The document discusses different types of mechanical heart valves that have been developed over time to replace dysfunctional natural heart valves. It describes early valve designs like the ball-and-cage Starr-Edwards valve and the tilting disc Bjork-Shiley valve. More modern bileaflet valves are also discussed. The key materials used in heart valves include metals for strength as well as pyrolytic carbon and polymers which are durable and promote blood compatibility. Researchers continue working to improve valve lifespan, reduce risk of blood clots, and develop less invasive implantation methods.

1. BT5011 : Biomaterials Engineering
MECHANICAL HEART VALVES
By
Yanamala Vijay Raj
Praveen Krishna V.
1

2. Heart/Heart Valves
A heart valve normally
allows blood to flow in only one
direction through the heart. The
four valves commonly represented
in a mammalian heart determine
the pathway of blood flow through
the heart. A heart valve opens or
closes incumbent upon
differential blood pressure on each
side
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2

3. When Heart Valves Stop Working
ARTIFICIAL VALVES:
An artificial heart valve is
a device implanted in the
heart of a patient with
valvular heart disease.
When one of the four
heart valves malfunctions,
the medical choice may
be to replace the natural
valve with an artificial
valve. This requires open-
heart surgery.
Need and function-when does natural valve
need be replaced
 Heart Valve diseases fall into two categories:
 Stenosis- hardening of the valve and
incompetence- permittance 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
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4. 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
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
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5. •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.
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 strut-and-leaflet valves and the
modern bileaflet valves, to human and animal tissue
So, To Summarize
•1952 – Dr. Charles Hufnagel
designed and implanted a mechanical
heart valve into a thirty year old
female.
•1960 – The Starr-Edwards ball valve
was created. It was based off of Dr.
Charles Hufnagel’s design.
•1969- The Bjork-Shiley valve started
being used and it was based on a
tilting disc design.
•1979 – Bileaflet valves start being
used and up to this day, their designs
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6. Types of valves - advantages and disadvantages
•Mechanical- There are three types. The caged ball, tilting disk, and
bileaflet. Lasts for over 20 years
•Tissue(biological)- valves that are used from animals to implant them
back into humans. Typically lasts between 10-15 years
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7. Characteristics of ideal heart valve
“Nine Commandments”:
oEmbolism Prevention
oDurability
oEase and Security of Attachment
oPreservation of Surrounding Tissue Function
oReduction of Turbulence
oReduction of Blood Trauma
oReduction of Noise
oUse of Materials Compatible with Blood
oDevelopment of Methods of Storage and Sterilization
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8.  Unidirectional flow
 Durable : 40million cycles/year
 Blood compatible: no thrombus, embolus
 Central flow: Laminar not turbulent
 Closing not damaging blood cells
 Last but not the least important – It should be quiet
“An ideal Prosthetic valve”
8

9. Starr-Edwards Ball-in-Cage Valve
The ball valve was the first mechanical heart
valve used and designed by Charles Hufnagel.
The Starr-Edwards ball valve was first used
clinically as a mitral valve replacement in
1960.
After the Starr-Edwards valve was established,
several other design variations were created
such as Magovern–Cromie, DeBakey–
Surgitool, and Smeloff–Cutter ball valves.
 Ball valves operate on the simple principle that
the ball will be forced to one side of the valve or
the other depending on which way blood is
flowing.
 They were modeled after ball valves used in
industrial applications to allow the flow of fluids
on only one direction.
 When the pressure exerted by the heart onto the
blood (and the ball) exceeds the pressure in the
aorta, the ball is pushed away from the heart.
 This is the open position of the valve and blood
can flow out of the heart into the aorta. After the
heart ejects blood, the pressure inside the heart is
greatly reduced so blood will try to flow back
inside the heart.
 The negative pressure sucks the ball valve
backwards. It fits over the opening of the heart
and prevents backflow of blood
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9

10. Björk–Shiley valve
Construction
• The Björk–Shiley valve consists of
a single carbon-coated disc in a
metal housing.
• The disc is held in place by two
metal struts, an inflow and an
outflow strut.
• The housing is made from the
alloy Haynes 25, which is
composed of 51% cobalt,
20% chromium, 15% tungsten,
and 10% nickel.
• The Björk–Shiley valve was
considered very durable and was
widely used in the 1970
The Björk–Shiley valve is a mechanical
prosthetic heart valve. The valve was co-
invented by American engineer Donald
Shiley and Swedish heart surgeon Viking
Björk.
Beginning in 1971, it has been used to
replace aortic valves and mitral valves. It was
the first successful tilting-disc valve
Tilting disc valves can open at an angle of
60° and at a rate of 70 beats per minute.
The angular opening of this valve reduces
damage to blood cells.
These are major improvements over the ball
design but the struts of the tilting disc valves
tend to fatigue and fracture over long
periods of time.
The convexo concave shape of disc was
replaced by flat discs starting 1986
following lawsuits due to failure of 619
valves out of 80,000 implanted.
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10

11. Medtronic-Hall Valve Tilting Disk
The Medtronic-Hall valve was developed to improve on existing tilting disc valves by
reducing the risk of valvular thrombosis.
This was to be accomplished by improving the hemodynamics and by allowing the
disc to move
downstream away from the orifice during opening.
The valve was also designed for maximal structural durability to minimize the risk of
mechanical breakage.
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12.  Two semicircular leaflets that rotate about struts attached to the valve housing
 Good hemodynamic performance - improved flow characteristics, lower
transvalvular pressure gradients, less blood flow turbulence, improved
hemodynamics at a given annular diameter, a larger orifice area and low bulk
and flat profile
 the least thrombogenic of the artificial valves
 most commonly implanted mechanical valve
Bileaflet valves
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14. Hemodynamics of blood flow
However, in spite of improved design and hemodynamics – still haunted by numerous
complications and the most dreaded one of valve thrombosis
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15. Biomaterials used
•Many different materials are used in the creation of artificial heart valves.
• Metal alloys consisting of stainless steel or titanium are often used to give mechanical
strength and for their corrosion resistance properties.
• The struts on some leaflet valves and the cage on caged-ball models are commonly made
of metal alloys due to their strength and durability requirements
Pyrolytic carbon is another valuable material for its strength and its ability to prevent clotting.
This material has a similar structure to graphite and was originally developed for
applications in the nuclear fuel industry as a coating for nuclear fuel particles. However, it was
soon realized that pyrolytic carbon had biomedical applications.
 It is biocompatible, thromboresistant, resistant to wear, and has high strength and durability.
It is able to stand up to the repeated opening and closing cycles it must endure when used in
mechanical heart valve.
 It is commonly used for the inner orifice and the leaflets of bileaflet valves. The ATS Bi-leaflet
valve shown here has leaflets made of pyrolytic carbon 15

16. oA material often used for the suture ring (which is used to attach the valve to the body) is
Dacron.
o Dacron is a long chain polyester made from ethylene glycol and terephthalic acid. It is a
synthetic fiber that has many uses in industry, including thermal insulation and sails for
boats.
o In biomedical applications this material is also commonly used for vascular grafts. It is
relatively inert and its porosity allows tissue in growth.
oAnother material that is commonly used for the suture ring is Teflon
oTeflon is used in many medical applications because of its signature low coefficient of
friction
o Teflon is relatively inert and highly biocompatible. As with Dacron it is often used for
vascular grafts. 16

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18. 18
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19. Failure modes in mechanical valve
Problems that interfere with the successful performance of valves can be grouped as
below.
•Degradation of valve components
•Structural failure
•Clinical complications associated with the valve.
Clinically, valve failure has been considered to be present if any of the following
events require reoperation and/or cause death:
•Anticoagulant-related hemorrhage (ACH),
•Prosthetic valve occlusion (thrombosis or tissue growth),
•Thromboembolism
•Prosthetic valve endocarditis (PVE),
•Hemodynamic prosthetic dysfunction, including structural failure of prosthetic
components (strut failure, poppet escape, ball variance),
•Reoperation (valve replacement) for any other reason (e.g.; hemolysis, noise,
incidental) etc
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20. Evaluation of Prosthetic Valves
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Patient’s height, weight, and BSA should be recorded to assess whether
prosthesis-patient mismatch (PPM) is present.
Valves should be imaged from multiple views, with attention to:
Opening & closing motion of the moving parts (leaflets for bioprosthesis and occluders for
mechanical ones)
Presence of leaflet calcification or abnormal echo density attached to the sewing ring,
occluder, leaflets, stents, or cage
Appearance of the sewing ring, including careful inspection for regions of separation from
native annulus & for abnormal rocking motion during the cardiac cycle
Echo Imaging of Prosthetic Valves
 Regurgitation occurs at the disc margins
 The regurgitant jets converge toward the center of the valve
PARAMENTERS
CLINICAL INFORMATION Date of valve replacement
Type and size of the prosthetic valve
Height, weight and body surface area
Symptoms and related clinical findings
BP and Heart Rate
IMAGING OF THE VALVES Motion of leaflets or occluder
Presence of calcification on the leaflets or
abnormal densities on the various
components of the prosthesis
Valve sewing ring integrity and motion
PARAMENTERS
DOPPLER ECHOCARDIOGRAPHY OF
THE VALVE
Contour of jet velocity signal
Peak velocity and gradient
Mean pressure gradient
VTI of the jet
DVI
Pressure half time in MV and TV
EOA
Presence, location and severity of
regurgitation

21. Caged-Ball Valve

22. Single-Leaflet Valve

23. Bileaflet Valve

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Improvements that researchers will attempt to make in the future include:
•Longer lifespan of the heart valves.
•Lower rejection rate.
•Less risk of blood clots in mechanical heart valves.
•Remove the need for blood thinning medication.
•Implant the artificial heart valves through a less intrusive method (currently open-
heart surgery).
•Polymeric Heart Valves - Scientists are looking more into polymer materials for heart
valves because it’s easy to fabricate, has a large range of polymer properties, and
durability.
•Tissue engineered heart valves- Obtaining the number of types of cells for tissue
valves, lack of scaffold material

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