U.S. patent application number 09/899828 was filed with the patent office on 2002-02-14 for polyether block amide catheter balloons.
This patent application is currently assigned to Advanced Cardiovascular Systems, Inc.. Invention is credited to Dutta, Debashish, Lee, Jeong S..
Application Number | 20020018866 09/899828 |
Document ID | / |
Family ID | 25463141 |
Filed Date | 2002-02-14 |
United States Patent
Application |
20020018866 |
Kind Code |
A1 |
Lee, Jeong S. ; et
al. |
February 14, 2002 |
Polyether block amide catheter balloons
Abstract
An inflatable member such as a balloon which is formed at least
in part of a polyamide/polyether block copolymer thermoplastic
elastomer, commonly referred to as polyether block amide (PEBA).
The presently preferred PEBA copolymer is polyamide/polyether
polyester copolymer, such as PEBAX.RTM.. The balloon of the
invention exhibits high tensile strength, high elongation, and low
flexural moduli. The balloon may be formed as a single layer of
PEBA, or as a multilayer coextrudate having at least one PEBA
layer. The balloon may be 100% PEBA or a blend of PEBA with another
polymer, such as nylon.
Inventors: |
Lee, Jeong S.; (Diamond Bar,
CA) ; Dutta, Debashish; (Santa Clara, CA) |
Correspondence
Address: |
COUDERT BROTHERS
FOUR EMBARCADERO CENTER
SUITE 3300
SAN FRANCISCO
CA
94111
|
Assignee: |
Advanced Cardiovascular Systems,
Inc.
|
Family ID: |
25463141 |
Appl. No.: |
09/899828 |
Filed: |
July 5, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09899828 |
Jul 5, 2001 |
|
|
|
08932908 |
Sep 17, 1997 |
|
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Current U.S.
Class: |
428/36.8 ;
604/96.01 |
Current CPC
Class: |
A61L 29/06 20130101;
Y10T 428/1386 20150115; A61L 29/06 20130101; C08L 77/00
20130101 |
Class at
Publication: |
428/36.8 ;
604/96.01 |
International
Class: |
B65D 001/00 |
Claims
What is claimed is:
1. A balloon for a medical device formed from a length of tubing of
a polymer material by radial expansion of the tubing under
pressure, the polymer material comprising a block copolymer
thermoplastic elastomer characterized as follows: the block
copolymer is represented by the formula: 2in which PA is a
polyamide hard segment of molecular weight in the range of
500-8,000; PE is a polyether soft segment of molecular weight in
the range of 500-2,500 and the repeating number n is between 5 and
10, the polyamide hard segments are polyamides of C.sub.6 or higher
carboxylic acids and C6 or higher organic diamines or of C.sub.6 or
higher aliphatic .omega.-amino-.alpha.-acids, and the polyether
soft segments are polyethers of C.sub.2-C.sub.10 diols; the block
copolymer has a flexural modulus of less than about 150,000 psi;
the block copolymer has a hardness, Shore D scale, of greater than
60; and the percentage by weight of the block polymer attributable
to the hard segments is between about 50% and about 95%.
2. A balloon as in claim 1 wherein the block copolymer segment, PA,
is an aliphatic polyamide of one or more C.sub.10-C.sub.12
aliphatic acids and one or more C.sub.10-C.sub.12 aliphatic
diamines or of a C.sub.10-C.sub.12 aliphatic
.omega.-amino-.alpha.-acid.
3. A balloon as in claim 1 wherein the polyamide segment, PA, is
selected from the group consisting of nylon 12, nylon 11, nylon 9,
nylon 6, nylon 6/12, nylon 6/11, nylon 6/9 and nylon 6/6.
4. A balloon as in claim 1 wherein the polyamide segment, PA, is
nylon 12 of a molecular weight of 3,000-5,000, and the polyether
segment, PE, is poly(tetramethylene ether) of molecular weight
between 500 and 1250.
5. A balloon as in claim 1 wherein the polyamide segments, PA,
comprise between 80 and 90% by weight of the polyamide/polyether
polyester.
6. A balloon as in claim 1 wherein said polyether segment, is
selected from the group consisting of poly(tetramethylene ether),
poly(pentamethylene ether) and poly(hexamethylene ether).
7. A balloon as in claim 1 wherein the wall strength of the balloon
is at least 15,000 psi.
8. A balloon as in claim 7 wherein the wall thickness, single wall
basis, is no more than 0.0015 inches and said wall strength is
greater than 18,000 psi.
9. A balloon as in claim 8 wherein said wail thickness is no more
than 0.0009 inches.
10. A balloon as in claim 7 wherein said wall strength is greater
than 20,000 psi.
11. A balloon as in claim 1 wherein the polymer material forming
the tubing further comprises a second polymer blended with the
block copolymer thermoplastic elastomer.
12. The balloon as in claim 11 wherein the second polymer is
nylon.
13. The balloon as in claim 12 wherein the nylon is selected from
the group consisting of nylon 11 and nylon 12.
14. The balloon as in claim 13 wherein the percentage by weight of
the nylon is about 30% to about 95%.
15. The balloon as in claim 13 wherein the block copolymer
thermoplastic elastomer has a hardness of Shore D durometer of
about 60D to about 72 D.
16. A balloon for a medical device, comprising a) a first polymeric
layer; and b) at least a second polymeric layer coextruded with the
first layer, comprising a block copolymer thermoplastic elastomer
represented by the formula: 3in which PA is a polyamide hard
segment of molecular weight in the range of 500-8,000; PE is a
polyether soft segment of molecular weight in the range of
500-2,500 and the repeating number n is between 5 and 10, the
polyamide hard segments are polyamides of C.sub.6 or higher
carboxylic acids and C6 or higher organic diamines or of C.sub.6 or
higher aliphatic .omega.-amino-.alpha.-acids, and the polyether
soft segments are polyethers of C.sub.2-C.sub.10 diols; the block
copolymer has a flexural modulus of less than about 150,000 psi;
the block copolymer has a hardness, Shore D scale, of greater than
30; and the percentage by weight of the block polymer attributable
to the hard segments is between about 50% and about 95%.
17. The balloon as in claim 16 wherein the first polymeric layer
comprises nylon.
18. The balloon as in claim 17 wherein the nylon is selected from
the group consisting of nylon 11 and nylon 12.
19. The balloon as in claim 18 wherein the block copolymer
thermoplastic elastomer has a hardness of Shore D durometer of
about 35D to about 72 D.
20. An intravascular catheter, comprising: a) an elongated catheter
shaft having a proximal end, a distal end, and a lumen extending
therein; and b) an inflatable member on the distal end of the
catheter shaft having an interior in fluid communication with the
lumen of the catheter shaft, and being formed from a
polyether/polyamide polyester block copolymer having a flexural
modulus of less than about 150,000 psi.
21. The intravascular catheter of claim 20 further including a
stent disposed about the inflatable member.
Description
BACKGROUND OF THE INVENTION
[0001] This invention generally relates to intravascular catheters,
such as balloon dilatation catheters used in percutaneous
transluminal coronary angioplasty (PTCA).
[0002] PTCA is a widely used procedure for the treatment of
coronary heart disease. In this procedure, a balloon dilatation
catheter is advanced into the patient's coronary artery and the
balloon on the catheter is inflated within the stenotic region of
the patient's artery to open up the arterial passageway and thereby
increase the blood flow there through. To facilitate the
advancement of the dilatation catheter into the patient's coronary
artery, a guiding catheter having a preshaped distal tip is first
percutaneously introduced into the cardiovascular system of a
patient by the Seldinger technique through the brachial or femoral
arteries. The catheter is advanced until the preshaped distal tip
of the guiding catheter is disposed within the aorta adjacent the
ostium of the desired coronary artery, and the distal tip of the
guiding catheter is then maneuvered into the ostium. A balloon
dilatation catheter may then be advanced through the guiding
catheter into the patient's coronary artery until the balloon on
the catheter is disposed within the stenotic region of the
patient's artery. The balloon is inflated to open up the arterial
passageway and increase the blood flow through the artery.
Generally, the inflated diameter of the balloon is approximately
the same diameter as the native diameter of the body lumen being
dilated so as to complete the dilatation but not over expand the
artery wall. After the balloon is finally deflated, blood flow
resumes through the dilated artery and the dilatation catheter can
be removed therefrom.
[0003] To reduce the restenosis rate and to strengthen the dilated
area, physicians frequently implant an intravascular prosthesis,
generally called a stent, inside the artery at the site of the
lesion. Stents may also be used to repair vessels having an intimal
flap or dissection or to generally strengthen a weakened section of
a vessel. Stents are usually delivered to a desired location within
a coronary artery in a contracted condition on a balloon of a
catheter which is similar in many respects to a balloon angioplasty
catheter, and expanded to a larger diameter by expansion of the
balloon. The balloon is deflated to remove the catheter and the
stent left in place within the artery at the site of the dilated
lesion. See for example, U.S. Pat. No. 5,507,768 (Lau et al.) and
U.S. Pat. No. 5,458,615 (Klemm et al.), which are incorporated
herein by reference.
[0004] One type of catheter frequently used in PTCA procedures is
an over-the-wire type balloon dilatation catheter. When using an
over-the wire dilatation catheter, a guidewire is usually inserted
into an inner lumen of the dilatation catheter before it is
introduced into the patient's vascular system and then both are
introduced into and advanced through the guiding catheter to its
distal tip which is seated within the ostium. The guidewire is
first advanced out the seated distal tip of the guiding catheter
into the desired coronary artery until the distal end of the
guidewire extends beyond the lesion to be dilatated. The dilatation
catheter is then advanced out of the distal tip of the guiding
catheter into the patient's coronary artery, over the previously
advanced guidewire, until the balloon on the distal extremity of
the dilatation catheter is properly positioned across the lesion to
be dilatated. Once properly positioned across the stenosis, the
balloon is inflated one or more times to a predetermined size with
radiopaque liquid at relatively high pressures (e.g., generally
4-12 atmospheres) to dilate the stenosed region of a diseased
artery. After the inflations, the balloon is finally deflated so
that the dilatation catheter can be removed from the dilated
stenosis to resume blood flow.
[0005] Another type of dilatation catheter, the rapid exchange type
catheter, was introduced by ACS under the trademark ACS RX.RTM.
Coronary Dilatation Catheter. It is described and claimed in U.S.
Pat. No. 5,040,548 (Yock), U.S. Pat. No. 5,061,273 (Yock), and U.S.
Pat. No. 4,748,982 (Horzewski et al.) which are incorporated herein
by reference. This dilatation catheter has a short guidewire
receiving sleeve or inner lumen extending through a distal portion
of the catheter. The sleeve or inner lumen extends proximally from
a first guidewire port in the distal end of the catheter to a
second guidewire port in the catheter spaced proximally from the
inflatable member of the catheter. A slit may be provided in the
wall of the catheter body which extends distally from the second
guidewire port, preferably to a location proximal to the proximal
end of the inflatable balloon. The structure of the catheter allows
for the rapid exchange of the catheter without the need for an
exchange wire or adding a guidewire extension to the proximal end
of the guidewire.
[0006] The perfusion type dilatation catheter is another type of
dilatation catheter. This catheter, which can take the form of an
over-the-wire catheter or a rapid exchange type catheter, has one
or more perfusion ports proximal to the dilatation balloon in fluid
communication with an guidewire receiving inner lumen extending to
the distal end of the catheter. One or more perfusion ports are
preferably provided in the catheter distal to the balloon which are
also in fluid communication with the inner lumen extending to the
distal end of the catheter. This provides oxygenated blood
downstream from the inflated balloon to thereby prevent or minimize
ischemic conditions in tissue distal to the catheter. The perfusion
of blood distal to the inflated balloon allows for long term
dilatations, e.g. 30 minutes or even several hours or more.
[0007] The balloons for prior dilatation catheters utilized in
angioplasty procedures generally have been formed of relatively
inelastic polymeric materials such as polyvinyl chloride,
polyethylene, polyethylene terephthalate (PET), polyolefinic
ionomers, and nylon. An advantage of such inelastic materials when
used in catheter balloons is that the tensile strength, and
therefore the mean rupture pressure, of the balloon is high.
Catheter balloons must have high tensile strength in order to exert
sufficient pressure on the stenosed vessel and effectively open the
patient's passageway. Consequently the high strength balloon can be
inflated to high pressures without a risk that the balloon will
burst during pressurization. Similarly, the wall thickness of high
strength balloons can be made thin, in order to decrease the
catheter profile, without a risk of bursting.
[0008] Those inelastic materials having the least elasticity are
also classified as "non-compliant" and "semi-compliant" materials,
and include PET and nylon. Such non-compliant material exhibits
little expansion in response to increasing levels of inflation
pressure. Because the non-compliant material has a limited ability
to expand, the uninflated balloon must be made sufficiently large
that, when inflated, the balloon has sufficient working diameter to
compress the stenosis and open the patient's passageway. However, a
large profile non-compliant balloon can make the catheter difficult
to advance through the patient's narrow vasculature because, in a
uninflated condition, such balloons form flat or pancake shape
wings which extend radially outward. Therefore, some compliance is
desirable in an angioplasty catheter balloon. Additionally,
balloons formed of material with high compliance have increased
softness, which improves the ability of the catheter to track the
tortuous vasculature of the patient and cross the stenosis, to
effectively position the balloon at the stenosis. The softness of a
balloon is expressed in terms of the balloon modulus, where a
relatively soft balloon has a relatively low flexural modulus of
less than about 150,000 psi (1034 MPa).
[0009] Therefore, what has been needed is a relatively soft
catheter balloon having a high rupture pressure. The present
invention satisfies these and other needs.
SUMMARY OF THE INVENTION
[0010] The invention is directed to an inflatable member such as a
balloon which is formed at least in part of a polyamide/polyether
block copolymer thermoplastic elastomer, commonly referred to as
polyether block amide (PEBA). The balloon of the invention exhibits
high tensile strength, high elongation, and low flexural
modulus.
[0011] A balloon catheter of the invention generally comprises a
catheter having an elongated shaft with an inflatable balloon
formed of PEBA thermoplastic elastomer on a distal portion of the
catheter. Suitable PEBA balloon materials include, but are not
limited to, PEBAX.RTM., a polyamide/polyether polyester available
from Atochem and described in U.S. Pat. Nos. 4,331,786 and
4,332,920 (Foy et al.), which are incorporated herein by reference.
The presently preferred PEBA copolymer is polyamide/polyether
polyester copolymer.
[0012] The presently preferred balloon is formed from 100% PEBA.
However, the balloon can be formed of a blend of PEBA with one or
more different polymeric materials. Suitable polymeric materials
for blending with PEBA include those polymers listed above used to
make balloons for prior dilatation catheters, such as nylon. In a
presently preferred embodiment, the balloon is a single polymeric
layer. However, the balloon may also be multilayered, where the
balloon is formed by coextruding two or more layers with one or
more layers formed at least in part of PEBA.
[0013] Various designs for balloon catheters well known in the art
may be used in the catheter of the invention having a balloon
formed at least in part PEBA. For example, the catheter may be a
conventional over-the-wire dilatation catheter for angioplasty
having a guidewire receiving lumen extending the length of the
catheter shaft from a guidewire port in the proximal end of the
shaft, or a rapid exchange dilatation catheter having a short
guidewire lumen extending to the distal end of the shaft from a
guidewire port located distal to the proximal end of the shaft.
Additionally, the catheter may be used to deliver a stent mounted
on the catheter balloon.
[0014] The balloon of the invention formed of PEBA thermoplastic
elastomer, combines improved softness and tensile strength, to
provide low profile balloon catheters having excellent ability to
tract the patient's vasculature, cross the stenosis, and compress
the stenosis to open the patient's vessel. These and other
advantages of the invention will become more apparent from the
following detailed description of the invention and the
accompanying exemplary drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an elevational view partially in section of the
catheter of the invention showing the balloon in an unexpanded
state.
[0016] FIG. 2 is a transverse cross sectional view of the catheter
of FIG. 1 taken along lines 2-2.
[0017] FIG. 3 is a transverse cross sectional view of the catheter
of FIG. 1 taken along lines 3-3.
[0018] FIG. 4 is an elevational view partially in section of the
catheter of the invention.
[0019] FIG. 5 is a transverse cross sectional view of the catheter
of FIG. 4 taken along lines 5-5.
DETAILED DESCRIPTION OF THE INVENTION
[0020] As shown in FIG. 1, the catheter 10 of the invention
generally includes a an elongated catheter shaft 11 having a
proximal section 12 and distal section 13, an inflatable balloon 14
formed at least in part of PEBA on the distal section 13 of the
catheter shaft 11, and an adapter 17 mounted on the proximal
section 12 of shaft 11 to direct inflation fluid to the interior of
the inflatable balloon. FIGS. 2 and 3 illustrate transverse cross
sections of the catheter shown in FIG. 1, taken along lines 2-2 and
3-3 respectively.
[0021] In the embodiment illustrated in FIG. 1, the intravascular
catheter 10 of the invention is an over-the-wire catheter, and is
illustrated within a patient's body lumen 18 with the balloon 14 in
an unexpanded state. The catheter shaft 11 has an outer tubular
member 19 and an inner tubular member 20 disposed within the outer
tubular member and defining, with the outer tubular member,
inflation lumen 21. Inflation lumen 21 is in fluid communication
with the interior chamber 15 of the inflatable balloon 14. The
inner tubular member 20 has an inner lumen 22 extending therein,
which is configured to slidably receive a guidewire 23 suitable for
advancement through a patient's coronary arteries. The distal
extremity of the inflatable balloon 14 is sealingly secured to the
distal extremity of the inner tubular member 20 and the proximal
extremity of the balloon is sealingly secured to the distal
extremity of the outer tubular member 19.
[0022] The balloons of the invention are formed at least in part of
polyamide/polyether block (PEBA) copolymers. The presently
preferred PEB copolymers have polyamide and polyether segments
linked through ester linkages, i.e. polyamide/polyether polyesters.
However, other linkages, such as amide linkages, can also be used.
Polyamide/polyether polyester block copolymers are made by a molten
state polycondensation reaction of a dicarboxylic polyamide and a
polyether diol. The result is a short chain polyester made up of
blocks of polyamide and polyether. The polyamide and polyether
blocks are not miscible. Thus, the materials are characterized by a
two phase structure having a thermoplastic region that is primarily
polyamide and an elastomer region that is rich in polyether. The
polyamide segments are semicrystalline at room temperature. The
generalized chemical formula for these polyamide/polyether
polyester block copolymers may be represented by the following
formula: 1
[0023] in which PA is a polyamide hard segment, PE is a polyether
soft segment, and the repeating number n is between 5 and 10. The
polyamide hard segment is a polyamide of C.sub.6 or higher,
preferably C.sub.10-C.sub.12, carboxylic acids; C.sub.6 or higher,
preferably C.sub.10-C.sub.12, organic diamines; or C.sub.6 or
higher, preferably C.sub.10-C.sub.12, aliphatic
.omega.-amino-.alpha.-acids. The percentage by weight of the block
copolymer attributable to the polyamide hard segments is between
about 50% to about 95%. The polyether soft segment is a polyether
of C.sub.2-C.sub.10 diols, preferably C.sub.4-C.sub.6 diols. The
block copolymer has a flexural modulus of less than about 150,000
psi (1034 MPa), preferably less than 120,000 psi (827 MPa).
[0024] The polyamide segments are suitably aliphatic polyamides,
such as nylons 12, 11, 9, 6, 6/12, 6/11, 6/9, or 6/6. Most
preferably they are nylon 12 segments. The polyamide segments may
also be based on aromatic polyamides but in such case significantly
lower compliance characteristics are to be expected. The polyamide
segments are relatively low molecular weight, generally within the
range of 500-8,000, more preferably 2,000-6,000, most preferably
about 3,000-5,000. Another range which is of interest is
300-15,000.
[0025] The polyether segments are aliphatic polyethers having at
least 2 and no more than 10 linear saturated aliphatic carbon atoms
between ether linkages. More preferably the ether segments have 4-6
carbons between ether linkages, and most preferably they are
poly(tetramethylene ether) segments. Examples of other polyethers
which may be employed in place of the preferred tetramethylene
ether segments include polyethylene glycol, polypropylene glycol,
poly(pentamethylene ether) and poly(hexamethylene ether). The
hydrocarbon portions of the polyether may be optionally branched.
An example is the polyether of 2-ethylhexane diol. Generally such
branches will contain no more than two carbon atoms. The molecular
weight of the polyether segments is suitably between about 400 and
2,500, preferably between 650 and 1,000. Another range which is of
interest is 200-6,000.
[0026] The weight ratio of polyamide to polyether in the
polyamide/polyether polyesters used in the invention desirably
should be in the range of 50/50 to 95/5, preferably between 60/30
and 92/08, more preferably, between 70/30 and 90/10.
[0027] Polyamide/polyether polyesters are sold commercially under
the PEBAX trademark by Atochem North America, Inc., Philadelphia,
Pa. A suitable polymer grade for the intravascular balloon catheter
of the invention is the PEBAX.RTM. 33 series. In the embodiment in
which the balloon is 100% PEBA or a blend of PEBA and a polyamide,
preferably PEBA and nylon, the presently preferred PEBAX.RTM.
polymers have a hardness of Shore D durometer of at least about
60D, preferably between about 60D to about 72D, i.e. PEBAX.RTM.
6033 and 7233. In the embodiment in which the balloon is a
coextruded multilayered balloon with at least one layer formed of
PEBA, the presently preferred PEBAX.RTM. polymers have a hardness
of Shore D durometer of at least about 35 D, preferably between
about 35D to about 72D, i.e. PEBAX.RTM. 3533 and 7233.
[0028] The PEBAX.RTM. 7033 and 6333 polymers are made up of nylon
12 segments and polytetramethylene ether segments in about 90/10
and about 80/20 weight ratios, respectively. The average molecular
weight of the individual segments of nylon 12 is in the range of
about 3,000-5,000 grams/mole and of the polytetramethylene ether
segments are in ranges of about 750-1,250 for the 6333 polymer and
about 500-800 for the 7033 polymer. The intrinsic viscosities of
these polymers are in the range of 1.33 to 1.50 dl/g. Generally
speaking, balloons of PEBAX.RTM. 7033 type polymer exhibit
borderline non-compliant to semi-compliant behavior and balloons of
Pebax.RTM. 6333 type polymer show semi-compliant to compliant
distention behavior, depending on the balloon forming
conditions.
[0029] While the PEBAX.RTM.-type polyamide/polyether polyesters are
most preferred, it is also possible to use other PEBA polymers with
the physical properties specified herein and obtain similar
compliance, strength and softness characteristics in the finished
balloon.
[0030] The presently preferred PEBA material has an elongation at
failure at room temperature of at least about 150%, preferably
about 300% or higher, and an ultimate tensile strength of at least
6,000 psi. The balloon has sufficient strength to withstand the
inflation pressures needed to inflate the balloon and compress a
stenosis in a patient's vessel. The burst pressure of the balloon
is at least about 10 ATM, and is typically about 16-21 ATM. The
wall strength of the balloon is at least about 15,000 psi (103
MPa), and typically from about 25,000 psi (172 Mpa) to about 35,000
psi (241 MPa).
[0031] As best illustrated in FIG. 3, the inflatable balloon 14
shown in FIG. 1 is formed of a single layer of polymeric material.
The balloon may be 100% PEBA or a PEBA/polymer blend. The presently
preferred polymer blend is a PEBAX.RTM./nylon blend, and the
preferred weight percent of nylon is from about 30% to about 95% of
the total weight. The inflatable balloon 14 may also have multiple
layers formed from coextruded tubing, in which one or more layers
is at least in part formed from PEBA. In a presently preferred
embodiment, the multilayered balloon is made from coextruded tubing
have at least a nylon layer and a PEBA layer. The presently
preferred PEBA is PEBAX.RTM., and the presently preferred nylon is
nylon 11, nylon 12, or blends thereof. The PEBAX.RTM. may be the
inner layer or the outer layer of the balloon.
[0032] The balloon of the invention can be produced by conventional
techniques for producing catheter inflatable members, such as blow
molding, and may be preformed by stretching a straight tube before
the balloon is blown. The balloons may be formed by expansion of
tubing, as for example at a hoop ratio of between 3 and 8. The
presently preferred PEBA balloon material is not crosslinked. The
bonding of the balloon to the catheter may be by conventional
techniques, such as adhesives and fusion with compatibilizers.
[0033] FIG. 2, showing a transverse cross section of the catheter
shaft 11, illustrates the guidewire receiving lumen 22 and
inflation lumen 21. The balloon 14 can be inflated by radiopaque
fluid from an inflation port 24, from inflation lumen 21 contained
in the catheter shaft 11, or by other means, such as from a
passageway formed between the outside of the catheter shaft and the
member forming the balloon, depending on the particular design of
the catheter. The details and mechanics of balloon inflation vary
according to the specific design of the catheter, and are well
known in the art.
[0034] The length of the balloon 14 may be about 0.5 cm to about 6
cm, preferably about 1.0 cm to about 4.0 cm. After being formed,
the balloon working length outer diameter at nominal pressure (e.g.
6-8 ATM) is generally about 0.15 cm to about 0.4 cm, and typically
about 0.3 cm, although balloons having an outer diameter of about 1
cm may also be used. The single wall thickness is about 0.0004
inches (in) (0.0102 mm) to about 0.0015 in (0.0381 mm), and
typically about 0.0006 in (0.0152 mm). In the embodiment in which
the coextrusion balloon has two layers, the nylon layer single wall
thickness is about 0.0003 in (0.0076 mm) to about 0.0006 in (0.0152
mm), and the PEBAX layer is about 0.0002 in (0.0051 mm) to about
0.0005 in (0.0127 mm).
[0035] Another embodiment of the invention is shown in FIG. 4, in
which a stent 16 is disposed about the balloon 14 for delivery
within patient's vessel. FIG. 5 illustrates a transverse cross
section of the catheter shown in FIG. 4, taken along line 5-5. The
stent 16 may be any of a variety of stent materials and forms
designed to be implanted by an expanding member, see for example
U.S. Pat. Nos. 5,514,154 (Lau et al.) and 5,443,500 (Sigwart),
incorporated by reference. For example, the stent material may be
stainless steel, a NiTi alloy, a plastic material, or various other
materials. The stent is shown in an unexpanded state in FIG. 4. The
stent has a smaller diameter for insertion and advancement into the
patient's lumen, and is expandable to a larger diameter for
implanting in the patient's lumen. The balloon of the invention
formed at least in part of PEBA has improved abrasion resistance,
useful in stent delivery, due to the PEBA. In the embodiment of the
invention in which the balloon has at least two coextruded layers,
a balloon used for stent delivery preferably has the PEBA layer as
the outer layer, to provide improved resistance to puncture by the
stent. Additionally, the stent retention force is improved when the
balloon is formed by coextrusion.
[0036] The following examples more specifically illustrate the
invention.
EXAMPLE 1
[0037] PEBAX.RTM. 7033 was extruded into tubular stock having 0.035
in (0.889 mm) outer diameter (OD) and 0.019 in (0.483 mm) inner
diameter (ID). The tubing was necked on one side at room
temperature to ID of 0.018 in (0.457 mm). The tubing was then made
into 20 balloons using a glass mold at a temperature of 242.degree.
F. (116.7.degree. C.) inside the mold and a blow pressure of 340
psi (2343 kPa). The balloons had an OD of 3 mm and a length of 20
mm. The balloon working length had a wall thickness of 0.0006 in
(0.0152 mm) to 0.0007 in (0.0178 mm). The mean rupture pressure of
the balloons was found to be 310 psi (2136 kPa) with a standard
deviation of 17.21 psi (119 kPa).
EXAMPLE 2
[0038] PEBAX.RTM. 6033 and nylon 12 was coextruded into two layered
tubing, with PEBAX.RTM. as the outer layer and nylon as the inner
layer. The tubing had a 0.035 in (0.889 mm) OD and a 0.0195 in
(0.495 mm) ID, and a nylon layer thickness of 0.004 in (0.102 mm)
and a PEBAX.RTM. layer thickness of 0.002 (0.051 mm). The tubing
was then made into 20 balloons using a glass mold as in Example 1,
at a temperature of 235.5.degree. F. (113.degree. C.) inside the
mold and a blow pressure of 300 psi (2067 kPa). The balloon working
length had a wall thickness of 0.0005 in (0.0127 mm) to 0.00065 in
(0.0165 mm). The mean rupture pressure of the balloons was found to
be 317 psi (2184 kPa) with a standard deviation of 23.3 psi (161
kPa).
EXAMPLE 3
[0039] Twenty percent PEBAX.RTM. 7233 and 80% nylon 12 was blended
in a single screw extruder, and extruded into tubular stock having
0.0325 in (0.826 mm) OD and 0.015 in (0.381 mm) ID. The tubing was
then made into 10 balloons using a glass mold as in Example 1, at a
temperature of 320.degree. F. (160.degree. C.) inside the mold and
a blow pressure of 225 psi (1550 kPa). The balloon working length
had a wall thickness of 0.00045 in (0.0114 mm). The mean rupture
pressure of the balloons was found to be 280 psi (1929 kPa).
[0040] It will be apparent from the foregoing that, while
particular forms of the invention have been illustrated and
described, various modifications can be made without departing from
the spirit and scope of the invention. For example, while the
balloon catheter illustrated in FIG. 1 has inner and outer tubular
members with independent lumens, a single tubular membered shaft
having two lumens therein may also be used. Other modifications may
be made without departing from the scope of the invention.
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