MECHANICAL HEART VALVE SUBSTITUTES

1. HEART VALVE SUBSTITUTES
(Mechanical)

2. DWIGHT EMARY HARKEN-IDEAL
PROSTHETIC HEART VALVE(1950’s)
Dwight Emary Harken (1910–1993)

3. HARKEN’s -TEN COMMANDMENTS
The IDEAL prosthesis MUST
1. technically practical to insert.
2. inserted in a physiological site (generally the normal anatomic site).
3. capable of permanent fixation
4. chemically inert and not damage blood elements.
5. offer no resistance to physiological flows.
Ann Thorac Surg 1989;48:18-19

4. HARKEN’s -TEN COMMANDMENTS
6. close promptly (less than 0.05 second).
7. remain closed during the appropriate phase of the cardiac cycle.
8. not propagate emboli.
9. have lasting physical and geometric features.
10 It must not annoy the patient.
Ann Thorac Surg
1989;48:18-19

5. MECHANICAL VALVE SUBSTITUTES
• BALL AND CAGE VALVES
• NONTILTING DISC PROSTHESES
• TILTING DISC PROSTHESES
• BILEAFLET VALVE

6. PRE CPB ERA

7. EVOLUTION OF PROSTHETIC HEART
VALVES
• 1950’s : Idea of prosthetic
heart valve consisting of cage
with mobile spherical poppet
• Resembled a bottle stopper.

8. IGNITING THE FIRE OF PROSTHETIC
VALVE IMPLANTATION- 1952

9. HUFNAGEL’S BALL AND CAGE DEVICE
• No anticoagulation was used
• Drawbacks:
– Mortality
– cumbersome insertion during brief cross‐clamp period
– Valve noise : hollow nylon ball coated with silicone
rubber
– Poor hemodynamics
– embolization and thrombosis

10. DR. JUDSON CHESTERMAN-1955
• First ball valve implantation in
mitral position
• Cage and poppet device :
Perspex
• Fixed to outside of heart with
two buttons attached to device
• Patient died 14 hours after
surgery

11. ERA OF CARDIOPULMONARY
BYPASS

12. DWIGHT EMARY HARKEN- 1960
• Double cage-ball valve
• Cage : stainless steel
• Lucite ball- changed to silicone-
rubber
• sewing ring Ivalon or Teflon
backing.
• Placed subcoronary location
• Two survivors among first seven
patients

13. STARR-EDWARDS BALL VALVE-1960
• "The need exists and it will eventually be
met. That is the law that all nature
follows.“-Lowell Edward
• Our job is not to design a valve identical
to nature‘s,not to see how close we can
come to duplicating a natural
phenomenon, but to overcome the
clinical problem of the diseased heart
valve. If we can do this with a valve
similar to the natural one-fine. But we
must evaluate on the basis of function
rather than form.—Albert Starr
(Tex Heart Inst J

14. DEVELOPMENT OF STARR-EDWARDS
BALL VALVE
• Bileaflet valve : silicone-
rubber leaflets hinged on a
central crossbar made of
solid Teflon
•Teflon cloth margin for
fixation.
•Thrombus formation
originate at suture line and
grow by direct extension
onto leaflets. (Tex Heart Inst J

15. DEVELOPMENT OF STARR-EDWARDS BALL
VALVE
• Adopted idea of ball and cage
valve from Ellis and Bulbulian
• Cage : Lucite cage
(methacrylate)thick struts
• Ball : compression moulded
Silicone elastomer rubber
• Sewing ring : Knitted teflon
• 1960 in mitral position

16. DEVELOPMENT OF STARR-EDWARDS BALL
VALVE
• First successful human
implantation: Philip
Admunson on September 21,
1960
• He had undergone 2 previous
commissurotomies and was
in NYHA functional class IV
• Admunson survived for 15
years after the implantation

17. DESIGN CHANGES OF STARR
EDWARD PROSTHESIS

18. SE model 6120/1260
• Heat cured ball – disapperance of ball variance
• Thrombo embolic problem: extending cloth of sewing ring
to edge of inflow orifice(decreasing amount of metal
exposed)
• Lowering of cage
• Barium sulfate impregnated silastic ball to make radio-
opaque.
• Teflon and polypropylene sewing ring.

19. DRAWBACK OF STARR-EDWARDS
BALL VALVE
• Ball variance.
– Hollow stellite-21 balls
– Heat cured silicone rubber balls
• High profile
• Difficult implantation in small ventricles and
small aortic root
• Inherently high gradients

20. DRAWBACK OF STARR-EDWARDS BALL
VALVE
• Less favorable thromboembolic profiles
• Wear and tear of cloth
• Edwards Lifesciences (Irvine, CA) discontinued
production of the Starr-Edwards valve in 2007.

21. MAGOVERN-CROMIE BALL VALVE-1962
• Sutureless valve
• Ball-Silicone rubber
with barium
• cage-titanium
• 25-year experi- ence
– 728 patients between
1962 and 1988
– ball variance occurred in
14 patients (2%)

22. SMELOFF (SCDK) -CUTTER BALL VALVE-
1964
• “full-flow” orifice
concept
• Double set of cages
• Ball-Silicone rubber
• cage-titanium
• Sewing ring-Teflon

23. DEBAKEY-SURGITOOL CAGED BALL
VALVE,1967
• hollow pyrolytic carbon
poppet
• first use of new carbon
material developed by Dr
Jack Bokros
• Drawback:
• strut wear and strut
fracture

24. DR JACK BOKROS
• Invented pyrolytic carbon :
Pyrolyte
• Exceptional
biocompatibility (highly
thromboresistant)
• Founded Medical Carbon
Research Institute ,Austin
• silicone-free pyrolytic
carbon: On-X Valve.

25. PYROLYTIC CARBON
• Isotropic form of carbon.
• distorted lattice structure with random unassociated carbon
atoms
• Formed by pyrolysis of hydrocarbon gas creating random
crystallization
• Excellent stability, strength, wear resistance, fatigue resistance
and biocompatibility
• Originally developed for the encapsulation of nuclear fuel rods

26. NINA STARR BRAUNWALD -1960
• Flexible polyurethane-
Dacron fabric mitral
valve prosthesis with
attached Teflon-tape
chordae ten- doneae
• 44 year old female with
mitral regurgitation
Nina Starr
Braunwald (1928–
1992)

27. BRAUNWALD-CUTTER BALL VALVE,1968
• Cloth covered caged ball valve
• Struts : knit Dacron tubing
• Inflow ring : ultrathin polypropylene
mesh fabric
• Drawbacks:
– fabric wear
– silicone poppet abrasion in aortic valves
leading to poppet escape.

30. NONTILTING DISC VALVES
• Closing component was a poppet that was held in a cage
(open position) or obturated the ring (closed position)
• Differed in material of disc, housing, ring and cage
design.
• Advantages:
– low-profile design
– easier implantation
– very little opening resistance
– very short closure delay (and therefore very little
regurgitation)

31. NONTILTING DISC VALVES
Drawback:
• higher flow gradients
• significant turbulence
• frequent thromboembolic complications
• higher hemolysis

32. NONTILTING DISC VALVES
• Kay-Shiley Disc Valve
• Beall-Surgitool Disc Valve
• Cooley-Cutter Biconical Disc Valve

33. KAY-SHILEY DISC VALVE-1965
• First disc valve to achieve
worldwide use
• Stellite housing and flat silicone
elastomer disc
• Delrin polymer disc in 1975.
• Improved durability

34. BEALL-SURGITOOL DISC VALVE -1967
• Teflon disc valve.
• Pyrolyte disc -1971
• 5,000 mitral valves
were implanted
• Drawback:
– fabric wear on the
annular apron.

35. COOLEY-CUTTER BICONICAL DISC
PROSTHESIS, 1973
• Nontilting disc valve with
biconical silicone rubber
poppet.
• Double set of struts and
equator-seating disc
• silicone disc replaced with
pyrolyte disc in 1973
• 3000 valves implanted

36. NONTILTING DISC VALVES

37. TILTING DISC VALVES
• Designed on principle of tilting disc : differences
in disc housing and angle of tilting
• Tilting angle : eventual diagnostics of valve failure
• Discs are radio-opaque , fluoroscopy imaging
– normal mobility
– restricted range of motion
– complete occluder blockade.

38. LILLEHEI-CRUZ-KASTER TILTING DISC
VALVE, 1963
• Free-floating disc tilting on
edge of orifice ring
• Good hemodynamic qualities
• Disadvantage: Area of stasis
between open disc & aortic
wall

39. BJORK-SHILEY FLAT DISC VALVE-1969
• Flat occluder disc
• Disc : Delrin(POM=polyoxymethylene);
Pyrolyte disc
• Stellite housing
• Disc tilting up to 60°
• Inlet and outlet struts welded to flange
•
• Early failures of inlet strut welds eliminated
with change to welding process.

40. BJORK-SHILEY CONVEXO-CONCAVE TILTING
DISC VALVE-1976

41. BJORK-SHILEY CONVEXO-CONCAVE
TILTING DISC VALVE-1976
Advantages:
• Decreased thromboembolic complications by 50 %
• superior hemodynamic characteristics
• valve completely open with half flow required with
straight disc
• much more rapid reaction on closure resulting in
reduced regurgitation

42. BJORK-SHILEY CONVEXO-CONCAVE TILTING
DISC VALVE-1976
• 1986: Removed from market due to serious safety
concerns.
• outlet strut fracture causing death in 2/3rd of patients
• After recall, not all Bjork Shiley valves were removed
from patients
• 1991 : class action lawsuit filed against Pfizer
• 1992: lawsuit settled, with Pfizer expecting to pay
between $155 and $205 million total.

43. BJORK-SHILEY MONOSTRUT VALVE-1982
• Single perpendicular strut
• Weld-free mechanism.
• Pyrolytic carbon disc
• Angle of tilting = 70°
• Improved hemodynamics

44. LILLEHEI-KASTER TILTING DISC
PROSTHESIS, 1970
• Pivot point moved forward to cord
measuring one-third of
circumference of orifice.
• Lateral guides replaced cage of Cruz
valve.
• Seating : titanium
• Disc : Pyrolyte.
• Disc opening = 80° and closing = 18°

45. OMNISCIENCE-1978 AND
OMNICARBON-1984
• Omniscience valve:
– two tabs as catch mechanism.
– titanium housing ,Pyrolyte disc.
• Omnicarbon Valve
– disc and housing -pyrolytic
carbon.
– disc opens up to 80° and closes
at 12°, thus achieving the tilting
range of 68°.

46. MEDTRONIC-HALL-KASTER TILTING
DISC, 1977
• Titanium housing
• Pyrolytic carbon disc with a
small central perforation.
• Disc slides over a guidewire
through its central perforation
to tilt open
• opens up to 75° (aortic valve)
and 70° (mitral valve)

48. TTK CHITRA VALVE
• Distributed by TTK (Tiruvellore Thattai
Krishnamachari) pharma Chennai
• The first human implant was December 6,
1990 at Sree Chitra Tirunal Institute for
Medical Sciences and Technology, Trivandrum
Marthanda Varma Sankaran
Valiathan

49. TTK CHITRA VALVE

50. BILEAFLET MECHANICAL VALVES
• Gott-Daggett Valve - 1963
• Kalke-Lillehei Bileafet Valve - 1965
• St. Jude Medical Heart Valve -1977
• ATS Medical mechanical heart valve -1992
• On-X mechanical prosthesis - 1996

51. Kalke-Lillehei Bileafet Valve
• Based on configuration of Indian tidal floodgates
• peripheral hinging leaflets and central opening.
• Implanted on May 20, 1968, woman with advanced
rheumatic mitral disease.
• She developed low cardiac output and died 48
hours postoperatively.

52. St. Jude Medical Heart Valve-1977
• Pyrolytic carbon over graphite substrate for
housing and leaflets
• Opening angle = 85o : central near laminar flow
• SJM Standard series
• SJM Masters series
• SJM HP (hemodynamic plus, since 1992)
• SJM Regent (since 1998)

53. SJM valves

54. SJM valves

55. SJM Masters HP(Hemodynamic Plus)
• Sewing cuff reduced-> supra-annular
placement
• Increased EOA
• Minimizes interference with subvalvular
structures in mitral position.
• Aortic and Mitral sizes: 17 to 27 mm.

56. SJM REGENT
• Supra-annular placement only for aortic position(size 19-27
mm)
• Significantly larger EOAs
– Less gradient even in valve sizes as small as 19 mm
– Renders root enlargement practically unnecessary
• Low-implant height
• Flexi cuff and Standard cuff

57. ATS (Advancing The Standard) MEDICAL
MECHANICAL HEART VALVE
• Pyrolytic carbon over graphite
substrate for housing and leaflets
• opening angle is 85o.
• Open pivot :decrease blood stasis
and thrombus formation near
hinge
• Standard series
• Advanced Performance series

58. ATS (Advancing The Standard) MEDICAL
MECHANICAL HEART VALVE

59. Medtronic Open Pivot Mechanical
Valve
• Originally developed and owned by ATS Medical,Inc,
(Minneapolis, MN)
• Open pivot design
– Eliminates shallow recessess in hinge area where clots may
form
– Continous gentle flow of blood across valve-> low
hemolysis,low level of clotting
– Continous passive washing of valve

60. ON-X MECHANICAL PROSTHESIS -1996
• Housing: pure, non-silicon
carbide alloyed pyrolytic-carbon
• Leaflets : pyrolytic carbon-coated
over tungsten-loaded graphite
substrate
• curved housing in flow geometry
and an orifice diameter-to-
housing height ratio to minimize
vena contracta phenomenon and
facilitate laminar blood flow.
• opening angle 90o

61. On-X mechanical valve
• Manufactured by On-X Life
Technologies,Austin,TX
• Decreased thrombogenicity
• Tall, flared inlet
• Stasis free pivot design

62. On-X mechanical valve
Standard ring
• aortic 19 to 27/29mm,mitral 23 to 31/33 mm
Conform-x sewing ring(more flexible)
• Aortic 19 to 27/29 mm,mitral –one size 25/33
Anatomic sewing ring( aortic valve annulus only)
• Sizes 19 to 27/29 mm

63. On-X mechanical valve

64. VALVE CONSTITUENTS
• Housing
• Occluder mechanism- ball, tilting, nontilting
disc, bileaflet
• Occluder
• Sewing ring

65. TERMINOLOGY & PARAMETERS
• Valve size :outer diameter of the valve housing
(TAD - tissue annulus diameter)
• Internal orifice diameter (IOD) of the valve is
smaller than labeled valve size
• ESRD (external sewing ring diameter) larger
than TAD

66. TERMINOLOGY & PARAMETERS

67. TERMINOLOGY & PARAMETERS

68. HEMODYNAMIC PARAMETERS

69. PATIENT–PROSTHESIS MISMATCH
(PPM).
• First described in 1978 by Rahimtoola
• “Mismatch can be considered to be present when the effective
prosthetic valve area, after insertion into the patient, is less than
that of a normal human valve”
• Smaller than expected effective orifice area (EOA) in relation to
the patient's body surface area (BSA) will result in higher
transvalvar gradients.
Circulation vol 58 ,No
1,July 1978

70. PATIENT–PROSTHESIS MISMATCH (PPM).
• Aim : Implant a valve large enough to avoid hemodynamically
significant patient–prosthesis mismatch (PPM).
• Aortic position -IEOA of implanted valve should be > 0.85
cm2/m2.
• Mitral position- IEOA of implanted valve should be > 1.2
cm2/m2.
• Severe patient–prosthesis mismatch occurs
– IEOA <0.65 cm2/m2 in aortic position
– IEOA <0.9 cm/m2 in mitral position

71. PERFORMANCE INDEX (PI)
– Better indicator of hydraulic function efficiency of
particular prosthesis
– Ratio of effective orifice area (EOA) to sewing ring area
– Size-independent measure of valve’s resistance
characteristics
– Bileaflet valves typically have higher PI’s than tilted-disc
models, which in turn have higher PI’s than caged-ball
model

72. GOOD HEMODYNAMICS
• minimal resistance to forward blood flow
• only trivial regurgitant backflow as the occluder closes
• minimal turbulence and stasis in vivo during physiologic
flow conditions
• durable enough to last a lifetime
• constructed of biomaterials that are nonantigenic,
nontoxic, nonimmunogenic, nondegradable, and
noncarcinogenic.
• low incidence of thromboembolism.

73. HEMODYNAMICS
Factors determining opening resistance to blood flow
• orifice diameter
• size, shape, and weight of occluder
• opening angle
• orientation of leaflet or disk occluders with respect
to plane of annular orifice for any given annular size

75. HEMODYNAMICS
Hemolysis
• cavitation and shearing stresses of turbulence
• high-velocity flow, regurgitation
• mechanical damage during valve closure

76. HEMODYNAMICS
Thrombosis:
• Areas of perivalvular blood stagnation and
turbulence
• increase platelet aggregation
• activation of the coagulation proteins
• thrombus formation.

77. HEMODYNAMICS
Dynamic regurgitation
• sum of closing volume and leakage volume
Closing volume
• function of EOA and time needed for closure.
• Closure time is influenced by difference between the
opening and closing angles of occluder and valve ring.

78. HEMODYNAMICS
Leakage volume(washing jets)
• inherent to design of valve
• depends on amount of time valve remains in closed
position
• small amount of regurgitant volume can be beneficial by
• minimizing stasis and reducing platelet aggregation
• decreases incidence of valve thrombosis and valve-
related thromboembolism

79. Hemodynamics: Ball and cage valves
• Minimal leakage
• Leakage volumes - indicate pathologic process
• Annular area for flow creates turbulenece
• Cage may contact ventricular wall during contraction
• Partial obstruction by ball in aortic position
• Increase risk of hemolysis and thromboembolic
complications

80. Hemodynamics : Tilting disc valve
• Less obstruction to flow
• Gradient of 6- 7 mm Hg
• Opening angle high- less
gradient, more
regurgitation
• Opening angle low- more
gradient and less
regurgitation

81. Hemodynamics : Bileaflet valve
• more uniform central, and laminar flow
• less turbulence
• decreased transvalvular pressure gradients
• favorable hemodynamics in smaller sizes makes it
especially useful in children.
• large EOA for each valve size at the expense of
greater regurgitant volumes, especially at low heart
rate

82. Hemodynamics : Bileaflet valve
• Lowest gradient
• Low profile
• Minimal turbulence
– wide opening angle
– thin leaflets
– large cross sectional area

83. Hemodynamics

85. valve housing Sewing ring leaflets Opening
angle
Implantatio
n
ROTATABLE
SJM PYROLYTIC
CARBON
COATED
GRAPHITE
SUBSTRATE
POLYESTER/
PTFE
PYROLYTIC
CARBON
COATED
GRAPHITE
SUBSTRATE
850 Masters:
intraannular
HP and
Regent:
supra
annular
YES
MEDTRONIC 100%
PYROLYTIC
CARBON
with
titanium
strengthnin
g band
Double-
velour
POLYESTER
Cuff marker
present
PYROLYTIC
CARBON
COATED
GRAPHITE
SUBSTRATE,
20%
tungsten
impregnate
d
850 Standard:
intra
annular
AP: supra
annular
yes
On-X GRAPHITE
SUBSTRATE
coated with
On-X
carbon-pure
unalloyed
PTFE
mounted
using
titanium
retaining
rings and 5-
On-X
CARBON
COATED
GRAPHITE
SUBSTRATE,
10%
900 Mitral:
supra
annular
Aortic(19-
25mm):intra
supra-
yes

87. MORBIDITY AND MORTALITY
GUIDELINES
• The councils of the Society of Thoracic Surgeons
(STS) and the American Association of Thoracic
Surgery (AATS) formulated the Ad Hoc Liaison
Committee for Standardizing Definitions of
Prosthetic Heart Valve Morbidity.
• The initial report of this committee was issued in
1988 with an update in 1996
• The report strictly defines types of morbidity and
mortality that can occur after valvular surgery.

88. Early Mortality
• Early mortality is to be reported as all-cause
mortality at 30, 60, or 90 days and depicted by
actuarial estimates (with number remaining at
risk and confidence intervals [CIs]) or as
simple percentages, regardless of the patient’s
location, be it home or in a health care facility

89. STRUCTURAL VALVE DETERIORATION
• Includes dysfunction or deterioration
involving the operated valve (exclusive of
infection or thrombosis), as determined by
reoperation, autopsy, or clinical
investigation.

90. STRUCTURAL VALVE DETERIORATION
changes intrinsic to the valve:
• such as wear, fracture, poppet escape, calcification,
leaflet tear, stent creep
• suture line disruption of components of a prosthetic
valve
• new chordal rupture, leaflet disruption, or leaflet
retraction of a re- paired valve.

91. NONSTRUCTURAL DYSFUNCTION
• abnormality not intrinsic to the valve itself
that results in stenosis or regurgitation of
the operated valve or hemolysis.
• do not directly involve valve components
yet result in dysfunction

92. NONSTRUCTURAL DYSFUNCTION
• entrapment by pannus, tissue, or suture
• paravalvular leak
• inappropriate sizing or positioning
• residual leak or obstruction after valve
implantation or repair
• clinically important intravascular hemolytic
anemia

93. VALVE THROMBOSIS
• any thrombus not caused by infection attached to or
near an operated valve that occludes part of the blood
flow path, interferes with valve function, or is sufficiently
large to warrant treatment.
• Valve thrombus found at autopsy in a patient whose
cause of death was not valve related or found at
operation for an unrelated indication should also be
counted as valve thrombosis.

94. EMBOLISM
• Embolism is any embolic event that occurs in
the absence of infection after the immediate
perioperative period.
• Embolism may be manifested by a neurologic
event or a noncerebral embolic event.

95. BLEEDING EVENT
• A bleeding event is any episode of major
internal or external bleeding that causes
death, hospitalization, or permanent injury
(eg, vision loss) or necessitates transfusion.

96. OPERATED VALVE ENDOCARDITIS
• Operated valve endocarditis is any infection
involving a valve on which an operation has
been performed.
• Positive blood cultures are not required for the
diagnosis of operated valve endocarditis.

97. OPERATED VALVE ENDOCARDITIS
The diagnosis is based on one of the following criteria:
• (1) reoperation with evidence of abscess, paravalvular leak, pus,
or vegetation confirmed as secondary to infection by histologic
or bacteriologic studies
• (2) autopsy findings of abscess, pus, or vegetation involving a
repaired or replaced valve
• (3) in the absence of reoperation or autopsy, meeting of the
Duke Criteria for endocarditis

98. Morbidity data
• Rate for nonstructural dysfunction of mechanical valves
– 0.2 to 0.8 (events/ patient-years) for the aortic position
– 0.3 to 1.4 (events/patient-years) for the mitral position
• Rate of thrombosis of mechanical valves
– 0 to 0.2 (events/patient-years) in the aortic position
– 0.4 to 0.8 (events/patient-years) for the mitral position

99. Morbidity data
Rate of thromboembolism
• 1.4 to 2.5 (events/patient-years) for the aortic position
• 1.8 to 3.6 (events/patient-years) for the mitral position
Rate of bleeding event
• 0.8 to 2.5 (events/patient-years) for the aortic position
• 1.2 to 2.2 (events/patient-years) for the mitral position
Rates for prosthetic valve endocarditis
• 0.4 to 0.7 (events/patient-years) for both the aortic and mitral
positions.