Upstream high wall shear stress associated with artery-to-artery embolism and recurrent stroke in symptomatic intracranial atherosclerotic stenosis

Background and Aims: To investigate associations of local wall shear stress (WSS) with artery-to-artery embolism (AAE) and risk of stroke recurrence, in symptomatic intracranial atherosclerotic stenosis (sICAS).

Methods: Patients with 50-99% sICAS in M1 middle cerebral artery in CTA were included in this cohort study. AAE as a baseline stroke mechanism was determined by MRI infarct patterns. Computed fluid dynamics models were built based on CTA; relative WSS (rWSS) at any locus across the sICAS lesion was quantified, as relative to mean WSS at proximally normal vessel segment. For each sICAS lesion, high WSS score (HWSSs) was calculated as the mean rWSS multiplied by the proportional area in the high WSS regions (rWSS>3.0) across the lesion. HWSSs were also calculated in the upstream and downstream segments of the plaque divided at the stenotic throat. HWSSs ≥4th quartile was considered as high HWSSs. We associated HWSSs with AAE at baseline and the primary outcome (same-territory ischemic stroke within 1 year).

Results: Among 102 sICAS patients, 46 had AAE. Upstream high HWSSs (OR=5.133, 95% CI 1.334-19.751; p=0.017) was independently associated with AAE at baseline in multivariate logistic regression, and associated with higher risk of primary outcome in log-rank test (26.7% versus 5.36%; HR= 6.01, 95% CI, 1.06-34.07; p=0.043). Such association was not found with HWSSs across the entire plaque or in the downstream segment.

Conclusions: Upstream high HWSSs, i.e., higher WSS and/or larger area with high WSS in the upstream segment of sICAS plaque, was associated with increased risks of AAE and recurrent, same-territory stroke.