Effects of arterial geometry on aneurysm growth: three-dimensional computational fluid dynamics study

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Object. Few researchers have quantified the role of arterial geometry in the pathogenesis of saccular cerebral aneurysms. The authors investigated the effects of parent artery geometry on aneurysm hemodynamics and assessed the implications relative to aneurysm growth and treatment effectiveness.

Methods. The hemodynamics of three-dimensional saccular aneurysms arising from the lateral wall of arteries with varying arterial curves (starting with a straight vessel model) and neck sizes were studied using a computational fluid dynamics analysis. The effects of these geometric parameters on hemodynamic parameters, including flow velocity, aneurysm wall shear stress (WSS), and area of elevated WSS during the cardiac cycle (time-dependent impact zone), were quantified. Unlike simulations involving aneurysms located on straight arteries, blood flow inertia (centrifugal effects) rather than viscous diffusion was the predominant force driving blood into aneurysm sacs on curved arteries. As the degree of arterial curvature increased, flow impingement on the distal side of the neck intensified, leading to elevations in the WSS and enlargement of the impact zone at the distal side of the aneurysm neck.

Conclusions. Based on these simulations the authors postulate that lateral saccular aneurysms located on more curved arteries are subjected to higher hemodynamic stresses. Saccular aneurysms with wider necks have larger impact zones. The large impact zone at the distal side of the aneurysm neck correlates well with other findings, implicating this zone as the most likely site of aneurysm growth or regrowth of treated lesions. To protect against high hemodynamic stresses, protection of the distal side of the aneurysm neck from flow impingement is critical.

Article Information

Address reprint requests to: Hui Meng, Ph.D., Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, 324 Jarvis Hall, Buffalo, New York 14620. email: huimeng@buffalo.edu.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Conventional digital subtraction angiograms demonstrating a typical saccular cerebral aneurysm arising from the lateral wall of a curved parent artery (enlarged view on right).

  • View in gallery

    Geometric representation of an aneurysm located on a curved parent artery. Two groups of aneurysm models are represented: R1 through R6 and N1 through N4. In the R models the degree of the parent artery curvature is varied, whereas in the N models the size of the aneurysm orifice is varied. Arrows indicate the direction of blood flow (or of inflow and outflow). D = diameter of the aneurysm; d = internal diameter of the parent artery; N = width (major axis) of the aneurysm neck; 1/R = curvature of the parent artery.

  • View in gallery

    Drawing showing the results of the simulation of blood-particle paths in model R5 at a steady state. Some blood paths never enter the aneurysm, whereas others enter it from the distal side of the neck. Of those paths entering the aneurysm, some leave at the distal side of the neck, whereas others join the inflow and whirl irregularly inside the lesion. The paths flow from left to right (left) and off the paper, toward the reader (right).

  • View in gallery

    Comparative drawings of the velocity field at the symmetry plane in different models at maximum systole. The curvature increases from 0 (straight vessel) in model R1 to 0.167 mm−1 in model R6. As the degree of arterial curvature increases, the flow impingement on the distal side of the aneurysm neck intensifies.

  • View in gallery

    Photographs and drawings showing the WSS distribution at the distal side of the neck in models R4, R5, R6, N2, N3, and N4 at maximum systole during the pulsatile flow simulations. The figures shown here are viewed from the Y direction (see lower diagram), looking at the distal side of the aneurysm dome and neck.

  • View in gallery

    Graph demonstrating that the impact zone at peak systole is a function of aneurysm neck size (N) and curvature (1/R). A larger aneurysm neck size on a more curved artery may promote artery remodeling and an increased likelihood of aneurysm growth.

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    Graph showing that with increasing curvature of the vessel, the impact zone size increases almost linearly. Higher degrees of arterial curvature or higher rates of flow may induce more active arterial remodeling and promote aneurysm growth.

  • View in gallery

    Graph demonstrating that the size of the impact zone at the distal neck varied dynamically during a cardiac cycle. This variation is more pronounced with increasing arterial curvature in models R2, R4, and R6. The smaller graph (inset) shows the velocity profile over a cardiac cycle in a pulsatile flow simulation.

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