Hemodynamic and Geometrical Parameters Associated with Carotid Artery Stenosis: A Cross-Sectional Study Using 4D Flow...

Carotid geometry and local hemodynamics are closely associated with atherosclerosis, yet how anatomy and disturbed flow jointly mark disease presence and relate to pro-atherogenic flow in still-non-stenosed bifurcations remains unresolved. This study quantifies the cross-sectional association between three-dimensional carotid bifurcation geometry and pro-atherogenic flow and identifies anatomical biomarkers for non-invasive risk stratification.

Geometric analyses included 346 carotid bifurcations, comprising 240 stenosed and 106 non-stenosed bifurcations. Patient-specific CFD was performed in 176 bifurcations: 101 stenosed and 75 non-stenosed. Eight geometric descriptors, including a new offset flow divider capturing bifurcation apex asymmetry, and four ICA bulb hemodynamic indices (TAWSS, OSI, RRT, BFI) were extracted; logistic and linear regression assessed the association of geometry with (i) stenosis presence and (ii) pro-atherogenic flow.

Bifurcation angle, ICA angle, tortuosity, and offset flow divider were significantly elevated in stenosed bifurcations (all $p<0.001$ ); a four-feature geometric model showed moderate discrimination between stenosed and non-stenosed bifurcations (cross-validated $\text{AUROC}=0.767$ ). The post-stenotic expansion ratio was more strongly associated with local flow disturbance than the degree of luminal narrowing. In non-stenosed bifurcations, multivariable geometric models explained 49 to $60\%$ of the variance in the flow-normalized low-TAWSS, elevated-OSI, and elevated-RRT outcomes, with bulb area and area ratio providing the largest independent contributions, indicating that geometric variation is strongly associated with candidate pro-atherogenic flow patterns even in the absence of detectable luminal narrowing.

Carotid geometry carries two complementary signals: markers of disease presence (bifurcation angle, ICA angle) and candidate anatomical substrates of pro-atherogenic flow in still-non-stenosed bifurcations (bulb area, area ratio). Together with the post-stenotic expansion ratio, these geometric features define a compact, image-derivable set of candidate biomarkers for future early carotid risk stratification.