VALVE PROSTHESIS

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
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Cloth-covered Starr–Edwards valve
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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
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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.
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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.
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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.
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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°.
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Carbomedics Standard Mitral Valve


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 

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

CarboMedics Orbis: 
  • Universal Aortic and Mitral Valve: Enabling implantation of the same valve either to the aortic or mitral position
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
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ON X Standard Mitral
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Ascending Aortic Prosthesis - CryoLife, Inc.

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