U.S. patent application number 11/035671 was filed with the patent office on 2005-09-22 for everting stent and stent delivery system.
This patent application is currently assigned to ev3 Inc.. Invention is credited to Kusleika, Richard S..
Application Number | 20050209676 11/035671 |
Document ID | / |
Family ID | 28039045 |
Filed Date | 2005-09-22 |
United States Patent
Application |
20050209676 |
Kind Code |
A1 |
Kusleika, Richard S. |
September 22, 2005 |
Everting stent and stent delivery system
Abstract
Devices and methods for delivering stents to target vessel
regions, including stent delivery through microcatheters to narrow
cerebral arteries. One stent delivery device includes a stent
having the distal region everted over the distal end of a delivery
tube, having the everted stent distal end captured by a distal
element of a elongate release member disposed through the delivery
tube. The delivery tube can have a distal taper to a small profile
distal end. The everted stent distal region can be captured between
the release member distal element and the surrounding delivery tube
distal region walls. The captured and everted stent can be distally
advanced to a target site, followed by manipulating the release
member to free the captured stent. Some devices utilize distal
advancement of the release member while other devices use proximal
retraction of the release member to free the captured stent distal
end. Once released, the stent is free to self-expand or be expanded
against the surrounding blockage and/or vessel walls. In some
methods, a guide catheter or microcatheter is also included and
disposed about the everted and captured stent to advance the stent,
delivery tube, and release member to a location near the site to be
stented. The devices and methods provide stent delivery not
requiring an enclosing delivery sheath about the stent. The everted
stent can thus have a very small distal profile enabling small
diameter vessels to be crossed and treated.
Inventors: |
Kusleika, Richard S.; (Eden
Prairie, MN) |
Correspondence
Address: |
KUDIRKA & JOBSE, LLP
ONE STATE STREET
SUITE 800
BOSTON
MA
02109
US
|
Assignee: |
ev3 Inc.
Plymouth
MN
|
Family ID: |
28039045 |
Appl. No.: |
11/035671 |
Filed: |
January 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11035671 |
Jan 14, 2005 |
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10096628 |
Mar 12, 2002 |
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6866679 |
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Current U.S.
Class: |
623/1.11 |
Current CPC
Class: |
A61F 2/95 20130101; A61F
2/82 20130101 |
Class at
Publication: |
623/001.11 |
International
Class: |
A61F 002/06 |
Claims
What is claimed is:
1. An elongate stent delivery assembly, the assembly comprising: a
delivery tube having a distal region, a proximal region, and a
lumen therethrough; a stent including a tubular body having a
distal region, a proximal region, and an intermediate region
disposed between the distal region and the proximal region, the
stent body having a lumen therethrough, wherein the stent distal
region is disposed over the delivery tube distal region, and
everted over the delivery tube distal end, such that the stent body
distal end is disposed within the delivery tube distal region
lumen; and an elongate release member having a proximal region, a
distal region, and a distal end, wherein the release member distal
region is releasably coupled to the everted stent body distal
region, such that releasing the releasable coupling between the
release member distal region and the everted stent body distal
region frees the stent from the delivery tube.
2. An assembly as in claim 1, wherein the stent is biased to
radially expand when freed from the delivery tube.
3. An assembly as in claim 1, wherein the elongate release member
distal profile is dimensioned to form a friction fit between the
everted stent body distal end disposed about the elongate release
member distal portion and the delivery tube distal region disposed
about the everted stent distal region.
4. An assembly as in claim 3, wherein the elongate release member
has sufficient strength in compression to allow for advancing the
release member distal region distally from the delivery tube distal
region, such that the everted stent is released from the delivery
tube distal end.
5. An assembly as in claim 4, wherein the release member proximal
region is externally accessible.
6. An assembly as in claim 3, wherein the elongate release member
has sufficient strength in tension to allow for retracting the
release member distal region proximally free of the everted stent
body distal region, thereby releasing the stent from the delivery
tube.
7. An assembly as in claim 6, wherein the release member proximal
region is externally accessible.
8. An assembly as in claim 3, wherein the delivery tube has an
intermediate region disposed between the delivery tube distal and
proximal regions, wherein the delivery tube intermediate region has
an inside diameter dimensioned to provide columnar support for the
enclosed release member.
9. An assembly as in claim 1, wherein the delivery tube has an
intermediate region, wherein the delivery tube distal region is
tapered, having a smaller outer diameter at the delivery tube
distal end than in the delivery tube intermediate region.
10. An assembly as in claim 1, further comprising a microcatheter
having a distal region, a proximal region, and a lumen through at
least the distal region, wherein the microcatheter distal region is
disposed over the delivery tube distal region.
11. An elongate stent delivery device for delivering a stent, the
stent including a tubular body having a distal region delivery tube
distal region lumen, the device comprising: a delivery shaft having
a distal region, a proximal region, and a lumen through at least
the shaft distal region; and an elongate release member having a
proximal region, a distal region, and a distal end, wherein the
elongate release member distal region is disposed within the
delivery shaft distal region lumen, wherein the release member
distal region is cooperatively dimensioned to releasably secure to
the stent body distal region between the release member shaft
distal region and the delivery shaft distal region, such that
releasing the releasable coupling between the release member distal
region and the stent body distal region frees the stent from the
delivery shaft.
12. A device as in claim 11, wherein the elongate release member
distal profile is dimensioned to form a friction fit between the
stent body distal end disposed about the elongate release member
distal portion and the delivery shaft distal region disposed about
the stent distal region.
13. A device as in claim 12, wherein the elongate release member
has sufficient strength in compression to allow for advancing the
release member distal region distally from the delivery shaft
distal region, such that the stent is released from the delivery
tube distal end.
14. A device as in claim 13, wherein the release member proximal
region is externally accessible.
15. A device as in claim 12, wherein the elongate release member
has sufficient strength in tension to allow for retracting the
release member distal region proximally free of the stent body
distal region, thereby releasing the stent from the delivery
shaft.
16. An assembly as in claim 13, wherein the release member proximal
region is externally accessible.
17. A device as in claim 11, wherein the delivery shaft has a lumen
through a majority of its length.
18. A device as in claim 17, wherein the delivery shaft has an
intermediate region disposed between the delivery shaft distal and
proximal regions, wherein the delivery shaft intermediate region
lumen has an inside diameter dimensioned to provide columnar
support for the enclosed release member.
19. A device as in claim 11, further comprising a microcatheter
having a distal region, a proximal region, and a lumen through at
least the distal region, wherein the microcatheter distal region is
disposed over the delivery shaft distal region.
20. A method for delivering a tubular stent to a target vessel
region, the method comprising the steps of: providing a stent
having a substantially tubular body, a distal region, a proximal
region, an intermediate region disposed between the distal and
proximal regions, and a distal end; providing a delivery shaft
having a distal region, a proximal region, and a distal end,
wherein the distal region has a lumen therethrough, wherein the
stent distal region is everted over the delivery shaft distal end
such that the stent proximal and intermediate regions are disposed
over the delivery shaft while the stent distal end is disposed
inside the delivery tube distal region lumen; providing an elongate
release member having a distal region, a proximal region, an
intermediate region disposed between the distal and proximal
regions, and a distal end, wherein the release member distal region
is releasably coupled to the everted stent distal region to secure
the everted stent to the release member; advancing the everted
stent, delivery shaft, and release member distally to a location
near the target vessel region; and releasing the release member
from the stent distal region such that the stent is no longer
secured to the delivery shaft distal region.
21. A method as in claim 20, wherein the releasing step includes
proximally retracting the release member such that the everted
stent distal region is no longer captured between the release
member distal region and the delivery shaft distal region.
22. A method as in claim 21, wherein the release member proximal
region is externally accessible, wherein the proximally retracting
step includes manipulating the release member from the release
member proximal region.
23. A method as in claim 20, wherein the releasing step includes
distally advancing the release member distal region, such that the
everted stent distal region is no longer captured between the
elongate release member distal region and the delivery shaft distal
region.
24. A method as in claim 23, wherein the release member proximal
region is externally accessible, wherein the distally advancing
step includes manipulating the release member from the release
member proximal region.
25. A method as in claim 20, further comprising radially expanding
the stent after the releasing step.
26. A method as in claim 24, wherein the radially expanding step
includes allowing the stent to radially expand upon release,
wherein the provided stent is biased to expand radially when freed
from the delivery shaft distal region.
27. A method as in claim 25, wherein the radially expanding step
includes radially expanding the stent from within the stent lumen
after the releasing step.
28. A method as in claim 27, wherein the radially expanding step
includes providing an inflatable balloon catheter having a distal
region and a proximal region, having an inflatable balloon disposed
about the distal region, wherein the radially expanding step
includes inflating the balloon catheter within the stent after the
releasing step to radially expand the stent at the target vessel
region.
29. A method as in claim 20, further comprising: providing a
microcatheter having a distal region, a proximal region, an
intermediate region disposed between the distal and proximal
regions, a distal end, and a lumen therethrough; advancing the
microcatheter to near the target vessel region; and distally
advancing the everted stent, delivery shaft, and release rod within
the microcatheter; and advancing the everted stent, delivery shaft,
and release rod distally from the microcatheter distal end across
the target vessel region.
30. A method as in claim 20, further comprising: providing a
microcatheter having a distal region, a proximal region, an
intermediate region disposed between the distal and proximal
regions, a distal end, and a lumen therethrough; advancing the
microcatheter to near the target vessel region; and distally
advancing the everted stent, delivery shaft, and release rod within
the microcatheter; advancing the microcatheter, everted stent,
delivery shaft, and release rod distally across the target vessel
region; proximally retracting the microcatheter from the target
vessel region to expose the stent; and manipulating the release
member to release the stent from the release member and delivery
shaft.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to medical devices.
More specifically, the present invention relates to stents. The
stents may find particular use in intravascular procedures in
general, and in cardiovascular procedures in particular, as well as
other areas.
BACKGROUND OF THE INVENTION
[0002] Stents are well known to those skilled in the biomedical
arts. In particular, stents are commonly used in cardiovascular
applications. Stents have gained increasing acceptance,
particularly when used in conjunction with minimally invasive
procedures such as angioplasty. Blockages of the coronary arteries
may result from various causes, including plaque build-up, and
stenosed or thrombosed vessel regions. The vessel regions thus
partially occluded can cause angina and, when totally occluded,
myocardial infarction, and even death. Minimally invasive
procedures such as balloon angioplasty have been used to dilate
such blocked vessel regions, thereby at least partially restoring
patent vessel lumens.
[0003] In a significant percentage of cases, a stenosed, then
dilated vessel region may narrow after treatment over a period
ranging from days to months. This re-narrowing or restenosis,
limits the efficacy of the angioplasty procedures, may require
further angioplasty, or can lead to myocardial infarction and even
death.
[0004] Cerebral blockages are typically caused by a thrombus. The
thrombus can form or lodge in a cerebral artery, preventing brain
regions downstream from receiving perfusing blood flow. The loss of
oxygen can rapidly cause brain death in the affected brain regions
if the blockage is not soon treated. The cerebral arteries are
generally smaller and more tortuous than the corresponding coronary
arteries. The required timing and difficult vessel characteristics
make reaching and treating the thrombus to prevent brain cell death
a most difficult task. The narrow cerebral vessels make placing
stents within the brain very difficult using current stents and
stent delivery systems. Microcatheters are currently used to infuse
drugs into cerebral blood vessels. The microcatheters are typically
not greater than about 4 Fr. (11/3 mm.) in outer diameter,
currently being generally unsuitable for delivery of cerebral
stents.
[0005] Stents have been extensively utilized in an attempt to
prevent or limit restenosis. Stents are typically tubular devices
delivered to the stenosed and dilated site. The stents can be
expanded into place against the treated region walls, hopefully
preventing restenosis and further narrowing at the stented
location. Stents are often formed of metal, commonly stainless
steel or Nitinol. The stents can be open walled structures formed
from lattice-like cages, spiral wire structures, braided
structures, and helically wound and counter-wound structures.
Stents can be self-expanding, designed to expand radially when
distally advanced from a restraining delivery catheter. Stents can
also be balloon-expandable. Balloon-expandable stents can be
positioned and then expanded from within using a stent delivery
balloon and/or an angioplasty balloon.
[0006] A typical stent delivery device includes a stent constrained
within an outer delivery sheath extending over the length of the
stent. When the device is advanced to the target site, the outer
sheath is proximally retracted and/or the stent is distally
advanced from within the sheath to the target site. The delivery
sheaths may work as intended, but do add bulk to the distal end of
the delivery device. In particular, the delivery sheath adds at
least one additional layer surrounding the stent. The delivery
sheaths are generally cylindrical in nature and extend over the
entire length of the stent. The stent can act to reinforce the
outer sheath. The delivery sheath and enclosed stent thus act to
form a rather rigid composite structure that is not as able to bend
and traverse the tortuous vessel regions often found in the human
body. The composite structure is thus not as flexible as either the
stent or sheath alone would be in traversing these passages.
[0007] The added bulk and profile or cross-sectional area of the
delivery device can thus act to restrict the use of such stents to
larger vessels. In particular, this may leave smaller vessels
unreachable and untreatable. Sites requiring treatment disposed on
the distal side of a tortuous curve may also be unreachable and
untreatable.
[0008] In use, some currently available stents and delivery systems
also have another limitation. For self-expanding stents, stent
placement is often imprecise. The placed or final stent length is
related to the final stent diameter that is related to the vessel
diameter. Within a vessel, the diameter is not always precisely
known, and can vary over the region to be stented. It may be nearly
impossible to predict the final stent length before the stent is
fully expanded in the vessel.
[0009] The difficulty in accurate stent placement can become an
issue in stenting a vessel ostium. It is often desirable to place a
stent precisely at the ostium of a vessel, especially in coronary
and renal vessels. If the stent is positioned too proximal, the
stent extends into the trunk line, and can cause flow disturbance.
If the stent is positioned too distal, the disease at the ostium is
not treated. Self-expanding stent delivery systems typically deploy
the stent from distal to proximal, with the distal stent end being
advanced distal-most. In particular, a self-expanding stent may be
advanced while disposed within a delivery sheath. When the sheath
distal end is in position, the sheath can be retracted, allowing
the accurately placed stent distal end to expand first. The
proximal end of the stent can vary depending on the vessel
diameter. In order to accurately place the stent proximal end, the
treating physician thus needs to guess at the position to start
stent deployment based on the assumed final stent length, so that
the proximal end of the stent ends up at the precise ostial
location desired.
[0010] What would be desirable are devices and methods for
delivering stents to target vessel regions that do not require the
added bulk of an external restraint or capture sleeve over the
stent. Applicants believe that devices and methods not absolutely
requiring a delivery sheath over the stent would allow smaller,
more tortuous, and more distal vessels to be effectively
treated.
SUMMARY OF THE INVENTION
[0011] The present invention includes devices and methods for
delivering stents to target vessel regions within the body. Methods
and devices for delivering everted stents are preferred and
disclosed. One stent delivery assembly includes a delivery tube
having a stent slidably disposed over the delivery tube distal
region, and having the stent distal region everted over the
delivery tube distal end, such that the stent distal end is tucked
inside of the delivery tube distal end lumen. An elongate release
member having a distal element can be slidably disposed within the
delivery tube lumen. The release member distal element can be
dimensioned relative to the surrounding delivery tube distal end
inside diameter so as to form a tight fit between the release
member distal element and the surrounding delivery tube. The stent
distal region can be held by a friction or interference fit between
the release member distal element and surrounding delivery tube
walls. The stent is thus everted and reduced in outer diameter at
the leading, everted distal end.
[0012] In one delivery device, the elongate release member is
pulled from the proximal region, thereby proximally urging the
release member distal element free of the stent distal end captured
between the release member distal element and the surrounding
delivery tube distal end. In such embodiments, the release member
function may be served by an elongate string or wire having
significant strength mainly in tension rather than compression. In
another embodiment of the invention, the elongate release member
function is served by a shaft having sufficient strength in
compression to distally urge the release member distal element by
manipulating the release element proximal region, forcing the
distal element from the surrounding delivery tube distal end,
thereby freeing and unconstraining the stent distal region. In some
embodiments, the delivery tube functionality is served by a
delivery shaft having only the distal region being tubular in
nature. In one such embodiment, the delivery shaft has a distal
hoop or annular ring for surrounding and capturing the everted
stent distal region within.
[0013] In use, the stent can be everted over the delivery tube or
shaft, with the stent distal end everted and captured by the
elongate release member. The everted stent, delivery shaft or tube,
and release member can be advanced distally to a target vessel
region to be stented. Once at the target region location, the
everted and constrained stent may be freed of the delivery shaft or
tube by the release member. The release member may be retracted
proximally in some embodiments, and advanced distally in other
embodiments, as previously discussed, to release the everted stent.
Once released, the stent is free to expand radially and approach
the surrounding vessel walls or blockage.
[0014] Self-expanding stents can be used in some embodiments of the
invention. The stents are preferably biased to radially expand when
freed of the constraints of the delivery tube and release member.
In other embodiments, balloon expandable stents are used, which can
be expanded using inflatable balloon catheters or other stent
delivery devices.
[0015] Some methods according to the present invention can utilize
a guide wire to facilitate advancement of a guide catheter or
microcatheter to a location near the vessel region to be stented.
The guide wire can be retracted, and the carried everted stent
advanced by the release member and guide tube together through the
guide catheter or microcatheter to the target region. In one
method, the everted stent carried by the delivery tube and release
member are advanced distally from the guide catheter to cross the
target region, for example, a blood vessel stenosis. In another
method, the microcatheter together with the everted stent carried
by the delivery tube and release member are advanced through the
stenosis or other blockage, followed by proximally retracting the
microcatheter, leaving the everted stent to expand against the
target region vessel or blockage walls. Once the everted stent is
in location, the release member can be activated by advancing or
retracting the member to free the everted stent.
[0016] Once unconstrained, the stent, for example, a self-expanding
stent, may expand to approach the vessel walls or the blockage. In
some embodiments, the release member may be advanced distally
through the previously placed stent lumen to guarantee a minimal
lumen through the stent and/or to act as a guide member for other
devices to be passed through the now stented region. In one method,
the delivery tube is advanced through the now stented region, which
can act to further dilate the stent. In another method, the guide
catheter or microcatheter can also be advanced through the now
stented region, which can act to further dilate the stent. Thus, a
succession of ever increasing diameter devices may be advanced
through the stent after stent deployment in some methods. In
another method, a balloon catheter is advanced through the now
stented region followed by inflation of the balloon and concomitant
dilation of the stent.
[0017] In another use of the present invention, an everted porous
stent carried by a delivery tube can be distally advanced through a
thrombosed blood vessel region. A wire mesh or braided stent may be
used. The everted stent can be released from the delivery tube to
expand against the thrombus. The delivered stent can thus act to
stabilize the thrombus. After stenting, the thrombus can be treated
by infusing thrombolytic agents near the thrombus, through the
walls of the porous stent. The stent can thus act to stabilize the
thrombus, preventing large pieces from breaking off and being
carried downstream during the thrombolysis.
[0018] Some embodiments of the present invention have distally
tapered delivery tubes having very small distal end profiles. In
these embodiments, the release member distal element may be very
small in profile as well. The limit of the distal profile in such
devices may approach the lower size limit in gathering, everting,
and compressing the distal region of the stent to be delivered. In
these and other embodiments, the leading edge of the stent delivery
device can be very benign and atraumatic due to the everted stent
forming the distal-most leading edge of the device. Many
embodiments of the device thus eliminate the absolute need for a
delivery sheath or tube disposed about the stent, thereby
eliminating one set of tube profiles from the device, making the
distal region more flexible, smaller in profile, and able to reach
even more distal and smaller diameter vessels which will benefit
from treatment.
DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a fragmentary, longitudinal, cross-sectional view
of a stent delivery assembly including a stent captured between the
distal ends of an elongate release member and the surrounding stent
delivery tube shown prior to everting the stent proximally over the
delivery tube;
[0020] FIG. 2 is a fragmentary, longitudinal, cross-sectional view
of the stent delivery assembly of FIG. 1 after the stent has been
everted and the device disposed within a guide catheter or
microcatheter;
[0021] FIG. 3 is a fragmentary, longitudinal, cross-sectional view
of the stent delivery assembly of FIG. 2 after the microcatheter
has been advanced proximal of a blockage and the captured, everted
stent carried further distally by the release member and delivery
tube;
[0022] FIG. 4 is a fragmentary, longitudinal, cross-sectional view
of the assembly of FIG. 3 after the stent has been released and
expanded within the target vessel region;
[0023] FIG. 5A is a fragmentary, longitudinal, cross-sectional view
of an alternate embodiment of the invention where the delivery tube
is a delivery shaft having a distal tube or ring;
[0024] FIG. 5B is a wafer view taken through 5B of FIG. 5A,
illustrating the fit between the release member distal end, everted
stent, and delivery shaft distal end; and
[0025] FIG. 5C is a fragmentary, longitudinal, cross-sectional view
of another embodiment of the invention, where the delivery tube has
a tubular distal region and coupled to a proximal shaft.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] The following detailed description should be read with
reference to the drawings, in which like elements in different
drawings are numbered identically. The drawings, which are not
necessarily to scale, depict selected embodiments and are not
intended to limit the scope of the invention. Several forms of
invention have been shown and described, and other forms will now
be apparent to those skilled in art. It will be understood that
embodiments shown in drawings and described above are merely for
illustrative purposes, and are not intended to limit scope of the
invention as defined in the claims that follow.
[0027] FIG. 1 illustrates a stent delivery assembly including a
stent delivery device 20, a stent 26, a delivery shaft or tube 22,
and an elongate release member 24. Release member 24 can be used to
releasably secure or couple stent 26 to delivery shaft or tube 22.
Stent 26 is illustrated in a configuration prior to being everted
and proximally disposed about delivery tube 22. Delivery tube 22
may be seen to have a distal region 30, a distal end 28, an
intermediate region 32, a tube wall 38, a tube wall inner surface
36, and a lumen 34 therethrough. Release member 24 may be seen to
have a distal region 40 and a distal end 42 having a distal element
43. In the embodiment illustrated in FIG. 1, release member distal
end 42 is dimensioned so as to form an interference fit between
stent 26 and delivery tube wall inner surface 36. Delivery tube
wall 38 may be seen to be slightly distended in the area of release
member distal end 42. Stent 26, described with reference to the
everted state, has generally a distal region 46, a distal end 47,
an intermediate region 44, a proximal region 48, a proximal end 50,
and a lumen 52 therethrough.
[0028] Release member 24 may be seen, at distal end 42, to have an
outside diameter D1 which closely approximates the inside diameter
of delivery tube 22 in the distal region. Stent 26 may be seen
gripped between release member distal end 42 and delivery tube 22.
Stent 26, in some embodiments, may be biased to expand radially
when unconstrained. As illustrated in FIG. 1, stent proximal end 50
has an unconstrained diameter D2 that is substantially larger than
the constrained diameter D1. Self-expanding stents are well known
to those skilled in the art. Such self-expanding stents may be
formed, for example, from Nitinol, which can be heat set to assume
a desired shape when unconstrained. Stent 26 in FIG. 1 is
illustrated in an intermediate step during assembly. Stent proximal
end 50 may be everted and pulled proximally as a sleeve over
delivery tube 22. Other methods of assembly are possible. In
preferable methods, stent 26 may be heat set in an uneverted shape
and disposed as a sleeve over delivery tube distal region 30 in the
uneverted state. Stent distal region 46 may then be everted and
tucked within delivery tube distal end 28. Release member 24 may
then have its proximal end threaded through stent lumen 52 and
delivery tube lumen 34 until release member distal end 42 has been
proximally retracted within delivery tube distal region 28, firmly
capturing stent distal region 46 between the elongate member distal
end 42 and the delivery tube distal region 28.
[0029] FIG. 2 illustrates stent delivery device 20 further included
within a more comprehensive stent delivery assembly 60. Stent
delivery assembly 60 includes generally a guide catheter or
microcatheter 62 having a distal region 64, an intermediate region
69, a proximal region 72, and a distal end 66 having a lumen 68
therethrough. Release member 24 can have an optional collar 51
disposed about the release member distal region and dimensioned to
slidably fit within delivery tube 22. FIG. 2 further illustrates
release member 24 having a proximal region 25 coupled to an
optional larger diameter proximal end 27 dimensioned so as to form
an axially slidable seal between release member proximal end 27 and
the surrounding delivery tube proximal region 33. FIG. 2 also
illustrates optional annular seal member 29 forming a larger
diameter proximal region 33 for the delivery tube 22. Annular
element 29 may be seen to form a slidable seal between delivery
tube 22 and the surrounding guide catheter or microcatheter 62.
FIG. 2 also illustrates that stent 26 can expand outward radially
while within guide catheter 62. In particular, stent intermediate
region 44, proximal region 48, and proximal end 50 may be seen to
have expanded radially to the extent permitted by the surrounding
guide catheter 62. The dimensions illustrated for the proximal
region of stent delivery assembly 62 and FIG. 2 may vary depending
on the embodiment and the intended use. FIG. 2 illustrates only
one, non-limiting example of the invention.
[0030] Microcatheters are well known devices, commonly used to
deliver drugs to cerebral arteries. "Microcatheters", as the term
is used herein, is defined to be a tubular catheter having an
outside diameter less than about 5 Fr. (12/3 mm.). Microcatheters
used with the present invention preferably have an outside diameter
between about 1.5 Fr. (1/2 mm.) and 4 Fr. (11/3 mm.), inclusive.
Microcatheters preferably have a floppy distal region and tip, the
distal region being more pliable and softer than the intermediate
and proximal microcatheter regions.
[0031] FIG. 3 illustrates one use of assembly 60 in a body conduit
or vessel 82 having a target region 80 at least partially occluded
by a blockage 84. Blockage 84 can at least partially block vessel
82, thereby reducing the effective size of vessel lumen 86.
Blockage 84 represents any of a number of blockages, including, but
not limited to plaque, thrombus, and a stenosed vessel region
generally.
[0032] In one method according to the present invention, a
guidewire is advanced distally through the vessel until the
guidewire distal tip is across or proximally near vessel target
region 80. Guide catheter or microcatheter 62 can then be advanced
over the placed guidewire until microcatheter distal end 66 is
disposed proximal of blockage 84. In some methods, the guidewire is
now retracted proximally from microcatheter 62.
[0033] With microcatheter 62 in place, stent delivery device 20 may
be advanced through microcatheter lumen 68 to a position within
microcatheter 60 proximal of vessel target region 80. As may be
seen from inspection of FIG. 3, stent 26 is everted over the distal
end of delivery tube 22 and releasably secured to delivery tube 22
with elongate release member distal end 42. In the embodiment
illustrated, stent 26 is a self-expanding stent, with proximal end
50 having a larger outside diameter than constrained distal end
47.
[0034] With release member 24, delivery tube 22, and everted stent
26 in position, the release member, the delivery tube, and the
captured, constrained and everted stent 26 may be distally advanced
across the target site 80 having blockage 84. In some methods, the
advancing of release member, delivery tube, and everted stent is
accomplished while leaving guide catheter or microcatheter 62
positioned proximal of the vessel target site. In other methods,
guide catheter or microcatheter 62 is advanced across target vessel
region 80. In one method, microcatheter 62, everted stent 26,
delivery tube 22, and release member 24 are all advanced together
across target region 80. In this method, after microcatheter 62 and
constrained, everted stent 26 are across target vessel region 80,
microcatheter 62 can be proximally retracted, exposing the
stent.
[0035] As may be seen from inspection of FIG. 3, stent 26 is still
releasably secured to delivery tube 22 and may be further advanced
distally. In some uses of the invention, a microcatheter such as
microcatheter 62 may be used to advance the releasably secured
stent and delivery tube only so far as the microcatheter can reach,
followed by the distal exit of the everted stent from the
microcatheter to attain even greater distal reach for the stent.
FIG. 3 also illustrates that stent 26 can be axially elongated as
the stent is pulled through narrow passages, which can reduce the
stent profile while the stent is being pulled.
[0036] Once everted stent 26 is at the desired location, the stent
can be released from delivery tube 22. In one example of the
invention, release member 24 is urged proximally, thereby pulling
the release member distal end proximally until release member
distal end 42 is disposed proximally of everted stent distal end
47. Stent 26 may then expand further radially to embrace the
surrounding vessel target region 80. In another example of the
invention, elongate release member 24 can be distally urged,
thereby forcing release member distal end 42 distally from delivery
tube 22, thereby releasing stent 26 from delivery tube 22. In
embodiments having optional collar 51, the collar can be used to
help push out the stent after release. Both distal and proximal
movement of release member 24 can be accomplished by manipulating
the proximally accessible portion of the release member. Stent 26
is then free to radially expand and retain its previous,
non-everted shape.
[0037] It may be seen from inspection of FIG. 3 that everted stent
26 has a smaller distal profile than proximal profile, allowing
easier entry into narrow target sites. In some embodiments of the
invention, delivery tube 22 has a tapered distal tip, such that the
profile of the distal end of delivery tube 22 is smaller than the
profile of delivery tube 22 in an intermediate or proximal
location. FIG. 3 also illustrates that the everted distal region 46
of stent 26 forms a rather atraumatic tip, relative to many other
distal delivery devices and, in most embodiments, more benign than
the delivery tube distal end 28. Due in part to the self-expanding
nature of the stent illustrated in FIG. 3, distally urging the half
released, half secured stent forms a proximally widening shape that
can act to initially penetrate, then dilate a blocked vessel
region, prior to totally releasing the stent.
[0038] The distance between release member 24 and delivery tube 22
is indicated at D3 in FIG. 3. In some embodiments, the proximal and
intermediate regions of delivery tube 22 have a very tight fit
between release member 24 and delivery tube 22. A close tolerance
between the release member and the delivery tube can provide
columnar support for advancing release member 24. Such close
tolerance can also provide strength and stability when the elongate
release member 24 is retracted proximally to release stent 26, in
embodiments calling for such retraction.
[0039] FIG. 4 illustrates vessel target region 80 after stent 26
has been expanded to create and stabilize an expanded or dilated
flow channel 87 through vessel 82. Stent proximal region 48 and
distal region 46 may be seen to have expanded radially against
blockage 84. Stent 26 is preferably radially expanded outwardly
against the vessel walls and/or blockage once released by release
member 24. In one method, stent 26 is biased to radially expand
outwardly, once unconstrained. Some self-expanding stents useful
with the present invention are formed of Nitinol. Stents may be
heat-set to radially expand and assume the heat-set diameter once
released in some methods.
[0040] In one method according to the invention, after stent 26 has
been allowed to expand radially, this process may be assisted using
parts of the device previously described. In embodiments where the
release rod has sufficient strength in compression to be pushed,
release member 24 maybe advanced distally through deployed stent 26
to ensure that an initial clear flow passage exists through stent
26. Elongate release member 24 may be followed by distally
advancing delivery tube 22 through deployed stent 26. In other
methods, guide catheter or microcatheter 62 may be advanced through
deployed stent 26, to further widen the already stented passage.
These methods may also be employed to assist with eversion of the
distal end of the released but incompletely deployed stent. In some
methods, the delivery tube and release member may be retracted
proximally, and an inflatable balloon catheter advanced to the now
stented vessel site to further dilate the deployed stent by
inflating the inflatable balloon disposed in the balloon catheter
distal region.
[0041] FIG. 3 illustrates only one embodiment of the invention,
which is not necessarily drawn to scale. In particular, in some
embodiments, the distal region of delivery tube 22 can be
significantly smaller in profile. In one embodiment, release member
24 has distal end 42 being substantially smaller in profile than
that illustrated in FIG. 3. In one embodiment, distal end 42 is
tapered distally or proximally to facilitate the frictional fit
between the stent and the delivery catheter. The inside of the
delivery catheter distal region and/or outside of the release
member distal end 42 can be coated with a compressible, tacky,
flowable, or high friction material to augment the security of
reversible stent engagement. In one device, release member distal
end 42 is only slightly larger in profile than the intermediate
portion of release member 24. In one embodiment, release member 24
has strength substantially only in tension rather than compression,
and acts as a string. This string or wire can be very small in
profile, and can be coupled to a very small release member distal
element. In one embodiment, elongate release member 24 is a fine
gauge wire, metallic or polymeric, coupled to a small distal plug.
Delivery tube distal end 28 may also be much smaller and
significantly distally tapered relative to that illustrated in FIG.
3. Delivery tube distal end 28 may also be reinforced against
diametric enlargement by incorporation of a strong circular loop or
band within or outside of the wall of the delivery tube distal end.
Preferably the loop or band is metallic and more preferably
radiopaque so as to facilitate visualization under fluoroscopy.
[0042] Inspection of FIG. 3 indicates that the lower limit on the
transverse cross-sectional size or profile of the stent delivery
assembly may be limited by the profile of the everted stent 26. In
one embodiment of the invention, elongate release member 24 is
effectively a thin wire or string terminating distally in a plug or
ball shape only slightly larger in profile than the wire or string.
Delivery tube 22 may be significantly distally tapered such that
the inside diameter of the delivery tube distal end approaches the
outer diameter of the release member distal end or plug 42. The
stent may thus be everted and the stent distal region tightly
bunched or gathered together between the small distal ball or plug
and the surrounding, tapered, distal end of the delivery tube.
While the release member and delivery tube occupy space, it may be
seen that the absolute lower limit of the cross-sectional profile
in some embodiments may be ultimately bounded by the lower size
limit in releasably compressing the stent distal end.
[0043] FIG. 5A illustrates another embodiment of the invention. The
stent delivery assembly 100 illustrated in FIG. 5A can be similar
to that of assembly 20 as illustrated in FIGS. 1 and 2. Delivery
assembly 100 may be seen to have an everted stent 26 and an
elongate release member 24 as previously discussed. Assembly 100
has a delivery shaft 122 rather than a delivery tube. Delivery
shaft 122 has an intermediate region 132 extending to a distal
region 124. Distal region 124 includes support struts 128 extending
distally and radially outward to support a short tube section or
annular ring 126. In some embodiments, annular tube or ring 126 may
be significantly longer than that illustrated in FIG. 5A, which is
not necessarily to scale. The distal region of delivery shaft 122
may thus form a delivery tube in the many respects previously
discussed. Stent 26 may be seen to be everted over distal annular
ring or hoop 126 and held in place by a tight, interference fit
between release member distal element 42 and annular ring 126. As
may be seen from inspection of FIG. 5A, everted stent 26 may be
released from the assembly 100 by proximally retracting release
member 24 or distally extending release member 24, depending on the
embodiment and the properties of the release member shaft forming
release member 24. FIG. 5B illustrates a transverse cross-sectional
view of the assembly 100 of FIG. 5A, showing release end element 43
disposed within one layer of stent 26 which is in turn disposed
within annular ring 126 which has a second layer of stent 26
disposed to the outside.
[0044] FIG. 5C illustrates another stent delivery assembly 160,
somewhat similar to that of delivery assembly 100 of FIG. 5A and
having the same reference numerals for similar elements. Assembly
160 includes elongate release member 24 and stent 26 as previously
discussed. The delivery device includes a distal tube 166 coupled
to a proximal elongate member or shaft 162. Tube 166 includes a
proximal end 174, a distal region 170, a distal end 172, and a
lumen 168 extending through the tube. Proximal shaft 162 can be
coupled to tube 160 at a shaft distal region 164. Proximal shaft
162 can extend distally along or within tube 166 in some
embodiments. Tube 166 may be slit to accommodate proximal shaft
162.
[0045] Stents that may be used with the present invention include
self-expanding and balloon expandable stents, well known to those
in the cardiovascular arts. Stents may be formed from many of the
well known stent materials, including Nitinol, stainless steel, and
polymers. The stents may be braided, knit, meshed, formed of
non-woven wires, helically wound and helically counterwound. Stents
according to the present invention are preferably porous, wire,
braided stents, with various embodiments having an average pore or
inter-wire opening size of at least about 20 microns in one
embodiment, and at least 50 microns in another embodiment. In a
preferred embodiment the stent ends are coated with flexible
adherent material to prevent unraveling of, for example, braided
stents. Alternatively, the stent strands can be welded or otherwise
fastened to one another to prevent unraveling during eversion.
[0046] In one use of the invention, the everted stent may be used
to stabilize a blockage such as a thrombus, while providing a
perfusing path through the dilated thrombus. In another use, the
stent may be positioned across a stenosed blood vessel region, and
the region treated with a restenosis inhibiting agent. The
restenosis inhibiting agent can be infused through the porous stent
wall or reside on the stent itself and release into the vessel
wall. FIGS. 3 and 4 may be used to visualize blockage 84 being
formed primarily of thrombus, with stent 26 being put in place to
primarily stabilize the thrombus and to provide oxygenating blood
flow to downstream brain regions, preventing brain cell death.
Small distal profile catheters as previously discussed and as
illustrated in FIG. 3 may thus be used to advance an everted stent
across a thrombus and deploy the stent. The stent, which can be
either self-expanding or expandable from within using a stent
placement device, can then expand against the vessel walls and/or
blockage. In some methods, an infusion catheter is advanced to
within vessel site 80, and thrombolytic agents infused through the
porous stent wall. Various therapeutic agents may be applied in
this way. A non-limiting list of such therapeutic agents includes
thrombolytic agents, anticoagulants, anti-platelet agents, and
tissue plasminogen activator. In a similar way, stents according to
the present invention can be used to treat an area stenosed because
of arteriosclerosis.
[0047] The present invention can be used to accurately position the
stent proximal end. The stent proximal end may be positioned
accurately relative to a vessel ostium. The stent can be positioned
near the proximal end of a stenosis located near or at an ostium.
The everted stent can be advanced as previously discussed, until
the proximal end is positioned at the desired location. The stent
proximal end can be allowed to radially expand against the vessel
walls. In some methods, the stent can be advanced further distally
until the expanded proximal end is at the desired position. The
stent placement may be followed using fluoroscopy. This desired
position may be exactly at the ostium beginning, slightly within
the ostium, or extending slightly from the ostium. The stent distal
region can be released and allowed to expand. In this way, the
stent proximal end can be positioned accurately relative to the
ostium.
[0048] In one embodiment of the invention, the elongate release
member has a length of between about 100 cm. and 200 cm. In one
embodiment, the outer diameter of the release member distal element
is less than 2 mm. In various embodiments, the release member may
be formed from stainless steel, Nitinol, polyimide, reinforced
polymer, or PEEK and the like.
[0049] The delivery tube or shaft in some embodiments has a length
of between about 75 cm. and 175 cm. The delivery tube can have an
outside diameter of between about 6 Fr. and 1 Fr. In various
embodiments of the invention, the distal region of the delivery
tube may be distally tapered. In some embodiments, the
cross-sectional outer diameter of the delivery tube distal end is
less than about 6 Fr. Delivery tubes can be made from flexible
polymers such as PEBAX, nylon, polyester, polyurethane,
polyethylene, FEP, Teflon, silicone, and the like, with or without
reinforcement by metallic or polymeric elements. Microcatheters are
well known to those skilled in the art and any suitably sized guide
catheter or microcatheter may be used in combination with the
present invention, preferably about 3 Fr. or 4 Fr. in outer
diameter. Some exemplary sized catheters that can be used with the
present invention are between about 75 cm. and 175 cm. in length.
Guide or microcatheters useful in conjunction with the present
invention may be formed from Nylon, PEBAX, polyurethane, and the
like. Guide catheters can be reinforced with metallic braids, with
microcatheters preferably having very flexible distal end regions.
The catheters can have a distal outer diameter of less than about 8
Fr. for guides and 4 Fr. for microcatheters.
* * * * *