Association Between the Degree of Vertebrobasilar Stenosis, Location, Infarction Pattern and QMRA Flow State

Abstract

Background and Purpose: The relationship between the degree and location of vertebrobasilar stenosis and QMRA distal-flow status is uncertain. Our aim was to investigate the relationship between QMRA distal-flow status with degree and location of vertebrobasilar stenosis. <break><break> 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 performed within one year of stroke, between 2009 and 2021. Standardized methods were used to measure the degree of stenosis and to dichotomize vertebrobasilar distal-flow status. Patients were grouped based on the involved artery and the location and severity of disease. P-values were calculated using chi-squared analysis and Fisher exact test with statistical significance defined as p <0.05.<break> <break> Results: Sixty-nine patients met study inclusion, consisting of 31 with low distal-flow and 38 with normal distal-flow states. Low distal-flow states were found exclusively in patients with severe stenosis or occlusion; however, severe stenosis or occlusion was poorly predictive of distal-flow status as nearly half of these patients had normal flow states (47%). Bilateral vertebral disease was significantly associated with low distal-flow states compared to patients with unilateral vertebral (70.8% versus 14.3%; p = 0.01), isolated basilar (70.8% versus 28.6%; p = 0.01), or mixed (71.4% versus 47.1%; p = 0.01) disease.<break> <break> Conclusions: Severe stenosis of 70% may mark the minimal threshold required to cause hemodynamic insufficiency in the posterior circulation, but nearly half of these patients may remain hemodynamically sufficient. The presence of bilateral vertebral stenosis resulted in a five-fold increase in the probability of QMRA low distal-flow status compared to unilateral vertebral disease. Our findings may have implications for the design of future treatment trials of endovascular versus medical management that may use hemodynamic markers as inclusion criteria.