Abstract Number ‐ 248: Association Between Vertebrobasilar Stenosis, Location, and Quantitative Magnetic Resonance Angiography Flow State

Introduction The relationship between the degree of vertebrobasilar stenosis and QMRA distal‐flow status is uncertain. Our aim was to investigate this relationship. Methods We retrospectively reviewed patients who presented with acute ischemic stroke, had neurovascular imaging demonstrating ≥ 50% stenosis of extracranial or intracranial vertebral or basilar arteries, and QMRA within one year of stroke, between 2009 and 2021 at two institutions. The WASID and CAVATAS methods were used to measure the degree of intracranial and extracranial vertebrobasilar stenosis, respectively. Patients were grouped as: high‐grade (≥ 70% stenosis) in (1) one vertebral artery; (2) two vertebral arteries; or (3) basilar artery; and (4) moderate grade (≤70% stenosis) in either intracranial vertebral and basilar arteries or exclusive extracranial vertebral stenosis or occlusion. QMRA distal‐flow status was used to dichotomize patients into low‐flow and normal‐flow states based on VERiTAS criteria. P‐values were calculated using chi‐squared analysis and Fisher exact test with statistical significance defined as p < 0.05. Results Of the 303 patients undergoing QMRA for vertebrobasilar disease, 69 met study inclusion, consisting of 31 patients with low‐flow and 38 patients with normal‐flow states. High‐grade stenosis was most commonly found in one vertebral artery (34.8%), followed by both vertebral arteries (29.0%), and the basilar artery (27.5%), and moderate stenosis or exclusive extracranial disease made up 21.7% of patients. High‐grade stenosis in at least one vertebral or basilar artery was significantly associated with low‐flow states compared to patients with moderate‐grade stenosis or exclusive extracranial disease (53.7% versus 13.3%, p = 0.007). High‐grade stenosis in both vertebral arteries was significantly more likely to result in a low‐flow state compared to high‐grade stenosis in one vertebral artery (75.0% versus 41.7%, p = 0.001) or to high‐grade stenosis in the basilar artery (75.0% versus 42.1%, p = 0.040). Conclusions Low distal flow status on QMRA is strongly associated with high‐grade intracranial stenosis compared to moderate‐grade or exclusive extracranial stenosis and is nearly twice as frequent with high‐grade intracranial stenosis of both vertebral arteries compared to one. The location, degree of stenosis, and distal‐flow status should be considered as possible entry points for future prospective treatment trials in intracranial atherosclerotic disease.