Heart Disease

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Heart Disease

• Number one cause of death in Canada, U.S. and
  most of rest of world
• 1993 - heart failure was the principle or
  contributing cause of 261 819 deaths in the U.S.
• 4.8 million Americans have chronic heart failure
  and are alive today
• About 400 000 new cases of CHF each year
• Sudden death occurs at a rate 6-9 times that of
  the general population

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Total Artificial Heart

• 700 000 people die each year from heart disease
• 2000 donor hearts available
• For every three patients who can bridge to
  transplant using LVADs, one has a heart that is
  so badly damaged that a bi-ventricular device
  (TAH) is needed

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History

• 1969 - Liotta TAH - bridge to transplantation
  patient survived 64 hours, 32 hours following
  transplant
• 1981 Akustu TAH 9 days as bridge, death 9 days
  following transplantation
• 1985 Phoenix TAH - 12 hours - patient died
  following transplant
• Jarvik 7 1982 -
• Barney Clark - 112 days
• Michael Drummond 7 days prior to transplant

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Cross sectional view of a Jarvik series total
artificial heart
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Jarvik 7
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• Pneumatic drive system
• Each ventricle
• Two mechanical disc valves to control blood
  inflow and outflow
• Flexing diaphragm made up of two to four layers
  of elastomer membrane
• Pneumatic system uses compressed air
• Pressure modulated so that over the course of the
  cycle, air pressure applied decreases
• Pressure falls below that of atria, valves open

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• Problems with diaphragm
• Creases and pinhole leaks at edges where it is
  attached to the wall
• Bubbles in the diaphragm material
• Problems with valve holding rings
• Polycarbonate which cracked

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Cardiowest System

• New version of Jarvik 7
• Ventricles made of biomer (PU)
• Valves - pyrolitic carbon disks, titanium rings
  and struts
• Pneumatically driven
• 9 L/minute, maximum stroke volume of 70 mL

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Cardiowest Total Artificial Heart
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Photograph of the Cardiowest total artificial
heart
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The Milwaukee Heart Project

• Constructed of polyurethane
• Graft attachment of Dacron polyester
• Motor / power source electrically powered
  throughout the skin
• Continuous motion, unidirectional, brushless DC
  motor
• No pneumatic tubes or wires penetrating the skin
• Pumps 4-10 L of blood per minute
• Mobility to patient

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• Power pack belt may be removed for up to 30
  minutes
• Device lined with thin yet durable plastic blood
  sac
• Sac may be lined with single layer of recipients
  endothelial cells before implantation

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• Engineering - 22 of annual budget
• Motors
• Materials for cell attachment (tissue
  engineering)
• Physiology - 22 of annual budget
• Animal studies
• Cardiomyoplasty - 14 of annual budget
• Alternative power sources
• Hemostasis - 10 of annual budget
• Clotting studies
• Cell Biology - 32 of annual budget
• Vascular endothelial cells

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Worldheart (Ottawa ON)

• Totally implantable
• Can be remotely powered, monitored and controlled
  (TET)
• Adaptable to being either a left, right or
  biventricular device

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• Size and anatomical fit
• Based on fluid mechanics research
• Remote power transfer
• No perforation of the skin
• Remote Monitoring
• Total implantability
• Blood clotting
• Flow optimized
• Proprietary coating technology
• Quality of life
• Cost

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Transcutaneous Energy Transfer System (TET)
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The Future

• Living Implants from Engineering
• Tissue engineering techniques to grow an
  artificial heart
• Heart suitable for transplantation within 10
  years (from 1998)

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• But
• Remains largely unfunded
• Heart is extremely complex
• Focus has shifted somewhat to developing
  component parts
• Patches of cardiac muscle
• Valves
• Coronary blood vessels
• BEAT (Bioengineered Autologous Tissue) create
  patches of cardiac muscle

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• Cardiac muscle cells tend not to divide so
  necessary to use alternative cell sources
• Stem cells have significant potential
• Materials degradable polymers or natural
  materials?
• Growth of three dimensional structures
• Human heart is typically 2 cm thick
• Growth normally limited beyond thickness of 100
  mm
• Mass transfer problem

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• Create layers of cells (not use 3D scaffolds)
• Perfusion of nutrients in a similar manner to
  blood vessels

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• See Nature 421 884 (2003)