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Utility of FEM and FEA. Evaluate possible designs without manufacturing a prototype Augment experimental capabilities time money. Heart Disease. 4 million patients in the U.S. are victims of heart failure, and nearly 400,000 new cases are diagnosed each year 2,800 receive heart transplants

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Utility of fem and fea l.jpg
Utility of FEM and FEA

  • Evaluate possible designs without manufacturing a prototype

  • Augment experimental capabilities

    • time

    • money


Heart disease l.jpg
Heart Disease

  • 4 million patients in the U.S. are victims of heart failure, and nearly 400,000 new cases are diagnosed each year

  • 2,800 receive heart transplants

  • Heart disease is the leading cause of death and disability in the U.S.


Arrow lionhearttm l.jpg
Arrow LionHeartTM

  • LVAD (Left Ventricular Assist Device)

    • electric pulsatile blood pump

    • fully implanted in upper abdomen

    • 70 cc volume

8 L/min at beat rate of 135 =

stroke volume of 60 cc


Introduction l.jpg
Introduction

Poly(urethaneurea)

Blood Sac

Pusher-

plate

Titanium

Pump Case


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Introduction

  • Design goal: 2 yrs @50,000,000 cycles/yr = 100,000,000 cycles

  • FEA used to evaluate various pump designs and their effectiveness at reducing the material stresses


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Finite Element Model

  • Axisymmetric

  • Pusherplate and pump case treated as rigid

  • 8-node continuum elements

  • Blood sac : homogeneous,

    hyperelastic (non-linear)

  • Frictionless contact


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0.9 in

2.86 in

Finite Element Model


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Boundary Conditions

  • Internal pressure = 100 mm Hg

  • Rigid pump case was fixed in space

  • Pusherplate displaced 0.8 inches

    • 30 increments

    • simulating ejection stroke of pump


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Parametric Study

  • 3 different thickness sacs (0.015, 0.02, 0.025 inches)

  • 2 pump case designs (tapered, not tapered)

  • 2 radii of curvature for sac (3/16 and 7/16 inch)

  • Total of 12 cases


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3/16 inch of stroke

3/8 inch of stroke

end of stroke


Slide11 l.jpg

2

3

4

1


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Conclusions

  • Material stresses and strains are sensitive to the thickness of the blood sac

  • Radius of curvature has little influence on the peak stress in the blood sac, however, it does affect when the peak stress occurs during the stroke cycle


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Conclusions

  • Tapering the pump case can significantly alter blood sac stresses

  • All stresses and strains were much lower than the yield stress and strain for poly (urethaneurea)


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News Release (Feb. 28th, 2001)

  • First fully implantable heart assist device implanted

  • As of March 12th, Arrow LionHeartTM recipient is stable and recovering as expected


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Total Artificial Heart

  • Fit into chest cavity

    • 50 cc

  • Develop a model to predict and minimize stresses in biomaterials, so that the durability of a reduced-size device is not adversely affected by pump scaling


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