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Lower Limb Exercise and Abdominal Aortic Hemodynamics

Lower Limb Exercise and Abdominal Aortic Hemodynamics. Christopher P. Cheng, Ph.D. Glagov Symposium February 20 th , 2003. Introduction: Disease Localization. Supraceliac. Infrarenal. Spiral CT. Introduction: Hemodynamics. Good.

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Lower Limb Exercise and Abdominal Aortic Hemodynamics

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  1. Lower Limb Exercise and Abdominal Aortic Hemodynamics Christopher P. Cheng, Ph.D. Glagov Symposium February 20th, 2003

  2. Introduction: Disease Localization Supraceliac Infrarenal Spiral CT

  3. Introduction: Hemodynamics Good Must quantify hemodynamics to understand disease processes High, steady shear Bad Low, oscillating shear (Cybulsky and Gimbrone 1991, Nobutaka et al. 1996, Sessa et al. 1994, Zarins et al. 1983)

  4. Introduction: Exercise • Systemic  Exercise capacity, HDL • Body fat, blood pressure, LDL • Heart disease and other • Local •  Blood flow • Aortic and lower extremity vascular disease Exercise is the most effective treatment for arterial insufficiency in the lower extremities * Hinder, halt, regress atherosclerosis (Weitz et al.1996)

  5. 1.5T Conventional Magnet 0.5T Open Magnet (Designed and constructed by Doug Schwandt, Eric Topp, James Anderson, ME282 group) Methods:Exercise MRI

  6. Methods:Data Acquisition • 2 hours fasting • Rest acquisition • Exercise = 150% RestHR • Respiratory comp. • Cardiac gating • Surface coil

  7. Methods: Image Data Rest Exercise Supraceliac Infrarenal

  8. Methods: Flow and Wall Shear Stress

  9. Methods: Flow and Shear Oscillations (Taylor et al. 2002) (He and Ku 1996)

  10. Results: Outline • Healthy subjects aged 20 to 30 (11 subjects) • Healthy subjects aged 50 to 70 (8 subjects)

  11. Supraceliac Infrarenal Results: Young Normals Rest Exercise

  12. A A B C B C 120 Velocity (cm/s) 120 Velocity (cm/s) 0 0 -40 -40 -40 120 120 Velocity (cm/s) Velocity (cm/s) 0 0 -40 -40 A A A A B B B B C C C C Results: Young Normals Rest Exercise Supraceliac Infrarenal

  13. Results: Young Normals Mean Blood Flow Flow Oscillations * ** Supraceliac * ** * ** * ** Infrarenal * ** * ** * p<0.05 Supraceliac/Infrarenal ** p<0.05 Rest/Exercise

  14. Results: Young Normals Wall Shear Stress Supraceliac Infrarenal

  15. Results: Young Normals Mean Wall Shear Stress Shear Oscillations * ** * ** Supraceliac * ** * ** * ** Infrarenal * ** ** * p<0.05 Supraceliac/Infrarenal ** p<0.05 Rest/Exercise

  16. Results: Young Normals Summary • Significant increases in flow and wall shear stress as a result of light exercise • More dramatic increases at infrarenal level • Oscillations present at the infrarenal level at rest eliminated with exercise

  17. Results: Young vs. Older Normals • With advancing age • Incidence and severity of atherosclerosis increases • Reduced nitric oxide release • Elastin degrades • Collagen/Elastin ratio increases • Aorta dilates and stiffens Groups anthropometrically similar Same % heart rate increase

  18. Results: Young vs. Older Normals Young Older

  19. Results: Young vs. Older Normals Mean Blood Flow Flow Oscillations Supraceliac Infrarenal * p<0.05 between Young and Older

  20. Results: Young vs. Older Normals Mean Wall Shear Stress Shear Oscillations * * Supraceliac * * * * * * Infrarenal * p<0.05 between Young and Older

  21. Results: Young vs. Older Normals Summary • Older subjects experience lower wall shear stress at the supraceliac level at rest • Older subjects experience greater oscillations in wall shear stress at supraceliac and infrarenal locations at rest • Older subjects may achieve greater benefit from exercise

  22. Future Directions • Vascular Biology • Exercise Blood Flow Simulations • Applications to Congenital Heart Disease • Pre- and Post-operative Studies

  23. Whitaker Foundation Acknowledgments MR-Cycle Team Doug Schwandt Eric Topp Jim Anderson ME282 Charles Taylor and Cardiovascular Biomechanics Laboratory Experimental Subjects & Patients Palo Alto VA Ronald Dalman Sheila Coogan Shawna Thunen Phyllis Mcgrath Surgery Residents Radiology Claudia Cooper Robert Herfkens Norbert Pelc

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