U.S. patent application number 10/273585 was filed with the patent office on 2003-05-08 for systems and methods for forming large lesions in body tissue using curvilinear electrode elements.
Invention is credited to Bourne, Thomas, Fleischman, Sidney D., Panescu, Dorin, Swanson, David K., Whayne, James G..
Application Number | 20030088244 10/273585 |
Document ID | / |
Family ID | 27558198 |
Filed Date | 2003-05-08 |
United States Patent
Application |
20030088244 |
Kind Code |
A1 |
Swanson, David K. ; et
al. |
May 8, 2003 |
Systems and methods for forming large lesions in body tissue using
curvilinear electrode elements
Abstract
Systems and associated methods form larger and deeper lesion
patterns by shaping a support body with multiple electrodes in ways
that increase the density of the electrodes per given tissue area.
The support body can carry either elongated, continuous electrodes
or arrays of non-contiguous, segmented electrodes.
Inventors: |
Swanson, David K.; (Mountain
View, CA) ; Bourne, Thomas; (Mountain View, CA)
; Fleischman, Sidney D.; (Menlo Park, CA) ;
Panescu, Dorin; (Sunnyvale, CA) ; Whayne, James
G.; (Saratoga, CA) |
Correspondence
Address: |
HENRICKS SLAVIN AND HOLMES LLP
SUITE 200
840 APOLLO STREET
EL SEGUNDO
CA
90245
|
Family ID: |
27558198 |
Appl. No.: |
10/273585 |
Filed: |
October 18, 2002 |
Related U.S. Patent Documents
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10273585 |
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09111308 |
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6514246 |
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5582609 |
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08287310 |
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08138142 |
Oct 15, 1993 |
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08287310 |
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08137576 |
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08138235 |
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08138452 |
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Current U.S.
Class: |
606/41 |
Current CPC
Class: |
A61B 2018/00196
20130101; A61B 2018/1253 20130101; A61B 2018/1435 20130101; A61L
31/10 20130101; A61B 2018/00357 20130101; A61B 2018/00755 20130101;
A61L 29/145 20130101; A61M 25/0041 20130101; A61B 18/1402 20130101;
A61B 18/1815 20130101; A61B 2018/1497 20130101; A61B 18/1492
20130101; A61B 2562/043 20130101; A61B 5/6855 20130101; A61B
2018/00869 20130101; A61B 2018/0016 20130101; A61L 31/145 20130101;
A61B 5/6857 20130101; A61B 5/6858 20130101; A61B 2018/00107
20130101; A61N 1/056 20130101; A61B 2017/00292 20130101; A61N 1/40
20130101; A61B 2018/00083 20130101; A61B 2018/1407 20130101; A61B
2017/00084 20130101; A61B 2018/00875 20130101; A61B 2017/003
20130101; A61N 1/06 20130101; A61B 2018/1861 20130101; A61M
2025/09141 20130101; A61B 2018/124 20130101; A61B 2018/126
20130101; A61B 2018/00267 20130101; A61B 5/287 20210101; A61B
2018/00148 20130101; A61B 2018/00214 20130101; A61B 2018/00839
20130101; A61N 1/403 20130101; A61B 2018/00577 20130101 |
Class at
Publication: |
606/41 |
International
Class: |
A61B 018/14 |
Claims
We claim:
1. A device for ablating body tissue comprising a support element
having a curved region to peripherally contact a tissue area, and
at least two energy emitting zones on the curved region mutually
separated across the contacted tissue area, the mutual separation
between the zones across the contacted tissue area creating, when
the zones simultaneously emit energy, an additive heating effect to
form a continuous lesion pattern in the contacted tissue area that
spans across the contacted tissue area.
2. A device according to claim 1 and further including a continuous
energy emitting electrode on the curved region of the support
element.
3. A device according to claim 2 wherein the continuous electrode
includes at least two energy applying zones spaced apart along the
curved region and separated across the contacted tissue area.
4. A device according to claim 1 wherein the two energy emitting
zones comprise non-contiguous energy emitting segments spaced apart
on the curved region and mutually separated across the contacted
tissue area.
5. A device for ablating body tissue comprising a support element
having a curved region to peripherally contact a tissue area, and
at least two energy emitting zones on the curved region mutually
separated across the contacted tissue area, each zone having a
diameter, the radius of curvature of the curved region being equal
to or less than about 3.5 times the smaller of the diameters of the
first and second zones to create, when the zones simultaneously
emit energy, a continuous lesion spanning across the contacted
tissue area.
6. A device for ablating body tissue comprising a support element
having a curved region to peripherally contact a tissue area, and
at least two energy emitting zones on the curved region mutually
separated across the contacted tissue area, each zone having a
length and a diameter, the length of each zone being greater than
about 5 times the diameter of the respective zone, the radius of
curvature of the curved region being equal to or less than about
3.5 times the smaller of the diameters of the first and second
zones to create, when the zones simultaneously emit energy, a
continuous lesion spanning across the contacted tissue area.
7. A device according to claim 5 or 6 and further including a
continuous energy emitting electrode on the curved region of the
support element.
8. A device according to claim 7 wherein the continuous electrode
includes at least two energy applying zones spaced apart along the
curved region and separated across the contacted tissue area.
9. A device according to claim 7 wherein the continuous electrode
comprises a material extending about the curved region of the
support element through which energy is emitted.
10. A device according to claim 7 wherein the continuous electrode
comprises a coating of material on the curved region of the support
element through which energy is emitted.
11. A device according to claim 7 wherein the continuous electrode
comprises wire helically wrapped about the curved region of the
support element.
12. A device according to claim 5 or 6 wherein the two energy
emitting zones comprise non-contiguous electrode segments spaced
apart on the curved region of the support element.
13. A device according to claim 12 wherein at least one of the
electrode segments comprise metallic material attached about the
support element.
14. A device according to claim 12 wherein at least one of the
electrode segments comprises wire helically wrapped about the
curved region of the support element.
15. A device according to claim 12 wherein at least one of the
electrode segments comprise a coating of material on the support
element through which energy is emitted.
16. A device according to claim 5 or 6 wherein the support element
is flexible and includes means for flexing the element to form the
curved region.
17. A device according to claim 16 wherein the flexing means flexes
the support element from a generally straight configuration to form
the curved region.
18. A device according to claim 16 wherein flexing means flexes the
support element from a generally straight configuration to
selectively form the curved region on opposite sides of the
generally straight configuration.
19. A device according to claim 5 or 6 wherein the curved region is
formed in the shape of a hoop.
20. A device according to claim 5 or 6 wherein the curved region is
formed in the shape of a hook.
21. A device according to claim 5 or 6 wherein the radius of
curvature of the curved region is equal to or less than about 2.5
times the smaller of the diameters of the first and second
zones.
22. A device according to claim 21 wherein the radius of curvature
of the curved region is equal to or less than about 1.5 times the
smaller of the diameters of the first and second zones.
23. A device for ablating body tissue comprising a support element
having a curved region to peripherally contact a tissue area, and
at least two non-contiguous energy emitting zones on the curved
region mutually separated across the contacted tissue area, each
zone having a diameter, the separation between the zones across the
contacted tissue area being equal to or less than about 7 times the
smaller of the diameters of the first and second zones to create,
when the zones simultaneously emit energy, a continuous lesion
spanning across the contacted tissue area.
24. A device for ablating body tissue comprising a support element
having a curved region to peripherally contact a tissue area, and
at least two non-contiguous energy emitting zones on the curved
region mutually separated across the contacted tissue area, each
zone having a length and a diameter, the length of each zone being
equal to or less than about 5 times the diameter of the respective
zone, the separation between the zones across the contacted tissue
area being equal to or less than about 7 times the smaller of the
diameters of the first and second zones to create, when the zones
simultaneously emit energy, a continuous lesion spanning across the
contacted tissue area.
25. A device according to claim 23 or 24 wherein the separation
between the zones across the contacted tissue area is equal to or
less than about 5 times the smaller of the diameters of the first
and second zones.
26. A device according to claim 25 wherein the separation between
the zones across the contacted tissue area is equal to or less than
about 3 times the smaller of the diameters of the first and second
zones.
27. A device for ablating body tissue comprising a support element
having a curved region to peripherally contact a tissue area, and
at least two non-contiguous energy emitting zones on the curved
region mutually separated across the contacted tissue area, each
zone having a length, the separation between the zones across the
contacted tissue area being equal to or less than about 4 times the
longer of the lengths of the first and second zones to create, when
the zones simultaneously emit energy, a continuous lesion spanning
across the contacted tissue area.
28. A device for ablating body tissue comprising a support element
having a curved region to peripherally contact a tissue area, and
at least two non-contiguous energy emitting zones on the curved
region mutually separated across the contacted tissue area, each
zone having a length and a diameter, the length of each zone being
equal to or less than about 5 times the diameter of the respective
zone, the separation between the zones across the contacted tissue
area being equal to or less than about 4 times the longer of the
lengths of the first and second zones to create, when the zones
simultaneously emit energy, a continuous lesion spanning across the
contacted tissue area.
29. A device according to claim 27 or 28 wherein the separation
between the zones across the contacted tissue area is less than
about 3 times the longer of the lengths of the first and second
zones.
30. A device according to claim 23 or 24 or 27 or 28 wherein at
least one of the two energy emitting zones comprise metallic
material attached about the support element.
31. A device according to claim 23 or 24 or 27 or 28 wherein at
least one of the two energy emitting zones comprise wire helically
wrapped about the support element.
32. A device according to claim 23 or 24 or 27 or 28 wherein at
least one of the two energy emitting zones comprise a coating of
material on the support element through which energy is
emitted.
33. A device according to claim 23 or 24 or 27 or 28 wherein the
support element is flexible and includes means for flexing the
element to form the curved region.
34. A device according to claim 33 wherein the flexing means flexes
the support element from a generally straight configuration to form
the curved region.
35. A device according to claim 33 wherein flexing means flexes the
support element from a generally straight configuration to
selectively form the curved region on opposite sides of the
generally straight configuration.
36. A device according to claim 22 or 24 or 27 or 28 wherein the
curved region is formed in the shape of a hoop.
37. A device according to claim 22 or 24 or 27 or 28 wherein the
curved region is formed in the shape of a hook.
38. A method for ablating body tissue comprising the steps of
positioning at least two energy emitting zones along a curve in
peripheral contact with a tissue area in a mutually closely
separated relationship across the contacted tissue area, and
conditioning the zones to simultaneously emit energy to create an
additive heating effect to form a continuous lesion pattern in the
contacted tissue area that spans across the contacted tissue
area.
39. A method for ablating body tissue comprising the steps of
positioning at least two energy emitting zones along a curve in
peripheral contact with a tissue area, each zone having a diameter,
the radius of curvature of the curved region being equal to or less
than about 3.5 times the smaller of the diameters of the first and
second zones, and conditioning the zones to simultaneously emit
energy to create a continuous lesion spanning across the contacted
tissue area.
40. A method for ablating body tissue comprising the steps of
positioning at least two energy emitting zones along a curve in
peripheral contact with a tissue area, each zone having a length
and a diameter, the length of each zone being greater than about 5
times the diameter of the respective zone, the radius of curvature
of the curved region being equal to or less than about 3.5 times
the smaller of the diameters of the first and second zones, and
conditioning the zones to simultaneously emit energy to create a
continuous lesion spanning across the contacted tissue area.
41. A method according to claim 39 or 40 wherein the radius of
curvature of the curved region is equal to or less than about 2.5
times the smaller of the diameters of the first and second
zones.
42. A method according to claim 41 wherein the radius of curvature
of the curved region is equal to or less than about 1.5 times the
smaller of the diameters of the first and second zones.
43. A method for ablating body tissue comprising the steps of
positioning at least two non-contiguous energy emitting zones along
a curve in peripheral contact with a tissue area, the zones being
mutually separated across the contacted tissue area, each zone
having a diameter, the separation between the zones across the
contacted tissue area being equal to or less than about 7 times the
smaller of the diameters of the first and second zones, and
conditioning the zones to simultaneously emit energy to create a
continuous lesion spanning across the contacted tissue area.
44. A method for ablating body tissue comprising the steps of
positioning at least two non-contiguous energy emitting zones along
a curve in peripheral contact with a tissue area, the zones being
mutually separated across the contacted tissue area, each zone
having a length and a diameter, the length of each zone being equal
to or less than about 5 times the diameter of the respective zone,
the separation between the zones across the contacted tissue area
being equal to or less than about 7 times the smaller of the
diameters of the first and second zones, and conditioning the zones
to simultaneously emit energy to create a continuous lesion
spanning across the contacted tissue area.
45. A method according to claim 43 or 44 wherein the separation
between the zones across the contacted tissue area is equal to or
less than about 5 times the smaller of the diameters of the first
and second zones.
46. A method according to claim 45 wherein the separation between
the zones across the contacted tissue area is equal to or less than
about 3 times the smaller of the diameters of the first and second
zones.
47. A method for ablating body tissue comprising the steps of
positioning at least two non-contiguous energy emitting zones along
a curve in peripheral contact with a tissue area, the zones being
mutually separated across the contacted tissue area, each zone
having a length, the separation between the zones across the
contacted tissue area being equal to or less than about 4 times the
longer of the lengths of the first and second zones, and
conditioning the zones to simultaneously emit energy to create a
continuous lesion spanning across the contacted tissue area.
48. A method for ablating body tissue comprising the steps of
positioning at least two non-contiguous energy emitting zones along
a curve in peripheral contact with a tissue area, the zones being
mutually separated across the contacted tissue area, each zone
having a length and a diameter, the length of each zone being equal
to or less than about 5 times the diameter of the respective zone,
the separation between the zones across the contacted tissue area
being equal to or less than about 4 times the longer of the lengths
of the first and second zones, and conditioning the zones to
simultaneously emit energy to create a continuous lesion spanning
across the contacted tissue area.
49. A method according to claim 47 or 48 wherein the separation
between the zones across the contacted tissue area is less than
about 3 times the longer of the lengths of the first and second
zones.
Description
FIELD OF THE INVENTION
[0001] The invention relates to systems and methods for ablating
myocardial tissue for the treatment of cardiac conditions.
BACKGROUND OF THE INVENTION
[0002] Physicians make use of catheters today in medical procedures
to gain access into interior regions of the body to ablate targeted
tissue areas. It is important for the physician to be able to
precisely locate the catheter and control its emission of energy
within the body during tissue ablation procedures.
[0003] For example, in electrophysiological therapy, ablation is
used to treat cardiac rhythm disturbances.
[0004] During these procedures, a physician steers a catheter
through a main vein or artery into the interior region of the heart
that is to be treated. The physician places an ablating element
carried on the catheter near the cardiac tissue that is to be
ablated. The physician directs energy from the ablating element to
ablate the tissue and form a lesion.
[0005] In electrophysiological therapy, there is a growing need for
ablating elements capable of providing lesions in heart tissue
having different geometries.
[0006] For example, it is believed the treatment of atrial
fibrillation requires the formation of long, thin lesions of
different curvilinear shapes in heart tissue. Such long, thin
lesion patterns require the deployment within the heart of flexible
ablating elements having multiple ablating regions. The formation
of these lesions by ablation can provide the same therapeutic
benefits that the complex suture patterns that the surgical maze
procedure presently provides, but without invasive, open heart
surgery.
[0007] As another example, it is believed that the treatment of
atrial flutter and ventricular tachycardia requires the formation
of relatively large and deep lesions patterns in heart tissue.
Merely providing "bigger" electrodes does not meet this need.
Catheters carrying large electrodes are difficult to introduce into
the heart and difficult to deploy in intimate contact with heart
tissue. However, by distributing the larger ablating mass required
for these electrodes among separate, multiple electrodes spaced
apart along a flexible body, these difficulties can be
overcome.
[0008] With larger and/or longer multiple electrode elements comes
the demand for more precise control of the ablating process. The
delivery of ablating energy must be governed to avoid incidences of
tissue damage and coagulum formation. The delivery of ablating
energy must also be carefully controlled to assure the formation of
uniform and continuous lesions, without hot spots and gaps forming
in the ablated tissue.
SUMMARY OF THE INVENTION
[0009] A principal objective of the invention is to provide
improved systems and methodologies to form larger and deeper
lesions using curvilinear ablating elements.
[0010] One aspect of the invention provides a device and associated
method for creating large lesion patterns in body tissue. The
device and method use a support element having a curved region to
peripherally contact a tissue area. The support element carries at
least two energy emitting zones on the curved region, which are
mutually separated across the contacted tissue area. The mutual
separation between the zones across the contacted tissue area is
sufficient to create, when the zones simultaneously emit energy, an
additive heating effect to form a continuous lesion pattern in the
contacted tissue area that spans across the contacted tissue
area.
[0011] In one embodiment, a continuous energy emitting electrode is
present on the curved region of the support element.
[0012] In another embodiment, the two energy emitting zones
comprise non-contiguous energy emitting segments on the curved
region mutually separated across the contacted tissue area.
[0013] Another aspect of the invention provides a device and
associated method for ablating body tissue using a support element
having a region curved along a preselected radius to peripherally
contact a tissue area. The device and method include at least two
energy emitting zones on the curved region, which are mutually
separated across the contacted tissue area. The radius of curvature
of the curved region is equal to or less than about 3.5 times the
smaller of the diameters of the first and second zones. When the
zones are conditioned to simultaneously emit energy, a continuous
large lesion forms that spans across the contacted tissue area.
[0014] In one embodiment implementing this aspect of the invention,
the device and method employ a continuous energy emitting electrode
on the curved region of the support element.
[0015] In another embodiment that implements this aspect of the
invention, the two energy emitting zones comprise non-contiguous
electrode segments separated on the curved region of the support
element. In a preferred embodiment, the length of each zone is
greater than about 5 times the diameter of the respective zone.
[0016] Another aspect of the invention provides a device and
associated method for ablating body tissue that also use a curved
support element that peripherally contact a tissue area. The device
and method include at least two non-contiguous energy emitting
zones on the curved region, which are mutually separated across the
contacted tissue area.
[0017] According to this aspect of the invention, the separation
between the zones across the contacted tissue area is equal to or
less than about 7 times the smaller of the diameters of the first
and second zones. When the zones are conditioned to simultaneously
emit energy, a continuous large lesion is formed spanning across
the contacted tissue area.
[0018] In one embodiment implementing this aspect of the invention,
the device and method employ a continuous energy emitting electrode
on the curved region of the support element.
[0019] In another embodiment that implements this aspect of the
invention, the two energy emitting zones comprise non-contiguous
electrode segments separated on the curved region of the support
element. In a preferred embodiment of this aspect of the invention,
the length of each zone is equal to or less than about 5 times the
diameter of the respective zone.
[0020] Other features and advantages of the inventions are set
forth in the following Description and Drawings, as well as in the
appended Claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1. is a view of a probe that carries a flexible
ablating element having multiple temperature sensing elements;
[0022] FIG. 2 is an enlarged view of the handle of the probe shown
in FIG. 1, with portions broken away and in section, showing the
steering mechanism for flexing the ablating element;
[0023] FIGS. 3 and 4 show the flexure of the ablating element
against different tissue surface contours;
[0024] FIG. 5 is a side view of a flexible ablating element
comprising a rigid tip electrode element and a rigid body electrode
segment;
[0025] FIG. 6 is a perspective view of a segmented flexible
electrode element, in which each electrode segment comprises a
wrapped wire coil;
[0026] FIGS. 7A/B are, respectively, side and side section views of
different wrapped wire coils comprising flexible electrode
elements;
[0027] FIGS. 8A/B are, respectively, a side and side section view
of multiple wrapped wire coils comprising a flexible electrode
element;
[0028] FIG. 9 is a side view of a flexible ablating element
comprising a rigid tip electrode element and a flexible body
electrode segment;
[0029] FIG. 10 is a perspective view of a continuous flexible
electrode element comprising a wrapped wire coil;
[0030] FIG. 11 is a perspective view of a continuous flexible
electrode element comprising a wrapped ribbon;
[0031] FIGS. 12A/B are views of a flexible ablating element
comprising a wrapped wire coil including a movable sheath for
changing the impedance of the coil and the ablating surface area
when in use;
[0032] FIGS. 13A/B are side views of, respectively, segmented
electrode elements and a continuous electrode element which have
been masked on one side with an electrically and thermally
insulating material;
[0033] FIGS. 14A/B are schematic views of electrically connecting
electrode segments to, respectively, single and multiple wires;
[0034] FIGS. 15A/B are side section views of forming flexible coil
segments from the electrical conducting wires;
[0035] FIGS. 16A/B are views of various shaped multiple electrode
structures for making lesions that span across diagonally and/or
diametric spaced electrode regions;
[0036] FIGS. 17A/18A are views of a generally circular multiple
electrode structure for making lesions that span across diagonally
and/or diametric spaced electrode regions;
[0037] FIGS. 17B/18B are views of a generally spiral multiple
electrode structure for making lesions that span across diagonally
and/or diametric spaced electrode regions;
[0038] FIGS. 19A/B/C are views of a generally hoop-shaped multiple
electrode structure for making lesions that span across diagonally
and/or diametric spaced electrode regions;
[0039] FIG. 20 is an end section view of an ablating electrode
element carrying one temperature sensing element;
[0040] FIG. 21 is an end section view of an ablating electrode
element carrying two temperature sensing elements;
[0041] FIG. 22 is an end section view of an ablating electrode
element carrying three temperature sensing elements;
[0042] FIG. 23 is a side section view of a flexible ablating
element comprising multiple rigid electrode elements, showing one
manner of mounting at least one temperature sensing element beneath
the electrode elements;
[0043] FIG. 24 is a side section view of a flexible ablating
element comprising multiple rigid electrode elements, showing
another manner of mounting at least one temperature sensing element
between adjacent electrode elements;
[0044] FIG. 25 is a side section view of a flexible ablating
element comprising multiple rigid ablating elements, showing
another manner of mounting at least one temperature sensing element
on the electrode elements;
[0045] FIG. 26 is an enlarged top view of the mounting the
temperature sensing element on the rigid electrode shown in FIG.
26;
[0046] FIGS. 27 and 28 are side section views of the mounting of
temperature sensing elements on the ablating element shown in FIG.
5;
[0047] FIG. 29 is a view of a flexible ablating element comprising
a continuous wrapped coil, showing one manner of mounting
temperature sensing elements along the length of the coil;
[0048] FIG. 30 is a view of a flexible ablating element comprising
a continuous wrapped coil, showing another manner of mounting
temperature sensing elements along the length of the coil;
[0049] FIG. 31 is an enlarged view of the mounting of the
temperature sensing element on the coil electrode shown in FIG.
30;
[0050] FIG. 32 is a view of a flexible ablating element comprising
a continuous wrapped ribbon, showing a manner of mounting
temperature sensing elements along the length of the ribbon;
[0051] FIG. 33A is a top view of an elongated lesion pattern that
is generally straight and continuous, which non-contiguous energy
emitting zones form, when conditioned to simultaneous transmit
energy to an indifferent electrode, provided that they are spaced
sufficiently close to each other to generate additive heating
effects;
[0052] FIG. 33B is a top view of an elongated lesion pattern that
is generally straight and segmented, which non-contiguous energy
emitting zones form when they are not spaced sufficiently close to
each other to generate additive heating effects;
[0053] FIG. 34A is a top view of an elongated, curvilinear lesion
pattern that is continuous, which non-contiguous energy emitting
zones create when they are sufficiently close to each other along
the periphery of a curvilinear path generate additive heating
effects between them when they simultaneoulsy emit energy, but when
they are otherwise positioned far enough apart across from each
other to not generate additive heating effects that span across the
curvilinear path;
[0054] FIG. 34B is a top view of an elongated, curvilinear lesion
pattern that is segmented or interrupted, which non-contiguous
energy emitting zones create when they are not sufficiently
adjacent to each other either along or across the periphery of a
curvilinear path to generate additive heating effects between them;
and
[0055] FIG. 35 is is a top view of a large lesion pattern that
spans across a curvilinear path, which non-contiguous energy
emitting zones create when they are sufficiently adjacent to each
other to generate additive heating effects across the periphery of
the curvilinear path.
[0056] The invention may be embodied in several forms without
departing from its spirit or essential characteristics. The scope
of the invention is defined in the appended claims, rather than in
the specific description preceding them. All embodiments that fall
within the meaning and range of equivalency of the claims are
therefore intended to be embraced by the claims.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0057] This Specification discloses multiple electrode structures
that embody aspects the invention. This Specification also
discloses tissue ablation systems and techniques using multiple
temperature sensing elements that embody other aspects of the
invention. The illustrated and preferred embodiments discuss these
structures, systems, and techniques in the context of
catheter-based cardiac ablation. That is because these structures,
systems, and techniques are well suited for use in the field of
cardiac ablation.
[0058] Still, it should be appreciated that the invention is
applicable for use in other tissue ablation applications. For
example, the various aspects of the invention have application in
procedures for ablating tissue in the prostrate, brain, gall
bladder, uterus, and other regions of the body, using systems that
are not necessarily catheter-based.
[0059] I. Flexible Ablating Elements
[0060] FIG. 1 shows a flexible ablating element 10 for making
lesions within the heart.
[0061] The element 10 is carried at the distal end of a catheter
body 12 of an ablating probe 14. The ablating probe 14 includes a
handle 16 at the proximal end of the catheter body 12. The handle
16 and catheter body 12 carry a steering mechanism 18 for
selectively bending or flexing the ablating element 10 in two
opposite directions, as the arrows in FIG. 1 show.
[0062] The steering mechanism 18 can vary. In the illustrated
embodiment (see FIG. 2), the steering mechanism 18 includes a
rotating cam wheel 20 with an external steering lever 22 (see FIG.
1). As FIG. 2 shows, the cam wheel 20 holds the proximal ends of
right and left steering wires 24. The wires 24 pass through the
catheter body 12 and connect to the left and right sides of a
resilient bendable wire or spring 26 (best shown in FIGS. 20 and
23) enclosed within a tube 28 inside the ablating element 10.
[0063] Further details of this and other types of steering
mechanisms for the ablating element 10 are shown in Lundquist and
Thompson U.S. Pat. No. 5,254,088, which is incorporated into this
Specification by reference.
[0064] As FIG. 1 shows, forward movement of the steering lever 22
flexes or curves the ablating element 10 down. Rearward movement of
the steering lever 22 flexes or curves the ablating element 10
up.
[0065] Various access techniques can be used to introduce the probe
14 into the desired region of the heart. For example, to enter the
right atrium, the physician can direct the probe 14 through a
conventional vascular introducer through the femoral vein. For
entry into the left atrium, the physician can direct the probe 14
through a conventional vascular introducer retrograde through the
aortic and mitral valves.
[0066] Alternatively, the physician can use the delivery system
shown in pending U.S. application Ser. No. 08/033,641, filed Mar.
16, 1993, and entitled "Systems and Methods Using Guide Sheaths for
Introducing, Deploying, and Stabilizing Cardiac Mapping and
Ablation Probes."
[0067] The physician can verify intimate contact between the
element 10 and heart tissue using conventional pacing and sensing
techniques. Once the physician establishes intimate contact with
tissue in the desired heart region, the physician applies ablating
energy to the element 10. The type of ablating energy delivered to
the element 10 can vary. In the illustrated and preferred
embodiment, the element 10 emits electromagnetic radio frequency
energy.
[0068] The flexible ablating element 10 can be configured in
various ways. With these different configurations, the flexible
ablating element can form lesions of different characteristics,
from long and thin to large and deep in shape.
[0069] A. Segmented, Rigid Electrode Elements
[0070] FIGS. 3 and 4 show one implementation of a preferred type of
flexible ablating element, designated 10(1). The element 10(1)
includes multiple, generally rigid electrode elements 30 arranged
in a spaced apart, segmented relationship upon a flexible body
32.
[0071] The flexible body 32 is made of a polymeric, electrically
nonconductive material, like polyethylene or polyurethane. The body
32 carries within it the resilient bendable wire or spring with
attached steering wires (best shown in FIGS. 20 and 23), so it can
be flexed to assume various curvilinear shapes.
[0072] The segmented electrodes 30 comprise solid rings of
conductive material, like platinum. The electrode rings 30 are
pressure fitted about the body 32. The flexible portions of the
body 32 between the rings 30 comprise electrically nonconductive
regions.
[0073] The body 32 can be flexed between the spaced apart
electrodes 30 to bring the electrode 30 into intimate contact along
a curvilinear surface of the heart wall, whether the heart surface
curves outward (as FIG. 3 shows) or curves inward (as FIG. 4
shows).
[0074] FIG. 5 shows an implementation of another preferred type of
a flexible ablating element, of the same general style as element
10(1), designated 10(2). Element 10(2) includes two generally rigid
electrode elements 34 and 36 arranged in a spaced apart
relationship at the distal tip of a flexible body 38. The flexible
body 38 is made of electrically insulating material, like
polyurethane and PEBAX.RTM. plastic material. The body 38 carries
one relatively large, rigid metal electrode 34 at its tip, which
comprises a body of electrically conductive material, like
platinum. The body 38 also carries another rigid electrode 36,
which comprises a solid ring 36 of electrically conductive
material, like platinum, pressure fitted about the body 38. As FIG.
5 shows, the ablating element 10(2) can also include one or more
conventional sensing ring electrodes 40 proximally spaced from the
ablating ring electrode 36. The sensing ring electrodes 40 serve to
sense electrical events in heart tissue to aid the physician in
locating the appropriate ablation site.
[0075] As shown in phantom lines in FIG. 5, the flexible body 38,
when pressed against the endocardial surface targeted for ablation,
bends to place the sides of the rigid electrodes 34 and 36 in
intimate contact against the particular contour of the surface. The
flexible nature of the ablating element 10(2) can be further
augmented by the inclusion of the resilient bendable wire or spring
26 within it (best shown in FIG. 27). In this embodiment, the
steering wires 24 connect to the left and right sides of the
bendable wire 26. The opposite ends of the steering wires 24
connect to a steering mechanism of the type previously described
and shown in FIG. 2. In this arrangement, the physician can use the
steering mechanism to remotely flex the electrodes 34 and 36 in the
manner shown in FIG. 5.
[0076] Preferably, as FIG. 27 shows, the steering wires 24 are
secured to the bendable wire 26 near its distal end, where the
bendable wire 26 is itself secured to the tip electrode 34. Bending
of the wire 26 thereby directly translates into significant
relative flexing of the distal end of the catheter body 38, which
carries the electrodes 34 and 36.
[0077] Alternatively, the region between the electrodes 34 and 36
can be stiff, not flexible. In this arrangement, pressing the 34
and 36 against tissue brings the tissue into conformance about the
electrodes 34 and 36.
[0078] The generally rigid, segmented electrodes 30 in element
10(1) and 34/36 in element 10(2) can be operated, at the
physician's choice, either in a unipolar ablation mode or in a
bipolar mode. In the unipolar mode, ablating energy is emitted
between one or more the electrodes 30 (in element 10(1)) or
electrodes 34/36 (in element 10(2)) and an external indifferent
electrode. In the bipolar mode, ablating energy is emitted between
two of the electrodes 30 (in element 10(1)) or the electrodes 34
and 36 (in element 10(2)), requiring no external indifferent
electrode.
[0079] B. Flexible Electrode Elements
[0080] FIG. 6 shows an implementation of another preferred style of
a flexible ablating element, designated 10(3). The element 10(3),
unlike elements 10(1) and 10(2), includes generally flexible
electrode elements 44 carried on a likewise flexible body 42.
[0081] The flexible body 42 is made of a polymeric, electrically
nonconductive material, like polyethylene or polyurethane, as the
flexible body of elements 10(1) and 10(2). The body 42 also
preferably carries within it the resilient bendable wire or spring
26 with attached steering wires 24 (best shown in FIGS. 29 and 30),
so it can be flexed to assumed various curvilinear shapes, as FIG.
6 shows.
[0082] The body 32 carries on its exterior surface an array of
segmented, generally flexible electrodes 44 comprising spaced apart
lengths of closely wound, spiral coils. The coil electrodes 44 are
made of electrically conducting material, like copper alloy,
platinum, or stainless steel. The electrically conducting material
of the coil electrode 44 can be further coated with
platinum-iridium or gold to improve its conduction properties and
biocompatibility.
[0083] The coils 44 can be made of generally cylindrical wire, as
the coil 44(a) shown in FIGS. 7A/B. Alternatively, the wire forming
the coils 44 can be non-circular in cross section. The wire, for
example, have a polygon or rectangular shape, as the coil 44(b)
shown in FIGS. 7A/B. The wire can also have a configuration in
which adjacent turns of the coil nest together, as the coil 44(c)
shown in FIGS. 7A/B. Coils 44(b) and 44(c) in FIGS. 7A/B present a
virtually planar tissue-contacting surface, which emulates the
tissue surface contact of the generally rigid electrode 30 shown in
FIGS. 3 and 4. However, unlike the electrode 30, the coils 44(b)
and 44(c), as well as the cylindrical coil 44(a), are each
inherently flexible and thereby better able to conform to the
surface contour of the tissue.
[0084] In another alternative arrangement, each coil 44 can
comprise multiple, counter wound layers of wire, as the coil 44(d)
shown in FIGS. 8A/B. This enhances the energy emitting capacity of
the coil 44(d), without significantly detracting from its inherent
flexible nature. The multiple layer coil 44(d) structure can also
be formed by using a braided wire material (not shown).
[0085] An alternative arrangement (shown in FIG. 9) uses the
generally rigid tip electrode 34 (like that in element 10(2), shown
in FIG. 5) in combination with a generally flexible electrode
segment 44 made of a closely wound coil. Of course, the tip
electrode 34, too, could comprise a generally flexible electrode
structure made of a closely wound coil. It should be apparent by
now that many combinations of rigid and flexible electrode
structures can be used in creating a flexible ablating element.
[0086] Furthermore, the inherent flexible nature of a coiled
electrode structures 44 makes possible the constructure of a
flexible ablating element (designated 10(4) in FIG. 10) comprising
a continuous elongated flexible electrode 46 carried by a flexible
body 48. The continuous flexible electrode 46 comprises an
elongated, closely wound, spiral coil of electrically conducting
material, like copper alloy, platinum, or stainless steel, wrapped
about the flexible body. For better adherence, an undercoating of
nickel or titanium can be applied to the underlying flexible body.
The continuous coil electrode 46 can be arranged and configured in
the same fashion as the segmented coil electrodes 44 shown in FIGS.
7A/B and 8A/B.
[0087] The continuous coil electrode 46 is flexible and flexes with
the underlying body 48, as FIG. 10 shows. It can be easily placed
and maintained in intimate contact against heart tissue. The
continuous flexible coil structure shown in FIG. 10 therefore makes
possible a longer, flexible ablating element.
[0088] In an alternative arrangement (shown in FIGS. 12A/B), the
elongated coil electrode 46 can include a sliding sheath 50 made of
an electrically nonconducting material, like polyimide. A stylet
(not shown) attached to the sheath 50 extends through the
associated catheter body 12 to a sliding control lever carried on
the probe handle 16 (also not shown). Moving the sheath 50 varies
the impedance of the coil electrode 46. It also changes the surface
area of the element 10(4).
[0089] Further details of this embodiment can be found in copending
U.S. patent application Ser. No. 08/137,576, filed Oct. 15, 1993,
and entitled "Helically Wound Radio Frequency Emitting Electrodes
for Creating Lesions in Body Tissue," which is incorporated into
this Specification by reference.
[0090] FIG. 11 shows another implementation of a generally flexible
element, designated element 10(5). The element 10(5) comprises a
ribbon 52 of electrically conductive material wrapped about a
flexible body 54. The ribbon 52 forms a continuous, inherently
flexible electrode element.
[0091] Alternatively, the flexible electrodes can be applied on the
flexible body by coating the body with a conductive material, like
platinum-iridium or gold, using conventional coating techniques or
an ion beam assisted deposition (IBAD) process. For better
adherence, an undercoating of nickel or titanium can be applied.
The electrode coating can be applied either as discrete, closely
spaced segments (to create an element like 10(3)) or in a single
elongated section (to create an element like 10(4) or 10(5)).
[0092] The flexible electrodes of elements 10(3) can be operated,
at the physician's choice, either in a unipolar ablation mode or in
a bipolar mode.
[0093] C. Controlling Lesion Characteristics Using Flexible
Electrodes
[0094] The ablating elements 10(1) to 10(5), as described above,
are infinitely versatile in meeting diverse tissue ablation
criteria.
[0095] For example, the ablating elements 10(1) and 10(3) to 10(5)
can be conditioned to form different configurations of elongated
(i.e., generally long and thin) lesion patterns. These elongated
lesion patterns can be continuous and extend along a straight line
(as lesion pattern 200 in FIG. 33A shows) or along a curve (as
lesion pattern 204 in FIG. 34A shows). Alternatively, these
elongated lesion patterns can be segmented, or interrupted, and
extend along a straight line (as lesion pattern 202 in FIG. 33B
shows) or along a curve (as lesion pattern 206 in FIG. 34B shows).
Elongated lesion patterns can be used to treat, for example, atrial
fibrillation.
[0096] Alternatively, the ablating elements 10(1) to 10(5) can be
conditioned to form larger and deeper lesions in the heart, as
lesion pattern 208 in FIG. 35 shows. These lesion large and deep
lesion patterns can be used to treat, for example, atrial flutter
or ventricular tachycardia.
[0097] The characteristics of lesions formed by the ablating
elements 10(1) to 10(5) can be controlled in various ways. For
example, lesion characteristics are controlled by employing one or
more of the following techniques:
[0098] (i) selectively adjusting the size and spacing of energy
emitting regions along the elements.
[0099] (ii) selectively masking the energy emitting regions on the
elements to focus ablating energy upon the targeting tissue.
[0100] (iii) selectively altering the electrical connections of
wires conveying ablating energy to the energy emitting regions on
the elements, to thereby affect the distribution of ablation
energy.
[0101] (iv) selectively altering the shape of the flexible support
body, to thereby affect the distribution and density of energy
emitting regions on the elements.
[0102] (v) selectively controlling temperature conditions along the
energy emitting regions of the elements.
[0103] These various techniques of controlling lesion
characteristics will now be individually discussed in greater
detail.
[0104] 1. Size and Spacing of Energy Emitting Regions
[0105] The number of electrode segments that the elements 10(1),
(2); (4); and (5) carry, and the spacing between them, can vary,
according to the particular objectives of the ablating procedure.
Likewise, the dimensions of individual electrode segments and
underlying body in elements 10(1) to 10(5) can also vary for the
same reason. These structural features influence the
characteristics of the lesion patterns formed.
[0106] The continuous electrode structure of 10(4) is well suited
for creating continuous, elongated lesion patterns like the
patterns 200 and 204 shown in FIGS. 33A and 34A, when the entire
electrode is conditioned to emit energy. The segmented electrode
structures of elements 10(1); (3); and (5) are also well suited for
creating continuous, elongated lesion patterns like the pattern 200
shown in FIG. 33A, provided that the electrode segments are
adjacently spaced close enough together to create additive heating
effects when ablating energy is transmitted simultaneously to the
adjacent electrode segments. The same holds true when the
continuous electrode structure 10(4) is conditioned to function
like a segmented electrode structure by emitting energy from
adjacent zones along its length, in which case the zones serve as
electrode segments. Stated another way, the segments comprise zones
which emit energy to tissue to obtain the desired therapeutic
tissue heating effect.
[0107] The additive heating effects along a continuous electrode
structure or between close, adjacent electrode segments intensify
the desired therapeutic heating of tissue contacted by the
segments. The additive effects heat the tissue at and between the
adjacent electrode segments to higher temperatures than the
electrode segments would otherwise heat the tissue, if conditioned
to individually emit energy to the tissue, or if spaced apart
enough to prevent additive heating effects. The additive heating
effects occur when the electrode segments are operated
simultaneously in a bipolar mode between electrode segments.
Furthermore, the additive heating effects also arise when the
continuous electrode or electrode segments are operated
simultaneously in a unipolar mode, transmitting energy to an
indifferent electrode.
[0108] Conversely, when the energy emitting segments are not
sufficiently spaced close enough to each other to generate additive
heating effects, the continuous electrode structure 10(4) and the
segmented electrode structures 10(1); (3); and (5) create
elongated, segmented lesion patterns like the pattern 202 shown in
FIG. 33B.
[0109] More particularly, when the spacing between the segments is
equal to or less than about 3 times the smaller of the diameters of
the segments, the simultaneous emission of energy by the segments,
either bipolar between the segments or unipolar to an indifferent
electrode, creates an elongated continuous lesion pattern in the
contacted tissue area due to the additive heating effects.
Conversely, when the spacing between the segments is greater than
about 5 times the smaller of the diameters of the segments, the
simultaneous emission of energy by the segments, either bipolar
between segments or unipolar to an indifferent electrode, does not
generate additive heating effects. Instead, the simultaneous
emission of energy by the zones creates an elongated segmented, or
interrupted, lesion pattern in the contacted tissue area.
[0110] Alternatively, when the spacing between the segments along
the contacted tissue area is equal to or less than about 2 times
the longest of the lengths of the segments the simultaneous
application of energy by the segments, either bipolar between
segments or unipolar to an indifferent electrode, also creates an
elongated continuous lesion pattern in the contacted tissue area
due to additive heating effects. Conversely, when the spacing
between the segments along the contacted tissue area is greater
than about 3 times the longest of the lengths of the segments, the
simultaneous application of energy, either bipolar between segments
or unipolar to an indifferent electrode, creates an elongated
segmented, or interrupted, lesion pattern.
[0111] The continuous electrode structure 10(4) and the segmented
electrode structures 10(1); (3); and (5), when flexed can also
create curvilinear lesion patterns like the patterns 204 and 206
shown in FIGS. 34A and 34B. The peripheral shape of the lesion
pattern can be controlled by flexing the body from straight to
curvilinear. As already explained, the body can be remotely steered
to flex it into a desired shape, or it can possess a preformed
shape memory. In the latter situation, removing a constraint (such
as a sheath, not shown), enables the operator to change the segment
from straight to curvilinear.
[0112] To consistently form these curvilinear lesion patterns,
additional spacial relationships among the electrode segments must
be observed. The particular nature of these relationships depends
in large part upon the length to diameter ratio of the individual
electrode segments.
[0113] More particularly, when the length of each energy applying
segment is equal to or less than about 5 times the diameter of the
respective segment, the curvilinear path that support element takes
should create a distance across the contacted tissue area that is
greater than about 8 times the smaller of the diameters of the
first and second zones. In this arrangement, the simultaneously
application of energy forms an elongated lesion pattern in the
tissue area that follows the curved periphery contacted by the
support element, but does not span across the contacted tissue
area. The curvilinear lesion pattern is continuous (as FIG. 34A
shows) if the spacing between the segments along the support
element is sufficient to create an additive heating effect between
the segments, as above described. Otherwise, the curvilinear lesion
pattern is segmented or interrupted along its length, as FIG. 34B
shows.
[0114] When the length of each energy applying segment is greater
than about 5 times the diameter of the respective segment (which
generally results in an elongated electrode structure like 10(4)),
the curvilinear path that support element takes should create a
radius of curvature that is greater than about 4 times the smallest
the diameters segments. In this arrangement, the simultaneous
application of energy by the segments (by the entire elongated
electrode) forms an elongated lesion pattern in the tissue area
that follows the curved periphery contacted by the support element,
but does not span across the contacted tissue area. Again, the
curvilinear lesion pattern is continuous if the spacing between the
energy applying segments along the support body is sufficient to
create an additive heating effect. Otherwise, the curvilinear
lesion pattern is segmented or interrupted along its length.
[0115] Wider and deeper lesion patterns uniformly result by
increasing the surface area of the individual segments, due to the
extra additive effects of tissue heating that the larger segments
create. For this reason, the larger surface areas of the electrode
segments 34/36 in element 10(2) are most advantageously used for
forming large and deep lesion patterns, provided that both
electrode segments 34/36 are conditioned to emit ablating energy
simultaneously.
[0116] However, with all elements 10(1) to 10(5), ablating energy
can be selectively applied individually to just one or a selected
group of electrode segments, when desired, to further vary the size
and characteristics of the lesion pattern.
[0117] Taking the above considerations into account, it has been
found that adjacent electrode segments having lengths of less than
about 2 mm do not consistently form the desired continuous lesion
patterns. Using rigid electrode segments, the length of the each
electrode segment can vary from about 2 mm to about 10 mm. Using
multiple rigid electrode segments longer than about 10 mm each
adversely effects the overall flexibility of the element 10(1).
[0118] However, when flexible electrode segments are used,
electrode segments longer that about 10 mm in length can be used.
Flexible electrode segments can be as long as 50 mm. If desired,
the flexible electrode structure can extend uninterrupted along the
entire length of the body, thereby forming the continuous elongated
electrode structure 46 of element 10(4).
[0119] In the electrode structures of elements 10(1) to 10(5), the
diameter of the electrode segments and underlying flexible body can
vary from about 4 french to about 10 french. When flexible
electrode segments are used (as in elements 10(3) to 10(5)), the
diameter of the body and electrode segments can be less than when
more rigid electrode segments are used (as in element 10(1)). Using
rigid electrodes, the minimum diameter is about 1.35 mm, whereas
flexible electrodes can be made as small as about 1.0 mm in
diameter.
[0120] In a representative segmented electrode structure using
rigid electrode segments, the flexible body is about 1.35 mm in
diameter. The body carries electrode segments each having a length
of 3 mm. When eight electrode segments are present and
simultaneously activated with 100 watts of radio frequency energy
for about 60 seconds, the lesion pattern is long and thin,
measuring about 5 cm in length and about 5 mm in width. The depth
of the lesion pattern is about 3 mm, which is more than adequate to
create the required transmural lesion (the atrial wall thickness is
generally less than 3 mm).
[0121] In a representative segmented electrode structure using
flexible electrode segments, the coil electrode 56 is about 1.3 mm
in diameter, but could be made as small as 1.0 mm in diameter and
as large as 3.3 mm in diameter. In this arrangement, the coil
electrode 56 is about 5 cm in total length. When activated with 80
watts of radio frequency energy for 60 seconds, the coil electrode
56 forms a contiguous lesion pattern that is about 3 mm in width,
about 5 cm in length, and about 1.5 mm in depth.
[0122] Regarding the ablating element 10(2), the tip electrode 34
can range in length from about 4 mm to about 10 mm. The electrode
segment 36 can vary in length from about 2 mm to about 10 mm (or
more, if it is a flexible elongated electrode, as FIG. 9 shows).
The diameter of the electrodes 34 and 36, and thus the flexible
body 38 itself, can vary from about 4 french to about 10
french.
[0123] In element 10(2), the distance between the two electrodes 34
and 36 can also vary, depending upon the degree of flexibility and
the size of the lesion pattern required. In a representative
embodiment, the electrode segment 36 is spaced from the tip
electrode 34 by about 2.5 mm to about 5 mm. Thus, the effective
ablating length presented by the combined electrodes 34 and 36 can
vary from about 8.5 mm to about 25 mm. Preferably, the effective
ablating length presented is about 12 mm.
[0124] 2. Focusing Ablating Energy
[0125] As shown in FIGS. 13A/B, a side of one or more electrode
segments of elements 10(1), (2), and (3) (generally designated
E.sub.SEG in FIG. 13A), or a side of at least a portion of the
continuous elongated electrode of element 10(4), and 10(5)
(generally designated E.sub.CON in FIG. 13B), can be covered with a
coating 56 of an electrically and thermally insulating material.
This coating 56 can be applied, for example, by brushing on a
UV-type adhesive or by dipping in polytetrafluoroethylene (PTFE)
material.
[0126] The coating 56 masks the side of the electrode E.sub.SEG and
E.sub.CON that, in use, is exposed to the blood pool. The coating
56 thereby prevents the transmission of ablating energy directly
into the blood pool. Instead, the coating 56 directs the applied
ablating energy directly toward and into the tissue.
[0127] The focused application of ablating energy that the coating
56 provides helps to control the characteristics of the lesion. The
coating 56 also minimizes the convective cooling effects of the
blood pool upon the electrode E.sub.SEG and E.sub.CON while
ablating energy is being applied, thereby further enhancing the
efficiency of the lesion formation process.
[0128] 3. Uniformly Distributing Ablating Energy
[0129] As FIG. 14A shows, the segmented electrodes E.sub.SEG are
electrically coupled to individual wires 58, one serving each
electrode segment, to conduct ablating energy to them. As FIG. 15A
shows, in the case of a segmented coil electrode, the end of the
connecting wire 50 itself can be wrapped about the flexible body to
form a flexible coil segment 44.
[0130] In the case of a continuous elongated electrode structure
(like coil electrode 46 of element 10(4)), wires 58 are preferable
electrically coupled to the coil 46 at equally spaced intervals
along its length. This reduces the impedance of the coil along its
length. As already explained, and as FIGS. 12A/B show, the
elongated coil electrode can also include a sliding sheath 50 to
vary the impedance.
[0131] In an alternative embodiment, shown in FIG. 14B, there are
two spaced apart wires 58(1) and 58(2) electrically coupled to each
segmented electrode E.sub.SEG. In this arrangement, power is
delivered in parallel to each segmented electrode E.sub.SEG. This
decreases the effect of voltage gradients within each segmented
electrode ESEG, which, in turn, improves the uniformity of current
density delivered by the electrode E.sub.SEG. The spacing between
the multiple wires serving each electrode segment E.sub.SEG can be
selected to achieve the uniformity of current density desired.
[0132] As FIG. 15B shows, each flexible coil segment 44 can also
comprise two or more individual wires 58(1) and 58(2) wrapped at
their ends, which together form the coil segment. The multiple
wires can be wrapped sequentially or in a staggered arrangement to
form the coil segment. Similarly, an elongated flexible electrode
can be formed by individual lengths of wire wrapped about the body,
either sequentially or in a staggered pattern.
[0133] 4. Distribution and Density of Energy Applying Segments
[0134] The flexible ablating elements 10(1) and 10(3) to 10(5) can
also be used to form larger and deeper lesion patterns by specially
shaping the support body to increase the density of electrodes per
given tissue area. Structures suited for creating larger lesion
patterns result when the flexible body is generally bent back upon
itself to position electrode regions either diagonally close to
each other (as structure 60 in FIG. 16A shows) or both diagonally
close and diametrically facing each other (as structure 62 in FIG.
16B shows). The electrode regions can be either energy emitting
portions of a continuous flexible electrode E.sub.CON, as in
structure 60 in FIG. 16A, or energy emitting segments E.sub.SEG of
a segmented electrode structure, as in structure 62 in FIG.
16B.
[0135] This close diagonal spacing and/or close diametric facing of
electrodes that the structures 60 and 62 provide, coupled with the
simultaneous emission of ablating energy by the electrodes on the
structures 60 and 62, significantly concentrates the distribution
of ablating energy. These specially shaped electrode structures 60
and 62 provide an additive heating effect that causes lesions to
span across electrodes that are diagonally close and/or
diametrically facing. The spanning lesions create large and deep
lesion patterns in the tissue region that the structures 60 and 62
contact.
[0136] The structures 60 and 62 best provide these larger and
deeper lesion patterns when they maintain a prescribed relationship
among the electrode regions that takes into account the geometry of
the structure, the dimension of the structure, and the dimension of
the electrode regions it carries.
[0137] More particularly, when the length of each energy emitting
region or zone is greater than about 5 times the diameter of the
respective region or zone (as would be the case in the continuous
electrode E.sub.CON in FIG. 16A, or with a segmented electrode
having large electrode segments), the support structure should be
bent back upon itself to maintain a minimum radius of curvature
(designated R.sub.D in FIG. 16A) that does not exceed about 3.5
times the diameter of the smallest electrode area (designated
E.sub.D in FIG. 16A). The support structure can be shaped as a hook
(as structure 60 in FIG. 16A) or as a circle (as structure 62 in
FIG. 16B) to present this minimum radius of curvature.
[0138] When the support structure establishes and maintains this
relationship, the emission of ablating energy by the electrode
E.sub.CON along its length will create a lesion that spans across
the interior of the structure 60 or 62, between the diagonal and
facing electrode regions, due to additive heating effects. A large
and deep lesion pattern like the pattern 208 shown in FIG. 35
results, which occupies essentially all of the interior region
enclosed by the structure 60 or 62. For uniformity of lesion
generation, R.sub.D should preferably not exceed about 2.5 times
E.sub.D. Most preferably, R.sub.D is less than about 1.5 times
E.sub.D.
[0139] Conversely, as described earlier, with energy emitting
segments of this size, if the curvilinear path that support element
takes creates a radius of curvature R.sub.D that is greater than
about 4 times the smallest the diameters segments, the simultaneous
emission of energy by the segments forms an elongated lesion
pattern in the tissue area that follows the curved periphery
contacted by the support element, but does not span across the
contacted tissue area (like the lesion patterns 204 and 206 shown
in FIGS. 34A and 34B). The curvilinear lesion pattern is
continuous, as shown in FIG. 34A, if the spacing between the energy
emitting segments along the support body is sufficient close to
create an additive heating effect between the segments, as would be
the case for a continuous electrode or closely spaced large
segmented electrodes. Otherwise, the curvilinear lesion pattern is
segmented or interrupted along its length, as in FIG. 34B.
[0140] When the length of each energy applying region or zone is
less than or equal to about 5 times the diameter of the respective
region or zone (as would be the case of an array of smaller
segmented electrodes E.sub.SEG, like elements 10(1) and 10(3) and
as shown in FIG. 16B), the support structure should be bent back
upon itself so that the longest distance between facing electrode
pairs diagonally or diametrically spaced to provide an additive
heat effect (designated S.sub.D in FIG. 16B) does not exceed about
7 times the diameter of the smallest electrode segment (also
designated E.sub.D in FIG. 16B). In isoradial circular or hook
shaped configurations, the longest distance S.sub.D will occur
between diametrically facing electrode segments (as FIG. 16B
shows). When facing electrode segments, subject to the above
constraints, emit ablating energy simultaneously, a lesion
uniformly spanning the space between them will result due to
additive heating effects. A large deep lesion uniformly occupying
the region enclosed by the structure will be formed, as FIG. 35
shows.
[0141] For uniformity of lesion generation, S.sub.D should be also
preferably no greater than about 5 times, and most preferably no
greater than 3 times, E.sub.D. Conversely, if S.sub.D exceeds about
8 times E.sub.D, a long and thin lesion pattern results, which
follows the periphery of the structure, but does not uniformly span
across the interior of the structure 60 between diagonal or facing
electrode regions. The curvilinear lesion pattern is continuous, as
shown in FIG. 34A, if the spacing between the energy applying
segments along the support body is sufficient close to create an
additive heating effect between the segments, as would be the case
for a continuous electrode or closely spaced large segmented
electrodes. Otherwise, the curvilinear lesion pattern is segmented
or interrupted along its length, as in FIG. 34B.
[0142] Preferably, to further assure uniformity of lesion
generation when segmented electrodes are used, the S.sub.D of the
support structure 62 should not exceed about 4 times the length of
the longest facing segment (designated E.sub.L in FIG. 16B). Most
preferably, in a segmented electrode structure for creating large
deep lesions, S.sub.D should be less than about 3 times E.sub.L.
This criterion holds true when the length is not substantially
larger than the diameter. When the length is more than about 5-fold
larger than the diameter, the ablating element is similar to a
continuous electrode and the determining criterion for the lesion
structure is the diameter of the ablation structure.
[0143] A large lesion can be created by placing in parallel facing
relationship 6 mm apart, two energy applying segments that are each
8F in diameter and 3 mm in length, and applying RF energy
simultaneously to both segments. When the application of energy by
both segments is controlled to maintain temperatures at the
segments of 80.degree. C. for two minutes, the lesion width is
about 12 mm, the lesion length is about 4 mm, and the lesion depth
is about 7 mm.
[0144] Structures like those shown in FIGS. 16A and B that meet the
above criteria can be variously constructed, depending upon the
particular ablation objectives desired. They can be in the shape of
a doubled back, open circular structure like a hook (as structure
60 generally represents), or a closed or concentric spiral
structure (as structure 62 generally represents).
[0145] As a further example, a preshaped circular structure 64 like
FIGS. 17A and 18A show can be used for creating lesion patterns for
treating atrial fibrillation. The structure 64 can extend axially
from the distal end of the catheter body 12, as FIG. 17A shows.
Alternatively, the structure 64 can extend generally perpendicular
to the distal end of the catheter body, as FIG. 18A shows. The
structure 64 can either carry rigid or flexible electrode segments
66 (as FIGS. 17A and 18A show), or, alternatively, the structure 64
can carry a continuous flexible electrode along its length.
[0146] As another example, a preshaped spiral structure 68 like
FIGS. 17B and 18B show can be used to form large lesion patterns
for treating ventricular tachycardia. The structure 68 can extend
axially from the distal end of the catheter body 12, as FIG. 17B
shows. Alternatively, the structure 68 can extend generally
perpendicular to the distal end of the catheter body, as FIG. 18B
shows. The structure 68 can either carry flexible electrode
segments 70 (as FIGS. 17B and 18B show), or, alternatively, the
structure 64 can carry a continuous flexible electrode along its
length. The longest distance between the facing electrodes
throughout the spiral determines whether the lesion will span the
regions between electrodes when they are simultaneously supplied
with energy, following the criterion established above. If the
above criterion is met, then the resulting lesion will be large and
deep.
[0147] Further details of the spiral structure 68 are described in
copending patent application Ser. No. 08/138,452, filed Oct. 14,
1993, and entitled "Systems and Methods for Locating and Ablating
Accessory Pathways in the Heart," which is incorporated herein by
reference.
[0148] As yet another example, a preshaped hoop structure 72 like
FIGS. 19A/B/C show can be used to create lesion patterns useful in
treating atrial fibrillation. The hoop structure 72 extends
generally perpendicular from the distal end of the catheter body
12. As shown in FIG. 19A, the hoop structure 72 can carry a
continuous flexible electrode 74. Alternatively, the structure 72
can carry segmented flexible electrodes 76, as FIG. 19B shows.
Still alternatively, the structure 72 can carry rigid electrode
segments 78.
[0149] 5. Temperature Control at Multiple Energy Emitting
Regions
[0150] In the illustrated and preferred embodiments, each flexible
ablating element 10(1) to 10(5) carries at least one and,
preferably, at least two, temperature sensing element 80. The
multiple temperature sensing elements 80 measure temperatures along
the length of the element 10.
[0151] (i) Temperature Sensing with Rigid Electrode Elements
[0152] In the segmented element 10(1) (see FIGS. 3 and 4), each
electrode segment 30 preferably carries at least one temperature
sensing element 80. In this configuration, the sensing elements 80
are preferably located in an aligned relationship along one side of
each segmented electrode 30, as FIGS. 3 and 4 show.
[0153] The body 32 preferably carries a fluoroscopic marker (like
the stripe 82 shown in FIGS. 3 and 4) for orientation purposes. The
stripe 82 can be made of a material, like tungsten or barium
sulfate, which is extruded into the tubing 12. The extruded stripe
can be fully enclosed by the tubing or it can be extruded on the
outer diameter of the tubing making it visible to the eye. FIG. 5
shows the marker in the wall of the tubing 12. An alternative
embodiment can be a fluoro-opaque wire like platinum or gold which
can be extruded into the tubing wall. Yet another embodiment is to
affix a marker in the inner diameter of the tubing during
manufacturing.
[0154] The sensing elements 80 can be on the same side as the
fluoroscopic marker 82 (as FIGS. 3 and 4 show), or on the opposite
side, as long as the physician is aware of the relative position of
them. Aided by the marker 82, the physician orients the element
10(1) so that the temperature sensing elements 80 contact the
targeted tissue.
[0155] Alternatively, or in combination with the fluoroscopic
marker 82, the sensing elements 80 can be consistently located on
the inside or outside surface of element 10(1) when flexed in a
given direction, up or down. For example, as FIG. 3 shows, when the
element 10(1) is flexed to the down, the sensing elements 80 are
exposed on the inside surface of the element 10(1). As FIG. 4
shows, when the element 10(1) flexed to the upward, the sensing
elements 80 are exposed on the outside surface of the element 10
(1).
[0156] Each electrode segment 30 can carry more than a single
temperature sensing element 80. As FIGS. 20 to 22 show, each
electrode segment 30 can carry one, two, three, or more
circumferentially spaced apart temperature sensing elements 80. The
presence of multiple temperature sensing elements 80 on a single
electrode segment 30 gives the physician greater latitude in
positioning the ablating element 10(1), while still providing
temperature monitoring.
[0157] As FIG. 20 shows, a mask coating 56, as above described, can
also be applied to the side of the single sensor-segmented
electrode 30 opposite to the temperature sensing element 80, which,
in use, is exposed to the blood pool. As FIG. 21 shows, the mask
coating 56 lies between the two sensors 80 on the bi-directional
segmented electrode 30. The mask coating 56 minimizes the
convective cooling effects of the blood pool upon the regions of
the electrode segment 80 that are exposed to it. The temperature
condition sensed by the element 80 facing tissue is thereby more
accurate. When more than two temperature sensors 80 are used on a
given electrode segment 30, masking becomes less advisable, as it
reduces the effective surface of the electrode segment 30 available
for tissue contact and ablation.
[0158] The temperature sensing elements 80 can comprise thermistors
or thermocouples. When using thermocouples as the sensing elements
80, a reference or cold junction thermocouple must be employed,
which is exposed to a known temperature condition. The reference
thermocouple can be placed within the temperature processing
element itself. Alternatively, the reference thermocouple can be
placed within the handle 18 of the catheter probe 14.
[0159] Further details regarding the use of thermocouples can be
found in a publication available from omega, entitled Temperature,
pages T-7 to T-18. Furthermore, details of the use of multiple
thermocouples as temperature sensing elements 80 in tissue ablation
can be found in copending patent application Ser. No. ______, filed
on the same date as this application, entitled "Systems and Methods
for Controlling Tissue Ablation Using Multiple Temperature Sensing
Elements."
[0160] The sensing element or elements 80 can be attached on or
near the segmented electrodes 30 in various way.
[0161] For example, as FIG. 23 shows for the element 10(1), each
sensing element 80 is sandwiched between the exterior of the
flexible body 32 and the underside of the associated rigid
electrode segment 30. In the illustrated embodiment, the sensing
elements 80 comprise thermistors. The body 32 is flexible enough to
fit the sensing element 80 beneath the electrode segment 30. The
plastic memory of the body 32 maintains sufficient pressure against
the temperature sensing element 80 to establish good thermal
conductive contact between it and the electrode segment 30.
[0162] In an alternative embodiment (as FIG. 24 shows), the
temperature sensing element 80 is located between adjacent
electrode segments 30. In this arrangement, each sensing element 80
is threaded through the flexible body 32 between adjacent electrode
segments 30. In the illustrated embodiment, the temperature sensing
elements 80 comprise thermocouples. When the sensing element 80
comprises a thermocouple, an epoxy material 46, such as Master Bond
Polymer System EP32HT (Master Bond Inc., Hackensack, N.J.),
encapsulates the thermocouple junction 84, securing it to the
flexible body 32. Alternatively, the thermocouple junction 84 can
be coated in a thin layer of polytetrafluoroethylene (PTFE)
material. When used in thicknesses of less than about 0.002 inch,
these materials have the sufficient insulating properties to
electrically insulate the thermocouple junction 84 from the
associated electrode segment 30, while providing sufficient
thermally conducting properties to establish thermal conductive
contact with electrode segment 30. The use of such materials
typically will not be necessary when thermistors are used, because
conventional thermistors are already encapsulated in an
electrically insulating and thermally conducting material.
[0163] In another alternative embodiment (as FIGS. 25 and 26 show),
the temperature sensing element 80 physically projects through an
opening 86 in each electrode segment 30. As in the embodiment shown
in FIG. 24, the sensing elements 80 comprise thermocouples, and a
thermally conducting and electrically insulating epoxy material
encapsulates the thermocouple junction 84, securing it within the
opening 86.
[0164] It should be appreciated that some sensing elements 80 can
be carried by the electrode segments 30, while other sensing
elements 80 can be carried between the element segments 30. Many
combinations of sensing element locations are possible, depending
upon particular requirements of the ablating procedure.
[0165] In the element 10(2) (see FIG. 27), each electrode segment
34 and 36 carries at least one temperature sensing element 80. In
the illustrated embodiment, the sensing element 80 comprises a
thermistor.
[0166] The tip electrode segment 34 carries a temperature sensing
element 80 within a cavity 88 drilled along its axis. The body
electrode segment 36 also carries at least one temperature sensing
element 80, which is sandwiched beneath the electrode segment 36
and the flexible body 38, in the manner previously described and
shown in FIG. 23. The sensing element 80 in the electrode segment
36 can be alternatively secured in the manners previously described
and shown in FIGS. 24 and 25. Alternatively, as earlier described,
the side of the electrode segment 36 opposite to the single sensing
temperature element 80 can carrying the mask coating 56.
[0167] As shown in FIG. 28, either or both electrodes 34 and 36 of
element 10(2) can carry more than one temperature sensing element
80. In this arrangement, the tip electrode 34 carries additional
temperature sensing elements 80 in side cavities 90 that extend at
angles radially from the axis of the electrode 34. The body
electrode segment 36 carries additional sensing elements 80 in the
manner shown in FIGS. 21 and 22.
[0168] As the diameter of the electrodes 34 and 36 increases, the
use of multiple temperature sensing elements 80 becomes more
preferred. The multiple sensing elements 80 are circumferentially
spaced to assure that at least one element 80 is in thermal
conductive contact with the same tissue area as the associated
electrode 34 or 36.
[0169] (ii) Temperature Sensing with Flexible Electrode
Elements
[0170] In the flexible electrode elements 10(3) and 10(4) (earlier
shown in FIGS. 6 and 10), the multiple temperature sensing elements
80 are preferably located at or near the electrical connection
points between the wires 58 and the coil electrode segments 44 or
continuous coil electrode 46, as FIGS. 29 and 30 best show. This
location for the temperature sensing elements 80 is preferred
because higher temperatures are typically encountered at these
connection points along the coil electrode 44 or 46.
[0171] As FIG. 29 shows, the sensing elements 80 can be secured to
the inside surface of the coil electrode 44 or 46. Alternatively,
the sensing elements 80 can be sandwiched between the inside
surface of the electrode 44 or 46 and an underlying flexible body,
as FIGS. 15A/B show. In FIGS. 15A/B and 29, the sensing elements 80
comprise thermistors.
[0172] Alternatively, as FIGS. 30 and 31 show, the sensing elements
80 can be threaded up through the windings in the coil electrode 44
or 46 to lay upon its exterior surface. In the illustrated
embodiment, the sensing elements 80 comprise thermocouples, and the
thermocouple junction 84 is encapsulated in on an epoxy or PTFE
coating, as previously described.
[0173] When the elongated electrode 46 includes a sliding sheath 50
see FIGS. 12A/B), the movable sheath 50 carries, in addition to the
temperature sensing elements 80 spaced along the length of the coil
electrode 56, another temperature sensing element 80 at its distal
end.
[0174] In the case of flexible electrode element 10(5) (earlier
shown in FIG. 11), the sensing elements 80 are sandwiched between
the wrapped ribbon 52 and the underlying flexible body 54, as FIG.
32 shows. In the illustrated embodiment, the sensing elements 80
comprise thermocouples having junctions 84 encapsulated in an
electrically insulating and thermally conducting coating.
[0175] The various shaped electrode structures 64, 68, and 72 (see
FIGS. 17A/B; 18A/B; and 19A/B/C, respectively), can also carry
multiple temperature sensing elements 80 secured at spaced
intervals along the shaped structure, as these Figures show.
[0176] An external temperature processing element (not shown)
receives and analyses the signals from the multiple temperature
sensing elements 80 in prescribed ways to govern the application of
ablating energy to the flexible ablating element 10.
[0177] The ablating energy is applied to maintain generally uniform
temperature conditions along the length of the element.
[0178] When the element 10 carries segmented electrode structures,
each having more than one sensing element 80, the controller
selects the sensing element 80 having the most intimate contact
with tissue by selecting among the sensed temperatures the highest
sensed temperature. The temperature sensing element 80 providing
the highest sensed temperature for a given electrode segment 30 is
the one in most intimate contact with heart tissue. The lower
sensed temperatures of the other sensing elements 80 on the given
electrode segment 30 indicate that the other sensing elements 80
are not in such intimate contact, and are instead exposed to
convective cooling in the blood pool.
[0179] Further details of the use of temperature sensing in tissue
ablation can be found in copending patent application Ser. No.
08/037,740, filed Mar. 3, 1993, and entitled "Electrode and
Associated Systems Using Thermally Insulated Temperature Sensing
Elements." Also, further details of the use of multiple temperature
sensing elements in tissue ablation can be found in copending
patent application Ser. No. ______, filed on the same date as this
application, entitled "Systems and Methods for Controlling Tissue
Ablation Using Multiple Temperature Sensing Elements."
[0180] Various features of the invention are set forth in the
following claims.
* * * * *