U.S. patent application number 13/733755 was filed with the patent office on 2013-05-16 for vascular prosthesis and methods of use.
This patent application is currently assigned to NovoStent Corporation. The applicant listed for this patent is Michael Hogendijk, Eric W. Leopold, Gerald Ray Martin, John Peckham. Invention is credited to Michael Hogendijk, Eric W. Leopold, Gerald Ray Martin, John Peckham.
Application Number | 20130123899 13/733755 |
Document ID | / |
Family ID | 39742439 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130123899 |
Kind Code |
A1 |
Leopold; Eric W. ; et
al. |
May 16, 2013 |
Vascular Prosthesis and Methods of Use
Abstract
An implantable vascular prosthesis is provided for use in a wide
range of applications wherein at least first and second helical
sections having alternating directions of rotation are coupled to
one another. The alternating helical section includes a first and
second helical portions each having a flange and having adjacent
ends joined directly to one another to define an apex. Each helical
portion has a widened flange portion adjacent to the apex, the
widened flange portions extending into a space between the helical
portions. The prosthesis is configured to conform to a vessel wall
without substantially remodeling the vessel, and permits accurate
deployment in a vessel without shifting or foreshortening.
Inventors: |
Leopold; Eric W.; (Redwood
City, CA) ; Martin; Gerald Ray; (Redwood City,
CA) ; Hogendijk; Michael; (Mountain View, CA)
; Peckham; John; (St. Louis, MO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Leopold; Eric W.
Martin; Gerald Ray
Hogendijk; Michael
Peckham; John |
Redwood City
Redwood City
Mountain View
St. Louis |
CA
CA
CA
MO |
US
US
US
US |
|
|
Assignee: |
NovoStent Corporation
San Francisco
CA
|
Family ID: |
39742439 |
Appl. No.: |
13/733755 |
Filed: |
January 3, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11716472 |
Mar 9, 2007 |
8348994 |
|
|
13733755 |
|
|
|
|
Current U.S.
Class: |
623/1.11 |
Current CPC
Class: |
A61F 2/885 20130101;
A61F 2220/0058 20130101; A61F 2/95 20130101; A61F 2210/0076
20130101; A61F 2/91 20130101 |
Class at
Publication: |
623/1.11 |
International
Class: |
A61F 2/95 20060101
A61F002/95 |
Claims
1. A method of deploying a vascular prosthesis, comprising:
advancing a guidewire to a diseased vessel segment; advancing a
delivery system having a vascular prosthesis loaded therein over
the guidewire to the diseased vessel segment, the vascular
prosthesis including an alternating helical section, the
alternating helical section comprising a first helical portion
including a flange and a second helical portion including a flange,
the first and second helical portions having adjacent ends joined
directly to one another to define an apex, each of the first and
second helical portions comprising a widened flange portion
adjacent to the apex, the widened flange portions extending into a
space between the first and second helical portions, the first
helical portion having a direction of rotation opposite to that of
the second helical portion, and the vascular prosthesis being wound
onto a catheter body of the delivery system when the vascular
prosthesis is in a contracted configuration; retracting an outer
sheath of the delivery system proximally to expose the alternating
helical section, the alternating helical section expanding to a
deployed configuration; overlapping a portion of the apex by the
widened flange portions during at least a portion of a treatment
range between the radially contracted and expanded states; and
retracting the delivery system from the vessel.
2. The method of deploying a vascular prosthesis of claim 1,
wherein the vascular prosthesis further comprises an anchor section
coupled to an end of the alternating helical section, the method
further comprising retracting the outer sheath proximally to allow
the anchor section to expand to a deployed configuration prior to
retracting the delivery system from the vessel.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 11/716,472; filed on 9 Mar. 2007 (NOCO 1013-1).
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, to a prosthesis having an alternating helical
section.
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" or "jumping") and may shift within the vessel
prior to engaging the vessel wall, resulting in improper placement.
Another disadvantage is that after the stent is deployed it can
experience longitudinal movement within the vessel (also referred
to as "migration"), which can be attributed to repetitive
longitudinal loading and unloading of the stent.
[0005] Additionally, repetitive loading and unloading of a stent
have also been known to cause fatigue induced strut failure, which
may contribute to restenosis and subsequent vessel narrowing and/or
occlusion. 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.
[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,
and 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, 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] In another example, U.S. Pat. No. 5,603,722 to Phan et al.
describes a stent formed of expandable strip-like segments. The
strip-like segments are joined along side regions in a ladder-like
fashion along offsetting side regions. A shortcoming of such a
stent is that the junctions between adjacent segments are not
provided with a means of addressing longitudinal loading. As a
result, such a stent is susceptible to strut fracture.
[0009] In another example, U.S. Pat. No. 5,607,445 to Summers
describes a balloon expandable stent. In one embodiment, the stent
is constructed from a single wire that is configured so that each
half of the wire is zig-zagged and curved to generally form a
half-cylinder. The zig-zags of each half-cylinder are intermeshed
so that they combine to form a cylindrical stent. The stent
described in the foregoing publication has several drawbacks. The
stent does not allow for longitudinal loading. As a result,
applying a longitudinal load will cause the bends to move radially
inward which will bias them into the vessel flow. Additionally, the
stent design may be susceptible to fracture with repetitive loading
and unloading.
[0010] In yet another example, U.S. Pat. No. 5,707,387 to Wijay
describes a stent constructed from a plurality of bands, where each
band is composed of a solid wire-like material formed into a
closed, substantially rectangular shape. Each band is
circumferentially offset from the adjacent band and adjacent bands
are connected by one or more cross-tie members. This stent also has
several drawbacks. The rectangular cell design does not allow for
longitudinal loading because the cells are not flexible. Therefore,
under a longitudinal load the apex will move out of plane and will
be biased into the vessel (i.e., into the vessel flow). Secondly
the stent may be susceptible to fracture with repetitive loading
and unloading because of the rigid cells.
[0011] When utilizing stents in interventional procedures, it may
be advantageous to deliver therapeutic agents to a vessel wall via
the surface of the stent. 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. This would be especially beneficial if other
attributes such as radial strength and flexibility are not
compromised.
[0012] In view of the drawbacks of previously known devices, it
would be desirable to provide apparatus and methods for an
implantable vascular prosthesis comprising a plurality of helical
portions joined together, wherein the prosthesis is configured to
be used in a wide range of applications including maintaining
patency in a vessel and delivering drugs to a vessel.
[0013] It also would be desirable to provide apparatus and methods
for a vascular prosthesis that is flexible enough to conform to a
natural shape of a vessel without substantially remodeling the
vessel.
[0014] It further would be desirable to provide apparatus and
methods for a vascular prosthesis having one or more radially
expanding anchors that allow for additional control over the
deployment of the vascular prosthesis at a desired location within
a vessel.
[0015] It still further would be desirable to provide apparatus and
methods for a vascular prosthesis that has a surface area that may
be selected to facilitate in-vivo delivery of therapeutic agents
without adversely impacting the mechanical properties (e.g., radial
strength, flexibility, etc.) of the prosthesis.
[0016] It additionally would be desirable to provide apparatus and
methods for a vascular prosthesis that has a strut configuration
that allows for repetitive longitudinal loading and unloading of
the prosthesis.
[0017] It further would be desirable to provide apparatus and
methods for a vascular prosthesis that has a structure having the
ability to absorb or distribute loads.
[0018] It yet further would be desirable to provide apparatus and
methods for a vascular prosthesis that has a small delivery
configuration to allow the prosthesis to be used in smaller
vessels.
SUMMARY OF THE INVENTION
[0019] 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 plurality of helical stent
portions having alternating directions of rotation joined together,
wherein the prosthesis is configured to be used in a wide range of
applications including, but not limited to, maintaining patency in
a vessel and delivering drugs to a vessel.
[0020] It is a further object of the present invention to provide
apparatus and methods for a vascular prosthesis that is flexible
enough to conform to a natural shape of a vessel without
substantially remodeling the vessel.
[0021] It is another object of the present invention to provide
apparatus and methods for a vascular prosthesis having at least one
alternating helical section that allows for controlled deployment
of the vascular prosthesis at a desired location within a
vessel.
[0022] It is another object of the present invention to provide
apparatus and methods for a vascular prosthesis having a strut
configuration that dampens the stresses associated with repetitive
longitudinal loading and unloading, torsional loads, buckling and
bending.
[0023] It is another object of the present invention to provide
apparatus and methods for a vascular prosthesis having independent
cells that absorb and/or distribute loads applied to the
prosthesis.
[0024] It is a further object of the present invention to provide
apparatus and methods for a vascular prosthesis that has a surface
area that facilitates in-vivo delivery of therapeutic agents.
[0025] It is a further object of the present invention to provide
apparatus and methods for a vascular prosthesis that has a small
delivery configuration to allow the prosthesis to be used in
smaller vessels.
[0026] These and other objects of the present invention are
accomplished by providing a vascular prosthesis comprising a
plurality of helical portions having alternating directions of
rotation that are joined together. The prosthesis is configured to
engage a vessel wall and adapt to a natural curvature of the
vessel. The vascular prosthesis may be used in a wide range of
applications.
[0027] In a preferred embodiment, the vascular prosthesis comprises
a shape memory material, such as Nitinol, and includes an
alternating helical section. As used in this specification, an
"alternating helical section" is formed of two or more helical
portions that are joined together and have at least one change in
direction of rotation of the helices.
[0028] Prostheses of the present invention are 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 anchor section(s). In the
contracted state, the helical section is wound down to a reduced
diameter configuration, so that adjacent turns preferably partially
overlap. As an alternative, the helical section may be configured
so that there is no overlap if desired. As a still further
alternative, the helical section may be compressed radially to a
reduced diameter configuration in addition to or in lieu of
winding.
[0029] In a preferred method of operation of a prosthesis the
alternating helical section is provided in its contracted state
within an outer sheath and the prosthesis is fluoroscopically
advanced into a selected vessel using techniques that are known in
the art. The alternating helical section then is positioned
adjacent a target region of a vessel, such as a stenosed region.
The outer sheath then is retracted proximally to cause the first
helical portion(s) of the alternating helical section to
self-deploy and engage the vessel wall at the target region.
Advantageously, by overlapping portions of the alternating helical
section, the alternating helical section will expand in a
controlled manner. This technique ensures that the prosthesis will
not shift within the vessel during deployment.
[0030] The vascular prosthesis of the present invention is flexible
enough to conform to the shape of a vessel without substantially
remodeling the vessel.
[0031] Additionally, the mesh configuration of the alternating
helical section preferably conforms to the 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 alternating helical section of the
vascular prosthesis has a ribbon-like helical structure, it may be
rolled down to a contracted state with a more accurate 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.
[0032] In accordance with another aspect of the present invention,
the plurality of turns of the alternating helical section 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.
[0033] Methods of using the vascular prosthesis of the present
invention, for example, in the treatment of the peripheral
vasculature, also are provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] 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:
[0035] FIG. 1 is a schematic representation of a vascular
prosthesis of the present invention in a deployed state;
[0036] FIG. 2 is a schematic representation of the vascular
prosthesis of the present invention in a contracted state;
[0037] FIG. 3 is a side view of a vascular prosthesis of the
present invention;
[0038] FIG. 4 is a schematic representation of the vascular
prosthesis of FIG. 3 shown in a flattened configuration;
[0039] FIG. 5 is an enlarged side view of a vascular prosthesis of
the present invention in a deployed state;
[0040] FIG. 6 is an enlarged side view of a portion of an
embodiment of a vascular prosthesis of the present invention;
[0041] FIG. 7 is an enlarged side view of a portion of an
embodiment of a vascular prosthesis of the present invention;
[0042] FIG. 8 is an enlarged side view of a portion of an
embodiment of a vascular prosthesis of the present invention;
[0043] FIG. 9 is an enlarged side view of a portion of an
embodiment of a vascular prosthesis of the present invention;
[0044] FIG. 10 is an enlarged side view of a portion of an
embodiment of a vascular prosthesis of the present invention;
[0045] FIG. 11 is an enlarged side view of a portion of an
embodiment of a vascular prosthesis of the present invention;
[0046] FIG. 12 is an enlarged side view of a portion of an
embodiment of a vascular prosthesis of the present invention;
[0047] FIG. 13 is an enlarged side view of a portion of an
embodiment of a vascular prosthesis of the present invention;
[0048] FIG. 14 is an enlarged side view of a portion of an
embodiment of a vascular prosthesis of the present invention;
[0049] FIG. 15 is an enlarged side view of a portion of an
embodiment of a vascular prosthesis of the present invention;
[0050] FIGS. 16A and 16B are side views of an apex portion of a
vascular prosthesis according to the present invention;
[0051] FIG. 17 is a side view of another embodiment of a vascular
prosthesis of the present invention;
[0052] FIG. 18 is a side view of another embodiment of a vascular
prosthesis of the present invention;
[0053] FIG. 19 is a side view of another embodiment of a vascular
prosthesis of the present invention;
[0054] FIG. 20 is a cross-sectional view of a delivery system
suitable for use in delivering the vascular prosthesis of FIGS. 3;
and
[0055] FIGS. 21A-21D are side sectional views illustrating use of
the vascular prosthesis in the treatment of an aneurysm;
[0056] FIG. 22 is a side view of a vascular prosthesis of the
present invention that includes distal and proximal anchors;
[0057] FIG. 23 is a schematic representation of the vascular
prosthesis of FIG. 22 shown in a flattened configuration;
[0058] FIG. 24 is a side view of another embodiment of a vascular
prosthesis of the present invention; and
[0059] FIG. 25 is a side view of another embodiment of a vascular
prosthesis of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0060] The vascular prosthesis, according to the present invention,
has an alternating helix configuration that provides a more
accurate reduced delivery profile than previously known devices.
Additionally, the prosthesis is configured to conform to a vessel
wall without substantially remodeling the vessel, to provide
improved compression resistance, deployment accuracy, migration
resistance and load dampening characteristics.
[0061] Referring now to FIGS. 1 and 2, a schematic representation
of a vascular prosthesis constructed in accordance with principles
of the present invention is described. Vascular prosthesis
("stent") 20 illustratively comprises alternating helical section
21 capable of assuming contracted and deployed states. In FIG. 1,
alternating helical section 21 is depicted in the deployed
state.
[0062] Alternating helical section 21 is constructed from two or
more helical portions having at least one change in the direction
of rotation of the helices, and being joined at apex portions where
the directions of rotation of adjacent helices change. In
particular, first (i.e., proximal-most) helical portion 24a has a
generally clockwise rotation about longitudinal axis X of
prosthesis 20. Helical portion 26a adjoins the distal end of
helical portion 24a at apex 28a and has a generally
counter-clockwise rotation about longitudinal axis X. Helical
portion 24b adjoins the distal end of helical portion 26a at apex
28b, and in turn is coupled to the proximal end of helical portion
26b at apex 28c. As a result of the alternating direction of
rotation of the adjoining helical portions 24a, 26a, 24b and 26b of
vascular prosthesis 20 includes three apices 28a, 28b and 28c that
are oriented such that they point in alternating directions about
the circumference of vascular prosthesis 20, generally in a plane
that is normal to longitudinal axis X of vascular prosthesis 20.
Preferably, each helical portion includes at least one full helical
turn between adjacent apices. However, each helical portion may
include more or less turns between adjacent apices, for example a
helical portion may include 0.5-2.0 helical turns between adjacent
apices.
[0063] The terminal ends of the alternating helical section may
have any desired configuration. For example, as shown in FIG. 1,
the terminal ends, or tails, of alternating helical section 21 cut
along a plane that is perpendicular to the longitudinal axis of
vascular prosthesis 20. Alternatively, the terminal ends may be cut
along any plane, such as for example parallel to the longitudinal
axis. The terminal ends may end in a pointed or rounded tip or they
may be truncated. As a further alternative, the width of the ribbon
or mesh that forms the terminal helical portions may be varied. For
example, the width of the ribbon of the terminal helical portion
may taper so that it has the largest width adjacent the nearest
apex and the smallest width near the terminal end. These features
may be selected to provide a desired transitional flexibility at
the ends of the alternating helical portion. That transitional
flexibility may be used to assure that the curvature of a vessel
remains smooth near the end of the stent.
[0064] A significant advantage of alternating helical section 21 as
compared to other vascular prosthesis structures, is that the
apices of the alternating helical section provide additional
anchoring force at discrete locations along the length of the
alternating helical section. That anchoring force may be used to
increase the radial force applied by the vascular prosthesis to a
vessel wall as well as providing additional migration resistance.
That anchoring force may be increased if desired by flaring out the
ends and/or apices of the alternating helical section. Those
portions may be flared outward by applying expansion and heat
treatment so that those portions have a larger expanded diameter
than the remainder of alternating helical section 21. Additionally,
the alternating helical configuration also allows the wall
thickness of the device to be reduced because the design provides
increased radial strength.
[0065] Flanges 29 are included at each apex 28. Each flange 29 is
configured so that a portion of a corresponding apex 28 may overlap
a portion of flange 29 in both the contracted and deployed states.
Overlap of apex 28 and a corresponding flange 29 provides
reinforcement at apex 28 to increase the radial strength (i.e.,
resistance to radial compression) of the alternating helical
section at the apex. Additionally, the flange provides improved
metal coverage because it may be used to reduce or eliminate a gap
between an apex and the corresponding flange when the stent is in a
deployed configuration. The flange allows the stent to be
configured so that there is overlap at a small diameter and a
controlled gap at a large diameter without requiring side-to-side
overlap throughout the alternating helical section.
[0066] In the illustrated embodiment, each helical portion 24, 26
includes flange 29 adjacent apex 28, which is a widening of the
adjacent helical portions 24, 26 so that the gap therebetween is
reduced. For example, in an embodiment apices 28a and 28c remain
radially inward of flanges 29 while apex 28b remains radially
outward of flanges 29 throughout use. It should be appreciated
however that the stent may be configured so that at the largest
expanded diameter there is a gap between an apex and the
corresponding flange.
[0067] Alternating helical section 21 preferably is formed from a
solid tubular member comprised of a shape memory material, such as
nickel-titanium alloy (commonly known in the art as Nitinol).
However, it should be appreciated that alternating helical section
21 may be constructed from any suitable material recognized in the
art. The solid tubular member then is laser cut, using techniques
that are known in the art, to define a specific pattern or geometry
in the deployed configuration. Preferably, alternating helical
section 21 is cut from the tube so that helical portions 24a, 26a,
24b, 26b are integrally formed as a single monolithic body.
However, it should be appreciated that separate helical portions
may be mechanically coupled, such as by welding, soldering or
installing mechanical fasteners to construct alternating helical
section 21. An appropriate expansion and heat treatment then may be
applied to alternating helical section 21 of vascular prosthesis 20
so that the device may be configured to self-deploy from a
contracted, delivery configuration to the deployed
configuration.
[0068] Referring now to FIG. 2, vascular prosthesis 20 is shown in
the contracted, delivery configuration, wherein alternating helical
section 21 is in the contracted, reduced diameter state.
Alternating helical section 21, however, is placed in the
contracted state by winding helical portions 24, 26 about
longitudinal axis X. In FIG. 2, apices 28a and 28c may be
temporarily engaged to the inner shaft of a delivery catheter, and
the shaft is rotated while apex 28b and the distal and proximal
ends of alternating helical section 21 are held stationary.
[0069] Consequently, apices 28a and 28c are tightly wound onto the
shaft of the delivery catheter and the remainder of each helical
portion 24, 26 is wound against the shaft so that each turn of each
portion 24, 26 overlaps an adjacent turn. For example, in some
embodiments, approximately 2/3 of a layer is overlapped by the next
layer. As a result, apex 28b and the distal and proximal ends of
alternating helical section 21 are located furthest radially
outward on the rolled alternating helical section 21. The overlap
of the turns of helical portions 24, 26 are indicated by dashed
lines in FIG. 2. The overlapping turns and flanges 29 of
alternating helical section 21 thus secure apices 28a and 28c when
vascular prosthesis 20 is disposed within a delivery system.
[0070] Referring now to FIGS. 3 and 4, an embodiment of vascular
prosthesis 20, constructed in accordance with principles of the
present invention, is described. It should be appreciated that FIG.
4 is a schematic view of vascular prosthesis 20 as it would appear
if it were flattened. The components of vascular prosthesis 20 are
identical to those depicted in FIGS. 1 and 2 and identical
reference numbers are employed in the following description.
[0071] Alternating helical section 21 preferably comprises a
helical mesh configuration including two or more helical portions
27. Helical portions 27 may include multiplicity of openings 53,
54, 56 of different shapes and sizes. The shape, size and
orientation of any particular opening is selected to provide a
desired response to longitudinal loads and also may be dependent
upon the location of the openings within the mesh structure. The
shape, size and orientation of the opening may also be selected to
provide desired deployment, unwrapping, radial force and surface
area coverage characteristics.
[0072] As shown in FIG. 4, alternating helical section 21 includes
diamond-shaped openings 53 of generally equal size through the
majority of each helical portion 24, 26.
[0073] A wide variety of openings may be employed at apices 28a,
28b and 28c, where the helical portions adjoin adjacent helical
portions and flanges 29. The openings may have any shape and/or
size desired. Some designs include diamond, polygon, circles,
ellipses, elongated diamonds, etc. In addition, the openings of
apices 28 and flanges 29 need not be symmetric with respect to a
centerline of apex 28. It should be appreciated that the size,
shape and orientation of any of the openings may be selected so
that in the deployed state some struts may bow radially outward or
inward so that they interlock with adjacent overlapping
openings.
[0074] In FIG. 4, each apex includes plurality of openings 54 and
one tip opening 56 that forms a tip of the respective apex, which
may be triangular as shown. Openings 54 are defined by struts 55
that extend between adjacent helical portions 24, 26.
[0075] Referring to FIG. 5, the interaction between apices 28 and
flanges 29 will be described in greater detail. Flanges 29 are
formed by widened helical portions 24, 26 adjacent to apices 28. In
particular, helical portions 24, 26 are widened so that the gap
between two adjacent portions 24, 26 is reduced. As shown by dashed
lines, in the deployed state a tip portion of each apex 28 overlaps
flange 29 in the deployed state. In the present embodiment, it is
preferred to maintain the two lateral apices, 28a, 28c, radially
inward and flanges 29 assure that they remain in that position. It
will be appreciated that flanges 29 of adjacent helical portions
24, 26 may be joined if desired to provide additional overlap
between flange 29 and apex 28.
[0076] Referring to FIGS. 6-15, exemplary embodiments of flange 29
will be described. In one embodiment, shown in FIG. 6, flange is
constructed from additional struts 60 that extend from each of
adjacent helical portions 24, 26 into the space between the helical
portions. Struts 60 form a plurality of openings 61 that are
generally irregularly shaped. However, it will be appreciated that
struts 60 may be configured so that openings 61 have any desired
shape. As shown in FIG. 7, openings 61 may be enlarged by removing
struts 60. FIGS. 8-15 illustrate various other possible
configurations of flange 29. In some embodiments, such as those
shown in FIGS. 8 and 15, the flange may include a wavy edge. In
others, such as those shown in FIGS. 9-14, the flange may include a
smooth edge. It should be appreciated, upon inspection of the
exemplary embodiments illustrated in FIGS. 6-15 that any shaped
cells may be utilized to form flanges with desired
characteristics.
[0077] The number of and configuration of struts may be tailored as
desired to provide various characteristics. For example, including
struts 60 that are parallel to the longitudinal axis of the
vascular prosthesis may increase longitudinal rigidity and the
strength of helical portions 24, 26 near flanges. Additionally,
including struts 60 oriented circumferentially about vascular
prosthesis may increase radial stiffness of apex 28 of the vascular
prosthesis. The flexibility is tailored to improve radial force
applied by and/or fatigue strength of the prosthesis or to aid
deployment. Additionally, the strut configuration throughout
helical portions 24, 26 may also be tailored to provide such
characteristics as will be discussed in greater detail below.
[0078] Referring to FIGS. 16A and 16B, an alternative strut
configuration for the apices of the vascular prosthesis is
described. Apex 28' is constructed with struts 55 that form
plurality of cells 59 defining elongate openings 58. Elongate
openings 58 allow cells 59 to be compressed in response to
longitudinal loads (shown by arrows F) placed on vascular
prosthesis 20.
[0079] In addition, tip aperture 51, or eyelet, is included in apex
28'. Apertures 51 are provided so that apex 28' may be easily
coupled to a delivery device, as will be described in greater
detail below. As shown, aperture 51 is generally elliptical, but it
should be appreciated that the shape of aperture 51 will generally
correspond to the structure of the intended delivery device.
[0080] Elongate openings 58 each generally have major axis B
corresponding to the longest distance across opening 58 and minor
axis C corresponding to the shortest distance across opening 58.
Referring to FIG. 16B, a portion of apex 28' of FIG. 16A is shown
with cells 59 compressed under the influence of longitudinal force
F. Elongate openings 58 are oriented so that major axis B of each
opening 58 is parallel with center line 57 of apex 28' and minor
axis C of each opening 58 is perpendicular to center line 57.
During compression minor axis C is reduced while major axis B
remains generally unchanged. As a result, the longitudinal load may
be dampened by compression of the mesh structure of vascular
prosthesis 20.
[0081] Elongate openings 58 preferably are shaped to reduce stress
concentration. In the present embodiment, elongate openings 58 are
generally diamond-shaped with rounded corners 49 at the junctions
of adjacent struts 55. It should be appreciated that elongate
openings may be any elongate shape. The size, shape and orientation
of cells 59 on either side of center line 57 are shown generally
identical. With such a configuration, dampening occurs equally from
both sides of center line 57 when a longitudinal load is applied.
However, it should be appreciated that the dampening
characteristics of vascular prosthesis 20 may be tailored by
including cells having different size, shape and/or orientation on
either or both sides of center line 57. Furthermore, it should be
appreciated that the apices included throughout vascular prosthesis
20 need not be identical and may be configured to provide differing
dampening characteristics throughout vascular prosthesis 20.
[0082] Referring to FIG. 17, another embodiment of vascular
prosthesis 70 will be described. Vascular prosthesis 70 generally
includes alternating helical section 71. Alternating helical
section 71 includes a plurality of helical portions 74, 76 that
have alternating directions of rotation and are joined by apices
78. The edges of helical portions 74, 76 are wavy, which may be
provided so that a relative sliding of the portions of alternating
helical section 81 may provide a ratchet effect so that the
overlapping portions may be incrementally and temporarily
interlocked during deployment. A flange 79 is included on each
helical portion adjacent to apices 78. As described previously,
flanges 79 are widened portions of helical portions 74, 76 that are
used to maintain a desired amount of metal coverage and may be used
to retain apices in their respective radial position throughout a
portion of use of vascular prosthesis 70. For example, when
vascular prosthesis 70 is in a contracted state, apices 78 are
either located radially outward or inward of corresponding flanges
79. Flanges 79 are configured so that when vascular prosthesis is
transitioned to a deployed state, each apex 78 remains in the same
radial relationship with corresponding flange 79. It will be
appreciated that although vascular prosthesis 70 is illustrated
having flanges 79 with configurations generally corresponding to
those of FIG. 6, any flange configuration may be incorporated.
[0083] Referring to FIG. 18, another embodiment of vascular
prosthesis 80 will be described. Vascular prosthesis 80 generally
includes alternating helical section 81. Alternating helical
section 81 includes a plurality of helical portions 84, 86 that
have alternating directions of rotation and are joined by apices
88. In addition, the edges of helical portions 84, 86 are straight
rather than wavy, which may be provided so that relative sliding of
portions of alternating helical section 81 may be simplified during
deployment. Moreover, the tip or tail portion of each of the
helical portions on the proximal and distal ends of alternating
helical portion 81 have been truncated. A flange 89 also is
included on each helical portion adjacent to apices 88. As
described previously, flanges 89 are widened portions of helical
portions 84, 86 that retain apices in their respective radial
position throughout use of vascular prosthesis 80. It will be
appreciated that although vascular prosthesis 80 is illustrated
having flanges 89 with configurations generally corresponding to
those of FIG. 6, any flange configuration may be incorporated.
[0084] In yet another embodiment, shown in FIG. 19, alternating
helical section 91 includes helical portions 94, 96 that are formed
with elongated openings 93 that extend substantially the entire
length of the respective helical portion. The struts that form
openings 93 have a greater thickness adjacent apices 98 than the
thickness at locations spaced between apices 98. Such graduated
thickness may be used to control radial strength of the stent or so
that the radial forces exerted by vascular prosthesis during
expansion and compression are uniform at different locations around
the circumference of the vascular prosthesis. For example, the
radial force exerted by apices 98 may be altered so that it is
approximately equal to the force exerted by the remainder of each
helical portion of alternating helical section 91 by altering the
thickness of the struts. As shown, the struts near apex 98 have a
greater thickness to reduce the flexibility of the vascular
prosthesis near apex 98.
[0085] As will be apparent to one skilled in the art, the
configuration of the alternating helical sections depicted herein
is merely for illustrative purposes. Any combination of covered
portions and openings of any shape and size may be provided along
the helical portions, as desired to provide a desired amount of
metal coverage. Alternatively, one or more helical portions may be
completely solid, such that the openings are omitted entirely from
that portion.
[0086] As will be apparent to those skilled in the art, a
combination of solid regions and openings may be provided along the
length of the alternating helical section, for example, to
selectively increase surface area and drug delivery capabilities
along the alternating helical section, or to influence flow
dynamics within a vessel.
[0087] It will be appreciated that different drug delivery
modalities may be used in conjunction with the vascular prosthesis
of the present invention. For example, vascular prosthesis may
include one or more dimples and/or through holes that may have a
therapeutic agent disposed therein. As a further alternative, a
therapeutic agent may be incorporated into the any of the openings
previously described above. As a still further alternative, a
therapeutic agent may be disposed in the matrix of a bioabsorbable
polymer coated on any portion of the vascular prosthesis, and the
drug may be gradually released into a localized region of a vessel
wall.
[0088] One or more of the helical portions also may be selectively
coated with an elastomeric polymer, such as polyurethane. The
elastomeric polymer may partially or fully cover the selected
portions. For example, the elastomeric polymer may be disposed on a
portion of the circumference of the alternating helical section,
e.g., to reduce blood flow into a sac of the aneurysm. As a further
alternative, the entire alternating helical section may be covered
so that the device may be used as a stent graft. In such an
embodiment, ePTFE and DACRON are examples of materials that may be
used to cover the alternating helical section. It should also be
appreciated that covering material may be included within the
openings of the mesh structure so that it fills the openings
without increasing the overall diameter of the struts.
Additionally, a therapeutic agent may be disposed on the
elastomeric polymer to increase the working surface area of the
alternating helical section. Alternatively, the therapeutic agent
may be disposed directly on the alternating helical section, either
with or without the use of a elastomeric polymer.
[0089] The therapeutic agent may include, for example, antiplatelet
drugs, anticoagulant drugs, antiproliferative 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) also may be selectively disposed on
any portion of vascular prosthesis including 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 the vascular prosthesis
of the present invention, relative to previously known coils or
stents having interconnected struts, due to the increased surface
area associated with the alternating helical section.
[0090] In operation, the overlap of portions of the alternating
helical section when it is in the contracted state and the number
of helical portions, causes alternating helical section 101 to
deploy in a unique sequence, as will be described in greater detail
below with reference to FIGS. 21A-21D. Advantageously, the order of
deployment of the portions of alternating helical section 101
alleviates drawbacks associated with the prior art such as the
tendency of the turns of the helical section to jump or shift
during deployment and also results in the location of deployment
being more easily controlled. Another benefit is that deployment of
discrete segments may be more easily controlled. Additionally, the
alternating helical section may be balloon expandable. In
particular, the structure allows a user to post dilate discrete
sections with a balloon. For example, a user may expand a selected
portion of the device adjacent a specific apex.
[0091] In FIG. 20, a delivery system 100 suitable for use in
delivering a vascular prosthesis of the present invention is
described. Delivery system 100 comprises catheter body 102, outer
sheath 104, and a lumen dimensioned for the passage of guidewire
108. Catheter body 102 preferably includes distal marker 111 and
stop 110 located adjacent the distal end of alternating helical
section 101 and proximal stop 112 located adjacent the proximal end
of alternating helical section 101.
[0092] Distal stop 110 may comprise a raised ledge on catheter body
102 so that the distal end of alternating helical section 101 bears
on the ledge to prevent relative movement between alternating
helical section 101 and catheter body 102 in the distal direction.
Alternatively, distal stop 110 may comprise a plurality of raised
pins or knobs that prevent relative motion between alternating
helical section 101 and catheter body 102 parallel to the
longitudinal axis. Proximal stop 112 also may comprise a raised
ledge, pins or knobs on catheter body 102, and both distal and
proximal stops 110 and 112 may be radiopaque, so as to be visible
under a fluoroscope and provide a radiopaque marker. It should be
appreciated that any portion of the delivery device or vascular
prosthesis may include one or more radiopaque markers.
[0093] Vascular prosthesis 109 is collapsed onto catheter body 102
by winding alternating helical section 101 around catheter body
102. In order to wind alternating helical section 101 on catheter
body 102, apices 103a and 103c may be temporarily coupled to
catheter body 102 and the remainder of alternating helical section
101 is wound around catheter body 102 until it is collapsed as
shown in FIG. 20.
[0094] After alternating helical section 101 is wound on catheter
body 102, outer sheath 104 is advanced distally over catheter body
102 to capture alternating helical section 101 between catheter
body 102 and outer sheath 104.
[0095] Referring to FIG. 21A, in operation, guidewire 108 is
percutaneously and transluminally advanced through a patient's
vasculature, using techniques that are known in the art. Guidewire
108 is advanced until a distal end of guidewire 68 is positioned
distal of aneurysm A, which is situated in vessel V. Delivery
system 100, having vascular prosthesis 109 contracted therein, then
is advanced over guidewire 108 through the central lumen of
catheter body 102. Delivery system 100 preferably is advanced under
fluoroscopic guidance until distal marker 111 is situated distally
to aneurysm A and alternating helical section 101 and apex 103b are
situated adjacent to the aneurysm.
[0096] Once alternating helical section 101 is located adjacent to
aneurysm A, outer sheath 104 is refracted proximally to cause
alternating helical sections to deploy until outer sheath 104 is
retracted to proximal stop 112.
[0097] Referring to FIGS. 21B and 21C, after the distal end of
alternating helical section 101 is secured distal of aneurysm A,
outer sheath 104 is further retracted proximally to allow
alternating helical section 101 to continue to expand and deploy to
its predetermined deployed shape. During proximal retraction of
outer sheath 104, the stent rotates within the artery, or may be
manually rotated through rotation of the delivery system, to enable
alternating helical section 101 to unwind. Because central portions
of the alternating helical section are over-wrapped, rotation of
catheter body 102 is not required for the alternating helical
section to expand.
[0098] As outer sheath 104 is further refracted, the turns of
alternating helical section 101 unwinds and engages and conforms to
an inner wall of vessel V in a controlled manner. Helical portion
116b expands as outer sheath 104 is moved proximal of the distal
end of alternating helical section 101. Helical portion 116b is not
able to expand until the distal end of outer sheath 104 is moved
proximal of apex 103b because alternating helical section 101 is
wound so that apex 103b is located radially outward (i.e.,
outer-wrapped) and overlaps the adjacent helical portions. After
the distal end of outer sheath 104 is moved proximal of apex 103b,
helical portions 114b and 116a are allowed to expand. For example,
inner-wrapped apices, such as apices 103a and 103c, are constrained
by the adjacent helical portions 114 and 116 and as a result those
apices remain constrained until sufficient exposure of the stent
occurs to release the helical portions, thereby creating a
controlled release of the stent. Finally, after sheath 104 is moved
proximal of the proximal end of alternating helical section 101,
helical portion 114a is able to expand, as illustrated in FIG.
21C.
[0099] Proximal movement of outer sheath 104 may be halted once the
distal edge of outer sheath 104 is substantially aligned with
proximal stop 112 to allow alternating helical section 101 to
expand. It will be appreciated that because of the sequence of
deployment of alternating helical section 101, the location of the
deployed alternating helical section 101 may be easily controlled
and the problems encountered in previous systems (e.g., stent
jumping) may be avoided.
[0100] When vascular prosthesis 109 is fully deployed, delivery
system 100 is proximally refracted over guidewire 108 and withdrawn
from the patient's vessel, and guidewire 108 is removed. After
removal of delivery system 100 and guidewire 108, vascular
prosthesis 109 remains deployed, as shown in FIG. 21D.
[0101] In the present invention, the partial overlap of portions of
alternating helical section 101 reduce the surface area that is
available to frictionally engage an inner surface of outer sheath
104. Furthermore, the sequence of deployment of the alternating
helices included in alternating helical section 101 also assures
that the prosthesis remains properly located during deployment.
Advantageously, the helical portions of the alternating helical
section will be accurately deployed within vessel V, with
substantially no proximal or distal shifting or foreshortening of
the prosthesis with respect to the vessel as the outer sheath of
the delivery device is refracted.
[0102] It should be appreciated that the furthest proximal and the
furthest distal helical portions may be configured so that the
proximal and distal tips of the alternating helical section are
either inner-wrapped or outer-wrapped as desired. As shown in FIGS.
21A-D both tips may be outer-wrapped. As a further alternative, one
tip may be inner-wrapped. It will be appreciated that inner-wrapped
portions of the alternating helical section generally require
expansion of complimentary portions of the alternating helical
section before the entire prosthesis is capable of expansion.
[0103] Referring to FIGS. 22 and 23, another embodiment of vascular
prosthesis 20 is shown, which includes optional distal and proximal
anchor sections 22, 23. Distal anchor section 22 preferably is a
tubular mesh structure that is coupled to a distal end of
alternating helical section 21. In particular, distal anchor
section 22 includes a pair of concentrically aligned zig-zag rings
30 that are spaced from one another and coupled by struts 32.
Struts 32 extend between corresponding apices 34 of rings 30 and
are oriented parallel to a longitudinal axis of vascular prosthesis
20. Apices 34 may comprise one or more radiopaque markers 33 such
as a radiopaque marker band or coating. As a result, rings 30 and
struts 32 combine to define a plurality of openings 36 shaped as
parallelograms, thereby forming a tubular mesh. The tubular mesh
preferably is formed by laser cutting a solid tube.
[0104] Distal anchor section 22 preferably is formed from a solid
tubular member comprising a shape memory material, such as
nickel-titanium alloy, which is laser cut, using techniques that
are known in the art, to a desired deployed configuration.
Preferably, distal anchor section 22 is cut from the tube so that
rings 30 and struts 32 are formed as a single monolithic body.
However, it should be appreciated that distal anchor section 22 may
be constructed from separate rings 30 and struts that are
mechanically coupled in a secondary operation, such as by welding,
soldering or employing a mechanical fastener, such as a rivet. An
appropriate heat treatment then may be applied so that distal
anchor section 22 may be configured to self-deploy radially outward
from a contracted, delivery configuration to a deployed
configuration in conjunction with alternating helical section 21,
described above. Alternatively, distal anchor section 22 may be
configured to be balloon expandable.
[0105] Proximal anchor section 23 also preferably has a tubular
mesh construction. Proximal anchor section 23 includes pair of
concentrically aligned zig-zag rings 40 that are spaced from one
another and coupled by struts 42. Struts 42 extend between
corresponding apices 44. Apices 44 may comprise one or more
radiopaque markers 43 such as a radiopaque marker, band or coating.
Rings 40 are oriented parallel to longitudinal axis X of vascular
prosthesis 20. Rings 40 and struts 42 combine to define a plurality
of openings 46 shaped as parallelograms. Similar to distal anchor
section 22, the tubular mesh structure of proximal anchor section
23 preferably is formed by laser cutting a solid tube. Proximal
anchor section 23 may be constructed in the same manner described
above with respect to distal anchor section 22. Alternatively,
proximal anchor section 23 also may be constructed to be balloon
expandable.
[0106] Moreover, distal anchor section 22 and proximal anchor
section 23 may have different constructions. Although distal anchor
section 22 and proximal anchor section 23 as described above are
identical, they alternatively may have different zig-zag or cell
structures or deployment modes (e.g., self-expanding at the distal
end and balloon expandable at the proximal end). For example,
anchor sections 22, 23 may be constructed as a single zig-zag ring.
As a further alternative, anchor sections 22, 23 may be configured
so that openings 36, 46 have shapes other than parallelograms,
e.g., openings 36, 46 may be shaped as diamonds or any other
polygonal shape, circles or ellipses. Furthermore, although anchor
sections 22, 23 are illustrated as including struts 32, 42
extending between each set of corresponding apices, struts 32, 42
may extend between fewer sets of corresponding apices. For example,
struts may extend between relatively few apices. In addition, the
distance between the zig-zag rings of anchor sections 22, 23 may
also be selected to provide an anchor section of any desired
length.
[0107] Furthermore, the outer edges of anchor sections 22, 23 may
be biased so that the proximal-most edge of anchor section 23 and
the distal-most edge of anchor section 22 expand further radially
outward than with respect to longitudinal axis X than the remainder
of the anchor section. This configuration may be useful to increase
radial outward force upon a patient's vessel and thus improve
anchoring of vascular prosthesis 20 within the vessel. Such a
biased configuration may be established by heat-treating a shape
memory material using techniques that are known in the art.
[0108] Distal anchor section 22 is coupled to the distal end of
alternating helical section 21 at junction 48. Similarly, proximal
anchor section 23 is coupled to the proximal end of alternating
helical section 21 at junction 50. Preferably, junctions 48, 50 are
formed from a strut of alternating helical section 21 that extends
from that section and is coupled to a portion of the adjacent
zig-zag rings 30, 40 of the respective anchor section 22, 23.
[0109] Junctions 48, 50 may comprise one or more radiopaque markers
52 such as a radiopaque marker band or coating. Radiopaque marker
52 facilitates positioning of junctions 48, 50 at a desired
longitudinal position within a patient's vessel, and further
facilitates alignment of vascular prosthesis 20 at a desired axial
orientation within the vessel. For example, radiopaque markers 52
may be used to orient alternating helical section 21 so that a
desired lateral surface of alternating helical section 21 deploys
to overlay the diseased vessel segment.
[0110] It will be apparent to those skilled in the art that
junctions 48, 50 may comprise other strut arrangements to connect
distal anchor section 22 and proximal anchor section 23 to
alternating helical section 21. For example, more than one strut
may extend from alternating helical section 21 to a respective
anchor 22, 23.
[0111] In one preferred embodiment, alternating helical section 21,
distal anchor section 22 and proximal anchor section 23 are
integrally formed as a single monolithic body, such as by laser
cutting all three components from a single tube. In such a
construction of vascular prosthesis 20, the struts extending from
alternating helical section 21 that form junctions 48, 50 also may
form struts 32, 42 of the respective anchor section 22, 23.
Alternatively, anchor sections 22, 23 may be manufactured
separately from alternating helical section 21 and mechanically
coupled in a subsequent process, such as by soldering, welding,
installing mechanical fasteners (e.g., rivets) or other means, as
will be apparent to one skilled in the art.
[0112] Referring to FIG. 24, another embodiment of the vascular
prosthesis will be described. The present embodiment illustrates a
version of vascular prosthesis 70, described above that includes
distal anchor 72 and proximal anchor 73. Distal and proximal
anchors 72, 73 are similar in construction to those described with
respect to FIGS. 22 and 23. Alternating helical section 71 is
similar in construction to that described with respect to FIG. 17
and will not be further described.
[0113] Referring to FIG. 25, another embodiment of the vascular
prosthesis will be described. The present embodiment illustrates a
version of vascular prosthesis 80, described above, that includes
distal anchor 82 and proximal anchor 83. Distal and proximal
anchors 82, 83 are similar in construction to those described with
respect to FIGS. 22 and 23 but include zig-zag rings that are
slightly offset to define diamond-shaped openings and fewer struts
between the rings are employed. Alternating helical section 81 is
similar in construction to that described with respect to FIG. 18
and will not be further described.
[0114] A further advantage over the above-mentioned publications is
that the configuration of the alternating helical section provides
dampening characteristics for longitudinal, torsional and buckling
forces applied to the vascular prosthesis.
[0115] Although a method of treating diseased vessels has been
described, it will be apparent from the method described herein
that the vascular prosthesis may be used in a variety of
procedures. For example, vascular prosthesis 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.
[0116] In accordance with another aspect of the present invention,
the vascular prosthesis 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
alternating direction of rotation of the helical portions of the
alternating helical section allow for increased flexibility of the
prosthesis.
[0117] 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.
* * * * *