FYP

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Monash Uni - Final Year Project Presentation

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FYP

  1. 1. FINITE ELEMENT MODELING OF A LEFT VENTRICLE & HEART PATCH Presented by : Han Yee Lee Supervisor: Dr Wenyi Yan
  2. 2. Presentation Outline •Background / Motivation •Objectives •Methodology •Results / Discussion •Conclusion •Future recommendations http://wayoffside.files.wordpress.c om/2007/11/heart.jpg
  3. 3. Background / Motivation The human heart weights around one pound The heart beats approximately 70 times a minute and 100,000 times a day http://www.livescience.com/images/human_heart_graphic_03
  4. 4. • Cardiac Cycle  Cardiac cycle is a sequence of mechanical events of the heart pumping blood through our body  The heart pumps blood to the lungs, back to the heart, out to the body and back to the heart again in about 23 seconds http://www.youtube.com/watch?v=_YuX7CtClyg&feature=related
  5. 5. • Myocardial Infarction Myocardial Infarction is a medical term for a heart attack Myocardial infarction is a death of heart muscle from a sudden blockage of a coronary artery http://www.healthcentral.com/common/images/1/18 048_3691_5.jpg
  6. 6. http://www.asir-journal.com/content/3/1/6/figure/F1?highres=y
  7. 7. • Heart Patch Strategy  Developed during the mid 1990s  Serves two function: -Cell delivery -Left ventricular restraint  Heart Patch could decrease the heart wall stress Chen et al 2008 ‘Characterization of a Soft Elastomer Poly designed to match the mechanical properties of Myocardial Tissue’
  8. 8. http://www.asir-journal.com/content/3/1/6/figure/F1?highres=y
  9. 9. Objectives  The primary objectives of this research are 1) Model a healthy dog’s left ventricle 2) Model an infarct dog’s left ventricle 3) Implement the heart patch strategy onto the infarct left ventricle
  10. 10. Methodology  Continuity 6 is a problem-solving environment for finite element analysis in bioengineering and physiology  Finite 1) 2) 3) 4) element modeling steps: Geometry Boundary Conditions Material properties Solving
  11. 11. • Geometry Healthy Model  Prolate spheroidal coordinates(λ,v,θ)  consists of 210 nodes and 150 elements • Boundary conditions  There are 3 rigid body motions  Ensure all rigid body motions are suppressed http://en.wikipedia.org/wiki/Prolate_spheroidal _coordinates
  12. 12. Infarct Model Infarct Patch Model t = 1.1mm
  13. 13. •Material Properties  Material based on Constitutive Law (Transversely Isotropic & Hyper Elastic Material ) Left Ventricle’s Parameters Healthy Infarct Section Patch Stress Scaling Coefficient (kPa) 0.14638 2.9 0.14638 Fiber Strain Coefficient 67.069 33.17 67.069 Transverse Strain Coefficient 26.571 41.56 26.571 Bulk Modulus 100 100 1000 Fiber_Trans_Shear_coefficient 21.604 21.604 21.604 •Pressure A pressure increment of 1kPa is being applied in the inner surface of the left ventricle
  14. 14. Results & Discussion •Deformed Geometry Internal Pressure = 0 kPa Internal Pressure = 1kPa (7.5mmHg) When the left ventricle contracts (filling state), there is a change in volume from 26ml40ml
  15. 15. •Fiber Stress across the ventricular thickness at the  Healthy Section  Infarct Section  Infarct Patch Section Healthy Section Infarct Section Infarct Patch Section
  16. 16. Healthy versus Infarct versus Infarct Patch section (1kPa Internal Pressure) 8 6.90 Healthy section Fiber Stress (kPa) 7 6 5.98 5 Infarct section 3.81 4 3.90 3 2.47 2 1 0 0.56 Infarct Patch section 0.60 0.58 0.60 0.62 0.64 0.66 0.68 0.70 Longitudinal coordinates •Approximately there is a 76% increase of stress at the infarct section •Approximately there is a 13% decrease of stress at the infarct section when the patch is applied
  17. 17. •Fiber Stress along the ventricular wall  Healthy  Infarct versus Infarct Model Model versus Infarct Patch Model
  18. 18. Healthy Model •Average Fiber Stress = 12.36 kPa Infarct Model •Average Fiber Stress = 13.55 kPa
  19. 19. Infarct Patch Model •Average Fiber Stress = 13.2 kPa Infarct Model •Average Fiber Stress = 13.55 kPa
  20. 20. Conclusion  Fiber stress at the ventricular thickness -Approximately 76% increase of stress (infarct) -Approximately 13% decrease of stress (patch)  Fiber stress along the ventricular wall -An average of 1.2kPa fiber stress increased (infarct) -An average of 0.35kPa fiber stress decreased (patch) The heart patch strategy WORKS!!!
  21. 21. Future Recommendations  Different material properties for the patch  Increase the size of the patch  Results comparison with previous research  Consider the ‘relaxation state’ for the left ventricle
  22. 22. QUESTIONS

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