U.S. patent application number 09/382610 was filed with the patent office on 2001-08-23 for shaft for medical catheters.
Invention is credited to LEGUIDLEGUID, ROY, MUNI, KETAN P., OMALEKI, SAMUEL L..
Application Number | 20010016705 09/382610 |
Document ID | / |
Family ID | 21829947 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010016705 |
Kind Code |
A1 |
OMALEKI, SAMUEL L. ; et
al. |
August 23, 2001 |
SHAFT FOR MEDICAL CATHETERS
Abstract
Several improvements are provided in the design of a catheter
shaft to reduce costs and improve performance. In one aspect, a
small notch is fabricated into a catheter tube by a nonlaser
process such as electric discharge machining (EDM) or mechanical
grinding. This notch in the catheter tube is necessary for fluid
communication between the catheter lumen and a balloon or other
element in communication with the tube. Use of a nonlaser process
reduces the costs of fabrication while ensuring a high degree of
structure integrity. In another aspect, a method is provided to
produce a nonuniform polymer coating on a catheter shaft to reduce
friction and to maintain a catheter with a low profile. In another
aspect, the catheter is provided with a radiopaque marker which is
more visible and is more effective at identifying the location of a
balloon. The marker is moved closer to a distal balloon by placing
it within an adhesive taper adjacent the balloon.
Inventors: |
OMALEKI, SAMUEL L.; (MORGAN
HILL, CA) ; LEGUIDLEGUID, ROY; (UNION CITY, CA)
; MUNI, KETAN P.; (SAN JOSE, CA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
620 NEWPORT CENTER DRIVE
SIXTEENTH FLOOR
NEWPORT BEACH
CA
92660
US
|
Family ID: |
21829947 |
Appl. No.: |
09/382610 |
Filed: |
August 25, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09382610 |
Aug 25, 1999 |
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09026105 |
Feb 19, 1998 |
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6228072 |
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Current U.S.
Class: |
604/103.06 ;
604/265 |
Current CPC
Class: |
A61M 25/1036 20130101;
A61M 25/104 20130101; A61M 2025/0046 20130101; A61M 2025/1079
20130101 |
Class at
Publication: |
604/103.06 ;
604/265 |
International
Class: |
A61M 029/00 |
Claims
What is claimed is:
1. A catheter, comprising: a tubular body having proximal and
distal sections, the tubular body having a lumen extending
therethrough; an expandable member with an interior volume mounted
on the distal section of the tubular body, the expandable member
having proximal and distal ends; a notch formed by electric
discharge machining in the tubular body for providing fluid
communication between the lumen and the interior volume of the
expandable member; a nonuniform polymer coating formed on at least
a portion of the tubular body to provide a substantially
frictionless surface; a marker mounted on the distal section of the
tubular body adjacent the proximal end of the expandable member;
and a taper formed from the proximal end of the expandable member
and covering the distal marker.
2. A catheter, comprising: a tubular body having proximal and
distal sections, the tubular body having a lumen extending
therethrough; and a notch formed by electric discharge machining in
the tubular body.
3. The catheter of claim 2, further comprising an expandable member
with an interior volume mounted on the distal section of the
tubular body, wherein the notch provides fluid communication
between the lumen and the interior volume of the expandable
member.
4. The catheter of claim 3, wherein the notch has a length of about
1.5 mm and a width of about 0.003 inches.
5. A notch for a catheter body formed by electric discharge
machining.
6. A method of manufacturing a notch in a catheter body, comprising
the step of electric discharge machining at least a portion of the
catheter body.
7. A catheter, comprising: a tubular body having proximal and
distal sections, the tubular body having a lumen extending
therethrough; and a notch formed by mechanical grinding of the
tubular body.
8. The catheter of claim 7, further comprising an expandable member
with an interior volume mounted on the distal section of the
tubular body, wherein the notch provides fluid communication
between the lumen and the interior volume of the expandable
member.
9. The catheter of claim 8, wherein the notch has a length of about
1.5 mm and a width of about 0.003 inches.
10. A notch for a catheter body formed by mechanical grinding.
11. A method of manufacturing a notch in a catheter body comprising
the step of mechanically grinding at least a portion of the
catheter body.
12. A catheter, comprising: an elongate shaft; a nonuniform polymer
coating formed onto at least a portion of the shaft to provide a
substantially frictionless surface.
13. The catheter of claim 12, wherein the nonuniform polymer
coating is produced by sputter coating.
14. The catheter of claim 12, wherein the nonuniform coating is
produced by selectively spraying a polymer coating onto the
shaft.
15. The catheter of claim 12, wherein the elongate shaft is
substantially cylindrical.
16. The catheter of claim 13, wherein the nonuniform coating formed
onto at least a portion of the shaft provides a coating
substantially 360 degrees around the shaft.
17. The catheter of claim 13, wherein the nonuniform coating formed
onto at least a portion of the shaft provides a coating less than
360 degrees around the shaft.
18. The catheter of claim 12, wherein the nonuniform coating is
formed by coating the shaft with a polymer coating of varying
thickness.
19. The catheter of claim 12, wherein the nonuniform coating is
formed by providing coated and uncoated portions on the shaft.
20. The catheter of claim 12, wherein the polymer coating is made
of a polytetrafluoroethylene.
21. A method of lubricating a catheter shaft, comprising the step
of coating the catheter shaft with a polymeric material to form a
nonuniform coating on the catheter shaft.
22. The method of claim 21, wherein the step of coating comprises
selectively spraying the polymeric material onto the shaft.
23. The method of claim 21, wherein the step of coating comprises
sputter coating the polymeric material onto the shaft.
24. The method of claim 21, wherein the step of coating produces a
nonuniform coating of varying degrees of thickness.
25. The method of claim 21, wherein the step of coating produces a
nonuniform coating on the shaft wherein coated and uncoated
portions are provided on the shaft.
26. A method of reducing the profile of a medical catheter,
comprising the step of producing a nonuniform coating on the
catheter.
27. The catheter of claim 26, wherein the nonuniform coating is
formed by coating the catheter with a polymer coating of varying
thickness.
28. The catheter of claim 26, wherein the nonuniform coating is
formed by providing coated and uncoated portions on the
catheter.
29. The catheter of claim 26, wherein the coating is made of a
polytetrafluoroethylene.
30. A catheter, comprising: an elongate body having proximal and
distal sections; an expandable member mounted on the distal section
of the tubular body, the expandable member having proximal and
distal ends; a marker mounted on the distal section of the elongate
body adjacent the proximal end of the expandable member; and a
taper formed from the proximal end of the expandable member in a
proximal direction to the elongate body and covering the distal
marker.
31. The catheter of claim 30, wherein the marker is a tube.
32. The catheter of claim 30, wherein the marker is radiopaque.
33. The catheter of claim 30, wherein the marker is located within
about 3 mm of the proximal end of the expandable member.
34. The catheter of claim 30, wherein the taper is formed from a
cyanoacrylate adhesive.
35. The catheter of claim 30, wherein the marker has an outer
diameter of at least about 0.020 inches.
36. A method of manufacturing a balloon catheter having a
radiopaque marker, comprising the steps of: providing an elongate
body with proximal and distal ends; providing a balloon having
proximal and distal ends; providing a radiopaque marker; mounting
the balloon over the elongate body so that the balloon is in an
appropriate position for balloon bonding; mounting the marker over
the elongate body at a position adjacent the proximal end of the
balloon forming a gap between the marker and the balloon; and
forming a taper from the proximal end of the balloon to the
elongate body toward the proximal end of the elongate body, the
taper filling the gap between the balloon and the marker and
covering the marker.
37. The method of claim 36, wherein the taper is a cyanoacrylate
adhesive.
38. The method of claim 36, wherein the marker is positioned within
about 3 mm of the proximal end of the balloon.
39. A catheter, comprising: an elongate shaft; a radiopaque marker
for locating a desired point on the shaft; and an adhesive taper
covering the marker.
40. A method of locating a desired point on a catheter when
inserted inside a human body, comprising the steps of: providing an
elongate catheter shaft; providing a radiopaque marker located at
the desired point on the catheter shaft; and forming a taper
covering the marker.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to surgical device
design and fabrication and, more particularly, to a shaft for
medical catheters.
[0003] 2. Background of the Invention
[0004] Medical catheters, such as balloon catheters, have been
proven efficacious in treating a wide variety of blood vessel
disorders. Moreover, these types of catheters have permitted
clinicians to treat disorders with minimally invasive procedures
that, in the past, would have required complex and perhaps life
threatening surgeries. For example, balloon angioplasty is now a
common procedure to alleviate stenotic lesions (i.e., clogged
arteries) in blood vessels, thereby reducing the need for heart
bypass operations.
[0005] Previously known catheters are of complex construction,
requiring expensive manufacturing steps and construction of great
precision to navigate the tortuous pathways of a vessel network.
For instance, when a catheter provides inflation fluid to a
balloon, a small notch is typically provided in the catheter tube
to allow fluid to pass from a lumen within the tube to the balloon.
The conventional method for manufacturing this notch is with a
laser, which is expensive and often cannot be done in-house.
Further, use of a laser creates a heat-affected zone which can lead
to fracture of the notch. Moreover, the heat from the laser may
cause deformation of the material. This is especially problematic
when a straight catheter made of a nickel-titanium alloy is
desired. Because the properties of NiTi alloys are extremely
temperature sensitive, laser notching may cause buckling or
unwanted curvature in the material. Accordingly, there is a need
for a notch-forming process which will not cause damage to the
material.
[0006] Further, profile is often a concern for catheters because of
the small space in which the catheters will be inserted. In
addition, because catheters must be passed through a tortuous blood
vessel network to reach the intended treatment site, it is
desirable that the catheters be substantially frictionless to
reduce harmful contact with blood vessel walls. Catheters therefore
are generally provided with a coating that will increase lubricity
of the catheter. These coatings add additional, undesired size to
the catheter. Thus, there is a need for a substantially
frictionless catheter surface which does not add significant
profile to a catheter tube.
[0007] In navigating the pathways of a vessel network, a radiopaque
marker is often necessary to identify a specified location on the
catheter. Such markers are typically placed on the catheter tube
near the location of a distal balloon. However, in medical devices
employing aspiration catheters and the like, visibility problems
often arise with such markers because they are typically made small
in order to allow the aspiration catheter to be passed over the
marker as it extends towards the distal balloon. Accordingly, there
is a need for balloon catheters having markers which can better
identify the location of a balloon while inside a blood vessel.
SUMMARY OF THE INVENTION
[0008] The present invention addresses the needs raised above by
providing several improvements in the design of a shaft for medical
catheters. In one aspect, a small notch is fabricated into a
catheter tube by a nonlaser process such as electric discharge
machining (EDM) or mechanical grinding. This notch in the catheter
tube is necessary for fluid communication between the catheter
lumen and a balloon or other element in communication with the
tube. Use of a nonlaser process reduces the costs of fabrication
while ensuring a high degree of structural integrity.
[0009] In another aspect of the present invention, a method is
provided to produce a thinner coating on a catheter shaft to reduce
friction with vessel walls. To maintain a surface with a low
friction coefficient while keeping the profile of the catheter low,
the catheter is sputter coated with Teflon or similar material to
produce a nonuniform coating. This nonuniform coating may extend
360 degrees around the catheter tube, and may even provide a
coating of less than 360 degrees while still maintaining good
lubricity.
[0010] In yet another aspect, a catheter wire or tube is provided
with a radiopaque marker which is more visible and is more
effective at identifying the location of a balloon on the catheter.
The marker is moved closer to a distal balloon by placing it within
an adhesive taper adjacent the balloon. By placing the marker in
the taper, the marker can be made larger and more visible without
obstructing the placement of an aspiration catheter or other type
of catheter over the catheter wire or tube. Specifically, the
marker in being placed inside the taper and closer to the balloon
can act as a stopper to the aspiration catheter and prevent damage
to the balloon.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a side view of the catheter of the present
invention.
[0012] FIG. 2 is a longitudinal cross-sectional view of the distal
end of a catheter having the improvements of the present
invention.
[0013] FIG. 3 is an enlarged cross-sectional view along area 3-3 of
FIG. 2.
[0014] FIG. 4A is a cross-sectional view along line 4-4 of FIG. 1
showing a nonuniform coating on the catheter.
[0015] FIG. 4B is a cross-sectional view along line 4-4 of FIG. 1
showing an alternate embodiment of a nonuniform coating on the
catheter.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] Referring to FIG. 1, there is depicted a catheter 10
incorporating the improvements of the present invention. Although
the improvements of the present invention are depicted and
discussed in the context of being part of a simple occlusive device
having a single lumen, it should be appreciated that the present
invention is applicable to more complex occlusive devices having
structures and functionalities not discussed herein. For example,
the present inventors contemplate that the improvements of the
present invention may be used in occlusive devices functioning as
anchorable guide wires or filters. In addition, the improvements of
the present invention are also applicable to catheters having other
types of balloons, such as latex or silicone, or to catheters
having dilatation balloons, made of materials such as polyethylene
terephthalate. Moreover, the improvements of the present invention
may also be adapted to other types of catheters used in drug
delivery or radiation therapy, such as irrigation catheters, and to
catheters having no balloon at all. The manner of adapting the
improvements of the present invention to these various structures
and functionalities will become readily apparent to those of skill
in the art in view of the description which follows.
[0017] In FIG. 1, an occlusion balloon catheter 10 is shown.
Catheter 10 generally comprises an elongate flexible shaft or
tubular body 12 extending between a proximal control end 14,
corresponding to a proximal section of tubular body 12, and a
distal functional end 16, corresponding to a distal section of
tubular body 12. Tubular body 12 has a central lumen 18 which
extends between ends 14 and 16. An inflation port 20 is provided on
tubular body 12 near the proximal end 14. Inflation port 20 is in
fluid communication with lumen 18, such that fluid passing through
inflation port 20 into or out of lumen 18 may be used to inflate or
deflate inflation balloons in communication with lumen 18. Lumen 18
is sealed fluid tight at distal end 16. Inflation port 20 may be
similar to existing female luer lock adapters or would be a
removable valve at the end, as disclosed in assignee's co-pending
application entitled LOW PROFILE CATHETER VALVE AND INFLATION
ADAPTER, application Ser. No. 08/975,723 filed Nov. 20, 1997, the
entirety of which is incorporated by reference.
[0018] The length of tubular body 12 may be varied considerably
depending upon the desired application. For example, where catheter
10 serves as a guidewire for other catheters in a conventional
percutaneous transluminal coronary angioplasty procedure involving
femoral artery access, tubular body 12 is comprised of a hollow
hypotube having a length in the range of from about 160 to about
320 centimeters with a length of about 180 centimeters being
optimal for a single operator device and 300 centimeters for over
the wire applications. Alternately, for a different treatment
procedure, not requiring as long a length of tubular body 12,
shorter lengths of tubular body 12 may be provided. Moreover, the
catheter 10 may comprise a solid shaft rather than a hollow
hypotube.
[0019] Tubular body 12 generally has a circular cross-sectional
configuration with an outer diameter within the range of from about
0.008 inches to 0.14 inches. In many applications where catheter 10
is to be used as a guidewire for other catheters, the outer
diameter of tubular body 12 ranges from 0.010 inches to 0.038
inches, and preferably is about 0.014 to 0.018 inches in outer
diameter or smaller. Noncircular cross-sectional configurations of
lumen 18 can also be adapted for use with the present invention.
For example, triangular, rectangular, oval, and other noncircular
cross-sectional configurations are also easily incorporated for use
with the present invention, as will be appreciated by those of
skill in the art.
[0020] Tubular body 12 has sufficient structural integrity, or
"pushability," to permit catheter 10 to be advanced through
vasculature to distal arterial locations without buckling or
undesirable kinking of tubular body 12. It is also desirable for
tubular body 12 to have the ability to transmit torque, such as in
those embodiments where it may be desirable to rotate tubular body
12 after insertion into a patient. A variety of biocompatible
materials, known by those of skill in the art to possess these
properties and to be suitable for catheter manufacture, may be used
to produce tubular body 12. For example, tubular body 12 may be
made of stainless steel such as Elgiloy (TM), or may be made of
polymeric materials such as nylon, polyimide, polyamides,
polyethylene or combinations thereof. In one preferred embodiment,
the desired properties of structural integrity and torque
transmission are achieved by forming tubular body 12 out of an
alloy of titanium and nickel, commonly referred to as nitinol. In a
preferred embodiment, the nitinol alloy used to form tubular body
12 is comprised of about 50.8% nickel and the balance titanium,
which is sold under the trade name Tinel (TM) by Memry Corporation.
It has been found that a catheter tubular body having this
composition of nickel and titanium exhibits an improved combination
of flexibility and kink resistance in comparison to other
materials. Further details are disclosed in assignee's co-pending
applications entitled HOLLOW MEDICAL WIRES AND METHODS OF
CONSTRUCTING SAME, application Ser. No. 08/812,876, filed on Mar.
6, 1997, CATHETER BALLOON CORE WIRE, application Ser. No.
08/813,024, filed Mar. 6, 1997, and CORE WIRE WITH SHAPEABLE TIP
(Attorney Docket PERCUS.053A), application Ser. No. ______, filed
on the same date herewith, all of which are hereby incorporated by
reference in their entirety.
[0021] As illustrated in FIG. 1, an expandable member such as an
inflatable balloon 22 is mounted on tubular body 12. Balloon 22 may
be secured to tubular body 12 by any means known to those skilled
in the art, such as adhesives or heat bonding. In one preferred
embodiment, balloon 22 is a compliant balloon formed out of a
material comprising a block polymer of
styrene-ethylene-butylene-styrene (SEBS). As shown in FIGS. 2 and
3, balloon 22 has a proximal end 24 and a distal end 26 which are
both secured to the outer surface of tubular body 12. Balloon 22
may be secured to the tubular body 12 by any means known to those
of skill in the art, such as adhesives or heat bonding. FIGS. 2 and
3 show the use of adhesives 28 bonding the balloon at its proximal
end 24 and distal end 26, respectively, up to adhesive stops 32 and
34, the distance between the adhesive stops defining the working
length of the balloon. Further details are disclosed in assignee's
co-pending application entitled BALLOON CATHETER AND METHOD OF
MANUFACTURE (Attorney Docket PERCUS.010CP1), application Ser. No.
______, filed on the same date herewith, the entirety of which is
hereby incorporated by reference.
[0022] A notch 36 is provided in the tubular body 12, as shown on
the back side of tubular body 12 in FIG. 2, within the working
length of the balloon to provide fluid communication between the
lumen 18 and the balloon 22. A core wire 38 is provided at the
distal end of the tubular body 12, inserted into the lumen 18 so
that part of the core wire 38 is visible through the notch 36. Coil
40 surrounds the core wire 38 and is soldered at a distal end into
a rounded tip 42. The core wire 38 is secured within the lumen 18
of tubular body 12 by a combination of adhesive bonding and
crimping at points 44 and 46 of the tubular body 12. Tapers 48 and
50 are shown at the proximal and distal ends of the balloon 22,
respectively. A radiopaque marker 52 is located within the proximal
taper 48.
[0023] The core wire 38 and the coil 40 are formed into a
subassembly prior to attachment to tubular body 12. Once the coil
40 is attached to the core wire, a proximal end of core wire 38 is
inserted into tubular body 12 at distal end 54. Two crimps 44 and
46 are provided near the distal end 54 of the tubular body 12 to
secure the core wire 38 to the tubular body. The crimps are
preferably located in a location between the notch 36 and the
distal end 54 of the tubular body 12. The crimps are preferably
located a distance 0.5 to 1.5 mm apart, and more preferably, about
1.0 mm apart. The more distal crimp 46 preferably is located about
0.5 mm from the distal end 54 of tubular body 12. Further details
are disclosed in the above-referenced application CORE WIRE WITH
SHAPEABLE TIP (Attorney Docket PERCUS.053A), application Ser. No.
______, filed on the same date herewith.
Fabrication of the Notch
[0024] In one aspect of the present invention, the notch 36 shown
in FIG. 2 is formed by a nonlaser process. Preferably, the process
used is electric discharge machining (EDM). This method allows
removal of metal by a series of rapidly recurring electrical
discharges between an electrode (the cutting tool) and the
workpiece in the presence of a liquid (usually hydrocarbon
dielectric). Using EDM, the notch 36 can be made economically but
also with great precision. The notch 36 preferably has a length
between 0.001 and 0.005 inches and a width between 0.001 and 0.005
inches, depending on the working length of the balloon 22 and the
diameter of the tubular body 12. As shown in FIG. 2, when the
distance between the inner surfaces of the adhesive stops 32 and 34
is 4 mm and the outer diameter of the tubular body 12 is 0.0132
inches, the notch 36 preferably has a length of 1.5 mm and a width
of 0.003 inches. The notch 36 may be centered within the working
length of the balloon, such that the distance between the ends of
the notch and each of the adhesive stops 32 and 34 is the same.
Alternatively, when the core wire 38 extends into the lumen 18 of
the tubular body 12 and is visible in the notch 36, the location of
the notch 36 may be shifted towards distal end 54 of the tubular
body. In FIG. 2, where the distance between adhesive stops 32 and
34 is 4 mm, the core wire 38 extends 0.5 mm into the notch 36. The
notch 36 is 1.5 mm long, with the proximal end 56 of the notch 36
located a distance 1.5 mm from the first adhesive stop 32, and the
distal end 58 of the notch 36 located 1 mm from the second adhesive
stop 34.
[0025] To manufacture the notch, preferably, an EDM with a
0.0055.+-.0.0005 inch electrode is used. A current of 0.5 amps is
applied, with an on time of 6 seconds and an off time of 50
seconds. Although the EDM processing of the notch has been
described with respect to specific parameters, it should be
recognized that other parameters as well may be used for the EDM.
Furthermore, EDM may be used not only for fabrication of a distal
notch to inflate a balloon, but also for a notch such as inflation
port 20 at the proximal end of the tubular body as shown in FIG. 1,
or other types of notches that may be provided for a medical
catheter.
[0026] Although fabrication of the notch has been described with
reference to an EDM procedure, other nonlaser processes may be used
as well. For instance, mechanical grinding is another low cost
procedure for fabricating a notch that can be performed
in-house.
Nonuniform Coating
[0027] In another aspect of the present invention, the shaft or
tubular body 12 is sputter-coated with a polymeric material to
reduce friction between the catheter and blood vessels and produce
a lubricious, nonuniform coating on the tubular body 12. As used
herein, "nonuniform" refers either to a coating that is variable in
thickness along the circumference or length of the body 12, or to a
coating which covers the body 12 in some areas but not at all in
others. As shown in FIG. 1, a coating 60 is applied to the tubular
body 12 between a proximal marker 62 and the balloon 22. The
coating begins at a distance preferably within about 5 mm of the
marker 62, and more preferably within about 2 mm. The coating 60
terminates preferably within about 1 cm of the proximal taper 48.
Preferred coating materials include polytetrafluoroethylene (TFE),
with Teflon being a desired material for the coating 60. Those
skilled in the art will recognize that similar materials with high
lubricity may be used.
[0028] As shown in FIGS. 4A and 4B, a nonuniform coating 60 adds
very little dimension to the tubular body 12. FIG. 4A shows one
embodiment where the coating 60 is thin with a variable thickness
that covers substantially the entire circumference of the tubular
body 12. FIG. 4B shows another embodiment where the coating 60 is
thin but does not coat the entire circumference of tubular body 12.
Thicknesses in the range of about 0.001 to about 0.0035 inches are
preferred. In both of the embodiments shown in FIGS. 4A and 4B,
preferably, the coating 60 has a thickness of no greater than about
0.01 inches, and more preferably, the coating thickness is no
greater than about 0.0035 inches. Thus, it has been discovered that
sufficient lubricity can be achieved with a nonuniform or even
intermittent, sporadic coating, while simultaneously maintaining a
low profile.
[0029] To apply the polymeric coating 60 to the tubular body 12,
the surface of the tubular body 12 is first cleaned. Preferable
cleaning methods are by preparing a cleaning solvent blend using a
1:1 (by volume) mixture of acetone and isopropyl alcohol. The
tubular body 12 may be cleaned by wiping the body with a lint-free
towel or cloth wetted by this solvent blend. After the solvent
wipe, the tubular body 12 is heat cleaned in an oven for 15 minutes
at 540.degree. F.
[0030] The Teflon coating solution may be Xylan 1006/870 Black
Teflon coating as obtained from Whitford Corporation. To achieve a
thinner film thickness, the coating can be mixed with a thinner
such as thinner #99B from Whitford Corporation. To mix the coating
solution with the thinner, the coating solution is first mixed well
in a container using a mechanical stirrer for about 5 to 10 minutes
to remove residue and Teflon particles from the bottom of the
container. About 80 parts by volume of the coating solution is
mixed with about 20 parts by volume of the thinner with a
mechanical stirrer until the blend is uniform to achieve 0.0035
inch thickness. This blend is filtered using a cone type coarser
filter paper to remove lumps. After completing these steps, the
coating solution is ready to spray.
[0031] The coating is produced on the tubular body by a spray gun,
preferably with an agitating pressure pot, although a spray gun
without an agitating pressure pot may be used. The spraying process
of the present invention preferably produces a nonuniform Teflon
coating 360 degrees around the tubular body and extending
continuously along the length of the tubular body 12. When applying
the coating with the spray gun, rather than pulling the trigger all
the way and holding it continuously, the trigger can be selectively
depressed and released, or depressed with various degrees of
pressure, as the gun passes from left to right over a portion of
the tubular body. This process is repeated as the tubular body is
rotated and a coating is applied 360 degrees around the tubular
body. Coating on the tubular body by the spray gun can also be
adjusted by controlling the flow rate of the spray exiting the gun.
Moreover, the motion of the gun over the body allows control of the
thickness and uniformity of the coating. These factors allow the
coating 60 to be a thin, nonuniform coating covering substantially
all of the tubular body, as shown in FIG. 4A.
[0032] Alternatively, the profile of the catheter can be reduced
even further by spraying less than 360 degrees around the tubular
body 12, as shown in FIG. 4B. The nonuniformity of the coating,
thus, results from the tubular body 12 having portions that are
coated with the polymer and other portions having no coating at
all. The degree of nonuniformity depends on how the trigger of the
spray gun is selectively activated and deactivated. Other methods
to produce nonuniformity on the tubular body 12, such as masking
portions of tubular body 12, may also be used. Moreover, the
nonuniformity may result from the coating not being sprayed
continuously over the circumference and/or length of the body.
[0033] After spraying, the coating should be flashed off to avoid
any blistering. The coated tubular bodies are flashed off in an
oven at 200.degree. F. for 15 minutes. Then, the tubular body is
cured. When a NiTi material is used for the tubular body, a curing
temperature of about 540.degree. F. is used in order to maintain
the heat treated superelastic properties of NiTi. The curing step
takes about one-half hour. After allowing the coated tubular bodies
to cool, parts of the tubular body may be stripped to remove the
coating from undesired areas. For instance, at the location of the
proximal marker 62 shown in FIG. 1, no coating is desired. Suitable
means for stripping include an abrasive and a razor blade, as well
as other stripping means known to those skilled in the art.
Distal Marker
[0034] In another aspect of the present invention, a tubular marker
52, as shown in FIG. 2, is located within an adhesive taper 48
adjacent the balloon 22. Although the marker 52 is shown in the
form of a tube, it will be appreciated by those skilled in the art
that markers of other shapes may be used as well. To place the
marker 52 within the taper 48, the marker is first slid over the
coil 40 and core wire 38 and over the distal tip of the tubular
body 12 past the inflation notch 36 so that it is out of the way
for balloon bonding. Adhesive stops 32 and 34 and the balloon 22
are then mounted to the tubular body 12 using adhesives or other
means known to those skilled in the art. One preferred method for
mounting the adhesive stops and balloon to the tubular body is
described in the above-referenced application BALLOON CATHETER AND
METHOD OF MANUFACTURE (Attorney Docket PERCUS.010CP1), application
Ser. No. ______, filed on the same day as the present
application.
[0035] After balloon bonding, the marker 52 is slid towards the
balloon 22 such that it is between about 0.5 and 3 mm from the
proximal end of the balloon. More preferably, the marker 52 is
located within about 1.0 mm from the proximal end 24 of the balloon
22. In the preferred embodiment shown in FIG. 2, the marker 52 is
located about 0.75 mm from the balloon. The gap between the balloon
22 and the marker 52 is filled with an adhesive material taper 48.
Preferably, a cyanoacrylate adhesive such as LOCTITE 4011 is used.
However, as will be appreciated by those of skill in the art, other
adhesives may be used. The taper 48 also extends from the proximal
end 64 of the marker to point 66 on the tubular body 12, as well as
from the proximal end 24 of balloon 22 to proximal end 64 of marker
52.
[0036] Because the marker is placed within the adhesive taper 48 of
the balloon 22, the marker can be made larger and closer to the
balloon, thereby increasing visibility without obstructing
advancement of an aspiration catheter or the like when the tubular
body 12 is used as a guidewire. Further details regarding an
aspiration catheter are disclosed in assignee's co-pending
application entitled ASPIRATION CATHETER, application Ser. No.
08/813,308, filed Mar. 6, 1997, the entirety of which is hereby
incorporated by reference. The marker preferably has an outer
diameter of at least about 0.02 inches. More preferably, the marker
52 has an inner diameter of about 0.017 inches and an outer
diameter of about 0.024 inches. The proximal cyanoacrylate balloon
taper 48 is preferably about 4 mm long, extending from point 24 on
the balloon 22 to point 66 on the tubular body. The marker taper,
extending from point 24 to distal point 68 on marker 52, is
preferably about 0.75 mm long.
[0037] It will be appreciated that certain variations of the shaft
of the present invention may suggest themselves to those skilled in
the art. The foregoing detailed description is to be clearly
understood as given by way of illustration, the spirit and scope of
this invention being limited solely by the appended claims.
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