U.S. patent application number 10/551293 was filed with the patent office on 2007-11-29 for method and apparatus for adjusting electrode dimensions.
Invention is credited to Ryan Amara, Erik Brown, David MacAdam, Debbie Stevens-Wright.
Application Number | 20070276361 10/551293 |
Document ID | / |
Family ID | 33136300 |
Filed Date | 2007-11-29 |
United States Patent
Application |
20070276361 |
Kind Code |
A1 |
Stevens-Wright; Debbie ; et
al. |
November 29, 2007 |
Method and apparatus for adjusting electrode dimensions
Abstract
Extendable and expandable ablation electrodes are disclosed.
Electrophysiology catheter systems include ablation electrodes that
maintain a reduced cross-sectional profile during introduction into
a patient and are extendable and/or expandable once positioned at a
lesion site. The expanded electrodes having a larger length or
and/or diameter can help to produce large lesions. Controllability
of the dimensions of the ablation electrodes may be improved.
Inventors: |
Stevens-Wright; Debbie;
(Andover, MA) ; Amara; Ryan; (Tewksbury, MA)
; Brown; Erik; (Portland, OR) ; MacAdam;
David; (Millbury, MA) |
Correspondence
Address: |
WOLF GREENFIELD & SACKS, P.C.
600 ATLANTIC AVENUE
BOSTON
MA
02210-2206
US
|
Family ID: |
33136300 |
Appl. No.: |
10/551293 |
Filed: |
March 29, 2004 |
PCT Filed: |
March 29, 2004 |
PCT NO: |
PCT/US04/09618 |
371 Date: |
August 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60458489 |
Mar 28, 2003 |
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60458490 |
Mar 28, 2003 |
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60458491 |
Mar 28, 2003 |
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60458643 |
Mar 28, 2003 |
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60458856 |
Mar 28, 2003 |
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Current U.S.
Class: |
606/29 |
Current CPC
Class: |
A61B 2018/00898
20130101; A61B 2018/00875 20130101; A61B 2018/00702 20130101; A61B
18/1492 20130101; A61B 2018/00214 20130101; A61B 2018/00005
20130101; A61B 18/1815 20130101 |
Class at
Publication: |
606/029 |
International
Class: |
A61B 18/14 20060101
A61B018/14 |
Claims
1. A catheter comprising: a longitudinal catheter shaft for
positioning an ablation electrode within a patient's body; and an
ablation electrode disposed on the shaft and having an outer
surface, wherein the electrode is convertible from a first
configuration in which the electrode outer surface has a first
axial size and a first radial size to a second configuration in
which the electrode outer surface has a second axial size and
maintains the first radial size.
2. The catheter according to claim 1, wherein the ablation
electrode comprises a first electrode portion and a second
electrode portion, the second electrode portion having a length and
being moveable in the axial direction of the catheter, wherein in
the first configuration more of the second electrode portion length
is contained within the first electrode portion than in the second
configuration.
3. The catheter according to claim 2, wherein in the first
configuration, the second electrode portion length is fully
contained within the first electrode portion.
4. The catheter according to claim 2, wherein the ablation
electrode comprises a third electrode portion that is at least
partially contained within the second electrode portion in the
first configuration.
5. The catheter according to claim 2, wherein a pull wire is
connected to the second electrode portion.
6. The catheter according to claim 1, wherein the ablation
electrode is a ring electrode.
7. The catheter according to claim 6, wherein the first electrode
portion and the second electrode portion are cylindrical.
8. A catheter comprising: a longitudinal catheter shaft for
positioning an ablation electrode within a patient's body; and an
ablation electrode disposed on the shaft and having an outer
surface, wherein the electrode is convertible from a first
configuration in which the electrode outer surface has a first
axial size and a first radial size to a second configuration in
which the electrode outer surface has a second radial size and
maintains the first axial size.
9. The catheter according to claim 8, further comprising an inner
shaft portion and an outer shaft portion, the outer shaft portion
having a longitudinal slot, wherein the ablation electrode
comprises a flexible, electrically-conductive plate having a first
end and a second end; and the first end is attached to the outer
shaft portion, the plate passes through the longitudinal slot, and
the second end is attached to the inner shaft portion.
10. The catheter according to claim 9, wherein rotation of the
inner shaft portion relative to the outer shaft portion converts
the electrode from the first configuration to the second
configuration.
11. A catheter comprising: a longitudinal catheter shaft for
positioning an ablation electrode within a patient's body; and an
ablation electrode disposed on the shaft, the electrode having a
continuous outer ablating surface area, wherein the outer ablating
surface area is adjustable; and wherein the electrode is
substantially comprised of metal.
12. The catheter according to claim 11, wherein the electrode is
substantially comprised of at least one of: platinum; silver; gold;
chromium; aluminum and tungsten.
13. The catheter according to claim 11, wherein the electrode is
substantially comprised of a combination of at least two of:
platinum; silver; gold; chromium; aluminum and tungsten.
14. A catheter comprising: a longitudinal catheter shaft for
positioning an ablation electrode within a patient's body; and an
ablation electrode comprising a metal sheet disposed on the shaft,
the metal sheet forming an electrode outer surface that is
substantially continuous along both a longitudinal direction and a
circumferential direction; wherein the electrode is convertible
from a first configuration in which the electrode outer surface has
a first radial size to a second configuration in which the
electrode outer surface has a second radial size.
15. The catheter according to claim 14, wherein the ablation
electrode is cylindrical.
16. An ablation electrode for ablating tissue, comprising: a first
ablation electrode portion configured for mounting on a catheter
shaft, the first ablation electrode portion having an outer surface
configured to emit electrical energy; and a second ablation
electrode portion configured for mounting on the catheter shaft,
the second ablation electrode portion having a surface configured
to emit electrical energy; wherein the second ablation electrode
portion is moveable from a first position substantially inside the
first ablation electrode portion to a second position substantially
outside the first ablation electrode portion.
17. The ablation electrode according to claim 16, further
comprising a third ablation electrode portion configured for
mounting on the catheter shaft, the third ablation electrode
portion having a surface configured to emit electrical energy,
wherein the third ablation electrode portion is moveable from a
first position substantially inside the second ablation electrode
portion to a second position substantially outside the second
ablation electrode portion.
18. The ablation electrode according to claim 16, in combination
with a longitudinal catheter shaft for positioning an ablation
electrode within a patient's body, wherein the first ablation
electrode and the second ablation electrode are mounted on the
catheter shaft.
19. The combination according to claim 18, further comprising a
pull wire configured to move the second electrode portion.
20. A catheter shaft comprising: an outer shaft portion having a
longitudinal passage extending through an outer surface; an inner
shaft portion; an electrode surface with a first end and a second
end, the first end coupled to the inner shaft portion, and the
second end coupled to the outer shaft portion, wherein the
electrode surface passes through the longitudinal passage; one of
the outer shaft portion and the inner shaft portion is rotatable
relative to the other of the outer shaft portion and the inner
shaft portion; and relative rotation of the inner shaft portion and
the outer shaft portion extends the electrode surface in a radial
direction away from the outer shaft portion.
21. The catheter shaft according to claim 20, wherein relative
rotation of the inner shaft portion and the outer shaft portion
retracts the electrode surface in a radial direction toward the
outer shaft portion.
22. The catheter shaft according to claim 20, wherein the inner
shaft portion and the outer shaft portion are cylindrical.
23. The catheter shaft according to claim 20, wherein the electrode
surface comprises at least one of: platinum; silver; gold;
chromium; aluminum and tungsten.
24. A catheter shaft comprising: an outer shaft portion having a
passage extending through an outer surface; an inner shaft portion;
an ablation electrode member configured to pass through the
passage; and a biasing element that biases the electrode
member.
25. The catheter shaft according to claim 24, wherein the inner
shaft portion is configured to urge the ablation electrode member
through the passage in a direction away from the inner shaft
portion when the inner shaft portion rotates.
26. The catheter shaft according to claim 25, wherein the biasing
element is configured to bias the electrode member toward the inner
shaft member.
27. The catheter shaft according to claim 26, wherein the passage
is a longitudinal slot.
28. the catheter shaft according to claim 27, wherein the ablation
electrode member is a fin.
29. The catheter shaft according to claim 27, comprising two
ablation electrode members.
30. The catheter shaft according to claim 27, wherein the two
ablation electrode members extend in opposite directions to one
another.
31. The catheter according to claim 24, wherein the ablation
electrode member is comprised substantially of metal.
Description
RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn.
19(e) to U.S. Provisional Application Ser. No. 60/458,489, entitled
"Electrode for Electrophysiology Catheter Having an Eccentric
Surface", filed on Mar. 28, 2003, U.S. Provisional Application Ser.
No. 60/458,490, entitled "Electrophysiology Catheter Allowing
Adjustment Between Electrode and Tissue Gap", filed on Mar. 28,
2003, U.S. Provisional Application Ser. No. 60/458,491, entitled
"Shape Shifting Electrode Geometry for Electrophysiology
Catheters", filed on Mar. 28, 2003, U.S. Provisional Application
Ser. No. 60/458,643, entitled "Method and Apparatus for Selecting
Temperature/Power Set Points in Electrophysiology Procedures",
filed on Mar. 28, 2003, and U.S. Provisional Application Ser. No.
60/458,856, entitled "Catheter Tip/Electrode Junction Design for
Electrophysiology Catheters" filed on Mar. 28, 2003, all five of
which are each incorporated herein by reference in their
entireties.
BACKGROUND OF INVENTION
[0002] 1. Field of Invention
[0003] The invention relates to medical devices and methods for
performing ablation procedures. More particularly, the invention
relates to methods and apparatus for extending and/or retracting
ablation electrode surfaces in vivo.
[0004] 2. Discussion of Related Art
[0005] The human heart is a very complex organ, which relies on
both muscle contraction and electrical impulses to function
properly. The electrical impulses travel through the heart walls,
first through the atria and then the ventricles, causing the
corresponding muscle tissue in the atria and ventricles to
contract. Thus, the atria contract first, followed by the
ventricles. This order is essential for proper functioning of the
heart.
[0006] Over time, the electrical impulses traveling through the
heart can begin to travel in improper directions, thereby causing
the heart chambers to contract at improper times. Such a condition
is generally termed a cardiac arrhythmia, and can take many
different forms. When the chambers contract at improper times, the
amount of blood pumped by the heart decreases, which can result in
premature death of the person.
[0007] Techniques have been developed which are used to locate
cardiac regions responsible for the cardiac arrhythmia, and also to
disable the short-circuit function of these areas. According to
these techniques, electrical energy is applied to a portion of the
heart tissue to ablate that tissue and produce scars which
interrupt the reentrant conduction pathways or terminate the focal
initiation. The regions to be ablated are usually first determined
by endocardial mapping techniques. Mapping typically involves
percutaneously introducing a catheter having one or more electrodes
into the patient, passing the catheter through a blood vessel (e.g.
the femoral vein or artery) and into an endocardial site (e.g., the
atrium or ventricle of the heart), and deliberately inducing an
arrhythmia so that a continuous, simultaneous recording can be made
with a multichannel recorder at each of several different
endocardial positions. When an arrythormogenic focus or
inappropriate circuit is located, as indicated in the
electrocardiogram recording, it is marked by various imaging or
localization means so that cardiac arrhythmias emanating from that
region can be blocked by ablating tissue. An ablation catheter with
one or more electrodes can then transmit electrical energy to the
tissue adjacent the electrode to create a lesion in the tissue. One
or more suitably positioned lesions will typically create a region
of necrotic tissue which serves to disable the propagation of the
errant impulse caused by the arrythromogenic focus. Ablation is
carried out by applying energy to the catheter electrodes. The
ablation energy can be, for example, RF, DC, ultrasound, microwave,
or laser radiation.
[0008] Atrial fibrillation together with atrial flutter are the
most common sustained arrhythmias found in clinical practice.
[0009] Another source of arrhythmias may be from reentrant circuits
in the myocardium itself. Such circuits may not necessarily be
associated with vessel ostia, but may be interrupted by means of
ablating tissue either within the circuit or circumscribing the
region of the circuit. It should be noted that a complete `fence`
around a circuit or tissue region is not always required in order
to block the propagation of the arrhythmia; in many cases simply
increasing the propagation path length for a signal may be
sufficient. Conventional means for establishing such lesion
`fences` include a multiplicity of point-by-point lesions, dragging
a single electrode across tissue while delivering energy, or
creating an enormous lesion intended to inactivate a substantive
volume of myocardial tissue.
[0010] The size of a lesion is dependent on many factors, including
energy emission and electrode size. Generally, higher applications
of electrical power and larger electrodes lead to larger lesion
sizes. However, overly high energy delivery can lead to undesirable
effects such as tissue desiccation or charring, and in some
circumstances, blood coagulation. Increased electrode dimensions
present problems with insertion into a patient and introduction
into the heart because the larger dimensions can make it difficult
to maneuver a catheter through arteries and veins.
SUMMARY OF INVENTION
[0011] Embodiments of the present invention encompass apparatus and
method for creating lesions in heart tissue (ablating) to create a
region of necrotic tissue which serves to disable the propagation
of errant electrical impulses caused by an arrhythmia. Embodiments
of the present invention also encompass apparatus and methods for
adjusting the dimensions of ablation electrodes that are positioned
in a patient.
[0012] In one embodiment, a catheter comprises a longitudinal
catheter shaft for positioning an ablation electrode within a
patient's body. An ablation electrode is disposed on the shaft and
has an outer surface. The electrode is convertible from a first
configuration in which the electrode outer surface has a first
axial size and a first radial size to a second configuration in
which the electrode outer surface has a second axial size and
maintains the first radial size.
[0013] According to another embodiment, a catheter comprises a
longitudinal catheter shaft for positioning an ablation electrode
within a patient's body. An ablation electrode is disposed on the
shaft and has an outer surface. The electrode is convertible from a
first configuration in which the electrode outer surface has a
first axial size and a first radial size to a second configuration
in which the electrode outer surface has a second radial size and
maintains the first axial size.
[0014] In a further embodiment, a catheter comprises a longitudinal
catheter shaft for positioning an ablation electrode within a
patient's body. An ablation electrode is disposed on the shaft, and
the electrode has a continuous outer ablating surface area that is
adjustable. The electrode is substantially comprised of metal.
[0015] According to another embodiment, a catheter shaft comprises
an outer shaft portion having a longitudinal passage extending
through an outer surface, an inner shaft portion, and an electrode
surface with a first end and a second end. The first end is coupled
to the inner shaft portion, and the second end is coupled to the
outer shaft portion. The electrode surface passes through the
longitudinal passage. One of the outer shaft portion and the inner
shaft portion is rotatable relative to the other of the outer shaft
portion and the inner shaft portion, and relative rotation of the
inner shaft portion and the outer shaft portion extends the
electrode surface in a radial direction away from the outer shaft
portion.
[0016] According to another embodiment, a catheter shaft comprises
an outer shaft portion having a passage extending through an outer
surface, an inner shaft portion, an ablation electrode member
configured to pass through the passage, and a biasing element that
biases the electrode member.
BRIEF DESCRIPTION OF DRAWINGS
[0017] The accompanying drawings are not intended to be drawn to
scale. In the drawings, like components that are illustrated in
various figures are represented by a like numeral. For purposes of
clarity, not every component may be labeled in every drawing. In
the drawings:
[0018] FIG. 1 illustrates a catheter system according to
embodiments of the present invention;
[0019] FIG. 2 illustrates a perspective view of a portion of a
catheter shaft and an electrode according to one embodiment of the
present invention;
[0020] FIG. 3 illustrates a perspective view of the embodiment
shown in FIG. 2 with the electrode extended axially.
[0021] FIG. 4 illustrates a perspective view of a portion of a
catheter shaft and an electrode according to another embodiment of
the invention;
[0022] FIG. 5 illustrates the embodiment shown in FIG. 4 with an
electrode surface expanded radially;
[0023] FIG. 6 illustrates a perspective view of another embodiment
of a portion of a catheter shaft with an electrode surface in a
retracted configuration;
[0024] FIG. 7 illustrates a cross-sectional view of the embodiment
shown in FIG. 6 in a retracted configuration;
[0025] FIG. 8 illustrates a cross-sectional view of the embodiment
shown in FIG. 6 in an expanded configuration;
[0026] FIG. 9 illustrates a perspective view of a portion of a
catheter shaft and an electrode that includes extendable fins
according to another embodiment of the invention;
[0027] FIG. 10 illustrates a cross-sectional view of the embodiment
shown in FIG. 9 with the fins in a retracted configuration;
[0028] FIG. 11 illustrates a cross-sectional view of the embodiment
shown in FIGS. 9 and 10 with the fins in an extended
configuration;
[0029] FIG. 12 illustrates a cross-sectional view of another
embodiment of an electrode that includes extendable fins in a
retracted configuration; and
[0030] FIG. 13 illustrates a cross-sectional view of the embodiment
shown in FIG. 12 with the fins in an extended configuration.
DETAILED DESCRIPTION
[0031] This invention is not limited in its application to the
details of construction and the arrangement of components and acts
set forth in the following description or illustrated in the
drawings. The invention is capable of other embodiments and of
being practiced or of being carried out in various ways. Also, the
phraseology and terminology used herein is for the purpose of
description and should not be regarded as limiting. The use of
"including," "comprising," or "having," "containing", "involving",
and variations thereof herein, is meant to encompass the items
listed thereafter and equivalents thereof as well as additional
items.
[0032] In ablation procedures, lesion size may be improved by
increasing the surface extension of an ablation electrode. By
extending the surface geometry of the electrode radially, the reach
of the electrical potential field created by the ablation electrode
extends further into the ablation domain. It is desirable, however,
to limit the cross-sectional size of catheters being inserted into
patients. As a catheter is maneuvered through the vasculature,
small sizes and flexibility are preferred.
[0033] Longer electrode sizes can also improve the uniformity of
lesions by reducing the number of electrodes used. With a single,
long electrode, overlapping electric fields and gaps in tissue
ablation may be reduced. Longer electrodes, however, can reduce the
flexibility of catheters, which may be undesirable when maneuvering
a catheter within a patient.
[0034] Embodiments of the invention include expandable electrodes
that may provide large surface areas for ablation procedures, but
may maintain reduced cross-sectional profiles when being maneuvered
through a patient's veins or arteries.
[0035] System Overview
[0036] Reference is now made to FIG. 1, which figure illustrates an
overview of an ablation catheter system in accordance with
embodiments of the present invention. The system includes a
catheter 10 having a shaft portion 12, a control handle 14, and a
connector portion 16. A control module 8 is connected to connector
portion 16 via cable 6. An ablation energy supply 4 may be
connected to control module 8 via cable 3. Control module 8 is used
to control ablation energy provided by ablation energy supply 4 to
catheter 10. Ablation energy may include, as examples, RF,
microwave, DC, ultrasound, or laser radiation. Although illustrated
as separate devices, ablation energy supply 4 and control module 8
may be incorporated into a single device.
[0037] In this description, various aspects and features of
embodiments of the present invention will be described. The various
features of the embodiments of the invention are discussed
separately for clarity. One skilled in the art will appreciate that
the features may be selectively combined in a device depending upon
the particular application. Furthermore, any of the various
features may be incorporated in a catheter and associated methods
of use for ablation procedures.
[0038] Catheter Overview
[0039] Still referring to FIG. 1, catheter 10 may include a distal
tip electrode 18 and/or one or more ring electrodes 20. Distal tip
electrode 18 may be affixed to the distal tip of shaft 12 in such a
manner as to not move relative to the distal tip, or distal tip
electrode 18 may be moveable relative to shaft 12. Catheter 10 may
be a steerable device. FIG. 1 illustrates the distal tip portion 18
being deflected by the mechanism contained within control handle
14. Control handle 14 may include a rotatable thumb wheel (not
shown) which can be used by a user to deflect the distal end of the
catheter. The thumb wheel (or any other suitable actuating device)
is connected to one or more pull wires which extend through shaft
portion 12 and are connected to the distal end 18 of the catheter
at an off-axis location, whereby tension applied to one or more of
the pull wires causes the distal portion of the catheter to curve
in a predetermined direction or directions.
[0040] Electrodes with Adjustable Dimensions
[0041] In producing long lesions, it may be desirable to use a
continuous electrode that extends longitudinally along a catheter
shaft. A series of ring electrodes that are spaced axially from one
another may not reach all targeted tissue with adequate electrical
potential. The potential fields of the series of electrodes do not
necessarily sufficiently reach one another and certain volumes of
tissue may not receive transmitted energy. Attempts to ablate those
tissue volumes by increasing the power applied to the ring
electrodes might result in overlapping potential fields that could
lead to tissue overheating.
[0042] A single, long electrode may help to create a continuous
lesion with a more uniform temperature and/or power distribution.
Because electrodes are typically made with stiff materials such as
metals, long electrodes can reduce the maneuverability of the
catheter through arteries and veins. It would be desirable to have
a maneuverable catheter that positions ablation electrodes able to
produce continuous lesions.
[0043] Referring now to FIG. 2, one embodiment of an axially
extendable ablation electrode assembly 100 is illustrated. In a
retracted configuration, the shorter axial length of an electrode
102 does not reduce the maneuverability of the catheter as much as
a longer electrode of similar stiffness might. In an extended
configuration, the longer length of the electrode may be capable of
producing long lesions in a target tissue volume which are more
uniform than lesions created by a series of separate
electrodes.
[0044] In the retracted configuration, as illustrated, an outer
electrode portion 104 encompasses inner electrode portions 106 and
108. Two additional electrode portions 110 and 112 are not visible
in this configuration, but are illustrated in FIG. 3. A
longitudinal slot 114 is disposed along shaft 12 such that inner
electrode portion 108 may be connected to pull wires 116 and 118.
Any suitable barrier may be included in longitudinal slot 114 to
prevent penetration of blood but allow inner electrode portion 108
to remain connected to pull wires 116 and 118.
[0045] In some embodiments, one electrode portion, such as the
innermost electrode portion 108, is connected to an electrical lead
120 that delivers energy to electrode 102. The other electrode
portions may remain electrically connected to ablation energy
supply 4 by staying in electrical contact with an adjacent
electrode portion regardless of whether electrode assembly 100 is
in the retracted or extended configuration. In other embodiments,
each electrode portion may be separately connected to electrical
lead 120.
[0046] Electrode 102 is shown in an axially extended configuration
in FIG. 3. Inner electrode portions 106 and 108 may be moved along
catheter shaft 12 by pulling on pull wire 116. This pulling may be
achieved with any suitable actuating device on control handle 14.
Pull wire 116 may be attached to only one inner electrode portion,
such as inner electrode portion 108, which then pulls on inner
electrode portion 106 upon reaching a certain extension. In other
embodiments, pull wire 116 may be attached to multiple electrode
portions, or there may be multiple pull wires. In this embodiment,
pull wire 118 is used to retract inner electrode portion 108. Pull
wire 118 may pass through a pulley (not shown) or around a standoff
(not shown) inside shaft 12 so that tension applied in the
direction of control handle 14 moves inner electrode portion 108
toward outer electrode portion 104.
[0047] Instead of passing pull wires 116, 118 through slot 114,
pull wires 116, 118 may be attached to slidable magnets on an inner
surface of shaft 12. Magnetically coupling these magnets to magnets
attached to the electrode portions allows the pull wires 116, 118
to move the electrode portions without the use of a slot or other
passage. In other embodiments, a series of electromagnets mounted
internally or externally on shaft 12 may be consecutively energized
to move electrode portions along shaft 12.
[0048] One outer electrode portion 104 and four inner electrode
portions 106, 108, 110, 112 are provided in the embodiment
illustrated in FIGS. 2 and 3, but a greater or lesser number of
inner electrode portions may be included. Inner portions 106, 108,
110, 112 do not necessarily have to be positioned entirely within
outer electrode portion 104 in a retracted configuration. In some
embodiments, extended configurations may provide for electrode
portions 104, 106, 108, 110, 112 that do not form a single
continuous electrode 102. In these embodiments, the electrode
portions may be axially spaced from one another upon extension.
[0049] Typically, the further an ablation electrode extends
radially from an catheter shaft, the larger the volume of tissue
that can be ablated because a larger electrode can extend the
potential field further into the domain than a smaller electrode.
The diameter of an ablation electrode is limited, however, because
the catheter and electrodes move through a patient's arteries
and/or veins. An electrode with a large diameter also may be
difficult to initially introduce into a patient.
[0050] One embodiment of an electrode assembly 200 that extends an
ablation electrode surface radially is illustrated in FIGS. 4 and
5. In a retracted configuration, shown in FIG. 4, an electrode
surface 202 is held closely to an outer shaft portion 204 such that
a cross-sectional profile of electrode assembly 200 is not much
larger than shaft 12. In an expanded configuration, as illustrated
in FIG. 5, electrode surface 202 is extended radially away from
shaft 12. In the expanded configuration, electrode surface 202 may
have a larger cross-sectional profile and extends further from
shaft 12 than a non-expandable electrode that is sized to be
maneuverable within a patient.
[0051] Of course in some embodiments, even in an expanded
configuration, electrode assembly 200 may be smaller than
non-expandable electrodes which are sized to be maneuverable within
a patient. Control of the size of electrode surface 202 may be one
objective for the use of an electrode assembly such as electrode
assembly 200, rather than increasing electrode size beyond a
typically maneuverable size. By using a metal plate, metal sheet,
or other stiff materials in constructing an electrode assembly, the
dimensions and/or placement of an electrode surface may be known or
measured to a greater accuracy than electrode surfaces associated
with balloon inflation or flexible surfaces.
[0052] In the embodiment illustrated in FIG. 4, outer shaft portion
204 is positioned over an inner shaft portion 206. Electrode
surface 202, which in this embodiment is a flexible metal plate, is
attached to outer shaft portion 204 along a first end 208. The
metal plate extends around outer shaft portion 204, passes through
a slot 210, and a second end (not shown in FIG. 4) of the metal
plate attaches to inner shaft portion 206.
[0053] Rotation of outer shaft portion 204 relative to inner shaft
portion 206 adjusts electrode surface 202 between the retracted
configuration and the expanded configuration. In the embodiment
illustrated in FIG. 4, inner shaft portion 206 comprises shaft 12.
In other embodiments, inner shaft portion 206 may comprise an
element that is not a part of shaft 12 or not integral to shaft
12.
[0054] Electrode surface 202 includes an electrically-conductive
material such as platinum, silver, gold, chromium, aluminum,
tungsten, or any other suitable electrically-conductive material.
In some embodiments, electrode surface 202 is substantially
comprised of an electrically-conductive material such as metal,
that is, electrode surface 202 is not made up of a non-conductive
material that is coated with a conductive material.
[0055] In another embodiment, illustrated in FIGS. 6-8, outer shaft
portion 204 is shaft 12, while inner shaft portion 206 extends
axially for approximately the length of electrode surface 202. With
this arrangement, electrode surface 202 may be held directly
against shaft 12 such that the cross-sectional profile of electrode
assembly 200 is slightly larger than the cross-sectional profile of
shaft 12. FIG. 6 shows electrode surface 202 in a retracted
configuration. Of course, inner shaft portion 204 may extend for a
greater length than electrode surface 202.
[0056] FIG. 7 shows a cross-section of electrode assembly 200 in a
retracted configuration. Inner shaft portion 206 is rotated
clockwise to pull a section of electrode surface 202 inside outer
shaft portion 204 through a slot 210 in outer shaft portion 204.
Because of the reduced length of electrode surface 202 that remains
on the exterior of outer shaft portion 204, electrode surface 202
moves inwardly toward outer shaft portion 204 and decreases the
overall diameter of electrode assembly 200.
[0057] Electrode surface 202 is attached to outer shaft portion 204
by passing first end 208 of electrode surface through a slot 212 in
outer shaft 204 and fixing first end 208 to an inside surface 214
of outer shaft portion 204. Similarly, second end 209 may be
attached to inner shaft portion 206 by passing second end 209
through a slot 216 in inner shaft portion 206. As should be evident
to one of skill in the art, other suitable methods of attaching
first end 208 and second end 209 to their respective shaft portions
may be employed.
[0058] FIG. 8 shows electrode assembly 200 in an expanded
configuration. Inner shaft portion 206 is rotated counterclockwise
to force a section of electrode surface 202 outside of outer shaft
portion 204 through slot 210. With a longer length of electrode
surface 202 exterior to the outer shaft portion 204, the diameter
of electrode assembly 300 is increased.
[0059] In some embodiments, electrode assemblies may be provided
that allow adjustment of electrode dimensions in both the radial
direction and the axial direction. Such embodiments may include
combinations of structures disclosed herein or equivalents.
[0060] An electrode surface that extends from shaft 12 along
certain radii may allow for deeper embedding of an electrode
surface into tissue. Additionally, electric fields may be more
directed than with cylindrical electrodes.
[0061] One embodiment of an electrode assembly 300 that allows for
the extension and retraction of an electrode surface along certain
radii is illustrated in FIG. 9. In this embodiment, two fins 302
are extendable from shaft 12. Two fins 302 are shown in this
embodiment, but any suitable number of fins may be used such as one
fin, three fins, four fins, etc. With retractable fins, shaft 12
may be maneuvered through the patient with a limited
cross-sectional diameter. Once satisfactorily positioned, fins 302
may be extended. As shown in FIG. 10, fins 302 may be attached to
an inner shaft portion 306 that is rotatable relative to an outer
shaft portion 304. In this embodiment, outer shaft portion 302 is
shaft 12. In other embodiments, inner shaft portion 306 may be
shaft 12 and outer shaft portion 204 may comprise a collar that is
mounted around shaft 12.
[0062] In the illustrated embodiment of FIGS. 9-11, rotation of
inner shaft portion 304 clockwise relative to outer shaft portion
306 pulls fins 302 inwardly through slots 310 in outer shaft
portion 304.
[0063] Fins 302 may be constructed with an electrically-conductive
material that is flexible enough to be extended and retracted
through slots 310. In further embodiments, fins 302 may be
constructed of a non-electrically conducting material, such as a
plastic or a rubber, that is coated with an electrically-conductive
coating.
[0064] As shown in FIG. 11, clockwise rotation of inner shaft
portion 306 relative to outer shaft portion 304 pushes fins 302
through slots 310 to extend them beyond an outer surface 318 of
outer shaft portion 304. Fins 302 may be of any suitable shape, and
they may extend further in the circumferential direction than an
axial direction.
[0065] Referring now to FIG. 12, electrode assembly 400 includes a
cam arrangement to extend fins 402. In this arrangement, an
eccentric shaft 406 is rotated to push fins 402 beyond an outer
surface 418 of shaft 12. A biasing element, such as a spring 420,
presses against an inner surface 422 of shaft 12 and a stop 424
that is attached to fin 402. In this manner, when eccentric shaft
406 is oriented as shown in FIG. 12, fins 402 are urged inward of
outer surface 418. When eccentric shaft 406 is oriented as shown in
FIG. 13, fins 402 are urged outward of outer surface 418. In some
embodiments, rotation of eccentric shaft 406 may be achieved with
an actuator on control handle 14.
[0066] Having thus described several aspects of at least one
embodiment of this invention, it is to be appreciated various
alterations, modifications, and improvements will readily occur to
those skilled in the art. Such alterations, modifications, and
improvements are intended to be part of this disclosure, and are
intended to be within the spirit and scope of the invention.
Accordingly, the foregoing description and drawings are by way of
example only.
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