U.S. patent application number 11/945142 was filed with the patent office on 2008-03-27 for custom-length self-expanding stent delivery systems with stent bumpers.
This patent application is currently assigned to Xtent, Inc.. Invention is credited to Bernard Andreas, Jeffry J. Grainger.
Application Number | 20080077229 11/945142 |
Document ID | / |
Family ID | 35507044 |
Filed Date | 2008-03-27 |
United States Patent
Application |
20080077229 |
Kind Code |
A1 |
Andreas; Bernard ; et
al. |
March 27, 2008 |
CUSTOM-LENGTH SELF-EXPANDING STENT DELIVERY SYSTEMS WITH STENT
BUMPERS
Abstract
Custom-length self-expanding stent delivery systems and methods
enable precise control of prosthesis position during deployment.
The stent delivery systems carry multiple stent segments and
include a stent bumper for helping control the axial position of
the stent segments during deployment. This enables the deployment
of multiple prostheses at a target site with precision and
predictability, preventing stent segment recoil and ejection from
the delivery device and thus eliminating excessive spacing or
overlap between prostheses. In particular embodiments, the
prostheses of the invention are deployed in stenotic lesions in
coronary or peripheral arteries or in other vascular locations.
Inventors: |
Andreas; Bernard; (Redwood
City, CA) ; Grainger; Jeffry J.; (Portola Valley,
CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP;(CLIENT NO 021629-000000)
TWO EMBARCADERO CENTER
8TH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
Xtent, Inc.
Menlo Park
CA
|
Family ID: |
35507044 |
Appl. No.: |
11/945142 |
Filed: |
November 26, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10944282 |
Sep 17, 2004 |
7300456 |
|
|
11945142 |
Nov 26, 2007 |
|
|
|
10879949 |
Jun 28, 2004 |
|
|
|
10944282 |
Sep 17, 2004 |
|
|
|
Current U.S.
Class: |
623/1.11 |
Current CPC
Class: |
A61F 2002/826 20130101;
A61F 2/958 20130101; A61F 2/97 20130101; A61F 2002/9511 20130101;
A61F 2/95 20130101; A61F 2002/9505 20130101; A61F 2/966 20130101;
A61F 2002/9583 20130101; A61F 2002/9665 20130101 |
Class at
Publication: |
623/001.11 |
International
Class: |
A61F 2/06 20060101
A61F002/06 |
Claims
1. A catheter system for delivery of a stent to a body lumen
comprising: a stent delivery catheter comprising: a sheath having a
first lumen; a shaft extending through the first lumen and slidable
relative to the sheath; a stent bumper mounted to the shaft
distally of the sheath and movable from a contracted shape to an
expanded shape; and a plurality of self-expanding stent segments
carried within the first lumen in a collapsed configuration, the
stent segments being adapted to resiliently expand from the
collapsed configuration to an expanded configuration, and wherein
the stent segments are deployable from the first lumen so as to
resiliently expand into the expanded configuration, the stent
bumper being expandable independently of the stent segments and
configured in the expanded shape to engage a first stent segment
during deployment thereof to maintain its position relative to an
adjacent stent segment disposed proximal to the first stent
segment, and wherein the sheath is disposed over the balloon and
the sheath is retractable to expose a portion of the stent bumper
to allow it to expand from the contracted shape to the expanded
shape.
2. A system as in claim 1, wherein the stent bumper in the expanded
shape has an outer diameter sized to contact an inner wall of the
body lumen.
3. A system as in claim 1, wherein the stent bumper in the expanded
shape has an outer diameter sized to contact an inner wall of at
least one of the expanded stents.
4. A system as in claim 1, wherein the stent bumper comprises an
inflatable balloon.
5. A system as in claim 4, wherein the balloon is adapted to be
deflated, positioned within the deployed first stent segment, and
re-inflated to the expanded shape.
6. A system as in claim 5, wherein the balloon in the expanded
shape is adapted to further expand the deployed first stent
segment.
7. A system as in claim 1, wherein the axial length of the elongate
balloon is between 20 mm and 250 mm.
8. A system as in claim 1, wherein each of the stent segments has a
length of between 3 mm and 30 mm.
9. A system as in claim 1, wherein the plurality of stent segments
comprises between 2 and 50 segments.
10. A system as in claim 1, further comprising a pusher slidably
disposed over the shaft, proximal to the stent segments, for
advancing the stent segments relative to the sheath or holding the
stent segments in place while the sheath is retracted.
11. A system as in claim 1, wherein the stent bumper is adapted to
be moved to the expanded shape while at least a portion of the
stent segments remain in the collapsed configuration.
12. A system as in claim 1, wherein the stent bumper engages the
first stent segment as it expands thereby maintaining position of
the first stent segment relative to the sheath.
13. A system as in claim 1, wherein two or more stent segments are
deployed sequentially without repositioning the delivery catheter
relative to the body lumen.
14. A system as in claim 1, wherein the stent bumper maintains the
position of each stent segment during deployment such that adjacent
stent segments do not overlap and a spacing between adjacent stent
segments is no more than about 1 mm after deployment.
15. A method of delivering a stent to a body lumen comprising:
positioning a stent delivery catheter in the body lumen, the
delivery catheter carrying at least first and second stent
segments; expanding a stent bumper on the delivery catheter;
releasing the first stent segment from the delivery catheter into
the body lumen after the stent bumper has been fully expanded, the
first stent segment resiliently self-expanding into an expanded
configuration in the body lumen, wherein the stent bumper expands
independently of the first stent segment and engages the first
stent segment during expansion thereof to maintain its position
relative to the delivery catheter; before releasing the second
stent segment, contracting the stent bumper; positioning the
contracted stent bumper within the expanded first stent segment;
re-expanding the stent bumper, wherein the stent bumper engages the
second stent segment during expansion thereof to maintain its
position relative to the delivery catheter and the first segment;
and releasing the second stent segment from the delivery catheter
into the body lumen adjacent to the first stent segment, wherein
the stent bumper maintains the position of each stent segment
during deployment such that adjacent stent segments do not overlap
and a spacing between adjacent stent segments is no more than about
1 mm after deployment.
16. A method as in claim 15, wherein expanding the stent bumper
comprises inflating a balloon.
17. A method as in claim 16, further comprising, before inflating
the balloon, exposing a portion of the balloon from the distal end
of an inner sheath disposed over the balloon.
18. A method as in claim 15, wherein releasing each stent segment
comprises: maintaining an axial position of the stent segments
relative to the delivery catheter using a pusher member of the
catheter; and retracting an outer sheath disposed over the stent
segments.
19. A method as in claim 15, wherein releasing each stent segment
comprises: maintaining an axial position of an outer sheath
disposed over the stent segments relative to the delivery catheter;
and advancing the stent segments out of a distal end of the sheath
using a pusher member of the catheter.
20. A method as in claim 15, wherein the first and second stent
segments are released sequentially without repositioning the
delivery catheter relative to the body lumen.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/944,282 (Attorney Docket No.
021629-003000US) now U.S. Pat. No. 7,300,456 which is a
continuation-in-part of U.S. patent application Ser. No. 10/879,949
(Attorney Docket No. 021629-002700US), filed Jun. 28, 2004, all of
which are hereby incorporated fully by reference.
BACKGROUND OF THE INVENTION
[0002] Stents are tubular prostheses designed for implantation in a
vessel to maintain patency of the vessel lumen. Stents are used in
various vessels throughout the body, including the coronary
arteries, femoral arteries, iliac arteries, renal artery, carotid
artery, vascular grafts, biliary ducts, trachea, and urethra.
Stents are typically implanted by means of long, flexible delivery
catheters that carry the stents in a compact, collapsed shape to
the treatment site and then deploy the stents into the vessel. In
some applications, balloon expandable stents are used. These stents
are made of a malleable metal such as stainless steel or cobalt
chromium and are expanded by means of a balloon on the tip of the
delivery catheter to plastically deform the stent into contact with
the vessel wall. In other applications, self-expanding stents are
used. These are made of a resilient material that can be collapsed
into a compact shape for delivery via catheter and that will
self-expand into contact with the vessel when deployed from the
catheter. Materials commonly used for self-expanding stents include
stainless steel and elastic or superelastic alloys such as nickel
titanium (Nitinol.TM.).
[0003] While self-expanding stents have demonstrated promise in
various applications, such stents face a number of challenges. One
such challenge is that in some cases the disease in a vessel may be
so extensive that a stent of very long length, e.g. 30-200 mm, is
called for. Currently available stents are typically less than 30
mm in length, and suffer from excessive stiffness if made longer.
Such stiffness is particularly problematic in peripheral vessels
such as the femoral arteries, where limb movement requires a high
degree of flexibility in any stent implanted in such vessels.
[0004] To overcome the stiffness problem, the idea of deploying
multiple shorter stents end-to-end has been proposed. However, this
approach has suffered from several drawbacks. First, currently
available delivery catheters are capable of delivering only a
single stent per catheter. In order to place multiple stents,
multiple catheters must be inserted, removed and exchanged,
heightening risks, lengthening procedure time, raising costs, and
causing excessive material waste. In addition, the deployment of
multiple stents end-to-end suffers from the inability to accurately
control stent placement and the spacing between stents. This
results in overlap of adjacent stents and/or excessive space
between stents, which is thought to lead to complications such as
restenosis, the renarrowing of a vessel following stent placement.
With self-expanding stents the problem is particularly acute,
because as the stent is released from the catheter, its resiliency
tends to cause it to eject or "watermelon seed" distally from the
catheter tip by an unpredictable distance. During such deployment,
the stent may displace not only axially but rotationally relative
to the delivery catheter resulting in inaccurate, uncontrollable,
and unpredictable stent placement.
[0005] Interleaving stents or stent segments such as those
disclosed in co-pending U.S. patent application Ser. No. 10/738,666
(Attorney Docket No. 021629-000510US), filed Dec. 16, 2003, which
is incorporated herein by reference, present even greater
challenges to conventional delivery systems. Interleaving stents
have axially extending elements on each end of the stent that
interleave with similar structures on an adjacent stent. Such
interleaving minimizes the gap between adjacent stents and
increases vessel wall coverage to ensure adequate scaffolding and
minimize protrusion of plaque from the vessel wall. However, such
interleaving requires that the relative rotational as well as axial
positions of the adjacent stents be maintained during deployment to
avoid metal overlap and excessive gaps between stents. Conventional
delivery systems suffer from the inability to control both the
axial and rotational positions of self-expanding stents as they are
deployed. These issues are addressed, in part, in co-pending U.S.
patent application Ser. No. 10/879,949, which was previously
incorporated by reference. "Watermelon seeding" of self-expanding
stents, where the resiliency of the stents causes them to eject
distally from the catheter tip by an unpredictable distance,
continues to be a challenge.
[0006] What are needed, therefore, are stents and stent delivery
system that overcome the foregoing problems. In particular, the
stents and stent delivery systems should facilitate stenting of
long vascular regions of various lengths without requiring the use
of multiple catheters. Such stents and delivery systems should also
provide sufficient flexibility for use in peripheral vessels and
other regions where long and highly flexible stents might be
required. In addition, the stents and stent delivery systems should
enable the delivery of multiple stents of various lengths to one or
more treatment sites using a single catheter without requiring
catheter exchanges. Further, the stents and stent delivery systems
should facilitate accurate and repeatable control of stent
placement and inter-stent spacing to enable deployment of multiple
self-expanding stents end-to-end in a vessel at generally constant
spacing and without overlap. In particular, the stents and delivery
systems should enable the deployment of interleaving stents or
stent segments with precision and control over the axial spacing of
each stent or segment.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention provides prostheses, prosthesis
delivery systems, and methods of prosthesis deployment that enable
the precise and controllable delivery of multiple prostheses using
a single delivery catheter. The prostheses, delivery systems, and
methods of the invention provide for the precise control of
prosthesis placement so that inter-prosthesis spacing is maintained
at a constant and optimum distance. In some embodiments, both axial
and rotational displacement of the prostheses relative to the
delivery catheter is controlled during deployment, enabling the
delivery of multiple prostheses that interleave with one another
without overlap. The prostheses, prosthesis delivery systems, and
methods of the invention further enable the length of prostheses to
be customized in situ to match the length of the site to be
treated. The invention is particularly useful for delivery of
self-expanding prostheses, but balloon expandable prostheses are
also contemplated within the scope of the invention. The invention
is well-suited to delivery of stents to the coronary arteries and
to peripheral vessels such as the popliteal, femoral, tibial,
iliac, renal, and carotid arteries. The invention is further useful
for delivery of prostheses to other vessels including biliary,
neurologic, urinary, reproductive, intestinal, pulmonary, and
others, as well as for delivery of other types of prostheses to
various anatomical regions, wherever precise control of prosthesis
deployment is desirable.
[0008] In a first aspect of the invention, a catheter system for
delivery of a stent to a body lumen includes a stent delivery
catheter and a plurality of stent segments. The stent delivery
catheter includes a sheath having a first lumen, a shaft extending
through the first lumen and slidable relative to the sheath, and a
stent bumper mounted to the shaft distally of the sheath and
movable from a contracted shape to an expanded shape. The plurality
of self-expanding stent segments is carried within the first lumen
in a collapsed configuration, and the segments are adapted to
resiliently expand from the collapsed configuration to an expanded
configuration. The stent segments are deployable from the first
lumen so as to expand into the expanded configuration, while the
stent bumper is configured to engage a first stent segment during
deployment thereof to maintain its position relative to an adjacent
stent segment disposed proximal to the first stent segment.
[0009] In a number of embodiments, the stent bumper in the expanded
shape has an outer diameter sized to contact an inner wall of the
body lumen. The bumper may thus prevent distal migration of the
stent segments and be stable in the vessel, without tilting,
deflecting or slipping. In some embodiments, at least a portion of
the stent bumper includes a lubricious surface for contacting one
or more of the stent segments. For example, a proximal surface or
portion of the stent bumper may have such a coating.
[0010] The bumper itself may have any of a number of suitable
shapes, sizes and configurations, and may be made of any suitable
material or combinations of materials. In some embodiments, for
example, the stent bumper may comprise an expandable basket, a
plurality of expandable blades, rods or petals, an expandable disk,
a proximal portion of a nosecone at the distal end of the catheter
shaft, or the like. In a preferred embodiment, the stent bumper
comprises an inflatable balloon. In such embodiments, the catheter
typically further includes an inflation lumen in the shaft (or
elsewhere in the catheter), which is in fluid communication with
the inflatable balloon. In some embodiments, the balloon is adapted
to be deflated, positioned within the deployed first stent segment,
and re-inflated to the expanded shape. Optionally, the balloon in
the expanded shape may be adapted to further expand the deployed
first stent segment. In an alternative embodiment, an elongate
balloon is used, the balloon having an axial length at least as
long as two stent segments. In one embodiment, for example, the
axial length of the elongate balloon is between about 20 mm and
about 250 mm. In such embodiments, the catheter may further include
an inner sheath disposed over the balloon, with the inner sheath
being retractable to expose a portion of the balloon to allow it to
be inflated from the contracted shape to the expanded shape. In
some embodiments, the balloon is adapted to be expanded within one
or more deployed stent segments to further expand the segments.
[0011] Any suitable stents or stent segments may be used. Examples
of self-expanding stents are described in U.S. patent application
Ser. No. 10/879,949, which was previously incorporated by
reference, but any other suitable self-expanding stents or stent
segments may be substituted in various embodiment. In some
embodiments, balloon expandable stents may be used. In various
embodiments, the stent segments may be made of Nitinol, other
superelastic alloys, stainless steel, cobalt chromium, other
resilient metals, polymers or any other suitable material.
Additionally, each stent segment may have any suitable length. In
some embodiments, for example, each stent segment has a length of
between about 3 mm and about 30 mm, and more preferably between
about 4 mm and about 20 mm. Furthermore, any suitable number of
stent segments may be loaded onto the catheter in various
embodiments. For example, some embodiments may include between 2
and 50 segments. In some embodiments, the catheter may additionally
include a pusher slidably disposed over the shaft, proximal to the
stent segments, for advancing the stent segments relative to the
sheath or holding the stent segments in place while the sheath is
retracted.
[0012] In another aspect of the invention, a method of delivering a
stent to a body lumen involves: positioning a stent delivery
catheter in the body lumen, the delivery catheter carrying at least
first and second stent segments; expanding a stent bumper on the
delivery catheter; releasing the first stent segment from the
delivery catheter into the body lumen proximal to the stent bumper,
the first stent segment self-expanding into an expanded
configuration in the body lumen, wherein the stent bumper engages
the first stent segment during expansion thereof to maintain its
position relative to the delivery catheter; and releasing the
second stent segment from the delivery catheter into the body lumen
adjacent to the first stent segment.
[0013] In a preferred embodiment, expanding the stent bumper
involves inflating a balloon. Optionally, such a method may further
include, before releasing the second stent segment: deflating the
balloon; positioning the deflated balloon within the expanded first
stent segment; and inflating the balloon, wherein the balloon
engages the second stent segment during expansion thereof to
maintain its position relative to the delivery catheter and the
first segment. In some embodiments, inflating the balloon within
the first segment further expands the first segment. The method may
further involve: deflating the balloon; positioning the deflated
balloon within the expanded second stent segment; and inflating the
balloon, wherein the balloon engages a third stent segment during
expansion thereof to maintain its position relative to the delivery
catheter and the first and second segments. These steps of
deflating, positioning and inflating may be repeated as many times
as desired to deploy a desired number of stent segments.
[0014] In an alternative embodiment, before expanding the balloon,
a portion of the balloon is exposed from the distal end of an inner
sheath that is disposed over the balloon. Such a method may
optionally further involve, before releasing the second stent
segment: exposing an additional portion of the balloon from the
distal end of the inner sheath, the additional portion disposed
within the expanded first stent segment; and inflating the balloon,
wherein the balloon engages the second stent segment during
expansion thereof to maintain its position relative to the delivery
catheter and the first segment. In some embodiments, inflating the
additional portion of the balloon further expands the expanded
first stent segment.
[0015] Rather than inflating a balloon, in alternative embodiments
expanding the stent bumper involves deploying one or more other
structures on the catheter device. In one embodiment, for example,
a basket of resilient polymer or metal mesh is expanded. In some
embodiments, expanding the stent bumper involves releasing one or
more shape-memory members from constraint. For example, the
shape-memory member(s) may include blades, rods, petals, rings or
the like, made of metal, polymer or other resilient material.
[0016] The stents may be released from the delivery catheter via
any suitable means. In one embodiment, for example, releasing each
stent segment involves maintaining an axial position of the stent
segments relative to the delivery catheter using a pusher member of
the catheter and retracting an outer sheath disposed over the stent
segments. Alternatively, releasing each stent segment may involve
maintaining an axial position of an outer sheath disposed over the
stent segments relative to the delivery catheter and advancing the
stent segments out of a distal end of the sheath using a pusher
member of the catheter.
[0017] Further aspects of the nature and advantages of the
invention will be apparent from the following detailed description
of various embodiments of the invention taken in conjunction with
the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a side, partially cut-away view of a prosthesis
delivery catheter according to one embodiment of the present
invention.
[0019] FIGS. 2A and 2B are side cross-sectional views of a distal
portion of a prosthesis delivery catheter with a stent bumper in a
vessel according to one embodiment of the present invention,
showing outer shaft retracted with prosthesis partially deployed,
and prosthesis fully deployed, respectively.
[0020] FIGS. 3A-3F are side cross-sectional views of a distal
portion of a prosthesis delivery catheter with a stent bumper in a
vessel according to one embodiment of the present invention,
demonstrating a method for deploying stents in a vessel.
[0021] FIGS. 4A-4C are side cross-sectional view of a distal
portion of a prosthesis delivery catheter with a stent bumper in a
vessel according to another embodiment of the present invention,
demonstrating an alternative method for deploying stents in a
vessel.
[0022] FIG. 5 is a side cross-sectional view of a distal portion of
a prosthesis delivery catheter with a stent bumper in a vessel
according to another embodiment of the present invention.
[0023] FIG. 6 is a side cross-sectional view of a distal portion of
a prosthesis delivery catheter with a stent bumper in a vessel
according to another embodiment of the present invention.
[0024] FIG. 7 is a side cross-sectional view of a distal portion of
a prosthesis delivery catheter with a stent bumper in a vessel
according to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Referring to FIG. 1, a first embodiment of a prosthesis
delivery catheter 20 according to the invention is illustrated.
Delivery catheter 20 may have any of various constructions,
including those described in co-pending U.S. patent application
Ser. No. 10/637,713, (Attorney Docket No. 021629-000340US), filed
Aug. 8, 2003; Ser. No. 10/874,859 (Attorney Docket No.
021629-000350US), filed Jun. 22, 2004; and Ser. No. 10/884,616,
(Attorney Docket No. 021629-000360US), filed Jul. 2, 2004, all of
which are hereby incorporated by reference. Delivery catheter 20
has a handle assembly 21 and an elongated catheter body 22 that
includes three concentric tubular shafts, all axially slidable
relative to one another: an outer shaft 24, a pusher 26, and an
inner shaft 28. A distal portion of delivery catheter 20 is shown
schematically and in partial cutaway view for clarity. The distal
portion, as well as other portions of delivery catheter 20 may
include additional features not shown. For example, a typical
embodiment includes a guidewire tube/lumen for allowing passage of
a guidewire. Such features are described in further detail, for
example, in the co-pending patent applications described
immediately above.
[0026] Outer shaft 24 has a distal extremity 46 defining a first
lumen 48. A plurality of stents 50 (or stent segments) are disposed
in a collapsed configuration within first lumen 48. Stents 50 are
preferably composed of a resilient material such as stainless steel
or Nitinol so as to self-expand from the collapsed configuration to
a radially expanded configuration when deployed from first lumen
48. While stents 50 as illustrated have a wave-like or undulating
pattern in a plurality of interconnected circumferential members,
the pattern illustrated is merely exemplary and the stents of the
invention may have any of a variety of strut shapes, patterns, and
geometries. From 2 up to 10 or more stents may be carried by outer
shaft 24. Optionally, a valve member 49 is mounted within first
lumen 48 to facilitate separating those stents 50 to be deployed
from those to remain within outer shaft 24, as described in
co-pending U.S. patent application Ser. No. 10/412,714 (Attorney
Docket No. 021629-000330US), filed Apr. 10, 2003, which is
incorporated herein by reference.
[0027] Coupled with inner shaft 28 is an expandable stent bumper
60. In various embodiments, stent bumper 60 may comprise an
expandable wire or mesh basket, an expandable ring, shape-memory
members such as petals, blades, prongs or other protrusions, or any
of a number of other configurations. In a preferred embodiment, as
shown, stent bumper 60 is an inflatable balloon. In some
embodiments, stent bumper 60 is inflatable via an inflation lumen
disposed within inner shaft 28. Such an inflation lumen may
alternatively be disposed on an outer surface of inner lumen 28 or
the like. In some embodiments, stent bumper 60 may be attached to,
or a proximal extension of, a nosecone 36 of delivery catheter 20.
When expanded, stent bumper 60 helps control the deployment of
stents 50. For example, if stent bumper 60 is expanded and a stent
50' is deployed out of the distal end of catheter body 46, stent
bumper 60 has a diameter large enough, in its expanded
configuration, to stop deployed stent 50' from moving distally,
thus preventing "watermelon seeding" of stent 50'. The operation of
stent bumper 60 will be described further below with reference to
subsequent drawing figures.
[0028] Handle assembly 21 has a rotatable retraction knob 52
coupled to a shaft housing 53, to which outer shaft 24 is fixed. By
rotating retraction knob 52, outer shaft 24 may be retracted
proximally relative to pusher 26 and inner shaft 28. A switch 56
engages and disengages pusher 26 with outer shaft 28, so that
pusher 26 either moves with outer shaft 24 or remains stationary as
outer shaft 24 is retracted. Indicia 58 on shaft housing 53
indicate the extent of retraction of outer shaft 28 by distance,
number of stents, or other suitable measure. Other aspects of
handle assembly 21 are described in co-pending application Ser. No.
10/746,466 (Attorney Docket No. 021629-002200US), filed Dec. 23,
2003, which is hereby incorporated by reference. Except as stated
otherwise, any of the embodiments of the stent delivery catheter
described below may incorporate the features, and be otherwise
constructed as, just described.
[0029] With reference now to FIGS. 2A and 2B, in some embodiments,
a stent delivery catheter 180 includes an stent bumper 160
comprising an inflatable balloon. Delivery catheter 180 has a
plurality of stents 182 disposed in an outer shaft 184. An inner
shaft 186, with a distal nosecone 190, extends through outer shaft
184 and stents 182 and is axially movable relative thereto. A
pusher shaft (not shown) is slidably disposed over inner shaft 186
and engages stents 182 for purposes of deploying stents 182 from
outer shaft 186 and repositioning the remaining stents 182 within
outer shaft 186, as in earlier embodiments. In this embodiment,
stents 182 comprise a plurality of struts 191 forming a series of
rings 192 interconnected at joints 193. Each ring 192 has a series
of closed cells 194 interconnected circumferentially and having an
"I" shape in the unexpanded configuration. Other aspects of stents
182 are described in co-pending U.S. application Ser. No.
10/738,666, which was previously incorporated by reference.
[0030] As outer shaft 184 is retracted to deploy one or more stents
182, at least a distal ring 192' is configured to expand into
engagement with stent bumper 160 before the entire length of stent
182 is deployed from outer shaft 184 (FIG. 2A). Once distal ring
192' is engaged with stent bumper 160, the remainder of stent 182
is deployed (FIG. 2B), stent bumper 160 thus preventing "watermelon
seeding" of stent 182 from catheter 180. Each stent 182 has at
least two, and preferably four or more rings 192, each ring being
about 2-5 mm in length, giving stent 182 an overall length of at
least about 8-20 mm. Of course, stents of shorter or longer length
are also contemplated within the scope of the invention. Lesions
longer than each stent 182 may be treated by deploying multiple
stents 182 end-to-end. Advantageously, each stent 182 can be
deployed precisely at a desired spacing from a previously-deployed
stent 182 because stent bumper 160 prevents unwanted overlapping
of, or gaps between, stents 182 caused by watermelon seeding.
[0031] Rings 192 are preferably formed from a common piece of
material and are integrally interconnected at joints 193, making
joints 193 relatively rigid. In this embodiment, the majority of
flexibility between rings 192 is provided by struts 191 rather than
by joints 193. Alternatively, joints 193 may comprise welded
connections between rings 192 which are also fairly rigid. As a
further alternative, joints 193 may comprise hinge or spring
structures to allow greater deflection between adjacent rings
192.
[0032] In various alternative embodiments, any of a number of
alternative stents with alternative designs, shapes, sizes,
materials and/or the like may be used. For example, a number of
exemplary self-expanding stents that may be used with delivery
catheter 180 are described in co-pending U.S. patent application
Ser. Nos. 10/879,949 and 10/738,666, which were previously
incorporated by reference. Stents 192 may be made of any suitable
material, such as but not limited to Nitinol.TM., a superelastic
alloy, stainless steel, cobalt chromium, other resilient metals,
resilient polymers or the like. In some embodiments, stent 192 may
be balloon expandable, rather than self-expanding, although this
description focuses on the preferred self-expanding
embodiments.
[0033] Various alternative types of interconnecting structures
between adjacent stents and between the stents and the pusher shaft
are also possible within the scope of the invention, including
those described in co-pending application Ser. No. 10/738,666,
previously incorporated by reference. Such interconnecting
structures may also be breakable or frangible to facilitate
separation as the stent expands. In addition, a mechanism such as
an expandable balloon or cutting device may be disposed at the
distal end of delivery catheter 180 to assist in separating stents
192 upon deployment. Further, the interconnections between stents
may be different than the interconnection between the proximal-most
stent and the pusher shaft. For example, the pusher shaft may have
hooks, magnets, or other mechanisms suitable for releasably holding
and maintaining traction on the proximal end of a stent until it is
deployed.
[0034] Referring to FIGS. 3A-3F, a method for deploying stents in a
vessel is shown schematically. In FIG. 3A, a stent delivery
catheter 210 is positioned within a vessel V, such that a nosecone
212 attached to the distal end of an inner shaft 216 of catheter
210 is distal to a lesion L. A stent bumper 260 coupled with inner
shaft 216 is expanded (in this case an inflated balloon) to contact
the vessel wall. Multiple stents 250 (or stent segments) are housed
within an outer shaft 220 or sheath of catheter 210, and a pusher
214 is used to maintain the axial position of stents 250 relative
to outer shaft 220.
[0035] In FIG. 3B, outer shaft 220 is retracted relative to stents
250 and inner shaft 216, while pusher 214 maintains the relative
axial position of stents 250. As outer shaft 220 is retracted, a
distal stent 250' begins to be deployed out of its distal end.
Distal stent 250' contacts stent bumper 260, which prevents stent
250' from ejecting ("watermelon seeding") distally. FIG. 3C shows
distal stent 250' fully deployed within the vessel V.
[0036] As shown in FIG. 3D, after a first distal stent 250' has
been fully deployed, stent bumper 260 may be deflated, repositioned
with distal stent 250', and re-expanded. In some cases, this
re-expansion helps further expand distal stent 250', thus enhancing
its ability to prop open the vessel V. Turning to FIG. 3E, after
re-expansion of stent bumper 260, outer shaft 220 may again be
retracted relative to stents 250 and inner shaft 216, thus
deploying a second distal stent 250''. Second distal stent 250''
contacts stent bumper 260, thus again avoiding watermelon seeding,
which might cause stents 250'' and 250' to overlap. FIG. 3F shows
first distal stent 250' and second distal stent 250'' fully
deployed within the vessel. This process may be repeated as many
times as desired, to deploy as many stents 250 (or stent segments)
as desired.
[0037] Referring now to FIGS. 4A-4C, in an alternative embodiment,
a stent delivery catheter 310 may include a stent bumper 360 that
comprises an elongate inflatable balloon. In such an embodiment,
first distal stent 250' is deployed the same way as shown in FIGS.
3A-3C. As shown in FIG. 4A, after deployment of first distal stent
250', a sheath 322 disposed over a proximal portion of stent bumper
360 is retracted proximally to expose an additional portion of
stent bumper 360, and the newly exposed portion of the inflatable
balloon stent bumper 360 is inflated within first distal stent
250'. As described above, stent bumper 360 in some embodiments may
be used to further expand an already-expanded distal stent
250'.
[0038] As shown in FIG. 4B, second distal stent 250'' is then
deployed from the distal end of outer shaft 220 to contact stent
bumper 360. In FIG. 4C, second distal stent 250'' is fully
deployed, sheath 322 has been retracted farther proximally, and an
additional portion of stent bumper 360 has been inflated within
second distal stent 250''. This process may be repeated as many
times as desired to deploy as many stents 250 as desired.
[0039] Referring now to FIG. 5, an alternative embodiment of a
stent delivery catheter 410 includes an expandable wire structure
460 that acts as a stent bumper. Wire structure 460 acts
analogously to the stent bumpers described above. In the embodiment
shown, wire structure 460 is made of shape memory, super-elastic or
other resilient material and assumes its expanded shape when
exposed from the distal end of a sheath 422. Sheath 422 may be
retracted farther proximally to expose additional portions of wire
structure 460 to help deploy additional stents 250. In other
embodiments, a wire ring or tube, expandable wire basket, mesh
basket or the like may be pushed by a proximal pusher member or
pulled by a puller coupled to its distal end to force the
expandable stent bumper to buckle or otherwise expand.
[0040] In another embodiment, and with reference now to FIG. 6, a
stent delivery catheter 510 include a stent bumper 560 comprising
multiple self-expanding petals 562 (or alternatively prongs,
blades, bristles or the like) coupled to an outer shaft 522
slidable over inner shaft 216. Petals 562 are normally disposed
within nosecone 212 and deploy/expand when inner shaft 216, to
which nosecone 212 is attached, is advanced distally relative to
outer shaft 522, thereby exposing petals 562. Nosecone 212 may be
advanced further to allow greater expansion of petals 562 or to
expose additional sets of petals 562. Petals 562 may be made of
metal, polymer or any other suitable resilient material(s).
[0041] Referring now to FIG. 7, in another embodiment, a stent
delivery catheter 610 includes a stent bumper 660 comprising
multiple self-expanding prongs 662 coupled with inner shaft 216.
Before deployment, prongs 662 are disposed with a sheath 632
slidably disposed over inner shaft 216. When sheath 632 is
retracted proximally relative to inner shaft 216 and/or inner shaft
216 is advanced relative to sheath 632, prongs 662 are exposed,
thus allowing them to assume their expanded configuration, as
shown. After deploying first stent 250', which is prevented from
watermelon seeding by stent bumper 660, sheath 632 may be retracted
farther proximally and/or inner shaft 216 may be advanced farther
distally to expose a second set of prongs 662 (not shown). A second
stent 250 may then be deployed to contact the second set of prongs
662. In various embodiments, any number of stent bumpers 660/sets
of prongs 662 may be included, for promoting deployment of any
number of stents 250. Prongs 662 may be made of any resilient
material, such as Nitinol, spring stainless steel, or other
shape-memory or super-elastic materials.
[0042] While the above is a complete description of the preferred
embodiments of the invention, various alternatives, modifications,
improvements and additions are possible without departing from the
scope thereof, which is defined by the claims.
* * * * *