The Artificial Heart: A Design Example

1
The Artificial HeartA Design Example

• BIOE 1000
• October 18, 2001

2
The Human Heart

• Heart has four chambers
• Right chambers pump blood to lungs to receive
  oxygen
• Left chambers pump oxygenated blood from lungs to
  rest of the body

3
The Human Heart

• Right and left atria receive blood
• Right and left ventricles pump blood
• Valves produce one-way blood flow from atria ?
  ventricles ? arteries
• Energy to pump blood comes from nutrients and
  oxygen in blood
• The blood supply to the heart is provided by
  coronary arteries

4
Heart Disease

• Heart attack blockage of coronary artery
  damages portion of heart muscle
• Congestive heart failure gradual weakening of
  heart
• Millions suffer from heart disease
• Many cases are treatable with lifestyle changes,
  drugs and/or surgery
• Surviving patients suffering from most severe
  cases need new hearts!

5
The Need for a Heart Substitute

• 100,000 Americans/year suffering from severe
  heart disease need new hearts
• Only 2,000 patients receive heart transplants
• Conclusion many patients die waiting for a new
  heart!
• A suitable alternative to donor hearts could
  prolong thousands of lives

6
History of Heart Substitutes

• WWII first open heart surgeries
• 1953 heart-lung machine successfully used
  during heart surgery
• 1958 Drs. Willem Kolff and Tetsuzo Akutsu
  sustain a dog for 90 minutes with a PVC
  artificial heart
• 1967 Dr. Christian Barnard transplants a donor
  heart into a 59 year old man (he survived 18 days)

PVC heart (1958)
silicone heart (1965)
7
History of Heart Substitutes

• 1969 Dr. Denton Cooley uses an artificial heart
  to sustain a patient waiting for a donor
  (survived 3 days)
• 1972 Cyclosporine introduced to suppress immune
  responses of transplant recipients
• 1982 Dr. William DeVries implants the Jarvik-7
  artificial heart into Dr. Barney Clark (he
  survived 112 days)

Liotta heart (1969)
Jarvik-7 (1982)
8
Why Heart Substitutes Fail

• Immune response rejects transplant or side
  effects due to immune suppression
• Infection due to tubes and wires passing through
  skin
• Formation of clots
• Damage to red blood cells
• Lack of pulsatile blood flow?

9
Design Process

• Identify the problem or need to address
• Specify details/criteria of an adequate solution
  to your problem
• Implement various solutions that meet the
  criteria you specified
• Test to determine which solution is most viable
• Further testing to refine the solution you chose

10
Design Refinement

• Process is iterative
• You need to repeat various steps after testing
• Make design changes based on test results
• Failed designs
• Design didnt meet criteria
• Could be due to inappropriate criteria

11
Criteria for a Heart Substitute

• Must fit into chest cavity and connect to atria,
  pulmonary artery and aorta quickly
• Provide an adequate blood flow (8 10
  liters/min)
• Send deoxygenated blood to the lungs and
  oxygenated blood to the body
• Operate continuously for an indefinite period of
  time
• Provide adequate warning if something is wrong or
  if it is going to fail

12
Criteria for a Heart Substitute

• Should increase/decrease blood flow based on
  patient activity level
• Should not evoke an immune response
• No wires or tubes that penetrate the skin
• Should not produce blood clots
• Should not damage red blood cells
• Ideally should have pulsatile blood flow
• Many others we havent thought of!

13
The AbioCor Heart

• Implanted into 59 year old Robert Tools on July
  2, 2001 at Jewish Hospital in Louisville KY (96
  days)
• Patient is able to walk around, organs are
  functioning normally, undergoing daily
  rehabilitation for eventual release

14
How the AbioCor Heart Works

• Hydraulic pump forces blood to lungs and body
• Power is provided by an internal rechargeable
  battery
• Battery is recharged by coils on surface and
  below skin
• Internal controller monitors system and controls
  pump speed

15
Surgical Procedure

• Implant controller, battery and coil
• Connect patient to heart-lung machine
• Cut away ventricles
• Sew grafts onto atria and arteries
• Connect implants to grafts
• Remove patient from heart-lung machine

16
AbioCor Design Criteria

• Grapefruit size, weighs 2 lbs, requires a 7 hour
  surgery for implantation
• Can provide up to 8 liters/min of blood to the
  lungs and body
• Has two chambers for pumping deoxygenated blood
  to the lungs and oxygenated blood to the body
• Wireless energy transfer system allows for
  continuous operation
• Internal controller monitors operation

17
AbioCor Design Criteria

• Internal controller increases/decreases blood
  flow based on blood oxygen levels
• Materials are inert to the immune system
• Completely contained within the chest no wires
  or tubing through skin!
• Made of special materials and special pump design
  to prevent clots and RBC damage
• Pumping alternates between chambers, creating a
  pulsatile blood flow