U.S. patent application number 17/577931 was filed with the patent office on 2022-05-05 for stent valve, delivery apparatus and method therefor.
The applicant listed for this patent is BOSTON SCIENTIFIC LIMITED. Invention is credited to Youssef Biadillah, Stephane Delaloye, Jacques Essinger, Jean-Luc Hefti, Fabien Lombardi, Luc Mantanus.
Application Number | 20220133476 17/577931 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-05 |
United States Patent
Application |
20220133476 |
Kind Code |
A1 |
Lombardi; Fabien ; et
al. |
May 5, 2022 |
STENT VALVE, DELIVERY APPARATUS AND METHOD THEREFOR
Abstract
A delivery catheter for a stent valve, the delivery catheter
having a distal portion insertable into an anatomy, the distal
portion comprising an accommodation region for accommodating a
stent-valve for delivery into the anatomy, the delivery catheter
further comprising at least one sheath that is translatable between
a closed position for at least partly closing the accommodation
region and an open position for at least partly opening the
accommodation region.
Inventors: |
Lombardi; Fabien; (Prilly,
CH) ; Essinger; Jacques; (St-Prex, CH) ;
Delaloye; Stephane; (Bulach, CH) ; Hefti;
Jean-Luc; (Cheseaux-Noreaz, CH) ; Mantanus; Luc;
(Lausanne, CH) ; Biadillah; Youssef; (Lausanne,
CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BOSTON SCIENTIFIC LIMITED |
Hamilton |
|
BM |
|
|
Appl. No.: |
17/577931 |
Filed: |
January 18, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15235977 |
Aug 12, 2016 |
11253362 |
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17577931 |
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13825219 |
Jul 2, 2013 |
9414915 |
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PCT/EP2011/066677 |
Sep 26, 2011 |
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15235977 |
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61431710 |
Jan 11, 2011 |
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International
Class: |
A61F 2/24 20060101
A61F002/24 |
Foreign Application Data
Date |
Code |
Application Number |
May 15, 2011 |
EP |
11004013.6 |
May 16, 2011 |
EP |
11166201.1 |
Jul 26, 2011 |
EP |
11006142.1 |
Claims
1. A method of introducing a delivery catheter into an haemostasis
valve of an arterial introducer, wherein the delivery catheter 5 is
for introducing a stent-valve into the anatomy and comprises: a
distal portion having a stent-valve accommodation region; a
flexible stem portion extending proximally from the distal portion,
and comprising a plurality of control tubes nested one within
another, and axially slidable relative to each other to manipulate
the distal portion for deploying a stent-valve; and a sleeve
slidable on the stem portion, the sleeve having an interior
configured for permitting substantially unobstructed sliding of the
stem portion with respect to the sleeve; wherein the sleeve
slidable on the stem portion is advanced into the haemostasis valve
of the arterial introducer.
2. The method of claim 1, wherein the sleeve comprises a seal
member for forming a substantially blood-tight seal between an
interior surface of the sleeve and an exterior surface of the stem
portion.
3. The method of claim 2, wherein the seal member is formed by an
O-ring.
4. The method of claim 1, wherein the sleeve is slidably captive on
the stem portion.
5. The method of claim 1, wherein the sleeve is proximal of the
distal portion and configured for insertion into an introducer
after the distal portion has been inserted through the
introducer.
6. A delivery catheter for introducing a stent-valve into the
anatomy, the delivery catheter comprising: a distal portion having
a stent-valve accommodation region; a flexible stem portion
extending proximally from the distal portion, and comprising a
plurality of control tubes nested one within another, and axially
slidable relative to each other to manipulate the distal portion
for deploying a stent-valve; and a sleeve slidable on the stem
portion, the sleeve having an interior configured for permitting
substantially unobstructed sliding of the stem portion with respect
to the sleeve.
7. The delivery catheter of claim 6, wherein the sleeve comprises a
seal member for forming a substantially blood-tight seal between an
interior surface of the sleeve and an exterior surface of the stem
portion.
8. The delivery catheter of claim 7, wherein the seal member is
formed by an O-ring.
9. The delivery catheter of claim 7, wherein the sleeve is slidably
captive on the stem portion.
10. The delivery catheter of claim 8, wherein the sleeve is
proximal of the distal portion and configured for insertion into an
introducer after the distal portion has been inserted through the
introducer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/235,977, filed Aug. 12, 2016, which is a continuation of
U.S. application Ser. No. 13/825,219, filed Jul. 2, 2013, now U.S.
Pat. No. 9,414,915, which is a 371 of PCT/EP2011/066677, filed Sep.
26, 2011, which claims the benefit of priority of U.S. Provisional
Application No. 61/386,393 filed Sep. 24, 2010, and claims benefit
of U.S. Provisional Application No. 61/431,710, filed Jan. 11,
2011. The entirety of these disclosures of which are hereby
incorporated by reference.
[0002] Non-limiting aspects of the present invention relate to
transcatheter implantation of prosthetic stent-valves within the
anatomy, to methods of production, and to methods and apparatus for
delivering a stent-valve for implantation at a desired implantation
site. In some non-limiting aspects, the invention is directed to
cardiac stent-valves and/or to delivery to the heart. Additionally
or alternatively, some non-limiting aspects relate to stent-valves
and their delivery via a transvascular access route.
[0003] Traditional approaches for aortic 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 reduce invasiveness by using a
transcatheter procedure, namely by delivering and implanting a
prosthetic valve via a catheter inserted through a smaller skin
incision, using either a transvascular route or a transapical route
to the valve implantation site. The prosthetic valve is referred to
as a stent-valve or a valved-stent.
[0004] While less invasive and arguably less complicated,
transcatheter heart valve replacement devices and procedures still
face various difficulties. One issue is the unpredictability of the
anatomical condition of the aortic valve, for example in the
presence of severe calcification. Achieving controllable,
consistent deployment and anchoring of a stent-valve in such
variable conditions, with access only via a remote catheter, is a
challenge. An incorrectly positioned valve may fail to function
well, or may damage delicate heart tissue (which may result in the
patient having to be fitted with a pacemaker), or may result in
leakage of blood at the interface between the stent-valve and the
native tissue. A further issue for transvascular delivery is
difficulty of navigating, along a tortuous and often stenosed
vasculature, a delivery catheter large enough to accommodate a
stent-valve for implantation. The distal end of the delivery
catheter is typically in the range of 6-8 mm in diameter (18-24
French) to accommodate the stent-valve. The design of a delivery
catheter has to address requirements for (i) atraumatic
introduction, navigation and later withdrawal through the
vasculature, and (ii) support, for example, for applying force
along the length of the catheter from the proximal end, to traverse
the existing valve, and manipulate the distal end to unsheath and
deploy the stent-valve. These requirements often conflict, leading
to compromises in design. For example, softness and flexibility of
the catheter are desired for autraumaticity and ease of navigation,
but reduce the ability of the catheter to provide support for force
applied from the proximal end remotely to the distal end.
Additional complications relate to the small size desired for the
delivery catheter, without affecting the reliability, accuracy or
controllability of the deployment of the stent-valve, and ability
to withdraw the catheter following deployment of a stent, for
example, through a tightly-fitting introducer.
[0005] One particular type of stent-valve having a geometry
promising for self-alignment and self-location even in a severely
calcified native valve, is described in co-owned WO-A-2009/053497
and WO-A-2011/051043. The stent component comprises a conical lower
anchoring crown defining an inflow end, a conical upper anchoring
crown sloping outwardly in an opposite direction to the lower crown
towards the outflow end, and stabilization arches at the outflow
end. As described, the stabilization arches are deployed first for
aligning the stent-valve, followed by deployment of the upper crown
and finally deployment of the lower crown. A transapical delivery
device is described that is easy and intuitive to use for deploying
the stent-valve according to the above sequence. It may be
desirable to refine the stent-valve and/or the delivery device for
transvascular use.
[0006] A further issue is that it is sometimes necessary to rotate
the stent about the delivery axis, such that the stent has a
certain rotational alignment with regard to the native anatomy.
Certain previously described designs of stent rely on correct
rotational alignment between the native anatomy and the stent, in
order to locate/function correctly. Other previously shown designs
of stent include apertures or clearances that, when aligned
properly with respect to local anatomy, permit the entrance to each
coronary artery to be kept relatively clear. This benefits blood
flow to the coronary arteries and/or permits later treatment of the
coronary arteries by allowing access for implanting coronary
stents, should this be desired for the patient in a subsequent
treatment.
[0007] In devices previously described, rotation is achieved by
applying a torsional force to the catheter from the proximal handle
end. Ideally, the distal end should rotate at a constant rate in
response to torsional force. While rotation is not generally a
problem with a short catheter in a relatively straight run from the
handle to the stent-carrying end (e.g. transapical), it is much
more problematic with a long catheter extending on a relatively
twisting and/or substantially bent path (e.g. transvascular). The
friction against the arterial walls obstructs free rotation,
distributing the torsion to the artery itself. As the handle-end is
turned, the distal end tends to remain fixed. The torsional energy
tends to build-up along the length of the catheter until the handle
has been turned sufficiently that the total energy exceeds
frictional resistance, whereupon the distal end springs free, and
rotates through a large angle. This makes rotation adjustment
relatively coarse, with it being extremely difficult to achieve
fine adjustment. Thus, there is a need for a stent delivery system
that enables easy rotation and flexibility when delivering a stent
through a longer or curving route.
[0008] The present invention has been devised bearing all of the
aforementioned issues in mind. It may be desirable (although not
essential) to address and/or mitigate at least one of the foregoing
issues.
[0009] Throughout this description, including the foregoing
description of related art, any and all publicly available
documents described herein, including any and all U.S. patents, are
specifically incorporated by reference herein in their entirety.
The foregoing description of related art is not intended in any way
as an admission that any of the documents described therein,
including pending United States patent applications, are prior art
to embodiments according to the present disclosure. Moreover, the
description herein of any disadvantages associated with the
described products, methods, and/or apparatus, is not intended to
limit the disclosure. Indeed, aspects of the disclosed embodiments
may include certain features of the described products, methods,
and/or apparatus without suffering from their described
disadvantages.
[0010] Broadly speaking, one aspect of the present invention
provides a delivery catheter for transvascular delivery of a
stent-valve to an implantation site. The delivery catheter may be
defined independently of the stent-valve or as part of a system in
combination with a stent-valve. The invention may further comprise
any one or a combination of two of more of the following features,
which are all optional: [0011] (a) The delivery catheter may have a
distal portion for insertion into the anatomy, and a proximal
portion, a stent-valve accommodation region at the distal portion
for accommodating the stent-valve in the compressed condition for
delivery, and a stem portion extending from the accommodation
region towards the proximal portion (e.g., to a control handle at
the proximal portion). Where defined, the stent-valve may be
radially compressible to a compressed state for delivery, and
radially expandable to a functional state. The stent-valve may
comprise a plurality of valve leaflets, and a stent component for
supporting and/or housing the valve leaflets. The stent component
may be self-expanding from the compressed state, or the stent
component may be non-self-expanding (in which case the delivery
catheter may comprise a device for applying an expansion force to
cause or force expansion). (b) The delivery catheter may comprise
may comprise a first sheath for covering a first portion of the
accommodation region and/or stent-valve to constrain a first
portion of the stent-valve compressed, and a second sheath for
covering a second portion of the accommodation region and/or the
stent-valve to constrain a second portion of the stent-valve
compressed.
[0012] The second sheath may be translatable in a proximal
direction to uncover the second portion. The first sheath may be
translatable in a distal direction to uncover the first portion.
Use of such sheaths moving in opposite directions can reduce the
total distal extension of the catheter when the sheaths are open
(e.g., compared to a catheter employing a single distally-moving
sheath).
[0013] The first and second sheaths may be independently
translatable.
[0014] The stem may have a smaller outer diameter than the first
sheath and/or the second sheath.
[0015] The delivery catheter may further comprise a stent holder at
the accommodation region for retaining the stent-valve in a
predetermined axial position during deployment. The stent-holder
may restrain the stent-valve against substantial axial movement
(for example in both the distal and proximal directions). The stent
holder may have a profile that mates with a portion of the stent
component. For example, the mating may be such as to permit
self-detachment of the stent component from the stent holder when
the portion of the stent component mating with the stent holder is
ultimately allowed to expand by removal of a respective sheath. In
some embodiments, the stent holder is positioned towards a distal
end of the accommodation region and/or is configured to mate with a
distal end portion and/or inflow end portion of the stent
component. Optionally, the stent holder may be at least partly
overlapped by the first sheath. Optionally, the stent holder may
not be overlapped by the second sheath.
[0016] The second sheath may be longer than the first sheath. Such
an arrangement can reduce even further distal extension of the
delivery catheter when translating the sheaths to deploy the
stent-valve. The ratio of the length of second sheath divided by
the length of the first sheath may, for example, be at least 1.1,
or at least 1.5, or at least 2, or at least 2.5, or at least 3, or
at least 3.5, or at least 4, or at least 4.5, or at least 5.
[0017] The first and second sheaths may be configured such that
there is no overlap of the ends of the sheaths with each other.
Avoiding an overlap can avoid excess diameter of the distal portion
that might otherwise be caused by the sheath walls overlapping each
other. The first and second sheaths may have substantially the same
internal and/or external diameter as each other.
[0018] In some embodiments, the first and second sheaths may, in
one configuration, meet substantially end to end. The delivery
catheter may be used, when containing the stent-valve ready for
introduction into a patient, such that the sheaths meet
substantially end to end, thereby covering the length of
stent-valve substantially entirely.
[0019] Alternatively, whether or not the sheaths are capable of
being positioned to meet end to end, in use when containing the
stent-valve ready for introduction into a patient, the sheath ends
may be spaced apart from each other such that a portion of the
stent-valve is not covered by either sheath. The spacing between
the sheaths 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. Additionally or alternatively, the spacing may 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. In one form, the spacing is
between about 4 mm and about 6 mm. The spacing may correspond (e.g.
approximately) to a region of the stent-valve in which inner and
outer skirts overlap, and/or may reduce stress within the
stent-valve in the region of the spacing.
[0020] At the accommodation region the stent-valve may be
orientated with the inflow end of the stent-valve distal of the
outflow end of the stent-valve.
[0021] The catheter may further comprise an interface member,
having any of the associated features described hereinafter. [0022]
(c) The delivery catheter may comprise at least one sheath that is
translatable from a restraining position for restraining at least a
portion of the stent-valve compressed at the accommodation region,
to an open position in which the respective portion of the
stent-valve is uncovered for deployment from the accommodation
region; and an interface member that is deployable to provide a
guide surface for aiding withdrawal of the delivery catheter from
the anatomy after the stent-valve has been deployed. Optionally,
the catheter may be withdrawable with the interface member in a
deployed state. Optionally the interface member may be retained
captive on the delivery catheter, for example, at the accommodation
region.
[0023] The interface member can provide significant performance
advantages. In some embodiments, the distal portion of the delivery
catheter may include one or more abrupt surfaces or edges that are
exposed when the at least one sheath is translated open. The abrupt
surfaces/edges may, for example, obstruct removal of the catheter
through a tightly fitting introducer if the at least one sheath
remains open. Closing the at least one sheath may be problematic if
the open end an open end of the sheath initially relies on the
presence of the compressed stent-valve for concentric relation with
another part of the delivery catheter (e.g. concentricity of
opposed first and second sheaths).
[0024] In some embodiments, the interface member may provide a
guide surface for cooperating with an exposed abrupt edge of a
stent holder or other component of the distal portion that is
exposed when the at least one sheath is open, the guide surface
defining a less-abrupt and/or a more streamlined exposed profile if
the sheath remains open. The more streamlined profile can permit
the distal portion of the delivery catheter to be withdrawn without
substantial obstruction, even into and through a tightly fitting
introducer.
[0025] Additionally or alternatively, in some embodiments, the
guide surface of the interface member may serve to: [0026] (i) at
least partly cover, and/or define a profile accommodating, the edge
of the sheath at its open end, and/or (ii) centre the open end of
the sheath with respect to an axis of the catheter.
[0027] Such a function may permit easier closing of the sheath if
desired.
[0028] In some embodiments, the delivery catheter may comprise
first and second sheaths, at least one of which is translatable as
aforesaid. The other sheath may also be translatable or it may be
substantially fixed. The sheaths may have respective open ends that
generally face one another when the (or each) sheath is in the
closed position (whether or not the sheaths contact each other end
to end).
[0029] In some embodiments, the interface member may be deployable
to: [0030] (i) provide an interface at or between the generally
facing open ends, and/or (ii) align the open ends of the sheaths to
be substantially in register with each other and/or centered with
respect to the catheter axis, and/or (iii) define a bridge and/or a
smooth profile between the facing open ends of the sheaths.
[0031] Whatever the function of the interface member, in some
embodiments, the interface member may be translatable along the
catheter axis from a non-deployed condition to a deployed
condition. For example, the interface member may initially be
stowed within one of the sheaths in a non-deployed condition, and
be translatable to or towards the open end of the sheath to
transition to its deployed condition. In some embodiments, the
interface member may be substantially freely translatable within a
predetermined range of movement, and be configured to move with, or
in response to, sheath movement.
[0032] Additionally or alternatively, in some embodiments, the
interface member (or at least a portion thereof) may be expandable.
Transition from a non-deployed condition to a deployed condition
may include expansion of the expandable portion. For example, the
expandable portion of the interface member may be radially
expandable. The expandable portion may be self-expandable from a
compressed state.
[0033] In some embodiments, the interface member may be both
movable and self-expandable. For example, the interface member may
initially be stowed within one of the sheaths in a compressed
non-deployed condition. The sheath may constrain the interface
member in a compressed condition. Relative movement between the
sheath and the interface member may cause the interface member to
transition towards the open end of the sheath. When the interface
member is no longer constrained by the sheath, the interface member
may self-expand to deploy. Upon expansion, the interface member may
float or self-position at or near the open end of the sheath and/or
an exposed edge of the stent-holder, in its deployed condition.
[0034] (d) The delivery catheter may comprise a sleeve or skirt (or
segments) of flexible material for fitting between the outer
surface of a portion of the stent-valve, and an interior surface of
a translatable sheath of the delivery catheter. The sleeve/skirt
segments may also be referred to as petals or tabs. The
sleeve/skirt (or segments) may be of flexible film or wafer
material. The sheath may translate relative to the sleeve/skirt (or
segments). The sleeve/skirt (or segments) may optionally be mounted
on a stent holder of the delivery catheter. The sleeve/skirt (or
segments) may optionally be made from balloon material of a balloon
catheter, for example, a valvuloplasty balloon catheter. Such
material is strong, resistant to tearing, yet flexible.
[0035] The sleeve/skirt (or segments) may reduce friction between
the sheath and the stent-valve, for example, facilitating easier
loading of the stent-valve within the sheath of the delivery
catheter. The sleeve/skirt (or segments) may also avoid the sheath
from catching against an edge of an outer skirt of the
stent-valve.
[0036] In some embodiments, the sleeve/skirt may comprise a sleeve
section having a closed-loop shape at one end, and slits at an
opposite end defining segments that can flex outwardly
independently of each other. [0037] (e) In further feature similar
to (d), the delivery catheter may comprise a stent holder for
mating engagement with a stent-valve when in a compressed state for
axially restraining the stent-valve against axial movement in at
least one direction, the stent holder having attached thereto a
sleeve/skirt (or segments) of flexible material.
[0038] In some embodiments, the sleeve/skirt (or segments) may be
configured for overlapping an outer surface portion of a
stent-valve mating with the stent holder.
[0039] In some embodiments, the stent holder may comprise a
radially recessed portion for receiving a portion of a stent-valve.
The sleeve/skirt (or segments) may cover the radially recessed
portion, at least in one position of the sleeve/skirt (or
segments).
[0040] In some embodiments, the sleeve/skirt may comprise a sleeve
section having a closed-loop shape at one end, and slits at an
opposite end defining segments that can flex outwardly
independently of each other.
[0041] In some embodiments, the sleeve/skirt may overlap
substantially the entire axial length of the stent holder.
[0042] In some embodiments, the sleeve/skirt (or segments) may be
made from balloon material of a balloon catheter, for example, a
valvuloplasty balloon catheter. Such material is strong, resistant
to tearing, yet flexible. [0043] (f) The distal portion of the
delivery catheter may comprise: at least one sheath that is
translatable from a restraining position for restraining at least a
portion of the stent-valve compressed, to an open position in which
the respective portion of the stent-valve is uncovered for
deployment; and a stent holder relative to which the at least one
sheath translates. The stent holder may be configured to cooperate
with the stent-valve for retaining the stent-valve in a
predetermined axial position during sheath translation.
[0044] The delivery catheter may comprise a stem portion extending
between the distal and proximal ends. The stem portion may comprise
a first tube within which a second tube is nested. One of the first
and second tubes may be coupled to the sheath, and the other to the
stent holder. The first and second tubes may be relatively slidable
to transmit relative motion from the proximal end to the distal
end, for translating the sheath relative to the stent holder.
[0045] The second tube may be hollow to define a guide-wire lumen
for receiving (directly or indirectly) a guide wire. The second
tube may comprise polyamide material and polyimide material. The
polyamide and polyimide may be layered one over the other to define
an integral tubular laminate having a radially inner layer and a
radially outer layer, for example, by coextrusion. In some
embodiments, the radially inner layer may be of polyimide, and the
radially outer layer of polyamide. However, in other embodiments,
the order could be reversed if desired. Polyimide has a desirably
high modulus and strength, but is expensive to manufacture in
significant thickness. The addition of a polyamide layer can
complement the physical properties of the polyimide, providing a
thicker tube of high tensile and column strength, good flexibility,
and high modulus. For example, the polyimide and polyamide
combination can provide properties similar to far more expensive
materials such as PEEK (poly-ether-ether-ketone) tubing that is
sometimes used in catheter delivery systems.
[0046] The first tube may be of plastics in which is embedded a
braid. The plastics may, for example, be polyamide. The braid may,
for example, be of stainless steel filaments. [0047] (g) The stem
portion may comprise tubes (referred to later as first and third
tubes) nested one within the other. The tubes may be of plastics in
which is embedded a respective braid. The braids may be different
to provide different properties. The braids may be defined by a
density or PPI ("picks per inch") and/or by a braid angle. One
braid (for example, for the radially outer of these tubes) may have
a lower density (e.g. PPI) than the other braid (for example, for
the radially inner of these tubes). The density may, for example,
be at least twice, optionally at least 5 times, optionally at least
10 times, the density of the other. In one form, the radially inner
of these tubes may have a PPI of between 5 and 10, for example
about 8. Additionally or alternatively, the radially out of these
tubes may have a PPI of between about 50 and 100, for example,
about 80.
[0048] A higher density of braid may provide good column strength
by virtue of the amount of braid filament embedded in the tube. A
good column strength may enable transmission of a compression force
axially along the tube.
[0049] A lower density of braid and/or a braid angle of about 45
degrees may provide good for good torque transmission along the
length of the respective tube. The combination of two different
braid densities may provide better characteristics than an
identical braid in both tubes. [0050] (h) The stem portion may
comprise at least three tubes nested one within another, and
defining at least two spaces (e.g. generally annular but subject to
relative movement between the tubes) therebetween. The delivery
catheter may further comprise a flushing port for receiving a
liquid for flushing both spaces. The same flushing port may
communicate with both the first and second spaces to supply the
liquid directly to both the first and second spaces. Alternatively,
the flushing port may communicate with one of the first and second
spaces for supplying liquid thereto, and a communication channel
may be provided for passing liquid from one space to the other. For
example, the communication channel may be an opening in the wall of
one of the tubes.
[0051] Such an arrangement can avoid having to provide a different
flushing port for each space to be flushed. It can also simplify
the flushing operation for an operator. [0052] (i) The delivery
catheter may comprise first and second hollow flexible tubes
extending between the distal and proximal portions of the catheter.
A first tube coupling may couple the first tube to a stent holder
tube on which a stent holder is mounted. An end of the stent holder
tube may be received within the first tube at the first tube
coupling. The second tube may be nested within the first tube and
translatable relative to the first tube. The second tube may be
coupled (directly or indirectly) to a sheath for applying a
translation force to the sheath. The second tube may provide a
guide-wire receiving lumen for receiving (directly or indirectly) a
guide wire. The second tube may include a distal extension having a
smaller outer diameter than a main portion of the second tube, and
communicating therewith at an interface point. The distal extension
of the second tube may be nested within the stent holder tube, and
be translatable relative to the stent holder tube (in response to
relative translation forces being applied via the first and second
tubes). The first tube coupling may be distal of the interface
point of the second tube. The interface point of the second tube
may be spaced axially from the first tube coupling in the closed
position of the sheath. The interface point of the second tube may
displace relatively towards the first tube coupling as the sheath
is moved towards its open position. (j) The delivery catheter may
comprise first and second flexible tubes extending between the
distal and proximal portions of the catheter. A handle portion of
the catheter may be operable to tension and/or "pre-tension" at
least one of the flexible tubes, for example, prior to insertion
into the body, and/or prior to arrival at the desired site of
implantation, and/or prior to opening of a sheath. Pre-tensioning
may avoid any tendency for the respective tube to further elongate
when a manipulation force is applied through a neighboring
tube.
[0053] In some embodiments, the tensioned tube may be coupled to a
sheath that translates distally from a closed position for
restraining a portion of the stent-valve to an open position for
deploying the respective portion of the stent-valve. Tensioning the
tube may bias the sheath in a proximal direction, in order to
restrain the sheath against distal creep when manipulation forces
are applied through at least one other tube, for example, for
translating open a second sheath.
[0054] The use of tension or "pre-tension" can avoid any need for a
locking mechanism, or sheath overlap, or additional sheath length
that might otherwise be used to counter distal creep. The use of
tension can therefore provide a more compact and/or less
complicated distal portion. [0055] (k) The delivery catheter may
further comprise a member (e.g. interface member) captive on the
catheter, and slidable with respect to the sheath. The member may
initially be stowed within the sheath, and may be displaced out of
the sheath by relative movement of the sheath (e.g. between the
sheath and the member). The member may be self-expandable (or
include a self-expandable portion) such that, once displaced out of
the sheath, the member (or portion) self-expands to become oversize
compared to the sheath. The oversize member may tend to remain at
least partly outside the interior of sheath. (l) The delivery
catheter may comprise a stent holder for mating engagement with a
stent-valve when in the compressed state, for restraining the
stent-valve against axial movement, the stent holder comprising a
body having a plurality of substantially radial projections for
mating with attachment elements of a stent-valve, each projection
having at least one ramp surface extending partly therearound to
define ramp surface portions circumferentially either side of the
projection and axially to one side of the projection, the ramp
surface portions inclined outwardly away from the projections.
[0056] With such an arrangement, the ramp surface portions may aid
separation of the stent-valve attachment element from the
stent-holder when the stent-valve is completed unsheathed for
expansion to the functional state. Small axial or rotational
movement of the delivery system can cause the attachment elements
to ride up one of the ramp surface portions and be urged radially
away from the stent holder, if the attachment element might
otherwise remain in proximity to the projection.
[0057] In some embodiments, the stent holder body has a portion
defined by surface of rotation in which radial recesses are
provided. A respective projection may project within each recess.
The radial length of the projection may be accommodated entirely or
substantially within the recess. A respective ramp surface may
define one axial side and opposite circumferential sides of the
recess. The other axial side of the recess may be open. The recess
may open radially outwardly.
[0058] Such an arrangement of stent holder may have a generally
smooth outer contour provided by the surface of revolution. A
smooth surface may, for example, facilitate withdrawal of the
distal portion of the delivery catheter (including the stent
holder) through the valve of the stent-valve following deployment
of the stent-valve. [0059] (m) The delivery catheter may further
comprise a ball joint located proximal of the stent accommodation
region. The ball joint may be formed in an outer tube at or leading
to the distal portion.
[0060] In such a delivery catheter, the proximal portion can
include a distal (first) sheath that is slidably configured to
cover at least a portion of the distal end of the accommodation
region and configured to slide distally to reveal the distal end of
the accommodation region for the collapsible stent, and a proximal
(second) sheath that is slidably configured to cover at least a
portion of the proximal end of the accommodation region for the
collapsible stent and to slide proximally to reveal the proximal
end of the accommodation region for the collapsible stent. In some
embodiments, the distal sheath and the proximal sheath meet at the
proximal end of the distal sheath and the distal end of the
proximal sheath when they cover the distal and proximal ends of the
collapsible stent.
[0061] The ball joint can be less than 5 cm proximal of the stent
accommodation region of the catheter. It can also be less than 2 cm
proximal of the stent accommodation region of the catheter. It can
also be less than 1 cm of the stent accommodation region of the
catheter. It can also be between 1 and 2 cm proximal of the stent
accommodation region of the catheter. The ball joint of the cardiac
stent delivery system can also be hollow. Also, one or more inner
tubular members can pass through the hollow portion of the ball
joint. The ball joint can also allow the outer and inner tubular
members to bend, according to some embodiments, at least 20.degree.
or at least 30.degree. or at least 40.degree. or at least
45.degree.
[0062] In some embodiments, the ball joint of the cardiac stent
delivery catheter can also allow an axial force to be applied on
the inner tubular member and the outer tubular member causing the
distal sheath to be moved distally and/or the proximal sheath to be
moved proximally. This motion of the distal sheath distally and the
proximal sheath proximally can reveal the collapsible stent on the
attachment region, for example.
[0063] In some embodiments, the ball joint of the cardiac stent
delivery catheter can also allow the outer and inner tubular
members to rotate with regards to each other. The outer and inner
tubular members can be allowed to rotate with regards to each other
for one rotation, or for unlimited rotations, for example. [0064]
(n) The system may comprise:
[0065] an aortic stent-valve comprising a stent component and a
plurality of valve leaflets supported by the stent component, the
stent component having an inflow end and an outflow end and being
self-expandable from a compressed state for delivery towards a
functional state upon implantation, the stent component comprising
outflow structure at or towards the outflow end, a crown
intermediate the inflow and outflow ends, the crown having a free
extremity intermediate the inflow and outflow ends and directed
towards the outflow end, and the stent-component further comprising
a fixation section between the crown and the inflow end;
[0066] a delivery catheter having a distal portion for insertion
into the anatomy, and a proximal portion, a stent-valve
accommodation region at the distal portion for accommodating the
stent-valve in the compressed state for delivery, the distal
portion comprising a first sheath for covering at least a portion
of the fixation section to constrain the fixation section
compressed, and a second sheath for covering at least a portion of
the arches and at least a portion of the crown to constrain the
arches and the crown compressed.
[0067] The second sheath may be translatable in a proximal
direction to uncover the crown and the outflow structure. The first
sheath may be translatable in a distal direction to uncover the
fixation section. Use of such sheaths moving in opposite directions
can permit at least partial deployment of the crown and outflow
structure without substantial distal extension of the catheter. It
can also reduce the total distal extension of the catheter when the
sheaths are open (compared to a catheter employing a single
distally-moving sheath).
[0068] The outflow section may comprise a plurality of arches at
the outflow end each having an apex at the outflow end.
[0069] Translation of the second sheath (for example, in a proximal
direction) may uncover the crown for deployment followed by
uncovering the outflow structure (e.g. arches) for deployment. Such
a sequence is different from that described in the aforementioned
WO-A-2009/053497 and WO-A-2011/051043. Nevertheless, it has been
appreciated that deploying the outflow structure (e.g. arches)
after the crown is still highly effective in permitting the arches
to function. Notably, the outflow structure (e.g. arches) may be
deployed prior to uncovering of the fixation section for
deployment.
[0070] In some embodiments, the outflow structure (e.g. arches) may
be configured for aligning the stent-valve with respect to an axis
of the ascending aorta by contact with a wall of the ascending
aorta. For example, the arches may be bendable independently of
each other. The crown may be configured for engaging and/or seating
against existing leaflets from an outflow side. The fixation
section may be configured for engaging an existing annulus.
[0071] Deploying the outflow structure (e.g. arches) before the
fixation section may permit self-alignment of the stent-valve by
the action of the outflow structure (e.g. arches), before the
fixation section deploys to anchor the stent-valve at the annulus
of the existing valve.
[0072] Further aspects of the invention relates to methods of use
of the stent-valve and/or delivery catheter by using process steps
corresponding to any of those described above.
[0073] Further aspects of the invention relate to a stent-valve.
Optionally, the stent-valve may be for use in a system as described
above and/or for use with a delivery catheter as described above.
The following definitions are therefore intended to be combined
with any of the foregoing aspects. The stent-valve may comprise a
valve component and a plurality of leaflets supported by the valve
component. The stent-valve may further comprise any one or a
combination of two of more of the following features, which are all
optional: [0074] (a) The stent component may be configured to be
radially compressible into a compressed state and expandable to a
functional state. The stent component may be self-expanding from
the compressed state, or the stent component may be
non-self-expanding (in which case the delivery catheter may
comprise a device for applying an expansion force (for example,
from within the stent-valve) to cause expansion). Non-limiting
example materials for a self-expanding stent component include
shape memory materials, especially metals alloys, such as nitinol.
Non-limiting example materials for a non-self-expanding
stent-component include shape memory materials, and stainless
steel.
[0075] The stent component may comprise commissural supports (e.g.
posts) for supporting the valve leaflets. The commissural supports
may support edges of valve leaflets that meet at the commissural
supports.
[0076] The commissural supports may be defined by a section of the
stent component that is intermediate opposite end sections of the
stent. Each commissural support may have opposite ends that each
communicate with a respective stent section that is axially
adjacent to the commissural support. The commissural support may
optionally not have a free end.
[0077] Additionally or alternatively, the commissural supports may
each have a slot for receiving a tab of a leaflet. The commissural
supports may further comprise a plurality of bores flanking one or
both long sides of the slot. The bores may be configured for
receiving suture thread.
[0078] Additionally or alternatively, each commissural support may
comprise a post. Each commissural support may have a wishbone
shape. The wishbone shape may include first and second legs
diverging from one end of the post.
[0079] In some embodiments, the stent component may comprise a
lattice structure having at least one row of cells, the lattice
structure including a sequence of cells that repeats in the
circumferential direction, the sequence including cell apexes
defining: a first apex node communicating at least with a first leg
of a wishbone commissural support, at least one free apex spanned
by the wishbone commissural post, a second node apex communicating
at least with a second leg of the wishbone commissural support, and
at least one further node apex communicating with an element of a
crown. The first and second node apexes may communicate
additionally with one or more respective elements of a crown. As
mentioned above, the commissural support may comprise a post
communicating at one end with the legs of the wishbone shape, and
communicating at the other end with an outflow section of the stent
component (e.g. comprising stabilization arches).
[0080] The above forms of construction can provide a stent that is
functional to support a valve component, yet can be compressed to a
small size. [0081] (b) The stent-valve (e.g. stent component) may
comprise at least one (and preferably a plurality) of attachment
elements for cooperating with a stent-holder of the delivery
catheter. 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
a collapsed (e.g. compressed) condition 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)
condition 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 condition, the attached element may define a
substantially straight-sided U-shape with an arcuate apex.
[0082] The delivery catheter may comprise a sent-holder provided
within the accommodation region. The stent-holder may comprise
[0083] (i) one or more projections receivable within the eyelet.
The projection may be dimensioned such that, when the stent is in
its collapsed condition, the projection is trapped within the
eyelet and unable to pass between the adjacent struts, and/or
[0084] (ii) one or more recesses or interstices for accommodating
the eyelet substantially therewithin, at least in the collapsed
state of the stent.
[0085] 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. [0086] (c) The stent-valve may comprise at
least two leaflets. The leaflets may be of pericardium tissue, most
preferably porcine pericardium tissue or bovine pericardium.
Porcine pericardium may provide desirable tissue thinness. Bovine
pericardium may be slightly thicker but more durable.
[0087] Each valve leaflet may include at least two tabs. The tabs
may serve for supporting the leaflets relative to the stent
component.
[0088] 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 a slot 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
slot. 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.
[0089] 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 slots (e.g.,
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 slots (e.g., slits)
are provided.
[0090] Additionally or alternatively, the material defining the
inner skirt may include integral extension portions that wrap at
least around the commissural supports, for covering 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.
[0091] 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 a slot in the inner skirt,
and through a slot in the commissural support. 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 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. For example, 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. [0092] (d)
The stent-valve may comprise a stent-component, 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. At least a portion of the
stent component over which at least one of the skirts extends, may
comprise a lattice structure having at least one row of a plurality
of cells.
[0093] In some embodiments, 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 outer skirt may extend further towards an inflow
extremity of the stent component than does the inner skirt.
Additionally or alternatively, the inner skirt may extend further
towards an outflow extremity of the stent component than does the
outer skirt.
[0094] 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 interstices). 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.
[0095] Providing both skirts may be beneficial in terms of
obstructing leakage. 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).
[0096] 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.
[0097] 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.
[0098] In some embodiments, the inflow end or edge 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 define an
alternating sequence of free apexes (e.g., at 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.
[0099] In some embodiments, the inner skirt may be attached to an
inflow edge and/or an outflow edge of valve leaflets. 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.
[0100] 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.
[0101] Additional aspects of the invention are defined in the
claims. Although certain features and ideas have been highlighted
above and/or in the 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.
[0102] Preferred embodiments of the invention are now described, by
way of example only, with reference to the accompanying drawings,
in which:
[0103] FIG. 1 is a schematic partial section view of a delivery
catheter and stent-valve;
[0104] FIG. 2 is a schematic section showing the distal portion of
the delivery catheter partly open;
[0105] FIG. 3 is a schematic section showing the distal portion of
the delivery catheter full open;
[0106] FIG. 4 is a schematic section showing the distal portion of
the delivery catheter in more detail. The axial (horizontal) scale
is compressed relative to the radial (vertical) scale to permit all
elements to be shown in a single view;
[0107] FIG. 5 is a schematic perspective view showing the distal
portion of the delivery catheter full open deploying the interface
element;
[0108] FIG. 6 is a schematic side view of the interface element in
isolation, shown in a deployed condition;
[0109] FIG. 7 is a schematic perspective view showing the initial
closing of the second sheath;
[0110] FIG. 8 is a schematic perspective view showing the second
sheath in its closed position;
[0111] FIG. 9 is a schematic side view showing the first and second
sheaths reclosed with the interface element deployed;
[0112] FIGS. 10a-c are schematic sections showing in isolation
example attachment elements of a stent-valve for attachment to a
stent-holder of the delivery catheter. The attachment elements are
shown in an expanded condition of the stent-valve;
[0113] FIG. 11 is a schematic perspective view showing in isolation
one example of a stent holder for the delivery catheter;
[0114] FIG. 12 is a schematic side view illustrating engagement
between the attachment element of FIG. 10a and the stent holder of
FIG. 11;
[0115] FIG. 13 is a schematic side view illustrating engagement
between the attachment elements of FIGS. 10a/10b and a second
example of stent holder;
[0116] FIG. 14 is a schematic perspective section illustrating
petals on the stent holder;
[0117] FIG. 15 is a schematic section similar to FIG. 14
illustrating a combined stent holder and interface element;
[0118] FIG. 16 is a schematic section illustrating a handle with
controls at the proximal end of the deliver catheter; and
[0119] FIG. 17 is a schematic side view illustrating one example of
stent-valve;
[0120] FIG. 18 is a schematic profile view illustrating the profile
envelope of the stent component of the stent-valve of FIG. 17;
[0121] FIG. 19 is a schematic view illustrating a developed
geometry of the stent component in a single plane;
[0122] FIG. 20 is a schematic section illustrating a liner sleeve
for the catheter;
[0123] FIG. 21 is a schematic section illustrating the interface
member for streamlining the stent holder to permit withdrawal of
the catheter through an introducer while open. In FIG. 21, the
sheaths are omitted to avoid clutter;
[0124] FIG. 22 is a schematic perspective view of a stent holder in
isolation, as a single-piece item having a geometry similar to FIG.
13;
[0125] FIG. 23 is a schematic perspective view of the stent holder
of FIG. 22 with a sheath thereon, and mounted on the stent holder
support tube; and
[0126] FIG. 24 is a schematic section illustrating a delivery
catheter with a ball joint.
[0127] In the drawings, the same reference numerals are used to
denote the same, or equivalent, features amongst different
embodiments and examples. Unless described to the contrary, the
description of a feature in one embodiment or example may also
apply to the same or equivalent feature in another embodiment or
example. Features may also be interchanged between embodiments as
desired.
[0128] Referring to FIGS. 1-3, a stent-valve 10 and a delivery
catheter 12 therefor are illustrated. The delivery catheter 12 may
have a distal portion 14 towards one end for insertion into a
patient's anatomy, and a proximal portion 16 towards an opposite
end from which the delivery catheter is manipulated in use by an
operator. A barrel or stem portion 15 may extend between the distal
and proximal portions.
[0129] As used herein, the terms "distal" and "proximal" for the
delivery catheter may refer to relative position with respect to an
operator.
[0130] The distal portion 14 of the catheter 12 may comprise an
accommodation region 18 for accommodating the stent-valve 10 in a
collapsed form for introduction into the anatomy. The stent-valve
10 may be a cardiac stent-valve. The delivery catheter 12 may be
configured to permit delivery of the stent-valve 10 to, and
deployment at, a desired site of implantation while the heart
remains beating, for example, using a minimally invasive surgical
and/or percutaneous procedure. In some embodiments, the catheter 12
may be configured for introduction into the anatomical vascular
system, and for advancement along the vasculature system to the
desired site of implantation. For example, the catheter 12 may be
configured for introduction into the femoral artery, and guided
retrograde via the descending aorta, aortic arch, and ascending
aorta to the heart (sometimes called a transfemoral access). The
catheter 12 may have a length of at least about 1 m to provide
sufficient length insertable into the anatomy. In other
embodiments, the catheter 12 may be insertable via the subclavian
artery and guided retrograde to the heart (sometimes call
transubclavian access). In other embodiments, the catheter 12 may
be inserted directly into a chamber of the heart such as a
ventricle (for example, left ventricle) via a direct access route
while the heart remains beating. For example, a direct access route
may be through an aperture opened in the apex of the heart
(sometimes called a transapical access).
[0131] The size of access aperture into the anatomy may depend on
the outer diameter of the distal portion 14. The barrel portion 15
may be slightly smaller than, or the same diameter as, the distal
portion 14 as desired. For minimally invasive surgery, it is
desired that the access aperture into the anatomy be as small as
practical, bearing in mind the size to which the stent-valve 10 can
be collapsed without risk of damage. An introducer 19, for example,
a standard arterial introducer, may optionally be used at the
access aperture into the anatomy. The optional introducer 19 may
have a size of 20 French or smaller, for example, 18 French or
smaller. The distal portion 14 may be dimensioned for insertion
through such a size of introducer 19.
[0132] The stent-valve 10 may be expandable from a compressed or
collapsed condition to a functional and/or expanded condition, in
order to anchor the stent-valve 10 at the implantation site. For
example, the stent-valve 10 may form a friction and/or interference
fit with respect to the native anatomy. Various shapes and
geometries of stent-valve 10 may be used to fit the anatomy at the
site of implantation. A generally cylindrical stent-valve 10 is
illustrated here for clarity, but the invention is not limited to a
cylindrical shape, and may be especially advantageous with
non-cylindrical shaped stent-valves 10. A more detailed example of
stent-valve 10 is described later, and all details of the delivery
catheter 12 are explicitly applicable to the stent-valve shape
described later.
[0133] The stent-valve 10 may be self-expanding and/or may be
configured to be expandable by swelling of an expander (for
example, a balloon not shown). Self-expanding stent-valves 10 may
be constructed from, or use, shape-memory material, for example a
shape-memory metal alloy (such as nitinol). A self-expanding
stent-valve 10 may be retained in its compressed state by being
constrained within a sheath 20/22 of the delivery catheter 12. Upon
at least partial release from the sheath 20/22, the released
portion of the stent-valve 10 may be free to expand.
Non-self-expanding stent-valves 10 may also be made of shape-memory
material, or from stainless steel, or cobalt-chromium alloy. A
non-self-expanding stent-valve 10 may also be contained at least
partly within a sheath 20/22 to protect the stent-valve 10 and/or
facilitate smooth introduction through the anatomy.
[0134] The distal portion 14 of the catheter 12 may comprise at
least one sheath 20 and/or 22 that is translatable between a closed
position at least partly covering the accommodation region 18
and/or the stent-valve 10 therein, and an open position at least
partly opening or exposing the accommodation region 18 and/or at
stent-valve 10 therein. In the present example, the catheter 12
comprises two sheaths 20 and 22, both shown in their respective
closed positions in FIG. 1 to at least partly (optionally
substantially entirely) cover the stent-valve 10 in the
accommodation region 18. The sheaths 20 and 22 may be translatable
in opposite directions to respective open positions. A first (e.g.
more distal) of the sheaths 20 may be translatable in a distal
direction (indicated by arrow 20a in FIG. 1) to an open position
(FIG. 3). The first sheath 20 may also be referred to as the distal
sheath. A second (e.g. more proximal) of the sheaths 22 may be
translatable in a proximal direction (indicated by arrow 22a in
FIG. 1) to an open position (FIGS. 2 and 3). The second sheath 22
may also be referred to as the proximal sheath. Use of first and
second opposed sheaths 20 and 22 may provide good versatility for
release of the stent-valve 12 from the accommodation region. For
example, referring to FIG. 2, by translating the second sheath 22
to or towards its open position without translating the first
sheath 20, a portion 10a of the stent-valve 10 previously covered
by the second sheath 22 may be released (at least partly) before a
portion 10b of the stent-valve 10 covered by the first sheath 20.
The portion 10b may be released subsequently by translation of the
first sheath 20 to or towards its open position (FIG. 3). The
length of the second sheath 22 may be greater than the length of
the first sheath 20. For example, the ratio of the second sheath
length divided by the first sheath length may be at least 1.1,
optionally at least 1.2, optionally at least 1.3, optionally at
least 1.4, optionally at least 1.5, optionally at least 1.6,
optionally at least 1.7, optionally at least 1.8, optionally at
least 1.9, optionally at least 2.0, optionally at least 2.1,
optionally at least 2.2, optionally at least 2.3, optionally at
least 2.4, optionally at least 2.5, optionally at least 2.6,
optionally at least 2.7, optionally at least 2.8, optionally at
least 2.9, optionally at least 3, optionally at least 3.5,
optionally at least 4 or optionally at least 4.5, or optionally at
least 5. Use of a relatively short first sheath 20 may reduce risk
of trauma in use. The first sheath 20 advances distally along a
path that may be less controlled than the second sheath that
benefits from a more controlled path defined by the path adopted by
the barrel portion 15 of the catheter. For example, in the case of
transvascular access (e.g. transfemoral access), the first sheath
20 may advance into the ventricle of the heart. Use of a relatively
short first sheath 20 may reduce the degree to which the catheter
12 has to penetrate into the ventricle, and risk interfering with
delicate tissue surfaces. In the case of direct access (e.g.
transapical access), the first sheath 20 may advance into the
ascending aorta. Use of a relatively short first sheath 20 may
reduce the degree to which the first sheath 20 has to penetrate the
space of the ascending aorta, and risk interfering with the aorta
wall.
[0135] One or both of the sheaths 20 and 22 may be of plastics
optionally including reinforcement to resist radial expansion of
the sheath. One suitable plastics is a poly ether block amide
(PEBA), for example PEBAX.TM.. Reinforcement may be provided by a
helical coil embedded within the sheath. The helical coil may be of
metal, for example, stainless steel filament.
[0136] The sheaths 20 and 22 may have the same inner and/or outer
diameter. The sheaths 20 and 22 may be configured not to overlap
each other. Avoiding an overlap can avoid excess diameter of the
distal portion that might otherwise be caused by the sheath walls
overlapping each other.
[0137] The sheaths 20 and 22 may be capable of being positioned
such that the sheaths 20 and 22 meet substantially end to end.
Alternatively, the sheaths 20 and 22 may be configured such that
the sheaths 20 and 22 always remain spaced from each other, even in
mutually closed positions of the first and second sheaths 20 and
22. For example, the minimum spacing may 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. Additionally or alternatively, the spacing may 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. In one form, the
spacing is between about 4 mm and about 6 mm.
[0138] During the translations of the sheaths 20 and 22 a
stent-holder 24 may retain the stent-valve 10 axially in position
and/or restrain the stent-valve 10 against axial movement. The
stent-holder 24 is represented purely schematically in FIGS. 1-3,
and is described in more detail later. The stent-holder 24 may
prevent and/or obstruct any tendency of the stent-valve 10 to be
dragged by translation of a sheath 20 or 22. Additionally or
alternatively, the stent-holder 24 may prevent and/or obstruct any
tendency for a self-expanding stent-valve 10 to jump free of the
catheter if only a small portion of the stent-valve 10 remains
constrained by the sheath 20 or 22. The stent holder 24 may be
positioned in the accommodation region 18 at a position appropriate
to engage the stent-valve 10 until final release of the stent-valve
10 from the accommodation region. In the illustrated example, a
distal portion of the stent-valve 10 may be intended to be released
last, and the stent-holder 24 may be positioned towards the distal
end of the accommodation region 18. In other embodiments, if the
proximal portion of the stent-valve 10 is intended to be released
last, the stent-holder 24 could instead be positioned towards the
proximal end of the accommodation region 18.
[0139] FIG. 4 illustrates one example construction of the distal
portion 14 of the catheter 12 in more detail. The barrel portion 15
comprises a plurality of flexible tubes 26, 28 and 30 extending
between the distal portion 14 and the proximal portion 16. The
tubes 26-30 may be nested at least one within another, and coupled
to the sheaths 20 and 22 and the stent holder 24. The sheaths 20
and 22 may be translated by relative translation of respective
tubes. At least one, optionally two, optionally three, optionally
more, of the flexible tubes may be of plastics, optionally with
reinforcement.
[0140] For example, at least one tube may comprise a combination of
polyamide material and polyimide material. The polyamide and
polyimide may be layered one over the other to define an integral
tubular laminate having a radially inner layer and a radially outer
layer, for example, by coextrusion. In some embodiments, the
radially inner layer may be of polyimide, and the radially outer
layer of polyamide. However, in other embodiments, the order could
be reversed if desired. Polyimide has a desirably high modulus and
strength, but is expensive to manufacture in significant thickness.
The addition of a polyamide layer can complement the physical
properties of the polyimide, providing a thicker tube of high
tensile and column strength, good flexibility, and high modulus.
For example, the polyimide and polyamide combination can provide
properties similar to far more expensive materials such as PEEK
(poly-ether-ether-ketone) tubing that is sometimes used in catheter
delivery systems.
[0141] Additionally or alternatively, reinforcement may be provided
by a braid, for example, a metal braid, within the plastics. The
plastics may, for example, be a polyamide, and/or the braid of
stainless steel filament. The reinforcement may, compared to a tube
of the same plastics without the reinforcement: (i) increase the
modulus of elasticity yet retain flexibility; and/or (ii) improve
resistance to kinking when the tube is flexed; and/or (iii)
increase the ability for transmission of torque from the proximal
portion to the distal portion. Respective different tubes may have
respective different braids. The braids may be defined by a density
or PPI ("peaks per inch") and/or by a braid angle. For example, a
lower density may imply that the winding angle is closer to the
axial direction; a higher density implies that the winding angle is
closer to the radial direction. One braid (for example, a more
radially outer tube) may have a lower density (e.g. PPI) than
another braid (for example, for a more radially inner tube). The
density may, for example, be at least twice, optionally at least 5
times, optionally at least 10 times, the density of the other. A
higher density may provide for greater column strength. A lower
density and/or a braid angle closer to 45 degrees may provide for
greater torque transmission. The combination of two different braid
densities may provide better characteristics than an identical
braid in both tubes. In some embodiments, one tube may have a braid
PPI of between about 5 and about 10, for example, about 8.
Additionally or alternatively, the other tube may have a braid PPI
of between about 50 and about 100, for example, about 80.
[0142] Referring to the specific structure in FIG. 4, a first tube
26 may be coupled for controlling the stent holder 24. The first
tube 26 may optionally comprise plastics with braid reinforcement,
as described above. A first tube coupling 34 may couple the first
tube 26 to a stent holder support tube 32 on which the stent holder
24 is mounted. For example, the stent holder support tube 32 may be
inserted into the end of the first tube 26 and/or attached thereto,
at the first tube coupling 34. The stent holder support tube 32 may
have a smaller outer diameter than the first tube 26. The stent
holder support tube 32 may be less flexible than the first tube 26.
The stent holder support tube 32 may, for example, be of polyimide.
The stent holder support tube 32 may act as an extension of the
first tube 26 adapted to pass within the relatively confined space
of the accommodation region 18. The reduced flexibility can
compensate for smaller diameter to provide adequate column strength
along the axis of the stent holder support tube 32.
[0143] A second tube 28 may be coupled to control the first
(distal) sheath 20. The second tube 28 may optionally comprise a
tubular laminate of a polyimide layer radially within a polyamide
layer, including any of the associated details described above. The
second tube 28 may be nested within the first tube 26 and be
translatable relative thereto. The second tube 28 may include a
distal extension 38 having a smaller outer diameter than a main
portion of the second tube, and communicating therewith at an
interface point 36. The distal extension 38 may, for example, be an
extension of the polyimide inner layer without the polyamide outer.
The distal extension 38 may support (directly or indirectly) the
first sheath 20. The sheath 20 is mounted to the distal extension
38 by a tip member 40. The tip member 40 may have a tapered
atraumatic shape to aid advancement of the catheter 12 within the
anatomy without trauma to the surrounding anatomy. The tip member
40 may have a rear extension 42 around which the first sheath 20 is
attached immovably to the tip member 40. The smaller outer diameter
of the distal extension 38 may be configured to pass within the
small diameter of the stent holder support tube 32. The distal
extension 38 may translate within the stent holder support tube 32,
and move therewithin as the second tube 28 moves within the first
tube 26. To move the first sheath 20 to its open position, a
translation force may be applied to advance the second tube 28
distally relative to the first tube 26. The translation force and
movement is applied from the second tube 28 to the distal extension
38, which pulls the first sheath 20 distally (for example, the
translation force and movement being applied through the tip member
40). Concurrently, the stent holder 24 may hold the stent-valve 10
relatively stationary under the control of the first tube 26 and
the stent holder support tube 32 on which the stent holder 24 is
mounted.
[0144] The optional diameter difference between the first tube 26
and the stent holder support tube 32 may define a profile step or
change at the first tube coupling 34. The optional diameter
difference between the second tube 28 and the distal extension 38
may define a profile step or change at the interface point 36. The
outer diameter of the second tube 28 may be greater than the inner
diameter of the stent holder support tube 34 (for example such that
the second tube cannot translate beyond the first tube coupling
34). In the closed position of the first sheath 20, the first tube
coupling 34 and the interface point 36 may be spaced apart. The
interface point 36 may be proximal of the first tube coupling 34.
The spacing may be at least as large as the amount of linear
translation of the first sheath 20 when the sheath moves between
its open and closed positions. The spacing may permit the interface
point 36 to advance distally.
[0145] The second tube 28 and the distal extension 38 may define a
lumen 46 extending through the catheter. The lumen 46 may be a
guidewire receiving lumen for receiving a guide wire (not shown)
along which the catheter 12 may be advanced within the anatomy to
guide the distal portion 14 to the desired site of
implantation.
[0146] A third tube 30 may be coupled for controlling the second
(proximal) sheath 22. The third tube 30 may optionally comprise
plastics with braid reinforcement, as described above. The first
tube 26 may be nested with the third tube 30. The third tube may be
translatable relative to the first tube 26 and/or the second tube
28. A third tube coupling 44 may couple the third tube 30 to the
second sheath 22. The third tube coupling 44 may include a tapered
surface for defining a smooth atraumatic transition between the
outer surfaces of the third tube 30 and the second sheath 22. The
third tube coupling 44 may be integral with the second sheath 22,
and may be a narrowed end portion thereof.
[0147] To move the second sheath 32 to its open position, a
translation force (e.g. tension) may be applied to retract the
third tube 30 proximally relative to the first tube 26. The
translation force and movement is applied from the third tube 30 to
the second sheath 22, which pulls the second sheath 22 proximally.
Concurrently, the stent holder 24 may hold the stent-valve 10
relatively stationary under the control of the first tube 26 and
the stent holder support tube 32 on which the stent holder 24 is
mounted.
[0148] As described above, the braids in the first and third tubes
26 and 30 may have different characteristics according to their
respective inner and outer radial relationship.
[0149] The sequential order in which the first and second sheaths
are translated to their open position may depend on the design of
the stent-valve. In at least some embodiments, the second sheath 22
may be translated before the first sheath 20. An example deployment
sequence is described later.
[0150] Also, in some embodiments, at least one of the tubes may be
pre-tensionable at least prior to opening the distal portion 14 for
deploying a stent-valve. Pre-tensioning the tube may compensate for
any tendency of the portion of the catheter controlled by the tube
to creep distally in response to forces applied during manipulation
to open other portion(s) of the catheter controlled by other
tube(s). For example, the second tube 28 may be pre-tensioned from
the proximal end, in order to prevent the first sheath 20 from
creeping distally when the second sheath 22 is pulled back while
applying a maintaining force to the first tube 26. Creeping of the
first sheath 20 is undesirable as it may result in movement of the
deployment position, or premature release of the stent.
Pre-tensioning the second tube 28 may maintain the first sheath 20
firmly closed, thereby preventing premature release. When it is
desired to open the first sheath 20 by applying a pushing force
through the second tube 28, the pre-tension is removed as part of
the transition to applying a pushing force. The pre-tension may be
generated by controls within the handle, as described later. The
amount of pre-tension may be sufficient to counter the reaction
force applied through the first tube when translating the third
tube to move the second sheath proximally. The amount of
pre-tension appropriate for a specific embodiment of delivery
catheter may, for example, be derivable empirically.
[0151] The above arrangements can provide a delivery catheter that
combines the desirable properties of compact size, good flexibility
without kinking, good transmission of torque, good column strength,
and avoidance of distal creep of a sheath, all without using exotic
materials that are prohibitively expensive.
[0152] Where additional flexibility is desired, the invention also
contemplates inclusion of a ball joint (not shown) that is just
proximal of the distal portion. The ball joint may be provided in
the third tube, or the connecting portion between the third tube
and the second sheath. The ball joint may be hollow to allow the
first and second tubes to pass therethrough.
[0153] As may be seen generally in FIGS. 1-4, the first and second
sheaths 20 and 22 may have respective mouths or open ends 20b, 22b,
respectively, that may generally confront or lap one another when
the (or each) sheath 20, 22 is in the closed position, or may
remain slightly spaced apart. In the illustrated embodiments, both
sheaths 20 and 22 are translatable, but in some embodiments it is
possible that only one of the sheaths 20 and 22 might be
translatable.
[0154] Prior to release of the stent-valve 10, the presence of the
stent-valve 10 within the accommodation region 18 may cause the
sheaths 20 and 22 to be generally aligned in register. Even if the
open ends 20b and 22b are spaced from each other or confront each
other without lapping, the open ends 20b and 22b may thus align in
register. Such alignment may avoid any abrupt edges in the outer
profile of the sheaths, and facilitate insertion of the distal
portion 14 into the anatomy (optionally through the introducer 19
and/or advancement through vasculature). However, after the
stent-valve 10 has been released from the accommodation region 18,
if the operator may desire to close the sheaths, there may be a
tendency for the open ends 20b and 22b no longer to be closely
aligned. Such misalignment may result in an abrupt edge in a case
of confronting or slightly spaced open ends and/or difficulty of
re-engaging the open ends in the case of trying to lap the open
ends. It may be desirable to avoid an abrupt edge, especially at
the open end 20b of the first sheath 20. When the catheter 12 is
withdrawn after having released the stent-valve 10, the open end
20b may interfere with native tissue on the return path, or it may
make it difficult to extract the distal portion through an
introducer 19, especially if the distal portion 14 is a tight fit
within the introducer 19. During such withdrawal, the second sheath
22 may be guided smoothly into the introducer 19 by the ramp
surface 44 at the third tube coupling 44. However, an abrupt edge
at the open end 20b of the first sheath 20 may obstruct smooth
passage of the first sheath 20 for withdrawal through the
introducer 19.
[0155] Alternatively, if the catheter 12 is withdrawn with one or
both of the sheaths 20 and 22 in an open condition, an exposed
abrupt edge (e.g. end face 92 in FIGS. 11-13) of the stent holder
24 may make it difficult to extract the distal portion through an
introducer 19, especially if the distal portion 14 is a tight fit
within the introducer 19. During such withdrawal, the second sheath
22 may be guided smoothly into the introducer 19 by the ramp
surface 44 at the third tube coupling 44. However, the abrupt edge
92 of the stent holder 24 may obstruct smooth passage of the first
sheath 20 for withdrawal through the introducer 19.
[0156] To address this, the distal portion 14 may comprise an
interface member 50 (FIGS. 4 to 9). The interface member 50 may be
deployable to:
[0157] (i) provide an interface at or between the generally
confronting open ends 20b and 22b when (at least nearly) closed;
and/or (ii) align the open ends 20b and 22b to be substantially in
register with each other and/or centred with respect to the
catheter axis; and/or (iii) define a bridge and/or a smooth profile
between the confronting open ends 20b and 22b; and/or (iv) provide
an interface for the stent-holder 24 less abrupt than the exposed
edge 92.
[0158] In some embodiments, the interface member 50 may be
deployable as part of the sequence during or after release of the
stent-valve 10.
[0159] In some embodiments, the interface member 50 may be
translatable along the catheter axis from a non-deployed condition
(FIG. 4) to a deployed condition (FIGS. 5 to 9). For example, the
interface member 50 may be initially be stowed within one of the
sheaths (for example the second sheath 22) in a non-deployed
condition, and be translatable to or towards the open end of the
sheath (22) to transition to its deployed condition. Stowing a
movable interface member 50 initially within the second sheath 22
may avoid having to elongate the first sheath 20 unnecessarily to
accommodate the interface member 50. As illustrated below, in some
embodiments, the interface member 50 may be substantially freely
translatable within a predetermined range of movement, and be
configured to move with, or in response to, sheath movement. The
interface member 50 may be referred to as a shuttle. The interface
member 50 may be slidable (e.g. captively slidable) on one of the
tubes 26, 28, 32, 38.
[0160] In some embodiments, the interface member 50 (or at least a
portion 52 thereof) may be expandable. Transition from a
non-deployed condition (FIG. 4) to a deployed condition (FIGS. 5 to
9) may include expansion of the expandable portion 52. For example,
the expandable portion 52 of the interface member may be radially
expandable. The expandable portion may be self-expandable from a
compressed state.
[0161] In the illustrated embodiment, the interface member 50 may
be both movable and self-expandable. Referring to FIG. 4, the
interface member 50 may initially be stowed within one of the
sheaths (for example the second sheath 22 as mentioned above) in a
compressed non-deployed condition. The sheath 22 may constrain the
interface member 50 in a compressed condition. The interface member
50 may be accommodated at one end of the accommodation region 18
where the interface member 50 may not interfere with the
stent-valve 10.
[0162] As part of the release of the stent-valve 10 as explained
above, the second sheath 22 may be retracted proximally. However,
travel of the interface member 50 in the proximal direction may be
restrained, for example, by the step profile of the first tube
coupling 34. Retraction of the second sheath 22 may therefore cause
relative movement between the second sheath 22 and the interface
member 50, resulting in the interface member 50 transitioning
towards the open end 22b of the sheath 22. When the interface
member 50 may no longer be constrained by the sheath 22, the
interface member 50 (or the portion 52) may self-expand. Upon
expansion, the interface member 50 may become too large to be
received again entirely within the sheath 22. The interface member
50 may at least partly "float" captive on the catheter between the
stent holder 24 and the second sheath 22.
[0163] In some embodiments, it be may desired to re-close the
sheaths 22 and 24 prior to removing the catheter 12 from the body.
When the second sheath 22 is reclosed after release of the
stent-valve 10, the interface member 50 may at least partly
self-locate or "float" at the open end 22b. The interface member 50
may be pushed distally towards the stent holder 24 and/or the open
end 20b of the first sheath. Optionally, the interface member 50
may be pushed distally until its travel is stopped by the stent
holder 24 and/or the first sheath 20. For example, if the first
sheath 20 is currently in its open position, the interface member
50 may advance until its travel is stopped by the stent holder 24.
Thereafter, when the first sheath 20 is closed, the interface
member 50 may cooperate with the open end 20b of the first sheath
20 as explained above.
[0164] Optionally, the interface member 50 may be dimensioned at
one end, or both ends, to be partly insertable into a respective
open end of a sheath even when the expandable portion 52 (for
example, intermediate the ends) is expanded and is oversize with
respect to the open ends of the sheaths. Such insertion can provide
positive engagement and cooperation between the (or each) sheath
and the interface member. Such insertion can also provide a degree
of self-alignment or self-centering between the (or each) sheath
and the interface member. If both ends of the shuttle insert into
respective sheaths, the sheaths may also self-align or self-center
in register with each other.
[0165] Additionally or alternatively, the expandable portion 52 of
the interface member 50 may have a generally smooth annular bulge,
or bulb, shape. The expandable portion may have generally rounded
or ramp surfaces at its opposite axial ends. Such a shape or shapes
may provide a smooth transition between the interface member 50 and
each open end 20b and 22b, and/or a generally smooth profile or
bridge between the open ends 20b and 22b. The shape may further
enhance self-alignment or self-centering of the open ends 20b and
22b in register with each other.
[0166] The expandable portion 52 may be dimensioned such that, in
the expanded state of the expandable portion 52, at least one of
the open ends 20b and 22b will not pass entirely over the
expandable portion. For example, in the case of confronting open
ends 20b and 22b, optionally neither open end 20b and 22b may pass
entirely over the expandable portion 52. In the case of lapping
open ends 20b and 22b, optionally one of the open ends may pass
over the expandable portion 52.
[0167] The ends of the interface member may be generally
asymmetric. In the illustrated form, the proximal end 62 may be
formed as a cone. The cone shape may provide a mounting surface for
an optional skirt 60 described below, and/or provide a nesting
profile to fit the within the third tube coupling 44. The distal
end 64 may be formed as a generally annular rim with a smooth, e.g.
rounded, edge for guiding the open end 20b of the first sheath 20
as the first sheath 20 is closed thereover.
[0168] Referring to FIG. 21, in some embodiments, instead of
closing the sheaths 20 and 22, it may be desired to remove the
catheter 12 from the body while the distal portion 14 remains in an
"open" condition. For example, at least the first sheath 20 may
remain "open", whether or not the second sheath 22 is left "open"
or is at least partly closed. In such case, the stent holder 24 and
the interface member 50 may remain exposed at the distal portion
14. The interface member 50 may tend to slide towards the stent
holder 24, either as a result of movement through the anatomy, or
when the distal portion reaches the site of a closely fitting
introducer 19. The interface member 50 may cooperate with the stent
holder 24 to provide a more streamlined profile than the abrupt
edge 92. In particular, the interface member 50 may comprise a
conical surface 62 that defines a smooth ramp profile that will
slide over the edge of an introducer 19 to guide the stent-holder
24 into the interior of the introducer and/or through the
haemostasis valve. The interface member 50 may comprise an enlarged
oversize portion 52 that acts as a stop to prevent the interface
member 50 from passing through the introducer until the interface
member 50 abuts or engages the stent holder 24. At that point,
continued pulling to withdraw the catheter causes the enlarged
portion 52 to collapse slightly, allowing the interface member 50
and stent holder 24 to pass smoothly through the introducer. The
interface member 50 may optionally be configured to form a snug
interference fit over the end of the stent holder 24 so that it
remains in intimate contact with the stent holder 24.
[0169] The interface member 50 as described above may comprise any
suitable materials, including one or more of: plastics, resiliently
compressible plastics, metal and shape-memory alloys (e.g.
nitinol). In the illustrated form, the interface member 50
comprises a generally non-compressible core member 54 carrying a
shell 56 defining the expandable portion 52. The non-compressible
core may, for example, be of plastics. The core member 54 may be
longer than the shell 56, and define the end profiles 62 and 64
described above. The shell 56 may, for example, be of metal or
shape-memory alloy (e.g. nitinol) to provide a well-defined
expanded shape. The expandable portion 52 may comprise segments
defining a cage-like bulge or bulb.
[0170] In addition to, or as an alternative to, any or all of the
above constructional features, the interface member 50 may
optionally comprise a flexible sleeve or skirt 60. The sleeve or
skirt 60 may optionally be constructed as plural petals or segments
of material that may overlap or not overlap, and collectively
behave as a sleeve or skirt, and all references herein to a skirt
are intended to refer also to such petals or segments. The skirt 60
may be deployable from a folded or collapsed state to an expanded
state. The skirt 60 may be substantially self expanding. In the
folded/collapsed state, the skirt 60 may be retained and/or
restrained within one of the sheaths 20 and 22. In the expanded
state once the skirt 60 has been released, the skirt 60 may be
dimensioned to fit outside the open end 20b, 22b or at least one of
the sheaths 20, 22, respectively. In particular, the skirt 60 may
cover at least partly the open end 20b of the first sheath 20. The
skirt 60 may be made of any suitable material, for example,
flexible plastics. In one form, the skirt 60 may be cut from a
shaped balloon member, for example, as used in a known balloon
catheter. A balloon catheter may be used for valvuloplasty. Such a
balloon may be molded in its expanded shape, and a skirt 60 cut
from such a balloon may be self-biased towards the expanded shape,
but also be flexible and easily foldable to a collapsed state. Such
a balloon is also designed to be of thin material having atraumatic
characteristics.
[0171] In the illustrated example, the skirt 60 may be bonded to be
an integral part of the interface member 50. The skirt 60 may be
bonded to the proximal cone 62. The cone 62 may provide a suitable
divergent surface for supporting the natural shape of the skirt
60.
[0172] Instead of being slidable, the deployable interface member
50 and/or skirt 60 could be substantially stationary with respect
to the stent holder 24. In one example described later, the
deployable interface member 50 and/or skirt 60 may be mounted on
the stent holder 24.
[0173] FIGS. 10a-c illustrate different examples of attachment
element 68 of the stent-valve for engaging different examples of
stent holder 24, as illustrated in FIGS. 11-13 and 22. The
stent-valve may comprise at least one attachment element 68,
optionally two or three attachment elements 68, optionally more.
Generally, each attachment element 68 may be defined by an apex 74
or 76, joining first and second struts 70 and 72 that extend from
an end of the stent-valve 10. The struts 70 and 72 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
70 and 72 may project axially beyond neighboring cells of the
lattice.
[0174] In FIG. 10a, the struts 70 and 72 may extend generally
linearly to meet at apex 74 defining a generally V-shape. In FIGS.
10b and 10c, the apex 76 is slightly different by incorporating a
U-shape between the ends of the struts 70 and 72. The U-shape may
be straight sided (e.g., FIG. 10b) or it may have curved sides
(e.g. FIG. 10c).
[0175] Referring to FIG. 11, a two-piece stent holder construction
is described. However, it will be appreciated that the stent holder
may id desired by made as a one-piece item. A two-piece example
construction of stent holder 24 may generally comprise first and
second parts 78 and 80 assembled together. The first part 78 may
comprise a hub 82 from which project a plurality of projections 84.
The second part 80 may comprise a casing having a hollow interior
for fitting around at least a portion of the hub 82 from which the
projections 84 project, and defining interstices 86 for
accommodating the locking projections 84 with a space or clearance
88 therearound. The casing may be forked to define the interstices.
The edge 90 of each interstice 86 may optionally be rounded or
chamfered. A two-part assembly may enable a complex shape of stent
holder 24 to be formed reliably and cost effectively. It may also
permit different materials to be used as appropriate (for example,
the first part may be of metal for strength, and the second part
may be of plastics). However, as already mentioned, the
stent-holder 24 may be formed as unitary item instead of an
assembly of plural parts.
[0176] The projections 84 may be configured for fitting within the
interior of the apex 74 or 76 of each attachment element 68, when
the stent-valve 10 is in its collapsed state. The engagement
between the projection 84 and the apex 74/76 traps the attachment
element (and hence the stent-valve 10) against axial movement, at
least in an axial direction away from the stent holder 24.
[0177] The projection 84 may be referred to as a radial projection
because it generally projects in a radial direction. In some
embodiments, the projection, or an edge thereof, may be inclined
towards the distal direction, by an angle of, for example, not more
than about 20 degrees, optionally not more than about 10 degrees,
optionally not more than about 5 degrees.
[0178] In the example of FIGS. 11 and 12, the projection 84 has an
elongate blade or fin shape, suitable for fitting within the
interior of apex 74 (FIG. 10a). Use of a fin or blade can enable
the projection 84 to have a desirably thin shape, while remaining
strong (especially in the axial, elongate direction). In addition
to the projection 84 trapping the stent-valve 10 against axial
movement away from the stent-holder, the shape of the interstice 86
cupping the apex 74, and/or engagement between an end face 92 of
the stent holder 24 and neighboring cell apexes of the stent, may
restrain the stent-valve 10 against axial movement in the opposite
direction. The stent-valve 10 may thereby be retained firmly in
position until expansion of the stent-valve 10 may disengage the or
each attachment element 68 from the stent-holder 24.
[0179] In the case of a self-expanding stent-valve 10, the
attachment elements may disengage when the portion of the
stent-valve 10 from which the attachment elements 68 extend, is
uncovered by a sheath (for example, the first sheath 20). Upon
expansion of the stent-valve 10, the struts 70 and 72 move apart to
open the V-shape of the apex 74. As the V-shape opens, this
enlarges the interior of the attachment element 68 to facilitate
disengagement between the projection 84 and the apex 74. The
chamfered edge 90 of the interstice 86 also acts as a ramp surface
to "lift" radially the struts 70 and 72 out of the clearance 88 as
the struts 70 and 72 expand circumferentially and bear against the
edge 90. In case the attachment elements 68 may stick accidentally
within the interstice 86, the attachment elements 68 may be freed
by slight rotation and/or axial displacement of the catheter, to
promote further riding against the edge 90.
[0180] In the example of FIGS. 13 and 22, the projections 84 are
fingers or pins, suitable for fitting within the interior of apex
76 (FIGS. 10b/c). Each pin (FIG. 13) may have a larger thickness
than an equivalent fin (FIG. 12). In a collapsed condition of the
stent-valve 10 (FIG. 13), the struts 70 and 72 may lie closely
adjacent each other at the attachment element 68, such that the arc
of the U-shape portion 76 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 U-shape may be referred to as a horseshoe U-shape. The
eyelet aperture and space between the struts may together define a
keyhole type shape. Alternatively, the struts 70 and 72 may bear
against each other at the attachment element 68 to close the
eyelet. Either arrangement can restrain the attachment element 68
in both axial directions, merely by engagement between the
attachment element 68 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 24 and first sheath 20
through the stent-valve 10 once implanted.
[0181] In the expanded (or functional or non-collapsed) condition
of the stent-valve 10 the struts 70 and 72 may move apart, and the
arc of the U-shape apex 76 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. For example, the
apex may have a substantially straight-sided U-shape. In a similar
manner to that described above, opening of the apex 86 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 70 and 72 out of the clearance 88 as the struts
70 and 72 expand circumferentially and bear against the edge
90.
[0182] FIG. 22 shows a stent holder equivalent to FIG. 13,
optionally for production as a single-piece item. All of the stent
holders illustrated in FIGS. 11-13 and 22 illustrate the provision
of at least one ramp surface extending partly around each
projection, to define ramp surface portions circumferentially
either side of the projection and axially (e.g. distally) to one
side of the projection. The ramp surface portions are inclined
outwardly away from the projections. The clearance around the
projection is open to the other axial (proximal side) and/or open
radially outwardly. The radial height of the projection 84 may be
accommodated entirely or at least substantially within the profile
of the stent holder body. The stent holder body may be a surface of
revolution. One difference that may be noted between on the one
hand the example of FIGS. 11 and 12, and on the other hand the
examples of FIGS. 13 and 22, is that in the latter example, the
ramp surface extends to the floor of the clearance or interstice
around the projection 84. The ramp surface may generally be
inclined at an angle of between about 20 and about 40 degrees,
optionally around 30 or 35 degrees.
[0183] Referring to FIGS. 14 and 23, the stent-holder 24 may carry
a skirt (or may also be referred to as sleeve) 94. The skirt 94 may
optionally be constructed as plural petals or segments of material
that collectively behave as a sleeve or skirt, and all references
herein to a sleeve/skirt are intended to refer also to such petals
or segments. The skirt 94 may be similar to the skirt 60 described
above, and the same constructional details may be used. FIG. 23
illustrates one example structure in more detail. The skirt 94 may
comprise a generally tubular sleeve section 94a and a plurality of
cuts or slits 94b defining joined petals or segments 94c. The
petals 94c may substantially cover the projections 84 and/or the
radial recess therearound. The slits 94b may permit the petals 94c
to fold or flex outwardly open. The slits 94b may be aligned
generally with the projections 84 or the radial recesses
therearound. Such positioning of the slits 94b can ensure that the
petals 94c do not obstruct expansion and detachment of the
attachment elements of the stent-valve. Outward flexing of the
petals may automatically cause the slits 94b to open, to allow the
attachment elements to expand through the open slits.
[0184] The skirt 94 may function to facilitate loading of the
collapsed stent-valve 10 into especially the first sheath 20, prior
to use of the delivery catheter 12. Loading may be achieved by
first opening the first sheath 20 (arrow 20a), folding back or open
the skirt 94 (or the petals 94c thereof), collapsing the
stent-valve 10 such that the attachment elements 68 engage in the
stent-holder 24, and then moving the first sheath 20 its closed
position (arrow 20c) covering the distal portion of the stent-valve
10. The skirt 94 may return flat to cover, at least partly, the
attachment elements 68. Covering the attachment elements 68 may
avoid the apex 74 or 76 creating an abrupt edge that obstructs
closing of the first sheath 10, if the attachment element 68 is not
perfectly flush with the surface of the stent holder 24. Covering
the attachment elements 68 may also avoid one of the attachment
elements accidently passing outside the open end 20b of the first
sheath 20. It will be appreciated that, when the stent-valve 10
comprises plural attachment elements 68, it may be difficult to see
whether all of the attachment elements 68 are engaged perfectly
into the stent holder 24 during loading. Covering the attachment
elements 68 with the skirt 94 may reduce this problem, and may
compensate to guide the open end 20b of the first sheath 20 over
the attachment elements 68 even if not perfectly positioned. The
skirt 94 may also protect the open end of the first sleeve 20 from
rubbing aggressively on the edge of outer skirt material of the
stent-valve.
[0185] The skirt 94 on the stent holder may also find use in a
delivery catheter 12 that has only a single sheath (not shown).
[0186] In the arrangement of FIG. 14, the skirt 94 may be distinct
from the optional skirt 60 of the separate interface member 50.
FIG. 15 may illustrate an alternative arrangement in which a single
sleeve or skirt 94 may additionally perform the function of skirt
60 as an interface element.
[0187] Referring to FIG. 15, following release of the stent-valve
10, the skirt 94 may be directed with its open end facing distally,
in order to cover the open end 20b of the first sheath 20. The
skirt 94 may extend outside the first sheath 20. Within the
terminology of an interface member, the skirt 94 may be in a
deployed state when extending outside the first sheath 20. The
second sheath 22 may be advanced distally towards the first sheath
20. The second sheath 22 may optionally be advanced distally beyond
its normal closed position.
[0188] Additionally or alternatively to the skirt 94, it will be
appreciated that other deployable interface elements may be
provided on, or form part of, the stent holder 24, or be mounted on
the stent holder support tube. This would illustrate a further
example of a deployable interface element that is not freely
slidable within the accommodation region 18.
[0189] FIG. 16 illustrates a handle 100 for the proximal portion 16
of the delivery catheter, for controlling the distal portion 14 via
the tubes 26-30 extending between the proximal and distal portions
of the delivery catheter. The tubes 26 may optionally include or be
connected to respective rigid portions that extend through the
handle 100.
[0190] The handle 100 may comprise a fixed body 102 which extends
substantially the length of the handle 100, and may have an
elongate slot 104 through which control pins can slide, as
described herein after. A fixing 106 may fixedly couple the body
102 to the first tube 26, such that the body 102 may control the
relative position of the first tube 26. A grippable "first tube"
handle 108 may be coupled to the body 102, for example, at the
distal end of the handle 100.
[0191] The handle 100 may further comprise a "second tube" handle
110 having a helical guide 112 associated therewith. The helical
guide 112 may optionally be formed in a separate component 112a
that is coupled to rotate with the "second tube" handle 110. A
slider 114 coupled to the second tube 28 may have a pin 116 that
extends through the slot 104 into engagement with the helical guide
112. The "second tube" handle 110 may be rotatable about the body
102. Rotation of the "second tube" handle 110 (relative to the body
102) rotates the helical guide 112, causing the pin 116 and hence
the slider 114 to move axially. The slider 114 transmits the axial
movement to translate the second tube 28 relative to the first tube
26, thereby to translate the first (distal) sheath 20 with respect
to the stent holder 24.
[0192] The handle 100 may further comprise a "third tube" handle
118 having a helical guide 120 associated therewith. The helical
guide 120 may optionally be formed in a separate component 120a
that is coupled to rotate with the "third tube" handle 118. A
slider 122 coupled to the third tube 30 may have a pin 124 that
extends through the slot 104 into engagement with the helical guide
120. The "third tube" handle 118 may be rotatable about the body
102. Rotation of the "third tube" handle 118 (relative to the body
102) rotates the helical guide 120, causing the pin 124 and hence
the slider 122 to move axially. The slider 122 transmits the axial
movement to translate the third tube 30 relative to the first tube
26, thereby to translate the second (proximal) sheath 22 with
respect to the stent holder 24.
[0193] Optionally, the handle 100 may comprises at least one
flushing port 126 through which liquid (e.g. saline) may be
injected, in order to flush air from spaces that are open to the
anatomy. In particular, it may be desired to flush the space
between the first and second tubes, and the space between the
second and third tubes. In some embodiments, a single or common
flushing port 126 may be provided for flushing both spaces. A
communication port or aperture (the position of which is indicated
schematically at 128 and referred to hereinafter by the same
numeral) may be provided for allowing liquid in one space to enter
the other. For example, the flushing port 126 may be configured to
admit liquid into the space between the first and second tubes. A
communication port 128 in the second tube may permit the liquid
also to enter the space between the second and third tubes. The
communication port 128 is optionally positioned at the handle 100,
or at least closer to the proximal portion of the catheter than to
the distal portion, in order to flush the spaces thoroughly to the
distal portion. Provision of a single or common flushing port 126
for flushing plural spaces may be advantageous in simplifying the
number of connections and operations that an operator has to
perform when preparing the catheter for use. Alternatively, if it
is desirable to have independent control over flushing of each
space, plural flushing ports 128 may be provided, each
communicating individually with a respective space to be
flushed.
[0194] The handle 100 may be configured to apply pre-tension to one
or more of the tubes, as described above. Various mechanisms for
applying pre-tension are envisaged. The mechanism may be part of
the "second tube" handle 110, or it may be a separate mechanism
capable of applying tension. In a simple, yet effective and
intuitive form, the "second tube" handle 110 may be rotatable to
generate pre-tension, and may be lockable in the tensioning
position. The handle may be lockable using any suitable locks, such
as a removable pin, or a ratchet mechanism. Additionally, the
handle 100 may include an indicator ring for indicating the amount
of rotation of the handle 110 to generate a desired amount of
pre-tension. The indicator ring may be manually settable such that
a first marker is in register with a counter-marker on the handle
110 when the first sheath is in a closed position without
pre-tension. Once set, the indicator ring may indicate, by a second
marker, the degree of further rotation by which the handle 110
should be turned or displaced to generate the pre-tension. The lock
for locking the handle 110 in position, and/or the settable
indicator ring, are generally indicated schematically at 110a.
However, it will be appreciated that the lock and indicator ring
may be separated and/or placed at different positions on the handle
100 as desired.
[0195] FIG. 20 illustrates a liner sleeve 150 that may be used with
the catheter 12. The liner sleeve 150 may act as a friction
reducing liner between the catheter 12 and an introducer 19 (for
example, a standard arterial introducer) through which the catheter
is inserted into the body. The liner sleeve 150 may reduce friction
on the catheter tubes, especially the outer tube 30, permitting
easier deployment of the stent 10. A standard arterial introducer
includes a haemostasis valve 19a for preventing blood reflux and
air aspiration. The haemostasis valve 19a may be a quite aggressive
multiple flap valve in order to function with a wide range of
different equipment types and sizes that could be introduced into
the artery. The aggressiveness of the haemostasis valve may tend to
obstruct fine displacement of the tubes of the delivery catheter 12
for controlling translation of the sheaths at the distal portion.
The liner sleeve 150 provides a low friction interface between the
third tube 30 and the introducer 19. The liner sleeve 150 may be
captive on the catheter 12, and slidable axially along the catheter
length. The liner sleeve 150 may include, at its proximal end, a
stop 152 that limits the extent of entry into the introducer.
Additionally or alternatively, the liner sleeve 150 may include a
portion 154 for removable interference fit with a socket 156 of the
handle 100. This permits the liner sleeve 150 to be stowed
connected to the socket 156 of the handle 100, and separated from
the handle 100 when desired to advance the liner sleeve 150 into
operative position within an introducer 19. The liner sleeve 150
may optionally additionally comprise a seal 158 for effecting a
substantially blood-tight seal between the liner sleeve 150 and the
outer tube 30 of the catheter 12. The seal 158 may be configured
uniquely for the dimension of the catheter 12, and so may be
substantially less aggressive than the haemostasis seal 19a of the
introducer 19. For example, the seal 158 may be formed by an
O-ring. The seal 158 may optionally be provided at the stop 152 or
the connector 154, such that the seal 158 is not subjected to the
forces within the introducer 19. Alternatively, the seal 158 may be
positioned elsewhere along the length of the liner sleeve 150.
[0196] When deployed into the introducer, the liner sleeve 150 may
not be fixed axially and/or rotationally with respect to the
remainder of the catheter 12, allowing the catheter to be
manipulated without obstruction. In some embodiments, the length of
the liner sleeve 150 projecting distally from the stop 152 may be
not be greater than about 30 cm, optionally not greater than about
25 cm, optionally not greater than about 20 cm, optionally not
greater than about 15 cm, optionally not greater than about 10
cm.
[0197] FIG. 24 illustrates a modification of the delivery catheter
including a ball joint (the terms ball joint, ball socket, ball
socket articulation, and ball socket connection are all
interchangeable) in at least one tubular member of the catheter.
The ball joint may be provided just proximal to the stent
accommodation region (also referred to herein as stent-holding
region or compartment) of the catheter, such that the ball joint
can provide a high-flexibility region just proximal to the
stent-holding compartment. The ball joint can be within 5 cm
proximal of the stent holding compartment. The ball joint can also
be 0.1, 0.5, 1, 2, 3, 4 or 4.5 cm proximal of the stent holding
compartment. The ball joint can also be between 1 and 2 cm proximal
of the stent holding compartment. The ball joint may be provided in
a tubular member of the catheter that moves axially with respect to
the position of the stent. That is, the tubular member, according
to some embodiments, can be moved in a proximal 22A or distal 20A
direction (also as shown in FIG. 1) to release the stent. In this
case, the distance measurement above is defined to be when the
tubular member is in a position corresponding to a closed position,
e.g. a most closed position for that tubular member. An example of
this closed position is shown in FIG. 24. In the closed position,
the sheaths may meet end to end, or remain spaced from each
other.
[0198] The ball joint may be provided in the outer tubular member
of the catheter assembly. The ball joint is preferably hollow or
includes an aperture to permit passage of one or more inner tubular
members. In some embodiments, there is a single inner tubular
member that passes through the outer tubular member. This inner
tubular member can be a guide-wire receiving lumen. Also a stent
holder can be mounted on this inner tubular member. There can also
be at least two tubular members that pass through the outer tubular
member. These two or more inner tubular members can be arranged one
within the other. There can also be three, four, five, six, seven,
eight, nine or ten inner tubular members. Each of these can be
nested within each other.
[0199] In some embodiments, the ball joint can allow bending of the
tubular members through a range of up to at least 45.degree.,
compared to the straight-axis of the catheter at that point. The
ball joint can also allow bending of the tubular members of up to
at least 40.degree., compared to the straight-axis of the catheter
at that point. The ball joint can also allow bending of the tubular
members of up to at least 30.degree., compared to the straight-axis
of the catheter at that point. The ball joint can also allow
bending of the tubular members of up to at least 20.degree.,
compared to the straight-axis of the catheter at that point. The
ball joint can also allow bending of the tubular members through
20.degree., 21.degree., 22. degree., 23.degree., 24.degree.,
25.degree., 26.degree., 27.degree., 28.degree., 29.degree.,
31.degree., 32.degree., 33.degree., 34.degree., 35.degree.,
36.degree., 37.degree., 38.degree., 39.degree., 41.degree.,
42.degree., 43.degree. and 44.degree., compared to the
straight-axis of the catheter at that point. Such high flexibility
would be difficult to achieve with a continuous bending member of
equivalent cross-section diameter, without risk of kinking the
continuous member.
[0200] In some embodiments, the ball joint has a transverse outer
diameter (e.g., measured in a cross-section direction to the axis
of the catheter) that is not greater than a diameter of at least
one adjacent tubular member of the catheter assembly. This enables
the ball-joint to be accommodated without enlarging the size
profile of the catheter assembly. The profile of the tubular member
adjacent to the ball joint may blend smoothly into the profile of
the ball joint, to define a generally smooth continuous surface,
even when the catheter assembly is flexed at the ball joint. If
desired, the transverse outer diameter of the ball joint may be
larger than the a diameter of both adjacent tubular members of the
catheter assembly leading to the ball joint.
[0201] In some embodiments, the transverse outer diameter of the
ball joint is not greater than a largest tubular member diameter of
the catheter assembly. For example, for a catheter assembly
insertable into the body using an introducer of 18 French size, the
maximum diameter of an outer tubular member is approximately 6 mm
(not greater than 7 mm). The transverse outer diameter of the ball
joint might then be no larger than this maximum diameter. In some
embodiments, the length of the ball joint (in an axial direction of
the catheter assembly) may be up to about two thirds of the
transverse outer diameter of the ball joint.
[0202] In some embodiments, the ball joint can also allow an axial
force to be applied along the length of the tubular members, for
pushing forward (distally) or drawing back (proximally) the tubular
members. For example, the outer tubular member may comprise a
sheath (e.g. proximal sheath part) that at least partly encompasses
the stent, and the sheath may translate axially forwards or
backwards under the axial force to shift from a closed state to an
open state. The axial force may be applied through the ball joint.
The ball joint can thus form part of a portion or sub-assembly of
the catheter that moves axially with regards to the stent position
on the catheter.
[0203] In some embodiments, the ball joint can also allow relative
rotation between the two parts of the tubular members on either
side of the ball joint. The relative rotation may be limited up to
one turn, or in some embodiments, the relative rotation may also be
limited up to two, three, four, five, six, seven, eight, nine or
ten turns. Alternatively, it may be unlimited. Either arrangement
may enable the stent-holding compartment of the catheter to be
rotated, while the outer body of the catheter remains stationary in
the artery without rotation. The outer body of the catheter can act
like a bushing within which the other tubular members turn, without
friction with regards to the artery wall. The torsion can be
applied via the other (one or more) tubular members carried within
the catheter and passing through the ball joint to the distal
section of the delivery device (at least distal of the ball joint).
Alternatively, a hydraulic or electronic actuator may generate
rotary movement at the distal part (stent-holding compartment) in
response to a suitable fluid/electronic signal supplied via a
electronic signal line or a fluid conduit.
[0204] FIG. 24 presents an example of a stent delivery device with
a ball joint according to some embodiments of the present
disclosure. As shown, ball joint 1 is provided in the outer tubular
member 30 of the catheter, which is the tubular member for drawing
back (proximally 22A towards the catheter handle) the proximal
outer sheath (second sheath) 22 that covers (at least) a portion of
the stent 10. For pulling back the proximal sheath, an axial force
is applied from a handle along the catheter length, and then
through the ball joint to the outer sheath. Rotation is achieved by
applying a torsional force to inner tubular members 26 and/or 28
within the catheter. These turn the stent from within. The stent
holder 30 transmits the torsional force from the other interior
tubular members to rotate the stent about the catheter axis. The
friction between the stent and the outer sheath also turns the
outer sheath. The ball joint enables the outer sheath to turn
freely without torsion being applied to (or resisted) by the body
of the catheter. FIG. 1 also shows that the stent holder can be
located distally 6A or proximally 6B. The stent-holding compartment
is made up of the proximal sheath 22 and the distal sheath 20. The
distal sheath is attached to the inner tubular members. When the
inner tubular members are extended distally, the distal sheath can
also be pushed distally and off of the stent. Likewise, the
proximal sheath can be pulled proximally, as described above. The
inner most tubular member also forms a guidewire lumen 3 that
extends through the center of the catheter.
[0205] The ball joint and the portions of the tubular member
coupled thereto may be of any suitable material, e.g. metal (e.g.
stainless steel) or plastics (e.g. nylon).
[0206] The socket part of the ball joint may communicate with a
stepped-down, or even necked-down, region of the tubular member, in
order to allow the spherical extent of the socket surface to be
increased.
[0207] A related aspect may be to provide a high-flexibility
portion of the catheter adjacent to the stent-holding compartment.
The high-flexibility may be defined as having a bending resistance
less than 50% of the tubular member on either side of the
high-flexibility region. The high flexibility region may also have
a resistance of 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45% of the
tubular member on either side of the high-flexibility region. The
high-flexibility region may have an axial length of less than 5 cm.
The high-flexibility region may also have an axial length of
between 1 and 2 cm. One implementation for the high-flexibility
region may be using a ball joint as above. Another may be to use a
segment of high-flexibility tubing joined to (or integral with) the
catheter tubing.
[0208] The flexing and rotary articulation of a ball joint may even
be separated into two separate connections, joints or couplings,
provided that both of these are close to the stent-holding
compartment of the catheter. The two couplings are generally not
more than 5 cm apart. The two couplings can also be between 1 and 2
cm apart. The flexing connection can be positioned closer to the
stent-holding compartment to compensate for the rigidity of the
adjacent stent, but the order could easily be reversed according to
a particular implementation.
[0209] It will be appreciated that including a ball joint in the
outer tube may restrict the amount of torque transmittable through
the outer tube. The construction of other inner tubes may
optionally be modified to transmit torque, for example, using the
principles described previously.
[0210] FIGS. 17, 18 and 19 illustrate a detailed example of a
stent-valve 10 for which the delivery catheter 12 of any of the
preceding embodiments may be eminently suitable. The stent-valve 10
may be of a self-expanding type that is resiliently biased towards
the expanded and/or functional state, and is compressible to a
compressed state by application of suitable radial compression
forces. The stent-valve 10 remains in its compressed state while
constrained. When the constraint is removed, the stent-valve 10
self expands towards the expanded and/or functional state.
Alternatively, the stent-valve 10 may be of a non-self-expanding
type that requires application of an expansion force to transform
the stent-valve 10 from the compressed state 10' to the expanded
state.
[0211] The stent-valve 10 may comprise a stent component 134
supporting a plurality of valve leaflets 136. The leaflets 136 may
collectively be referred to as a valve component, whether or not
the leaflets 136 form an integral unit. The stent component 134 may
provide an anchoring function for anchoring the stent-valve in the
native anatomy and/or a support function for supporting the valve
leaflets 136. The stent component 134 may be of any suitable
material or materials. The stent component 14 may be of metal.
Example materials include shape memory and/or superelastic alloys
(for example, nitinol), stainless steel, or cobalt-chromium alloy.
In the illustrated form, the stent component 134 is self-expanding
and is of shape memory/superelastic alloy (e.g. nitinol). However,
the stent component 134 could also be substantially non-self
expanding.
[0212] The stent component 134 may have any profile desired for
anchoring and/or aligning the stent-valve 10 with respect to the
native anatomy at the desired implantation site. In some
embodiments, the stent component 134 may be generally cylindrical
in shape, or comprise one more generally cylindrical portions or
portions lying on a generally cylindrical surface (e.g. 140c and
142a). Additionally or alternatively, the stent component 134 may
be generally non-cylindrical in shape or comprise one or more
generally non-cylindrical portions or portions lying on a
non-cylindrical surface (e.g. 140a, 140b, and 144). Additionally or
alternatively, the stent component 134 may comprise one or more
anchor projections, and/or one or more stabilization portions.
[0213] Viewed in one aspect, the stent component 134 optionally has
an inflow end and an outflow end, optionally is self-expandable
from a compressed state for delivery towards a functional state
upon implantation, the stent component 134 comprising an outflow
structure, for example, in the form of a plurality of arches 144a
at the outflow end each having an apex at the outflow end, the
stent component further comprising a crown (e.g. superior crown)
140b intermediate the inflow and outflow ends, the crown 140b
having a free extremity intermediate the inflow and outflow ends
and directed towards the outflow end, and the stent-component
further comprising a fixation section (e.g. inferior crown) 140a
between the crown and the inflow end.
[0214] Additionally or alternatively, the stent component 134
optionally comprises an anchoring portion 140 defined, for example,
by an inferior crown 140a and a superior crown (or other fixation
section) 140b that together define a groove and/or waist 140c
therebetween. The anchoring portion 140 may have a first resistance
to compression, and may comprise a cellular lattice.
[0215] The stent component 134 optionally (further) comprises a
valve support portion 142 comprising, for example, a plurality
(e.g. three) commissural support posts 142a. The commissural
support posts 142a may be arranged on a pitch circle diameter
smaller than an extremity of at least one of the crowns 140a and
140b. The commissural support posts 142a may be arranged on a pitch
circle diameter corresponding to the waist 140c. The commissural
support posts 142a may partly overlap at least one of the crowns
140 and 142 in the axial direction, and extend axially beyond that
respective crown. The commissural support posts 142a may be
frame-like. The commissural support posts 142a may have a shape
that follows, at least approximately, a peripheral contour of the
valve, at least in the region of the valve periphery adjacent to
the commissural support posts.
[0216] The stent component 134 optionally (further) comprises a
stabilization or alignment portion 144 which may represent an
outflow structure. The portion 144 may be defined, for example, by
a plurality (e.g. three) wings or arches 144a. The arches 144a may
extend from tips of the commissural support posts 142a, to define a
vaulted structure thereover. The alignment portion 144 may have a
greater flexibility than the anchoring portion 140 and/or the valve
support portion 142. The alignment portion 144 may have a second
resistance to compression that is smaller than the first resistance
to compression of the anchoring portion 140. The alignment portion
144 may be less rigid (e.g. radially) than the anchoring portion
140 and/or the valve support portion 142.
[0217] The stent component 134 optionally (further) comprises an
attachment element 68 for attaching the stent component 134 to a
stent holder 24 of the delivery catheter 12. In the present
embodiment, the attachment portion 68 is defined by a plurality
(e.g. three) of extensions of cells of the inferior crown 140a, and
have a shape corresponding to one of the examples of FIGS.
10a-c.
[0218] The valve component or leaflets 136 may be of any suitable
natural and/or synthetic material(s). For example, the valve
component/leaflets 136 may comprise porcine and/or bovine
pericardium and/or harvested natural valve material. The leaflets
may be supported to coapt or collapse to a closed position to
obstruct flow in one direction therepast, while flexing apart to an
open position to allow flow in an opposite direction. The valve
component/leaflets 136 may be accommodated at the valve support
portion 142 and/or at least partly within the anchoring portion
140. The leaflets may have side tabs. The tabs of adjacent pairs of
leaflets may pass in pairs through slots in the support posts 142,
be folded back and sutured on either side of the slot. The support
posts 142a may have lines of suture holes either side of the slot
to accommodate the sutures. Further suture holes may be provided
above and/or below the slots. If desired the suture hole above the
slot (indicated at A in FIG. 19) and/or the suture hole below the
slot, may be omitted to save space.
[0219] The stent-valve 10 (e.g. the valve component 136) may
further comprise an inner skirt and/or an outer skirt covering at
least partly a respective inner or outer surface portion of the
stent component 14. For example, the skirt(s) may cover at least a
portion of the anchoring portion 140 and/or at least a portion of
the valve support portion 142. The skirt(s) may be made of any
suitable material, including PET and/or pericardium. The
pericardium may be of the same material as the leaflets. In some
embodiments, the inner and outer skirts may partly overlap each
other in a skirt overlap region A in FIG. 17, and include
non-overlapping portions extending axially above and below,
respectively, the overlap region A. The inner skirt may be
advantageous in channel blood towards the leaflets and preventing
leakage of blood through the interstices of the lattice structure.
The outer skirt may be advantageous in preventing leakage of blood
at the interface between the stent-valve and surrounding tissue.
Providing both skirts, but with only partial overlap, may enable
the advantages of both to be obtained, but also reducing full
overlap of material (which would otherwise increase the thickness
of material of the stent-valve, making it more difficult to
compress the stent-valve to a small size). The partial overlap
nevertheless enables a reliable seal to be achieved between the
inner and outer skirts.
[0220] In use, viewed in one general aspect, at least a portion of
the inferior crown (or other fixation section) 140a may be received
and constrained by the first sheath 20. At least a portion of the
stent-component 134 not covered by the first sheath 20 may be
received and constrained by the second sheath 22. As explained
earlier and described in more detail below, a method of releasing
the stent-valve 10 may include moving the second sheath 20 to an
open position in order to deploy the crown/superior crown 140b,
followed by the support section 142, and finally the arches 144a.
For example, these elements may be deployed on an aorta side of a
native and/or failed valve. Thereafter, once the operator is
satisfied with the position and/or function of the stent-valve 10
within the native anatomy, the first sheath 10 may be moved to its
open position in order to deploy the inferior crown 140a.
Simultaneously, the attachment elements 68 may release from the
stent-holder 24.
[0221] Such a deployment sequence is different from that described
in the aforementioned WO-A2009/053497 and WO-A-2011/051043.
Nevertheless, it has been appreciated that deploying the arches
144a after the crown 140b is still highly effective in permitting
the arches to function. Notably, the arches may be deployed prior
to uncovering of the fixation section 140a for deployment.
[0222] In some embodiments, the arches may be configured for
aligning the stent-valve with respect to an axis of the ascending
aorta by contact with a wall of the ascending aorta. For example,
the arches may be bendable independently of each other. The crown
may be configured for engaging and/or seating against existing
leaflets from an outflow side. The fixation section may be
configured for engaging an existing annulus.
[0223] Deploying the arches before the fixation section may permit
self-alignment of the stent-valve by the action of the arches,
before the fixation section deploys to anchor the stent-valve at
the annulus of the existing valve.
[0224] There now follows a detailed description of how the
apparatus described above may be used in one example. The
description may be modified according to which features of the
apparatus may be implemented according to the actual embodiment
used. The order of the individual steps may be changed as desired.
The steps are grouped by topic. The order of the topics may be
changed as desired. The order of steps within each topic may be
changed as desired. The following description may focus principally
on features of the delivery catheter previously described;
additional steps not described here may be included as part of the
procedure, as may be known to practitioners in the field of
transcatheter stent-valve implantation. [0225] A: Loading of the
stent-valve into the accommodation region:
[0226] A1: The first and second sheaths 20 and 22 are each
translated open by using the controls 110 and 118 of the handle
100. The petals 94c of the skirt 94 are folded back to expose the
projections 84 of the stent holder.
[0227] A2: The stent-valve 10 is compressed in place in the
accommodation regions. A conventional crimper may be used. The
stent-valve is arranged with its end (for example, inflow end)
having the attachment elements positioned distally in the
accommodation region, and in register with the projections 84. The
fixation section/inferior crown 140a may be compressed first, such
that the attachment elements 68 mate with the projections 84. Using
the handle 110, the first sheath 20 may be translated proximally to
at least partly cover the fixation section/inferior crown 140a, and
capture the stent-valve by its attachment elements. During such
translation, the petals 94 may unfold flat to lie between the
interior surface of the first sheath 20, and an exterior surface
portion of the stent-valve. Next the remaining sections of the
stent-valve may be compressed (e.g. the crown/superior crown 140b;
the valve support section; and the arches) and the second sheath 22
is translated distally to at least partly cover the stent-valve
from the arches to the crown/superior crown 140b to constrain these
sections of the stent-valve compressed. As mentioned previously, in
the closed positions of the first and second sheaths, the ends of
the sheaths may meet substantially end to end, or the sheaths may
remain spaced apart. [0228] B: Preparation of the delivery catheter
for introduction into the body (following steps A):
[0229] B1: The delivery catheter may be flushed by injecting liquid
(e.g. saline) via the at least one flushing port 126. Optionally,
plural spaces within the delivery catheter may be flushed by
injecting liquid through a single and/or common port 126.
[0230] B2: The first tube 26 may be pre-tensioned by rotating the
second tube handle 110 to "over-close" the first sheath. The amount
of pre-tension to apply may be indicated by manually setting the
indicator ring such that a first marker on the indicator ring
aligns with a counter-marker on the handle 100. The second tube
handle 110 is further rotated manually by an amount indicated by a
second marker on the ring to generate the pre-tension. The second
tube handle 100 may optionally be locked in the pre-tensioning
position, in order to avoid the handle slipping in use and relaxing
the pre-tension before the moment intended. [0231] C: Steps carried
out on the patient prior to implantation (following steps A or
B):
[0232] C1: An arterial introducer 19 is placed to penetrate
percutaneously an artery, for example, the femoral artery or the
subclavian artery. A guide wire is introduced through the
introducer 19 and navigated along the vasculature to traverse the
valve to be replaced, for example, an aortic valve.
[0233] C2: A balloon catheter may optionally be introduced through
the introducer 19 and advanced along the guide wire to the valve to
be replaced. Valvuloplasty may be performed to free the valve
leaflets in the case of a stenosed valve. The balloon catheter is
then removed. [0234] D: Stent-Valve Implantation (following steps
A, B and C):
[0235] D1: The delivery catheter may be fed over the guidewire
towards the introducer 19, with the guidewire being received within
the lumen of the first tube 26. The distal portion of the delivery
catheter may be introduced through the introducer. Thereafter the
delivery catheter may be fed progressively through the introducer,
to advance the distal portion along the guidewire to the location
of the valve to be replaced.
[0236] D2: At some stage, at least after the distal portion has
passed through the introducer 19, the liner sleeve 150 may be
separated from the handle 100, and slid distally along the catheter
stem and into the introducer 19 to provide a reduced friction fit
in the introducer. This may permit easier advancement of the
catheter through the vasculature, and/or easy manipulation of the
sheaths at the following steps.
[0237] D3: When the distal portion is approximately in position, or
slightly high in the ascending aorta, the operator may, if desired,
rotate the delivery catheter, to rotationally align the stent-valve
with the native anatomy. Although the geometry of the stent-valve
itself may not require such rotational alignment, some
practitioners may prefer the possibility to align the stent-valve
with the native valve, such that the stent-valve can replicate the
natural valve function as closely as possible. As described
previously, the combination of the braided tubes 26 and 30, and/or
the braid characteristic of the third tube 30, permits good
transmission of torque from the handle 100 to the distal portion,
despite the relatively long length of the delivery catheter. The
rotational orientation of the stent-valve may be observed using
suitable imaging equipment, for example, X-ray imaging
equipment.
[0238] D4: With the distal portion still approximately in position,
or slightly high in the ascending aorta, the third tube handle 118
may be operated to translate the second sheath 22 proximally, and
release the sections of the stent-valve previously covered by the
second sheath 22. This may include the crown/superior crown 140b,
the arches 144a, and any stent sections in between (e.g. the
support section 142). The translation of the second sheath 22 may
release first the crown/superior crown 140b, followed last by the
arches 144a. If pre-tension is used in step B2, the pre-tension may
bias the first sheath proximally preventing any tendency for the
first sheath to creep distally as a result of the reaction forces
applied though the tubes during the manipulation of the second
sheath. It may be appreciated that although the pre-tensioning step
is described as part of the preparation at step B2, the application
of pre-tension may be performed later at any stage before D4, even
after the catheter has been advanced to the valve to be replaced.
Performing the pre-tensioning step later may, in some cases,
improve the flexibility of the catheter for tracking along the
guidewire. Additionally or alternatively, it may be appreciated
that if the liner sleeve 150 if used at step D2, the liner sleeve
150 may reduces frictional resistance against movement of the third
tube 30 within the introducer 19, thereby making the operation of
translating the second sheath 22 easier and smoother.
[0239] D5: The operator may push the catheter gently until the
deployed crown/superior crown 140b bears against the existing
leaflets of the valve to be replaced. Upon such placement, the
operator may feel resistance, and effectively feel that the
crown/superior crown 140b is seated correctly against the leaflets.
Additionally or alternatively, the position may be monitored by
suitable imaging equipment, such as X-ray imaging equipment. During
such manipulation of the catheter with the stent-valve partly
deployed, the engagement between the stent holder 24 and the
attachment elements 68 keeps the stent-valve firmly anchored to the
delivery catheter.
[0240] D6: When the operator is satisfied about the position of the
crown/superior crown 140b, the operator may operate the second tube
handle 110 to translate the first sheath 20 distally in order to
release the fixation section/inferior crown 140a. If the second
tube handle 110 has been locked in position as part of the
pre-tensioning operation, the lock may be removed or disengaged to
allow the pre-tension to be relaxed, and the second tube instead to
apply a compression force for translating the first sheath
distally. As mentioned previously, the construction of the second
tube 28 provides good column strength for transmitting the
compression force from the handle 100 to the first sheath 20.
[0241] D7: Upon removal of the first sheath 20, the fixation
section/inferior crown 140a deploys to anchor the stent-valve in
position. The attachment elements 68 expand radially outwardly and
may expand circumferentially, to release automatically from the
projections 84 of the stent holder 24. The ramp surfaces at least
partly surrounding the projections 84 lift the expanding attachment
elements radially clear of the stent holder 24. In the unlikely
event that any attachment element 68 may remain engaged to the
stent holder 24, the ramp surfaces also provide a facility to free
the attachment elements by slight axial and/or rotational movement
of the delivery catheter, which encourages the attachment element
to ride against a ramp surface.
[0242] D8: Following release of the stent-valve 10 from the
accommodation region, a first step of removal of the delivery
catheter may be to withdraw the portion of the delivery catheter
that is distal of the valve leaflets 136, through the valve
leaflets to the proximal side (e.g. into the ascending aorta).
Thereafter the, the delivery catheter may be withdrawn with the
sheaths 20 and 22 open or closed.
[0243] It may be appreciated that the [0244] E: Removal of delivery
catheter while open (after step D):
[0245] E1: The delivery catheter may be withdrawn without any
further manipulation or translation to close the sheaths 20 and 22.
If the interface member 50 has not already been deployed from the
second sheath 22, the second sheath 22 may be further translated
open (proximally) to release and deploy the interface member
50.
[0246] E2: The delivery catheter may be withdrawn by pulling
proximally through the introducer 19. The liner sleeve 150, if
used, may remain in place at the introducer, as the stem is pulled
through, or the liner sleeve 150 may manually withdrawn or may
self-withdraw as a result of friction.
[0247] E3: As the distal portion of the delivery catheter
approaches the introducer, the second sheath 22 may pass smoothly
into the introducer, by virtue of the streamlined shape of the
third tube coupling 44. The interface member 50 may translate
distally to abut the stent holder 24, either by virtue of the
movement of the catheter in the blood stream, or by contact between
the interface member 50 and the end of the introducer 19. As
explained previously, the interface member 50 has a shape that
presents a streamlined profile to guide the distal portion, with
the stent holder 24, smoothly into the introducer. The distal
portion may thus be withdrawn through the introducer even when the
sheaths are open. The interface member 50 remains deployed during
the withdrawal. [0248] F: Removal of the delivery catheter with
sheaths closed (after step D, and instead of step E):
[0249] F1: If the interface member 50 has not already been deployed
from the second sheath 22, the second sheath 22 may be further
translated open (proximally) to release and deploy the interface
member 50.
[0250] F2: The first and second sheaths may be translated towards a
closed state, with the first sheath being translated proximally,
and the second sheath being translated distally. As explained
previously, the interface member 50 has a shape that may provide a
bridge or interface between the ends of the two sheaths to define a
smooth profile without abrupt edges. The distal portion may thus be
withdrawn smoothly through the introducer. The interface member 50
remains deployed during the withdrawal.
[0251] F3: The liner sleeve 150, if used, may remain in place at
the introducer, as the stem is pulled through, or the liner sleeve
150 may manually withdrawn or may self-withdraw as a result of
friction.
[0252] It will be appreciated that the foregoing description is
merely illustrative of preferred forms of the invention, and that
many modifications, equivalents and improvements may be used within
the scope of the invention.
* * * * *