U.S. patent number RE38,653 [Application Number 10/287,745] was granted by the patent office on 2004-11-16 for luminal stent, holding structure therefor and device for attaching luminal stent.
This patent grant is currently assigned to Kabushikikaisha Igaki Iryo Sekkei. Invention is credited to Keiji Igaki, Hideo Tamai.
United States Patent |
RE38,653 |
Igaki , et al. |
November 16, 2004 |
Luminal stent, holding structure therefor and device for attaching
luminal stent
Abstract
A luminal stent is a tubular body formed by knitting a sole yarn
of a bioresorbable polymer fiber, such as fiber of polylactic acid,
polyglycol acid or a polylactic acid--polyglycol acid copolymer.
When introduced into and attached to the inside of the vessel by a
catheter fitted with a balloon, the tubular member may retain its
shape for several weeks to several months after attachment and
subsequently disappears by being absorbed into the living tissue.
In this manner, the luminal stent is not left as a foreign matter
semi-permanently in the living body without producing inflammation
or hypertrophy in the vessel. There is also provided a method for
attaching the luminal stent in the vessel.
Inventors: |
Igaki; Keiji (Kyoto,
JP), Tamai; Hideo (Moriyama, JP) |
Assignee: |
Kabushikikaisha Igaki Iryo
Sekkei (Kyoto, JP)
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Family
ID: |
33425642 |
Appl.
No.: |
10/287,745 |
Filed: |
November 5, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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398047 |
Mar 2, 1995 |
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946297 |
Nov 2, 1992 |
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Reissue of: |
794396 |
Feb 5, 1997 |
06045568 |
Apr 4, 2000 |
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Foreign Application Priority Data
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Mar 8, 1991 [JP] |
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P3-068933 |
Oct 7, 1991 [JP] |
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P3-324960 |
Nov 20, 1991 [WO] |
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PCT/JP91/01601 |
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Current U.S.
Class: |
606/198;
604/96.01; 606/108; 606/192; 623/1.11; 623/1.2 |
Current CPC
Class: |
A61F
2/90 (20130101); A61F 2/958 (20130101); A61L
31/06 (20130101); A61L 31/06 (20130101); C08L
67/04 (20130101); A61F 2210/0004 (20130101); A61F
2220/0008 (20130101) |
Current International
Class: |
A61F
2/06 (20060101); A61L 31/04 (20060101); A61L
31/06 (20060101); A61F 2/02 (20060101); A61M
029/00 () |
Field of
Search: |
;606/108,192,194,195,198
;623/1.11,1.2,1.49,1.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2025626 |
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Mar 1991 |
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CA |
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U-9 014 845 |
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Feb 1991 |
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DE |
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0 183 372 |
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Jun 1986 |
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EP |
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0 326 426 |
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Aug 1989 |
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EP |
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3-21262 |
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Jan 1991 |
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JP |
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WO 90/04982 |
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May 1990 |
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WO |
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WO 91/12779 |
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Sep 1991 |
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WO |
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Other References
Abstracts of 63.sup.rd Scientific Session, III-72, Supplemental III
Circulation, vol. 82, No. 4, Oct. 1990..
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Primary Examiner: Truong; Kevin T.
Attorney, Agent or Firm: Rader, Fishman & Grauer
PLLC
Parent Case Text
This is a continuation of co-pending application Ser. No.
08/398,047 filed on Mar. 2, 1995 which was a Continuation of
application Ser. No. 07/946,297 filed on Nov. 2, 1992.
Claims
We claim:
1. A luminal stent attachment device comprising: a luminal stent,
which is to be inserted into a vessel of a living body, comprising
a homogeneous tubular member produced by knitting a sole
bioresorbable polymer yarn; and a catheter having a balloon forming
portion in the vicinity of a distal end of said catheter.
2. The luminal stent attachment device as defined in claim 1
wherein the luminal stent produced by knitting is contracted in
diameter from the as-knitted state.
3. The luminal stent attachment device according to claim 1,
wherein the bioresorbable polymer is polylactic acid (PLA).
4. The luminal stent attachment device according to claim 1,
wherein the bioresorbable polymer is polyglycolic acid (PGA).
5. The luminal stent attachment device according to claim 1,
wherein the bioresorbable polymer is a mixture of polylactic acid
(PLA) and polyglycolic acid (PGA).
6. The luminal stent attachment device according to claim 1,
wherein the luminal stent has two ends, the luminal stent
attachment device further comprising: two holders, secured to the
catheter, for respectively holding the two ends of the luminal
stents.
7. The luminal stent attachment device according to claim 1,
wherein the catheter includes a hollow part by which a balloon is
formed in the balloon forming portion under a fluid pressure
supplied into said hollow part and wherein the luminal stent is
dilated by the balloon.
8. A luminal stent attachment device comprising: a luminal stent,
which is to be inserted into a vessel of a living body, comprising
a homogeneous heat-set tubular member produced by knitting a sole
bioresorbable polymer yarn; and a catheter having a balloon forming
portion in the vicinity of a distal end of said catheter.
9. A luminal stent attachment device comprising: a luminal stent,
which is to be inserted into a vessel of a living body, comprising
a homogeneous double heat-set tubular member produced by knitting a
sole bioresorbable polymer yarn; and a catheter having a balloon
forming portion in the vicinity of a distal end of said catheter.
Description
TECHNICAL FIELD
This invention relates to a stent introduced into a vessel, such as
a blood vessel, lymph vessel, bile duct or ureter for maintaining
the shape of the vessel. More particularly, it relates to a luminal
stent attached to a site of angioplasty after the operation of
percutaneous angioplasty of a stenotic part of the blood vessel,
such as artery (the operation of introducing a balloon forming
portion annexed to the end of a catheter into a constricted portion
of the blood vessel for forming a ballooning for dilating the
constricted portion for improving blood flow) and a device for
attaching the luminal stent.
BACKGROUND TECHNOLOGY
As this type of the luminal stent, there is known a tubular stent
constituted by wrapping a meshed structure formed by intertwining
longitudinal and transverse wires of e.g. stainless steel. Such
tubular stent is introduced into the site of angioplasty and
dilated there so as to be attached thereto.
This known type of the stent however suffers from the problems that
it is hard and tends to stress the vessel to produce inflammation
or hypertrophy in the vessel which may cause reconstriction in the
vessel, and that the stent is semipermanently left as a foreign
matter within the living body, which is inherently not desirable to
the living body.
If the metal stent, which is left in the vessel semi-permanently or
for a time longer than is necessary, is attached within the vessel,
it may occur that the stent turns out to be a kind of a nucleus and
the risk is high that stenosis be again caused in the site of
attachment of the stent. Besides, an injury done to the vessel
around the stent tends to cause abnormal multiplication of living
cells on the inner wall of the vessel to contract the vessel.
It is therefore an object of the present invention to provide a
luminal stent free from these problems and a device for attachment
of the stent.
DISCLOSURE OF THE INVENTION
According to the present invention, the above object is
accomplished by a luminal stent consisting of a tubular member
produced by knitting a bioresorbable polymer yarn, and a luminal
stent attachment device comprising the luminal stent which is
fitted over a balloon forming portion in the vicinity of a distal
end of a catheter.
The bioresorbable polymers may be enumerated by polylactic
acid(PLA), polyglycolic acid(PGA), polyglactin (PGA-PLA copolymer),
polydioxanone, polyglyconate (copolymer of trimethylene carbonate
and glycolide) and a copolymer of polyglycolic acid or polylactic
acid with .di-elect cons.-caprolactone.
The bioresorbable polymer may be admixed with a variety of
materials, including pharmaceuticals. The materials may also be
deposited on the fiber surface.
The luminal stent of the present invention is introduced into and
attached to the site of angioplasty by a catheter fitted with a
balloon and attached in place by dilating the balloon. The luminal
stent may retain its shape for several weeks to several months
after attachment and disappears in several months after attachment
by being absorbed in the living tissue after lapse of several
months after attachment.
If an X-ray impermeable agent is admixed in the bioresorbable
polymer, the state of the luminal stent may be observed after
attachment by irradiation of X-rays from outside.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be explained in detail by referring to
the accompanying drawings in which:
FIG. 1 shows the process of producing a luminal stent according to
the present invention, in the diametrically contracted state.
FIG. 2 is a conceptual view showing the luminal stent of the
present invention as it is introduced into and attached to the
vessel.
FIG. 3 shows an alternative method for contracting the luminal
stent, woven from a yarn of PGA fibers of the present invention, in
the direction along its diameter.
FIG. 4 is schematic views showing essential parts of a device for
attachment of the luminal stent according to the present invention,
where FIG. 4 shows the attachment device in its entirety and FIG. 4
shows a part thereof in cross-section.
FIG. 5 is an explanatory view showing the process of attachment of
the luminal stent by the attachment device of the present
invention.
FIG. 6 shows another embodiment of the attachment device of the
luminal stent according to the present invention.
FIGS. 7A, 7B and 7C show the state of attachment between the vessel
and the luminal stent, where FIG. 7A shows an illustrative vessel,
FIG. 7B shows the state of attachment of the luminal stent of the
present invention, and FIG. 7C shows an undesirable state of
attachment of a conventional luminal stent, for comparison
sake.
FIG. 8 shows the possibility of attachment of the luminal stent of
the present invention in various vessel sites.
BEST MODE FOR CARRYING OUT THE INVENTION
Basically, the luminal stent of the present invention is fabricated
by knitting a sole yarn, so that a tubular product as a luminal
stent which is more homogeneous than a fabric formed by weaving a
so-called warp yarn and a weft yarn may be produced.
Besides, it is by far easier for the knitted luminal stent of the
present invention to pass through various meandering vessels before
reaching the target site. That is, the luminal stent formed from a
knitted cloth exhibits trackability with respect to a variety of
meandering passages, while it can be introduced into and attached
to a site of bend, because the tubular knitted product tends to be
dilated and is not likely to mar the shape of the lumen. According
to the present invention, the tubular wove stent having a diameter
of about 5 mm is heat-treated and set so as to be contracted in
diameter to about 2 mm or less for being introduced into and
attached to the inside of the vessel of a lesser diameter in the
living body than the stent. This process is explained by referring
to FIG. 1.
The process of attachment of the heat-set luminal stent to the
inside of the vessel is shown in a conceptual view of FIG. 2.
An alternative method of contracting the luminal stent 1 knitted
from PGA (polyglycolic acid) polymer fiber is shown in FIG. 3. The
method shown in FIG. 3 has an advantage that, since a tube formed
of metal or a heat-resistant resin is not used, the stent can be
directly attached to a ballooning portion at the distal end of the
catheter.
The present invention provides a tubular luminal stent formed by
knitting a sole yarn of a biologically resorbable polymer fiber.
The luminal stent is superior in pliability and shape retention
properties to other cloth forms, such as a non-woven fabric, e.g. a
felt, or a woven fabric formed by weaving weft and warp yarns. The
knitted luminal stent is additionally heat set for exhibiting more
prominent effects in pliability and shape retention
characteristics.
The tubular luminal stent 1 knitted from a yarn of a bioresorbable
polymer fiber has a diameter of an order of 4 to 5 mm and is heat
set after it is introduced or as it is introduced into a tube 7 of
heat-resistant resin or metal having an inside diameter of about 1
to 3 mm, preferably 2 mm, to produce a luminal stent 11 having a
set shape with a diameter of about 2 mm, as shown in FIG. 1.
Besides, the heat setting has such a meaning that, by heat-treating
(heat-setting) the knitted tubular luminal stent while it has a
larger diameter, or after it is contracted in diameter, the knitted
fabric has terminal fibers, yarns or meshes which are excellent in
shape retention characteristics, such that the heat setting affords
superior shape retention characteristics while minimizing the
stress otherwise applied to the inner wall of the vessel of the
living body.
By using PLA+PGA as bioresorbable polymer fibers, and by changing
the mixing ratio, the half value period in strength of the luminal
stent of the present invention, that is the period in which the
bioresorbability disappears, may be freely controlled within a time
period of from three weeks to three months.
Besides, by adding an X-ray impermeable agent at the time of
spinning the fibers, the state of the introduced luminal stent may
be observed with X-rays. Thrombus lysing agents or anti-thrombotic
agents, such as heparin, urokinase or t-PA may also be added, if so
desired.
Besides, by taking advantage of the fact that the luminal stent of
the present invention, produced by knitting a yarn of the
bioresorbable polymer fibers, is vanished after a predetermined
time lapse from the site into which it has been introduced,
carcinostatics or anti-thrombotic agents may be mixed into or
attached to the fibers for concentrated administration of these
agents to the site of lesion.
In addition, the fibers used in knitting the luminal stent of the
present invention may be rendered variable in the cross-sectional
shape thereof more easily than if the luminal stent is formed from
metal. That is, affinity with the living body or shape retention
characteristic may be controlled by affording the hollow or
profiled cross-sectional shape to the filaments during spinning or
by using a monofilament yarn or a multifilament yarn.
Besides, the yarn of synthetic polymers may be processed in many
ways on its fiber surface. That is, using a yarn having a
substantially circular cross-section as usual and which is not
processed in any particular manner on its surface, a yarn having
the above-mentioned so-called profiled cross-section, or the
above-mentioned processed yarn, anti-thrombotic materials,
thrombus-lysing agents or cells of the living bodies may be
attached to is yarn for promoting multiplication of the endothelial
cells. Alternatively, X-ray non-transmitting materials may also be
attached to the yarn.
Meanwhile, if it is desired to dilate the stenotic site of the
vessel to the diameter of, for example, 4 mm, and to maintain the
diameter, the site is not dilated at a time. That is, for avoiding
an abrupt stress to the vessel or to the living body per se, the
vessel is first dilated to a diameter of 3 mm by an extender having
a balloon-forming portion of a diameter of 0.8 to 1.2 mm. After the
catheter 2 fitted with a ballooning portion 3 is extracted, a
catheter not fitted with a luminal stent and fitted only with the
balloon-forming portion 3 is introduced into the vessel for
dilating the vessel to a diameter of 4 mm or more. Finally, the
knitted luminal stent 11 is attached in place by a luminal stent
attachment device in which a luminal stent 11 according to the
present invention is attached to the balloon forming portion 3 of
the device. However, it is not absolutely necessary to dilate the
vessel by steps in this manner, and the luminal stent 11 may be
introduced into and attached to the target site after the stenotic
portion of the vessel is dilated at a time to the desired
diameter.
Alternatively, a luminal stent attachment device per se, which is
the catheter fitted with the ballooning device and with the luminal
stent of the present invention, may be used for introducing and
attaching the luminal stent into the vessel of the living body
simultaneously with vessel dilation.
The device for introducing and attaching the luminal stent of the
present invention in the stenotic portion of the vessel of the
living body is explained in detail. In the vicinity of the distal
end of the catheter 2, there exists a region capable of forming a
balloon 6 of a desired diameter by a gas or a liquid, such as an
X-ray contrast medium, which is injected via a hollow part within
the catheter 2 under a liquid pressure of 8 to 10 atmospheres. The
above-mentioned heat-set luminal stent, having the diameter of
about 2 mm, is applied over the balloon forming portion 3, which is
about 20 mm long, with both ends of the luminal stent 4 being
clamped by holding member 4 of silicone resin or the like between
the catheter (2 at fixing part 26) and the outer periphery of the
balloon-forming thin film 16 at holder 24, as shown in FIG. 4.
However, the length of the balloon forming portion 3 or the
diameter of the luminal stent 11 may be optionally set depending on
the types of the luminal stent or the specific nature of the
vessel.
Meanwhile, the distal end of the catheter is occasionally provided
with a guide wire which plays the role of a guide wire when the
catheter is introduced into the vessel.
For attachment of the luminal stent, a communication orifice 14
(see FIG. 4) is formed at a mid part along the length of the
balloon forming portion 3 of the catheter 2 for permitting the
fluid injected for forming the balloon to exit from the hollow part
of the catheter to be charged between the hollow part of to the
catheter and the balloon-forming thin film 16. A balloon is formed
by being dilated under a fluid pressure of 8 to 10 atmospheres via
the orifice and maintained for 30 to 60 seconds or for a longer
time. The stent 11 undergoes a kind of plastic deformation at this
time under the force of dilation of the balloon so as to be
maintained in the dilated state 20. At this time, the polymer
itself is changed in the molecular level, or the knitted structure,
that is the mesh shape, is changed, that is, the stent 11 is
contracted along its length and dilated along its radius so as to
be changed in shape to maintain the thus changed shape.
FIG. 5 shows the process of introducing and attaching the luminal
stent of the present invention within the vessel of a living body.
As shown therein, the luminal stent is contracted in length with
balloon dilation so that both ends of the stent are detached from
the holding members 4. By the subsequent operation of contracting
the balloon, the catheter 2 may be removed in its entirety.
FIG. 6 shows another example of a luminal stent attachment device
according to the present invention. In this case, the catheter 2
fitted with a balloon 6 is covered with a sheath 5 of a teleguide
catheter and introduced in this state into the vessel of the living
body. Then, with the sheath 5 extracted slightly, the balloon 6 is
dilated and maintained in the dilated state. The balloon 6 is then
contracted and the sheath 5 is extracted simultaneously with the
catheter 2, while the luminal stent 11 is left in the vessel.
Meanwhile, the thin film for balloon forming may be formed of a
variety of synthetic polymeric materials, such as polyethylene
terephthalate or polyethylene.
It is noted that the luminal stent of the present invention may be
introduced into a bend in the vessel so as to adapt itself to the
bent shape of the vessel, as best shown in FIG. 7B. On the other
hand, FIG. 7C shows the state in which a metal stent consisting in
a tubular mesh or screen formed by weaving a weft material and a
warp material or a stent of a woven fabric is introduced into a
bend in the vessel. The metal stent or the stent of the woven
fabric is bent at a bend of the vessel so that the shape of the
vessel cannot be correctly maintained in the site of the bend.
Meanwhile, the luminal stent of the present invention is superior
in follow-up characteristics so that it can reach the target site
even if there exist branched parts in the vessel, as discussed
previously. FIG. 7A shows an example of the vessel of the living
body in which it is assumed that a site 22 shown by an arrow
therein be the target site for attachment of the luminal stent.
The luminal stent knitted from a yarn of the bioresorbable polymer
fiber and heat-set according to the present invention may cope with
any thickness of the vessel with the use of the luminal stent
attachment device of the present invention. If, for example, the
luminal stent is loaded in an attachment device which is dilated to
a diameter of about 4 mm on dilating the balloon, the luminal stent
may be attached to the vessel site having a diameter of 2.5 mm by
controlling the degree of dilation of the balloon. The luminal
stent may similarly be attached to the vessel site having a
diameter of 3 or 4 mm. That is, the luminal stent 11 may be
introduced and attached in any site of a lumen 18 shown in FIG. 8
by using the same catheter 2 fitted with the balloon. It is because
the inside diameter of the luminal stent may be maintained at the
thickness of the dilated balloon.
If re-constriction of the vessel should occur in several months
after the luminal stent of the present invention is decomposed and
absorbed into a living body, the luminal stent may again be
introduced and attached in the same site. This is rendered possible
by using the bioresorbable polymer.
Meanwhile, if a thin sheet of a non-woven fabric of a bioresorbable
polymer, such as a felt, bent into a shape of a tube, exhibits
shape retention characteristics and flexibility comparable to those
of the luminal stent of the present invention, such sheet may be
used in place of the knitted material.
With the above-described luminal stent of the present invention,
such meritorious effects may be achieved that inflammation or
excess hypertrophy of the vessel may be prevented and consequently
reconstriction of the vessel may be inhibited. The luminal stent of
the present invention is absorbed in several months into a living
tissue, which is favorable for the living body.
If an X-ray impermeable agent is applied to the bioresorbable
polymer fibers or yarns of the luminal stent of the present
invention, the state of attachment of the stent within the vessel
may be easily observed by X-ray irradiation from outside.
Besides, the luminal stent may be applied over the balloon forming
portion of the catheter according to the present invention so that
the stent may be easily attached in the desired site within the
vessel.
.[.EXPERIMENT 1
Plural luminal stents formed by knitting a yarn of polylactic acid
fibers admixed with barium sulfate were introduced and attached in
the coronary of a test animal in a tubular state of 4 mm in
diameter and 20 mm in length by using a catheter fitted with a
balloon, and the state of attachment was observed by irradiation of
X-rays. It was seen that the stents substantially maintained their
shape until after about three to six months. It was seen that the
stents disappeared by being absorbed into living tissue in about 6
to 12 months. During this time, no abnormalities such as
inflammation or hypertrophy of the intima of the blood vessel were
observed.
EXPERIMENT 2
Plural luminal stents formed by knitting a yarn of polyglycolic
acid fibers admixed with barium sulfate were introduced and
attached in the femoral artery of a test animal in a tubular state
of 4 mm in diameter and 20 mm in length and the state of attachment
was observed by irradiation of X-rays. It was seen that the stents
substantially maintained their shape until after about two to three
weeks and were absorbed into the living tissue in about two to
three months. The shape retention period and the period of
existence in the living body attained in Experiment 2 are thought
to be more safe than the corresponding periods attained in
Experiment 1. Meanwhile, no inflammation or hypertrophy of the
intima of the blood vessel was observed during these
periods..].
* * * * *