Relative Residence Time Prolongation in Intracranial Aneurysms: A Possible Association With Atherosclerosis

BACKGROUND: Intracranial aneurysms can have atherosclerotic wall properties that may be important in predicting aneurysm history or estimating the potential risks of surgical treatments. OBJECTIVE: To investigate hemodynamic characteristics of atherosclerotic lesions in intracranial aneurysms using computational fluid dynamics. METHODS: Intraoperative video recordings of 30 consecutive patients with an unruptured middle cerebral artery aneurysm were examined to identify atherosclerotic lesions on an aneurysm wall. For computational fluid dynamics analyses, geometries of aneurysms and adjacent arteries were reconstructed from 3-dimensional rotational angiography. Transient simulations were conducted under patient-specific pulsatile inlet conditions measured by phase-contrast magnetic resonance velocimetry. Three hemodynamic wall parameters were calculated: time-averaged wall shear stress, oscillatory shear index, and relative residence time (RRT). Statistical analyses were performed to discriminate the risk factors of atherosclerotic lesion formation. RESULTS: Among 30 aneurysms, 7 atherosclerotic lesions with remarkable yellow lipid deposition were identified in 5 aneurysms. All 7 atherosclerotic lesions spatially agreed with the area with prolonged RRT. Univariate analysis revealed that male sex (P = .03), cigarette smoking (P = .047), and maximum RRT (P = .02) are significantly related to atherosclerotic lesion on the intracranial aneurysmal wall. Of those variables that influenced atherosclerotic lesion of the intracranial aneurysmal wall, male sex (P = .005) and maximum RRT (P = .004) remained significant in the multivariate regression model. CONCLUSION: The area with prolonged RRT colocalized with atherosclerotic change on the aneurysm wall. Male sex and maximum RRT were independent risk factors for atherogenesis in intracranial aneurysms.