U.S. patent application number 11/953604 was filed with the patent office on 2008-04-17 for steerable catheter using flat pull wires and having torque transfer layer made of braided flat wires.
Invention is credited to Sarah Cumming, Mark Dustrude, Allan M. Fuentes, Wayne Heideman, Richard E. Stehr.
Application Number | 20080091169 11/953604 |
Document ID | / |
Family ID | 40756177 |
Filed Date | 2008-04-17 |
United States Patent
Application |
20080091169 |
Kind Code |
A1 |
Heideman; Wayne ; et
al. |
April 17, 2008 |
Steerable catheter using flat pull wires and having torque transfer
layer made of braided flat wires
Abstract
A catheter assembly includes an inner liner made of flexible
material and an outer layer having a steering mechanism. The
steering mechanism includes at least one flat wire and a
corresponding lumen through which the flat wire may travel. The
steering mechanism may also include at least one pull ring to which
the flat wires are attached. A layer of heat shrink material may
encompass the outer layer. A braided wire assembly may also be
provided in the outer layer, and may be formed by braiding a
plurality of flat wires into a wire mesh. The overall cross-section
of the catheter assembly is preferably substantially circular. A
catheter shaft may include a plurality of segments of differing
hardness characteristics. The outer layer typically comprises a
melt processing polymer such that the catheter assembly may be
laminated using heat.
Inventors: |
Heideman; Wayne;
(Minnetonka, MN) ; Fuentes; Allan M.; (Mound,
MN) ; Stehr; Richard E.; (Stillwater, MN) ;
Cumming; Sarah; (Plymouth, MN) ; Dustrude; Mark;
(Minnetonka, MN) |
Correspondence
Address: |
ST. JUDE MEDICAL, ATRIAL FIBRILLATION DIVISION
14901 DEVEAU PLACE
MINNETONKA
MN
55345-2126
US
|
Family ID: |
40756177 |
Appl. No.: |
11/953604 |
Filed: |
December 10, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11647313 |
Dec 29, 2006 |
|
|
|
11953604 |
Dec 10, 2007 |
|
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60800373 |
May 16, 2006 |
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Current U.S.
Class: |
604/527 ; 156/86;
604/528 |
Current CPC
Class: |
A61M 25/0053 20130101;
A61M 25/0045 20130101; A61M 25/01 20130101; A61M 2025/015 20130101;
A61M 25/0012 20130101; A61M 25/0147 20130101 |
Class at
Publication: |
604/527 ;
156/086; 604/528 |
International
Class: |
A61M 25/01 20060101
A61M025/01 |
Claims
1. A catheter assembly, comprising: an inner liner made of flexible
material; and an outer layer having a steering mechanism, the
steering mechanism comprising: at least one flat wire; and a
corresponding lumen for each of the at least one flat wire through
which the flat wire may travel; wherein the outer layer comprises a
braided wire assembly that includes at least two flat wires braided
into a wire mesh.
2. The catheter assembly of claim 1, further comprising a layer of
heat shrink material encompassing the outer layer, wherein the
inner liner includes a central lumen, and wherein the catheter
assembly has a cross section with an outer shape that is
substantially circular.
3. The catheter assembly of claim 2, further comprising at least
one pull ring to which the at least one flat wire is secured,
whereby the catheter assembly may be steered by controlling the at
least one flat wire.
4. The catheter assembly of claim 3, wherein the outer layer
comprises a melt processing polymer, wherein the steering mechanism
comprises a pull ring to which the at least one flat wire is
secured, and wherein the pull ring comprises at least two flow
holes, said outer layer being bonded to the pull ring such that the
melt processing polymer occupies the at least two flow holes.
5. The catheter assembly of claim 3, wherein the steering mechanism
comprises at least two flat wires and at least two corresponding
preformed tubes through which the at least two flat wires may
travel, wherein the at least two flat wires are secured to the at
least one pull ring, and wherein the at least two preformed tubes
have cross-sections that are different in shape from a
cross-section of the corresponding flat pull wires.
6. The catheter assembly of claim 5, wherein the steering mechanism
comprises a single pull ring to which the at least two flat wires
are secured.
7. The catheter assembly of claim 6, wherein the single pull ring
comprises a right circular cylinder having a slot for each of the
at least two flat wires.
8. The catheter assembly of claim 7, wherein the outer layer
comprises a melt processing polymer, wherein the steering mechanism
comprises a pull ring to which the at least two flat wires are
secured, and wherein the pull ring comprises at least two flow
holes, said outer layer being bonded to the pull ring such that the
melt processing polymer occupies the at least two flow holes.
9. The catheter assembly of claim 2, wherein the steering mechanism
comprises at least two flat wires and at least two corresponding
lumens through which the at least two flat wires may travel.
10. The catheter assembly of claim 9, wherein each of the at least
two flat wires has a cross-section that is rectangular, and wherein
each of the at least two lumens has a cross-section selected from
the group consisting of oval, round, and elliptical.
11. The catheter assembly of claim 9, wherein each of the at least
two flat wires has a cross-section that is measured X in one
direction and at least 3X in a second direction, said second
direction being substantially orthogonal to the first
direction.
12. The catheter assembly of claim 9, wherein each of the at least
two flat wires is manufactured with a smooth surface to reduce
friction between the flat wire and the corresponding lumen.
13. The catheter assembly of claim 1, wherein the inner liner is
polymeric and has a lumen diameter of at least about 6 French, and
wherein the flat wires in the braided wire assembly are
substantially rectangular in cross-section and have a width of at
least about 0.007 inches and a depth of at least about 0.004
inches.
14. The catheter assembly of claim 13, wherein the outer layer
comprises a melt processing polymer, and wherein the
melt-processing polymer occupies a plurality of voids of the wire
mesh in the braided wire assembly.
15. The catheter assembly of claim 13, wherein the inner liner has
a lumen diameter of between about 7 French and about 32 French.
16. The catheter assembly of claim 13, wherein the at least two
flat wires have a ratio of width to thickness of at least about
2:1.
17. The catheter assembly of claim 13, wherein the braided wire
assembly has a braid density between about 5 PPI and about 100
PPI.
18. The catheter assembly of claim 1, wherein the braided wire
assembly is braided in a one-over, one-under pattern.
19. The catheter assembly of claim 1, wherein the braided wire
assembly comprises at least four flat wires braided in a two-over,
two-under pattern.
20. A method of manufacturing a catheter, comprising the steps of:
providing a mandrel; placing a lining material over the mandrel to
form an inner liner; providing at least one flat shaped wire;
placing a flexible liner over each of the at least one flat shaped
wires to create at least one flat lumen; placing a braided wire
assembly over the inner liner and the at least one flat lumen, the
braided wire assembly including at least two flat wires braided
into a wire mesh; covering the braided wire assembly with a melt
processing polymer; applying sufficient heat to the melt processing
polymer to raise the temperature of the polymer above its melting
point; cooling the assembly; and removing the mandrel, thereby
forming a catheter.
21. The method of claim 20, further comprising: covering the melt
processing polymer with shrink wrap tubing; and removing the shrink
wrap tubing after the melting process.
22. The method of claim 20, further comprising: covering the
braided wire assembly with one or more flexible layers; and
covering the melt processing polymer with shrink wrap tubing.
23. The method of claim 20, wherein the step of providing at least
one flat shaped wire comprises providing at least one flat wire
having a cross-section that is rectangular, and wherein the step of
placing a flexible liner over each of the at least one flat shaped
wires comprises placing a preformed flexible tube over each of the
at least one flat shaped wires, wherein the preformed flexible tube
has a cross-section selected from the group consisting of oval,
round, and elliptical.
24. The method of claim 20, wherein the inner liner is polymeric
and has a lumen diameter of at least about 6 French, and wherein
the flat wires in the braided wire assembly are substantially
rectangular in cross-section and have a width of at least about
0.007 inches and a depth of at least about 0.004 inches.
25. The method of claim 20, wherein the flat wires of the braided
wire assembly are braided at a braid density of about 5 PPI to
about 100 PPI.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 11/647,313, filed 29 Dec. 2006, which claims
the benefit of U.S. Provisional Patent Application No. 60/800,373,
filed 16 May 2006. The entire disclosures of these applications are
hereby expressly incorporated by reference as though fully set
forth herein.
BACKGROUND OF THE INVENTION
[0002] a. Field of the Invention
[0003] The present invention pertains generally to catheters that
are used in the human body. More particularly, the present
invention is directed to steerable catheters using flat pull wires
to reduce the overall outer dimension of the catheter and a torque
transfer layer made of braided flat wires and configured to provide
increased strength, flexibility, and kink resistance.
[0004] b. Background Art
[0005] Catheters are used for an ever-growing number of procedures.
For example, catheters are used for diagnostic, therapeutic, and
ablative procedures, to name just a few examples. Typically, the
catheter is manipulated through the patient's vasculature and to
the intended site, for example, a site within the patient's heart.
The catheter typically carries one or more electrodes, which may be
used for ablation, diagnosis, or the like.
[0006] Many prior catheters use round wires as pull wires, and they
typically either embed the wire directly into the catheter wall so
that the pull wire and the lumen through which it runs are
substantially the same size, or use a round wire to create a pull
wire lumen and then place a smaller wire in the lumen as a pull
wire. These conventional techniques and methods result in a
catheter that is elliptical in its outer shape. An example of an
elliptical catheter is disclosed and taught in U.S. Pat. No.
6,582,536, the contents of which are incorporated herein by
reference.
[0007] As catheters are used in smaller and smaller passages, there
is a growing need to use catheters that have a smaller outer
dimension. Accordingly, there is a need to use steerable catheters
that have smaller cross-sections.
[0008] It is known that, to facilitate placement of the diagnostic
or therapeutic catheter at a location of interest within the
patient, it may be introduced through another catheter, commonly
known as a "guiding catheter" or "introducer catheter," and the
terms will be used interchangeably herein. Generally speaking, an
introducer catheter is a tube having a high degree of directional
control that is used to place other catheters, which may have
little or no directional control, into specific areas of the
patient's body.
[0009] In the field of cardiac ablation, for example, introducer
catheters may be used to negotiate the patient's vasculature such
that an ablation device may be passed therethrough and positioned
to ablate arrhythmia-causing cardiac tissue. The introducer
catheter itself may be advanced over a guide wire.
[0010] Generally, it is known that the introducer catheter must
have an overall diameter small enough to negotiate blood vessels
while retaining an inner diameter (or "bore size") large enough to
accommodate the ablation device therethrough. Furthermore, since
the path within the patient is often long and tortuous, steering
forces must be transmitted over relatively great distances.
Accordingly, it is desirable for the introducer catheter to have
sufficient axial strength to be pushed through the patient's
vasculature via a force applied at its proximal end
("pushability"). It is also desirable for the introducer catheter
to transmit a torque applied at the proximal end to the distal end
("torqueability"). An introducer catheter should also have
sufficient flexibility to substantially conform to the patient's
vasculature and yet resist kinking as it does so. One of ordinary
skill in the art will recognize that these various characteristics
are often in tension with one another, with improvements in one
requiring compromises in others. For example, increasing the bore
size of an introducer catheter having a given overall diameter
requires utilizing a thinner wall. A thin-walled introducer,
however, is more likely to collapse upon itself when a torque is
applied at its proximal end.
[0011] To improve pushability, torqueability, flexibility, and kink
resistance, many extant introducer catheters utilize one or more
reinforcing layers in their construction. For example, the guiding
catheter disclosed in U.S. Pat. No. 4,817,613 to Jaraczewski et al.
("Jaraczewski") includes a pair of braided torque transmitting
layers sandwiched between a flexible tubular member and a flexible
plastic casing applied as a viscous material and subsequently
cured. Jaraczewski also teaches, however, that to a certain degree,
flexibility comes at the expense of torqueability. Further,
depending on the thickness of the torque transfer layers, they may
increase the wall thickness, thereby either increasing the overall
diameter of the introducer catheter for a given bore size or
decreasing the bore size for a given overall diameter.
[0012] Many extant large bore introducers (i.e., an introducer
catheter with bore size of greater than about 6 French), in order
to find a suitable balance of pushability, torqueability,
flexibility, and kink resistance, have outer layers that are
relatively stiff, which compromises torqueability, kink resistance,
and flexibility for pushability.
BRIEF SUMMARY OF THE INVENTION
[0013] According to a first embodiment of the invention, a catheter
assembly includes an inner liner made of flexible material and an
outer layer having a steering mechanism. The steering mechanism
includes at least one flat wire and a corresponding lumen for each
of the at least one flat wire through which the flat wire may
travel. Optionally, the catheter assembly may include a layer of
heat shrink material encompassing the outer layer, a central lumen,
and/or a braided wire assembly contained in the outer layer. The
overall cross-section of the catheter assembly may be substantially
circular. The outer layer typically comprises a melt processing
polymer such that the catheter assembly may be laminated using
heat.
[0014] Optionally, the flat wire or wires may be encased in a
preformed tube in which the flat wire may travel. The flat wire may
have a rectangular cross-section, typically having dimensions of
about X by about 3.times., and the cross-section of the preformed
tube may be oval, round, or elliptical. That is, the cross-section
of the preformed tube may be of a different shape than the
cross-section of the flat wire disposed therein. The flat wire may
be coated with a lubricious substance to permit the flat wire to
slide in its lumen, or optionally, the flat wire may be
manufactured with a smooth surface to reduce friction between the
flat wire and its lumen.
[0015] The braided wire assembly may extend from a base of the
catheter assembly to a distal end of the catheter assembly, and a
braid density may transition from a first braid density at the base
to a lower braid density at the distal end. For example, the braid
density may be about 50 PPI at the base and about 10 PPI at the
distal end. Alternatively, the braid density at the distal end may
be about 20% to about 35% of the braid density at the base.
[0016] Also disclosed is a method of manufacturing a catheter
including the steps of: providing a mandrel; placing a lining
material over the mandrel to form an inner liner; providing at
least one flat shaped wire; placing a flexible liner over each of
the at least one flat shaped wires to create at least one flat
lumen; placing a braided wire assembly over the inner liner and the
at least one flat lumen; covering the braided wire assembly with a
melt processing polymer; applying sufficient heat to the melt
processing polymer to raise the temperature of the polymer above
its melting point; cooling the assembly; and removing the mandrel,
thereby forming a catheter. Typically, the catheter is manufactured
such that it has a cross-section with an outer shape that is
substantially circular with an outer diameter of less than about
12F. Optionally, the melt processing polymer may be covered with
shrink wrap tubing to help promote the polymer flowing through the
braided wire assembly. The shrink wrap tubing may be left in place
after manufacturing, or it may be removed as part of the
manufacturing process. The melt processing polymer is typically
selected from Nylon, Pebax and other thermal elastomers.
Optionally, additional layers of melt processing polymers may be
placed over the flat lumen and the inner liner. Typically, the flat
wire and the flexible liner being placed over the flat wire will
each have different cross-sectional shapes.
[0017] Also disclosed is a method of manufacturing a steerable
introducer catheter, including the steps of: providing a mandrel;
laminating the mandrel with a lining material to form an inner
liner; providing at least one flat shaped wire; covering the inner
liner and the at least one flat shaped wire with a melt processing
polymer; applying sufficient heat to the melt processing polymer to
raise the temperature of the polymer above its melting point;
cooling the assembly; and removing the mandrel, thereby forming a
steerable introducer catheter. Optionally, a flexible tube is
placed over each of the at least one flat shaped wires to create at
least one corresponding lumen for each of the wires, and further,
the melt processing polymer may be covered with a layer of shrink
wrap tubing. The braided wire assembly may be characterized by a
braid density that transitions from a first number at the base to a
lower number at the tip. The variation in braid density may range
from about 50 PPI at the base to about 10 PPI at the distal
end.
[0018] In accordance with another aspect of the present invention,
a catheter or an introducer catheter for cardiac surgery comprises
a tubular inner liner, a torque transfer layer, or reinforcing
layer, surrounding at least a portion of the inner liner, the
torque transfer layer comprising at least two flat wires braided
into a wire mesh, and an outer sheath formed over to the torque
transfer layer. The flat wires are substantially rectangular in
cross-section and have a width of at least about 0.007 inches and a
depth of at least about 0.003 inches. The tubular inner liner has a
lumen diameter of at least about 6 French. In specific embodiments,
the catheter is an introducer catheter. The tubular inner liner is
polymeric and the outer sheath comprises a melt-processing polymer.
The ratio of width to thickness of the introducer catheter may be
between about 2:1 and about 5:1. The torque transfer layer has a
braid density of between about 5 PPI and about 100 PPI and may be
braided in a one-over, one-under pattern, or a two-over, two-under
pattern. The outer sheath comprises a plurality of segments having
differing hardness characteristics, and the segments are reflow
bonded together.
[0019] The catheter assembly of the present invention may also
include a pull ring to which the at least two flat wires are
secured. The pull ring may be a right circular cylinder having a
slot for each of the at least two flat wires. Typically, there are
two flat wires, the pull ring has two slots spaced on opposite
sides of the pull ring, and each of the flat wires is secured in
the slot by a laser weld. The pull ring may further include at
least two flow holes such that the outer layer will bond to the
pull ring during melt processing as the melt processing polymer
flows through the flow holes and then becomes rigid after
cooling.
[0020] The catheter assembly of the present invention may also
include a shaft made of at least three segments, wherein each
segment has a different hardness characteristic. For example, a
first shaft segment may be made of nylon, a second segment may be
made of a first Pebax, and a third segment may be made of a second
Pebax that is more flexible than both the nylon and the first
Pebax. Additional segments may be used to form the shaft, each of
which may have greater or lesser degrees of stiffness.
[0021] Also disclosed is a pull ring assembly for a catheter
including a pull ring having at least one rectangular slot and at
least one flat pull wire, wherein each of the at least one flat
pull wires is secured to the at least one rectangular slot of the
pull ring. Typically, the pull ring assembly will include at least
two slots and at least two flat pull wires secured in the slots.
Optionally, the pull ring may include flow holes though which a
melt processing polymer may flow during lamination.
[0022] According to still another embodiment of the invention, a
pull ring assembly includes a pull ring having at least two
rectangular slots and at least two pull wires, wherein each of the
at least two pull wires is secured to the rectangular slot of the
pull ring. Optionally, the pull ring may include flow holes though
which a melt processing polymer may flow during lamination.
[0023] A technical advantage of the present invention is that
overall cross-section of the catheter may be reduced.
[0024] Another technical advantage of the present invention is that
a steerable catheter using flat pull wires may be provided that
enjoys greater flexibility.
[0025] Yet another technical advantage of the invention is it may
utilize an improved braided wire assembly that provides for greater
flexibility and control of a catheter.
[0026] A further technical advantage of the invention is that a
method of manufacturing an improved steerable catheter is
provided.
[0027] Yet another technical advantage of the invention is that a
catheter shaft having greater flexibility and control may be
utilized.
[0028] A further technical advantage of the invention is that a
method of manufacturing an introducer with a lower profile outer
diameter with improved steerability is provided.
[0029] The foregoing and other aspects, features, details,
utilities, and advantages of the present invention will be apparent
from reading the following description and claims, and from
reviewing the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is perspective view of an embodiment of a catheter of
the present invention.
[0031] FIG. 2 illustrates a perspective view of a section of a
catheter according to an embodiment of the present invention, cut
away to show details.
[0032] FIG. 3 is a cross-sectional view taken along line 3-3 in
FIG. 2.
[0033] FIG. 4 is a cross-sectional view taken along line 4-4 in
FIG. 2.
[0034] FIG. 5 is a cross-sectional view taken along line 5-5 in
FIG. 2.
[0035] FIG. 6 is a cross-sectional view of a catheter assembly
prior to the application of heat to melt process the outer
layer.
[0036] FIG. 7 is a cross-sectional view of a catheter after the
application of heat to melt process the outer layer.
[0037] FIG. 8 illustrates a perspective view of a partially
assembled catheter in accordance with another embodiment of the
invention, cut away to show details.
[0038] FIG. 9 illustrates a pull ring that may be used in a
catheter according to the present invention.
[0039] FIG. 10 is a sectional view of the pull ring of FIG. 9 taken
along line 10-10.
[0040] FIG. 11 is a cross-sectional view of a steerable, large bore
introducer in accordance with another embodiment of the present
invention.
[0041] FIG. 12 depicts a reflow mandrel assembly used in the method
of manufacturing introducers in accordance with the present
invention.
[0042] FIG. 13 depicts an inner layer disposed over a reflow
mandrel assembly in accordance with a preferred method of
manufacture.
[0043] FIG. 14 depicts a torque transfer layer disposed over an
inner layer in accordance with a preferred method of
manufacture.
[0044] FIG. 15 depicts an outer sheath of varying components
disposed over a torque transfer layer in accordance with a
preferred method of manufacture.
[0045] FIG. 16 depicts the components of an introducer assembled
over a reflow mandrel assembly having a distal configuration for a
tip assembly.
[0046] FIG. 17 depicts a tip component, having a radiopaque marker,
attached to the distal end of the introducer depicted in FIG.
16.
[0047] FIG. 18 depicts another tip component, having a radiopaque
marker, attached to the distal end of the introducer depicted in
FIG. 16.
DETAILED DESCRIPTION OF THE INVENTION
[0048] Flat Pull Wires
[0049] The present invention provides an improved steerable
catheter that minimizes the overall outer dimensions by utilizing a
variety of improved techniques. One technique is to utilize flat
wire as the pull wires for the steerable catheter.
[0050] For purposes of this invention, a "flat wire" or a "flat
pull wire" refers to a wire that is characterized by a
cross-section that, when measured along two orthogonal axes, is
substantially flat. A flat wire typically has a rectangular
cross-section. For example, the rectangular cross-section may be
approximately 0.004''.times.0.012''. The cross-section need not be
perfectly rectangular. For example, the present invention
contemplates a cross-section of the flat wire may be oval, provided
that the overall cross-section is generally flat. For example, a
wire may be properly characterized as a flat wire if it has a
cross-section that is measured X in one direction and at least 3X
in a second direction generally orthogonal to the first direction.
A wire whose cross-section is substantially I-shaped may also be a
flat wire if, generally, its height is substantially greater than
its width at its widest measurement. One of ordinary skill will
appreciate that a flat wire may be defined in the context of the
overall teachings of this application.
[0051] The use of a flat wire as a pull wire also has the added
benefit that it provides greater resistance to deflection in
certain directions. The shape of a round wire is not predisposed to
resist deflection in any particular direction, whereas the shape of
a flat wire will be predisposed to resist deflection on a first
axis, and yet predisposed to permit deflection on a second axis
that is orthogonal to the first axis. Thus, by using a pull wire
that is not circular, a catheter can be predisposed to permit and
favor deflection in one direction over another.
[0052] The outer diameter of the catheter may also be minimized at
the distal tip by an improved braided wire assembly. In particular,
a braid may be used that is characterized by a varying braid
density from the proximal end to the distal tip. Preferably, the
braid is less dense at the tip than at the proximal end of the
catheter. Some applications may be better suited if the braid
density is more dense at the tip than at the proximal end, while
other applications may be better suited if the braid density is
greater on both ends than in the middle of the catheter.
[0053] FIG. 1 is a perspective view of a catheter assembly 110
according to one embodiment of the present invention comprising a
catheter or an introducer catheter 100 having a proximal portion
110 and a distal portion 190. The catheter 100 may be operably
connected to a handle assembly 106 which assists in guiding or
steering the introducer during procedures. The catheter assembly
110 further includes a hub 108 operably connected to an inner lumen
(not shown) within the handle assembly 106 for insertion or
delivery of catheter assemblies, fluids, or any other devices known
to those of ordinary skill in the art. Optionally, the catheter
assembly 110 further includes a valve 112 operably connected to the
hub 108.
[0054] FIG. 2 illustrates a perspective view of a catheter
according to a preferred embodiment of the present invention, cut
away to show details.
[0055] The basic method of manufacture of catheter 100 according to
an embodiment of the present invention will be described with
reference to FIGS. 2, 3, 4, 6, 7 and 8. As they are assembled, the
catheter components will be collectively referred to as a catheter
assembly.
[0056] As depicted in FIG. 6, a mandrel 10, which is preferably
round in cross-section and preferably from about 6 inches to about
4 feet in length, is a component of the catheter assembly 200, and
may be the first component thereof during manufacture of catheter
100. Mandrel 10 has a distal end and a proximal end. An inner liner
20 is placed on mandrel 10. Inner liner 20 may be knotted at one
end (e.g. the distal end) and then fed onto mandrel 10.
[0057] Preferably, inner liner 20 is an extruded
polytetrafluoroethylene (PTFE) tubing, such as Teflon.RTM. brand
tubing, which is available commercially. Inner liner 20 may also be
made of other melt processing polymers, including, without
limitation, etched polytetrafluoroethylene, polyether block amides,
nylon and other thermoplastic elastomers. Once such elastomer is
Pebax.RTM., made by Arkema, Inc. Pebax of various durometers may be
used, including, without limitation, Pebax 30D to Pebax 70D. In a
preferred embodiment, inner liner 20 is made of a material with a
melting temperature higher than that of an outer layer 60, which
will be further described below, such that inner liner 20 will
withstand melt processing of outer layer 60.
[0058] A flat wire 30 is placed longitudinally along inner liner
20. Flat wire 30 is preferably composed of stainless steel and is
preferably about 0.002'' by about 0.016'', and more preferably
about 0.004'' by about 0.012''. In one embodiment, at least a
portion of flat wire 30 is encased inside another preformed tube 40
before placement along inner liner 20 to form a flat lumen 42.
Preformed tube 40 need not have the same shape as the cross-section
of flat wire 30, but instead may be round, oval, rectangular, or
another like shape. Preferably, preformed tube 40 has a
cross-section that is not the same shape as the cross-section of
flat wire 30 in order to facilitate movement of flat wire 30 in
preformed tube 40. Preformed tube 40 may be formed of
polytetrafluoroethylene, polyether block amides, nylon, other
thermoplastic elastomers, or another substance. Preferably,
preformed tube 40 has a higher melting point than outer layer 60,
which will be further described below, so that preformed tube 40
will not melt when outer layer 60 is subjected to melt
processing.
[0059] In alternative embodiments, flat wire 30 may be covered with
lubricious materials including silicone, Teflon.RTM., siloxane, and
other lubricious materials (not shown), before placement.
Alternatively, flat wire 30 may also be coated with a lubricious
layer to promote slideability. It is also contemplated that flat
wire 30 may be manufactured with a smooth surface to promote
slideability. While stainless steel is a preferred material from
which to compose flat wire 30, other materials may be used,
including, without limitation, materials that are used for
conventional round pull wires.
[0060] More than one flat wire 30 may also be used. In such cases,
each such flat wire 30 may be encased inside its own flexible tube
40 to form separate flat lumens 42. Preferably, a pair of flat
wires 30 are used, spaced apart about 180 degrees about the
circumference of inner liner 20.
[0061] Outer layer 60 is then placed over inner liner 20, flat
wires 30, and preformed tube 40 forming flat lumen 42. Outer layer
60 may be made of either single or multiple sections of tubing that
may be either butted together or overlapped with each other.
Preferably, outer layer 60 is an extruded polytetrafluoroethylene
tubing, such as Teflon.RTM. brand tubing, which is available
commercially. Outer layer 60 may also be made of other melt
processing polymers, including, without limitation, etched
polytetrafluoroethylene, polyether block amides, nylon and other
thermoplastic elastomers. Once such elastomer is Pebax.RTM. made by
Arkema, Inc. Pebax of various durometers may be used, including,
without limitation, Pebax 30D to Pebax 70D. Outer layer 60 may also
comprise more than one layer, including for example two or more
tubes of a melt processing polymer.
[0062] Optionally, a braided wire assembly 50 may be placed over
inner liner 20 and any flat wires 30 before outer layer 60 is
applied. Braided wire assembly 50 may be formed of stainless steel
wire, including for example 0.003'' high tensile stainless steel
wire. Braided wire assembly 50 may be formed in a standard braid
pattern and density, for example, about 16 wires at about 45 to
about 60 picks per inch ("PPI") density. Alternatively, a braid may
be used that is characterized by a varying braid density. For
example, braided wire assembly 50 may be characterized by a first
braid density at proximal end 110 of catheter 100 and then
transition to one or more different braid densities as braided wire
assembly 50 approaches distal end 190 of catheter 100. The braid
density of distal end 190 may be greater or less than the braid
density at proximal end 110. In a specific example, the braid
density at the base (i.e., proximal end 110) is about 50 PPI and
the braid density at distal end 190 is about 10 PPI. In another
embodiment, the braid density at distal end 190 is about 20% to
about 35% of the braid density at the base/proximal end 110.
[0063] Braided wire assembly 50 may be formed separately on a
disposable core. One or more portions of braided wire assembly 50
may be heat tempered and cooled before incorporation into catheter
assembly 200 though methods that are known to those of ordinary
skill. The action of heat tempering may help to release the stress
on the wire and help reduce radial forces.
[0064] FIG. 6 displays a cross-section of catheter assembly 200
having two flat wires 30 and braided wired assembly 50 encompassed
by outer layer 60 before lamination of the materials by heating. In
one preferred embodiment, a layer of heat shrink 70 is placed over
the top of outer layer 60 as depicted in FIG. 6. Heat shrink 70 is
preferably a fluoropolymer or polyolefin material.
[0065] FIG. 7 depicts catheter assembly 200 after a lamination
process. Catheter assembly 200 may be laminated by heating catheter
assembly 200 until the material comprising outer layer 60 flows and
redistributes around the circumference thereof as depicted in FIG.
7. Heat shrink 70 has a higher melting temperature than outer layer
60; and during the melt process, heat shrink 70 retains its tubular
shape and forces the liquefied outer layer 60 material into braided
wire assembly 50 (if present) and into contact with flat wires 30
and inner liner 20. Catheter assembly 200 may then be cooled. In
FIG. 7, mandrel 10 is still in place.
[0066] Mandrel 10 may be removed from catheter assembly 200,
leaving behind a lumen 80 as illustrated in FIG. 4, which depicts a
catheter 100 made in accordance with the method of the present
invention subsequent to the application of heat for the lamination
process. Optionally, heat shrink 70 may be left in place around
outer layer 60, as depicted in FIG. 7, even after mandrel 10 is
removed.
[0067] If heat shrink 70 is removed, outer layer 60 becomes the
outermost layer of catheter 100. The result is a substantially
circular catheter 100 with pull wires 30 embedded within outer
layer material as illustrated in FIGS. 3 and 4. FIG. 3 is a
cross-sectional view taken at the point of a pull ring 90 as
depicted in FIG. 2, while FIG. 4 is a cross-sectional view taken at
a point proximal to pull ring 90. FIG. 8 is a perspective view of
catheter assembly 200, cut away to show certain details of
construction.
[0068] Catheter assembly 200 may be manufactured using alternative
techniques. In one embodiment, outer layer 60 may be formed by
extruding outer layer 60 over catheter assembly 200.
[0069] In another embodiment, catheter assembly 200 may formed by
using a combination of heat and a press that has a mold for
defining the final shape of catheter 100.
[0070] Catheter 100 formed using the methods of this invention may
have varying sizes and various uses. For example, catheter 100 may
be used in atrial fibrillation cases as well as atrial tachycardia
cases. In connection with certain heart applications, catheter 100
manufactured using the improvements discussed herein is preferably
less than about 12F outer diameter, and more preferably less than
about 10F outer diameter. For use as a steerable introducer, a
catheter size of less than about 11F outer diameter may be
preferred. As discussed below, larger catheter sizes are feasible,
particularly when the torque transfer layer is made of braided flat
wires.
[0071] In another embodiment, catheter 100 construction may be
modified to utilize materials of various durometer hardness (as
measured, for example, using a Shore durometer hardness scale). For
example, proximal end 110 of catheter 100 may be made of a material
such as nylon 11, and the remainder of catheter 100 may be made of
one or more Pebax materials. Preferably, the durometer hardness
levels will decrease as catheter 100 shaft approaches distal end
190. For example, a nylon base may then be followed by one or more
of the following Pebax segments: 70D Pebax; 60D Pebax; 55D Pebax;
40D Pebax; 35D Pebax; 30D Pebax. Catheter 100 may also use one or
more blends of the foregoing Pebax materials, including for
example, a 70D/60D Pebax blend made by co-extrusion, or a 40D/35D
Pebax blend made by co-extrusion. Preferably, catheter 100 made
with one or more segments of varying durometers will be reflowed
together during manufacturing. The length of the segments may vary.
Proximal end 110 of catheter 100 is preferably the longest segment,
and more distal segments may preferably vary between about 0.25''
to about 6'', and more preferably from about 0.25'' to about 3''.
Preferably, the hardness levels of the segments and the lengths of
the segments may be adjusted for specific applications, and
preferably, the distal tip segment may have the lowest durometer of
all segments. The segments may be selected to optimize stability
and torque delivery for the specific application.
[0072] FIG. 5 illustrates another embodiment of the invention in
which outer layer 60 is composed of multiple segments 61, 62, 63,
64, each of which has different material properties, such as degree
of hardness, stiffness, or tensile strength. In a preferred
embodiment, segment 61 has the greatest degree of hardness;
segments 62, 63, and 64 are more flexible than segment 61; segments
63 and 64 are more flexible than segments 61 and 62; and finally,
segment 64 is more flexible than each of segments 61, 62 and 63.
The number of segments may vary, as well as the relative lengths of
the segments.
[0073] In yet another embodiment, a modified braided wire assembly
50 is inserted between inner liner 20 and outer layer 60. Braided
wire assembly 50 may be designed to have transitional braid
densities starting at one braid density and transitioning to a
lower braid density. In one embodiment, the braid may begin at a
braid density of about 50 to about 60 PPI, and more preferably
between about 50 and about 55 PPI, and then transition to a braid
density at the tip of about 5 to about 20 PPI, and more preferably
between about 5 to about 15 PPI. The braid density may transition
slowly, or it may change using one or more segments. For example,
there may be an intermediate zone with a braid density of about 30
to about 45 PPI. Variations in the braid density of braided wire
assembly 50 may be used to increase or decrease flexibility of
catheter 100 depending on the desired application.
[0074] In another embodiment, pull ring 90 is utilized to provide
steerability. FIGS. 9 and 10 illustrate a preferred embodiment for
pull ring 90. Pull ring 90 is a generally circular band with a
cross-sectional shape (measured orthogonally to a tangential line
relative to the circle of the band) that is substantially
rectangular. The rectangular cross-section is more clearly depicted
in FIG. 10. The outer dimension of pull ring 90 is preferably
determined based on the application for catheter 100 to be
manufactured. In one embodiment, pull ring 90 is about 0.10'' in
diameter.
[0075] Pull ring 90 preferably has at least one slot 91 that is
configured to accommodate flat pull wire 30. Flat pull wire 30 may
secured within slot 91 by any technique that is appropriate given
the materials of pull ring 90 and flat pull wires 30. Acceptable
techniques may include, but are not limited to, laser welding
and/or other welding and bonding techniques.
[0076] In another embodiment, pull ring 90 may contain one or more
flow holes 95 as illustrated in FIGS. 9 and 10. During a melting
process, the material of outer layer 60 melts and flows through
flow holes 95. Upon cooling, the material of outer layer 60 bonds
to pull ring 90 to provide better adhesion between pull ring 90 and
the remaining components of catheter assembly 200, thereby
improving performance of catheter 100. While flow holes 95 are
depicted as circular, other shapes may be used. In one embodiment,
pull ring 90 includes two 0.025'' flow holes 95 spaced about 180
degrees apart around the circumference of pull ring 90. The size
and shape of flow holes 95 may be adjusted based on the materials
being used to form inner liner 20 and/or outer layer 60.
[0077] In another embodiment, pull ring 90 is utilized with
non-flat pull wires. Pull ring 90 of this embodiment is preferably
a circular band with a cross-sectional shape (measured orthogonally
to a tangential line relative to the circle of the band) that is
substantially rectangular. Preferably, pull ring 90 has at least
one slot that is configured to accommodate a non-flat pull wire
(such as a round wire). Preferably, the tip of the non-flat pull
wire is tapered to facilitate joinder with pull ring 90. The
non-flat pull wire may be secured within the slot by any technique
that is appropriate given the materials of pull ring 90 and the
pull wires. Acceptable techniques may include, but are not limited
to, laser welding and/or other welding and bonding techniques.
Preferably, the non-flat pull wire is located within a preformed
tube. The preformed tube need not be the same shape as the
cross-section of the pull wire, but instead, may be round, oval,
rectangular, or another like shape. Preferably, the preformed tube
has a cross-section that is not the same shape as the cross-section
of the pull wire in order to facilitate movement of the pull wire
in the preformed tube. The preformed tube may be formed of
polytetrafluoroethylene, polyether block amides, nylon, other
thermoplastic elastomers or another substance. Preferably, the
preformed tube has a higher melting point than outer layer 60 so
that the preformed tube will not melt when outer layer 60 is
subjected to melt processing. In alternative embodiments, the pull
wire may be covered with lubricious materials, such as silicone and
other lubricious materials, before placement. Alternatively, the
pull wire may be coated with a lubricious layer to promote
slideability, and it is also contemplated that the pull wire may be
manufactured with a smooth surface to promote slideability. While
stainless steel is a preferred material to compose the pull wire,
other materials may be used, including, without limitation,
materials that are used for conventional pull wires.
[0078] Pull ring 90 is typically utilized near distal end 190 of
catheter 100, but it is anticipated that pull ring 90 may be
located at any position along catheter 100. Moreover, more than one
pull ring 90 may be utilized in the same catheter 100. In one
embodiment of catheter 100, two separate pull rings 90 may be
utilized, each of which has its own flat pull wires 30 connected
thereto.
[0079] Although multiple embodiments of this invention have been
described above with a certain degree of particularity, those
skilled in the art could make numerous alterations to the disclosed
embodiments without departing from the spirit or scope of this
invention. For example, pull ring 90 may be made of stainless steel
or other materials, including, without limitation, materials that
are used to form conventional pull ring assemblies. In addition,
braided wire assembly 50 may be made of stainless steel or other
materials, including materials that are used to form conventional
braided wire assemblies.
[0080] Torque Transfer Layer Using Braided Flat Wires
[0081] The present invention further provides a torque transfer
layer using braided flat wires for a catheter and a large bore
introducer catheter. For purposes of description, embodiments of
the present invention will be described in connection with a flat
wire guided, or steerable, introducer catheter. It is contemplated,
however, that the described features may be incorporated into any
number of catheters or introducer catheters as would be appreciated
by one of ordinary skill in the art. The large bore introducer
catheter is comprised of a combination of components and
manufactured by either a reflow process or an extrusion process,
which provide the surprising benefits of allowing for introducer
catheters having an internal diameter of at least about 6 French
while maintaining the desirable improved properties of pushability,
torqueability, and flexibility, for outer diameters of sufficient
size for navigation of cardiac vasculature.
[0082] FIG. 11 depicts a cross-sectional view of an introducer
catheter 1200 in accordance with one embodiment of the present
invention. The introducer catheter 1200 is comprised of a tubular
polymeric inner liner 1202, a torque transfer layer 1204, an outer
sheath 1206 comprised of a melt-processing polymer, and a heat
shrink layer 1208. In the instance where the introducer is a
steerable introducer, the introducer catheter 1200 further includes
at least one flat wire 1210 disposed longitudinally along the
length of the introducer catheter 1200. For purposes of this
invention, a "flat wire" refers to a wire that is characterized by
a cross-section that, when measured along two orthogonal axes, is
substantially flat. A flat wire typically has a rectangular cross
section, though the cross section need not be perfectly
rectangular. For example, the present invention contemplates that a
cross section of the flat wire may be oval, provided that the
overall cross section is generally flat. As the term is used
herein, a wire may be properly characterized as a flat wire if it
has a cross section that is measured x in one direction and at
least 2x in a second direction generally orthogonal to the first
direction. A wire whose cross section is substantially I-shaped may
also be a flat wire if, generally, its height is substantially
greater than its width at its widest measurement. One of ordinary
skill will appreciate that a flat wire may be defined in the
context of the overall teachings of this application.
[0083] The at least one flat wire 1210 may be further encased
inside another polymeric tubular member 1212 forming a lumen 1214
for housing the flat wire 1210. The introducer catheter according
to this embodiment is manufactured by a reflow bonding process in
which the components are individually fed over a mandrel as
discussed in more detail below.
[0084] The inner liner 1202 is preferably a polymeric material,
such as polytetrafluoroethylene (PTFE) or etched PTFE. The inner
liner 1202 may also be made of other melt processing polymers,
including, without limitation, polyether block amides, nylon and
other thermoplastic elastomers. Once such elastomer is Pebax.RTM.
made by Arkema, Inc. Pebax of various durometers may also be used,
including without limitation, Pebax 30D to Pebax 70D. In a
preferred embodiment, the inner liner 1202 is made of a material
with a melting temperature higher than the outer sheath 1206 such
that the inner liner 1202 will withstand the melt processing of the
outer sheath 1206.
[0085] Inner liner 1202 defines a lumen 1216 therethrough,
preferably having a diameter 1218 of at least about 6 French, more
preferably of at least about 7 French, and most preferably of
between about 10 French and about 24 French. However, in some
embodiments of the invention, it is contemplated that lumen 1216
may have a diameter 1218 of up to about 32 French or more, such as
between about 7 French and about 32 French.
[0086] A torque transfer layer 1204 is preferably disposed between
the inner liner 1202 and the heat shrink layer 1208, more
preferably between the outer sheath 1206 and the inner liner 1202.
In the instance where the introducer is a steerable introducer
utilizing, for example, at least one longitudinal wire 1210, the
torque transfer layer 1204 may be disposed either between the inner
layer 1202 and the outer sheath 1206 or between the outer sheath
1206 and the heat shrink layer 1208. The torque transfer layer 1204
may be made of stainless steel (304 or 316) wire or other
acceptable materials kown to those of ordinary skill in the
art.
[0087] The torque transfer layer 1204 is preferably formed of a
braided wire assembly comprised of flat wires, preferably stainless
steel wires including, for example, high tensile stainless steel
wires. The torque transfer layer 1204 may be formed in any number
of known braid patterns, including one-over-one (involving at least
two wires) or two-over-two (involving at least four wires)
crossover patterns. The braided flat wires typically have a
thickness of at least about 0.0005'' and a width of at least about
0.005''. Examples of larger sizes include 0.001''.times.0.005'' and
0.002''.times.0.006''. For lumen diameters of at least about 6
French, braided flat wires of at least about 0.003'' thick by at
least about 0.007'' wide, which heretofore were not used to form a
wire mesh for the torque transfer layer, have produced surprisingly
good results of increased pushability, torqueability, flexibility,
and kink resistance over non-flat wires and smaller flat wires. In
general, the individual wires have a ratio of width to the
thickness of at least about 2:1, including, for example, 2:1 to
5:1. Flat wires of about 0.004'' thick by about 0.012'' wide and of
about 0.004'' thick by about 0.020'' wide have also been braided
with success to form torque transfer layers of superior
performance.
[0088] The braid density, commonly measured in pixels per inch
("PPI"), is typically between about 5 and 100, and will depend on
the size of the flat wires as well as the size of the catheter. For
flat wires of at least about 0.003'' thick by about 0.007'' wide
and a catheter having an inner lumen of at least about 6 French,
the PPI is preferably between about 10 and about 90, more
preferably between about 10 and about 55. For example, the PPI for
flat wires of about 0.003'' thick by about 0.007'' wide is
preferably between about 20 and about 90, more preferably between
about 35 and about 55 for an inner lumen of at least 6 French, and
most preferably between about 35 and about 45 for an inner lumen of
at least about 10 French. The PPI for flat wires of about 0.004''
thick by about 0.012'' wide is preferably between about 15 and
about 70, and more preferably between about 15 and about 22 for an
inner lumen of at least about 6 French. The PPI for flat wires of
about 0.004'' thick by about 0.020'' wide is preferably between
about 5 and about 50, and more preferably between about 10 and
about 20 for an inner lumen of at least about 6 French, and most
preferably between about 10 and about 20 for an inner lumen of at
least about 16 French.
[0089] Alternatively, the torque transfer layer 1204 may utilize a
varying braid density construction along the length of the
introducer catheter 1200. For example, the torque transfer layer
may be characterized by a first braid density at the proximal end
of the introducer catheter 1200 and then transition to one or more
braid densities as the torque transfer layer 1204 approaches the
distal end of the introducer catheter 1200; the braid density of
the distal end may be greater or less than the braid density at the
proximal end. In a specific example, the braid density at the
proximal end is about 50 PPI and the braid density at the distal
end is about 10 PPI. In another embodiment, the braid density at
the distal end is about 20-35% of the braid density at the proximal
end.
[0090] The torque transfer layer 1204 may be formed separately on a
disposable core and subsequently slipped around the inner liner
1202. One or more portions of the torque transfer layer 1204 may be
heat tempered and cooled before incorporation into the introducer
body 1200 through methods that are known to those of ordinary
skill. The action of heat tempering may help to release the stress
on the wire and help reduce radial forces. It is also contemplated
that torque transfer layer 1204 may be braided directly on the
inner liner 1202.
[0091] A particularly preferred torque transfer layer 1204 is
comprised of 0.003'' by 0.007'' 304 stainless steel wires at 35 PPI
for an inner lumen of 6-10 French. Another preferred torque
transfer layer 1204 is comprised of 0.004'' by 0.012'' 304
stainless steel wires at 22 PPI for an inner lumen of 12 French.
Yet another preferred torque transfer layer 1204 is comprised of
0.004'' by 0.020'' 304 stainless steel wires at 13 PPI for an inner
lumen of 16 French. These particularly preferred torque transfer
layers may manufactured on a commercially available horizontal
braid machine set at 225 rpm utilizing a commercially available
mandrel. Other suitable methods of manufacturing the torque
transfer layer 1204 will be apparent to those of ordinary skill in
the art.
[0092] The outer sheath 1206 is preferably either an extruded Pebax
or PTFE tubing. The melt-processing polymer of the outer sheath
1206 occupies a plurality of voids of the wire mesh in the torque
transfer layer. The outer sheath 1206 may also be made of other
melt processing polymers, including, without limitation, etched
PTFE, polyether block amides, nylon and other thermoplastic
elastomers, at varying durometers. The outer sheath 1206 may also
comprise more than one layer, including, for example, two or more
tubes of a melt processing polymer. Alternatively, as shown in FIG.
15, the outer sheath 306 may be comprised of varying segments 322,
324, 326, 328, 330 differing in hardness and/or material along the
length of the introducer 300 and being reflow bonded together. This
may be accomplished by layering or by placing annular rings of
differing materials along the length of the introducer 300. Varying
the sheath composition in this manner provides the additional
benefit of adjusting flexibility, torqueability, and pushability at
various points along the introducer 300.
[0093] In embodiments where the introducer is a steerable
introducer (as shown in FIG. 11), at least one flat wire 1210 is
provided, preferably extending along substantially the entire
length of the introducer. The flat wire 1210 is preferably composed
of stainless steel and is preferably about 0.002''.times. about
0.016'', and more preferably about 0.004''.times. about 0.012'' or
0.016''. The flat wire may be selected such that the ratio of the
width to thickness is at least about 2:1. In one embodiment, at
least a portion of the flat wire is encased inside a preformed tube
1212 before placement along the inner liner 1202 to form a flat
lumen 1214. The preformed tube 1212 need not be the same shape as
the cross section of the flat wire, but instead, may be round,
oval, rectangular, or another like shape. Preferably, the preformed
tube 1212 has a cross section that is not the same shape as a cross
section of the flat wire 1210, in order to facilitate movement of
the flat wire in the preformed tube. The preformed tube may be
formed of PTFE, etched PTFE, polyether block amides (such as
Pebax), nylon, other thermoplastic elastomers, or any other known
material to one of ordinary skill in the art. Preferably, the
preformed tube 1212 has a higher melting point than the outer
sheath 1206 so that the preformed tube 1212 will not melt when the
introducer catheter 1200 is subjected to melt processing. In
alternative embodiments the flat wire 1210 may be covered with
lubricious materials (not shown) before placement, including
silicone and other lubricious materials. Alternatively, the flat
wire 1210 may also be coated with a lubricious layer to promote
slideability, and it is also contemplated that the flat wire 1210
may be manufactured with a smooth surface to promote slideability.
While stainless steel is a preferred material to compose the flat
wire 1210, other materials may be used, including, without
limitation, materials that are used for conventional round pull
wires. More than one flat wire 1210 may also be used, and in such
cases, each such flat wire 1210 may be encased inside its own
flexible tube 1212. Preferably, as shown in FIG. 11, a pair of flat
wires 1210 are used that are spaced at 180 degrees apart. The flat
wires 1210 are preferably connected to at least one steering ring
typically located near the distal end of the introducer (see, e.g.,
similar flat wires 30 connected to steering ring 90 in FIG. 2). The
proximal ends of the flat wires 1210 are then operably connected to
a steering mechanism (not shown) allowing for manipulation, or
steering, of the introducer catheter 1200 during use.
[0094] The basic method of manufacture according to an embodiment
of the present invention will be described in reference to FIGS.
12-18. As the various components are assembled, the introducer
components will be collectively referred to as an introducer. As
depicted in FIGS. 12-18, a mandrel 300, which is preferably round
in cross-section and preferably from about 6 inches to about 4 feet
in length, is provided. As depicted in FIG. 12, the mandrel 300 has
a distal end 350 and a proximal end 352. As depicted in FIG. 13, an
inner liner 302 is placed on the mandrel 300. The inner liner 302
is fed on to the mandrel 300 and is then knotted on one end 320, or
both ends.
[0095] As depicted in FIG. 14, a torque transfer layer 304 is then
placed over the inner liner 302. In the case of a steerable
introducer catheter, the flat wire assembly (not shown) may then be
placed over the torque transfer layer 304. Alternatively, the flat
wire assembly may be placed over an outer sheath 306. Another
sheath layer (not shown) may additionally be placed over the flat
wire assembly. The torque transfer layer terminates proximally of
the distal end of the catheter.
[0096] Next, as depicted in FIG. 15, an outer sheath 306 is placed
over the torque transfer layer 304 and may be made of either single
or multiple sections of tubing that are either butted together or
overlapped with each other. The multiple segments, or layers, of
sheath material may be any length and/or hardness (durometer)
allowing for flexibility of design. FIG. 15 identifies a plurality
of segments, 322, 324, 326, 328 and 330. In this embodiment, the
proximal end 330 of the outer sheath 306 may be made of a material
such as nylon, and the remainder of the introducer may be made of
one or more Pebax materials. The lengths of the various segments
may vary, but preferably, the durometer hardness levels will
decrease as the outer sheath 306 approaches its distal end. For
example, a nylon base may then be followed by one or more of the
following Pebax segments: 70D Pebax; 60D Pebax; 55D Pebax; 40D
Pebax; 35D Pebax; 30D Pebax. The introducer shaft may also use one
or more blends of the foregoing Pebax materials, including, for
example, 70D/60D Pebax blend made by co-extrusion, or a 40D/35D
Pebax blend made by co-extrusion. Preferably, the various
components of the outer sheath 306 according to this embodiment
will be reflowed together during manufacturing. The proximal end of
the shaft is preferably the longest segment, and more distal
segments may preferably vary between 0.25'' to 6'', and more
preferably from 0.25'' to about 3''. Preferably, the hardness
levels of the segments and the lengths of the segments may be
adjusted for specific applications, and preferably, the distal end
may have the lowest durometer levels of all segments. The shaft
segments may be selected to improve flexibility, torqueability, and
pushability for the specific application, as appreciated by one of
ordinary skill in the art. Alternatively, the catheter may be
formed by placing a thin inner jacket or layer (e.g., PTFE layer)
onto a mandrel (e.g., stainless steel mandrel) or extruding a thin
inner jacket or layer (e.g., Pebax layer) onto an extrusion mandrel
(e.g., acetal mandrel), forming a torque transfer layer over the
inner layer, and extruding an outer jacket or sheath (e.g., Pebax
jacket) over the torque transfer layer.
[0097] Lastly, a heat shrink layer 308 is placed over the assembled
introducer assembly prior to reflow lamination. The heat shrink
layer 308 is preferably a fluoropolymer or polyolefin material,
such as FEP, or other suitable material as appreciated by one of
ordinary skill in the art.
[0098] After assembly of the various components, the introducer
assembly 300 is subjected to a reflow lamination process. FIG. 11
depicts a cross sectional view of the introducer assembly after
this reflow process. Introducer assembly 1200 may be laminated by
heating the assembly until the material comprising the outer sheath
1206 flows and redistributes around the circumference. Preferably,
the heat shrink layer 1208 has a higher melt temperature than the
outer sheath 1206, and during the melt process, the heat shrink
layer 1208 retains its tubular shape and forces the liquefied
sheath layer material 1206 into the torque transfer layer 1204 and
into contact with the flat wires 1210/preformed tubes 1212 (if
present) and the inner liner 1202. The introducer assembly 1200 may
then be cooled. The mandrel is preferably left in place during the
cooling process as it helps the introducer assembly to retain its
inner lumen of at least about 6 French. The heat shrink layer 1208
may be left on the introducer assembly 1200, or optionally removed.
If the heat shrink layer 1208 is removed, the outer sheath 1206
becomes the outside layer of the introducer catheter 1200.
[0099] Additionally, as shown in FIGS. 16-18, the present invention
contemplates the inclusion of a tip assembly for use in medical
procedures, such as an atraumatic tip, including, for example, a
radiopaque material contained therein for location of the tip
during use. For example, FIGS. 16-18 depict a cross section of an
introducer catheter 700 having a distal portion 730 configured to
accept a tip assembly 732 or 734. In both examples, the tip 732 or
734 includes a ring 736, e.g., a radiopaque marker, for location of
the tip 732 or 734 during use. Additionally, FIG. 18 further
includes a tip assembly 734 configured with a plurality of port
holes 738 for delivery of, for example, irrigation fluid. The tip
assembly may further be configured with ablation electrodes (not
shown) operably connected to a power supply (not shown), for use in
cardiac ablation procedures.
[0100] Although several embodiments of this invention have been
described above with a certain degree of particularity, those
skilled in the art could make numerous alterations to the disclosed
embodiments without departing from the spirit or scope of this
invention. All directional references (e.g., upper, lower, upward,
downward, left, right, leftward, rightward, top, bottom, above,
below, vertical, horizontal, clockwise, and counterclockwise) are
only used for identification purposes to aid the reader's
understanding of the present invention, and do not create
limitations, particularly as to the position, orientation, or use
of the invention. Joinder references (e.g., attached, coupled,
connected, and the like) are to be construed broadly and may
include intermediate members between a connection of elements and
relative movement between elements. As such, joinder references do
not necessarily infer that two elements are directly connected and
in fixed relation to each other. It is intended that all matter
contained in the above description or shown in the accompanying
drawings shall be interpreted as illustrative only and not
limiting. Changes in detail or structure may be made without
departing from the spirit of the invention as defined in the
appended claims.
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