Title: Catheter shaft with coextruded stiffener
Abstract: A steerable catheter having a shaft with one or more internal stiffeners coextruded within the shaft along a portion of its length. The internal stiffeners have a higher or lower hardness than the body of the catheter shaft. The overall stiffness of the shaft varies along its length for improved steerability.
Patent Number: 6,855,137 Issued on 02/15/2005 to Bon
| Inventors:
|
Bon; Edwin (Canton, GA)
|
| Assignee:
|
Visionary Biomedical, Inc. (Roswell, GA)
|
| Appl. No.:
|
093757 |
| Filed:
|
March 7, 2002 |
| Current U.S. Class: |
604/525; 264/634; 604/164.13; 604/528 |
| Intern'l Class: |
A61M 025//00; A61M 025//01; A61M 025//02; A61M 025//04; A61M 025//06; A61M 025//08; A61M 025//08.2; A61M 025//08.5; A61M 025//08.8; A61M 025//09; A61M 025//09.5; A61M 025//09.8; A61M 005//17.8; C04B 035//64 |
| Field of Search: |
604/510,95.04,164.13,524,525,528
600/434
264/514,515,516,541,171.26-171.29,172.1-172.15,173.11-173.17,177.1
|
References Cited [Referenced By]
U.S. Patent Documents
| 4250072 | Feb., 1981 | Flynn | 524/288.
|
| 5226899 | Jul., 1993 | Lee et al.
| |
| 5453099 | Sep., 1995 | Lee et al.
| |
| 5542937 | Aug., 1996 | Chee et al.
| |
| 5797882 | Aug., 1998 | Purdy et al.
| |
| 5902287 | May., 1999 | Martin.
| |
| 5976120 | Nov., 1999 | Chow et al. | 604/525.
|
| 6004310 | Dec., 1999 | Bardsley et al. | 604/524.
|
| 6027477 | Feb., 2000 | Kastenhofer.
| |
| 6030369 | Feb., 2000 | Engelson et al.
| |
| 6325790 | Dec., 2001 | Trotta.
| |
| 6530897 | Mar., 2003 | Nardeo | 604/95.
|
Other References
Plastics Technology Online Article "Medical Tubing Coextrusion Brings a New
Level of Care" by Jan H. Schut, 6 pgs.
|
Primary Examiner: Lucchesi; Nicholas D.
Assistant Examiner: Williams; Catherine S.
Attorney, Agent or Firm: Gardner Groff, P.C.
Claims
What is claimed is:
1. A steerable catheter comprising:
a handle comprising at least one steering actuator;
a catheter shaft having a proximal end connected to the handle, a distal
end opposite the proximal end, and defining a length between said proximal
and distal ends, said catheter shaft comprising at least steering wire
lumen;
at least one steering wire extending through said at least one steering
wire lumen of the catheter shaft and connected to said steering actuator;
two instrument lumens extending along the length of the catheter shaft,
each of said two instrument lumens having a central axis lying on a first
plane being extending through said catheter shaft; and
two stiffeners coextruded within said catheter shaft and extending along at
least a portion of the length of the catheter shaft, each of said two
stiffeners having a central axis lying on a second plane extending through
said catheter shaft, the second plane being generally perpendicular to the
first plane.
2. The steerable catheter of claim 1, wherein a steering wire lumen extends
through each stiffener.
3. The steerable catheter of claim 1, wherein each stiffener has a first
dimension in a direction parallel to said first plans, and a second
dimension in a direction parallel to said second plane, and wherein said
first dimension is greater than said second dimension.
4. The steerable catheter of claim 3, wherein said first dimension is at
least twice said second dimension.
5. The steerable catheter of claim 1, wherein the stiffeners have a higher
hardness than the catheter shaft.
6. The steerable catheter of claim 1, wherein the catheter shaft has a
higher hardness than the stiffeners.
7. The steerable catheter of claim 1, wherein the stiffeners extend through
less than the entire length of the catheter shaft.
8. A method of forming a catheter shaft, said method comprising:
extruding a first polymeric material to form a shaft body, the first
polymeric material having a first hardness;
coextruding a second polymeric material to form two stiffeners within the
shaft body, the second polymeric material having a second hardness
different from the first hardness;
wherein at least one of said stiffeners is sequentially coextruded from
said second polymeric material and a third polymeric material, said third
polymeric material having a third hardness different from the first and
second hardnesses; and
wherein the shaft body has at least one steering wire extending through at
least one steering wire lumen of the shaft body and two instrument lumens
extending along the length of the shaft body, each of said two instruments
lumens having a central axis lying on a first plane extending through said
shaft body, and said two stiffeners extending along at least a portion of
the length of the shaft body, each of said two stiffeners having a central
axis lying on a second plane extending through said shaft body, the second
plane being generally perpendicular to the first plane.
9. The method of claim 8, wherein the first polymeric material has a higher
hardness than the second polymeric material.
10. The method of claim 8, wherein the second polymeric material has a
higher hardness than the first polymeric material.
11. The method of claim 8, wherein the at least one stiffener is coextruded
within only a portion of the length the shaft body.
12. The method of claim 8, wherein the at least one stiffener is coextruded
into the shaft body at a distance from a central longitudinal axis of the
shaft body.
13. The method of claim 8, wherein the at least one stiffener is coextruded
to have a cross sectional length and a cross sectional width, said cross
sectional length being greater than said cross sectional width.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to remote access devices, and more
particularly to a steerable catheter having one or more stiffeners
coextruded into the catheter shaft.
2. Description of Related Art
Modern medical practitioners frequently gain access to internal regions of
a human or animal patient's body through the use of medical catheters in a
variety of medical procedures. For example, medical catheters may be used
to access internal body regions with a fiberoptic scope, light bundles,
surgical instruments, medications, and/or other substances and devices,
for a variety of diagnosis, treatment and/or material delivery purposes.
These minimally invasive catheter access techniques can significantly
reduce or eliminate the need for more invasive procedures.
Steerable catheters have been developed to provide improved access to
remote sites such as internal body tissue. These catheters typically
include a flexible catheter shaft and steering wires or other means for
controlling the flexure of the catheter shaft. Steerable catheters find
application in the observation and treatment of tissue in and around the
joints in arthroscopic procedures, in and around the abdominal cavity in
laparoscopic procedures, in spinal epiduroscopy, in the cardio-pulmonary
and circulatory systems, and in other endoscopic procedures. Steerable
catheters are also used for remote visualization and access in non-medical
applications such as in the inspection and repair of internal engine
components and other devices and structures.
A commonly encountered problem in the design of steerable catheters is the
provision of acceptable flexibility of the catheter shaft, particularly
near the shaft tip, while still maintaining adequate overall shaft
stiffness for pushing through tissue openings and other access pathways.
Difficulties are also encountered in providing a desired degree of
stiffness to a catheter shaft formed from the relatively softer shaft
materials that are often preferred for their trauma minimization
qualities. Also, in most instances it would be desirable to provide a
catheter shaft with a more "in-plane" steering bias for improved steering
control, rather than a shaft that tends to twist or "pig-tail" out of the
intended steering plane when steered. Another problem suffered by some
previously existing catheter shafts is "socking", wherein the shaft
material crumples along the shaft's longitudinal axis when tension is
applied to the steering wires, rather than bending along a smooth arcuate
path.
Previously known methods of forming catheter shafts have also been found to
have certain drawbacks. For example, some catheter shafts incorporate wire
reinforcements encapsulated into their wall material or concentrically
coextruded layers, which result in manufacturing difficulties and add
considerably to the shaft's expense. In addition, the inclusion of wire
within a catheter shaft may interfere with the guidance and placement of
the catheter under flouroscopic observation, or may adversely impact
regulatory approvals. Also, the material dissimilarities between the metal
wire and the polymeric catheter shaft may result in slippage therebetween,
possibly producing unpredictable steering characteristics. Welding shaft
segments of differing durometer hardness together to form a catheter shaft
also requires considerable effort and expense in ensuring proper alignment
and connection between the segments.
Thus, it has been found that needs exist for an improved steerable catheter
shaft and to related production methods. It is to these and other needs
that the present invention is primarily directed.
SUMMARY OF THE INVENTION
Briefly described, in its preferred embodiments, the present invention
provides a steerable catheter shaft having one or more internal stiffeners
coextruded or otherwise formed into the shaft material along a selected
portion of the length of the shaft. The stiffener(s) assist in maintaining
the overall stiffness of the shaft, and resist socking. Because the
stiffener(s) is/are embedded within the body of the shaft, the shaft's
exterior can be formed of a softer, atraumatic material. Eccentric
placement of the stiffener(s) biases the shaft to steer in an in-plane
manner. The configuration of the stiffener(s)--including the size, shape,
number and location of the stiffener(s) within the shaft's cross-section
and/or along the shaft's length--can be selectively controlled to vary the
flexibility and steerability characteristics of the shaft. One or more
instrument lumens preferably extend through the catheter shaft for
instrument access and/or passage of fluids, medication and the like. One
or more steering wires preferably pass through at least a portion of the
catheter shaft to effect steering of the shaft. Optionally, the lumen(s)
and/or the steering wire(s) pass through the stiffener(s) within the
catheter shaft.
In one embodiment, the present invention is a catheter shaft. The catheter
shaft preferably includes a shaft body formed of a polymeric material
having a first hardness, and the shaft body has a first end and a second
end and defines a length therebetween. The shaft preferably also includes
at least one stiffener embedded within the shaft body along at least a
portion of the length of the shaft body. Each stiffener is preferably
formed of a polymeric material having a second hardness different than the
first hardness.
In another embodiment, the present invention is a steerable catheter. The
catheter preferably includes an elongate catheter shaft having a first end
and a second end, and defines a length between the first and second ends.
The catheter preferably also includes at least one internal stiffener
embedded within the catheter shaft, and at least one steering wire
extending through at least a portion of the length of the catheter shaft.
Another embodiment of the present invention is a steerable catheter. The
catheter preferably includes a handle having at least one steering
actuator. The catheter preferably also includes a catheter shaft having a
proximal end connected to the handle, a distal end opposite the proximal
end, and defining a length between the proximal and distal ends. The
catheter shaft preferably includes at least one instrument lumen and at
least one steering wire lumen. The catheter preferably also includes at
least one stiffener coextruded within the catheter shaft, and at least one
steering wire extending through the at least one steering wire lumen of
the catheter shaft and being connected to the steering actuator.
In another embodiment, the present invention is a method of forming a
catheter shaft. The method preferably includes extruding a first polymeric
material to form a shaft body, the first polymeric material having a first
hardness; and coextruding a second polymeric material to form at least one
stiffener within the shaft body, the second polymeric material having a
second hardness different from the first hardness.
These and other features and advantages of preferred forms of the present
invention are described herein with reference to the drawing figures.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
FIG. 1 shows a perspective view of a shaft portion of a steerable catheter
in partial cutaway, according to one embodiment of the present invention.
FIG. 2 shows a cross-sectional view of the shaft portion of a steerable
catheter shown in FIG. 1.
FIG. 3 shows a perspective view of a catheter according to an embodiment of
the present invention.
DETAILED DESCRIPTION
Referring now to the drawing figures, in which like reference numbers refer
to like parts throughout, preferred forms of the present invention will
now be described by way of example embodiments. It is to be understood
that the embodiments described and depicted herein are only selected
examples of the many and various forms that the present invention may
take, and that these examples are not intended to be exhaustive or
limiting of the claimed invention. Also, as used in the specification
including the appended claims, the singular forms "a," "an," and "the"
include the plural unless the context clearly dictates otherwise. Ranges
may be expressed herein as from "about" or "approximately" one particular
value and/or to "about" or "approximately" another particular value. When
such a range is expressed, another embodiment includes from the one
particular value and/or to the other particular value. Similarly, when
values are expressed as approximations, by use of the antecedent "about,"
it will be understood that the particular value forms another embodiment.
As seen best with reference to FIGS. 1 and 3, a catheter 10 according to
one example embodiment of the present invention generally comprises a
handle 12 and a shaft 14 extending from the handle. The handle 12
preferably comprises one or more steering actuator(s), such as a steering
dial, one or more steering buttons, one or more levers or wire pulls, or
the like. The catheter 10 optionally further comprises one or more inlet
housings 16 in communication with lumens extending through the shaft 14.
U.S. Pat. No. 6,030,360, which is hereby incorporated herein by reference,
shows an example of a steerable catheter with a dial-actuated steering
mechanism.
In example embodiments, the catheter shaft 14 of the present invention has
a proximal end connected to the handle 12 and a distal free end or tip
opposite the proximal end, and defines a shaft length between the proximal
and distal ends. The body of the shaft 14 is preferably formed of a
flexible and biocompatible polymeric material, for example a 5533
Pebax.RTM. polyether block amide. The shaft 14 optionally is marked,
compounded, coated, or otherwise provided with one or more additive
materials, colorants, or markings such as barium sulfate and/or titanium
oxide to permit flouroscopic observation and positioning of the shaft. In
one example embodiment, the shaft 14 has an outside diameter of about
0.100", and a length of about 12". Of course, shafts of larger or smaller
diameter and length may be desirable for particular applications, and are
within the scope of the invention. Although the embodiment of the shaft 14
depicted in the figures has a generally round cross-sectional profile (see
FIG. 2), shafts of flat, oval, triangular, square, rectangular, polygonal
or other cross-sectional profiles are also within the scope of the
invention.
One or more instrument lumens 18 preferably extend through at least a
portion of the length of the shaft 14. The instrument lumens 18 are
preferably sized and/or shaped to accommodate passage of various medical
instruments, light guides, fiberscopes and/or other items, and/or to
communicate fluids, medication and/or other materials for the treatment,
aspiration, dilation, distension, insufflation, etc. of targeted body
tissue. In the depicted embodiment, the catheter shaft 14 defines two
instrument lumens 18, each extending through substantially the entire
length of the shaft 14, and each having a central axis lying on a first
plane X extending through the shaft. In an example embodiment of the
invention, each of the instrument lumens 18 have an inside diameter of
about 0.042" and are separated by a web thickness of at least 0.006". Of
course, larger or smaller diameter instrument lumens 18 and lumens of
different sizes and/or shapes are also within the scope of the invention.
The interior surface of the instrument lumens may be coextruded or coated
with a low friction material, a chemical-resistant material, and/or other
material(s) having qualities desirable for particular applications.
One or more steering wire lumens 20 preferably also extend through at least
a portion of the length of the shaft 14. One or more steering wires 22
preferably extend through the steering wire lumens 20 and are attached to
the steering actuator of the handle 12 to permit a user to selectively
steer or flex at least a portion of the shaft 14 in a desired direction
and to a desired degree of flexure. In the depicted embodiment, the
catheter shaft 14 defines two steering wire lumens 20. Each of the
steering wire lumens 20 has a central axis lying on a second plane Y
extending through the shaft, the second plane Y being oriented generally
perpendicular to the first plane X In an example embodiment of the
invention, each of the steering wire lumens 20 have an inside diameter of
about 0.014". Of course, larger or smaller diameter instrument lumens 18
and lumens of shapes other than round are also within the scope of the
invention.
One or more stiffeners 30 are preferably embedded within the body of the
catheter shaft 14, as shown for example in FIGS. 1 and 2. The stiffener(s)
30 are preferably formed of a material having a different hardness than
the material of the body of the shaft 14, whereby the stiffeners alter the
steering characteristics of the shaft. The stiffener(s) 30 are preferably
formed of a polymeric material, such as for example Pellethane.RTM.
2363-75D thermoplastic polyurethane elastomer. In preferred form, the
stiffener(s) 30 are embedded within the body of the shaft 14 by
coextrusion, and are entirely surrounded on their sides and ends by the
shaft body material. In this manner, the stiffeners 30 do not
substantially alter the surface characteristics of the exterior of the
shaft 14 or of the interior of the lumens. For example, the atraumatic
qualities of a relatively soft material forming the body of the shaft 14
will not be adversely affected to any significant degree by an
encapsulated stiffener 30 of a relatively harder material. Also,
encapsulation of the stiffener(s) 30 within the material of the body of
the shaft 14 prevents the stiffener(s) from slipping within the shaft,
even in the absence of a material bond between the shaft and the
stiffener(s).
The presence of a "stiffener" can increase or decrease the stiffness of the
portion of the shaft that the stiffener is contained within. For example,
the material of the stiffener 30 can be harder than the catheter body
material, such that a portion of the shaft comprising the stiffener is
more stiff (i.e., less steerable) than a portion of the shaft from which
the stiffener is omitted (i.e., a "positive" stiffener); or alternatively
the material of the stiffener 30 can be softer than the catheter body
material, such that the portion of the shaft comprising the stiffener is
less stiff (i.e., more steerable) than the portion of the shaft from which
the stiffener is omitted (i.e., a "negative" stiffener).
The stiffener(s) 30 extend through at least a portion of the length of the
shaft 14, and preferably extend generally parallel to the central
longitudinal axis (the intersection of plane X and plane Y) of the shaft
body. Most preferably, the stiffeners 30 extend only partially through the
length of the shaft 14, and are omitted from the remainder of the length
of the shaft. Segments of the shaft from which stiffeners are omitted
preferably comprise a homogenous cross section entirely formed of the
shaft body material. For example, and with particular reference now to
FIG. 3, one or more positive stiffeners 30 are preferably embedded within
a proximal segment 14a of the shaft 14, and stiffeners are omitted from a
distal segment 14b of the shaft. In this manner, actuation of the steering
mechanism results in flexure of the distal segment 14b, whereas the
proximal segment 14a remains generally straight or flexes to a lesser
degree than the distal segment. In an alternate embodiment, one or more
negative stiffeners are embedded within the distal segment 14b of the
shaft, and stiffeners are omitted from the proximal segment 14a, thereby
also resulting in a greater degree of flexure of the distal segment upon
steering. In still another embodiment, one or more stiffeners 30 extend
through substantially the entire length of the shaft 14, each stiffener
comprising a first stiffener section formed of a first material and a
second stiffener section formed of a second material having a hardness
different than that of the first material. This embodiment can, for
example, be formed by sequentially coextruding the first stiffener section
of a relatively harder material into the proximal shaft segment 14a, and
the second stiffener section of a relatively softer material into the
distal shaft segment 14b. Of course, depending upon the intended
application, it may be desirable to provide greater flexibility to
proximal and/or medial shaft segments than to distal shaft segments,
and/or to provide two or more segments of increased flexibility spaced at
different locations along the shaft.
One or more additional shaft segments, such as tip segment 14c and cover
segment 14d are optionally provided, and may or may not include stiffeners
30. These additional segments, for example, can be sequentially coextruded
with or adhered or welded onto the remainder of the shaft 14, and can be
formed of the same or different materials as the remainder of the shaft,
as to provide an atraumatic tip, improved flouroscopic visibility of the
tip, resistance to steering wire pull-through, and/or other desired shaft
characteristics.
One or more of the stiffeners 30 is preferably positioned eccentrically
within the cross-sectional profile of the body of the catheter shaft 14,
with its center located a distance away from the central longitudinal axis
(the intersection of plane X and plane Y) of the shaft body. This
off-center location of the stiffener(s) helps bias the shaft 14 to flex in
an in-plane manner, rather than twisting or "pig-tailing" when steered.
Additionally or alternatively, one or more of the stiffeners 30 are
asymmetric, having a first dimension in one direction that is greater than
a second dimension in another direction. For example, in the depicted
embodiment, and with particular reference now to FIG. 2, each of the two
stiffeners 30 has a central axis lying on plane Y, and has a first
dimension or length L in a direction parallel to plane X that is greater
than a second dimension or width W in a direction parallel to plane Y.
More preferably the first dimension L is at least twice the second
dimension W. The asymmetric nature of the stiffeners also helps bias the
shaft 14 to steer in an in-plane manner. For example, the shaft 14 will
generally tend to flex in the direction of the minor (i.e., smaller)
dimension of the stiffeners. In other words, in the depicted embodiment,
the shaft 14 will be biased to flex in plane Y. In addition to the size,
shape, number and location of the stiffeners 30, the steering bias of the
shaft 14 can be selectively varied by appropriate selection of the size,
shape, number and location of the lumens 18, 20 and of the steering wires
22. For example, in the depicted embodiment, the two steering wire lumens
20 extend through the central axes of the stiffeners 30, which lie on
plane Y, further biasing the shaft 14 to flex in plane Y.
The stiffeners 30 and the body of the shaft 14 are preferably formed of
dissimilar materials that are not entirely compatible with one another, in
that the materials do not blend freely or molecularly integrate with one
another during coextrusion. For example, a shaft body 14 of a polyether
block amide material and a stiffener 30 of thermoplastic polyurethane
elastomer have been found to resist significant blending during
coextrusion. In this manner, the material of the stiffeners 30 remains
generally heterogenous from the material of the shaft body 14, and the
intended geometry and location of the stiffeners within the shaft body is
maintained. Preferably, however, a slight degree of melting together of
the materials occurs at the transition between the stiffeners and the
shaft body to create a material bond and prevent slippage therebetween,
ensuring that the shaft and stiffeners flex as a unitary body.
Alternatively, the materials of the stiffeners and the shaft body are
compatible and some degree of intermixing occurs during coextrusion; but
the stiffeners nevertheless remain generally in the intended location and
geometry, albeit with some spreading at the material transition.
The present invention also includes methods of forming a steerable catheter
as disclosed herein. Example embodiments of fabrication methods according
to the present invention include extruding a first polymeric material to
form a shaft body, the first polymeric material having a first hardness;
and coextruding a second polymeric material to form at least one stiffener
within the shaft body, the second polymeric material having a second
hardness different from the first hardness. In one embodiment, the first
polymeric material has a higher hardness than the second polymeric
material. In an alternate embodiment, the second polymeric material has a
higher hardness than the first polymeric material. The at least one
stiffener is preferably coextruded within only a portion of the length of
the shaft body, to form shaft segments of differing degrees of
steerability. Preferably, at least one of the stiffeners is coextruded
into the shaft body at a distance from a central longitudinal axis of the
shaft body. Additionally or alternatively, at least one of the stiffeners
is coextruded to have a cross sectional length and a cross sectional
width, the cross sectional length being greater than the cross sectional
width. In alternate embodiments, at least one of the stiffeners is
sequentially coextruded from the second polymeric material and a third
polymeric material, the third polymeric material having a third hardness
different from the first and second hardnesses. An entire catheter shaft
can be formed as a single extrusion by sequential coextrusion of the
respective segments of the entire shaft, including segments having one or
more stiffeners embedded therein and segments without stiffeners.
Alternatively, segments having one or more stiffeners are coextruded
separately from segments without stiffeners, the segments are cut to the
intended lengths, and the segments are then aligned and welded or
otherwise attached to one another to form the catheter shaft.
While the invention has been described in its preferred forms, it will be
readily apparent to those of ordinary skill in the art that many
additions, modifications and deletions can be made thereto without
departing from the spirit and scope of the invention.
*
