Computational fluid dynamics-derived flow helicity and recurrent stroke risk in symptomatic intracranial stenosis

Background Patients with symptomatic intracranial atherosclerotic stenosis (ICAS) remain at risk of recurrent ischemic events despite treatment. Stenosis severity is routinely used for risk assessment, but does not describe the lesion-level flow field. We used computational fluid dynamics (CFD) to assess whether flow helicity within the culprit stenosis was associated with 1-year target-vessel stroke. Methods We studied 204 adults with symptomatic ICAS who underwent CT angiography-based vascular reconstruction and CFD analysis. The prespecified exposure was maximum absolute flow helicity at the narrowest cross-sectional plane of the culprit stenosis, transformed using log(1+x) and standardized per SD. The primary outcome was 1-year target-vessel stroke, and the secondary endpoint was target-territory stroke or vascular death. Multivariable Cox models adjusted for major clinical, anatomical, and hemodynamic covariates were supplemented by Kaplan-Meier, cutpoint, tertile, subgroup, and Winsorization analyses. Results Multivariable analyses included 203 patients. During follow-up, 31 target-vessel strokes and 33 composite events occurred. Each 1 SD increase in log-transformed maximum absolute helicity was associated with target-vessel stroke (HR 1.461, 95% CI 1.049 to 2.035, P=0.0249). The association with the composite endpoint was directionally similar but not significant (HR 1.351, 95% CI 0.973 to 1.875, P=0.0720). Median-split Kaplan-Meier curves separated for both outcomes, and tertile analysis showed higher target-vessel stroke risk in the highest versus lowest tertile (HR 2.951, 95% CI 1.067 to 8.160, P=0.0371). Conclusions In symptomatic ICAS, higher lesion-level maximum absolute helicity was associated with 1-year target-vessel stroke, supporting further evaluation of helicity as a CFD-derived marker of flow disturbance.