U.S. patent application number 11/466448 was filed with the patent office on 2007-03-08 for axially compressible flared stents and apparatus and methods for delivering them.
Invention is credited to Eliot Kim, Jeffrey A. Krolik.
Application Number | 20070055358 11/466448 |
Document ID | / |
Family ID | 37491977 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070055358 |
Kind Code |
A1 |
Krolik; Jeffrey A. ; et
al. |
March 8, 2007 |
AXIALLY COMPRESSIBLE FLARED STENTS AND APPARATUS AND METHODS FOR
DELIVERING THEM
Abstract
A stent includes a flaring portion and a main portion connected
to the flaring portion. The main portion includes a plurality of
bands of cells spaced apart axially from one another, adjacent
bands of cells being intermittently connected to one another.
During use, the stent is introduced into a main vessel in a
contracted condition and positioned with the flaring portion
adjacent an ostium. The flaring portion is flared, and the stent is
advanced at least partially into the ostium. The stent is expanded
further such that the main portion expands within the branch body
lumen and/or the flaring portion expands adjacent the ostium. The
main portion compresses axially during at least one of the steps
when the stent is expanded, which may enhance conformance of the
stent relative to the ostium and/or enhance reinforcement of the
ostium.
Inventors: |
Krolik; Jeffrey A.;
(Campbell, CA) ; Kim; Eliot; (Santa Clara,
CA) |
Correspondence
Address: |
Vista IP Law Group LLP
2040 MAIN STREET, 9TH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
37491977 |
Appl. No.: |
11/466448 |
Filed: |
August 22, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60710521 |
Aug 22, 2005 |
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60727703 |
Oct 17, 2005 |
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60757600 |
Jan 9, 2006 |
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60743880 |
Mar 28, 2006 |
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60745177 |
Apr 19, 2006 |
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Current U.S.
Class: |
623/1.31 |
Current CPC
Class: |
A61F 2/915 20130101;
A61F 2230/0067 20130101; A61F 2250/0039 20130101; A61M 25/1002
20130101; A61F 2250/0018 20130101; A61F 2002/91525 20130101; A61F
2250/0026 20130101; A61F 2/958 20130101; A61F 2002/30322 20130101;
A61F 2/91 20130101; A61F 2230/005 20130101; A61F 2002/821 20130101;
A61F 2002/91533 20130101; A61F 2002/91558 20130101; A61F 2230/0054
20130101 |
Class at
Publication: |
623/001.31 |
International
Class: |
A61F 2/06 20060101
A61F002/06 |
Claims
1. A stent comprising a tubular member including first and second
ends defining a longitudinal axis therebetween and a plurality of
cells disposed between the first and second ends, the tubular
member being expandable from a contracted condition to an enlarged
condition, the stent comprising: a first flaring portion configured
to flare outwardly when the stent is expanded from the contracted
condition to the enlarged condition; and a second main portion
adjacent the first portion, the second portion comprising a
plurality of bands of cells connected to one another such that the
main portion is axially compressible when the stent is expanded
from the contracted condition to the enlarged condition.
2. The stent of claim 1, wherein the first flaring portion has a
radial strength less than the main portion.
3. The stent of claim 1, wherein adjacent bands of cells of the
main portion are only intermittently connected to one another.
4. The stent of claim 1, wherein each of the bands of cells of the
main portion comprises axial segments connected by alternating
curved segments around a circumference of the stent, and wherein a
plurality of links extend between opposing curved segments of
adjacent bands of cells to connect the adjacent bands of cells.
5. The stent of claim 4, wherein the links extend between only some
of the opposing curved segments of adjacent bands of cells.
6. The stent of claim 4, wherein the links extend between only
every other set of opposing curved segment of adjacent bands of
cells.
7. The stent of claim 4, wherein at least one set of unconnected
opposing curved segments is disposed between opposing curved
segments connected by links.
8. The stent of claim 1, wherein the first flaring portion
comprises: a first set of cells disposed at the first end, the
first set of cells comprising first axial segments in the
contracted condition; and a second set of cells disposed adjacent
the first set of cells, the second set of cells comprising second
axial segments in the contracted condition, wherein the first axial
segments transition to extend at least partially circumferentially
in the expanded configuration, and the second axial segments
transition to extend at least partially radially outwardly in the
expanded configuration.
9. The stent of claim 8, wherein a ratio of a diameter of the first
flaring portion to the second main portion in the enlarged
condition is between about 1.1 and 1.8.
10. The stent of claim 1, wherein the first flaring portion is
connected to the second main portion by a plurality of connectors
comprising curvilinear segments having a thickness and a width, at
least one of the thickness and the width being thinner than
segments comprising the first flaring portion.
11. A stent comprising a tubular member including first and second
ends defining a longitudinal axis therebetween and a plurality of
cells disposed between the first and second ends, the tubular
member being expandable from a contracted condition to an enlarged
condition through an intermediate condition, the stent comprising:
a first flaring portion configured to flare outwardly when the
stent is expanded from the contracted condition to the intermediate
condition, the first flaring portion comprising a first set of
cells at the first end and a second set of cells adjacent the first
set of cells, the second set of cells comprising segments extending
substantially axially in the contracted condition; a second main
portion adjacent the first flaring portion, the second main portion
comprising a plurality of bands of cells; and a plurality of links
intermittently extending between adjacent bands of cells of the
second main portion to allow axial compression or expansion of the
adjacent bands of cells when the stent is expanded from the
contracted condition to the expanded condition.
12. The stent of claim 11, wherein a ratio of a diameter of the
first end portion to the second end in the intermediate condition
is between about two and five.
13. The stent of claim 12, wherein a ratio of a diameter of the
first end portion to the second end in the enlarged condition is
between about 1.1 and 1.8.
14. An apparatus for treating an ostium communicating between a
main body lumen and a branch body lumen, comprising: an elongate
member comprising a proximal end, a distal end sized for
introduction into the main body lumen and the branch body lumen; a
first expandable member on the distal end, the first expandable
member being expandable from a collapsed configuration to a
generally spherical expanded configuration; a second expandable
member on the distal end adjacent the first expandable member, the
second expandable member being expandable from a collapsed
configuration to a substantially cylindrical expanded
configuration; and a stent on the distal end over the first and
second expandable members, the stent comprising a first flaring
portion overlying a portion of the first expandable member, and a
second main portion overlying the second expandable member, the
second main portion being axially compressible during expansion of
at least one of the first and second expandable members.
15. The apparatus of claim 14, wherein the first expandable member
comprises a semi-compliant or substantially compliant balloon.
16. The apparatus of claim 15, wherein the second expandable member
comprises a balloon that is less compliant than the first
expandable member.
17. The apparatus of claim 15, wherein the second expandable member
comprises a substantially non-compliant balloon.
18. The apparatus of claim 17, wherein the first and second
expandable members require respective inflation pressures to expand
to the expanded configuration, and wherein the inflation pressure
of the first expandable member is less than the inflation pressure
of the second expandable member.
19. The apparatus of claim 14, wherein the first expandable member
is expandable independently of the second expandable member using
an inflation pressure that is less than an inflation pressure
necessary to expand the second expandable member.
20. The apparatus of claim 14, wherein the first flaring portion of
the stent comprises: a first set of cells disposed at the first
end; a second set of cells disposed adjacent the first set of
cells, and a plurality of flexible connectors connecting the second
set of cells to the second portion of the stent, wherein the second
set of cells comprises struts connected to curved segments, the
curved segments having a lower yield strength than the struts.
21. The apparatus of claim 20, wherein the struts are directed from
a generally axial orientation towards a generally radially outward
orientation when the first expandable member is expanded.
22. The apparatus of claim 20, wherein the struts are directed from
the generally radially outward orientation in the flared condition
towards a circumferential orientation when the second expandable
member is expanded.
23. The apparatus of claim 20, the first set of cells comprising
struts that extend substantially axially when the stent is in a
contracted condition, the first end portion flaring such that the
struts are directed towards a circumferential orientation in the
flared condition.
24. The apparatus of claim 20, wherein the connectors comprise
curvilinear segments having a thickness and a width, at least one
of the thickness and the width being thinner than segments
comprising the first end portion.
25. The apparatus of claim 14, further comprising a source of
inflation media communicating with an interior of the first
expandable member for delivering first and second predetermined
volumes into the first expandable member to partially and fully
expand the first expandable member, respectively.
26. The apparatus of claim 25, wherein the source of inflation
media comprises a syringe comprising a barrel including inflation
media therein and a plunger, the barrel comprising first and second
markers such that, when the plunger is depressed successively to
the first and second markers, the first and second predetermined
volumes are delivered into the interior of the first expandable
member, respectively.
27. A method for expanding a stent, comprising: providing a stent
on one or more expandable members, the stent comprising first and
second ends, a first flaring portion, and a second main portion
connected to the first flaring portion; expanding an expandable
member to flare the first flaring portion; expanding an expandable
member to expand the second main portion to an enlarged condition,
thereby causing the second main portion to shorten axially.
28. A method for delivering a stent within an ostium communicating
between a main body lumen and a branch body lumen, the stent
comprising first and second ends, a first flaring portion, and a
second main portion, the method comprising: introducing the stent
into the main body lumen with the stent in a contracted condition;
flaring the first flaring portion to a first expanded size;
advancing the stent into the ostium with the first flaring portion
flared; expanding the stent such that the second main portion
expands within the branch body lumen; and expanding the stent
further such that the first flaring portion expands to a second
expanded size greater than the first expanded size, wherein the
second main portion foreshortens when at least one of the second
main portion expands within the branch body lumen and the first
flaring portion expands to the second expanded size.
Description
[0001] This application claims benefit of provisional application
Ser. Nos. 60/710,521, filed Aug. 22, 2005, 60/727,703, filed Oct.
17, 2005, 60/757,600, filed Jan. 9, 2006, 60/743,880, filed Mar.
28, 2006, and 60/745,177, filed Apr. 19, 2006, the entire
disclosures of which are expressly incorporated by reference
herein.
FIELD OF THE INVENTION
[0002] The present invention relates generally to endoluminal
prostheses or "stents," and, more particularly, to flared stents,
and to apparatus and methods for delivering such stents into an
ostium of a blood vessel or other body lumen.
BACKGROUND
[0003] Tubular endoprosthesis or "stents" have been suggested for
dilating or otherwise treating stenoses, occlusions, and/or other
lesions within a patient's vasculature or other body lumens. For
example, a self-expanding stent may be maintained on a catheter in
a contracted condition, e.g., by an overlying sheath or other
constraint, and delivered into a target location, e.g., a stenosis
within a blood vessel or other body lumen. When the stent is
positioned at the target location, the constraint may be removed,
whereupon the stent may automatically expand to dilate or otherwise
line the vessel at the target location. Alternatively, a
balloon-expandable stent may be carried on a catheter, e.g.,
crimped or otherwise secured over a balloon, in a contracted
condition. When the stent is positioned at the target location, the
balloon may be inflated to expand the stent and dilate the
vessel.
[0004] Sometimes, a stenosis or other lesion may occur at an ostium
or bifurcation, i.e., where a branch vessel extends from a main
vessel or trunk. For example, such a lesion may form within a
coronary artery immediately adjacent the aortic root. U.S. Pat. No.
5,749,890 to Shaknovich discloses a stent delivery assembly for
placing a stent in an ostial lesion. U.S. Pat. No. 5,632,762 to
Myler discloses a tapered balloon on a catheter for positioning a
stent within an ostium. U.S. Pat. No. 5,607,444 to Lam discloses an
expandable ostial stent including a tubular body and a deformable
flaring portion. Published application US 2002/0077691 to
Nachtigall discloses a delivery system that includes a sheath for
holding a stent in a compressed state during delivery and a
retainer that holds a deployable stop in an undeployed position
while the delivery system is advanced to a desired location.
[0005] FIGS. 1, 2, and 3 show attempts to deploy flared stents
within various ostia having different shapes and/or sizes, and some
of the risks of improper deployment.
[0006] Accordingly, flared stents and apparatus and methods for
delivering stents within an ostium would be useful.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to endoluminal prostheses
or "stents," and, more particularly, to flared stents, and to
apparatus and methods for delivering such stents into an ostium of
a blood vessel or other body lumen.
[0008] In accordance with one embodiment, a stent is provided that
includes a tubular member including first and second ends defining
a longitudinal axis therebetween and a plurality of cells disposed
between the first and second ends. Generally, the stent includes a
first end portion configured to flare outwardly when the stent is
expanded from the contracted condition to an intermediate flared
condition, and a second portion adjacent the first portion
configured to expand when the stent is expanded from the flared
condition to a fully deployed condition. The second portion may be
connected to the first end portion by a plurality of flexible
connectors, which may facilitate the first end portion flaring
outwardly.
[0009] In accordance with another embodiment, a stent is provided
that includes a tubular member including first and second ends
defining a longitudinal axis therebetween and a plurality of cells
disposed between the first and second ends, the tubular member
being expandable from a contracted condition to a fully expanded or
deployed condition through an intermediate flared condition. The
stent may include a first end portion configured to flare outwardly
when the stent is expanded from the contracted condition to the
flared condition, a second portion adjacent the first portion, and
a plurality of flexible connectors connecting the second portion to
the first end portion.
[0010] In an exemplary embodiment, the first end portion may
include a first set of cells at the first end and a second set of
cells adjacent the first set of cells, the second set of cells
including struts or other segments extending substantially axially
in the contracted condition. The connectors may connect the second
set of cells to the second portion such that the connectors bend to
accommodate the struts of the second set of cells assuming a
generally radially outward orientation in the flared condition. In
addition or alternatively, the first set of cells may include a
plurality of struts or other segments extending substantially
axially in the contracted condition. The axial segments of the
first set of cells may assume a generally circumferential
orientation in the fully deployed condition.
[0011] In accordance with still another embodiment, a stent is
provided that includes a tubular member including first and second
ends defining a longitudinal axis therebetween and a plurality of
cells disposed between the first and second ends. Generally, the
stent includes a first flaring portion at the first end configured
to flare outwardly when the stent is expanded from the contracted
condition to an intermediate flared condition, and a second main
portion adjacent the flaring portion configured to expand when the
stent is expanded from the flared condition to a fully deployed
condition. The main portion may include a proximal portion
immediately adjacent the flaring portion and a distal portion
extending between the proximal portion and the second end.
[0012] In one embodiment, the proximal portion may have a greater
radial strength than the distal portion. In addition or
alternatively, the distal portion may have a radial strength
greater than the flaring portion. Thus, in an exemplary embodiment,
the flaring portion may be more easily expandable than the main
portion, and the proximal portion of the main portion may have the
greatest radial strength of the stent, e.g., to facilitate
maintaining an ostium dilated after implanting the stent.
[0013] In accordance with yet another embodiment, an apparatus is
provided for treating an ostium communicating between a main body
lurnen and a branch body lumen. Generally, the apparatus includes
an elongate member including a proximal end, a distal end sized for
introduction into at least one of the main body lumen and the
branch body lumen, and an expandable member on the distal end, the
expandable member being expandable from a first collapsed
configuration to a second flared configuration and to a third
expanded configuration. A stent may be provided on the distal end
over the expandable member that includes a first end portion and a
second portion connected to the first end portion by a plurality of
flexible connectors.
[0014] The stent and/or expandable member may be configured such
that, when the expandable member is expanded to the second
configuration, the first end portion of the stent is expanded to a
flared condition, and when the expandable member is expanded to the
third configuration, the second portion is expanded radially
outwardly and the first end portion is further expanded radially
outwardly. In one embodiment, the expandable member may include a
first balloon underlying the first end portion of the stent and a
second balloon underlying at least the second portion of the stent.
The first balloon may be expandable independent of the second
balloon, e.g., such that the second flared configuration is defined
by expansion of the first balloon.
[0015] In accordance with yet another embodiment, an apparatus is
provided for treating an ostium communicating between a main body
lumen and a branch body lumen. Generally, the apparatus includes an
elongate member including a proximal end, a distal end sized for
introduction into at least one of the main body lumen and the
branch body lumen, and proximal and distal balloons on the distal
end. The balloons may be expandable from a collapsed configuration
to an expanded configuration, e.g., such that the distal balloon
adopts a substantially cylindrical shape in the expanded
configuration and the proximal balloon adopts a substantially
spherical shape in the expanded configuration.
[0016] The balloons may be independently expandable and/or
deflatable from one another. In addition or alternatively, the
proximal balloon may be compliant or semi-compliant and the distal
balloon may be substantially non-compliant.
[0017] A stent may be provided on the distal end at least partially
over the balloons that includes a first flaring portion and a
second main portion. Optionally, the second main portion may
include a more rigid proximal main portion adjacent the flaring
portion and a less rigid distal main portion. In one embodiment,
the stent may be provided on the distal end of the elongate member
such that the first flaring portion and at least a portion of the
proximal main portion overly the proximal balloon and the distal
main portion overlies the distal balloon.
[0018] In accordance with still another embodiment, a method is
provided for expanding a stent. A stent may be provided on an
expandable member, the stent including first and second ends, a
first end portion including a first set of cells at the first end
and a second set of cells adjacent the first set of cells, and a
second portion connected to the first end portion. The expandable
member may be expanded from a first collapsed configuration to a
second flared configuration to flare the first end portion, thereby
causing first struts of the first set of cells to move from a
substantially axial orientation towards a radial and partial
circumferential orientation and causing second struts of the second
set of cells to move from a substantially axial orientation towards
a radial orientation. The expandable member may then be expanded
from the second configuration to a third enlarged condition,
thereby causing the first and second struts to move towards a more
circumferential orientation. Optionally, the second set of cells
may be coupled to the second portion of the stent by a plurality of
flexible connectors, the connectors accommodating radial and/or
circumferential movement of the second struts.
[0019] In accordance with yet another embodiment, a method is
provided for delivering a stent within an ostium communicating
between a main body lumen and a branch body lumen. The stent may
include first and second ends, a first end portion including a
first set of cells at the first end and a second set of cells
adjacent the first set of cells, and a second portion connected to
the first end portion.
[0020] Initially, the stent may be introduced into the main body
lumen with the stent in a contracted condition, and positioned such
that the first end portion is disposed adjacent the ostium and the
second portion is disposed within the branch body lumen. The first
end portion may be flared, thereby causing first struts of the
first set of cells to move from a substantially axial orientation
towards a radial and partial circumferential orientation and
causing second struts of the second set of cells to move from a
substantially axial orientation towards a radial orientation.
Optionally, the stent may be further positioned, the flared first
end portion facilitating positioning relative to the ostium. The
stent may then be expanded such that the second portion expands
within the branch body lumen, and the first and second struts move
towards a more circumferential orientation, thereby securing the
stent relative to the ostium.
[0021] In accordance with another embodiment, a method is provided
for expanding a stent that includes providing a stent on one or
more expandable members, the stent including first and second ends,
a first portion and a second portion connected to the first flaring
portion. An expandable member is expanded to flare the first
portion, the second portion having sufficient stiffness to resist
expansion when the first portion is flared. An expandable member is
expanded to expand the second portion to an enlarged condition,
thereby causing the first portion to expand further. In one
embodiment, the second portion includes a distal main portion and a
proximal main portion connecting the first portion to the distal
main portion. The proximal main portion may include a stiffness,
radial strength, and/or other characteristics such that the
proximal main portion resists expansion when the first flaring
portion is flared.
[0022] In accordance with yet another embodiment, a method is
provided for delivering a stent within an ostium communicating
between a main body lumen and a branch body lumen, the stent
including a first flaring portion, and a second main portion
including a distal main portion and a proximal main portion
connecting the distal main portion to the first flaring portion.
The stent is introduced into the main body lumen stent in a
contracted condition. The first flaring portion is expanded to a
flared configuration, e.g., by expanding a first expandable member.
The proximal main portion, which may partially overly the first
expandable member, may resist expansion when the first flaring
portion is flared by the first expandable member. The stent is
expanded further, e.g., by expanding a second expandable member,
such that the second main portion expands within the branch body
lumen, and the first flaring portion expands further adjacent the
ostium. The proximal main portion may have a greater radial
strength than the distal main portion, thereby providing enhanced
support of the ostium than more distally within the branch body
lumen.
[0023] In accordance with still another embodiment, a stent is
provided that includes a tubular member including first and second
ends defining a longitudinal axis therebetween and a plurality of
cells disposed between the first and second ends, the tubular
member being expandable from a contracted condition to an enlarged
condition. Generally, the stent includes a first flaring portion
configured to flare outwardly when the stent is expanded from the
contracted condition to the enlarged condition, and a second main
portion adjacent the first flaring portion.
[0024] The main portion may include a plurality of bands of cells
spaced apart axially from one another with adjacent bands of cells
connected to one another. In an exemplary embodiment, adjacent
bands of cells may be intermittently or otherwise connected, e.g.,
by links, such that the main portion is axially compressible when
the stent is expanded.
[0025] In accordance with yet another embodiment, a method is
provided for delivering a stent within an ostium communicating
between a main body lumen and a branch body lumen. Generally, the
stent may include first and second ends, a first flaring portion,
and a second main portion adjacent the flaring portion. The stent
may be introduced into the main body lumen with the stent in a
contracted condition, and the flaring portion may be flared to a
first expanded size. The stent may be advanced at least partially
into the ostium with the flaring portion flared, and the stent may
be further expanded.
[0026] For example, the main portion may be expanded within the
branch body lumen, e.g., to dilate a stenosis or other lesion
adjacent to or within the ostium and/or branch, and/or to anchor
the main portion relative to the branch. The flaring portion may
then be expanded further, e.g., to a second expanded size greater
than the first expanded size, e.g., to enhance seating of the stent
relative to the ostium. The main portion may foreshorten, e.g.,
when the main portion is expanded within the branch and/or when the
flaring portion is expanded to the second expanded size. This axial
compression of the main portion may enhance seating of the stent
and/or may enhance support within lesion and/or ostium.
[0027] In accordance with still another embodiment, a stent is
provided that includes a tubular member including first and second
ends defining a longitudinal axis therebetween, and a plurality of
cells disposed between the first and second ends. The tubular
member may be expandable from a contracted condition to an enlarged
condition, the first end having a larger cross-section than the
second end in the enlarged condition. In one embodiment, the
tubular member may include a first set of cells disposed at the
first end, and a second set of cells disposed adjacent the first
set of cells, the first and second sets of cells having first and
second axial lengths, respectively, in the contracted condition,
the first axial length being substantially shorter than the second
axial length.
[0028] In accordance with yet another embodiment, a stent is
provided that is configured to be expanded from a contracted
condition to an enlarged condition, the stent including a first end
portion configured to flare outwardly when the stent is expanded
from the contracted condition to the enlarged condition; a second
intermediate portion adjacent the first portion; and a third end
portion adjacent the second portion opposite the first portion,
wherein at least two of the first, second, and third portions have
different mechanical properties.
[0029] Other aspects and features of the present invention will
become apparent from consideration of the following description
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The drawings illustrate exemplary embodiments of the
invention, in which:
[0031] FIGS. 1A-1C are cross-sectional side views of different
configurations of an ostium, showing a flared stent being deployed
therein.
[0032] FIGS. 2A and 2B are cross-sectional side views of additional
configurations of an ostium, showing a flared stent being deployed
therein.
[0033] FIGS. 3A-3C are cross-sectional side views of still
additional configurations of an ostium, showing a flared stent
being deployed therein.
[0034] FIG. 4A is a top view of a cell pattern for a stent having a
flaring portion on a first end.
[0035] FIG. 4B is a top view of another cell pattern for a stent
having a flaring portion on a first end and including radiopaque
markers on the first end.
[0036] FIGS. 5A and 5B are ends views of the first end of the stent
of FIG. 4A, showing the stent in a flared condition and a fully
expanded condition, respectively.
[0037] FIGS. 6A and 6B are perspective views of a stent delivery
catheter including a stent over a balloon thereon, showing the
stent in a flared condition and a fully expanded condition,
respectively.
[0038] FIG. 6C is a perspective view of a stent including a first
end portion and a second portion, the first end portion being
flared while the second portion remains in a contracted
condition.
[0039] FIGS. 6D and 6E are perspective views of the stent of FIG.
6C, showing the stent fully expanded to be received in relatively
large and small vessels, respectively.
[0040] FIG. 7 is a top view of a cell pattern for a stent having a
first flaring portion and a second main portion including a
proximal main portion and a distal main portion.
[0041] FIG. 8 is a side view of an exemplary embodiment of a distal
end of a stent delivery catheter including inflated proximal and
distal balloons, the proximal balloon having a substantially
spherical shape and the distal balloon having a substantially
cylindrical shape when inflated.
[0042] FIG. 9 is a side view of the distal end of the stent
delivery catheter of FIG. 8 with the proximal and distal balloons
in a collapsed configuration and showing an exemplary arrangement
for loading the stent of FIG. 7 onto the distal end.
[0043] FIGS. 10A and 10B are side views of the distal end of the
stent delivery catheter of FIG. 9, showing the proximal balloon
inflated to flare the first flaring portion of the stent and
showing the distal balloon inflated to expand the second main
portion of the stent, respectively.
[0044] FIGS. 11A-11D are perspective views of an ostium
communicating between a main vessel and a branch vessel, showing a
method for delivering a stent using the stent delivery catheter of
FIGS. 10A and 10B.
[0045] FIG. 12 is a top view of another cell pattern for a stent
having a first flaring portion and a second main portion.
[0046] FIGS. 13-19 are perspective views of an ostium communicating
between a main vessel and a branch vessel, showing a method for
delivering the stent of FIG. 12.
[0047] FIGS. 20A and 20B are details of the stent of FIGS. 12-19
before and after final flaring of the stent, respectively.
[0048] FIGS. 21A and 21B are side views of an exemplary embodiment
of a stent in contracted and enlarged conditions, respectively.
[0049] FIG. 22 is a perspective detail of a first end of the stent
of FIG. 21B, showing a first end of the stent flared radially
outwardly in the enlarged condition.
[0050] FIG. 23 is a top view of a portion of a cell pattern for the
stent of FIGS. 21A-22.
[0051] FIG. 24 is a perspective view of another embodiment of a
stent expanded to an enlarged condition such one end of the stent
is flared radially outwardly.
[0052] FIG. 25 is a side view of another embodiment of a stent
including a flared first portion and an expanded second portion and
including a membrane on the first portion.
[0053] FIGS. 26A-26F are cross-sectional views of a patient's body,
showing a method for implanting a stent at a bifurcation.
[0054] FIGS. 27A-27F are cross-sectional views of a patient's body,
showing another method for implanting a stent at a bifurcation.
[0055] FIGS. 28A-28D are cross-sectional views of a patient's body,
showing yet another method for implanting a stent at a
bifurcation.
[0056] FIG. 29 is a perspective view of another embodiment of a
flared stent including multiple portions having different
mechanical properties.
[0057] FIG. 30 is a top view of a portion of a cell pattern for a
stent having variable properties along its length.
[0058] FIG. 31 is a cross-sectional view of a bifurcation where a
branch vessel extends from a main vessel.
[0059] FIG. 32 is a graph showing exemplary desirable mechanical
properties of a stent that may be implanted in the bifurcation of
FIG. 31.
[0060] FIGS. 33-36 are top views of exemplary cell patterns for
stents having variable properties along their lengths.
[0061] FIGS. 36A-36C are details showing alternative embodiments of
links for connecting adjacent bands of cells in a stent.
[0062] FIG. 37 is a perspective view of a rivet stent.
[0063] FIGS. 38A and 38B are cross-sectional views of a bifurcation
where a branch vessel extends from a main vessel, showing a method
for treating the bifurcation using the rivet stent of FIG. 37.
[0064] FIGS. 39A-39C are cross-sectional views of a bifurcation
where a branch vessel extends from a main vessel, showing another
method for treating the bifurcation using the rivet stent of FIG.
37.
[0065] FIG. 40 is a side view of an exemplary apparatus for
delivering a rivet stent, such as that shown in FIG. 37.
[0066] FIG. 41 is a cross-sectional side view of a delivery
catheter including a distal end carrying a stent over a pair of
balloons.
[0067] FIGS. 42 and 43 are perspective views of an apparatus for
delivering a stent, including a guide catheter and the delivery
catheter of FIG. 41, showing the balloons deflated and partially
inflated, respectively, to expand the stent.
[0068] FIGS. 44-51 are cross-sectional views of a patient's body,
showing a method for positioning and/or delivering a stent within
an ostium of a body lumen using the apparatus of FIGS. 41-43.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0069] Turning to the drawings, FIGS. 4-6 show exemplary
embodiments of a stent 40 that includes a generally cylindrical
tubular member including a proximal or first end 42 and a distal or
second end 44 defining a longitudinal axis 46 therebetween. The
stent 40 is generally radially expandable from a contracted or
delivery condition (not shown), to a flared condition (e.g., as
shown in FIGS. 5A, 6A, and 6C), and to an enlarged or fully
deployed condition (e.g., as shown in FIGS. 5B, and 6B-6E). For
example, the stent 40 may include a first end portion 41 at the
first end 42 and a second portion 43 adjacent the first end portion
41, and a plurality of connectors 10 connecting the second portion
43 to the first end portion 41.
[0070] In an exemplary embodiment, the stent 40 may include a
plurality of annular bands of cells 47-49 disposed between the
proximal and distal ends 42, 44. Each band of cells 47-49 may be
defined by a plurality of struts or other elements extending
axially along and/or circumferentially around the stent 40, e.g.,
in a zigzag or serpentine pattern, thereby defining an open-cell
structure. Adjacent bands of cells may be connected to one another,
e.g., directly or via links or other elements.
[0071] For example, with particular reference to FIG. 4A, the stent
40 may include first and second bands of cells 47, 48 defining the
first end portion 41 of the stent 40. The first band of cells 47 at
the first end 42 generally includes a zigzag or serpentine pattern
defined by a plurality of axial elements 2 connected alternately by
curved elements 3 extending about the circumference of the stent
40. The axial elements 2 may be substantially straight, e.g.,
extending substantially parallel to the longitudinal axis in the
contracted condition, as shown in FIG. 4A. Alternatively, the axial
elements 2 may include more complicated geometry, e.g., including
one or more curves or bends, thereby including both an axial
component and a circumferential component (not shown). Generally,
the first band of cells 47 includes a first axial length 16
substantially parallel to the longitudinal axis 46, which may be
defined at least partially by a length of the axial elements 2,
e.g., depending upon whether the axial elements 2 extend
substantially parallel to the longitudinal axis or extend at an
angle relative to the longitudinal axis (i.e., diagonally or
circumferentially).
[0072] The second band of cells 48 adjacent the first band of cells
47 also generally includes a zigzag or serpentine pattern defined
by axial elements 5 connected alternately by curved elements 6
extending about the circumference of the stent 40. As shown, the
second band of cells 48 may define an axial length 17, which may be
substantially similar to the first band of cells 47. For example,
the axial elements 2, 5 may have substantially the same length and
the curved elements 3, 6 may have substantially the same radius of
curvature.
[0073] As shown, the axial elements 2, 5 have a thickness and/or
width that is greater than the curved elements 3, 6. Thus, the
yield strength of the curved elements 3, 6 may be less than the
axial elements 2, 5, which may facilitate radial flaring of the
first end portion 41, as explained further below.
[0074] In addition, the second band of cells 48 is connected to the
first band of cells 47 by one or more struts or other connectors 7.
Generally, the connectors 7 extend between adjacent peaks of the
zigzag patterns of the first and second bands of cells 47, 48. For
example, the connectors may be a relatively short strut that
extends between each adjacent peak of the first and second bands of
cells 47, 48, i.e., the curved elements 3, 6 closer to the first
end 42. Alternatively, the adjacent peaks may be connected directly
to one another, e.g., by adjacent curved elements 3, 6. In a
further alternative, the adjacent peaks may be intermittently
connected, e.g., indirectly by connectors or directly. For example,
only every second, third, or fourth set of adjacent peaks around
the circumference may be connected to one another.
[0075] In addition, the stent 40 may include a plurality of
additional bands of cells 49 defining the second portion 43 of the
stent 40. Each of the additional bands of cells 49 may include
axial elements 8 connected alternately to curved elements 9,
thereby defining a zigzag or serpentine and a third axial length
19. Optionally, adjacent bands of cells 49 defining the second
portion of the stent 40 may be connected via links 11, as shown, or
directly (not shown).
[0076] As shown, the axial and curved elements 8, 9 may have a
thickness and/or width that is greater than the axial elements 2,
5, and/or curved elements 3, 6. For example, the adjacent bands of
cells 49 may be relatively stiff and/or may have a higher yield
strength than the first and second bands of cells 47, 48. Thus, in
one embodiment, the second portion 43 of the stent 40 may have a
substantially uniform configuration requiring substantial plastic
deformation to expand. This configuration may be particularly
useful for dilating a branch vessel extending from an ostium.
[0077] Although each of the bands of cells 49 in the second portion
43 of the stent 40 are shown having similar configurations and
axial lengths, it will be appreciated that the dimensions and
configurations may be varied between the second band of cells 48
and the second end 44 of the stent 40, if desired. Thus, the
portion of the stent 40 between the second band of cells 48 and the
second end 44 of the stent may have a substantially homogenous cell
structure or non-uniform cell and/or band configurations, e.g., as
described elsewhere herein and in the applications incorporated by
reference above. In addition, any number of annular bands 49 may be
provided, e.g., such that the second portion 43 has a predetermined
length corresponding to a length of a lesion being dilated or
otherwise treated using the stent 40, e.g., between about three and
twenty millimeters (3-20 mm).
[0078] Alternatively, the second (e.g., non-flaring) portion 43 of
the stent 40 may include other configurations. For example, the
second portion 43 may include cells that extend circumferentially,
axially, and/or helically along the second portion. The cells may
be formed from slotted tubes, rolled sheets, and/or other
materials, as described in the applications incorporated by
reference above. Alternatively, the second portion 43 may be formed
from one or more wire structures, e.g., one or more helical wires
extending from the first (e.g., flaring) portion 41 to the second
end 44, a braid of multiple wires, and the like. Thus, in some
embodiments, the second portion 43 may be formed from any known
stent structure or configuration, while the first end portion 41
has the flared configuration described in the embodiments
herein.
[0079] Returning to FIG. 4A, the first end portion 41 of the stent
40 may be connected to the second portion 43 by a plurality of
connectors 10. In an exemplary embodiment, the connectors 10 may be
relatively thin and/or otherwise more easily deformed than the
first end portion 41 and/or the second portion 43. For example, the
connectors 10 may include curvilinear struts, e.g., defining a
portion of a sinusoid or other curve. In particular, the connectors
10 may be more flexible and/or easily deformed than the bands of
cells 47-49, which may facilitate flaring and/or expansion of the
first end portion 41, as described further elsewhere herein.
[0080] If desired, one or more portions of the stent 40 (or any of
the other embodiments described herein) may include a membrane,
film, or coating, e.g., as described in the applications
incorporated by reference above. Optionally, the stent may include
one or more radiopaque or other markers, e.g., to facilitate
monitoring the stent during advancement, positioning, and/or
expansion. For example, FIG. 4B shows a stent 40' that includes a
plurality of rings 42a extending from the first end 42. The rings
42a may be formed or coated with radiopaque material. In addition
or alternatively, the spaces within the rings 42a may be filled
with radiopaque material, e.g., by melting, pressing, laser
welding, or otherwise fixing material in the spaces. In addition or
alternatively, the stent 40 may carry one or more therapeutic or
other compounds (not shown) that may enhance or otherwise
facilitate treatment of a target location within a patient's
body.
[0081] Turning to FIGS. 6A-6E, the stent 40 may be provided
initially in a contracted condition, in which the first end portion
41 has a reduced profile (not shown), which may be similar to the
reduced profile of the second portion 43 shown in FIGS. 6A, 6C. For
example, in the contracted condition, the stent 40 may have a
substantially uniform diameter, e.g., between about one half and
two millimeters (0.5-2 mm). The stent 40 may be configured to be
directed to a flared condition, e.g., in which the first end
portion 41 is flared and the second portion 43 remains in the
reduced profile, as shown in FIGS. 5A, 6A, and 6C.
[0082] More particularly, as best seen in FIG. 5A, the first end
portion 41 may be expanded such that the first end 42 defines a
diameter or other periphery that is much larger than the second
portion. For example, the first end portion 41 may be flared to an
outer diameter of between about three to twelve millimeters (3-12
mm), e.g., about seven millimeters (7 mm). Thus, in the flared
condition, the first end portion 41 may have an outer diameter that
is two to five (2-5) times the diameter of the second portion
43.
[0083] Also, in the flared condition, the orientation of the struts
2, 5 of the first and second bands of cells 47, 48 may be directed
from substantially axial orientations to at least partially radial
and/or circumferential orientations. For example, as best seen in
FIG. 5A, the struts 5 in the second set of cells 48 may be directed
from a substantially axial orientation (not shown, see FIG. 4A) to
a radially outward orientation. As shown, the struts 5 extend
substantially radially outwardly from the central longitudinal axis
46 in the flared condition.
[0084] In addition, in the flared condition, the struts 2 of the
first band of cells 47 may be directed from a substantially axial
orientation (not shown, see FIG. 4A) to an at least partially
radial and/or circumferential orientation. As shown in FIG. 5A, the
first band of cells 47 remains in a zigzag pattern except that the
struts 2 are forced away from one another by the connectors 7 to
accommodate the flaring of the first end portion 41. As this
occurs, the curved segments 3 of the first band of cells 47 may be
plastically expanded, e.g., at least partially straightened, such
that the struts 2 extend at least partially circumferentially
around the first end 42 of the stent 40.
[0085] One feature that may accommodate the flared condition is the
flexible connectors 10. The connectors 10 may bend easily compared
to other structures of the stent 40 to allow the second band of
cells 48 to move from a cylindrical shape to a flower-petal or
frustoconical shape. Thus, it may be possible that the curved
segments 6 further from the axis 46 remain substantially undeformed
in the flared condition, and the curved segments 6 closer to the
axis 46 may be minimally deformed, i.e., the connectors 10 may bear
most of the stress induced by expansion of the stent 40 to the
flared condition.
[0086] In addition, the relative flexibility of the connectors 10
may facilitate flaring the first end portion 41 closer to ninety
degrees (90.degree.). As the first end portion 41 is directed
outwardly towards the flared condition, the second band of cells 48
may be pivoted about the connectors from the axial orientation to
the radial orientation, thereby creating a more abrupt bend. In
exemplary embodiments, the angle between the longitudinal axis and
the second band of cells 48 may be between about forty five and
ninety degrees (45-90.degree.).
[0087] Thereafter, when the second portion 43 (and optionally the
first end portion 41) of the stent 40 is expanded to the fully
expanded or deployed condition, the struts 2, 5 of the first and
second bands of cells 47, 48 may be directed to a more
circumferential orientation. With particular reference to FIG. 5B,
the struts 2 of the first band of cells 47 may be directed to a
substantially circumferential orientation and the curved segments 3
may be further straightened, e.g., such that the first band of
cells 48 approximates a circle, e.g., which may distribute the
stresses substantially equally between the struts 2 and curved
segments 3.
[0088] As the first band of cells 47 becomes approximately
circular, the second band of cells 48 may be compressed between the
first band of cells 47 and the expanding second portion 43. This
may cause the struts 5 of the second band of cells 48 to separate
from one another and extend at least partially circumferentially
around the central axis 46, thereby causing the curved segments 6
to open. Thus, in the fully deployed condition, the ratio of the
outer diameter of the first end 42 to the enlarged diameter of the
second portion 43 may decrease, e.g., to about 1.1-1.8. For
example, in the fully deployed condition, the second portion 43 may
have a diameter between about two and eight millimeters (2-8 mm)
and the first end 42 may have an outer diameter between about four
and fifteen millimeters (4-15 mm).
[0089] The stent 40 may be delivered endoluminally, e.g., using a
delivery apparatus, such as those described elsewhere herein and in
the applications incorporated by reference herein. For example,
turning to FIGS. 6A and 6B, a balloon catheter 10 may be provided
that includes a catheter or other elongate tubular member 12 having
a proximal end (not shown), a distal end 16 and one or more lumens
(not shown) extending between the proximal end and distal end 16.
One or more balloons or other expandable members 22 are provided on
the distal end 16, e.g., a first proximal balloon 22a and a second
distal balloon 22b as shown. The stent 40 may be mounted around the
distal end 16 of the catheter 12, e.g., surrounding the one or more
expandable members 22.
[0090] Optionally, the apparatus 10 may include a sheath or other
cover (not shown) that may surround or otherwise cover the stent
40. The sheath may be removable from over the proximal or distal
portions of the stent 40 or the entire stent 40 to expose the stent
40 before deployment. In addition or alternatively, the catheter 12
may include one or more radiopaque markers, e.g., markers 29
positioned on the catheter 12 adjacent the ends 42, 44 of the stent
40.
[0091] The apparatus may be used to deliver the stent 40 into an
ostium or bifurcation (not shown), i.e., an opening in a wall of a
first or main body lumen that communicates with a second or branch
body lumen. In an exemplary embodiment, the main body lumen may be
the aortic root and the branch body lumen may be a coronary or
renal artery. In another embodiment, the main body lumen may be the
aorta, and the branch body lumen may be a renal artery, or other
peripheral vessel. It will be appreciated that the apparatus and
methods described herein may be applicable to a variety of
bifurcations or branch body lumens that extend transversely, e.g.,
laterally or substantially perpendicular, from a main body lumen,
e.g., within a patient's vasculature, gastrointestinal systems, or
other systems.
[0092] Initially, a guidewire or other rail may be introduced from
the main body lumen through the ostium into the branch, e.g.,
similar to the methods described elsewhere herein. Optionally, a
guide catheter may be advanced over the guidewire into the main
body lumen, e.g., until a distal end of the guide catheter is
disposed adjacent or proximal to the ostium. The guide catheter may
be used to advance one or more instruments over the guidewire and
into the main body lumen and/or branch body lumen.
[0093] With the stent 40 in the contracted condition, the distal
end 16 of the apparatus 10 may be advanced over the guidewire
and/or through the guide catheter from the entry site into the main
body lumen. The apparatus 10 may be positioned to place the stent
40 at least partially within the ostium, e.g., such that the first
end 42 is disposed adjacent the ostium and the second end 44 is
disposed within the branch.
[0094] As shown in FIG. 6A, the first balloon 22a may be inflated
to expand the first end portion 41 of the stent 40 to the flared
condition. If the first end portion 41 is expanded adjacent the
ostium, the apparatus 10 may be advanced to abut the flared first
end portion 41 against the ostium. Optionally, the apparatus 10 may
be advanced with sufficient force to cause partial deformation of
the flared first end portion 41, e.g., to conform the first end
portion 41 at least partially to the shape of the ostium.
Alternatively, if the first end portion 41 is disposed partially in
the ostium, flaring the stent 40 may cause the stent 40 to back
partially out of the ostium, e.g., as described in the applications
incorporated by reference herein.
[0095] Turning to FIG. 6B, the second balloon 22b may then be
inflated to expand the second portion 43 and/or further expand the
first end portion 41. Thus, the second portion 43 may be expanded
to engage the inner wall of the branch lumen and/or the first end
portion 41 may be further expanded to engage the wall of the
ostium, thereby substantially securing the stent 40 in position.
The balloons 22 may then be deflated, and the apparatus 10 removed,
leaving the stent 40 within the ostium.
[0096] As shown in FIGS. 6D and 6E, the stent 40 may be expanded to
a variety of different shapes to accommodate ostia having different
shapes. For example, as shown in FIG. 6D, the stent 40 may be
expanded such that the second portion 43 assumes a relatively large
diameter to accommodate a larger branch, while the first end
portion 41 is flared more abruptly to accommodate an ostium having
a minimal taper. By comparison, as shown in FIG. 6E, the stent 40
may also be expanded such that the second portion 43 assumes a
relatively small diameter to accommodate a smaller branch, while
the first end portion 41 is flared more gradually to accommodate an
ostium having a more tapered contour.
[0097] During expansion of the stent 40, the ratio of the diameter
or other cross-section of the ends of the stent 40 may vary. For
example, as described above, when the first end portion 41 is
flared, e.g., in the intermediate condition, the ratio of the
diameter of the first end portion 41 to the second portion 43 may
be relatively large, e.g., two to five. Thus, the first end portion
41 may be relatively large, which may facilitate positioning the
stent 40 relative to the ostium. When the stent 40 is further
expanded to the final deployed condition, the ratio of the first
end portion 41 to the second portion 43 may then decrease, e.g., to
between 1.1 and 1.8. This may be desirable to provide a more
uniform distribution of the stent 40 relative to the ostium after
deployment. In addition or alternatively, it may reduce the risk of
the first end portion 41 extending into the main lumen and/or may
facilitate recrossing the ostium later with a guidewire or other
device.
[0098] Turning to FIG. 7, another embodiment of a stent 140 is
shown that includes first and second ends 142, 144 defining a
longitudinal axis 146 therebetween. Generally, the stent 140
includes a first or flaring portion 141 and a second or main body
portion 143, similar to the previous embodiments.
[0099] Also similar to the previous embodiments, the stent 140 may
include first and second bands of cells 147, 148 defining the first
end portion 141 of the stent 140. The first band of cells 147 at
the first end 142 generally includes a zigzag or serpentine pattern
defined by a plurality of axial elements 102 connected alternately
by curved elements 103 extending about the circumference of the
stent 140. The axial elements 102 may be substantially straight,
e.g., extending substantially parallel to the longitudinal axis in
the contracted condition, as shown in FIG. 7.
[0100] Generally, the first band of cells 147 includes a first
axial length 118 substantially parallel to the longitudinal axis
146. The first axial length 118 may be defined at least partially
by a length of the axial elements 102, e.g., depending upon whether
the axial elements 102 extend substantially parallel to the
longitudinal axis 146, as shown, or extend at an angle relative to
the longitudinal axis (not shown).
[0101] The second band of cells 148 adjacent the first band of
cells 147 also generally includes a zigzag or serpentine pattern
defined by axial elements 105 connected alternately by curved
elements 106 extending about the circumference of the stent 140. As
shown, the second band of cells 148 may define an axial length 117,
which may be substantially similar to the first band of cells 147.
For example, the axial elements 102, 105 may have substantially the
same length and the curved elements 103, 106 may have substantially
the same radius of curvature. In the embodiment shown, the first
and second band of cells 147, 148 are substantial mirror images of
one another.
[0102] As shown, the axial elements 102, 105 have a thickness
and/or width that is greater than the curved elements 103, 106.
Thus, the yield strength of the curved elements 103, 106 may be
less than the axial elements 102, 105, which may facilitate radial
flaring of the first end portion 141, as explained elsewhere
herein.
[0103] In addition, the second band of cells 148 may be connected
to the first band of cells 147 by one or more struts or other
connectors 107. Generally, the connectors 107 extend between
adjacent peaks of the zigzag patterns of the first and second bands
of cells 147, 148. For example, the connectors 107 may be
relatively short, axial struts that extend between adjacent peaks
of the first and second bands of cells 147, 148, i.e., the curved
elements 103, 106 closer to the first end 142. Alternatively, the
adjacent peaks may be connected directly to one another, e.g., by
adjacent curved elements 103, 106, and/or the first and second
bands of cells 147, 148 may be only intermittently connected,
similar to other embodiments described elsewhere herein. In a
further alternative, the first and second bands of cells 147, 148
may be connected by sinusoidal struts (not shown).
[0104] With continued reference to FIG. 7, the second main portion
143 of the stent 140 may include a plurality of bands of cells 149
connected to one another along a length of the second portion 143.
Each band of cells 149 may include axial elements 108 connected
alternately to curved elements 109, thereby defining a zigzag or
serpentine pattern, which may define a third axial length 119.
Optionally, adjacent bands of cells 149 defining the second portion
143 of the stent 140 may be connected via links 111. The links 111
may be struts defining at least a portion of a generally sinusoidal
wave or other curvilinear shape, as shown. Alternatively, the links
111 may be axial struts (not shown), or the adjacent bands of cells
149 may be connected directly, e.g., by adjacent curved elements
109 (also not shown). The links 111 may be relatively narrow and/or
thin compared to the curved elements 109, e.g., to facilitate
bending or conformability of the second portion 143 of the stent
140.
[0105] In an exemplary embodiment, the bands of cells 149 of the
second main portion 143 may have a higher radial force than the
bands of cells 147, 148 of the first flaring portion 141. For
example, the axial and curved elements 108, 109 may have a
thickness and/or width greater than the axial elements 102, 105,
and/or curved elements 103, 106. Consequently, the bands of cells
149 may be relatively stiff and/or may have a higher yield strength
than the first and second bands of cells 147, 148. For example, the
bands of cells 149 may have a greater radial strength, thereby
providing greater luminal support than the bands of cells 147, 148.
In addition or alternatively, the bands of cells 149 may provide
greater resistance to expansion than the bands of cells 147, 148,
which may minimize expansion of the bands of cells 149 closest to
the flaring portion 141 when the flaring portion 141 is flared, as
described further below.
[0106] Unlike the previous embodiments, the second main portion 143
may include a proximal main portion 143a and a distal main portion
143b, having different characteristics from one another. For
example, the proximal main portion 143a may have a greater radial
strength than the distal main portion 143b, e.g., to enhance
dilation of an ostium, as described further below. In order to
increase the radial strength of the proximal main portion 143a, the
axial and/or curved elements 108a, 109a may have a greater width
than the axial and/or curved elements 108b, 109b. In an exemplary
embodiment, the elements 108a, 109a may have a width between about
0.007-0.009 inch (0.18-0.23 mm), e.g., about fifteen and fifty
percent (15-50%) greater than the elements 108b, 109b.
Alternatively, one or more other dimensions, e.g., thickness and
length, and/or cell configuration may be varied between the
proximal main portion 143a and the distal main portion 143b to
enhance the relative radial strength and/or stiffness of the
proximal main portion 143a compared to the distal main portion
143b.
[0107] It will be appreciated that any number of annular bands 149
may be provided, e.g., such that the second main portion 143 has a
predetermined length corresponding to a length of a lesion being
dilated or otherwise treated using the stent 140, e.g., between
about three and twenty millimeters (3-20 mm). Each of the proximal
and distal main portions 143a, 143b may include a plurality of
bands of cells 149a, 149b. In an exemplary embodiment, the distal
main portion 143b may include more bands of cells 149b than the
proximal main portion 143a. For example, as shown, the proximal
main portion 143a includes two bands of cells 149a, while the
distal main portion 143b includes at least three, four, five, six,
or more bands of cells 149b. Thus, the proximal main portion 143a
may be disposed in or immediately adjacent an ostium, while the
distal main portion 143b may extend across and beyond a lesion (not
shown) being treated, e.g., as explained further below.
[0108] Turning to FIGS. 8 and 9, an exemplary embodiment of a
delivery apparatus 110 is shown that includes a catheter or other
elongate tubular member 112 having a proximal end (not shown), a
distal end 116, and one or more lumens (also not shown) extending
between the proximal end and distal end 116. One or more balloons
or other expandable members 122 are provided on the distal end 116,
e.g., a first proximal balloon 122a and a second distal balloon
122b adjacent a distal tip 117 of the catheter 112. Materials and
methods for making the delivery apparatus 110 may be found in
co-pending application Ser. No. 11/136,266, filed May 25, 2006, the
entire disclosure of which is expressly incorporated by reference
herein, or in the other applications incorporated by reference
herein. In addition, the delivery apparatus 110 may include one or
more sources of inflation media (not shown), e.g., one or more
syringes filled with saline or other fluid that communicate with
respective balloons 122.
[0109] Generally, the balloons 122 are expandable from a contracted
condition (shown in FIGS. 9 and 10A) and an enlarged condition
(shown in FIGS. 8 and 10B). An interior of each balloon 122a, 122b
may communicate with a respective inflation lumen (not shown) in
the catheter 112 such that the balloons may be independently
inflated and/or deflated. In an exemplary embodiment, the proximal
balloon 122a may be formed from a substantially complaint or
semi-compliant material, e.g., polyethylene, polyurethane, and low
to mid durometer PEBAX, and the distal balloon 122b may be formed
from a semi-compliant or substantially non-compliant material,
e.g., mid to high durometer PEBAX, nylon, or PET.
[0110] In addition or alternatively, the balloons 122 may require
different internal pressures and/or pressures sufficient to fully
expand the respective balloons 122. For example, the distal balloon
122a may require a greater inflation pressure to fully expand than
the proximal balloon 122b. As explained further below, this may
allow the proximal balloon 122a to be expanded using a lower
inflation pressure to flare and/or shape a flaring portion of a
stent thereon without substantial expansion of a main portion of
the stent. Thereafter, the distal balloon 122b may be expanded
using a higher inflation pressure to expand the main portion of the
stent, which may enhance dilating an occlusion or other lesion at
or adjacent an ostium.
[0111] Alternatively, during use, the proximal balloon 122a may be
inflated based upon delivering one or more predetermined volumes of
fluid therein, e.g., in multiple stages of expansion, as described
further below. For example, the proximal balloon 122a may be
partially inflated upon delivering a first predetermined volume of
fluid therein to flare the stent before positioning the apparatus
110, e.g., between about 0.25-2 cubic centimeters. After
positioning the stent and expanding the distal balloon 122b, the
proximal balloon 122a may be fully inflated upon delivering a
second larger predetermined volume of fluid therein, e.g., between
about 0.5-4.2 cubic centimeters, to further flare or otherwise
shape the stent, as explained further below. Volume-based delivery
may be useful for describing the function of the proximal balloon
122a because of its relative compliance and/or low pressure
requirements.
[0112] Optionally, a source of inflation media communicating with
the proximal balloon 122a may include indicia or other features
that identify or limit the source to facilitate delivering the
first predetermined volume and the second predetermined volume
successively to facilitate two-stage expansion of the proximal
balloon 122a. For example, a syringe may be provided that includes
first and second position markers (not shown). When a plunger of
the syringe is depressed to the first marker, this may correspond
to delivering the first predetermined volume into the proximal
balloon 122a. When the plunger is depressed further to the second
marker, this may correspond to delivering the second predetermined
volume into the proximal balloon 122a.
[0113] As shown in FIG. 8, the proximal balloon 122a is shaped to
expand to a substantially spherical shape in the enlarged
condition, e.g., having a diameter between about ten and twenty
millimeters (10-20 mm) when expanded using an inflation pressure
between about one and five atmospheres (1-5 ATM). In an exemplary
embodiment, the proximal balloon 122a may have a diameter of about
thirteen millimeters (13 mm) at an inflation pressure of about two
atmospheres (2 ATM). In contrast, the distal balloon 122b may be
shaped to expand to a substantially cylindrical shape in the
enlarged condition, e.g., having a diameter between about two and
eight millimeters (2-8 mm) when expanded using an inflation
pressure between about eight and twenty atmospheres (8-20 ATM).
[0114] In addition, the distal balloon 122b may have a
substantially uniform diameter portion, e.g., having a length
between about eight and thirty millimeters (8-30 mm). Beyond the
uniform diameter portion, the distal balloon 122b may have a
transition portion 122c adjacent the distal tip 117. The transition
portion 122c may be tapered, as shown, or may be substantially
blunt, i.e., extending inwardly to the distal tip 117 (not shown).
Optionally, the distal balloon 122b may underlie at least a portion
of the proximal balloon 122a, e.g., as disclosed in the
applications incorporated by reference elsewhere herein. In an
exemplary embodiment, the distal balloon 122b may have a diameter
of about six millimeters (6 mm) in the enlarged condition and may
have a length of at least about seventeen millimeters (17 mm)
distally beyond the proximal balloon 122a.
[0115] With particular reference to FIG. 9, the stent 140 may be
mounted around the distal end 116 of the catheter 112, e.g.,
surrounding at least a portion of the balloons 122. Generally, the
first flaring portion 141 of the stent 140 overlies the proximal
balloon 122a, e.g., a distal portion of the proximal balloon 122a,
and the distal main portion 143b of the stent 140 overlies the
distal balloon 122b, i.e., between the proximal balloon 122a and
the transition portion 122c. The proximal main portion 143a of the
stent 140 may overlie one or both of the proximal and distal
balloons 122a, 122b. For example, as shown, at least a portion of
one of the bands of cells 149a may overlie the proximal balloon
122a, while the remainder of the bands of cells 149a may overlie
the distal balloon 122b. This overlap of the proximal main portion
143a of the stent 140 may allow a steeper flare of the stent 140,
as explained further below.
[0116] Optionally, similar to other embodiments herein, the
delivery apparatus 110 may include a sheath or other cover (not
shown) that may surround or otherwise cover the stent 140. The
sheath may be removable from over the proximal or distal portions
of the stent 40 or the entire stent 40 to expose the stent 40
before deployment.
[0117] Turning to FIGS. 11A-11D, the apparatus 110 may be used to
deliver the stent 140 into an ostium 90, i.e., an opening
communicating between a first or main body lumen 92 and a second or
branch body lumen 94, similar to other embodiments herein.
[0118] Initially, a guidewire or other rail 90 (see, e.g., FIG.
11D) may be introduced from the main body lumen 92 through the
ostium 90 into the branch 94. For example, a guidewire may be
advanced from a percutaneous puncture or other entry site (not
shown), e.g., into a peripheral vessel, such as a femoral or
carotid artery, through the patient's vasculature into the main
body lumen 92, and into the branch 94. Optionally, as shown in FIG.
11A, a guide catheter 160 may be advanced over the guidewire into
the main body lumen 92, e.g., until a distal end 164 of the guide
catheter 160 is disposed adjacent or proximal to the ostium 90.
[0119] With the stent 140 in the contracted condition, the distal
end 116 of the apparatus 110 may be advanced over the guidewire
and/or through the guide catheter from the entry site into the main
body lumen 92. The apparatus 110 may be positioned to place the
stent 140 at least partially within the ostium 90. For example, as
shown in FIG. 11A, the distal end 116 of the apparatus 110 may be
advanced through the ostium 90 and into the branch 94, i.e., such
that the stent 140 and/or balloons 122 cross the lesion being
treated. The apparatus 110 may then be withdrawn to position at
least the flaring portion 141 of the stent 140 within the main body
lumen 92.
[0120] Turning to FIG. 11B, the proximal balloon 122a may be
inflated to expand the flaring portion 141 of the stent 140, i.e.,
cause the first and second bands of cells 147, 148 to transition
from the axial to peripheral and/or radial configurations, as
described above. For example, as explained above, a first
predetermined volume of fluid may be delivered into the proximal
balloon 122a to partially expand the proximal balloon 122a.
Although a portion of the proximal main portion 143a of the stent
140 overlies the proximal balloon 122a, the proximal main portion
143a may resist expansion, e.g., because of the greater radial
strength of the proximal main portion 143a and/or the relatively
lower inflation pressure used to inflate the proximal balloon 122a.
Thus, the flaring portion 141 may be flared outwardly relatively
steeply from the proximal main portion 143a.
[0121] The apparatus 110 may then be advanced to abut the flared
flaring portion 141 against the ostium 90. Optionally, the
apparatus 110 may be advanced with sufficient force to cause
partial deformation of the flaring portion 141, e.g., to conform at
least partially to the shape of the ostium 90. Alternatively, if
the flaring portion 141 is disposed partially in the ostium 90 when
the proximal balloon 122a is inflated, flaring the stent 140 may
cause the stent 140 to back partially out of the ostium 90, e.g.,
as described further below.
[0122] Optionally, the apparatus 110 and/or stent 140 may be
monitored during this manipulation, e.g., using fluoroscopy or
other external imaging, to confirm proper positioning of the stent
140 within the ostium 90. In this option, the stent 140 and/or
apparatus 110 may include radiopaque markers and the like (not
shown), e.g., as described elsewhere herein.
[0123] Turning to FIG. 11C, with the stent 140 properly positioned,
the distal balloon 122b may be inflated to expand the main portion
143 of the stent 140 and/or further expand the flaring portion 141.
For example, the proximal main portion 143a may be expanded to
engage the inner wall of the ostium and/or branch, and the distal
main portion 143b may be expanded to engage the inner wall of the
branch, e.g., to dilate the lesion and/or substantially secure the
stent 140 in position. Because of the greater radial strength of
the main portion 143, the distal balloon 122b may be inflated to a
greater pressure than the proximal balloon 122a, thereby ensuring
the main portion 143 is expanded to dilate the lesion.
[0124] With the main portion 143 expanded, the stent 140 may be
substantially secured from axial movement relative to the branch,
e.g., to the friction or other engagement between the expanded main
portion 143 and the wall of the branch. If desired, the proximal
balloon 122a may then be expanded further, e.g., by delivering a
second predetermined volume of fluid therein. This may further
flare the flaring portion 141 of the stent 140 and/or compress the
flaring portion 141 against the wall of the ostium. The hydraulic
pressure applied to the flaring portion 141 by further expanding
the proximal balloon 122a may be apply a greater force than can be
applied manually, e.g., by advancing the apparatus 110 partially
into the ostium.
[0125] Turning to FIG. 11D, the balloons 122 may then be deflated,
and the apparatus 110 removed, leaving the stent 140 within the
ostium 90 and branch 94. Because of the greater radial strength of
the proximal main portion 143a, this portion of the stent 140 may
have enhanced resistance to being compressed by surrounding tissue.
For example, in some applications, the tissue surrounding a lumen
may want to recoil, i.e., contract radially inwardly, particularly
at the neck of an ostium. Thus, the main portion 143 of the stent
140, particularly, the proximal main portion 143 located within the
ostium 90, may resist such recoil, which may enhance maintaining
the ostium open for an indefinite time.
[0126] Turning to FIG. 12, still another embodiment of a stent 240
is shown that includes first and second ends 242, 244 defining a
longitudinal axis 246 therebetween. Generally, the stent 240
includes a first or flaring portion 241 and a second or main body
portion 243, similar to the previous embodiments.
[0127] Also similar to the previous embodiments, the stent 240 may
include first and second bands of cells 247, 248 defining the first
end portion 241 of the stent 240. The first band of cells 247 at
the first end 242 generally includes a zigzag or serpentine pattern
defined by a plurality of axial elements 202 connected alternately
by curved elements 203 extending about the circumference of the
stent 240. The axial elements 202 may be substantially straight,
e.g., extending substantially parallel to the longitudinal axis in
the contracted condition, as shown in FIG. 12. Generally, the first
band of cells 247 includes a first axial length 216 substantially
parallel to the longitudinal axis 246. The first axial length 216
may be defined at least partially by a length of the axial elements
202, e.g., depending upon whether the axial elements 202 extend
substantially parallel to the longitudinal axis 246, as shown, or
extend at an angle relative to the longitudinal axis (not
shown).
[0128] The second band of cells 248 adjacent the first band of
cells 247 also generally includes a zigzag or serpentine pattern
defined by axial elements 205 connected alternately by curved
elements 206 extending about the circumference of the stent 240. As
shown, the second band of cells 248 may define an axial length 217,
which may be substantially similar to the first band of cells 247.
For example, the axial elements 202, 205 may have substantially the
same length and the curved elements 203, 206 may have substantially
the same radius of curvature. In the embodiment shown, the first
and second band of cells 247, 248 are substantial mirror images of
one another.
[0129] As shown, the axial elements 202, 205 have a thickness
and/or width that is greater than the curved elements 203, 206.
Thus, the yield strength of the curved elements 203, 206 may be
less than the axial elements 202, 205, which may facilitate radial
flaring of the first end portion 241, as explained elsewhere
herein.
[0130] In addition, the second band of cells 248 may be connected
to the first band of cells 247 by one or more struts or other
connectors 207. Generally, the connectors 207 extend between
adjacent peaks of the zigzag patterns of the first and second bands
of cells 247, 248. For example, the connectors 207 may be
relatively short, axial struts that extend between adjacent peaks
of the first and second bands of cells 247, 248, i.e., the curved
elements 203, 206 closer to the first end 242. Alternatively, the
adjacent peaks may be connected directly to one another, e.g., by
adjacent curved elements 203, 206, and/or the first and second
bands of cells 247, 248 may be only intermittently connected. In a
further alternative, the first and second bands of cells 247, 248
may be connected by sinusoidal struts (not shown).
[0131] With continued reference to FIG. 12, the second main portion
243 of the stent 240 may include a plurality of bands of cells 249
connected to one another along a length of the second portion 243.
Each band of cells 249 may include axial elements 208 connected
alternately to curved elements 209, thereby defining a zigzag or
serpentine pattern, which may define a third axial length 219.
Optionally, adjacent bands of cells 249 defining the second portion
243 of the stent 240 may be connected via links 211. The links 211
may be struts defining at least a portion of a generally sinusoidal
wave or other curvilinear shape, as shown. Alternatively, the links
211 may be axial struts (not shown), or the adjacent bands of cells
249 may be connected directly, e.g., by adjacent curved elements
209 (also not shown). The links 211 may be relatively narrow and/or
thin compared to the curved elements 209, e.g., to facilitate
bending or conformability of the second portion 243 of the stent
240, as described elsewhere herein.
[0132] Unlike previous embodiments, as shown in FIG. 12, adjacent
bands of cells 249 are intermittently connected to one another.
Stated differently, the links 211 are provided only between every
other opposing set of curved elements 209 around the circumference
of the stent 240. It will be appreciated that other configurations
of intermittent connections may be provided, e.g., links extending
between every third, fourth, or fifth opposing set of curved
elements 209 around the circumference of the stent 240.
[0133] The combination of curved links 211 and intermittent links
211 may enhance axial compressibility of the stent 240. For
example, the links 211 may allow adjacent bands of cells 249 to
move towards and/or away from one another and/or allow localized
movement. Thus, particular opposing curved elements 209 that are
not connected to one another by links 211 may move towards or away
from one another relatively freely (as limited by the overall
configuration and structure of the cells defining the stent 240).
This feature may allow at least some of the bands of cells 249 to
compress axially during deployment within an ostium and/or branch,
which may facilitate seating of the stent 240 and/or increase
support at the ostium, as described further below.
[0134] Similar to some of the embodiments described above, the
bands of cells 249 of the second main portion 243 may have a higher
radial force than the bands of cells 247, 248 of the first flaring
portion 241. For example, the axial and curved elements 208, 209
may have a thickness and/or width greater than the axial elements
202, 205, and/or curved elements 203, 206. Consequently, the bands
of cells 249 may be relatively stiff and/or may have a higher yield
strength than the first and second bands of cells 247, 248. For
example, the bands of cells 249 may a greater radial strength,
thereby providing greater luminal support than the bands of cells
247, 248. In addition or alternatively, the bands of cells 249 may
provide greater resistance to expansion than the bands of cells
247, 248, which may minimize expansion of the bands of cells 249
closest to the flaring portion 241 when the flaring portion 241 is
flared, as described further elsewhere herein.
[0135] Optionally, similar to previous embodiments, the second main
portion 243 may include a proximal main portion and a distal main
portion, having different characteristics from one another (not
shown). For example, the proximal main portion may have a greater
radial strength than the distal main portion, e.g., to enhance
dilation of an ostium and/or enhance resistance to recoil. In an
exemplary embodiment, the elements of the proximal main portion may
have a width between about 0.007-0.009 inch (0.18-0.23 mm), e.g.,
about fifteen and fifty percent (15-50%) greater than the elements
of the distal main portion. Alternatively, one or more other
dimensions, e.g., thickness and length, and/or cell configuration
may be varied between the proximal main portion and the distal main
portion to enhance the relative radial strength and/or stiffness of
the proximal main portion compared to the distal main portion.
[0136] It will be appreciated that any number of annular bands 249
may be provided, e.g., such that the second main portion 243 has a
predetermined length corresponding to a length of a lesion being
dilated or otherwise treated using the stent 240, e.g., between
about three and twenty millimeters (3-20 mm).
[0137] Turning to FIGS. 13-19, the stent 240 may be delivered into
an ostium 90, i.e., an opening communicating between a first or
main body lumen 92 and a second or branch body lumen 94, e.g.,
using apparatus and methods described elsewhere herein. In an
exemplary embodiment, the main body lumen 92 may be the aortic root
and the branch body lumen 94 may be a coronary or renal artery
having a stenosis or other lesion 96 therein. It will be
appreciated that the stent 240 may be implanted within a variety of
bifurcations or branch body lumens that extend transversely, e.g.,
laterally or substantially perpendicular, from a main body
lumen.
[0138] Initially, as shown in FIG. 13, a guide catheter 160 may be
advanced into the main body lumen 92, e.g., until a distal end 164
of the guide catheter 160 is disposed adjacent or proximal to the
ostium 90. Optionally, as shown in FIG. 14, a guidewire or other
rail 98 may be introduced from the main body lumen 92 through the
ostium 90 into the branch 94, e.g., via the guide catheter 160. For
example, the guide catheter 160 may be advanced or otherwise
manipulated until the distal end 164 is engaged in the ostium 90,
and the guidewire 98 may be advanced through the guide catheter 160
and passed through the lesion 96. For vascular procedures, the
guidewire 98 may be advanced from a percutaneous puncture or other
entry site (not shown), through the patient's vasculature into the
main body lumen 92, and into the branch 94, using known methods.
Alternatively, the guidewire 98 may be introduced before or
independent of the guide catheter 160.
[0139] Similar to the apparatus and methods described above, as
shown in FIG. 14, the stent 240 may be loaded onto a delivery
apparatus 110 (which may be any of the embodiments described
herein). For example, the stent 240 may positioned over proximal
and distal balloons 122a, 122b on a distal end 116 of the apparatus
110 with the stent 240 in the contracted condition. The distal end
116 of the apparatus 110 may be advanced over the guidewire 98
and/or through the guide catheter 160 from the entry site into the
main body lumen 92.
[0140] For example, as shown in FIG. 14, the distal end 116 of the
apparatus 110 may be advanced through the ostium 90 and into the
branch 94, i.e., such that the stent 240 and/or balloons 122 at
least partially cross the lesion being treated. The guide catheter
160 may then be at least partially retracted, e.g., to expose a
proximal balloon 122a on the apparatus 110. If desired, the
apparatus 110 may be withdrawn partially to position at least the
flaring portion 241 of the stent 240 within the main body lumen
92.
[0141] Turning to FIG. 15, the proximal balloon 122a may be
inflated to expand the flaring portion 141 of the stent 140, i.e.,
cause the first and second bands of cells 247, 248 to transition
from the axial to peripheral and/or radial configurations, as
described above. For example, as explained above, a first
predetermined volume of fluid may be delivered into the proximal
balloon 122a to partially expand the proximal balloon 122a.
Optionally, although a portion of the main portion of the stent 240
may overly the proximal balloon 122a, the proximal main portion may
resist expansion, e.g., because of the greater radial strength of
the proximal main portion and/or the relatively lower inflation
pressure used to inflate the proximal balloon 122a. Thus, the
flaring portion 241 may be flared outwardly relatively steeply from
the proximal main portion, e.g., to provide a mechanical stop when
the apparatus 110 is advanced again into the ostium 90.
[0142] Turning to FIG. 16, the apparatus 110 may then be advanced
into the ostium 90 to abut the flared flaring portion 241 against
the ostium 90. This may be accomplished by pushing the apparatus
110 from its proximal end (not shown), thereby advancing the distal
end 116 through the lesion 98 and at least partially into the
branch 94. Alternatively, the guide catheter 160 may be advanced
distally, thereby pressing the distal end 164 against the inflated
proximal balloon 122a. Further advancement of the guide catheter
160 may push the proximal balloon 122a distally, thereby
automatically advancing the apparatus 110 into the ostium 90.
[0143] Optionally, the apparatus 110 may be advanced with
sufficient force to cause partial deformation of the flaring
portion 241, e.g., to conform at least partially to the shape of
the ostium 90. Alternatively, if the flaring portion 241 is
disposed partially in the ostium 90 when the proximal balloon 122a
is inflated, flaring the stent 240 may cause the stent 240 to back
partially out of the ostium 90, e.g., as described further
below.
[0144] Optionally, the apparatus 110 and/or stent 240 may be
monitored during this manipulation (and/or other portions of the
procedure), e.g., using fluoroscopy or other external imaging, to
confirm proper positioning of the stent 240 within the ostium 90.
In this option, the stent 240 and/or apparatus 10 may include one
or more radiopaque markers and the like (not shown) at
predetermined locations thereon.
[0145] Turning to FIG. 17, with the stent 240 properly positioned,
the distal balloon 122b may be inflated to expand the main portion
243 of the stent 240 and/or further expand the flaring portion 241.
For example, the main portion 243 may be expanded sufficiently to
engage the inner wall of the branch 94 and/or ostium 90, thereby
substantially anchoring the stent 240 and/or apparatus relative to
the branch 94 and/or ostium 90. Optionally, the main portion 243
may include proximal and distal portions that have different
properties and, therefore, are expanded to enhance dilation of the
lesion 98 and/or substantially secure the stent 140 in position, as
described above.
[0146] Turning to FIG. 18, with the main portion 243 expanded and
the stent 240 substantially secured within the branch 94, the
proximal balloon 122a may then be expanded further, e.g., by
delivering a second predetermined volume of fluid therein. This may
further flare the flaring portion 241 of the stent 240 and/or
compress the flaring portion 241 against the wall of the ostium 90.
During this expansion, the stent 240 may be further deformed, e.g.,
causing axial compression of the main portion 243, as explained
further below.
[0147] Finally, turning to FIG. 19, the balloons 122 may then be
deflated, and the apparatus 110 removed, leaving the stent 240
within the ostium 90 and branch 94. Once the pressure of the
balloons 122 is removed (upon deflation of the balloons 122), the
flaring portion 241 of the stent 240 may rotate relative to an axis
defined by the main body lumen 92, e.g., to define a smaller angle
compared to when the balloons 122 are inflated. This is
demonstrated by "Angle 2" shown in FIG. 19, which is smaller than
"Angle 1" shown in FIG. 18. This change may occur because the stent
240 and surrounding tissue reach a new mechanical equilibrium,
e.g., between the stored elastic forces in the stent 240 and in the
wall of the branch 94.
[0148] Turning to FIGS. 20A and 20B, the change in configuration of
the stent 240 during full inflation of the proximal balloon 122a is
shown in greater detail. As shown in FIG. 20A, before full
expansion of the proximal balloon 122a (but after expansion of the
distal balloon 122b), the stent 240 may have a first length
"L-Total" defined by a length "L-flare" of the flaring portion 241
and a length of the main portion 243, which is the sum of "L1" to
"L6." With additional reference to FIG. 12, the lengths L1 to L6
are defined at least partially by the length 219 of the bands of
cells 249. Although the lengths L1 to L6 are initially
substantially the same (as can be seen in FIG. 12), the lengths may
vary upon partial expansion, as shown in FIG. 20A.
[0149] In particular, at least some of the lengths, e.g., L1, L2,
and L3, may be shortened during expansion, e.g., to enhance
apposition of the stent 240 relative to the ostium 90. For example,
as shown in FIG. 20B, the stent 240 may be further compressed
axially during final inflation of the proximal balloon 122a. Thus,
the stent 240 may have a new overall length "L-Total" that is less
than "L-Total." Further, the bands of cells 249 of the main portion
243 may be further foreshortened relative to one another. For
example, the bands of cells 249 closest to the ostium 90 may be
shortened further, while the bands of cells 249 away from the
ostium 90 may remain substantially fixed relative to the branch 94.
Thus, at least some of the lengths, e.g., L1,' L2,' and L3' shown
in FIG. 20B, may be further shortened as compared to the lengths
L1, L2, and L3 shown in FIG. 20A.
[0150] This foreshortening may be facilitated by the intermittent
connection of the bands of cells 249 to one another, which may
increase the density of struts within the lesion 96. Thus, in
addition to facilitating conformance of the stent 240 to the ostium
90, the axial compression of the stent 240 may increase support
within the lesion 96. Because the ostium 90 may have a thicker
and/or more elastic wall than the branch 94, the stent 240 may
carry a greater load within the ostium 90, e.g., to prevent the
lesion 96 and/or ostium 90 from recoiling to a smaller diameter.
Additional information on the advantages of the stent 240 may be
found in provisional application Ser. No. 60/745,177, incorporated
by reference above.
[0151] Turning to FIGS. 21-23, another embodiment of a stent 340
that includes a generally cylindrical tubular member including a
proximal or first end 342 and a distal or second end 344 defining a
longitudinal axis 346 therebetween. The stent 340 is generally
radially expandable from a contracted or delivery condition (FIG.
21A) to an enlarged or deployed condition (FIG. 21B). The stent 340
includes a plurality of annular bands of cells 347-349 disposed
between the proximal and distal ends 342, 344. Each band of cells
347-349 may be defined by a plurality of struts or other elements
extending axially along and/or circumferentially around the stent
340, e.g., in a zigzag or serpentine pattern, thereby defining an
open-cell structure. Adjacent bands of cells may be connected to
one another, e.g., directly or via links or other elements, similar
to other embodiments described elsewhere herein.
[0152] As shown in FIG. 23, the stent 340 may include a first band
of cells 347 at the first end 342 that includes a zigzag or
serpentine pattern defined by a plurality of axial elements 347a
connected alternately by curved elements 347b extending about the
circumference of the stent 340. The axial elements 347a may be
substantially straight, e.g., extending substantially parallel to
the longitudinal axis 346 in the contracted condition, as shown in
FIG. 21A. Alternatively, the axial elements 347a may include more
complicated geometry, similar to other embodiments described
elsewhere herein. Generally, with continued reference to FIG. 23,
the first band of cells 347 includes a first axial length 347c
substantially parallel to the longitudinal axis 346, which may be
defined at least partially by a length of the axial elements 347a,
e.g., depending upon whether the axial elements 347a extend
substantially parallel to the longitudinal axis 46 or extend at an
angle relative to the longitudinal axis 46 (i.e., diagonally or
circumferentially).
[0153] Similarly, the stent 340 may include a second band of cells
348 adjacent the first band of cells 347 that includes a zigzag or
serpentine pattern defined by axial elements 348a connected
alternately by curved elements 348b extending about the
circumference of the stent 340. As shown, the second band of cells
348 may be connected directly to the first band of cells 347, e.g.,
at adjacent curved elements 347b, 348b. As shown, the second band
of cells 348 also includes a second axial length 348c, which may be
substantially longer than the first axial length 347c. The first
and second bands of cells 347, 348 may provide a first portion 341
of the stent 340 that may flare as the stent 340 is expanded, as
explained further below. The set of curved elements 347b at the
first end 342 may be substantially free to accommodate expansion
and/or flaring of the first portion 341, also as described further
below.
[0154] In addition, the stent 340 may include a plurality of
additional bands of cells 349 defining a second portion 343 of the
stent 340. Each of the additional bands of cells 349 may include
axial elements 349a connected alternately to curved elements 349b,
thereby defining a zigzag or serpentine and third axial length
349c. As shown in FIG. 23, the third axial length 349c may be
substantially shorter than the second axial length 348c.
Alternatively, the third axial length 349c may be substantially
longer, shorter, or similar to the first axial length 347c and/or
the second axial length 348c. The axial elements 349a may be
substantially straight, as shown, or may have a curvilinear shape,
such as that shown in FIG. 24.
[0155] Adjacent bands of cells 349 defining the second portion 343
of the stent 340 may be connected either directly or via links. For
example, returning to FIG. 23, the band of cells 349-1 adjacent the
second band of cells 348 may be connected directly to the second
band of cells 348, e.g., at adjacent curved elements 348b, 349b.
The next band of cells 349-2 are connected to the band of cells
349-1 by links 349d. Although the links 349d are shown being
substantially straight, i.e., extending substantially parallel to
the longitudinal axis 346, the links 349d may have other
configurations, e.g., including curved elements defining at least a
portion of a sinusoidal wave or other zigzag and the like (not
shown), as described further below. In addition or alternatively,
the length of the links 349d and/or the distance between the
adjacent bands of cells 349 may be varied, if desired.
[0156] Although each of the bands of cells 349 in the second
portion 343 of the stent 340 are shown having similar
configurations and axial lengths 349c, it will be appreciated that
the dimensions and configurations may be varied between the second
band of cells 348 and the second end 344 of the stent 340, if
desired. Thus, the portion of the stent 340 between the second band
of cells 348 and the second end 344 of the stent may have a
substantially homogenous cell structure or non-uniform cell and/or
band configurations, e.g., as described further below. In addition,
any number of annular bands 349 may be provided, e.g., such that
the second portion 343 has a predetermined length corresponding to
a length of a lesion being dilated or otherwise treated using the
stent 340, e.g., between about three and twenty millimeters (3-20
mm). Alternatively, the second portion 343 of the stent 340 may
include other configurations, similar to other embodiments
described elsewhere herein.
[0157] Returning to FIGS. 21A and 21B, the stent 340 may be
provided initially in the contracted condition shown in FIG. 21A,
e.g., having a diameter between about one half and two millimeters
(0.5-2 mm). The stent 340 may be delivered endoluminally, e.g.,
using a delivery apparatus, such as those described elsewhere
herein. The stent 340 may then be expanded to the enlarged
condition shown in FIG. 21B, e.g., using an internal balloon or
other expandable member (not shown). In the enlarged condition,
both of the first and second portions 341, 343 of the stent 340
define a circumference or other cross-sectional dimension that is
larger than in the contracted condition. More particularly, the
first portion 341 of the stent 340 may be expanded to assume a
flared shape, e.g., having an outer diameter between about four and
fifteen millimeters (4-15 mm), while the second portion 343 of the
stent may be expanded to a generally uniform cylindrical shape,
e.g., having a diameter between about two and seven millimeters
(2-7 mm).
[0158] Turning to FIG. 22, the flared shape of the first portion
341 is shown in more detail, i.e., after the stent 340 has been
expanded to the enlarged condition. Because of the difference in
lengths between the first and second bands of cells 347, 348, the
first portion 341 of the stent 340 flares radially outwardly as it
expands. This flaring may be created by the mismatch of the first
and second axial lengths 347c, 348c, i.e., because the first band
of cells 347 are substantially shorter than the second band of
cells 348. As the stent 340 expands, the axial elements 347a of the
first band of cells 347 may be deflected from a substantially axial
orientation in the contracted condition (as shown in FIG. 21A) to a
substantially circumferential orientation, thereby reducing the
curvature of the curved elements 347b at the first end 341 (as
shown in FIGS. 21B and 22). This causes the axial elements 348a of
the second band of cells 348 to expand to a greater diameter
adjacent the first band of cells 347 than the third band 349-1,
thereby causing the first portion 341 to flare radially outwardly.
Thus, the first end 342 may have a diameter or other
cross-sectional dimension that is substantially larger than the
transition between the first and second portions 341, 343 and/or
than the second end 344.
[0159] The stent 340 (or other embodiments described elsewhere
herein) may be formed from a variety of materials that may be
plastically deformed to allow expansion of the stent 340. For
example, the stent 340 may be formed from metal, such as stainless
steel, tantalum, MP35N, Niobium, Nitinol, and L605, plastic, or
composite materials. In particular, the materials of the stent 340
may be plastically deformed under the pressures experienced when
the stent 340 is expanded, e.g., such that the first and/or second
portions 341, 343 of the stent 340 are deformed beyond their
elastic limit. Thus, when the stent 340 is deployed, the stent 340
may maintain its enlarged condition (e.g., that shown in FIG. 21B)
with minimal recoil. Stated differently, the stent 340 material may
resist collapsing back towards its reduced configuration after
deployment, e.g., if the tissue surrounding the body lumen attempts
to constrict or otherwise return to its occluded shape.
[0160] Alternatively, at least a portion of the stent 340 may be
self-expanding. For example, one or both of the first and second
portions 341, 343 may be biased to expand at least partially
outwardly yet may be constrained on a delivery device in a
contracted condition to facilitate delivery. In this alternative,
the stent 340 may be formed from Nitinol or other shape memory or
superelastic materials.
[0161] The stent 340 may be formed from a tube of material having a
solid wall initially. For example, portions of the tube may be
removed, e.g., by laser cutting, etching, machining, and the like,
to define the elements of the bands of cells and/or links.
Alternatively, the stent 340 may be formed from a flat sheet and
rolled into a tubular shape. For example, portions of the sheet may
be removed and then the resulting cellular structure may be rolled
and attached along its length, e.g., by welding, bonding,
interlocking connectors (not shown), and the like. In other
alternatives, the stent 340 may be a braided or other structure,
e.g., formed from one or wires or other filaments braided or
otherwise wound in a desired manner. Additional possible stent
structures may include helical coil wires or sheets.
[0162] Optionally, the resistance of the stent 340 to expansion may
be varied along its length. This performance of the stent 340 may
be based upon mechanical properties of the material, e.g., which
may involve heat treating one or more portions of the stent 340
differently than other portions. In addition or alternatively, the
structure of the stent 340 may be varied, e.g., by providing
struts, fibers, or other components in different portions having
different widths, thicknesses, geometry, and the like, as described
further below.
[0163] If desired, one or more portions of the stent 340 (or other
embodiments described elsewhere herein) may include a membrane,
film, or coating (not shown), e.g., to create a nonporous,
partially porous, or porous surface between cells of the stent 340.
For example, as shown in FIG. 25, an alternative embodiment of a
stent 340'' is shown, that may be constructed and/or configured
similar to other embodiments described herein (e.g., with like
elements labeled with similar reference numbers followed by ("''").
The stent 340'' may include a first flared portion 342'' including
a membrane 350'' that may expand along with the first portion
342.''
[0164] The membrane 350'' may be formed from a relatively thin
layer of material, e.g., PTFE, ePTFE, silicone, polyurethane, or
polyethylene, that may be embedded into, coated onto, sandwiched
around, or otherwise carried by the stent 340.'' The membrane 350''
may be substantially elastic such that the membrane 350'' may
expand when the first portion 341'' is flared or otherwise
expanded. Alternatively, the membrane 350'' may be folded or
otherwise compressed such that the membrane 350'' may unfold or
otherwise to accommodate expansion as the stent 340'' is
expanded.
[0165] The membrane 350'' may be provided on an outer and/or inner
surface of the first portion 341.'' A membrane 350'' on the inner
surface may facilitate recrossing the stent 340'' at a later time
after implantation. For example, after the stent 340'' is implanted
within a patient, it may be desirable to advance a guidewire or
other instrument (not shown) through the ostium into the branch
vessel, e.g., to perform another procedure. This may occur during
the same surgical procedure, or some time after the patient has
recovered, e.g., when the branch vessel, lesion, or main vessel
need subsequent treatment. The membrane 350'' may prevent the tip
of a guidewire or other instrument from catching or tangling in the
struts, wires, cells, or other structures of the stent 340.''
Instead, the membrane 350'' may provide a substantially smooth,
possibly lubricious surface that may guide a guidewire through the
stent 340'' into the branch vessel.
[0166] In addition or alternatively, a membrane 350'' on the stent
340'' may carry therapeutic or other compounds or materials. For
example, a membrane 350'' on an outer surface of the stent 340''
may be pressed into contact with the plaque, damaged tissue, or
other material of the lesion, allowing the compound to act to
enhance healing or otherwise treat the lesion.
[0167] Optionally, any of the stents described herein may include
one or more radiopaque or other markers (not shown), e.g., to
facilitate monitoring the stent during advancement, positioning,
and/or expansion. For example, with reference to FIGS. 21A and 21B,
radiopaque material, e.g., gold, platinum, iridium, tungsten, or
their alloys, may be provided on each end 342, 344 of the stent 40
and/or adjacent the transition between the first and second
portions 341, 343. In addition or alternatively, wires, rods,
disks, or other components (not shown) may be provided on
predetermined locations on the stent 340 that are formed from
radiopaque material to facilitate monitoring the stent 340 using
fluoroscopy or other external imaging.
[0168] In addition or alternatively, the stent 340 (or other
embodiments described herein) may carry one or more therapeutic or
other compounds (not shown) that may enhance or otherwise
facilitate treatment of a target location within a patient's body.
For example, the stent 340 may carry compounds that prevent
restenosis at the target location.
[0169] Turning to FIGS. 26A-26F, another exemplary embodiment of an
apparatus 310 is shown for delivering a stent 340 (which may be any
of the embodiments described herein), e.g., into an ostium or other
bifurcation 90 where a branch lumen extends from a main lumen 92.
Generally, the apparatus 310 includes a catheter or other elongate
tubular member 312 having a proximal end (not shown), a distal end
316, and one or more lumens 318 extending between the proximal end
and distal end 316, thereby defining a longitudinal axis 320
therebetween. One or more balloons or other expandable members 322
are provided on the distal end 316, e.g., a first proximal balloon
322a and a second distal balloon 322b as shown.
[0170] The catheter 312 may include a plurality of lumens 318
extending between the proximal end (e.g., from a handle thereon,
not shown) and the distal end 316. For example, the catheter 312
may include an instrument lumen (not shown) that extends from the
proximal end to an opening in the distal tip 317. The instrument
lumen may have sufficient size to allow a guidewire 98 or other
rail or instrument (not shown) to be inserted therethrough, e.g.,
to facilitate advancing the catheter 312 over the rail, as
explained further below. Optionally, the proximal end (or handle)
may include one or more seals (not shown), e.g., a hemostatic seal
that prevents fluid, e.g., blood, from flowing proximally out of
the instrument lumen, yet allows one or more instruments to be
inserted therethrough and into the instrument lumen.
[0171] In addition, the catheter 312 may include inflation lumens
(not shown) that extend from respective ports in the proximal end
(or handle) through the catheter 312 to openings communicating
within an interior of a respective balloon 322a, 322b. A source of
inflation media and/or vacuum, e.g., a syringe filled with saline
(not shown), may be connected to the handle for expanding and/or
collapsing the balloons 322. Additional information on apparatus
and/or methods that may be used to deliver a stent may be found in
co-pending application Ser. No. 11/136,266, filed May 23, 2005,
incorporated by reference above.
[0172] As shown in 26A-26C, the apparatus 310 may initial carry a
stent 340, such as any of the embodiments described elsewhere
herein. The stent 340 may be mounted around the distal end 316 of
the catheter 312, e.g., such that a first portion 341 of the stent
340 at least partially surrounds the proximal balloon 322a and a
second portion 343 of the stent 340 surrounds the distal balloon
322b. Optionally, the apparatus 310 may include a sheath or other
cover (not shown) that may surround or otherwise cover the stent
340. The sheath may be removable from over the proximal or distal
portions 341, 343 of the stent 340 or the entire stent 340 to
expose the stent 340 before deployment, as described further
below.
[0173] Turning to FIGS. 26A-26F, an exemplary method is shown for
delivering the stent 340 into an ostium 90, e.g., using an
apparatus 310, which may be any of the embodiments described
herein. The ostium 90 may be an opening in a wall of a first or
main body lumen 92 that communicates with a second or branch body
lumen 94, similar to other embodiments described elsewhere herein.
An occlusion or other lesion 96 may exist at and/or adjacent to the
ostium 90, e.g., extending at least partially into the branch 94.
The lesion 96 may include atherosclerotic plaque or other material
that partially or completely occludes blood or other fluid flow
between the main body lumen 92 and the branch 94.
[0174] Initially, as shown in FIG. 26A, a guidewire 98 or other
rail may be introduced from the main body lumen 92 through the
ostium 90 into the branch 94. As shown, the lesion 96 at the ostium
90 partially occludes the ostium 90 and extends into the branch 94.
The guidewire 98 may be placed using conventional methods. For
example, a percutaneous puncture or cut-down may be created at a
peripheral location (not shown), such as a femoral artery, carotid
artery, or other entry site, and the guidewire 98 may be advanced
through the patient's vasculature from the entry site, e.g., alone
or with the aid of a guide catheter or sheath (not shown).
[0175] After the guidewire 98 is directed into the branch 94 beyond
the lesion 96, it may be desirable to at least partially dilate the
lesion 96. For example, a balloon or other dilatation catheter (not
shown) may be advanced over the guidewire 98 into and through the
lesion 96, whereupon a balloon or other element on the catheter may
be expanded to at least partially dilate the lesion 96. If desired,
other procedures may also be performed at the lesion 96, e.g., to
soften, remove, or otherwise treat plaque or other material forming
the lesion 96, before the stent 340 is implanted. After completing
any such procedures, instruments advanced over the guidewire 98 may
be removed.
[0176] Optionally, a guide catheter (not shown) may be advanced
over the guidewire 98 into the main body lumen 92, e.g., until a
distal end of the guide catheter is disposed adjacent or proximal
to the ostium 90. The guide catheter may be used to advance one or
more instruments (such as those just described) over the guidewire
98 and into the main body lumen 92 and/or branch body lumen 94. In
addition, the guide catheter may facilitate advancement of the
apparatus 310 into the main body lumen 92 and/or into the branch
94, in addition to or instead of the guidewire 98.
[0177] Turning to FIG. 26B, a distal end 316 of apparatus 310 may
be advanced over the guidewire 98 (and/or through the guide
catheter, not shown) from the entry site into the main body lumen
92 with the balloons 322 in their contracted conditions. When the
distal tip 317 is adjacent to the ostium 90, as shown in FIG. 26C,
the proximal balloon 322a may be expanded, for example, by
delivering saline, nitrogen, or other inflation media into the
interior of the proximal balloon 322a, e.g., from a syringe or
other fluid source (not shown) coupled to the proximal end (also
not shown) of the apparatus 310. As the proximal balloon 322a is
expanded, a first portion 341 of the stent 340 is expanded, e.g.,
into a flared configuration.
[0178] Alternatively, the apparatus 310 may be advanced initially
with the stent 340 and balloons 322 collapsed until the stent 340
passes entirely through the lesion into the branch vessel 94, e.g.,
to ensure that the stent 340 may be advanced sufficiently into the
ostium 90. The apparatus 310 may then be retracted until at least
the proximal balloon 322a is disposed within the main vessel 92,
whereupon the proximal balloon 322a may be expanded as described
above.
[0179] Turning to FIG. 26D, with the first portion 341 flared or
otherwise expanded, the apparatus 310 may be advanced distally over
the guidewire 98 into the ostium 90, e.g., until the first portion
341 contacts the wall of the main body lumen 92 surrounding the
ostium 90. As the apparatus 310 is advanced, the distal tip 317 of
the catheter 312 enters the ostium 90 and passes through the lesion
96 into the branch 94, e.g., until the second portion 343 of the
stent 340 is disposed within the lesion 96, as shown. Optionally,
if the stent 340 includes one or more radiopaque markers,
fluoroscopy or other external imaging may be used to ensure that
the stent 340 is positioned properly into the ostium 90 and branch
94.
[0180] Turning to FIG. 26E, with the second portion 343 disposed
within the lesion 96, the distal balloon 322b may be expanded,
thereby dilating or otherwise lining the branch 94 within the
lesion 96. For example, as the second portion 343 of the stent 340
is expanded, plaque and/or other material defining the lesion 96
may be directed radially outwardly to dilate the lesion 96 to a
diameter comparable to the branch 94 downstream of the lesion 96.
Again, if the stent 340 and/or apparatus 310 include one or more
radiopaque markers or if contrast is delivered into the main body
lumen 92 and/or into the branch 94, the ostium 90 and/or lesion 96
may be imaged to confirm the position of the stent 340 and/or to
monitor the extent of dilation of the lesion 96, e.g., until a
desired diameter or other cross-section is attained.
[0181] Optionally, additional distal force may be applied to the
apparatus 310, e.g., to force the first portion 341 of the stent
340 against the ostium 90. This pushing may cause the first portion
341 to plastically deform further, e.g., to at least partially
conform to the shape and/or contour of the ostium 90. This
additional force may be applied before, during, or after inflation
of the distal balloon 322b.
[0182] In addition or alternatively, if the proximal balloon 322a
is elastically expandable, the proximal balloon 322a may be
expanded initially (e.g., during the stage described with reference
to FIGS. 26C and 26D) to a first enlarged configuration to allow
the first portion 341 of the stent 340 to contact and/or otherwise
seat into the ostium 90. Once the distal balloon 322b is inflated
to expand the second portion 343 of the stent 340 and dilate the
lesion 96 to a desired extent (e.g., as described with reference to
FIG. 26F), the proximal balloon 322a may be inflated further, e.g.,
to further expand the first portion 341 of the stent 340 or cause
the first portion 341 to conform further to the contour of the
ostium 90. This additional expansion may further seat and/or secure
the stent 340, and/or to dilate the ostium 90.
[0183] Alternatively, the distal balloon 322b may be at least
partially expanded before expanding the proximal balloon 322a. In a
further alternative, the stent 340 may be positioned in the ostium
90 before expanding either balloon 322. For example, radiopaque
markers (not shown) on the stent 340 and/or delivery apparatus 310
may be monitored using fluoroscopy to facilitate positioning the
stent 340. Once the stent 340 is properly positioned, the balloons
322 may be expanded, e.g. simultaneously or sequentially as
described above. For example, the distal balloon 322b may be
expanded first to anchor the stent 340 in the branch 94, e.g., as
described elsewhere herein.
[0184] Turning to FIG. 26F, once the stent 340 is expanded and/or
positioned in a desired manner, the balloons 322 may be collapsed,
e.g., by evacuating the inflation media using a syringe or other
device (not shown) at the proximal end (also not shown) of the
catheter 312. The balloons 322 may be deflated simultaneously or
sequentially, e.g., first deflating the distal balloon 322b, and
then deflating the proximal balloon 322a (e.g., optionally after
applying further distal force, if desired). With the balloons 322
collapsed, the apparatus 310 is withdrawn from the main body lumen
92 and out of the patient's body. If a guide catheter or other
sheath (not shown) is used, the guide catheter or sheath may be
advanced against or into the ostium 90 before the apparatus 310 is
removed, e.g., to facilitate withdrawing the balloons 322 without
dislodging the stent 340. The guidewire 98 (and/or the guide
catheter or sheath, if used) may be removed before, after, or
simultaneously with the apparatus 310. Thus, the stent 340 remains
in place to dilate the lesion 96.
[0185] Other apparatus and methods for delivering a stent 340, such
as any of those described herein, may be found in application Ser.
Nos. 11/419,997 and 11/439,717, both filed May 23, 2006, the entire
disclosures of which are expressly incorporated by reference
herein. For example, application Ser. No. 11/419,997 discloses
various locator devices that may be provided on or with the
apparatus 310 to facilitate locating the ostium and/or positioning
the stent during delivery.
[0186] Turning to FIGS. 27A-27F, another method is shown for
delivering a stent 340 into a bifurcation 90, similar to those
described elsewhere herein. FIG. 27A shows the stent 340 in its
contracted condition mounted on a distal end 316 of a catheter 312.
Turning to FIG. 27B, after being delivered to a location adjacent
the bifurcation, a proximal balloon 322a may be inflated to a
predetermined size to expand and/or flare a first portion 341 of
the stent 340. As shown, the first portion 341 may be over-flared,
i.e., plastically deformed or otherwise flared to a greater angle
than the shape of the corresponding ostium into which the stent 340
is being delivered. For example, the first portion 341 may be
flared close to or even beyond ninety degrees (90.degree.) relative
to longitudinal axis 320.
[0187] Turning to FIG. 27C, after expansion and/or flaring, the
proximal balloon 322a may be partially deflated, e.g., such that
the flared first portion 341 of the stent 340 is removed from the
surface of the proximal balloon 322a.
[0188] Turning to FIG. 27D, the distal end 316 of the catheter 312
may be inserted into the branch vessel 94, e.g., over a guidewire
(not shown), similar to the embodiments described elsewhere herein.
Because of the over-flaring, the first portion 341 of the stent 340
may be advanced into the ostium 90 with sufficient force to cause
the first portion 41 to become slightly less flared, i.e., causing
the first portion 341 to conform at least partially to the shape of
the ostium 90. This advancement force may impose an elastic load on
the first portion 341, which may enhance apposition and/or
anchoring of the stent 340 relative to the ostium 90.
[0189] Turning to FIG. 27E, the apparatus 310 may be advanced to
substantially seat the stent 340 in the ostium 90, whereupon the
distal balloon 322b may be inflated to expand the second portion
343 of the stent 340, as shown in FIG. 27F. The balloons 322 may
then be collapsed and the apparatus 310 removed from the ostium 90
and the patient's body, leaving the stent 340 in the ostium 90.
[0190] Optionally, with additional reference to FIG. 27F, if
desired, the first and second portions 341, 343 of the stent 340
may be tempered to different degrees, e.g., to enhance the ability
of the first portion 341 to hold a spring force upon advancement
into the ostium 90. For example, the second portion 343 may be
annealed, while the first portion 341 may be relatively harder,
i.e., allowing a greater buildup of elastic deformation before
plastic deformation occurs. Alternatively, the entire stent 340 may
be hardened to a greater temper.
[0191] Turning to FIGS. 28A-28D, yet another method for delivering
a stent 340 into an ostium 90 where a branch vessel 94 extends from
a main vessel 92. In this embodiment, a distal portion of the
distal balloon 322b may be expanded first to substantially anchor
the stent 340 within the branch vessel 94 before the proximal
portion of the stent 340 is expanded. Initially, as shown in FIG.
28A, the apparatus 310 may be advanced through the patient's
vasculature and positioned such that the stent 340 extends into the
ostium 90, e.g., using external imaging, locators (not shown) on
the apparatus 310, and the like, similar to other embodiments
described herein.
[0192] Turning to FIG. 28B, the distal balloon 322b may be
inflated, which may cause the distal portion of the distal balloon
322b to inflate first, as shown, e.g., due to the lower resistance
to expansion of the distal portion 343 of the stent 340. As the
distal portion 343 of the stent 340 expands, it engages the wall of
the branch 94, thereby gaining traction that may prevent or reduce
migration of the stent 340. As shown in FIG. 28C, as the distal
balloon 322b is expanded, the distal portion 343 of the stent 340
and distal balloon 322b may expand in the direction of the main
lumen 92, thereby increasing traction and resistance of the stent
340 to migration, thereby substantially stabilizing the stent 340
relative to the ostium 90.
[0193] Turning to FIG. 28D, the proximal balloon 322a may be
inflated to expand and flare the proximal portion 341 of the stent
340. As represented by arrow "A," expansion of the proximal portion
341 of the stent 340 may apply a proximal force on the stent 340.
However, the traction provided by the expanded distal portion 343
may resist proximal movement, and allow the proximal portion 341 to
flare and expand without causing the stent 340 to migrate.
Optionally, the distal balloon 322b and/or proximal balloon 322a
may be expanded further simultaneously or separately, similar to
other embodiments described herein.
[0194] In an alternative embodiment, a separate balloon or other
expandable member (not shown) may be provided on the apparatus 310,
e.g., distally beyond the distal balloon 322b. This balloon may be
inflated after positioning the apparatus 310 and stent 340 in the
ostium to secure the apparatus 310, similar to the distal balloon
322b, as described above. The balloon may remain inflated until
after the stent 340 is fully expanded, and then deflated before the
apparatus 310 is removed.
[0195] Turning to FIG. 29, another embodiment of a stent 440 is
shown that includes multiple portions having different properties
than one another. Generally, the stent 440 is expandable from a
contracted condition to an enlarged condition, similar to the
embodiments described elsewhere herein. In the embodiment shown,
the stent 440 includes a first portion 441 adjacent a first end
442, a second intermediate portion 443, and a third portion 445
adjacent a second end 444. The first portion 441 may include one or
more bands of cells configured to expand and flare, e.g., similar
to other embodiments described herein. Thus, the first portion 441
may be configured for delivery into an ostium (not shown)
immediately adjacent a main lumen (also not shown). The first
portion 441 may be relatively stiff compared to the second and
third portions 443, 445, e.g., to resist elastic recoil of the
ostium, e.g., after delivering the stent 440 into the ostium, as
described further below.
[0196] The second, intermediate portion 443 may be relatively
flexible compared to the first and third portions 441, 445, e.g.,
to provide a flexible transition, e.g., if a branch lumen (not
shown) extends transversely other than perpendicularly from the
main lumen. Thus, the intermediate portion 443 may accommodate a
bend in the stent 440 between the first and third portions 441, 445
without substantial risk of kinking or otherwise significantly
compromising the lumen through the stent 440. In addition, the
second portion 443 may be relatively short compared to the third
portion 445, e.g., such that the second portion 443 does not extend
substantially into the branch lumen. For example, the second
portion 443 may include a plurality of links or other flexible
connectors (not shown), e.g., similar to those shown and described
with reference to FIGS. 4A-6E. Alternatively, the second portion
443 may include one or more bands of cells (not shown), e.g.,
having relatively thin or otherwise flexible elements, similar to
exemplary cell structures described elsewhere herein.
[0197] The third portion 445 may be relatively longer than the
first and second portions 441, 443. The mechanical properties of
the third portion 445 may be balanced, e.g., to provide desired
hoop strength to reinforce the branch lumen while providing
sufficient flexibility to facilitate delivery, similar to other
embodiments described herein.
[0198] Turning to FIGS. 31 and 32, an exemplary bifurcation is
shown, including an ostium 90 communicating between a main lumen 92
and a branch lumen 94. As explained elsewhere herein, the ostium 90
and/or branch lumen 94 may include plaque or other stenotic
material (not shown) that may at least partially occlude the ostium
90. The desired properties for a stent to be deployed in such an
ostium may be varied along its length, as just explained. In
contrast, stents that are delivered into a non-bifurcated body
lumen are generally designed to have substantially uniform
properties along their lengths. Such uniformity is generally
undesirable in a stent intended for delivery in a bifurcation.
[0199] For example, as shown in FIG. 31, the wall thickness of a
bifurcation may vary between the main lumen 92 and the branch lumen
94. As shown, the wall thickness in the main lumen 92 may be
substantially greater than the branch lumen 94. Thus, even if the
ostium 90 is dilated, the thicker wall may create greater risk of
recoil, i.e., of the wall at the ostium 90 being biased to
constrict again after dilation. FIG. 32 graphically depicts the
properties of a stent that may be desired given this problem. For
example, line "R" represents the elastic recoil that the vessel
wall may exhibit at the bifurcation. As shown, the recoil is
greater immediately adjacent the main lumen 92 at least partially
because of the greater wall thickness. The elastic recoil reduces
into the ostium 90, and may have a substantially uniform recoil
within the branch lumen 94 where the wall is located away from the
ostium 90 that is substantially less than at the ostium 90.
[0200] To overcome this recoil, line "S" represents the luminal
support desired for the stent along its length. Thus, it may be
desirable to provide greater luminal support or rigidity upon
expansion at the first end of the stent immediately adjacent the
main lumen 92, and provide a lesser but substantially uniform
rigidity within the branch lumen 94 away from the ostium 90.
Conversely, line "F" represents the desired flexibility that may be
desired for the stent along its length.
[0201] FIGS. 30 and 33-36 show various embodiments of cell patterns
that may be provided that have variable mechanical properties along
a length of a stent including the respective patterns. For example,
FIG. 30 shows an embodiment of a stent structure having four
different set of bands of cells. As shown, columns 1 and 2 include
zigzag patterns having a shorter period than columns 3 and 4.
Stated differently, columns 1 and 2 include more axial and curved
elements disposed around a circumference of the stent than columns
3 and 4. Because of these differences, the bands of cells in
columns 1 and 2 my have greater luminal support and/or less
flexibility than the bands of cells in columns 3 and 4.
[0202] In addition, columns 1 and 2 are connected together using
relatively short axial links extending between every adjacent
curved element. These connections may also increase the support
and/or reduce the flexibility in columns 1 and 2. In contrast,
columns 2 and 3 and columns 3 and 4 are connected intermittently by
longer diagonal links. These connections may increase flexibility
in these columns.
[0203] Turning to FIG. 33, another embodiment of a stent structure
including a plurality of bands of cells disposed along a length of
the stent. In this embodiment, the axial and curved elements
defining the cells have similar length and spacing in each of the
columns. However, the width or thickness of the axial and curved
elements and/or links varies along the length of the stent. As
shown, the thickness of the axial and curved elements and links is
reduced from column 1 to column 9. This effectively reduces the
luminal support from column 1 to column 9, while increasing
flexibility.
[0204] Turning to FIG. 34, another embodiment of a stent structure
is shown having variable properties along its length. In this
embodiment, the axial elements are longer at column 9 than at
column 1. This configuration may also reduce the luminal support
and/or increase flexibility from column 1 towards column 9. In
addition, the thickness of the axial and curved elements and links
may be reduced from column 1 to column 9, similar to the embodiment
shown in FIG. 33.
[0205] Turning to FIG. 35, yet another embodiment of a stent
structure is shown that includes different numbers of links along
its length. As shown, the bands of cells adjacent columns 1 and 2
include links connecting every adjacent curved element. Subsequent
bands of cells towards column 9 include intermittent links,
progressively increasing flexibility towards column 9. For example,
the bands of cells adjacent columns 3 and 4 are missing one in
every five links, the bands of cells adjacent column 5 are missing
one in every three links, and the bands of cells adjacent columns
6-9 are missing every other link.
[0206] Turning to FIG. 36, still another embodiment of a stent
structure is shown having different links between adjacent bands of
cells between columns 1 and 9. As shown, columns 1 and 2 do not
include links; instead adjacent curved elements are connected
directly to one another, thereby providing relatively strong
luminal support and reduced flexibility. Columns 4-6 include
progressively longer axial links, while columns 7-9 include curved
links, which may increase flexibility. The links in columns 7 and 8
have a slight curvature, e.g., defining an obtuse angle, while the
links in column 9 have greater curvature, e.g., defining close to a
ninety degree angle. Alternative embodiments of curved links
including more complicated geometries are shown in FIGS. 36A-36C,
e.g., including sinusoidal shapes.
[0207] Although different configurations are shown in these
embodiments, it will be appreciated that various combinations of
these features and configurations may be possible to provide a
desired variability along the length of a stent, e.g., for delivery
into an ostium, as described above.
[0208] Turning to FIG. 37, another embodiment of a flared stent 540
is shown, which may be generally constructed similar to other
embodiments described herein. Unlike previous embodiments, the
stent 540 may have a relatively short length, e.g., such that the
stent 540 may be deployed into an ostium 90 without extending
substantially into the branch lumen 94, as shown in FIG. 38A. For
example, the stent 540 may include a proximal or flaring portion
541 and a distal or substantially straight portion 543, which may
be connected by flexible connectors and/or a flexible intermediate
portion (not shown). The distal portion 543 may have a similar or
shorter length than the proximal portion 541, or may have a length
greater than the proximal portion 541, but less than two or three
times the length of the proximal portion 541.
[0209] As shown in FIG. 38B, unlike previous embodiments, a
separate stent 550 may be delivered into the branch lumen 94 beyond
or overlapping the distal portion 543 of the stent 550. The
additional stent may be any conventional uniform property stent or
a variable property stent, similar to the distal portions of the
stents described herein. FIGS. 39A-39C show another variation in
which the stent 540 of FIG. 37 is delivered along with a first
separate stent 550 in the branch lumen 94, e.g., similar to FIG.
38B, and a second separate stent 560 in the main lumen 92.
[0210] FIG. 40 shows an exemplary embodiment of a delivery
apparatus 510 that may be used to deliver the stent 540 of FIG. 37
or other similar stent, either alone or with a separate branch
lumen stent, such as the stent 550 shown in FIG. 38B. The apparatus
510 may include a locator device 520, e.g., such as those disclosed
in the applications incorporated by reference above. In addition,
the apparatus 510 may include one or more balloons, e.g., a larger
proximal balloon 522a and a smaller distal balloon 522b, which may
be inflated independently of one another to expand the stent 540
similar to other embodiments described elsewhere herein. For
example, the proximal flaring portion 541 of the stent 540 may at
least partially overly the proximal balloon 522a and the distal
portion 543 may overly the distal balloon 522b.
[0211] Turning to FIGS. 41-43, yet another exemplary embodiment of
an apparatus 610 for delivering a stent or other prosthesis 640,
e.g., into an ostium or other bifurcation between a main lumen and
a branch lumen (not shown). Generally, the apparatus 610 includes a
delivery catheter or other elongate tubular member 612 having a
proximal end 614, a distal end 616, and one or more lumens 618
extending between the proximal and distal ends 614, 616, thereby
defining a longitudinal axis 620 extending between the proximal and
distal ends 614, 616.
[0212] As shown, the delivery catheter 612 may include one or more
balloons or other expandable members 622 on the distal end 16 for
expanding and/or deploying the stent 640, similar to other
embodiments described herein. In addition, the distal end 616 may
include one or more markers, e.g., one or more bands of radiopaque
material 619 (two shown in FIG. 41), to facilitate positioning the
delivery catheter 612 and/or stent 640. In addition or
alternatively, the delivery catheter 612 may include one or more
therapeutic and/or diagnostic elements (not shown) on the distal
end 616, e.g., instead of or in addition to the stent 640 and/or
balloon(s) 622.
[0213] Optionally, the delivery catheter 612 may include one or
more locator elements (not shown) on the distal end 616, e.g.,
proximal or otherwise adjacent to the stent 640, such as those
disclosed in application Ser. No. 10/712,888, filed Nov. 12, 2003,
and Ser. No. 60/722,182, filed Sep. 29, 2005 the entire disclosures
of which are expressly incorporated by reference herein, and in
application Ser. No. 11/419,997, incorporated by reference
above.
[0214] The stent 640 may include a first or flaring portion 642 and
a second or tubular portion 644. As shown, the first portion 642 is
disposed proximal to the second portion 644, e.g., for antegrade
delivery. Alternatively, the first and second portions 642, 644 may
be reversed, e.g., for retrograde delivery, as may any of the other
embodiments described herein. In this alternative, the orientation
of the balloons 622 on the distal end 616 of the delivery catheter
612 (or other delivery device described herein) may be reversed
from that described herein.
[0215] The stent 640 may be formed from a variety of materials that
may be plastically deformed to allow expansion of the stent 640,
e.g., similar to other embodiments described herein. Alternatively,
at least a portion of the stent 640 may be self-expanding and/or
the resistance of the stent 640 to expansion may be varied along
its length, also similar to other embodiments described herein.
[0216] The stent 640 may be a generally tubular structure, e.g.,
including openings in a tubular wall that facilitate expansion of
the stent 640 and/or allow tissue ingrowth. For example, the stent
640 may be an elongate tube that has slots or other openings formed
in the tube wall, e.g., by laser cutting, mechanical cutting,
chemical etching, machining, and the like. Alternatively, the stent
640 may be a braided or other structure, e.g., formed from one or
wires or other filaments braided or otherwise wound in a desired
manner. Additional possible stent structures may include helical
coil wires or sheets, welding or otherwise attaching wire or other
structures together, and the like. If desired, one or more portions
of the stent 640 may include a membrane, film, or coating (not
shown), e.g., to create a nonporous, partially porous, or porous
surface between cells of the stent 640 and/or to carry one or more
therapeutic compounds, similar to other embodiments described
herein.
[0217] In addition, as shown in FIGS. 42 and 43, the apparatus 610
may include a guide catheter 660 including a proximal end 662, a
distal end 664, and a lumen 666 extending therebetween. The distal
end 664 may be sized and/or shaped to facilitate advancement into a
patient's vasculature or other body lumen, as described further
below. The lumen 666 may have sufficient size for receiving the
distal end 616 of the delivery catheter 612 therethrough, e.g.,
with any locator elements (not shown) in a contracted condition.
Optionally, the distal end 664 of the guide catheter 660 may be
biased to a predetermined shape, e.g., a "J" shape, which may
facilitate positioning the guide catheter 660 within or adjacent an
ostium. The guide catheter 660 may be constructed from
substantially flexible and/or floppy materials, e.g., plastic
having a braid or other reinforcement (not shown) that sufficiently
supports the guide catheter 660 to prevent kinking or buckling,
while allowing the guide catheter 660 to be directed easily through
tortuous anatomy.
[0218] Optionally, the apparatus 610 may include other components
to provide a system or kit for delivering the stent 640, e.g., a
sheath that may be advanced over and/or retracted from the distal
end 616 of the delivery catheter 612, one or more syringes or other
sources of inflation media and/or vacuum, tubing, and/or one or
more guidewires (all not shown).
[0219] Returning to FIGS. 41-43, the delivery catheter 612 may be
formed from one or more tubular bodies, e.g., having variable
flexibility along its length. For example, similar to other
embodiments described herein, the distal end 616 may be
substantially flexible to facilitate insertion through tortuous
anatomy, e.g., terminating in a rounded, tapered, and/or other
substantially atraumatic distal tip 617. The distal end 616 may be
sized and/or shaped for introduction into a body lumen, e.g.,
having a diameter between about one and seven millimeters (1-7 mm),
or less than 1.5 millimeters. The proximal end 614 may be
substantially flexible or semi-rigid, e.g., having sufficient
column strength to facilitate advancing the distal end 16 through a
patient's vasculature by pushing on the proximal end 614.
Optionally, as shown in FIG. 41, a shaft support wire or other
stiffener 615 may be provided within the proximal end 614, e.g., to
facilitate pushing the delivery catheter 12 from the proximal end
14. The delivery catheter 612 may be formed from plastic, metal, or
composite materials, e.g., a plastic material having a wire, braid,
or coil core, which may preventing kinking or buckling of the
delivery catheter 612 during advancement.
[0220] As shown, the delivery catheter 612 may include a handle 630
on the proximal end 614, e.g., to facilitate manipulating the
delivery catheter 612, which may be included in the other
embodiments described herein. The handle 630 may include one or
more ports 632 communicating with respective lumens 618 within the
delivery catheter 612. The handle 630 may be molded, machined, or
otherwise formed from plastic, metal, or composite material, e.g.,
providing an outer casing, which may be contoured or otherwise
shaped to ease manipulation. The proximal end 614 of the delivery
catheter 612 may be attached to the handle 630, e.g., by bonding,
cooperating connectors, interference fit, and the like. Optionally,
if the apparatus 610 includes any actuatable components (not shown)
on the distal end 616, the handle 630 may include one or more
actuators (not shown), such as one or more slides, dials, buttons,
and the like, for actuating or otherwise manipulating the
components from the proximal end 614.
[0221] As best seen in FIG. 41, the catheter 612 includes at least
three lumens 618 extending between the proximal and distal ends
614, 616. For example, the catheter 612 may include an instrument
lumen 618a that extends from a side port 632a to an opening 634 in
the distal tip 617. The instrument lumen 618a may have sufficient
size to allow a guidewire or other rail or instrument (not shown)
to be inserted therethrough, e.g., to facilitate advancing the
catheter 612 over the rail, as explained further below.
Alternatively, rather than a "rapid exchange" instrument lumen
618a, an instrument lumen (not shown) may be provided that extends
from the distal end 616 to the handle 630. In this alternative, the
handle 630 may include a port (not shown) and/or one or more seals
(also not shown) that prevent fluid, e.g., blood, from flowing
proximally out of the port, yet allows one or more instruments to
be inserted therethrough and into the instrument lumen 618a.
[0222] In addition, the catheter 612 may include inflation lumens
618b, 618c that extend from respective side ports 632b, 632c in the
handle 630 through the catheter 612 to openings 634b, 634c on the
distal end 616. Each opening 634b, 634c communicates within an
interior 623a, 623b of a respective balloon 622a, 622b. The side
ports 632b, 632c on the handle 630 may include connectors, e.g., a
luer lock connector (not shown), one or more seals (also not
shown), and the like. A source of inflation media and/or vacuum,
e.g., a syringe filled with saline (not shown), may be connected to
the side ports 632b, 632c, e.g., via tubing (also not shown), for
expanding and/or collapsing the balloons 622a, 622b.
[0223] As shown in FIG. 41, the lumens 618 are disposed adjacent
one another. Alternatively, the lumens 618 may be disposed in
concentric or other arrangements within the body of the catheter
612. In addition, if the apparatus 610 includes additional balloons
(not shown) on the distal end 616, the catheter 612 may include one
or more additional inflation lumens (also not shown), and the
handle 630 may include one or more additional ports (also not
shown), similar to those shown and described with reference to FIG.
41.
[0224] Alternatively, other configurations of lumens may be
provided for delivering fluid to and/or aspirating fluid from one
or both balloons 622. For example, a single lumen may be provided
(not shown) that communicates with the interiors 623 of both
balloons 622. This embodiment may allow the balloons 622 to be
expanded and/or collapsed substantially simultaneously using a
single syringe or other source of fluid/vacuum. In another
alternative, the catheter 612 may include separate inflation lumens
618b, 618c, but the handle 630 may include a single side port (not
shown) to which a syringe or other source of fluid/vacuum may be
connected. In this alternative, the handle 630 may include a
switch, stopcock, valve, or other device for selectively connecting
one or both inflation lumens 618b, 618c to the side port.
[0225] For example, a three-way valve (not shown) may be directed
to first or second positions to allow the side port to be connected
to either of the inflation lumens 618b, 618c, e.g., for
inflating/collapsing an individual balloon 622a, 622b. In a third
position, the side port may be connected to both lumens 618b, 618c
for inflating/collapsing both balloons 622 simultaneously. This
configuration may be particularly useful for quickly collapsing
both balloons 622 after implanting the stent 640 before removing
the apparatus 610. In addition, the configuration may facilitate
expanding the entire stent 640, e.g., after expanding and anchoring
the first portion 642 and/or after flaring the second portion
644.
[0226] Returning to FIGS. 41-43, the delivery catheter 612 includes
an outer or proximal balloon 622a and an inner or distal balloon
622b on the distal end 616. As shown, the first portion 642 of the
stent 640 is disposed over a portion of the proximal balloon 622a,
and the second portion 644 of the stent 640 is disposed over at
least a portion of the distal balloon 622b. Alternatively, the
delivery catheter 612 may include a single or multiple balloons
(not shown) on the distal end 616 over which the stent 640 may be
placed. Additional information on balloon catheters and methods for
using them are disclosed in the applications incorporated by
reference herein.
[0227] The balloons 622 may be bonded or otherwise secured to the
distal end 16 of the delivery catheter 612. For example, ends of
the balloons 622 may be attached to the distal end 616 by bonding
with an adhesive, by sonic welding, using an annular collar or
sleeve, and the like. The distal balloon 622b may include a
proximal end 624a attached to the distal end 616 of the catheter
612 proximal to opening 634c and a distal end 626a attached
adjacent the distal tip 617. The proximal balloon 622a may extend
at least partially over the distal balloon 622b. For example, the
distal end of the proximal balloon 622a may extend entirely over
the distal balloon 622b and be attached over or adjacent to the
distal end of the distal balloon 622b, e.g., by bonding, sonic
welding, and the like, as described elsewhere herein.
[0228] The distal balloon 622b may be expandable from a contracted
condition (shown in FIG. 42) to an enlarged condition (shown in
FIG. 41). Similarly, the proximal balloon 622a may also be
expandable from a contracted condition (shown in FIG. 42) to an
enlarged condition (shown in FIGS. 41 and 43). As shown, the
proximal balloon 622a and distal balloon 622b may be expandable
independently from one another.
[0229] With particular reference to FIG. 41, in the enlarged
condition, the proximal balloon 622a may include proximal and
distal ramped surfaces 628a, 628c meeting at an outermost
intermediate region 628b. As shown, the intermediate region 628b is
disposed proximal to the stent 640 such that the distal surface
628b extends beneath the first portion 642 of the stent 640, e.g.,
for flaring the first portion 642, and proximally beyond the first
portion 642, e.g., for facilitating positioning the stent 640, as
described further below.
[0230] The balloons 622 may be formed from substantially inelastic
material, e.g., PET, nylon, or PEBAX, such that each balloon 622
expands to a predetermined size in its enlarged condition once
sufficient fluid is introduced into the interior of the balloon
622. Alternatively, the balloon 622 may be formed from
substantially elastic material, e.g., silicone, polyurethane, or
polyethylene, such that the balloon 622 may be expanded to a
variety of sizes depending upon the volume and/or pressure of fluid
within the interior.
[0231] Optionally, the delivery catheter 612 may include a stop 650
disposed adjacent the second portion 644 of the stent 640. As shown
in FIG. 41, the stop 650 may be a section of tubular material
formed, bonded, or otherwise attached over a portion of the
balloons 622. The stop 650 may include a substantially blunt
proximal edge 652 adjacent the stent 640, which may abut the second
portion 644 of the stent 640, e.g., to prevent distal migration of
the stent 640 when the first portion 642 of the stent 640 is
flared, as described further below. In addition or alternatively, a
sleeve (not shown) may extend from the stop 650, e.g., to partially
cover the distal end 644 of the stent 644, e.g., to prevent the
distal end 644 from dislodging and passing over the stop 650.
Alternatively, other structures (not shown) may be provided to
constrain, secure, or otherwise limit distal migration of the stent
40, such as the sleeves disclosed in application Ser. No. 136,266,
incorporated by reference above.
[0232] Turning to FIGS. 44-48, an exemplary method is shown for
using the apparatus 610 (which may be any of the embodiments
described herein) to deliver a stent 640 into an ostium 90. The
ostium 90 may be an opening in a wall of a first or main body lumen
or trunk 92 that communicates with a second body lumen or branch
94, such as those described elsewhere herein. An occlusion or other
lesion 96 may exist at and/or adjacent to the ostium 90, e.g.,
extending at least partially into the branch 94. The lesion 96 may
include atherosclerotic plaque or other material that partially or
completely occludes blood or other fluid flow between the trunk 92
and the branch 94.
[0233] Initially, as shown in FIG. 44, a guidewire 98 or other rail
may be introduced from the trunk 92 through the ostium 90 into the
branch 94. As shown, the lesion 96 at the ostium 90 partially
occludes the ostium 90 and extends into the branch 94. The
guidewire 98 may be placed using conventional methods. For example,
a percutaneous puncture or cut-down may be created at a peripheral
location (not shown), such as a femoral artery, carotid artery, or
other entry site, and the guidewire 98 may be advanced through the
patient's vasculature from the entry site, e.g., alone or with the
aid of guide catheter 660. If the lesion 96 completely occludes the
branch 94, the guidewire 98 may be directed through the occlusion,
or other devices (not shown) may be advanced over the guidewire 98
or otherwise in conjunction with the guidewire 98 to create a
passage through the lesion 96 for the guidewire 98.
[0234] After the guidewire 98 is directed into the branch 94 beyond
the lesion 96, it may be desirable to at least partially dilate the
lesion 96. For example, an angioplasty catheter (not shown) may be
advanced through the guide catheter 660 and/or over the guidewire
98 into and through the lesion 96, whereupon a balloon or other
element on the catheter may be expanded to at least partially
dilate the lesion 96. If desired, other procedures may also be
performed at the lesion 96, e.g., to soften, remove, or otherwise
treat plaque or other material forming the lesion 96, before the
stent 640 is implanted. After completing any such procedures, any
instruments advanced over the guidewire 98 may be removed.
[0235] As shown in FIG. 44, the distal end 664 of the guide
catheter 660 has been advanced over the guidewire 98 into the trunk
92, e.g., until the distal end 664 is disposed adjacent or proximal
to the ostium 90. The guide catheter 660 may be used to advance one
or more instruments (such as those just described) over the
guidewire 98 and into the trunk 92 and/or branch 94.
[0236] Turning to FIG. 45, to deliver the stent 640, the distal end
616 of the delivery catheter 612 may be advanced over the guidewire
98 and through the lumen 666 of the guide catheter 660 from the
entry site into the trunk 92. As shown, the stent 640 and balloons
622 are in their contracted conditions during advancement. With the
distal end 664 of the guide catheter 660 against or adjacent the
ostium 90, the distal end 616 of the delivery catheter 612 may be
advanced from the guide catheter 660, through the ostium 90, and
into the branch 94. For example, as shown in FIG. 46, the delivery
catheter 612 may be advanced until the stent 640 extends into and
through the lesion 96, e.g., to ensure that the stent 640 may be
positioned fully within the lesion 96 before any portion of the
stent 640 is expanded.
[0237] Turning to FIG. 47, the delivery catheter 612 may be
partially withdrawn (or otherwise positioned) to dispose the stent
640 within the lesion 96, e.g., such that the first portion 642 of
the stent 640 is positioned adjacent the ostium 90 within the
branch 94. To facilitate positioning, the delivery catheter 612 may
be monitored using fluoroscopy or other external imaging, e.g., to
observe and monitor markers 619 (not shown, see FIG. 41) on the
distal end 616. In addition, if desired, the guide catheter 660 may
be partially withdrawn into the trunk 92 such that the guide
catheter 660 does not interfere with movement of the distal end 616
of the delivery catheter 612.
[0238] Turning to FIG. 48, with the delivery catheter 612 and stent
640 properly positioned, the proximal balloon 622a may be expanded,
e.g., by delivering saline, nitrogen, or other inflation media into
the interior 623a (not shown, see FIG. 41) of the proximal balloon
622a from a syringe or other fluid source (not shown) coupled to
the proximal end (also not shown) of the delivery catheter 612. As
the proximal balloon 622b is expanded, the first portion 642 of the
stent 640 is expanded, e.g., into a flared configuration conforming
to the distal surface 628c of the proximal balloon 622a.
[0239] As shown in FIG. 49, as the proximal balloon 622a is
expanded, the distal surface 628c of the proximal balloon 622a
beyond the stent 640 may contact the branch 94 adjacent the ostium
90. Because of the tapered or ramped shape of the distal surface
628c, the radial expansion of the proximal balloon 622a may
translate into a proximal force, causing the distal end 616 of the
delivery catheter, and consequently the stent 640, to move
proximally. Stated differently, as the proximal balloon 622a is
expanded, the stent 640 may migrate partially out of the branch 94,
e.g., such that the first portion 642 is disposed within the ostium
90. Thus, if the stent 640 is positioned distally further into the
branch 94 than desired (e.g., despite monitoring using
fluoroscopy), the proximal balloon 622a may automatically correct
the position of the stent 640 within the ostium 90. Optionally, at
least the distal surface 628c of the proximal balloon 622a may be
formed from a lubricious material and/or may include a lubricious
coating, e.g., to reduce friction between the distal surface 628c
and the wall of the branch 94 to facilitate migration and/or other
automatic correction in positioning of the stent 640.
[0240] Turning to FIG. 50, after inflating the proximal balloon
622a, the distal balloon 622b may be inflated to expand the stent
640 fully. With the distal balloon 622b disposed within the
proximal balloon 622a, as shown in FIG. 41, the distal balloon 622b
may cause the proximal balloon 622a, and consequently the first
portion 642 of the stent 640, to expand further. Thus, the distal
balloon 622b may expand the second portion 644 of the stent 640
within the branch 94, while simultaneously enhancing the proximal
balloon 622a further expanding and/or flaring the first portion 642
of the stent 640 to contact the wall of the ostium 90. In addition
or alternatively, the proximal balloon 622a may be inflated further
to flare and/or expand the first portion 642 of the stent 640 such
that the first portion 642 contacts and/or dilates the ostium 90.
As the stent 640 expands, the lesion 96 may be directed radially
outwardly, thereby dilating the ostium 90 and/or branch 94.
Optionally, if desired, distal force may be applied to the delivery
catheter 612 to direct the first portion 642 of the stent 640
against the ostium 90, e.g., to enhance securing the stent 640
and/or conforming the first portion 642 of the stent 640 to the
shape of the ostium 90.
[0241] Turning to FIG. 51, with the stent 640 fully deployed, the
balloons 622 may be deflated or otherwise collapsed, and the
delivery catheter 612 may be withdrawn into the guide catheter 660.
Optionally, the guide catheter 660 may be advanced towards or
against the ostium 90 and/or against a proximal end of the stent
640 before the delivery catheter 612 is removed. This action may
facilitate withdrawing the distal end 616 (and the balloons 622)
back through the stent 640, e.g., without substantial risk of
dislodging the stent 640 from the ostium 90 and/or branch 94. The
delivery catheter 612, guide catheter 660, and/or guidewire 98 may
then be removed from the patient's body, leaving the stent 640 in
place.
[0242] It will be appreciated that elements or components shown
with any embodiment herein are exemplary for the specific
embodiment and may be used on or in combination with other
embodiments disclosed herein.
[0243] While the invention is susceptible to various modifications,
and alternative forms, specific examples thereof have been shown in
the drawings and are herein described in detail. It should be
understood, however, that the invention is not to be limited to the
particular forms or methods disclosed, but to the contrary, the
invention is to cover all modifications, equivalents and
alternatives falling within the scope of the appended claims.
* * * * *