U.S. patent application number 12/178883 was filed with the patent office on 2008-11-13 for stent having helical elements.
This patent application is currently assigned to ORBUSNEICH MEDICAL, INC.. Invention is credited to Scott J. ADDONIZIO, Gary J. BECKER, David L. CAMP, JR., John D. PAZIENZA.
Application Number | 20080281406 12/178883 |
Document ID | / |
Family ID | 26146599 |
Filed Date | 2008-11-13 |
United States Patent
Application |
20080281406 |
Kind Code |
A1 |
ADDONIZIO; Scott J. ; et
al. |
November 13, 2008 |
STENT HAVING HELICAL ELEMENTS
Abstract
An expandable stent comprised of a plurality of helical segments
is disclosed. In one embodiment, the stent is generally cylindrical
in shape having a cylindrical axis, and comprises a first and
second set of helical segments. The helical segments in the first
set are substantially parallel and have a first pitch forming a
first helical angle with respect to the cylindrical axis. The
helical segments in the second set are also generally parallel to
each other and form a second pitch that differs from the first
pitch, thereby forming a second helical angle with respect to the
cylindrical axis. In an alternative embodiment, the stent comprises
one set of helical segments and a plurality of circumferential
elements that are joined together by the helical segments to form a
plurality of cylindrical elements which are joined together to form
a stent body. The stent may also have endzones.
Inventors: |
ADDONIZIO; Scott J.; (Fort
Lauderdale, FL) ; CAMP, JR.; David L.; (Hillsboro
Beach, FL) ; BECKER; Gary J.; (Miami, FL) ;
PAZIENZA; John D.; (Pompano Beach, FL) |
Correspondence
Address: |
CHRISTOPHER & WEISBERG, P.A.
200 EAST LAS OLAS BOULEVARD, SUITE 2040
FORT LAUDERDALE
FL
33301
US
|
Assignee: |
ORBUSNEICH MEDICAL, INC.
Fort Lauderdale
FL
|
Family ID: |
26146599 |
Appl. No.: |
12/178883 |
Filed: |
July 24, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12027382 |
Feb 7, 2008 |
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12178883 |
|
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|
10014705 |
Dec 11, 2001 |
7329277 |
|
|
12027382 |
|
|
|
|
09511481 |
Feb 23, 2000 |
7108714 |
|
|
10014705 |
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|
09094402 |
Jun 10, 1998 |
6117165 |
|
|
09511481 |
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60254688 |
Dec 11, 2000 |
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Current U.S.
Class: |
623/1.22 |
Current CPC
Class: |
A61F 2002/91541
20130101; A61F 2002/9155 20130101; A61F 2230/0013 20130101; A61F
2/91 20130101; A61F 2/88 20130101; A61F 2002/91583 20130101; A61F
2002/91533 20130101; A61F 2002/91525 20130101; A61F 2002/91508
20130101; A61F 2002/91516 20130101; A61F 2/915 20130101; A61F
2002/91558 20130101 |
Class at
Publication: |
623/1.22 |
International
Class: |
A61F 2/06 20060101
A61F002/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 1997 |
EP |
97201799 |
May 6, 1998 |
EP |
98201446 |
Claims
1. A stent comprising a main body formed from a plurality of
expandable helical segments that comprise a plurality of a single
substantially S-shaped portions and one or more substantially
H-shaped segments which connect a plurality of main body
cylindrical elements; said cylindrical elements comprising a
plurality of first circumferential segments having a repeating
pattern and second circumferential segments comprising the
substantially S-shaped portion; and wherein said S-shaped portion
comprises a linear element and a curved element, said linear
element lying an acute angle less than or equal to about 45 degrees
relative to a cylindrical axis of the main body.
2. The stent of claim 1 wherein the substantially S-shaped portion
further comprises an angled portion connected to the linear portion
at an end opposite to the curved portion.
3. The stent of claim 2 wherein the angled portion forms an angle
relative to the cylindrical axis of the stent greater than 0
degrees to about 45 degrees.
4. The stent of claim 3 wherein the angled portion forms an angle
of about 10 degrees.
5. The stent of claim 1 wherein the substantially S-shaped portion
has an amplitude ranging from about 0.5 mm to about 2.0 mm and a
period ranging from about 0.5 mm to about 2.0 mm.
6. The stent of claim 1 wherein the repeating pattern comprises a
sinusoidal wave.
7. The stent of claim 6 wherein the sinusoidal wave has an
amplitude ranging from about 0.5 mm to about 2.0 mm and a period
ranging from about 0.5 mm to about 2.0 mm.
8. A stent comprising a main body formed from a plurality of
expandable helical segments that comprise a single substantially
S-shaped portion and one or more substantially H-shaped segments
which connect a plurality of main body cylindrical elements; said
cylindrical elements comprising a plurality of first
circumferential segments having a repeating pattern and second
circumferential segments having the substantially S-shaped portion;
wherein said S-shaped portion comprises a linear element and a
curved element, said linear element lying an acute angle less than
or equal to about 45 degrees relative to a cylindrical axis of the
main body; and, wherein said H-shaped segment comprises two
generally parallel linear portions connected by a common connecting
element, said linear portions lying at an acute angle less than or
equal to about 14 degrees relative to the cylindrical axis.
9. The stent of claim 8 wherein the substantially S-shaped portion
further comprises an angled portion connected to the linear portion
at an end opposite to the curved portion.
10. The stent of claim 9 wherein the angled portion forms an angle
relative to the cylindrical axis of the stent greater than 0
degrees to about 45 degrees.
11. The stent of claim 8 wherein the substantially S-shaped portion
has an amplitude ranging from about 0.5 mm to about 2.0 mm and a
period ranging from about 0.5 mm to about 2.0 mm.
12. The stent of claim 8 wherein the repeating pattern comprises a
sinusoidal wave.
13. The stent of claim 12 wherein the sinusoidal wave has an
amplitude ranging from about 0.5 mm to about 2.0 mm and a period
ranging from about 0.5 mm to about 2.0 mm.
14. A stent comprising a main body formed from a plurality of
expandable helical segments that comprise a plurality of a single
substantially S-shaped portions and one or more substantially
H-shaped segments which connect a plurality of main body
cylindrical elements; said cylindrical elements comprising a
plurality of first circumferential segments having a pattern and
second circumferential segments comprising the substantially
S-shaped portion; and, wherein said S-shaped portion comprises a
linear element and a curved element, said linear element lying an
acute angle less than or equal to about 45 degrees relative to a
cylindrical axis of the main body.
15. The stent of claim 14 wherein the pattern is repeating.
16. The stent of claim 15 wherein the repeating pattern comprises
peaks and valleys.
17. The stent of claim 16 wherein the repeating pattern is
sinusoidal.
18. A stent comprising a main body formed from a plurality of
expandable helical segments that comprise a single substantially
S-shaped portion and one or more substantially H-shaped segments
which connect a plurality of main body cylindrical elements; said
cylindrical elements comprising a plurality of first
circumferential segments having a repeating pattern and second
circumferential segments having the substantially S-shaped portion;
and, wherein said H-shaped segment comprises two generally parallel
linear portions connected by a common connecting element, said
linear portions lying at an acute angle less than or equal to about
14 degrees relative to the cylindrical axis.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/027,382, filed on Feb. 7, 2008, which
application is a continuation of U.S. patent application Ser. No.
10/014,705, filed on Dec. 11, 2001, now issued U.S. Pat. No.
7,329,277, which application claims the benefit of U.S. Provisional
Application No. 60/254,688, filed on Dec. 11, 2000, all of which
are hereby incorporated in their entirety by reference. U.S. patent
application Ser. No. 10/014,705 is also continuation-in-part of
U.S. patent application Ser. No. 09/511,481, filed on Feb. 23,
2000, now U.S. Pat. No. 7,108,714, which is a continuation of U.S.
patent application Ser. No. 09/094,402, filed Jun. 10, 1998, now
U.S. Pat. No. 6,117,165, all of which are hereby incorporated in
their entirety by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to prosthetic stents. In
particular, the present invention relates to stents having helical
elements and to methods for manufacturing the stents of the present
invention.
BACKGROUND OF THE INVENTION
[0003] Stents are prosthetic devices that are implanted in the
lumen of a vessel inside the body to provide support for the
vessel's wall. Structural support from stents is particularly
important in angioplasty procedures. Typically, stents are
implanted within a vessel system to reinforce vessels that are
partially occluded, collapsing, weakened, or abnormally dilated.
More generally, stents can be used inside any physiological conduit
or duct including, for example, arteries, veins, bile ducts, the
urinary tract, alimentary tracts, the tracheobronchial tree, a
cerebral aqueduct or the genitourinary system. Stents may be used
in both humans and animals.
[0004] There are typically two types of stents: self expanding
stents and balloon expandable stents. Self expanding stents
automatically expand once they are released and assume a deployed,
expanded state. A balloon expandable stent is expanded using an
inflatable balloon catheter. The balloon is inflated to plastically
deform the stent. Balloon expandable stents may be implanted by
mounting the stent in an unexpanded or crimped state on a balloon
segment of a catheter. The catheter, after having the crimped stent
placed thereon, is inserted through a puncture in a vessel wall and
moved through the vessel until it is positioned in the portion of
the vessel that is in need of repair. The stent is then expanded by
inflating the balloon catheter against the inside wall of the
vessel. Specifically, the stent is plastically deformed by
inflating the balloon so that the diameter of the stent is
increased and remains at an increased state. In some situations,
the vessel in which the stent is implanted may be dilated by the
stent itself when the stent is expanded.
[0005] The Palmaz-Schatz.TM. stent, which is disclosed in the
Handbook of Coronary Stents by Patrick W. Serruys et al. (Martin
Dunitz, LTD 1998), is an example of a balloon expandable stent that
had been implanted in hundreds of thousands of patients. The
Palmaz-Schatz.TM. stent, like other known stents, has certain
limitations. These include, but are not limited to: (i) low
stent-to-vessel ratio uniformity, (ii) comparative rigidity of the
stent in a crimped as well as deployed state, and (iii) limited
flexibility making delivery and placement in narrow vessels
difficult. Stent-to-vessel ratio generally refers to the degree
that the vessel wall is supported by the stent in its expanded
state and preferably should be uniform throughout the length of the
stent. Furthermore because the Palmaz-Schatz.TM. stent consists of
one or more bridges that connect a number of consecutively slotted
tubes, there are a number of bare areas in the vessel after the
expansion of the stent. These shortfalls are common to many stents.
Id. at 36.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to expandable stents that
have relatively uniform stent-to-vessel ratios when expanded and
other desirable properties, as well as methods for making these
stents. The stents of the present invention comprise a generally
cylindrically shaped main body having a plurality of expandable
helical segments. The main body is comprised of a plurality of
cylindrical main body elements that are joined together by the
helical segments. The cylindrical elements have cylindrical axes
that are collinear with the cylindrical axis of the main body. The
cylindrical elements are formed from a plurality of circumferential
elements that are joined together by the expandable helical
segments. In some embodiments, the stent may comprise endzones that
straddle the main body.
[0007] In one embodiment of the present invention, the stent may
comprise a first non-helical endzone and a second non-helical
endzone that straddle the main body. The main body is generally
cylindrically shaped and has a cylindrical axis. A plurality of
adjacent main body cylindrical elements are connected together to
form the main body of the stent. Each main body cylindrical element
may be comprised of a plurality of expandable first and second
circumferential elements. In some embodiments, the second
circumferential elements have a circumferential dimension less than
the circumferential dimension of the first circumferential
elements. In yet other embodiments, the first and second
circumferential elements have the same circumferential dimensions
and are substantially identical except that, with respect to the
cylindrical axis of the stent, they are oriented differently. Each
second circumferential segment in each main body cylindrical
element is connected to two first circumferential segments. In
addition, each second circumferential segment in each main body
cylindrical element is connected to a second circumferential
segment in an adjoining main body cylindrical element thereby
forming a plurality of helixes in the main body of the stent.
[0008] In one embodiment, the main body may be comprised of a
plurality of first helical segments each having a substantially
identical first pitch and a plurality of second helical segments,
each having a substantially identical second pitch. The first and
second pitches are generally different. In at least one embodiment,
the second pitch is twice that of the first, and at least one first
helical segment crosses one of the second helical segments.
[0009] The stents of the present invention may be manufactured from
a tubular member by removing material from the tube to form a first
endzone region, a second endzone region, and a middle region. By
removing material from the middle region a plurality of parallel
helical segments will remain and a plurality of circumferential
segments will remain connecting the helical segments.
Alternatively, the stent may be formed from a tube by removing
material such that at least two sets of helical segments remain
with each set having a different pitch.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a three dimensional view of one embodiment of a
stent according to the present invention in its unexpanded
state.
[0011] FIG. 2 is planar view of a flattened portion of the
circumference of the stent in FIG. 1.
[0012] FIG. 3 is an enlarged portion of FIG. 2.
[0013] FIG. 4 is another planar view of a flattened portion of the
circumference of a stent according to the present invention in its
unexpanded state.
[0014] FIG. 5 is an enlarged view of a portion of FIG. 4 showing a
first circumferential element of the stent.
[0015] FIG. 6 is an enlarged view of a portion of FIG. 4 showing a
second circumferential element of the stent.
[0016] FIG. 7 is a planar view of a flattened portion of the stent
in FIG. 1 showing a plurality of sets of helical segments
propagating through the stent's body.
[0017] FIG. 8 is a planar view of a flattened endzone that may be
employed in a stent of the present invention.
[0018] FIG. 9 is a planar view of a flattened portion of part of
the endzone shown in FIG. 8.
[0019] FIG. 10 is a planar view of a flattened portion of an
expandable stent according to the present invention, after the
stent has been deployed in a lumen.
[0020] FIG. 11 is three dimensional view of an alternative
embodiment of the present invention.
[0021] FIG. 12 is a three dimensional view of an another stent
according to the present invention.
[0022] FIG. 13 is a planar view of the stent shown in 12.
[0023] FIG. 14 is a detailed view of a portion of FIG. 13.
[0024] FIG. 15 is a detailed view of another portion of FIG.
13.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present invention is directed to an expandable stent, as
well as a method of manufacturing the stent. In one embodiment, as
is shown in FIGS. 1 and 2, the stent comprises a generally
cylindrical shaped main body section 11 having a cylindrical axis 5
and a wall thickness 103. The wall thickness 103 may optionally be
uniform throughout the stent. The main body section 11 is comprised
of a plurality of helical segments 30 and 40 and a plurality of
main body cylindrical elements 100, each having cylindrical axes
(not shown) that are collinear with the main body cylindrical axis
5. The main body cylindrical elements 100 are each comprised of
circumferential elements 50 that are joined together by the helical
segments 30 and 40 to form individual cylinders 100.
[0026] The stent may also have a first endzone 10 and a second
endzone 20 that straddle the body section 11. In some embodiments,
such as the one shown in FIG. 1, the endzones 10 and 20 may
advantageously provide the stent with square outer edges 8. The
stent may be manufactured from stainless steel, or other suitable
materials. In most embodiments, it is desirable that the material,
or a portion of the material, be radiopaque and that the various
segments that form the stent be contiguous. Although, in some
embodiments, the various segments that make up the stent can be
distinct elements that are joined together.
[0027] The main body 11, shown in FIGS. 1 and 2, may be formed in
numerous ways. For example, the body 11 may contain two or more
first helical segment 30 and 40 that are generally parallel to each
other. In some embodiments they may be opposite each other by
180..degree. In general, the first helical segments 30 and 40 will
be spaced equidistant along the circumference 110 of the main body
11. The first helical segments 30 and 40 are joined by a plurality
of circumferential segments 50 to form a plurality of main body
cylindrical elements 100, which may be only generally cylindrically
shaped. In one embodiment, the circumferential segments 50 make up
a majority of the circumference 110 of each cylindrical element
100. In addition to joining the circumferential elements 50 to form
cylindrical elements 100, the helical segments 30 and 40 connect
each cylindrical element 100 to an adjacent cylindrical element 100
to form the main body 11.
[0028] As is shown in FIGS. 2 and 3, the body of the stent 11 may
comprise a plurality of main body cylindrical elements 100 formed
from first circumferential segments 50 that are joined with second
circumferential segments 60. The second circumferential segments 60
of each cylindrical element 100 may be joined with second
circumferential segments 60 of adjacent cylindrical elements 100 to
form a plurality of first helical segments 30 and 40 in the main
body 11. (See FIG. 2). Each first circumferential segment 50 may
have a circumferential dimension 55 and each second circumferential
segments 60 may have a circumferential dimension 66' (See FIG. 3).
In some embodiments, it may be desirable for the circumferential
dimension 55 of the first expandable element 50 to be larger than
the circumferential dimension 66' of the second expandable element
60.
[0029] The first circumferential segment 50 may be an expandable
segment formed from plurality of segments joined together to form a
pattern. The pattern, such as the one shown in the FIGS. 1-3, may
be a repeating pattern that resembles a square wave form having
curved peaks and valleys. Other patterns, both repeating and
non-repeating, may be used. For example, and without limitation,
the first circumferential segments 50 may resemble a triangle wave
form, a sinusoidal wave form, other repetitious patterns, or any
pattern that enables the segment to expand when a radial force is
exerted on the stent from the inside or collapse radially when an
external crimping force is applied.
[0030] The first circumferential elements 50 may have a filament
width 420 (see FIG. 4). In one embodiment, the filament width may
vary between 0.002 inches and 0.007 inches, but is preferably about
0.0050 inches. Other filament widths may be used depending on the
parameters of the stent.
[0031] In the embodiment shown in FIGS. 1-5, the first
circumferential elements 50 comprise linear portions 320 and curved
portions 328 that join the linear portions 320 together to form a
repeating pattern. In some, but not all, embodiments, the linear
portion 320 may be parallel to the cylindrical axis of the stent.
In other embodiments, the linear portion 320 lies at an angle of
between 0-45 degrees with respect to the cylindrical axis. The
first circumferential segment 50 has an amplitude 350 and a period
380. In one embodiment the amplitude may range from 0.5 mm to 2.0
mm and the period may range from 0.5 mm to 2.0 mm. In some
embodiments, the amplitude is less than the period. Other
amplitudes and periods may be used depending on the overall stent
design and performance constraints.
[0032] The second circumferential element 60, which may be joined
together in a helical pattern to form one or more helical segments
30 or 40, may also take numerous forms, in addition to the form
shown in FIG. 6. In the embodiment shown in FIG. 6, the second
circumferential element 60 comprises linear portions 412 and curved
portions 414 having a filament width 407, and resembles generally
an S-shaped structure. In addition, the second element
circumferential segment 60 may have an angled portion 417 attached
to the linear portion 412 at an end opposite that of the curved
portion 414. The angled portion may be oriented to form an angle
.alpha. relative to the cylindrical axis of the stent 5 in the
range of 0-45 degrees. In at least one embodiment, the preferable
angle .alpha. is about 10 degrees. In some embodiments, the linear
portions 412 of the second circumferential element 60 lies at an
angle .OMEGA. relative to the cylindrical axis of the stent,
wherein .OMEGA. preferably ranges from 0 to 45 degrees. When viewed
in a planar fashion as in FIG. 2, the linear portions 412 may, in
some embodiments, form an angle .OMEGA., relative to the
cylindrical axis of the stent. In some embodiments, .OMEGA. may be
approximately equal to the helical angle of the first helical
segments 30 and 40. In one embodiment, the second circumferential
elements 60 may have an amplitude 300 (see FIGS. 3, 4, and 6)
ranging from 0.5 mm to 2.0 mm and a period 310 ranging from 0.5 mm
to 2.0 mm. Other ranges may be used depending on the particular
stent size and design being employed. In one embodiment, the
preferred period is about 0.82 mm and the preferred length of the
linear portion 412 is about 0.5 mm and the amplitude 300 is about
0.38 mm. The amplitude of the second circumferential element 60 may
be greater than, equal to, or less than the amplitude of the first
circumferential element 50. In one embodiment, the circumferential
contributions of the first circumferential elements 50 to the
overall circumference of the main body 11 is greater than the
circumferential contribution of the second circumferential element
60, in terms of either circumferential length or circumferential
cylindrical surface area. In one embodiment, the stent may have an
overall outer surface area of about 0.029 square inches.
[0033] As is shown in FIG. 7, the stent may have a main body 11
comprised of two or more first helical segments 30 and 40, as well
as two or more second helical segments 200 and 210. The first and
second helical segments 30, 40 and 200, 210, respectively, are
joined together to form a generally cylindrically shaped body 11.
In some, but not all embodiments, the first and second helical
segments may share a common connecting element 250. In some
embodiments, the common connecting element 250 may be H-shaped and
the two generally parallel linear portions of the H-shaped
connecting segment 250 may form an angle .delta. relative to the
axis 5. (See FIG. 6)..delta. may, in one embodiment, be about 14
degrees. As is shown in FIG. 7, the first helical segments 30 and
40 and second helical segments 200 and 210 may have different
pitches, i.e. number of spirals per unit length, which results in
the first and second helical segments as having different helical
angles (.theta. and .beta., respectively) i.e. the angle of the
helical segment relative to the cylindrical axis 5 of the stent. In
one embodiment, the second helical segments 200 and 210 have a
pitch approximately twice that of the first helical segments. In
one embodiment .theta. may vary from 0 to 45 degrees and is
preferably about 40 degrees and .beta. is preferably about twice
.theta. In other embodiments the angle .theta. may range from 0 to
90 degrees. to the circumference 110 of each cylindrical element
100.
[0034] As is shown in FIGS. 2, 3, 4, and 6, the helical segments
30, 40 are circumferentially expandable (i.e. they expand along the
circumference of the stent) and may be formed from a plurality of
circumferential elements 60 that in turn are made up of linear 412
and/or curved 414 segments (see FIG. 6) that each have a filament
width 407 (see FIG. 6) that is less than the circumferential
dimension 66 of the circumferential element 60 (see FIG. 3). In
some embodiments, each helical segment 30 or 40 will make a total
contribution to the circumference of each cylindrical element 100
that is greater than the filament width 407. The circumferential
contribution of each helical segment 30 or 40 to the overall
circumference of the stent (110 in FIG. 1 or 105 in FIG. 11) may be
greater than the circumferential contribution of the filament
widths 407 of the segments (e.g. 412 and 414) making up the
circumferential elements 60 that in turn make up the helical
segments. (I.e., In some embodiments the circumferential
contribution of the helical segments 30 and 40 to the circumference
110 of each cylindrical element 100 is more than just a function of
the filament width 407, e.g., it may be a function of the geometry
of the element 60). For the embodiment shown in FIGS. 1 and 11,
this is the case when the stent is in both the unexpanded and
expanded state. The geometry of the helical segments 30 and 40 are
a factor in determining their expandability.
[0035] Likewise, the helical segments 200, 210 are
circumferentially expandable and may be comprised of other
circumferential elements 50 that are in turn comprised of linear
320 and/or curved segments 328 (see FIGS. 3 and 5) that have a
filament width 420 (see FIG. 4). The contribution of the helical
segments 200, 210 to the overall circumferential dimension 110 of
each cylindrical element 100 is greater than just the contribution
of the filament widths 420 of the individual segments 320 and 328
that make up the elements 50 that in turn make up the helical
segments 200, 210. The geometry of the elements 50 making up the
helical segments 200, 210 may be a more important factor in
determining the circumferential contribution of the helical
segments 200 and 210 to the overall stent circumference than the
filament width 420. Thus, in one embodiment of the present
invention, the circumference of the stent 110 in its unexpanded
state and the circumference 105 when the stent is expanded are
primarily functions of the geometry of the elements 50 and 60 that
make up the helical segments 30, 40 and 200, 210, respectively.
[0036] Some, but not all embodiments, of the present invention may
employ endzones 10 and 20. (See FIGS. 1, 2, and 11). Stents that
employ endzones will generally have two endzone regions straddling
a central zone in the middle of the stent. The stents may also have
a transition region between the endzone and the central zone. The
transition region serves to help smoothly transition between the
expanded middle region and portions of the end of the stent that
remain unexpanded after the stent is implanted. The size and
characteristics of the transition region are a function of the
material and geometry of the stent. For example, the transition
range properties vary as a function of, among other things, the
helical angle of the first helical segments, the number of curved
segments located in the endzones, and the angle .epsilon. of the
linear portions of the segments forming the endzones. (See e.g.
FIG. 8).
[0037] The endzones 10 and 20 may take numerous forms. In some
embodiments, the endzones may be comprised of one or more rings 17.
(See FIG. 8). The rings 17 may be generally cylindrically shaped,
and in some embodiments, right cylindrically shaped. In one
embodiment, the rings are formed from linear segments 28 joined
together by curved segments 29 to form a pattern. The pattern,
which is preferably--but not necessarily--a repeating pattern may
take numerous forms, including the one shown. The endzones 10 and
20 may be comprised of a plurality of rings 17 attached together.
Struts 15 may be used to attach the rings together to form the
endzone and to attach the endzone to the main body 11. The struts,
in some embodiments, act as cantilever springs and there stiffness,
which is a function of their width and thickness, may define
bending properties of the stent along its cylindrical axis 5.
[0038] In the embodiment shown in FIGS. 1, 7, 8, and 9, which is
exemplary only, the linear segments 28 in the endzone 10, are
oriented at an angle .epsilon. relative to the cylindrical axis of
the stent. In one embodiment, the angle .epsilon. is greater than 0
degrees. In another embodiment, .epsilon. may range from 0 to 45
degrees and in still another embodiment is preferably about 10
degrees. The segments of the endzone may have a filament width 13
of between 0.002 and 0.007 inches. In one embodiment, the repeating
pattern of the endzone has a period 2 of about 0.027 inches and an
amplitude 21 of about 0.043 inches. Other values may be used. As is
shown in FIG. 1, the struts 15, which are but one way to attach the
endzones 10 and 20 to the main body 11, may, in one embodiment have
a width of between 0.002 inches and 0.08 inches and preferably the
width does not exceed the wall thickness, which typically--but not
necessarily ranges from about 0.002 to 0.008 inches.
[0039] The stent of the present invention may, after insertion into
a vessel, be expanded such that it plastically deforms from the
unexpanded state to an expanded state having a diameter increase of
about 400 to 500%, which results in a larger circumference 105.
(See FIG. 11). FIG. 11 depicts the stent shown in FIG. 1 in an
expanded state. Upon expansion the stent's outer diameter in one
particular embodiment increases from 1.0 mm to 3.00 mm and
maintains a stent-to-vessel ratio in the expanded state that is
greater than on average 16%.
[0040] While endzones 10 and 20 may be used to provide square edge,
not all stents according to the present invention require endzones.
FIGS. 12-15 depict an endzoneless stent. Like the stent shown in
FIG. 19, the stent of FIGS. 12-15 comprises a plurality of adjacent
cylindrical elements 100. The cylindrical elements 100 are formed
from a plurality of first circumferential elements 50' and second
circumferential elements 60. The first circumferential elements 50'
of the stent in FIGS. 12-15 are substantially identical to the
second circumferential element 60 except that they are rotated to
have a different orientation. The circumferential elements may be
generally S-shaped having a linear portion 412, a curved portion
414 having a radius R, and an angled portion 417. R may vary widely
depending on overall stent characteristics and in one embodiment
varies between 0.001 and 0.02 inches and is preferably about 0.0083
inches. The angled portion 417 is spaced a distance 499 from the
linear portion. In one particular embodiment, the distance 499 may
vary from 0.002 to 0.020 inches and is preferably about 0.007
inches. The filament width 407 of the elements may, in one
embodiment, be about 0.13 mm. The circumferential elements depicted
in FIG. 14 and the expansion elements depicted in FIG. 15 are
positioned about the cylindrical axis 5 as defined by angle K and
may be generally S-shaped having a linear portion 412, a curved
portion 414 having a radius R, and an angled portion 417. The angle
K may vary widely depending on overall stent characteristics and
range of radial compression or expansion about the axis 5.
[0041] Adjacent cylindrical elements 100 are joined together by
connecting first circumferential elements 50' in each cylindrical
element 100 with first circumferential elements 50' in an adjacent
cylindrical element 100, such that the first circumferential
elements 50' in adjacent cylindrical elements 100 form helixes
through the stent and such that second circumferential elements
form helixes through the stent having an angle .theta. relative to
the axis 5. In some embodiments, a connecting segment 250 (see FIG.
7) is used to connect first circumferential elements in adjacent
cylindrical elements 100 and to connect second circumferential
elements 60 in adjacent cylindrical elements 100. In addition, the
connecting segment, connects first circumferential elements 50' in
each cylindrical element 100 with two second circumferential
elements 60 in each cylindrical element 100. In one embodiment, the
individual cylindrical elements 100 are adjacent to each other and
are located a distance 666 apart. In one embodiment, the preferred
may range between 0.002 and 0.020 inches, and is preferably about
0.009 inches.
[0042] The above description of the stent of the present invention
is illustrative and not exhaustive. Various modifications may be
made to the stent to change its overall characteristics without
deviating from the scope and spirit of the invention as defined by
the claims. For example and without limitation, the increasing the
length of the linear segments and or increasing the arc of the
second circumferential elements 60 will decrease the amount of
radial force required to expand each circular section and will
increase flexibility. Increasing the angle .OMEGA. of the second
circumferential element 60 will: (i) increase the amount of radial
force required for expansion, (ii) increase surface area, and (iii)
decrease flexibility. Likewise, various modifications may be made
to the struts 15. (See FIG. 2). Increasing strut width and wall
thickness will: (i) increase surface area, (ii) increase radial
strength, (iii) increase pressure required to expand the stent
radially, (iv) decrease flexibility, and, in the case of increased
wall thickness, (v) increase radiopacity.
[0043] The stent of the present invention may be manufactured in
numerous ways. The stent may be formed from a metallic tube by
removing various portions of the tube's wall to form the patterns
described herein. The resulting stent will thus be formed from a
single contiguous piece of material, eliminating the need for
connecting various segments together. Material from the tube wall
may be removed using various techniques including laser (YAG laser
for example), electrical discharge, chemical etching, metal
cutting, a combination of these techniques, or other well known
techniques. See e.g. U.S. Pat. Nos. 5,879,381 to Moriuchi et al.
and 6,117,165 to Becker, which are hereby incorporated in their
entirety by reference. Forming stents in this manner allows for
creation of a substantially stress-free structure where the helical
segments are integral with the circumferential elements. In one
embodiment, the tube from which the stent is formed may have an
internal diameter of about 3.0 mm, a wall thickness of about 1.0 mm
and a length of about 30 mm. Tubes having other dimensions may be
used. In particular, the length may be adapted to that of the
diseased part of the lumen in which the stent is to be placed. This
may avoid using separate stents to cover the total diseased
area.
[0044] Those skilled in the art will recognize that the stent and
manufacturing method described above are illustrative and not
exhaustive of the present invention and that modifications and
variations may be made without deviating from the scope and spirit
of the invention as defined by the following claims.
* * * * *