U.S. patent application number 10/699612 was filed with the patent office on 2004-09-30 for intravascular flow modifier and reinforcement device and deployment system for same.
Invention is credited to Friedmann, Josef L., Leopold, Eric W., Padilla, Neal H..
Application Number | 20040193141 10/699612 |
Document ID | / |
Family ID | 32912270 |
Filed Date | 2004-09-30 |
United States Patent
Application |
20040193141 |
Kind Code |
A1 |
Leopold, Eric W. ; et
al. |
September 30, 2004 |
Intravascular flow modifier and reinforcement device and deployment
system for same
Abstract
A stent includes a cylindrical frame consisting of a series of
helical winds containing a pattern of alternating zigzag bends. The
frame may be made of resilient wire or from a piece of laser cut
hypo tubing. The stent may be deployed by placing the stent over a
notched portion of a pusher catheter member, and retained on the
pusher catheter member by a release wire threaded through the
pusher catheter member and over the stent. The stent may also be
deployed by placing the stent over a pusher catheter member having
opposing notched portions, and retaining the stent and pusher
catheter member in a delivery catheter, which can be withdrawn when
stent reaches the site to be treated to release the stent.
Inventors: |
Leopold, Eric W.; (Redwood
City, CA) ; Friedmann, Josef L.; (Boulder Creek,
CA) ; Padilla, Neal H.; (San Jose, CA) |
Correspondence
Address: |
FULWIDER PATTON LEE & UTECHT, LLP
HOWARD HUGHES CENTER
6060 CENTER DRIVE
TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Family ID: |
32912270 |
Appl. No.: |
10/699612 |
Filed: |
October 31, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60447601 |
Feb 14, 2003 |
|
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|
Current U.S.
Class: |
604/527 |
Current CPC
Class: |
A61F 2220/0016 20130101;
A61F 2/89 20130101; A61F 2/95 20130101; A61F 2/88 20130101 |
Class at
Publication: |
604/527 |
International
Class: |
A61M 025/00 |
Claims
What is claimed is:
1. An intravascular flow modifier and reinforcement device for use
in the intravascular treatment of a target site in a blood vessel,
comprising: a generally cylindrical frame formed of an elongate
resilient wire configured as a series of helical windings, said
generally cylindrical frame having a deployed configuration and a
predeployed compressed configuration for placement of the
intravascular flow modifier and reinforcement device at the target
site, said generally cylindrical frame in its deployed
configuration having a helical pattern of sharp alternating zigzag
bends.
2. The intravascular flow modifier and reinforcement device of
claim 1, wherein said predeployed compressed configuration
comprises a substantially flattened configuration.
3. The intravascular flow modifier and reinforcement device of
claim 1, wherein said deployed configuration comprises a generally
cylindrical configuration.
4. The intravascular flow modifier and reinforcement device of
claim 1, wherein said generally cylindrical frame has a
cross-section formed in the shape of a polygon or modified polygon
having at least one straight portion.
5. The intravascular flow modifier and reinforcement device of
claim 1, wherein said deployed configuration varies in
cross-sectional area along its longitudinal axis.
6. The intravascular flow modifier and reinforcement device of
claim 1, wherein said windings of said generally cylindrical frame
vary in pitch along the longitudinal axis of said generally
cylindrical frame.
7. The intravascular flow modifier and reinforcement device of
claim 1, wherein said predeployed compressed configuration
comprises a radially compressed configuration.
8. The intravascular flow modifier and reinforcement device of
claim 1, wherein said helical windings have a range of pitch to
provide a wire coverage of the inner surface area of the target
site being treated of between about 7% and about 40%.
9. The intravascular flow modifier and reinforcement device of
claim 1, wherein said alternating zigzag bends have an angle that
is less than about 120.degree. to promote laminar arterial
flow.
10. The intravascular flow modifier and reinforcement device of
claim 1, wherein said helical windings have a variable pitch.
11. The intravascular flow modifier and reinforcement device of
claim 1, wherein said helical windings have a variable diameter
over the length of the intravascular flow modifier and
reinforcement device.
12. The intravascular flow modifier and reinforcement device of
claim 1, wherein each of said helical windings comprise a series of
between 4 and 8 alternating zigzag bends in a rotation of the
wire.
13. The intravascular flow modifier and reinforcement device of
claim 1, wherein each of said helical windings comprise a series of
4 alternating zigzag bends in a rotation of the wire.
14. The intravascular flow modifier and reinforcement device of
claim 1, wherein each of said helical windings comprise a series of
6 alternating zigzag bends in a rotation of the wire.
15. The intravascular flow modifier and reinforcement device of
claim 1, wherein said elongate resilient wire is formed of a
superelastic material.
16. The intravascular flow modifier and reinforcement device of
claim 1, wherein said elongate resilient wire is formed of a shape
memory material.
17. The intravascular flow modifier and reinforcement device of
claim 1, wherein said elongate resilient wire is formed of a
nickel-titanium alloy.
18. The intravascular flow modifier and reinforcement device of
claim 1, wherein said elongate resilient wire is coated with a
corrosion resistant material.
19. The intravascular flow modifier and reinforcement device of
claim 1, wherein said elongate resilient wire is coated with
Parylene.
20. The intravascular flow modifier and reinforcement device of
claim 1, wherein said elongate resilient wire is treated by
chemical electropolishing to maximize corrosion resistance.
21. The intravascular flow modifier and reinforcement device of
claim 1, wherein said elongate resilient wire comprises a stranded
cable including one or more radiopaque strands.
22. The intravascular flow modifier and reinforcement device of
claim 1, wherein said elongate resilient wire comprises a stranded
cable having radiopaque markers deployed along the said stranded
cable.
23. The intravascular flow modifier and reinforcement device of
claim 22, wherein said stranded cable is made of a material
selected from the group consisting of stainless steel, shape-memory
alloy, superelastic alloy, platinum and combinations thereof.
24. The intravascular flow modifier and reinforcement device of
claim 1, wherein said elongate resilient wire is formed by laser
cutting a piece of tubing.
25. A system for deploying an intravascular flow modifier and
reinforcement device for use in the intravascular treatment of a
target site in a patient's vasculature, the intravascular flow
modifier and reinforcement device including a generally cylindrical
frame formed of an elongate resilient wire configured as a series
of helical windings, the system comprising: a substantially tubular
pusher catheter member having an inner lumen, a proximal portion, a
distal portion, a tubular main shaft, and a notched portion having
at least one notch formed in a side of the pusher catheter member
for receiving at least one said helical winding; and means for
removably retaining said at least one helical winding on said
notched portion of said pusher catheter member, said means for
removably retaining being capable of being withdrawn from said
notched portion of said pusher catheter member when the
intravascular flow modifier and reinforcement device is positioned
at the site in the patient's vasculature to be treated to release
and deploy the intravascular flow modifier and reinforcement device
at the site in the patient's vasculature to be treated.
26. The system of claim 25, wherein said notched portion comprises
a plurality of alternating notches and tubular shoulder portions
formed in said substantially tubular pusher catheter member.
27. The system of claim 25, wherein said means for removably
retaining said at least one helical winding on said notched portion
of said pusher catheter member comprises a release wire threaded
through the lumen of the pusher catheter member and over said at
least one helical winding to retain said at least one helical
winding on said notched portion of said pusher catheter member.
28. The system of claim 26, wherein a plurality of said helical
windings of the intravascular flow modifier and reinforcement
device are received in each of said notches.
29. The system of claim 27, further comprising a delivery catheter,
and wherein said substantially tubular pusher catheter member and
the intravascular flow modifier and reinforcement device received
on said notched portion of said pusher catheter member are disposed
in the delivery catheter, and wherein said delivery catheter can be
withdrawn along with said release wire from said notched portion of
said pusher catheter member when the intravascular flow modifier
and reinforcement device is positioned at the site in the patient's
vasculature to be treated for delivery of the intravascular flow
modifier and reinforcement device to the site in the patient's
vasculature to be treated.
30. The system of claim 25, wherein said notched portion comprises
a first plurality of notches on one side of the shaft, and a second
plurality of notches on an opposing side of the shaft.
31. The system of claim 30, wherein said means for removably
retaining said at least one helical winding on said notched portion
of said pusher catheter member comprises a delivery catheter, and
wherein said substantially tubular pusher catheter member and the
intravascular flow modifier and reinforcement device received on
said notched portion of said pusher catheter member are disposed in
the delivery catheter, and wherein said delivery catheter can be
withdrawn from said notched portion of said pusher catheter member
when the intravascular flow modifier and reinforcement device is
positioned at the site in the patient's vasculature to be treated
for delivery of the intravascular flow modifier and reinforcement
device to the site in the patient's vasculature to be treated.
32. The system of claim 30, wherein individual ones of said notches
of said second plurality of notches are offset from corresponding
ones of said first plurality of notches.
33. The system of claim 31, wherein said delivery catheter has an
inner diameter that is only slightly larger than an outer diameter
of the pusher catheter member, so as to retain the intravascular
flow modifier and reinforcement device on the pusher catheter
member.
34. A method for deploying an intravascular flow modifier and
reinforcement device for use in the intravascular treatment of a
target site in a patient's vasculature, the intravascular flow
modifier and reinforcement device including a generally cylindrical
frame formed of an elongate resilient wire configured as a series
of helical windings, the steps of the method comprising: releasably
mounting at least one helical winding of the intravascular flow
modifier and reinforcement device on notched portion of a
substantially tubular pusher catheter member, said notched portion
having at least one notch formed in a side of the pusher catheter
member for receiving said at least one helical winding; disposing a
means for removably retaining said at least one helical winding on
said notched portion of said pusher catheter member over said at
least one helical winding; positioning said means for removably
retaining the intravascular flow modifier and reinforcement device
at the site in the patient's vasculature to be treated; and
withdrawing said means for removably retaining from said notched
portion of said pusher catheter member to release and deploy the
intravascular flow modifier and reinforcement device at the site in
the patient's vasculature to be treated.
35. The method of claim 34, wherein said means for removably
retaining said at least one helical winding on said notched portion
of said pusher catheter member comprises a release wire threaded
through the pusher catheter member and over said at least one
helical winding to retain said at least one helical winding on said
notched portion of said pusher catheter member, and said step of
withdrawing said means for removably retaining from said notched
portion of said pusher catheter member comprises withdrawing said
release wire from said notched portion.
36. The method of claim 34, wherein said means for removably
retaining said at least one helical winding on said notched portion
of said pusher catheter member comprises a delivery catheter having
an inner diameter that is only slightly larger than an outer
diameter of the pusher catheter member, so as to retain the
intravascular flow modifier and reinforcement device on the pusher
catheter member, said notched portion and said at least one helical
winding of the intravascular flow modifier and reinforcement device
being disposed in said delivery catheter, and said step of
withdrawing said means for removably retaining from said notched
portion of said pusher catheter member comprises withdrawing said
delivery catheter from said notched portion.
37. A system for deploying an intravascular flow modifier and
reinforcement device for use in the intravascular treatment of a
target site in a patient's vasculature, the intravascular flow
modifier and reinforcement device including a generally cylindrical
frame formed of an elongate resilient wire configured as a series
of helical windings, the system comprising: a substantially tubular
pusher catheter member having an inner lumen, a proximal portion, a
distal portion, a tubular main shaft, and a notched portion having
at least one notch formed in a side of the pusher catheter member
for receiving at least one said helical winding, said substantially
tubular pusher catheter member being formed of a nickel-titanium
alloy; and means for removably retaining said at least one helical
winding on said notched portion of said pusher catheter member,
said means for removably retaining being capable of being withdrawn
from said notched portion of said pusher catheter member when the
intravascular flow modifier and reinforcement device is positioned
at the site in the patient's vasculature to be treated to release
and deploy the intravascular flow modifier and reinforcement device
at the site in the patient's vasculature to be treated.
38. A system for deploying an intravascular flow modifier and
reinforcement device for use in the intravascular treatment of a
target site in a patient's vasculature, the intravascular flow
modifier and reinforcement device including a generally cylindrical
frame formed of an elongate resilient wire configured as a series
of helical windings, the system comprising: a substantially tubular
pusher catheter member having an inner lumen, a proximal portion, a
distal portion, a tubular main shaft, and a notched portion having
at least one notch formed in a side of the pusher catheter member
for receiving at least one said helical winding; and a release wire
for removably retaining said at least one helical winding on said
notched portion of said pusher catheter member, said release wire
being threaded through the lumen of the pusher catheter member and
over said at least one helical winding to retain said at least one
helical winding on said notched portion of said pusher catheter
member, said release wire being capable of being withdrawn from
said notched portion of said pusher catheter member when the
intravascular flow modifier and reinforcement device is positioned
at the site in the patient's vasculature to be treated to release
and deploy the intravascular flow modifier and reinforcement device
at the site in the patient's vasculature to be treated, said
release wire being formed of a nickel-titanium alloy.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon Provisional Application
Serial No. 60/447,601, filed Feb. 14, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an intravascular flow
modifier and reinforcement device, i.e., a stent, for use within a
body vessel, and more particularly, to a stent for use in
combination with vasoocclusive devices placed adjacent to an
aneurysm for the purpose of occluding the aneurysm and providing
reinforcement for the area of the blood vessel in the vicinity of
the aneurysm.
[0004] 2. Description of Related Art
[0005] The progress of the medical arts related to treatment of
vascular malformations has dramatically improved with the
availability of intravascular devices capable of operating entirely
within the vasculature. Thus, many highly invasive surgical
procedures and inoperable conditions have been treated by the use
of an expanding number of devices and procedures designed for those
purposes. One particularly useful development in the medical arts
has been the ability to treat defects in relatively small arteries
and veins, such as those in the neurovascular system, by use of an
infusion catheter and the placement of embolic coils and the like
in areas where the malformation is likely to cause or has already
caused a rupture in the blood vessel. More specifically, it has
been found that the treatment of aneurysms by such devices and
procedures allows the medical practitioner to avoid otherwise risky
medical procedures. For example, when the defect is located in the
brain, a great deal of difficulty is involved in treatment of small
defects in the blood vessels with conventional surgical techniques.
For these reasons, the progress in development of devices to treat
such defects has been encouraged and has produced useful results in
a wide variety of patients.
[0006] One aspect of these surgical treatments is that an aneurysm
or other malformation is symptomatic of a general weakening of the
vasculature in the area containing the aneurysm, and mere treatment
of the aneurysm does not necessarily prevent a subsequent rupture
in the surrounding area of the vessel. Moreover, it is often
desirable to provide a means to prevent the migration of the
vasoocclusive devices, such as coils and the like, out of the
aneurysm in the event that the aneurysm has a relatively large neck
to dome ratio.
[0007] Stents, which are tubular reinforcements inserted into a
blood vessel to provide an open path within the blood vessel, have
been widely used in intravascular angioplasty treatment of occluded
cardiac arteries. In such applications, the stent is inserted after
an angioplasty procedure or the like in order to prevent restenosis
of the artery. In these applications, the stents are often deployed
by use of inflatable balloons, or mechanical devices which force
the stent open, thereby reinforcing the artery wall and provide a
clear through-path in the center of the artery after the
angioplasty procedure to prevent restenosis.
[0008] While such procedures may be useful in certain aspects of
vascular surgery in which vasoocclusive devices are used, the
weakness of the vasculature and the tortuosity of the
neurovasculature places limits on the applicability of such stents
in procedures to repair neurovascular aneurysms. Furthermore, the
use of placement techniques, such as balloons or mechanical
expansions of the type often found to be useful in cardiac surgery,
are relatively less useful in vasoocclusive surgery, particularly
when tiny vessels, such as those found in the brain, are to be
treated.
[0009] Hence, those skilled in the art have recognized a need for a
stent compatible with techniques in vasoocclusive treatment of
aneurysms that provides selective reinforcement in the vicinity of
the aneurysm, while avoiding any unnecessary trauma or risk of
rupture to the blood vessel. The need for a highly flexible stent
with structural integrity that both allows for placement without a
balloon or mechanical expansion and provides sufficient radial
support for weakened arterial walls when in a deployed state has
also been recognized. It would also be desirable to have a stent
which allowed placement of embolic coils in the aneurysm after the
placement of the stent, but which can retain coils placed both
before and after the stent is inserted. The present invention
provides these and other advantages.
SUMMARY OF THE INVENTION
[0010] Briefly, and in general terms, the invention relates to
various configurations of stents designed for use in the treatment
of aneurysms and ischemic diseases.
[0011] The intravascular flow modifier and reinforcement device or
stent of the present invention is particularly useful for treatment
of damaged arteries having aneurysms and the like, and
reinforcement of the area in the vicinity of the areas of the
artery to be treated, particularly those areas which are treatable
by the use of embolic coils or other embolic devices or agents used
to occlude the aneurysm. More particularly, the device of the
present invention may be used to reinforce the area in the vicinity
of the aneurysm while allowing placement of one or more embolic
coils through the gaps in the device, while assisting in the
retention of the embolic devices within the aneurysm.
[0012] In general, an intravascular flow modifier and reinforcement
device or stent constructed according to the invention is formed of
superelastic or shape memory material, which, in its deployed
configuration comprises a helical series of alternating zigzag
bends. The device is radially compressed and retained in a delivery
sheath or microcatheter to access the aneurysm location. Upon
deployment, the device is placed within the vasculature so that it
extends from a position distal of the aneurysm to a position
proximal of the aneurysm to be treated. As used herein, the terms
"proximal" and "proximal direction" when used with respect to the
invention are intended to mean moving away from or out of the
patient, and the terms "distal" and "distal direction" when used
with respect to the invention are intended to mean moving toward or
into the patient. These definitions will apply with reference to
apparatus, such as catheters, guide wires, and stents.
[0013] The invention relates to an intravascular flow modifier and
reinforcement device or stent for use in the intravascular
treatment of blood vessels. In a first preferred embodiment, the
stent includes a generally cylindrical frame formed of an elongate
resilient wire configured as a series of helical windings. In an
alternate preferred embodiment, the generally cylindrical frame has
a polygonal cross-section in which the frame has one or more
straight cross-sectional portions to provide a predetermined
desired radial shape and stiffness at various points on the
circumference of the stent. Similarly, the pitch cross-section of
the windings of the stent may be varied to provide different
characteristics to more readily adapt the stent to the portion of
the anatomy being treated. In one aspect, the stent consists of a
series of between 4 and 8 sharp, alternating zigzag or sinusoidal
bends or turns in a rotation of wire. With a helical chevron
configuration consisting of four alternating zigzag bends per
rotation of wire, the wire extends distally from the proximal end
of the stent in a helical pattern with a chevron configuration when
viewed from a first direction transverse to the longitudinal axis
of the stent, and a reverse chevron or bowed configuration when
viewed from a second direction transverse to the longitudinal axis
of the stent and approximately 90.degree. rotationally offset from
the first direction.
[0014] In the first preferred embodiment, the stent is formed from
a material having properties that provide it with a predeployed
radially compressed configuration and a deployed generally
cylindrical configuration. In a detailed aspect of the embodiment,
the stent is formed from a material having properties that provide
it with a predeployed substantially flattened configuration and a
deployed generally cylindrical configuration.
[0015] In another aspect, the invention provides a range of stent
pitch to provide a wire coverage of the inner surface area of the
arterial wall and aneurysm being treated of between 7% and 40%. In
another aspect, the angle of the chevrons is less than 120.degree.
to promote laminar arterial flow.
[0016] The invention also provides for a system and method for
deploying an intravascular flow modifier and reinforcement device
or stent including a generally cylindrical frame formed of an
elongate resilient wire configured as a series of helical windings,
for use in the intravascular treatment of a target site in a
patient's vasculature. In one embodiment, the stent may be deployed
with a substantially tubular pusher catheter member having a
tubular main shaft and a notched portion, with one or more notches
formed in a side of the pusher catheter member for receiving one or
more of the helical windings of the stent. Means are provided for
removably retaining the one or more helical windings on the notched
portion of the pusher catheter member, with the means for removably
retaining being withdrawn from the notched portion of the pusher
catheter member when the intravascular flow modifier and
reinforcement device is positioned at the site in the patient's
vasculature to be treated to release and deploy the intravascular
flow modifier and reinforcement device at the site in the patient's
vasculature to be treated. Typically a plurality of the helical
windings of the intravascular flow modifier and reinforcement
device are received in each of the notches. In one embodiment, the
notched portion includes a plurality of alternating notches and
tubular shoulder portions formed in the substantially tubular
pusher catheter member. In one embodiment, the means for removably
retaining the at least one helical winding on the notched portion
of the pusher catheter member includes a release wire threaded
through the lumen of the pusher catheter member and over the at
least one helical winding to retain the one or more helical
windings on the notched portion of the pusher catheter member.
[0017] In a presently preferred aspect, the system includes a
delivery catheter, and the substantially tubular pusher catheter
member and the intravascular flow modifier and reinforcement device
received on the notched portion of the pusher catheter member are
disposed in the delivery catheter. The delivery catheter can thus
be withdrawn along with the release wire from the notched portion
of the pusher catheter member when the intravascular flow modifier
and reinforcement device is positioned at the site in the patient's
vasculature to be treated for delivery of the intravascular flow
modifier and reinforcement device to the site in the patient's
vasculature to be treated.
[0018] In an alternate embodiment of the system and method of the
invention for deploying the stent of the invention, the notched
portion of the pusher catheter member includes a first plurality of
notches on one side of the shaft, and a second plurality of notches
on an opposing side of the shaft. In this embodiment, the means for
removably retaining the one or more helical windings on the notched
portion of the pusher catheter member includes a delivery catheter,
and the substantially tubular pusher catheter member and the stent
received on the notched portion of the pusher catheter member are
disposed in the delivery catheter. In a presently preferred aspect,
the delivery catheter has an inner diameter that is only slightly
larger than an outer diameter of the pusher catheter member, so as
to retain the stent on the pusher catheter member. The delivery
catheter is withdrawn from the notched portion of the pusher
catheter member when the stent is positioned for delivery of the
stent to the site in the patient's vasculature to be treated.
Typically individual ones of the notches of the second plurality of
notches are offset from corresponding ones of the first plurality
of notches.
[0019] The devices, systems and methods of the present invention
provide important advantages over prior art devices in that they
eliminate the necessity for balloon or mechanical placement of
devices which can cause unnecessary trauma to the delicate
vasculature which has already been damaged by the presence of the
aneurysm. The invention additionally provides a flexible device
which promotes a non-turbulent flow pattern. For these reasons, the
invention is particularly useful to cover and reinforce large neck
aneurysms. The presence and design of the alternating zigzag bends
enhances the flexibility of the device and enhances the ability of
the stent to be flattened and compressed, and to subsequently
deploy the stent within the vasculature, an issue of considerable
importance if neither balloon nor mechanical placement methods are
to be used. The use of a helical pattern increases the structural
integrity of the stent and provides sufficient radial support for
weakened arterial walls when the stent is in a deployed state.
[0020] The present invention also contains numerous advantages over
the prior art, including enhanced flexibility and loop strength.
These characteristics are controlled by several factors including
the diameter of the helical winds, the axial spacing of the winds,
the diameter or thickness of the wire or hypo tubing and the angle
of the alternating zigzag bend pattern.
[0021] The collapsibility of the stent for deployment purposes is a
function of material and stent configuration. The use of
superelastic and/or shape-memory material in combination with the
unique helical pattern allows for the stent to be compressed or
flattened and stretched for placement within a sheath or catheter.
Thus, the invention provides a wide variety of performance
characteristics that can be designed as part of the stent
configuration.
[0022] While certain features of the invention and its use have
been described, it will be appreciated by those skilled in the art
that many forms of the invention may be used for specific
applications in the medical treatment of deformation of the
vasculature. Other features and advantages of the present invention
will become apparent from the following detailed description taken
in conjunction with the accompanying drawings, which illustrate by
way of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a perspective view of a stent in a deployed state
and configured in accordance with one embodiment of the invention,
having a four alternating zigzag bends per wind configuration.
[0024] FIG. 2 is a view of the deployed stent of FIG. 1 rotated
90.degree. from the view of FIG. 1.
[0025] FIG. 3 is a perspective view of a deployed stent
illustrating an alternate configuration in which each wind consists
of 6 alternating zigzag bends.
[0026] FIG. 4 is a side view of the deployed stent of FIG. 3.
[0027] FIG. 5 is an illustration of a mandrel upon which the stent
of FIG. 1 is formed in one preferred embodiment of the method of
manufacture.
[0028] FIG. 6 is a cross section of a vessel with the stent of FIG.
1 deployed in the vicinity of a berry shaped aneurysm.
[0029] FIG. 7 is a cross section of a vessel with the stent of FIG.
3 deployed in the vicinity of a fusiform type aneurysm.
[0030] FIG. 8 is an elevational view of a pusher catheter member
for deployment of the stent according to the invention.
[0031] FIG. 9 is an enlarged view of section 9 of the pusher
catheter member of FIG. 8.
[0032] FIG. 10 is an enlarged view of section 10 of the pusher
catheter member of FIG. 8.
[0033] FIG. 11 is an enlarged view of section 11 of the pusher
catheter member of FIG. 8.
[0034] FIG. 12 is an enlarged elevational view of the section 10 of
the pusher catheter member of FIG. 10, showing coils of a stent
according to the invention captured by a release wire threaded
through the pusher catheter member.
[0035] FIG. 13 is a cross-sectional view of the pusher catheter
member, coils and release wire of FIG. 12.
[0036] FIG. 14 is a cross-sectional view similar to that of FIG.
13, illustrating delivery of a stent according to the invention via
a delivery catheter.
[0037] FIG. 15 is a cross-sectional view similar to that of FIG.
14, showing release of the stent.
[0038] FIG. 16 is a cross-sectional view showing an alternate form
of a pusher catheter member with the stent according to the
invention mounted thereon in a delivery catheter.
[0039] FIG. 17 is a cross-sectional view showing release of the
stent from the pusher catheter member of FIG. 16.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] As shown in the exemplary drawings, which are provided for
the purposes of illustration and not by way of limitation, the
intravascular flow modifier and reinforcement device or stent of
the present invention is designed to be deployed intravascularly
without the necessity of balloons or other expansive elements. The
intravascular device of the present invention is particularly
useful for treatment of damaged arteries incorporating aneurysms
and the like, particularly those which are treatable by the use of
embolic coils or other embolic devices or agents used to occlude
the aneurysm. More particularly, the device of the present
invitation may be used to reinforce the area in the vicinity of the
aneurysm while allowing placement of one or more embolic coils
through the gaps in the device, while assisting in the retention of
the embolic devices within the aneurysm.
[0041] In general, an intravascular flow modifier and reinforcement
device or stent constructed according to the invention is formed of
superelastic or shape memory material, which, in its deployed
configuration comprises a helical series of alternating zigzag
bends. The device is radially compressed and retained in a deliver
sheath or microcatheter to access the aneurysm location. Upon
deployment, the device is placed within the vasculature so that it
extends from a position distal to a position proximal of the
aneurysm to be treated.
[0042] Turning now to the drawings, in which like reference
numerals are used to designate like or corresponding elements among
the several figures, in FIGS. 1 and 2, there is shown one
embodiment of an intravascular flow modifier and reinforcement
device 10, i.e., stent, for use in vasoocclusive procedures. The
stent includes a generally cylindrical frame 12 formed of an
elongate resilient wire 14 configured as a series helical windings.
The wire extends distally from a proximal end 16 of the stent to a
distal end 18 of the stent in a helical pattern of sharp
alternating, zigzag or sinusoidal bends or turns 20 formed as
chevrons 22 and reversed chevrons or bows 24, each having an angle
26 and a spacing or pitch 28. Referring to FIGS. 6 and 7, upon
deployment, the stent is placed within the vasculature so that it
extends from a position distal to a position proximal of the
aneurysm 30, 32 to be treated.
[0043] In one aspect of the invention, the stent typically consists
of a series of between 4 and 8 bends in a rotation of wire. In
FIGS. 1 and 2, the stent consists of a series of four alternating
zigzag bends per helical winding.
[0044] With the helical alternating zigzag bend configuration
consisting of four alternating zigzag bends per rotation of wire,
the wire extends distally from the proximal end of the stent in a
helical pattern with a chevron configuration when viewed from a
first direction transverse to the longitudinal axis of the stent,
and a reverse chevron or bowed configuration when viewed from a
second direction transverse to the longitudinal axis of the stent
and approximately 90.degree. rotationally offset from the first
direction.
[0045] With reference to FIGS. 3 and 4, in one configuration of the
stent, the frame is formed from at least one piece of wire
configured as a series of helical windings consisting of a series
of six alternating zigzag bends.
[0046] While the form for making the stent is shown in the figures
to be cylindrical, in another aspect of the invention, the form can
have a polygonal or non-circular cross-section to provide different
radial tension and/or vectoring capabilities for the stent when it
is installed. Similarly, the form can be non-cylindrical in the
longitudinal axis, generally providing characteristics to match
various anatomical configurations to be treated. In a further
aspect of a preferred embodiment, the pitch of the windings of the
stent may be altered longitudinally to allow for different radial
stiffness in the installed stent and to permit vasoocclusive
microcoils to be inserted more easily into the aneurysm or
malformation being treated.
[0047] In another aspect of the invention, the wire of the stent is
typically made of a superelastic material such as a nickel-titanium
alloy to allow for easy insertion of the radially compressed stent
within a sheath or microcatheter. The wire may be coated with a
corrosion resistant material such as Parylene or treated by a
process such as chemical electropolishing to maximize corrosion
resistance. Other materials, such as shape-memory alloys, may also
be used to provide for the dual purposes of ease of insertion into
a sheath or microcatheter and formation upon deployment into the
desired shape of the device. One material that is contemplated as a
wire from which the stent can be made is a stranded cable including
one or more radiopaque strands, or which has radiopaque markers
deployed along its length. Such a stranded cable can be made of a
variety of materials including stainless steel, shape-memory alloy,
superelastic ally, platinum or the like or combinations thereof.
While this configuration of the stent is shown in the form of a
cylindrical wire, those skilled in the art will realize that other
configurations of material may be used to form the stent, including
laminates, flattened wires and laser cut hypo tubing, each of which
are within the scope of the invention.
[0048] An alternate embodiment of the pre-deployed stent consists
of materials, such as shape-memory alloys, which provide for the
dual purpose of ease of insertion into a guiding catheter or
microcatheter and formation upon deployment into the desired shape
of the device.
[0049] In an alternate embodiment of the deployed stent
configuration not shown, the stent may have a variable pitch or
spacing of the helical windings to provide relatively higher
density of stent coverage within the aneurysm to support
vasoocclusive devices. Alternatively, decreased coverage can be
provided in the vessel outside of the aneurysm location to minimize
impact on potential perforators. Such configurations have numerous
benefits depending on the topology of the damage to the artery, and
can provide benefits for certain types of treatment therapies. The
stent may be formed in various different configurations. For
example, in one configuration the density of the helical winds can
be varied from the proximal to the distal end in order to provide a
relatively greater density in an area to be placed in a portion of
the vasculature that is particularly weak or is threatened by
treatment.
[0050] As another example (not shown), the stent may be configured
to have a variable diameter in the helical windings over the length
of the stent in order to provide relatively greater circumferential
tension against the wall of the vessel in some areas than others.
As another example, the diameter of the helical winds can be
increased at certain sections of the stent, for example, the end
regions, and thus provide a higher degree of circumferential
tension against the wall of the vessel in specific regions. Such a
configuration has numerous benefits depending on the topology of
the damage to the artery, and can provide benefits for certain
types of treatment therapies. Other arrangements are possible. For
example, the diameter may taper down in size from both ends of the
stent toward the middle. Any of the preceding configurations allow
the stent to modify the blood flow characteristics in the vessel in
which the stent is deployed.
[0051] In one embodiment, the stent, prior to deployment in a
vessel, can be compressed into an essentially flat configuration in
which one end, such as the proximal end 16 of the stent, is
connected to a deployment device on the distal end of a pusher
member which fits within a catheter (not shown). In this
configuration, the stent has increased flexibility, decreasing the
potential of kinking during delivery of the stent to the delivery
site.
[0052] This configuration of the stent may be formed in a number of
ways, but there are presently two preferred methods of manufacture.
In a first preferred method illustrated in FIG. 5, a longitudinal
cylindrical mandrel 34 made of tungsten, ceramic, stainless steel
or other heat resistant material has inserted into it pegs 36 of
heat resistant material around which the wire to be formed into the
stent is wound. The position of the pegs represents transitions
along the helical wind generating the alternating zigzag bends. The
diameter of the pegs and the spacing of the pegs may be altered in
order to provide certain characteristics that are desired in the
stent as it is formed. Alternatively, the mandrel can have a
grooved configuration formed into it in which the wire is placed
prior to heat treatment.
[0053] In either method, a single wire is wound progressively down
the mandrel forming helical winds until a desired length of the
stent is reached. The wire can then be heat treated on the mandrel
to create a shape memory or treated to reach a superelastic
state.
[0054] After formation, the stent is removed from the mandrel.
Thereafter, radiopaque markers are loaded and secured to the stent
and the stent can be stretched or radially compressed to be
inserted into a sheath or microcatheter prior to insertion into the
vasculature.
[0055] The resilience of the wire, in combination with the
alternating zigzag bend, or chevron and reversed chevron or bow
configuration, allows for transition between a predeployed radially
compressed configuration and a deployed generally cylindrical
configuration, as shown in FIGS. 1 and 3. When radially inward
pressure is applied to the stent, adjacent alternating chevron and
reversed chevron or bow sections of the stent collapse toward each
other. Accordingly, when the stent experiences radially inward
pressure on each of the top, bottom and opposite lateral sides of
the stent, the stent compresses in size radially. The reduction in
radial size allows for placement of the stent in a microcatheter or
sheath without having to flatten and stretch the stent as
previously described.
[0056] In another embodiment of the invention (not shown), a stent
is formed by laser cutting a piece of hypo tubing to form the
pattern. The hypo tubing may be formed from a shape-memory material
similar to that of the resilient wire of the previous
configuration.
[0057] The invention provides numerous important advantages in the
treatment of vascular malformations, and particularly malformations
which include the presence of aneurysms. Since the stents do not
require the use of a balloon or other mechanical device for
deployment, they are capable of deployment from a small sheath or
catheter which need not occlude the artery as it is put into a
position from which to deploy the stent. Furthermore, the stents
upon deployment can reinforce the artery without occluding access
to the aneurysm, thus allowing the stents to be deployed prior to
the placement of embolic coils or the like in the aneurysms.
Alternatively, depending on the nature of the vascular defect, the
embolic coils or other embolic occlusive or other vasoocclusive
devices can be placed and the stents deployed thereafter to hold
the devices in the aneurysm.
[0058] The present invention also contains numerous advantages over
the prior art, including enhanced flexibility and loop strength.
These characteristics are controlled by several factors including
the diameter of the helical winds, the axial spacing of the winds,
the diameter or thickness of the wire or hypo tubing and the angle
of the alternating zigzag bend pattern.
[0059] The collapsibility of the stent for deployment purposes is a
function of material and stent configuration. The use of
superelastic and/or shape-memory material in combination with the
unique helical pattern allows for the stent to be compressed or
flattened and stretched for placement within a sheath or catheter.
Thus, the invention provides a wide variety of performance
characteristics that can be designed as part of the stent
configuration.
[0060] With references to FIGS. 6 and 7, two configurations of
stents are shown deployed within a vessel in the vicinity of an
aneurysm. As shown, the alternating zigzag bends configuration of
the helical winds cause the stent to expand and fit tightly against
the interior wall of the vessel. The compliance of the stent allows
for the stent to expand to a generally uniform diameter along its
length without entering into the area of the aneurysm. Thus the
stent provides support for the vessel in the area around the
aneurysm while leaving room for the introduction of embolic coils
into the aneurysm.
[0061] As is illustrated in FIGS. 8-14, in another aspect of the
invention, the stent may be deployed with a substantially tubular
pusher catheter member 40 having an inner lumen 41, a proximal
portion 42 and a distal portion 44, a tubular main shaft 46 shown
in FIGS. 8 and 9, a notched portion 48, with one or more notches 49
formed in a side 50 of the pusher catheter member, as is
illustrated in FIGS. 8, 10 and 11. The notched portion is
preferably formed with several notches, such as five or more
notches, for example, leaving alternating notches and short tubular
shoulder portions 52, and the notched pusher catheter is currently
preferably formed of a nickel-titanium alloy, such as that
available under the trade name NITINOL, for example. The distal
portion terminates in a short tubular shaft 53, as is shown in
FIGS. 8 and 11.
[0062] Referring to FIGS. 12-14, one or more of the helical
windings 54 of the stent can be placed over the notches of the
pusher catheter member, and typically one to three helical windings
may be received in each notch. A release wire 56 can be threaded
through the lumen of the pusher catheter member, under the short
tubular shoulder portions of the notched portion, and over the
helical windings of the stent, to retain the stent on the pusher
catheter member. The release wire typically extends from the
notched portion of the pusher catheter member to the proximal
portion of the pusher catheter member, where the release wire can
be manipulated. The release wire is currently preferably formed of
a nickel-titanium alloy, such as that available under the trade
name NITINOL, for example. As shown in FIG. 14, the pusher catheter
member, with the stent loaded onto the notched portion of the
pusher catheter member, can be advanced via a delivery catheter 58
or guiding catheter through the vasculature of a patient to a site
of an aneurysm to be treated. When the stent is located at the site
to be treated, the delivery catheter and release wire can be
withdrawn from the notched portion of the pusher catheter member to
release and deploy the stent at the site to be treated, as is shown
in FIG. 15.
[0063] In an alternate embodiment illustrated in FIGS. 16 and 17,
the stent of the invention may be loaded for delivery on a
substantially tubular pusher catheter member 60 having a shaft 62,
a plurality of first notches 64 on one side 66 of the shaft, and a
plurality of second notches 68 on an opposing side 70 of the shaft
of the pusher catheter member, with individual notches of the
plurality of second notches typically being offset from
corresponding ones of the plurality of first notches. One or more
of the stent helical windings or coils can be loaded onto the first
and second pluralities of notches, and the pusher catheter member,
with the stent loaded and/or pressed into the notched portion of
the pusher catheter member, can be loaded into a delivery catheter
72 having an inner diameter 74 that is only slightly larger than
the outer diameter 76 of the pusher catheter member, so as to
retain the stent on the pusher catheter member, allowing the stent
to be advanced through the vasculature of a patient to a site of an
aneurysm to be treated. With reference to FIG. 17, when the stent
is located at the site to be treated, the delivery catheter can be
withdrawn, or the pusher catheter member can be pushed out of the
delivery catheter, to release the stent from the pusher catheter
member.
[0064] From the above, it may be observed that the present
invention provides significant benefits to the treatment of
vascular malformations, and particularly aneurysms in the
neurovasculature. Importantly, the invention is particularly
advantageous when used in combination with vasoocclusive devices
placed in the aneurysm by intravascular procedures. The stents of
the present invention may also find application in the treatment of
ischemic diseases.
[0065] It will be apparent from the foregoing that while particular
forms of the invention have been illustrated and described, various
modifications can be made without departing from the spirit and
scope of the invention. Accordingly, it is not intended that the
invention be limited, except as by the appended claims.
* * * * *