B6: Cardiovascular Mechanics II

COMPARISON OF HEMODYNAMICS BETWEEN MIDDLE CEREBRAL ARTERY AND ANTERIOR COMMUNICATING ARTERY ANEURYSMS

Yuji Shimogonya1, Shunichi Fukuda2

1Tohoku University, Japan, Japan; 
2National Hospital Organization Kyoto Medical Center, Japan

Since rupture of cerebral aneurysms is a major cause of life-threatening subarachnoid hemorrhage, it is important to identify aneurysms that are prone to rupture. However, prediction for aneurysm rupture is difficult since only a few pieces of information are known about risk factors of aneurysm enlargement and rupture. Therefore, we expect to identify additional risk factors. One important lead may be a difference in rupture rate among aneurysm location. It has been known that the rupture rate of anterior communicating (Acom) aneurysm is twice higher than that of middle cerebral artery (MCA) aneurysm, suggesting that hemodynamic factors determine the difference. Thus, examination of this difference may serve to clarify hemodynamic risk factors for aneurysm enlargement and rupture. In this study, we compared hemodynamic metrics between MCA and Acom aneurysms with computational fluid dynamics (CFD) analysis to examine their hemodynamic differences, which may be associated with the difference in rupture risk. Patient-specific 3D CT angiographic (CTA) images and flow velocities of 16 MCA and 12 Acom aneurysms were acquired in our multi-institutional prospective clinical trial “Computational Fluid Dynamics Analysis of Blood Flow in Cerebral Aneurysms: Prospective Observational Study (CFD ABO Study)”. Arterial geometries of the patients were reconstructed from the 3D CTA volume data set. Using a CFD software package, pulsatile blood flow was simulated based on the Navier-Stokes equations for incompressible fluid, under the patient-specific flow velocity boundary conditions. In both MCA and Acom aneurysms, timeaveraged wall shear stress (TAWSS) was lower over the entire aneurysm than neighboring arteries, but higher at neck of the aneurysm. Low WSS over cerebral aneurysms has been reported to be closely associated with aneurysm rupture in previous studies. Our results showed that area-averaged TAWSS is significantly lower in Acom aneurysms than MCA aneurysm. This may be associated with higher rupture rate in Acom aneurysms.

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