U.S. patent application number 14/200411 was filed with the patent office on 2014-11-27 for prosthesis seals and methods for sealing an expandable prosthesis.
This patent application is currently assigned to SYMETIS SA. The applicant listed for this patent is Symetis SA. Invention is credited to Youssef Biadillah, Stephane Delaloye, Jacques Essinger, Jean-Luc Hefti, Fabien Lombardi, Luc Mantanus.
Application Number | 20140350668 14/200411 |
Document ID | / |
Family ID | 50345995 |
Filed Date | 2014-11-27 |
United States Patent
Application |
20140350668 |
Kind Code |
A1 |
Delaloye; Stephane ; et
al. |
November 27, 2014 |
Prosthesis Seals and Methods for Sealing an Expandable
Prosthesis
Abstract
Embodiments of the present disclosure are related to devices and
techniques for para-valve sealing of an expandable stent-valve
implanted using a catheter. In some embodiments, a stent-valve is
provided which comprises a seal sleeve/cuff containing material
that swells when contacted by blood. A piercing tool may be
included and used to permit a user to puncture the sleeve/cuff
prior to introduction into a patient's body. In some embodiments,
the sleeve/cuff has an integral tubular structure configured to
withstand balloon expansion of the stent-valve during or after
implantation.
Inventors: |
Delaloye; Stephane; (Bulach,
CH) ; Essinger; Jacques; (St-Prex, CH) ;
Hefti; Jean-Luc; (Cheseaux-Noreaz, CH) ; Biadillah;
Youssef; (Lausanne, CH) ; Mantanus; Luc;
(Lausanne, CH) ; Lombardi; Fabien; (Prilly,
CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Symetis SA |
Lausanne |
|
CH |
|
|
Assignee: |
SYMETIS SA
Lausanne
CH
|
Family ID: |
50345995 |
Appl. No.: |
14/200411 |
Filed: |
March 7, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61779744 |
Mar 13, 2013 |
|
|
|
Current U.S.
Class: |
623/2.17 |
Current CPC
Class: |
A61F 2220/0058 20130101;
A61F 2210/0061 20130101; A61F 2/82 20130101; A61F 2/95 20130101;
A61F 2250/0063 20130101; A61F 2/2418 20130101; A61F 2220/0075
20130101; A61F 2220/005 20130101; A61F 2230/0065 20130101; A61F
2250/0069 20130101; A61F 2250/0056 20130101 |
Class at
Publication: |
623/2.17 |
International
Class: |
A61F 2/24 20060101
A61F002/24 |
Claims
1-84. (canceled)
85. A stent-valve for transcatheter implantation to replace a
cardiac valve, the stent-valve being compressible to a compressed
configuration for delivery, and expandable to an operative state
for implantation, the stent-valve comprising a stent, a plurality
of leaflets defining a prosthetic valve, and a seal for sealing
against surrounding tissue, wherein the seal comprises: a hollow
sleeve/cuff arranged to extend in a circumferential direction
substantially around the stent and containing swellable material
that swells when contacted by blood to distend the hollow cuff, the
hollow sleeve/cuff comprising an integral tubular structure.
86. The stent-valve of claim 85, wherein the hollow sleeve/cuff
comprises a tubular extrusion or blow molded tubing.
87. The stent-valve of claim 85, wherein the hollow sleeve/cuff
defines a hollow toroid shape around the stent, the toroid shape
being closed-loop or split or helical.
88. The stent-valve of claim 87, wherein the hollow sleeve/cuff
comprises an elongate tubular member bent to define the toroid
shape.
89. The stent-valve of claim 88, wherein the ends of the elongate
tubular member are joined together to define a closed-loop toroid
shape.
90. The stent-valve of claim 85, wherein the hollow sleeve/cuff
comprises a tubular segment from a valvuloplasty balloon.
91. The stent-valve of claim 85, wherein the hollow sleeve/cuff
comprises a laminate of (i) plastics film and (ii) a diffusion
barrier layer to obstruct diffusion of liquids from outside the
hollow sleeve/cuff to the hollow interior, the diffusion barrier
layer comprising metal or a metal compound.
92. A stent-valve for transcatheter implantation to replace a
cardiac valve, the stent valve being compressible to a compressed
configuration for delivery, and expandable to an operative state
for implantation, the stent-valve comprising a stent, a plurality
of leaflets defining a prosthetic valve, and a seal for sealing
against surrounding tissue, wherein the external seal comprises: a
hollow sleeve/cuff arranged to extend in a circumferential
direction substantially around the stent and containing swellable
material that swells when contacted by blood to distend the hollow
cuff, comprising a laminate of (i) plastics film and (ii) a
diffusion barrier layer to obstruct diffusion of liquids from
outside the hollow sleeve/cuff to the hollow interior, the
diffusion barrier layer comprising a layer comprising metal or a
metal compound.
93. The stent-valve of claim 92, wherein the diffusion barrier
layer is a plasma vapor deposited layer.
94. The stent-valve of claim 92, wherein the diffusion barrier
player is formed (i) on an interior face of the cuff, or (ii) as a
non-surface layer of the laminate.
95. The stent-valve of claim 92, wherein the diffusion barrier
layer has a thickness of less than 100 nm, optionally less than 50
nm, optionally less than 10 nm.
96. The stent-valve of claim 92, wherein the diffusion barrier
layer remains in position on the stent-valve when the valve is
implanted.
97. The stent-valve of claim 92, wherein the hollow sleeve/cuff is
configured to withstand post-implantation balloon expansion of the
stent-valve against a calcified anatomy without substantial loss of
structural integrity of the hollow cuff.
98. A stent-valve for transcatheter implantation to replace a
cardiac valve, the stent valve being compressible to a compressed
configuration for delivery, and expandable to an operative state
for implantation, the stent-valve comprising a stent, a plurality
of leaflets defining a prosthetic valve, and a seal for sealing
against surrounding tissue, wherein the external seal comprises: a
hollow sleeve/cuff arranged to extend in a circumferential
direction substantially around the stent and containing swellable
material that swells when contacted by blood to distend the hollow
cuff, the hollow sleeve/cuff being configured to withstand
post-implantation balloon expansion of the stent-valve against a
calcified anatomy without substantial loss of structural integrity
of the hollow cuff.
99. The stent-valve of claim 98, wherein the sleeve/cuff is
configured to be manually pierceable at one or more points to
define liquid admitting punctures permitting liquid entry into the
cuff.
100. The stent-valve of claim 98, wherein the sleeve/cuff has one
or more liquid admitting punctures made therein, prior to
introduction of the stent-valve into the body of a patient, for
admitting liquid into the seal.
101. A stent-valve for transcatheter implantation to replace a
cardiac valve, the stent valve being compressible to a compressed
configuration for delivery, and expandable to an operative state
for implantation, the stent-valve comprising a stent, a plurality
of leaflets defining a prosthetic valve, and a seal for sealing
against surrounding tissue, wherein the external seal comprises: a
hollow sleeve/cuff arranged to extend in a circumferential
direction substantially around the stent and containing swellable
material that swells when contacted by blood to distend the hollow
cuff, the hollow sleeve/cuff comprising a film made of
liquid-impermeable material, the sleeve/cuff having one or more
liquid admitting punctures made therein, prior to introduction of
the stent-valve into the body of a patient, for admitting liquid
into the seal.
102. The stent-valve of claim 101, wherein the number of punctures
is less than fifty, optionally less than forty, optionally less
than thirty, optionally less than twenty, optionally less than
ten.
103. The stent-valve of claim 101, wherein the seal further
comprises a skirt secured to the hollow cuff.
104. The stent-valve of claim 103, wherein the skirt is secured to
the sleeve/cuff by an attachment that does not puncture the cuff,
for example, an attachment selected from: fusion; welding;
adhesive.
105. The stent-valve of claim 103, wherein the skirt is secured to
the stent, thereby mounting the sleeve/cuff to the stent.
Description
RELATED APPLICATIONS
[0001] This application claims benefit under 35 U.S.C. .sctn.119(e)
of U.S. provisional patent application No. 61/779,744, entitled,
"Prosthesis Seals and Methods for Sealing and Expandable
Prosthesis", filed on Mar. 13, 2013, the entire disclosure of which
is herein incorporated by reference.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to the field of stents
implantable in the body. Embodiments have been devised to address
problems encountered in the field of stent-valves, for example
cardiac stent-valves (e.g., prosthetic heart valves). However, the
concepts disclosed herein may have broader application to any stent
or stented prosthesis where a seal is desired at an exterior
surface of a stent.
BACKGROUND OF THE DISCLOSURE
[0003] Transcatheter valve implantation (for example, transcatheter
aortic valve implantation (TAVI)) is an evolving technology for
replacement valve therapy that (i) avoids the trauma of
conventional open-chest surgery, and (ii) avoids the need for heart
and lung bypass. In such a technique, a stent-valve is compressed
and loaded into a delivery catheter. The delivery catheter is
introduced to the desired site of implantation (for example at the
heart) via a percutaneous route or via minimally invasive surgery.
The stent-valve is expanded into the implantation position from or
by the delivery catheter, and the delivery catheter is then
withdrawn.
[0004] Despite the successes of transcatheter stent-valves,
technological challenges remain. One such challenge is preventing
retrograde leakage of blood around the stent-valve (so called
para-valve leakage). The above-noted stents form a friction fit
with the native anatomy to anchor the stent-valve in position, and
are round in cross-section. However the native anatomy in which the
stent is implanted is often off-round and is different for each
person. Moreover, heavy calcification of the native anatomy may
obstruct full deployment of any stent and make the native anatomy
even more irregular. Thus, it can sometimes be difficult to provide
a perfectly sealing fit between the stent-valve and the surrounding
anatomy. Para-valve leakage is believed to be one of the factors
affecting the long-term efficacy of the prosthetic valve, and
possibly the life expectancy of the patient. One explanation is
that the heart may have to work harder to compensate for some blood
leaking retrograde at the entrance or exit of the heart. Therefore,
addressing para-valve leakage is a significant challenge.
[0005] It is known to incorporate an external skirt or cover as
part of the stent-valve. For example, the skirt is made of
compressible biocompatible material, such as pericardial tissue or
PET. The thicker the material of the skirt, the more able the skirt
is to occlude gaps and effect a seal. However, a disadvantage is
that such skirts add to the bulk of the stent-valve. A thick skirt
makes the stent-valve problematic to compress to a desirably small
size for implantation.
[0006] US-A-2005/0137688 is understood to describe compliant sacs
disposed around the exterior of a stent, that are said to provide a
more efficient seal along an irregular interface. The sacs may be
filled with an appropriate material, for example, water, blood,
foam or a hydrogel. Different arrangements of sacs are proposed in
principle, but this document neither describes any specific
construction technique nor does it describe handling of the fill
material.
[0007] U.S. Pat. No. 5,769,882 is understood to describe an
implantable expansible tubular vascular prosthesis carrying a
form-in-place sealing layer for occluding at least a
circumferential band at the interface between the prosthesis and
the native tissue wall. In one example, the sealing layer comprises
a hydrogel, arranged in a sleeve/cuff comprising a permeable
membrane.
[0008] EP 1262201 is understood to describe an implantable vascular
device having an external seal structure comprising a swellable
hydrogel. In use, the hydrogel absorbs a mass of liquid so as to
assume, as a result of the absorption, a certain degree of
mechanical consistency. An example hydrogel has a polyvinyl alcohol
(PVA) base, in combination with a polysaccharide.
[0009] WO-A-2008/070442 is understood to describe prosthetic heart
valves, both expanding and non-expanding types, each having an
anchoring sleeve that changes shape when the valve is implanted, to
prevent migration of the valve. The anchoring sleeve is at least
partly made of a material that swells due to absorption of body
fluids. In examples, the sleeve is made of an inner material that
swells upon contact with body fluids, and enclosed by a cover.
[0010] US-A-2007/0060998 and WO-A-2010/083558 are understood to
describe delivery of a dispensable or releasable reactive sealing
agent for endoluminal use around (at least substantially around) a
prosthetic device within a body lumen. The reactive sealing agent
is released or dispensed into a space between the prosthetic device
and the lumen wall, in response to exertion of a dispensing
pressure or by a configuration change causing the release. While
different arrangements of dispensing capsules are proposed,
reliable containment of the agent when the prosthesis is implanted
at the heart likely are not ensured, especially in view of the
constant movement and cyclic compression experienced by heart
valves.
[0011] Accordingly, it would be desirable to address one or more of
the above issues and/or provide a technique for mitigating
para-valve (or para-stent) leakage without substantially affecting
other desirable characteristics.
SUMMARY OF SOME OF THE EMBODIMENTS
[0012] The following disclosure presents a summary of the invention
in order to provide a basic, non-limiting, understanding of some
embodiments of the invention.
[0013] For example, in some embodiments of the present disclosure,
a seal is provided for a prosthesis. The seal may be configured for
obstructing para-prosthesis leakage. The prosthesis may, for
example be a stent-valve (for example a cardiac stent-valve, such
as an aortic stent-valve). The seal may comprise one or any
combination of two or more of the following features, which are all
optional. The list of optional features is bulleted by dashes
("-"). [0014] In some embodiments, the seal is provided as a
separate item from the prosthesis. The separate seal may be
mountable on the prosthesis prior to implantation of the
prosthesis. For example, the seal may be mountable on the
prosthesis as part of a pre-implantation preparation process.
[0015] Alternatively, the seal may be provided as an integral part
of the prosthesis. [0016] Alternatively, a flowable seal material
may be introduced into a seal sleeve or sleeve/cuff as part of a
pre-implantation preparation process. [0017] A pre-implantation
preparation process may, for example, be carried out at the same
hospital or clinic as the implantation procedure and/or within 2
hours or less before the implantation procedure (optionally about
90 minutes or less, optionally about 80 minutes or less, optionally
about 70 minutes or less, optionally about 60 minutes or less,
optionally about 50 minutes or less, optionally about 40 minutes or
less, optionally about 30 minutes or less, optionally about 20
minutes or less, optionally about 10 minutes or less). [0018] A
pre-implantation preparation process may comprise a step of rinsing
the prosthesis substantially clean of a storage solution in which
the prosthesis is stored and/or provided. The step of mounting the
seal on the prosthesis (if this step is implemented) may be carried
out after the prosthesis rinsing step.
[0019] Continuing from the above list, the seal may comprise one or
any combination of two or more of the following features, as well
as the above-noted features, which are all optional: [0020] The
seal may comprise a swellable material that swells in response to
contact with blood. [0021] The seal may comprise a hollow sleeve
and/or hollow cuff for containing the swellable material. The term
"cuff" may refer to the intended arrangement of the seal around the
prosthesis (for example, after mounting in the case of the
mountable separate seal, or as provided when integral with the
prosthesis). Throughout this specification the terms "sleeve/cuff"
and "cuff/sleeve" are used to mean "sleeve and/or cuff" whether or
not the "and/or" language is recited explicitly. [0022] The
sleeve/cuff may confine the swellable material captive within the
sleeve/cuff. In some embodiments, the swellable material may be
introduced into the sleeve/cuff during manufacture, and provided as
a sleeve/cuff containing the swellable material. In other
embodiments, the swellable material may be introducible into the
sleeve/cuff as part of a pre-implantation preparation process (for
example, as explained above, whether or not the seal is a mountable
separate seal). In some embodiments, the swellable material is
introducible by injecting into the interior of the sleeve/cuff (for
example, injecting through the wall of the sleeve/cuff or through a
dedicated port of the sleeve/cuff). [0023] The sleeve/cuff may
extend generally in a circumferential direction. In the case of a
mountable separate seal, the sleeve/cuff may extend generally in a
circumferential direction at least once mounted on the prosthesis.
[0024] The sleeve/cuff may define a single hollow interior space
for swellable material, or the sleeve/cuff may be partitioned to
define plural pockets or compartments for the swellable material.
At least some of the pockets may communicate with each other,
and/or at least some of the pockets may be closed spaces not in
communication with any other pocket. In some embodiments, the
internal partitioning may substantially prevent redistribution of
the swellable material between pockets, or alternatively permit
substantially free redistribution of the swellable material between
pockets, or alternatively permit restricted redistribution of the
swellable material between pockets. In some embodiments, the
internal partitioning may be frangible so as to permit
communication between two closed pockets upon rupture of the
internal partitioning. [0025] The sleeve/cuff may comprise a single
wall, or the sleeve/cuff may comprise plural walls nested one
behind, or within, another. At least one wall may comprise a single
layer of material, and/or at least one wall may comprise plural
layers of material (e.g. a multi-layered wall and/or a laminate).
[0026] The sleeve and/or cuff, or at least a wall or layer thereof,
may comprise a region that is permeable or at least semi-permeable
to liquid. The permeable/semi-permeable region may be configured to
(i) allow communication of blood components therethrough (for
example, into the interior of the sleeve/cuff to cause the
swellable material to swell), and/or (ii) obstruct passage
therethrough of blood emboli (for example, to substantially prevent
escape into the blood stream of any emboli that may form within the
sleeve/cuff), and/or (iii) obstruct passage therethrough of
swellable material particles (for example, to substantially prevent
escape into the blood stream of any loose particles of the
swellable material).
[0027] The permeable/semi-permeable region may have pores (e.g.
perforations). The pore size (e.g. average pore size) may, for
example, be not substantially greater than about 0.2 mm.
Optionally, the pore size may be not substantially greater than
about 0.15 mm, optionally not substantially greater than about 0.12
mm, optionally not substantially greater than about 0.11 mm,
optionally not substantially greater than about 0.1 mm, optionally
about 0.1 mm.
[0028] In some embodiments, the permeable/semi-permeable region may
be a layer of the sleeve/cuff.
[0029] In some embodiments, the permeable/semi-permeable region may
extend over only a portion of the sleeve/cuff, and/or over only a
portion of a wall of the sleeve/cuff, and/or a layer of the
sleeve/cuff.
[0030] The permeable/semi-permeable region may comprise perforated
film, for example, laser perforated film.
[0031] The (e.g. laser) perforated film may be a monolayer film, or
a laminate of two or more layers.
[0032] The pore size of the (e.g. laser) perforated film may
optionally have a variation of less than 20% from an average pore
size, optionally less than 15% from an average pore size,
optionally less than 10% from an average pore size, optionally less
than 5% from an average pore size.
[0033] In some embodiments, the (e.g. laser) perforated film may
have a thickness of not substantially greater than 0.05 mm. Use of
such a thin film can contribute to achieving a compact sleeve/cuff
for enabling the stent-valve to achieve a desirably small size for
delivery by catheterization. Optionally the film thickness is not
substantially greater than about 0.045 mm, optionally not
substantially greater than about 0.04 mm, optionally not
substantially greater than about 0.035 mm, optionally not
substantially greater than about 0.03 mm, optionally not
substantially greater than about 0.025 mm, optionally not
substantially greater than about 0.02 mm, optionally not
substantially greater than about 0.015 mm, optionally not
substantially greater than about 0.01 mm, optionally not
substantially greater than about 0.005 mm. In some embodiments, the
film thickness may be between about 0.005 mm and about 0.015 mm,
optionally between about 0.005 mm and about 0.01 mm.
[0034] In some embodiments, the (e.g. laser) perforated film may
have a strength (e.g. linear tensile strength) at least 50% of the
film strength prior to laser perforation, optionally at least 60%
of the strength prior to laser perforation, optionally at least 70%
of the strength prior to laser perforation, optionally at least 80%
of the strength prior to laser perforation, optionally at least 90%
of the strength prior to laser perforation. Such characteristics
can contribute to a strong film even with thin film thickness.
[0035] In some embodiments, the pores (or at least a majority
thereof) in the (e.g. laser) perforated film are substantially
round and/or have a cauterized perimeter and/or have a raised
margin around their perimeter. Such a feature or features may
contribute individually or in combination to film strength even
with thin film thickness. A round pore shape can avoid sharp
corners in the peripheral shape that could be points of stress
concentration or lead to outward crack propagation. Cauterization
of the material around the perimeter of the pore may also
advantageously reduce risk of outward crack propagation. A raised
margin of material around the pore perimeter may also provide
additional material, and hence strength, surrounding the open area
of the pore.
[0036] Continuing from the above list, the seal may comprise one or
any combination of two or more of the following features, as well
as any of the above-noted features, which are all optional: [0037]
The sleeve/cuff may comprise flexible material. The sleeve/cuff may
comprise material that is elastically stretchable, and/or material
that is substantially non-elastically-stretchable. [0038] The
swellable material may occupy only a portion of the (e.g.
circumferential) length of the sleeve/cuff, for example, optionally
not more than about 75%, optionally not more than about 60%,
optionally not more than about 50%, optionally not more than about
40%, optionally not more than about 30%, optionally not more than
about 25%, optionally not more than about 20%. [0039] The
sleeve/cuff may be transparent or translucent. The swellable
material may have a distinctive color (at least when dry) enabling
the position of the swellable material to be identified within the
sleeve/cuff. Such identification may aid a practitioner in deciding
where optionally to puncture the sleeve/cuff, if this technique is
used, as described later. [0040] The sleeve/cuff may have or
comprise an integral tubular structure. As used herein, the term
"integral tubular structure" may mean that the sleeve/cuff or a
wall thereof or a layer thereof, or in the case of a laminate, at
least a structural substrate within the laminate, is produced as an
original integral tube around an axis passing along a centerline of
the tube. As used herein, references to the sleeve/cuff having or
comprising an integral tubular structure apply to at least a wall,
or a layer, or at least a structural substrate of a laminate,
whether or not mentioned explicitly, and whether or not the entire
sleeve/cuff may have such a structure. For example, integral
tubular structures may be made by extrusion of material in tubular
form, or by blow molding a preform to define a tubular form.
[0041] In some embodiments, an integral tubular structure contrasts
from a tube that is non-integrally formed around an axis passing
along a centerline of the tube. Non-integral forming may include,
for example, wrapping a film or sheet around an axis and securing
portions to the film or sheet to define a hollow envelope enclosed
by the wrapping, or by attaching two sheets to define an
envelope.
[0042] In some embodiments, using an integral tubular structure for
the sleeve/cuff may enable the sleeve/cuff to achieve the otherwise
conflicting requirements of desirably thin wall thickness, and good
strength against bursting. Risk of bursting is often highest at
join-lines of non-integral structures. Forming an integral tubular
structure reduces the need for extensive join lines, in particular,
a join line extending circumferentially around the prosthesis (in
some embodiments, substantially around).
[0043] In some embodiments, in which the stent-valve is configured
to be expanded to an operative configuration by expansion by an
inflatable expansion balloon, providing a stent-valve with a seal
sleeve/cuff comprising an integral tubular structure may be highly
advantageous in enabling the seal sleeve/cuff to made desirably
thin, yet have good strength and resistance to bursting should the
seal be subject to the forces applied during the balloon-expansion,
especially against the irregular or sharp contours of a calcified
native anatomy
[0044] Although not immediately intuitive, some embodiments of the
present disclosure provide a technique of post-implantation
balloon-expansion of an implanted prosthesis stent-valve carrying a
swellable seal. Providing a stent-valve with a seal sleeve/cuff
comprising an integral tubular structure may be highly advantageous
in enabling the seal sleeve/cuff to made desirably thin, yet
include strength and resistance to bursting should the seal be
subject to the high forces applied during post-implantation
balloon-expansion, especially against the irregular or sharp
contours of a calcified native anatomy. For example, such forces
may be greater than normally experienced by the seal during initial
implantation (whether by self-expansion of the stent-valve, or by
manual manipulation, for example, initial balloon expansion).
Additionally or alternatively, it may permit a second implantation
procedure (for example, even many years into the future), which may
itself involve a valvuloplasty procedure using an expansion balloon
to prepare for implantation of a further prosthesis. The fact that
the current stent-valve comprises a seal configured to withstand
balloon expansion (e.g. valvuloplasty) forces without risk of
bursting, may continue to provide the patient with the full range
of options for future treatment (which might not be available to a
patient who has been implanted with a different type of swelling
seal not designed to withstand a future balloon expansion and/or
valvuloplasty procedure).
[0045] Continuing from the list above, the seal may comprise one or
any combination of two or more of the following features, as well
as any of the above-noted features, which are all optional. [0046]
Whether or not the sleeve/cuff is formed as or comprising an
integral tubular structure, the sleeve/cuff may comprise a tubular
extrusion or blow molded tubing. [0047] In addition to, or as an
alternative to, the above, the sleeve/cuff may be configured to be
able to withstand post-implantation balloon expansion of the
stent-valve against a calcified anatomy without substantial loss of
structural integrity of the hollow sleeve/cuff. This can provide
similar advantages for permitting balloon expansion (e.g.
post-implantation balloon expansion) and/or suitability for a
future valvuloplasty procedure. [0048] The hollow sleeve/cuff may
be formed from or using a tubular segment from an inflatable
cardiac valvuloplasty balloon. Such balloon material already has
desirable characteristics of being thin-walled yet strong to resist
bursting when the balloon is inflated and bears directly against
hard, irregular and sharp calcifications of a calcified vascular
anatomy. The balloon material is also established as being
bio-compatible and suitable for introduction into, and for direct
contact with, the human vasculature. Optionally, the material may
be laser-perforated, depending on whether it is desired to provide
a permeable (or at least semi-permeable) characteristic. [0049] The
sleeve/cuff may be formed by a method including providing an
elongate hollow tubular member (optionally with an integral tubular
structure), introducing the swellable material into the interior of
the tubular member, and optionally bending the elongate tubular
member to form a substantially toroid shape (e.g. when mounted on
the prosthesis). [0050] The opposite ends of the (e.g. bent)
elongate tubular member may be secured together (for example, by
fusion, welding, or adhesive) to define a closed-loop toroid form,
whether or not the ends of the tube communicate openly with each
other as a continuous open interior space. Alternatively, the
opposite ends of the (e.g. bent) elongate tubular member may remain
disconnected from each other, even after mounting on the
prosthesis. [0051] The hollow sleeve/cuff, or at least a layer or
wall thereof, may be liquid-tight, at least prior to use of the
prosthesis. [0052] The hollow sleeve/cuff, or at least a layer or
wall thereof, may comprise polymeric material and further comprise
a diffusion barrier layer to obstruct diffusion of liquid through
the sleeve/cuff wall and into the space containing the swellable
material. [0053] The hollow sleeve/cuff, or at least a layer or
wall thereof, may comprise a laminate of (1) plastics film and (2)
a diffusion barrier layer to obstruct diffusion of liquids from
outside the hollow sleeve/cuff to the hollow interior. The
diffusion barrier optionally is formed either on an interior face
of the sleeve/cuff or a layer or wall thereof (e.g. the hollow
interior face), or as a non-surface layer of the laminate. Such
positioning of the diffusion barrier layer may protect the
integrity of the diffusion barrier layer during production and
assembly of the prosthesis, enabling easier handling. [0054] The
diffusion barrier material of either of the above may be of or
comprise a metal or metal compound (e.g., an oxide). [0055] The
metal or metal compound may be formed by plasma vapour deposition.
The thickness of the layer may be optionally less than 100 nm,
optionally less than 50 nm, optionally less than 10 nm. [0056] The
diffusion barrier layer may be configured to remain in position on
the prosthesis when the prosthesis is implanted. [0057]
Additionally or alternatively, at least a portion of the
sleeve/cuff (or at least a portion of a layer or wall thereof) may
be configured to be removable to define an area through which
liquid (e.g. blood) may be admitted, in use, for causing the
swellable material to swell. The removable portion may, for
example, be a portion of the or a liquid-tight layer or wall.
[0058] Additionally or alternatively, the sleeve/cuff material is
configured to be pierced in use, prior to introduction into the
body of a patient, to create liquid-admitting punctures in the
sleeve/cuff material. [0059] The prosthesis may be provided as part
of a kit including a piercing tool usable to pierce the sleeve/cuff
to form liquid-admitting punctures in the cuff. The piercing tool
may comprise at least one pin or other sharp projection. The (or
each) pin or protection may be dimensioned to permit puncturing of
the sleeve/cuff without damaging other operative portions of the
prosthesis (for example, without damaging leaflets of a
stent-valve). The piercing tool may, for example, comprise a roller
carrying the at least one (and preferably plural) pin or other
sharp projection. The roller may be configured to be rollable over
a region of the cuff/sleeve to effect the piercing action. [0060]
In some embodiments, the sleeve/cuff may be pierced before, during,
or after, loading of the prosthesis (e.g. stent-valve) into a
delivery catheter. In some examples, the delivery catheter includes
a sheath within which the prosthesis (e.g. stent-valve) is at least
partly contained when loaded (or during loading). The sheath may
include at least one (and optionally a plurality) of apertures
aligned with the sleeve/cuff, and through which the piercing tool
may be introduced to pierce the sleeve/cuff while in situ in the
delivery catheter. [0061] In one example condition of a stent-valve
prior to introduction of the stent-valve into the body of a
patient, the stent-valve has a seal sleeve/cuff containing a
swellable material. The sleeve/cuff is liquid impermeable except
for at least one (and optionally a plurality) of liquid-admitting
punctures made therein, for admitting liquid into the seal.
Additionally or alternatively, the sleeve/cuff is made of
liquid-impermeable material, the sleeve/cuff having one or more
liquid admitting punctures made therein for admitting liquid into
the seal. [0062] In one example condition of a stent-valve prior to
introduction of the stent-valve into the body of a patient, the
stent-valve according to some embodiments includes a seal
sleeve/cuff containing a swellable material. The swellable material
is at least partly hydrated or wetted by liquid (e.g., prior to
introduction of the stent-valve into the body). The sleeve/cuff may
be constrained against substantial expansion by being constrained
within a sheath of a delivery apparatus. The hydrating or wetting
liquid may, for example, be saline. Allowing the seal sleeve/cuff
to at least partly hydrate or become at least party wetted prior to
introduction into the body may enable more efficient swelling of
the material, and therefore of the sleeve/cuff, when the
stent-valve is implanted. It can avoid the need for the seal to
have to become wetted by liquid only on implantation. For example,
speed of wetting and/or swelling may be a consideration if the
liquid-admitting apertures (e.g. punctures) in the sleeve/cuff are
relatively small and/or if a relatively "slow" hydrating/swelling
material is used within the sleeve/cuff. [0063] Additionally or
alternatively to the above, in one example condition of a
stent-valve prior to introduction of the stent-valve into the body
of a patient, the stent-valve is loaded at least partly into a
delivery catheter. The delivery catheter comprises a containment
sheath encompassing at least a portion of the stent-valve at which
the seal is located, the containment sheath being at least partly
filled with liquid, and the swellable material being exposed to the
liquid, the containment sheath obstructing expansion of the seal.
The liquid may, for example, be saline. [0064] The seal may further
comprise a skirt secured to the hollow sleeve/cuff, for example,
using an attachment that does not puncture the cuff Example
attachments may include one or more of: fusion; welding, adhesive.
The skirt may itself be attached to the stent, for example, by
sutures. The skirt may provide a means by which the seal is fixed
to the stent. Such a technique can enable the seal to be secured
fixed to the stent, without risk that the stent fixings may
compromise the integrity of the cuff. [0065] The stent-valve
(optionally all of the stent, valve-leaflets, and seal) may be
compressible to a compressed configuration for delivery, and
expandable to an operative configuration at implantation. In some
embodiments, the stent is a self-expanding type that self-expands
at least partly towards (and preferably self-expands entirely to)
the operative configuration. Additionally or alternatively, the
stent may be manually manipulable (e.g. plastically expandable) to
the operative configuration, for example, using an expansion
balloon or other expanding device or foreshortening device. The
material of the stent, in either case, may for example be selected
from one or more of: shape memory material; shape memory metal
alloy; nitinol; steel, nickel-chromium (containing) alloy;
chromium-cobalt (containing) alloy. [0066] As mentioned previously
above, the seal may be provided as a separate item from the
prosthesis (e.g. stent-valve), and be mountable to the stent-valve,
for example, as part of a pre-implantation preparation process.
[0067] Various techniques are envisaged for mounting a separate
seal to the prosthesis. [0068] One mounting technique may be using
adhesive, for example, an adhesive surface that is provided on the
prosthesis and/or the seal. The adhesive surface may initially be
protected by a release sheet or strip that is removable (e.g.
peelable) from the adhesive surface, to expose the adhesive surface
ready for attaching the seal to the prosthesis. [0069] Additionally
or alternatively, the prosthesis may comprise a dedicated seal
accommodation region to which the seal is mountable. [0070] The
seal accommodation region may comprise an adhesive surface or a
landing surface for adhesive engagement as aforementioned. [0071]
Alternatively, the seal accommodation region may comprise a
substantially continuous, or a discontinuous, accommodation channel
for receiving at least a portion of the seal. A discontinuous
channel may be formed, for example, by a series of spaced apart
loops similar to clothing belt loops. Each loop may be relatively
short in circumferential extent and/or the number of loops may be
relatively small, to define a relatively small mark/space ratio
(e.g. closed-area/open-area ratio) of less than 1, optionally less
than about 0.75, optionally less than about 0.5, optionally less
than about 0.25. Alternatively, each loop may have a
circumferential length such that, and/or the number of loops may be
relatively high such that, the ratio is at least about 1,
optionally at least about 1.25, optionally at least about 1.5,
optionally at least about 1.75, optionally at least about 2,
optionally at least about 2.5, optionally at least about 3. A
substantially continuous channel may be formed, for example, by one
of more of: a tubular structure; a circumferential flap; an open
sided channel; a circumferential envelope or pocket. [0072] A
loading filament (e.g. of suture wire), may be pre-laid within the
accommodation channel to facilitate loading of the seal into the
channel. For example, one end of the loading filament may be
attachable to the seal (for example, to one end of an elongate
seal). Pulling on the opposite end of the loading filament may draw
the seal into the channel. [0073] The accommodation channel may
include one or a plurality of openings and/or clearances for
admitting blood to the seal. At least some of the openings and/or
clearances may, for example, be arranged: (i) facing substantially
or at least partly towards the prosthesis blood outlet end; and/or
(ii) facing substantially or at least partly towards the prosthesis
blood inlet end; and/or facing substantially in a generally radial
inward and/or radial outward direction. The openings and/or
clearances, however arranged, may optionally be permanently open
such that the openings and/or clearances do not substantially
prevent entry of liquid to the accommodation channel. The openings
and/or clearances, however arranged, may have a size that does not
substantially obstruct communication therethrough. [0074] The
accommodation region (e.g. accommodation channel) may optionally
form part of or be coupled to an outer skirt fitting on an exterior
surface of the prosthesis. The skirt may optionally comprise film,
or fabric, or a combination of film and fabric. [0075] The outer
skirt may optionally be permanently attached to an inner skirt
positioned within the prosthesis. The permanent attachment may be
provided by, for example, welding, adhesive or suturing. The inner
and outer skirts may be attached together along at least one line
(or intermittent line) that is generally continuous at least in a
circumferential direction around the prosthesis. Such a line of
attachment can enhance the prevention of leak paths for blood that
could otherwise exist between the inner and outer skirts were the
skirts not so attached.
[0076] Further embodiments of the disclosure may relate to a method
of production of a prosthesis (e.g. a stent-valve), optionally as
defined by any one or any combination of two or more of the
foregoing aspects and features. The method may comprise one or any
combination of two or more of the following steps and/or features,
which are all optional. [0077] A seal of, or for, the prosthesis
may be provided comprising a sleeve/cuff containing a swellable
material. The sleeve/cuff may optionally be a sealed liquid tight
sleeve/cuff, and/or the sleeve/cuff may be provided within a sealed
liquid-tight container. [0078] The seal may be attached to the
prosthesis as an integral part of the prosthesis, or the seal may
be provided as a separate component that is attachable to the
prosthesis (for example, as part of a pre-implantation preparation
process), or the seal may comprise at least one component that is
introducible to (e.g. injectable into) a respective region of the
prosthesis (for example, as part of a pre-implantation preparation
process). [0079] During the method of production, after assembling
the components of the prosthesis (e.g. a stent, one or more
prosthetic valve leaflets, and optionally the seal if provided in
integrally attached form), the stent-valve may be immersed into a
liquid. For example, the liquid may be a sterilizing liquid and/or
a preservative liquid for packaging the stent-valve ready for use.
[0080] The liquid-tight sealed sleeve/cuff may prevent the liquid
from contaminating the swellable material of the seal prior to
intended use. [0081] The liquid may be toxic to the human blood
stream (for example, intended to be rinsed or otherwise cleaned off
the prosthesis (e.g. stent-valve) before the prosthesis is
introduced into a patient's body). [0082] A tubular sleeve/cuff of
the seal (and/or a wall and/or a layer and/or a structural
substrate of a laminate thereof) may be formed by an integral
tubular forming technique. Example techniques may include tubular
extrusion and/or blow molding. [0083] A tubular sleeve/cuff of the
seal (and/or a wall and/or a layer and/or a structural substrate of
a laminate thereof) may be obtained from a segment of a
valvuloplasty balloon. [0084] A tubular sleeve/cuff may be provided
by the steps including providing an elongate hollow tubular member
(optionally with an integral tubular structure), introducing the
swellable material into the interior of the tubular member.
Optionally the steps further include bending the elongate tubular
member to form a substantially toroid shape. [0085] The opposite
ends of the (e.g. bent) elongate tubular member may be closed (for
example, by fusion, welding or adhesive). Additionally or
alternatively, the opposite ends of the (e.g. bent) elongate
tubular member may be secured together (for example, by fusion,
welding, or adhesive) to define a closed-loop toroid form. The
opposite ends may be sealed closed to define a non-continuous
interior of the sleeve/cuff at the join in the toroid, or they may
communicate with each other to define a continuous open interior
across the join. [0086] A diffusion barrier layer may be formed on
a tubular sleeve/cuff of the seal, or on a material blank used to
form the tubular sleeve/cuff, and/or on other cover material for a
seal comprising swellable material. [0087] The diffusion barrier
layer may be or comprise a metal or metal compound. [0088] The
diffusion barrier layer may be formed by plasma vapour deposition.
[0089] The method may include sterilizing the seal, and/or
sterilizing a component used to form the liquid-tight sealed
sleeve/cuff containing swellable material, by irradiation. [0090]
The method may include sterilizing the prosthesis (e.g.
stent-valve), after assembly, by contacting the prosthesis with a
sterilizing fluid, e.g. immersing the stent-valve in a
sterilization liquid. If provided, the liquid-tight sealed
sleeve/cuff may prevent liquid contamination of the swellable
material. The sterilization liquid may optionally comprise an
aldehyde, optionally glutaraldehyde. [0091] The method may include
storing the prosthesis (e.g. stent-valve), ready for use, in liquid
preservative. If provided, the liquid-tight sealed sleeve/cuff may
prevent liquid contamination of the swellable material. The liquid
preservative may optionally comprise an aldehyde, optionally
glutaraldehyde. [0092] The method may include sterilizing a sealed
sleeve/cuff, and sterilizing swellable material therein, using a
different sterilizing technique from the remainder the prosthesis
(e.g. stent valve). For example, the sleeve/cuff, and the swellable
material may be sterilized using radiation. The remainder of the
prosthesis (e.g. stent-valve) may be sterilized by contacting the
prosthesis with a sterilizing liquid (or other sterilizing fluid).
[0093] In addition to or alternatively to any of the foregoing, a
method of producing a prosthesis or a seal for or of a prosthesis,
may comprise providing a wall or layer of material, the material
including at least a laser-perforated region. The wall or layer of
material may be provided as, or be formed into, a sleeve/cuff of a
seal for containing a swellable material that swells when contacted
by blood. The laser-perforated region may extend over substantially
the entire area of the material, or at least a majority of the
material, or over only a selected zone leaving a further zone
without any perforations. [0094] In addition to or alternatively to
any of the foregoing, a method of producing a prosthesis or a seal
for or of a prosthesis, may comprise the step of laser perforating
a region of material. The material may be in the form of, or
subsequently formed into, a sleeve/cuff of a seal for containing
swellable material that swells when contacted by blood. The step of
laser perforating may comprise perforating substantially the entire
area of the material, or at least a majority of the material, or
only a selected zone leaving a further zone without any
perforations.
[0095] Further embodiments of the present disclosure may relate to
a method of preparing and/or using a prosthesis (e.g. stent-valve)
for implantation, the prosthesis optionally as defined and/or
produced by any one or any combination of two or more of the
foregoing aspects and features. The method of using and/or
preparing may comprise one or any combination of two or more of the
following steps and/or features, which are all optional: [0096]
providing (i) the prosthesis (e.g. stent-valve) stored in a storage
solution, and (ii) a seal comprising a material that swells when
contacted. Optionally the seal is included as part of the
prosthesis. Alternatively, at least a component of the seal is
provided as a separate item from the prosthesis, and is mountable
to, and/or introducible to, and/or injectable into the prosthesis
as part of the method. For example, the seal or seal component may
be provided as a separate component mountable to the prosthesis, or
alternatively as a flowable component that is injectable into a
seal part of the prosthesis. [0097] The seal may comprise a
material that swells when contacted by liquid and a sleeve/cuff or
cover. The sleeve/cuff and/or cover may protect the seal from
contact by the storage solution, if the seal is provided as part of
the prosthesis within the storage solution. [0098] rinsing the
stent-valve to clean the stent-valve of the storage solution;
[0099] after rinsing, piercing the sleeve/cuff or cover at one or
more positions to break the integrity of the sleeve/cuff or cover,
in order to allow blood to contact the swellable material upon
implantation; [0100] after rinsing, mounting the seal to the
prosthesis (if the seal is provided as a separate component).
[0101] additionally or alternatively, after rinsing, compressing
and/or loading the stent-valve into a delivery apparatus for
introduction into the body; [0102] additionally or alternatively,
after rinsing and while the stent-valve is outside a human body,
exposing the swellable material to, and/or contacting the swellable
material with, liquid to allow at least partial wetting or
hydration of the swellable material; and [0103] the step of
exposing may be carried out before, or during, or after the step of
compressing. For example, the liquid may be liquid within which the
stent-valve is at least partly immersed (i) during compressing
and/or loading, or (ii) within the delivery catheter.
[0104] In a closely related aspect, the invention relates to a
further method of using a stent-valve for implantation, the
stent-valve optionally as defined and/or produced by any one or any
combination of two or more of the foregoing aspects and features.
The method of using may comprise one or any combination of two or
more of the following steps and/or features, which are all
optional: [0105] providing a stent-valve that is compressible to a
compressed configuration for delivery, and expandable to an
operative configuration for implantation, the stent-valve
comprising a stent, a plurality of leaflets defining a prosthetic
valve, and a seal for sealing against surrounding tissue, the seal
comprising a swellable material that swells when contacted by blood
(and the seal being optionally a part of the prosthesis, or at
least a component of the seal being a separate component that is
mounted to or injected into the prosthesis as part of the method);
[0106] introducing the stent-valve into the body in its compressed
configuration using a delivery device, and advancing the
stent-valve to a desired implantation site; [0107] causing the
stent-valve to expand at the implantation site, from the compressed
configuration to its operative configuration; [0108] observing one
or more characteristics of the operative stent-valve; and [0109] in
dependence on the result of the observation at step (d), performing
post-implantation balloon expansion of the stent-valve.
[0110] Features and advantages of some of the embodiments of the
disclosure, include: [0111] facilitating a seal construction that
is able to swell to automatically seal gaps between the stent-valve
and the surrounding tissue, even in the case of an irregular
anatomy; [0112] facilitating safe post-dilation of the stent-valve
as desired, without significant risk of seal rupture; [0113]
facilitating long storage times of a stent-valve without risk of
contaminating the swellable material of the seal by toxic storage
solution; [0114] facilitating thorough sterilization of a
stent-valve without contaminating or otherwise compromising the
swellable material of a seal; [0115] facilitating simple yet
effective activation of the swellable material of a seal without
having to separate components; [0116] facilitating early partial
hydration or wetting of a swellable seal before implantation, to
reduce the burden of seal to access liquid only at the instant of
deployment at the implantation site; [0117] avoiding the need for
any rupture of a capsule membrane during the implantation process,
by facilitating exposure of a swellable seal material to liquid
prior to introduction into the body, and carrying out such exposure
while the seal is constrained against expansion.
[0118] Additional and/or independent embodiments and features of
the disclosure are included in the claims.
[0119] Although certain features and aspects of the invention are
highlighted in the foregoing summary and in the appended claims,
protection is claimed for any novel concept described herein and/or
illustrated in the drawings, whether or not emphasis is placed
thereon.
BRIEF DESCRIPTIONS OF THE OF THE DRAWINGS
[0120] Non-limiting embodiments of the invention are now described
with reference to the accompanying drawings, in which:
[0121] FIG. 1 is a schematic drawing illustrating a stent-valve 10
with which some embodiments of the present disclosure are suitable
to be used. The figure is broken along a centre-line of the
stent-valve. The stent-structure is shown to the right, and a
profile showing the positions of the valve, skirt and seal is shown
to the left.
[0122] FIG. 2 is an enlarged schematic section showing the seal of
FIG. 1 in isolation.
[0123] FIG. 3a is a schematic perspective view of an elongate
tubular member for use in the production of a seal according to
some embodiments of the disclosure.
[0124] FIG. 3b is a schematic section illustrating obtaining the
tubular member from a valvuloplasty balloon according to some
embodiments of the disclosure.
[0125] FIG. 3c is a schematic partial perspective view of a
sub-assembly including tubing and outer skirt material according to
some embodiments of the disclosure.
[0126] FIG. 3d is a schematic section illustrating an example of
forming the sub-assembly of FIG. 3c, according to some embodiments
of the disclosure.
[0127] FIG. 3e is a schematic view illustrating insertion of
swellable material into the sub-assembly of FIG. 3c.
[0128] FIG. 3f is a schematic side view illustrating assembly of
the sub-assembly to the stent of FIG. 1.
[0129] FIG. 3g is a schematic side view illustrating formation of a
conical tubular sub-assembly for assembly to the stent of FIG.
1.
[0130] FIG. 4 is a schematic section illustrating a seal
sleeve/cuff provided with a diffusion barrier layer according to
some embodiments of the disclosure.
[0131] FIG. 5 is a schematic flow diagram illustrating steps of a
method for producing a stent-valve according to some embodiments of
the disclosure.
[0132] FIG. 6 is a schematic flow diagram illustrating steps of a
method of preparing a stent-valve for implantation according to
some embodiments of the disclosure.
[0133] FIG. 7 is a schematic side view of a piercing tool for
piercing a seal sleeve/cuff of a stent-valve according to some
embodiments of the disclosure.
[0134] FIG. 8 is a schematic section of a first example of delivery
catheter containing a stent-valve loaded therein according to some
embodiments of the disclosure.
[0135] FIG. 9 is a schematic section of a second example of
delivery catheter containing a stent-valve loaded therein according
to some embodiments of the disclosure.
[0136] FIG. 10 is a schematic flow diagram illustrating steps of a
method of implanting a stent-valve according to some embodiments of
the disclosure.
[0137] FIG. 11 is a schematic section of a first example of a seal
according to some embodiments of the disclosure.
[0138] FIG. 12 is a schematic section of a second example of a seal
according to some embodiments of the disclosure.
[0139] FIG. 13 is a schematic view of a first example of a
perforated film according to some embodiments of the
disclosure.
[0140] FIG. 14 is a schematic view of a second example of a
perforated film according to some embodiments of the
disclosure.
[0141] FIG. 15 is a schematic section illustrating a seal
sleeve/cuff provided with an impermeable layer according to some
embodiments of the disclosure.
[0142] FIG. 16 is a schematic drawing illustrating a stent-valve 10
with which some embodiments of the present disclosure are suitable
to be used. The figure is broken along a centre-line of the
stent-valve. The stent-structure is shown to the right, and a
profile showing the positions of exemplary valve and seal
accommodation regions is shown to the left. The figure also depicts
an exemplary separately-provided seal.
[0143] FIG. 17 is a schematic drawing illustrating an exemplary
seal accommodation region, as part of an outer skirt, including
spaced apart loops, according to some embodiments of the
disclosure.
[0144] FIG. 18 is a schematic drawing illustrating an exemplary
seal accommodation channel, as part of an outer skirt, including a
flap, according to some embodiments of the disclosure.
[0145] FIG. 19 is a schematic drawing illustrating an exemplary
seal accommodation channel, as part of an outer skirt, including a
flap comprising castellated extensions, according to some
embodiments of the disclosure.
[0146] FIG. 20 is a schematic drawing illustrating an exemplary
seal accommodation channel, as part of an outer skirt, including a
flap comprising a scalloped edge, according to some embodiments of
the disclosure.
[0147] FIG. 21 is a schematic drawing illustrating an exemplary
seal accommodation channel, as part of an outer skirt and
comprising a tube (or an envelope), according to some embodiments
of the disclosure.
[0148] FIG. 22 is a schematic drawing illustrating a stent-valve 10
with which some embodiments of the present disclosure are suitable
to be used. The figure is broken along a centre-line of the
stent-valve. The stent-structure is shown to the right, and a
profile showing the positions of exemplary valve and seal
accommodation regions is shown to the left. The figure also depicts
an exemplary separately-provided seal bearing an adhesive
region.
[0149] FIG. 23 is a schematic section showing an exemplary seal,
according to some embodiments of the disclosure. The figure also
depicts an exemplary introduction of a flowable swellable material
through an optional inlet port of the seal.
[0150] FIG. 24 is a schematic drawing illustrating an exemplary
outer skirt, according to some embodiments of the disclosure,
comprising attachment zones on either side of a seal accommodation
region.
[0151] FIG. 25 is a schematic section showing an exemplary outer
skirt comprising a sheet of film material, according to some
embodiments of the disclosure.
[0152] FIG. 26 is a schematic section showing a first example of an
outer skirt comprising a sheet of film material and fabric
material, according to some embodiments of the disclosure.
[0153] FIG. 27 is a schematic section showing a second example of
an outer skirt comprising a sheet of film material and fabric
material, according to some embodiments of the disclosure.
[0154] FIG. 28 is a schematic section showing a third example of an
outer skirt comprising a sheet of film material and fabric
material, according to some embodiments of the disclosure.
[0155] FIG. 29 is a schematic drawing illustrating a stent-valve 10
with which some embodiments of the present disclosure are suitable
to be used. The figure is broken along a centre-line of the
stent-valve. The stent-structure is shown to the right, and a
profile showing the positions of exemplary valve and seal
accommodation regions is shown to the left. The figure also depicts
an exemplary separately-provided seal that is correspondingly
broken along its centre-line, depicting a saddle/harness for
attachment to the stent.
[0156] FIG. 30 is a schematic flow diagram illustrating steps of a
method of using and/or preparing a stent-valve for implantation
according to some embodiments of the disclosure.
[0157] Referring to FIG. 1, a stented prosthesis according to some
embodiments is illustrated in the form of a stent-valve 10. A seal
40 (described further below) may be provided for sealing against
surrounding tissue when the stent-valve 10 is implanted. The
stent-valve 10 may be cardiac stent-valve, for example, an aortic
stent-valve, a mitral stent-valve, a pulmonary stent-valve or a
tricuspid stent-valve, for implantation at the respective valve
position in a human heart.
[0158] The stent-valve 10 may optionally comprise biological tissue
(for example, pericardium (such as porcine pericardium and/or
bovine pericardium) and/or natural cardiac valve leaflets (for
example, natural porcine cardiac valve leaflets, optionally
attached to a portion of natural cardiac wall tissue). The
biological tissue may be fixed, for example, using
glutaraldehyde.
[0159] The stent-valve 10 may be compressible to a radially
compressed condition (FIG. 8) for delivery using a delivery
catheter, and be expandable to an operative or expanded condition
(as shown) at implantation. The stent-valve 10 may comprise a stent
12 carrying a plurality of leaflets defining a valve 14 (the
position of which is depicted schematically by the bounding phantom
lines). Various geometries of stent 12 may be used. In some
embodiments, the stent 10 may include one of more of: a lower
tubular or crown portion 16, an upper crown portion 18, a plurality
of upstanding commissural supports 20, and a plurality of
stabilization arches 22. In use, the lower portion 16 of the stent
12 may be configured to be deployed after the other regions of the
stent 12. For example, the arches 22, the supports 20 and the upper
crown 18 may be deployed at least partly before the lower portion
16 (in that order, or in reverse order, or in a different order).
At the very least, once the upper crown 18 has been at least partly
deployed, the stent 12 may be urged and/or displaced in the
direction of arrow 24 to seat the upper crown 18 against native
leaflets at the implantation site. Deploying the lower portion 16
last fixes the stent 12 in its final position.
[0160] The lower portion 16, and optionally a portion of the upper
crown 18, may be formed by a lattice structure of the stent. The
lattice structure may define cells or apertures, for example,
generally diamond-shaped apertures.
[0161] The native leaflets may generally overlap a portion 26 of
the stent. The native valve annulus may overlap a portion 28 of the
stent.
[0162] Optionally, the stent-valve 10 may further include an inner
skirt 30 communicating with the leaflets 14 and carried on an
interior of the stent 12. Additionally or alternatively, the
stent-valve 10 may further comprise an outer skirt 32 carried on an
exterior of the stent 12. When both skirts are provided, the skirts
may partially overlap. The skirts may be offset such that one skirt
(e.g. the outer skirt 32) extends further towards a lower extremity
of the stent 12 than the other (e.g. inner skirt 30). Additionally
or alternatively, one skirt (e.g. the inner skirt 30) extends
further towards an upper extremity of the stent 12 than the other
(e.g. outer skirt 32). The skirts may be of any suitable flexible
and/or compliant material, for example, fabric (e.g. of PET) or of
biological tissue (e.g. of pericardium).
[0163] Optionally, the inner skirt 30 and the outer skirt 32 may be
attached directly to each other along at least one substantially
continuous or discontinuous line of attachment. The attachment may,
for example, be by one of more of: suturing, welding, fusion,
adhesive. The line of attachment may optionally extend around the
entire circumference of the stent-valve. The attachment may
mitigate risk of leakage of blood in the spaces of the stent
between the inner and outer skirts 30 and 32.
[0164] Optionally, at least the outer skirt 32 is positioned to
leave the upper crown 18 substantially unobscured by the outer
skirt 32. Such an arrangement may assist good blood flow to the
coronary arteries (for example, in the case of a stent-valve for
the aortic valve).
[0165] In some embodiments, the lower portion 16 has an extremity
formed with a substantially zig-zag shape. The zig-zag shape may
comprise lower apexes 16a and upper apexes 16b. The upper apexes
16b may be masked in FIG. 1 by the superimposed presentation of
both the frontmost and rearmost cells of the lattice structure. The
zig-zag shape may be substantially continuous around the
circumference of the stent 12. The outer skirt 32 may have a
peripheral edge having a zig-zag shape that matches substantially
the zig-zag shape of the extremity of the lower portion 16. Such an
arrangement can avoid excessive material at the extremity, and
thereby facilitate crimping of the stent-valve 10. At the same
time, the outer skirt 32 covers (for example, complete) open cells
of the lattice structure down to the stent extremity to reduce risk
of blood leakage through the apertures of the cells. The outer
skirt 32 can also provide a layer of material over the struts of
the stent, thereby to cushion the engagement between the stent and
the sensitive native heart tissue.
[0166] The valve 14 may comprise biological tissue, for example,
pericardium (such as porcine pericardium or bovine pericardium) or
natural cardiac valve leaflets (for example, natural porcine
cardiac valve leaflets, optionally attached to a portion of natural
cardiac wall tissue). Other biological or non-biological material
could also be used for the valve 14, as desired.
[0167] The stent 12 may optionally be of a self-expanding type that
is compressible to the compressed configuration for loading into a
delivery catheter 98 (FIG. 8) having a sheath 106 for constraining
the stent 12 in the compressed configuration for delivery to the
site of implantation. In use, by removal of the constraining effect
of the sheath, the stent 12 self-expands to or towards the
operative configuration. A self-expanding stent may, for example,
be of shape-memory material, for example, shape-memory metal alloy,
for example, nitinol. Alternatively, the stent 12 may be configured
to be expanded by application of a foreshortening force from the
delivery catheter and/or by application of expanding force from the
delivery catheter, such as by using an expansion balloon.
[0168] The seal 40 may be configured for sealing against
surrounding native tissue when the stent-valve 10 is implanted. In
some embodiments, the seal 40 may be provided as an integral part
of the stent-valve 10. Alternatively, in some embodiments, at least
a component of the seal 40 may be provided as a separate item from
the stent-valve. The at least one component may, for example, be
mountable to the stent-valve 10 prior to implantation, or it may be
introduced (e.g. injected) into a portion of the stent-valve. The
at least one component may be mounted/introduced as part of a
pre-implantation preparation process (for example, described
later).
[0169] The seal 40 may be arranged or arrangeable at any suitable
position on the stent 12. In some embodiments, the seal 40 may be
arranged between the upper crown portion 18 and the lower crown or
tubular portion 16. In some embodiments, the seal 40 may be
positioned optionally closer to the upper crown portion 18,
alternatively optionally closer to the lower crown or tubular
portion 16, alternatively optionally midway between the extremities
of the two crown portions 16 and 18, alternatively optionally at a
waist or trunk section between the two crown portions 16 and 18. In
some embodiments, the seal 40 is carried on the exterior of the
stent 12.
[0170] As mentioned above, in some embodiments, the (e.g. lower or
inlet) periphery of the stent 12 has a substantially zig-zag shape.
The zig-zag shape may comprise lower apexes 16a and upper apexes
16b. The upper apexes may be masked in FIG. 1 by the superimposed
presentation of both the frontmost and rearmost cells of the
lattice structure. The zig-zag shape may be substantially
continuous around the circumference of the stent 12. The seal 40
may be arranged or arrangeable to be positioned only between the
upper crown 18 and the upper apexes 16b. For example, the seal 40
does not extend to occupy space between the upper apexes 16b and
the lower apexes 16a. Positioning the seal 40 clear of the lower
apexes 16a can reduce the bulk of material at the extremity, and
facilitate crimping. Additionally or alternatively, the seal may be
positioned so as not to cover the upper crown 18. Leaving the upper
crown 18 clear may enhance blood flow to coronary arteries (for
example, in the case of a replacement valve for the aortic valve
position).
[0171] Referring to FIG. 2, the seal 40 may comprise a hollow
sleeve/cuff 42 arranged to extend substantially in a
circumferential direction around the stent 12, and containing
swellable material 44 that swells when contacted by blood to
distend the hollow sleeve/cuff 42. The swellable material 44 may
expand by absorbing blood or other liquids that contact the
material 44. Such a seal 40 may initially be very compact in form,
yet may expand significantly when contacted by blood, to fill gaps
between the stent-valve 10 and any irregularities in the
surrounding tissue. Examples of suitable swellable (e.g.
absorptive) material 44 may be any of the hydrogels referred to in
the aforementioned patents and applications: U.S. Pat. No.
5,769,882, EP 1262201, WO-A-2008/070442, US 2007/0060998,
WO-A-2010/083558. The sleeve/cuff 42 may comprise flexible
material. The sleeve/cuff 42 may comprise material that is
elastically stretchable, and/or material that is substantially
non-elastically-stretching.
[0172] In some embodiments, the hollow sleeve/cuff 42 or a wall or
layer thereof, has or comprises an integral tubular structure. An
integral tubular structure may mean that the sleeve/cuff (or wall
or layer) 42 is produced as or comprises an original integral tube
around an axis passing along a centerline of the tube; in the case
of the sleeve/cuff 42 having or comprising a laminate structure, at
least a structural substrate (e.g. substrate layer) within the
laminate may be produced as an integral tube around an axis passing
along a centerline of the tube. As used herein, references to the
sleeve/cuff 42 having or comprising an integral tubular structure
also apply to at least a wall or layer or a structural substrate of
the laminate, whether or not mentioned explicitly, and whether or
not the entire sleeve/cuff 42 may have such a structure. For
example, integral tubular structures may be made by extrusion of
the sleeve/cuff 42 material in tubular form, or by blow molding a
preform to define a tubular form. Using an integral structure for
the sleeve/cuff 42 may enable the sleeve/cuff 42 to achieve the
otherwise conflicting requirements of desirably thin wall
thickness, and good strength against bursting. Risk of bursting is
often highest at join-lines of non-integral structures. Forming an
integral tubular structure reduces the need for extensive join
lines, in particular, a join line extending circumferentially
around (and in some embodiments, substantially around) the
prosthesis.
[0173] As illustrated later below, in some embodiments, an
implantation method may include a step of (e.g., post-implantation)
balloon-expansion of an implanted prosthesis stent-valve 10
carrying a seal 40. Providing the stent-valve 10 with a seal
sleeve/cuff 42 having or comprising an integral tubular structure
may be highly advantageous in enabling the seal sleeve/cuff 42 to
made desirably thin, yet have good strength and resistance to
bursting should the seal be subject to the high forces applied
during (e.g. post-implantation) balloon-expansion, especially
against the irregular or sharp contours of a calcified native
anatomy.
[0174] Referring to FIG. 3, whether or not of an integral tubular
structure, the material for the sleeve/cuff 42 may initially be
provided in elongate tubular form 46 (FIG. 3a), for example, as an
elongate integral tube. In some embodiments, (whether or not of an
integral tubular structure) such an elongate tube 46 may be
obtained from a balloon section of an inflatable cardiac
valvuloplasty balloon 48 (FIG. 3b), for example, by cutting the
balloon 46a near its ends, to extract an elongate tubular segment
as the tube 46. Such balloon material already has desirable
characteristics of being thin-walled yet strong to resist bursting
when the balloon is inflated and bears directly against hard,
irregular and sharp calcifications of a calcified vascular anatomy.
The balloon material is also established as being bio-compatible
and suitable for introduction into, and for direct contact with,
the human vasculature.
[0175] Whether or not obtained from a cardiac valvuloplasty
balloon, and whether or not having an integral tubular structure,
example materials for the sleeve/cuff 42, or tube 46, may include
one or more of: polyamide (PA), polyimide (PI),
polyetheretherketone (PEEK), polyester (PE), for example,
polyethylene terephthalate (PET).
[0176] Referring to FIG. 3c, in some embodiments using a seal 40
that is integral with the stent-valve 10, the elongate tube 46 may
be attached to material 48, such as a material blank, for forming
the outer skirt 32. The attachment of the tube 46 to the blank 48
is preferably by an attachment that does not puncture the elongate
tube 46 for the sleeve/cuff 42. The tubular integrity of the tube
46 may be preserved. The attachment may, for example, be by fusion,
or welding, or adhesive. In some embodiments, the blank 48 may be
of the same material as the tube 46, to facilitate attachment, for
example, by fusion. Creation of a sub-assembly 50 comprising both
the seal sleeve/cuff 42 and the material 48 can facilitate easier
handling during manufacture and production of the stent-valve
10.
[0177] Various techniques are possible. Purely by way of example,
the material blank 48 may also be obtained from a section of a
cardiac valvuloplasty balloon. Referring to FIG. 3d, the blank 48
may be manipulated while in tubular form. For example, mandrels 52
may be inserted into both the elongate tube 46 and the tubular
blank 48. By a combination of heat and pressure (indicated by
arrows 54), the tubes 46 and 48 may be fused together along an
elongate line of attachment 56. Thereafter, the mandrels 52 are
withdrawn, and the tubular blank 48 may be cut along a line 58 to
define a planar section of material for the outer skirt 32.
[0178] To facilitate suturing the material 48 to the stent, the
material 48 may alternatively be, or comprise, a fabric. For
example, the material may comprise a film laminated to a fabric.
The fabric may be laminated over the entire area of the film or
merely in one of more zones intended to be sutured. The fabric may
be easier than film to suture without risk of crack propagation.
The presence of fabric in a laminate can also stabilize the
laminate against crack propagation when a suture hole is made
through the laminate. The fabric may be absent in the zone intended
for, or substantially in register with the seal 40. The absence of
fabric at this region may enable the material 48 to be thinner at
the seal 40, to achieve a compact skirt and seal arrangement
suitable for crimping.
[0179] Referring to FIG. 3e, and whether or not the tube 46 is a
separate item, or attached to material 48 as sub-assembly 50, the
swellable material 44 may be placed into the interior of the
elongate tube 46. The swellable material 44 may be substantially
smaller (e.g., shorter) than the tube 46, but be able to swell
significantly upon contact with blood, to distend the sleeve/cuff
42 substantially around its periphery. The swellable material 44
may occupy only a portion of the circumferential length of the
cuff, for example, optionally not more than about 75%, optionally
not more than about 60%, optionally not more than about 50%,
optionally not more than about 40%, optionally not more than about
30%, optionally not more than about 25%, optionally not more than
about 20%. Optionally, the ends of the elongate tube 46 are each
sealed to close the interior space of the tube 46 with the
swellable material 44 captive therewithin. The ends may, for
example, be sealed closed by welding, fusion, or adhesive.
[0180] Referring to FIG. 3f, the sub-assembly 50 (if used) may be
bent into a tubular form, and attached to the stent 12. In some
embodiments, the sub-assembly 50 is attached to the stent in sheet
form, by wrapping the sub-assembly 50 around the stent 12.
Alternatively, (FIG. 3g), the sub-assembly may be first secured in
a tubular form, and the tubular form attached to the stent 12. For
example, the ends of the sub-assembly may be partly overlapped and
welded together, to define a lapped join. The weld may seal closed
the ends of the sleeve/cuff 42 (tubing 46). The weld may be clear
of the swellable material within the sleeve/cuff 42. The tubular
sub-assembly 50 may have a conical shape to match the contour of
the lower portion of the stent 12. The tubular assembly 50 may have
a zig-zag edge 50a to match the peripheral edge at one end (e.g.
inlet end) of the stent. For example, the zig-zag edge 50a may be
cut and/or trimmed after assembly to the stent 12.
[0181] In either case, the sub-assembly 50 may be secured to the
stent 12 by sutures 60. Optionally, the sutures 60 pass only
through the material of the outer skirt 32, and do not penetrate
the material of the sleeve/cuff 42. The outer skirt 32 may act as
the means for securing the sleeve/cuff 42 to the stent 12 without
compromising the tubular integrity of the sleeve/cuff 42.
[0182] As can be seen in FIG. 3f, the elongate tube 46 is bent into
a toroid shape around, or to match, the stent 12. The toroid shape
may be a closed-loop toroid. Alternatively, the toroid shape may be
partial loop, a split-loop, or a helical shape, for example. In
some embodiments, the ends of the tube 46 are not sealed
independently, but are sealed together to communicate with each
other to define a circumferentially continuous hollow space across
the join. However, in other embodiments, the ends of the tube 46
may be sealed closed to define a non-continuous interior across the
join.
[0183] Referring to FIG. 4, the sleeve/cuff 42 may carry or
comprise a diffusion barrier layer 62. For example, the sleeve/cuff
material may comprise a laminate of (i) plastics film 64, and (ii)
the diffusion barrier layer 62. The diffusion barrier layer 62 may
serve to prevent diffusion of liquid, or other fluid, through the
sleeve/cuff wall material. As explained later below, the
stent-valve 10 may be immersed in liquid or other fluid during
manufacture (e.g. during sterilization) and/or during storage when
packaged ready for use. The diffusion barrier layer 62 can
substantially prevent any trace of liquid diffusing through the
sleeve/cuff wall, even though the plastics film 64 may be very
thin.
[0184] In some embodiments, the diffusion barrier layer 62 is a
metal or metal-compound. The diffusion barrier layer 62 may, for
example, be deposited by plasma vapour deposition. The diffusion
barrier layer 62 may have a thickness of less than 100 nm,
optionally less than 50 nm, optionally less than 10 nm. The
thickness of the diffusion barrier layer 62 may be exaggerated in
FIG. 4. The diffusion barrier layer 62 may optionally be provided
in a non-exterior-surface portion of the sleeve/cuff wall. For
example, the diffusion barrier layer 62 may be provided on an
interior face of the sleeve/cuff 42 (as shown in FIG. 4), or it may
be provided as a non-surface portion of the laminate. Avoiding
placing the diffusion barrier layer 62 on the exterior face of the
sleeve/cuff 42 may reduce the risk of damage to the integrity of
the diffusion barrier layer 62, for example, during subsequent
handling and production of the stent-valve.
[0185] When the diffusion barrier layer 62 is formed on a
sleeve/cuff 42 that has an integral tubular structure, plasma
vapour deposition may, for example, be used to deposit the
diffusion barrier layer in the hollow space of the sleeve/cuff 42,
on the interior face of the sleeve/cuff 42. The diffusion barrier
layer 62 may be deposited after the attachment of the sleeve/cuff
42 (or the tube 46) to the material 48 for the outer skirt 32, to
avoid risk of damage to the diffusion barrier layer during
attachment of the sleeve/cuff 42 or tube 46 to the material 48.
[0186] Alternatively, the exterior face of the sleeve/cuff 42 or
tube 46 may be coated with the diffusion barrier layer material,
and a further protective coating (not shown) applied over the
exposed face of the diffusion barrier layer, to complete the
laminate.
[0187] In either case, the tube 46 may act as a structural
substrate of the resulting laminate, providing the integral tubular
structure of the sleeve/cuff 42. Also, in either case, the
diffusion barrier layer 62 may be an integral part of the
stent-valve 10 that remains in place and is not removed at
implantation.
[0188] Referring to FIG. 5, a method of production of the
stent-valve 10 may generally comprise one or more of the steps
of:
[0189] Step 70: providing the stent 12;
[0190] Step 72: providing a prosthetic valve 14 (optionally
attached to the inner skirt 30);
[0191] Step 74: providing the seal 40 (for example, the
sub-assembly 50 including the sleeve/cuff 42 containing the
swellable material, and optionally the material 48 for the outer
skirt 32);
[0192] Step 76: assembling the valve 14 and the seal 40 to the
stent 12, for example, using sutures to secure the valve 14 within
the stent, and to secure the sub-assembly around an exterior
portion of the stent 12. This step may be omitted during production
if the seal 40 (or at least a component) is provided as a separate
item from the stent-valve 10.
[0193] Step 78: sterilizing the assembled stent-valve 10;
[0194] Step 80: placing the assembled stent-valve 10 into packaging
for storage; and
[0195] Optionally step 82: sterilizing the seal 40 using a
sterilization process different from step 78.
[0196] The step 78 of sterilizing the assembled stent-valve 10 may
be performed by contacting the stent-valve 10 with a sterilization
fluid, for sterilizing portions of the stent-valve contacted by the
fluid. The fluid may, for example, be a liquid. Alternatively, the
fluid may be a gas, or a liquid/gas combination. The sterilization
fluid may be, or comprise a component, toxic to the human
blood-stream. For example, the fluid may be intended to be rinsed
or otherwise cleaned from the stent-valve prior to implantation. An
example sterilization liquid comprises an aldehyde, for example,
glutaraldehyde. The liquid may be an aqueous solution. Step 78 may
optionally comprise heating the sterilization liquid to above room
temperature, optionally above body temperature, optionally at least
about 40.degree. C., optionally at least about 50.degree. C.
Heating the sterilization liquid may enhance efficacy and/or speed
of sterilization.
[0197] During step 78, the sleeve/cuff 42 prevents the sterilizing
fluid from contaminating the swellable material 44, in the case
that the seal 40 is integral with the stent-valve 10. As explained
previously, the swellable material 44 may swell as a result of
absorption of liquid. Toxic contamination of the swellable material
44 may make it difficult or impossible to remove the toxic liquid
if chemically absorbed by the swellable material 44. Toxic
contamination of the swellable material 44 may render the
stent-valve less appropriate for implantation, and in some cases
unimplantable. The sleeve/cuff 42 may prevent such contamination
(for example, even if a sterilization liquid is heated). If used,
the diffusion barrier layer 62 may further enhance the protective
properties of the sleeve/cuff 42 in preventing any liquid from
diffusing through the sleeve/cuff into the space used for the
swellable material.
[0198] Steps 78 and 80 may be carried out in either order, or at
least partly at the same time. For example, in some embodiments, at
step 80, the stent-valve 10 may be placed into its final packaging
and immersed in liquid. The stent-valve may be sterilized in its
final packaging, using the same liquid. Such a technique may be
referred to as "terminal sterilization". In other embodiments, the
stent-valve 10 may be sterilized by immersion in a first liquid
(step 78), and subsequently transferred to a second liquid or
storage liquid (step 80). The storage liquid may be similar to the
sterilization liquid, and may be or comprise a component that is
toxic to the human blood stream. In such case, provision of the
sleeve/cuff 42 (and optionally the diffusion barrier layer 62)
protects the swellable material against toxic contamination. The
stent-valve 10 may be stored in the storage liquid for an extended
period of time. The sleeve/cuff 42 may be configured to resist
penetration and/or diffusion of the storage liquid to the interior
space of the cuff, for a period of at least 1 month, optionally at
least 6 months, optionally at least 1 year.
[0199] Step 82 may be an optional separate step of sterilizing the
seal 40, especially the interior of the sleeve/cuff 42. When a
fluid-based sterilization technique may be used for step 78, such a
technique should not be used for the interior of the seal 40
because, as explained above, it may result in contamination of the
swellable material 44. Instead, in some embodiments, a different
non-fluid-contact sterilization technique may be used, for example,
using radiation sterilization. Step 82 may be carried out at any
suitable stage of the production process. In some embodiments, step
82 may be carried out as part of step 74. For example, the
sub-assembly 50 may be sterilized so that it is provided at step 74
with the sleeve/cuff 42 sterile (or at least having a sterile
interior). Alternatively, step 82 may be carried out at any stage
after step 76.
[0200] Referring to FIG. 6, a method of preparing the stent-valve
10 ready for implantation may comprise one or more of the following
steps (any of which, and optionally all of which, may be carried
out outside the body of the patient to be implanted):
[0201] Step 90: providing the stent-valve 10 in a storage liquid,
for example, as explained above;
[0202] Step 92: rinsing the stent-valve 10 to clean the storage
liquid off the stent-valve 10. During step 92, the liquid-tight
property of the sleeve/cuff 42 prevents liquid contact with the
swellable material 44. This permits thorough rinsing of the
stent-valve 10 desirable to remove substantially all of the storage
liquid.
[0203] Step 94: after step 92, exposing the swellable material 44
to permit contact with liquid; and
[0204] Step 96: after step 92, compressing the stent-valve 10
and/or loading the stent-valve 10 into a delivery apparatus 98
(FIG. 8).
[0205] Steps 94 and 96 may be carried out in either order or at
least partly at the same time as each other.
[0206] In some embodiments, step 96 may comprise the step of
piercing the sleeve/cuff 42 using a piercing tool 100, to penetrate
the sleeve/cuff material and create one or more liquid-admitting
punctures in the sleeve/cuff 42. Piercing the sleeve/cuff 42 may
leave the material of the sleeve/cuff 42 in place. For example, if
used, a diffusion barrier layer may remain in place on the
stent-valve 10, even after implantation. The punctures created in
the sleeve/cuff 42 may pass through the diffusion barrier layer. An
example piercing tool 100 is illustrated in FIG. 7. The piercing
tool 100 may comprise at least one sharp pin 102 (or other sharp
projection), and a handle portion 104 for enabling manual
manipulation of the tool. The pin 102 may be dimensioned such that
it can safely penetrate the sleeve/cuff 42 without reaching through
to the interior of the stent 12, and valve 14. Damage to the valve
14 can be prevented. In some embodiments, a face or flange 106 of
the handle portion 104 may act as an abutment that bears against
the sleeve/cuff 42 surface to limit the depth of penetration, or
another form of "stop" may be provided. In other embodiments, the
piercing tool may comprise a roller having a surface on which is
formed at least one sharp pin (preferably plural pins). In use, the
roller is rolled on the surface to be pierced, and the punctures
are created as the roller rotates on that surface.
[0207] Optionally, the step of piercing the sleeve/cuff 42 may
include piercing the sleeve/cuff 42 at one or more positions that
are clear of the location of the swellable material 44 within the
cuff. Piercing the sleeve/cuff 42 away from the swellable material
44 may avoid risk of physical damage to a swellable material
component. In some embodiments, the sleeve/cuff 42 may be
transparent, or translucent, and the swellable material 44 may have
a color (e.g. a distinctive color) to enable the location of the
swellable material inside the sleeve/cuff 42 to be identified. This
can help the medical practitioner if it is desired to pierce the
sleeve/cuff 42 at positions clear of the location of the swellable
material 44.
[0208] Additionally or alternatively, whether or not the
sleeve/cuff 42 is to be pierced at positions clear of the swellable
material 44, the sleeve/cuff 42 may comprise indicia to indicate
suitable positions on the sleeve/cuff 42 at which to
pierce/penetrate the sleeve/cuff material, to create the
liquid-admitting punctures.
[0209] Generally, the ability to complete the exposure step 94
prior to introduction into the patient's body can avoid any need to
rely on an exposure mechanism that is activated as part of the
implantation procedure once inside the body, for example, the
pressure responsive rupturing capsules described in the
aforementioned US-A-2007/0060998 and WO-A-2010/083558. This can
reduce the risk of complication should, in some cases, such an
exposure mechanism malfunction and fail to operate correctly at the
time of implantation and once already in the body, where the
possibility of further intervention may already be limited.
[0210] In some embodiments, step 96 may comprise using a
compressing tool (such as one or more funnel shaped tubes, not
shown) through which the stent-valve 10 is advanced in order to
compress the stent-valve 10 to its compressed configuration. The
stent valve 10 may be coupled to, and/or loaded within a
constraining sheath 106 of, the delivery catheter 98. The
constraining sheath 106 may constrain the stent-valve 10 in the
compressed configuration suitable for introduction into the patient
via minimally invasive surgery or a percutaneous procedure.
[0211] In some embodiments, step 96 may be carried out at least
partly while contacting the stent-valve 10 with liquid, for
example, at least partly immersing the stent-valve in liquid. The
liquid may be water or saline. The liquid may be cold, for example,
at a temperature less than room temperature (for example, cold
water or cold saline). For example, carrying out the compressing
step in cold liquid may make the stent 12 more supple and easier to
compress. Additionally or alternatively, the containment sheath 106
may be flushed or at least partly filled with liquid to purge air
from the containment sheath 106, prior to introduction into a
patient's body.
[0212] In some embodiments, especially where step 96 is carried out
at least partly while contacting the stent-valve 10 with liquid, it
may be decided to carry out step 94 after the stent-valve 10 (or at
least a portion of the stent-valve 10 carrying the seal 40) is
constrained in a compressed condition by the constraining sheath
106. Such a technique can (i) permit at least partial exposure of
the swellable material 44 to liquid to at least partly wet or
hydrate the swellable material 44 prior to introduction into the
patient's body, and (ii) prevent the seal 40 from swelling
prematurely, even though the swellable material 44 is exposed to
liquid.
[0213] Wetting or hydrating the swellable material 44, at least
partly, prior to introduction into the body may in some cases be
beneficial to enable more efficient swelling of the material 44,
and therefore of the seal 40 and/or sleeve/cuff 42, when the
stent-valve 10 is implanted. It can avoid the need for the seal 40
to have to become wetted or to hydrate only on implantation. For
example, speed of wetting and/or hydration and/or swelling may in
some cases be a consideration if the liquid-admitting apertures
(e.g. punctures) in the sleeve/cuff 42 are relatively small and/or
if a relatively "slow" wetting and/or hydrating and/or swelling
material 44 is used within the sleeve/cuff 42.
[0214] Additionally or alternatively, exposing the swellable
material 44 only relatively late in the preparation procedure may
combine (i) the advantage of being able to perform the exposure
step 94 outside the patient's body (to avoid having to rely, as
mentioned above, on an exposure mechanism that is activated as part
of the implantation procedure once in the body), while (ii)
limiting the amount of time during which the swellable material
(44) is exposed to liquid prior to the implantation. Exposure
during an excessive period of time might, in some cases and
depending on the materials used, be counterproductive to the use as
a dynamically swelling seal. In some embodiments, the swellable
material 44 might be exposed to liquid outside the patient's body,
for a time duration of: optionally not more than about 1 hour;
optionally not more than about 30 minutes; optionally not more than
about 20 minutes; optionally not more than about 15 minutes;
optionally not more than about 10 minutes; optionally not more than
about 9 minutes; optionally not more than about 8 minutes;
optionally not more than about 7 minutes; optionally not more than
about 6 minutes; optionally not more than about 5 minutes;
optionally not more than about 4 minutes; optionally not more than
about 3 minutes; optionally not more than about 2 minutes;
optionally not more than about 1 minute.
[0215] FIG. 8 illustrates a portion of a delivery catheter 98,
including a containment region 108 for the stent-valve 10
(indicated schematically in its compressed configuration by broken
lines), and a constraining sheath 106. The delivery catheter 98 is
illustrated in a condition optionally outside the patient's body,
but in which the stent-valve 10 is loaded, and the delivery
catheter 98 may be ready for introduction into the patient's body.
The constraining sheath 106 may be translatable between a closed
condition (as shown) in which the sheath 106 substantially
constrains the stent-valve 10 in its compressed configuration,
ready for introduction into the patient's body and delivery to the
implantation site, and an open position (not shown) in which the
sheath is translated in a direction (e.g. as illustrated by arrow
110 towards a handle portion 114, but optionally in the opposite
direction away from the handle portion 114) to expose the
stent-valve 10 for expansion to the operative configuration for
implantation. The delivery catheter 98 may further comprise a
flushing port 112 (which may optionally be at the handle portion
114 or handle-end of the delivery catheter). The flushing port 112
permits introduction of a liquid 116 (e.g. saline) for filling at
least the containment region 108, and for purging trapped air from
the containment region 108. The stent-valve 10 is immersed in the
liquid 116 inside the containment sheath 106.
[0216] The sheath 106 may comprise a plurality of guide apertures
118 which, in the closed condition of the sheath 106, align with,
or overlap or otherwise become in register with, the sleeve/cuff 42
and/or seal 40. The guide apertures 112 are intended to permit
insertion of the pin 102 of the piercing tool 100, in order to
create liquid-admitting punctures in the cuff, as described earlier
above. The liquid-admitting punctures may be formed before, or
after, or during, the introduction of liquid 116 into the
containment region 108. The punctures may cause the liquid 116 to
come into contact with the swellable material 44 of the seal 40.
However, the constraining sheath 106 can prevent substantial
expansion of the seal 40 until the moment of implantation.
[0217] FIG. 9 illustrates an alternative version of the delivery
catheter 98 comprising plural sheaths 106a and 106b. The sheaths
may meet substantially end to end (as shown), or they may be at
least partially overlapping (not shown). In a similar manner to
that described above, at least one of the sheaths 106a and 106b may
comprise guide apertures intended to permit insertion of the pin
102 of the piercing tool 100 to penetrate and pierce the
sleeve/cuff 42 of the stent-valve 10. Alternatively (as shown), a
small gap 118 at the interface between the two sheaths 106a and
106b may provide the guide aperture for insertion of the piercing
tool.
[0218] Referring to FIG. 10, a method of implanting the stent-valve
10 may comprise one or more of the following steps:
[0219] Step 120: providing the stent-valve 10 in its compressed
configuration ready for introduction into a patient's body.
Optionally this step may include the preparation steps of FIG. 6
and/or apparatus of any of FIGS. 7 to 9;
[0220] Step 122: introducing the stent-valve 10 in its compressed
configuration into the patient's body, and advancing the
stent-valve to a desired implantation site. By way of example, if
the sleeve/cuff 42 may include a diffusion barrier layer 62, then
step 122 may include introducing the stent-valve 10 with the
diffusion barrier layer 62 still in place on the sleeve/cuff 42.
Optionally, the sleeve/cuff 42 may have been pierced at once or
more positions to create liquid-admitting punctures in the
sleeve/cuff 42 that pass through the diffusion barrier layer
62.
[0221] Step 124: causing the stent-valve 10 to expand at the
implantation site, from the compressed configuration to the
operative configuration. If the stent 12 is of a self-expanding
type, the expansion may be caused by removing a constraining sheath
(e.g. sheath 106), in order to allow the stent 12 to self-expand
towards the operative configuration. Additionally or alternatively,
if the stent 12 is of a type in which manipulation of the
stent-valve 10 is used to cause the stent-valve 10 to adopt its
operative configuration, step 124 may include causing such
manipulation, for example, by inflating an expansion balloon and/or
foreshortening the stent 12 to a foreshortened state.
[0222] Step 126: observing one or more characteristics of the
operative stent-valve. For example, one such characteristic may be
the extent of para-valve leakage of blood. Such a characteristic
may be observed using any suitable technique, for example,
Doppler-effect ultrasound. Additionally or alternatively, the
implantation position, and/or the extent to which the stent has
expanded, and/or the pressure gradient through the valve, may be
observed.
[0223] Step 128: in dependence of the result of the observation in
step 126, performing post-implantation balloon expansion of the
stent-valve 10. For example, if the observation of step 126
indicates that a para-valve leakage condition is not acceptable,
and/or that the stent has not expanded as much as desired, and/or
that the pressure gradient is undesirably high, a balloon catheter
may be inserted into the interior of stent 12, and expanded to
improve the seating/expansion of the stent 12 within the native
anatomy at the implantation site. If the observation at step 126
indicates that a para-valve leakage condition and/or other
conditions is acceptable (for example, there is no substantial
leakage), then step 128 may be skipped.
[0224] Step 128 may be performed after a time interval sufficient
to permit swelling of the seal 40 to adapt to the native anatomy.
For example, the time interval may be at least about 30 seconds,
optionally at least about 40 seconds, optionally at least about 50
seconds, optionally at least about 1 minute, optionally at least
about 75 seconds, optionally at least about 90 seconds, optionally
at least about 105 seconds, optionally at least about 2 minutes,
optionally at least about two-and-a-half minutes, optionally at
least about 3 minutes, optionally at least about three-and-a-half
minutes, optionally at least about 4 minutes, optionally at least
about four-and-a-half minutes, optionally at least about 5 minutes.
Additionally or alternatively, the time interval may optionally be
not substantially more than about 10 minutes, optionally not
substantially more than about 9 minutes, optionally not
substantially more than about 8 minutes, optionally not
substantially more than about 7 minutes, optionally not
substantially more than about 6 minutes, optionally not
substantially more than about 5 minutes, optionally not
substantially more than about 4 minutes, optionally not
substantially more than about 3 minutes, optionally not
substantially more than about 2 minutes, optionally not
substantially more than about 1 minute.
[0225] It may not be intuitive to consider carrying out
post-implantation balloon-expansion of a stent-valve that includes
a swellable seal 40, because it might ordinarily be expected that
the seal 40 will be able to seal against the anatomy automatically.
However, steps 126 and 128 may permit the medical practitioner to
determine, at least prior to completion of the medical procedure
and while the patient is still in a condition ready for
intervention, the efficacy of the seal 40 in sealing between the
stent-valve 10 and the surrounding local anatomical tissue. If the
seal 40 is determined not to be sufficiently effective, then step
128 may be used to increase the seating of the stent-valve 10
within the local anatomy, and the associated sealing effect of the
seal 40. Steps 126 and 128 may be performed once, or repeated two
or more times, as desired, for example, until para-valve leakage is
reduced to an acceptable condition.
[0226] As explained earlier above, the seal 40 may be configured to
be able to withstand a post-implantation balloon-expansion
procedure, without risk of bursting.
[0227] Referring to FIGS. 11 and 12, alternative structures of seal
40 are illustrated. The seal 42 comprises sleeve/cuff 42 containing
swellable material 44. These embodiments may use any of the details
described above for the sleeve/cuff 42 of preceding embodiments. In
FIG. 11, the sleeve/cuff 42 may comprise an integral tubular
structure, providing equivalent advantages to those discussed
above. In FIG. 12, the sleeve/cuff 42 may comprise an envelope
formed of one or more walls of material welded together along one
or more peripheries.
[0228] However formed, the sleeve/cuff 42 may comprise a single
wall, or the sleeve/cuff may comprise plural walls nested one
behind, or within, another. At least one wall may comprise a single
layer of material, and/or at least one wall may comprise plural
layers of material (e.g. a multi-layered wall and/or a
laminate).
[0229] The sleeve and/or cuff 42, or at least a wall or layer
thereof, may comprise a region 200 that is permeable or at least
semi-permeable to liquid. The permeable/semi-permeable region may
be configured to (i) allow communication of blood components
therethrough (for example, into the interior of the sleeve/cuff 42
to cause the swellable material 44 to swell), and/or (ii) obstruct
passage therethrough of blood emboli (for example, to substantially
prevent escape into the blood stream of any emboli that may form
within the sleeve/cuff 42), and/or (iii) obstruct passage
therethrough of swellable material 44 particles (for example, to
substantially prevent escape into the blood stream of any loose
particles of the swellable material 44).
[0230] The permeable/semi-permeable region 200 may have pores (e.g.
perforations 202 of FIG. 13). The pore size (e.g. average pore
size) may, for example, be not substantially greater than about 0.2
mm Optionally, the pore size may be not substantially greater than
about 0.15 mm, optionally not substantially greater than about 0.12
mm, optionally not substantially greater than about 0.11 mm,
optionally not substantially greater than about 0.1 mm, optionally
about 0.1 mm.
[0231] In some embodiments, the permeable/semi-permeable region 200
may extend over only a portion of the sleeve/cuff 42, and/or over
only a portion of a wall of the sleeve/cuff 42, and/or a layer of
the sleeve/cuff 42.
[0232] The permeable/semi-permeable region 200 may comprise
perforated film, for example, laser perforated film.
[0233] The (e.g. laser) perforated film may be a monolayer film, or
a laminate of two or more layers. The pore size of the (e.g. laser)
perforated film may optionally have a variation of less than 20%
from an average pore size, optionally less than 15% from an average
pore size, optionally less than 10% from an average pore size,
optionally less than 5% from an average pore size.
[0234] In some embodiments, the (e.g. laser) perforated film may
have a thickness of not substantially greater than 0.05 mm. Use of
such a thin film can contribute to achieving a compact sleeve/cuff
42 for enabling the stent-valve to achieve a desirably small size
for delivery by catheterization. Optionally the film thickness is
not substantially greater than about 0.045 mm, optionally not
substantially greater than about 0.04 mm, optionally not
substantially greater than about 0.035 mm, optionally not
substantially greater than about 0.03 mm, optionally not
substantially greater than about 0.025 mm, optionally not
substantially greater than about 0.02 mm, optionally not
substantially greater than about 0.015 mm, optionally not
substantially greater than about 0.01 mm, optionally not
substantially greater than about 0.005 mm. In some embodiments, the
film thickness may be between about 0.005 mm and about 0.015 mm,
optionally between about 0.005 mm and about 0.01 mm.
[0235] In some embodiments, the (e.g. laser) perforated film may
have a strength (e.g. linear tensile strength) at least 50% of the
film strength prior to laser perforation, optionally at least 60%
of the strength prior to laser perforation, optionally at least 70%
of the strength prior to laser perforation, optionally at least 80%
of the strength prior to laser perforation, optionally at least 90%
of the strength prior to laser perforation. Such characteristics
can contribute to a strong film even with thin film thickness.
[0236] Referring to FIG. 13, in some embodiments, the pores 202 (or
at least a majority thereof) in the (e.g. laser) perforated film
are substantially round and/or have a cauterized perimeter 204
and/or have a raised margin 206 around their perimeter. Such a
feature or features may contribute individually or in combination
to film strength even with thin film thickness. A round pore shape
can avoid sharp corners in the peripheral shape that could be
points of stress concentration or lead to outward crack
propagation. Cauterization of the material around the perimeter 204
of the pore may also advantageously reduce risk of outward crack
propagation. A raised margin 206 of material around the pore
perimeter may also provide additional material, and hence strength,
surrounding the open area of the pore.
[0237] Referring to FIG. 14, the permeable/semi-permeable region
200 may extend substantially over the entire surface of the
sleeve/cuff 42, or the region 200 may be positioned in one or more
specific zones, leaving other zones substantially
non-perforated.
[0238] In some embodiments, the permeable/semi-permeable region may
be disposed in one or more of:
[0239] A zone 210 facing substantially or at least partly towards
the stent-valve blood outlet. When the valve 14 closes in use,
blood back-pressure may tend to urge blood towards the seal 40 from
the outlet direction, and placing the permeable region in zone 210
may provide good communication of blood to the seal for causing the
swellable material 44 to swell; and/or
[0240] A zone 212 facing substantially or at least partly towards
the stent-valve blood flow inlet. Blood passing dynamically through
the stent-valve generally approaches the stent-valve from the inlet
direction, and placing the permeable region in zone 121 may provide
good blood communication into the seal; and/or
[0241] A zone 214 facing substantially or at least partly radially
outwardly and/or a zone 216 facing substantially or at least partly
radially inwardly.
[0242] In some embodiments in which at least a wall or layer of the
cuff/sleeve 42 having the perforations is, in use, able to directly
contact the surrounding native tissue, the permeable region may
optionally be configured to be outside of the zone 214. Such an
arrangement can avoid or reduce any risk that hard calcification
217 of the native tissue could enlarge a perforation by direct
contact therewith, or otherwise damage the perforated region
200.
[0243] Referring to FIG. 15, in some embodiments, the cuff/sleeve
42 may further comprise an impermeable layer or wall 218 extending
partly or entirely around the periphery of the cuff/sleeve 42 when
viewed in cross-section, and/or partly or entirely in the
circumferential direction of the stent-valve 10.
[0244] Referring to FIG. 16, in some embodiments, at least a
component of the seal 40 may be provided as a separate item from
the stent-valve 10. The at least a component of the seal 40 may be
intended to be mounted or fitted or introduced to the stent-valve
10 as part of a pre-implantation preparation process, e.g. after
rinsing the stent-valve 10 clean of any storage solution. In the
embodiment of FIG. 16, the seal 40 is provided separately, and is
intended to be mounted to the stent-valve 10 as part of the
pre-implantation preparation process.
[0245] The seal 40 may comprise the swellable material 44 and a
cuff/sleeve 42. The cuff/sleeve 42 may comprise a permeable or
semi-permeable region 200. The seal 40 may be generally elongate.
The seal 40 may be provided in its own sterilized container 220,
e.g. a pouch. The pouch may be a tear-open pouch. The seal 40 may
have been sterilized using any suitable process, for example,
radiation sterilization. The seal 40 may have been sterilized in
its container 220.
[0246] In some embodiments, the stent-valve 10 comprises a
dedicated seal accommodation region 221 to which the seal is
mountable. The seal accommodation region 221 may be provided as
part of an outer skirt 32 of the stent-valve 10.
[0247] The seal accommodation region 221 may be or comprise a seal
accommodation channel 222. In some embodiments, the seal
accommodation channel may be discontinuous. Referring to FIG. 17, a
discontinuous channel 222 may be provided by a series of spaced
apart loops 224, for example, similar to clothing belt loops. The
number of loops 224, and the circumferential length of each loop
224, may be selected to provide a desired mark/space ratio (e.g.
closed-area/open-area ratio). The mark/space ratio may optionally
be about 1. Additionally or alternatively, the ratio may be less
than 1, optionally less than about 0.75, optionally less than about
0.5, optionally less than about 0.25. Additionally or
alternatively, the ratio may at least about 1, optionally at least
about 1.25, optionally at least about 1.5, optionally at least
about 1.75, optionally at least about 2, optionally at least about
2.5, optionally at least about 3.
[0248] Referring to FIG. 18, a substantially continuous
accommodation channel 222 may be provided by an (e.g. annular) flap
226 of material extending substantially continuously in a
circumferential direction around the stent-valve 10. The flap 226
may define a channel that is open in one direction, for example,
open in a direction facing towards the blood outlet end of the
stent-valve in FIG. 18, and/or open in an opposite direction facing
towards the blood inlet end of the stent-valve (not shown).
Referring to FIG. 19, the flap 226 may further comprise a series of
spaced apart extensions 228 that couple to the stent-valve, to
define a series of clearances between adjacent extensions 228
instead of a continuously open region. The extensions 228 may
define a castellated shape. Referring to FIG. 20, an edge 230 of
the flap may have a scalloped shape between the extensions 228 to
define a curved shape of the clearances thereby to avoid abrupt
edges.
[0249] Alternatively, referring to FIG. 21, a substantially
continuous accommodation channel 222 may be provided by a tube (or
an envelope) 232. The tube 232 may have an integral tubular
structure, provided similar advantages to those described
previously.
[0250] The tube 232 may have communication openings 234 for
admitting blood to the interior of the channel. In the example
shown, at least some of the openings 234 may be arranged facing
substantially or at least partly towards the stent-valve blood
outlet. When the valve 14 closes in use, blood back-pressure may
tend to urge blood towards the seal 40 from the outlet direction,
and such an arrangement of the openings may provide good
communication of blood to the seal 40 for causing the swellable
material 44 to swell. Additionally or alternatively, at least some
of the openings 234 may be arranged (not shown) facing
substantially or at least partly towards the stent-valve blood flow
inlet. Blood passing dynamically through the stent-valve generally
approaches the stent-valve from the inlet direction, and such an
arrangement of the openings may provide good blood communication
into the seal 40. Additionally or alternatively, at least some of
the openings may arranged (not shown) facing substantially or at
least partly radially outwardly and/or facing substantially or at
least partly radially inwardly.
[0251] For similar reasons to those discussed previously in
relation to FIG. 14, in some embodiments, the openings 234 may be
arranged so as not to face substantially radially outwardly. In
other words, the radially outward facing portion of the tube 232
may have a substantially continuous surface to shield the seal 40
within the tube 232 from direct contact with hard calcifications of
the surrounding native anatomy.
[0252] The seal 40 may be loadable or introducible into the channel
222 by any suitable means. In some embodiments, a loading filament
240 (e.g. made of medical suture thread) may be pre-laid within the
channel 222 along a predefined path, and used as device for pulling
or drawing the seal 40 into the channel 222. For example, the
opposite ends of the thread 240 may project outwardly from the
channel, for example through openings or clearances previously
described, or through additional and/or dedicated loading apertures
(not shown). In order to load the seal 40, one end of the filament
240 may be coupled to an end of the seal 40. Pulling on the
opposite end of the filament 240 withdraws the filament 240
progressively from the channel, at the same time drawing the seal
40 into the channel along the predefined path previously occupied
by the filament. The predefined path may extend at least partly
circumferentially around the periphery of the stent-valve, along a
path length corresponding to at least about 180 degrees, optionally
at least about 225 degrees, optionally at least about 270 degrees,
optionally at least about 315 degrees, optionally about or at least
about 360 degrees. 360 degrees corresponds to a complete
circumferential path length around the circumference of the
stent-valve. The path length may optionally be greater, and
correspond, for example, to about or at least about 1.5 turns, or
optionally to about or at least about 2 turns, or more. Once the
seal 40 is loaded, the filament 240 (or at least a projecting
portion of the filament 240) may be disconnected (e.g. cut) from
the seal 40 to leave the seal in place within the channel 222.
[0253] Alternatively, referring to FIG. 22, the seal 40 may be
adhesively attachable to the stent-valve 10. For example, at least
one of the seal 40 and the seal accommodation region 221 may
comprise an adhesive region, optionally protected by a respective
peelable release sheet. If adhesive is provided on only one part
(e.g. on the seal 40), the other part (e.g. the seal accommodation
region 221) may comprise a landing surface for adhesive attachment
by the other part.
[0254] Alternatively, referring to FIG. 23, the outer skirt 32 may
comprise a hollow band 242 into which the swellable material 44 may
be introduced in flowable form, as part of the pre-implantation
preparation process. An example flowable swellable material may,
for example, be or comprise swellable microspheres, for example,
poly(vinyl alcohol-sodium acrylate) copolymer microspheres. In some
embodiments, the flowable material may be injected into the band
242, either directly through the wall of the band, or using a
dedicated inlet port 244. The band 242 may represent or correspond
to a seal accommodation region 221 and/or a seal accommodation
channel 222 in any of the following description.
[0255] Referring to FIG. 16, if the stent geometry previously
described for FIG. 1 is used, the seal accommodation region 221
(e.g. seal accommodation channel 222) may be positioned to be clear
of the upper crown 18 in order not to interfere with blood through
the upper crown to coronary arteries (e.g. in the case of a
stent-valve for the aortic valve position).
[0256] Additionally or alternatively, if the stent geometry
previously described for FIG. 1 is used (referring also FIG. 16),
the seal accommodation region 221 (e.g. seal accommodation channel
222) may be positioned only between the upper crown 18 and the
upper apexes 16b of the lower and/or inlet extremity. For example,
the seal accommodation region 221 does not extend to occupy space
between the upper apexes 16b and the lower apexes 16a of the
extremity. Positioning the seal 40 clear of the lower apexes 16a
can reduce the bulk of material at the lower/inlet extremity of the
stent, and facilitate crimping.
[0257] Referring to FIGS. 16 and 24, the outer skirt 32 may
comprise at least one attachment zone 250 positioned axially above
and/or below the seal accommodation region 221. The skirt 32 may be
secured to the stent 12 and/or to the inner skirt 30 by the at
least one attachment zone 250, such that the attachment does not
interfere with, or increase the thickness of, the seal
accommodation region 221. The skirt 32 may be attached by any
suitable means, for example, suturing, welding, fusion or adhesive.
In FIG. 16, suturing is indicating by a broken line. In some
embodiments, two attachment zones 250 are provided, one above and
one below the seal accommodation region 221. The lower periphery of
the outer skirt 32 (and optionally of one of the attachment zones
250), may have a zig-zag shape to match a zig-zag shape of a lower
and/or inlet extremity of the lower portion of the stent 12.
[0258] Referring to FIG. 25, the outer skirt may comprise a sheet
of film material 252. The film material 252 may provide both the at
least one attachment zone 250, and a support for or at the seal
accommodation region 221, (indicated schematically in FIGS. 25-28).
Alternatively, referring to FIGS. 26-28, the outer skirt 32 may
comprise fabric material 254 at least at the one or more attachment
zones 250. Fabric material may be easier to attach by means of
suturing, with less risk to the integrity of the material than if a
film is sutured. A polymer film material, and especially a
crystalline polymer film material (such as PEEK, for example), may
be vulnerable to outward crack propagation from suture holes,
whereas a fabric made of the same material may much less
vulnerable. FIG. 26 illustrates a hybrid skirt that comprises only
fabric 254 for the attachment zones 250, and only film 252 at the
seal accommodation region 221. The fabric and film regions may be
welded together, for example. FIG. 27 illustrates a modified hybrid
skirt in which the film 252 extends substantially the entire axial
height of the skirt, and fabric material 254 is laminated at the
attachment zones 250. The fabric material 254 can support the film
252 to provide resistance to crack propagation. The fabric material
254 may be heat sealed or fused to the film in order to form the
laminate. FIG. 28 illustrates a further modified hybrid skirt in
which the fabric and film are substantially coextensive and form a
skirt consisting of laminate over substantially its entire axial
height.
[0259] Referring to FIG. 29, a further example of separate seal 40
is illustrated. The seal 40 comprises a saddle or harness 258 that
is clipped and/or hooked and/or threaded to the stent 12, for
example, by attaching to the projecting apexes or valleys of the
upper crown 18 and lower portion or crown 16.
[0260] Referring to FIG. 30, a method of using and/or preparing a
stent-valve 10 (especially as described in any of the embodiments
of FIGS. 11 to 29) is illustrated.
[0261] At step 260 and 262, a stent-valve 10 and at least a
component for a seal 40, are provided as separate items. The
separate items may optionally be provided as part of a kit (step
264), but nevertheless the at least a component of the seal 40 may
be non-integral with the stent-valve 10. Step 260 may comprise
providing the stent-valve immersed in a storage and/or
sterilization solution, as described above. Step 262 may comprise
providing the at least a component for a seal in a dry sterilized
state, such as in a sterilized pouch. By providing the at least a
component of the seal separately, there is substantially no risk
that the seal might be wetted or contaminated by the storage
solution in which the stent-valve is stored. A storage compartment
or container for the seal may be outside a storage compartment or
container for the stent-valve.
[0262] At step 266, the stent-valve 10 may be rinsed to remove
substantially traces of the storage solution. Step 266 may comprise
placing the stent-valve into a bath of a rinsing solution, for
example, water or saline. Step 266 may comprise placing the
stent-valve into one or more successive baths to provide a
multi-stage rinse.
[0263] At step 268, the at least a component of the seal may be
mounted to, or introduced to or into the stent valve 10. For
example, the seal may be loaded into a seal accommodation channel,
or the seal may be attached adhesively, or clipped or hooked to the
stent-valve. Alternatively, a flowable swelling material may be
injected into a seal band.
[0264] At step 270, the assembled stent-valve and seal is exposed
to liquid while outside the patient's body (e.g. similar to step 94
described previously), and at step 272 the assembled stent-valve is
compressed and/or loaded into a delivery catheter (e.g. similar to
step 96 described previously). As previously, steps 270 and 272 may
be carried out substantially at the same time, or one of the steps
may be started before the other in either order, or the steps may
be carried out separately in either order.
[0265] One loaded into the delivery catheter, the stent-valve 10
may be implanted using a method, for example, similar or the same
as that of FIG. 10.
[0266] Although the foregoing description has described the
embodiments in terms of a stent-valve 10, it will be appreciated
that many of the same techniques may be applied to other (e.g.
stented) prostheses.
[0267] It is emphasized that the foregoing description of preferred
embodiments does not limit the scope of the invention, and that
many alternatives, modifications, and improvements may be made
within the scope and/or principles of the invention.
* * * * *