Personnel: Prof. Ugo Piomelli, Dr. Matthew Ford, Prof. Colin Funk (Dept. of Physiology, Queen's University)
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 the 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 (geometries where constructed from 3D ultrasound data) in flow conditions typical of the mouse. The numerical results from one model showed a shed vortex which 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 still 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 remodelling that occurred between week one and week two, of the Ang II infusion, was measured and compared with hemodynamic wall parameters. The strongest correlation was found between the remodelled distance and the Oscillatory Shear Index, which had a correlation coefficient of 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 remodelling.
Streamwise vorticity in planes perpendicular to the flow direction at peak flow rate in three mouse models. |
R. Y. Cao, T. St. Amand, M. D. Ford, U. Piomelli, and C. D. Funk, The murine angiotensin II-induced abdominal aortic aneurysm model: rupture risk and inflammatory progression patterns, Frontiers in Pharmacology, 1 (2010), pp. 1–7.
