U.S. patent application number 11/182874 was filed with the patent office on 2005-12-08 for balloon catheter device.
Invention is credited to Campbell, Carey V., Laguna, Alvaro J., Spencer, Mark S..
Application Number | 20050273152 11/182874 |
Document ID | / |
Family ID | 27063990 |
Filed Date | 2005-12-08 |
United States Patent
Application |
20050273152 |
Kind Code |
A1 |
Campbell, Carey V. ; et
al. |
December 8, 2005 |
Balloon catheter device
Abstract
Balloon catheters having the strength and maximum inflated
diameter characteristics of an angioplasty balloon and having the
recovery characteristics during deflation of an elastic embolectomy
balloon. The balloon catheter can be made in very small sizes and
has a lubricious and chemically inert outer surface. The balloon
catheter is easy to navigate through tortuous passageways, is
capable of rapid inflation and deflation and has high burst
strengths. Balloon covers having these same characteristics are
also described for use with conventional embolectomy balloons or
angioplasty balloons.
Inventors: |
Campbell, Carey V.;
(Flagstaff, AZ) ; Laguna, Alvaro J.; (Flagstaff,
AZ) ; Spencer, Mark S.; (Phoenix, AZ) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
3 World Financial Center
New York
NY
10281-2101
US
|
Family ID: |
27063990 |
Appl. No.: |
11/182874 |
Filed: |
July 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11182874 |
Jul 15, 2005 |
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10300056 |
Nov 20, 2002 |
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6923827 |
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10300056 |
Nov 20, 2002 |
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09252322 |
Feb 18, 1999 |
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09252322 |
Feb 18, 1999 |
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08858309 |
May 19, 1997 |
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6120477 |
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08858309 |
May 19, 1997 |
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08673635 |
Jun 26, 1996 |
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5868704 |
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08673635 |
Jun 26, 1996 |
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08532905 |
Sep 18, 1995 |
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5752934 |
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Current U.S.
Class: |
623/1.11 |
Current CPC
Class: |
C08L 27/18 20130101;
C08L 27/12 20130101; A61M 25/1034 20130101; A61M 25/10 20130101;
A61M 25/0014 20130101; A61M 2025/1081 20130101; A61M 2025/1075
20130101; C08L 75/04 20130101; A61L 29/12 20130101; A61L 29/146
20130101; Y10T 428/1359 20150115; A61F 2/958 20130101; C08L 83/04
20130101; A61L 29/085 20130101; Y10T 428/1334 20150115; A61M
25/1029 20130101; A61F 2250/0039 20130101; A61L 29/041 20130101;
A61L 29/085 20130101; C08L 27/18 20130101; A61L 29/12 20130101;
C08L 83/04 20130101; C08L 75/04 20130101; C08L 27/18 20130101; C08L
27/12 20130101; A61L 29/041 20130101; C08L 27/18 20130101 |
Class at
Publication: |
623/001.11 |
International
Class: |
A61F 002/06 |
Claims
1-69. (canceled)
70. A balloon catheter comprising: a) a catheter shaft having a
longitudinal axis with a proximal end and a distal end, said
catheter shaft having an inflation lumen extending within at least
a portion of a distal shaft section; and b) a balloon comprising a
material having a microstructure of interconnected fibrils, said
balloon having a longitudinal axis, said material oriented
helically with respect to said longitudinal axis, wherein the
balloon is mounted on the distal section of the catheter shaft with
an interior chamber in fluid communication with the inflation
lumen; c) said balloon further comprising an elastomeric
material.
71. The balloon catheter according to claim 70 wherein the balloon
has substantially uniform radial expansion.
72. The balloon catheter according to claim 71 wherein the balloon
has an initial deflated diameter and a maximum inflated diameter,
and wherein the balloon is capable of being inflated to its maximum
diameter and then deflated to substantially its initial deflated
diameter.
73. The balloon catheter according to claim 70 wherein the material
having a microstructure of interconnected fibrils comprises
polytetrafluoroethylene.
74. The balloon catheter according to claim 70 wherein the material
having a microstructure of interconnected fibrils comprises
expanded polytetrafluoroethylene.
75. The balloon catheter according to claim 70 wherein the
elastomeric material comprises latex.
76. The balloon catheter according to claim 70 wherein the
elastomeric material comprises silicone.
77. The balloon catheter according to claim 70 wherein the
elastomeric material comprises polyurethane.
78. The balloon catheter according to claim 73 wherein the
elastomeric material comprises latex.
79. The balloon catheter according to claim 73 wherein the
elastomeric material comprises silicone.
80. The balloon catheter according to claim 73 wherein the
elastomeric material comprises polyurethane.
81. The balloon catheter according to claim 74 wherein the
elastomeric material comprises latex.
82. The balloon catheter according to claim 74 wherein the
elastomeric material comprises silicone.
83. The balloon catheter according to claim 74 wherein the
elastomeric material comprises polyurethane.
84. The balloon catheter according to claim 70 wherein the balloon
has a radial compliance of at least about 0.06
millimeters/atmospheres at inflation pressures of about 8 to about
15 atmospheres.
85. The balloon catheter according to claim 73 wherein the balloon
has a radial compliance of at least about 0.06
millimeters/atmospheres at inflation pressures of about 8 to about
15 atmospheres.
86. The balloon catheter according to claim 74 wherein the balloon
has a radial compliance of at least about 0.06
millimeters/atmospheres at inflation pressures of about 8 to about
15 atmospheres.
87. The balloon catheter according to claim 70 wherein the material
having a microstructure of interconnected fibrils is porous and
contains void spaces, said void spaces being substantially sealed
by the elastomeric material.
88. The balloon catheter according to claim 73 wherein the material
having a microstructure of interconnected fibrils is porous and
contains void spaces, said void spaces being substantially sealed
by the elastomeric material.
89. The balloon catheter according to claim 74 wherein the material
having a microstructure of interconnected fibrils is porous and
contains void spaces, said void spaces being substantially sealed
by the elastomeric material.
90. The balloon catheter according to claim 70 wherein the material
having a microstructure of interconnected fibrils is porous,
wherein at least a portion of the elastomeric material is
impregnated into said material having a microstructure of
interconnected fibrils.
91. The balloon catheter according to claim 73 wherein the material
having a microstructure of interconnected fibrils is porous,
wherein at least a portion of the elastomeric material is
impregnated into said material having a microstructure of
interconnected fibrils.
92. The balloon catheter according to claim 74 wherein the material
having a microstructure of interconnected fibrils is porous,
wherein at least a portion of the elastomeric material is
impregnated into said material having a microstructure of
interconnected fibrils.
93. The balloon catheter according to claim 70 further comprising
an expandable stent disposed about and mounted onto the
balloon.
94. The balloon catheter according to claim 71 further comprising
an expandable stent disposed about and mounted onto the
balloon.
95. The balloon catheter according to claim 72 further comprising
an expandable stent disposed about and mounted onto the
balloon.
96. The balloon catheter according to claim 73 further comprising
an expandable stent disposed about and mounted onto the
balloon.
97. The balloon catheter according to claim 74 further comprising
an expandable stent disposed about and mounted onto the
balloon.
98. The balloon catheter according to claim 75 further comprising
an expandable stent disposed about and mounted onto the
balloon.
99. The balloon catheter according to claim 76 further comprising
an expandable stent disposed about and mounted onto the
balloon.
100. The balloon catheter according to claim 77 further comprising
an expandable stent disposed about and mounted onto the
balloon.
101. The balloon catheter according to claim 78 further comprising
an expandable stent disposed about and mounted onto the
balloon.
102. The balloon catheter according to claim 79 further comprising
an expandable stent disposed about and mounted onto the
balloon.
103. The balloon catheter according to claim 80 further comprising
an expandable stent disposed about and mounted onto the
balloon.
104. The balloon catheter according to claim 81 further comprising
an expandable stent disposed about and mounted onto the
balloon.
105. The balloon catheter according to claim 82 further comprising
an expandable stent disposed about and mounted onto the
balloon.
106. The balloon catheter according to claim 83 further comprising
an expandable stent disposed about and mounted onto the
balloon.
107. The balloon catheter according to claim 84 further comprising
an expandable stent disposed about and mounted onto the
balloon.
108. The balloon catheter according to claim 85 further comprising
an expandable stent disposed about and mounted onto the
balloon.
109. The balloon catheter according to claim 86 further comprising
an expandable stent disposed about and mounted onto the
balloon.
110. The balloon catheter according to claim 87 further comprising
an expandable stent disposed about and mounted onto the
balloon.
111. The balloon catheter according to claim 88 further comprising
an expandable stent disposed about and mounted onto the
balloon.
112. The balloon catheter according to claim 89 further comprising
an expandable stent disposed about and mounted onto the
balloon.
113. The balloon catheter according to claim 90 further comprising
an expandable stent disposed about and mounted onto the
balloon.
114. The balloon catheter according to claim 91 further comprising
an expandable stent disposed about and mounted onto the
balloon.
115. The balloon catheter according to claim 92 further comprising
an expandable stent disposed about and mounted onto the balloon.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
08/858,309 filed May 19, 1997 which is a continuation-in-part of
application Ser. No. 08/673,635 filed Jun. 26, 1996 which is a
continuation-in-part of application Ser. No. 08/532,905 filed Sep.
18, 1995.
FIELD OF THE INVENTION
[0002] The present invention relates to catheter balloons used in a
variety of surgical procedures and to balloon covers for use with
catheter balloons.
BACKGROUND OF THE INVENTION
[0003] Balloon catheters of various forms are commonly employed in
a number of surgical procedures. These devices comprise a thin
catheter tube that can be guided through a body conduit of a
patient such as a blood vessel and a distensible balloon located at
the distal end of the catheter tube. Actuation of the balloon is
accomplished through use of a fluid filled syringe or similar
device that can inflate the balloon by filling it with fluid (e.g.,
water or saline solution) to a desired degree of expansion and then
deflate the balloon by withdrawing the fluid back into the
syringe.
[0004] In use, a physician will guide the balloon catheter into a
desired position and then expand the balloon to accomplish the
desired result (e.g., clear a blockage, or install or actuate some
other device). Once the procedure is accomplished, the balloon is
then deflated and withdrawn from the blood vessel.
[0005] There are two main forms of balloon catheter devices.
Angioplasty catheters employ a balloon made of relatively strong
but generally inelastic material (e.g., polyester) folded into a
compact, small diameter cross section. These relatively stiff
catheters are used to compact hard deposits in vessels. Due to the
need for strength and stiffness, these devices are rated to high
pressures, usually up to about 8 to 12 atmospheres depending on
rated diameter. They tend to be self-limiting as to diameter in
that they will normally distend up to the rated diameter and not
distend appreciably beyond this diameter until rupture due to
over-pressurization. While the inelastic material of the balloon is
generally effective in compacting deposits, it tends to collapse
unevenly upon deflation, leaving a flattened, wrinkled bag,
substantially larger in cross section than the balloon was when it
was originally installed. Because of their tendency to assume a
flattened cross section upon inflation and subsequent deflation,
their deflated maximum width tends to approximate a dimension
corresponding to one-half of the rated diameter times pi. This
enlarged, wrinkled bag may be difficult to remove, especially from
small vessels. Further, because these balloons are made from
inelastic materials, their time to complete deflation is inherently
slower than elastic balloons.
[0006] By contrast, embolectomy catheters employ a soft, very
elastic material (e.g., natural rubber latex) as the balloon. These
catheters are employed to remove soft deposits, such as thrombus,
where a soft and tacky material such as latex provides an effective
extraction means. Latex and other highly elastic materials
generally will expand continuously upon increased internal pressure
until the material bursts. As a result, these catheters are
generally rated by volume (e.g., 0.3 cc) in order to properly
distend to a desired size. Although relatively weak, these
catheters do have the advantage that they tend to readily return to
their initial size and dimensions following inflation and
subsequent deflation.
[0007] Some catheter balloons constructed of both elastomeric and
non-elastomeric materials have been described previously. U.S. Pat.
No. 4,706,670 describes a balloon dilatation catheter constructed
of a shaft made of an elastomeric tube and reinforced with
longitudinally inelastic filaments. This device incorporates a
movable portion of the shaft to enable the offset of the reduction
in length of the balloon portion as the balloon is inflated. The
construction facilitates the inflation and deflation of the
balloon.
[0008] While balloon catheters are widely employed, currently
available devices experience a number of shortcomings. First, as
has been noted, the strongest materials for balloon construction
tend to be relatively inelastic. The flattening of catheter
balloons made from inelastic materials that occurs upon inflation
and subsequent deflation makes extraction and navigation of a
deflated catheter somewhat difficult. Contrastly, highly elastic
materials tend to have excellent recovery upon deflation, but are
not particularly strong when inflated nor are they self-limiting to
a maximum rated diameter regardless of increasing pressure. This
severely limits the amount of pressure that can be applied with
these devices. It is also somewhat difficult to control the
inflated diameter of these devices.
[0009] Second, in instances where the catheter is used to deliver
some other device into the conduit, it is particularly important
that a smooth separation of the device and the catheter balloon
occur without interfering with the placement of the device. Neither
of the two catheter devices described above is ideal in these
instances. A balloon that does not completely compact to its
original size is prone to snag the device causing placement
problems or even damage to the conduit or balloon. Similarly, the
use of a balloon that is constructed of tacky material will
likewise cause snagging problems and possible displacement of the
device. Latex balloons are generally not used for device placement
in that they are considered to have inadequate strength for such
use. Accordingly, it is a primary purpose of the present invention
to create a catheter balloon that is small and slippery for initial
installation, strong for deployment, and returns to its compact
size and dimensions for ease in removal and further navigation
following deflation. It is also believed desirable to provide a
catheter balloon that will remain close to its original compact
pre-inflation size even after repeated cycles of inflation and
deflation. Other primary purposes of the present invention are to
strengthen elastic balloons, to provide them with distension limits
and provide them with a lubricious outer surface. The term
"deflation" herein is used to describe a condition subsequent to
inflation. "Pre-inflation" is used to describe the condition prior
to initial inflation.
SUMMARY OF THE INVENTION
[0010] The present invention is an improved balloon catheter device
for use in a variety of surgical procedures. The balloon catheter
device of the present invention comprises a catheter tube having a
continuous lumen connected to an inflatable and deflatable balloon
at one end of the catheter tube. The catheter tube may have
additional lumens provided for other purposes. The balloon can have
a burst strength equal to or greater than that of conventional PTA
catheter balloons. The balloon also has a maximum inflation
diameter in a similar fashion to conventional PTA catheter
balloons. The inventive balloon offers the recovery characteristics
of a latex balloon that when deflated is of about the same maximum
diameter as it was prior to inflation. This allows the inventive
balloon to be withdrawn following deflation more easily than
conventional PTA balloons which assume a flattened, irregular cross
section following deflation and so have a deflated maximum diameter
much larger than the pre-inflation maximum diameter. The balloon
also has a smooth and lubricious surface which also aids in
insertion and withdrawal. The inventive balloon possesses all of
the above attributes even when made in small sizes heretofore
commercially unavailable in balloon catheters without a movable
portion of the catheter shaft or some other form of mechanical
assist. The present invention eliminates the need for a movable
portion of the shaft and associated apparatuses to aid in balloon
deflation.
[0011] The present invention is made from polytetrafluoroethylene
(hereinafter PTFE) materials and elastomeric materials. The PTFE is
preferably porous PTFE made as taught by U.S. Pat. Nos. 3,953,566
and 4,187,390, both of which are incorporated by reference herein.
An additional optional construction step, longitudinally
compressing a porous PTFE tube prior to addition of the elastomeric
component, allows the balloon or balloon cover to sufficiently
change in length to enable the construction of higher pressure
balloons, again without the need for mechanical assist.
Particularly small sizes (useful in applications involving small
tortuous paths such as is present in brain, kidney, and liver
procedures) can be achieved by decreasing the wall thickness of the
balloon via impregnation of a porous PTFE tube with silicone
adhesive, silicone elastomer, silicone dispersion, polyurethane or
another suitable elastomeric material instead of using a separate
elastomeric member. Impregnation involves at least partially
filling the pores of the porous PTFE. The pores (void spaces) are
considered to be the space or volume within the bulk volume of the
porous PTFE material (i.e., within the overall length, width and
thickness of the of the porous PTFE material) not occupied by PTFE
material. The void spaces of the porous PTFE material from which
the balloon is at least partially constructed may be substantially
sealed in order that the balloon is liquid-tight at useful
pressures by either the use of a separate tubular elastomeric
substrate in laminated relationship with the porous PTFE, or by
impregnation of the void spaces of the porous PTFE with elastomeric
material, or by both methods. U.S. Pat. No. 5,519,172 teaches in
detail the impregnation of porous PTFE with elastomers. In that
this patent relates primarily to the construction of a jacket
material for the protection of electrical conductors, the
suitability of each of the various described materials for in vivo
use as catheter balloon materials must be considered.
[0012] The balloon may be made from the materials described herein
as a complete, stand-alone balloon or alternatively may be made as
a cover for either conventional polyester PTA balloons or for latex
embolectomy balloons. The use of the balloon cover of the present
invention provides the covered balloon, regardless of type, with
the best features of conventional PTA balloons and renders viable
the use of elastic balloons for PTA procedures. That is to say, the
covered balloon will have high burst strength, a predetermined
maximum diameter, the ability to recover to substantially its
pre-inflation size following deflation, and a lubricious exterior
surface (unless it is desired to construct the balloon such that
the elastomeric material is present on the outer surface of the
balloon). The balloon cover substantially reduces the risk of
rupture of an elastic balloon. Further, if rupture of the
underlying balloon should occur, the presence of the balloon cover
may serve to contain the fragments of the ruptured balloon. Still
further, the inventive balloon and balloon cover can increase the
rate of deflation of PTA balloons thereby reducing the time that
the inflated balloon occludes the conduit in which it resides.
[0013] The present invention also enables the distension of a
vessel and side branch or even a prosthesis within a vessel and its
side branch without exerting significant force on the vessel or its
branch. Further, it has been shown to be useful for flaring the
ends of prostheses, thereby avoiding unwanted constrictions at the
ends of the prostheses. Prostheses can slip along the length of
prior art balloons during distension; the present invention not
only reduces such slippage, it also can be used to create a larger
diameter at the end of the graft than prior art materials.
[0014] The inventive balloon and balloon cover also maintain a
substantially circular cross section during inflation and deflation
in the absence of external constraint. Plus, the balloon and
balloon cover can be designed to inflate at lower pressure in one
portion of the length than another. This can be accomplished, for
example, by altering the thickness of the elastomer content along
the length of the balloon in order to increase the resistance to
distension along the length of the balloon. Alternatively, the
substrate tube may be constructed with varying wall thickness or
varying amounts of helically-applied film may be applied along the
tube length in order to achieve a similar effect.
[0015] The balloon catheter according to the present invention has
opposing ends affixed to the catheter by opposing securing means.
The balloon has a length measured between the opposing ends wherein
the length preferably varies less than about ten percent, and more
preferably less than about five percent, between when the balloon
is in a deflated state and when the balloon is inflated to a
pressure of eight atmospheres.
[0016] Balloons of the present invention can also be constructed to
elute fluids at pressures exceeding the balloon inflation pressure.
Such balloons could have utility in delivering drugs inside a
vessel.
[0017] A catheter balloon of the present invention is anticipated
to be particularly useful for various surgical vascular procedures,
including graft delivery, graft distension, stent delivery, stent
distension, and angioplasty. It may have additional utility for
various other surgical procedures such as, for example, supporting
skeletal muscle left ventricular assist devices during the healing
and muscle conditioning period and as an intra-aortic balloon.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIGS. 1A, 1B and 1C are perspective views describing
manufacture of the tubular component forming the balloon or balloon
cover of the present invention.
[0019] FIG. 2 is a perspective view describing the tubular
component as it appears when inflated.
[0020] FIGS. 3A and 3B describe longitudinal cross sectional views
of a balloon cover of the present invention without elastomer.
[0021] FIGS. 4A and 4B describe longitudinal cross sectional views
of a balloon cover of the present invention incorporating a layer
of elastomer.
[0022] FIGS. 5A and 5B describe longitudinal cross sectional views
of a catheter balloon of the present invention having the same
material construction as the balloon cover of FIGS. 4A and 4B.
[0023] FIGS. 6A, 6B and 6C describe longitudinal cross sectional
views of a catheter balloon of the type described by FIGS. 5A and
5B using a non-elastomeric material in place of the layer of
elastomer.
[0024] FIG. 7 describes a transverse cross section taken at the
center of the length of a flattened, deflated angioplasty balloon
which describes how the compaction efficiency ratio of the deflated
balloon is determined.
[0025] FIG. 8 describes a longitudinal cross section of a balloon
affixed to the shaft of a dual lumen catheter, the balloon having a
first PTFE material oriented substantially parallel to the
longitudinal axis of the balloon and a second PTFE material
oriented substantially circumferential to the longitudinal axis,
wherein the PTFE materials is impregnated with an elastomer.
[0026] FIG. 8A describes a longitudinal cross section of an
alternative embodiment to that of FIG. 8 wherein the balloon during
inflation exhibits a larger diameter at a first portion of its
length than at a second portion of its length.
[0027] FIGS. 9 and 9A describe cross sections of the proximal end
of a balloon catheter of the present invention.
[0028] FIGS. 10A-10F describe the construction of an alternative
embodiment of a balloon catheter of the present invention wherein
the balloon has separate substrate layers of an elastomeric
material and a porous PTFE material in laminated relationship and
wherein each end of each substrate material is separately affixed
to a catheter shaft by separate wrappings of porous PTFE film.
[0029] FIGS. 11A, 11B and 11C describe the construction of an
alternative embodiment of a balloon catheter of the present
invention similar to that of FIGS. 10A-10F wherein a catheter shaft
is used which comprises a tubular elastomeric material provided
with a reinforcing wrapping of porous PTFE film.
[0030] FIGS. 12A, 12B and 12C describe the construction of an
alternative embodiment of a balloon catheter of the present
invention wherein a laminated tube of separate substrates of an
elastomeric material and helically wrapped porous PTFE film are
affixed to a catheter shaft by a wrapping of porous PTFE film at
each end of the laminated tube.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The catheter balloon and catheter balloon cover of the
present invention are preferably made from porous PTFE films having
a microstructure of interconnected fibrils. These films are made as
taught by U.S. Pat. Nos. 3,953,566 and 4,187,390. The balloon and
balloon cover may also incorporate a porous PTFE substrate tube in
the form, for example, of an extruded and expanded tube or a tube
constructed of film containing at least one seam. Also, the balloon
may be impregnated with an elastomeric material.
[0032] To form the balloon or balloon cover, both of which are made
in the shape of a tube, a thin, porous PTFE film of the type
described above is slit into relatively narrow lengths. The slit
film is helically wrapped onto the surface of a mandrel in two
opposing directions, thereby forming a tube of at least two layers.
FIGS. 1A, 1B and 1C describe this procedure. FIG. 1A shows the
first layer 14 of porous PTFE film helically wrapped over the
mandrel 12 with the traverse direction of the wrap applied in a
first direction 20 parallel to the longitudinal axis 18. The
longitudinal axis of a balloon is defined as coincident with the
longitudinal axis of the balloon catheter shaft, that is along the
length of the shaft. Substantially parallel is defined as between
about 0.degree. and 45.degree., or between about 135.degree. and
180.degree., with respect to the longitudinal axis of the catheter
shaft and substantially circumferential is defined as between about
45.degree. and 135.degree. with respect to the longitudinal axis of
the catheter shaft. FIG. 1B describes the application of the second
layer of porous PTFE film 16 helically wrapped over the top of the
first layer 14, wherein second layer 16 is wrapped in a second
traverse direction 22 parallel to longitudinal axis 18 and opposite
to the first traverse direction 20.
[0033] Preferably both layers 14 and 16 are wrapped with the same
pitch angle measured with respect to the longitudinal axis but
measured in opposite directions. If, for example, film layers 14
and 16 are applied at pitch angles of 70.degree. measured from
opposite directions with respect to longitudinal axis 18, then
included angle A between both 70.degree. pitch angles is
40.degree..
[0034] More than two layers of helically wrapped film may be
applied. Alternate layers of film should be wrapped from opposing
directions and an even number of film layers should be used whereby
an equal number of layers are applied in each direction.
[0035] Following completion of film wrapping, the helically wrapped
mandrel is placed into an oven for suitable time and temperature to
cause adjacent layers to heat-bond together. After removal from the
oven and subsequent cooling, the resulting film tube may be removed
from the mandrel. The film tube is next placed over the balloon,
tensioned longitudinally and affixed in place over the balloon.
[0036] During use, the inflated balloon or balloon cover 10 of the
present invention has an increased diameter which results in
included angle A being substantially reduced as shown by FIG. 2.
The balloon or balloon cover thus reaches its pre-determined
diametrical limit as included angle A approaches zero.
[0037] The inventive balloon or balloon cover 10 is reduced in
diameter following deflation by one of two ways. First, tension may
be applied to the balloon or balloon cover parallel to longitudinal
axis 18 to cause it to reduce in diameter following deflation to
the form described by FIG. 1C. The application of tension is
necessary if low profile is desired. Alternatively, a layer of
elastomer, applied to the luminal surface of the balloon 10 and
allowed to cure prior to use of the balloon, will cause the balloon
to retract to substantially its pre-inflation size shown by FIG. 1C
following deflation. The elastomer may take the form of a coating
of elastomer applied directly to the luminal surface of the balloon
or balloon cover 10, or an elastomeric balloon such as a latex
balloon or a silicone tube may be adhered to the luminal surface of
the inventive balloon 10 by the use of an elastomeric adhesive.
Alternatively, elastomer can be impregnated into the porous
material to create a balloon or balloon cover.
[0038] FIG. 3A describes a cross sectional view of a balloon cover
10 of the present invention in use with a conventional balloon
catheter of either the angioplasty or embolectomy type. The figure
describes a balloon cover without an elastomeric luminal coating.
The balloon cover 10 is closed at distal end 26 of the balloon
catheter 11. Balloon cover 10 extends in length part of the way to
the proximal end 27 of balloon catheter 11 whereby balloon cover 10
completely covers catheter balloon 25 and at least a portion of the
catheter 11. FIG. 3B describes the same balloon catheter 11 with
catheter balloon 25 in an inflated state. Layers 14 and 16 of
balloon cover 10 allow the cover to increase in diameter along with
catheter balloon 25. During or following deflation of catheter
balloon 25, tension is applied to the balloon cover 10 at the
proximal end 27 of balloon catheter 11 as shown by arrows 28,
thereby causing balloon cover 10 to reduce in diameter and
substantially return to the state described by FIG. 3A. FIG. 4A
describes a cross sectional view of a balloon cover 10 of the
present invention wherein the balloon cover 10 has a liquid-tight
layer of elastomer 34 applied to the inner surface of helically
wrapped porous PTFE film layers 14 and 16. Balloon cover 10 is
closed at distal end 26. The figure describes a ligated closure,
such as by a thread or filament, however, other suitable closing
means may be used. Proximal end 27 of balloon cover 10 is affixed
to the distal end 32 of catheter 24. Balloon 25 may be of either
the angioplasty or embolectomy type. If an elastomeric embolectomy
balloon is used, it is preferred that the cover be adhered to the
balloon by the use of an elastomeric adhesive to liquid-tight layer
of elastomer 34. During inflation of balloon 25 as shown by FIG.
4B, helically wrapped porous PTFE film layers 14 and 16 and
liquid-tight elastomer layer 34 increase in diameter along with
balloon 25. During subsequent deflation, liquid-tight elastomer
layer 34 causes helically wrapped porous PTFE film layers 14 and 16
to reduce in diameter as described previously, thereby returning
substantially to the state described by FIG. 4A.
[0039] FIGS. 5A and 5B describe cross sectional views of a catheter
balloon 10 made in the same fashion as the balloon cover described
by FIGS. 4A and 4B. The presence of liquid-tight elastomer layer 34
allows this construction to function as an independent balloon 42
as described previously without requiring a conventional
angioplasty or embolectomy balloon.
[0040] FIGS. 6A, 6B and 6C describe cross sectional views of an
alternative embodiment of the catheter balloon 10 of the present
invention. According to this embodiment helically wrapped porous
PTFE film layers 14 and 16 are provided with a luminal coating 44
which is liquid-tight but is not elastomeric. The resulting balloon
behaves in the fashion of a conventional angioplasty balloon but
offers the advantages of a lubricious and chemically inert exterior
surface. FIG. 6A describes the appearance of the balloon prior to
inflation. FIG. 6B describes the balloon in an inflated state. As
shown by FIG. 6C, following deflation, collapsed balloon 46 has a
somewhat wrinkled appearance and an irregular transverse cross
section in the same fashion as a conventional angioplasty balloon
made from polyester or similar inelastic material.
[0041] It is also anticipated that the balloon and balloon cover of
the present invention may be provided with an additional
reinforcing mesh or braid on the exterior or interior surface of
the balloon (or balloon cover), or more preferably between layers
of the film whereby the mesh or braid is in the middle.
[0042] Alternatively, a mesh or braid of PTFE may be used as a
balloon cover without including a continuous tube. A continuous
tube does not include openings through its wall as does a
conventional mesh or braid.
[0043] The following examples describe in detail the construction
of various embodiments of the balloon cover and catheter balloon of
the present invention. Evaluation of these balloons is also
described in comparison to conventional angioplasty and embolectomy
balloons. FIG. 7 is provided as a description of the maximum
dimension 72 and minimum dimension 74 (taken transversely to the
longitudinal axis of the balloon) of a flattened, deflated
angioplasty balloon 70 wherein the figure describes a transverse
cross section of a typical flattened angioplasty balloon. The
transverse cross section shown is meant to describe a typical
deflated, flattened inelastic angioplasty balloon 70 having a
somewhat irregular shape. Balloon 70 includes a catheter tube 76
having a guidewire lumen 78 and a balloon inflation lumen 79 and
two opposing sides 82 and 84 of balloon 70. Maximum dimension 72
may be considered to be the maximum width of the flattened balloon
70 while minimum dimension 74 may be considered to be the maximum
thickness across the two opposing sides 82 and 84 of the flattened
balloon 70. All balloon and catheter measurements are expressed in
terms of dimensions even if the shape is substantially
circular.
EXAMPLE 1
[0044] This example illustrates the use of a balloon cover of the
present invention over a commercially available angioplasty
balloon. The balloon cover provides a means of returning the
angioplasty balloon close to its original compact geometry after
inflation and subsequent deflation, as well as providing the known
chemical inertness and low coefficient of friction afforded by
PTFE.
[0045] The balloon used was a MATCH 35.RTM. Percutaneous
Transluminal Angioplasty (PTA) Catheter model number B508-412,
manufactured by SCHNEIDER (Minneapolis, Minn.). This balloon when
measured immediately after being removed from the protective sheath
provided by the manufacturer had a minimum dimension of 2.04 mm and
a maximum dimension of 2.42 mm. These measurements were taken from
approximately the center of the balloon, as defined by the midpoint
between the circumferentially-oriented radiopaque marker bands
located at both ends of the balloon. A Lasermike model 183,
manufactured by Lasermike, (Dayton, Ohio) was used to make the
measurements while the balloon was rotated about its longitudinal
axis. The shaft onto which the balloon was attached had a minimum
dimension of 1.74 mm and a maximum dimension of 1.77 mm measured
adjacent to the point of balloon attachment closest to the center
of the length of the shaft. The balloon, when inflated to 8
atmospheres internal water pressure, had a minimum dimension of
8.23 mm and a maximum dimension of 8.25 mm at the center of the
length of the balloon. When deflated by removing the entire volume
of water introduced during the 8 atmosphere pressurization, the
balloon at its mid-length, had a minimum dimension of 1.75 mm, and
a maximum dimension of 11.52 mm as measured using Mitutoyo digital
caliper model CD-6"P. Upon completion of the measurements the
balloon portion of the PTA catheter was carefully repackaged into
the protective sheath.
[0046] The inventive balloon cover was made from a length of porous
PTFE film made as described above cut to a width of 2.5 cm. The
film thickness was approximately 0.02 mm, the density was 0.2 g/cc,
and the fibril length was approximately 70 microns. Thickness was
measured using a Mitutoyo snap gauge model 2804-10 and density was
calculated based on sample dimensions and mass. Fibril length of
the porous PTFE films used to construct the examples was estimated
from scanning electron photomicrographs of an exterior surface of
film samples.
[0047] This film was helically wrapped onto the bare surface of an
8 mm diameter stainless steel mandrel at an angle of approximately
70.degree. with respect to the longitudinal axis of the mandrel so
that about 5 overlapping layers of film cover the mandrel.
Following this, another 5 layers of the same film were helically
wrapped over the first 5 layers at the same pitch angle with
respect to the longitudinal axis, but in the opposite direction.
The second 5 layers were therefore also oriented at an approximate
angle of 70.degree., but measured from the opposite end of the axis
in comparison to the first 5 layers. Following this, another 5
layers of the same film were helically wrapped over the first and
second 5 layers at the same bias angle with respect to the
longitudinal axis as the first 5 layers, and then another 5 layers
of the same film were helically wrapped over the first, second, and
third 5 layers at the same bias angle with respect to the
longitudinal axis as the second 5 layers. This resulted in a total
of about 20 layers of helically wrapped film covering the
mandrel.
[0048] The film-wrapped mandrel was then placed into an air
convection oven set at 380.degree. C. for 10 minutes to heat bond
the layers of film, then removed and allowed to cool. The resulting
8 mm inside diameter film tube formed from the helically wrapped
layers was then removed from the mandrel and one end was ligated
onto a self-sealing injection site (Injection Site with Luer Lock
manufactured by Baxter Healthcare Corporation, Deerfield, Ill.). A
hole was created through the injection site, and the balloon end of
the previously measured PTA catheter was passed through this hole,
coaxially fitting the film tube over the balloon portion as well as
a portion of the shaft of the PTA catheter. The film tube was
approximately 25 cm in length. With the film tube over the PTA
catheter and attached to the injection site, tension was applied
manually to the free end of the film tube while the injection site
was held fixed, causing the film tube to reduce in diameter and fit
snugly onto the underlying segment of PTA catheter. Next, the film
tube was ligated at the distal end of the PTA catheter shaft so
that the balloon cover remained taut and snugly fit.
[0049] At this point the now covered balloon was measured in a
deflated state. The minimum dimension was found to be 2.33 mm and
the maximum dimension 2.63 mm. As before, these measurements were
taken from approximately the center of the balloon, as defined by
the midpoint between the radiopaque marker bands, and a Lasermike
model 183, manufactured by Lasermike, (Dayton, Ohio) was used to
make the measurements. The balloon, when inflated to 8 atmospheres
internal water pressure had a minimum dimension of 7.93 mm and a
maximum dimension of 8.06 mm at the center of the balloon. When
deflated by removing the entire volume of water introduced during
the 8 atmosphere pressurization, the balloon at its mid-length, had
a minimum dimension of 1.92 mm and a maximum dimension of 11.17 mm.
Next, tension was manually applied to the injection site causing
the balloon cover to reduce the size of the underlying balloon,
particularly along the plane of the 11.17 mm measurement taken
previously. After the application of tension the covered balloon
was measured again, and the minimum and maximum dimensions were
found as 3.43 and 3.87 mm respectively.
[0050] This example shows that the balloon cover can be used
effectively to compact a PTA balloon which was inflated and
subsequently deflated to approximately the geometry of the balloon
in an unused state. The measurements taken on the balloon (in both
the uncovered and covered states) after inflation and subsequent
deflation show that rather than undergoing a uniform circular
compaction, the balloon tended to flatten. This flattening can be
quantified by calculating the ratio of the minimum dimension to the
maximum dimension measured after inflation and subsequent
deflation. This ratio is defined as the compaction efficiency
ratio. Note that a circular cross section yields a compaction
efficiency ratio of unity. For this example, the uncovered balloon
had a compaction efficiency ratio of 1.75 divided by 11.52, or
0.15. The balloon, after being provided with the inventive balloon
cover, had a compaction efficiency ratio of 3.43 divided by 3.87,
or 0.89. Additionally, the ratio of the maximum dimension prior to
any inflation, to the maximum dimension after inflation and
subsequent deflation, is defined as the compaction ratio. A balloon
which has the same maximum dimension prior to any inflation, and
after inflation and subsequent deflation, has a compaction ratio of
unity. For this example, the uncovered balloon had a compaction
ratio of 2.42 divided by 11.52, or 0.21. The balloon, after being
provided with the inventive balloon cover, had a compaction ratio
of 2.63 divided by 3.87, or 0.68.
EXAMPLE 2
[0051] This example illustrates the use of a balloon cover over a
commercially available latex embolectomy balloon. The balloon cover
provides a defined limit to the growth of the embolectomy balloon,
a substantial increase in burst strength, and the known chemical
inertness and low coefficient of friction afforded by PTFE.
[0052] The balloon used was a Fogarty.RTM. Thru-Lumen Embolectomy
Catheter model 12TL0805F manufactured by Baxter Healthcare
Corporation (Irvine, Calif.). This natural rubber latex balloon
when measured immediately after being removed from the protective
sheath provided by the manufacturer had a minimum dimension of 1.98
mm and a maximum dimension of 2.02 mm. These measurements were
taken from approximately the center of the balloon, as defined by
the midpoint between the radiopaque marker bands. A Lasermike model
183, manufactured by Lasermike, (Dayton, Ohio) was used to make the
measurements while the balloon was rotated about its longitudinal
axis. The shaft onto which the balloon was attached had a minimum
dimension of 1.64 mm and a maximum dimension of 1.68 mm measured
adjacent to the point of balloon attachment closest to the center
of the length of the shaft. The balloon, when filled with 0.8 cubic
centimeters of water had a minimum dimension of 10.71 mm and a
maximum dimension of 10.77 mm at the center of the balloon. When
deflated by removing the entire volume of water introduced, the
balloon at its mid-length, had a minimum dimension of 1.97 mm and a
maximum dimension of 2.04 mm. The balloon when tested using a
hand-held inflation syringe had a burst strength of 60 psi.
[0053] Another embolectomy catheter of the same type was covered
using a porous PTFE film tube made as described in Example 1. The
method used to cover the embolectomy catheter was the same as that
used to cover the PTA catheter in Example 1.
[0054] At this point, the now covered balloon was measured in a
pre-inflated state. The minimum dimension was found to be 2.20 mm
and the maximum dimension 2.27 mm. As before, these measurements
were taken from approximately the center of the balloon, as defined
by the midpoint between the radiopaque marker bands, and a
Lasermike model 183, manufactured by Lasermike (Dayton, Ohio) was
used to make the measurements. The balloon, when filled with 0.8
cubic centimeters of water had a minimum dimension of 8.29 mm and a
maximum dimension of 8.34 mm at mid-length. When deflated by
removing the entire volume of water introduced, the balloon at its
mid-length, had a minimum dimension of 3.15 mm and a maximum
dimension of 3.91 mm. Next, tension was manually applied to the
injection site causing the balloon cover to reduce in size. After
the application of tension the covered balloon was measured again,
and the minimum and maximum dimensions were found as 2.95 and 3.07
mm respectively. The covered balloon was determined to have a burst
strength of 188 psi, failing solely due the burst of the underlying
embolectomy balloon. The inventive balloon cover exhibited no
indication of rupture.
[0055] This example shows that the inventive balloon cover
effectively provides a limit to the growth, and a substantial
increase in the burst strength of an embolectomy balloon. The
measurements taken on the uncovered balloon show that when filled
with 0.8 cubic centimeters of water the balloon reached a maximum
dimension of 10.77 mm. Under the same test conditions, the covered
balloon reached a maximum dimension of 8.34 mm. The burst strength
of the uncovered balloon was 60 psi while the burst strength of the
covered balloon was 188 psi when inflated until rupture using a
hand-operated liquid-filled syringe. This represents more than a
three fold increase in burst strength.
EXAMPLE 3
[0056] This example illustrates the use of a composite material in
a balloon application. A balloon made from the composite material
described below exhibits a predictable inflated diameter, high
strength, exceptional compaction ratio and compaction efficiency
ratio, as well as the known chemical inertness and low coefficient
of friction afforded by PTFE.
[0057] A length of SILASTIC.RTM.Rx50 Silicone Tubing manufactured
by Dow Corning Corporation (Midland, Mich.) having an inner
diameter of 1.5 mm and an outer diameter of 2.0 mm was fitted
coaxially over a 1.1 mm stainless steel mandrel and secured at both
ends. The silicone tubing was coated with a thin layer of
Translucent RTV 108 Silicone Rubber Adhesive Sealant manufactured
by General Electric Company (Waterford, N.Y.). An 8 mm inner
diameter film tube made in the same manner described in Example 1
was fitted coaxially over the stainless steel mandrel and the
silicone tubing. Tension was manually applied to the ends of the
film tube causing it to reduce in diameter and fit snugly onto the
underlying segment of silicone tubing secured to the stainless
steel mandrel. With the film tube in substantial contact with the
silicone tubing, this composite tube was gently massaged to ensure
that no voids were present between the silicone tube and the porous
PTFE film tube. Next the entire silicone-PTFE composite tube was
allowed to cure in an air convection oven set at 35.degree. C. for
a minimum of 12 hours. Once cured, the composite tube was removed
from the stainless steel mandrel. One end of the composite tube was
then fitted coaxially over a section of 5 Fr catheter shaft taken
from a model B507-412 MATCH 35.RTM. Percutaneous Transluminal
Angioplasty (PTA) Catheter, manufactured by SCHNEIDER (Minneapolis,
Minn.) and clamped to the catheter shaft using a model 03.3 RER Ear
Clamp manufactured by Oetiker (Livingston, N.J.) such that a
watertight seal was present. The distal end of the balloon was
closed using hemostats for expediency, however, a conventional
ligature such as waxed thread may be used to provide a suitable
closure. In this manner a balloon catheter was fashioned, utilizing
the silicone-PTFE composite tube as the balloon material.
[0058] At this point, the balloon was measured in a pre-inflated
state. The minimum dimension was found to be 2.31 mm and the
maximum dimension 2.42 mm. As before, these measurements were taken
from approximately the midpoint of the balloon, and a Lasermike
model 183, manufactured by Lasermike, (Dayton, Ohio) was used to
make the measurements while the balloon was rotated about its
longitudinal axis. The balloon, when inflated to 8 atmospheres
internal water pressure, had a minimum dimension of 7.64 mm and a
maximum dimension of 7.76 mm at the center of the balloon. When
deflated by removing the entire volume of water introduced during
the 8 atmosphere pressurization, the balloon at its mid-length, had
a minimum dimension of 2.39 mm and a maximum dimension of 2.57 mm.
The silicone-PTFE composite balloon when tested using a hand-held
inflation device had a burst strength of 150 psi, reaching a
maximum dimension of about 7.9 mm prior to rupture.
[0059] This example illustrates that the balloon made from the
silicone-PTFE composite tube exhibited a predictable limit to its
diametrical growth as demonstrated by the destructive burst
strength test wherein the balloon did not exceed the 8 mm diameter
of the porous PTFE film tube component. The compaction ratio as
previously defined was 2.42 divided by 2.57, or 0.94, and the
compaction efficiency ratio as previously defined was 2.39 divided
by 2.57, or 0.93.
EXAMPLE 4
[0060] This example describes the construction of a PTA balloon
made by helically wrapping a porous PTFE film having a non-porous
FEP coating over a thin porous PTFE tube.
[0061] The FEP-coated porous expanded PTFE film was made by a
process which comprises the steps of:
[0062] a) contacting a porous PTFE film with another layer which is
preferably a film of FEP or alternatively of another thermoplastic
polymer;
[0063] b) heating the composition obtained in step a) to a
temperature above the melting point of the thermoplastic
polymer;
[0064] c) stretching the heated composition of step b) while
maintaining the temperature above the melting point of the
thermoplastic polymer; and
[0065] d) cooling the product of step c).
[0066] In addition to FEP, other thermoplastic polymers including
thermoplastic fluoropolymers may also be used to make this coated
film. The adhesive coating on the porous expanded PTFE film may be
either continuous (non-porous) or discontinuous (porous) depending
primarily on the amount and rate of stretching, the temperature
during stretching, and the thickness of the adhesive prior to
stretching.
[0067] The FEP-coated porous PTFE film used to construct this
example was a continuous (non-porous) film. The total thickness of
the coated film was about 0.02 mm. The film was helically wrapped
onto an 8 mm diameter stainless steel mandrel that had been
coaxially covered with a porous expanded PTFE tube, made as taught
by U.S. Pat. Nos. 3,953,566 and 4,187,390. The porous PTFE tube was
a 3 mm inside diameter tube having a wall thickness of about 0.10
mm and a fibril length of about 30 microns. Fibril length is
measured as taught by U.S. Pat. No. 4,972,846. The 3 mm tube had
been stretched to fit snugly over the 8 mm mandrel. The FEP-coated
porous PTFE film was then wrapped over the outer surface of this
porous PTFE tube in the same manner as described by Example 1, with
the FEP-coated side of the film placed against the porous PTFE tube
surface. The wrapped mandrel was placed into an air convection set
at 380.degree. C. for 2.5 minutes, removed and allowed to cool, at
which time the resulting tube was removed from the mandrel. One end
of this tube was fitted coaxially over the end of a 5 Fr catheter
shaft taken from a model number B507-412 PTA catheter manufactured
by Schneider (Minneapolis, Minn.), and clamped to the catheter
shaft using a model 03.3 RER Ear Clamp manufactured by Oetiker
(Livingston, N.J.) such that a watertight seal was present. The
resulting balloon was packed into the protective sheath which was
provided by Schneider as part of the packaged balloon catheter
assembly. The balloon was then removed from the protective sheath
by sliding the sheath proximally off of the balloon and over the
catheter shaft. Prior to inflation, the minimum and maximum
diameters of the balloon were determined to be 2.25 and 2.61 mm.
The distal end of the balloon was then closed using hemostats for
expediency, however, a conventional ligature such as waxed thread
could have been used to provide a suitable closure. When inflated
to a pressure of 6 atmospheres, the minimum and maximum diameters
were 8.43 and 8.49 mm. After being deflated the minimum and maximum
diameters were 1.19 and 12.27 mm. These diameters resulted in a
compaction ratio of 0.21 and a compaction efficiency of 0.10.
EXAMPLE 5
[0068] This example describes a balloon constructed by impregnating
silicone dispersion into a porous PTFE tube with helically applied
porous PTFE film. A balloon made in this way exhibits a very small
initial diameter, predictable inflated diameter, high strength,
exceptional compaction ratio and compaction efficiency ratio, as
well as the known chemical inertness and low coefficient of
friction afforded by PTFE. The impregnation with silicone
dispersion enables the construction of a thinner balloon. The use
of a thin porous PTFE tube as a substrate provides longitudinal
strength to resist elongation of the balloon at high pressures.
[0069] A longitudinally extruded and expanded porous PTFE substrate
tube was obtained. The substrate tube was 1.5 mm inside diameter,
having a wall thickness of about 0.17 mm and a fibril length of
about 45 microns. The tube was fitted coaxially onto a 1.5 mm
diameter stainless steel mandrel. Next, a length of porous expanded
PTFE film was obtained that had been cut to a width of 2.54 cm.
This film had a thickness of about 0.02 mm, a density of about 0.2
g/cc, and a fibril length of about 70 microns. Thickness was
measured using a Mitutoyo snap gauge model No. 2804-10. The film
bulk density was calculated based on dimensions and mass of a film
sample. Density of non-porous PTFE was considered to be 2.2 g/cc.
Fibril length of the porous PTFE film used to construct the example
was estimated from scanning electron photomicrographs of an
exterior surface of samples of the film.
[0070] This film was helically wrapped directly onto the bare metal
surface of a 7 mm diameter stainless steel mandrel at about
65.degree. with respect to the longitudinal axis of the mandrel so
that about two overlapping layers of film covered the mandrel. Both
edges of the film were colored with black ink in order to measure
the pitch angles of the film during the construction or use of the
completed balloon. Following this, another approximately two layers
of the same film were helically wrapped over the first two layers.
The second two layers were applied at the same bias angle with
respect to the longitudinal axis, but in the opposite direction.
This procedure was repeated three times, providing approximately 16
total layers of film. The film-wrapped mandrel was then placed into
a convection oven set at 380.degree. C. for 10 minutes to heat-bond
the adjacent layers of film, then removed and allowed to cool. The
resulting 7 mm inside diameter film tube formed from the helically
wrapped layers of films was then removed from the mandrel.
[0071] This 7 mm inside diameter porous PTFE film tube was then
fitted coaxially over the 1.5 mm inside diameter PTFE substrate
tube and mandrel. The film tube was then tensioned longitudinally
to cause it to reduce in diameter to the extent that it fit snugly
over the outer surface of the 1.5 mm tube. The ends of this
reinforced tube were then secured to the mandrel in order to
prevent longitudinal shrinkage during heating. The combined tube
and mandrel assembly was placed into an air convention oven set at
380.degree. C. for 190 seconds to heat bond the film tube to the
outer surface of the substrate tube. The reinforced tube and
mandrel assembly was then removed from the oven and allowed to
cool.
[0072] Additional porous PTFE film was then helically applied to
outer surface of the reinforced tube to inhibit wrinkling of the
tube in the subsequent step. The tube was then compressed in the
longitudinal direction to reduce the tube length to approximately
0.6 of the length just prior to this compression step. Care was
taken to ensure a high degree of uniformity of compression along
the length of the tube. Wire was used to temporarily affix the ends
of the tube to the mandrel. The mandrel-loaded reinforced tube with
the additional helically applied film covering was then placed into
a convention oven set at 380.degree. C. for 28 seconds, removed
from the oven and allowed cool.
[0073] The additional outer film was removed from the reinforced
tube, followed by removing the reinforced tube from the mandrel.
The reinforced tube was then gently elongated by hand to a length
of about 0.8 of the length just prior to the compression step.
[0074] The reinforced tube was then ready for impregnation with
silicone dispersion (Medical Implant Grade Dimethyl Silicone
Elastomer Dispersion in Xylene, Applied Silicone Corp., PN 40000,
Ventura, Calif.). The silicone dispersion was first prepared by
mixing 2.3 parts n-Heptane (J. T. Barker, lot #J07280) with one
part silicone dispersion. Another mixture with n-Heptane was
prepared by mixing 0.5 parts with 1 part silicone dispersion. Each
mixture was loaded into an injection syringe.
[0075] The dispensing needle of each of the injection syringes was
inserted inside one end of the reinforced tube. Wire was used to
secure the tube around the needles. One of the dispensing needles
was capped and the syringe containing the 2.3:1 silicone dispersion
solution was connected to the other. The solution was dispensed
inside the reinforced tube with about 6 psi pressure. Pressure was
maintained for approximately one minute, until the outer surface of
the tube started to become wetted with the solution, indicating
that the dispersion entered the pores of the PTFE material. It was
ensured that the silicone dispersion coated the inside of the PTFE
tube. At this point, the syringe was removed, the cap was removed
from the other needle, and the syringe containing the 0.5:1
silicone dispersion solution was connected to the previously-capped
needle. This higher viscosity dispersion was then introduced into
the tube with the syringe, displacing the lower viscocity
dispersion through the needle at the other end, until the higher
viscosity dispersion began to exit the tube through the needle.
After ensuring that the tube was completely filled with dispersion,
both needles were capped. Curing of the silicone dispersion was
effected by heating the assembly in a convection oven set at
150.degree. C. for a minimum of one hour. The solvent evaporated
during the curing process, thereby recreating the lumen in the
tube. The impregnated reinforced tube was removed from the oven and
allowed to cool. Both ends of the tube were opened and the 0.5:1
silicone dispersion solution was injected in one end to again fill
the lumen, the needle ends were then capped, then the dispersion
was cured in the same manner as described above. At this point the
balloon construction was complete.
[0076] The above-described process preserved PTFE as the outermost
surface of the balloon. Alternatively, longer impregnation times or
higher injection pressures during the initial impregnation could
cause more thorough wetting of the PTFE structure with the silicone
dispersion, thereby driving more dispersion to the outermost
surface of the balloon.
[0077] The balloon was then ready for mounting on a 5 Fr catheter
shaft obtained from a balloon dilatation catheter (Schneider Match
35 PTA Catheter, 6 mm dia., 4 cm length, model no. B506-412) This
balloon was mounted on the 1.67 mm diameter catheter shaft as
described by FIG. 8. Both ends of the balloon were mounted to the
shaft. The catheter tip portion plus the balloon of the balloon
dilatation catheter were cut off in the dual lumen portion of the
shaft leaving only the catheter shaft 24. Guidewires serving as
mandrels (not shown) were inserted into both lumens of the shaft. A
0.32 mm mandrel was inserted into the inflation lumen 87 and a 0.6
mm mandrel was inserted into the wire lumen 83. The portion 24A of
the shaft 24 containing the inflation lumen 87 was shaved off
longitudinally to a length approximately 1 cm longer than the
length of the balloon to be placed on the shaft; therefore, this
portion 24A of the shaft 24 then contained only the wire lumen 83
which possessed a semi-circular exterior transverse cross section.
(The extra 1 cm length accommodates room for a tip portion of the
catheter, without a balloon covering, in the final assembly.) With
the mandrels still in place, portion 24B of the shaft 24 was
inserted for about 30 seconds into a heated split die containing
1.5 mm diameter bore when the dies were placed together. The dies
were heated to a temperature of 180.degree. C. to form the
semicircular cross sectional shape of the portion of the shaft into
a round 1.5 mm cross section and to create a landing 91 in the area
proximal to the distal end of the inflation lumen 87. Next, the
balloon 10 (having circumferentially oriented film layers 14 and
16, and longitudinally oriented substrate tube 81) was slipped over
the modified distal end of the shaft 24 such that the proximal end
of the balloon 10 was approximately 0.5 cm from the end of the
landing 91. This approximately 0.5 cm segment of the landing 91
adjacent to the abutment was primed for fifteen seconds (Loctite
Prism.TM. Primer 770, Item #18397, Newington, Conn.) and then
cyanoacrylate glue (Loctite 4014 Instant Adhesive, Part #18014,
Rocky Hill, Conn.) was applied to that segment. The balloon 10 was
moved proximally such that the proximal end of the balloon abutted
against the end of the landing 91 and the glue was allowed to set.
The distal end of the balloon 10 was attached in the same manner,
while ensuring against wrinkling of the balloon during the
attachment. At this point, a radiopaque marker could have been
fitted at each end of the balloon. The last step in the mounting
process involved securing the ends of the balloon with shrink
tubing 93 (Advanced Polymers, Inc., Salem, N.H., polyester shrink
tubing--clear, item #085100CST). Approximately 0.25 cm of the
proximal end of the balloon and approximately 0.75 cm of the shaft
adjacent to the end of the balloon were treated with the same
primer and glue as described above. Approximately 1 cm length of
shrink tubing 93 was placed over the treated regions of the shaft
24 and balloon 10. The same process was followed to both prepare
the distal end the balloon and the adjacent modified shaft portion
and to attach another approximately 1 cm length of shrink tubing
93. The entire assembly was then placed into a convection oven set
at 150.degree. C. for at least about 2 minutes in order to shrink
the shrink tubing.
[0078] The pre-inflation balloon possessed 2.03 mm and 2.06 mm
minimum and maximum dimensions, respectively. the balloon catheter
was tested under pressure as described in Example 1. The inflated
balloon possessed 5.29 mm and 5.36 mm minimum and maximum
dimensions, respectively. The deflated balloon possessed 2.19 mm
and 3.21 mm minimum and maximum dimensions, respectively. The
resulting compaction efficiency and the compaction ratio were 0.68
and 0.64, respectively.
[0079] The pitch angles of the film were also measured
pre-inflation, at inflation (8 atm), and at deflation, yielding
values of about 20.degree., 50.degree., and 25.degree.,
respectively. The balloon was reinflated with 10 atm and the pitch
angles of the film were measured for the inflation and deflation
conditions. The angles were the same for both inflation
pressures.
[0080] The balloon was subjected to even higher pressures to
determine the pressure at failure. The balloon withstood 19.5 atm
pressure prior to failure due to breakage of the shrink tubing at
the distal end of the balloon. Another balloon catheter was made
using a piece of the same balloon material, following the same
procedures described in this example. This balloon catheter was
used to distend a 3 mm GORE-TEX Vascular Graft (item no. V03050L,
W. L. Gore and Associates, Inc., Flagstaff Ariz.) from which the
outer reinforcing film had been removed. The graft was placed over
the balloon such that the distal end of the graft was positioned
approximately 1 cm from the distal end of the balloon. The balloon
was inflated to 8 atm, the graft distended uniformly without moving
in the longitudinal direction with respect to the balloon. Another
piece of the same graft was tested in the same manner using a 6 mm
diameter, 4 cm long Schneider Match 35 PTA Catheter (model no.
B506-412). In this case, the graft slid along the length of the
balloon proximally during the balloon inflation; the distal end of
the graft was not distended.
EXAMPLE 6
[0081] A balloon catheter was made following all of the steps of
Example 5 with one exception in order to provide a balloon that
bends during inflation.
[0082] All of the same steps were followed as in Example 5 with the
exception of eliminating the manual elongation step that
immediately followed the longitudinal compression step. That is, at
the point of being impregnated with silicone dispersion, the
film-covered porous PTFE tube was 0.6 of its initial length
(instead of 0.8 as in Example 5).
[0083] A balloon catheter was constructed using this balloon. The
length of the balloon was 4.0 cm. The bend of the balloon was
tested by inflating the balloon to 8 atm and measuring the bend
angle created by inflation. Measurements were made via the balloon
aligned coincident with the 0.degree. scribe line of a protractor,
with the middle of the balloon positioned at the origin. The bend
angle was 50.degree.. The balloon was then bent an additional
90.degree. and allowed to relax. No kinking occurred even at
140.degree.. The angle of the still inflated, relaxed balloon
stabilized at 90.degree..
[0084] The balloon of an intact 6 mm diameter, 4 cm long Schneider
Match 35 PTA Catheter (model no. B506-412) was tested in the same
manner. The bend angle under 8 atm pressure was 0.degree.. The
inflated balloon was then bent to 90.degree., which created a kink.
The inflated balloon was allowed to relax. The balloon bend angle
stabilized at 25.degree.. The bending characteristics of an article
of the present invention should enable the dilatation of a vessel
and a side branch of the same vessel simultaneously. The inventive
balloon is easily bendable without kinking. Kinking is defined as
wrinkling of the balloon material.
EXAMPLE 7
[0085] This example illustrates an alternative construction for a
balloon catheter assembly of the present invention. The described
construction relates to a balloon made from tubular substrates of
helically-wrapped porous PTFE film and elastomeric tubing in
laminar relationship wherein ends of the balloon are secured to a
catheter shaft using wraps of porous PTFE film. The balloon does
not require an additional layer of porous PTFE having fibrils
oriented longitudinally with respect to the lengths of the balloon
and catheter shaft.
[0086] As shown by the longitudinal cross section of FIG. 9, the
proximal end of the balloon catheter assembly 100 was created using
three segments of catheter tubing joined together at an injection
molded Y-fitting. As described in this and subsequent examples, the
distal end of the balloon catheter is considered to be the end to
which is affixed the balloon and the end which is first inserted
into the body of a patient; the proximal end is considered to be
the end of the balloon catheter opposite the distal end. All tubing
segments were Pebax 7233 tubing unless noted otherwise; all of the
described tubing is available from Infinity Extrusions and
Engineering, Santa Clara, Calif. unless noted otherwise. The
primary component of catheter shaft 101 was a dual lumen segment of
tubing 103 having an outside diameter of about 2.3 mm, a guidewire
lumen 105 of about 1.07 mm inside diameter and a crescent-shaped
inflation lumen 107 of about 0.5 mm height. A transverse cross
section of this tubing is described by FIG. 9A. The guidewire lumen
105 of this main shaft 101 was joined at the Y-fitting 109 to one
end of a 12 cm length of single lumen tubing 111 having an outside
diameter of about 2.34 mm and an inside diameter of about 1.07 mm;
the inflation lumen 107 of the main shaft 101 was joined to a 12 cm
length of Pebax 4033 single lumen tubing 115. Joining was
accomplished by placing a length of 1.0 mm outside diameter steel
wire (not shown) into one end of the guidewire lumen 105 of the
dual lumen tubing 103 and sliding one end of single lumen tube 111
onto the opposite end of the steel wire until the ends of dual
lumen tube 103 and single lumen tube 111 abutted. A length of 0.48
mm diameter wire (also not shown) having a 30 degree bend at the
midpoint of its length was inserted into the crescent-shaped
inflation lumen 107 of the dual lumen tubing 103 up to the point of
the bend in the wire; the lumen 117 of the second length of single
lumen tubing 115 was fitted over the opposite end of this wire
until it also reached the bend point of the wire, abutting the end
of the dual lumen tubing 103 at that point. The presence of the
wires in the region of the abutted tube ends thus maintained the
continuity of both lumens at the point of abutment. The region of
the abutted tubing ends was placed into the cavity of a mold
designed to encapsulate the junction. Using a model IMP 6000
Injection Molding Press (Novel Biomedical Inc., Plymouth Minn.),
heated Pebax 7033 was injected into the mold to form Y-fitting 109.
After cooling, the resulting assembly was removed from the mold and
the lengths of steel wire were withdrawn from the lumens of the
tubing. Finally, a female Luer fitting (part no. 65250, Qosina
Corp., Edgewood, N.Y.) was affixed to the remaining ends of each of
the single lumen tubes 111 and 115 using Loctite 4014 Instant
Adhesive (Loctite Corp., Newington Conn.).
[0087] The distal or balloon end of the catheter assembly 100 was
then fabricated as follows, beginning according to the longitudinal
cross section shown by FIG. 10A. A 1.00 mm diameter stainless steel
wire (not shown) approximately 30 cm long was inserted
approximately 15 cm into the distal end of the guidewire lumen 105
of the dual lumen tubing 103. A 13 cm length of single lumen tubing
119 having an inner diameter of 1.02 mm and an outer diameter of
1.58 mm was placed over the exposed wire protruding from the
guidewire lumen 105 such that it abutted the end of the dual lumen
tubing 103. A 0.49 mm stainless steel wire approximately 30 cm long
was placed inside the distal end of the crescent-shaped inflation
lumen 107 of the dual lumen tubing 103. The abutted ends of the two
tubes 103 and 119 and the resident wires were placed into a
PIRF.RTM. Thermoplastic Forming and Welding System (part numbers
3220, 3226, 3262 and 3263, Sebra.RTM. Engineering and Research
Associates, Inc., Tucson Ariz.) and a butt connection between the
single lumen tubing 119 and the dual lumen catheter shaft 103 was
completed. The 0.49 mm stainless steel wire resident within the
distal portion of the crescent-shaped inflation lumen 107 of the
dual lumen catheter tubing 103 ensured that the distal end of lumen
107 would remain open during this operation. The heated die used in
this step was specifically fabricated to accommodate the dimensions
of the dual lumen catheter tubing 103 and the single lumen tubing
119. The heating and other parameters used in the operation were
derived by trial and error to result in adequate reflow and butt
welding of the abutted ends of the two tubes.
[0088] Next, with the 1.00 mm stainless steel wire still in place
within the guidewire lumens 105 and 121 of abutted tubes 103 and
119, the 0.49 mm stainless steel wire resident within the distal
portion of the inflation lumen 107 of the dual lumen catheter
tubing 103 was replaced by a 0.39 mm stainless steel wire
approximately 30 cm long (also not shown). Again the wire was
placed about 15 cm into the inflation lumen 107. The assembly
consisting of butt welded single lumen tube 119 and dual lumen tube
103, and the resident wire, was placed into the PIRF.RTM.
Thermoplastic Forming and Welding System which was refitted with a
different die. Upon heating, the assembly was advanced
approximately 2.0 cm into the heated die of the system, causing a 2
cm length of the distal end of the outer diameter of the dual lumen
catheter tubing 103 to decrease to the same dimension as the 1.83
mm inner diameter of the heated die. The longitudinal cross section
of FIG. 10B describes the appearance of the assembly after heating
wherein region "a" has the 1.58 mm outside diameter of single lumen
tube 119, region "b" has been modified to the outside diameter of
1.83 mm and region "c" retains the original 2.3 mm outside diameter
of dual lumen tubing 103. The 0.39 mm stainless steel wire resident
within the inflation lumen 107 of the dual lumen catheter tubing
103 ensured that the lumen 107 would remain open during this
operation. The heating and other parameters used in the operation
were derived by trial and error to result in adequate reflow of the
dual lumen tubing. Once this operation was completed, the entire
outer surface of the full length of the single lumen tubing 119
(region "a," distal from the butt-weld) was abraded with 220
abrasive paper to facilitate bonding of the ends of a silicone tube
123 as will be described.
[0089] With construction of the catheter shaft 101 completed, a
segment of silicone tubing 123 approximately 9 cm in length, having
an approximate inner diameter of 1.40 mm, an approximate outer
diameter of 1.71 mm, and a durometer of Shore 60A (Beere Precision
Silicone, Racine, Wis.) was placed over the distal end of the
catheter shaft 101 as shown by the longitudinal cross section of
FIG. 10C such that the proximal edge of the silicone tubing 123 was
approximately 7.5 mm distal from the point at which the outer
diameter of catheter shaft 101 changed from 1.83 mm to 2.3 mm. This
was done very carefully to ensure that no section of the silicone
tubing 123 was longitudinally stretched (i.e., under tension) when
at its final position on the catheter shaft 101. Isopropyl alcohol
was used as a lubricant between the catheter shaft 101 and the
silicone tubing 123.
[0090] While the elastomeric tubing used for this example was
silicone tubing, it is believed that tubings made from other
elastomeric materials such as polyurethane or fluoroelastomer
tubings may also be suitably employed.
[0091] With the silicone tubing 123 placed correctly on the
catheter shaft 101, any residual alcohol was allowed to evaporate
for a generous amount of time, ensuring that the shaft 101 was
completely dry. Once free of residual alcohol, a small amount of
Medical Implant Grade Dimethyl Silicone Elastomer Dispersion In
Xylene (Part 40000, Applied Silicone, Ventura, Calif.) was applied
between the ends of the silicone tubing 123 and the underlying
exterior surface of the catheter shaft 101. At each end of the
silicone tubing 123, a small blunt needle was inserted between the
ends of the silicone tubing 123 and the underlying catheter shaft
101 for a distance of approximately 7.5 mm as measured in a
direction parallel to the length of the catheter shaft 101. The
silicone elastomer dispersion was carefully applied, using a 3 cc
syringe connected to the blunt needle, around the entire
circumference of the catheter shaft 101 such that the dispersion
remained within and fully coated the 7.5 mm length of the area to
be bonded under the ends of silicone tubing 123. The silicone
elastomer dispersion was then allowed to cure for approximately 30
minutes at ambient temperature, and then an additional 30 minutes
in an air convection oven set at 150.degree. C. Next, a length of
porous PTFE film as described above, approximately 1.0 cm wide, was
manually wrapped over the end regions of the silicone tubing 123
under which the silicone elastomer dispersion was present, and onto
the adjacent portions of the catheter shaft 101 not covered by
silicone tubing 123, for a length of approximately 7.5 mm measured
from the ends of the silicone tubing 123. During wrapping, the
entire length of the porous PTFE film was coated with a small
amount of the silicone elastomer dispersion, the dispersion
impregnating the porous PTFE film such that the void spaces in the
porous PTFE film were substantially filled by the dispersion. The
dispersion was thus used as an adhesive material to affix the
porous PTFE film to the underlying components. It is believed that
other adhesive material may also be used such as other elastomers
(e.g., polyurethane or fluoroelastomers, also optionally in
dispersion form), cyanoacrylates or thermoplastic adhesives such as
fluorinated ethylene propylene which may be activated by the
subsequent application of heat. Great care was taken to ensure that
the porous PTFE film was applied so that approximately 3
overlapping layers (depicted schematically as layers 125 in FIG.
10C) covered each of the regions; the very thin porous PTFE film
did not add significantly to the outside diameter of the catheter
assembly 100. At this point the silicone elastomer dispersion used
to coat the porous PTFE film was allowed to cure for approximately
30 minutes at ambient temperature, and then an additional 30
minutes in an air convection oven set at 150.degree. C.
[0092] Next, a film tube was constructed in a fashion similar to
that described in example 1. A length of porous PTFE film, cut to a
width of 2.5 cm, made as described above, was wrapped onto the bare
surface of an 8 mm stainless steel mandrel at an angle of
approximately 70.degree. with respect to the longitudinal axis of
the mandrel so that about 5 overlapping layers of film covered the
mandrel (i.e., any transverse cross section of the film tube
transects about five layers of film). Following this another,
another 5 layers of the same film were helically wrapped over the
first 5 layers at the same pitch angle with respect to the
longitudinal axis, but in the opposite direction. The second 5
layers were therefore also oriented at an approximate angle of
70.degree., but measured from the opposite end of the axis in
comparison to the first 5 layers. In the same manner, additional
layers of film were applied five layers at a time with each
successive group of five layers applied in an opposing direction to
the previous group until a total of about 30 layers of helically
wrapped film covered the mandrel. This film-wrapped mandrel was
then placed into an air convection oven set at 380.degree. C. for
11.5 minutes to heat bond the layers of film, then removed and
allowed to cool.
[0093] The film tube may also be constructed using more film or
less film than described above; the use of increasing or decreasing
amounts of film will result in a catheter balloon that is
respectively stronger (in terms of hoop strength) and less
compliant, or weaker and more compliant. The use of slightly
different porous PTFE materials (e.g., porosity, thickness and
width), the amount of porous PTFE material used and its orientation
with respect to the longitudinal axis and adjacent material layers
can all be expected to affect the performance properties of the
resulting balloon; these variables may be optimized for specific
performance requirements by ordinary experimentation.
[0094] The resulting 8 mm inside diameter film tube was then
removed from the 8 mm mandrel, fitted coaxially over a 1.76 mm
diameter stainless steel mandrel, and manually tensioned
longitudinally to cause it to reduce in diameter. The ends of the
film tube (extending beyond the mandrel ends) were then placed into
a model 4201 Tensile Testing Machine manufactured by Instron
(Canton, Mass.) equipped with flat faced jaws and pulled at a
constant rate of 200 mm/min until a force between 4.8 and 4.9 kg
was achieved. The film tube was then secured to the mandrel ends by
tying with wire.
[0095] The 1.76 mm mandrel with the film tube secured onto it was
then placed into an air convection oven set at 380.degree. C. for
30 seconds. The mandrel and film tube were then removed, allowed to
cool, and then helically wrapped manually (using a pitch angle of
about 70 degrees with respect to the longitudinal axis) with a
length of 1.9 cm wide porous PTFE film made as described above, so
that about 2 overlapping layers of film covered the mandrel and
film tube. Following this, another 2 layers of the same film were
helically wrapped over the first 2 layers at the same pitch angle
with respect to the longitudinal axis, but in the opposite
direction. These layers of film (not shown) were applied
temporarily as a clamping means to secure the film tube to the
outer surface of the mandrel during the subsequent heating and
curing process. The 1.76 mm mandrel, with the film tube secured
onto it and the layers of porous PTFE film wrapped over the film
tube, was then placed into an air convection oven set at
380.degree. C. for 45 seconds, after which it was removed and
allowed to cool. Using an indelible pen, marks were then placed
along the length of wrapped film tube in 1 cm increments, and the
wrapped film tube was compressed longitudinally until these marks
were uniformly spaced approximately 5 mm apart. These pen marks
were placed on the external, helically-wrapped film such that the
ink penetrated the outer film layers and also marked the underlying
film tube. The 1.76 mm mandrel, with the longitudinally compressed
film tube secured onto it and the layers of porous PTFE film
wrapped over the film tube, was then placed into an air convection
oven set at 380.degree. C. for 45 seconds, after which it was
removed and allowed to cool. Once cool, the layers of porous PTFE
film wrapped over the film tube were completely removed, and the
resulting 1.76 mm inside diameter film tube was removed from the
mandrel. The film tube, having visible pen marks at 5 mm
increments, was manually tensioned longitudinally until the pen
marks were spaced at approximately 1 cm increments, and then
allowed to retract. The resulting 1.76 mm inside diameter film tube
then had visible pen marks spaced between 7 mm and 8 mm apart. The
film tube was then placed in a jar containing a mixture of 1 part
MED1137 Adhesive Silicone Type A manufactured by NuSil Silicone
Technology (Carpinteria, Calif.) to 6 parts n-Heptane (J. T. Baker,
Phillipsburg, N.J.) by weight, wetting the film tube with the
mixture. Void spaces within the porous PTFE film tube 127 were thus
impregnated with and substantially filled by the silicone adhesive
mixture. It is believed that this step may also be accomplished by
other types of elastomeric adhesives including fluoroelastomers and
polyurethanes.
[0096] The catheter shaft 101 with the silicone tubing 123 affixed
to it via porous PTFE film 125 and silicone elastomer dispersion
was then carefully coated with a thin layer of a mixture of 2 parts
MED1137 Adhesive Silicone Type A manufactured by NuSil Silicone
Technology (Carpinteria, Calif.) to 1 part n-Heptane (J. T. Baker,
Phillipsburg, N.J.) by weight. The 1.76 mm inside diameter film
tube was removed from the silicone-Heptane mixture, and the coated
catheter shaft 101 was carefully fitted coaxially within the film
tube 127 as shown by the longitudinal cross section of FIG. 10D
such that the entire silicone tube 123 affixed to the shaft 101 was
covered by film tube 127, as well as an adjacent portion of the
catheter shaft 101 proximal to the point at which the shaft outer
dimension changed from 1.83 mm to 2.3 mm. with the catheter shaft
101 and the affixed silicone tube 123 covered by the film tube 127,
the ends of film tube 127 were trimmed so that the proximal end was
coincident to the point at which the catheter shaft 101 outer
dimension changed from 1.83 mm to 2.3 mm, and the other end was
approximately 7.5 mm distal from the distal end of the silicone
tubing 123 affixed to the catheter shaft 101. The exterior surface
of film tube 127 was then helically wrapped by hand with a length
of 1.9 cm wide porous PTFE film, made as described above, so that
about 2 overlapping layers of film covered its length. This film
(not shown) was applied temporarily as a securing means desired
during the subsequent heating and curing step. This distal portion
of the catheter assembly 100 was then placed into a steam bath for
a period of time between 15 and 30 minutes to cure the previously
applied silicone adhesive mixture.
[0097] The catheter assembly 100 was then removed from the steam
bath, and the outer helically-wrapped film layers were removed.
Next, lengths of porous PTFE film as described above, approximately
1.0 cm wide, were manually wrapped over the ends of the film tube
127 approximately 15 mm distal from the point at which the shaft
outer dimension changed from 1.83 mm to 2.3 mm, and approximately
15 mm distal from the most proximal edge of the porous PTFE film
wrapped around the distal end of the silicone tubing. During
wrapping, the entire length of the porous PTFE film was coated with
a small amount of a mixture of equal parts of MED1137 Adhesive
Silicone Type A manufactured by NuSil Silicone Technology
(Carpinteria, Calif.) and n-Heptane (J. T. Baker, Phillipsburg,
N.J.) by weight. Great care was taken to ensure that the porous
PTFE film was applied so that approximately 3 overlapping layers
(shown schematically as layers 129 in FIG. 10D) covered the region
without adding significantly to the diameter of the catheter.
Because of the reduced diameter at region "b" and the thin
character of the porous PTFE film used for layers 129 and 125, the
diameter of the catheter assembly 100 at the location of film
layers 129 and 125 was very close to the diameter of catheter
tubing 101 proximal to these layers of film. The distal portion of
the catheter was then placed into a steam bath for a minimum of 8
hours to achieve final curing. After final curing the distal-most
portion of the catheter shaft was cut off transversely at the
distal-most edge 131 of the porous PTFE film on the exterior of the
film tube. The construction of the distal region of the catheter
assembly 100 incorporating the balloon portion was now complete.
The resulting balloon portion of this construction is represented
as region 133. The ends of the balloon and the length of the
balloon (taken as the distance measured between the ends of the
balloon) are defined by the bracketed region 133, shown as
beginning at the edges of porous PTFE film layer 129 (the
termination or securing means) closest to the balloon portion
133.
[0098] The balloon portion 133 thus was secured to the outer
surface of the catheter shaft by two separate terminations (or
securing means) at each end of the balloon; these take the form of
film layers 125 used to secure the silicone tube 123 and film
layers 129 used to secure the porous PTFE film tube 127. The
presence of two separate terminations (i.e., separate layers 125
and 129) at one end of the balloon can be demonstrated by taking a
transverse cross section through the termination region and
examining it with suitable microscopy methods such as scanning
electron microscopy.
[0099] The inflatable balloon portion 133 was the result of two
substrates, porous PTFE film tube 127 and elastomeric slilcone tube
123 being joined in laminated relationship. The void spaces of the
porous PTFE film tube 127 were thus substantially sealed by the
silicone tube 123 and the previously applied silicone adhesive
mixture which impregnated the void spaces of the porous PTFE film
tube 127 and adhered the film tube to the silicone tube 123.
[0100] At this point, the diameter of the balloon portion 133 was
measured in a pre-inflated state. The minimum diameter was found to
be 2.14 mm and the maximum diameter 2.31 mm. As before, these
measurements were taken from approximately the midpoint of the
balloon, and a Lasermike model 183, manufactured by Lasermike,
(Dayton, Ohio) was used to make the measurements while the balloon
was rotated about its longitudinal axis. The balloon when inflated
to 8 atmospheres internal water pressure (as described by the
longitudinal cross section of FIG. 10E) for a period of 1 minute or
less, had a minimum diameter of 6.89 mm and a maximum diameter of
6.93 mm at the center of its length. It was noted during the 8
atmosphere pressurization that the balloon portion 133 was
substantially straight with respect to the longitudinal axis of the
catheter shaft 101, and that the distance from the point at which
the balloon portion 133 was attached to the catheter shaft 101 to
the point on the balloon portion 133 at which the balloon was at
its full diameter was relatively short. This is to say that the
balloon when inflated possessed blunt ends of substantially the
same diameter as the midpoint of the length of the balloon portion
133, as opposed to having a tapered appearance along the length
with a smaller diameter adjacent the balloon ends. When deflated by
removing the entire volume of water introduced during the 8
atmosphere pressurization, the balloon at its mid-length had a
minimum diameter of 2.22 mm and a maximum diameter of 2.46 mm. This
silicone-PTFE composite balloon, when tested using a hand-held
inflation device, had a burst pressure of approximately 22
atmospheres (achieved beginning from zero pressure in about 30
seconds), reaching a maximum diameter of about 7.95 mm prior to
failure by rupture.
[0101] This example illustrates that the balloon, constructed as
described above using silicone and PTFE, exhibited a predictable
limit to its diametrical growth as demonstrated by the destructive
burst test wherein the balloon did not exceed the 8 mm diameter of
the porous PTFE film tube component prior to failure. The
compaction ratio as previously defined was 2.31 divided by 2.46, or
0.94, and the compaction efficiency ratio as previously defined was
2.22 divided by 2.46, or 0.90. The ability of the balloon to
inflate to the described pressures without water leakage
demonstrated effectively that the void spaces of the porous PTFE
had been substantially sealed by the elastomeric material.
[0102] A flow chart describing the process used to create the
balloon catheter described by this example is presented as FIG.
10F; it will be apparent that variations on this process may be
used to create the same or similar balloon catheters.
EXAMPLE 8
[0103] This example teaches a method of balloon catheter
construction using a catheter shaft made of elastomeric material.
While this example was made using only a single lumen silicone
catheter shaft with the lumen for intended for inflation, it will
be apparent that a dual or multiple lumen shaft may also be
used.
[0104] A silicone model 4 EMB 40 Arterial Embolectomy Catheter
manufactured by the Cathlab Division of American Biomed Inc.
(Irvine, Calif.) having a 4 fr shaft outside diameter (about 1.35
mm) and a length of 40 cm was acquired. The embolectomy catheter
included a Luer fitting at the proximal end of the shaft and a
balloon made of a silicone elastomer at the distal end of the
shaft. The most distal 20 cm portion of the catheter (including the
balloon) was cut off, and a 0.38 mm diameter wire was inserted
completely through the open lumen of the shaft. A cut,
approximately 5 mm in length, was made through the shaft wall
approximately 6.5 cm proximal from the distal end, exposing the
0.38 mm wire but not damaging the remainder of the shaft. As shown
by the longitudinal cross section of FIG. 11A, the resulting
opening 201 was intended to serve as the inflation port for the new
balloon which was to be constructed over this region of the
catheter shaft 219.
[0105] A segment of silicone tubing 123 approximately 8 cm in
length, having an approximate inner diameter of 1.40 mm, an
approximate outer diameter of 1.71 mm, and a durometer of Shore 60A
(Beere Precision Silicone, Racine, Wis.), was placed over the
distal end of the catheter shaft 219 such that the proximal edge of
the silicone tubing 123 was approximately 9.8 cm proximal from the
distal end of the catheter shaft 219. This was done very carefully
to ensure that no section of the silicone tubing 123 was
longitudinally stretched (i.e., under tension) when at its final
position on catheter shaft 219. Isopropyl alcohol was used as a
lubricant between the catheter shaft 219 and the silicone tubing
123.
[0106] While the elastomeric tubing used for this example was
silicone tubing, it is believed that other elastomeric tubing
materials such as polyurethane tubings may also be suitably
employed.
[0107] With the silicone tubing 123 placed correctly on the
catheter shaft 219, any residual alcohol was allowed to evaporate
for a generous amount of time, ensuring that the shaft 219 was
completely dry. Once free of residual alcohol, a small amount of
Medical Implant Grade Dimethyl Silicone Elastomer Dispersion In
Xylene (Part 40000, Applied Silicone, Ventura, Calif.) was applied
between the ends of the silicone tubing 123 and the underlying
exterior surface of the silicone catheter shaft 219. At each end of
the silicone tubing 123, a small blunt needle was inserted between
the ends of the silicone tubing 123 and the underlying silicone
catheter shaft 219 for a distance of approximately 7.5 mm as
measured in a direction parallel to the length of the catheter
shaft 219. The silicone elastomer dispersion was carefully applied,
using a 3 cc syringe connected to the blunt needle, around the
entire circumference of the shaft 219 such that the dispersion
remained within, and fully coated the 7.5 mm length of the area to
be bonded under the ends of the silicone tubing 123. The silicone
elastomer dispersion was then allowed to cure for approximately 30
minutes at ambient temperature, and then an additional 30 minutes
in an air convection oven set at 150.degree. C. Next, a length of
porous PTFE film as described above, approximately 1.0 cm wide, was
manually wrapped over the end regions of the silicone tubing 123
under which the silicone elastomer dispersion was present, and onto
the adjacent portions of the silicone catheter shaft 219 not
covered by the silicone tubing 123, for a length of approximately
7.5 mm measured from the ends of the silicone tubing 123. During
wrapping, the entire length of the porous PTFE film was coated with
a small amount of the silicone elastomer dispersion. Great care was
taken to ensure that the porous PTFE film was applied so that
approximately 3 overlapping layers (depicted schematically as
layers 125 in FIGS. 11A and 11B) covered each of the regions; the
very thin porous PTFE film did not add significantly to the outside
diameter of the catheter assembly 100. At this point the silicone
elastomer dispersion was allowed to cure for approximately 30
minutes at ambient temperature, and then an additional 30 minutes
in an air convection oven set at 150.degree. C.
[0108] Next, a film tube was constructed in the same manner as
described in Example 7. The silicone catheter shaft 219 with the
silicone tubing 123 affixed to it via porous PTFE film 125 and
silicone elastomer dispersion was then carefully coated with a thin
layer of a mixture of 2 parts MED1137 Adhesive Silicone Type A
manufactured by NuSil Silicone Technology (Carpinteria, Calif.) to
1 part n-Heptane (J. T. Baker, Phillipsburg, N.J.) by weight. The
1.76 mm inside diameter film tube was removed from the
silicone-Heptane mixture, and the coated silicone catheter shaft
219 was carefully fitted coaxially within the film tube 127 such
that the entire silicone tube 123 affixed to the catheter shaft
219, as well as an adjacent portion of the catheter shaft 219
proximal to both ends of the silicone tube 123, were covered by the
film tube 127. With the catheter shaft 219 and the affixed silicone
tube 123 covered by the film tube 127, the ends of the film tube
127 were trimmed so that the distal end of the film tube 127 was
located 7.5 mm distal from the distal end of the underlying
silicone tubing 123, and the proximal end was located 7.5 mm
proximal from the proximal end of the underlying silicone tubing
123. The exterior surface of film tube 127 was then helically
wrapped by hand with a length of 1.9 cm wide porous PTFE film, made
as described above, so that about 2 overlapping layers of film
covered its length. This film (not shown) was applied temporarily
as a securing means desired during the subsequent heating and
curing step. This distal portion of the catheter assembly 200 was
then placed into a steam bath for a period of time between 15 and
30 minutes.
[0109] The catheter assembly 200 was then removed from the steam
bath, and the outer helically-wrapped film layers were removed.
Next, lengths of porous PTFE film as described above, approximately
1.0 cm wide were manually wrapped over the ends of the film tube
127 approximately 15 mm proximal from the distal edge of the film
tube 127, and approximately 15 mm distal from the proximal edge of
the film tube 127. These regions were covered by approximately 3
overlapping film layers, shown schematically as layers 129.
Additionally a length of porous PTFE film (shown schematically as
layer 221) was wrapped helically along the length of the catheter
shaft 219 from the proximal edge of the silicone tube 123 to the
Luer fitting at the proximal end of the catheter shaft 219 so that
about 2 overlapping layers of film covered the catheter shaft 219,
and then another 2 layers of the same film were helically wrapped
over the first 2 layers at the same pitch angle (about 70 degrees)
with respect to the longitudinal axis, but in the opposite
direction. During wrapping, each length of porous PTFE film was
coated with a small amount of a mixture of equal parts of MED1137
Adhesive Silicone Type A, manufactured by NuSil Silicone Technology
(Carpinteria, Calif.), and n-Heptane (J. T. Baker, Phillipsburg,
N.J.) by weight. Great care was taken to ensure that the porous
PTFE film was applied without adding significantly to the catheter
diameter. This was possible as a result of the thin character of
the porous PTFE film. The catheter assembly 200 was then placed
into a steam bath for a minimum of 8 hours to achieve curing. After
curing the distal-most portion of the catheter shaft 219 was cut
off transversely at the distal-most edge 131 of the porous PTFE
film 129 on the exterior of the film tube 127, and the open
inflation lumen 107 was sealed by insertion of a 1 cm long section
of 0.38 mm wire 225 which was dipped into a mixture of equal parts
of MED1137 Adhesive Silicone Type A, manufactured by NuSil Silicone
Technology (Carpinteria, Calif.), and n-Heptane (J. T. Baker,
Phillipsburg, N.J.) by weight. The catheter assembly 200 was then
placed into a steam bath for a minimum of 8 hours to achieve final
curing.
[0110] At this point, the diameter of balloon portion 133 was
measured in a pre-inflated state. The minimum diameter was found to
be 2.13 mm and the maximum diameter 2.28 mm. As before, these
measurements were taken from approximately the midpoint of the
balloon, and a Lasermike model 183, manufactured by Lasermike,
(Dayton, Ohio) was used to make the measurements while the balloon
was rotated about its longitudinal axis. The balloon when inflated
to 8 atmospheres internal water pressure (as described by the
longitudinal cross section of FIG. 11B) for a period of 1 minute or
less, had a minimum diameter of 6.00 mm and a maximum diameter of
6.11 mm at the center of its length. When deflated by removing the
entire volume of water introduced during the 8 atmosphere
pressurization, the balloon at its mid-length had a minimum
diameter of 2.16 mm and a maximum diameter of 2.64 mm. This
silicone-PTFE composite balloon, when tested using a hand-held
inflation device had a burst pressure of approximately 21
atmospheres (achieved beginning from zero pressure in about 30
seconds), reaching a maximum diameter of about 7.54 mm prior to
failure. The balloon failed by developing a leak in the silicone
tubing component 123 of the balloon portion 133. The leak caused
separation between the film tube 127 and the silicone tubing 123,
allowing fluid to pass through the film tube 127.
[0111] This illustrates that the balloon, constructed as described
above using silicone and PTFE, exhibited a predictable limit to its
diametrical growth as demonstrated by the destructive burst test
wherein the balloon did not exceed the 8 mm diameter of the porous
PTFE film tube component prior to failure. The compaction ratio as
previously defined was 2.28 divided by 2.64, or 0.86, and the
compaction efficiency ratio as previously defined was 2.16 divided
by 2.64, or 0.82. Additionally, the presence of the porous PTFE
film helically wrapped around the silicone catheter shaft 219
provided sufficient strength to enable the silicone catheter shaft
219 to withstand the relatively high pressures associated with
angioplasty.
[0112] Another balloon was constructed in an identical manner as
described above, except that the length of the silicone catheter
shaft 219 from the proximal edge of the silicone tube 123 to the
Luer fitting at the proximal end of the shaft 219 was not covered
by porous PTFE film 221. When the balloon portion 133 was measured
in a pre-inflated state the minimum diameter was found to be 2.14
mm and the maximum diameter 2.21 mm. These measurements were made
as described above. The balloon when inflated to 8 atmospheres
internal water pressure for a period of 1 minute or less, had a
minimum diameter of 5.98 mm and a maximum diameter of 6.03 mm at
the center of its length. When deflated by removing the entire
volume of water introduced during the 8 atmosphere pressurization,
the balloon at its mid-length had a minimum diameter of 2.10 mm and
a maximum diameter of 2.45 mm. This silicone-PTFE composite
balloon, when tested using a hand-held inflation device had a burst
pressure of approximately 15 atmospheres, reaching a maximum
dimension of about 6.72 mm prior to failure. The failure mode of
the balloon was shaft rupture.
[0113] This illustrates that the balloon, constructed as described
above using silicone and PTFE exhibited a predictable limit to its
diametrical growth as demonstrated by the destructive burst test
wherein the balloon did not exceed the 8 mm diameter of the porous
PTFE film tube component prior to failure. The compaction ratio as
previously defined was 2.21 divided by 2.45, or 0.90, and the
compaction efficiency ratio as previously defined was 2.10 divided
by 2.45, or 0.86. The absence of the porous PTFE film helically
wrapped around shaft allowed the balloon to fail at the shaft. The
ability of the balloon to inflate to the described pressures
without water leakage demonstrated effectively that the void spaces
of the porous PTFE had been substantially sealed by the elastomeric
material. A flow chart describing the process used to create the
balloon catheter described by this example is presented as FIG.
11C; it will be apparent that variations on this process may be
used to create the same or similar balloon catheters.
EXAMPLE 9
[0114] This example describes an alternative method of creating a
silicone-PTFE laminated balloon portion, and the use of the balloon
portion as an angioplasty balloon.
[0115] First, a catheter shaft was constructed in the same manner
as described in Example 7.
[0116] After completion of the catheter shaft, a film tube was
created as follows. A length of porous PTFE film, cut to a width of
2.5 cm, made as described above, was wrapped onto the bare surface
of an 8 mm stainless steel mandrel at an angle of approximately
70.degree. with respect to the longitudinal axis of the mandrel so
that about 5 overlapping layers of film covered the mandrel (i.e.,
any transverse cross section of the film tube transects about five
layers of film). Following this, another 5 layers of the same film
were helically wrapped over the first 5 layers at the same pitch
angle with respect to the longitudinal axis, but in the opposite
direction. The second 5 layers were therefore also oriented at an
approximate angle of 70.degree., but measured from the opposite end
of the axis in comparison to the first 5 layers. In the same
manner, additional layers of film were applied five layers at a
time with each successive group of five layers applied in an
opposing direction to the previous group until a total of about 30
layers of helically wrapped film covered the mandrel. This
film-wrapped mandrel was then placed into an air convection oven
set at 380.degree. C. for 11.5 minutes to heat bond the layers of
film, then removed from the oven and allowed to cool. Once cool,
the resulting film tube was removed from the 8 mm mandrel.
[0117] Next a 24 cm length of silicone tubing having an approximate
inner diameter of 1.40 mm, an approximate outer diameter of 1.71
mm, and a durometer of Shore 60A (Beere Precision Silicone, Racine,
Wis.) was fitted coaxially over a 1.14 mm diameter stainless steel
mandrel. After one end of the silicone tubing was secured onto the
mandrel by tying with thin thread, tension was applied to the other
end, stretching the tubing until its overall length was 31 cm. With
the tubing stretched to 31 cm the free end was also secured to the
mandrel using thin thread.
[0118] The 8 mm inside diameter film tube was then manually
tensioned longitudinally, causing it to reduce in diameter. The
film tube was then knotted at one end, and a blunt needle was
inserted into the other. Using a 20 cc syringe connected to the
blunt needle, a mixture of 1 part MED1137 Adhesive Silicone Type A
manufactured by NuSil Silicone Technology (Carpinteria, Calif.) to
4 parts n-Heptane (J. T. Baker, Phillipsburg, N.J.) by weight was
injected into the film tube. The mixture while in the lumen of the
film tube was pressurized manually via the syringe, causing it to
flow through the porous PTFE, completely wetting and saturating the
film tube.
[0119] Next, the 1.14 mm mandrel and the overlying silicone tubing
were coated with a mixture of 2 parts MED1137 Adhesive Silicone
Type A manufactured by NuSil Silicone Technology (Carpinteria,
Calif.) to 1 part n-Heptane (J. T. Baker, Phillipsburg, N.J.) by
weight. The blunt needle was removed from the PTFE film tube. The
1.14 mm mandrel and overlying silicone tubing were then fitted
coaxially within the film tube with the ends of the film tube
extending beyond the mandrel ends. The ends of the film tube were
then placed into a model 4201 Tensile Testing Machine manufactured
by Instron (Canton, Mass.) equipped with flat faced jaws and pulled
at a constant rate of 200 mm/min until a force between 4.8 and 4.9
kg was achieved. During pulling, the film tube was massaged,
ensuring contact between the PTFE and the silicone tubing. Small
needle holes were made into the film tube so that the resident
silicone-heptane mixture could escape. Once a force between 4.8 and
4.9 kg was achieved, the film tube was left within the jaws of the
machine for a minimum of 24 hours, allowing the silicone to cure
completely. Once the silicone was completely cured, the resulting
silicone-PTFE composite tubing was carefully removed from the 1.14
mm mandrel.
[0120] Although this example used the silicone tubing and the
porous PTFE film tube as separate substrates joined together in
laminated relationship, the balloon has also been constructed using
only the porous PTFE film tube made as described for example 7 and
impregnated with the elastomeric material (i.e., the balloon was
constructed without the silicone tubing substrate). For such a
construction, the use of a silicone elastomer dispersion in Xylene
is preferred as the elastomeric material intended to substantially
seal the void spaces in the porous PTFE tube (i.e., wherein a
substantial portion of the elastomeric material is located within
the void spaces within the porous PTFE tube). The balloon so
constructed was joined to the catheter shaft in the same manner
described as follows. The resulting balloon had a particularly thin
wall having excellent compaction efficiency ratio and compaction
ratio; a balloon catheter incorporating this balloon is anticipated
to be particularly useful as a neural balloon dilatation
catheter.
[0121] As shown by the longitudinal cross section of FIG. 12A, a
segment of the silicone-PTFE composite tubing 223 (comprising the
inner substrate of the elastomeric material (silicone tubing)
joined to the outer substrate of the porous PTFE film tube in
laminated relationship) approximately 9 cm in length was placed
over the distal end of the catheter shaft 101 such that such that
the proximal edge of the composite tubing 223 was approximately 7
mm distal from the point at which the catheter shaft 101 outer
diameter changed from 1.83 mm to 2.3 mm. This was done very
carefully to ensure that no section of the composite tubing 223 was
longitudinally stretched (i.e., under tension) when at its final
position on the catheter shaft 101. Isopropyl alcohol was used as a
lubricant between the catheter shaft 101 and the composite tubing
223.
[0122] With the composite tubing 223 placed correctly on the
catheter shaft 101, any residual alcohol was allowed to evaporate
for a generous amount of time, ensuring that the catheter shaft 101
was completely dry. Once free of residual alcohol, a small amount
of a mixture of equal parts of MED1137 Adhesive Silicone Type A
manufactured by NuSil Silicone Technology (Carpinteria, Calif.) and
n-Heptane (J. T. Baker, Phillipsburg, N.J.) by weight was applied
between the ends of the tubing 223 and the underlying exterior
surface of the catheter shaft 101 At each end of the silicone
tubing 223, a small blunt needle was inserted between the ends of
the tubing 223 and the underlying catheter shaft 101 for a distance
of approximately 7.5 mm as measured in a direction parallel to the
length of the catheter shaft 101. The mixture was carefully applied
using a 3 cc syringe connected to the blunt needle, around the
entire circumference of the catheter shaft 101 such that the
mixture remained within, and fully coated the 7.5 mm length of the
area to be bonded under the ends of the composite tubing 223. To
ensure that the adhesive did not migrate into the inflatable length
of balloon portion 133, prior to the application of the adhesive a
thin thread was temporarily wrapped around composite tubing
adjacent to the edge of porous PTFE film layer 125 closest to
balloon portion 133. Also, to ensure contact between the composite
tubing 223 and the catheter shaft 101, lengths of porous PTFE film
as described above, approximately 1.0 cm wide were helically
wrapped by hand over the composite tube over the areas in which the
silicone mixture was applied. This film (not shown) was applied
temporarily as a securing means desired during the subsequent
heating and curing step. The silicone mixture was then allowed to
cure within a steam bath for approximately 30 minutes. The catheter
was then removed from the steam bath, and the 1.0 cm wide PTFE film
was removed along with the temporary thread.
[0123] Next, a length of porous PTFE film as described above,
approximately 1.0 cm wide was manually wrapped over the end regions
of the composite tubing 223 under which the silicone mixture was
present, and onto the adjacent portions of the catheter shaft 101
not covered by the composite tube 223, for a length of
approximately 7.5 mm measured from the ends of the composite tubing
223. During wrapping, the entire length of the porous PTFE film was
coated with a small amount of a mixture of equal parts of MED1137
Adhesive Silicone Type A manufactured by NuSil Silicone Technology
(Carpinteria, Calif.) and n-Heptane (J. T. Baker, Phillipsburg,
N.J.) by weight. Great care was taken to ensure that the porous
PTFE film was applied so that approximately 3 overlapping layers
(depicted schematically as layers 125 in FIG. 12) covered each of
the regions without adding significantly to the diameter of the
catheter. Because of the reduced diameter region at the distal end
of dual lumen tubing 103 and the very thin character of the porous
PTFE film used for layers 125, the diameter of the catheter
assembly 100 at the location of film layers 125 was very close to
the diameter of catheter shaft 101 proximal to film layers 125.
Finally, the silicone mixture used to coat the porous PTFE film was
allowed to cure for a minimum of 8 hours within a steam bath.
[0124] At this point, the diameters of the balloon portion 133 were
measured in a pre-inflated state using the same methods described
above. The minimum diameter was found to be 2.21 mm and the maximum
diameter 2.47 mm. The balloon when inflated to 8 atmospheres
internal water pressure (as described by the longitudinal cross
section of FIG. 12B) for a period of 1 minute or less, had a
minimum diameter of 6.51 mm and a maximum diameter of 6.65 mm at
the center. It was noted during the 8 atmosphere pressurization
that the balloon portion was substantially straight with respect to
the longitudinal axis of the catheter shaft, and that the distance
from the point at which the balloon portion was attached to the
catheter shaft to the point on the balloon portion at which the
balloon was at its full diameter was relatively short. When
deflated by removing the entire volume of water introduced during
the 8 atmosphere pressurization, the balloon at its mid-length, had
a minimum diameter of 2.28 mm and a maximum diameter of 2.58 mm.
This silicone-PTFE composite balloon, when tested using a hand-held
inflation device, had a burst pressure of approximately 15
atmospheres (achieved beginning from zero pressure in about 30
seconds), reaching a maximum diameter of about 7.06 mm prior to
failure.
[0125] This example illustrates that the balloon, constructed as
described above using a silicone-PTFE composite balloon portion,
exhibited a predictable limit to its diametrical growth as
demonstrated by the destructive burst test wherein the balloon did
not exceed the 8 mm diameter of the porous PTFE film tube
component. The compaction ratio as previously defined was 2.47
divided by 2.58, or 0.96, and the compaction efficiency ratio as
previously defined was 2.28 divided by 2.58, or 0.88. The ability
of the balloon to inflate to the described pressures without water
leakage demonstrated effectively that the void spaces of the porous
PTFE had been substantially sealed by the elastomeric material.
[0126] A flow chart describing the process used to create the
balloon catheter described by this example is presented as FIG.
12C; it will be apparent that variations on this process may be
used to create the same or similar balloon catheters.
[0127] While particular embodiments of the present invention have
been illustrated and described herein, the present invention should
not be limited to such illustrations and descriptions. It should be
apparent that changes and modifications may be incorporated and
embodied as part of the present invention within the scope of the
following claims.
* * * * *