U.S. patent application number 16/148873 was filed with the patent office on 2019-09-12 for catheter having flexible tip with multiple flexible segments.
The applicant listed for this patent is St. Jude Medical, Atrial Fibrillation Division, Inc.. Invention is credited to Alan de la Rama, Cary Hata.
Application Number | 20190275291 16/148873 |
Document ID | / |
Family ID | 45329305 |
Filed Date | 2019-09-12 |
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United States Patent
Application |
20190275291 |
Kind Code |
A2 |
de la Rama; Alan ; et
al. |
September 12, 2019 |
CATHETER HAVING FLEXIBLE TIP WITH MULTIPLE FLEXIBLE SEGMENTS
Abstract
A catheter apparatus includes an elongated body having a distal
portion including a distal end, a plurality of flexible segments,
and at least one intermediate segment that is less flexible than
the flexible segments. Adjacent flexible segments are spaced from
each other longitudinally by the at least one intermediate segment.
Each of the flexible segments include a sidewall having at least
one elongated gap extending at least partially therethrough and
forming interlocking members. The at least one intermediate segment
is shorter than the flexible segments.
Inventors: |
de la Rama; Alan; (Cerritos,
CA) ; Hata; Cary; (Irvine, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
St. Jude Medical, Atrial Fibrillation Division, Inc. |
St. Paul |
MN |
US |
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Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20190099585 A1 |
April 4, 2019 |
|
|
Family ID: |
45329305 |
Appl. No.: |
16/148873 |
Filed: |
October 1, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13704619 |
Dec 16, 2012 |
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PCT/US11/40781 |
Jun 16, 2011 |
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16148873 |
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61355242 |
Jun 16, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 25/0052 20130101;
A61B 18/1492 20130101; A61B 2018/00434 20130101; A61B 2018/00869
20130101; A61B 2018/00821 20130101; A61B 2018/00404 20130101; A61B
2018/00875 20130101; A61B 2018/00511 20130101; A61B 2018/1407
20130101 |
International
Class: |
A61M 25/00 20060101
A61M025/00; A61B 18/14 20060101 A61B018/14 |
Claims
1.-38. (canceled)
39. A catheter apparatus comprising: an elongated body having a
distal portion including a sidewall, a distal end, a plurality of
flexible segments, and at least one intermediate segment that is
less flexible than said flexible segments, wherein adjacent said
flexible segments are spaced from each other longitudinally by said
at least one intermediate segment, wherein each said flexible
segment comprises a sidewall formed of interlocking members,
wherein said at least one intermediate segment is shorter than said
flexible segments, a lumen extension member having a sidewall and a
lumen extending therethrough, said lumen extension member extends
beyond a proximal most flexible segment, has a length that does not
compromise a flexibility of said distal portion, and is coupled to
said distal portion; and a plurality of openings extending through
said lumen extension member.
40. A catheter in accordance with claim 39 wherein each said
flexible segment comprises an electrode and said at least one
intermediate segment comprises a non-conductive member.
41. A catheter in accordance with claim 39 wherein said plurality
of openings includes a first set of openings and a second set of
openings, a size of said openings in said first set being larger
than a size of said openings in said second set.
42. A catheter in accordance with claim 39 wherein a size of said
openings is configured to provide a substantially constant outflow
of fluid along said distal portion.
43. A catheter in accordance with claim 39, wherein said sidewall
is provided with gaps formed at least partially therethrough, the
gaps outlining alternating interlocking blocks.
44. A catheter in accordance with claim 39, wherein said distal
portion is bendable about 40 to about 44 degrees relative to a
longitudinal axis of said distal portion.
45. A catheter in accordance with claim 39, wherein said catheter
further comprises at least one biasing member that resiliently
biases at least one flexible segment of said plurality of flexible
segments to a pre-determined configuration when no applied force is
placed on said distal portion.
46. A catheter in accordance with claim 45, wherein said at least
one biasing member does not directly contact said at least one
flexible segment in an at rest position.
47. A catheter apparatus comprising: an elongated body having a
distal portion including a distal end, a plurality of flexible
segments, and at least one intermediate segment that is less
flexible than each flexible segment of said plurality of flexible
segments, wherein adjacent said flexible segments are spaced from
each other longitudinally by said at least one intermediate
segment, wherein each said flexible segment comprises a shape
memory alloy and a sidewall formed of interlocking members, and
wherein said at least one intermediate segment is shorter than said
flexible segments; and a lumen extension member having a sidewall
and a lumen extending therethrough, said lumen extension member
extending at least partially through said distal portion and
configured such that said lumen extension member does not
compromise a flexibility of said flexible segments; wherein a
plurality of openings extend through said sidewall of said lumen
extension member, and wherein said lumen extension member extends
beyond a most proximal said flexible segment.
48. A catheter apparatus in accordance with claim 47, wherein said
plurality of openings includes a first set of openings and a second
set of openings, a size of said openings in said first set being
larger than a size of said openings in said second set.
49. A catheter apparatus in accordance with claim 47, wherein a
size of said openings is configured to provide a substantially
constant outflow of fluid along said distal portion.
50. A catheter apparatus in accordance with claim 47, wherein each
said flexible segment is configured to be biased to an extended
configuration and configured to allow shortening of an axial length
when a force is applied to said flexible segment.
51. A catheter apparatus in accordance with claim 47, wherein each
said flexible segment is coated with at least one of gold and
platinum.
52. A distal portion for a catheter, said distal portion
comprising: a plurality of flexible segments, each flexible segment
of said plurality of flexible segments comprises an electrode
portion having a sidewall comprising interlocking members that
impart flexibility to said flexible segments and enable different
operating configurations relative to a longitudinal axis, at least
one intermediate segment adjacent at least one of said flexible
segments, and a lumen extension member having a sidewall and a
lumen extending therethrough, said lumen extension member coupled
to said distal portion and extending beyond a proximal most
electrode portion.
53. A distal portion in accordance with claim 52, wherein the
different configurations include at least one of a resting
configuration and a configuration having a changed cross sectional
shape.
54. A distal portion in accordance with claim 52, wherein said at
least one intermediate segment comprises a non-conductive
member.
55. A distal portion in accordance with claim 52, wherein said
lumen extension member includes a plurality of openings extending
therethrough.
56. A distal portion in accordance with claim 52, wherein said
electrode portion is configured to be biased to an extended
configuration and allow shortening of its axial length when a force
is applied to said electrode portion.
57. A distal portion in accordance with claim 52, wherein said
electrode portion comprises a shape memory alloy.
58. A distal portion in accordance with claim 52, wherein said
electrode portion is coated with at least one of gold and platinum.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This patent application is a Continuation of U.S. patent
application Ser. No. 13/704,015, filed Dec. 16, 2012, issued as
U.S. Pat. No. 10,118,015, which is a National Stage Entry of
PCT/US2011/040781 filed Jun. 16, 2011, which claims the benefit of
U.S. Provisional Application No. 61/355,242 filed Jun. 16, 2010.
The '015 patent, the '781 application, and the '242 application are
hereby incorporated by reference as though fully set forth
herein.
BACKGROUND OF THE INVENTION
[0002] The field of the invention relates generally to catheters
and more particularly to catheters having flexible tips and
including multiple flexible segments.
[0003] Catheters are flexible, tubular devices that are widely used
by physicians performing medical procedures to gain access into
interior regions of the body. Some known catheters include
electrodes that are used for electrically mapping a body part
and/or delivering therapy to an area of the body. These types of
catheters perform best when the electrode has good and sufficient
contact with the tissue that is being treated. It is also
advantageous that the catheter not inadvertently damage tissue
while it is inside the body.
BRIEF DESCRIPTION OF THE INVENTION
[0004] In one aspect, a catheter apparatus includes an elongated
body having a distal portion including a distal end, a plurality of
flexible segments, and at least one intermediate segment that is
less flexible than the flexible segments. Adjacent flexible
segments are spaced from each other longitudinally by the at least
one intermediate segment. Each of the flexible segments includes a
sidewall having at least one elongated gap extending at least
partially therethrough and forming interlocking members. The at
least one intermediate segment is shorter than the flexible
segments.
[0005] In another aspect, a distal portion for a catheter includes
a distal end, a plurality of flexible segments, and at least one
intermediate segment. Adjacent flexible segments are spaced from
each other longitudinally by the at least one intermediate segment.
Each flexible segment includes a sidewall having at least one
elongated gap extending at least partially therethrough and forming
interlocking members. The at least one intermediate segment is
shorter than the flexible segments. The elongated gaps impart
flexibility to the flexible segments and enable different operating
configurations relative to a longitudinal axis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic view of a distal portion of an
ablation catheter according to one embodiment of the invention.
[0007] FIG. 2 is an expanded view of an interlocking pattern formed
by channels in the catheter shown in FIG. 1.
[0008] FIG. 3 illustrates a stem member including interlocking
members formed by the channels shown in FIG. 2.
[0009] FIG. 4 illustrates an alternative interlocking pattern
having rounded members.
[0010] FIG. 5 is a partial cross-sectional view of the distal
portion of the ablation catheter shown in FIG. 1.
[0011] FIG. 6 is a schematic view of a distal portion of an
ablation catheter according to a second embodiment of the
invention.
[0012] FIG. 7 is a partial cross-sectional view of the distal
portion of the ablation catheter shown in FIG. 6.
[0013] FIG. 8 is a partial cross-sectional view of another
embodiment of a distal portion of an ablation catheter similar to
the catheter shown in FIG. 6 that has an alternative opening
pattern.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The invention can now be better understood by turning to the
following detailed description of numerous embodiments, which are
presented as illustrated examples of the invention defined in the
claims. It is expressly understood that the invention as defined by
the claims may be broader than the illustrated embodiments
described below.
[0015] Embodiments of ablation catheters having tips including
flexible and bendable electrodes, and also freedom of movement to
shorten an axial length of the catheter tip, while reliably
creating linear lesions in body tissues are described. The
flexibility of the electrodes increases an electrode-to-tissue
contact area, and in turn improves ablation of tissue. Especially
in tissue where ridges are present, the flexible tip electrodes can
be dragged across the ridges with improved continuous
electrode-to-tissue contact.
[0016] These and other benefits are accomplished by providing a
flexible distal portion for a catheter that includes a plurality of
flexible segments that each include a generally hollow cylindrical
structure having an interior lumen. A rounded distal end may be
provided. The cylindrical wall of the flexible segment may have a
variety of different types of channels or elongated grooves
defining gaps in the cylindrical wall and imparting some
flexibility thereto, including flexing and bending capability. In
some embodiments, the catheter is an ablation catheter and the
flexible segments are electrodes. This flexibility allows the
flexible electrodes to conform to and establish sufficient surface
contact with body tissues that may have irregular surface area
including ridges and the like, and tissues that may be contracting
and stretching, or moving, to more reliably create linear lesions
on the body tissue. The electrodes also are configured to provide a
freedom of movement and shortening of a length of the catheter tip
along its longitudinal axis to maintain surface contact with, for
example, contracting and stretching, or moving tissue that is
targeted for ablation. The channels, grooves, and associated
elongated gaps may have various shapes, sizes and overall
configurations as explained below in numerous exemplary
embodiments.
[0017] FIG. 1 is a schematic view of a distal portion 10 of an
ablation catheter according to one embodiment of the invention.
Distal portion 10 includes a flat distal end 12 that is
substantially circular and has a rounded edge at its perimeter. In
an alternative embodiment, distal end 12 is domed shaped and has a
curved distal end. In another embodiment, distal end 12 is oval or
elliptical shaped. Distal portion 10 also includes a distal
flexible segment 14 and a proximal flexible segment 16. Flexible
segments 14, 16 are separated by an intermediate segment 18. In one
embodiment, flexible segments 14, 16 are electrodes and
intermediate segment 18 is a nonconductive member, and intermediate
segment 18 is less flexible than flexible segments 14, 16. In an
alternative embodiment, intermediate segment 18 is as flexible as
flexible segments 14, 16. Distal flexible segment 14 is coupled to
distal end 12 and to intermediate segment 18. Proximal flexible
segment 16 is coupled to intermediate segment 18 and a catheter
shaft 20.
[0018] Non-conductive intermediate segment 18 electrically isolates
flexible electrode segments 14, 16 and secures flexible electrode
segments 14, 16 thereto. As seen in FIG. 1, intermediate segment 18
has T-shaped protrusions 19 that match and fit within corresponding
T-shaped voids or cavities on the edges of flexible electrode
segments 14, 16 to form interlocking connections that couple
flexible electrode segments 14, 16 to intermediate segment 18. Of
course, other configurations can be used to form the connections as
long as electrode segments 14, 16 are secured to intermediate
section 18. In one embodiment non-conductive intermediate segment
18 is made of polyimide or some other nonconductive material. It
may be formed as a strip and then bent into a tubular shape to form
the interconnecting coupling between flexible electrode segments
14, 16. The length of intermediate segment 18 is sufficiently small
to allow the ablation zones of flexible electrode segments 14, 16
to overlap and form a continuous lesion. The short length of
intermediate segment 18 also preserves the overall flexibility of
distal portion 10 by limiting the size of intermediate segment 18,
which is non-flexible or at least not as flexible as electrode
segments 14, 16. In one example, flexible electrode segments 14, 16
are each about 4 mm in length while intermediate segment 18 is
about 1 mm in length. Typically, intermediate segment 18 is
substantially shorter in length than flexible electrode segments
14, 16 (e.g., preferably less than a half, more preferably less
than a third, and most preferably less than a fourth).
[0019] Distal flexible electrode segment 14 includes a cylindrical
sidewall 22 and proximal flexible electrode segment 16 includes a
cylindrical sidewall 24. Sidewalls 22, 24 have helical or spiral
channels or grooves 26 cut or otherwise formed entirely through
sidewalls 22, 24 to create elongated gaps or openings. As used
herein, an elongated opening preferably has a length that is at
least about 3 times the width of the opening, more preferably at
least about 5 times, and most preferably at least about 10
times.
[0020] In an alternative embodiment, sidewalls 22, 24 include
helical or spiral channels or grooves forming elongated gaps or
openings that do not extend entirely through sidewalls 22, 24.
Channels or grooves 26 that do not extend entirely through
sidewalls 22, 24, define elongated openings of decreased wall
thickness and decreased cross-sectional area of sidewalls 22, 24
and hence the areas of the wall that include channels 26 are
structurally weaker and less rigid than areas of sidewalls 22, 24
where the elongated openings are not present, imparting flexible
properties to the electrode wall. As used herein, an elongated
opening preferably has a length that is at least about 3 times the
width of the groove, more preferably at least about 5 times, and
most preferably at least about 10 times. As can be appreciated,
channels 26 extending completely through electrode sidewalls 22, 24
will generally impart more flexibility, or less rigidity, to
sidewalls 22, 24 than will channels 26 that do not extend entirely
through sidewalls 22, 24.
[0021] In a further alternative embodiment, the channels extend in
a circular and planar configuration, with each channel being
equidistant from adjacent channels. In additional embodiments, the
channels have a non-planar helical configuration that completes
more or less than one 360 degree loop or turn on the surface of the
electrode sidewall. Each of these channels has discrete end points
and each electrode includes multiple channels.
[0022] In another embodiment, the electrode may include annular
rings extending in a plane that do not form a continuous unending
loop, but rather channels forming loops having two terminal ends
that are spaced apart from one another. A further embodiment may
include a combination of continuous and non-continuous, planar and
non-planar channel configurations.
[0023] As shown in FIG. 1, channels 26 each form interlocking
members and create an interlocking pattern that follows a
continuous helical path configuration from one end of flexible
segment 14 to the other and from one end of flexible segment 16 to
the other. Channels 26 outline alternating interlocking members, or
blocks 28.
[0024] Blocks 28 are disposed on both sides of channel 26. Each
block 28 has a head 30 and a neck 32, wherein head 30 is wider than
neck 32. As shown in FIG. 2, an interlocking pattern includes a
first head, represented by "Y", which has a neck 32 situated on one
side of channel 26, disposed between second and third heads,
represented by "X". Second and third heads X each have necks
situated on the other side of channel 26 and on opposite sides of
head Y. Adjacent blocks 28 are interlocked because head 30 is wider
than adjacent necks 32 and is therefore locked between adjacent
necks 32. For example, second and third heads X in FIG. 2 are
separated by a shortest distance A in FIG. 2, and distance A is
shorter than a width W of the head Y, thereby restricting relative
movement of two adjacent loops away from each other and preventing
adjacent blocks 28 from separating.
[0025] Contemplated patterns of elongated openings can also be
described according to structures of sidewalls 22, 24, instead of
the shape of channel 26. For example, FIG. 3 illustrates an
electrode wall including a stem member 34 that helically extends
about a longitudinal axis of the electrode forming a series of stem
loops (see FIG. 1). Stem member 34 includes a plurality of
protruding blocks 28 peripherally disposed on both sides of stem
member 34. Each block 28 transversely extends in a lateral
direction indicated by arrow T in FIG. 3 toward an adjacent stem
loop in electrode sidewall 22 shown in FIG. 1. Each adjacent stem
member 34 includes blocks 28 that are staggered from blocks 28 in
immediately adjacent stem members, resulting in an interlocking
block pattern. Blocks 28 extending from stem member 34 can have
various shapes. For example, at least some blocks 28 may have a
shape of an upside down triangle as illustrated, where one angle of
the triangle represents the neck region.
[0026] FIG. 4 illustrates an alternative embodiment having
alternatively shaped blocks 36 having a rounded bulbous shape.
Contemplated heads of the bulbous protrusions are wider than their
corresponding necks, facilitating an interlocking block
pattern.
[0027] Referring back to FIGS. 1 and 3, stem members 34 have an
axis 38 that extends in a helix about a longitudinal axis F with a
pitch between and including 0.5 to 10 degrees. Channels 26 between
blocks 28 of stem members 34 improve a flexibility of flexible
segments, or electrodes, 14, 16, and allow electrodes 14, 16 to
flex and bend along their longitudinal length and relative to the
catheter body to which they are attached. For example, the ability
of electrodes 14, 16 to flex allows an approximately 4 mm length of
a respective electrode 14, 16 to bend between and including 0.2
degrees to 70 degrees relative to the longitudinal axis from a
substantially straight position. More specifically, the ability to
flex allows an approximately 4 mm electrode length to bend between
and including 5 degrees to 50 degrees relative to the longitudinal
axis from a substantially straight position. Even more
specifically, the ability to flex allows an approximately 4 mm
electrode length to bend about 20 to 22 degrees relative to the
longitudinal axis from a substantially straight position and,
accordingly, distal portion 10 which has two 4 mm electrodes 14, 16
will bend approximately 40 to 44 degrees.
[0028] The ability of electrodes 14, 16 to flex provides better
contact with the target tissue, for example, in the trabeculated
endocardial tissue where there are valleys, ridges, and pockets in
the tissue surface. Electrode-to-tissue contact area is increased
by using sidewalls 22, 24 of electrodes 14, 16, respectively, to
deliver energy for ablation. The increased contact surface
increases the likelihood of creating larger lesions at a given
contact force and power setting. This in turn enables deeper
ablation without having to increase the power setting, which is
beneficial because increased power settings may undesirably
increase the likelihood of coagulation.
[0029] Flexible electrodes 14, 16 are configured to absorb
contraction and stretching of tissue, and improve continuous tissue
contact in a beating heart during systole and diastole, whether
electrodes 14, 16 contact the tissue in a parallel, perpendicular,
or other orientation. Continuous tissue contact is also maintained
regardless of whether the electrode is stationary at one location
or when the electrode is in motion and being dragged. Without such
flexibility, a standard rigid tip electrode would "jump off" of the
tissue in response to a beating heart.
[0030] Alternative embodiments of flexible electrodes for catheters
include physiologic-sensing capability to measure different aspects
of the body. Such capability is obtained by using one or more
sensors located at distal portion 10 of the catheter. Such a sensor
may be disposed within the hollow electrode to measure one or more
physiologic aspects related to a procedure. Such data can be
collected and monitored by the operator during the procedure.
[0031] Unlike known elongated electrodes (e.g., U.S. Pat. No.
6,063,080), which can be laid across a tissue to create relatively
long linear lesions, the flexible electrodes as described have the
unexpected advantage of improving precision in mapping and control
at specific locations within the heart for more precise ablation,
especially in relatively tight anatomical structures. Known
elongated electrodes have difficulty positioning in such tight
anatomical structures.
[0032] One unexpected advantage achieved with a flexible tip
electrode is minimized "flipping." When a standard rigid tip
electrode is manipulated within a body cavity having valleys and
pockets in the tissue, the tip electrode can get caught or stuck in
the tissue. As a physician continues to apply force in an attempt
to move the tip electrode even though it is caught or stuck, the
tip electrode may suddenly "flip" out of the tissue. Such
"flipping" is highly undesirable and should be avoided. The
proposed flexible tip electrodes greatly minimize "flipping"
issues, and allow smoother dragging and motion across valleys and
pockets in target tissue. In addition, one or more pulling wires
(not shown) can be utilized with distal portion 10. In one
embodiment, pulling wires are anchored to distal end 12 and extend
through a proximal end of the catheter such that an operator can
manipulate distal portion 10 of the catheter. In an alternative
embodiment, a distal end of the pulling wire is connected to the
catheter at a location other than distal end 12. The pulling wires
allow the operator to configure distal portion 10 in different
directions and curvatures during insertion of the catheter as well
as during the procedure. In one embodiment, the pulling wires are
anchored as traditionally known in the art and may extend through
the catheter wall or may extend through a lumen. Multiple wires may
be anchored at set lengths from distal end 12 in pairs on opposite
sides of the catheter, or the anchor points may be offset and thus
allow for asymmetric curvatures and sweep.
[0033] FIG. 5 is a partial cross-sectional view of distal portion
10 of the ablation catheter of FIG. 1. A tube 40 is disposed
internally between flexible electrode segments 14, 16, and is
attached to flexible electrode segments 14, 16 by an adhesive 42 or
the like. In one embodiment, tube 40 is fabricated from a PEEK
tube. In an alternative embodiment tube 40 is fabricated from other
suitable nonconductive materials. A distal spring coil 44 extends
between distal end 12 and tube 40. A proximal spring coil 46
extends between tube 40 and a tip stem 48 and is attached to
proximal electrode segment 16 and catheter shaft 20. Spring coils
44, 46 bias flexible electrode segments 14, 16 to stretch
lengthwise. Spring coils 44, 46 provide resilient biasing supports
for flexible electrode segments 14, 16, respectively, both when
sidewalls 22, 24 have channels 26 extending completely therethrough
and when sidewalls 22, 24 have channels that do not extend
completely therethrough. Spring coils 44, 46 provide structural
integrity to sidewalls 22, 24, respectively, and resiliently
maintain flexible electrode segments 14, 16 in a pre-determined
configuration when no applied force is placed on distal portion 10.
In an alternative embodiment, biasing members other than spring
coils can be used to bias electrode segments 14, 16 to stretch
lengthwise. As shown in FIG. 5, the pre-determined electrode
configuration at rest orients the longitudinal axis of each
flexible electrode segment 14, 16 along a straight line. In a
different embodiment, the pre-determined configuration at rest may
orient the longitudinal axes of electrode segments 14, 16 along a
curved or arcuate path. Such a configuration may be imparted to
distal portion 10 through use of suitable shape memory alloys.
[0034] Channels 26 that extend entirely through electrode sidewalls
22, 24 provide a sufficient gap in sidewalls 22, 24 to allow
shortening of a length of electrode segments 14, 16 when a
sufficient force is applied to the electrode. As explained above,
channel 26 extends, for example, between a head 30 and a neck 32 of
an adjacent loop in electrode sidewalls 22, 24, and allows a
freedom of movement between adjacent stems along the longitudinal
axis of the electrode wall when channel 26 is narrowed or closed.
Likewise, channel 26 between adjacent heads 30 provides a freedom
of movement for lengthening of electrode sidewalls 22, 24 along the
longitudinal length of electrode flexible segments 14, 16 when
channel 26 is opened or widened. Such shortening or lengthening may
involve widening or narrowing one or more channels 26 in the
various embodiments described above.
[0035] In an exemplary embodiment, flexible electrode segments 14,
16 can shorten between and including 0.2% to 10% of an axial
resting length of flexible electrode segments 14, 16 when channels
26 in electrode sidewalls 22, 24 are closed. In one embodiment,
channels 26 in electrode sidewalls 22, 24 allow shortening of the
axial length between and including 0.1% to 8% of the resting
length. More specifically, channels 26 in electrode sidewalls 22,
24 allow axial shortening of the length between and including 0.5%
to 5% of the resting length, and even more specifically, channels
26 in electrode sidewalls 22, 24 allow shortening of the resting
length between and including 0.1% to 0.5% of the length.
[0036] In one embodiment, an at rest electrode segment 14, 16,
assumes a pre-determined shape stretching in the longitudinal
direction and opening channels 26 a predetermined amount. When
electrode segments 14, 16 contact tissue, an applied compressive
force causes channels 26 to narrow or close and electrode segments
14, 16 shorten against the force. Once shortened, the width of
channels 26 is decreased and may fully close such that the length
of electrode segments 14, 16 reach a minimum axial length that is
substantially unaffected by further exertion of applied force.
[0037] In the exemplary embodiment, spring coils 44, 46, or
flexible electrodes 14, 16, or any combination thereof, may be, and
in one embodiment is, fabricated from biocompatible materials that
are suitable for ablation temperatures. Such materials include,
without limitation, natural and synthetic polymers, various metals
and metal alloys, Nitinol, naturally occurring materials, textile
fibers, and combinations thereof. In the exemplary embodiment,
distal portion 10, and other catheter components including, without
limitation, flexible segments 14, 16 and coils 44, 46, are
fabricated from a substantially or entirely non-magnetic,
non-electrically conductive, and non-RF reactive material to enable
magnetic resonance imaging (MRI) of distal portion 10 using an MRI
system (not shown) for positioning and/or orienting distal portion
10. While the above described catheter is advantageous for use with
an MRI system, it is contemplated that magnetic fields and
gradients to generate images of distal portion 10 may alternatively
be generated by other systems and techniques if desired. For
example, in one embodiment, all, or a portion of, distal portion 10
is fabricated from 90% platinum and 10% iridium, or other materials
known in the art, such that all or part of distal portion 10 is
viewable under fluoroscopic exposure.
[0038] Additionally or alternatively, distal portion 10 may include
and/or be coated with a conductive material including, without
limitation, gold and/or platinum, to increase a thermal
conductivity of the electrodes. Moreover, distal portion 10 can be
and, in one embodiment, is coated with heparin to provide an
anticoagulation effect. Furthermore, distal portion 10 can be and,
in one embodiment, is electro-polished to reduce sharp edges.
[0039] In a further alternative embodiment, the catheter can be
used with an electric field-based system, such as, for example, the
EnSite NavX.TM. system commercially available from St. Jude
Medical, Inc., and as generally shown with reference to U.S. Pat.
No. 7,263,397 entitled "Method and Apparatus for Catheter
Navigation and Location and Mapping in the Heart," the disclosure
of which is incorporated herein by reference in its entirety. In
other embodiments, the catheter can be used with systems other than
electric field-based systems. For example, a magnetic field-based
system such as the Carto.TM. system commercially available from
Biosense Webster, and as generally shown with reference to one or
more of U.S. Pat. No. 6,498,944 entitled "Intrabody Measurement;"
U.S. Pat. No. 6,788,967 entitled "Medical Diagnosis, Treatment and
Imaging Systems;" and U.S. Pat. No. 6,690,963 entitled "System and
Method for Determining the Location and Orientation of an Invasive
Medical Instrument," the disclosures of which are incorporated
herein by reference in their entireties. In other embodiments, the
catheter can be used with a magnetic field-based system such as the
gMPS system commercially available from MediGuide Ltd., and as
generally shown with reference to one or more of U.S. Pat. No.
6,233,476 entitled "Medical Positioning System;" U.S. Pat. No.
7,197,354 entitled "System for Determining the Position and
Orientation of a Catheter;" and U.S. Pat. No. 7,386,339 entitled
"Medical Imaging and Navigation System," the disclosures of which
are incorporated herein by reference in their entireties. In yet
another embodiment, the catheter can be used with a combination
electric field-based and magnetic field-based system, such as, for
example and without limitation, the Carto 3.TM. system also
commercially available from Biosense Webster, and as generally
shown with reference to U.S. Pat. No. 7,536,218 entitled "Hybrid
Magnetic-Based and Impedance Based Position Sensing," the
disclosure of which is incorporated herein by reference in its
entirety. In yet still other exemplary embodiments, the catheter
can be used in conjunction with other commonly available systems,
such as, for example and without limitation, fluoroscopic, computed
tomography (CT), and magnetic resonance imaging (MRI)-based
systems. In these embodiments, the catheter includes one or more
tracking elements that enable the location of the catheter to be
tracked. Such tracking elements can include active and/or passive
elements such as sensors and/or electrodes.
[0040] As seen in FIGS. 1 and 5, a pair of band electrodes 50 is
provided on catheter shaft 20 and may be used for diagnostic
purposes or the like. A pair of electrode wires 51 extends to band
electrodes 50 and provides energy to band electrodes 50. Distal
portion 10 also includes conductor wires 52, 53 and thermocouples
54, 55. An adhesive 56, such as urethane, maintains conductor wire
52 and thermocouple 54 in place at distal end 12. In one
embodiment, distal end 12 is in electrical and thermal contact with
distal flexible electrode segment 14. Conductor wire 53 and
thermocouple 55 are coupled to tip stem 48 and held in place with
an adhesive, such as urethane. In one embodiment, tip stem 48 is in
electrical and thermal contact with proximal flexible electrode
segment 16. Conductor wires and thermocouples may also be provided
at other locations at or near other electrodes or electrode
segments. Wires 51, 52, 53 are coupled at their proximal end to an
energy source as is well known in the art. In addition,
thermocouples 54, 55 are coupled to an energy source at their
proximal end as is well known in the art. Accordingly, flexible
electrodes 14, 16 can be energized sequentially or simultaneously.
In one embodiment, distal portion 10 can be operated in a
temperature control mode and/or in a power control mode. In an
alternative embodiment, distal end 12 is unitary with flexible
electrode segment 14 and tip stem 48 is unitary with proximal
flexible electrode segment 16.
[0041] Catheters having flexible tip electrodes such as those
described above can optionally be coupled to an irrigation system.
That is, the catheter may include a fluid delivery lumen in the
tubular catheter body, with the fluid delivery lumen in fluid
communication with electrode segments 14, 16 and distal end 12.
When one or more of the flexible electrodes change shape under an
applied force, the elongated gap(s) will undergo changes in size
and/or shape, thereby affecting the fluid flow therethrough. A
cooling fluid, for example, may be pumped in an open flow path
through the catheter body to the hollow lumen of the electrode,
where it may pass through the gap(s) in the electrode sidewall to
the exterior of the electrode, bathing the electrode and adjacent
body tissue with cooling fluid. Alternatively, an internal,
closed-loop irrigation system using re-circulated cooling fluid as
known in the art is also possible. Also, catheters having flexible
electrodes can be coupled to an energy source, such as a radio
frequency (RF) generator to provide energy needed for tissue
ablation. RF signal generators are known and are disclosed, for
example, in U.S. Pat. No. 6,235,022.
[0042] In one embodiment, and as shown in FIG. 5, distal portion 10
includes a lumen tubing 60 leading distally to a lumen extension
member 62 which extends through proximal flexible segment 16 and
partially through distal flexible segment 14. Alternatively, lumen
extension member 62 extends through proximal flexible segment 16,
completely through distal flexible segment 14 and is in fluid
communication with exit ports 63 that extend through distal end 12.
In a further embodiment, lumen extension member 62 may have any
suitable length that does not compromise a flexibility of distal
potion 10, such as, for example, a length that is up to
approximately 90 percent of a length of distal portion 10. Lumen
extension member 62 defines an extended fluid lumen extending
through flexible segments 14 and 16, and enables fluid to be
channeled from lumen tubing 60 along a longitudinal length of
distal portion 10. As such, lumen extension member 62 is in fluid
communication with lumen tubing 60. Lumen extension member 62 is
configured to provide a substantially constant outflow of fluid
along the longitudinal length thereof. Such configurations include
openings 64 of sizes and arrangements that may vary from a proximal
end 66 to a distal end 68 of lumen extension member 62 to provide a
desired (e.g., substantially uniform) irrigation pattern or fluid
flow through distal portion 10 and channels 26, as well as lumen
shapes and sizes to provide for a substantially constant outflow of
fluid.
[0043] Lumen extension member 62 can be, and in one embodiment is,
fabricated from a suitable biocompatible material including at
least one of a polyimide material, a polyether block amide
material, a silicone material, and a polyurethane material. In the
exemplary embodiment, lumen extension member 62 is fabricated from
a material that is substantially similar to the material used to
fabricate catheter shaft 20. Alternatively, lumen extension member
62 can be and, in one embodiment, is fabricated from a
biocompatible material that is different from the biocompatible
material used to fabricate catheter shaft 20. In the exemplary
embodiment, lumen extension member 62 is fabricated from a
polyimide material.
[0044] Lumen extension member 62 may have any suitable
cross-sectional shape to enable channeling fluid therethrough. In
the exemplary embodiment, lumen extension member 62 has a
substantially rounded cross-sectional shape such as one of a
circle, an ellipse, and an oval. Moreover, lumen extension member
62 may have any suitable number of portions each having any
suitable geometry extending along a longitudinal length of lumen
extension member 62. For example, lumen extension member 62 may
have a substantially uniform geometry extending along the
longitudinal length of lumen extension member 62. Moreover, lumen
extension member 62 may have a funnel-shaped geometry extending
along the longitudinal length of lumen extension member 62. For
example, a funnel-shaped lumen-extension member has a diameter that
gradually increases along the longitudinal length of lumen
extension member 62 from proximal end 66 to distal end 68. In the
exemplary embodiment, lumen extension member 62 includes a proximal
portion having a first geometry and a distal portion having a
second geometry. Lumen extension member 62 can be formed of, or is
partially or entirely coated or lined with, a thermally conductive
material to insulate the irrigation fluid, chemicals, therapeutic
substances, gels, cooling or heating solutions, and the like from
the body or electrode energy.
[0045] In one embodiment, a flow constrictor (not shown) is
utilized to manipulate the fluid outflow through openings 64. In
this embodiment, the flow constrictor decreases a lumen diameter
along a longitudinal length of lumen extension member 62 between
successive sets of openings 64. Such a flow constrictor can be
configured to provide a substantially constant fluid flow through
openings 64 along a longitudinal length of lumen extension member
62, when utilized with appropriately sized and shaped openings.
[0046] In the exemplary embodiment, openings 64 extend through a
sidewall of lumen extension member 62 to enable channeling fluid
flow along the longitudinal length of distal portion 10. Each
opening 64 may have any suitable configuration. In the exemplary
embodiment, each opening 64 has a substantially rounded shape such
as a circle, an ellipse, and an oval. Moreover, in the exemplary
embodiment, at least one opening 64 has an axis that is
substantially perpendicular to the longitudinal length of lumen
extension member 62. Furthermore, in the exemplary embodiment, at
least one opening 64 has a diameter of approximately 0.05 mm to
approximately 0.20 mm. In one embodiment, lumen extension member 62
is fabricated from a material that enables openings 64 to change
size and or configuration when member 62 is flexed. Such changes
include openings 64 becoming larger or smaller as member 62 flexes
and/or openings 64 changing shape from circular to oval or
elliptical, or changing shape from oval or elliptical to circular.
This embodiment would enable more fluid to flow towards tissue
being ablated due to the curvature of distal portion 10 as tissue
is contacted.
[0047] In one embodiment, openings 64 include a first set of
openings 65 and a second set of openings 67. Openings in first set
65 are larger than openings in second set 67. In one embodiment,
second set openings 67 are about half the size of first set
openings 65. These differently sized openings 64 allow for a
substantially constant fluid flow through openings 64. As shown in
FIG. 5, first set of openings 65 are proximal to second set of
openings 67 within each flexible electrode 14, 16. FIG. 8
illustrates another configuration of openings 64 in which second
set of openings 67 is proximal to the first set of openings 65
within flexible electrode 16 and first set of openings 65 is
proximal second set of openings 67 within flexible electrode 14.
Alternatively, any pattern of openings could be utilized that
provides a substantially constant fluid flow such as first set of
openings 65 proximal to second set of openings 67 within flexible
electrode 16 and second set of openings 67 proximal to first set of
openings 65 within flexible electrode 14, as well as second set of
openings 67 proximal to first set of openings 65 within each
flexible electrode 14, 16. First set of openings 65 and second set
of openings 67 each may include any suitable quantity of openings.
For example, first set of openings 65 may include a first quantity
of openings, and second set of openings 67 may include a second
quantity of openings. In the exemplary embodiment, the first
quantity is equal to the second quantity. Alternatively, the first
quantity can be and, in one embodiment, is more or less than the
second quantity.
[0048] In an alternative embodiment, a dedicated lumen extension
member (not shown) extends to each flexible segment and to distal
end 12 such that a uniform amount and rate of fluid is delivered to
each flexible segment 14, 16 and to distal end 12 to provide
uniform fluid outflow through channels 26 in each flexible segment
14, 16 and through exit ports 63. Such dedicated lumen extension
members can extend through an entire length of catheter 20 or they
may each connect to, and extend from, lumen tubing 60. In a further
alternative embodiment, no lumen extension member is utilized and
lumen tubing 60 ends proximally of proximal flexible segment 16 to
allow for increased flexibility of flexible segments 14, 16 and
hence distal portion 10. In one embodiment, distal end 68 of lumen
extension member 62 is plugged to prevent fluid outflow therefrom.
Alternatively, one or more openings can extend through plugged
distal end 68 to allow fluid to flow therethrough.
[0049] Embodiments of ablation catheters including a distal portion
10 and a lumen extension member 62 facilitate providing a radially
directed irrigation pattern that is substantially uniform along a
longitudinal length of distal portion 10 when distal portion 10 is
in the unflexed, or relaxed state. In addition, lumen extension
member 62 provides a varying fluid flow along the longitudinal
length of distal portion 10 due to the variations in size of the
openings or gaps formed by channels 26 when flexible electrodes 14,
16 are in the flexed position. For example, more fluid flows toward
the tissue surface than away from the tissue surface during a
procedure due to the gaps becoming more open toward the tissue
surface and less open away from the tissue surface.
[0050] As seen in FIG. 5, fluid that exits within proximal flexible
electrode 16 can flow through tube 40 and exit distal portion 10
through channels 26 that extend through distal flexible electrode
14. As well, fluid that exits within distal flexible electrode 14
can flow through tube 40 and exit distal portion 10 through
channels 26 that extend through proximal flexible electrode 16.
Alternatively, tube 40 can be plugged so fluid cannot flow
therethrough between proximal flexible electrode 16 and distal
flexible electrode 14.
[0051] Flexible tip electrodes for ablation catheters may be formed
and fabricated, for example, according to the following
methodology. An exemplary method includes providing a hollow
cylindrical electrode, and applying a laser to the cylindrical wall
of the electrode to cut through a wall of the electrode. The laser
cuts the wall in a pre-determined pattern that may extend helically
around the circumference of the electrode wall, or may conform to
any of the elongated groove or opening patterns previously
described above in the various embodiments. The cuts create
channels 26 that are consistently wider in some sections and
narrower in other sections. The wider sections allow freedom of
movement to narrow or widen channels 26 as previously described,
making it possible to shorten an axial length of at least one of
flexible electrodes 14, 16 when a force is applied proximally at
distal portion 10.
[0052] FIG. 6 is a schematic view of a distal portion 70 of an
ablation catheter according to a second embodiment of the present
invention. FIG. 7 is a partial cross-sectional view of distal
portion 70 of the ablation catheter shown in FIG. 6. FIGS. 6 and 7
differ from FIGS. 1 and 2 in the configurations of intermediate
segment 72 and tube 74 and the connection they provide to flexible
electrode segments 14, 16. As shown in FIGS. 6 and 7, tube 74 has
external threads that engage internal threads of intermediate
segment 72 and flexible electrode segments 14, 16, so as to provide
a threaded connection. In addition, a band electrode 76 is included
on an external surface of intermediate segment 70 and an electrode
wire 77 extends to band electrode 76 and provides energy to band
electrodes 76. Wire 77 is coupled at its proximal end to an energy
source as is well known in the art.
[0053] FIGS. 1-8 illustrate a distal portion of an ablation
catheter that includes two flexible electrode segments. In other
embodiments, there may be three or more flexible electrode
segments. Each pair of neighboring flexible electrode segments are
separated by an electrically nonconductive segment.
[0054] Recent angiographic studies have shown a highly variable
cavotricuspid isthmus anatomy with various configurations and
topography, which may lead to difficulties in some atrial flutter
cases. Placing a long-tipped, rigid 8 mm electrode into pouch-like
recesses found in these patients may present technical challenges.
The multi-segmented flexible tip catheter design may better enable
the electrodes to synchronously maintain tissue contact with the
beating heart and also facilitate the creation of a linear lesion.
This tip may also be advantageous in ablating within the
trabeculated endocardial regions of patients with ventricular
tachyarrhythmias, and in ablating the roof lines in atrial
fibrillation procedures. It may also be useful when ablating within
the coronary sinus.
[0055] The many embodiments of flexible electrodes facilitate
performing linear ablation procedures. As with typical ablation
catheters, a physician can perform mapping using the electrodes,
and determine a target site for ablation. Once determined, the
physician drags the flexible tip electrode across the target tissue
to start ablation while applying energy to the tissue. Because the
electrode is flexible, the electrode can be more easily dragged
across tissue surfaces having ridges and bumps while keeping
constant electrode-to-tissue contact. This is possible because the
flexible tip electrode deforms and/or flexes when it is dragged
across a tissue surface. The flexible and deformable properties of
the flexible tips results in greater electrode-to-tissue surface
area than would otherwise be possible with a rigid tip electrode.
And because the gaps in the electrode wall allows the electrode to
be shortened when pressed tip-down against tissue surface,
accidental tissue-perforation is largely avoided if not
eliminated.
[0056] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. Many alterations and modifications may be made by those
having ordinary skill in the art without departing from the spirit
and scope of the invention. Therefore, it must be understood that
the illustrated embodiments have been set forth only for the
purposes of example and that it should not be taken as limiting the
invention as defined by the following claims.
[0057] The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
* * * * *