Note: Descriptions are shown in the official language in which they were submitted.
CA 02211567 1997-07-28
WO 96/24404 PCT/US96/01524
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ESOPHAGEAL DILATION BALLOON CATHETER
CONTAINING FLEXIBLE NITINOL WIRE
Descrit~tion
Technical Field
This invention relates generally to surgical devices, and
more particularly to catheters, dilators and other devices for
establishing, restoring or enlarging lumens in the body,
especially in the esophagus.
Background of the Invention
A variety of body lumens are subject to undesired
strictures or narrow regions. For example, blood vessels can be
blocked cr narrowed by atherosclerosis, while esophageal
strictures can arise from individual anatomical differences, or
from diseases such as connective tissue disorder. Procedures for
dilating or enlarging such strictures or narrowed regions often
entail the use of a balloon dilation catheter. Such catheters
include a deflated balloon which can be positioned across a
particular stricture or narrowed region, and which is then
inflated with a fluid in order to widen the lumen without trauma
to the wall of the lumen.
A variety of balloon catheters and dilators are known
which include a balloon attached to the distal end of a catheter
tube or shaft, and which also include a stainless steel wire
stiffener extending through the catheter shaft and balloon. For
example, a balloon dilator as disclosed in U.S. Patent No.
5,087,246 and sold under the tradename "ELIMINATOR" by C.R. Bard,
Inc. (Tewksbury, MA) includes a radiopague polyurethane catheter
tube having a stainless steel guide wire internally fixed therein
by an insert, and a high pressure, nondistending PET (polyethylene
terephthalate) balloon through which the guide wire also passes.
The stainless steel wire has a blunt end contained in a plastic
a 30 tip on the catheter. In use, the catheter is passed through the
channel of an endoscope until the balloon fully clears the distal
end of the endoscope channel and is positioned across the
stricture to be dilated, and a pressurizing liquid is supplied to
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the balloon through the catheter tube, so as to expand the balloon
and dilate the stricture.
A similar balloon catheter is sold under the tradename
"MaxForce TTS" and the registered trademark "MICROVASIVE" by
Boston Scientific Corporation (Watertown, MA). The insert for
fixing the stainless steel wire it contains is somewhat longer
than the insert of the Bard device, however, and its taz~ered
plastic catheter tip includes a ball on the end. A 'more
significant structural difference lies in the way in which the end
of the stainless steel wire stiffener is formed in the plastic
tip. In the plastic tip, fully outside and distal to the catheter
balloon, a second wire having a reduced and tapering diameter is
affixed by wrapping or welding to the stiffener wire.
A significant problem with these types of balloon
catheters is that their stainless steel stiffener wires tend to
kink or bend during introduction of the catheter into the
esophagus. Such kinking undesirably increases the risk that the
distal portion of the catheter will unintentionally advance
through the lumen wall, and perforate or rupture the esophagus or
other tissue defining the lumen. This trauma to the esophagus or
other tissue not only requires immediate termination of the
specific dilation procedure, it also requires immediate surgical
repair and drainage of the traumatized area, to avoid
complications such as mediastinitis and pleural effusion.
Tapering of the distal end of the stainless steel
stiffener wire, that is, at the catheter tip, is inadequate to
solve this problem. It has been found that the tapered portion
of the steel wire is even more susceptible to kinking than is the
rest of the steel wire, despite encasement of the taper in a
flexible plastic catheter tip. As a result, the catheter kinks
or bends at its distal end, and thereby retains the potential for
injuring the esophagus or other lumen wall during introduction
past the distal end of the endoscope channel. Even if the kinks
and permanent bends are not so severe as to penetrate the body
lumen, they are still undesirable because they restrict movement
of the catheter within the endoscope channel, making manipulation
of the catheter more difficult and prolonging the dilation
procedure.
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Other dilators and catheters are known, but they similarly
fail to solve this problem, or have their own drawbacks during
use. For example, U.S. Patent No. 4,597,755 (Samson et al., Jul.
1, 1986) discloses a large bore balloon catheter having a coil
spring secured to the distal end of a main shaft tube in the
region of a balloon, and flexible tubing positioned over the
exterior of the coil spring and extending beyond the distal end
of the spring. The coil spring aids resistance to kinking. U.S.
Patent No. 5,242,394 (Tremulis, Sep. 7, 1993) discloses a similar
l0 steerable dilation catheter which includes an elongated tubular
member, preferably a hypotube of stainless steel or nitinol. U.S.
Patent No. 5,232,445 (Bonzel, Aug. 3, 1993) discloses a coronary
dilation balloon catheter which is slidable along a guidewire
extending through a balloon, and which includes a segment of
flexible tubing through the balloon for passage of the guidewire.
Finally, U.S. Patent No. 5,269,793 (Simpson, Dec. 14, 1993)
discloses a guide system for intravascular catheters which
includes both a fixed guide wire extending through and secured to
the distal end of a balloon, and a movable guide wire. With
respect to the present disclosure, it should be noted that the use
of the guide wires in these latter two devices may encounter the
same risks of tissue perforation or rupture as may be encountered
in the use of the Bard and Boston Scientific devices.
Summary of the Invention
The foregoing problems are solved and a technical advance
is achieved in an illustrative balloon dilation catheter or other
catheter. Applicant has discovered that the undesirable kinking
and bending encountered in the use of balloon catheters having
stainless steel stiffener wires can be reduced several or even
many times, by an elegant yet remarkably simple expedient -- using
a nitinol wire stiffener in place of the stainless steel stiffener
wire. The nitinol wire has a transition temperature well below
the temperature of the body and thereby remains superelastic and
extremely flexible during the use of the catheter, permitting the
catheter to remain essentially unkinked during use. The nitinol
wire thereby improves the pushability and trackability of the
-,
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catheter, that is, it renders the catheter easier to manipulate,
in contrast to catheters containing stainless steel wires.
More particularly, balloon and other catheters according
to the present invention can be passed through turns of
substantially sharper radius without encountering appreciable
kinking or permanent bending, in comparison to prior catheters of
comparable size employing stainless steel. "Substantially sharper
radius" means that the radius of curvature at the bend can be a
small fraction, typically one-third to one-tenth, of a radius bend
which would appreciably kink a stainless steel-stiffened catheter.
The determination of whether a particular degree of kinking or
bending is appreciable is a practical one, and is not readily
subject to being stated in numerical terms. However, it is
believed that those even rudimentarily skilled in this art should
readily be able to determine whether a particular kink or
permanent bend unacceptably interferes with the utility of a
particular catheter or dilator. In the absence of any practical
interference, and in the absence of any increase in the risk of
tissue perforation or rupture, a particular kink or bend should
not be considered appreciable. The important point to note in
this regard is that the catheter of the present invention remains
usable when subjected to turn radii which would unarguably render
stainless steel-stiffened catheters unusable.
In a first aspect, then, the present invention is directed
to a flexible and kink-resistant balloon catheter comprising: a
catheter shaft including a flow lumen defined therein, the
catheter shaft having a distal end; a catheter balloon connected
to the distal end of the catheter shaft, having an interior in
fluid communication with the flow lumen of the catheter shaft; a
flexible catheter tip on the catheter balloon opposite the
catheter shaft; and a nitinol wire positioned in at least the
catheter balloon and the flexible tip on the catheter balloon, the
nitinol wire including a distal end contained in the flexible
catheter tip; characterized in that the nitinol wire is solid but
flexible and comprises a uniformly tapered portion extending from
the location within the catheter balloon interior the entire
length of the wire distal to the location, such that the nitinol
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wire solely and by itself provides the balloon catheter with a
continuous resistance to transverse deflection over its entire
length distal to the location, whereby the nitinol wire itself
prevents appreciable kinking of the balloon catheter distal to the
location.
Preferably, the nitinol wire extends the entire length of
the catheter shaft within the flow lumen. Also preferably, the
catheter further comprises a radiopaque insert in the distal end
of the catheter shaft which fixes the longitudinal position of the
nitinol wire and catheter balloon with respect to one another.
The catheter balloon is conveniently nondistending and can be -
composed of PET or another medical grade material. Also
conveniently, the catheter can further include a Luer-lock hub
connected to the catheter shaft opposite the distal end of the
shaft .
This first aspect of the invention finds particular
utility in esophageal dilators.
In a second aspect, the present invention is directed to
an improvement in catheters of any type, balloon or otherwise,
which include a flexible catheter shaft with a flow lumen defined
therein, a flexible catheter tip connected to the catheter shaft
and a flexible nitinol wire contained in the catheter shaft and
the catheter tip, the nitinol wire including a distal end
contained in the flexible catheter tip; the improvement comprising
a uniformly tapered portion on the nitinol wire extending from a
location proximal of the flexible catheter tip, the uniformly
tapered portion extending the entire length of the wire distal to
the location, such that the nitinol wire solely and by itself
provides the catheter with a continuous resistance to transverse
deflection over its entire length distal to the location, whereby
the nitinol wire itself prevents appreciable kinking of the
catheter distal to the location. The improvement is preferably
embodied in a balloon catheter in which the catheter balloon
connects the catheter tip to the catheter shaft. The improvement
preferably further comprises the various parts mentioned above.
It is important to note that this aspect of the present invention
is not limited to balloon or large bore catheters, such as
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esophageal dilators. It does, however, find particular utility
in esophageal dilators.
Brief Description of the Drawing
A better understanding of the present invention will now
be had upon reference to the following detailed description, when
read in conjunction with the accompanying drawing, wherein like
reference characters refer to like parts throughout the several
views, and in which:
FIG. 1 is a perspective view of the preferred embodiment
of the present invention;
FIG. 2 is an enlarged cross-sectional view taken in the
plane of FIG. 1 and as taken along line 2-2 of FIG. 3;
FIG. 3 is a cross-sectional view taken along line 3-3 of
FIG. 2; and
FIG. 4 is a partial view of the preferred embodiment of
the present invention, during endoscopic use.
Detailed Description
With reference to FIGs. 1 and 2, a flexible and kink-
resistant catheter according to the present invention is
thereshown, embodied in an esophageal dilation balloon catheter
10. The balloon catheter 10 first comprises a tubular catheter
shaft 12 including a flow lumen defined therein, and a distal end
16 adapted for insertion into the body through an endoscopic
channel. The catheter shaft 12 is preferably composed of a
flexible, medical grade tubing such as polyurethane. The
particular dimensions of the catheter shaft 12 are selected as
convenient; for esophageal applications, for example, the shaft
12 can be about 200 cm long (but, as explained further below, cut
to match the size of the contained nitinol wire), 2.16 mm (0.085
inches) in outer diameter, and about 1.47 mm (0.058 inches) in
inside diameter.
The catheter 10 also comprises a nondistending catheter
balloon 18 connected to the distal end 16 of the catheter shaft
12. The balloon 18 is preferably composed of a physiologically
inert, medical grade synthetic, such as PET (polyethylene
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FIy-5095 PCT
terephthalate) or the like. The balloon 18 has an interior 20 in
fluid communication with the flow lumen 14 in the catheter shaft
12. However, for ease of introduction of the balloon 18 into the
body and across the stricture of interest, the balloon 18 is
initially maintained in an empty, collapsed state. The balloon
18 overlaps the distal end 16 of the catheter shaft 12 and is
connected to and sealed to it by a suitable medical grade
adhesive, for example, an ultraviolet curing adhesive. For
esophageal applications, it has been found convenient to employ
a balloon 18 having length of about 8 cm and a diameter (when
expanded from its collapsed state) of about 6 to 18 mm. The
process for making the balloon 18 is explained in more detail
below.
The catheter 10 next comprises a flexible catheter tip 22
attached to the catheter balloon 18 opposite the catheter shaft
12. The balloon 18 thus connects the catheter tip 22 to the
catheter shaft 12. The flexible tip 22 is conveniently composed
of a medical grade elastomeric tubing such as Pellethane 2363-
80AE, and can be attached to the balloon 18 with the same adhesive
as is used to affix the balloon 18 to the catheter shaft 12. Most
conveniently, the flexible tip 22 can be formed from tubing
composed of the indicated.elastomer, and the central bore of the
tubing filled with the adhesive during assembly of the catheter
10. The most distal end of the flexible catheter tip 22 is
rounded; conveniently, however, an additional round bead (not
shown) may be formed on the most distal end of the flexible tip
22, to facilitate introduction of the catheter 10 into the
endoscope channel and the body lumen.
The catheter 10 of the present invention further comprises
a solid but flexible nitinol wire 24 positioned in at least the
catheter balloon 18 and the flexible catheter tip 22. Preferably,
the nitinol wire 24 is located within the catheter shaft flow
lumen 14, and extends the entire length of the catheter shaft 12.
The length of the nitinol wire 24 is selected as convenient; for
example, for esophageal applications, the wire 24 can be about 195
cm long.
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The precise nitinol composition used for the wire 24 is
not believed to be critical to the successful practice of the
present invention, as long as the nitinol being used possesses a
transition temperature well below body temperature, and possesses
its conventional superelasticity and flexibility at body
temperature.
As more clearly shown in FIG. 2, the nitinol wire 24
includes a distal end 26 contained in the flexible catheter tip
22, and a uniformly tapered portion 28 extending from a location
30 within the catheter balloon interior 20 to the distal wire end
26. Preferably, the diameter of the tapered portion 28 of the
nitinol wire 24 decreases by about two-thirds from the location
30 within the balloon interior 20, to the distal wire end 26. For
esophageal applications, the tapered portion 28 of the nitinol
wire 24 is conveniently about 2.5 to 7.6 cm (one to three inches)
and preferably about 5.1 cm (2 inches) long, but these limits
arise as much from manufacturing concerns as from criteria for
utility.
Conveniently, the nitinol wire 24 is uniform throughout
its length, except for the tapered portion 28. For esophageal
applications, the bulk of the nitinol wire 24 has a diameter of
about 0.69 mm (0.027 inches), while the diameter of the tapered
portion 28 ranges from this same diameter at the location 30 where
tapering begins, down to about 0.25 mm (0.010 inches) at the
distal end 26 of the wire 24.
It may be desirable to select a material for the catheter
shaft 12 which is radiopaque. This allows the position of the
catheter balloon 18 to be established during introduction into the
body lumen, for example, the esophagus. However, the same effect
may be achieved by positioning an axially perforate, radiopaque
insert 32 in the distal end 16 of the catheter shaft 12, and
making the shaft 12 of a material which is not radiopaque and
which may be less costly than radiopaque materials. The insert
32 preferably simultaneously serves another purpose, specifically,
to fix the longitudinal position of the nitinol wire 24 and the
catheter balloon 18 with respect to one another.
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The insert 32 is conveniently composed of a
physiologically inert, radiopaque material such as 303 stainless
steel. The insert 32 is conveniently retained in the distal end
16 of the catheter shaft 12 by a plurality of barbs 33 on its
outer surface, which embed in the material of the shaft 12. When
retained in this manner, the insert 32 can have an outside
diameter about the same as the outside diameter of the catheter
shaft 12, and an inside diameter slightly smaller than the inside
diameter of the shaft 12.
It has been found that it is difficult to affix the
nitinol wire 24 directly to the stainless steel insert 32 by
conventional methods such as soldering. This problem is solved
by using a separate element connected to and between the insert
32 and the wire 24. More particularly, as more clearly shown in
FIG. 3, the insert 32 comprises an internally located cannula 34
through which the nitinol wire 24 passes. The cannula 34 is
composed of any physiologically inert metal which can be easily
affixed to stainless steel in any conventional manner, for
example, by soldering with No. 430 solder (4o Ag, 96% Sn).
Conveniently, the cannula 34 is composed of a 1.3 cm (half-inch)
long piece of 304 stainless steel of size GA-21XX. The wire 24
is secured in the insert 32 by firmly crimping the cannula 34 onto
the wire 24. This positively fixes the longitudinal position of
the nitinol wire 24 and the catheter balloon 18 with respect to
one another, since each is affixed to the catheter shaft 12.
Returning again to FIGS. 1 and 2, the catheter 10
preferably includes a conventional means for engaging the catheter
10 with devices (not shown) for supplying an inflation fluid to,
and withdrawing an inflation fluid from, the flow lumen 14 of the
catheter 10. Conveniently, this engaging means can be a female
luer hub 38 connected to the catheter shaft 12 opposite the distal
end 16 of the shaft 12. The luer hub 38 is of any convenient size
or style, for example, ANSI/HIMA MD70.1-1983. The hub 38 can be
composed of any physiologically inert, medical grade and generally
rigid material. In order to ensure that the nitinol wire 24 does
not interfere with connection to the luer hub 38, and to further
fix the position of the nitinol wire 24, the wire 24 is formed so
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as to pass through a lateral port 40 formed through the catheter
shaft 12, and embedded inside the luer hub 38.
Manufacture of the balloon catheter 10 described above
entails several steps, but can be readily understood. It is
important that the manufacture be carried out in compliance with
good manufacturing practices (GMPs) and that the construction,
attachment and sealing of the various parts be monitored
carefully, to ensure that the balloon 18 can expand to its desired
diameter when inflated under pressure, without leaking or release
of the inflating liquid.
The nitinol wire 24 is first prepared by cutting it to the
indicated length, grinding the tapered portion 28 to the indicated
diameter and length. The wire is then inserted into a length of
catheter shaft tubing, the formed portion passed through the port
40, and the tubing and wire 24 positioned in the luer hub 38.
Depending upon the materials used, the hub 38 may be and
preferably is molded about the tubing and nitinol wire 24.
Next, the cannula 34 is soldered to the balance of the
stainless steel insert 32, the catheter tubing cut to the desired
length of the catheter shaft 12, the insert 32 placed into the
distal end 16 of the catheter shaft 12 so that the nitinol wire
24 passes through the cannula 34, and the cannula 34 firmly
crimped on the wire 24. This assembly is now ready for attachment
of the catheter balloon 18.
The balloon 18 is then slipped over the distal end 26 of
the wire 24 and the flexible tip 22 bonded to the distal end of
the balloon 18. The proximal end of the balloon 18 is then bonded
to the distal end 16 of the catheter shaft 12, and the flexible
tip 22 bonded to the distal end 26 of the wire 24. Again, all of
this bonding is conveniently carried out with a UV-curing adhesive
or the like. A bit of excess adhesive is left to form a rounded
end or ball on the extremity of the flexible tip 22. The balloon
18 is then compressed or folded to facilitate its introduction
into the channel of the endoscope. For convenience, between its
manufacture and use the balloon 18 may be covered with a
polyurethane or other protective sleeve (not shown).
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. CA 02211567 1997-07-28
PH- 5 (1 ~ 5 PC'I-
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Use of the catheter 10 for enlarging a stricture in the
esophagus is straightforward and conventional. Only a general
outline of the procedure follows; those skilled in the art will
be well aware of such procedures, and the major difference between
the use of prior devices and the catheter of the present invention
lies in the substantial reduction in kinking that will be
encountered.
As generally shown in FIG. 4, an endoscope 46 is first
introduced into a body lumen, such as the esophagus 44, and the
distal end 48 of the endoscope channel 50 positioned next to the
stricture to be dilated. The catheter 10 is inspected to ensure
that it is initially undamaged and free of kinks, and to ensure
that the catheter balloon 18 is fully deflated. The catheter 10
is attached at the luer hub 38 to a conventional coupling or
connector 42, for supplying an inflating fluid to the balloon 18
(through the catheter shaft flow lumen 14), and withdrawing the
fluid from the balloon 18 (again, through the lumen 14).
Conveniently, the fluid may be either radiopaque or transparent;
saline, water or a contrast mixture are all suitable as inflation
fluids. A vacuum draw to ensure initial deflation of the balloon
18 may be established through one arm of the coupling 42 to
achieve deflation.
The flexible tip 22, the catheter balloon 18 and the
distal end 16 of the catheter shaft 12 are then introduced in
sequence into the endoscope channel 50, and the catheter shaft 12
manipulated to advance the balloon 18 and flexible tip 22 through
the endoscope channel 50 to the stricture. The balloon 18 is
advanced until it lies across the stricture. Care must be taken
to ensure that the balloon 18 is completely beyond the distal end
48 of the endoscope channel 50 before inflation of the balloon 18
is begun.
The inflating fluid is supplied under pressure through the
. coupling 42, and thus through the flow lumen 14 of the catheter
shaft 12, to the interior 20 of the balloon 18 in order to inflate
the balloon 18 and dilate the stricture in the body lumen 44. The
catheter balloon 18 is shown in its inflated condition in FIG. 4,
where dilation of the body lumen 44 has been achieved.
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Removal of the catheter 10 from .the body lumen 44 is
essentially a reversal of the introduction scheme. First, the
catheter balloon 18 must be fully deflated, and all fluid possible
drawn from it. Care must be taken to ensure that the balloon 18
is not withdrawn back into the endoscope channel 50 until the
balloon 18 is fully deflated. The proximal end of the catheter
is grasped, and the catheter 10 carefully withdrawn from the
endoscope channel.
It is thus clear that the present invention provides a
10 simple yet extremely kink-resistant balloon dilation catheter or
other catheter which is useful in endoscopic or other surgical
procedures. This resistance to kinking is achieved by the use of
a nitinol wire extending through at least the catheter balloon and
catheter tip, and preferably extending through the entire length
of the catheter lumen.
Industrial Agplicability
The present invention is useful in the performance of
surgical procedures, and therefore finds applicability in human
and veterinary medicine.
It is to be understood, however, that the above-described
dilator, catheter or the like is merely an illustrative embodiment
of the principles of this invention, and that other dilators,
catheters or the like, and methods for using them, may be devised
by those skilled in the art, without departing from the spirit and
scope of the invention. It is also to be understood that the
invention encompasses embodiments both comprising and consisting
of the disclosed parts. It is also to be understood that the
proximal end of balloon 18 does not need to be connected to the
distal end 16 of catheter shaft 12. The connection of the balloon
can be proximal to distal end 16, namely in the region of or in
the vicinity of the distal end. It is also to be understood that
catheter tip 22 on catheter balloon 18 can be part of the balloon
itself or merely attached on the end of the balloon. Catheter
shaft 12 can, with holes in it, extend towards the distal end of
the balloon. Accordingly, the catheter tip can extend from or is
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a part of the balloon, i.e., a flexible catheter tip of or on the
catheter balloon.
It is further contemplated that flexible nitinol wire 24
defines a particular type of composition exhibiting well-known
S "superelastic" properties. This superelastic property is
typically exhibited when a composition is in an austenitic state
above its transformation temperature and the martensitic state.
Thus, it is contemplated that a nitinol wire includes all types
of a nitinol like material which exhibits a superelastic property.
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