U.S. patent application number 12/896601 was filed with the patent office on 2011-01-27 for intraparietal aortic valve reinforcement device and a reinforced biological aortic valve.
This patent application is currently assigned to Leman Cardiovascular SA. Invention is credited to Norman Jaffe, Afksendiyos Kalangos, Yuri Zhivilo.
Application Number | 20110022167 12/896601 |
Document ID | / |
Family ID | 40076800 |
Filed Date | 2011-01-27 |
United States Patent
Application |
20110022167 |
Kind Code |
A1 |
Jaffe; Norman ; et
al. |
January 27, 2011 |
INTRAPARIETAL AORTIC VALVE REINFORCEMENT DEVICE AND A REINFORCED
BIOLOGICAL AORTIC VALVE
Abstract
A reinforcement device for a biological valve includes an
arrangement of supports configured to establish a double-trigone
geometry in the valve and coupled to a base upon which the valve
may be mounted. A plurality of commissural supports establish the
geometry of a commissural trigone, and a plurality of
intercommissural supports establish the geometry of an
intercommissural trigone. A method for reinforcing a biological
valve includes using commissural supports in conjunction with
intercommissural supports, both sets of supports coupled to a base
upon which the valve is mounted.
Inventors: |
Jaffe; Norman; (Dana Point,
CA) ; Kalangos; Afksendiyos; (Geneva, CH) ;
Zhivilo; Yuri; (Moscow, RU) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
Leman Cardiovascular SA
Lonay
CH
|
Family ID: |
40076800 |
Appl. No.: |
12/896601 |
Filed: |
October 1, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11775043 |
Jul 9, 2007 |
7815677 |
|
|
12896601 |
|
|
|
|
Current U.S.
Class: |
623/2.14 ;
29/890.124 |
Current CPC
Class: |
A61F 2250/006 20130101;
A61F 2230/0013 20130101; Y10T 29/49412 20150115; A61F 2/2409
20130101; A61F 2220/0033 20130101; A61F 2/2418 20130101 |
Class at
Publication: |
623/2.14 ;
29/890.124 |
International
Class: |
A61F 2/24 20060101
A61F002/24; B21D 51/16 20060101 B21D051/16 |
Claims
1. A method of reinforcing a biological valve, the valve comprising
leaflets attached to an external wall at commissures, the method
comprising: securing a commissural support to the external wall
approximately at each commissure; coupling the commissural supports
to a base; securing an intercommissural support to the external
wall between each pair of commissural supports; and coupling the
intercommissural supports to a base.
2. The method of claim 1, wherein the securing of the commissural
supports to the external wall comprises inserting the commissural
supports into the external wall in a generally longitudinal
direction.
3. The method of claim 1, wherein the securing of the commissural
supports to the external wall comprises suturing the commissural
supports to the external wall.
4. The method of claim 1, further comprising the step of adjusting
tension in the biological valve by adjusting the location of the
commissural supports with respect to the base.
5. The method of claim 1, wherein the base is provided with a first
plurality of holes configured to receive the commissural supports
and a second plurality of holes configured to receive the
intercommissural supports.
6. The method of claim 5, wherein the first plurality of holes
includes five holes configured to allow adjustable placement of the
commissural supports.
7. The method of claim 5, wherein the coupling of the commissural
supports to the base comprises crimping the commissural supports to
the base.
8. The method of claim 5, wherein the coupling of the
intercommissural supports to the base comprises crimping the
intercommissural supports to the base.
9. A method of making a reinforced biological valve, the method
comprising: providing a biological valve comprising biological
tissue, the biological tissue having been fixed in a physically
unconstrained state, the biological valve having a valve wall and a
plurality of commissures; securing a commissural support to the
valve wall near each commissure; and securing an intercommissural
support to the valve wall between each pair of commissural
supports.
10. The method of claim 9, further comprising: providing a base
configured to couple with the commissural supports and
intercommissural supports; and adjusting tension in the biological
valve by adjusting the location of the commissural supports with
respect to the base.
11. The method of claim 9, wherein the biological valve has an
inflow region and an outflow region, and the commissural supports
and the intercommissural supports are discontinuous around the
biological valve in the outflow region.
12. The method of claim 9, wherein the securing of the commissural
supports to the valve wall comprises inserting the commissural
supports into the valve wall in a generally longitudinal
direction.
13. A method of making a reinforced biological valve, the method
comprising: fixing biological tissue in a physically unconstrained
state; forming a biological valve from the biological tissue, the
biological valve having a valve wall, a plurality of commissures,
an inflow region, and an outflow region; attaching a commissural
support to the valve wall near each commissure; and attaching an
intercommissural support to the valve wall between each pair of
commissural supports.
14. The method of claim 13, wherein the commissural supports and
the intercommissural supports do not continuously surround the
biological valve in the outflow region.
15. The method of claim 14, wherein the attaching of the
commissural supports to the valve wall comprises placing the
commissural supports substantially within the valve wall.
16. A method of replacing a malfunctioning valve in a subject, the
method comprising: removing the malfunctioning valve from said
subject; providing a reinforced biological valve comprising a
plurality of commissural supports and a plurality of
intercommissural supports, each commissural support being
configured to stabilize a commissure of the biological valve, each
intercommissural support being configured stabilize a wall of the
biological valve between each pair of commissural supports, the
commissural supports and intercommissural supports being disposed
at discrete locations about an outflow region of the biological
valve; and implanting said reinforced biological valve in said
subject in place of said malfunctioning valve.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/775,043, filed Jul. 9, 2007, the disclosure of which is
hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This application generally relates to biological valve
reinforcement devices, and, more particularly, to unstented
biological heart valve reinforcement devices.
[0004] 2. Description of the Related Art
[0005] Cardiac surgery often involves replacement of the patient's
native valve with either a mechanical or biological (e.g., porcine,
bovine, or homograft) valve.
[0006] A mechanical valvular prosthesis consists essentially of a
mechanical valve device, such as a metal ball-and-cage or carbon
bileaflet valve device, placed inside a ring covered by synthetic
fabric. The ring facilitates incorporation of the device into the
periphery of the orifice receiving the device. While mechanical
prostheses have extremely long service lives, they present a
significant clotting (thrombosis) risk and thus require the patient
to undergo lifelong anticoagulation therapy. Furthermore, when
mechanical valves do fail, the failure is likely to be
catastrophic.
[0007] Biological valvular prostheses, on the other hand, comprise
biological tissue taken from animals and treated by a suitable
process so as to prepare them for implantation in the human body.
Examples of biological valves include porcine aortic and mitral
valves, porcine pulmonary valves, and aortic and mitral tissue
valves that are reconstructed from a bovine pericardium. These
valves have the advantage of a lower incidence of thrombosis, and
thus minimize the need for prolonged anticoagulation therapy.
Biological replacement valves further reduce the risk of
catastrophic failure, as any problems that may occur tend to
manifest symptomatically.
[0008] Biological valvular prostheses may either be stented or
unstented. A stented valve comprises a biological tissue valve
mounted on a metal or plastic frame (stent) which is covered by
synthetic cloth. A stented design facilitates implantation of the
biological prosthesis in that it requires only a single level of
suture around its annular periphery. The tissue valve's position
and configuration within the valve seat are maintained by the
stent. An unstented biological valvular prosthesis, on the other
hand, is not mounted on an external frame, but may be provided with
synthetic cloth around the inflow opening. Implantation of
unstented valves requires a more exacting surgical procedure than
implantation of stented valves, due at least in part to the fact
that unstented valves require more complex suturing in order to
preserve the valve configuration once implanted. Furthermore, due
to the geometry of the heart, unstented valves are generally
restricted to use in the aortic position and are thus of limited
application.
SUMMARY OF THE INVENTION
[0009] In accordance with one embodiment, a reinforcement device
comprising a plurality of commissural supports, a plurality of
intercommissural supports, and a base is described. Each
commissural support is configured to stabilize a valve wall of a
biological valve at a commissure of the biological valve. Each
intercommissural support is configured to stabilize the valve wall
at a location circumferentially between two of the commissures. The
base is attached to the plurality of commissural supports and the
plurality of intercommissural supports, and is configured to
receive the biological valve mounted thereon at an inflow region of
the biological valve. In one aspect of this embodiment, the
commissural supports are configured to stand substantially within
the valve wall. In the preceding aspect, the intercommissural
supports may also be configured to stand substantially within the
valve wall. In a further aspect, the commissural supports are
configured to stand outside the valve wall. In the preceding
aspect, the commissural supports may be configured to be sutured to
the valve wall. In another aspect, the base is continuous around
the valve wall in the inflow region of the biological valve. In
another aspect, the commissural supports and intercommissural
supports are discontinuous around the valve wall in an outflow
region of the biological valve. In yet another aspect, the
commissural supports and intercommissural supports are disposed at
discrete locations of the valve wall in the outflow region of the
biological valve. In another aspect, the commissural supports and
the intercommissural supports comprise metal wire. The metal wire
may comprise titanium. In another aspect, each of the commissural
supports comprises first and second straight portions. The first
and second straight portions may be spaced apart by a distance
sufficient to avoid damaging a marking zone near the commissure
when the commissural support is affixed to the valve wall. The
first and second straight portions may be substantially parallel.
Further, the first and second straight portions may be joined
together by a curved portion. The curved portion may have a
constant radius of curvature equal to half the distance between the
first and second straight portions. The first and second straight
portions may be configured to stand within the wall of the
biological valve. The curved portion may be configured to stand at
least partially outside the wall of the biological valve. In
another aspect of the embodiment, each of the intercommissural
supports comprises substantially parallel first and second straight
portions. The first and second straight portions may be joined
together by a curved portion. In yet another aspect, the plurality
of commissural supports includes three commissural supports
disposed generally symmetrically about the base. In a further
aspect, the plurality of commissural supports includes three
commissural supports disposed asymmetrically about the base. In the
preceding aspect, the plurality of intercommissural supports may
include three intercommissural supports, each one disposed between
a pair of commissural supports. Each intercommissural support may
be disposed approximately midway between each pair of commissural
supports. In another aspect, the base comprises a ring and a cover.
In the preceding aspect, the ring may be as thick or thicker than
the valve wall. In another aspect, the base includes a first
plurality of holes configured to closely receive the commissural
supports and a second plurality of holes configured to closely
receive the intercommissural supports. The first plurality may
comprise five holes for each commissural support, for adjustable
placement of the commissural supports with respect to the base. In
a further aspect, the reinforcement device comprises a crimping
wall configured to secure the commissural supports and
intercommissural supports to the base when the crimping wall is
pressed against the supports. In another aspect, the base comprises
metal. The metal may comprise titanium. In these and other aspects,
the biological valve may be an aortic or mitral valve.
[0010] In another embodiment, a reinforced prosthetic valve is
described. This reinforced prosthetic valve comprises a biological
valve mounted on a base, a plurality of commissural supports
extending from the base, and a plurality of intercommissural
supports extending from the base. The biological valve has leaflets
attached to an external wall at commissures, and has an inflow and
an outflow region. Each commissural support is configured to
stabilize the external wall at one of the commissures. Each
intercommissural support is configured to stabilize the external
wall at a location circumferentially between two of the
commissures. In one aspect of this embodiment, the commissural
supports and intercommissural supports do not continuously surround
the valve in the outflow region. In a further aspect, the
commissural supports and the intercommissural supports are disposed
substantially within the external wall. In another aspect, the
commissural supports and the intercommissural supports are disposed
outside the external wall. In the preceding aspect, the commissural
supports and the intercommissural supports may be secured to the
external wall with sutures.
[0011] In another embodiment, a method of reinforcing a biological
valve is described. The biological valve has leaflets attached to
an external wall at commissures. The method comprises securing a
commissural support to the external wall at or near each commissure
and coupling the commissural supports to a base. The method also
comprises securing an intercommissural support to the external wall
between each pair of commissural supports and coupling the
intercommissural supports to a base. In one aspect of this
embodiment, the securing of the commissural supports to the
external wall comprises inserting the commissural supports into the
external wall in a generally longitudinal direction. In a further
aspect, the securing of the commissural supports to the external
wall comprises suturing the commissural supports to the external
wall. In another aspect of the embodiment, the method further
comprises the step of adjusting tension in the biological valve by
adjusting the location of the commissural supports with respect to
the base. In yet another aspect, the base is provided with a first
plurality of holes configured to receive the commissural supports
and a second plurality of holes configured to receive the
intercommissural supports. The first plurality of holes may include
five holes configured to allow adjustable placement of the
commissural supports. The coupling of the commissural supports and
intercommissural supports to the base may comprise crimping the
commissural supports and intercommissural supports to the base.
[0012] In a further embodiment, a method of making a reinforced
biological valve is described. A biological valve is provided which
has a valve wall and a plurality of commissures. The biological
valve comprises biological tissue that has been fixed in a
physically unconstrained state. The method comprises securing a
commissural support to the valve wall near each commissure and
securing an intercommissural support to the valve wall between each
pair of commissural supports. In one aspect of this embodiment, the
method further comprises providing a base configured to couple with
the commissural supports and intercommissural supports and
adjusting tension in the biological valve by adjusting the location
of the commissural supports with respect to the base. The
biological valve may have an inflow region and an outflow region,
and the commissural and intercommissural supports may be
discontinuous around the valve in the outflow region. The
commissural supports may be secured to the valve wall by inserting
them, longitudinally, into the valve wall.
[0013] Yet another embodiment is a method of making a reinforced
biological valve. The biological valve has a valve wall, a
plurality of commissures, an inflow region, and an outflow region.
The method comprises fixing biological tissue in a physically
unconstrained state, forming a biological valve from the biological
tissue, attaching a commissural support to the valve wall near each
commissure, and attaching an intercommissural support to the valve
wall between each pair of commissural supports. In one aspect of
this embodiment, the commissural and intercommissural supports do
not continuously surround the biological valve in the outflow
region. The commissural supports may be attached to the valve wall
by placing them substantially within the valve wall.
[0014] Still another embodiment is a method of replacing a
malfunctioning valve in a subject. The method comprises removing
the malfunctioning valve from the subject, providing a reinforced
biological valve comprising a plurality of commissural supports and
a plurality of intercommissural supports, and implanting the
reinforced biological valve in the subject in place of the
malfunctioning valve. Each commissural support is configured to
stabilize a commissure of the biological valve and each
intercommissural support is configured to stabilize a wall of the
biological valve between each pair of commissural supports. The
commissural supports and intercommissural supports are disposed at
discrete locations about an outflow region of the biological
valve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a perspective representation of a reinforcement
device according to an embodiment, placed within the walls of a
biological tissue valve (valve leaflets not shown).
[0016] FIG. 2 is a perspective representation of the intramural
reinforcement device of FIG. 1.
[0017] FIG. 3 is a perspective drawing of a reinforced biological
valve according to a further embodiment and showing the direction
of flow through the valve.
[0018] FIG. 4 is a bottom plan view of the reinforced biological
valve of FIG. 3, showing the valve inflow and illustrating the
commissural and intercommissural trigone geometries.
[0019] FIG. 5A is a perspective view of a ring portion of a base
according to an embodiment.
[0020] FIG. 5B is a bottom plan view of the ring of FIG. 5A.
[0021] FIG. 5C is a cross-sectional view of the ring shown in FIG.
5A taken along line 5C-5C of FIG. 5B.
[0022] FIG. 5D is a cross-sectional view of the ring shown in FIG.
5A taken along line 5D-5D of FIG. 5B.
[0023] FIG. 6A is a perspective view of a cover portion of a base
according to an embodiment.
[0024] FIG. 6B is a cross-sectional view of the cover of FIG. 6A
taken along line 6B-6B of FIG. 6A.
[0025] FIG. 7 is a perspective representation of a reinforcement
device according to an alternative embodiment (valve leaflets not
shown).
DETAILED DESCRIPTION OF CERTAIN INVENTIVE ASPECTS
[0026] The features, aspects and advantages of the present
invention will now be described with reference to the drawings of
several embodiments, which are intended to be within the scope of
the invention herein disclosed. These and other embodiments will
become readily apparent to those skilled in the art from the
following detailed description of the embodiments having reference
to the attached figures, the invention not being limited to any
particular embodiment(s) disclosed.
[0027] As mentioned in the Background section, stented valves
comprise an external frame (stent) on which a biological tissue
valve is mounted. The stent continuously surrounds and supports the
outflow region of the valve (the region beyond the leaflet plane,
in the direction of flow) to hold the valve wall in an open
configuration. While stented valves offer relative ease of
implantation and configurational stability after implantation,
stented designs also add bulk to a replacement valve device.
Stented designs can result in a significant (on the order of 3-8
mm) reduction in the diameter of the ventricular outflow tract,
thereby artificially increasing the pressure gradient in the valve.
Stented designs can also decrease the effective orifice area (EOA)
of a valve. Stented designs may thus offer relatively poor
hemodynamics as compared with unstented designs.
[0028] Because unstented valves introduce little or no added bulk,
the pressure gradient in the replacement valve more closely
resembles the natural value. Unstented designs can also offer
increased flexibility over stented designs. Unstented designs thus
offer an advantage in terms of hemodynamics. Conventional unstented
designs, however, are more difficult to orient during implantation
and require more complex suturing in order to preserve the valve
configuration after implantation. This undesirably leads to longer
surgery times and adds both risk and expense to procedures.
Furthermore, complex intra-operative suturing can alter the
intended geometry of the valve.
[0029] Another disadvantage of conventional biological replacement
valve designs is that, in order to establish the root geometry,
they require some artificial external stress (axial, radial, and/or
circumferential) to be placed on the valve leaflets during the
crosslinking (fixation) process. This undesirably affects both the
biomechanical properties of the leaflet tissue and the anatomical
configuration of the leaflets with respect to each other, because
the tissue is effectively fixed in a somewhat pre-stressed state.
This diminishes the leaflets' ability to function normally and
negatively impacts the valve's performance characteristics.
Conventional methods also compensate for tissue shrinkage--which
tends to occur during fixation--by starting (pre-fixation) with an
oversized valve. Post-fixation, this results in extra tissue bulk,
reducing the EOA of conventional reinforced valves.
[0030] Various embodiments of the invention advantageously provide
a device for and method of supporting and stabilizing a biological
heart valve without adding significant bulk or reducing the
operative diameter of the valve. Embodiments thus allow for
replacement of a native valve with an optimally-sized prosthesis.
Embodiments of the invention additionally provide a reinforced
prosthetic valve which may be prepared in advance of surgery and
installed in a relatively quick and simple manner, without the need
for complex suturing during implantation. Certain reinforced
prosthetic valves are described in U.S. patent application Ser. No.
10/550,297 entitled "Intraparietal Aortic Valve Reinforcement
Device and Reinforced Aortic Valve," and PCT Application No.
PCT/IB2005/000573 entitled "A Reinforcing Intraparietal Device for
a Biological Cardiac Prosthesis and a Reinforced Biological Cardiac
Prosthesis," the disclosures of which are incorporated by reference
herein in their entireties.
[0031] Additionally, the commissural and intercommissural supports
used in these and other embodiments can provide points of reference
for the surgeon, aiding the surgeon in marking the proper
orientation of a prosthesis and facilitating its implantation.
Thus, these and other embodiments combine the advantages of
conventional stented and unstented valves, while reducing or
eliminating their related disadvantages.
[0032] Embodiments also desirably allow for the reestablishment of
the natural heart valve root configuration--which will be further
described below as a "double-trigone" geometry--without the need
for mechanical, hydrostatic, or other external stabilization means
during crosslinking. Instead, the biological tissue may be fixed in
a zero-stress environment, without affecting the morphology of the
collagen or elastin of the tissue, thereby fixing the tissue in a
natural, unstressed state. The root geometry may then be
re-established (and manipulated if necessary) post-fixation, using
supports placed close to or inside the valve walls at the
commissures and in the intercommissural spaces. Stabilizing the
valve wall at discrete locations, discontinuously about the outflow
region, reinforces the root geometry while allowing some
flexibility in the non-reinforced portions of the valve wall during
operation of the valve.
[0033] Furthermore, as mentioned above, the fixation process may
cause a certain amount of shrinkage in the biological tissue.
Providing zero-stress fixation, according to embodiments of the
invention, allows for optimal sizing of the valve tissue with a
reinforcement device, because the slightly shrunken (fixed) tissue
can be stretched back to approximately its original size
post-fixation. This reduces or eliminates undesirable added tissue
bulk, increasing the EOA of the valve as compared to conventional
configurations. Providing zero-stress fixation also minimizes the
introduction of undesirable artificial stresses on the valve
leaflets during operation of the valve. Embodiments thus require
less work to open the leaflets, minimizing energy loss across a
reinforced valve.
A Reinforced Valve
[0034] With reference now to FIG. 1, an embodiment of a reinforced
biological valve 50 is illustrated. The reinforced valve 50
includes a biological valve reinforcement device 10 having
commissural supports 14(a)-14(c) and intercommissural supports
16(a)-16(c) disposed largely within an external wall 24 of a
biological valve 20 (the valve leaflets are not shown in FIG. 1).
Alternatively, the device 10 may include commissural and
intercommissural supports disposed just outside the valve 20 and
secured to the valve tissue, for example by suturing. As better
illustrated in FIG. 3, the biological valve 20 includes three
leaflets 22(a)-26(c) attached laterally to the external wall 24 at
three commissures 26(a)-26(c). At the intersection of each of the
commissures 26(a)-26(c) with the wall 24 is a "marking zone" having
a complex fortified anatomy. The marking zone 36(c), corresponding
to commissure 26(c), is illustrated in dashed lines. A native
channel 30 into which the reinforced valve 50 may be implanted is
also illustrated with dashed lines. The native channel 30 may, for
example, be an aortic channel. The direction of flow through the
valve 20 is indicated by arrows 32 (inflow) and 34 (outflow).
A Reinforcement Device
[0035] In the embodiment illustrated in FIG. 1, the device 10
generally includes a base 12 (upon which the biological valve 20
may be mounted), a plurality of commissural supports 14(a)-14(c)
(shown largely in hidden lines), and a plurality of
intercommissural supports 16(a)-16(c) (also shown largely in hidden
lines). The commissural supports 14(a)-14(c) may be disposed
generally at the commissures of the valve 20, and the
intercommissural supports 16(a)-16(c) may be disposed in or near
the valve wall 24. In some embodiments the intercommissural
supports 16(a)-16(c) are positioned approximately midway between
each pair of commissures. However, it will be appreciated that the
intercommissural supports may be positioned anywhere consistent
with their intended function. Both the commissural and
intercommissural supports 14(a)-14(c) and 16(a)-16(c) may be
coupled to the base 12.
Base
[0036] With continued reference to FIG. 1, the base 12 may have an
internal diameter which is substantially equivalent to an internal
diameter of the biological valve 20. Thus, the inflow region of the
valve 20 (the region before the leaflet plane, moving in the
direction of flow) may be mounted directly on top of the base 12,
as shown in the figure, with the inner wall of the valve 20 being
essentially flush with the inner surface of the base 12. The base
12 may further have a thickness which may preferably be
substantially equivalent to a thickness of the wall 24 of the
biological valve 20. Accordingly, the base 12 may have an external
diameter which may preferably be substantially equivalent to an
external diameter of the wall 24 of the biological valve 20. The
thickness of the base 12 may also be greater than or smaller than
the thickness of the biological valve 20. With a smaller sized
valve, for example, the base 12 may have a thickness slightly
larger than the thickness of the valve wall.
[0037] As shown in FIG. 2, the base 12 may be provided with a
plurality of holes 13. The holes 13 may be disposed on the top
surface of the base 12 midway between the inner and outer walls of
the base 12 (as shown in FIG. 2) or at the outer edge of the top
surface of the base (see FIG. 7). The holes 13 may also be disposed
at any other position consistent with their intended use. The holes
13 may be configured to receive the commissural and
intercommissural supports 14(a)-14(c) and 16(a)-16(c) (which will
be described in further detail below).
[0038] As better illustrated in FIGS. 5A-5B, one or more holes
13(a) may be provided for each commissural support 14(a)-14(c) to
allow for adjustable placement of the commissural supports
14(a)-14(c) around the base 12. For example, if the supports
14(a)-14(c) have legs spaced 4 mm apart, five holes may be provided
and spaced 2 mm apart so that a support may fit in the first and
third holes, the second and fourth holes, or the third and fifth
holes. The holes 13(a) or sets of holes 13(a) may be disposed
somewhat asymmetrically around the base 12; for example, in some
embodiments, they may be spaced approximately 120.degree.,
105.degree., and 135.degree. from each other. The holes 13(a) or
sets of holes 13(a) may alternatively be disposed generally
symmetrically around the base 12, depending upon the requirements
of the particular application.
[0039] Additionally, one or more holes 13(b) may be provided for
each intercommissural support 16(a)-16(c). As illustrated in FIG.
5B, each hole 13(b) or set of holes 13(b) may be disposed
approximately midway between each set of commissural support holes
13(a). Of course, the commissural support holes 13(a) and the
intercommissural support holes 13(b) may be disposed in any other
configuration consistent with their intended use. For example, the
base 12 may be provided with evenly spaced holes 13 to allow for
maximum adjustability, or may be provided with holes 13 located in
discrete positions to ensure precise positioning of the supports
14(a)-14(c) and 16(a)-16(c).
[0040] With reference now to FIGS. 5A-5D and 6A-6B, in some
embodiments, the base 12 may comprise a ring 60 and a cover 70. The
ring 60 may be provided with a plurality of holes 13 as described
above. As shown in FIGS. 5C-5D, the ring 60 may have an inner wall
62, a crimping wall 64, and an outer lip 66. The crimping wall 64
may be configured to provide a friction crimp against a support 14,
16 inserted into one of the holes 13 when the wall 64 is pressed
against the support 14, 16. As shown in FIGS. 6A-6B, the cover 70
may have an inner lip 72, configured to mate with the inner wall 62
of the ring 60, and an outer wall 76, configured to mate with the
outer wall 66 of the ring 60. The outer wall 76 may be provided
with a chamfer 73 configured to allow the cover 70 to slip over the
crimped surfaces of the crimping wall 64 of the ring 60. The outer
wall 76 may further be provided with an annular groove 75
configured to clip to the crimped surfaces of the crimping wall 64.
In alternative embodiments, the base 12 may have any other
configuration allowing it to secure the supports 14, 16 and to
support a biological valve mounted thereon.
[0041] The base 12 may comprise any suitable material for receiving
and/or securing the supports 14(a)-14(c) and 16(a)-16(c). For
example, the base 12 may be formed from a metal such as titanium.
Alternatively, the base 12 may be formed from a rigid, semi-rigid,
or flexible polymer.
Commissural Supports
[0042] Referring once again to the embodiment depicted in FIG. 2,
the commissural supports 14(a)-14(c) may be disposed at each of the
commissures 26 and coupled to the base 12. The commissural supports
14(a)-14(c) may each comprise two legs connected by a curvilinear
portion at an end of the support distal of the base 12. The two
legs may be generally straight and generally parallel (as
illustrated in the figure) or may be curved or angled apart
somewhat. The two legs may also be spaced apart by a distance
sufficient to avoid damaging the biological tissue in the marking
zones 36(a)-36(c) (marking zone 36(c) is illustrated in FIG. 3) of
the biological valve 20, thereby preserving the structural
integrity of the biological valve 20. For example, the legs may be
separated by a distance of 4 mm, or 3 mm (especially in the case of
smaller-sized valves). The legs may also be separated by any
distance compatible with the valve's intended use. In some
embodiments, the curvilinear portion may have a constant radius of
curvature, which may be equivalent to half the distance between the
parallel legs.
[0043] In the embodiment shown in FIG. 1, the commissural supports
14(a)-14(c) may be configured to stand largely within the external
wall 24 of the biological valve 20. Alternative embodiments may
include commissural supports having any configuration capable of
providing adequate support to the commissures during exposure to
physiological flow pressures and rates. For example, the embodiment
illustrated in FIG. 7 has commissural supports 84(a)-84(c) disposed
external to the valve wall 24 around the outer periphery of a base
82, the valve 20 being disposed on top of the base 82 and having
its inner wall essentially flush with the inner periphery of the
base 82. An external commissural support may comprise a single
straight rod, a T-shaped rod, a curved wire, or a narrow blade or
plate which may be sutured to or otherwise attached to biological
valve tissue at the valve commissures (see FIG. 7). Depending upon
the geometry of the biological valve 20, the commissural supports
may be disposed somewhat asymmetrically around the base, as
described above in connection with FIGS. 5A-5B. The commissural
supports may also be disposed about the base in any other
configuration consistent with their intended use.
[0044] Referring again to the embodiment depicted in FIG. 1, the
commissural supports 14(a)-14(c) may be disposed in a direction
substantially parallel to the direction of flow 32 through the
valve 20. The legs of the commissural supports 14(a)-14(c) may be
disposed entirely within the tissue of the wall 24, while the
curvilinear portions of the commissural supports 14(a)-14(c) may
extend partially or entirely outside of the tissue at an end distal
of the base 12. The commissural supports 14(a)-14(c) may each
comprise a continuous wire, such as a titanium wire, for example.
Alternatively, the commissural supports 14(a)-14(c) may comprise a
rigid, semi-rigid, or flexible polymer.
[0045] With reference now to the embodiment depicted in FIG. 4,
which illustrates a bottom plan view of the device 10 incorporated
into the reinforced biological valve 50, the commissural supports
14(a)-14(c) may together define a commissural trigone 44 (shown in
dashed lines).
Intercommissural Supports
[0046] Referring once again to the embodiment depicted in FIG. 1,
the intercommissural supports 16(a)-16(c) (shown largely in hidden
lines) may be disposed in the intercommissural spaces, preferably
approximately midway between each pair of commissural supports
14(a), 14(b); 14(b), 14(c); and 14(c), 14(a). The intercommissural
supports 16(a)-16(c) may also be coupled to the base 12. In the
embodiment in FIG. 1, the intercommissural supports 16(a)-16(c) may
be configured to stand largely within the external wall 24 of the
biological valve 20. Alternative embodiments may include
intercommissural supports disposed externally to the biological
valve tissue, which supports may be sutured or otherwise attached
to the valve tissue in the intercommissural spaces (see FIG.
7).
[0047] Referring again to the embodiment depicted in FIG. 2, the
intercommissural supports 16(a)-16(c) may each comprise two legs
connected by a curvilinear portion at an end of the support distal
of the base 12. The two legs may be generally straight and
generally parallel (as illustrated in the figure) or may be curved
or angled apart somewhat. The curvilinear portion may have a
constant radius of curvature equivalent to half the distance
between the parallel legs. Alternatively, because the
intercommissural spaces include no especially fragile marking
zones, the intercommissural supports may each comprise a single
straight rod, a T-shaped rod, or a narrow blade or plate.
Embodiments may include intercommissural supports having other
shapes, such as helical shapes, which may aid in insertion of the
support into the valve tissue.
[0048] In the embodiment depicted in FIG. 1, the intercommissural
supports 16(a)-16(c) may be disposed in a direction substantially
parallel to the direction of flow 32. The legs of the
intercommissural supports 16(a)-16(c) may be disposed entirely
within the tissue of the wall 24, while the curvilinear portions of
the intercommissural supports 16(a)-16(c) may extend partially or
entirely outside of the tissue at an end distal of the base 12. In
the embodiment depicted in FIG. 2, because the wall 24 is typically
cut shorter in the intercommissural spaces than near the
commissures 26, the intercommissural supports 16(a)-16(c) may be
shorter than the commissural supports 14(a)-14(c). The
intercommissural supports 16(a)-16(c) may each comprise a
continuous wire, such as a titanium wire, for example.
Alternatively, the intercommissural supports 16(a)-16(c) may
comprise a rigid, semi-rigid, or flexible polymer.
[0049] Referring once again to FIG. 4, the intercommissural
supports 16(a)-16(c) may together define an intercommissural
trigone 46 (shown in dashed lines). The intercommissural trigone
configuration 46 may serve to resist radial forces on the
intercommissural spaces when the valve leaflets 22 close. Thus, the
commissural supports 14(a)-14(c) and intercommissural supports
16(a)-16(c) together define a double-trigone geometry (see lines
44, 46) which closely resembles the natural geometry of the
biological valve 20.
[0050] Referring now to FIG. 3, the reinforced biological valve 50
may be provided with a suture ring 52, which may comprise a
flexible synthetic fabric. The entire outside periphery of the
valve 50 may also be covered by a synthetic fabric 54.
Making a Reinforcement Device and a Reinforced Valve
[0051] A method of reinforcing a biological valve is also provided.
The method may include placing a commissural support at or near
each commissure of a biological valve and securing the commissural
supports to the valve tissue. The method may also include placing
an intercommissural support approximately midway between each pair
of commissural supports and securing the intercommissural supports
to the valve tissue. The method may further include coupling the
commissural supports and intercommissural supports to a base, which
may be disposed underneath the biological valve.
[0052] In some embodiments, after biological material to be used
for the replacement valve is first harvested, it may be stored in a
preservative solution. The biological material may then be
subjected to one or more pre-fixation treatments, such as a
decellularization treatment to reduce the risk of post-implantation
mineralization. Such pre-fixation treatments are more fully
described in U.S. Pat. Nos. 5,595,571; 5,720,777; and 5,843,181;
the entire disclosures of which are herein incorporated by
reference.
[0053] The biological material may then be subjected to a fixation
(crosslinking) treatment to preserve the structural integrity of
the biological valve. Such fixation may include exposing the
biological material to gluteraldehyde. Such fixation may occur
without any mechanical, hydrostatic, or other external stress
placed on the valve leaflets. Fixing the biological tissue in a
"relaxed" state allows for some shrinkage of the material to occur
without affecting the orientation of collagen or elastin in the
tissue, and thus without affecting the biomechanical properties of
the tissue. The tissue may be then be dissected and composited into
a composite biological valve, according to known practices.
Embodiments of the invention may also use an intact biological
valve.
[0054] Next, commissural supports may be inserted into the wall of
the biological valve. Each commissural support may comprise two
legs, each leg being provided with a sharp tip for piercing the
wall of the tissue valve at either side of the commissural marking
zone. The legs may have differing lengths to facilitate insertion.
The legs may enter the valve wall at the outflow region of the
valve and be pushed through the wall in a direction generally
parallel to the central axis of the valve until the legs exit the
tissue at the inflow region of the valve. Alternatively, the
commissural supports may be placed outside the valve wall at each
commissure and secured to the valve tissue in any suitable fashion,
for example by suturing.
[0055] Once each commissural support is inserted through (or
otherwise coupled to) the valve wall, the supports may be coupled
to a base. The commissural supports may be removably coupled to the
base at first, to allow a practitioner to choose a
differently-sized base if necessary. In view of the size of the
biological tissue, the commissural supports may also be adjustably
positioned on the base to allow a practitioner to adjust the height
of the supports and to adjust tension among the valve leaflets as
necessary. As noted above, the valve tissue may have shrunken to a
certain extent (on the order of one valve size, that is,
approximately 2 mm in diameter) during the zero-stress fixation.
Thus, the process of coupling the commissural supports to the base
may involve stretching the valve tissue slightly to re-establish
the original valve size.
[0056] After the proper sizing and positioning has been determined,
the commissural supports may be more permanently fixed to the base
to establish the commissural trigone. The commissural supports may
be fixed by crimping a wall of the base against the legs of the
supports. The supports may be fixed using a friction crimp,
allowing adjustment of the height of supports, or may be fixed
using a fixed crimp so that the supports become firmly positioned
with respect to the base. The commissural supports may
alternatively be fixed by any other manner consistent with the
valve's intended use. Once the commissural supports are secured to
the base, the supports may be bent at an approximately 90.degree.
angle (tangentially from the base) and trimmed.
[0057] After the commissural trigone has been established, the
intercommissural supports may be inserted into the valve wall. Each
intercommissural support may comprise one or more legs, each leg
being provided with a sharp tip for piercing the wall of the tissue
valve. The legs may enter the valve wall at the outflow region of
the valve and be pushed through the wall until the legs exit the
tissue wall at the inflow region of the valve. As with the
commissural supports, the intercommissural supports may
alternatively be placed outside the valve wall at each
intercommissural space and secured to the valve tissue in any
suitable fashion, for example by suturing. The intercommissural
supports may then be coupled to the base and trimmed in a similar
manner as the commissural supports. Where a base comprising a ring
and a cover is used, a cover may then be placed on the ring and
secured to the ring.
[0058] Finally, the reinforced valve may be covered or partially
covered with a flexible synthetic fabric. The reinforced valve may
also be encircled by a suture ring, such as a flexible fabric ring,
which can be used to facilitate implantation of the device.
Using a Reinforced Valve
[0059] During an aortic valve replacement surgery, a diseased or
malfunctioning native valve is removed from the native aortic
annulus. The aortic annulus is then sized, and a pre-manufactured
reinforced biological valve of the appropriate size is selected for
implantation. As mentioned earlier, providing reinforcement of the
double-trigone geometry for a biological valve allows for optimal
sizing of the replacement valve, thereby maintaining a more natural
pressure gradient and reducing or eliminating the need to perform
root enlargement or other such procedures. The surgeon then sutures
the replacement valve within the aortic annulus or supra-annularly,
using the commissural reinforcement points as markers to properly
orient the reinforced valve. Since the double-trigone geometry of
the valve is reinforced at discrete locations around the
circumference of the valve, no complex suturing is required to
secure the valve's configuration.
[0060] Although the hemodynamic characteristics of bioprosthetic
heart valves measured in flow testing have not been proven to be
proportional to their in situ clinical performance, there is a
general agreement that for a particular cardiac output, expressed
as liters of blood passing through in any one minute, the degree to
which the valve opens and the effort necessary to accomplish
adequate flow during flow tests are most likely related to the
clinical outcome. In flow tests, embodiments of the invention have
demonstrated enhanced hemodynamics when compared with even the most
hemodynamically efficient conventional bioprostheses. For example,
flow testing has shown that a 25 mm diameter valve, configured in
accordance with embodiments of the invention, has an approximately
20 to 25% greater EOA than a conventional stented bioprosthetic
valve of the same size. An increased EOA results in more blood flow
per heart beat, and also results in a lower total energy loss
during valve operation. Thus, to accommodate a given cardiac
output, the 25 mm valve mentioned above only requires about half
the work as a conventional stented bioprosthetic valve of the same
size. This indicates that, for aortic applications, the left
ventricle of the heart will be required to perform less work,
resulting in an accelerated return of normal function.
[0061] Although illustrated within the context of a prosthetic
aortic valve, the present invention may also be used with other
prosthetic valves, such as a mitral valve, tricuspid valve, or any
other valve for which unobstructing reinforcement is desirable. It
will be understood by those of skill in the art that numerous and
various modifications can be made without departing from the spirit
of the present invention. Therefore, it should be clearly
understood that the forms of the invention described herein are
illustrative only and are not intended to limit the scope of the
invention.
* * * * *