time window by dynamic axial computed tomographic angiography with a focus on the middle cerebral artery for mechanical thrombectomy.

BACKGROUND Dynamic axial computed tomographic angiography (dynax-CTA), covering a thin width, with a focus on the bilateral middle cerebral artery (MCA), can quickly visualize the internal carotid artery (ICA) or MCA occlusion. We aimed to investigate whether dynax-CTA appropriately evaluated the collateral status coupled with the upper limit of the onset-to-reperfusion (OtR) time to achieve a major neurological improvement (MNI) at a 24-h follow-up examination after mechanical thrombectomy (MT). METHODS We included acute ischemic stroke patients admitted from 2018 to 2020 who underwent dynax-CTA on admission and emergent MT for ICA or MCA occlusion. We performed dynax-CTA using an 80-row CT scanner and acquired 25 volume scans, consisting of 40 images of 1-mm thickness and 4-cm width. We classified the collateral status as good, intermediate, and poor based on MCA branch opacification. We evaluated the collateral status and the upper OtR time limit to achieve MNI. RESULTS Forty-eight patients met our inclusion criteria. Dynax-CTA findings demonstrated MCA and ICA occlusion in 30 and 18 patients, respectively. The collateral status was good, intermediate, and poor in four, 25, and 19 patients, respectively. The upper limits of the OtR time for MNI were 3.63, 8.08, and 8.67 h in patients with poor, intermediate, and intermediate or good collateral status, respectively. CONCLUSIONS Dynax-CTA appropriately evaluated the collateral status coupled with the upper limit of the OtR time before performing MT.