U.S. patent application number 10/723565 was filed with the patent office on 2005-07-28 for vascular prosthesis including torsional stabilizer and methods of use.
Invention is credited to Hogendijk, Michael.
Application Number | 20050165469 10/723565 |
Document ID | / |
Family ID | 32685982 |
Filed Date | 2005-07-28 |
United States Patent
Application |
20050165469 |
Kind Code |
A1 |
Hogendijk, Michael |
July 28, 2005 |
Vascular prosthesis including torsional stabilizer and methods of
use
Abstract
The present invention is directed to an implantable vascular
prosthesis configured for use in a wide range of applications, such
as treating aneurysms, maintaining patency in a vessel, and
allowing for the controlled delivery of therapeutic agents to a
vessel wall. The prosthesis comprises a helical proximal section
coupled to a distal anchoring section having a generally zig-zag or
cell-like configuration. The prosthesis is configured to conform to
a vessel wall without substantially remodeling the vessel, and
further is configured to be precisely deployed in a vessel without
shifting during deployment. The prosthesis also has a substantially
small delivery profile compared to other known stents, while having
an increased surface area to enhance delivery of therapeutic
agents.
Inventors: |
Hogendijk, Michael; (Santa
Clara, CA) |
Correspondence
Address: |
David E.Heisey, Esq.
Luce, Forward, Hamilton & Scripps LLP
11988 El Camino Real, Suite 200
San Diego
CA
92130
US
|
Family ID: |
32685982 |
Appl. No.: |
10/723565 |
Filed: |
November 25, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10723565 |
Nov 25, 2003 |
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10342427 |
Jan 13, 2003 |
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60436516 |
Dec 24, 2002 |
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Current U.S.
Class: |
623/1.15 |
Current CPC
Class: |
A61F 2/885 20130101;
A61F 2250/0068 20130101; A61F 2/91 20130101; A61F 2002/068
20130101; A61F 2/966 20130101; A61F 2230/0054 20130101; A61F 2/95
20130101; A61F 2220/0016 20130101; A61F 2002/828 20130101; A61F
2/88 20130101 |
Class at
Publication: |
623/001.15 |
International
Class: |
A61F 002/06 |
Claims
1. A vascular prosthesis for implantation in a body vessel having a
vessel wall, the vascular prosthesis comprising: a proximal section
comprising a plurality of helical turns and a distal end; a distal
section joined to the distal end, the distal section forming a
self-expanding anchor; and a torsional stabilizer coupled to the
distal end of the proximal section.
2. The vascular prosthesis of claim 1, wherein the proximal
section, distal section and torsional stabilizer each are capable
of assuming a contracted state suitable for transluminal insertion
into the body vessel and a deployed state wherein the proximal
section, distal section and torsional stabilizer engage the vessel
wall.
3. The vascular prosthesis of claim 2, wherein the distal section
is configured to be deployed within the body vessel before the
proximal section and torsional stabilizer are deployed.
4. The vascular prosthesis of claim 2, wherein the torsional
stabilizer is configured to be deployed before the proximal section
is deployed, but after the distal section is deployed.
5. The vascular prosthesis of claim 2, wherein the distal section
is configured to engage the vessel wall to retain the vascular
prosthesis in position during deployment of the torsional
stabilizer and proximal section.
6. The vascular prosthesis of claim 1, wherein the torsional
stabilizer enhances frictional engagement with the vessel wall.
7. The vascular prosthesis of claim 1, wherein the torsional
stabilizer comprises a loop.
8. The vascular prosthesis of claim 1, wherein the torsional
stabilizer comprises a continuation of the proximal section.
9. The vascular prosthesis of claim 1, wherein the torsional
stabilizer is configured to partially overlap the distal
section.
10. The vascular prosthesis of claim 1, wherein, in a fully
deployed configuration, the torsional stabilizer and the distal
section are oriented substantially parallel to one another.
11. The vascular prosthesis of claim 1, wherein the torsional
stabilizer is biased outwardly to provide increased frictional
contact with the vessel wall.
12. The vascular prosthesis of claim 1, wherein the proximal
section, distal section and torsional stabilizer comprise a nickel
titanium alloy.
13. The vascular prosthesis of claim 1, wherein the proximal and
distal sections may be manufactured as two distinct sections, then
coupled together.
14. The vascular prosthesis of claim 1, further comprising at least
one through-hole disposed on a solid portion of the torsional
stabilizer, the through-hole configured to contain a therapeutic
agent.
15. The vascular prosthesis of claim 1, wherein the torsional
stabilizer is used to orient the prosthesis axially within the body
vessel.
16. A vascular prosthesis for implantation in a body vessel having
a vessel wall, the vascular prosthesis including a longitudinal
axis, the vascular prosthesis comprising: a proximal section
comprising a plurality of helical turns and a distal end; a
self-expanding distal section coupled to the distal end of the
helical body at a junction; and a torsional stabilizer coupled to
the distal end of the proximal section.
17. The vascular prosthesis of claim 16, wherein the junction
defines an origin of an X-Y coordinate system, wherein an X-axis is
substantially parallel to a longitudinal axis of vascular
prosthesis and a Y-axis is substantially orthogonal to the
longitudinal axis of vascular prosthesis.
18. The vascular prosthesis of claim 16, wherein the torsional
stabilizer extends past a plane of the X-axis.
19. The vascular prosthesis of claim 16, wherein the torsional
stabilizer extends past a plane of the Y-axis.
20. The vascular prosthesis of claim 16, wherein the torsional
stabilizer includes one or more radiopaque markers to facilitate
alignment of the vascular prosthesis at a desired radial
orientation within the vessel.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 10/342,427, filed Jan. 13, 2003, which claims
priority from U.S. provisional patent application Ser. No.
60/433,065, filed Dec. 24, 2002.
FIELD OF THE INVENTION
[0002] The present invention relates to an implantable vascular
prosthesis configured for use in a wide range of applications, and
more specifically, a ribbon-type prosthesis having a torsional
stabilizer that increases frictional engagement with a vessel
wall.
BACKGROUND OF THE INVENTION
[0003] Today there are a wide range of intravascular prostheses on
the market for use in the treatment of aneurysms, stenoses, and
other vascular irregularities. Balloon expandable and
self-expanding stents are well known for restoring patency in a
stenosed vessel, e.g., after an angioplasty procedure, and the use
of coils and stents are known techniques for treating
aneurysms.
[0004] Previously-known self-expanding stents generally are
retained in a contracted delivery configuration using an outer
sheath, then self-expand when the sheath is retracted. Such stents
commonly have several drawbacks, for example, the stents may
experience large length changes during expansion (referred to as
"foreshortening") and may shift within the vessel prior to engaging
the vessel wall, resulting in improper placement. Additionally,
many self-expanding stents have relatively large delivery profiles
because the configuration of their struts limits further
compression of the stent. Accordingly, such stents may not be
suitable for use in smaller vessels, such as cerebral vessels and
coronary arteries.
[0005] Other drawbacks associated with the use of coils or stents
in the treatment of aneurysms is that the coils or stents, when
deployed, may have a tendency to straighten or otherwise remodel a
delicate cerebral vessel, which may cause further adverse
consequences. Moreover, such devices may not adequately reduce
blood flow from the cerebral vessel into the sac of the aneurysm,
which may increase the likelihood of rupture. Generally, if a
greater surface area is employed to cover the sac, the delivery
profile of the device may be compromised due to the increased
surface area, and the device also may be more rigid and cause
remodeling of the vessel.
[0006] For example, PCT Publication WO 00/62711 to Rivelli
describes a stent comprising a helical mesh coil having a plurality
of turns and including a lattice having a multiplicity of pores.
The lattice is tapered along its length. In operation, the
plurality of turns are wound into a reduced diameter helical shape,
then constrained within a delivery sheath. The delivery sheath is
retracted to expose the distal portion of the stent and anchor the
distal end of the stent. As the delivery sheath is further
retracted, the subsequent individual turns of the stent unwind to
conform to the diameter of the vessel wall.
[0007] The stent described in the foregoing publication has several
drawbacks. For example, due to friction between the turns and the
sheath, the individual turns of the stent may bunch up, or overlap
with one another, when the delivery sheath is retracted. In
addition, once the sheath is fully retracted, the turns may shift
within the vessel prior to engaging the vessel wall, resulting in
improper placement of the stent. Moreover, because the distal
portion of the stent may provide insufficient engagement with the
vessel wall during subsequent retraction of the remainder of the
sheath, ambiguity concerning accuracy of the stent placement may
arise.
[0008] When utilizing stents in interventional procedures, it may
be advantageous to deliver therapeutic agents to a vessel wall via
the surface of the stent. Such drug eluting stents have many
advantages, such as controlled delivery of therapeutic agents over
an extended period of time without the need for intervention, and
reduced rates of restenosis after angioplasty procedures.
Typically, the drug is disposed in the matrix of a bioabsorbable
polymer coated on an exterior surface of the struts of the stents,
and then gradually released into a vessel wall. The quantity of the
therapeutic agent provided by the stent generally is limited by the
surface area of the struts. Increasing the surface area of the
struts may enhance drug delivery capability, but may compromise the
overall delivery profile of the stent. There therefore exists a
need for a prosthesis having a reduced delivery profile and
enhanced drug delivery capabilities.
[0009] In view of these drawbacks of previously known devices, it
would be desirable to provide apparatus and methods for an
implantable vascular prosthesis comprising a ribbon-type stent
having a torsional stabilizer, wherein the prosthesis is configured
to be used in a wide range of applications including, but not
limited to, treating aneurysms, maintaining patency in a vessel,
and delivering drugs to a vessel.
[0010] It also would be desirable to provide apparatus and methods
for a vascular prosthesis comprising a ribbon-type stent having a
torsional stabilizer that enhances frictional engagement with the
vessel.
[0011] It further would be desirable to provide apparatus and
methods for a vascular prosthesis having a distal anchoring section
that allows for controlled deployment of a ribbon-type stent at a
desired location within a vessel.
[0012] It yet further would be desirable to provide apparatus and
methods for a vascular prosthesis that has a substantially small
delivery configuration to allow the prosthesis to be used in
smaller vessels.
SUMMARY OF THE INVENTION
[0013] In view of the foregoing, it is an object of the present
invention to provide apparatus and methods for an implantable
vascular prosthesis comprising a ribbon-type stent having a
torsional stabilizer, wherein the prosthesis is configured to be
used in a wide range of applications including, but not limited to,
treating aneurysms, maintaining patency in a vessel, and delivering
drugs to a vessel.
[0014] It is also an object of the present invention to provide
apparatus and methods for a vascular prosthesis comprising a
ribbon-type stent having a torsional stabilizer that provides
frictional engagement with the vessel wall.
[0015] It is another object of the present invention to provide
apparatus and methods for a vascular prosthesis having a distal
anchoring section that allows for controlled deployment of the
prosthesis at a desired location within a vessel.
[0016] It is a further object of the present invention to provide
apparatus and methods for a vascular prosthesis that has a
substantially small delivery configuration to allow the prosthesis
to be used in smaller vessels.
[0017] These and other objects of the present invention are
accomplished by providing a vascular prosthesis comprising a distal
anchor section joined a helical mesh proximal section and including
a torsional stabilizer, wherein the prosthesis is configured to
engage a vessel wall and adapt to a natural curvature of the vessel
wall. The torsional stabilizer is an extension of the proximal
section and enhances contact and friction with the vessel wall. The
vascular prosthesis may be used in a wide range of applications,
such as treating aneurysms, maintaining patency in a vessel, e.g.,
after an angioplasty procedure, and other procedures requiring a
controlled delivery of therapeutic drugs to a vessel.
[0018] In a preferred embodiment, the vascular prosthesis comprises
a shape memory material, such as Nitinol, and includes a distal
anchor section having a generally zig-zag or cell-like
configuration coupled to a proximal helical section having a
helical mesh configuration formed of a plurality of turns.
[0019] The prosthesis is delivered to a target vessel in a
contracted state, constrained within an outer sheath, in which
radially inwardly directed compressive forces are applied by the
outer sheath to the distal section. In the contracted state, the
helical proximal section and torsional stabilizer are wound down to
a smaller configuration, so that adjacent turns preferably
partially overlap, and are constrained in the contracted state by
the outer sheath.
[0020] In a preferred method of operation, the distal section,
proximal section and torsional stabilizer are provided in their
respective contracted states within the outer sheath and the
prosthesis is fluoroscopically advanced into a selected vessel
using techniques that are per se known in the art. The proximal
section then is positioned adjacent a target region of a vessel,
such as an aneurysm or a stenosed region, with the distal section
positioned distal of the target region. The outer sheath then is
retracted proximally to cause the distal section to self-deploy and
engage an inner wall of the vessel distal of the target region. A
distal portion of the distal section may be biased radially
outward, or provided with proximally-directed barbs, to facilitate
secure anchoring of the distal section within the vessel.
[0021] Once the distal section is securely anchored distal of the
target region, the outer sheath further is retracted to cause the
proximal section to self-deploy and engage the vessel wall at the
target region. Advantageously, by providing a distal anchoring
element prior to deploying the proximal section, each turn of the
helical proximal section will unwind in a controlled manner as the
outer sheath is retracted. This technique ensures that the
prosthesis will not shift within the vessel during deployment.
[0022] The vascular prosthesis of the present invention is flexible
enough to conform to the shape of a delicate vessel without
substantially remodeling the vessel. In particular, the zig-zag or
cell-like configuration of the distal section may conform to a
natural curvature of a vessel wall better than traditional stents
having interconnected struts, which may be more rigid.
Additionally, the helical mesh configuration of the proximal
section conforms to vasculature of the target region since each of
the plurality of turns is free to assume a curved configuration
substantially independently of one another. Also, because the
proximal section of the vascular prosthesis has a ribbon-like
structure, the proximal section may be wound down to a contracted
state with a substantially reduced delivery profile, compared to
slotted-tube stents. This feature makes the stent of the present
invention especially useful for treating defects in smaller
vessels, such as cerebral arteries.
[0023] In accordance with another aspect of the present invention,
the plurality of turns may comprise a substantially increased
surface area relative to conventional stents that have a plurality
of interconnected struts. The increased surface area of the turns
is particularly advantageous for localized drug delivery. The turns
may be coated with a drug-laden polymer coating or, alternatively,
one or more dimples or through-holes may be disposed in a lateral
surface of the turns to elute drugs over an extended period of
time.
[0024] Methods of using the vascular prosthesis of the present
invention, for example, in the treatment of an aneurysm, also are
provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Further features of the invention, its nature and various
advantages will be more apparent from the accompanying drawings and
the following detailed description of the preferred embodiments, in
which:
[0026] FIGS. 1A-1B are, respectively, side and perspective views of
a vascular prosthesis of the present invention;
[0027] FIG. 2 is a side view describing features of the junction of
the prosthesis of FIG. 1;
[0028] FIG. 3 is a side view of a vascular prosthesis having a
distal section that is biased radially outward;
[0029] FIG. 4 is an enlarged view of the distal end of the
prosthesis of FIG. 3;
[0030] FIG. 5 is a side view illustrating different drug delivery
modalities;
[0031] FIG. 6 is a side sectional view of a delivery system that
may be used in conjunction with the vascular prosthesis of FIG.
1;
[0032] FIGS. 7A-7C are side sectional views illustrating use of the
vascular prosthesis of FIG. 1 in the treatment of an aneurysm;
[0033] FIGS. 8A-8B are, respectively, side and perspective views of
an alternative embodiment of the vascular prosthesis of the present
invention;
[0034] FIGS. 9A-9B are, respectively, side and perspective views of
a vascular prosthesis including a torsional stabilizer according to
the present invention;
[0035] FIG. 10 is a detailed side view of the torsional stabilizer
portion of the vascular prosthesis of FIG. 9;
[0036] FIG. 11 is a side view of the torsional stabilizer portion
of an alternative vascular prosthesis; and
[0037] FIG. 12 is a side view of the torsional stabilizer portion
of another alternative vascular prosthesis.
DETAILED DESCRIPTION OF THE INVENTION
[0038] The present invention is directed to an implantable vascular
prosthesis configured for use in a wide range of applications, such
as treating aneurysms, maintaining patency in a vessel, and
allowing for the controlled delivery of therapeutic agents to a
vessel wall. The prosthesis has a ribbon-type configuration that
provides a substantially smaller delivery profile than other known
devices, while having an increased surface area to allow for
delivery of the therapeutic agents. Additionally, the prosthesis is
configured to conform to a vessel wall without substantially
remodeling the vessel, and further is configured to provide
improved accuracy during deployment relative to previously known
devices.
[0039] Referring now to FIGS. 1, a first embodiment of a vascular
prosthesis constructed in accordance with principles of the present
invention is described. Vascular prosthesis 20 comprises proximal
section 22 and distal section 24, each capable of assuming
contracted and deployed states. In FIGS. 1, proximal and distal
sections 22 and 24 are each depicted in their respective deployed
states.
[0040] Vascular prosthesis 20 preferably is formed from a solid
tubular member comprising a shape memory material, such as
nickel-titanium alloy (commonly known in the art as Nitinol). The
solid tubular member then is laser cut, using techniques that are
per se known in the art, to a desired deployed configuration, as
depicted in FIG. 1A. An appropriate heat treatment, per se known in
the art, then may be applied to solid regions 33 of vascular
prosthesis 20 while the device is held in the desired deployed
configuration. The treatment of the shape memory material allows
vascular prosthesis 20 to self-deploy to the desired deployed
configuration, depicted in FIGS. 1, for purposes described
hereinafter.
[0041] Distal section 24 preferably has a generally zig-zag
configuration in the deployed state, as shown in FIG. 1A. The
zig-zag configuration preferably is formed by laser cutting a solid
tube, as described hereinabove, to form a pattern comprising
plurality of struts 31 disposed between plurality of bends 32.
[0042] Proximal section 22 preferably comprises a helical mesh
configuration in the deployed state, as depicted in FIGS. 1. The
helical mesh configuration includes a plurality of substantially
flat turns 26. Plurality of turns 26 may include a multiplicity of
openings provided in different shapes and sizes, as illustrated by
larger rectangular openings 25, smaller rectangular openings 28 and
small circular openings 29. The multiplicity of openings are
disposed between solid regions 33 of the shape memory material used
to form vascular prosthesis 20. Alternatively, turns 26 may
comprise fully covered sections 39, as depicted hereinbelow in FIG.
7C.
[0043] As will be apparent to one skilled in the art of stent
design, the configuration of proximal section 22 depicted herein is
merely for illustrative purposes. Any combination of covered
sections 39, circular openings 29, large or small rectangular
openings, or any other shape may be provided along portions of
turns 26, as desired. Plurality of turns 26 similarly may comprise
exclusively one type of opening, such as small circular openings
29. Alternatively, plurality of turns 26 may be completely solid,
such that the openings are omitted altogether. As will be apparent
to those skilled in the art, the combination of solid regions and
openings may be selectively provided along the length of proximal
section 22, for example, to selectively increase surface area and
drug delivery capabilities along proximal section 22, or to
influence flow dynamics within a vessel.
[0044] Proximal section 22 includes distal turn 34 that transitions
into bend 32 of distal section 24, thereby forming junction 23.
Proximal turn 35 of proximal section 22 forms a free end that
permits proximal section 22 to conform to a natural configuration
of a patient's vessel, as described hereinbelow with respect to
FIGS. 7.
[0045] Referring now to FIG. 2, features of junction 23 of FIGS. 1
are described in greater detail. Junction 23 is disposed between
proximal and distal sections 22 and 24 of vascular prosthesis 20.
Junction 23 preferably comprises extension strut 47 that is coupled
to at least one bend 32 of distal section 24. Junction 23 extends
in a proximal direction towards proximal section 22 and ultimately
transitions into proximal wall 42 of distal turn 34, as shown in
FIG. 2.
[0046] Junction 23 further preferably comprises substantially
orthogonal segment 48, i.e., a segment that is substantially
orthogonal to a longitudinal axis of vascular prosthesis 20.
Segment 48 transitions into extension strut 47 in the vicinity of
bend 32, and further transitions into distal wall 41 of distal turn
34, as shown in FIG. 2.
[0047] Junction 23 may comprise one or more radiopaque markers 44,
such as a radiopaque marker band or coating. Radiopaque marker 44
facilitates positioning of junction 23 at a desired longitudinal
position within a patient's vessel, and further facilitates
alignment of vascular prosthesis 20 at a desired radial orientation
within the vessel. For example, radiopaque marker 44 may be used to
orient proximal section 22 so that a desired lateral surface of
proximal section 22, e.g., comprising covered sections 39 or small
circular openings 29, deploys to overlay the arc of a vessel in
which an aneurysm is situated.
[0048] It will be apparent to those skilled in the art that
junction 32 may comprise other strut arrangements to connect distal
section 24 to proximal section 22. For example, more than one
extension struts 47 may be coupled between bends 32 and distal turn
34 of proximal section 22. Alternatively, proximal and distal
sections 22 and 24 may be manufactured as two distinct sections,
then coupled together to form a junction. In this embodiment, the
junction may be formed when distal turn 34 of proximal section 22
is coupled to one or more bends 32 situated at proximal end 37 of
distal section 24. Distal turn 34 may be coupled to one or more
bends 32 using a means for bonding, such as a solder, or the
sections alternatively may be mechanically coupled together, for
example, using a rivet or any other means, as will be apparent to
one skilled in the art.
[0049] Referring now to FIG. 3, an alternative embodiment of distal
section 24 of FIGS. 1 is described. In FIG. 3, distal section 24'
has proximal end 37 and distal end 38. Distal end 38 is biased
radially outward with respect to the longitudinal axis of vascular
prosthesis 20. The deployed configuration of distal section 24' may
be established by heat treating a shape memory material, using
techniques that are per se known in the art, as described above.
Distal section 24' is configured to impose an increased radial
outward force upon a patient's vessel and may further improve
anchoring of the prosthesis within the vessel.
[0050] Distal end 38 of distal section 24' further may comprise at
least one barb 40 protruding from bend 32 and/or a distal portion
of strut 31, as depicted in FIG. 4. Barb 40 is configured to extend
radially outward and in a proximal direction with respect to a
longitudinal axis of vascular prosthesis 20. Each barb 40 may
comprise sharpened tip 41, which is configured to engage a
patient's vessel when distal section 24' is deployed in a vessel,
as described in hereinbelow with respect to FIGS. 7.
[0051] Referring now to FIG. 5, different drug delivery modalities
that may be used in conjunction with vascular prosthesis 20 of the
present invention are described. In FIG. 5, illustrative turn 26'
of proximal section 22 comprises multiplicity of openings 28
disposed between solid regions 33, and further comprises at least
one dimple 50 and/or through hole 52 disposed in solid regions 33.
Each dimple 50 and through hole 52 may have therapeutic agent 54
disposed therein. Therapeutic agent 54 may be disposed in the
matrix of a bioabsorbable polymer, and the drug may be gradually
released into a localized region of an arterial wall. Dimples 50
may be selectively disposed on an interior surface of turn 26',
and/or disposed on an exterior surface of turn 26', as depicted in
FIG. 5.
[0052] One or more turns 26 may be selectively coated with
elastomeric polymer 56, such as polyurethane. Elastomeric polymer
56 may partially or fully cover selected regions of turns 26. For
example, elastomeric polymer 56 may be disposed on one arc of the
circumference of proximal section 22 to overlay an aneurysm and
reduce blood flow into a sac of the aneurysm. Additionally,
therapeutic agent 54 may be disposed on elastomeric polymer 56,
which increases the working surface area of proximal section 22.
Alternatively, the therapeutic agent may be disposed directly on
solid region 33, either with or without the use of elastomeric
polymer 56.
[0053] Referring now to FIG. 6, a delivery system suitable for use
with the vascular prosthesis of the present invention is described.
In FIG. 6, delivery system 60 is similar to that disclosed in U.S.
Pat. No. 4,665,918 to Garza et al., and includes catheter 61 having
central lumen 62, nose cone 63 and outer sheath 64. Catheter 61
includes recessed portion 65 that cooperates with outer sheath 64
to retain proximal and distal sections 22 and 24 of vascular
prosthesis 20 in their respective contracted states for
transluminal delivery.
[0054] Delivery system 60 also may comprise fluid delivery lumen
67, which may be used to deliver chilled saline to vascular
prosthesis 20 during delivery of the device. Fluid delivery lumen
67 may be disposed within catheter 61, as depicted in FIG. 6, and
one or more ports 68 may be formed in a distal lateral surface of
catheter 61 to facilitate fluid communication between lumen 67 and
recessed portion 65.
[0055] Turning now to FIGS. 7, a preferred method of using vascular
prosthesis 20 of the present invention, for example, in the
treatment of an aneurysm, is described. It will be apparent from
the method steps described herein that vascular prosthesis 20 also
may be used in general stenting procedures, for example, to
maintain patency in a vessel after a carotid angioplasty procedure,
or may be used as an intravascular drug delivery device, or may be
used in other applications apparent to those skilled in the
art.
[0056] In FIG. 7A, vascular prosthesis 20 of FIG. 1 is provided in
the fully contracted state disposed between recessed portion 65 of
catheter 61 and outer sheath 64 of FIG. 6. Specifically, distal
section 24 is compressed to its contracted delivery state about
recessed portion 65 of catheter 61, and the plurality of turns of
proximal section 22 are wound down to a contracted delivery state
about recessed portion 65, as shown in FIG. 7A. Outer sheath 64 is
disposed over proximal and distal sections 22 and 24, as depicted,
to retain both sections in their contracted states.
[0057] First, guide wire 70 is percutaneously and transluminally
advanced through a patient's vasculature, using techniques that are
per se known in the art, until a distal end of guide wire 70 is
positioned distal of aneurysm A, which is situated in vessel V.
Delivery system 60, having vascular prosthesis 20 contracted
therein, then is advanced over guide wire 70 via central lumen 62
of catheter 61. Nose cone 63 serves as an atraumatic bumper during
advancement of delivery system 60. Delivery system 60 is advanced
under fluoroscopic guidance until proximal section 22 is situated
adjacent aneurysm A, as shown in FIG. 7A.
[0058] During advancement of delivery system 60 though a patient's
vasculature, chilled saline preferably is delivered to vascular
prosthesis 20 via fluid delivery lumen 67 and port 68. The chilled
saline may be used to increase the flexibility of prosthesis 20 to
facilitate advancement of delivery system 60 over guide wire
70.
[0059] In a next step, outer sheath 64 is retracted proximally to
cause distal section 24 to self-deploy distal of aneurysm A, as
shown in FIG. 7B. Struts 31 of distal section 24 expand in a radial
direction to engage an inner wall of vessel V. Barbs 40 of FIG. 3
may engage vessel V, and/or the distal end of distal section 24 may
be biased radially outward with respect to the proximal end (see
FIG. 3) to enhance the engagement between distal section 24 and the
vessel wall.
[0060] With distal section 24 anchored distal of aneurysm A, outer
sheath 64 then is further retracted proximally to cause distal turn
34 of proximal section 22 to unwind and deploy to its predetermined
shape, as shown in FIG. 7C. As the outer sheath is further
retracted, each subsequent turn 26 unwinds one at a time and
engages and conforms to an inner wall of vessel V in a controlled
manner. When prosthesis system 20 is fully deployed, delivery
system 60 then is proximally retracted over guide wire 70 and
withdrawn from the patient's vessel, and guide wire 70 is
removed.
[0061] In accordance with one aspect of the present invention,
deploying distal section 24 prior to deploying proximal section 22
allows distal section 24 to serve as an anchoring mechanism that
allows for a controlled deployment of the helical turns of proximal
section 22. Advantageously, turns 26 of proximal section 22 will be
accurately deployed within vessel V, with substantially no proximal
or distal shifting with respect to the vessel as outer sheath 64 is
retracted.
[0062] Moreover, by deploying distal section 24 prior to deploying
proximal section 22, drawbacks associated with the device described
in the above-referenced publication to Rivelli may be overcome.
Specifically, without a distal anchoring element, the multiplicity
of turns of the stent described in the Rivelli publication may
experience a tendency to "bunch up," i.e., overlay one another, as
the outer sheath is retracted due to friction between the turns and
the outer sheath. In the present invention, distal section 24
serves as an anchoring mechanism prior to retraction of the outer
sheath over the proximal section. Accordingly, such a distal
anchoring mechanism overcomes potential friction and turns 26 will
be less likely to bunch up.
[0063] In accordance with another aspect of the present invention,
vascular prosthesis 20 of the present invention is configured to be
flexible enough to substantially conform to the shape of vessel V
without causing the vessel to remodel. In particular, the zig-zag
configuration of distal section 24 and the helical configuration of
proximal section 22 allow for increased flexibility of prosthesis
20. The pitch associated with plurality of turns 26 may be varied
to vary the overall flexibility of proximal section 22. A lower
pitch, whereby adjacent turns 26 are spaced relatively close
together, may be employed to increase flexibility of proximal
section 22. A lower pitch is desirable, for example, to treat
cerebral aneurysms so that turns 26 may conform to the vasculature
without causing remodeling of the vessel. Conversely, a higher
pitch, whereby adjacent turns 26 are spaced further apart, may be
employed to increase the rigidity of proximal section 22. Such a
design may be desirable for use in maintaining patency in a
stenosed vessel by increasing rigidity of proximal section 22. As a
yet further embodiment, the width of the coil may be tapered, as
described in the Rivelli publication.
[0064] In accordance with another aspect of the present invention,
covered sections 39 may be positioned to overlay aneurysm A to
significantly reduce blood flow into aneurysm A. Alternatively,
smaller rectangular openings 28 or small circular openings 29 may
overlay aneurysm A to reduce blood flow into the sac of the
aneurysm. Over time, the intima of vessel V will grow over
plurality of turns 26 of proximal section 22 to completely exclude
the aneurysm A from vessel V.
[0065] As noted hereinabove, the configuration of proximal section
22 depicted in FIG. 7C is merely for illustrative purposes. Any
combination of covered sections 39, circular openings 29, large or
small rectangular openings, or any other shape may be provided
along turns 26, as desired. Plurality of turns 26 similarly may
exclusively comprise one type of opening, e.g., small circular
openings 29. Alternatively, plurality of turns 26 may be completely
solid such that the openings are omitted altogether.
[0066] In accordance with yet another aspect of the present
invention, therapeutic agents may be delivered to expedite
treatment of the aneurysm or prevent restenosis. As described
hereinabove with respect to FIG. 5, therapeutic agent 54 may be
delivered to a desired location within vessel V, either using
internal or external dimples 50, through holes 52, elastomeric
polymer 56 and/or solid regions 33 of one or more turns 26.
[0067] Therapeutic agent 54 may include, for example, antiplatelet
drugs, anticoagulant drugs, agents used for purposes of providing
gene therapy to a target region, or any other agent, and may be
tailored for a particular application. Radiopaque markers (not
shown) may be selectively disposed on turns 26 in the vicinity of
the therapeutic agents to facilitate alignment of the therapeutic
agents with a target site of a vessel wall. Advantageously, higher
doses of such agents may be provided using vascular prosthesis 20
of the present invention, relative to previously known coils or
stents having interconnected struts, due to the increased surface
area associated with turns 26.
[0068] Referring now to FIGS. 8, an alternative embodiment of the
vascular prosthesis of the present invention is described. Vascular
prosthesis 120 comprises proximal section 122 and distal sections
124. Distal section 124 preferably is provided in accordance with
distal section 24 of FIG. 1 and comprises a generally zig-zag
configuration including struts 131 and bends 132.
[0069] Proximal section 122 includes a plurality of individual
helical turns 126. Each turn has a distal end that is coupled to a
respective bend 132 of distal section 124 at junctions 127, as
shown in FIGS. 8. Individual helical turns 126 are aligned in a
pattern such that each turn maintains its own helical curvature
without overlapping with an adjacent turn, as depicted in FIG. 8.
Individual helical turns 126 of vascular prosthesis 120 may be heat
treated to self-deploy to the configuration shown, and may be wound
down to a small diameter in which turns 126 are constrained within
delivery system 60 of FIG. 6. The deployment of vascular prosthesis
120 is substantially similar to the deployment of prosthesis 20, as
described in detail hereinabove with respect to FIGS. 7, and
vascular prosthesis 120 encompasses many of the advantages noted
hereinabove with respect to vascular prosthesis 20.
[0070] Referring to FIGS. 9A and 9B, vascular prosthesis 140 is
described and includes torsional stabilizer 146 according to the
principles present invention. Vascular prosthesis 140 comprises a
proximal section 142, distal section 144 and torsional stabilizer
146. Proximal section 142, distal section 144 and torsional
stabilizer 146 are joined at junction 148. Each of the proximal
section, distal section and torsional stabilizer are capable of
assuming contracted and deployed states, and each are depicted in
their respective deployed states in FIGS. 9A and 9B.
[0071] In operation, distal section 144 is configured to be
deployed within a vessel before torsional stabilizer 146, which is
configured to be deployed before proximal section 142. Deploying
distal section 144 first allows the distal section to serve as an
anchor controls subsequent deployment of the helical turns of
proximal section 142. Torsional stabilizer 146 provides further
contact with the vessel wall, thereby providing an additional
anchor that transmits torsional forces proximally during deployment
of proximal section 142. Distal section 144 and torsional
stabilizer 146 preferably work in conjunction to balance the
torsional force of the proximal section and thus stabilize the
vascular prosthesis. This action is expected to further reduce
shifting with respect to the vessel wall during deployment of
proximal section 142. Advantageously, the above-identified order of
deployment alleviates drawbacks associated with the prior art such
as the tendency of the turns of the proximal section to "bunch up"
during deployment.
[0072] The vascular prosthesis, including distal section 144,
proximal section 142 and torsional stabilizer 146, preferably is
formed from a solid tubular member comprising a shape memory
material, such as Nitinol, processed as described above with
respect to the embodiment of FIGS. 1. According to some
embodiments, torsional stabilizer 146 includes at least one dimple
or through-hole disposed on a solid portion of the torsional
stabilizer.
[0073] Referring still to FIGS. 9, in the deployed state distal
section 144 has a cell-like configuration comprising a pair
zig-zags 144a, 144b joined by struts 144c. Alternatively, distal
section 144 may include a single zig-zag configuration, such as
described with respect to FIGS. 1. The cell configuration of FIGS.
9 is expected to be more rigid than the single zig-zag
configuration, and hence is capable of applying, and withstanding,
greater radial force. Either configuration of distal section 144
may be formed by laser cutting a solid tube, as described
hereinabove, to form the requisite pattern. Of course, as would be
understood by those of ordinary skill in the art, distal section
144 may have many other configurations without departing from the
scope of the present invention.
[0074] Proximal section 142 preferably comprises a helical ribbon
including plurality of turns 152 having multiplicity of openings
154 provided in varying shapes and sizes. The multiplicity of
openings are disposed between solid regions 150 of the shape memory
material used to form vascular prosthesis 140. Proximal section 142
alternatively may comprise the helical mesh configuration of FIGS.
1 or any other suitable pattern. Proximal section 142 includes
distal turn 156 that transitions into torsional stabilizer 146.
Torsional stabilizer 146 comprises strut 158 that preferably
remains substantially parallel to distal section 144.
[0075] Referring to FIGS. 9 and 10, distal section 144 is coupled
to proximal section 142 at junction 148. More particularly, strut
144b extends in a proximal direction forming neck 149, which is
attached to proximal section 142 at junction 148. It will be
apparent to those skilled in the art that other strut arrangements
may be employed to connect distal section 144 to proximal section
142. For example, more than one strut may be coupled between
proximal section 142 and distal section 144. Alternatively,
proximal section 142 and distal section 144 may be manufactured as
two distinct sections, then coupled together.
[0076] In FIG. 10, the distal section and proximal section are
mapped onto an X-Y coordinate system with junction 148
substantially defining an origin (X=0, Y=0). The X-axis is
substantially parallel to a longitudinal axis of vascular
prosthesis 140 and the Y-axis is substantially orthogonal to the
longitudinal axis of vascular prosthesis 140. Torsional stabilizer
146 generally comprises the portion of the proximal section that
extends past the plane of the X-axis junction 148. According to one
aspect of the present invention, torsional stabilizer 146 is an
extension of proximal section 142 and may comprise a continuation
of the helical pattern of the proximal section.
[0077] Torsional stabilizer 146 optionally may be biased outwardly
to provide increased frictional contact with the vessel wall.
Torsional stabilizer 146 also may comprise one or more radiopaque
markers 160, such as a radiopaque marker band or coating.
Radiopaque marker 160 facilitates positioning of torsional
stabilizer 146 at a desired longitudinal position within a
patient's vessel, and further facilitates alignment of vascular
prosthesis 140 at a desired radial orientation within the vessel.
For example, radiopaque marker 160 may be used to orient the
prosthesis axially within the body vessel.
[0078] In FIG. 11, alternative vascular prosthesis 140' is shown
having torsional stabilizer 162 in accordance with the principles
of the present invention. Torsional stabilizer 162 comprises loop
164 of material that extends past the plane of the X-axis. Loop 164
is shaped substantially triangularly and includes first segment
164a disposed substantially parallel to the Y-axis, second segment
164b coupled to the proximal section, and third segment 164c. As
would be appreciated by those of skill in the art, torsional
stabilizer 162 may include other shapes and configurations without
departing from the scope of the present invention. By way of
example, torsional stabilizer 162 may comprise two or more
interconnected curvilinear loops.
[0079] In FIG. 12, further alternative vascular prosthesis 140"
includes torsional stabilizer 168. Torsional stabilizer 168
comprises loop 170 of material that extends past the plane of both
the X-axis and Y-axes, and illustratively includes semicircular
portion 170a. Of course, as would be appreciated by those of skill
in the art, torsional stabilizer 168 may include other shapes and
configurations without departing from the scope of the present
invention.
[0080] While preferred illustrative embodiments of the invention
are described above, it will be apparent to one skilled in the art
that various changes and modifications may be made therein without
departing from the invention. The appended claims are intended to
cover all such changes and modifications that fall within the true
spirit and scope of the invention.
* * * * *