U.S. patent application number 10/245000 was filed with the patent office on 2003-01-16 for flexible heart valve leaflets with concave free edges.
Invention is credited to Cao, Dongbu.
Application Number | 20030014105 10/245000 |
Document ID | / |
Family ID | 24683245 |
Filed Date | 2003-01-16 |
United States Patent
Application |
20030014105 |
Kind Code |
A1 |
Cao, Dongbu |
January 16, 2003 |
Flexible heart valve leaflets with concave free edges
Abstract
A flexible prosthetic tissue-type heart valve having commissures
that are substantially decoupled from a cusp support structure. The
valve includes three leaflets having arcuate cusp edges and opposed
concave shaped free edges, with outwardly-directed attachment tabs
therebetween. A cusp support structure in either one or more pieces
attaches to the leaflet cusp edges. Three commissures are each
formed partly with an axially-extending insert member to which two
adjacent leaflet tabs attach. An inverted V-shaped clip maintains
close contact between the adjacent leaflet tabs and provides a
stress-relieving clamping action in conjunction with the insert
member. The insert member attaches about its lower end to base
sections of the cusp support structure, or to an intermediate
sewing ring, so that the commissures may pivot about the cusp
support structure. The sewing band is scalloped and enables
attachment of the valve along the scalloped aortic root so as to
couple the valve to the natural motion of the aorta. Increased
vibrational damping results from this biomechanical coupling.
Inventors: |
Cao, Dongbu; (Parma,
OH) |
Correspondence
Address: |
Edwards Lifesciences LLC
Law Dept.
One Edwards Way
Irvine
CA
92614
US
|
Family ID: |
24683245 |
Appl. No.: |
10/245000 |
Filed: |
September 17, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10245000 |
Sep 17, 2002 |
|
|
|
09668660 |
Sep 22, 2000 |
|
|
|
6461382 |
|
|
|
|
Current U.S.
Class: |
623/2.15 ;
623/2.41 |
Current CPC
Class: |
A61F 2/2409 20130101;
A61F 2/2412 20130101; A61F 2/2418 20130101; A61F 2220/0075
20130101 |
Class at
Publication: |
623/2.15 ;
623/2.41 |
International
Class: |
A61F 002/24 |
Claims
What is claimed is:
1. A tissue-type heart valve adapted to have reduced stress risers
in the leaflets, comprising: three leaflets each having arcuate
cusp edges on their inflow ends, free edges on the outflow ends,
and two side tabs, the free edges extending between the side tabs
in a concave fashion.
2. The heart valve of claim 1, further including commissure posts
to which adjacent leaflet tabs attach, each post including an
insert around which the leaflet tabs wrap, the valve further
including a cusp support structure attached to the cusps of each
leaflet, wherein the insert is pivotally coupled to the cusp
support structure.
3. The heart valve of claim 2, further a sewing band for attachment
to a valve annulus that surrounds the cusp support structure and is
truncated in the region of the inserts to permit direct attachment
of the commissure posts to an anatomical wall structure adjacent
the annulus.
4. The heart valve of claim 1, wherein each leaflet free edge
further includes a region that is above a line extending between
the middle of the free edge and the side tabs so that the region is
not placed in direct tension during closure of the valve.
5. The heart valve of claim 4, wherein the region is generally
triangular and culminates in an apex.
6. The heart valve of claim 5, wherein a concave filet exists
between the apex and the side tab.
Description
RELATED APPLICATION
[0001] The present application is a divisional of application Ser.
No. 09/668,660, filed on Sep. 22, 2000.
FIELD OF THE INVENTION
[0002] The present invention relates generally to medical devices
and particularly to flexible tissue-type heart valve prostheses
designed to attach along the valve annulus and adjacent anatomical
wall structure.
BACKGROUND OF THE INVENTION
[0003] Prosthetic heart valves are used to replace damaged or
diseased heart valves. In vertebrate animals, the heart is a hollow
muscular organ having four pumping chambers: the left and right
atria and the left and right ventricles, each provided with its own
one-way valve. The natural heart valves are identified as the
aortic, mitral (or bicuspid), tricuspid and pulmonary valves.
Prosthetic heart valves can be used to replace any of these
naturally occurring valves, although repair or replacement of the
aortic or mitral valves is most common because they reside in the
left side of the heart where pressures are the greatest.
[0004] Where replacement of a heart valve is indicated, the
dysfunctional valve is typically cut out and replaced with either a
mechanical valve, or a tissue valve. Tissue valves are often
preferred over mechanical valves because they typically do not
require long-term treatment with anticoagulants. The most common
tissue valves are constructed with whole porcine (pig) valves, or
with separate leaflets cut from bovine (cow) pericardium. Although
so-called stentless valves, comprising a section of porcine aorta
along with the valve, are available, the most widely used valves
include some form of stent or synthetic leaflet support. Typically,
a wireform having alternating arcuate cusps and upstanding
commissures supports the leaflets within the valve, in combination
with an annular stent and a sewing ring. The alternating cusps and
commissures mimic the natural contour of leaflet attachment.
Importantly, the wireform provides continuous support for each
leaflet along the cusp region so as to better simulate the natural
support structure. However, the tissue material tends to calcify
after the long term implantation. That is, calcium compound
accumulates in the tissue leaflets, eventually making them stiff.
The tissue leaflet area along the wireform is especially
susceptible to the calcification because of the high bending
stresses imposed at that interface.
[0005] Many prior art stented valves are relatively rigid,
typically containing an annular metal or plastic stent ring that
provides internal support for an outer sewing ring and the
wireform-mounted valve cusps and commissures. This design also
provides a basic structure to facilitate valve assembly, which is
hand made by highly skilled workers. Although this type of valve
has been proven effective, some researchers assert that it
excessively occludes the natural orifice area, and thus reduces
potential blood flow therethrough. Although stentless valves
generally provide greater orifice area, they do not have the
advantage of the reliable leaflet support structure of stented
valves. Moreover, a stentless valve is more difficult to make, and
the implantation of such a device requires much more skill and
experience of the cardiac surgeon. Only a few heart centers in the
United States are able to perform such a procedure and thus the use
of stentless valves is restricted.
[0006] More flexible stented valves have been proposed, including
U.S. Pat. No. 5,549,665 to Vesely, et al. In the Vesely patent, the
valve stent commissures may attach to the ascending aorta and may
pivot outward for the purpose of reducing localized stresses in the
leaflets: The stent commissures are prevented by stops from inward
pivoting to ensure proper valve functioning. However, the stent
structure appears to be relatively complex, with numerous interior
surfaces, thus raising concerns of thromboembolisms and even
component failure.
[0007] In view of the foregoing, it is evident that an improved
flexible valve that addresses the apparent deficiencies in existing
heart valves is necessary and desired. In particular, there is a
need for a bioprosthetic valve that provides a large orifice
opening and has a dimensionally stable stent to facilitate the
valve assembly and implantation.
SUMMARY OF THE INVENTION
[0008] This invention details a partially stented valve design. The
stent is to be completed by the natural aortic root when the valve
is implanted. The final valve conforms to the movement of the
natural aortic root and therefore provides a larger orifice area
like a stentless valve. The valve, however, includes a stent
structure that will facilitate the valve assembly and implantation
procedures. The movement of the stent structure and leaflet shape
also helps to reduce stress concentration in the valve leaflet.
[0009] In one embodiment, the present invention provides a heart
valve for implantation in an annulus of a heart having commissures
on an outflow end adapted to move in conformity with an anatomical
wall structure adjacent the annulus. The heart valve comprises
three leaflets made of a biocompatible and compliant material, each
leaflet having a rounded cusp edge opposite a free edge, and a pair
of generally oppositely-directed tabs separating the cusp edge and
free edge. A cusp support structure generally defines a ring and a
valve axis and has three rounded sections each adapted to conform
to the cusp edge of the leaflets. The cusp edge of each leaflet is
attached to a different rounded section of the cusp support
structure so that the three leaflets are arranged generally evenly
about the valve axis, the attached leaflet cusp edges and rounded
sections together defining valve cusps curving toward an inflow end
of the valve. Three valve commissure posts disposed between the
valve cusps project generally axially toward an outflow end of the
valve. The commissure posts are defined by two adjacent leaflet
tabs, a generally axially extending insert member, and an inverted
V-shaped clip positioned radially inward from the insert member.
The adjacent leaflet tabs are juxtaposed to extend radially outward
with respect to the axis through the inverted V-shaped clip and are
wrapped around and secured to the insert member, an inflow end of
each commissure post is generally pivotally coupled with respect to
the cusp support structure so as to permit both radially inward and
outward movement thereof, the valve commissure posts being
attachable to the anatomical wall structure. Finally, a sewing band
shaped to follow the valve cusps and being attached therealong
provides a platform for implanting the heart valve such that the
valve cusps are attachable adjacent the annulus or in the
supraannular position (i.e., just above the annulus).
[0010] In another aspect of the invention, an aortic heart valve
adapted to have reduced vibration-related strain is provided,
comprising three leaflets each having arcuate cusp edges on their
inflow ends, free edges on the outflow ends, and two side tabs.
Three cusp supports each attach to the cusp edge of one of the
leaflets to define valve cusps, the cusps being disposed generally
in a circle about a valve axis at an inflow end of the valve. Three
generally axially extending commissure posts are disposed in
between the valve cusps around the circle and extend toward an
outflow end of the valve. The commissure posts are defined by a
relatively rigid insert and adjacent tabs of two leaflets attached
thereto. The inserts are structurally separate from the three cusp
supports but coupled thereto at an end closest to the cusp supports
to enable radial pivoting of the outflow end of the commissure
posts. Finally, a sewing band shaped to follow the valve cusps and
attached therealong is provided. The sewing band and inserts
providing a platform for implanting the aortic heart valve such
that the valve cusps are attachable adjacent the annulus, and the
inserts are attachable to the ascending aorta. In this manner, the
commissure posts are freely moveable with respect to the valve
cusps so as to generally pivot radially in and out in conjunction
with movement of the ascending aorta during the repetitive cycles
of systole and diastole such that the heart valve is dynamically
coupled to the damping characteristics of the ascending aorta.
[0011] In a further aspect of the invention, a tissue-type heart
valve adapted to have reduced stress risers in the leaflets,
comprises three leaflets each having arcuate cusp edges on their
inflow ends, free edges on the outflow ends, and two side tabs, the
free edges extending between the side tabs in a concave fashion.
The valve may include commissure posts to which adjacent leaflet
tabs attach, each post including an insert around which the leaflet
tabs wrap. The valve further may include a cusp support structure
attached to the cusps of each leaflet, wherein the insert is
pivotally coupled to the cusp support structure. Desirably, a
sewing band for attachment to a valve annulus that surrounds the
cusp support structure and is truncated in the region of the
inserts to permit direct attachment of the commissure posts to an
anatomical wall structure adjacent the annulus. Each leaflet free
edge further may include a region that is above a line extending
between the middle of the free edge and the side tabs so that the
region is not placed in direct tension during closure of the valve.
The region is preferably generally triangular and culminates in an
apex, and a concave filet may exist between the apex and the side
tab.
[0012] A further understanding of the nature advantages of the
invention will become apparent by reference to the remaining
portions of the specification and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is an assembled perspective view of the flexible
heart valve of the present invention;
[0014] FIG. 2 is an exploded perspective view of the heart valve of
FIG. 1;
[0015] FIG. 2A is a sectional view through a cusp support structure
of the heart valve of FIG. 1, taken through line 2A-2A of FIG.
2;
[0016] FIG. 3 is a perspective view of components of the three
commissures of the heart valve of FIG. 1 positioned with respect to
the cusp support structure shown in phantom;
[0017] FIG. 4A is an elevational view of an inverted V-shaped clip
forming a portion of each of the valve commissures;
[0018] FIG. 4B is a perspective view of the inverted V-shaped clip
of FIG. 4A showing a fabric-covering thereon;
[0019] FIGS. 5A and 5B are front and side elevational views,
respectively, of an insert member that forms another portion of
each of the valve commissures;
[0020] FIG. 6 is a vertical sectional view through a valve cusp
taken along line 6-6 of FIG. 1;
[0021] FIG. 7 is a vertical sectional view through a valve
commissure taken along line 7-7 of FIG. 1;
[0022] FIG. 8 is a horizontal sectional view through a valve
commissure taken along line 8-8 of FIG. 1;
[0023] FIG. 9 is a perspective view of an alternative three-piece
cusp support structure for the flexible valve of the present
invention, also showing the positioning of valve commissure
components;
[0024] FIG. 10 is an elevational view of the alternative cusp
support structure and valve commissure components of FIG. 9,
further illustrating a sewing band in phantom;
[0025] FIG. 11 is a top plan view of the alternative three-piece
cusp support structure of FIG. 9;
[0026] FIG. 12 is a plan view of a valve leaflet of the prior
art;
[0027] FIG. 13A is a plan view of a first embodiment of a valve
leaflet for use in the flexible valve of the present invention;
[0028] FIG. 13B is a plan view of a second embodiment of a valve
leaflet for use in the flexible valve of the present invention;
[0029] FIG. 14 is a perspective view of a cusp support structure as
seen in FIG. 2, and alternative commissure components for use in a
flexible valve of the present invention;
[0030] FIG. 15 is an elevational view of the assembly of FIG. 14,
further illustrating a sewing band in phantom; and
[0031] FIGS. 16A and 16B are front and side elevational views,
respectively, of an insert member of the valve of FIG. 14 coupled
to a cusp support structure.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] The following detailed description, and the figures to which
it refers, are provided for the purpose of describing examples and
specific embodiments of the invention only and are not intended to
exhaustively describe all possible examples and embodiments of the
invention. Identical elements and features are given the same
reference number as appropriate for purposes of describing the
various embodiments of the present invention.
[0033] Referring now to FIGS. 1 and 2, a replacement tissue type
heart valve 21 of the present invention for implantation in an
annulus of a heart is constructed about a valve axis 25 that
defines an outflow end 27 and an inflow end 29. The valve includes
commissures 23 directed to the outflow end and adapted to move in
conformity with an anatomical wall structure adjacent the annulus
of the heart. Although the valve 21 of the present invention is
particularly suitable for implantation at the aortic valve
position, it may also function adequately in other valve positions.
The valve has three leaflets 31 made of a biocompatible compliant
material, each of which has a rounded cusp edge 33 opposite a free
edge 35 and a pair of generally oppositely-directed tabs 37
separating the cusp edge and the free edge. The specific shapes of
alternative embodiments of the leaflets 31 of the present invention
are shown in FIGS. 13A and 13B, and will be described in more
detail below.
[0034] A valve cusp support structure 39 is provided, generally
defining a ring comprised of three rounded sections 41 connected by
commissure base sections 43. The entire support structure 39,
including the rounded sections 41 and base sections 43, is covered
with a fabric sleeve 44. Each of the rounded sections 41 conforms
and attaches to a rounded cusp edge 33 of a leaflet via the fabric
sleeve 44. As seen in the cross-section of FIG. 2A, the fabric
sleeve 44 exhibits a flap 47 formed by juxtaposed free ends of the
fabric material to which the cusp edge 33 of each leaflet 31
attaches, such as with sutures (not shown). The cusp edge 33 of
each leaflet 31 is attached to a different rounded section 41 of
the cusp support structure 39 so that the three leaflets 31 are
arranged generally evenly distributed 120.degree. apart about the
valve axis 25. The attached leaflet cusp edges 33 and rounded
sections 41 together define valve cusps 45 concavely curved toward
the inflow end 29 of the valve.
[0035] The three valve commissure posts 23 are disposed between the
valve cusps 45 and project generally axially toward the outflow end
27 of the valve. The commissure posts 23 include a generally
axially extending insert member 51 attached to two adjoining
leaflet tabs 37, here shown sutured together at butt joint 49.
Alternatively, as will be described below with respect to FIG. 8,
the leaflet tabs 37 may overlap and can be mutually attached via
stitching through holes in the insert member 51. The leaflet free
edges 35 coapt in the middle of the valve and the free edges of
each two adjacent leaflets are juxtaposed so that the tabs 37
extend radially outwardly from the valve axis 25 through an
inverted V-shaped clip 53 positioned radially inward from the
insert member 51. Each insert member 51 is sutured to the cover
fabric of the commissure base section 43 so as to permit both
radially inward and outward movement of the outflow end of the
commissure posts. This generally pivoting attachment (shown by
arrow 54 in FIG. 7) may be accomplished in a number of ways,
several of which are disclosed herein, and to some extent decouples
the radial movement of the valve commissures 23 from its cusps
45.
[0036] A sewing band 55 shaped to follow the valve cusps 45 and to
an extent the valve commissures 23 provides a platform for
attaching the heart valve to vestigial heart tissue, such as the
aortic annulus or aortic root tissue. As partially seen in FIG. 1,
the sewing band 55 is encompassed within a fabric cover 61 (shown
partially cutaway). The valve cusps 45 are attachable adjacent the
annulus with the valve commissures 23 attachable to the adjacent
anatomical wall structure itself. Consequently, when implanted,
structural support for each valve commissure 23 is provided by the
native aorta, through the V-shaped clip 53 and insert member 51. In
the preferred embodiment, the valve 21 is attached to the root
tissue that comprised part of the native aortic heart valve.
Attachment in this manner allows the replacement valve to more
freely move and thus exhibit greater flexibility to match the blood
flow capacity of the native aortic heart valve. Moreover, this
biomechanical coupling provides natural tissue damping to help
suppress excessive vibrations within the valve 21 during its rapid
closing.
[0037] Referring to the exploded view of FIG. 2, the component
parts of the invention will be described in more detail. As
mentioned, the three tissue leaflets 31 have a tab section 37, a
rounded cusp edge 33 and a free edge 35. The insert members 51 rest
on the relatively rigid fabric-covered commissure base sections 43
(in this embodiment a rod-like element), and are attached thereto.
For instance, sutures are passed through each insert member 51 and
around the associated commissure base section to allow the insert
member to move both radially inwardly and radially outwardly. This
allows the finished commissure posts (FIGS. 7 and 8) to move both
radially inwardly and radially outwardly. V-clips 53 and sewing
band 55 are shown in their relative orientation in FIG. 2 without
connecting structure, to be described below.
[0038] FIG. 3 shows the relative orientation of the V-shaped clip
53 (shown isolated in FIGS. 4A and 4B), and the insert member 51 on
the cusp support structure 39 (shown in phantom) when they are
assembled. The cusp support structure 39 may be formed in a
generally annular or ring like shape. The V-shaped clips 53, seen
in FIGS. 4A and 4B, cinch the tissue leaflet free edges 35 to the
commissure posts, as indicated in FIG. 8. In a preferred
embodiment, a shroud-like fabric cover 56 is provided around each
V-shaped clip 53 to facilitate attachment to the adjacent valve
components. FIGS. 5A and 5B show front and side views of the insert
member 51 having a series of through holes 52.
[0039] FIG. 6 is a sectional view taken along the 6-6 line of FIG.
1, showing the attachment of the rounded cusp edge 33 of the tissue
leaflet, the rounded section 41 of the cusp support structure 39
and the sewing band 55. The three pieces are sutured or otherwise
attached together in this manner at least along the valve cusps 45
shown in FIG. 1.
[0040] FIG. 7 illustrates one embodiment of the attachment of the
insert member 51 to the commissure base section 43 of the cusp
support structure utilizing a suture 59 looped through holes 52 in
the insert member and then around the base section. The insert 51
is thereby freely attached to the commissure base section 43 to
allow its outflow end to move radially inwardly and outwardly, as
indicated by arrow 54. The sewing band 55 is not connected to the
insert member 51 but instead receives each commissure base section
43 in a groove portion 60. An outflow flange 62 stops short of the
insert members 51 and the V-shaped clip 53. That is, the flange 62
of the sewing band 55 is axially truncated so as not to extend
fully up each commissure 23. In this arrangement, the valve
commissures 23 are exposed to the aortic wall so that they can be
sutured directly thereto.
[0041] In an alternative embodiment, the commissure base sections
43 of the cusp support structure 39 are omitted to result in three
separate cusp supports that attach to the sewing ring 55, such as
seen in FIG. 6. In such an alternative, each insert member 51 will
rest directly on the sewing ring, and its inflow end may be sutured
to the sewing ring.
[0042] 1. FIGS. 7 and 8 illustrate the complete structure of the
commissures 23 wherein adjacent leaflet tabs 37 wrapped around the
insert member 51 and are sutured together on the radially outward
side of the insert member. Fabric-covered V-shaped clip 53 is
placed over adjoining leaflet tabs 37 and the fabric cover 56
includes a shroud long enough to wrap around the insert member 51.
After the V-shaped clip 53 is placed over the leaflets at the
commissure 23, the shroud of the fabric cover 56 is pulled down to
cover the outward side of the insert member 51 and the leaflet tabs
37, and the free ends thereof are wrapped around the insert member
51 and sutured together (using sutures, not shown). Also, the
fabric cover 56 may be sutured to the insert member 51 and leaflet
tabs 37 through the aligned holes at the insert member 51 for
additional support, such as by using a stitch 57. The V-shaped
clips 53 are desirably formed of a flexible material that flexes
apart during an opening cycle of the valve wherein fluid flow
through the valve causes the free edges 35 of adjacent leaflet tabs
37 to separate.
[0043] In this manner the leaflet tabs 37 are anchored to the
commissures 23 by the clamping action between the insert 51 and the
V-shaped clip 53. That is, each leaflet 31 experiences radially
inward forces upon closing of the valve 21, which also tends to
pull the insert member 51 inwardly. Because the fabric cover 56
attaches to the surrounding native aorta, and thus the V-shaped
clip 53 is retained thereby, this radially inward movement of the
insert member 51 clamps the leaflet tabs 37 between the insert
member and the clip. This anchoring prevents the sutures, such as
suture 57, from being directly stressed and pulled apart through
the leaflet material when the valve closes by blood flow during
diastole. Further, this anchoring prevents any tissue stitches from
being exposing to direct hemodynamic loading and thus prevent
stress concentration.
[0044] FIGS. 9-11 show an alternative embodiment of the invention
wherein a cusp support structure 39' comprises three separate
rounded sections 65 each respectively supporting the rounded cusp
edge 33 of a leaflet. Adjacent rounded sections maybe
interconnected with separate connector sections 67 and intermediate
V-shaped clips 53. The connector sections 67 may be made of a
highly compliant material, for example a fabric, silicone or other
elastomer to allow the rounded sections to move with respect to one
another and more flexibly accommodate static or dynamic distortions
in the shape of the native heart tissue. As before, insert 51 and
V-shaped clips 53 are shown in the relative orientation as before
to form the valve commissures to which the leaflet tabs (not shown)
attach.
[0045] The three separate rounded sections 65 may be relatively
rigid rod-like elements made of biocompatible metals or polymers.
Alternatively, the rounded sections 65 may be made of a preformed
biocompatible fabric having a radially outward tab to which the
cusp edge of a leaflet attaches. In the latter case, the rounded
sections 65 are less rigid than a metal or polymer material, but
provide sufficient stiffness to facilitate fabrication and
implantation.
[0046] FIG. 10 shows the use of the scalloped-shaped cusp support
structure of FIG. 9 with a corresponding scalloped shaped sewing
band 55. As is known, this scalloped shape more readily
accommodates use of the sewing band as a platform to suture the
sewing band to aortic root tissue, which is likewise scalloped. In
this embodiment the sewing band is sutured directly to the valve
annulus, with the commissure posts attached to the aortic wall to
allow the leaflets to fluctuate radially inwardly and outwardly in
a more natural manner. The inserts 51 are desirably directly
sutured to the sewing band 55, and thus there is no direct
connection between the inserts 51 and the cusp support structure
39', and the valve commissures remain free to move inwardly and
outwardly.
[0047] FIG. 12 shows a leaflet of prior art tissue-type replacement
heart valves. The free edge 71 of prior art leaflets generally
extends straight across between the opposed tabs 73.
[0048] For the present invention, the tissue leaflets should be
configured as shown in either FIG. 13A or 13B for reduced stress in
the highly flexible valves. Leaflet free edge 35 between the tabs
37 is concave with either one or more curvatures (i.e., simple or
complex curves). The outline of the free edge 71 of a prior art
leaflet is shown in phantom superimposed over the new leaflets. As
can be seen, extra material 75 is provided at the leaflet tabs 37
to accommodate the additional stresses imposed upon the leaflets
from the increased radially inward and outward movement of the
valve commissures. That is, the leaflet tabs 37 are axially higher
than the middle portions of the free edges. In the embodiment of
FIGS. 13A, the leaflet tabs 37 continue outward a straight edge 77
from the concave free edge 35. In the embodiment of FIG. 13B, a
concave transition filet 79 is provided from an apex 81 of the free
edge 35 to reduce the height of the tabs at the valve commissures
from that shown in FIG. 13A. The triangular region near the apex 81
is not placed in direct tension from valve closure forces, and
helps reduce stress concentrations in the integrally connected
regions that are in direct tension.
[0049] Referring now to FIG. 14, in an alternative embodiment, the
lower end of each insert member 51' bifurcates to straddle the
commissure base section 43. The lower end of the insert member 51
thus straddles the base section 43 to facilitate radially inward
and outward pivoting and reduces the tendency to slip off of the
commissure base section. The bifurcation ends 83 seen in FIGS. 16A
and 16B are disposed on either side of the commissure base section
43 and are secured thereto using a suture 85.
[0050] FIG. 14 shows the relative orientation of the three valve
commissure posts, each including a V-shaped clip 53, an insert
member 51' and the cusp support structure 39, when they are
assembled. FIG. 15 shows the embodiment of FIG. 14 further
including the sewing band 55 in phantom.
[0051] In the various valves of the present invention, structural
support from the cusp supports is provided to facilitate
fabrication and implantation. The commissures remain flexibly
coupled to the rest of the valve to enable aortic wall mounting,
and dynamic coupling with the natural tissue. A concave free edge
of the leaflet, preferably with an apex region that is not placed
in direct tension, further prevents stress risers in the leaflets,
and contributes to durability.
[0052] While the foregoing is a complete description of the
preferred embodiments of the invention, various alternatives,
modifications, and equivalents may be used. Moreover, it will be
obvious that certain other modifications may be practiced within
the scope of the appended claims.
* * * * *