U.S. patent application number 11/344692 was filed with the patent office on 2006-08-17 for method of making a catheter ballon using a tapered mandrel.
Invention is credited to Alfredo Bayot, Fozan El-Nounou, Florencia Lim.
Application Number | 20060184111 11/344692 |
Document ID | / |
Family ID | 32042576 |
Filed Date | 2006-08-17 |
United States Patent
Application |
20060184111 |
Kind Code |
A1 |
Lim; Florencia ; et
al. |
August 17, 2006 |
Method of making a catheter ballon using a tapered mandrel
Abstract
A method of making a catheter balloon, and a balloon catheter
formed thereby, in which a layer of a catheter balloon is formed by
decreasing the inner diameter of a first end section of a polymeric
tube, so that the tube has a reduced diameter first end section
with an inner diameter less than the inner diameter of a central
section of the tube. The reduced diameter first end section of the
tube is bonded to a catheter shaft to form at least a portion of a
skirt section of the balloon, and the skirt section has an improved
high rupture pressure.
Inventors: |
Lim; Florencia; (Union City,
CA) ; El-Nounou; Fozan; (Santa Clara, CA) ;
Bayot; Alfredo; (Newark, CA) |
Correspondence
Address: |
FULWIDER PATTON
6060 CENTER DRIVE
10TH FLOOR
LOS ANGELES
CA
90045
US
|
Family ID: |
32042576 |
Appl. No.: |
11/344692 |
Filed: |
January 31, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10266010 |
Oct 7, 2002 |
7025745 |
|
|
11344692 |
Jan 31, 2006 |
|
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Current U.S.
Class: |
604/103.06 |
Current CPC
Class: |
A61M 2025/1075 20130101;
A61M 25/1034 20130101; B29K 2027/18 20130101; A61M 25/1036
20130101; B29C 55/22 20130101; B29C 67/0014 20130101; B29L
2031/7542 20130101; A61M 25/1029 20130101 |
Class at
Publication: |
604/103.06 |
International
Class: |
A61M 29/00 20060101
A61M029/00; A61M 37/00 20060101 A61M037/00; A61M 31/00 20060101
A61M031/00 |
Claims
1-17. (canceled)
18. A balloon catheter, comprising: a) an elongated shaft having a
proximal end, a distal end, and at least one lumen; and b) a
balloon having a proximal skirt section and a distal skirt section
bonded to the shaft, an inflatable section therebetween having an
interior in fluid communication with the at least one lumen of the
shaft, a porous polymer first layer, and an elastomeric second
layer bonded to the first layer, the porous polymer first layer
extending from the proximal skirt section to the distal skirt
section and having a distal end section bonded directly to the
shaft to define at least a portion of the distal skirt section, the
balloon distal skirt section having a rupture pressure of not less
than about 14 atm.
19. The balloon catheter of claim 17 wherein the distal end section
of the first layer bonded directly to the shaft has a wall
thickness less than or equal to the wall thickness of a part of the
first layer defining at least a portion of the inflatable section
of the balloon prior to inflation of the balloon.
20. The balloon catheter of claim 17 wherein the first layer
defines at least a portion of the proximal skirt section bonded
directly to the shaft, the proximal skirt section of the balloon
having a rupture pressure of not less than about 14 atm.
21. The balloon catheter of claim 17 wherein the porous polymer is
selected from the group consisting of expanded
polytetrafluoroethylene, ultra high molecular weight polyolefin,
porous polyolefin, and porous polyurethane.
Description
BACKGROUND OF THE INVENTION
[0001] This invention generally relates to catheters, and
particularly intravascular catheters for use in percutaneous
transluminal coronary angioplasty (PTCA) or for the delivery of
stents.
[0002] In percutaneous transluminal coronary angioplasty (PTCA)
procedures a guiding catheter is advanced in the patient's
vasculature until the distal tip of the guiding catheter is seated
in the ostium of a desired coronary artery. A guidewire is first
advanced out of the distal end of the guiding catheter into the
patient's coronary artery until the distal end of the guidewire
crosses a lesion to be dilated. A dilatation catheter, having an
inflatable balloon on the distal portion thereof, is advanced into
the patient's coronary anatomy over the previously introduced
guidewire until the balloon of the dilatation catheter is properly
positioned across the lesion. Once properly positioned, the
dilatation balloon is inflated with inflation fluid one or more
times to a predetermined size at relatively high pressures so that
the stenosis is compressed against the arterial wall and the wall
expanded to open up the vascular passageway. 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 overexpand the artery wall. After
the balloon is finally deflated, blood flow resumes through the
dilated artery and the dilatation catheter and the guidewire can be
removed therefrom.
[0003] In such angioplasty procedures, there may be restenosis of
the artery, i.e. reformation of the arterial blockage, which
necessitates either another angioplasty procedure, or some other
method of repairing or strengthening the dilated area. To reduce
the restenosis rate of angioplasty alone and to strengthen the
dilated area, physicians now normally 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 or to maintain its patency. A tubular cover
formed of synthetic or natural material may be present on an outer
or inner surface of the stent. 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 within the patient's
artery 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] In the design of catheter balloons, characteristics such as
strength, compliance, and profile of the balloon are carefully
tailored depending on the desired use of the balloon catheter, and
the balloon material and manufacturing procedure are chosen to
provide the desired balloon characteristics. A variety of polymeric
materials are conventionally used in catheter balloons. Use of
polymeric materials such as PET that do not stretch appreciably
consequently necessitates that the balloon is formed by blow
molding, and the deflated balloon material is folded around the
catheter shaft in the form of wings, prior to inflation in the
patient's body lumen. However, it can be desirable to employ
balloons, referred to as formed-in-place balloons, that are not
folded prior to inflation, but which are instead expanded to the
working diameter within the patient's body lumen from a generally
cylindrical or tubular shape (i.e., essentially no wings) that
conforms to the catheter shaft.
[0005] Catheter balloons formed of expanded polytetrafluoroethylene
(ePTFE) expanded in place within the patient's body lumen without
blow molding the ePTFE tubing have been disclosed. Prior disclosed
methods of forming an ePTFE balloon involved wrapping a sheet of
ePTFE on a mandrel and heating the wrapped sheet to fuse the layers
of wrapped material together to form a tube. The resulting ePTFE
tube may be subsequently heated in one or more additional heating
steps and otherwise further processed, and combined with a
nonporous liner to complete formation of the balloon. However, one
difficulty has been the failure of the bonds between the balloon
and the catheter shaft during inflation of the balloon at the
relatively high inflation pressures required in angioplasty or
stent delivery. Thus, it would be a significant advance to provide
a balloon catheter having strong, durable bonds between the balloon
and the shaft.
SUMMARY OF THE INVENTION
[0006] This invention is directed to a method of making a catheter
balloon, and a balloon catheter formed thereby, in which a layer of
a catheter balloon is formed by decreasing the inner diameter of a
first end section of a polymeric tube, so that the tube has a
reduced diameter first end section with an inner diameter less than
the inner diameter of a central section of the tube. The reduced
diameter first end section of the tube is bonded to a catheter
shaft to form at least a portion of a skirt section of the balloon,
providing a skirt section with an improved high rupture
pressure.
[0007] The method of making a catheter balloon of the invention
generally comprises providing a polymeric tube having a central
section and a first end section with an inner diameter, and
decreasing the inner diameter of the first end section of the
polymeric tube to form a reduced diameter first end section. In one
embodiment, the reduced diameter first end section has at least a
portion having an inner diameter about 10% to about 45% less than
an inner diameter of the central section of the tube.
[0008] In a presently preferred embodiment, the inner diameter of
the first end section of the polymeric tube is decreased by
longitudinally stretching the tube onto an outer surface of a
mandrel. The outer surface of the mandrel transitions from a first
outer diameter to a second smaller outer diameter. The stretched
tube is preferably heated on the mandrel in the stretched
configuration to stabilize the tube in the stretched configuration,
and the stretched tube may be further processed after heating, and
attached to a catheter shaft to form a layer of a catheter balloon
having at least one layer.
[0009] A balloon which embodies features of the invention can be
used on a variety of suitable balloon catheters including coronary
and peripheral dilatation catheters, stent delivery catheters, drug
delivery catheters and the like. The balloon catheter of the
invention generally comprises an elongated shaft having at least
one lumen, and the balloon secured to a distal shaft section so
that the balloon has an interior in fluid communication with the
shaft lumen for delivery of inflation media to the balloon
interior. The balloon typically has a proximal skirt section bonded
to a first portion of the shaft, a distal skirt section bonded to a
second portion of the shaft, and an inflatable section
therebetween. The balloon is bonded to the shaft by a variety of
suitable methods including fusion bonding and adhesive bonding. The
reduced diameter end section of the porous polymeric tube
preferably forms at least a portion of the distal skirt section of
the balloon. Although discussed below primarily in terms of the
embodiment in which the reduced diameter distal end section forms
at least a portion of the distal skirt section, it should be
understood that in an alternative embodiment the balloon has a
proximal skirt section formed at least in part by a reduced
diameter proximal end section of the polymeric tube forming a layer
of the balloon. For example, in one embodiment, the balloon has a
polymeric layer with a reduced diameter distal end section forming
at least a portion of the distal skirt section of the balloon, and
with a reduced diameter proximal end section forming at least a
portion of the proximal skirt section of the balloon, both reduced
diameter end sections being formed according to the method of the
invention.
[0010] The reduced diameter distal end section of the polymeric
tube forms a balloon distal skirt section with an improved strong
bond to the catheter shaft. The high rupture pressure of the distal
skirt section of the balloon allows the balloon to be inflated at
relatively high inflation pressures. Moreover, the reduced diameter
section has a reduced wall thickness which provides a low profile
skirt section. Additionally, the reduced wall thickness of the
distal skirt section reduces the disadvantageously high stiffness
which is otherwise present at balloon skirt sections. In one
embodiment, the reduced diameter distal end section tapers
throughout all or a substantial portion of the length thereof,
which further improves the stiffness transition of the distal skirt
section.
[0011] In a presently preferred embodiment, the polymeric material
of the polymeric tube forming a layer of the catheter balloon
comprises a polymer having a porous structure, which in one
embodiment is selected from the group consisting of expanded
polytetrafluoroethylene (ePTFE), an ultra high molecular weight
polyolefin such as ultra high molecular weight polyethylene, and
porous polyolefins such as polyethylene and polypropylene, and
porous polyurethane. In one embodiment, the porous material has a
node and fibril microstructure. The node and fibril microstructure,
when present, is produced in the material using conventional
methods. For example, ePTFE and ultra high molecular weight
polyethylene (also referred to as "expanded ultra high molecular
weight polyethylene") typically have a node and fibril
microstructure, and are not melt extrudable. However, a variety of
suitable polymeric materials can be used in the method of the
invention, including conventional catheter balloon materials which
are melt extrudable. In one presently preferred embodiment, the
polymeric material cannot be formed into a balloon by conventional
balloon blow molding, and is formed into a balloon by heat fusing
wrapped layers of the polymeric material together to form a tubular
member. Porous materials such as ePTFE and ultrahigh molecular
weight polyethylene typically require a nonporous second layer or
liner when used to form an inflatable balloon. Thus, the balloon
layer formed according to the method of the invention is a layer of
a balloon having at least one layer, and in one embodiment, is a
layer of a multilayered balloon having a nonporous second layer. In
a presently preferred embodiment having the nonporous second layer,
a second polymer tube which forms the nonporous second layer (and
which is preferably formed of an elastomeric polymer) is positioned
in at least the central section of the porous polymeric tube before
the reduced inner diameter end section of the porous polymeric tube
is bonded to the shaft. The elastomeric polymer layer is typically
an inner layer, and has proximal and distal end sections bonded to
the shaft. The elastomeric polymer tube is preferably bonded to the
shaft during the bonding of the porous polymeric tube to the shaft,
although it may alternatively be bonded to the shaft before the
porous polymeric tube.
[0012] In one embodiment, the entire length of the reduced diameter
end section of the porous polymeric tube is bonded directly to the
shaft. Alternatively, some or all of the length of the reduced
diameter end section of the porous polymeric tube is bonded to an
underlying section of the elastomeric polymer tube which is bonded
to the shaft. The porous polymeric tube is typically longitudinally
compacted before being secured to the balloon second layer, and the
second (e.g., elastomeric) layer is typically not longitudinally
compacted. Longitudinal compaction of the porous polymeric tube
decreases the length of the section and preferably also decreases
the porosity of the material forming the section.
[0013] The invention provides a balloon catheter having a balloon
secured to the shaft by an improved strong bond, providing an
improved increased rupture pressure at the bond between the balloon
skirt section and the shaft. Moreover, the method provides a
balloon having a low profile skirt section with an improved
flexibility transition along the length thereof. 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
[0014] FIG. 1 is an elevational view, partially in section, of a
stent delivery balloon catheter embodying features of the
invention.
[0015] FIG. 2 is a transverse cross sectional view of the balloon
catheter shown in FIG. 1, taken along line 2-2.
[0016] FIG. 3 is a transverse cross sectional view of the balloon
catheter shown in FIG. 1, taken along line 3-3.
[0017] FIG. 4A is an enlarged longitudinal cross section of the
balloon catheter of FIG. 1, taken along line 4A-4A.
[0018] FIG. 4B illustrates the balloon catheter of FIG. 4A, with
the balloon inflated.
[0019] FIG. 5 illustrates an assembly of a tube of porous polymeric
material on a mandrel before the tube is longitudinally stretched
onto the outer surface of the mandrel which transitions from a
first outer diameter to a second small outer diameter.
[0020] FIG. 6 illustrates the assembly of FIG. 5, after the porous
polymeric tube is longitudinally stretched onto the mandrel surface
to decrease the inner diameter of the distal end section of the
tube.
[0021] FIG. 7 illustrates the porous polymeric tube of FIG. 5,
positioned around a catheter shaft and with an elastomeric polymer
layer in a central section of the tube, prior to bonding to the
catheter shaft.
[0022] FIG. 8 illustrates the porous polymeric tube and elastomeric
polymer layer of FIG. 7, after bonding to the catheter shaft.
DETAILED DESCRIPTION OF THE INVENTION
[0023] FIG. 1 illustrates an over-the-wire type stent delivery
balloon catheter 10 embodying features of the invention. Catheter
10 generally comprises an elongated catheter shaft 12 having an
outer tubular member 14 and an inner tubular member 16. Inner
tubular member 16 defines a guidewire lumen 18 configured to
slidingly receive a guidewire 20, and the coaxial relationship
between outer tubular member 14 and inner tubular member 16 defines
annular inflation lumen 22, as best shown in FIG. 2 illustrating a
transverse cross section view of the distal end of the catheter
shown in FIG. 1, taken along line 2-2. An inflatable balloon 24
disposed on a distal section of catheter shaft 12 has a proximal
skirt section 25 sealingly secured to the distal end of outer
tubular member 14 and a distal skirt section 26 sealingly secured
to the distal end of inner tubular member 16, so that its interior
is in fluid communication with inflation lumen 22. An adapter 30 at
the proximal end of catheter shaft 12 is configured to provide
access to guidewire lumen 18, and to direct inflation fluid through
arm 31 into inflation lumen 22. FIG. 1 illustrates the balloon 24
in a low profile tubular configuration prior to complete inflation,
with an expandable stent 32, with a stent cover 35 thereon, mounted
on the balloon for delivery within a patient's body lumen 27. The
distal end of the catheter may be advanced to a desired region of
the body lumen 27 in a conventional manner, and balloon 24 inflated
to expand covered stent 32, and the balloon deflated, leaving
covered stent 32 implanted in the body lumen 27.
[0024] In the embodiment illustrated in FIG. 1, balloon 24 has a
first layer 33 and a second layer 34. In a presently preferred
embodiment, the balloon 24 first layer 33 comprises a microporous
polymeric material, and preferably a microporous polymeric material
having a node and fibril microstructure, such as ePTFE. In the
embodiment illustrated in FIG. 1, first layer 33 is formed of
ePTFE, and the second layer 34 is formed of a polymeric material
preferably different from the polymeric material of the first layer
33. Although discussed below in terms of one embodiment in which
the first layer 33 is formed of ePTFE, it should be understood that
the first layer may comprise other materials, including ultrahigh
molecular weight polyethylene. The second layer 34 is preferably
formed of an elastomeric material, such as polyurethane elastomers,
silicone rubbers, styrene-butadiene-styrene block copolymers,
polyamide block copolymers, and the like. In a preferred
embodiment, layer 34 is an inner layer relative to layer 33,
although in other embodiments it may be an outer layer. Layer 34
formed of an elastomeric material limits or prevents leakage of
inflation fluid through the microporous ePTFE to allow for
inflation of the balloon 24, and expands elastically to facilitate
deflation of the balloon 24 to a low profile deflated
configuration. The elastomeric material forming layer 34 may
consist of a separate layer which neither fills the pores nor
disturbs the node and fibril structure of the ePTFE layer 33, or it
may at least partially fill the pores of the ePTFE layer.
[0025] FIG. 4A is an enlarged, longitudinal cross section of the
balloon catheter 10 of FIG. 1, taken along line 4A-4A. FIG. 4B
illustrates the balloon catheter of FIG. 4A with the balloon in an
inflated configuration. The inflated balloon 24 has a central
working section with stent 32 mounted thereon, a proximal tapered
section between the working section and the proximal skirt section
25, and a distal tapered section between the distal skirt section
26 and the working section. The section of the first layer 33
extending along the working section of the balloon is hereafter
referred to as the first layer working section. Similarly, the
first layer proximal and distal tapered sections refer to the
sections of the first layer 33 extending along the proximal and
distal tapered sections of the balloon, and the first layer skirt
sections refer to the sections of the first layer 33 extending
along the balloon skirt sections 25, 26. Although the balloon 24 is
illustrated in FIG. 4B with a conventional inflated configuration
having a central working length between two tapered inflatable
sections, it should be understood that the inflated balloon may
have a variety of suitable configurations including balloon
configurations specially shaped for a particular anatomy such as a
focal balloon configuration, a conical balloon configuration, and
the like, as are conventionally known to one of skill in the
art.
[0026] The first and second layers 33, 34 of balloon 24 each extend
from the proximal skirt section 25 of the balloon to the distal
skirt section 26 of the balloon. The first layer 33 can have a
length which is the same as or shorter than the length of the
second layer 34, or alternatively, can have end sections which
extend beyond the end sections of the second layer 34 and onto the
shaft. The skirt sections 25, 26 of the balloon typically comprise
end sections of the second (inner) layer 34 having an inner surface
bonded to the shaft, and sections of the first (outer) layer 33
having an inner surface bonded to the end sections of the second
layer 34 which are bonded to the shaft. In the embodiment of FIG.
4, the skirt sections 25, 26 are also formed in part by end
sections of the first layer 33 which extend beyond the end sections
of the second layer 34 and which are bonded directly to the shaft
without the second layer 34 or another member therebetween. The
terminology "directly bonded" should be understood to include a
variety of bonding methods including fusion and adhesive
bonding.
[0027] FIGS. 5 and 6 illustrate an assembly of a porous polymeric
tube 40 on a mandrel 41, during formation of a layer of a catheter
balloon in a method which embodies features of the invention. The
polymeric material of the tube 40 is ePTFE in the embodiment in
which the tube forms ePTFE layer 33 of the balloon 24 of FIG. 1.
The mandrel 41 has a first section 42 with a first outer diameter,
and a second section 43 with a second smaller outer diameter. A
tapered section 44 tapers from the first section 42 to the second
section 43. The mandrel can have a variety of suitable
configurations forming a transition from a first outer diameter to
a second smaller outer diameter. For example, although the mandrel
second section 43 has a uniform diameter in the illustrated
embodiment, in an alternative embodiment (not shown), the second
section 43 has a tapered outer diameter either with or without
tapered section 44 being present.
[0028] FIG. 5 illustrates the ePTFE tube 40 around the mandrel 41
before the tube is longitudinally stretched onto the mandrel. The
ePTFE tube 40 has a distal end section 45 overlying the second
section 43 and the tapered section 44 of the mandrel 41, and a
central section 46 overlying the first section 42 of the mandrel
41. A proximal end section 47 of the tube 40 is at the proximal end
of the central section 46. The first section 42 of mandrel 41 has
an outer diameter which is preferably not significantly smaller
than the inner diameter of the central section 46 of the ePTFE tube
40. The outer diameter of the mandrel first section 42 is typically
about 0.7 to about 1 mm, and the second section 43 outer diameter
is typically about 0.5 to about 0.7 mm.
[0029] The ePTFE tube 40 is longitudinally stretched, as for
example by being pulled at either end, to stretch it down on to the
mandrel. The tube 40 may be at an elevated temperature during
stretching, or alternatively at ambient (i.e., room) temperature.
FIG. 6 illustrates the ePTFE tube 40 of FIG. 5 after being
longitudinally stretched onto the surface of the mandrel 41 to form
longitudinally stretched tube 40'. The stretched tube 40' has a
reduced diameter distal end section 45' on sections 43 and 44 of
the mandrel 41, and central section 46' and proximal end section
47' on the first section 42 of the mandrel.
[0030] In the illustrated embodiment, the reduced diameter distal
end section 45' of the stretched tube 40' has a uniform diameter
portion 50 and a tapered portion 51 tapering distally away from the
central section 46' to the uniform diameter portion 50. The uniform
diameter portion 50 has an inner diameter about 10 to about 45%,
preferably about 15 to about 35% less than the inner diameter of
the central section 46' of stretched tube 40'. Specifically, in one
embodiment, the uniform diameter portion 50 inner diameter is about
0.4 to about 0.8 mm, preferably about 0.5 to about 0.7 mm, and the
central section 46' inner diameter is about 0.6 to about 1 mm,
preferably about 0.7 to about 0.9 mm. The tapered portion 51
typically tapers at an angle of about 15 to about 90 degrees,
preferably about 30 to about 80 degrees, and has a length of about
0.5 to about 6 mm, preferably about 1 to about 3 mm. The uniform
diameter portion 50 has a length of about 1 to about 6 mm,
preferably about 2 to about 4 mm, and the central section 46' has a
length of about 8 to about 60 mm.
[0031] During the longitudinal stretching of the ePTFE tube 40 onto
mandrel 41, the inner diameter of the ePTFE tube 40 at distal end
section 45 decreases by about 60% to about 90%, more specifically
by about 70% to about 80%, to form reduced diameter distal end
section 45' (of longitudinally stretched tube 40'). The inner
diameter of the ePTFE tube 40 at the central section 46 decreases a
smaller amount, and specifically about 50% to about 85%, more
specifically about 60% to about 75%, to form central section 46'
(of longitudinally stretched tube 40') during the longitudinal
stretching of the ePTFE tube 40 onto mandrel 41. Although the wall
thickness of the stretched tube 40' is illustrated as being the
same as the wall thickness of the tube 40 for ease of illustration,
it should be understood that the tube 40' along at least the
reduced diameter distal end section 45' typically has a reduced
wall thickness as a result of the process of stretching the tube 40
down onto the mandrel 43.
[0032] The longitudinally stretched tube 40' is preferably heated
on the mandrel 41 in the stretched configuration to stabilize the
tube 40' in the stretched configuration. The tube 40' is typically
heated at an elevated temperature of about 320.degree. C. to about
400.degree. C., and specifically in the embodiment in which tube
40' is ePTFE, at an elevated temperature of about 350.degree. C. to
about 380.degree. C.
[0033] After being longitudinally stretched and before bonding to
the shaft, the tube 40' is preferably longitudinally compacted,
optionally while still on mandrel 41. After being longitudinally
compacted, the tube 40' may be heat treated or otherwise further
processed before being secured to the second layer 34 and to the
shaft 12 to form balloon 24.
[0034] FIG. 7 illustrates the tube 40' positioned around the shaft
11 outer tubular member 14 and inner tubular member 16. An
elastomeric tube 60 which forms second/inner layer 34 of balloon 24
is positioned in the central section 46' of the tube 40'. The
distal end of the elastomeric tube 60 is at the distal end of the
central section 46' of the tube 40'. Portion 50 of the reduced
diameter distal end section 45' of the tube 40' has an inner
diameter about 0% to about 30%, more specifically about 1% to about
18% greater than an outer diameter of the inner tubular member 16,
so that the gap (if any) between the tube 40' and the inner tubular
member 16 is smaller than it otherwise would be (i.e., the gap is
smaller than would be present if the inner diameter of the distal
end section of the tube 40 had not been reduced to form reduced
diameter section 45'). In embodiments in which the inner diameter
of the reduced diameter distal end section 45' is not greater than
the outer diameter of the inner tubular member 16, the distal end
of the section 45' is typically flared or otherwise opened up to
allow the section 45' to be placed around the inner tubular member
16 for bonding thereto. The reduced diameter distal end section 45'
is bonded to the shaft, thereby forming part of the distal skirt
section 26 of the balloon 24. Specifically, in a presently
preferred embodiment, a heating nozzle traverses a portion of the
tube 40' to be bonded to the inner tubular member, optionally with
heat shrink tubing around the tube portion to heat and bond the
tube 40' onto the inner tubular member 16. In a presently preferred
embodiment, the portion of the tube 40' which is bonded to the
inner tubular member 16 extends from a distal portion of the
central section 46' having elastomeric tube 60 therein, and along
the reduced diameter distal end section 45'. Thus, a distal portion
of central section 46' of tube 40' with an underlying portion of
the elastomeric tube 60 bonds to the inner tubular member 16, while
the uniform diameter portion 50 and tapered portion 51 extending
distally of the elastomeric tube 60 are bonded directly to the
inner tubular member 16. FIG. 8 illustrates the tube 40' of FIG. 7,
after bonding to the inner tubular member 16 and outer tubular
member 14. The reduced diameter distal end section 45' (made up of
the uniform diameter portion 50 and tapered portion 51) of tube 40'
form the part of the ePTFE tube 40' bonded directly to the shaft,
to form a distal portion of the distal skirt section 26 of the
balloon 24. The balloon is shown partially inflated in FIG. 8
[0035] Balloon 24 of catheter 10, formed according to a method
embodying features of the invention, preferably has a distal skirt
section 26 with a rupture pressure of about 14 atm (210 psi) to
about 28 atm (410 psi) depending on the desired working pressure of
the balloon 24. In the embodiment in which balloon 24 is a
relatively high pressure balloon (i.e., rated to about 18 atm or
above), the distal skirt section 26 preferably has a rupture
pressure of not less than about 22 atm (320 psi). Similarly, a
proximal skirt section formed according to the method of the
invention with a first layer reduced diameter end section would
have rupture pressure similar to the distal skirt section, and
generally of not less than 20 atm. The longitudinal stretching
decreases the wall thickness of the tube, so that the reduced
diameter distal end section 45' has a smaller wall thickness than
the central section 46' of the tube 40', at least prior to
inflation of the balloon 24. Thus, the distal portion of the distal
skirt section 26 (defined by the uniform diameter portion 50 and
tapered portion 51 of tube 40') bonded directly to shaft has a low
profile. The wall thickness of the distal portion of the distal
skirt section 26 is typically about 0.07 to about 0.2 mm, and the
wall thickness of central section 46' of the tube 40' is about 0.1
to about 0.25 mm.
[0036] To the extent not previously discussed herein, the various
catheter components may be formed and joined by conventional
materials and methods. For example, the outer and inner tubular
members can be formed by conventional techniques, such as by
extruding and necking materials found useful in intravascular
catheters such as polyethylene, polyvinyl chloride, polyesters,
polyamides, polyimides, polyurethanes, and composite materials.
[0037] The length of the balloon catheter 10 is generally about 108
to about 200 centimeters, preferably about 137 to about 145
centimeters, and typically about 140 centimeters for PTCA. The
outer tubular member 14 has an outer diameter (OD) of about 0.017
to about 0.036 inch (0.43-0.91 mm), and an inner diameter (ID) of
about 0.012 to about 0.035 inch (0.30-0.89 mm). The inner tubular
member 16 has an OD of about 0.017 to about 0.026 inch (0.43-0.66
mm), and an ID of about 0.015 to about 0.018 inch (0.38-0.46 mm)
depending on the diameter of the guidewire to be used with the
catheter. The balloon 24 has a length of about 8 mm to about 80 mm,
typically about 8 mm to about 38 mm, and an inflated working
diameter of about 1.5 mm to about 20 mm, typically about 2 mm to
about 10 mm.
[0038] While the present invention has been described herein in
terms of certain preferred embodiments, those skilled in the art
will recognize that modifications and improvements may be made
without departing from the scope of the invention. For example,
although the embodiment illustrated in FIG. 1 is an over-the-wire
stent delivery catheter, balloons of this invention may also be
used with other types of intravascular catheters, such as rapid
exchange balloon catheters. Rapid exchange catheters generally
comprise a distal guidewire port in a distal end of the catheter, a
proximal guidewire port in a distal shaft section distal of the
proximal end of the shaft and typically spaced a substantial
distance from the proximal end of the catheter, and a short
guidewire lumen extending between the proximal and distal guidewire
ports in the distal section of the catheter. Additionally, although
not illustrated, a soft distal tip member may be provided at the
distal end of the catheter, and bonded to the balloon distal skirt
section 26, as is conventionally known. While individual features
of one embodiment of the invention may be discussed or shown in the
drawings of the one embodiment and not in other embodiments, it
should be apparent that individual features of one embodiment may
be combined with one or more features of another embodiment or
features from a plurality of embodiments.
* * * * *