the artificial heart: a design example bioe 1000 october 18, 2001
TRANSCRIPT
The Artificial Heart:A Design Example
BIOE 1000
October 18, 2001
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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
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The Human Heart
Right and left atria receive bloodRight and left ventricles pump bloodValves produce one-way blood flow
from atria ventricles arteriesEnergy to pump blood comes from
nutrients and oxygen in bloodThe blood supply to the heart is
provided by coronary arteries
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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!
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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
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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)
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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)
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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 clotsDamage to red blood cellsLack of pulsatile blood flow?
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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
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Design Refinement
Process is iterative– You need to repeat
various steps after testing
– Make design changes based on test results
Failed designs– Design didn’t meet
criteria– Could be due to
inappropriate criteria
Identify Problem
Specify Criteria
Implement Design
Test Design
Refine Design
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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
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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 haven’t thought of!
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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
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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
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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
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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
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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