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Prosthetic Heart Valves
Presentation by Brian
Meyer
Topics to Be Discussed:
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Introduction: How the Heart/Heart Valves
Work
Brief History of Artificial Heart Valves
Types of Artificial Valves
(Examples,Materials Used)
In-Depth Look Bjork-Shiley Valves (Why
Failed? And Lessons to be learned)
Heart/Heart Valves
Heart consists of:
Right Atrium and Ventricle
Atrium
Left Atrium and Ventricle
Two Types of Valves:
Atrioventricular Valve:
separates the atrium from
the ventricle
Semi-Lunar Valve: separates
the ventricles from the
outgoing blood vessels
Heart/Heart Valves
Right Atrioventricular Valve:
Tricuspid Valve
Left Atrioventricular Valve:
Bicuspid Valve
Right Semi-Lunar Valve:
Pulmonary Valve
Left Semi-Lunar Valve:
Aortic Valve
Purpose of Valves: Prevent
backflow, or flow of blood back
into chamber from which it
came
Heart/Heart Valves
When Ventricle expands:
atrioventricular valve allows blood
to flow forward to the atrium into
the ventricle while the semilunar
valve prevents blood from flowing
back in heart
When Ventricle contracts:
atrioventricular valve closes to
prevent backflow while semilunar
valve allows blood to body or lungs
Prevention of backflow: ensures the
proper direction of flow and
reduces amount of work heart must
do to pump blood
When Heart Valves Stop Working
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Heart Valve diseases fall into two categories:
stenosis- hardening of the valve
incompetence- permittence of backflow
3 causes of Heart Disease:
Rheumatic Fever: stiffens valve tissue, causing stenosis
Congenitally defective valves: do not form properly as the heart
develops, but often go unnoticed until childhood
Bacterial infection: causes inflammation of valves, tissue
scarring, and permanent degradation
Evolution of Prosthetic Heart Valves
The development of the
original ball-and-cage valve
design can be attributed to
the bottle stopper in 1858
In the early 1950’s, it led to
the idea of a prosthetic
heart valve consisting of a
cage with a mobile spherical
poppet
Evolution of Prosthetic Heart Valves
This first heart valve was
made of a Plexiglass(methyl
methacylate)cage
surrounding a siliconecoated nylon poppet
First implanted in a human in a
closed procedure in
September of 1952
(descending thoracic aorta)
Evolution of Prosthetic Heart Valve
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Significant advances were made soon after to help
the development of the heart valve:
In 1953, marked successful use of the heart and
lung machine, paving the way for the 1st open heart
operations
The idea of using blood from another patient to
oxygenate the blood of the patient was developed
New methods were came for evacuating air from
the heart
New materials (Plexiglass, Teflon, and Dacron)
Evolution of the Prosthetic Heart Valve
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On July 22, 1955, at the City General Hospital in
Sheffield, England, Judson Chesterman implanted
the first successful heart valve
The patient lived 14 hours after the valve was
placed, but died when the poppet twisted out of
position
Valve was made of Perspex, an outer cage, a poppet,
and 2 buttons to fasten the valve to the outside of
the heart
Evolution of the Prosthetic Heart Valve
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Starr-Edwards valve was
first successful long-term
valve created
It was implanted in its first
8 patients in 1961 (6 of 8
survived
Ball-and-Cage design
Devised important “Nine
Commandments” in
developing a prosthetic
heart valve
Evolution of Prosthetic Heart Valves
“Nine Commandments”:
Embolism Prevention
Durability
Ease and Security of Attachment
Preservation of Surrounding Tissue Function
Reduction of Turbulance
Reduction of Blood Trauma
Reduction of Noise
Use of Materials Compatible with Blood
Development of Methods of Storage and Sterilization
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Evolution of the Prosthetic Heart Valve
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Since this time, over 30
mechanical heart designs
have been marketed in the
U.S. and abroad
These valves have
progressed from the simple
caged ball valves, to strutand-leaflet valves and the
modern bileaflet valves, to
human and animal tissue
Artificial Heart Valve Types
Mechanical Valves:
Ball Valves
This design uses a spherical occluder, or blocking
device, held in place by a welded metal cage
Problem and Why failed: Natural heart valves allow
blood to flow straight through the center of the
valve (central flow)
Caged-ball valves completely blocked central flow and
collisions with the occluder ball caused damage to
blood cells
Finally, these valves stimulated thrombosis, or
formation of blood clots
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Starr-Edwards Ball Valve
Model: Starr-Edwards
Type: Aortic Caged Ball
Materials: Silicone Rubber ball
with 2% barium sulfate,
cage-Stellite alloy No. 21,
sewing ring- knitted Teflon
and polypropelene cloth
1 of 4 Starr-Edwards models
developed are still used
today, and is the only ball
valve currently used in U.S.
Magovern-Cromie Ball Valve
Model: Magovern-Cromie
valve
Type:Aortic Caged Ball
Materials: Ball-Silicone
rubber with barium,
cage-titanium, sewing
ring-none, Cage open at
top
Smeloff-Suttor Ball Valve
Model: Smeloff-Suttor valve
Type: Aortic, Mitral, Tricuspid
caged ball
Materials: Ball-Silicone rubber,
cage-titanium,
sewing ring-Teflon
Problems: Ball Variance,
swelling of ball from lipid
absorbtion, can cause
sticking of ball in inflow
orifice
Mechanical Valves:
Single Leaflet Disc Valves
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Uses a tilting occluder disk
to better mimic natural flow
patterns through the heart
tilting pattern allow more
central flow while still
preventing backflow
Some damage still occurs to
blood cells
Reduces thrombosis and
infection, but does not
eliminate either problem
Bjork-Shiley Standard Aortic Valve
Model: Bjork-Shiley
Standard
Type: Aortic Tilting Disc
Materials: Disk-Pyrolytic
Carbon, cage-Haynes
25, sewing ring-Teflon
Medtronic-Hall Valve
Model: Medtronic-Hall
A7700 (aortic), M7700
(mitral)
Type: Aortic and Mitral
Tilting Disk
Materials: Cage-titanium,
Disk-Pyrolytic carbon,
sewing ring-knitted
teflon
Other Single Leaflet Disc Valves
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Another similar valve is
the caged disc valve
Examples are StarrEdward Model 6500
and the Kay-Shiley
Model
Mechanical Valves:
Bileaflet Disc Heart Valves
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Consists of two semicircular
leaflets that pivot on hinges
integrated onto the flange
Carbon leaflets and flange
exhibit high strength and
excellent biocompatibility
Provide closest
approximation to central
flow
Allows small amount of
backflow as leaflets cannot
close completely
St. Jude Bileaflet Valve
Model: St. Jude Valve
Standard
Design :Mitral, Aortic,
Tricuspid Bileaflet
Valve
Materials-Cage and diskpyrolytic carbon,
sewing ring-double
velour knitted
polyester
Animal Tissue Valves
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Heterograft or
Xenograft Vavles
Most commonly used
tissues are the porcine
(pig) valve tissue and
Bovine (cow) pericardial
tissue
Porcine (pig) Valves
Two major brands of porcine
available today, Hancock and
Carpentier-Edwards
 Has good durability and and
good hemodynamics
Materials: Porcine valve tissue,
stents made of wire,
Elgiloy(cobalt-nickel alloy),
sewing ring-knitted Teflon
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Pericardial (cow) Valves
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Lasts as long as standard
porcine valves at 10 years
The pericardial valve has
excellent hemodynamics,
even in smaller sizes(19mm
to 21mm)and has gained a
large market share (about
40% of US tissue valves) in
this group of patients
Stentless Porcine Valve
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Stentless valves are made
by removing the entire
aortic root and adjacent
aorta as a block from the
pig
Drawbacks: Valve is more
difficult to to implant and
requires special
measurements for
successful implantation
Homografts(Human to Human)
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Homografts are valves transplanted from
one human to another
After donation, valves are preserved in
liquid nitrogen(cyropreserved) until needed
Since the valve must be thawed overnight,
the patient’s size must be known beforehand
As with heart transplants, homograft
availability is limited by donor availability
Autografts (Ross Procedure)
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Autografts are valves taken from the same patient
in which the valve is implanted
Used for patients with diseased aortic valves
Advantages: patient receives a living valve in the
aortic position
Better durability and hemodynamics
Disadvantages: difficult procedure for the surgeon
and involves considerable skill and time
most common problem is leakage of the valve (aortic
regurgitation)
Animal Tissue Valves vs. Mechanical Valves
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With the animal tissue, patients do not need lifelong
anticoagulant therapy required with mechanical
valves
Animal tissue is also inexpensive and mass-produced
However, animal tissue has uncertain durability (515 years )that will inevitably require a risky reoperation
Mechanical valves can also fail suddenly and
catastrophically
Have serious problem with thromboembolism
Bjork-Shiley Prosthetic Heart Valve
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In 1979, the Bjork-Shiley
valve was modified to open
from 60 to 70 degrees
(Convexo-Concave valve)
82,000 were implanted
between the time of its
invention and its removal
from the market in 1986
Between 1979 and 1990,
600 fractures occurred
with 2 out of 3 fractures
resulting in death
Bjork-Shiley Valve:
Initial Fracture Assessment
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Investigators determined
that the floating disc opens
and slams shut at least 70
times per minute or 40
million times per year,
causing fatigue failure
Although changes were
made, fractures continued
to occur
Finally, in 1984, Shiley
discovered the source,
known as “Bimodal Closure
Phenomenon”
Bjork-Shiley Valve:
Role of the FDA
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In 1979, the Bjork-Shiley valve was approved very
quickly, only six months after Shiley’s first request
The main criticism of the FDA was its delay in
removing the valve from the market despite
knowledge of the outlet struts susceptibility to
fracture
The Bjork-Shiley heart valve failure prompted the
FDA to make substantial changes in its policies
Impact of Bjork-Shiley ConvexoConcavo(BSCC) Heart Valves
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The deaths and sicknesses have greatly
effected Shiley Incorporated, the FDA, and
the medical industry
Overall, Shiley and its associate company,
Pfizer, have faced hundreds of lawsuits and
paid more in legal fees and lobbying costs
than if they had simply replaced the valves
According to the Federal Device
Amendments, the BSCC is a justified killer