Atherosclerotic middle cerebral artery stenosis: adjacent arterial geometry, hemodynamics and plaque features

Adjacent vessel geometry may affect focal hemodynamics and plaque features in intracranial atherosclerotic disease.

To investigate the correlations of upstream (internal carotid artery (ICA) bifurcation) and focal arterial geometry of M1 middle cerebral artery (MCA-M1) with location of MCA-M1 plaques and focal hemodynamics, particularly wall shear stress (WSS) metrics.

In patients with symptomatic atherosclerotic stenosis (50-99%) of MCA-M1, we assessed vessel geometry at ICA bifurcation and MCA-M1, including diameters and diameter ratios of different arterial segments, angles between arteries, and MCA-M1 tortuosity. The MCA-M1 plaque was defined as in proximal or distal halves of MCA-M1. Computational fluid dynamics (CFD) modeling was conducted to simulate adjacent blood flow and quantify relative wall shear stress (relative WSS, rWSS) across the MCA-M1 plaque (as relative to mean WSS at proximal normal segment). We investigated the associations of vessel geometry with the plaque location and rWSS metrics.

Among 132 patients (median age 62 years), smaller diameter of MCA-M1 origin (adjusted odds ratio = 0.19, 95%CI 0.08-0.43, p < 0.001), smaller diameter ratio of MCA-M1 origin and terminal (0.04, 0.01-0.17, p < 0.001), and larger MCA-M1 tortuosity (1.03, 1.00-1.05, p = 0.045) were associated with proximal (versus distal) MCA-M1 plaques, independent of patient characteristics. These geometric parameters were associated with higher rWSS and larger area of high-rWSS region, throughout the MCA-M1 plaque and in upstream and downstream plaque segments, in patients with proximal MCA-M1 plaques (most p < 0.05), but not in those with distal MCA-M1 plaques. CFD models also revealed different velocity profiles and flow patterns in cases with different ICA bifurcation and MCA-M1 geometry.

Adjacent arterial geometry may affect plaque distribution in MCA-M1. Focal hemodynamics e.g., WSS and velocity profiles, may play a role underlying the associations.