U.S. patent number RE30,912 [Application Number 05/915,451] was granted by the patent office on 1982-04-27 for stent for heart valve.
This patent grant is currently assigned to Hancock Laboratories, Inc.. Invention is credited to Warren D. Hancock.
United States Patent |
RE30,912 |
Hancock |
April 27, 1982 |
Stent for heart valve
Abstract
A heart valve stent that includes an annular framework,
preferably of bendable material, having three rounded apexes
interconnected by support arms curved to incline away from the
apexes. Additional support arms are included parallel to and
axially beyond the first support arms. For use in the mitral
position, the framework is circumscribed by an outer ring, which
receives an annular element of felt or other suitable material. The
heart valve is positioned on the stent, with its marginal portions
overlapping it and affixed to it by sutures.
Inventors: |
Hancock; Warren D. (Newport
Beach, CA) |
Assignee: |
Hancock Laboratories, Inc.
(Anaheim, CA)
|
Family
ID: |
27116747 |
Appl.
No.: |
05/915,451 |
Filed: |
June 14, 1978 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
759858 |
Sep 16, 1968 |
03570014 |
Mar 16, 1971 |
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Current U.S.
Class: |
623/2.18;
623/900 |
Current CPC
Class: |
A61F
2/2418 (20130101) |
Current International
Class: |
A61F
2/24 (20060101); A61F 001/22 () |
Field of
Search: |
;3/1.5,1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
"Homograft Aortic Valve Replacement in Aortic Incompetence and
Stenosis" by B. G. Barratt-Boyes, Thorax (1964), 19, pp. 131-150.
.
"Fixation of Aortic Valve Homografts with Metal Rings" by A. S.
Geha et al., The Journal of Thoracic & Cardiovascular Surgery,
vol. 54, No. 5, pp. 605-615, Nov. 1967. .
"Memoires de l'Academie de Chirurgie" published Jun. 1967, vol. 93,
No. 19-20-21, pp. 617-622, by A. Carpentier et al. .
"Replacement of the Mitral Valvular Apparatus by Hetertopic
Heterografts" by A. Carpentier et al., La Presse Medicale, Jun. 24,
1967, 75-No. 31, pp. 1603-1606. .
"Simplified Insertion of Aortic Homograft Valves with
_Nonthrombogenic Frames" by N. Braunwald et al., Transactions,
American Society for Artificial Internal Organs, vol. XIII, Jun.
16, 1967, pp. 111-115. .
"A Prefabricated Semirigid Tricusp Aortic Valve Prosthesis" by E.
Hessel et al., Journal of Thoracic & Cardiovascular Surgery,
vol. 54, No. 2, Aug. 1967, pp. 227-245. .
"A Prosthetic Stented Aortic Homograft for Mitral Valve
Replacement" by C. Weldon et al., Journal of Surgical Research,
vol. 6, No. 12, Dec. 1966, pp. 548-553. .
"Mitral Valve Replacement with Aortic Heterografts in Humans" by M.
I. Ionescu et al., Thorax, vol. 22, No. 4, Jul. 1967, pp. 305-313.
.
"A Method for Placing a Total Homologous Aortic Valve in
Subcoronary Position" by Duran and Gunning, The Lancet, Sep. 8,
1962, pp. 488 and 489. .
"A Method for Preparing and Inserting a Homograft Aortic Valve" by
B. G. Barratt-Boyes, British Journal of Surgery, vol. 52, No. 11,
Nov. 1965, pp. 847-856..
|
Primary Examiner: Frinks; Ronald L.
Attorney, Agent or Firm: Gausewitz, Carr, Rothenberg &
Edwards
Claims
I claim:
1. A stent for .[.a.]. .Iadd.an animal .Iaddend.heart valve
.Iadd.for supporting such a heart valve in its natural contour
.Iaddend.comprising a framework of annular configuration,
said framework including .[.spaced.]. .Iadd.three rounded
.Iaddend.apical portions .Iadd.at one end thereof, said apical
portions being rounded convexly as viewed from said one end and
being spaced apart unequal angular distances, .Iaddend.and arms
interconnecting said apical portions,
.Iadd.each of said apical portions having a substantial
circumferential dimension for permitting said apical portions to
accommodate heart valves of different dimensions, .Iaddend.for
thereby providing an attachment for the commissures and cusps of a
heart valve, said arms being in two sets .Iadd.spaced apart
axially.Iaddend.,
one of said sets being adjacent said apical portions and the other
of said sets being remote from said apical
portions.[...]..Iadd.,
all of said arms in at least the one of said sets adjacent said
apical portions being curved in a scalloped configuration so as to
incline away from said apical portions intermediate said apical
portions, for conforming to the shape of and supporting the margins
of the cusps of an animal heart valve such that the peripheral
parts of said heart valve can be attached to said arms while
preserving the natural contour of said heart valve,
said arms of said set remote from said apical portions being more
nearly flat than are said arms of said set adjacent said apical
portions. .Iaddend.
2. A device as recited in claim 1 in which said arms in both of
said sets incline axially away from said apical portions
intermediate said apical portions. .[.3. A device as recited in
claim 2 in which at least some of said arms are deflectable for
varying the distances thereof from the axis
of said framework..]. 4. A device as recited in claim 2 in which
said sets of said arms .[.are spaced apart axially and.]. are
generally equally spaced from the axis of said framework,
thereby providing said set of said arms adjacent said apical
portions and
said set of said arms remote from said apical portions. 5. A device
as recited in claim 4 including, in addition, a cloth member
extending over
and receiving said arms. 6. A device as recited in claim 4
including, in addition, a cloth ring attached to and extending
outwardly from said remote set of said arms for providing a means
for attachment to a heart. .[.7. A device as recited in claim 4
including in addition
a ring circumscribing said framework adjacent said remote set of
arms,
and including means projecting radially outwardly from said
framework for securing said ring thereto..]. .[.8. A device as
recited in claim 4 in which said arms in said one set are
deflectable toward said apical portions for thereby increasing the
radial spacing of said adjacent arms from the axis of said
framework..]. .[.9. A device as recited in claim 4 in which said
arms are curved in a scalloped configuration to so incline away
from said apical portions intermediate said apical portions,
said arms in said one set being deflectable and having a greater
inclination away from said apical portions than that of said arms
in said other set,
for providing a relatively large increase in the spacing of said
arms in said one set from the longitudinal axis of said framework
upon deflection
of said arms in said one set toward said apical portions..]. 10. A
device as recited in claim 1 including in addition a ring attached
to said framework for providing a means for attachment of said
framework in a heart in the mitral position, said ring
circumscribing said framework adjacent said arms. .[.11. A device
as recited in claim 10 in which said
ring is a rigid member integral with said framework..]. 12. A
device as recited in claim 10 in which said ring is a cloth member
secured to said arms. .[.13. A device as recited in claim 1 in
which each of said apical portions is rounded and has a substantial
circumferential dimension for permitting said apical portions to
accommodate heart valves of different dimensions..]. .[.14. A
device as recited in claim 1 in which
said arms are arcuate and concave on the sides thereof adjacent
said apical portions,
said arms in said one set being bendable toward said apical
portions for
thereby increasing their spacing from the axis of said
framework..]. 15. A device as recited in claim 1 in which the
spacing between two adjacent apical portions is less than the
spacing between either of said two
adjacent apical portions and the third of said apical portions. 16.
A device as recited in claim 15 in which said spacing between said
two adjacent apical portions is within the range of 17% to 33% less
than said spacing between either of said two adjacent apical
portions and the third
of said apical portions. 17. A device as recited in claim 15 in
which said spacing between said two adjacent apical portions is
within the range of 20% to 25% less than said spacing between
either of said two adjacent apical portions and the third of said
apical portions. .[.18. A device as recited in claim 1 in which
said framework is an integral member of substantially noncorrosive
metal..]. .[.19. A device as recited in claim 18 in which said
metal is malleable..]. .[.20. A device as recited in claim 1 in
which said framework is an integral member of plastic
material..]. 21. The invention as claimed in claim 1 in which there
are three apical portions spaced unequal angular distances from
each other, one space between two adjacent apical portions being a
reference space, another space between two adjacent apical portions
being 4-10% less than said reference space, another space between
two adjacent apical portions
being 17-33% less than said reference space. .[.22. A heart valve
assembly comprising a stent,
said stent including a generally tubular framework having spaced
apexes at one end,
a first seet of arms adjacent and interconnecting said apexes,
and a second set of arms spaced from said first set of arms and
remote from said apexes,
said arms being inclined away from said apexes at locations
intermediate said apexes,
a heart valve on said framework,
said heart valve having commissures substantially at said apexes
and cusps having marginal portions adjacent said arms, the marginal
portions of said heart valve overlapping said framework so that the
interior of said framework is covered by said marginal portions of
said heart valve,
and means for attaching said heart valve to said framework..]. 23.
A device as recited in claim .[.22.]. .Iadd.37 .Iaddend.in which
said marginal portions of said heart valve are doubled over said
framework. .[.24. A device as recited in claim 22 in which said
heart valve includes a free marginal edge extending from said one
end for providing a means for attachment to a heart..]. .[.25. A
device as recited in claim 22 including in addition a ring of
clothlike or spongelike material circumscribing said
framework inwardly of said one end of said framework..]. 26. A
device as recited in claim .[.22.]. .Iadd.37 .Iaddend.including in
addition a sleeve .Iadd.of cloth material .Iaddend.receiving said
arms, portions of said heart valve extending over said sleeve.
.[.27. A device as recited in claim 26 in which said sleeve is of
cloth material..]. .[.28. A heart valve assembly for use in the
mitral position comprising
a stent,
said stent including a generally tubular framework having spaced
apexes at one end and arms interconnecting said apexes,
said arms being inclined away from said apexes at locations
intermediate said apexes,
a ring extending outwardly of said arms adjacent the opposite end
of said framework,
an annular member circumscribing said arms,
means attaching said annular member to said framework,
a heart valve on said framework,
said heart valve having cusps having marginal portions overlapping
said framework,
means attaching said marginal portions to said framework,
said heart valve having additional portions extending over the end
of said ring remote from said apexes and toward said annular
member,
and means attaching said additional portion of said heart valve to
said annular member..]. .[.29. A device as recited in claim 28 in
which said annular member is constructed of felt..]. .[.30. A
device as recited in claim 28 including in addition a layer of
cloth over said overlapping marginal portions for covering the same
and providing for fibrous ingrowth upon being grafted in a
heart..]. .[.31. A device as recited in claim 28 in which said ring
is integral with said framework..]. .[.32. A device as recited in
claim 28 in which said ring is a cloth member attached to said
arms..]. .[.33. A stent for a heart valve comprising
a framework of annular configuration,
said framework including spaced apical portions and arms
interconnecting said apical portions,
for thereby providing an attachment for the commissures and cusps
of a heart valve,
a ring attached to said framework for providing a means for
attachment of said framework in a heart in the mitral position,
said ring circumscribing said framework adjacent said arms,
and an annular member interposed between said ring and said
framework for providing a bed for the attachment of portions of the
valve extended over the atrial aspect of said ring, and for
providing a hemodynamic seal upon grafting in a heart..]. .[.34. A
device as recited in claim 33 in which
said annular member is constructed of felt..]. 35. A stent for
.[.a.]. .Iadd.an animal .Iaddend.heart valve .Iadd.for supporting
such a heart valve in its natural contour .Iaddend.comprising
a framework of annular configuration,
said framework including .Iadd.three .Iaddend.spaced apical
portions .Iadd.at one end thereof .Iaddend.and arms interconnecting
said apical portions,
for thereby providing an attachment for the commissures and cusps
of a heart valve, .Iadd.said arms being in two sets spaced apart
axially, one of said sets being adjacent said apical portions and
the other of said sets being remote from said apical portions, said
arms in at least the one of said sets adjacent said apical portions
being curved in a scalloped configuration so as to incline away
from said apical portions intermediate said apical portions for
conforming to the shape of and supporting the margins of the cusps
of an animal heart valve such that the peripheral parts of said
heart valve can be attached to said arms while preserving the
natural contour of said heart valve, .Iaddend.
each of said apical portions being rounded .Iadd.convexly as viewed
from said one end, .Iaddend.and having a substantial
circumferential dimension for permitting said apical portions to
accommodate heart valves of different dimensions, said apical
portions being annular and of generally
oval shape. .[.36. A stent for a heart valve comprising
a framework of annular configuration,
said framework including spaced apical portions,
arms interconnecting said apical portions, for thereby providing an
attachment for the commissures and cusps of a heart valve, said
arms inclining away from said apical portions intermediate said
apical portions, said arms including a set of at least two of said
arms intermediate each adjacent pair of apical portions,
said arms in each set being spaced apart axially and generally
equally spaced from the axis of said framework, thereby providing
arms adjacent said apical portions and arms remote from said apical
portions,
a ring circumscribing said framework adjacent said remote arms,
and a relatively short post extending axially away from said apical
portions at the junctures of said remote arms,
said posts including portions bent outwardly to provide a
radially
projecting means for securing said ring to said framework..].
.Iadd.37. A heart valve assembly comprising
a stent, said stent including
a generally tubular framework having three apexes at one end
thereof,
said apexes being rounded convexly as viewed from said one end and
being spaced apart unequal angular distances,
each of said apexes having a substantial circumferential
dimension,
a first set of arms adjacent and interconnecting said apexes, and a
second set of arms spaced from said first set of arms and remote
from said apexes,
all of said arms of at least said first set being arcuate so as to
incline away from said apexes at locations intermediate said
apexes,
an animal heart valve on said framework,
said heart valve having commissures substantially at said apexes
and cusps having marginal portions substantially conforming to said
arms of said first set, the marginal portions of said heart valve
overlapping said framework so that the interior of said framework
is covered by said marginal portions of said heart valve,
sutures attaching said heart valve to said framework so that said
commissures are secured to said apexes and said marginal portions
of said cusps are secured to said arms, and said heart valve is
supported in substantially its natural contour with all its
peripheral parts securely attached to said framework,
and a ring of clothlike or spongelike material circumscribing said
framework inwardly of said one end of said framework for conforming
to and providing a hemodynamic seal at the aortic root of a heart
upon implantation. .Iaddend.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a supporting framework, or stent, for a
natural or synthetic heart valve.
The prior art
At the present time, surgical techniques allow the transplanting of
aortic valves in the hearts of human patients, where they are
located in either the aortic or mitral position. In such an
operation, a natural valve from an animal or human, or
alternatively a synthetic valve, is implanted in the heart. There
exists, however, the need for an improved means for securing and
supporting the valve in the heart to assure its proper functioning
and to avoid clotting or other difficulties. In addition, there has
been lacking a suitable means for preparing natural heart valves in
advance for implantation so that they may be stored until the
requirement for use arises.
SUMMARY OF THE INVENTION
The present invention provides a stent for natural or synthetic
heart valves that results in an improved means for supporting and
grafting the heart valve in the patient. This invention makes
possible the preparation of natural heart valves, such as those
from animals or from humans, which are applied to the stents under
controlled conditions and may be stored suitably so that an
adequate supply of the heart valves may be maintained.
The stent is usable for valves to be used in both the aortic and
mitral positions. It comprises a frame of generally tubular
configuration that includes three arcuate apexes interconnected by
support arms. The apexes are positioned at the approximate
locations of the aortic commissures. By having an arcuate contour,
they have a finite dimension in a direction circumferential of the
stent, so that dimension variations in the valves may be
accommodated. Upper and lower support arms interconnect the apexes,
being scalloped to extend downwardly intermediate the apexes. Both
serve as a means for securing the perimeter of the valve cusps to
the stent by suturing or other appropriate means. Preferably, the
stent is of deflectable material, such as stainless steel having
some malleability, so that the upper support arms may be bent
upwardly. By virtus of their scalloped shape, this increases the
spacing of the arms from the central axis of the stent, so that the
stent may be increased in width to fit individual valves of
different configurations. The scalloped shape of the upper arms
also allows placement of the valve in the aortic position without
obstructing the coronary ostia.
When the stent is used for valves that are to be installed in the
mitral position, it may be provided with a ring outwardly of the
lower support arms. This ring provides a means for affixing the
stent to the heart. A felt ring is secured to the stent at the
location of the attaching ring, providing a hemodynamic seal and a
suitable bed over which tissue can be attached. The mitral leaflet
and endocardium are brought over the atrial aspect of the attaching
ring and affixed to the felt ring.
Thus, as either version of the stent is used, there is no exposure
of metal to the portions of the heart where clotting is a problem,
and with only tissue exposed to the blood in the critical areas
tendencies toward clotting are minimized.
An object of this invention is to provide an improved stent for
natural or synthetic heart valves.
Another object of this invention is to provide a heart valve stent
that can accommodate valves of different dimensions.
A further object of this invention is to provide an arrangement by
which a heart valve is supported on a stent and secured so that
only tissue or other material that does not promote the formation
of clots will be exposed in critical areas of the heart when
clotting might occur.
An additional object of this invention is to provide a stent that
permits advance preparation under controlled conditions of heart
valves which may be stored under suitable conditions until
required.
A still further object of this invention is to provide a stent
contoured to accommodate animal heart valves for use in
xenografts.
These and other objects will become apparent from the following
detailed description taken in connection with the accompanying
drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view of the stent of this invention
constructed for use in the aortic position;
FIG. 2 is an enlarged fragmentary sectional view taken along line
2--2 of FIG. 1, illustrating the rounded cross-sectional contour of
the elements of the stent;
FIG. 3 is a perspective view, partialy broken away, showing the
stent of FIG. 1 with an aortic valve affixed thereto;
FIG. 4 is a side elevational view of the stent, showing how the
support arms may be deflected for increasing the transverse
dimension;
FIG. 5 is a perspective view of the stent constructed for use in
the mitral position;
FIG. 6 is a perspective view, partially broken away, of an assembly
of the stent of FIG. 5 and a heart valve;
FIG. 7 is a perspective view, partially broken away, illustrating a
modified attachment of the heart valve to the stent;
FIG. 8 is an enlarged sectional view taken along line 8--8 of FIG.
7;
FIG. 9 is a sectional view similar to FIG. 8 with the addition of a
ring around the outer perimeter of the assembly;
FIG. 10 is a view similar to FIG. 9, but in which a cloth member
has been applied over the stent prior to attachment of the heart
valve;
FIG. 11 is a perspective view, partially broken away, of a heart
valve assembly for use in the mitral position in which a cloth
covering is provided over certain marginal portions;
FIG. 12 is a perspective view of a heart valve for use in the
mitral position in which there is a cloth attaching ring instead of
a metal ring; and
FIG. 13 is an enlarged sectional view taken along line 13--13 of
FIG. 12.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The stent 10, shown in FIGS. 1, 2 and 3, is for use in the aortic
or pulmonary location. It constitutes an annular framework,
circular in plan, that may be constructed of noncorrosive metal,
such as stainless steel, or of plastic. When made of metal, it
should have some malleability which permits the device to be
deflected to alter its shape slightly from that illustrated. This
has the advantage of allowing it to accommodate valves of different
dimensions, as will be explained below. Preferably, the metal stent
is produced from a single piece of material. This avoids any
welded, brazed or other connections, eliminating the likelihood of
galvanic corrosion after it has been implanted. All portions of the
stent are rounded at their edges so that no sharp corners are
presented (see FIG. 2).
The stent 10 includes three apical portions 11, 12 and 13, which
are of generally oval shape including rounded upper portions. The
central areas 14, 15 and 16 of the apical portions 11, 12 and 13
are cut away. Particularly when the stent is intended for use with
animal valves, the apical portions are not distributed evenly
around the perimeter of the stent 10. There is an equal angular
spacing between the apical portions 11 and 12, and between the
apical portions 12 and 13. However, the spacing between the apical
portions 11 and 13 is less than that between the other two
adjoining apexes. Usually, the spacing between the apexes 11 and 13
is within the range of approximately 17% to 33% under the spacing
of the other apexes, preferably around 20% to 25% less. This is in
order that the stent will conform to the spacing of the commissures
of the valve to be applied to it, which, for animals, is very close
to this proportioning.
Interconnecting the lower sides of the apical portions 11, 12 and
13 are upper support bars 18, 19 and 20. These are scalloped, being
curved away from the apical portions 11, 12 and 13 so that they are
concave toward the end of the stent where the apical parts are
located.
Beneath the apexes 11, 12 and 13, as the device is illustrated, are
short depending posts 22, 23 and 24 which extend parallel to the
axis of the stent 10. To these posts are attached lower support
arms 25, 26 and 27. The latter elements are shaped generally the
same as the upper support arms 18, 19 and 20 and are spaced an
equivalent distance from the stent axis. Again, therefore, the
lower support arms are of scalloped configuration, being inclined
downwardly intermediate the support posts. However, the lower
support arms 25, 26 and 27 are not scalloped as deeply as are the
upper arms.
As shown in FIG. 3, an animal aortic valve 28 is associated with
the stent 10 for use in a xenograft. The valve 28 is secured to the
stent by appropriate means, such as sutures 29. The valve
commissures are positioned at the apexes, while the margins of the
cusps conform to the scalloped configuration of the support arms.
The marginal portions 30 and 31 of the valve cusps are extended
over the support arms of the stent and overlap them, being doubled
over the stent where the attachments are made. Consequently, the
stent 10 is covered after the valve 28 is affixed.
The presence of the various apexes and support arms assures that
there is a portion of the stent conforming to the shape of the
valve 28 that is available for secure attachment of all peripheral
parts of the valve. The arcuate upper portions of the apexes 11, 12
and 13 allow latitude in positioning of the commissures of the
valve. There are some dimensional differences among all natural
valves, and the spacing of the commissures may vary to some degree.
With the upper portions of the apexes 11, 12 and 13 being arcuate,
valves of different proportions may be accommodated and allowed to
assume their natural contour while still being afforded ready and
appropriate locations for attachment. In other words, if the
spacing of the commissures does not correspond exactly to the
distances between the centers of the apexes, the commissures
nevertheless may be affixed to side portions of the apexes and
thereby supported properly and in conformance with the natural
valve contour.
Another advantage lies in the scalloped configuration and
deflectable characteristics of the upper support arms 18, 19 and
20. By bending the support arm upwardly, as indicated in phantom in
FIG. 4, the spacing of the arm from the central axis of the stent
10 becomes increased. Therefore, for valves of larger dimensions or
those of irregular proportions, the arms may be deflected as
required to assure that the stent provides the precise fit needed
for the valve. Accordingly, the stent may be given an exact
configuration to conform to the individual valve being assoicated
with it. The upper arms 18, 19 and 20 are scalloped more deeply
than are the lower support arms to provide for a maximum amount of
dimensional variation upon deflection of the upper arms.
This advantage is realized with stents of metal construction in
which the upper support arms may be deflected. This does not hold
true, however, for stents made of plastic, as suitable plastics
cannot be bent to assume different shapes permanently. The
scalloped configuration of the upper support arms not only makes
dimensional changes possible, but also allows placement of the
valve in the aortic position without obstructing the coronary
ostia.
The stent 32 shown in FIG. 5, for mitral or tricuspid location, has
the same general configuration as the aortic stent, but is of
larger and slightly heavier construction. Additionally, it includes
an outer ring, which is used in securing the stent to the
heart.
The stent 32, as illustrated, includes rounded apexes 33, 34 and
35, each being cut away interiorly so as to be of annular and
generally oval configuration. Downwardly scalloped upper support
arms 36, 37 and 38 interconnect the apexes. Beneath the upper arms
are similarly shaped but more shallowly scalloped lower support
arms 40, 41 and 42. These connect at their ends to posts 43, 44 and
45 that extend below the apexes 33, 34 and 35, respectively.
Additional short posts 46, 47 and 48 extend downwardly, as the
device is shown, from the junctures between the adjacent lower
support arms 40, 41 and 42. At their upper ends, the posts 46, 47
and 48 are generally parallel to the axis. The bottom portions of
the posts 46, 47 and 48, however, are bent substantially at right
angles to extend generally radially to an outer attaching ring 50.
The latter element is circular and of greater diameter than the
annulus defined by the support arms.
The attachment of the valve 51 to the stent 32 for the mitral
position is essentially the same as that of the valve 28 to the
aortic stent 10. Again, suturing 52 normally is employed to effect
the attachment of the marginal portions of the valve 51. In
addition, however, an annular member 53 of felt or other suitable
material is positioned around the stent 32 between the outer ring
50 and the annular structure provided by the posts 46, 47 and 48
and the lower arms 40, 41 and 42. The felt ring 53 provides a
hemodynamic seal and a suitable bed over which tissue can be
affixed. The mitral leaflet and the endocardium 54 are brought over
the atrial aspect of the outer ring 50 (i.e., the end remote from
the apexes) and affixed by sutures to the felt ring 53. This serves
an important function in the prevention of blood clots. The ring 50
and other parts of the stent 32 are completely covered in the
portions of the assembly that are positioned in localities of the
heart where clotting is likely to take place. Therefore, in the
critical zones of the heart where a thrombus may occur, any
exposure of material that might promote clotting is minimized. The
ring 50 provides a stable and secure means for affixing the stent
and associated mitral valve to the heart. This is accomplished
normally by sutures to attach the valve in the mitral position
between the left atrium and ventricle.
Various modifications may be made in the manner in which the heart
valve is mounted on the stent. For example, as shown in FIGS. 7 and
8, the heart valve 55 attached to the aortic stent 10 is not
doubled over the upper perimeter of the stent. In other words, the
upper margin of the heart valve is not arranged as illustrated in
FIG. 3, where the margin 31 is shown doubled over the upper arms
18, 19 and 20 and the apexes 11, 12 and 13. Instead, the margin 56
of the heart valve 55 of FIGS. 7 and 8 is allowed to project beyond
the stent to provide a free edge portion of tissue. Inwardly of
this, sutures 57 secure the upper part of the heart valve to the
stent. The marginal edge portion 56 provides a flap of material
which may be used in attaching the heart valve 55 to the heart
wall. This technique is preferred in some instances.
The arrangement of FIG. 9 is similar to that of FIG. 8 except that
a ring has been added around the perimeter of the stent. This is an
annular member, normally of a suitable cloth such as felt, or of
sponge, held in place by sutures and extending around the exterior
of the support arms below the apexes of the stent. This ring
provides a suitable bed for fibrous ingrowth after the grafting of
the valve in the heart. This also provides a compliant member
capable of conforming to an irregular aortic root to assure a snug
fit and a hemodynamic seal. Moreover, the annulus of the valve
supported on the stent often is irregular, further adding to the
desirability of the exteriorly applied member in such
instances.
While illustrated in FIG. 9 in conjunction with an attachment of
the heart valve to leave a free marginal flap 56, the ring 58 also
is applicable when the heart valve is attached upon a doubling over
of the tissue as indicated in FIG. 3. The ring 58 may be used on
either the stent 10 for the aortic position or the stent 32 for the
mitral position.
FIG. 10 illustrates a further modification in which an annular
cloth element 60 is provided on the stent prior to attachment of
the heart valve. The cloth 60 is, in effect, tubular in shape,
providing a sleeve that has a continuous transverse wall which
overlaps and receives the upper and lower arms of the stent.
However, the annular cloth member 60 does not extend over the stent
apexes. Normally, a ring 58 will be utilized in conjunction with an
assembly that embodies the annular cloth element 60. This cloth
covering of the inner and outer stent surfaces, which can be
applied to either the aortic or the mitral stent, provides a means
by which the tissue is more easily attached to the stent. It
results also in a matrix for ingrowth and subsequent fixation of
the donor valve by the host tissue.
In FIG. 11, there is illustrated a heart valve 51 on the stent 32
for use in the mitral position similar to the arrangement of FIG. 6
but with a cloth layer 62 added over the periphery of the stent and
inwardly of the outer ring 50. The layer of cloth 62 follows the
contour of the stent and is fixed in place by sutures. The cloth
layer 62 adds a matrix for fibrous ingrowth, facilitating the
binding of the host tissue to the graft tissue. It also covers the
sutures and the ragged edges of the margins of the heart valve that
overlap the framework of the stent, providing an assembly of an
improved neat appearance.
In the arrangement of FIGS. 12 and 13, the stent is intended for
use in the mitral position, but is constructed without the metal
ring 50 around its periphery. Instead, a cloth ring is provided,
which serves a similar purpose, providing a means for attachment to
the heart. The stent 63 shown in FIG. 12 is similar to the stent 32
in that it is provided with a comparable grouping of apexes and
support arms, and larger and heavier than the stents for use in the
aortic position. Thus, there are apexes 64, 65 and 66
interconnected by downwardly scalloped upper arms 67, 68 and 69
beneath which are lower arms 70, 71 and 72. Extending around the
bottom periphery of the stent is a cloth ring 73. This is of
doubled-over construction, with the lower arms 70, 71 and 72
received inside it. The outer edge, where the attachment is made to
complete the double-walled cloth construction, is inwardly folded,
as seen in FIG. 13. At the locations of the posts 75, 76 and 77,
where the lower arms are connected to the upper portion of the
stent, it is necessary to omit the outer layer of the cloth ring
73, as shown in FIG. 12.
It is to be remembered that the heart has four primary valves: two
of which carry the blood away from the heart, the aortic and
pulmonary valves; and two atrioventricular valves, the mitral and
tricuspid valves. Since the aortic and pulmonary valves are similar
in configuration as are the mitral and tricuspid valves, and since
the device referred to herein as an aortic valve stent is equally
suited to the pulmonary location, it is to be understood that the
terms aortic and mitral are descriptive of the type of application
and are not restrictive to a particular anatomic location.
The present invention also comprehends a device in which the
spacings between the various apical portions are all unequal (each
space being different from each other space). Using one space as
the reference the second is approximately 4-10% less than said
reference (space), and the third space is 17% to 33% less than said
reference (space).
It is to be understood that cloth may be used to cover the frame in
any one of a number of configurations. The cloth may be a seamless
cylinder, or flat stock cut, formed and seamed, or specially
preformed material. The methods described previously in this
specification are by way of specific illustration.
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