U.S. patent application number 16/950292 was filed with the patent office on 2021-03-11 for valve replacement devices, delivery device for a valve replacement device and method of production of a valve replacement device.
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, Jean-Luc Hefti, Fabien Lombardi.
Application Number | 20210068949 16/950292 |
Document ID | / |
Family ID | 1000005223226 |
Filed Date | 2021-03-11 |
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United States Patent
Application |
20210068949 |
Kind Code |
A1 |
Biadillah; Youssef ; et
al. |
March 11, 2021 |
VALVE REPLACEMENT DEVICES, DELIVERY DEVICE FOR A VALVE REPLACEMENT
DEVICE AND METHOD OF PRODUCTION OF A VALVE REPLACEMENT DEVICE
Abstract
A device for heart valve replacement comprises a valve component
having at least two valve leaflets preferably made of pericardium
tissue. Each valve leaflet includes at least two tabs. The device
further includes a stent component configured to be radially
compressible into a compressed state and expandable into a
functional state. The stent component comprises a first end, a
second end and at least one intermediate section arranged between
said first and said second end. The intermediate section has at
least two commissural posts generally aligned parallel to an axis
spanning from the first end to the second end. The commissural
posts are formed in the shape of a wishbone.
Inventors: |
Biadillah; Youssef;
(Lausanne, CH) ; Delaloye; Stephane; (Bulach,
CH) ; Lombardi; Fabien; (Prilly, CH) ; Hefti;
Jean-Luc; (Cheseaux-Noreaz, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Symetis SA |
Ecublens |
|
CH |
|
|
Assignee: |
Symetis SA
Ecublens
VD
|
Family ID: |
1000005223226 |
Appl. No.: |
16/950292 |
Filed: |
November 17, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16272369 |
Feb 11, 2019 |
10869760 |
|
|
16950292 |
|
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|
|
15143166 |
Apr 29, 2016 |
10201418 |
|
|
16272369 |
|
|
|
|
13821476 |
Oct 3, 2013 |
9333075 |
|
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PCT/EP2011/065744 |
Sep 12, 2011 |
|
|
|
15143166 |
|
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|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2002/9505 20130101;
A61F 2230/001 20130101; A61F 2/2418 20130101; A61F 2220/0075
20130101; A61F 2230/0013 20130101; A61F 2250/0039 20130101; A61F
2/2436 20130101 |
International
Class: |
A61F 2/24 20060101
A61F002/24 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 10, 2010 |
EP |
10176281.3 |
Jan 11, 2011 |
EP |
11150544.2 |
May 15, 2011 |
EP |
11004013.6 |
May 16, 2011 |
EP |
11166201.1 |
Claims
1. A valve replacement device for transcatheter implantation,
comprising: a stent component having an inflow section with an
inflow extremity, an intermediate section, and an outflow section
with an outflow extremity, a maximal diameter of the inflow section
being smaller than a maximal diameter of the outflow section; the
intermediate section having a diameter which is smaller than the
maximal diameter of either of an inflow or an outflow section; the
stent component being radially compressible to a compressed state
for delivery to a site of implantation and radially expandable to a
functional state; the stent component further comprising at least
one attachment element for mating engagement with a delivery
device; valve leaflets mounted at least partly within the stent
component; an inner skirt and an outer skirt of porcine pericardial
tissue; an inner skirt attached to the valve leaflets and having
commissural portions spaced apart by scalloped clearances, each
clearance spanned by a respective leaflet, the inner skirt
extending at least partly within the stent component towards the
inflow extremity; and an outer skirt extending at least partly
outside the stent component, the outer skirt extending further than
the inner skirt towards the inflow extremity.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
U.S. application Ser. No. 16/272,369, filed Feb. 11, 2019, which is
a continuation of and claims priority to U.S. application Ser. No.
15/143,166, filed Apr. 29, 2016, which is a continuation of U.S.
application Ser. No. 13/821,476, filed Oct. 3, 2013, which in turn
claims priority to International Patent Application No.
PCT/EP2011/065744, filed Sep. 12, 2011, which claims priority to
European Patent Application No. 10176281.3, filed Sep. 10, 2010,
European Patent Application No. 11150544.2, filed Jan. 11, 2011,
European Patent Application No. 11004013.6, filed May 15, 2011, and
European Patent Application No. 11166201.1, filed May 16, 2011. The
present application incorporates herein by reference the
disclosures of each of the above-referenced applications in their
entireties.
TECHNICAL FIELD
[0002] Valve replacement devices, delivery device for a valve
replacement device and method of production of a valve replacement
device
[0003] The present invention is directed to devices for valve
replacement, especially of the aortic valve. Further, the present
invention is also related to a delivery device for a valve
replacement device and to a method of production of a valve
replacement device. Valve replacement devices may also be referred
to a stent-valves or valved-stents.
BACKGROUND
[0004] Conventional approaches for cardiac valve replacement
require the cutting of a relatively large opening in the patient's
sternum ("sternotomy") or thoracic cavity ("thoracotomy") in order
to allow the surgeon to access the patient's heart. Additionally,
these approaches require arrest of the patient's heart and a
cardiopulmonary bypass (i.e., use of a heart-lung bypass machine to
oxygenate and circulate the patient's blood). In recent years,
efforts have been made to establish a less invasive cardiac valve
replacement procedure, by delivering and implanting a cardiac
replacement valve via a catheter inserted through a smaller skin
incision via either a transvascular approach--delivering the new
valve through the femoral artery, or by transapical route, where
the replacement valve is delivered between ribs and directly
through the wall of the heart to the implantation site.
[0005] Stent valves and delivery systems for placing a replacement
valve via a catheter are known in the art, and are disclosed for
example in WO 2007/071436 and WO 2009/053497.
[0006] Some known stents are made from a shape memory material,
such as Nitinol, and are self-expanding. The valves may be from
animals, for example porcine aortic valves. Alternatively the
valves may at least partly be made of synthetic material, such as
Dacron.
[0007] For example, the WO 2007/071436 discloses a valve
replacement device comprising a valve element and a stent element.
The stent element includes three different sections, wherein one
section houses the valve element. The valve element includes three
leaflets, which may be made of biological or artificial material.
The three different sections may be provided with different
diameters.
[0008] One major drawback of some known replacement valve stents is
that even in a collapsed (crimped) state their diameter is often
too big for transvascular delivery of the stent. Transfemoral
delivery of the stent, where the stent has to be advanced over the
aortic arch, requires even smaller diameters of less than 18 French
(6 mm). Such small diameters may also be useful in transapical
delivery if a smaller skin incision and/or smaller cut in the heart
wall may be used.
[0009] Crimping some known stent valves to a diameter of less than
18 French would produce high strains on the replacement valve,
which may lead to damages.
[0010] Thus there is a need for replacement valve devices, which
avoid the disadvantages of the known and which in particular may be
crimped to small diameters without the risk of damaging the
replacement valves and which may be reliably placed and tightly
anchored over an aortic annulus.
SUMMARY
[0011] Aspects of the invention are defined in the claims.
[0012] Broadly speaking, one aspect of the invention provides a
device for heart valve replacement, comprising a valve component
(and/or a tissue valve) with at least two valve leaflets. The term
"valve component" is used herein to refer to the leaflets
collectively, whether or not the leaflets are secured together to
define a unitary valve structure independent of other
components.
[0013] The leaflets are preferably made of pericardium tissue, most
preferably from porcine pericardium tissue or bovine pericardium.
Porcine pericardium may be desirably thin and sufficiently durable.
Bovine pericardium may be thicker and even more durable when this
is desired. Each valve leaflet includes at least two tabs. The
device further includes a stent component configured to be radially
compressible into a compressed state and expandable into a
functional state. The stent component comprises a first end, a
second end and at least one intermediate section arranged between
said first and said second end. The intermediate section has at
least two commissural posts optionally and/or generally aligned
parallel to an axis spanning from the first end to the second end.
The tabs of the leaflets are directly attached to the commissural
posts, preferably to attachment means provided on said commissural
posts.
[0014] The valve leaflets are configured and dimensioned such as to
form a replacement valve. In some embodiments, the leaflets have a
straight or slightly curved upper free edge, two lateral edges and
a substantially arcuate lower edge. At least one tab is arranged on
each lateral edge, preferably in the area of the upper free edge of
the leaflet. In the valve replacement device, the at least two
leaflets are positioned such that their upper free edges may be
pressed together to prevent blood flow in one direction, e.g.
towards the heart during diastole in the case of an aortic valve
replacement, and move apart to allow blood flow in the other
direction, e.g. away of the heart during systole.
[0015] More preferably, three valve leaflets are provided. This
allows to mimic the natural tricuspid valve architecture e.g. of
the aortic, pulmonary, tricuspid or mitral valve. Alternatively,
the valve replacement device may also comprise more leaflets, such
as four, five or more.
[0016] While it is known to use a large selection of different
artificial materials for replacement valves, it is preferred that
the at least two leaflets of the valve replacement device according
to the present invention are made of pericardium tissue. Most
preferably, the at least two leaflets are made from porcine
pericardium tissue. Pericardium tissue is sufficiently thin and yet
durable enough to be used as leaflet material. The porcine heart
shows a lot of similarities to the human heart. Therefore it is
advantageous to use porcine pericardium tissue. Further, porcine
pericardium tissue is readily available. For the present invention,
the use of a porcine aortic valve is not indicated, since it is too
thick and would not allow the crimping of the valve replacement
device to less than 20 French. As mentioned previously, bovine
pericardium may also be used for the leaflets where even greater
durability is desired, optionally at the expense of thicker
tissue.
[0017] The stent component preferably is of the self-expanding
type. Such stents are known in the art and often comprise or are
made of a shape-memory material, such a Nitinol. Alternatively, the
stent component may be made of or comprise a plastically
deform-able material and may be expanded to the functional state by
external means, such as a balloon catheter.
[0018] In the compressed, e.g., the crimped state, the stent
component may be inserted in the area of a heart valve of a
patient, such as the aortic valve. Further, the diameter of the
stent component in the compressed state is such that it may be
advanced into a patient's heart through an artery, such as the
femoral artery. The diameter and/or the flexibility of the stent
component in the compressed state are therefore preferably such
that the valve replacement device may be advanced through the
aortic arch.
[0019] In the functional state, the stent component is in an at
least partly expanded, or non-compressed configuration. Optionally,
the stent component defines an interior conduit space. The conduit
space may be generally cylindrical and/or tubular. The valve
leaflets are arranged to span the interior space within the stent
component. Once the valve replacement device is positioned at a
target position close to the natural valve of a patient, the stent
component is expanded to its functional state. Preferably the stent
component may additionally comprise anchoring elements which allow
a secure attachment of the device within a cardiovascular vessel
upon expansion of the stent element.
[0020] The natural valve leaflets of the patient may be pushed
aside by the expanding stent component. Once fully expanded, the
valve component arranged within the stent component will take over
the function of the natural valve.
[0021] The stent component preferably comprises a first end, a
second end and at least one intermediate section arranged between
said first and said second end. The valve component is thereby
preferably arranged within said intermediate section of the stent
component. Optionally, the stent component is configured such that
said intermediate section includes a conical and/or cylindrical
conduit space, optionally with a constant diameter, said diameter
most preferably being in the range of 15 mm to 35 mm. The length of
said intermediate section thereby preferably is in the range of 10
mm to 50 mm.
[0022] In the functional state, said first and said second ends
define inflow and outflow openings through or around which blood
may flow in use. A simple embodiment of a valve replacement device
according to the present invention may comprise only the
intermediate section including a first and a second end. However,
more preferably a valve replacement device according to the present
invention comprises at least an additional inflow and/or an
additional outflow section arranged between said intermediate
section and said first and/or said second end.
[0023] "Inflow section" as understood herein is the section of the
stent component where blood enters into said conduit space and/or
the section of the stent component that, in use, is upstream of the
valve leaflets; for example, in the case of a semilunar and/or
aortic valve, the section of the stent component which is oriented
towards the ventricle.
[0024] Accordingly, an "outflow section" as understood herein is
the section of the stent component where blood leaves said conduit
space and/or the section of the stent component that, in use, is
downstream of the valve leaflets; for example, the section which is
located in the artery for semilunar valves.
[0025] Said inflow and said outflow section may thereby have the
same length or have different lengths. Further, said inflow and/or
said outflow section may define a generally tubular conduit
interior conduit space. The conduit space may be generally
cylin-drical. More preferably, said inflow and/or said outflow
section include a generally conical conduit, i.e. a conduit with an
increasing or a decreasing diameter. Alternatively, the inflow and
the outflow section may include an interior conduit space of any
appropriate geometric shape.
[0026] Optionally, said inflow and said outflow section may have
the same maximal diameter or varying maximal diameters. A "maximal
diameter" as understood herein is the largest diameter within such
a section. Optionally, said inflow section has a smaller maximal
diameter than said outflow section. Further, said intermediate
section has a diameter which is smaller than the maximal diameter
of either of said inflow or said outflow section. Most preferably
said inflow and said outflow sections have a diameter which
increases in the direction of said first and said second end.
Alternatively, further sections may be arranged between said inflow
and/or said outflow section and said intermediate section.
[0027] In a preferred embodiment, the inflow section has a maximal
diameter in the range from 20 mm to 35 mm and the outflow section
has a maximal diameter in the range from 20 mm to 55 mm.
[0028] The stent component may further comprise a lower anchoring
crown. The lower anchoring crown may define an at least partly
conical body. Said lower anchoring crown preferably is located
between the second end and the intermediate section of the stent
component and preferably configured as to be placed within the
annulus and/or extend to the ventrical side of the annulus.
[0029] Additionally, the stent component may further comprise an
upper anchoring crown in communication with or adjacent to the
lower anchoring crown. The upper anchoring crown may define an at
least partly conical body. Said conical body of said lower
anchoring crown may slope outwardly in the direction of the second
end and the conical body of the upper anchoring crown may slope
outwardly in the direction of the intermediate section, e.g. such
as to be placed on the aortic side of the annulus.
[0030] Preferably, the stent component further includes
stabilization arches which are in communication with the
commissural posts and extend towards the first end. The
stabilization arches are preferably configured to engage the
ascending aorta to orient the stent component longitudinally within
the aorta or the aortic annulus, thus tending to correct any
tilting of the stent component, with respect to the ascending
aorta, during implantation. The commissural posts are thereby
connected to each other through the stabilization arches, whereby
two adjacent commissural posts are in connection with each other by
means of one stabilization arch. Further, the commissural posts
preferably are also in communication with the upper anchoring crown
and/or the lower anchoring crown.
[0031] Further, the stent component preferably comprises at least
one attachment element for mating engagement with a delivery device
(for example, a stent holder of the delivery device). The at least
one attachment element may be configured for restraining axial
displacement of the stent component until the stent component is
fully released. In some embodiments, the at least one attachment is
provided at the lower crown, such that the ventrical part and/or
inflow section of the valve replacement device is the last part to
expand during placement of the device. The stent component may
comprise any suitable number of attachment elements, for example,
two, three, or more. The attachment elements may be spaced
substantially uniformly in the circumferential direction.
[0032] Optionally, the at least one attachment element may comprise
a U-shape portion joining two stent struts. The term U-shape is
used herein to include any shape including a generally arcuate
apex, whether or not the sides are straight or curved, bulged
outwardly, parallel or non-parallel. In a collapsed (e.g.
compressed) state of the stent when received within the
accommodation region of the delivery catheter, the struts may lie
adjacent each other at the attachment element, such that the arc of
the U-shape portion extends around a first angle more than 180
degrees to define, for example, a closed or near closed (e.g.
horseshoe shape) eyelet having an aperture larger than the spacing
of the struts. The horseshoe shape of the eyelet aperture and the
adjacent space between the struts may together define a keyhole
type shape. In an expanded (or non-collapsed) state of the stent
when released from the accommodation region of the delivery
catheter, the struts may move apart, and the arc of the U-shape
portion may extend around a second angle that is less than the
first angle, to at least partly open the eyelet further. For
example, the second angle may be about 180 degrees or less. In the
expanded state, the attached element may define a substantially
straight-sided U-shape with an arcuate apex.
[0033] The delivery catheter may comprise a sent-holder provided
within a stent accommodation region. The stent-holder may comprise
[0034] (ii) a respective projection receivable within each eyelet.
The projection may be dimensioned such that, when the stent
component is in its collapsed state, the projection is trapped
within the eyelet and unable to pass between the adjacent struts,
and/or [0035] (ii) one or more recesses or interstices for
accommodating the attachment element substantially therewithin, at
least in the collapsed state of the stent component.
[0036] The above forms can provide for a compact, yet reliable and
self-opening and/or self-releasing attachment between a stent-valve
and a delivery system. The provision of the attachment elements
also does not impede compressing of the stent component to a
desirably small size.
[0037] In some embodiments, the intermediate section comprises at
least two commissural posts generally aligned parallel to an axis
spanning from the first end to the second end. The tabs of the
leaflets are directly attached to said commissural posts,
preferably to attachment means provided on said commissural
posts.
[0038] The direct attachment of said leaflets to said commissural
posts provides a high strain resistance of the leaflets.
Optionally, in comparison to valve replacement stents as known in
the art, the direct attachment of the leaflets to the commissural
posts may optionally reduce the thickness of the crimped stent
element, if excess layers of tissue between the leaflets and the
commissural posts capable of withstanding the strain resistance may
be avoided.
[0039] According to another aspect of the present invention, a
device for heart valve replacement is provided which comprises a
valve component and/or tissue valve having at least two valve
leaflets. Said at least two valve leaflets are preferably made of
pericardium tissue, most preferably porcine pericardium tissue.
Each of said at least two valve leaflets includes at least two
tabs. The device further includes a stent component configured to
be radially compressible into a compressed state and expandable
into a functional state. The stent component comprises a first end,
a second end and at least one intermediate section arranged between
said first and said second end. The intermedi-ate section has at
least two commissural posts generally aligned parallel to an axis
spanning from the first end to the second end. Said commissural
posts are formed in the shape of a wishbone and said tabs are
directly attached to said commissural posts, preferably to
attachment means provided on said commissural posts.
[0040] A wishbone is generally shaped like an inverted letter "Y".
The commissural posts therefore include two inclined legs (also
referred to sometimes as arms) and one stem. The inclined legs may
be straight, but preferably the two inclined legs are curved (e.g.
around the axis of the stent component and/or in a circumferential
plane). The shape, whether straight or curved, is preferably
selected such that the legs of the wishbone are substantially in
register and/or congruent with the lateral edges of the valve
leaflets. This allows the commissural post to provide good support
to the lateral edges of the valve leaflets. The lateral edges of
the valve leaflets may be attached to the legs, and/or to inner
skirt material between the leaflets and the commissural posts. The
legs are thereby shaped such as to match generally the contour of
the lateral edges of the leaflets. This allows the attachment of
the lateral edges of the leaflets directly or indirectly to the
legs of the wishbone shaped commissural posts, e.g. by means of a
suture, for close support of the leaflets.
[0041] The configuration of other elements of this embodiment of a
stent valve replacement device is similar to the ones described for
the first embodiment above.
[0042] The commissural posts preferably comprise attachment means
for the tabs of the valve leaflets, said attachment means including
at least one opening adapted for the insertion of at least one
tab.
[0043] Said openings are preferably configured as through holes,
i.e. the openings are bounded and/or flanked on all sides by the
commissural posts. Alternatively, said openings may also be
configured as channel slits, i.e. bounded and/or flanked by the
commissural posts only on three sides, while one side is open. The
openings may be in any suitably form, like rectangular, round,
oval, etc. Most preferably the openings are in the form of a
long-hole. The openings are further adapted such that at least one
tab of said valve leaflets may be inserted therethrough. Therefore
the position of the openings on the commissural posts as well as
their size is selected such that at least one tab of a valve
leaflet may be inserted. Preferably said openings are adapted such
that two tabs, e.g. from two neighbouring valve leaflets, may be
inserted. Alternatively, the commissural posts may include more
than one such openings. In this way, attachment of valve leaflets
having more tabs, such as two tabs on each lateral edge, may be
attached to said commissural posts. In a further alternative, the
commissural posts may include two openings arranged parallel to
each other, such that tabs of neighbouring valve leaflets may each
be inserted into a separate opening. The tabs are preferably
inserted into an opening, folded back over the commissural post
towards the valve leaflet and sutured thereto.
[0044] Said attachment means may additionally include at least two
bores adapted for the insertion of a suture wire, said bores
preferably being in the form of round-bores. Provision of such
additional bores facilitates the attachment of said tabs and/or of
the lateral edges of the leaflets to said commissural posts.
[0045] These additional at least two bores are preferably provided
flanking said at least one opening.
[0046] The stent component preferably comprises a substantially
parallel and/or non-parallel tubular portion arranged between said
intermediate section and said second end, said tubular portion
having a lattice structure of at least one row of cells, the
wishbone shape of each commissural post spanning a respective
sequence of at least three adjacent cells, such that the wishbone
extends from outer cells of the sequence without attachment to the
at least one intermediate cell of the sequence. Such an arrangement
provides for ease of compression, while allowing the wishbone legs
to have sufficient divergence to match the shape of the lateral
edges of the leaflets.
[0047] In some embodiments, the legs of the wishbone are joined to
the outer cells of the sequence in the lattice structure, therefore
allowing the commissural post to span over at least three adjacent
cells without being attached to the at least one intermediate cell.
Alternatively, each commissural post may be configured to span over
more than three adjacent cells, such as four, five, etc. Further
alternatively, each commissural post may be configured to span a
different number of adjacent cells. Preferably, the stems of the
wishbone shaped commissural posts are in communication with each
other by means of stabilization arches. The stems of two adjacent
wishbone shaped commissural posts are thereby in communication with
each other by means of one stabilization arch.
[0048] The valve replacement device additionally may comprise an
inner skirt, preferably made of pericardium tissue, and attached to
the leaflets. The inner skirt may serve to channel blood within the
conduit space of the stent component, and obstruct leakage of blood
through interstices of the stent component (e.g. through cells of a
lattice structure).
[0049] In some embodiments, the inner skirt may have commissural
portions spaced apart by scalloped clearances (e.g. scalloped
cutouts). Each clearance is spanned by a respective valve leaflet.
The lateral edges and/or lower edges of the leaflets may be
attached to the inner skirt, for example, by sutures.
[0050] In some embodiments, the inner skirt may extend towards said
second end, said skirt preferably being sutured to said stent
device. Said skirt preferably covers at least partly an interior
surface of the stent component. This reduces the occurrence of
turbulent flow of the blood which may be triggered by the material
of the stent component. Said skirt preferably is further sutured to
said at least two valve leaflets.
[0051] Additionally, at least one section of said stent component
is at least partially covered on the outside by an outer skirt.
[0052] The stent component is preferably configured such that when
the valve replacement device in the compressed state is inserted
into the sheath of a delivery device, such as a catheter, the
aggregated diameter of the delivery device and the sheath is less
than 20 French, preferably less than 18 French. This allows the
insertion of the valve replacement device along an artery,
preferably the femoral artery or the subclavian artery. It may also
enable the valve replacement device to be inserted transapically
using a small skin incision and/or cut through the heart wall.
[0053] According to yet another aspect of the invention there is
provided a device for heart valve replacement comprising a valve
component and/or tissue valve, including at least two valve
leaflets each having at least two tabs. The at least two leaflets
may be attached to an annular skirt on the inside of the skirt. The
term "annular" as used herein is meant to designate a
circumferentially running structure and is not limited to an
exactly circular or ring like structure. A portion of the skirt
material wraps at least partially around the commissural post
without passing through the tab opening.
[0054] According to still another aspect of the invention there is
provided a device for heart valve replacement comprising a stent
component having at least one section defining an at least
partially conical body. The device further has a plurality of valve
leaflets. An inner skirt is disposed within the stent component
overlapping said at least partially conical body to define a
conduit therewithin. An outer skirt is disposed outside the stent
component overlapping only a portion of said at least partially
conical body.
[0055] The inner skirt and/or the outer skirt are preferably made
of pericardium tissue, most preferably porcine pericardium
tissue.
[0056] Another aspect of the invention provides a valve replacement
device comprising a stent component that is radially compressible
to a compressed state for delivery and radially expandable to a
functional state. The stent component may comprise at least one
(and preferably a plurality) of attachment elements for cooperating
with a stent-holder of a delivery device. Each attachment element
(or at least one of the attachment elements) may comprise a U-shape
portion joining two stent struts. The term U-shape is used herein
to include any shape including a generally arcuate apex, whether or
not the sides are straight or curved, bulged outwardly, parallel or
non-parallel. In the compressed state of the stent when received
within an accommodation region of the delivery catheter, the struts
may lie adjacent each other at the attachment element, such that
the arc of the U-shape portion extends around a first angle more
than 180 degrees to define, for example, a closed or near closed
(e.g. horseshoe shape) eyelet having an aperture larger than the
spacing of the struts. The horseshoe shape of the eyelet aperture
and the adjacent space between the struts may optionally together
define a keyhole type shape. In an expanded (or non-collapsed)
state of the stent when released from the accommodation region of
the delivery catheter, the struts may move apart, and the arc of
the U-shape portion may extend around a second angle that is less
than the first angle, to at least partly open the eyelet further.
For example, the second angle may be about 180 degrees or less. In
the expanded state, the attached element may define a substantially
non-horseshoe U-shape, for example, a straight-sided U-shape with
an arcuate apex.
[0057] A delivery device for use with a valve replacement device as
aforesaid may comprise a sent-holder provided within an
accommodation region. The stent-holder may comprise [0058] (ii) a
projections receivable within each eyelet. The projection may be
dimensioned such that, when the stent is in its collapsed state,
the projection is trapped within the eyelet and unable to pass
between the adjacent struts, and/or [0059] (ii) one or more
recesses or interstices for accommodating the attachment element
substantially therewithin, at least in the collapsed state of the
stent.
[0060] The above forms can provide for a compact, yet reliable and
self-opening and/or self-releasing attachment between a valve
replacement device and a delivery device.
[0061] Another aspect of the present invention provides a valve
replacement device comprising a stent component supporting at least
two leaflets. The leaflets may be of pericardium tissue, most
preferably porcine pericardium tissue or bovine pericardium. As
mentioned previously, porcine pericardium may provide desirable
tissue thinness. Bovine pericardium may be slightly thicker but
more durable.
[0062] Each valve leaflet may include at least two tabs. The tabs
may serve for supporting the leaflets relative to the stent
component.
[0063] In some embodiments, the tabs may be attached directly to
commissural supports (e.g. posts) of the stent component. The tabs
may attach to attachment means provided on the commissural support.
For example, a tab may pass through an opening (e.g. a slot or
slit) in a commissural support, from an interior of the stent
component to an exterior. The portion of the tab exterior to the
stent component may be folded to lie against the commissural
support and/or sutured to the commissural support. Optionally
respective tabs of two adjacent leaflets that meet at the
commissural support pass through the same opening. Each tab may be
folded to lie against the exterior of the commissural support
without overlapping the other tab. The two tabs optionally are not
directly attached to each other.
[0064] Additionally or alternatively, the leaflets may be attached
to an inner skirt. The leaflets may be attached to an interior
portion of the inner skirt, the tabs passing through openings
(e.g., slots or slits) in the inner skirt to the exterior of the
inner skirt. The inner skirt may have scalloped clearances, each
such clearance being spanned by a respective leaflet. The inner
skirt may have commissural portions or upstands in which the
openings (e.g., slots or slits) are provided.
[0065] Additionally or alternatively, the material defining the
inner skirt may include integral extension portions (e.g. flaps)
that wrap around at least a portion of the commissural supports,
for covering portions of the commissural supports and/or for
covering the leaflet tabs secured to the commissural supports. The
extension portions may be sutured to the commissural supports.
[0066] In some embodiments, a combination of any two or all three
of the above arrangements may be used. For example, a pair of tabs
of adjacent leaflets may pass through an opening in the inner
skirt, and through an opening in the commissural support. The two
openings may generally be in register. The tabs may be folded back
in opposite directions, and sutured to the exterior of the
commissural support (optionally without the tabs being sutured
directly to each other). One or more flaps or extensions of the
inner skirt at the commissural support may be wrapped around the
exterior of the commissural support to cover the tabs and/or the
commissural support. The extension (s) may be sutured to the
commissural support. Optionally, the sutures may pass through the
same suture holes in the commissural support as those used for
attaching the tabs. The extension (s) may extend axially beyond the
tab(s), such that the edges of the tabs are shrouded and
protected.
[0067] Another aspect of the invention provides a valve replacement
device comprising a stent component that is radially compressible
to a compressed state for delivery and radially expandable to a
functional state, a plurality of valve leaflets mounted within the
stent component, an inner skirt attached to the valve leaflets, the
inner skirt extending at least partly within the stent component,
and an outer skirt extending at least partly outside the stent
component.
[0068] In some embodiments, the outer skirt may extend further
towards an inflow extremity of the stent component than does the
inner skirt. Additionally or alternatively, the inner and outer
skirts may partly overlap, at least with respect to the surface of
at least one of the skirts. Additionally or alternatively, the
inner and outer skirts may not have any coterminous extremity.
Additionally or alternatively, the inner skirt may extend further
towards an outflow extremity of the stent component than does the
outer skirt.
[0069] At least a portion of the stent component over which at
least one of the skirts extends, may optionally comprise a lattice
structure having at least one row of a plurality of cells.
[0070] A function of the inner skirt may be to define a conduit
within the stent to channel blood towards the valve leaflets, and
obstruct leakage of blood through interstices of the stent
component (e.g., lattice intertices). A function of the outer skirt
may be to provide a seal surface outside the stent component for
sealing with surrounding tissue, to obstruct leakage at the
interface with surrounding tissue. Providing both skirts may be
beneficial in terms of obstructing leakage overall. However, the
presence of both skirts can add significantly to the thickness of
material carried by the stent, and thereby increase the difficulty
of compressing the stent-valve to a desirably small size. By
providing both skirts, with only partial overlap in an axial
direction, the benefits of both skirts can be obtained, but with a
reduced thickness profile in the regions where only one skirt
extends. Overlapping the skirts can provide better sealing between
the skirts than were the skirts to be arranged edge to edge on the
interior and exterior respectively of the stent component (for
example, especially bearing in mind that the stent-valve is to be
deformed substantially by compression for delivery and re-expansion
at implantation).
[0071] The degree of skirt overlap in the axial direction may, for
example, by at least 1 mm, or at least 2 mm, or at least 3 mm, or
at least 4 mm, or at least 5 mm, or at least 6 mm, or at least 7
mm, or at least 8 mm. Additionally or alternatively, the degree of
skirt overlap in the axial direction may, for example, be less than
10 mm, or less than 9 mm, or less than 8 mm, or less than 7 mm, or
less than 6 mm, or less than 5 mm, or less than 4 mm. For example,
the degree of skirt overlap in the axial direction may be about 4-6
mm.
[0072] At least one of the skirts (optionally each skirt) may
extend a non-overlapped axial distance of at least 1 mm away from
the region of overlap. The non-overlapped distance for the or each
skirt may, for example, be at least 2 mm, or at least 3 mm, or at
least 4 mm or at least 5 mm or at least 6 mm, or at least 7 mm or
at least 8 mm or at least 9 mm, or at least 10 mm.
[0073] In some embodiments, the inflow edge or mouth of the stent
component may have a zig-zag shape defined by a lattice structure
of at least one row of cells. The zig-zag shape may be defined an
alternating sequence of free apexes (e.g., at or defining an inflow
extremity), and connected apexes (e.g. connected to lattice
structure extending away from the inflow end towards the outflow
end). In some embodiments, the inner skirt may extend only to the
connected apexes. The outer skirt may overlap the inner skirt and
extend further than the inner skirt, to a level corresponding to at
least some of the free apexes.
[0074] In some embodiments, the inner skirt may extend towards the
inflow extremity of the stent component. The outer skirt may
overlap only partly the inner skirt while remaining spaced from an
uppermost edge of the inner skirt. The outer skirt may extend
towards (or optionally to) the inflow extremity of the stent
component. The outer skirt may optionally not overlap (e.g.,
directly or indirectly through the stent component) any portion of
the leaflets.
[0075] The inner skirt and/or outer skirt may be of any suitable
material, such as pericardial tissue (e.g. porcine pericardium for
thinness), PET, Dacron, etc. The inner and outer skirts may
optionally be made of the same material as each other.
[0076] Another object of the present invention is to provide a
delivery system for delivering a device for heart valve
replacement. The delivery system comprises a flexible tubular
catheter including a proximal end (or portion) and a distal end (or
portion) with connection means (e.g. a stent holder). The delivery
device further includes a device for heart valve replacement as
described hereinabove. The delivery device is connected with said
connection means such that the portion of the device adapted to be
placed in or towards the ventricle is oriented towards the distal
end of said catheter and the portion of said device adapted to be
placed in the aorta is oriented toward said proximal end. In
connection with the delivery device, the term "distal" means
oriented away and the term "proximal" means oriented towards an
operator of the delivery device.
[0077] The proximal end of the tubular catheter preferably includes
a handle member for an operator. The distal end of the tubular
catheter comprises connection means (e.g. stent holder) for
re-leasably connecting a valve replacement device according to the
present invention. The connection means may be of any suitable
type. Preferably, the connection means are configured as pins or
other projections that mate with corresponding attachment elements
(e.g. hooks and/or eyelets) on the valve replacement device. Upon
expansion of the stent component of the replacement device, the
attachment elements are released from the pins, thus uncoupling the
device from the tubular catheter.
[0078] The orientation of the valve replacement device on the
tubular catheter allows the insertion of the device along an artery
of a patient, preferably along the femoral or the subclavian
artery. An arterial insertion is beneficial for some patients, as
the procedure is less traumatizing than a surgical procedure. If
desired, the tubular catheter may also be configured for
transapi-cal insertion.
[0079] According to still another aspect of the invention there is
provided a method of replacement of a heart valve. A delivery
device as disclosed above is inserted in a compressed state to the
site of a heart valve to be replaced. The sent element is then
expanded. The delivery device is optionally inserted by means of a
flexible tubular catheter along an artery, preferably a femoral
artery or a subclavian artery. Alternatively the delivery device is
inserted transapically into a ventricle of the heart.
[0080] It is another objective of the present invention to provide
a method of producing a valve replacement device having a reduced
size when radially compressed which is quick and easy to per-form.
This objective is met by a manufacturing method as defined in the
appended claims.
[0081] In some embodiments, in a first step of the method of
production of a valve replacement device according to the present
invention, a tubular skirt, preferably made of pericardium tissue,
is provided. The term "tubular" has to be understood as to also
encompass skirts which are generally shaped like a cylinder or a
conical frustum. It also comprises skirts having elliptical cross
sections, varying radii along an axis and the like. The tubular
skirt preferably is made of porcine pericardium tissue.
[0082] In a next step, at least two leaflets, preferably also made
of pericardium tissue are arranged adjacent to each other around
the tubular skirt. The size of the leaflets is thereby selected
such that once the leaflets are each arranged adjacent to each
other, they span around the entire circumference of the tubular
skirt. The lateral edges of said leaflets are thereby in contact at
least in the area of their upper free edge.
[0083] The leaflets may be cut out of pericardium tissue. The
leaflets include a free edge which is optionally curved. The
curvature ay be a convex curvature. The size of the leaflets as
well as the curvature of the free edge are thereby chosen in such a
way as to allow the free edges to sealingly contact each other
(e.g. coapt) when the stent component is in the functional state.
The leaflets further include two lateral edges tapering towards a
lower edge of the leaflet. The lower edge is shorter than the free
edge. Preferably, said lower edge is also curved, more preferably
with a convex curvature. The term "convex" is understood to define
the curvature of an edge of the leaflet in relation to the surface
of the leaflet. Therefore, a convexly curved edge bulges out of the
leaflet.
[0084] Prior to the cutting, the pericardium tissue is preferably
treated to avoid any shrinkage of the leaflets at a later
stage.
[0085] The lateral edges and the bottom edge of the leaflets are
then attached onto the surface of the tubular skirt, preferably by
means of a suture. Alternatively, the leaflets may also be attached
by other means, such as gluing or the like. The free edges must
remain unattached to the skirt, as they will form the replacement
valve in the assembled valve replacement device.
[0086] In the next step, the tubular skirt is everted, so that the
leaflets now lie inside the generally tubular conduit of the
tubular skirt. The everted skirt is then finally attached to a
stent component.
[0087] As the valve component of a valve replacement device
produced according to the method of the present invention is made
"inside out", the attachment of the leaflets to the skirt is much
easier and requires lesser steps.
[0088] To further reduce the size of the crimped valve replacement
device, at least some skirt tissue overlapping the leaflets is
preferably removed. This may be done by cutting the skirt along the
suture attaching the leaflets to the skirt. The removal of the
tissue is preferably performed using scissors or a scalpel. This
allows to further reduce the diameter of the valve replacement
device, as, with the exception of the area of sutures, only one
layer of tissue is present. Removal of such skirt tissue creates
scalloped clearances in the skirt tissue, spanned by the leaflets.
The skirt tissue may include commissural portions where neighboring
leaflets meet. The commissural portions may include circumferential
and/or axial extensions (e.g. flaps) for providing protective wrap
material for wrapping around the exterior of a commissural post of
a stent component.
[0089] The at least two leaflets preferably additionally comprise
at least two tabs, preferably one tab is thereby arranged on each
lateral edge of each leaflet, most preferably in the area of said
free edge. Alternatively, the at least two leaflets may comprise
more tabs, e.g. two tabs on each lateral edge of each leaflet.
After eversion of the tubular skirt, at least two slits are cut
into the skirt and at least one tab is inserted through each slit.
Alternatively, two tabs of adjacent leaflets are inserted through
the same slit. This allows to pass the tabs from the inside of the
skirt to the outside.
[0090] The tabs are then preferably directly attached to the stent
component, preferably to attachment means provided on the stem of a
wishbone shaped commissural post, most preferably by pulling said
tabs through openings provided on said commissural posts, followed
by suturing said tabs to said commissural posts. Superfluous
material of said tabs may then be removed.
[0091] The extensions of the commissural portions of the skirt
material may be wrapped around the commissural posts without
passing through the same openings as the tabs.
[0092] Preferably, said tubular skirt is made by wrapping a
generally rectangular piece of pericardium having an appropriate
size around a mandrel having a size and form corresponding to the
intended size and form of the valve component of the valve
replacement device. The piece of pericardium is then stitched
together such as to yield a generally tubular skirt. The
pericardium is then preferably treated to cause shrinkage of the
tissue, whereby the annular skirt will adopt the form of the outer
contour of the mandrel. The mandrel may therefore additionally
impart a specific shape to the annular skirt. In a especially
preferred embodiment, said mandrel will impart a circumferential
bulge on said skirt. During attachment of said at least two
leaflets to said annular skirt, the annular skirt may remain on
said mandrel.
[0093] Further, said flaps of the skirt material may be wrapped
over said tabs and said openings, such as to cover the suture
holding the tabs on said commissural posts. This further protects
the valve replacement device from any damage when crimping the
device to less than 18 French in diameter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0094] While certain aspects of the invention have been defined
above and/or in the appended claims, protection is claimed for any
novel feature or idea described herein and/or illustrated in the
drawings, whether or not emphasis has been placed thereon.
[0095] Further advantages and characteristics of the present
invention are described in the following description of examples
and figures.
[0096] FIG. 1: Shows an exemplary embodiment a valve replacement
device according to the present invention;
[0097] FIG. 2: shows a leaflet of a valve component according to
the present invention;
[0098] FIG. 3: shows a detailed view of commissural posts having a
wishbone shape;
[0099] FIG. 4a-d: are representations of different configurations
of attachment means for the tabs of the leaflets;
[0100] FIG. 5a-e: shows a method of producing a valve replacement
device according to the present invention;
[0101] FIG. 6: shows an alternative embodiment of stent component,
in a view similar to FIG. 3;
[0102] FIG. 7: shows a schematic view of a delivery device for the
valve replacement device;
[0103] FIG. 8: shows a schematic close-up showing the relation
between a stent holder and attachment element when the stent
component is in its compressed condition; and
[0104] FIG. 9: shows schematically the attachment element when the
stent component is expanded to its functional state.
DETAILED DESCRIPTION
[0105] FIG. 1 shows a preferred embodiment of a valve replacement
device 15 according to the present invention. The valve replacement
device 15 is adapted to be inserted by a transfemoral approach, but
the device may also be inserted generally by another transvascular
approach or by a transapical approach. The replacement device 15
has a first end 26, a second end 27 and an intermediate section 17
and comprises a stent component 20 and a valve component 5. In this
embodiment, the first end 26 is intended to be positioned in an
artery, while the second end 27 is intended to be positioned in or
towards the ventricle of the heart of a patient. When the valve
replacement device 15 is in place, blood will flow from the second
end 27 to the first end 26 via the intermediate section 17.
Therefore, the section between the second end 27 and the
intermediate section 17 is also referred to as "inflow section".
Accordingly, the section be-tween the intermediate section 17 and
the second end 26 is referred to as "outflow section".
[0106] The stent component 20 comprises stabilization arches 21,
commissural posts 22, upper anchoring crown 23, lower anchoring
crown 24 as well as attachment elements 25. The configuration of
the stent component is thereby similar to the configuration as
described in the co-pending application EP 2 205 183. The
stabilization arches 21 serve to stabilize the stent 15 in a blood
vessel, preferably the aorta, during deployment. The arches 21 are
attached with their proximal end directly to an upper, i.e. distal
end of the commissural posts 22. Starting from the proximal end the
arches 21 diverge radially outwardly over a part of their length
and converge radially inwardly towards their distal end. The terms
"distal" and "proximal" are used hereunder to designate the parts
of the valve replacement device 15 or of its components lying
further away or closer to the heart, respectively. The distal end
sometimes is also referred to as the aortic end and the proximal
end as the ventricular end.
[0107] Three leaflets 31 of a replacement heart valve are attached
to the commissural posts 22. The leaflets 31 are formed from
porcine pericardium tissue. The upper anchoring crown 23 serves to
attach the stent 15 to the aortic side of a heart valve, while the
lower anchoring crown 24 serves to attach the stent 15 in the
native annulus, or towards the ventricular side of the heart valve.
Attachment means 25 enable the removable attachment of the stent 15
to a delivery device.
[0108] The commissural posts 22 have an axial length L2
corresponding substantially to the axial length LI of the
stabilization arches 21. Typically the length LI is about 90% to
110% of the length L2. The commissural posts 22 have a wishbone
shape and each in-clude an upper part 22a for direct fixation of
tabs 30 of valve leaflets 31 and a lower part 22b with two legs or
arms 32, 33. The tabs 30 are fixed to the upper part 22a by
wrapping around and suturing. Lateral sides of the leaflets 31 are
sutured directly or indirectly to the two arms 32, 33 of the lower
part 22b. The lower crown 24 is formed by a substantially tubular
portion having a lattice structure of cells 34, 35, 36. The two
arms 32, 33 of each wishbone shaped commissural post 22 span a
respective sequence of at least three adjacent cells 34, 35, 36.
The wishbone extends from outer cells 34, 36 of the sequence
without attachment to at least one intermediate cell 35 of the
sequence.
[0109] The lower, i.e proximal end of the stent is covered by an
outer skirt 34 extending axially along about half of the height of
the cells 34, 35, 36. On the inner side of the stent 15 there is an
inner skirt 35 preferably made of pericardium material sealing the
space between two neighbouring arms 32, 33 of a wishbone shaped
commissural post 22.
[0110] FIG. 2 is a representation of a leaflet 10 according to the
present invention. A free edge 10 is configured such as to
sealingly engage free edge 10 of at least one further leaflet 31 to
form a tightly closing valve. Preferably, the free edge 10 is
arcuate, although a straight edge may also be used. The leaflet 31
further includes two lateral edges 11 and a lower edge 12. The
lower edge 12 is arcuate, while the lateral edges 11 are linear.
The surface framed by the lateral edges 11 and the lower edge 12 is
frequently referred to as "belly" of the leaflet 31. Two tabs 30
are arranged on both lateral edges 11 in the area of the free edge
10. The tabs 30 are sized and shaped such as to be insertable into
attachment means provided on commissural posts of the stent
component of a valve replacement device (see also FIGS. 3 and 4).
At least two leaflets 31 are positioned in such a device to form a
valve component, but preferably the valve component comprises three
leaflets 31.
[0111] FIG. 3 shows a detailed view showing the configuration of a
stent component 20 having commissural posts 22 in a wishbone shape.
The stent component 20 is shown in its collapsed, i.e. crimped
state. The upper parts 22a of commissural posts 22 are joined
together by stabilization arches 21. Further, these upper parts 22a
comprise fixation means for tabs 30 of leaflets 31, here
represented by openings 19 and holes 18. The lower part 22b of
commissural posts 22 comprises two arms 32, 33. The commissural
posts 22 thereby have an overall wishbone shaped configuration. As
can be readily seen on this figure, both arms 32, 33 of commissural
posts 22 span a sequence of three consecutive cells 34, 35, 36 of
the lower crown 24. The arms 32, 33 are thereby connected to the
outer cells 34, 36 of the sequence without attachment to the
intermediate cell 35 of the sequence. The lower crown 24 further
comprises attachment elements 25 in the form of hooks. These
attachment elements 25 allow the removable attachment of the valve
replacement device 15 to a delivery device.
[0112] FIG. 4 shows different configuration of attachment means on
the upper part 22a of commissural posts 22. The configuration shown
in FIG. 4a corresponds to the configuration of the commissural
posts 22 as shown on FIG. 3. An opening 19 in the form of a long
hole is arranged in the centre of the upper part 22a. The opening
19 is shaped and sized such as to allow insertion of at least one
tab 30. However, the size of the opening 19 is preferably such that
two tabs 30 may be inserted. Further, the opening 19 is flanked on
both sides by four holes 18. A further hole 18 is arranged on top
of the opening 19. The holes 18 are intended to accommodate suture
wire used to attach the tabs 30 to the commissural posts 22. An
alternative configuration of the opening 19 is shown on FIG. 4b. In
this embodiment, the opening 19 is configured as longitudinal slit
in the middle of the upper part 22a. Again, the opening 19 is
flanked by holes 18. FIG. 4c shows a further embodiment without any
holes 18. The opening 19 is shown as longitudinal slit, but may
alternatively also be configured as long hole. In this embodiment,
tabs 30 are inserted through opening 19, folded back towards the
leaflet 31 and sutured thereto. A further alternative embodiment is
shown on FIG. 4d. In this embodiment, the attachment means only
comprise holes 18. A tab 30 is thereby folded backward onto the
leaflet 31 and sutured thereto. A further suture is sewn from the
fold of the tab 30 into the openings 18, thereby attaching the tabs
30 to commissural posts 22.
[0113] FIG. 5 represents a method of producing a valve replacement
device 15 according to the present invention. FIG. 5a shows the
first step of the method. A generally rectangular piece of
pericardium tissue 2 having an appropriate size is wrapped around a
mandrel 1 having an appropriate shape. The mandrel preferably
comprises specific shape elements, here exemplarily shown as bulges
4 to be imparted to the inner skirt of the valve replacement
device. The pericardium tissue is then sewn together with suture 3
and optionally treaded to impart some shrinkage of the tissue. In
the next step, shown on FIG. 5b, at least two but preferably three
tabs 31 are arranged around said piece of pericardium tissue 2 on
its outside surface. The tabs 31 are thereby arranged such that
tabs 30 of neighbouring leaflets 31 are at the same height along
the longitudinal axis of the mandrel 1. Further, neighbouring
leaflets 31 contact each other at their lateral edges in the area
of the tabs 30. The leaflets 31 are then sewn to the pericardium
tissue 2 along the lower edge 12 and the lateral edges 11. The tabs
30 remain free. Thereafter, the pericardium tissue 4 is removed
from the mandrel 1 and everted (see FIG. 5c). The leaflets 31 are
now located on the inside of the cylindrically shaped pericardium
tissue 4. Excess material 6 of the pericardium tissue is removed,
e.g. by cutting. At least a portion of the pericardium tissue 4
located on the exterior of the leaflets 31 is also removed along
suture 7 which connects the pericardium tissue 4 with the leaflets
31. At the area of the tabs, slits 8 are provided in the
pericardium tissue 4 which are arranged and sized such as to be
able to pass tabs 30 therethrough. At the area of the slits 8, two
flaps 9 of the pericardium tissue 4 are left. The tabs 30 are then
passed through the slits 8. The now finished valve component 5
includes inner skirt 28 and leaflets 31. With the exception of the
area around suture 7, the valve component 5 consists of a single
layer of pericardium tissue. In a next step shown on FIG. 5d, the
valve component 5 is inserted into the stent component 20. The tabs
30 are inserted through the openings 19 located on the commissural
posts 22, folded back toward leaflets 31 and further attached to
the commissural posts 22 by suturing. The suture stitches are
passed through holes 18. Superfluous material of the tabs 30 is
subsequently removed. Then, the flaps 9 are folded over the upper
part 22a of the commissural posts 22 to cover the suture of the
tabs 30, thus forming a kind of sleeve around the upper part 22a of
the commissural posts 22. FIG. 5e shows the finished valve
replacement device 15. The valve component 5 is additionally
attached to the stent component 20 by means of sutures 13 in the
area of the arms 32, 33 of each wishbone shaped commissural posts
22. Further, the inner skirt 28 is attached to the cells of the
lower crown 24 by means of sutures 14. The lower crown 24 may
additionally be covered on the outside by an outer skirt 29, as
shown on the embodiment of FIG. 1.
[0114] In some embodiments, the flaps 9 may have an axial extent
that is greater, in the inflow and/or outflow direction, than the
tabs 30. When the flaps 9 are folded around the commissural post,
the flaps 9 may extend axially beyond the edge of the tabs 30,
thereby covering and protecting the tabs 30. As can be seen in FIG.
5e, the flaps 9 may extend axially above the level of the
leaflets.
[0115] FIG. 6 illustrates schematically a modified arrangement of
stent component, and a modified arrangement of inner skirt 35 and
outer skirt 34. The inflow end or mouth of the stent component has
a zig-zag shape defined by cells of a lattice structure including
at least one row of lattice cells. The zig-zag shape is defined by
alternating free apexes 50 and connected apexes 52. The free apexes
50 define an inflow extremity. The connected apexes 52 communicate
with adjacent cells in the row.
[0116] The position of the inner skirt 35 is indicated by lines 54
and 56, and extends from the commissural posts and/or leaflets
towards the inflow extremity. The line 54 indicates generally the
level of the lower edges of the leaflets, although it is to be
appreciated that the inner skirt 35 may have commissural portions
that extend axially up the commissural posts of the stent
component. The position of the outer skirt 34 is indicated by lines
58 and 60 and extends further than the inner skirt 35 towards the
inflow extremity.
[0117] In the illustrated example, as indicated by the line 56, the
inner skirt 35 extends to a level corresponding to (at least some
of) the connected apexes 52. The outer skirt 34 extends to a level
corresponding to (at least some of) the free apexes 50.
[0118] The outer skirt 34 may have a zig-zag shaped edge that
matches substantially the zig-zag shape of the inflow edge.
[0119] The inner skirt 35 extends further than the outer skirt 34
in the opposite direction towards the outflow end (and/or
extremity) of the stent. The inner and outer skirts may partly
overlap each other in the axial direction. The degree of axial
overlap may, for example, be at least 1 mm, or at least 2 mm, or at
least 3 mm, or at least 4 mm, or at least 5 mm, or at least 6 mm,
or at least 7 mm, or at least 8 mm. Additionally or alternatively,
the degree of skirt overlap in the axial direction may, for
example, be less than 10 mm, or less than 9 mm, or less than 8 mm,
or less than 7 mm, or less than 6 mm, or less than 5 mm, or less
than 4 mm. For example, the degree of skirt overlap in the axial
direction may be about 4-6 mm.
[0120] As can be seen in FIG. 6, at least some of the cells have an
exposed free apex 50a that extends beyond the free apexes 50 of
adjacent cells in the row, and is not covered by the outer skirt
34. The exposed free apexes 50a provide attachment elements 25 for
engaging a stent holder of a delivery device.
[0121] Also as can be seen at the circle A in FIG. 6, and the
corresponding area in FIG. 3, suture bores may be provided along
each side of the opening in the commissural post, and at only one
axial end of the stem. Such an arrangement can enable the size of
the stem of the commissural post to be reduced compared to an
arrangement in which suture bores might be provided at both axial
opposite ends.
[0122] FIG. 7 illustrates schematically a delivery device 62, e.g.
delivery catheter, for inserting the valve replacement device at
the heart. The catheter may be advanced over a guidewire (shown by
the broken line). The catheter comprises a distal portion 64 for
insertion into the anatomy and having an accommodation region for
accommodating the valve replacement device in its compressed state.
A stent holder (described below) is provided at the accommodation
region for restraining the valve replacement device against axial
movement until the stent component expands to its functional state,
whereupon the stent component detaches from the stent holder. The
distal portion 64 may also include a sheath arrangement for
constraining the stent-component in its compressed state for
delivery, the sheath arrangement being operable to unsheath the
stent component to allow the stent-component to expand to its
functional state. The delivery catheter 62 further comprises a stem
portion 66, which is optionally flexible, extending towards a
proximal portion 68 having a control handle.
[0123] Different examples of attachment elements 25 are envisaged.
Generally, each attachment element 25 may be defined by an apex
joining first and second struts that extend from an end of the
stent component. The struts may be members defining a lattice or
skeletal stent structure of the stent-valve 10. In the case of a
lattice, the cell associated with the struts may project axially
beyond neighbouring cells of the lattice.
[0124] In FIG. 3, the struts may extend generally linearly to meet
at an apex defining a generally straight-sided U-shape in the
compressed state (illustrated in FIG. 3), and expanding to a
V-shape when the stent component expands to its functional state.
In FIG. 6, the apex is slightly different by having a generally
rounded or horseshoe U-shape when in the compressed state
(illustrated in FIG. 6), and expanding to a generally non-horseshoe
shape, e.g. to a straight sided U-shape (FIG. 9), when the stent
component expands to its functional state.
[0125] Referring to FIG. 8, the stent holder 78 may generally
comprise a plurality of projections 84 and/or interstices 86 for
accommodating the attachment elements 25 of FIG. 3 and/or FIG. 6.
The edge 90 of each interstice 86 may optionally be rounded or
chamfered. The projections 84 may be configured for fitting within
the interior of the apex of each attachment element 25, when the
stent component is in its collapsed state. The engagement between
the projection 84 and the attachment element restrains the
attachment element (and hence the stent-valve 10) against axial
movement, at least in an axial direction away from the stent holder
24, and optionally in both axial directions.
[0126] In the case of a self-expanding stent component, the
attachment elements 25 may disengage when the portion of the stent
component from which the attachment elements 25 extend, is
uncovered by the sheathing arrangement of the delivery catheter.
Upon expansion of the stent component, the struts move apart to
open the U- or V-shape of the attachment element apex. As the apex
opens, this enlarges the interior of the attachment element 25 to
facilitate disengagement between the projection 84 and the
attachment element 25. The chamfered edge 90 of the interstice 86
also acts as a ramp surface to "lift" radially the struts out of
the clearance 88 as the struts expand circumferentially and bear
against the edge 90. In case the attachment elements 25 may stick
accidentally within the interstice 86, the attachment elements 25
may be freed by slight rotation and/or axial displacement of the
catheter, to promote further riding against the edge 90.
[0127] In the specific example of FIGS. 6, 8 and 9, the projections
84 are fingers or pins, suitable for fitting within the interior of
the horseshoe shape of the attachment element. The projections may
be generally radially projecting, or may be inclined at an angle
away from the stent component, for example, at an angle of up to
about 10 degrees (e.g. about 5 degrees). In a collapsed state of
the stent component (FIGS. 6 and 8), the struts may lie closely
adjacent each other at the attachment element 25, such that the arc
of the U-shape portion 25 extends around a first angle more than
180 degrees to define a closed or near closed eyelet having an
aperture larger than the spacing of the struts, to accommodate the
pin 84. The eyelet aperture and space between the struts may
together define a keyhole type shape. Alternatively, the struts may
bear against each other at the attachment element 25 to close the
eyelet. Either arrangement can restrain the attachment element 25
in both axial directions, merely by engagement between the
attachment element 25 and the projection 84. This may be
advantageous by enabling a larger chamfer surface to be used at the
edge 90 of the interstice 86 and/or at the end face 92 of the
stent-holder. A chamfered end face 92 may be desirable to
facilitate withdrawal of the stent holder 78 through the valve
replacement device once implanted. The arrangement also allows the
struts of the attachment element to be compressed close together,
such that the provision of the attachment element does not impede
compressing the stent component to a desirably small size.
[0128] Optionally, the interstice 86 is closed at one axial end, to
provide additional protection against the attachment element 25
displacing axially in a direction that would force the projection
84 into the space between the struts.
[0129] Referring to FIG. 9, in the expanded (or non-collapsed)
functional state of the stent component, the struts may move apart,
and the arc of the U-shape apex may extend around a second angle
that is less than the first angle, to at least partly open the
eyelet. The second angle may be about 180 degrees or less. In a
similar manner to that described above, opening of the apex may
facilitate disengagement from the projection 84. The chamfered edge
90 of the interstice 86 also acts as a ramp surface to "lift"
radially the struts out of the clearance 88 as the struts 70 and 72
expand circumferentially and bear against the edge 90.
[0130] It is emphasized that the foregoing description is merely
illustrative of non-limiting preferred forms of the invention. Many
modifications and equivalents may be used within the scope of the
invention.
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