Annals of Biomedical Engineering

, Volume 39, Issue 8, pp 2186–2202 | Cite as

Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics

  • Ga-Young Suh
  • Andrea S. Les
  • Adam S. Tenforde
  • Shawn C. Shadden
  • Ryan L. Spilker
  • Janice J. Yeung
  • Christopher P. Cheng
  • Robert J. Herfkens
  • Ronald L. Dalman
  • Charles A. Taylor


Abdominal aortic aneurysm (AAA) is a vascular disease resulting in a permanent, localized enlargement of the abdominal aorta. We previously hypothesized that the progression of AAA may be slowed by altering the hemodynamics in the abdominal aorta through exercise [Dalman, R. L., M. M. Tedesco, J. Myers, and C. A. Taylor. Ann. N.Y. Acad. Sci. 1085:92–109, 2006]. To quantify the effect of exercise intensity on hemodynamic conditions in 10 AAA subjects at rest and during mild and moderate intensities of lower-limb exercise (defined as 33 ± 10% and 63 ± 18% increase above resting heart rate, respectively), we used magnetic resonance imaging and computational fluid dynamics techniques. Subject-specific models were constructed from magnetic resonance angiography data and physiologic boundary conditions were derived from measurements made during dynamic exercise. We measured the abdominal aortic blood flow at rest and during exercise, and quantified mean wall shear stress (MWSS), oscillatory shear index (OSI), and particle residence time (PRT). We observed that an increase in the level of activity correlated with an increase of MWSS and a decrease of OSI at three locations in the abdominal aorta, and these changes were most significant below the renal arteries. As the level of activity increased, PRT in the aneurysm was significantly decreased: 50% of particles were cleared out of AAAs within 1.36 ± 0.43, 0.34 ± 0.10, and 0.22 ± 0.06 s at rest, mild exercise, and moderate exercise levels, respectively. Most of the reduction of PRT occurred from rest to the mild exercise level, suggesting that mild exercise may be sufficient to reduce flow stasis in AAAs.


Cycling exercise Phase-contrast magnetic resonance imaging Mean wall shear stress Oscillatory shear index Particle residence time Particle clearance 



Abdominal aortic aneurysm


Computational fluid dynamics


Diastolic blood pressure






Magnetic resonance imaging


Mean wall shear stress


Oscillatory shear index


Particle residence index


Particle residence time


Resistance (proximal)–capacitance–resistance (distal)




Systolic blood pressure


Splanchnic and renal blood flows



This research was supported by the National Institutes of Health (P50 HL083800, P41 RR09784), the Lucas Center for Magnetic Resonance Imaging, and the Veterans Affairs Palo Alto Health Care System (VAPAHCS) for the acquisition of experimental data, and NSF (CNS-0619926) for computer resources. Allen Chiou, Victoria Yeh, Yash Narang, and Bartlomiej R. Imielski provided assistance with imaging and modeling. Nan Xiao provided help with quantification of PRT data. We thank all research subjects for their participation.


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Copyright information

© Biomedical Engineering Society 2011

Authors and Affiliations

  • Ga-Young Suh
    • 1
  • Andrea S. Les
    • 2
  • Adam S. Tenforde
    • 3
  • Shawn C. Shadden
    • 4
  • Ryan L. Spilker
    • 5
  • Janice J. Yeung
    • 6
  • Christopher P. Cheng
    • 6
  • Robert J. Herfkens
    • 5
  • Ronald L. Dalman
    • 6
  • Charles A. Taylor
    • 2
    • 7
  1. 1.Department of Mechanical EngineeringStanford UniversityStanfordUSA
  2. 2.Department of BioengineeringStanford UniversityStanfordUSA
  3. 3.Department of Orthopedics, Division of Physical Medicine and RehabilitationStanford UniversityStanfordUSA
  4. 4.Department of Mechanical and Aerospace EngineeringIllinois Institute of TechnologyChicagoUSA
  5. 5.Department of RadiologyStanford UniversityStanfordUSA
  6. 6.Division of Vascular SurgeryStanford UniversityStanfordUSA
  7. 7.James H. Clark CenterStanfordUSA

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