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
Article

Abstract

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.

Keywords

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

Abbreviations

AAA

Abdominal aortic aneurysm

CFD

Computational fluid dynamics

DBP

Diastolic blood pressure

IR

Infrarenal

MA

Mid-aneurysm

MRI

Magnetic resonance imaging

MWSS

Mean wall shear stress

OSI

Oscillatory shear index

PRI

Particle residence index

PRT

Particle residence time

RCR

Resistance (proximal)–capacitance–resistance (distal)

SC

Supraceliac

SBP

Systolic blood pressure

SRBF

Splanchnic and renal blood flows

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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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