U.S. patent application number 09/185211 was filed with the patent office on 2001-09-06 for catheter support structure.
Invention is credited to KLIMA, DANIEL J., THOMPSON, PAUL J..
Application Number | 20010020161 09/185211 |
Document ID | / |
Family ID | 22680064 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010020161 |
Kind Code |
A1 |
KLIMA, DANIEL J. ; et
al. |
September 6, 2001 |
CATHETER SUPPORT STRUCTURE
Abstract
The present disclosure relates to a catheter including a segment
having a longitudinal axis, and a plurality of circumferential
supports surrounding the axis. A plurality of filaments surround
the circumferential supports to enhance torque transmission through
the catheter segment.
Inventors: |
KLIMA, DANIEL J.; (PLYMOUTH,
MN) ; THOMPSON, PAUL J.; (NEW HOPE, MN) |
Correspondence
Address: |
MERCHANT & GOULD PC
1050 17TH STREET, SUITE 1400
DENVER
CO
80265
US
|
Family ID: |
22680064 |
Appl. No.: |
09/185211 |
Filed: |
November 3, 1998 |
Current U.S.
Class: |
604/524 |
Current CPC
Class: |
A61M 25/0052 20130101;
A61M 25/0054 20130101 |
Class at
Publication: |
604/524 |
International
Class: |
A61N 001/30 |
Claims
What is claimed is:
1. A catheter including a segment having a longitudinal axis, said
segment comprising: a plurality of circumferential supports
surrounding said axis; and a plurality of filaments surrounding
said circumferential supports.
2. A catheter according to claim 1, wherein said circumferential
supports are axially spaced along said longitudinal axis.
3. A catheter according to claim 1, further comprising an elongated
inner liner positioned within the circumferential supports.
4. A catheter according to claim 3, further comprising a flexible
outer layer surrounding an outer surface of said circumferential
supports.
5. A catheter according to claim 3, wherein the filaments have
components extending in both a circumferential direction and an
axial direction relative to the longitudinal axis.
6. A catheter according to claim 1, wherein said segment is sized
to fit within a blood vessel.
7. A catheter according to claim 1, wherein said segment further
includes an inner layer of flexible material surrounded by said
circumferential supports and an outer layer of flexible material
surrounding said circumferential supports, said inner layer having
an inner surface defining a catheter bore.
8. A catheter according to claim 1, wherein said circumferential
supports are cylindrical rings.
9. A catheter according to claim 1, wherein the filaments are
interwoven and form a braid surrounding the circumferential
supports.
10. A catheter according to claim 1, wherein said circumferential
supports are helical coils.
11. A catheter according to claim 1, wherein the filaments provide
means for increasing a torsional stiffness of the segment.
12. A catheter according to claim 1, wherein the filaments are
interwoven.
13. A catheter including a segment having a longitudinal axis, said
segment comprising; a tubular inner liner surrounding said axis;
circumferential supports surrounding said inner liner; a plurality
of interwoven filaments forming a braid that surrounds the
circumferential supports; and an outer polymeric jacket that covers
the circumferential supports and the braid.
Description
I. BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention pertains to catheters for passage through a
vasculature system. More particularly, this invention pertains to a
novel construction of at least a segment of a catheter.
[0003] 2. Description of the Prior Art
[0004] Catheters are widely used in medical treatment. A catheter
is an elongated flexible member advanced through the vasculature
system to a desired site. The catheter may be advanced over a
previously inserted guide wire.
[0005] With the catheter in place, a wide variety of substances may
be passed through the catheter to the site. For example, drugs may
be moved through the catheter for site-specific drug delivery.
Also, implements may be passed through the catheter. The catheter
may also be used to remove fluids from the site. Still further, a
catheter may be equipped with implements (e.g., balloon tips) for
performing procedures (e.g., angioplasty) at the site.
[0006] Catheters have long been used in cardiovascular treatment.
More recently, catheters are used in neurological procedures
requiring advancement of the catheter through very narrow vessels.
To accomplish these advances, a high degree of flexibility is
desired. Also, catheters need very thin walls in order to retain an
internal bore having as large a diameter as possible.
[0007] While advancing a catheter, a physician may twist a proximal
end of the catheter in order to cause a corresponding twist of the
distal end of the catheter (referred to as "torque transmission
response"). A consistently reliable torque transmission response a
consistent one-to-one torque transmission response) is desired.
[0008] In designing catheters, it is desirable to provide a
catheter which is kink resistant. Namely, a catheter typically is a
tube with an internal bore of circular cross-section. When a
catheter bends, it may be inclined to kink resulting in closure or
geometric deformation of the circular bore. Such closure or
deformation is undesirable. Further, in certain applications, the
catheter may be subjected to high internal pressures (e.g., 300
psi). Such pressures tend to burst the catheter or expand the
catheter geometry.
[0009] Catheter geometry can also by deformed by torque applied to
the catheter. Many catheters are designed to have a reinforcing
coil extending along the length of the catheter. If torque is
applied in the direction of the coil winding, the internal diameter
of the catheter may reduce. If torque is applied in the opposite
direction, the diameter may expand. Dual coil catheters (i.e.,
catheters having two coils extending the length of the catheter
with one coil being a clockwise wind and the other being a
counter-clockwise wind) have been developed to retain dimensional
stability regardless of direction of torque and to increase torque
transmission. Unfortunately, such catheters are costly and have an
extra layer of coil which takes up an already limited space within
the vasculature. Thus a need exists to develop catheters that are
kink resistant, able to transmit torque effectively and take up a
minimal amount of space within the vasculature.
II. SUMMARY OF THE INVENTION
[0010] One aspect of the present invention relates to a catheter
including a segment having a longitudinal axis, and a plurality of
circumferential supports surrounding the axis. A plurality of
filaments surround the circumferential supports. The
circumferential supports assist in providing kink resistance, while
the filaments provide enhanced torque and axial load transmission
through the catheter segment.
III. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is an overall view of a catheter according to the
present invention;
[0012] FIG. 2 is a cross-sectional, longitudinal view of a
longitudinal segment of the catheter of FIG. 1;
[0013] FIG. 3 is the view of FIG. 2 with the inner liner removed to
expose circumferential supports of the catheter segment;
[0014] FIG. 4 is a perspective view of an embodiment of a
circumferential support structure of the segment of FIG. 2;
[0015] FIG. 5 is a perspective view of another embodiment of a
circumferential support structure of the segment of FIG. 2;
[0016] FIG. 6 is a perspective view of another embodiment of a
circumferential support structure;
[0017] FIG. 7 is a cut-away view of the segment of FIG. 2;
[0018] FIG. 8 is a cross-sectional, longitudinal view of a
longitudinal segment of an alternative catheter with the inner
liner removed to expose circumferential supports of the catheter
segment; and
[0019] FIG. 9 is a perspective view of one of the circumferential
supports of the catheter segment of FIG. 8.
IV. DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] Referring now to the several drawing figures in which
identical elements are numbered identically throughout, a
description of a preferred embodiment of the present invention will
now be provided.
[0021] FIG. 1 illustrates a catheter 10. The catheter 10 extends
from a proximal end 12 to a distal end 14. At the proximal end 12,
a hub 16 is provided to be gripped by a physician as well as having
an inlet 18 for injection of fluids into the catheter 10. A
flexible hollow shaft 20 is connected to the hub 16. The shaft 20
is sized to be inserted into a patient's vasculature. The shaft 20
is commonly about 150 cm long. A strain relief jacket 22 connects
the shaft 20 to the hub 16. The foregoing description forms no part
of this invention and is given to facilitate an understanding of
the present invention.
[0022] The catheter 10 includes a segment 60 having the novel
construction of the present invention. (For purposes of the
remainder of this description, the word "catheter" is generally
used to refer to the flexible shaft 20 of FIG. 1 having the segment
60 which a construction as will be described.) While the entire
length of the catheter 10 can be constructed as will be described
with reference to segment 60, it may be desirable to have a
catheter 10 of multiple segments of different construction to
impart different properties to different regions of the catheter 10
along its length. For example, it may be desirable to provide a
catheter 10 having a proximal portion stiffer than a more flexible
distal portion. While the present invention is suitable for forming
catheter segments of varying degrees of flexibility and other
properties, the present invention is described with reference to a
segment 60 of the length of the catheter 10. This is to allow for
catheters where the entire length is constructed according to the
teachings of this application as well as catheters where only a
discrete portion is so constructed and where the remainder is
constructed according to conventional catheter construction
techniques.
[0023] With reference to FIGS. 2 and 3, the segment 60 is shown to
illustrate the novel construction. The segment 60 has a multi-layer
construction including a flexible inner layer 62. By way of
non-limiting example, the inner layer 62 is polytetraflouroethylene
(PTFE) more commonly known by the trademark Teflon.TM.. In a
preferred embodiment, layer 62 has an outer diameter D.sub.1 of
0.0230 inch (0.58 mm) and an inner diameter D.sub.2 of 0.0210 inch
(0.53 mm) to define an internal bore 64 surrounded by the Teflon
inner tube layer 62.
[0024] The segment 60 also includes a circumferential support
structure 70 as will be more fully described. The circumferential
support structure 70 is generally tubular and is adhered to the
external surface of the inner layer 62 by a thin bonding layer of
any suitable adhesive 66 (e.g., polyurethane having a thickness
T.sub.A of about 0.0004 inch or 0.01 mm). The circumferential
support structure 70 has an outer diameter D.sub.3 of about 0.025
inch (0.635 mm). The circumferential support structure 70 provides
circumferential strength and kink resistance.
[0025] Surrounding the exterior of the circumferential support
structure 70, a monofilament or a filament layer 80 is provided.
The filament layer 80 is composed of a plurality of filaments 81
that are preferably arranged in one or more strands 83. The strands
83 are wrapped, intermeshed or braided about the support structure
70. The filaments 81 of each strand 83 can be twisted, plaited or
laid parallel relative to one another. In one particular
embodiment, the filaments 80 are laid parallel to one another to
form a generally flat strip. Such a strip is advantageous because
it can be wrapped flat about the circumference of the support
structure 70 thereby minimizing the radial thickness occupied by
the filaments.
[0026] The filaments 81 may be composed of any suitable flexible
material which will provide torsional stiffness and axial strength
to the segment 60. Such materials may include, for example, metal,
plastics, polymers, nylon or other materials. A preferred material
is a liquid crystal polymer sold under the name Vectran.TM. by
Hoechst Celanese Corporation, of Charlotte, N.C. The filament layer
80 typically has a thickness TB of about 0.001-0.003 inch. The
filament layer 80 provides enhanced torque transmission by
increasing the torsional stiffness of the segment 60. The filaments
81 themselves are preferably limp or flexible. In certain
embodiments, the filaments 81 can each have a diameter less than
0.001 inch, or about 0.0008 inch.
[0027] Surrounding the exterior of the filament layer 80, an outer
polymer jacket 90 is provided. The outer jacket 90 may be any
suitable flexible material for use in the vascular system. Such
materials may be nylon or urethane. The outer jacket 90 has an
outer diameter D.sub.4 of 0.029 inch (0.74 mm).
[0028] In the foregoing, Applicants have provided a specific
description of various layers of segment 60 as well as describing
specific materials and dimensions. Such specificity has been given
to describe a preferred embodiment of a specific catheter 10
utilizing the circumferential support structure 70 and filament
layer 80 as will be described. More or fewer layers of materials
could be used with the circumferential support structure 70 and
filament layer 80 to impart desired properties (e.g., varying
stiffness, strength, etc.) to segment 60. Similarly, specific
materials and dimensions may be varied to alter the properties of
segment 60. However, the combination of the circumferential support
structure 70 and the filament layer 80 provides excellent kink
resistance while still being capable of transmitting torque better
than the circumferential support structure 70 alone.
[0029] Referring now to FIG. 3, the circumferential support
structure 70 includes a plurality of circumferential supports 52a,
52b. Each of the supports 52a, 52b is a ring surrounding the axis
X-X. The supports 52a, 52b may differ in shape for reasons that
will be described. FIG. 3 illustrates that different shaped
supports 52a, 52b may be included within segment 60 to alter
properties (e.g., flexibility or torque transmission response along
the length of segment 60). Alternatively, segment 60 could include
circumferential supports which are of identical construction along
its length (e.g., all having the shape of supports 52a) to impart
more uniform properties to segment 60 along its length.
[0030] The circumferential supports 52a, 52b are positioned in
parallel, spaced-apart alignment about axis X-X. Adjacent supports
52a, 52b are disjointed. Namely, each support 52a, 52b is an
independent ring of rigid material. There is no rigid material
(e.g., the material of rings 52a, 52b) interconnecting the rings
52a, 52b. Instead, adjacent rings are interconnected only by the
flexible material of the liners 62, 90 and the filaments 80.
Therefore, the rings 52a, 52b are non-integrally connected. As a
result of the disjointed alignment of rings 52a, 52b, the segment
60 is highly flexible with the rings 52a, 52b providing structural
integrity to retain the cross-sectional geometry of bore 64.
[0031] By way of example, the circumferential supports 52a, 52b
have a width W of about 0.003 inch (0.076 mm). The width is the
dimension parallel to the axis X-X. The circumferential supports
52a, 52b have a thickness T of about 0.001 inch (0.025 mm) (i.e.,
the radial dimension measured between the inner and outer surfaces
51a, 51b and 53a, 53b of the circumferential supports 52a, 52b).
Finally, the circumferential supports 52a, 52b have an axial
spacing S between opposing/adjacent supports 52a, 52b of about
0.005 inch (0.127 mm).
[0032] FIGS. 4 and 5 illustrate two possible geometries of supports
52a, 52b. Since the supports 52a, 52b are formed by removing
material from a cylindrical tube, the rings 52a, 52b are each
complete circumferential surfaces surrounding the axis and are
segments of a cylindrical tube. In FIG. 4, the ring 52a has
parallel and planar axial ends 55a. In FIG. 5, the axial ends 55b
are parallel but non-planar such that the ring 52b, in
cross-section presents a V-shaped profile (see FIG. 3). Also, the
circumferential supports 52a, 52b can be made narrower or thinner
than the dimensions disclosed as well as changing the shape (as
illustrated comparing FIGS. 4 and 5). Such modifications (as well
as modifying the spacing S between supports 52a, 52b) alter the
flexibility of segment 60. Therefore, the present invention
provides a catheter designer with a wide variety of design options
to use the present invention to fabricate catheters of varying
properties for specific applications.
[0033] Referring to FIG. 6, an alternate circumferential support
structure 70 includes a plurality of helical support struts 72a,
72b. As will become apparent, the plurality of support struts
includes first and second sets of struts. Struts of the first set
are designated 72a while struts of the second set are designated
72b.
[0034] While having an open structure, circumferential support
structure 70 is generally tubular and extends from a first end 74
to a second end 76. The circumferential support structure 70
surrounds the longitudinal axis X-X. As indicated, the length of
the circumferential support structure 70 (i.e., the distance
between ends 74, 76) may be the entire length of the catheter or
only a portion of the entire length.
[0035] Each of the struts 72a, 72b extends from a first end 71a,
71b to a second end 73a, 73b. The first and second ends 71a, 73a
and 71b, 73b of a strut 72a, 72b are spaced apart longitudinally
with respect to axis X-X. Additionally, each of the struts 72a, 72b
curves around the axis X-X between ends 71a, 73a and 71b, 73b. In
atypical embodiment shown in FIG. 6, the struts 72a, 72b are
helical about axis X-X and curve substantially 360.degree. about
axis X-X.
[0036] Viewed from the first end 74 of the circumferential support
structure 70, the struts 72a curve about axis X-X in a clockwise
direction. Struts 72b curve in an opposite counter-clockwise
direction.
[0037] In the embodiment shown, the struts 72a alternate in series
with struts 72b along the length of the circumferential support
structure 70. Adjacent ends 73a, 71b and 71a, 73b of adjacent
struts 72a, 72b are connected such that all struts 72a, 72b along
the length of circumferential support structure 70 are
interconnected.
[0038] In the embodiment shown, a plurality of circumferential
cylindrical rings or supports 78 are disposed between each of
adjacent struts 72a, 72b. Accordingly, the adjacent ends 73a, 71b
and 71a, 73b are not directly interconnected but, instead, are
connected to opposite ends of a common circumferential support
78.
[0039] By way of example, the circumferential supports 78 and the
struts 72a, 72b have a width of about 0.003 inch (0.076 mm). In the
case of circumferential supports 78, the width is the dimension
parallel to the axis X-X. In the case of the struts 72a, 72b, the
width is the dimension transverse to the helical path of the struts
72a, 72b. The circumferential supports 78 and the struts 72a, 72b
have a thickness T of about 0.001 inch (0.025 mm) (Le., the radial
dimension measured between the inner and outer diameters of the
circumferential supports 78 and the struts 72a, 72b). Finally, the
circumferential supports 78 have an axial spacing S between
opposing/adjacent supports 78 of about 0.005 inch (0.127 mm).
[0040] Referring to FIGS. 2, 3, and 7, the filament layer 80
includes a plurality of filaments 81. The filaments 81 surround the
circumferential support structure 70. The filaments 81 extend in
both a circumferential direction and an axial direction relative to
the longitudinal axis. Typically, the filaments 81 are interwoven
and form a braid surrounding the circumferential support structure
70. The filament layer 80 functions to increase the torsional
stiffness of the segment 60.
[0041] Preferably, the circumferential support structure 70 is
fabricated from a solid blank of medical grade stainless steel
tubing. Other possible materials include nickel-titanium alloys
(e.g., nitinol) and cobalt-chromium-nickel alloys (e.g.,
Elgiloy.TM. alloy of Elgiloy, Inc. of Elgin, Ill., U.S.A.). Such a
fabrication process includes starting with a rod (not shown) having
an outer diameter equal to the desired inner diameter of the PTFE
layer 62. The PTFE layer 62 is placed over the rod which acts as a
jig to hold the elements of catheter 10 during fabrication. The
adhesive 66 is applied to the external surface of PTFE layer 62. A
solid tube of medical grade stainless steel (referred to as a
hypotube) is then adhered to PTFE layer 62 by adhesive 66. As an
alternative, the PTFE layer 62 and the metal tube can be assembled
without the adhesive 66 with parts held in alignment until the
final outer layer 90 is applied.
[0042] The solid metal tube is then milled to remove excess
material of the tube as waste and leaving only the material of the
circumferential supports 78, and struts 72a, 72b or the
circumferential supports 52a and 52b as the circumferential support
structure 70. In a typical embodiment, the metal tube is milled by
a chemical milling process. In such a process, a pattern mask of
the desired pattern of the circumferential supports 78 and struts
72a, 72b or the circumferential supports 52a, 52b is placed over
the metal tube. A light source sensitizes a photoresist applied to
the metal to create a pattern on the metal tube matching the mask.
The photo-sensitized tube is then chemically etched to dissolve
away the areas of the tube corresponding to the waste leaving only
the desired material of the circumferential supports 78 and struts
72a, 72b or the circumferential supports 52a, 52b. It will be
appreciated that this description of a chemical milling of the
metal tube forms no part of this invention per se. Such a process
is more fully described in commonly assigned and copending U.S.
patent application Ser. No. 08/645,607 the specification of which
was published on Dec. 5, 1996 as International Publication No.
WO96/38193 or PCT International application Ser. No.
PCT/US96/08232.
[0043] After the tube is so milled, the filament 80 layer is
applied to or wrapped about the outer surface of the
circumferential support structure 70. The outer layer 90 is then
applied over the filament 80 layer. The material of the outer layer
90 may, at the option of a designer, fill in the axial spacing S
between the circumferential supports 52, 78 and filaments 81 or
leave such spacing as voids to enhance flexibility. The rod is then
removed from the PTFE layer 62 leaving a completed segment 60.
[0044] The present invention has been described in a preferred
embodiment and may be modified while keeping with the teachings of
the present invention. For example, the circumferential support
structure 70 need not be formed of metal or fabricated in the
chemical milling manner indicated. The circumferential support
structure 70 can be formed from any structural material in any
manner including, without limitation, electrical discharge
machining, laser cutting, or assembly of individual components.
[0045] Similarly, while a preferred circumferential support
structure 70 has been disclosed, numerous modifications can be made
to the structure to vary the properties of the catheter 10 to meet
design objectives for a specific application. For example, geometry
of the support rings can be varied (e.g., thicker, wider, narrower,
closer or more distant spacing as well as non-symmetrical shapes
compared to the symmetrical shapes shown) to vary strength and
flexibility.
[0046] FIG. 8 shows a longitudinal cross-sectional view of a
catheter segment 160 that is a further embodiment of the present
invention. The catheter segment 160 includes a plurality of
circumferential supports 152 mounted on flexible inner liner (not
shown) and surrounded by a flexible outer jacket 190.
[0047] FIG. 9 shows a single one of the circumferential supports
152 in isolation from the liners. As shown in FIG. 8, the
circumferential supports 152 are positioned in parallel, spaced
apart alignment along a longitudinal axis X'-X' and each comprises
an independent ring.
[0048] Distal and proximal projections 152a and 152b project
axially or longitudinally outward from opposite axial ends of each
circumferential support 152. Adjacent circumferential supports 152
are disjointed. The axial projections 152a and 152b extend in a
direction generally parallel to the longitudinal axis X'-X'. Gaps
153a are formed between the distal projections 152a, while gaps
153b are formed between the proximal projections 152b.
[0049] Adjacent circumferential supports 152 are positioned in
different circumferential or rotational orientations about the
longitudinal axis X'-X'. For example, as shown in FIG. 8, the
projections 152a and 152b of adjacent circumferential supports 152
are not in axial alignment with one another. Instead, the axial
projections 152a are aligned with the axial gaps 153b, and the
axial projections 152b are aligned with the axial gaps 153a. The
axial projections 152a and 152b are preferably larger than the gaps
153a and 153b to inhibit meshing between the circumferential
supports 152. However, in alternative embodiments, adjacent rings
can be configured to intermesh with one another. For example, axial
projections of one ring can fit between the axial projections of an
adjacent ring. In still other embodiments, rings can be used that
have only proximal axial projections, or only distal axial
projections.
[0050] As shown in FIG. 8, the catheter segment 160 also includes a
filament layer 180 including a plurality of filaments 181 similar
to those previously described in the specification. The filaments
181 surround the circumferential supports 152 and extend in both a
circumferential direction and an axial direction relative to the
longitudinal axis X'-X'. In certain embodiments, the filaments 181
can be interwoven to form a braid surrounding the circumferential
supports 152. In other embodiments, the filaments 181 can be
aligned parallel to one another to form a strip-like structure.
[0051] In the embodiment of FIGS. 8 and 9, the axial projections
152a and 152b preferably have lengths 1 in a range of 0.005-0.010
inches, and an unloaded spacing S (i.e., a spacing when no torque
or axial load is being applied to the catheter segment) of
0.010-0.025 inches preferably exists between the circumferential
supports 152. The segment 160 can be manufactured by a similar
process to that described above with respect to the embodiment of
FIGS. 2-5 and 7.
[0052] From the foregoing, the present invention has been disclosed
in a preferred embodiment. The invention permits construction of a
catheter overcoming disadvantages of prior designs as well as
providing a structure having various features which can be modified
to design catheters with optimum performance for a wide variety of
applications. It is intended that modifications and equivalents of
the disclosed concepts, such as those which readily occur to one of
skill in the art shall be included within the scope of the claims
appended hereto.
* * * * *