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VALVE PROSTHESIS


PROSTHESES PARAMETERS
MECHANICAL PROSTHESeS
BIOLOGICAL PROSTHESeS
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MECHANICAL PROSTHESIS

  • In use since 1960s
  • Divided into caged-ball, disc (monodisc) and bileaflet valves
Caged-Ball Valves
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Caged-ball valve Starr–Edwards (aortic model 1260)

Caged-Ball Valves
Starr-Edwards valve
  • Best known valve
  • The most often implanted valve in the world in 1960s-1970s
  • Mitral and aortic models are still being implanted at some countries
  • Closing component: Silastic ball held within a stellite alloy care (open position) which obstructs the metallic ring in closed position which is covered with a Teflon (Dupont, Wilmington, Del) fabric sewing ring for implantation.
Caged-ball valve Smelo
Caged-ball valve Smelo–Cutter

Caged-Ball Valves
Smeloff–Cutter valve
  • Introduced to practice in 1964
  • Has not been used since 1988
  • The silastic ball does not sit at the titanium alloy ring but is stopped by a second smaller cage.
  • The three struts of the upper and the lower cage are not connected
Disadvantage:
  • Frequent thromboembolic complications
  • Efforts to reduce this has led to development of the cloth-covered caged-ball valves
  • Best valves were the  Braunwald–Cutter valve and Cloth-covered Starr–Edwards valve
  • Struts and the ring were covered with polypropylene into which endothelium grew within several weeks or months after implantation
  • Thereby, except for the ball, blood did not contact a foreign surface
  • Limited reduction in the incidence of thromboembolic events and haemolysis was achieved but remained limited to the first months or few years after implantation.
  • Tearing of the cloth covering occurred as a result of hardness and disparity between the ball and the endothelialized covering
  • This initiated thrombus formation with subsequent thromboembolic events
  • Also caused clinically significant haemolysis
  • All prompted reoperation and valve reimplantation
Picture
Cloth-covered Starr–Edwards valve
Picture
Braunwald–Cutter valve




​Caged-Ball Valves

Cloth-covered Starr–Edwards valve
  • Edwards valve, manufactured between 1967 and 1976
  • The valve was explanted due to tearing of the cloth 22 years after implantation
Caged-Ball Valves
Cloth-covered Braunwald–Cutter valve 
  • Implanted between 1968-1979.

Disc Valves
Can be divided into Non-tilting and Tilting Disc valves

Non-Tilting Disc Valves 
  • Non-tilting disc valves were introduced into clinical practice in the late 1960s into clinical practice. 
  • The closing component was a poppet that was held in a cage (open position) or obturated the ring (closed position)
  • Best known valves:
               1. Beall valve    2. Starr-Edwards    3. Kay–Shiley   4. Kay–Suzuki   5.Cooley–Cutter   6. Cross–Jones
Picture
Non-tilting disc valves

Non-tilting disc valves
a) Beall






b) Starr–Edwards
Advantage:
  • Low profile design
  • Easier implantation
  • Very little opening resistance 
  • Very short closure delay (hence very little regurgitation)

Disadvantage:
  • Higher flow resistance
  • Significant turbulence 
  • Frequent thromboembolic complications
  • Higher haemolysis rate
Due to these drawbacks, the non-tilting disc valves fell into disuse and were replaced by modern tilting disc valves
Tilting Disc Valves 

  • Were the most-often implanted valves in the 1970s and 1980s.
  • Precise knowledge of the tilting angle in monodisc and bileaflet valves is important for eventual diagnostics of the valve failure. 
  • Discs are radio-opaque and therefore fluoroscopy imaging can confirm their normal mobility or diagnose restricted range of motion, or even complete occluder blockade.
Picture
Disc valve Björk–Shiley
Disc valve Björk–Shiley
Standard type with at disc:
  • The most commonly used valves In Europe .
  • The First Model had a delrin disc, tilted up to 60°.
  • Soon replaced by a the standard type with pyrolytic carbon at disc tilting up to 60°.
Convex–concave type:
  • Introduced in 1976.
  • Has a significantly improved haemodynamics.
  • Discontinued in the late 1980s because the  inflow bar broke in some after 2–3 years of perfect performance, causing escape of the disc and acute valve regurgitation (can be lethal).
  • Since then, the struts in all heart valves are not welded but manufactured from a single block of metal or alloy or from pyrolytic carbon.
Monostrut:
  • The latest Model.
  • Introduced into clinical practice in 1982.
  • The disc-housing system was changed and the angle of tilting was increased  to 70°.
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Disc valve Omniscience

Disc valve Omniscience
  • Manufactured since 1978 
  • Modified in 1984 under the name Omnicarbon
  • The disc opens up to 80° and closes at 12°, achieving the tilting range of 68°
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Disc valve Allcarbon–Sorin

Disc valve Allcarbon–Sorin
  • In use since 1989
  • The pyrolytic carbon disc tilts up to 60°
  • All metallic components and sewing ring, are carbon-film coated for better biocompatibility
  • Older designs: Sorin–Monocast and  Carbocast
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Disc valve Medtronic–Hall

Medtronic–Hall (originally Hall–Kaster)
  • The most frequently implanted disc valve worldwide
  • In clinical use without modication since 1977 
  • The housing is made from titanium and the pyrolytic carbon disc opens up to 75° (aortic valve) and 70° (mitral valve) 
The Ultracor–Aortech valves (developed in 1985), the tilting angle of which is 73° in the aortic model and 68°  in the mitral model, have also been implanted.

Bileaflet Valves
Gained popularity since the mid-1980s
Currently are the most frequently implanted valves in the world
Different types but all based on the same or similar principle but differ in:
  1. Angle of tilting.
  2. Design of the pivots.
  3. Material and shape of the sewing ring.
  4. Depth of the leaflets in their open position.
Picture
Bileaflet valve St. Jude Medical
St Jude Medical (SJM) valve:
  • Best-known and most implanted mechanical bileaflet valve.
  • In clinical practice in 1977 (SJM Standard).
  • Semilunar leaflets open up to 85° and close at 30°, yielding a tilting range of 55°.
  • SJM  HP (hemodynamic plus, since 1992) and SJM  Regent (since 1998) with a reduced sewing ring, which results in significant enlargement of the effective  orifice area (EOA) (avoiding patient-prosthesis mismatch - PPM)
  • EOA for Size 21-mm SJM is:
                      Standard SJM model(EOA) = 1.51cm2, 
                      SJM HP EOA = 2.03cm2,
                      SJM Regent EOA = , 2.47cm2 Nonetheless, even a “small-size” SJM 
  • SJM Regent 19-mm valve has an EOA of 1.84cm2 which is sufficient to prevent PPM in a patient with a body-surface area of 2cm2.
Picture
Bileaflet valve Sorin–Bicarbon Slimline
Bileaflet Bicarbon–Sorin 
  • Second most commonly implanted bileaflet valve.
  • Manufactured since 1990.
  • Semilunar leaflets are convex–concave shaped and tilt up to 80° and close at 20° .
  • Sewing rings  Fitline or  Slimline (suitable for small annuli).
  • Overline (intended solely for supra-annular implantation).
  •  The same mechanism, but a different sewing cuff material, is typical for the  Edwards MIRA valve (since 1997).
CarboMedics Valves 
  • In clinical use since 1986.
  • Semilunar leaflets tilt up to 78° and close at 25°, which gives a tilting range of 53°.
Picture
Carbomedics Standard Mitral Valve
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Picture


CARBOMEDICS OPTIFORM:
Adaptable for:
  • Heavily calcified annulus
  • Mitral redo surgery
  • Double valve replacement
  • Endocarditis

​

CARBOMEDICS R (Reduced) 
  • Has been in clinical use since 1986
  • In 1991 the type CarboMedics R (with a significantly reduced sewing ring) in response to the problem of a small aortic annulus 
Picture

Carbomedics Top Hat
  • Designed for totally supra-annular implantation (both the housing and sewing ring are placed supra-annulary)
Picture

CarboMedics Orbis: 
  • Universal Aortic and Mitral Valve: Enabling implantation of the same valve either to the aortic or mitral position

Picture
ATS Medical:
  • In clinical use since 1992
  • Standard Type and AP type (advanced Performance) for small Annuli
  • Medtronic Advantage has, since 2003, A modification for supra-annular implantation named Medtronic Advantage Supra. 
  • The most recent bileaflet valve introduced into clinical practice is the valve CardiaMed.

oN X VALVE

On-X Life Technologies, Austin, TX​
  • Bileaflet valve
  • Constructed completely from pyrolytic carbon.
  • Lack of silicon doping in the carbon construction potentially decreases its thrombogenicity.
  • Has a tall flared inlet that increases the orifice area and decreases the ability of retained valve tissue to interfere with the opening and closing mechanisms.
  • Has a stasis free pivot that allow the valve to wash out itself.
  • Has a 90-degree leaflet opening which provides improved laminar flow and reduce turbulence.
  • Available is three different sewing rings:
    • Standard: 
      • Aortic: sizes from 19 to 27/29 mm
      • Mitral: sizes from 23 to 31/33 mm.
    • Conform X:  has a more flexible sewing ring.
      • Aortic: sizes from 19 to 27/29 mm.
      • Mitral: only one size that fits an annular size ranging from 25 to 33 mm.
    • Anatomic:
      • Designed to for the contours of the aortic valve annulus.
      • ​Sizes from 19 to 27/29 mm.
  • PROACT Trial ( Prospective Randomised On-X Anticoagulation Clinical Trial)
    • Compared low dose Warfarin plus low dose aspirin (81mg)  to standard warfarin.
    • The first showed a significantly lower major and minor bleeding rates.
    • The incidence of stroke, TIA, total neurologic events and all cause mortality were similar
Picture
ON X Standard Mitral
Picture
Ascending Aortic Prosthesis - CryoLife, Inc.

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