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Quantification of Hemodynamics in Abdominal Aortic Aneurysms During Rest and Exercise Using Magnetic Resonance Imaging and Computational Fluid Dynamics

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Abstract

Abdominal aortic aneurysms (AAAs) affect 5–7% of older Americans. We hypothesize that exercise may slow AAA growth by decreasing inflammatory burden, peripheral resistance, and adverse hemodynamic conditions such as low, oscillatory shear stress. In this study, we use magnetic resonance imaging and computational fluid dynamics to describe hemodynamics in eight AAAs during rest and exercise using patient-specific geometric models, flow waveforms, and pressures as well as appropriately resolved finite-element meshes. We report mean wall shear stress (MWSS) and oscillatory shear index (OSI) at four aortic locations (supraceliac, infrarenal, mid-aneurysm, and suprabifurcation) and turbulent kinetic energy over the entire computational domain on meshes containing more than an order of magnitude more elements than previously reported results (mean: 9.0-million elements; SD: 2.3 M; range: 5.7–12.0 M). MWSS was lowest in the aneurysm during rest 2.5 dyn/cm2 (SD: 2.1; range: 0.9–6.5), and MWSS increased and OSI decreased at all four locations during exercise. Mild turbulence existed at rest, while moderate aneurysmal turbulence was present during exercise. During both rest and exercise, aortic turbulence was virtually zero superior to the AAA for seven out of eight patients. We postulate that the increased MWSS, decreased OSI, and moderate turbulence present during exercise may attenuate AAA growth.

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Abbreviations

AAA:

Abdominal aortic aneurysm

DBP:

Diastolic blood pressure

IR:

Infrarenal

Mid-An:

Mid-aneurysm

MRI:

Magnetic resonance imaging

MWSS:

Mean wall shear stress

OSI:

Oscillatory shear index

SB:

Suprabifurcation

SBP:

Systolic blood pressure

SC:

Supraceliac

TKE:

Turbulent kinetic energy

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Acknowledgments

The authors would like to thank Victoria Yeh and Allen Chiou for their assistance in constructing the computer models, Mary McElrath and Julie White for their assistance with patient recruitment, and Sandra Rodriguez, Romi Samra, Anne Sawyer, Dr. Janice Yeung, Dr. Geoffrey Schultz, and Dr. Byard Edwards and all staff at the Lucas Center at Stanford University for assistance with imaging. This study was supported by the National Institutes of Health (Grants P50 HL083800, 2RO1 HL064338, P41 RR09784, and U54 GM072970) and the National Science Foundation (0205741, and CNS-0619926 for computer resources).

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Authors and Affiliations

  1. Department of Bioengineering, Stanford University, Stanford, CA, USA

    Andrea S. Les, C. Alberto Figueroa & Charles A. Taylor

  2. Department of Mechanical and Aerospace Engineering, Illinois Institute of Technology, Chicago, IL, USA

    Shawn C. Shadden

  3. Department of Radiology, University of Southern California, Los Angeles, CA, USA

    Jinha M. Park

  4. Division of Vascular Surgery, Stanford University, Stanford, CA, USA

    Maureen M. Tedesco & Ronald L. Dalman

  5. Department of Radiology, Stanford University, Stanford, CA, USA

    Robert J. Herfkens

  6. James H. Clark Center, Room E350B, 318 Campus Drive, Stanford, CA, 94305-5431, USA

    Charles A. Taylor

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  1. Andrea S. Les
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Les, A.S., Shadden, S.C., Figueroa, C.A. et al. Quantification of Hemodynamics in Abdominal Aortic Aneurysms During Rest and Exercise Using Magnetic Resonance Imaging and Computational Fluid Dynamics. Ann Biomed Eng 38, 1288–1313 (2010). https://doi.org/10.1007/s10439-010-9949-x

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