U.S. patent application number 11/094025 was filed with the patent office on 2005-08-04 for compacted catheter balloon and method of incremental compaction.
This patent application is currently assigned to Advanced Cardiovascular Systems, Inc.. Invention is credited to Lim, Florencia, Owens, Timothy.
Application Number | 20050167888 11/094025 |
Document ID | / |
Family ID | 31976469 |
Filed Date | 2005-08-04 |
United States Patent
Application |
20050167888 |
Kind Code |
A1 |
Owens, Timothy ; et
al. |
August 4, 2005 |
Compacted catheter balloon and method of incremental compaction
Abstract
A catheter balloon or other expandable tubular medical device or
component, having at least a first layer with a first section and a
second section longitudinally compacted by more than the first
section. In a presently preferred embodiment, the second section of
the first layer extends at least in part along a central portion of
the length of the first layer. The longitudinal compaction of the
material of the first layer preferably results in a balloon or
other expandable tubular medical device or component having
improved performance characteristics such as compliance and
dimensional stability. One aspect of the invention is directed to a
method of longitudinally compacting a porous polymeric tube
incrementally along the length of the tube, to compact sections of
the tube.
Inventors: |
Owens, Timothy; (Dublin,
CA) ; Lim, Florencia; (Union City, CA) |
Correspondence
Address: |
FULWIDER PATTON LEE & UTECHT, LLP
HOWARD HUGHES CENTER
6060 CENTER DRIVE
TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Assignee: |
Advanced Cardiovascular Systems,
Inc.
|
Family ID: |
31976469 |
Appl. No.: |
11/094025 |
Filed: |
March 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11094025 |
Mar 29, 2005 |
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10230432 |
Aug 29, 2002 |
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6902571 |
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Current U.S.
Class: |
264/321 |
Current CPC
Class: |
Y10T 428/1359 20150115;
A61M 25/104 20130101; A61M 2025/1075 20130101 |
Class at
Publication: |
264/321 |
International
Class: |
B29C 067/20 |
Claims
1-25. (canceled)
26. A method of making at least a first layer of an expandable
tubular medical device or component, comprising: a) placing a
porous polymeric tube having a length and an outer diameter on a
mandrel, with a diameter limiting member around at least a portion
of the tube; b) releasably securing at least a first compactor
member to the tube at a first location on the tube, the secured
compactor member being slidably disposed relative to the mandrel;
c) moving the compactor member a distance, to compact a first
segment of the tube in the diameter limiting member and having a
length less than the entire length of the tube, and releasing the
compactor member; d) releasably securing the compactor member to
the tube at a second location on the tube; and e) moving the
compactor member a distance, to compact a second segment of the
tube in the diameter limiting member which has a length less than
the entire length of the tube, and releasing the compactor
member.
27. The method of claim 26 wherein the diameter limiting member is
selected from the group consisting of a die, a polymeric tube, a
mold, and a sheet of polymeric material wrapped around the porous
polymeric tube, and compacting the tube comprises pushing the tube
in a lumen defined by the diameter limiting member so that the
segment of the tube compacts and the outer diameter of the tube
does not increase to greater than the inner diameter of the lumen
of the diameter limiting member.
28. The method of claim 26 including a second compactor member
releasably secured to the tube at a location on the tube
longitudinally spaced apart from the at least a first compactor
member and slidably disposed relative to the mandrel, and
compacting the segment of the tube comprises moving the first and
second compactor members together toward a center of the length of
the tube.
29. The method of claim 26 including a fixing member releasably
securing the tube to the mandrel, and compacting the segment of the
tube comprises moving the first compactor member towards the fixing
member.
30. The method of claim 29 wherein the diameter limiting member is
a die, and the fixing member is on the tube at an outlet of the
die, and the distance of c) equals the distance between the first
location on the tube and an inlet of the die.
31. The method of claim 26 wherein the second segment is compacted
by an amount different than the first section.
32. The method of claim 31 wherein the first segment has a length
equal to the second segment, and the distance the compactor is
moved in e) is different than the distance the compactor is moved
in b).
33. The method of claim 31 wherein the first segment has a length
greater than the second segment, and the distance the compactor is
moved in e) is equal to the distance the compactor is moved in
b).
34. A method of making at least a first layer of a catheter
balloon, the balloon having an inflatable working length and
inflatable sections proximal and distal to the working length,
comprising: a) placing a porous polymeric tube having a length and
an outer diameter on a mandrel with a portion of the polymeric tube
in a die, the die having an inlet and an outlet; b) releasably
securing a compactor member to the tube at a location on the tube
spaced from the inlet of the die, the secured compactor member
being slidably disposed relative to the mandrel, and releasably
securing the tube to the mandrel with a fixing member at a location
on the tube adjacent the outlet of the die; c) moving the compactor
member toward the inlet of the die, to compact a first segment of
the tube located between the compactor and the die outlet, the
first segment having a length less than the entire length of the
tube, releasing the compactor member and fixing member and
repositioning the tube to place a noncompacted portion of the tube
in the lumen of the die; d) releasably securing the compactor
member to the tube at a location on the tube spaced from the inlet
of the die and releasably securing the tube to the mandrel with the
fixing member at a location on the tube adjacent the outlet of the
die; and e) moving the compactor member toward the inlet of the
die, to compact a second segment of the tube located between the
compactor and the die outlet, the second segment having a length
less than the entire length of the tube.
35. The method of claim 34 wherein the first segment is compacted
by the same amount as the second segment.
36. The method of claim 35 wherein the first and second segments
form a first compacted section at least in part forming one of the
proximal or distal inflatable sections of the balloon.
37. The method of claim 36 wherein the first and second segments
are each compacted by about 5% to about 15%.
38. The method of claim 36 including after e) compacting one or
more additional segments of the tube to form a second compacted
section at least in part forming the working length of the
balloon.
39. The method of claim 38 wherein the second compacted section is
compacted by about 30% to about 50%.
40. The method of claim 38 including after forming the second
compacted section, compacting one or more additional segments of
the tube to form a third compacted section at least in part forming
the distal tapered section of the balloon.
41. The method of claim 40 wherein the third compacted section is
compacted by about 5% to about 15%.
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 vary depending on
the desired use of the balloon catheter. A variety of polymeric
materials are conventionally used in catheter balloons, and the
balloon material and manufacturing procedure are chosen to provide
the desired balloon characteristics. 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 typically combined with
a nonporous liner to complete formation of the balloon. It would be
a significant advance to provide an ePTFE tube for forming a
balloon or other expandable medical device or component, with
improved performance characteristics and manufacturability.
SUMMARY OF THE INVENTION
[0006] This invention is directed to a catheter balloon or other
expandable tubular medical device or component, having at least a
first layer with a first section, and a second section
longitudinally compacted by more than the first section. The second
section of the first layer is typically longitudinally adjacent to
the first section of the first layer, and preferably extends at
least in part along a central portion of the length of the first
layer. The longitudinal compaction of the material of the first
layer in accordance with the invention results in a balloon or
other device or component having improved performance
characteristics such as compliance and dimensional stability. One
aspect of the invention is directed to a method of longitudinally
compacting a porous polymeric tube incrementally along the length
of the tube, to compact sections of the tube.
[0007] Longitudinal compaction of a section of the first layer
decreases the length of the section and preferably also decreases
the porosity of the material forming the section, so that in one
embodiment, the first layer first section, which is more highly
longitudinally compacted than the first layer second section, has a
lower porosity than the first layer second section. The degree of
longitudinal compaction is expressed herein as a percentage length
reduction. Thus, a section having a precompaction length (i.e., the
length of the section just prior to being longitudinally compacted
in accordance with the invention) of 2 cm, which is subsequently
longitudinally compacted to a length of 1 cm, has a longitudinal
compaction of 50% (i.e., (2 cm-1 cm).div.2 cm).
[0008] In a presently preferred embodiment, the medical device
tubular component is an inflatable balloon for a catheter. 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. A balloon catheter of the
invention generally comprises an elongated shaft having a proximal
shaft section, a distal shaft section, at least a first lumen, and
a balloon on a distal shaft section with an interior in fluid
communication with the first lumen of the shaft. Although discussed
below primarily in terms of the embodiment in which the medical
device component is an inflatable member such as a balloon for a
catheter, it should be understood that other expandable medical
devices and components are included within the scope of the
invention, including stent covers and vascular grafts.
[0009] The catheter balloon typically has a proximal and a distal
skirt section secured to the shaft, an inflatable working length
section, an inflatable proximal section between the proximal skirt
section and the working length which inflates to a tapered
configuration ("the proximal tapered section"), and an inflatable
distal section between the distal skirt section and the working
length which inflates to a tapered configuration ("the distal
tapered section"). It should be understood that in at least in one
embodiment the balloon is not blow molded or otherwise preexpanded
into the inflated configuration prior to use. Thus, the "proximal
and distal tapered sections" typically do not have a tapered
configuration prior to the balloon being inflated during use of the
balloon catheter.
[0010] In a presently preferred embodiment, the section of the
first layer located at the central working length section of the
balloon (hereafter the first layer working section) has a
longitudinal compaction greater than the sections of the first
layer located at the proximal and distal tapered sections of the
balloon (hereafter the first layer tapered sections). The inflated
tapered sections of the balloon form the transition between the
skirt sections bonded to the shaft and the inflated working length
of the balloon. Thus, depending on the length and the diameter of
the inflated tapered sections, this transition can range from a
gradual shallow taper to a short sharp transition. In one
embodiment, the first layer tapered sections have a longitudinal
compaction such that, when inflated, the tapered sections have a
desired length and a desired inflated outer diameter tapering
between the inflated working length to the skirt section, to
decrease the hoop stress and stress concentration at the end of the
skirt section. Thus, the 5 rupture pressure of the balloon is
increased by increasing the rupture pressure of the bond between
the skirt section and the shaft. Specifically, in one embodiment,
in the inflated configuration, the tapered sections taper at an
angle of about 5.degree. to about 45.degree., and with an inflated
length of about 1 to about 5 mm. Thus, in one embodiment, the
longitudinal compaction percentages of the sections are selected to
provide a balloon having a desired inflated dimension and
shape.
[0011] Additionally, in one embodiment, axial shrinkage of the
balloon sections which would otherwise occur during inflation of
the balloon is decreased by the longitudinal compaction of the
first-layer sections. Specifically, for no axial shrinkage or a
minimal amount of axial shrinkage (i.e., less than 5%), the
presently preferred the inflatable length of a porous polymeric
layer of a balloon has a longitudinal compaction of about 10% to
about 60%, preferably about 20% to about 50%. When not compacted,
the axial shrinkage is believed to be about 10% to about 30% ofthe
length of the balloon.
[0012] In one embodiment, the sections ofthe first layer located at
the skirt sections of the balloon (hereafter the first layer skirt
sections) have a longitudinal compaction which is less than or at
least not greater than the longitudinal compaction of the first
layer tapered sections. In one embodiment the first layer skirt
sections are not longitudinally compacted, and thus have a
longitudinal compaction of 0%. The first layer skirt section
preferably has improved flexibility and low profile due to the low
or zero percent longitudinal compaction of the skirt section. The
skirt sections of the first layer extend along the section of the
balloon secured to the shaft. However, the skirt sections of the
first layer are not necessarily directly secured to the shaft, and
may instead have at least a portion secured to a section of a
second (inner) layer of the balloon which is directly secured to
the shaft. The terminology "directly secured" to the shaft should
be understood to include a variety of bonding methods including
fusion and adhesive bonding.
[0013] In a presently preferred embodiment, the polymeric material
of the first layer of the balloon comprises a polymer having a
porous structure, which in one embodiment is selected from the
group consisting of expanded polytetrafluoroethylene (ePTFE), 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. For example,
ePTFE and ultra high molecular weight polyethylene typically have a
node and fibril microstructure, and are not melt extrudable. The
node and fibril microstructure, when present, is produced in the
material using conventional methods. 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 is typically not formed into a balloon by conventional
balloon blow molding, and is instead 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 or other tubular medical device or component having a first
layer with longitudinally compacted sections, should be understood
to include an embodiment where the first layer forms at least a
layer of a multilayered catheter balloon. The balloon first layer
is typically longitudinally compacted before being secured to the
balloon second layer, and the second layer is typically not
longitudinally compacted.
[0014] A method of making a first layer of an expandable tubular
medical device or component having at least one layer, generally
comprises individually compacting incremental segments of a porous
polymeric tube to incrementally compact the porous polymeric tube.
In one embodiment, the method comprises placing a porous polymeric
tube having a length and an outer diameter on a mandrel, with a
diameter limiting member around at least a portion of the tube. In
one embodiment, the diameter limiting device is selected from the
group consisting of a die, a polymeric tube, and a sheet of
polymeric material wrapped around the porous polymeric tube. A mold
may also be used as the diameter limiting device, although
preferably such that the mold uniformly limits the diameter of the
segment of the tube during compaction, to thereby produce uniform
compaction along the length of the individual segment avoiding
buckling of the segment into an accordion-like configuration during
compaction. At least a first compactor member is releasably secured
to the tube at a first location on the tube, the secured compactor
member being slidably disposed relative to the mandrel, and the
compactor member is moved a distance, to thereby compact a first
segment of the tube which is within the diameter limiting member
and which has a length less than the entire length of the tube. The
compactor member is released and repositioned on the tube at a
second location on the tube, and the compactor member is releasably
secured to the tube at the second location. The compactor member is
then moved a distance, to compact a second segment of the tube
which is adjacent to the first segment and which is within the
diameter limiting member and which has a length less
than-the-entire length of the tube. In one embodiment, the
incremental compaction method of the invention produces uniform
compaction along the length of the porous polymeric tube. In an
alternative embodiment, one or more segments are compacted by an
amount different than the first segment, so that the incremental
compaction method of the invention produces variable compaction
along the length of the porous polymeric tube.
[0015] The invention provides a catheter balloon or other
expandable tubular medical device or component, having improved
performance characteristics due to the longitudinal compaction of
sections of the porous polymeric layer. In one embodiment, the
compacted sections provide a balloon having an inflated
configuration with a desired shape and dimensions, and with reduced
stress at the skirt sections. An improved method of compacting
porous polymeric material during formation of a tubular medical
device or component, provides controllable incremental compaction
of the porous polymeric material to produce uniform or variable
compaction along the length of the tube. 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
[0016] FIG. 1 is an elevational view, partially in section, of a
stent delivery balloon catheter embodying features of the
invention.
[0017] FIG. 2 is a transverse cross sectional view of the balloon
catheter shown in FIG. 1, taken along line 2-2.
[0018] FIG. 3 is a transverse cross sectional view of the balloon
catheter shown in FIG. 1, taken along line 3-3.
[0019] FIG. 4 illustrates the balloon catheter of FIG. 1, with the
balloon inflated.
[0020] FIGS. 5a-d illustrate an assembly of a tube of polymeric
material on a mandrel, partially in section, during longitudinal
compaction of portions of the tube to form a layer of the balloon
of FIG. 1, in a method which embodies features of the invention, in
which a block is moved to compact a portion of the tube into a
die.
[0021] FIGS. 6a-c illustrate an assembly of a tube of polymeric
material on a mandrel, partially in section, during longitudinal
compaction of portions of the tube to form a layer of the balloon
of FIG. 1, in an alternative method which embodies features of the
invention, in which two blocks are moved together to compact a
portion of the tube in a diameter limiting member between the
blocks.
DETAILED DESCRIPTION OF THE INVENTION
[0022] 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 having a stent cover 35, mounted on the
balloon 24 for delivery within a patient's body lumen 27. The
distal end of catheter 10 may be advanced to a desired region of
the patient's 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. FIG. 3
illustrates a transverse cross section view of the distal end of
the catheter shown in FIG. 1, taken along line 3-3.
[0023] 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.
[0024] FIG. 4 illustrates the balloon catheter 10 of FIG. 1, with
the balloon in an inflated configuration. The inflated balloon 24
has a central working section with covered stent 32 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. In one presently
preferred embodiment, the inflated first layer working section has
a length of about 8 to about 80 mm, the inflated first layer
proximal tapered section has a length of about 1 to about 5 mm, and
the inflated first layer distal tapered section has a length of
about 1 to about 5 mm. Although the balloon 24 is illustrated in
FIG. 4 with a conventional inflated configuration having a cental
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.
[0025] 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 a 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 directly
onto the shaft. FIG. 4 illustrates one embodiment in which the
layers 33,34 of the balloon have the same length, so that the skirt
sections 25, 26 consist of end sections of the second (inner) layer
34 having an inner surface bonded to the shaft, and end sections of
the first (outer) layer 33 having an inner surface bonded to the
end sections of the second layer 34. However, in an alternative
embodiment (not shown), the ends of the first layer 33 extend
beyond the end sections of the second layer 34 and onto the shaft
12, so that 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 bond directly to the shaft 12
without the second layer 34 therebetween. The lengths of the first
layer skirt sections will vary depending on a variety of factors
including the method of bonding the balloon to the shaft. In one
presently preferred embodiment, the first layer proximal skirt
section has a length of about 1 to about 5 mm, and the first layer
distal skirt section has a length of about 1 to about 5 mm.
[0026] The ePTFE layer 33 of balloon 24 has sections with different
amounts of longitudinal compaction, at least prior to being
inflated. Preferably, the ePTFE layer 33 has a first section, and a
second section longitudinally adjacent to the first section and
extending at least in part along a central portion of the length of
the balloon, the second section being longitudinally compacted by
more than the first section. In a presently preferred embodiment,
the second section of the ePTFE layer 33 is located at the first
layer working length (i.e., the section of the first layer 33
extending along the working section of the inflated balloon), and
the first section of the ePTFE layer 33 is located at the first
layer proximal or distal tapered sections. In a presently preferred
embodiment, the section of the first layer located at the working
length of the balloon has a greater longitudinal compaction than
the sections of the first layer located at both the proximal and
the distal inflated tapered sections of the balloon. Thus, in one
embodiment, the central working section of the ePTFE layer 33 has a
greater longitudinal compaction than the remaining inflatable
sections of the ePTFE layer 33.
[0027] In one embodiment, the first layer working section has a
longitudinal compaction of about 10% to about 60%, more
specifically about 20% to about 50% of a prelongitudinal compaction
length of the section, and the first layer tapered sections have a
longitudinal compaction of about 10% to about 40%, more
specifically about 15% to about 30% of a prelongitudinal compaction
length of the sections. The percent longitudinal compaction values
should be understood to refer to values existing prior to inflation
of the balloon, and defined as a percentage length reduction from
before to after the compaction process. For example, longitudinally
compacting an ePTFE tube so that a section corresponding to the
first layer working section is compacted from a prelongitudinal
compaction length of about 2.86 cm to a compacted length of about 2
cm, produces a 2 cm first layer working section having a
longitudinal compaction of about 30% prior to inflation of the
balloon.
[0028] The first layer skirt sections have a longitudinal
compaction which is not greater than, and preferably is less than
the longitudinal compaction of the first layer tapered sections. In
a presently preferred embodiment, the first layer skirt sections
are not longitudinally compacted, and thus have a longitudinal
compaction of 0%. In one embodiment, the first layer skirt sections
have a longitudinal compaction of about 0% to about 30%, more
specifically about 10% to about 20%.
[0029] Thus, in one presently preferred embodiment, a balloon ePTFE
layer having a post-compaction working length of 20 mm compacted by
40%, post-compaction tapered sections of 2 mm compacted by 30%, and
post-compaction skirt sections of 2 mm compacted by 20%, had an
original pre-compaction working length of 33.3 mm, original
pre-compaction tapered sections of 2.86 mm, and original
pre-compaction skirt sections of 2.5 mm.
[0030] The first layer working section, prior to inflation of the
balloon 24, preferably has a lower porosity than the first layer
proximal and distal tapered sections and lower than the first layer
proximal and distal skirt sections. Specifically, in one
embodiment, the first layer working section (prior to inflation)
has a porosity about 0 to about 40% lower than a porosity of the
first layer proximal and distal tapered sections, and about 10 to
about 60% lower than a porosity of the first layer proximal and
distal skirt sections. In one embodiment, the first layer proximal
and distal tapered sections have a porosity lower than the first
layer proximal and distal skirt sections, and specifically about 10
to about 30% lower than the porosity of the first layer proximal
and distal skirt sections.
[0031] The ePTFE layer 33 is preferably formed according to a
method in which an ePTFE tube used to form layer 33 is
incrementally compacted. Specifically, the individual sections of
layer 33 having specific longitudinal compaction values (e.g., the
working length, and the proximal and distal tapered sections) are
each produced by compacting multiple smaller length portions of the
tube. For example, to produce a working length having a length of 2
cm and a longitudinal compaction of about 30%, 3 portions each
having an initial precompaction length of 0.95 cm would each be
successively compacted to a compacted length of 0.65 cm (i.e.,
(0.7)(0.95 cm)), to collectively produce the 2 cm working length
having a 30% longitudinal compaction.
[0032] FIGS. 5a-d illustrate an assembly with a polymeric tube 40
during incremental longitudinal compaction of the tube 40 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 tube 40
may be provided with uniform longitudinal compaction such that each
incremental segment is compacted by the same amount, or
alternatively, it may be provided with variable compaction in which
one or more incremental segments are longitudinally compacted by
different amounts.
[0033] In the embodiment illustrated in FIG. 5, the tube 40 is on a
mandrel 41 with a portion of the tube 40 in a die 42 having an
inlet 43 and an outlet 44. The mandrel 41 may optionally have a
polymeric jacket (not shown) on an outer surface of the metallic
body. A compactor member 45 is releasably secured to the tube at a
location on the tube 40 spaced from the die inlet 43 by a distance
"d". In the embodiment of FIG. 5, the compactor member 45 comprises
a block with a bore configured to surround and clamp onto the tube
40 with the mandrel 41 therein, such as with a collet-type clamping
mechanism. However, a variety of suitable compactor members may be
used including a hydraulic clamp. The compactor member 45 is
secured to the tube 40 such that it is slidably disposed relative
to the mandrel within the tube. A fixing member 46 releasably
secures the tube 40 to the mandrel at a location on the tube
adjacent the outlet 44 of the die 42. In the embodiment of FIG. 5,
the fixing member 46 comprises a block similar to the compactor
member 45, with a bore configured to surround and clamp onto the
tube 40 and mandrel 41 therein. With the compactor member 45
releasably secured to the tube 40 the distance "d" from the inlet
43 of the die 42, a first segment "S.sub.1" of the tube 40 is
located between the compactor member 45 and the outlet 44 of the
die 42, as illustrated in FIG. 5a. The compactor member 45 is then
moved toward the inlet 43 of the die 42 to compact the first
segment "S.sub.1" of the tube 40 into the die, thereby forming
compacted segment "CS.sub.1", as illustrated in FIG. 5b. The
compacted segment is illustrated in the figures by closer-spaced
cross hatching. The difference between the original precompacted
length "S.sub.1" of the segment, and the compacted length
"CS.sub.1" of the segment, expressed as a percentage of the
original precompacted length "S.sub.1", is the percent longitudinal
compaction of the segment. The die may be heated to thereby heat
the compacted segment "CS.sub.1" in the die, to heat stabilize the
compacted segment in the compacted configuration. In a presently
preferred embodiment, the die is heated to an elevated temperature
of about 320.degree. C. to about 400.degree. C., preferably about
350.degree. C. to about 370.degree. C. to heat stabilize the
compacted segment. The compactor member 45 and fixing member 46 are
then released, and the tube 40 is repositioned by sliding the
compacted segment "CS.sub.1" through the die outlet 44 to place
another noncompacted portion of the tube 40 in the die lumen, as
illustrated in FIG. 5c. With the compactor member 45 and fixing
member 46 again releasably secured to the tube 40, the second
segment "S.sub.2" is compacted as outlined above. The second
segment "S.sub.2" may be compacted by the same amount as the first
segment "S.sub.1" in order to continue formation of a first
compacted section, or it may be compacted by a different amount in
order to provide for a second compacted section. FIG. 5d
illustrates the assembly after the compaction of the second segment
"S.sub.2" to produce compacted segment "CS.sub.2", with the
compactor member and fixing member again repositioned and secured
on the tube 40, ready for compaction of a third segment
"S.sub.3".
[0034] During compaction, the compactor member 45 may be moved the
entire distance "d" to the die inlet 43, or alternatively, it may
be moved a distance less than "d" depending on the amount of
longitudinal compaction desired for the segment being compacted.
For example, in the embodiments illustrated in FIGS. 5a-d, the
length of the first, second, and third segments S.sub.1, S.sub.2,
S.sub.3 are approximately equal, so that the compactor member 45
could be moved the entire distance "d" to produce an amount of
compaction in one of the segments, and moved a distance less than
"d" in order to produce a smaller amount of compaction in one or
more of the remaining segments.
[0035] The inner diameter of the inner chamber of die 42 is sized
so that the tube 40 compacts without the outer diameter of the tube
increasing. The inner diameter of the inner chamber of die 42 is
typically about equal to the outer diameter of the tube 40 on the
mandrel 41. Alternatively, the inner diameter of the inner chamber
of die 42 may be smaller than the outer diameter of the tube 40 on
the mandrel 41, so that it provides resistance to movement of the
tube 40 therein to increase the percent compaction of the tube 40.
The length of the inner chamber of the die 42 in which tube is
compacted is typically about 1 to about 5 cm, preferably about 2 to
about 3 cm. The length of the tube 40 is typically about 4 to about
20 cm to produce a layer 33 of a balloon having a length of about 2
to about 10 cm. The length of the segments S.sub.1, S.sub.2,
S.sub.3 is typically about 5 to about 25 mm, preferably about 5 to
about 15 mm. The length of the segment is preferably sufficiently
short such that the segment compacts uniformly along the length of
the segment and without buckling.
[0036] After being longitudinally compacted, the tube 40 may be
heat treated or otherwise further processed and secured to the
second layer 34, to complete formation of the balloon 24. The tube
40 is typically longitudinally stretched prior to being
longitudinally compacted, as for example by being placed on a
mandrel and pulled at either end to stretch down on to the mandrel,
although it can be longitudinally stretched using a variety of
suitable methods. With the tube 40 restrained in the longitudinally
stretched configuration, the tube 40 is typically heated, to
stabilize the tube in the stretched configuration prior to being
longitudinally compacted.
[0037] FIGS. 6a-c illustrate an assembly of polymeric tube 40 on
mandrel 41 during incremental longitudinal compaction of the tube
in an alternative method which embodies features of the invention.
Similar to the embodiment of FIG. 5, the tube 40 may be provided
with uniform longitudinal compaction, or alternatively, with
variable compaction.
[0038] In the embodiment illustrated in FIG. 6, the tube 40 is on a
mandrel 41 with a portion of the tube 40 in a diameter limiting
member 52 comprising a sheet of polymeric material wrapped around
the tube 40. In a presently preferred embodiment, the sheet of
polymeric material forming the diameter limiting member 52 is
ePTFE, although other polymeric materials may be used, including
Teflon, and polyolefins such as high density polyethylene (HDPE),
low density polyethylene (LDPE), and linear low density
polyethylene (LLDPE). At least a first compactor member 53 is
releasably secured at a first location to the tube and slidably
disposed relative to the mandrel 41. In the embodiment of FIG. 6,
the first compactor member 53 is a block similar to the block of
the embodiment of FIG. 5. In the embodiment of FIG. 6, a second
compactor member 54 is releasably secured at a second location to
the tube 40 longitudinally spaced apart from the first compactor
member 53 with at least a portion of the diameter limiting device
52 therebetween. With the first and second compactor members 53, 54
releasably secured to the tube 40 a distance apart, a first segment
"S.sub.1" of the tube 40 is located between the compactor members,
as illustrated in FIG. 5a. The first and second compactor members
53, 54 are then moved toward one another toward a center of the
length of the tube 40 to longitudinally compact the first segment
"S.sub.1" therebetween in the diameter limiting device 52, thereby
forming compacted segment "CS.sub.1", as illustrated in FIG. 6b.
The compactor members 53, 54 are then released and resecured to the
tube. In a presently preferred embodiment, the compactor members
53, 54 are resecured to the tube 40 at locations further apart on
the tube and closer to the ends of the tube 40, with second segment
"S.sub.2" greater than "S.sub.1" therebetween, as illustrated in
FIG. 6c. The compactor members 53, 54 are illustrated in FIG. 6c
ready to be moved toward one another toward a center of the length
of the tube 40, to longitudinally compact the second segment
"S.sub.2" therebetween in the diameter limiting device 52. The
ePTFE tape 52 typically has a length sufficient to cover the entire
length of the tube 40 to be compacted, so that the ePTFE tape 52
does not have to be removed and replaced with a longer length of
ePTFE tape 52 between the compaction of each individual segment of
tube 40. In alternative embodiments (not shown) using alternative
diameter limiting members such as a tube, die, or mold, the
diameter limiting device is typically released from the compacted
segment and a longer diameter limiting device is secured to the
tube to accommodate the longer length of the next segment to be
compacted. The compacted tube 40 may be heated to heat stabilize
the compacted segments, as discussed above in relation to the
embodiment of FIG. 5, as for example by traversing a heating nozzle
along the length of the compacted segments. In the illustrated
embodiment in which the diameter limiting member 52 is ePTFE tape
wound around the tube 40, the tube may be heated at the end of the
compaction of the final segment rather than after each individual
compaction, because the ePTFE tape 52 is typically not removed
between the compaction of each individual segment of the tube 40.
The length of the segments being compacted is typically about 10 to
about 50 mm, preferably about 20 to about 30 mm.
[0039] In an alternative embodiment (not shown), a fixing member is
used in place of the second compaction member 54, which is
releasably secures the tube 40 to the mandrel 41, so that
compacting the segment therebetween comprises moving the first
compactor member 53 toward the fixing member. The distance between
the first compaction member 53 and the fixing member is then
increased, for compacting another segment of the tube as described
above.
[0040] 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 14, 16 can be formed by conventional techniques, such as by
extruding and necking materials found useful in intravascular
catheters such a polyethylene, polyvinyl chloride, polyesters,
polyamides, polyimides, polyurethanes, and composite materials.
[0041] 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 14 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 is 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.
[0042] 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. 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.
* * * * *