Note: Descriptions are shown in the official language in which they were submitted.
~154553
This invention relates to fluid valves, and more p~rticular-
ly, to such fluid valves which permit fluid flow in one directlon and
~, .
prevent fluid flow in the opposite direction. Such a valve may be
used as a replacement valve in a human heart or in artificial heart
pumps . ,
~eart valve disease in advanced forms causes severe
disability and ultimately death. The quality and length of life for
patients suffering from valve disease can be remarkably improved by
surgical treatment, which usually involves the total replacement of
the diseased valve with a prosthetic valve.
In the two decades since the first successful implantation
in a human, nearly 50 different valve types have been introduced and
many have been discarded; of those remaining, two basic types are in
use - those constructed of human or animal tissues (tissue valves) and
those constructed of cloth, metals, carbon, and plastic components
(nontissue or mechanical valves).
These devices have come ln various forms of flexible
unicusp, bicuspid, and tricuspid valves, ball valves and "butterfly"
or flapper valves.
Significant late complications following implantation of
these valves can occur and are related to valve design and materials.
Present valve replacements do not permit restoratlon of normal
- 2 - ~
1~L54553
pressure-flow dynamics at all levels of cardiac f~mction. Thus, there is
still no clearcut choice for the surgeon and the search for the ideal
replacement heart valve is continuing.
In addition artificial heart pumps are now known which have been
developed to simulate the action of the human heart. Critical components
in the artificial heart pump include the fluid control valves and they
must operate faultlessly for an indefinite period of time with a mechani-
cal action that does not produce excessive blood damage (haemolysis).
Stented tissue valves, that is, supported valvular grafts which
may be either xenografts (heterografts) or allografts (homografts), have
been used as replacement heart valves. (See, for example, Carpentier et
al., J. Thorac. Cardiovasc. Surg. 68:771 (1974); Zuhdi et al., Ann. Thorac.
Surg. 17:479 (l974); Horowitz et al., J. Thorac. Cardiovasc. Surg. 767:
885 (1974)). In general, such grafts have been mounted on supporting
frames (stents) which provide rigid orifice rings (See Weldon et al., J.
Surg. Research 6:548 (1966)). Some stents have included struts capable
of flexing inwardly to a limited extent, thereby reducing stresses im-
posed on the grafts and decreasing possible erosion of surrounding tissues
of the patient (See Sugie et al., J. Thorac. Cardiovasc. Surg. 57:455
(1969); and Hardy, Human Organ Support and Replacement, 333 et. seq.).
Despite the encouraging results with prosthetic tissue heart valves and
in contrast to non-tissue prosthetic valves, there is a continuing need
for improvement, particularly with regard to the
1154~
hydrodynamic performance and lony-range durability of the tissue valve.s.
The art is still faced with the desirability of providing an im-
proved stent for a tissue (xenograft or allograft) heart valve which is
capable of yielding to a limited extent in response to forces which tend
to alter the configuration and circumference of the orifice ring, thereby
improving the long-range reliability of the valves. Accordingly, con-
tinued efforts are being made to develop more efficient, reliable and
biocompatible prostheses.
The results of such continued efforts are evidenced in heart
valves which are disclosed in issued United States Patents.
United States Patent No. 2,832,078 issued April 29, 1958 to D.T.
Williams discloses an aortic heart valve including a slotted cylindrical
shell with an internal three-sac membrane to provide opening and closing
ports, which seal at the centre of the cylindrical shell.
United States Patent No. 3,199,788 issued August 3, 1965 to F.J.
Segger, provides an aortic heart valve including a deformable cone-shaped
cusp-supporting ring, with the cusps having smooth curved surfaces.
~nited States Patent No. 3,548,418 issued December 22, 1970 to W.W.
Angell et al., provides a graft-supporting ring for grafting porcine
aortic valves in which the ring is generally in the form of the residual
portion of a conical shell, having three struts, the ring being completely
covered and having three internal depressed valve cusps.
United States Patent N0. 3,570,014 issued March 16, 1971 to W.D.
Hancock provides a stent for aortic and mitral heart valves in which the
stent includes a ring and three support arms rising therefrom, to which
commissures and cusps of a heart valve are attached.
United States Patent No. 3,714,671 issued February 6, 1973 to W.S.
Edwards et al. provides a stent for supporting a tricuspid heart valve, in
- 4 -
.,:.
~.154553
which the ring comprises portions of ellipses, in which the upstanding por-
tions are covered with fabric and which terminate in radial wings, and to
which three valve cusps are sutured, the valve cusps having straight trimmed
edges, and being supported without tension.
United States Patent No. 3,736,598 issued June 5, 1973 to B.J.
Bellhouse et al. provides ab aortic valve including a ring having three legs
folded to U-shaped sections to which are attached three valve cusps whose
free edges meet in radial planes of abutment.
U-ited States Patent No. 3,739,402 issued June 19, 1973 to D.A.
Cooley et al., provides a graft support for a bicusp valve which includes
a frusto-conical ring and a pair of inverted frusto-conical segments defin-
ing struts, all provided with a fabric cover, to,which are secured a pair
of cusps whose upper edges lie adjacent to each other to form the valve
opening.
Vnited States Patent No. 3,744,062 issued July 10, 1973 to V.
Parsonnet provides a heart valve construction including a stent having
three lower arcuate protions and three upstanding posts, to which a fabric
sheath is secured, and from which three valve leaflets, each having an
arcuate edge and a straight edge are secured, so that the straight edges
provide an upper meeting closure.
Vnited States Patent No. 3,755,823 issued September 4, 1973 to
W.D. Hancock provides a stent for heart valves in the form of a flexible
stent including a ring having three spaced-apart apexes to which a cloth
sleeve is attached and to which three valvc cusps are attached, so that the
free edges sag towards the centre, at which point they meet at a central,~
slightly raised point. This valve utilizes a whole porcine aortic valve
which is pretreated before mounting on the stent.
- 5 -
115~S53
Vnited States Patent No. 3,938,197 issued Pebruary 17, 1976 to S.
~i]o provides a heart valve including a ring to which are attached a
plurality of flat valve flaps whose free edges all meet in abutting rela-
tion.
United States Patent No. 3,983,581 issued October 5, 1976 to W.W.
Angell et al. provides a heart valve stent of a particular shape, to
which a covering is attached, and from which three valve cusps are
attached so that their free edges meet at three commissures, and so that
their common points meet at a central depression. A whole porcine xeno-
graft is mounted to the stent.
United States Patent No. 4,035,849 issued July 19, 1977 to W.W.
Angell et al. provides; a heart valve stent of a particular shape, to
which a covering having a bead along its perimeter is attached and from
which three valve cusps are attached, so that their free edges meet at
three commissures and so that their common points meet at a central depres-
sion. A whole porcine xenograft is mounted to the stent.
United States Patent No. 4,084,268 issued April 18, 1978 to M.I.
Ionescu et al. provides a heart valve including a dish-shaped cloth-
covered stent having three upright posts, to which three cusps are attached,the cusps meeting at their upper edges at a flat closed portion, and in
which the knots of the stitches are covered by a pledget and cover. This
valve uses pretreated bovine pericardium for its three leaflets.
United States Patent No. 4,106,129 issued August 15, 1978 to A.F.
Carpentier et al. provides a heart valve including a deformable wire-frame
stent having three inverted V-shaped commissure supports, to which are se-
cured a cover, and from which are suspended three valve leaflets meeting
along the commissures. A whole porcine xenograft is mounted to the stent.
1:154553
United States Patent No. 4,164,046 issued August 14, 1979 to ~.A.
Cooley provides a mitral or tricuspid valve replacement which i.s based on
an open ring stent.
United States Patent No. 4,172,295 issued October 30, 1979 to R.J.
Batten provides a tricuspid heart valve dish-shaped cloth-covered stent
having three upright ports to which are attached three cusps meeting at
their upper edges at a flat closed position, in
/
//////'// .
~1~455;3
which the knots of the stitches are covered by a pledget and cover, and
in which securing holes are provided between the cusps.
~ nited States Patent No. 4,178,639 issued December 18, 1979 to
J.C. Bokros provides a heart valve having an annular valve body and a pair
of pivotally secured valve leaflets.
In spite of all these prior patents, improvements are still
required to provide improved valves which: provide minimal obstruction to
the flow of blood; have smooth surfaces to minimize haemolysis; must not
be too slow in closing, thereby permitting a substantial and undesirable
reflux caused by the relatively high head pressure of the pump system; in
opening and closing, there should be a minimum amount of mechanical
stress and strain to the valve which wou~.d materially contribute to
shortening the life of the valve; provide adequate support for attachment
within the heart; minimize adverse clotting effects; should not create
significant turbulence in the blood stream in both systole and diastole,
which can damage blood elements; provide acduracy in the si~e and shape
of the cusps; provide accuracy in the shape and size of the stent ring;
have improved reliability by minimizing stresses in the flexing cusps
tissue; incorporate flexibility and deformability in their functional
operation; and improve the structural alignment of the tissue relative to
the stent.
~1~455~3
Accordingly, an object of a msin aspect of this invention is
to provide an improved one-way valve~
An object of another aspect of this invention is to provide
an improved one-way valve which may be used in artifi~ial heart pumps as
well as for heart valve replacements.
Objectives of further aspects of this invention are to provide
heart valves having the following characteristics:
1. free flow central orifice configuration;
2. rapid opening and closing;
3. potent~al mimimal compressive and tensile stress distrlbution on
flexing leaflets and hence improved valve reliability;
4. high ratio of available valve flow area to implant site area;
. relative ease of fabrication of all sizes compared to other
tissue type valves;
6. mimimal obstruction to the left ventricular outflow tract;
7. negligible retrograde flow;
8. maximal conformity to the natural anatomic valve configuration;
9. mimimal thromboembolic potential;
; 20 10. e~se of handling and insertion; snd
11. silent operatlon.
l~LS4~53
By one aspect of ehis invention, a one-way valve is provided corn-
prising: a stent including a circular base and a pair of diametrically
opposed struts, separating a pair of diametrically opposed, arcuately
shaped, depressed reliefs, each such relief being bounded by a smooth curve
interconnecting the struts to the circular base; a flexible, durable,
covering secured to the stent, and providing two equal, opposed, molded,
flexible, flappably-movable, valve leaflets secured along a smooth curve
defining the upper perimeter of the reliefs; the valve leaflets each
being preformed and molded so that the free margins of the covering along
the free edges Of each of the leaflets between the tips of each associated
strut is so related to the circumference of the circular base that, when
the valve is in its open position, the cross-sectional area of the exit is
substantially equal to the cross-sectional area of the inside of the
circular base; and, when the valve is in its relaxed and natural, closed
position, the shape of the leaflets is such that the free edges of the
leaflets drop down and sealingly meet in substantially wri.nkle-free form at
a curve of apposition in the plane defined bv the tips of the struts and
the axis of the valve, and follow the approximate shape of a catenary curve.
By another aspect of this invention, a mitral heart valve com-
prising: a stent including a circular base and a pair of upstanding,diamet-
rically opposed struts, separating a pair of di.ametrically opposed, arcu-
ately shaped, depressed reliefs, each such relief bcing bounded by a smooth
curve interconnecting the struts to the circular base; a flexible, durable,
biocompatible covering secured to the stent and providing a pair of equal,
opposed, molded, flexible, flappably-movable, valve leaflets secured
along the smooth curve defining the upper perimeter of the reliefs; the
valve leaflets each being preformed and molded so that the free margins of
the biocompatible covering along the free edges of each of the leaflets be-
-- 10 --
~s~s~
tween the tips of each associated strut is so related to thc circurn-
ference of the circular base that, when the valve is in ils open
position, the cross-sectional area of the exit is substantially equal to
the cross-sectional area of the inside of the circular base, and, when the
valve is in its relaxed and natural closed position, the shape of the leaf-
lets is such that the free edges of the leaflets drop down and sealingly
meet in substantially wrinkle-free form at a curve of apposition in the
plane defined by the tips of said struts, and the axis of the valve and
follow the approximate shape of a catenary curve.
By a variant of these aspects the struts are substantially identi-
cal.
By another variant, the reliefs are symmetrically disposed equi-
distant from the struts.
By another variant of these two aspects of this invention, the
struts are made to be flexibly elastically deformable to minimize stresses
on the valve leaflets when the valve closes.
By a further variant thereof, the free edges of the leaflets follow
a precise catenary curve in the closed position.
By yet another variant thereof, the reliefs are disposed equidis-
tant from the struts.
By yet another variant of the second aspect of this invention, the
valve leaflets are formed of pcricardium trcated with glutaral-
dehyde.
By a variation thereof, the valve leaflets are formed of other
flexible materials, e.g., polyurethane-type compounds.
By a further variant, the leaflets of pericardium are secured to
each other and to the struts by sutures.
By another variant, the struts lie within the surface of a cone
having the circular stent base as the conic base.
- 11 -
1154~5~3
By a further variant, the smooth curve inLerconnecting the struts
is a parabola.
By yet another variant, the stent is formed of a ~lexible, elas-
tically deformable material, so that the struts may llex slightly.
By still another variant, the material is polypropylene of is an
acetal copolymer.
By a still further variant, the valve cusps are formed of bovine,
porcine or human fascia lata or dura mater, or of polyurethane.
By another aspect of this invention, a method is provided for mak-
ing a mitral heart valve comprising the steps of: (a) providing a stent in-
cluding a circular base:and a pair Of upstanding, diametrically opposed,
struts separating a pair of diametrically opposed~arcuately shaped~depressed
reliefs, each releif being bounded by smooth curve interconnecting the
struts to the circular base, the hei~ht of the struts bein~ a selected
value derived from the outside circumference of the circular base; (b) pro-
viding a shape for the valve leaflets in their closed position by requiring
that the length of leaflet tissue from the strut to the free èdge provides
the apprcximate shape of a catenary or other curve; (c) generating the
sectional contours of the leaflets in the closed position; (d) provide a
mold of the shape selected around which a leaf].et is to be formed; (e) mold-
ing the leaflets on the mold so that the free margins of a biocompatible
covering along the free edge of each of the leaflets between the tips of
each associated strut is so related to the circumference of the circular
base that, when the valve is in its open position, the cross-
sectional area of the exit is substantially equal to the cross-sectional area
of the inside of the circular base, and, when the valve i.s in its relaxed
and natural closed position, the shape of the leaflets is such that the free
edges of the leaflets drop down and sealingly meet in substantially wrinkle-
- 12 -
llS4SS;~
free form at a curve of apposition in t-he plane defined by the tips of the
struts, and the axis of the valve and follow the approximate shape of a
catenary curve; (f) securing the molded, leaflets so formed to the circular
base and securing the leaflets to each other and to the struts; and (g)
fixing the valve in the closed position while maintaining the leaflets in
their shaped condition.
By a variant of this aspect of this invention, the height of the
struts is one-quarter of the outside circumference of the circular base.
By yet another variant thereof, the leaflets are secured to each
other and to the struts by sutures.
The heart valve provided herein in one preferred embodiment is
designed specifically for the mitral position which has the bicuspid
character of the natural mitral valve. Such a design more likely takes
advantage of the anatomic configuration and flow patterns of the natural
left ventricle then, for example, a tricuspid tissue valve or a non-tissue
valve in the mitral position. When closed, a bicuspid or bi-leaflet valve
has the advantage of presenting minimal obstruction of the ventricular
outflow tract.
In the accompanying drawings,
Figure 1 is a perspective view of the stent forming part of the
mitral valve replacement of an embodiment of this invention;
Figure 2 is a perspective view of the mitral valve of an embodi-
ment of this invention, in the open position; and
Figure 3 is a perspective view of the mitral valve of an embodi-
ment of this invention in the closed position.
As seen in Figure 1, the stent includes diametrically opposed
reliefs which are slightly splayed from the vertical axis of the valve to
allow for tissue anchoring at the valve outlet without causing obstruction
- 13 -
11545~3
to flow with the valve fully open. The stent also includes a low cylindri-
cal base member or ring 11. Disposed about the cylindrical base member or
ring 11 are a pair of identical, diametrically opposed struts 12 between
which are a pair of identical, diametrically opposed reliefs 13. The
struts can, of course, be less than true conical segments and still provide
a stent 10 which can be used in providing the mitral valve replacement of
an embodiment of this invention.
The stent 10 is made as light and unbulky as is compatible with
the needed strength and with avoidance of sharp edges. Preferably it is
made of a flexible elastically deformable material, i.e., synthetic
~plastic materials, e.g.Jpolypropylene or acetal copolymer~ so that the
struts 12 may flex slightly. The struts 12 have rounded extremities 14
and are connected to the cylindrical base member or ring 11 by smooth
curvés 15 to give the reliefs 13 an arcuate shape. Each strut 12 has an-
chor openings 16.
The mitral valve 18 is`formed on the stent 10 by a suitable cover-
ing material so secured to the cylindrical base member or circle 11 to pro-
vide a pair of opposed surfaces 21 secured to the struts 12 of the stent 10
and a pair of opposed cusps or leaflets 22 which are flexible and flappably
movable. The free margin or perimeter 23 at the free edges of the cusps
or leaflet 22 is preferably of such length that when the free edges of
the leaflets meet, the valve is closed to form the approximate shape of
catenary curve 24 or lenyth equal to the perimeter 23.
In the embodiment of this invention as shown in Figures 2 and 3,
the mitral valve 18 in its closed position has two equal or leaflets cusps
22 which form a curve of apposition in the plane defined by the tip of each
stent strut 12 and the axis of symmetry of the valve 18. In the open
position, the valve 18 provides an approximately cylindrical shape of tis-
:llS45r~
sue with an exit area equal to the inside area of the cylindrical memberor circular base 11 of the stent lO.
In this embodiment, the length 23 of tissue between the tips of
each stent strut 12 in the closed position equals half the circumference of
the exit aperture of the valve 18. This is achieved by having a curved
closure line which appears to be like a line dropping from the stent strut
tips 14 towards the cylindrical base member or ring 11. The curve is
preferably a catenary, i.e., the curve formed by a uniform chain hanging
freely between two points but may assume other curved configurations pro-
vided the specified tissue length is adhered to.
Calf pericardium was selected as the material for construction of
the valve or cusps leaflets since, when treated with glutaraldehyde, it has
acceptable durability and biocompatibility. Other naturally-occurring
materials, e.g., bovine, porcine, human (pericardium, fascia lata, dura
mater) or synthetic materials, e.g. polyurethanes e.g. that known by the
Trade Mark of AVCOTHANE of acceptable durability and biocompatibility may
also be used. A flexible stent made of acetal copolymer, is preferably
used since it allows flexibility and thereby provides greater valve dura-
bility.
In the preparation of one variant embodiment of this invention, a
prototype stent 10 was machined from an acetal copolymer rod. The height
of the s~rut 12 above the cylindrical base member or ring 11 was equal to
one-quarter of its outside circumference. The shape of the cusps or leaf-
lets 22 in the closed position was determined by requiring that the
lengths of tissue shown for the open valve 18 from the tip 14 of the
strut 12 to the free edge of the cusps or leaflets 22 should form catenar-
ies in the closed position. The sectional contours of the cusps or leaf-
lets 22 in the closed position were then generated. A mold was then made
- 15 -
~5~S5~3
around which each cusps or leaflet 22 could be formed. The moist tissue
for the cusps or leaflets 22 was attached to the stent 10, then sutures 25
were used to secure the cusps or leaflets 22 to each other and to the
tips 14 of the stent struts 12. The valve 18 was fixed in the closed
position using 0.625~ glutaraldehyde solution while the shape of the cusps
or leaflets 22 was maintained by cotton batting and by a negative mandrel
shape. The shape was further maintained after initial fixation by cotton
batting once the negative mandrel molding was removed.
The mitral replacement valve 18 of an embodiment of this inven-
tion was compared against different conventional types of prostheses using
a hydromechanical apparatus which provided a realistic simulation of heart
geometries, pressures, and flows. The hydrodynamic performance of each of
the valves tested was compared at three different pulse rates (60, 80, and
120 beats per minute). The three measures used to characterize valvular
performance were:
- Table I, mean and maximum transmitral pressure difference
- Table II, observed and calculated open valve area
- Table III, total transmitral energy loss per cycle
- 15 a -
~1~45~;~
TABLE I
Transmitral. pressure difference; mean, maximum
~mmHg) at
Valves 60 80 120
beats/min beats/minbeats/min
(1) ~icusp ~ 1.3, 11.5 1.8, 12.02.9, 11.0
(2) Bjork-Shiley, c.c. 1.2, 14.22.1, 13.3 4.8, 13.0
(3) St. Jude Medical 1,3, 13.62.9, 15.0 5.0, 13.4
(4) Hall-Kaster 1.4, 16.0 1.9, 14.45.5, 15.8
(5 ) Ionescu-Shiley 1.6, 7.83.0, 11.0 5.9, 13.4
(6) Omniscience 1.8, 15.6 2.5, 14.76.2, 16.8
(7) Bjork-Shiley 1.6, 14.2 2.9, 14.46.9, 13.9
(8) Lillehei-Kaster 3.9, 18.23.5, 14.1 8.4, 17.0
(9) C~rpentier-Edwards 2.9, 15.54.6, 17.5 8.7, 18.7
(10) Starr-Edwards 4.1, 14.1 6.2, 18.111.4, 22.1
(11) Hancock 4.4, 16.9 6.7, 20.413.4, 25.4
Note: Bracketed numbers indicate order of merit with (1) being the best
value and (ii) the worst.
- 16 -
~:~54S5~3
~ABLE II
._
Open valve area; calculated, o~served (cm )
at
Valves 60 80 120
beats/min beats/min beats/min
(1) Bicusp 3.0, 3 9 3.6, 4.1 5.3, 4.7
(2) Bjork-Shiley, c.c. 3.6, 4.2, 4.2
(3) St. Jude Medical 2.8, 3.5, 3.8,
10(4) Hall-Kaster 2.9, 3.7, 3.3,
(5) Omniscience 2.7, 3.2, 3.0,
(6) Ionescu-Shiley 2.7, 2.9 2.4, 3.2 2.9, 3.2
(7) Bjork-Shiley 2.8, 3.5, 2.8,
(8) Lillehei-Kaster 2.0, 2.7, 2.3,
(9) Carpentier-Edwards 2.1, 2.0 2.1, 2.0 2.2, 2.1
(10) Hancock 1.9, 1.5 1.5, 1.6 1.9, 1.7
(11) Starr-Edwards 1.7, 1.7, 1.7,
.. ... . ... _ _ . ... _ _
No-te: -Bracketed numbers indicate order of merit with (1) being the best
valve and (11) the worst.
-Non tissue type valves do not have an observed area.
- 17 -
~S9tS5~
TABLE III
Total transmitral energy loss (~) at
Valves 60 80 120
beats/min beats/min beats/min
(1) Bicusp 7 8 7
(2) Ionescu-Shiley 7 9 11
(3) Carpentier-Edwards 9 9 11
(4) Omniscience 9 10 12
(5) Hall-Kaster 10 11 12
(6) St. Jude Medical 10 12 13
(7) Bjork-Shiley, c.c. 12 12 13
(8) Starr--Edwards 7 8 14
(9) Bjork-Shi.ley15 16 18
(10) Lillehei-Kaster 15 17 18
(11) Hancock 12 13 19
Total model ventricular 0.935 1.066 1.105
energy (Joules)
. ____ _
20 Note: Bracketed numbers i.ndicate order of merit with (1) being the best
valve and (11) the worst.
- 18 -
~15~55;~
The B~ork--Shiley may be descrlbed as a -valve which uti1izes a
single spherical tilting disc occluder. The dLsc is made fro~
pyrolytic carbon and the metal housing ls made of a mctal known by
the Trade Mark STELI.ITE. Cloth of a polytetrafluoroethylene known
by the Trade Mark TEFLON is used for the s~lturing ring.
~le Omniscierlce may be described as a valve wh;ch utilizes a single
pivoting curvilinear - shell occluder. The disc is made from
pyrolytic carbon and the metal housing is made of titanium. The
suturing ring is made of knitted polyester.
The Bjork-Shiley (cc) may be described as a valve which utilizes a
single convexo-concave tilting disc occluder. ~e disc is made of
pyrolytic carbon and the metal housing is made of STELLITE. The
sutu~~ing r;ng is made of knitted TEFLON. (See Canadian Patent
1,066,853)
The ~all-~aster may be described as a valve wllich utilizcs a single
spherical pivoting disc occluder. The disc is made from pyrolytic
carbon and the metal housing is made of titanillm. The suturing
ring is mL~de of knitted TEFLON.
The Starr-Edwards may be describcd as a valvc which u~ilizes a
silicone rubber ball occluder. The netal housing is made of
STELLITE. The suturing ring is m~de of knitted ~EFLON and
polypropylene .
--19--
llS4S5~3
me Carpentier-Edwards may be described as a valve which u-tilizes a
glutaraldehyde preserved flexible support mounted porcine xenograft.
m e flexible support is comprised of wire frame formed of a wire known
by the Trade Mark ELGILOY, having an insert of a material known by the
Trade Mark REEMAY, with a support of a synthetic plastic known by the
Trade Mark MYLAR and a TEFLON cloth. (See Canadian Patent 1,069,652 and
V.S. Patent 4,106,129).
m e Hancock may be described as a valve which utilizes a glutaraldehyde
preserved flexible support mounted porcine xenograft. The fle-xible
support is comprised of polypropylene, STELLITE, silicone foam, and
knitted synthetic fabric known by the Trade Mark DACRON. (See U.S.
Patent 3,755,823).
me St. Jude Medical may be described as a valve which utilizes two
center opening tilting disc occluders. The discs and housing are made
from pyrolytic carbon. m e suturing ring is made of a D~CRON velour.
(See U.S. Patent 4,178,639).
The Ionescu-Shiley may be described as a valve which utilizes bovine
pericardial xenograft material for construction of three equal cusps
mounted on a symmetrlcal titanium frame covered with DACRON cloth. The
suturing ring is also made of DACRON cloth. (See U.S. Patent 4,084,
268).
_ 20 -
~L~X4~
The Lillehei-Kaster may be described as a valve which utilizes a free -
floating pyrolytic carbon disc for an occluder. The housing is made from
titanium and the suturing ring is made from DACRON cloth.
The Bicusp or Bi-leaflet Mitral Valve of an embodiment o the
present invention as described in Figures 1-3.
From the results shown in the Tables, the bicusp or bi-leaflet
mitral valve of an embodiment of this invention, tested under simulated
conditions in a model left heart as described have shown significantly re-
duced obstruction to flow through the valve demonstrated by showing the
smallest transmitral pressure, largest open area, and least transvalvular
energy loss as compared to existing devices.
As noted above, the hydrodynamic performance of the bicusp valve
has been assessed by comparison with existing prostheses, namely, with
seven non-tissue valves and three tissue valves. The parameters measured
were: mean and maximum transvalvular pressure difference; maximum observed
or calculated open area; and total transmitral energy loss. The bicusp
mitral valve of an embodiment of this invention demonstrates performance
superior to all tested prosthesis as assessed by these parameters.
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