Note: Descriptions are shown in the official language in which they were submitted.
A-37711 CARDIOVASCULAR CATHETER AND METHOD OF M~NUFACTURE
This invention pertains generally to catheters for insertion
into the cardiovascular system, and more particularly to a
catheter which can be steered or turned as it is inserted
and to a method of manufacturing the same.
Guiding catheters and other catheters (e.g. balloon catheters
and angiographic catheters) which are inserted into the
cardiovascular system must, at times, be turned and steered
in order to achieve the desired placement. With many catheters
heretofore provided, this process is difficult because the
catheters tend to twist and untwist in an unpredictable
manner as they are turned in an effort to steer them~
In an attempt to overcome this problem, some catheters have
been provided with a wire braid (e.g. stainless steel)
imbedded in the wall of the catheter. While the wire braid
does provide some stiffening, and therefore better control,
the wire tends to be brittle if made fine enough not to
increase the thickness of the wall by an appreciable amount.
While the use of a heavier wire might overcome the problem
of breakage, it would require a thicker wall and would,
therefore, increase the outer diame-ter of the catheter
and/or decrease the size of the central passageway or lumen.
Either of these alternatives would be contrary to the fundamental
objective of providing the largest possible lumen and the
smallest possib~e outer diameter so that the catheter will
fit in a relatively small opening in the body. In addition,
the manufacture of a catheter having a wire braid imbedded
therein is relatively time consuming and expensive.
It is in genexal an ob~ect of the invention to provide a new
and improved cardiovascular catheter and method of manufacturing
the same.
Another object of the invention is to prov:Lde a catheter of
the above character having torsional rigidity and a relatively
thin wall thickness.
Another object of the invention is to provide a catheter and
method of the above character in which the stiffness of the
catheter can be controlled along the length of the cathe-ter.
Another object of the invention is to provide a catheter and
method of the above character in which the catheter can be
manufactured quickly and economically.
These and other objects are achieved in accordance with the
invention by providing a catheter and a method of manufacturing
the same wherein a length of flexible filament is wound in
helical fashion about the lumen or passageway of the catheter.
In one embodiment, the flexible filament is wrapped about a
tubular inner liner which defines the lumen, an outer jacket
is formed over the filament, and the inner liner, the filament
2Q and the outer jacket are bonded together to form a unitary
structure with torsional rigi~ity~ The pitch of the helically
wound filament can be varied along the length of the linèr
to vary the stiffness of the catheter.
Figure 1 is an elevational view, partly broken away, of one
~5 embodiment of a cardiovascular catheter incorporating the
invention.
Figure ~ is an isometric view, somewhat schematic, of apparatus
employed in one embodiment of a method of manufacturing the
catheter of Figure 1.
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As illustrated in Figure 1, the catheter (cles:igllatecl generally as 11)
comprises a tubular i.nner liner 12 whi.ch defines all axially extending
passageway or llmlen 13. l,iner 12 is -Fabricatecl o-f a flex;.ble,
relatively slippery material such as polyte-trof]uoroe-thylerle (Teflon),
with a relatively thin wall thiclcness, e.g. .0U3 inC]l.
An elongated -Filament 16 o:F flexible material is wrapped
in helical fashion about the outer wall o:F liner 12 to give
torsional rigidity to the catheter. In the embodiment illustrated,
the filament is wrapped in two layers 17, 18 of opposite pitch, and
the filament comprises a generally flat ribbon having a thickness
on the order of .001 inch. In one presently preferred embodiment,
the :Filament comprises a carbon -Filament having approxilllately 1,000
:incl:ividunl stral-cls -Formed into a bunclle o-f the cles.i.recl flat shape.
ln allotller, alld presently pre:Fcrred cmbodilllent, the f.i:lalllent comprises
a 380 denier Kevlar (DuPont Trademarli) :fiber. This fiber is an
aromatic polyamide material which has the advantage of being rela-
tively flexible and less likely to break than a more brit-tle fiber.
}lowever, it will be understood that other :flexible fibers o:F high
tensile strengt}- (i.e. 250,000 lbs./in.2!, such as boron filaments,
can be used. Likewise, more than two layers of -Filament can be employ-
ecl, if desirecl.
The pi-tc]-l o:F the filament windings can be variecl along
the length of the liner to vary the stiffness of the catheter. In
the embodiment of Figure 1, or example, the pitch is greater in
regions 21, 22 toward the ends of the catheter than in central regi.on
23, and this catheter is stiffer in the central region than toward
the ends.
- 3a -
An outer jacket 26 o:E flex:ible ma-ter:ial :is formed over
the outer layer 18 of Lilament 16 iand encases the :Filament. This
jacket is fabricated oE a tllermop:Lastic materi.ll such as po:Ly-
etllylene whic]l can be sterilized so as not to contamillate the body
into which it is inserted. In one presently preferred embod:imen-t~
the outer jacket is fabricated oE a heat shrinkable tubing which
is drawn tightly about the inner liner and the windings o:E
filament.
~4--
Inner liner 12, filament 16 and outer jacket 26 are bonded
together by suitable means such as epoxy to form a unitary
structure. The unitary nature of the structure has been
found to improve the torsional rigidity of the catheter and
thereby facilitate turning and steering of the catheter
during emplacement in the body.
A connecter 28, illustrated as a female Luer fitting, is
attached to the inlet end of the catheter, and the distal
end 29 can be formed with any desired bend, as in conventional
guiding catheters.
Referring now to Figure 2, a preferred method of manufacturing
the catheter is illustrated. Inner liner 12 is mounted on a
wire-like mandrel 31 which extends axially through the
opening in the tubing which forms the liner. To facilitate
later removal, a lubricant such as silicon is applied to the
mandrel before it is inserted into the tubing. The tubing
is then temporarily affixed to the mandrel by suitable
means, and in presently preferred embodiment the liner is
fabricated of a heat shrinkable tubing which is heated and
shrunk about the mandrel.
Mandrel 31 is mounted between the chucks 32, 33 of a winding
machine 34 and drawn taut by suitable means such as a spring
36. A drive motor 37 is connected to chuck 32 to rotate the
same about its axis, and chuck 33 is provided with a bearing
2~ which permits it to turn freely about its axis
A spool 38 holding a filament 16 to be wrapped about liner
1~ is rotatively mounted on a carriage 39. This carriage is
mounted on ways 41 for movement in the longitudinal direction
between the chucks, and it is driven by a lead screw 42 and
3Q a reversible, variable speed drive motor 43.
' ?
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Before the filament is wound on the liner, the surface of
the liner is cleaned (e.g. by etching~, and a bonding agent
such as epoxy is applied to the cleaned surface. The filament
is affixed to the liner near one end thereof, and drlve
motor 37 is energized to turn the mandrel about its axis and
thereby wind the filament onto the liner. Drive motor 43 is
also energi~ed to move carriage 39 toward the other end of
the liner. ~s the carriage travels, the filament is wound
onto the liner in helical fashion, with a pitch determined
by the relative speeds of the two drive motors. With winding
motor 37 turning at a relatively constant speed, the pitch
of the winding is controlled by varying the speed of carriage
motor 43.
For the catheter of Figure 1, inner liner 17 is wound as the
carriage travels from one end of the liner to the other in
one direction. When this layer is completed, the direction
of carriage travel is reversed, and outer layer 18 is wound
over the i.nner layer as the carriage returns to the start}ng
position. In this embodiment, the speed of carriage motor
43 is increased for the central portions of the windings and
decreased for the end portions, whereby the pitch of t~le
windings is greater toward the end of the catheter.
When the winding is completed, additional bonding agent is
applied to the filament, and outer jacket 26 is installed.
In one presently preferred embodiment, the outer jacket
comprises a length of heat shrinkable tubing which is placed
over the filament winding and the inner liner and heated to
shrink about the filament and liner. Alternatively, the
bonding agent can be applied to the filament before it is
wrapped about the liner, in which case it is not necessary
to make separate applications of the bonding agent to the
liner and to the filament windings~
r- ~ ~
After the bonding agent has cured, the outer ~acket is
ground to the desired outer diameter and the surface finish
by a centerless grinding process. Thereafter, the mandre]
is removed from the central passageway, the catheter is cut
to length, connector 28 is installed, and any desired bend
can be formed in the distal end of the catheter.
Rather than using a separate inner liner, the filament can
be impregnated with epoxy or another suitable material and
wound directly on the winding mandrel. The outer jacket can
then be formed over the filament as discussed above, following
which the mandrel can be removed to form ~he central passageway
or lumen.
The invention has a number of important features and advantages.
The helically wound filament and the unitary structure give
the catheter a tortional rigidity which make it relatively
eas~ to turn and steer the catheter as it is inserted into
the body. The catheter has a relatively end wall and the
stiffness of the catheter can be varied simply by varying
the pitch of the helical filament windings. In addition,
the catheter can be manufactured ~uickly and economically.
It is apparent from the foregoing that a new and improved
catheter and method of manufacturing ~he same have been
provided. While only certain presently preferred embodiments
have been described in detail, as will be apparent to those
familiar with the art, certain changes and modifications can
be made without departing from the scope of the invention as
def.ined by the followin~ claims.
