Utility of FEM and FEA n Evaluate possible designs without manufacturing a prototype n Augment experimental capabilities –time –money

Heart Disease n 4 million patients in the U.S. are victims of heart failure, and nearly 400,000 new cases are diagnosed each year n 2,800 receive heart transplants n Heart disease is the leading cause of death and disability in the U.S.

Arrow LionHeartTM n 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 Titanium Pump Case Pusher- plate Poly(urethaneurea) Blood Sac

Introduction n Design goal: 2 cycles/yr = 100,000,000 cycles n FEA used to evaluate various pump designs and their effectiveness at reducing the material stresses

Finite Element Model n Axisymmetric n Pusherplate and pump case treated as rigid n 8-node continuum elements n Blood sac : homogeneous, hyperelastic (non-linear) n Frictionless contact

2.86 in 0.9 in Finite Element Model

Boundary Conditions n Internal pressure = 100 mm Hg n Rigid pump case was fixed in space n Pusherplate displaced 0.8 inches –30 increments –simulating ejection stroke of pump

Parametric Study n 3 different thickness sacs ( 0.015, 0.02, inches ) n 2 pump case designs (tapered, not tapered) n 2 radii of curvature for sac (3/16 and 7/16 inch) n Total of 12 cases

3/16 inch of stroke 3/8 inch of stroke end of stroke

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

Conclusions n Tapering the pump case can significantly alter blood sac stresses n All stresses and strains were much lower than the yield stress and strain for poly (urethaneurea)

News Release (Feb. 28th, 2001) n First fully implantable heart assist device implanted n As of March 12 th, Arrow LionHeartTM recipient is stable and recovering as expected

Total Artificial Heart n Fit into chest cavity –50 cc n 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