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Research Papers

Hemodynamics of the Mouse Abdominal Aortic Aneurysm

[+] Author and Article Information
Matthew D. Ford1

Department of Mechanical and Materials Engineering,  Queen’s University, Kingston, ON, K7L 3N6, Canadamatthew.david.ford@gmail.comDepartment of Biomedical and Molecular Sciences,  Queen’s University, Kingston, ON, K7L 3N6, Canadamatthew.david.ford@gmail.comDepartment of Mechanical and Materials Engineering,  Queen’s University, Kingston, ON, K7L 3N6, Canadamatthew.david.ford@gmail.com

Ariel T. Black, Richard Y. Cao, Colin D. Funk, Ugo Piomelli

Department of Mechanical and Materials Engineering,  Queen’s University, Kingston, ON, K7L 3N6, CanadaDepartment of Biomedical and Molecular Sciences,  Queen’s University, Kingston, ON, K7L 3N6, CanadaDepartment of Mechanical and Materials Engineering,  Queen’s University, Kingston, ON, K7L 3N6, Canada

1

Corresponding author.

J Biomech Eng 133(12), 121008 (Dec 23, 2011) (9 pages) doi:10.1115/1.4005477 History: Received May 02, 2011; Revised November 17, 2011; Published December 23, 2011; Online December 23, 2011

The abdominal aortic aneurysm (AAA) is a significant cause of death and disability in the Western world and is the subject of many clinical and pathological studies. One of the most commonly used surrogates of the human AAA is the angiotensin II (Ang II) induced model used in mice. Despite the widespread use of this model, there is a lack of knowledge concerning its hemodynamics; this study was motivated by the desire to understand the fluid dynamic environment of the mouse AAA. Numerical simulations were performed using three subject-specific mouse models in flow conditions typical of the mouse. The numerical results from one model showed a shed vortex that correlated with measurements observed in vivo by Doppler ultrasound. The other models had smaller aneurysmal volumes and did not show vortex shedding, although a recirculation zone was formed in the aneurysm, in which a vortex could be observed, that elongated and remained attached to the wall throughout the systolic portion of the cardiac cycle. To link the hemodynamics with aneurysm progression, the remodeling that occurred between week one and week two of the Ang II infusion was quantified and compared with the hemodynamic wall parameters. The strongest correlation was found between the remodeled distance and the oscillatory shear index, which had a correlation coefficient greater than 0.7 for all three models. These results demonstrate that the hemodynamics of the mouse AAA are driven by a strong shear layer, which causes the formation of a recirculation zone in the aneurysm cavity during the systolic portion of the cardiac waveform. The recirculation zone results in areas of quiescent flow, which are correlated with the locations of the aneurysm remodeling.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

(A) DUS image overlaid with both the inner and outer contours of the vessel. The darker area corresponds to the lumen, the gray area to the remodelled tissue. (B) Same contours after low-pass filtering.

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Figure 2

Left column: reconstructed inner (opaque) and outer (transparent) contour surfaces for the three mouse models. Right column: longitudinal images from day 7 with the edges of the reconstructed surfaces overlaid in white.

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Figure 3

Left-hand column: contours of the magnitude of the vorticity on the nominal center-plane of mouse model A. The streamlines overlaid on the contours indicate the position of the vortex. Right-hand column: corresponding DUS-EKV images (the DUS-EKV images were registered to the numerical data by choosing the frame of vortex formation as the initial registration time). The dots indicate the approximate center of the vortex in the DUS-EKV images.

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Figure 4

Left-hand column: contours of the magnitude of the vorticity on the nominal center-plane of mouse model B. The streamlines overlaid on the contours indicate the position of the vortex. Central column: same quantities for mouse model C. Right-hand column: Contours of vorticity magnitude and streamlines for mouse model C in a plane perpendicular to the previous one.

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Figure 5

Streamwise vorticity in planes perpendicular to the flow direction

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Figure 6

Velocity magnitude contours. The light-gray color highlights regions where the velocity is less than 10% of the peak mean velocity in the parent vessel.

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Figure 7

Contours of the magnitude of the normalized instantaneous wall shear stress, |τw|

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Figure 8

From top to bottom, contours of: distance from the inner to outer surface (mapped to the outer surface); oscillatory shear index (OSI); 〈|τw|〉; relative residence time (RRT); |τw,max|. The correlation coefficient between that parameter and the remodeling distance is also shown.

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Figure 9

Contours of the integrand of Eq. 7 for 〈|τw|〉, OSI and RRT versus remodelled distance, respectively

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