U.S. patent application number 14/276761 was filed with the patent office on 2014-09-04 for steerable catheter having intermediate stiffness transition zone.
This patent application is currently assigned to BOSTON SCIENTIFIC SCIMED, INC.. The applicant listed for this patent is BOSTON SCIENTIFIC SCIMED, INC.. Invention is credited to MARK FORREST, JOSEF V. KOBLISH, ZAYA TUN.
Application Number | 20140249510 14/276761 |
Document ID | / |
Family ID | 42077525 |
Filed Date | 2014-09-04 |
United States Patent
Application |
20140249510 |
Kind Code |
A1 |
KOBLISH; JOSEF V. ; et
al. |
September 4, 2014 |
STEERABLE CATHETER HAVING INTERMEDIATE STIFFNESS TRANSITION
ZONE
Abstract
A flexible, steerable intravascular catheter includes an
elongate flexible shaft having a heterogeneous or multi-zone
stiffness profile or structure. A first or distal portion of the
catheter shaft may have a substantially constant or distinct
stiffness or flexibility, a second, intermediate or transition
section is proximal relative to, and less flexible than, the first
section, and a third section is proximal relative to, and also less
more flexible than, the first section. The third section also
includes a substantially constant or distinct stiffness or
flexibility. The flexibility or stiffness of the second section
varies along its length, e.g., in a substantially linear, step-like
or ramp-like manner to provide a smooth or gradual transition
between the stiffness of the first or distal section and the
flexibility or stiffness of the third or proximal section.
Inventors: |
KOBLISH; JOSEF V.;
(SUNNYVALE, CA) ; FORREST; MARK; (SUNNYVALE,
CA) ; TUN; ZAYA; (LIVERMORE, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BOSTON SCIENTIFIC SCIMED, INC. |
MAPLE GROVE |
MN |
US |
|
|
Assignee: |
BOSTON SCIENTIFIC SCIMED,
INC.
MAPLE GROVE
MN
|
Family ID: |
42077525 |
Appl. No.: |
14/276761 |
Filed: |
May 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12708114 |
Feb 18, 2010 |
8725228 |
|
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14276761 |
|
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61154087 |
Feb 20, 2009 |
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Current U.S.
Class: |
604/525 |
Current CPC
Class: |
A61M 25/0144 20130101;
A61M 25/0147 20130101; A61M 25/0141 20130101 |
Class at
Publication: |
604/525 |
International
Class: |
A61M 25/01 20060101
A61M025/01 |
Claims
1. An intravascular steerable catheter, comprising: an elongate
flexible shaft having a proximal portion and a distal portion, the
distal portion of the shaft comprising: first, second, and third
sections extending in order from a distal end of the distal portion
towards the proximal portion, wherein an overall stiffness of the
shaft increases from a distal end towards the proximal portion;
wherein a stiffness of the second section increases gradually along
its entire length from its distal end to its proximal end; wherein
the third section includes a distal segment and a proximal segment,
the distal segment having a substantially constant stiffness along
its length, the proximal segment being stiffer than the distal
segment, and the stiffness of the proximal segment increasing
gradually along its entire length from its distal end to its
proximal end; wherein a rate at which the stiffness changes in the
second section is less than a rate at which the stiffness changes
in the proximal segment of the third section.
2. The catheter of claim 1, wherein the stiffness of the second
section increases substantially linearly along its length between
the first and third sections in a step-like or ramp-like
manner.
3. The catheter of claim 1 wherein the first section has a
substantially constant stiffness along its length.
4. The catheter of claim 1 wherein the first section comprises an
internal support member made of a material having a yield strength
greater than 120,000 psi.
5. The catheter of claim 4, wherein the support member is made of
Type 301 stainless steel.
6. The catheter of claim 1, wherein at least the third section
includes a braid.
7. An intravascular catheter, comprising: a handle; an elongate
flexible shaft extending from the handle and having a proximal
portion and a distal portion, the distal portion of the shaft
comprising, in order from a distal end of the distal portion
towards the proximal portion: a first sheath; a stiffening sheath
connected to a proximal end of the first sheath, the stiffening
sheath being stiffer than the first sheath and having a stiffness
that increases gradually along its length from its distal end to
its proximal end; and a main sheath connected to a proximal end of
the stiffening sheath, the main sheath being stiffer than the first
sheath and the stiffening sheath, wherein at least one of the first
or main sheaths has a stiffness that increases gradually along at
least a portion of its length, wherein a rate at which the
stiffness changes in the stiffening sheath is less than a rate at
which the stiffness changes in the at least one of the first or
main sheaths; an electrode carried on the distal portion of the
elongate flexible shaft.
8. The catheter of claim 7, wherein the stiffness of the stiffening
sheath increases substantially linearly along its length between
the first and main sheaths in a step-like or ramp-like manner.
9. The catheter of claim 7, wherein the stiffness of at least a
portion of the main sheath varies along its length.
10. The catheter of claim 129, the main sheath comprising: a distal
segment that is adjacent to the stiffening sheath, the distal
segment having a substantially constant stiffness along its length;
and a proximal segment that is stiffer than the distal segment,
wherein the stiffness of the proximal segment increases gradually
along its length from a distal end to a proximal end.
11. The catheter of claim 10, wherein a rate at which the stiffness
changes in the stiffening sheath is less than a rate at which the
stiffness changes in the proximal segment of the main sheath.
12. The catheter of claim 7, wherein the first sheath has a
substantially constant stiffness along its length.
13. The catheter of claim 7, wherein the first sheath includes an
internal support member.
14. The catheter of claim 13, wherein the internal support member
is made of a material having a yield strength greater than 120,000
psi.
15. The catheter of claim 14, wherein the internal support member
is made of Type 301 stainless steel.
16. The catheter of claim 7, wherein the first sheath includes a
braid.
17. An electrophysiology catheter, comprising: a handle; an
elongate flexible shaft extending from the handle, the shaft having
a proximal portion and a distal portion, the distal portion of the
shaft comprising: first, second, third, and fourth sections
extending in order from a distal end of the distal portion towards
the proximal portion, wherein an overall stiffness of the shaft
increases from a distal end towards the proximal portion; wherein a
stiffness of the second section increases gradually along its
entire length from its distal end to its proximal end; wherein the
third section includes a distal segment and a proximal segment, the
distal segment having a substantially constant stiffness along its
length, the proximal segment having a stiffness that increases
gradually along its entire length from its distal end to its
proximal end, wherein a rate at which the stiffness changes in the
second section is less than a rate at which the stiffness changes
in the proximal segment of the third section; wherein the fourth
section extends from the handle and is stiffer than each of the
first, second, and third sections; wherein the electrophysiology
catheter is a closed system from the distal end of the distal
portion to the handle.
18. The catheter of claim 17, wherein the stiffness of the second
section increases substantially linearly along its length between
the first and third sections in a step-like or ramp-like
manner.
19. The catheter of claim 17, wherein at least the first section
comprises an internal support member made of a material having a
yield strength greater than 120,000 psi.
20. The catheter of claim 19, wherein the support member is made of
Type 301 stainless steel.
Description
RELATED APPLICATION DATA
[0001] The present application is a continuation of U.S. patent
application Ser. No. 12/708,114, filed Feb. 18, 2010, now U.S. Pat.
No. 8,725,228, which claims the benefit under 35 U.S.C. .sctn.119
to U.S. provisional patent application Ser. No. 61/154,087 filed
Feb. 20, 2009, the disclosures of which are hereby incorporated by
reference into the present application in its entirety.
FIELD OF INVENTION
[0002] The disclosed inventions relate to steerable intra-vascular
catheters, such as endovascular electrophysiology mapping and
ablation catheters.
BACKGROUND
[0003] Electrophysiology is the study of electrical impulses that
are transmitted through the heart and is focused primarily on
diagnosing and treating arrhythmias, or conditions in which
electrical impulses within the heart vary from the normal rate or
rhythm of a heartbeat. A common arrhythmia is atrial fibrillation
(AF), which is characterized by rapid, disorganized contractions of
the heart's upper chambers, the atria. AF results from abnormal
electrical impulses propagating through aberrant myocardial tissue
pathways, which leads to ineffective pumping of the blood through
the heart, as well as other complications. Atria flutter (AFL),
another type of arrhythmia, is characterized by a rapid beating of
the atria. Unlike AF, AFL arises from a single electrical wave that
circulates rapidly throughout the right side of the heart. Since
this arrhythmia can arise from multiple electrical sites, effective
treatment of these conditions requires electrical isolation of the
aberrant signal sites, thereby forcing the heart's normal
conduction pathway to take over.
[0004] The practice of interventional electrophysiology for
treating arrhythmias generally involves inserting catheters into a
patient's vasculature (e.g., through the groin and inferior vena
cava) and navigating the distal or "working" end of the catheters
into the patient's heart chambers to identify or "map" the
locations of heart tissue that are a source of the arrhythmias. The
mapping of the heart's electrical activity is typically
accomplished using one or more pairs of electrodes that are axially
spaced apart from each other along the working end of the catheter.
Following or in conjunction with the mapping procedure, the
attending physician may use a separate ablation catheter or
ablation electrode carried by the catheter that is also used for
mapping to disable (or "ablate") the tissue containing the aberrant
signal(s) or signal pathway(s), thereby restoring the heart to its
normal rhythm.
[0005] Electrical activity is normally mapped using much smaller
electrodes (in surface area) than are used for performing ablation
procedures. Because there is significantly less current transmitted
through a mapping electrode circuit than through an ablation
circuit, lead wires that connect mapping electrodes to processing
circuitry (e.g., via a pin connector in the catheter handle) are
much smaller than are used to couple ablation electrodes to an RF
generator. As such, a larger number of electrodes may be provided
on a mapping catheter than on an ablation catheter having a same or
similar profile.
[0006] Examples and further aspects of known catheters are
described in U.S. Pat. Nos. 4,739,768; 5,257,451; 5,273,535;
5,308,342; 5,984,907; and 6,485,455, the contents of which are
incorporated herein by reference.
SUMMARY
[0007] Embodiments include steerable catheters having a
heterogeneous, multi-zone stiffness profile such that a catheter
shaft has smooth or gradual transitions between different
stiffnesses of distal and proximal portions of the shaft, thereby
providing for improved distal torque transmission (ability of the
steerable distal portion to transmit input rotational force from
the handle to a distal tip), trackability (ability of the entire
catheter to follow itself through varying and tortuous anatomy),
pushability (ability of the catheter to efficiently move axially
through the anatomy), lateral stability (ability of a distal tip
electrode to remain stable on the heart tissue when subjected to
side loading) and distal durability (ability of the steerable
distal portion to remain undamaged when subjected to clinical use).
For example, in one embodiment, the shaft is structured such that
catheter pushability and torque transmission are maximized, while
the most distal portion is structured to emphasize stiffness
transition and lateral stability.
[0008] In one embodiment, a steerable intravascular catheter
comprises an elongate flexible shaft or tube having a proximal
portion and a steerable distal portion and that includes a first,
distal section, a second, transition section that is proximal
relative to, and less flexible than, the first section, and a third
section that is proximal relative to, and less flexible than, the
first and second sections. The flexibility or stiffness of the
second section varies along its length to gradually transition
between the first and third sections. The steering apparatus can be
integrated into various shafts of various catheters.
[0009] In another embodiment, a steerable intravascular catheter
comprises an elongate flexible shaft or tube having a proximal
portion and a steerable distal portion. The shaft includes a first,
distal section, a second, transition section that is proximal
relative to, and stiffer or less flexible than, the first section,
and a third section that is proximal relative to, and stiffer or
less flexible than, the first and second sections, and a fourth
section that is proximal relative to the third section and stiffer
or less flexible than the first, second and third sections. The
flexibility or stiffness of the first section is substantially
constant along its length, and the flexibility or stiffness of the
second section varies along its length to gradually transition
between the first section and the third section. The steering
apparatus can be incorporated into a shaft of various
catheters.
[0010] According to a further embodiment, a steerable intravascular
catheter comprises an elongate, flexible shaft, a steering
apparatus and an electrode. The shaft has a proximal portion, which
may extend from a handle, and a steerable distal portion. The
electrode is carried on the steerable distal portion of the shaft.
The steering apparatus is positioned within the shaft and includes
a first, distal section, a second, transition section that is
proximal relative to and stiffer or less flexible than, the first
section, and a third section that is proximal relative to, and
stiffer or less flexible than, the first section. The flexibility
or stiffness of the second section varies along its length to
transition between the first and third sections. The catheter shaft
may also include one or more control elements or wires that can be
manipulated to move the steering apparatus and catheter shaft in
different directions.
[0011] In one or more embodiments, the stiffness of the catheter
shaft is varied along the length to provide a gradual transition by
incorporating various stiffness zones directly into an outer tubing
of the catheter shaft or body. For example, tubing segments of
various stiffnesses may be stacked on a common inner core and
thermally fused into a single shaft. In this manner, the resulting
shaft has at least two distinct stiffness zones and a "transition
zone" or "step-like" or "ramp-like" transition between the two
stiffness zones. In another embodiment, extrusion technologies such
as interrupted co-extrusion may be used that directly integrate
materials of different stiffnesses into a single tube over a common
lumen. The resulting tube will have at least two distinct stiffness
zones and a transition zone between the two stiffness zones.
[0012] In one or more embodiments, a gradual transition between two
adjacent stiffness zones of a distal portion of a shaft is may be
substantially linear, e.g., as a step-like or ramp-like transition
or slope between two stiffness levels. The gradual transition may
also be non-linear, e.g., parabolic or exponential. The first or
distal section may also transmit less torque than the second
section, which may transmit less torque than the third section.
[0013] In one or more embodiments, a catheter may include one or
more additional sections. For example, a fourth section may be
proximal relative to the third section and stiffer or less flexible
than each of the more distal sections. The fourth section may have
a substantially constant or distinct stiffness or flexibility.
[0014] In one or more embodiments, at least one other section of a
catheter steering apparatus other than an intermediate or second
section includes a variable flexibility or stiffness along at least
a portion of its length. For example, the flexibility or stiffness
of at least a portion of the third section can vary along its
length. In this embodiment, the third section may include multiple
segments. A first segment of the third section is proximal relative
to and adjacent to the second section. A second segment of the
third section is proximal relative to and adjacent to the first
segment of the third section and is stiffer or less flexible than
the first segment of the third section. The first or distal section
of the steering apparatus has a substantially constant or distinct
flexibility or stiffness along its length, and the flexibility or
stiffness of the second segment of the third section also varies
along its length. The rate at which the stiffness or flexibility
changes in the second section is more gradual than the rate which
stiffness or flexibility changes in the second segment of the third
section.
[0015] In one or more embodiments, the first or distal section of a
catheter shaft includes a substantially constant or distinct
flexibility or stiffness along its length. At least a portion of
the third section is stiffer than the first section and has a
substantially constant or distinct flexibility or stiffness.
[0016] In one or more embodiments, the first or distal section of a
catheter shaft includes an internal support member, which may be
formed from or made of a material that has a yield strength greater
than about 120,000 pounds per square inch (psi). In one embodiment,
the internal support member has a yield strength of about 140,000
psi and may be Type 301 stainless steel.
[0017] Other and further aspects and embodiments of the disclosed
inventions are described in the detailed description of the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] It will be appreciated that the embodiments and components
thereof shown in the drawings are not necessarily drawn to scale,
with emphasis instead being placed on illustrating the various
aspects and features of the illustrated embodiments, in which:
[0019] FIG. 1 illustrates a catheter constructed according to one
embodiment that includes a multi-zone structure having sections of
different stiffness or flexibility;
[0020] FIG. 2 illustrates bending of the catheter shown in FIG. 1
in a first direction;
[0021] FIG. 3 illustrates bending of the catheter shown in FIG. 1
in a second direction;
[0022] FIG. 4 illustrates a distal bending portion of a catheter
and mapping and ablation electrodes;
[0023] FIG. 5A is a graph generally illustrating stiffness
attributes of different sections of a catheter constructed
according to one embodiment and having a step-like or ramp-like
stiffness profile;
[0024] FIG. 5B is a graph illustrating bending stiffness attributes
of different sections of a catheter constructed according to one
embodiment and having a multi-zone stiffness structure;
[0025] FIG. 6 illustrates different components or layers of a
catheter that may be constructed to have stiffness profiles as
shown in FIGS. 5A-B;
[0026] FIG. 6A is a cross-sectional view of FIG. 6 along line
A-A;
[0027] FIG. 6B is a cross-sectional view of FIG. 6 along line
B-B;
[0028] FIG. 7 is a partial cross-sectional view of a distal portion
of the catheter shown in FIGS. 6 and 6A;
[0029] FIG. 8 is a cross-sectional view of a multi-layer
reinforcing sleeve constructed according to one embodiment;
[0030] FIG. 8A is a side view of a reinforcing sleeve constructed
according to one embodiment that includes a tube having a fabric
material wound around an inner tube to a pitch of about 30-35 wraps
per inch;
[0031] FIG. 8B is a side view of a reinforcing sleeve constructed
according to one embodiment that includes a tube having a fabric
material wound around an inner tube to a pitch of about 15-20 wraps
per inch; and
[0032] FIG. 9 is a cross-sectional view of distal tubing
constructed according to one embodiment.
DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS
[0033] Referring to FIG. 1, a bi-directional steerable catheter 100
constructed according to certain embodiments includes an elongate,
flexible shaft 110 that is structurally configured to have a
heterogeneous, multi-zone stiffness profile or structure 120 having
different or variable rigidity, stiffness or flexibility along its
length. For ease of explanation, this specification generally
refers to a multi-zone structure or profile 120 having different
stiffness attributes, noting that sections having different
stiffnesses have different flexibilities.
[0034] As shown in FIG. 1, the shaft 110 extends from a distal
portion of a handle 130, as is known in the art of
electrophysiology catheters. The catheter shaft 110 generally
includes a proximal section or portion 111 and a steerable distal
section or portion 112 that is sized and configured for placement
and manipulation within in a heart of patient without prolapsing.
FIG. 1 generally illustrates proximal and distal portions 111, 112,
but the lengths of these portions 111, 112 and the dividing line
between these portions 111, 112 may vary in different
implementations and catheter designs. An electrical cable or other
suitable connector 140 extending from a proximal end of the handle
130 may be coupled to a source of energy or other equipment (not
shown in FIG. 1) for transmitting one or more ablation signals
and/or receiving signals or data from mapping electrodes. FIG. 1
generally illustrates electrodes as a distal tip electrode 141 and
shaft or ring electrodes 142.
[0035] With further reference to FIGS. 2-3, during use, the
catheter shaft 110 is advanced into a patient, e.g., through a
puncture into the femoral vein of a patient, through the inferior
vena cava and into the right atrium using a bi-directional steering
support member 610 (shown in FIG. 6A) that is embedded in the
distal portion 112. An actuator 131, such as a rotatable knob or
dial as shown in FIG. 2, can be manipulated by the surgeon to
position the distal section 112 of the shaft 110 as desired by
adjusting tension on the steering member, e.g., forming the distal
section 112 into a three-quarter loop in different directions as
shown in FIGS. 2-3. After the catheter's distal section 112 is
properly positioned, an electrical current can be applied to one or
more electrodes through the connector or cable 140 to map and/or
ablate target tissue. For example, non-ablative energy can be
applied to target tissue through one or more mapping electrodes
142, and ablation energy can be applied to target tissue through a
distal tip ablation electrode 141. While FIGS. 1-3 illustrate one
manner in which electrodes 141, 142 may be configured, other
electrode configurations may be utilized. For example, FIG. 4 shows
ring electrodes 142, 143, and an ablation tip electrode 141. Thus,
various electrode configurations may also be utilized, and the
electrodes may be used for ablation and/or mapping.
[0036] In the embodiment illustrated in FIG. 1, and with further
reference to FIG. 5A (illustrating a distal-to-proximal bending
stiffness profile of a catheter 100 constructed according to one
embodiment), the shaft 110 includes, or is formed or designed to
have, a heterogeneous, multi-zone structure or profile 120 that
includes different stiffness zones. The embodiment of a stiffness
profile illustrated in FIG. 5A includes four different stiffness
zones 121-124, but other embodiments may include different numbers
of stiffness zones, e.g., three, five or other numbers of stiffness
zones. In the illustrated embodiment, zones 121 and 122 form a
distal section 112 of the shaft, and zones 123 and 124 form a
proximal portion 111 of the shaft 110. At least one stiffness zone,
e.g., zone 122 of the distal portion 111 in the illustrated
embodiment, is an intermediate stiffness zone that is configured to
provide a smooth, gradual transition, step or ramp between two
other zones 121 and 123 having different stiffness attributes.
[0037] Different zones 121-124 may have different stiffness
attributes as a result of having different stiffness magnitudes,
i.e., one zone is stiffer or more flexible than another, different
stiffness profiles or patterns, i.e., a zone may have a constant or
substantially constant (i.e., distinct) stiffness, a variable
stiffness, or both. Different zones of the multi-zone structure 120
can be formed or fabricated in different ways. In one embodiment,
the stiffness of the catheter shaft 110 is varied along the length
by incorporating various stiffness zones directly into an outer
tubing of the catheter shaft 110 or body. For example, sections of
tubing with varying stiffness may be stacked on a common inner core
and thermally fused into a single shaft 110. In this manner, the
resulting shaft 110 has at least two distinct stiffness zones and
one transition zone there between. In another embodiment, extrusion
technologies such as interrupted co-extrusion may be used to
directly integrate varying stiffness materials into a single tube
over a common lumen. The resulting tube(s) will have at least two
distinct stiffness zones and at least one intermediate transition
zone between two stiffness zones. Each of the zones 121-124 can be
same length or different lengths. It should be understood that a
multi-zone structure 120 can be constructed in other ways, e.g., by
selection and configuration of certain internal materials and
components, and that these configurations and methods of
fabrication are provided as examples of how embodiments may be
implemented to provide for more gradual transitions between
different sections of the catheter shaft 110, thereby providing
improved pushability, tracking, and torsional strength and a
smoother transition of flexibility along the length of the shaft
110 to optimize each section of the shaft 110. For ease of
explanation, this specification refers to different materials and
material configurations that can be used to implement a particular
zone, but it should be understood that a multi-zone structure 120,
including the multi-zone structure 120 illustrated in FIG. 5A, can
be implemented in other ways.
[0038] With further reference to FIGS. 5B and 6, in one embodiment,
the catheter shaft 110 is structured to include four different
stiffness zones 121-124. FIG. 5B illustrates stiffness in terms of
lbf-in.sup.2, how bending stiffness varies across a length of a
catheter shaft 110 constructed according to one embodiment, and how
the bending stiffness of the intermediate or transition portion 122
varies according to embodiments. In the embodiment illustrated in
FIG. 5B, the bending stiffness 510 increases across four zones
121-124 from the distal portion 112 (left edge of the graph shown
in FIG. 5) to the proximal portion 111 (right edge of the graph
shown in FIG. 5B) of the catheter shaft 110. In one embodiment, as
shown in FIG. 5B, a catheter shaft 110 can have a length of about
35-45 inches, and the first or distal zone 121 of the distal
portion 111 of the shaft 110 can have a length of about 1.5 inches
to about 4.5 inches, e.g., about 2.5 inches, a diameter of about
0.092 inches (and other suitable diameters), and be made of or
include a polyether-polyamide block copolymer and Type 301
stainless steel (and other suitable materials). The second zone 122
of the distal portion 111 of the shaft 110 can have a length of
about 1.0 inch to about 4.0 inches, e.g., about 1.75 inches, a
diameter of about 0.092 inches (and other suitable diameters) and
be made of or include a polyether-polyamide block copolymer and
Type 301 stainless steel (and other suitable materials). Thus, in
the illustrated embodiment, the distal portion 112 of the shaft 110
includes the intermediate or stiffness transition zone and can have
a length of about 6 to about 9 inches, e.g., about 7 inches.
[0039] In the embodiment illustrated in FIG. 5B, the third zone
123, which can be a part of the proximal portion 112 of the shaft
110, can have a length of about 1 to 4 inches and a diameter of
about 0.092 inch (or other suitable diameters) and be made of or
include a polyether-polyamide block copolymer and Type 301
stainless steel (and other suitable materials). The fourth zone
124, which is also part of the proximal portion 112 extends to the
handle 130 and can have various lengths, e.g., about 25.5 inches to
about 36.0 inches and may have a diameter of about 0.092 inches (or
other suitable diameter) and be made of or include a
polyether-polyamide block copolymer and Type 301 stainless steel
(or other suitable materials).
[0040] Different zones 121-124 can be defined by sections having
different diameters and including or being made of different
materials. Thus, the dimensions, ranges of dimensions, and
materials mentioned above are provided as examples of how
embodiments may be implemented, and stiffness profiles according to
embodiments can be implemented using components and structures that
are described in U.S. Pat. No. 5,984,907, the contents of which
were previously incorporated herein by reference as though set
forth in full.
[0041] With a shaft 110 configured as in the embodiment illustrated
in FIGS. 5B and 6, the bending stiffness 510 of the first zone 121
of the distal portion 111 is distinct (constant or substantially
constant) across its length, e.g., about 0.01 lbf-in.sup.2 to about
0.1 lbf-in.sup.2, e.g., about 0.07 lbf-in.sup.2 along its length,
which may be about 2.5''. As shown in FIG. 5B, the stiffness of the
proximal end of the first zone 121 may begin to step or ramp up and
increase slightly at or near the proximal end of the first zone 121
or at or near the distal end of the second zone 122, depending on
the type of transition that is utilized in the second zone 122.
[0042] In the embodiment illustrated in FIG. 5B, the second zone
122 of the distal portion 112, which is proximal relative to and
adjacent to the first or distal zone 121, is an intermediate
transition zone located between the first zone 121 of the distal
portion 112 and the third zone 123, which is shown as being a part
of the proximal portion 111 of the shaft 110. The second zone 122
has a bending stiffness 510 that varies across its length. In other
words, the bending stiffness profile of the second zone 122 is not
distinct or substantially constant along its length as in the first
zone 121 and/or the third zone 123 or other, more proximal zones.
In one embodiment, the stiffness varies in a substantially linear
manner and may do so in a step-like or ramp-like manner.
[0043] In the embodiment illustrated in FIG. 5B, the bending
stiffness varies substantially linearly in a step-like or ramp-like
manner from about 0.01 lbf-in.sup.2 to about 0.10 lbf-in.sup.2,
e.g., 0.07 lbf-in.sup.2, to up to about 0.2 lbf-in.sup.2, e.g., up
to about 0.17 lbf-in.sup.2 over a length of about 1.5'' to about
4'', e.g., about 2.5''. Thus, in one embodiment, the intermediate
or transition zone 122 has a bending stiffness that varies by about
0.04 lbf-in.sup.2 per inch of length. For this purpose, the second
zone 122 may include or be composed of a polyether-polyamide block
copolymer and Type 301 stainless steel and have a diameter of about
0.092 inches.
[0044] Although FIG. 5B illustrates an intermediate transition zone
122 including a substantially linear step-like or ramp-like
stiffness profile, in other embodiments, the stiffness profile of
the transition zone 122 may vary in a non-linear manner, e.g., in a
curved or exponential manner. Thus, FIG. 5B is provided to
illustrate one example of how embodiments can be implemented.
[0045] In one embodiment, the bending stiffness 510 of the third
zone 123, which can be a part of the proximal portion 111 and is
proximal relative to the first and second zones 121, 122 of the
distal portion 112, is distinct (constant or substantially
constant) along its length. According to one embodiment, the
bending stiffness of the third zone 123 is about 0.17 lbf-in.sup.2.
In this manner, the third zone 123 may be structured in a manner
that is similar to the first zone 121 of the distal portion 111
except that the third zone 123 is stiffer or less flexible than the
first zone 121.
[0046] In another embodiment, the third zone 123 includes multiple
sub-zones or segments. For example, as shown in FIG. 5B, the third
zone 123 includes a first sub-zone or segment 531 and a second
sub-zone or segment 532. The length of the first segment 531 can be
about 0.5'' to about 2'', and the length of the second segment 532
can also be about 0.5'' to about 2''. In the illustrated
embodiment, the first segment 532 has a distinct (constant or
substantially constant) stiffness 510 of about 0.17 lbf-in.sup.2,
and the second sub-zone or segment 532 has a stiffness 510 that
varies in a step-like or ramp-like manner across its length from
about 0.17 lbf-in.sup.2 up to about 0.5 lbf-in.sup.2, e.g., about
0.32 lbf-in.sup.2. In the illustrated embodiment, the bending
stiffness across the second segment 532 varies in a substantially
linearly manner. Thus, in the illustrated embodiment, the third
zone 123 is a "combination" transition zone that includes multiple
transition zones and at least one segment 531 (other than the
transition zone 120) that has a distinct stiffness and another
segment 532 that provides a transition or stiffness that varies
along its length. This type of stiffness profile of the first,
second and third zones 121-123 as illustrated in FIG. 5B enhances
trackability of a catheter 100 through a tortuous vasculature.
[0047] In the illustrated embodiment, the rate at which the
stiffness 510 changes in the second zone 122 is less than the rate
at which the stiffness 510 changes in the second segment 532 of the
third zone 123. In one embodiment, the rate at which stiffness 510
changes in the second zone 122 is about 0.04 lbf-in.sup.2 per inch,
and the rate at which stiffness 510 changes in the second segment
532 of the third zone 123 is about 0.1 lbf-in.sup.2 per inch. In
other embodiments, the rate at the stiffness 510 varies in the
second zone 122 may be greater than or the same as, the rate at
which the stiffness 510 varies in a segment of the third zone
123.
[0048] In the illustrated embodiment, the stiffness 510 of the
fourth zone 124, which is proximal relative to the first, second
and third zones 121-123, also has a distinct (constant or
substantially constant) stiffness across its length, similar to the
stiffness profile of the first zone 121 and the third zone 123 (or
segment 531 thereof). In one embodiment, as illustrated in FIG. 5B,
the stiffness 510 of the fourth zone 124 is substantially constant
and is about 0.32 lbf-in.sup.2 over a length to the handle 130.
[0049] Thus, in the illustrated embodiment, the particular
stiffness values of each zone 121-124, and the manner in which the
stiffness profiles of respective zones 121-124 are substantially
constant or vary across a length of a zone, result in an
intermediate or transition section or zone 122 that is stiffer or
less flexible than the most distal or first section or zone 121,
and more flexible than the proximal portion 111, which includes
zones 123 and 124. With this particular structural configuration,
embodiments provide for a more gradual transition between two
distinct stiffness zones (or a segment thereof) and enhance
pushability, tracking, and the torsional strength or rigidity of
the catheter 100.
[0050] Referring again to FIG. 6, and with further reference to
FIGS. 6A-B and 7, the distal or first zone or section 121 of a
catheter shaft 110 includes a center support member 610 that is
encased in a reinforcing sleeve 612. The center support member 610
terminates in a rounded tip 617 and is embedded within and
connected to the tip 617 by solder or another suitable connection.
As shown in FIG. 6A, the sleeve 612 maintains steering wires 614a,b
(generally 614) in position against the center support member 610
in order to prevent kinking or tangling of the steering wires 614.
The first zone 121 also includes tubing 616 that surrounds the
sleeve 612 and the center support 610, as shown in phantom in FIG.
6. The first zone 121 may optionally include leaf springs that are
attached to the center support 610.
[0051] In one embodiment, the material of the center support 610 is
a high yield strength material having a yield strength that is
greater than about 120,000 psi. In one embodiment, the internal
support member has a yield strength of about 140,000 psi and may be
made of Type 301 stainless steel. Such material attributes
advantageously provide increased lateral rigidity and greater
resistance to permanent deformation of the distal portion 112 of
the catheter shaft 110. In other embodiments, the material of the
center support 610 may be Type 17-7 PH stainless steel, which has a
yield strength of 185,000 psi, Type 440C stainless steel, which has
a yield strength of 275,000 psi, and other suitable high yield
strength materials.
[0052] Referring to FIG. 8, the reinforcing sleeve 612 encasing the
center support 610 may, for example, be made from an inner shrink
tube 801, an outer shrink tube 802, and a reinforcing fabric 803
there between. The inner and outer tubes 801, 802 may be made of
Teflon.RTM. polytetrafluoroethylene and the fabric 803 may be a
Kevlar.RTM. polyaramid material, e.g., in the form of a yarn, which
is wrapped in tension over the inner shrink tube 801 as a single
spiral about the tube 801 in order to obtain a desired, closely
spaced pitch, and the outer shrink tube 802 may be positioned over
the reinforcing fabric 803.
[0053] For example, the fabric 803 can be wrapped around the tube
801 to a pitch of about 30 to 35 wraps per inch (e.g., as shown in
FIG. 8A). Alternatively, the pitch may be 15 to 20 wraps per inch
(e.g., as shown in FIG. 8B). If necessary, a first shrink step may
be performed on the inner shrink tube 801 before the reinforcing
fabric 803 is applied thereto, and a second shrink step may be
performed on the second shrink tube 802 after the second shrink
tube 802 is positioned over the reinforcing fabric. 803. The
configuration of the sleeve 612 may vary as necessary and depending
on the manufacturing method and braid density employed. Thus, the
cross-sectional view of a sleeve 612 may be as shown in FIG. 8, in
which the fabric or braiding 803 extends around the inner tube 801,
or the layer 803 may be less dense, e.g., as shown by the braiding
pattern employed in FIG. 8B.
[0054] The tubing 616 may be composite tubing comprised of a
fiber-reinforced dual polymer layer. The tubing 616 material may
depend on the desired bending stiffness and torsional rigidity in
the first zone 121. For example, with reference to FIG. 9, stiffer,
distal tubing 616, having a higher torsional rigidity, may include
an inner layer 901 of 63D Pebax.RTM. fiber, a Vectran.RTM. liquid
crystal polymer reinforcing braid 902, and a 40D outer layer 903,
while softer, composite tubing, having a lower torsional rigidity,
may include an inner layer 901 of 55D Pebax.RTM., a Vectran.RTM.
liquid crystal polymer reinforcing braid 902, and a 35D outer layer
903. The reinforcing fabric braid 902 may add torsional rigidity to
the first zone 121 without the risk of the electrical shorting that
a metallic braid would impart. The increased torsional strength
provided by the braid 902 may help to prevent wind-up of the distal
section 112 of the catheter 100 when the handle 130 and/or proximal
portion 111 of the catheter 100 are rotated. The fabric braid 902
may also add to the lateral or side load strength of the steered
distal portion 112 because the braid 902 adds to the torsional
strength of the tubing 616.
[0055] Referring again to FIGS. 6A-B, in the illustrated
embodiment, the proximal ends of the center support 610 and the
reinforcing sleeve 612 are coupled to a flexible inner shaft 620 at
the junction between the distal or first zone 121 and the
transition or second zone 122. The flexible inner shaft 620 may
extend from the center support 610 to a handle assembly 130 on the
proximal end of the catheter 100 and may comprise a stainless steel
coil. The proximal end of the center support 610 may fit within the
distal end of the inner shaft 620, and the proximal end of the
reinforcing sleeve 612 may fit over the distal end of the inner
shaft 620, thereby providing a smoother transition between the
center support 610 and the coil inner shaft 620.
[0056] In the second or transition zone 122, the flexible inner
shaft or tubing 122 may be enclosed by a stiffening sheath 622,
while in the third zone 123 and the fourth zone 124, the flexible
inner shaft 620 may be enclosed by a main sheath or tubing 630
(shown in phantom in FIG. 6). The mechanical properties of the
stiffening sheath 622 are such that the stiffness of the second
zone 122 is between the stiffness of the first zone 121 and the
stiffness of the third zone 123, thus advantageously providing a
gradual transition between the first zone 121 and the third zone
123 over the length of the second or transition zone 122. The
gradual transition achieved with embodiments over a length of the
second zone 122 improves the trackability of the catheter 100. For
this purpose, the second zone may be comprised of a stiffening
sheath 622.
[0057] In the third and fourth zones 123 and 124, respectively, the
inner shaft 620 is covered by the main sheath 630. While the third
zone 123 is stiffer than the first and second zones 121, 122, the
third zone 123 should be sufficiently compliant or flexible to bend
freely as the catheter 100 tracks through the anatomy (e.g., an
aortic arch), yet sufficiently stiff or rigid to be highly
pushable. For this purpose, a main sheath 134 may surround the
inner shaft 620, and the main sheath 630 may be comprised of a
braided material.
[0058] The fourth zone 124 comprises the proximal portion of the
main sheath 630 (which may also form a part of the third zone 123
as shown in FIG. 6) and may have increased stiffness compared to
the third zone 123. The added stiffness of the fourth zone 124 may
be accomplished by inserting a stiff metallic rod (not shown)
within the catheter shaft 110. For example, a long steel wire may
be inserted into the proximal shaft for increased rigidity. Such a
wire may be positioned within a lumen of the inner shaft 620 or
between an outer surface of the inner shaft 620 and an inner
surface of the main sheath 630. The resulting enhanced stiffness of
the fourth zone 124 may provide increased pushability, torque, and
steering fidelity of the catheter shaft 110.
[0059] Further aspects of certain components and examples of
components that may be utilized to implement embodiments are
described in further detail in U.S. Pat. No. 5,984,907, the
contents of which were previously incorporated herein by reference
as though set forth in full.
[0060] It will be apparent to those skilled in the art that the
invention may be embodied in other specific forms besides and
beyond those described herein. For example, a multi-zone structure
120 may have different numbers of zones and different zone
profiles, while still having an intermediate or transition zone to
provide a smooth or gradual transition between distal and more
proximal portions of a shaft. Further, different stiffness zones
can be formed in various ways, e.g., by adding layers around a
catheter, or forming a catheter section of a different material,
and/or integrating different internal materials such as an internal
distal support member made of Type 301 stainless steel.
[0061] Additionally, a transition zone may vary in different
manners and by different degrees. Moreover, different stiffness
zones can be implemented using different catheter materials,
diameters, and/or thicknesses and may extend for different lengths.
Thus, the stiffness profile illustrated in FIG. 5 and the materials
and dimensions described are provided as one example of how
embodiments can be implemented.
[0062] Moreover, a stiffness profile may include a single
transition zone or multiple transition zones. The stiffness within
multiple transition zones may change at the same or different
rates.
[0063] Thus, the foregoing embodiments are therefore to be
considered in all respects illustrative rather than limiting.
* * * * *