Key result
Coil embolization reduces aneurysm flow velocity and wall shear stress, whereas simulated exercise increases both.
Why the study?
Physiological flow characteristics and the effects of exercise and coil embolization on cerebral aneurysm hemodynamics are not fully understood.
Computational modeling demonstrates that exercise increases wall shear stress in cerebral aneurysms, while coil embolization effectively reduces flow velocities and shear stress.
Coil embolization may reduce aneurysm hemodynamics in models; leaves open exercise effects on wall shear stress pending clinical data.
Physiological flow under rest and exercise conditions in patient-specific cerebral aneurysm models is numerically investigated. A finite-volume based code with BiCGStab as the linear equation solver is used to simulate unsteady three-dimensional flow field through the incompressible Navier-Stokes equations. Flow characteristics are first established in a healthy cerebral artery for both physiological conditions. The effect of saccular aneurysm on cerebral hemodynamics is then explored through a comparative analysis of the velocity distribution, nature of flow patterns, wall pressure and wall shear stress (WSS) against the reference configuration. The efficacy of coil embolization as a potential strategy of surgical intervention is also examined by modelling coil as a homogeneous and isotropic porous medium where the extended Darcy's law, including Forchheimer and Brinkman terms, is applicable. The Carreau-Yasuda non-Newtonian blood model is incorporated to capture the shear thinning behavior of blood. Rest and exercise conditions correspond to normotensive and hypertensive blood pressures respectively. The results indicate that the fluid impingement on the outer wall of the arterial bend leads to abnormality in the distribution of wall pressure and WSS, which is expected to be the primary cause of the localized aneurysm. Exercise correlates with elevated flow velocity, vortex strength, wall pressure and WSS inside the aneurysm sac. With the insertion of coils in the aneurysm cavity, the flow bypasses the dilatation, leading to a decline in flow velocities and WSS. Lower particle residence time under exercise conditions arrests atherosclerosis.
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Usmani et al. (2018) studied Cerebral aneurysm. Coil embolization and exercise conditions vs. Reference configuration (uncoiled) and rest conditions was evaluated on Velocity distribution, flow patterns, wall pressure, and wall shear stress (WSS). Coil embolization in cerebral aneurysm models bypassed dilatation, leading to a decline in flow velocities and wall shear stress, while exercise correlated with elevated flow velocity and WSS.
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