U.S. patent application number 14/764190 was filed with the patent office on 2016-01-14 for ablation catheter with insulation.
The applicant listed for this patent is RENAL DYNAMICS LTD.. Invention is credited to David PRUTCHI.
Application Number | 20160008059 14/764190 |
Document ID | / |
Family ID | 50190505 |
Filed Date | 2016-01-14 |
United States Patent
Application |
20160008059 |
Kind Code |
A1 |
PRUTCHI; David |
January 14, 2016 |
ABLATION CATHETER WITH INSULATION
Abstract
An ablation device and/or method of ablation may include placing
one or more ablation electrodes in contact with a target tissue in
a lumen. An electrical insulator may be positioned between the
electrode and a lumen fluid and an electrical signal (for example a
radio frequency signal) may be conveyed between the electrodes to
heat and/or ablate the target tissue. Ablation may be bipolar
and/or an in lumen disperse electrode may be supplied for unipolar
ablation. Ablation progress may be sensed and ablation may be
adjusted to produce a desired level and/or geometry of
ablation.
Inventors: |
PRUTCHI; David; (Voorhees,
NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RENAL DYNAMICS LTD. |
Road Town, Tortola |
|
VG |
|
|
Family ID: |
50190505 |
Appl. No.: |
14/764190 |
Filed: |
January 30, 2014 |
PCT Filed: |
January 30, 2014 |
PCT NO: |
PCT/IB2014/058677 |
371 Date: |
July 29, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61759066 |
Jan 31, 2013 |
|
|
|
Current U.S.
Class: |
606/41 |
Current CPC
Class: |
A61B 2018/00267
20130101; A61B 2018/124 20130101; A61B 2018/00434 20130101; A61B
2018/00083 20130101; A61B 5/0215 20130101; A61B 2018/1253 20130101;
A61B 2018/00821 20130101; A61B 2018/00011 20130101; A61B 2018/00875
20130101; A61B 2018/00654 20130101; A61B 2018/00839 20130101; A61B
2018/00285 20130101; A61B 2018/162 20130101; A61B 5/02416 20130101;
A61B 2018/00214 20130101; A61B 18/1492 20130101; A61B 2018/126
20130101; A61B 2090/065 20160201; A61B 2018/00404 20130101; A61B
2018/00511 20130101; A61B 2018/00702 20130101; A61B 2018/00827
20130101; A61B 2018/00101 20130101; A61B 2018/00577 20130101 |
International
Class: |
A61B 18/14 20060101
A61B018/14 |
Claims
1. (canceled)
2. The ablation catheter of claim 39 wherein, said insulator is a
radially expanding tubular insulator sized and shaped to fit in a
lumen of a blood vessel in an expanded configuration.
3. The ablation catheter of claim 2, wherein an inner passageway of
said radially expanding insulator expands toward walls of said
lumen by plastic deformation of said radially expanding
insulator.
4. (canceled)
5. The ablation catheter of claim 39, wherein said insulator is
configured to contact an area of an inner surface of said walls of
the lumen surrounding at least one of said at least one ablation
electrode.
6. (canceled)
7. The ablation catheter of any of claim 39, wherein said at least
one ablation electrode includes at least four pairs of ablation
electrodes.
8. The ablation catheter of claim 7 further comprising: a control
unit selectively conveying an ablation signal between electrodes of
each of said at least four pairs of ablation electrodes.
9. The ablation catheter of claim 7, wherein said at least four
pairs of ablation electrodes are helically distributed around said
insulator.
10-14. (canceled)
15. The ablation catheter according to claim 39, wherein said area
of said tissue surrounding said electrode includes a margin of at
least 3 mm surrounding said at least one electrode.
16-27. (canceled)
28. An ablation catheter comprising: a plurality of ablation
electrodes configured to be in contact with a target tissue in a
lumen; a dispersive electrode configured to be provided in the
lumen, the dispersive electrode having a conducting contact area at
least 20 times as large as the ablation electrode; and a control
unit conveying: a first signal between a pair of said plurality of
ablation electrodes; and a second signal between said dispersive
electrode and at least one of said plurality of ablation
electrodes.
29. The ablation catheter of claim 28, further comprising: an
insulator electrically insulating at least one of the plurality of
ablation electrodes from a fluid in said lumen.
30. (canceled)
31. The ablation catheter according to claim 28, configured to
define a passageway for a fluid to pass through the lumen.
32. The ablation catheter according to claim 29, wherein a first
side of the insulator is in contact with the target tissue in a
vicinity of said ablation electrode and a second side of the
insulator is in contact with fluid when the fluid is in a
passageway and heat transfer to said fluid across said insulator
cools said target tissue in said vicinity of said ablation
electrode.
33. The ablation catheter according to claim 28, wherein the
dispersive electrode is in contact with a fluid inside said
lumen.
34. A method of ablation therapy inside a lumen of a patient
comprising: positioning a plurality of ablation electrodes in
contact with a target tissue in said lumen; conveying through said
target tissue a first electrical signal between a pair of said
ablation electrodes; conveying through said target tissue a second
electrical signal between at least one of said plurality of
ablation electrodes and a dispersive electrode having an active
surface area at least twenty times an active surface area of said
ablation electrode; and placing at least a portion of said
dispersive electrode in said lumen.
35. The method of claim 34, wherein the plurality of ablation
electrodes form part of a catheter comprising an expandable
insulator insulating electrically at least one of said ablation
electrodes from fluid in said lumen.
36. The method of claim 34, further comprising: contacting said
dispersive electrode with fluid in said lumen.
37. (canceled)
38. The method of claim 34, wherein said placing is by means of a
catheter.
39. An ablation catheter comprising: at least one ablation
electrode in contact with a tissue on an inner wall of a lumen; an
insulator including: a tissue side in contact with an area of said
tissue surrounding said electrode; and a lumen side in contact with
fluid in the lumen, the insulator electrically insulating the at
least one ablation electrode from a fluid in the lumen and cooling
said at least one ablation electrode by conducting heat to said
fluid in the lumen; and a passageway allowing fluid flow through
the lumen.
Description
RELATED APPLICATION
[0001] This application claims the benefit of priority under 35 USC
.sctn.119(e) of U.S. Provisional Patent Application No. 61/759,066
filed 31 Jan. 2013, the contents of which are incorporated herein
by reference in their entirety.
FIELD AND BACKGROUND OF THE INVENTION
[0002] The present invention, in some embodiments thereof, relates
to an ablation catheter and, more particularly, but not
exclusively, to a radio frequency ablation catheter that may
optionally be suited for renal artery denervation.
SUMMARY OF THE INVENTION
[0003] According to an aspect of some embodiments of the present
invention there is provided an ablation catheter fitting into a
lumen of a patient comprising: a radially expanding tubular
insulation member sized and shaped to fit in a lumen of a blood
vessel in an expanded configuration; an expansion mechanism for
radially expanding an inner passageway of the radially expanding
tubular insulation member toward walls of the blood vessel, from a
retracted configuration to the expanded configuration; and a
plurality of ablation electrodes mounted along an outer surface of
the radially expanding insulation tubular member. In the expanded
configuration a hydraulic radius of the passageway is at least 50%
of a hydraulic radius of the lumen.
[0004] According to some embodiments of the invention, the
insulator fits into the lumen which is a blood vessel.
[0005] According to some embodiments of the invention, the
expansion is by plastic deformation of the insulator.
[0006] According to some embodiments of the invention, at least one
of the plurality of ablation electrodes is mounted with an active
surface tangent to the outer surface of the expanding tubular
insulator the active surface facing the inner surface of the
lumen.
[0007] According to some embodiments of the invention, the
insulator contacts an area on the inner surface of the lumen. The
contact area may surround at least one of the plurality of ablation
electrodes.
[0008] According to some embodiments of the invention, the
insulator separates between at least one of the plurality of
ablation electrodes and fluid in the passageway.
[0009] According to some embodiments of the invention, the
plurality ablation electrodes include at least four pairs of
ablation electrodes.
[0010] According to some embodiments the invention further includes
a control unit selectively conveying an ablation signal between
electrodes of each of the at least four pairs of ablation
electrodes.
[0011] According to some embodiments the invention further includes
a dispersive electrode, for conveying a signal to one or more of
the ablation electrodes.
[0012] According to some embodiments the invention further includes
the expansion mechanism includes a plurality of supports.
[0013] According to some embodiments the invention further includes
the insulator transfers heat from the plurality of ablation
electrodes to a heat sink.
[0014] According to some embodiments the invention further includes
the heat sink includes the fluid flowing through the lumen.
[0015] According to some embodiments the invention further includes
the heat sink includes the fluid flowing through the expandable
passageway.
[0016] According to some embodiments the invention further includes
an area of the inner surface of the lumen in contact with the
insulator surrounding at least one ablation electrode of the
plurality of ablation electrodes is at least 50 mm2.
[0017] According to some embodiments the invention further includes
an area of target tissue in contact with the insulator surrounding
at least one ablation electrode of the plurality of ablation
electrodes includes a margin of at least 3 mm surrounding the at
least one electrode.
[0018] According to some embodiments the invention further includes
in the expanded configuration a cross sectional area of the
passageway is at least 50% of a cross sectional area of the
lumen.
[0019] According to some embodiments the invention further includes
in the expanded configuration a hydraulic radius of the passageway
is at least 70% of a hydraulic radius of the lumen.
[0020] According to an aspect of some embodiments of the present
invention there is provided a method of ablation therapy in a lumen
in a patient comprising: positioning one or more electrodes in
contact with a wall of the lumen; and expanding an insulator
thereby contacting by an outer surface of a wall of the insulator
an inner surface of a wall of the lumen; an area of the contacting
surrounding at least one of the one or more electrodes defining by
an inner surface of the insulator a passageway along the lumen for
flow of a fluid through the lumen, and electrically insulating
between the fluid and the at least one of the electrodes and
heating the tissue by means of an electrical signal from the at
least one electrode.
[0021] According to some embodiments the invention further includes
cooling at least a portion of at least one of the tissue and the
electrode simultaneous to the heating.
[0022] According to some embodiments of the invention, the cooling
includes transferring heat between the portion and a heat sink.
[0023] According to some embodiments of the invention, the
transferring includes conducting heat across the wall of the
insulator.
[0024] According to some embodiments of the invention, the heat
sink includes the fluid in the lumen.
[0025] According to some embodiments of the invention, the heat
sink includes fluid in the passageway.
[0026] According to some embodiments of the invention, the
passageway passes along a surface of the insulator opposite an
ablation zone.
[0027] According to some embodiments of the invention, the
contacting includes contacting an area of the inner surface of the
wall of the lumen surrounding the electrode.
[0028] According to some embodiments of the invention, the area of
the inner surface of the wall of the lumen surrounding the
electrode includes an area of at least 50 mm2.
[0029] According to some embodiments of the invention, the
contacting includes a margin around the electrode of at least 3 mm
in every direction.
[0030] According to an aspect of some embodiments of the present
invention there is provided an ablation catheter comprising: a
plurality of ablation electrodes in contact with a target tissue in
a lumen; a dispersive electrode provided in the lumen, the
dispersive electrode having a conducting contact area at least 20
times a large as the ablation electrode, and a control unit
conveying a first signal between a pair of the plurality of
ablation electrodes and a second signal between the dispersive
electrode and at least one of the plurality of ablation
electrodes.
[0031] According to some embodiments the invention further includes
an insulator electrically insulating at least one of the ablation
electrodes from a fluid in the lumen.
[0032] According to some embodiments the invention the dispersive
electrode is not in contact with the target tissue.
[0033] According to some embodiments the invention further includes
a passageway for a fluid to pass through the lumen.
[0034] According to some embodiments the invention a first side of
the insulator is in contact with the target tissue in a vicinity of
the ablation electrode and a second side of the insulator is in
contact with the fluid in the passageway and heat transfer to the
fluid across the insulator cools the target tissue in the vicinity
of the ablation electrode.
[0035] According to some embodiments the invention the dispersive
electrode is in contact with a fluid inside the lumen.
[0036] According to an aspect of some embodiments of the present
invention there is provided a method of ablation therapy inside a
lumen of a patient comprising: positioning a plurality of ablation
electrodes in contact with a target tissue in the lumen; conveying
through the target tissue a first electrical signal between a pair
of the ablation electrodes; and conveying through the target tissue
a second electrical signal between at least one of the plurality of
ablation electrodes and the a dispersive electrode having an active
surface area at least twenty times an active surface area of the
ablation electrode.
[0037] According to some embodiments the invention further includes
insulating electrically at least one of the ablation electrodes
from a fluid in the lumen.
[0038] According to some embodiments the invention further includes
placing the dispersive electrode into contact with a fluid in the
lumen.
[0039] According to some embodiments the invention further includes
placing at least part of the dispersive electrode into the
lumen.
[0040] According to some embodiments the invention the placing is
by means of a catheter.
[0041] According to an aspect of some embodiments of the present
invention there is provided at least one ablation electrode in
contact with a tissue on an inner wall of a lumen; an insulator
including a tissue side in contact with an area of the tissue
surrounding the electrode and a lumen side in contact with fluid in
the lumen, the insulator electrically insulating the at least one
ablation electrode from a fluid in the lumen; and a passageway
allowing fluid flow through the lumen.
[0042] Unless otherwise defined, all technical and/or scientific
terms used herein have the same meaning as commonly understood by
one of ordinary skill in the art to which the invention pertains.
Although methods and materials similar or equivalent to those
described herein can be used in the practice or testing of
embodiments of the invention, exemplary methods and/or materials
are described below. In case of conflict, the patent specification,
including definitions, will control. In addition, the materials,
methods, and examples are illustrative only and are not intended to
be necessarily limiting.
[0043] Implementation of the method and/or system of embodiments of
the invention can involve performing or completing selected tasks
manually, automatically, or a combination thereof. Moreover,
according to actual instrumentation and equipment of embodiments of
the method and/or system of the invention, several selected tasks
could be implemented by hardware, by software or by firmware or by
a combination thereof using an operating system.
[0044] For example, hardware for performing selected tasks
according to embodiments of the invention could be implemented as a
chip or a circuit. As software, selected tasks according to
embodiments of the invention could be implemented as a plurality of
software instructions being executed by a computer using any
suitable operating system. In an exemplary embodiment of the
invention, one or more tasks according to exemplary embodiments of
method and/or system as described herein are performed by a data
processor, such as a computing platform for executing a plurality
of instructions. Optionally, the data processor includes a volatile
memory for storing instructions and/or data and/or a non-volatile
storage, for example, a magnetic hard-disk and/or removable media,
for storing instructions and/or data. Optionally, a network
connection is provided as well. A display and/or a user input
device such as a keyboard or mouse are optionally provided as
well.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] Some embodiments of the invention are herein described, by
way of example only, with reference to the accompanying drawings.
With specific reference now to the drawings in detail, it is
stressed that the particulars shown are by way of example and for
purposes of illustrative discussion of embodiments of the
invention. In this regard, the description taken with the drawings
makes apparent to those skilled in the art how embodiments of the
invention may be practiced.
[0046] In the drawings:
[0047] FIG. 1 is a flowchart illustrating a method of ablation in
accordance with some embodiments of the present invention;
[0048] FIG. 2 is a flowchart illustrating a method of bipolar
ablation in accordance with some embodiments of the present
invention;
[0049] FIG. 3 is a flowchart illustrating a method of unipolar
ablation in accordance with some embodiments of the present
invention;
[0050] FIGS. 4A-D are illustration of an ablation device in
accordance with some embodiments of the present invention;
[0051] FIG. 5 illustrates a windsock type insulator in accordance
with some embodiments of the present invention;
[0052] FIGS. 6A-B illustrate a laser-cut tube type support
structure in accordance with some embodiments of the present
invention;
[0053] FIG. 7 is an illustration of a support structure formed of
spiral wire in accordance with some embodiments of the present
invention;
[0054] FIG. 8 is a an illustration of an insulating frame in
accordance with some embodiments of the present invention;
[0055] FIGS. 9A-B illustrate a support structure and insulator in
accordance with some embodiments of the present invention;
[0056] FIG. 10 illustrates a laser-cut tube support structure and
insulator in accordance with some embodiments of the present
invention;
[0057] FIGS. 11A-B illustrate a laminar support structure in
accordance with some embodiments of the present invention;
[0058] FIGS. 12A-B illustrate a support structure including braided
wires in accordance with some embodiments of the present
invention;
[0059] FIGS. 13A-C illustrate a support structure including a break
out malecot in accordance with some embodiments of the present
invention;
[0060] FIGS. 14A-C illustrate a support a distal-extending malecot
in accordance with some embodiments of the present invention;
[0061] FIGS. 15A-B illustrate a hydraulic support structure in
accordance with some embodiments of the present invention;
[0062] FIGS. 16A-C illustrate a printed circuit board support
structure and insulator in accordance with some embodiments of the
present invention;
[0063] FIG. 17 illustrates control unit in accordance with some
embodiments of the present invention;
[0064] FIG. 18 is a flow chart illustration of a method of ablation
and/or measuring evoked response in accordance with some
embodiments of the present invention;
[0065] FIG. 19 illustrates simulated measurements of an evoked
response in accordance with some embodiments of the present
invention;
[0066] FIG. 20 illustrates a ablation device included sensors for
evoked response in accordance with some embodiments of the present
invention; and
[0067] FIGS. 21A-B illustrate an alternate ablation device included
sensors for evoked response in accordance with some embodiments of
the present invention;
DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION
[0068] The present invention, in some embodiments thereof, relates
to an ablation catheter and, more particularly, but not
exclusively, to a radio frequency (`RF`) ablation catheter that may
optionally be used for renal artery denervation.
[0069] In some embodiments, the present invention relates to
methods and/or devices (e.g., control unit) for ablation using
ablation catheter, e.g., RF ablation catheter.
Overview
[0070] 1 Ablation Device with Electrical Insulation and Cooling
[0071] An aspect of some embodiments of the current invention
relates to a method of catheter ablation wherein an ablation
electrode is optionally introduced into a lumen and/or positioned
in contact with a tissue to be ablated. For example the tissue may
be part of the inner surface of the lumen. The ablation catheter
may be provided with an insulator, for example a polyurethane
membrane. In some embodiments the insulator may be tubular. For the
sake of the current application a tubular insulator may have
insulating wall surrounding one or more passageways. The wall and
the passageways may have a non-circular cross section. The cross
section may change along the length (for example to fit a changing
cross section of lumen in a patient). A tubular insulator may be
elongated (the axis may be greater than the width) or short (the
axis may shorter than the width). An outer surface of the insulator
may be optionally pressed against tissue surrounding the location
of the ablation electrode. The membrane may for example
electrically insulate the ablation electrode and/or an ablation
zone from a fluid in the lumen. The ablation zone may be heated
and/or ablated by conveying an electrical signal (for example an RF
signal) between the ablation electrode and a second electrode. A
portion of the ablation zone may optionally be cooled. For example
the insulator may transfer heat away from the electrode and/or the
lesion formed by the ablation and/or the tissue in the vicinity of
the electrode and/or tissue in the vicinity of the lesion.
Optionally, the insulator may conduct the heat to a heat sink. For
example a heat sink may include a fluid. The fluid may be in
contact with the inner surface of the insulator that is opposite
the ablation zone. For example the heat sink may include lumen
fluid (for example blood) flowing across the inner surface of the
insulator opposite the ablation zone and/or an artificial cooling
fluid. The local thickness and/or heat conductivity of the
insulator may optionally be adjusted to preferentially cool one
portion of the ablation zone more than another portion.
[0072] In some embodiments, the insulator may optionally be pressed
against the inner wall of the lumen and/or expanded by supports
that open like a tent and/or an umbrella and/or an expandable
basket and/or a malecot. The support structure may optionally
include for example ribs and/or stretchers like an umbrella and/or
other support (e.g., brace, buttress, stanchion, cantilever, strut,
frame and/or spines). The supports may include, for example,
inflatable (hydraulic and/or pneumatic) supports, supports made of
nitinol, a folding basket, a malecot, a stent, a folding stent, a
laminated structure, a balloon and/or an expandable woven
structure. The insulator may allow fluid flow through the lumen.
For example, the insulator may be open at a distal end, allowing
blood to continue to flow through the delivery vessel. For example,
the insulator may include a passageway to allow flow past the
insulator. For example the insulator may have an open ended tubular
geometry. Fluid may optionally flow along the lumen through a
passageway along the axis of a tubular insulator while the
insulator walls insulate the inner surface of the lumen from the
fluid. Optionally, the insulator may be expanded to fill the lumen.
Optionally, as the insulator expands, the passageway may also
expand. For example the passageway may have a cross section open to
flow that has an area of least 50% of the area of the cross section
of the lumen that is open to flow. Alternatively or additionally
the hydraulic radius of the passageway (defined for example as the
four times cross sectional area divided by the wetted perimeter) by
may be 70% of the hydraulic radius of the lumen. In some
embodiments the cross sectional area of flow the passageway may
range between 25% and 50% of the cross sectional area of flow in
the lumen and/or the hydraulic radius of the pathway way may range
between 50% and 70% of the hydraulic radius of the lumen.
[0073] The expanding tent, basket and/or umbrella structure may for
example have a expanded width ranging for example between 4 and 8
mm and/or ranging for example between 1 and 10 mm. The length of
the basket, tent and/or umbrella structure may for example range
between 10 and 40 mm and/or between 20 and 30 mm. optionally, in
its expanded configuration the insulator may be spread against all
wall of the lumen.
[0074] For example, the insulator may include a membrane of
thickness ranging between for example 0.1 and 0.01 mm and/or may
pose impedance (against isoconductive saline solution) for example
ranging between 50 to 150 k.OMEGA. at 460 kHz (e.g., 50 to 100
k.OMEGA., 100 to 150 k.OMEGA. etc.). The membrane may be made from,
for example, Urethane and/or a polyurethane polymer. In some
embodiments, the basket may have a diameter of less than 6 French
(2 mm) when out of an intravascular delivery sheath but before
expanding. In some embodiments, the basket may contract to a
diameter of less than 6 French (2 mm) contracted but before being
reinserted into the sheath that is commonly used to introduce a
catheter to its intended delivery location within the
vasculature.
2 General
[0075] Some embodiments of the current invention may include a
multi-electrode ablation device. The device may be inserted into a
body lumen via a catheter. At times the ablation device may be
referred to as an ablation catheter or a catheter. A
multi-electrode ablation catheter may be powered by a control unit
(e.g., including an RF generator). The control unit may have a
number of channels that convey an electrical signal bipolarly (for
example from a first ablation electrode in contact with the target
tissue at a first location to a second ablation electrode in
contact with the target tissue at a second location) through a
target tissue between electrode pairs (for example, the ablation
electrodes may be mounted on the catheter's working [distal] end),
and/or unipolarly through a target tissue between an ablation
electrode (that may optionally be in contact with the target
tissue) and a dispersive (reference) electrode (e.g., a shaft
electrode in contact with lumen fluid (for example blood) and/or an
external electrode). The electrodes may be activated in accordance
with a switch configuration set by a multiplexer. Multiplexer RF
channels may be used to transmit radio frequency (RF) ablation
energy to the electrodes. The RF channels may optionally include
means to measure electrode/tissue impedance. In some embodiments,
measurements may be made with high accuracy and/or repeatability.
The RF channels may optionally be controlled by a controller (e.g.,
a microcontroller and/or single-board computer).
[0076] Optionally a catheter according to some embodiments of the
current invention may be used for renal denervation. Renal
denervation, is a minimally invasive, endovascular catheter based
procedure using radiofrequency ablation aimed at treating resistant
hypertension. Radiofrequency pulses may be applied to the renal
arteries. Ablation in some embodiments may denude nerves in the
vascular wall (adventitia layer) of nerve endings. This may causes
reduction of renal sympathetic afferent and efferent activity
and/or blood pressure can be decreased. During the procedure, a
steerable catheter with a radio frequency (RF) energy electrode tip
may deliver RF energy to a renal artery via standard femoral artery
access. A series of ablations may be delivered along each renal
artery.
[0077] As used herein, the term "controller" may include an
electric circuit that performs a logic operation on input or
inputs. For example, such a controller may include one or more
integrated circuits, microchips, microcontrollers, microprocessors,
all or part of a central processing unit (CPU), graphics processing
unit (GPU), digital signal processors (DSP), field-programmable
gate array (FPGA) or other circuit suitable for executing
instructions or performing logic operations. The instructions
executed by the controller may, for example, be pre-loaded into the
controller or may be stored in a separate memory unit such as a
RAM, a ROM, a hard disk, an optical disk, a magnetic medium, a
flash memory, other permanent, fixed, or volatile memory, or any
other mechanism capable of storing instructions for the controller.
The controller may be customized for a particular use, or can be
configured for general-purpose use and can perform different
functions by executing different software.
[0078] The controller may optionally be able to calculate the
temperature of some or all of the electrodes and/or near some or
all of the electrodes. For example, temperature measurements may be
sensed by means of the thermocouple attached to each electrode and
the output of the means is forwarded to the controller for
calculation. Interaction with the user (e.g., a physician
performing the ablation procedure) may optionally be via a
graphical user interface (GUI) presented on for example a touch
screen or another display.
[0079] In some embodiments, electrode impedance measurements may be
used to estimate contact (estimated contact) between electrode and
tissue as surrogate for thermal contact between electrode interface
and target tissue. In some embodiments, power being converted to
heat at electrode/tissue interface may be estimated (estimated
power) for example based on the estimated contact, applied power
and/or electrode temperature. Together with the time of RF
application to the tissue, the estimated contact and/or estimated
power and/or electrode temperature may optionally be used to
calculate energy transferred to target tissue and/or resulting
target tissue temperature locally at individual ablation electrode
locations. Optionally, the results may be reported in real-time.
Optionally, based for example on the calculated cumulative energy
transferred to target tissue, the duration of ablation may be
controlled to achieve quality of lesion formation and/or avoid
undesirable local over-ablation and/or overheating. Control
algorithms may deem to have completed lesion formation successfully
for example when the quality of lesion at each electrode location
reaches a predetermined range.
[0080] Some embodiments of the current invention may combine a
multi-electrode ablation device with blood exclusion. In some
embodiments, the distance from the proximal end of the insulating
basket to the distal end (toward the catheter tip) of an
in-catheter dispersive electrode may range for example between 10
to 75 mm (e.g., between 10 to 15 mm, between 10 to 25 mm, between
25 to 50 mm, between 50 to 75 mm etc.). For renal artery
denervation, the distance between the dispersive electrode and the
proximal end of the expandable structure may range preferably
between 20 to 50 mm (e.g., 20 mm, 30 mm, 40 mm, 50 mm etc.) to
ensure that the dispersive electrode is within the aorta, and away
from the desired ablation area within the renal artery.
[0081] Various embodiments of the current invention may be
configured to fit for example in a 5 French (1.33 mm diameter)
catheter with a lumen extending from the handle through the distal
tip making it possible to insert it with the aid of a standard
0.014 inch (0.36 mm) guide wire. The flexibility of the assembly
may optionally be compatible with applicable medical standards. A
catheter (for example the various embodiments described below) may
include a guidewire. For example, the guidewire may be inserted
through a lumen of the catheter. Optionally, the guidewire may help
position the catheter. The guidewire may optionally be able to
extend past an orifice at the distal end of the catheter.
3 Bipolar and Unipolar Ablation
[0082] An aspect of some embodiments of the current invention
relates to a method of catheter ablation using bipolar and/or
unipolar ablation, e.g., to achieve a desired lesion geometry. For
example, bipolar ablation between a first and a second ablation
electrode may be used to convey an electrical signal through a
target tissue to produce a lesion. Ablation may progress more
quickly at the location of the first electrode than at the location
of the second electrode. Bipolar ablation may optionally be paused
and unipolar ablation may be initiated between the second ablation
electrode and a dispersive electrode to increase progress of
ablation in the vicinity of the second electrode. A balance of
unipolar and/or bipolar ablation may be used to adjust a geometry
of a lesion. For example, bipolar ablation may be used to achieve
spreading of a lesion along a tissue surface. For example, unipolar
ablation may be used to deepen a lesion.
[0083] In some cases it may be desired to ablate tissue in a given
area to an effective level (for example effective ablation may
occur for heating to a temperature of between 60.degree. and
70.degree. C. for a time between 20 and 180 sec.). Tissue and/or
contact with electrodes may be heterogeneous. Tissue may heat
and/or ablate unevenly. Overheating and/or over-ablating tissue may
have serious consequences (for example heating to over 90.degree.
C. and/or over-ablating may cause blood coagulation and/or blood
clots and/or damage to arteries and/or internal bleeding etc.). In
some embodiments, the current invention may facilitate monitoring
and/or control of ablation within parts of a lesion. In some
embodiments, local monitoring and/or control may produce more even
ablation. For example a desired level of ablation may be reached in
multiple regions of a lesion without over ablating any region.
4 In-Lumen Dispersive Electrode
[0084] An aspect of some embodiments of the current invention
relates to an in-lumen dispersive electrode for unipolar ablation.
The dispersive electrode may be introduced into a body lumen and/or
electrical contact may be supplied by a fluid in the lumen. The
dispersive electrode may be inserted into the same lumen as an
ablation electrode. The dispersive electrode may be part of the
same catheter as an ablation electrode. Optionally, a single
catheter may include a dispersive electrode and a plurality of
ablation electrodes. The catheter and/or electrodes may be
configured to operate in unipolar and/or bipolar modes.
[0085] In some embodiments, a control unit may supply power for
ablation (for example: a radio frequency (RF) generator). For
example the control unit may be a rechargeable and/or
battery-powered. The ablation generator may operate for example
around the 460 kHz frequency and/or ranging for example between 400
and 600 kHz or other RF frequency ranges assigned to ISM
(Industrial, Scientific, and Medical) applications within the
low-frequency (LF: 30 to 300 kHz), medium-frequency (300 kHz to 3
MHz), and high-frequency (HF 3 to 30 MHz) portions of the RF
spectrum. The control unit may have a number of channels that allow
ablation to be conducted bipolarly between electrode pairs through
the target tissue. The generator may optionally be able to deliver
ablation energy to be conveyed simultaneously between one, some
and/or all bipolar ablation electrode pairs in the catheter. For
example a catheter may include four or more bipolar ablation
electrode pairs. In some embodiments, the generator may supply a
maximum power of, for example, between 3-10 W per bipolar channel.
The generator may optionally be able to ablate unipolarly between
one, some and/or all of the contact electrodes and a dispersive
electrode, e.g., catheter-borne reference in-lumen dispersive
electrode. Lesion formation may for example take between 15 to 180
seconds. Each channel may have a minimum voltage compliance of 100
V. In some embodiments, the minimum voltage compliance may permit,
for example, an average of between 2 and 10 W to be delivered per
bipolar electrode pair presenting an impedance for example ranging
between 1.0 and 1.5 k.OMEGA..
[0086] In some embodiments, an ablation electrode of the current
invention may be made for example of between 80% and 95% Platinum
and/or between 20% and 5% Iridium. The ablation electrodes may
range for example between 0.5 and 4 mm long and/or have an
electrically active area for example of between 0.1 and 1 mm.sup.2
and/or have a diameter ranging from 0.01 to 0.05 inch (0.25 to 1.27
mm). The electrically active area of the ablation electrodes may be
in contact with a target tissue. The distance between ablation
electrodes may range for example between 0.5 and 3 mm or more.
[0087] In some embodiments, a dispersive electrode may for example
have a length ranging for example between 4 to 20 mm and/or have a
diameter ranging between 2 and 5 French (between 0.67 and 1.67 mm).
The dispersive electrode may have an electrically active area
ranging for example, 20 to 50 times or more than the electrically
active area and/or surface of contact of the ablation electrodes.
For example the electrically active area of the dispersive
electrode may range between 50 to 150 mm.sup.2 (e.g., between 50 to
100 mm2, between 100 to 150 mm2, between 75 to 120 mm2 etc.).
Optionally the electrically active surface of the disperse
electrode may be in electrical contact with a fluid in a lumen of a
patient. In some embodiments, the dispersive electrode may be
coated with a material such as porous titanium nitride (TiN) or
iridium oxide (IrOx). The coating may increase microscopic surface
area of the electrode in electrical contact with lumen fluid.
5 Local Measurement of Ablation Progress
[0088] An aspect of some embodiments of the current invention
relates to a method of catheter ablation wherein ablation progress
may be measured locally at the site of one, some and/or all
ablation electrodes. For example, during a pause in the bipolar
ablation signal, impedance may be measured locally at an ablation
electrode for example by measuring impedance between the ablation
electrode and a dispersive electrode.
[0089] For example, the system may measure the complex bipolar and
unipolar electrode impedance at the ablation frequency. Optionally
when not ablating, an auxiliary signal may include an auxiliary
current not meant to cause significant physiological effect.
Electrode Impedance measurements may optionally be possible within
the 100.OMEGA. to 1 k.OMEGA. range within a minimum accuracy
ranging for example between 2 to 10%, and within the 100.OMEGA. to
2 k.OMEGA. range with a minimum accuracy ranging for example
between 5 to 20%. Minimum repeatability within the 100.OMEGA. to 2
k.OMEGA. range may range for example between 2 to 10%. Ablation
interruptions may range from 1 to 100 ms when measuring unipolar
impedance during bipolar ablation segments. Impedance measurements
may be taken at a minimum rate ranging for example between 50 to
200 samples for use by the control algorithm.
[0090] In some embodiments, temperature may be measured
individually at one, some and/or all of the contact electrodes.
Temperature measurements may use, for example, a thermocouple. The
thermocouple may optionally be formed between the main electrode's
wire and an auxiliary thermocouple wire. Temperature measurement
range may be for example between 30.degree. C. to 100.degree. C. or
more. Temperature measurement accuracy range between .+-.0.2 to
.+-.1.degree. C. or may be more accurate. Temperature measurement
repeatability may range for example between 0.1 to 0.5.degree. C.
or less. Target temperatures may range for example between 60 to
80.degree. C.
[0091] Before explaining at least one embodiment of the invention
in detail, it is to be understood that the invention is not
necessarily limited in its application to the details of
construction and the arrangement of the components and/or methods
set forth in the following description and/or illustrated in the
drawings and/or the Examples. The invention is capable of other
embodiments or of being practiced or carried out in various
ways.
Exemplary Embodiments
1 Outline of Method of Ablation
[0092] Referring now to the drawings, FIG. 1 is a flow chart
illustration of a method of therapy using unipolar and/or bipolar
ablation, in accordance with some embodiments of the invention. The
exemplary method, illustrated for example in FIG. 1, of unipolar
and bipolar ablation may be used to achieve a desired lesion
geometry, to measure the progress of ablation locally near
electrodes and/or in an area between electrodes and/or to adjust a
geometry of a lesion. The method may be used to control power and
duration of ablation at one or more electrodes, e.g., to ensure
quality of lesion formation.
[0093] In some embodiments, an ablation device may be set up 101.
In some embodiments, a catheter with the ablation device may be
inserted 102 into a patient. A dispersive electrode may optionally
be placed 104 in contact with a large area of the patient.
Optionally, the dispersive electrode may be inserted into the
patient with the catheter (e.g., the dispersive electrode may be
part of the catheter). Alternatively or additionally the dispersive
electrode may be independent of the catheter. The large contact
area, for example the contact area may range between 50 to 150
cm.sup.2 or more of the dispersive electrode may reduce tissue
damage and/or impedance in the vicinity of the dispersive
electrode.
[0094] In some embodiments, a two or more ablation electrodes may
be positioned 106 in contact with a target tissue in an area to be
ablated. The ablation electrodes may have a small contact area with
the target tissue. Current flowing from the ablation electrode may
be concentrated in the small contact area causing local ablation.
The high current flowing through a small contact area in the
vicinity of the ablation electrode may produce a high electrical
impedance in the vicinity of the ablation electrode. For example,
most of the impedance for current between the dispersive electrode
and the ablation electrode may occur in the vicinity of the
ablation electrode.
[0095] The ablation device may optionally include an insulator. The
insulator may optionally be expanded 107 and/or spread 108 across a
surface of a target tissue. Optionally, the insulator may isolate
the electrode from a fluid in a lumen (for example blood in an
artery). Optionally, the insulator may prevent leaking and/or or
shunting of ablative energy away from a target.
[0096] In some embodiments, after positions 106 the ablation
electrodes and/or expanding 107 and/or spreading 108 the insulator,
the contact of the ablation electrodes with the target tissue may
be tested 109. For example, the impedance may be measured between
the ablation electrode and the dispersive electrode and/or the
temperature may be tested at the ablation electrode while applying
current. If the contact is not good 110 (Step 110: no) (for example
the impendence is high) then the ablation electrode may be
repositioned (for example by re-inserting 102 the catheter and/or
moving and/or re-positioning 106 the ablation electrodes).
[0097] In some embodiments, once the ablation electrodes are proper
positioned and/or contact is good 110 (Step 110: yes), ablation may
proceed. For example, bipolar ablation 112 may take place between
two ablation electrodes (note as used herein bipolar ablation may
also include multipolar ablation between more than two ablation
electrodes). Optional details of bipolar ablation 112 are
described, for example, in FIG. 2. In some embodiments, unipolar
ablation 114 may take place between one or more ablation electrodes
and a dispersive reference electrode. For example, if during
bipolar ablation 112 it is observed that ablation is proceeding
faster near one of the ablation electrodes than near the other
electrode of the pair and/or that one electrode is heating up too
much and/or that ablation is taking place too near the surface
etc., bipolar ablation 112 may be interrupted (for example not
passing current and/or passing a reduced current) and/or optionally
the fast and/or overheating electrode may be allowed to rest (for
example not passing current or passing a reduced current). Unipolar
ablation 114 may optionally continue at all or some of the
electrodes. One or more rounds of bipolar ablation 112 and/or rest
and/or unipolar ablation 114 may continue (Step 115: no) until the
ablation is finished (Step 115: yes). When ablation is finished at
a given location, the process may be repeated at another location
116.
2 Bipolar Ablation
[0098] FIG. 2 is a flow chart illustration of a method of bipolar
ablation in accordance with some embodiments of the current
invention. Bipolar ablation 112 may optionally start after prior
processes 201 as illustrated for example in FIG. 1. Bipolar (or
multipolar) ablation 112 may proceed by applying a high current
220, e.g., resulting in the desired power delivered to the tissue,
for example, an average of between 2 and 10 W (e.g., 2 W, 4 W, 5 W,
10 W etc.) between one or more pairs of ablation electrodes. During
the application of current 220, the temperature at one, some or all
of the ablation electrodes and/or the current and/or the impedance
between pairs of electrodes may optionally be monitored.
Application of current may continue for example between 5-200
milliseconds (e.g., 50-200 milliseconds, 100-200 milliseconds,
150-200 milliseconds etc.) at a power ranging for example between
2.0 to 10 WATT between each pair of ablation electrodes. Current
application may be interrupted 221 for a short period, for example
between 50-200 milliseconds at which time impedance and/or
temperature may be tested 222 at the location of one or more of the
ablation electrodes and/or other locations. For example, impedance
may be tested 222 by applying a small current between the ablation
electrode and a dispersive electrode. After testing 222,
application 220 of current may optionally continue (for example as
long as bipolar ablation 112 has not been completed (step 224 "no")
and/or if there are no signs of overheating and/or over-ablation).
The interruption of current application 220 may optionally be short
enough that the target tissue does not significantly cool and/or
ablation is not adversely affected. Optionally, when bipolar
ablation 112 at a particular location is completed (step 224 yes),
for example it reaches a desired level and/or ablation and/or
temperature at a location reaches a safety limit, bipolar ablation
112 at that location may stop. Completion 224 of a lesion may, for
example may be evaluated by a "quality of lesion formula" which may
be some function of impedance, temperature, and energy delivered.
The total length of the bipolar ablation 112 at a single location
may range for example between 15-300 sec. Bipolar ablation may
continue at other locations and/or a next process 214 may
start.
3 Unipolar Ablation
[0099] FIG. 3 is a flow chart illustration of a method of unipolar
ablation in accordance with some embodiments of the current
invention. Unipolar ablation may be performed by passing current
between for example an ablation electrode (e.g., an ablation
electrode of a pair) and a dispersive electrode. Optionally, the
dispersive electrode may have a large area of contact with the
patient. Typically the majority of the impedance and/or ablation
occurs at the location and/or near the ablation electrode.
Sometimes, unipolar ablation may cause deeper lesions than bipolar
ablation. In some embodiments, unipolar ablation may be used to
preferentially ablate tissue at a single location and/or to achieve
preferred ablation geometry, for example to achieve a deeper
lesion.
[0100] Unipolar ablation may optionally follow after a previous
process 312. For example, after bipolar ablation achieves a large
and/or shallow and/or heterogeneous lesion, unipolar ablation may
be used to ablate a small area and/or to achieve a deeper lesion
and/or even out a lesion (for example to ablate a portion of a less
well done portion of a lesion).
[0101] Unipolar ablation 114 may proceed by applying a high current
320, e.g., resulting in the desired power delivered to the tissue,
for example, an average of between 2 and 10 W (e.g., 2 W, 4 W, 5 W,
10 W etc.) between one or more ablation electrodes and a dispersive
electrode. During the application of current 320, the temperature
at one, some or all of the ablation electrodes and/or the current
and/or the impedance between the electrodes (e.g., an ablation
electrode and dispersive electrode) may optionally be monitored.
Application of current may continue for example between 50-200
milliseconds and/or between 200 milliseconds and 20 seconds and/or
between 20 seconds and 200 seconds at a power of 0.5-10 WATT
between each ablation electrode and the dispersive electrode. High
current application may be interrupted for a short period for
example between 0.5-100 milliseconds at which time impedance and/or
temperature may be tested 322 at the location of one or more of the
ablation electrodes and/or other locations. For example, testing
322 may include measuring local impedance for example by applying a
small current between one of the ablation electrodes and the
dispersive electrode. Alternatively or additionally testing 322 may
include calculating a "quality of lesion". After testing 322,
application 320 of current may optionally be resumed (step 324 no)
(for example if local ablation has not been completed and/or if
there are no signs of local overheating and/or over-ablation). The
interruption of current application 320 may optionally be short
enough that the target tissue does not significantly cool and/or
ablation is not adversely affected.
[0102] In some embodiments, when ablation at a particular location
reaches a desired level and/or ablation and/or temperature at a
location reaches a safety limit (step 324 yes) unipolar ablation
114 at that location may be stopped. Unipolar ablation 114 may
continue at other locations or other ablation electrodes and/or a
next process 316 may start. For example, bipolar ablation may
proceed between two electrodes until ablation reached a desired
limit and/or a safety limit (step 324 yes) at some location (for
example ablation may reach a limit near a first of two electrodes).
Bipolar ablation may be stopped. Ablation may optionally be
continued at the second of the two electrodes. For example,
unipolar ablation may be used in order to "touch up" the ablation
at each site of the second electrode. Alternatively or
additionally, bipolar ablation may continue between the second
electrode and another electrode for example as described herein
below.
4 Exemplary Ablation Devices
[0103] FIGS. 4A-16C illustrate various embodiments of ablation
devices and/or insulators in accordance with some embodiments of
the current invention. An ablation device may optionally include an
insulator, for example the insulator may include a membrane and/or
a frame. The membrane may optionally have a tubular form. In some
embodiments, the insulator outer surface of the insulator may
optionally be pressed against an inner surface of a wall of a lumen
or vessel in the vicinity of an ablation target and or in an area
surrounding an electrode. For example the insulator may exclude
lumen fluid from an area on the inner wall of the lumen ranging
between 0.1 mm.sup.2 and 40 mm.sup.2 around one or more electrodes.
Optionally the insulator may electrically isolate the electrode
and/or the area of tissue surrounding the electrode from the lumen
fluid. In some embodiments, expansion of a support structure may
press an insulator against an inner wall of a lumen.
[0104] FIGS. 4A-C illustrates a schematic view of an exemplary
ablation device 400, in accordance with some embodiments of the
current invention. In some embodiments, an ablation catheter may be
inserted into a lumen and/or opened to contact a target tissue. The
ablation device may include an insulator that may optionally
prevent shunting of ablation energy away from a target tissue
and/or may cool a portion of the ablation zone. For example, the
insulator may transfer heat to a heat sink. For example, heat
transfer may be by conduction. For example the heat sink may
include fluid to flowing past the ablation zone cooling a surface
of the insulator opposite the ablation zone. Optionally, a highly
heat conductive material (for example metal) may be added to the
insulator in a certain location to preferentially cool that
location and/or the insulator may be made thinner in a particular
location to allow more heat conduction away from that location. In
some embodiments, the ablation catheter may include a dispersive
electrode with large surface area. The dispersive electrode may
provide a unipolar reference. The dispersive electrode may
optionally be inserted into the lumen with the ablation electrodes.
Optionally, the dispersive electrode may be in electrical contact
with fluid (for example blood) within the lumen. For example, the
dispersive electrode may surround the ablation catheter's
shaft.
[0105] Some embodiments of an ablation device may optionally
include a tubular insulator. For example, an insulator may include
a membrane 434 that has an tubular form. Membrane 434 may
optionally be expanded and/or spread against a target tissue, for
example an inner surface of a lumen. Membrane 434 may optionally
prevent shunting of ablation energy away from the target tissue.
For example, membrane 434 may optionally prevent shunting of
ablation energy into a fluid (for example, blood) in vicinity of an
ablation electrode 436. In some embodiments, an ablation electrode
436 may optionally be coated with a non-electrically conductive
material 435 except for the segment that protrudes through the
blood-exclusion membrane to contact the target tissue. In some
embodiments, decreasing shunting may decrease the power necessary
for ablation and/or increase the control and/or precision of
measurement of the power applied to the target tissue.
[0106] Membrane 434 may optionally allow fluid to flow 439 (for
example see FIG. 4B) along the lumen. For example, membrane 434 may
have a tubular form allowing fluid flow 439 along a passageway 477
along the axis of the insulator. Membrane 434 may be thin taking
only a small portion of the cross section of the lumen. Passageway
477 may optionally include more than half the cross section of the
lumen. The hydraulic radius of passageway may be more than 70% of
the hydraulic radius of the lumen. Membrane 434 may optionally
transfer heat away from the ablation zone. For example membrane 434
may conduct heat to fluid flowing 439 in passageway 477. For
example, blood flow 439 across the inside surface of the insulator
(opposite the target tissue) may cool the outside surface that is
against the target tissue and/or a portion of the target tissue. By
cooling the target tissue, the lesion may be made deeper and/or
more even (as has been observed for example in irrigated ablation
procedures). Alternatively or additionally, blood flow 439 across
the inside surface of the insulator may cool electrodes 436.
Reducing the temperature of the electrode may reduce the
temperature in the interface between electrode 436 and the tissue.
Reducing the temperature at the tissue electrode interface may
allow more power to be delivered deeper into the tissue.
Alternatively or additionally, allowing fluid flow 439 in the lumen
may reduce pain and/or secondary tissue damage due to blockage of
circulation during the ablation procedure.
[0107] In some embodiments, an ablation device may include one or
more markers. For example, device 400 includes two individually
recognizable radio opaque markers 455a,b. Markers 455a,b may
optionally be easily recognized in radiographic and/or other extra
body images (for example an image may be made using ultrasound
and/or magnetic resonance MRI and/or x-ray and/or other imaging
techniques). Distinguishing markers 455a,b may help a clinician
locate and/or determine the orientation of a catheter and/or a
support structure and/or individual electrodes 436.
[0108] In some embodiments, a guidewire 442 may be inserted through
a lumen of the catheter. For example, guidewire 442 may help
position the catheter. Guidewire 442 may optionally be able to
extend past an orifice 445 at the distal end of the catheter.
[0109] In some embodiments, a dispersive electrode 440 may be
inserted into a lumen in the patient being treated. For example, in
device 400, dispersive electrode 440 may be inserted into the same
lumen as ablation electrodes 436. Dispersive electrode 440 may
optionally have a large surface of contact. For example, dispersive
electrode 440 may be in contact with fluid inside the lumen. The
large contact area may decrease local impedance and/or heating near
dispersive electrode 440. Dispersive electrode 440 may optionally
be coated with a material such as porous titanium nitride (TiN) or
iridium oxide (IrOx) for example to increase its microscopic
surface area in electrical contact with the fluid.
[0110] Ablation device 400 may include, for example a plurality of
ablation electrodes 436. Ablation electrodes may optionally be used
in pairs for bipolar ablation. Optionally a signal may be
transmitted between any two electrodes 436. Dispersive electrode
440 may be used for example to pass a high current to one, some or
all of the ablation electrodes to perform unipolar ablation.
Dispersive electrode 440 may optionally be used for measuring the
local impedance near one or more of the ablation electrodes 436.
For example a small current may be passed between dispersive
electrode 440 and one of the ablation electrodes 436 to test
impedance in the local area of the ablation electrode 436. An
optional multiplexed power source 441 (e.g., current source) (for
example see FIG. 4B) may be used to supply current to a selected
group of electrodes (for example including some or all of ablation
electrodes 436 and/or dispersive electrode 440) during a time slice
and/or a different group of electrodes (for example including some
or all of ablation electrodes 436 and/or dispersive electrode 440)
during a different time slice.
[0111] For example, ablation device 400 may optionally include a
"basket" made out of nitinol wire spines and/or supports 432.
Ablation electrodes 436 may optionally be positioned on supports
432. For example pairs of ablation electrodes 436 may be
distributed along the periphery of the basket to ablate the
intrabody target tissue. Optionally, each electrode may be fitted
with a thermocouple and/or other suitable sensor.
[0112] For example, an insulator may include a polyurethane
membrane 434. Membrane 434 may be is placed onto the supports 432.
Upon deployment, the basket including supports 432 and/or membrane
434 may optionally open up like an umbrella. In the exemplary
embodiment, ablation electrodes 436 may optionally be exposed to
target tissue on the inner walls of the lumen into which the
catheter is deployed.
[0113] The insulator may optionally include non-porous membrane 434
covering the mid-section of the expandable basket structure. The
membrane may optionally separate blood from the treatment area.
Membrane 434 may optionally increase the portion of electrical
ablation energy delivered to the target tissue for example by
reducing the shunting of the ablation energy to the blood. In
contrast to some occluding means to exclude blood (for example
balloons), the basket and/or membrane 434 may be open at the distal
and/or proximal ends, allowing blood to continue to flow 439
through the lumen (for example the delivery vessel and/or artery).
During the ablation procedure tissue and/or organs may continue to
receive blood. During the ablation procedure blood passing along
the inside surface of membrane 434 may cool the surface of the
target tissue.
[0114] In some embodiments, an ablation catheter may include a
plurality of ablation electrode pairs. For example ablation device
400 may include four pairs of ablation electrodes 436 helically
distributed around an open tubular basket near the end of a
catheter shaft 430 (as illustrated for example in FIG. 4A). During
ablation, some or all of the four pairs of ablation electrodes 436
may be activated simultaneously. For example, four lesions can be
made simultaneously in a helical pattern along the wall of a lumen.
Additionally, ablation current may be delivered between ablation
electrodes on adjacent spines, for example between electrodes 436b
and 436c, between electrodes 436d and 436e, etc.
[0115] In some embodiments, flow 439 in a lumen may help hold
membrane 434 in an expanded configuration. For example, as shown in
FIG. 4B, the downstream (distal) opening 437b of membrane 434 may
be narrower than the upstream (proximal) opening 437a. When placed
inside an artery, downstream opening 437b may present resistance
against blood flow 439. Resistance to flow 439 exiting membrane 434
may cause pressure within membrane 434 to increase. Increased
internal pressure may make membrane 434 expand against an artery
wall and/or spread out, for example like a parachute and/or a
windsock.
[0116] FIG. 5 illustrates a tubular insulator 534 having a form of
a windsock and/or a parachute deployed from a catheter 530 in
accordance with some embodiments of the current invention.
Optionally fluid may flow 539 through a passageway 577 through
insulator 534. For example fluid may enter a large opening 537a
(illustrated for example at the proximal end of insulator 534).
Optionally the fluid may exit a smaller opening 537b (for example
windows at the distal end of insulator 534). The dynamic pressure
of the fluid flow 539 (for example blood flow in an artery) may
help keep the insulator 534 inflated. For example, fluid pressure
may press insulator 534 against walls of a lumen. Optionally,
insulator 534 and/or other structural members 532 may insulate
electrodes 536 from lumen fluids. Internal pressure may optionally
be used to cause expansion on its own or along with another
mechanism. In some embodiments, pressure against an inner surface
of a lumen may be augmented by structural members. Some structural
members may carry an electrode. Alternatively or additionally some
structural members that do not carry electrodes may be introduced
for example to provide support for the insulator. For example, in
the exemplary embodiment of FIGS. 6A and 6B, a basket may be formed
by cutting out from a nitinol tube. The deploying of the basket may
optionally include supports springing out (where the direction of
expansion has been determined by heat setting the memory of the
nitinol wire). FIG. 6A illustrates the basket in a collapsed
configuration and FIG. 6B illustrates the basket in an expanded
configuration. Production of the tube and/or the cutting may
optionally be similarly to production of a stent. The basket may
include various structural elements, for example struts 632, cross
members 633, support members 643, end members 647 and/or cantilever
members 645. Supports 643 may for example retain a preferred
geometry of other structural members and/or also provide a support
for the geometry of the insulator. Cantilever members may for
example supply pressure on parts of the insulator.
[0117] In some embodiments, support for electrodes and/or an
insulator may be supplied by a spiral wire basket. For example as
shown in the exemplary embodiment of FIG. 7 a spiral element 732
may be expanded by twisting in one direction 751 and/or collapsed
by twisting in the opposite direction. Optionally, an axial wire
753 may be used for twisting spiral element 732. For example,
spiral element 732 may be located at the distal end of a catheter
730. Catheter 730 may include multiple spiral elements and/or other
elements that may be expanded and/or collapsed to form a desired
shape. The expanding elements may optionally cause an insulating
membrane to take a circular cross section and/or press an
insulating membrane against the walls of a lumen. The resulting
shape of the membrane in an expanded configuration may depend on
the way in which the spiral elements of the basket deploy. In some
embodiments, electrodes and/or markers and/or an insulating frame
and/or an insulating membrane may be mounted and/or included on
element 732.
[0118] In some embodiments, support members for an insulator may
extend around an electrode, for example as illustrated in FIG. 8.
Optionally, a strut 832 may hold an electrode 836 and/or a frame
853 against a tissue to be ablated. Frame 853 may optionally
electrically insulate electrode 836 and/or an area of tissue around
electrode 836 from fluid in a lumen. In some embodiments, frame 853
may conduct heat away from electrode 836 and/or the tissue near
electrode 836. For example, the heat may be conducted to a heat
sink cooling electrode 836 and/or the tissue around electrode
836.
[0119] FIGS. 9A-B, illustrate an insulating membrane 934 wrapped
around a support structure in accordance with some embodiments of
the current invention. Electrodes 836 may optionally protrude
through holes in membrane 934 to contact the tissue. Frame 853 may
hold membrane against the tissue around electrode 836 optionally
insulating electrode 836 from a bodily fluid. Optionally,
additional support members (for example members 943) may supply
further support to membrane 934. Alternatively or additionally,
frame 853 may be an insulator. In some embodiments may not a
surrounding membrane 934. Alternatively or additionally a nitinol
stent type support structure may support electrodes 836 and/or a
frame 853 and/or a membrane 934. Exemplary nitinol stent type
support structures are illustrated for in FIGS. 6 and 10.
[0120] FIG. 10 illustrates a nitinol support structure with a
surrounding membrane 934 and a frame 853 around electrodes 836 in
accordance with some embodiments of the current invention.
Optionally, an ablation device (for example as illustrated in FIG.
8 and/or FIGS. 9A-B and/or FIG. 10) may include one or more markers
for example similar to markers 455a,b.
[0121] In some embodiments, a ablation device may include a
laminated membrane. For example as shown in FIGS. 11A-B, the
membrane may be formed by laminating several layers of polymers
with similar and/or different characteristics. Optionally, the
laminated membrane may tend to expand outwardly. For example, the
laminated membrane may push outward against a lumen wall,
insulating the wall from fluid inside the lumen.
[0122] FIG. 11A illustrates a balloon 1134a insulator in accordance
with some embodiments of the current invention. In some
embodiments, balloon 1134a may be fitted inside a support structure
1132. Optionally, support structure 1132 may include a stent type
support (for example as illustrated in FIG. 6). As illustrated for
example in FIG. 11B, balloon 1134a may be welded to the support
structure 1132. For example, welding may be by adhering balloon
1134a to a layer of polymer film 1134b in a lamination that
sandwiches the support structure 1132 between the two layers
(balloon 1134a and film 1134b). Further layers may optionally be
added, for example to achieve a desired stiffness, elasticity,
deformability, heat conductivity and/or electrical
conductivity.
[0123] Optionally, the ends of the balloon may be trimmed and/or
removed to produce a tubular form and/or a passageway for fluid
flow. Optionally, heat conducting elements may be introduced
between the layers to preferentially cool particular areas of an
ablation zone (for example a portion of the target tissue and/or an
electrode).
[0124] In some embodiments, a braid of wires that forms a catheter
shaft may be expanded to form a basket support for an insulator.
For example, spiral element 732 of FIG. 7 may form part of a
braided casing of a catheter. FIGS. 12A-B illustrate a catheter
having braided elements in accordance with some embodiments of the
current invention. For example, the braided elements may include
one or more insolated Copper wires 1232a (for example copper with a
polyimide insulation [Cu-Pi]) and/or one or more stainless steel
[SST] wires 1232b. Optionally, Cu-Pi wires 1232a may be used to
carry current and/or signals between a control unit, a signal
generator and/or an antenna in the catheter. The catheter may also
include one or more axial wires 1232c. The axial wires 1232c may
for example be formed of Nitinol. For example, at a distal end of a
catheter one or more nitinol wire 1232c may form a support
structure; for example as illustrated in FIG. 12B. One or more
Cu-Pi wire 1232a may carry a current and/or a signal between a
signal generator and/or a receiver at a proximal end of the
catheter and an electrode 1236 and/or a sensor and/or an electrode
at a distal end of the catheter, for example as illustrated in FIG.
12B. Alternatively or additionally an expanding basket may be made
of radial and/or spiral elements. Alternatively or additionally, a
pull wire 1257 may be provided to deploy an expanding support
structure. For example, in some embodiments, a guidewire tube may
be used as a pull wire.
[0125] In some embodiments, the wires that form the basket may not
be formed as a separate distal head to the catheter. Optionally,
the wires that form the basket may be part of the conductors that
come all the way through a catheter's shaft 1230. For example, a
conductor (for example bringing current and/or a signal to or from
an electrode) may be an insulation-coated nitinol wire. The wire
may provide structural support, for example forming a spline strut.
The same wire may also serve as an electrical conductor.
[0126] FIGS. 13A-C and FIGS. 14A-C illustrate embodiments of
insulators and support structures formed as a malecot in accordance
with some embodiments of the current invention. For example in
FIGS. 13A-C tubing inside of a catheter expands out of slits in a
malecot break configuration. Alternatively or additionally in FIGS.
14A-C a malecot extends out a distal end of a catheter.
[0127] In some embodiments, for example as illustrated in FIGS.
13A-C a catheter may have malecot 1363 and/or a multi-lumen profile
with wire breakout slits 1359. FIG. 13A illustrates malecot 1363 in
an expanded configuration in accordance with some embodiments of
the present invention. At slits 1359 an outer sheath 1330 of the
catheter may allow an inner tubing 1332 to expand into a basket
shape during actuation. Conducting wires may optionally run through
a lumen of tubing 1332. Electrodes 1336 and/or markers may be
mounted on tubing 1332 and/or connected to a signal generator
and/or signal receiver via the conducting wires. An insulator may
include a tubular membrane 1334 surrounding sheath 1330 at the
location of slits 1359. When malecot 1363 expands it may be
surrounded by membrane 1334. Membrane 1334 may have openings
through which electrodes 1336 protrude to contact the tissue to be
ablated. FIG. 13B,C illustrate malecot 1363 in a retracted
configuration. An inner lumen of the catheter may include a pull
wire 1357 that may be used to expand and/or retract malecot 1363.
Alternately or additionally the insulator may include a frame
mounted on tubing 1332 surrounding electrodes 1336 for example
similar to frame 853 of FIG. 8. Alternately or additionally an
insulating membrane may surround tubing 1332 on the inside of
sheath 1330. When the malecot 1363 is expanded, the alternative
membrane may expand out of slits 1359 in a star shape.
[0128] FIGS. 14A-C illustrate a malecot 1463 extending out of a
distal end of a catheter in accordance with some embodiments of the
current invention. Optionally malecot 1463 may be formed of a
laser-cut Nitinol tube. Optionally malecot 1463 may have an
retracted configuration where it fits in a catheter 1430 with an
outer diameter of less than 2 mm and/or an extended configuration
wherein malecot 1463 extends out of the distal end of catheter
1430. In some embodiments in the extended configuration malecot may
have a diameter of less than 3 mm. For example malecot 1463 is
illustrated in an extended configuration in FIGS. 14A and 14B. In
the extended configuration struts 1432 of malecot 1463 may be
slightly expanded. Optionally malecot 1463 may have an expanded
configuration. For example, FIG. 14C illustrates malecot 1463 in an
expanded configuration. For example, an axial compressing force
(for example exerted by pulling a pull wire) may cause malecot 1463
to expand radially from the extended configuration to the expanded
configuration. The degree of expansion and/or pressure on the
tissue to be ablated may optionally be user controllable according
to the tension on the pull cord. In the expanded configuration the
diameter of malecot 1463 may be larger than the diameter in the
extended configuration and less than for example 7.5 mm. Malecot
1463 may carry electrodes 4136 and/or markers. Malecot 1463 may
include an insulating sleeve for example similar to membrane 1334
and/or an insulating frame (for example similar to frame 854) for
insulating electrodes 1336.
[0129] FIGS. 15A-B illustrate insulators for an ablation device
that may be expanded by hydraulic pressure in accordance with some
embodiments of the current invention. For example, FIG. 15A
illustrates an exemplary support structure including a hydraulic
struts 1532a. FIG. 15B illustrates an exemplary insulator for an
ablation device including a tube formed as a double hydraulic
sleeve 1532c which may be inflated by increasing hydraulic pressure
between the sleeves. Lumen fluids (for example blood) may flow 1539
through a passageway in the inner sleeve. Struts 1532a and or
sleeve 1532c may optionally carry electrodes 1536 and/or an
insulator (for example a membrane sleeve and/or a frame around
electrodes 1536 and/or wires 1532b and/or markers.
[0130] Insulating sleeves and/or hydraulic sleeves may be
constructed for example by blow molding. Blow molding may
optionally allow for secure mounting of a membrane proximal and
distal to an expandable support.
[0131] FIG. 16A-C illustrate a flexible circuit board ablation
device in accordance with some embodiments the present invention.
For example a flexible printed circuit board (PCB) may be made of
polyimide (PI). Circuits may optionally be printed on one or more
surfaces. FIG. 16A illustrates a flexible circuit board 1663 for an
ablation device laid out flat, according to some embodiments of the
present invention. Board 1663 may include electrodes 1636 that may
optionally be mounted on flexible struts 1632. The ablation device
may optionally be connected to a support structure, for example a
nitinol basked and/or an inflatable strut. The ablation device may
include connections to other devices for example electrical leads
and/or rings 1565 for connecting to structural supports and/or
shaft transition pads 1667 through which electrical connection is
made between the printed circuit board and the wires within the
catheter's shaft that transmit and/or receive energy to/from an RF
generator and/or receiver. FIG. 16B illustrates circuit board 1663
rolled up as a tube in a retracted configuration for mounting into
a catheter. FIG. 16C illustrates a cross sectional view of an
embodiment of board 1663 inserted in a body lumen 1669 in an
expanded configuration. Electrodes 1636 may optionally contact with
the inner surface of the walls of lumen 1669. Struts 1632 may
optionally serve as an insulator. For example, the outer surface of
struts 1632 may contact the wall of lumen 1669 in an area
surrounding electrodes 1636. For example, struts 1632 may prevent
shunting of current from electrodes 1636 to fluid inside of lumen
1669. Alternatively and/or additionally, struts 1632 may transfer
heat from electrodes 1636 and or the wall of lumen 1669 to the
lumen fluid. The lumen fluid may flow across the inner surface of
struts 1632. For example the thickness and/or material of struts
1632 may be adjusted to achieve a desired conductivity and/or
resistance to electrical current and/or heat flow. For example, a
heat sink may be printed on board 1663 and/or a channel may be
printed to conduct heat from one or more electrodes 1636 and/or
tissue in contact with board 1663 to a heat sink and/or lumen
fluid. For example heat may be conducted and/or absorbed by a high
heat conductivity channel and/or a high heat capacity element such
as a metal insert and or channel in the insulator.
[0132] Optionally the geometry of a heat sink and/or heat
conduction channel may be adjusted to cool a particular area more
than another area. For example, a highly heat conductive region may
be formed near an electrode, preferentially cooling an area near
the electrode. Further from the electrode the heat conductivity may
be smaller. Thus, cooling may be increased near the electrode where
overheating is more prevalent.
5 Control Unit
[0133] FIG. 17 illustrated a control unit for an ablation device in
accordance with some embodiments of the current invention. For
example a control unit may include one or more radio frequency (RF)
channels 1776. The control unit may optionally have a number of
channels 1776 that convey electrical signals for bipolar ablation
between multiple electrode pairs (for example between specific
pairs and/or any combination of a large number of electrodes, e.g.,
electrodes 436a-h, electrodes 1336 etc., mounted for example on a
spine of the catheter's working end). Alternatively or
additionally, RF channels 1776 may convey a signal for unipolarly
ablation (for example between one or more ablation electrodes e.g.,
electrodes 1336 and a dispersive electrode, e.g., electrode 440).
In some embodiments the dispersive electrode may be located inside
a catheter (for example a shaft electrode). For example, an
internal dispersive electrode may be placed in contact with fluid
(e.g. blood) inside a lumen (e.g. a blood vessel) wherein the
ablation is taking place.
[0134] In some embodiments, signal of a single frequency may be
conveyed for one or more electrodes, e.g., to pair of electrodes in
bipolar ablation or one or more electrodes in unipolar ablation).
In some embodiments, signals of a plurality of frequencies may be
conveyed for one or more electrodes. For example, in bipolar
ablation: a first pair of electrodes may receive signal of a first
frequency and a second pair of electrodes may receive signal of a
second frequency. For example, in unipolar ablation: a first
electrode may receive signal of a first frequency and a second
electrode may receive signal of a second frequency.
[0135] In some embodiments, a phase difference of the signal
conveyed to a pair of electrodes may be controlled, e.g., by
controller 1774. Optionally, the phase difference may be controlled
based on impedance and/or temperature measurements. In some
embodiments, other parameters of a signal conveyed to one or more
electrodes may be controlled, e.g., based on impedance and/or
temperature measurements.
[0136] Selecting electrodes may optionally be according to a switch
configuration. The selection may optionally be set by a multiplexer
1778. Optionally, RF channels 1776 may have the means to measure
electrode/tissue impedance under whatever selection is set by the
switch configuration of the multiplexer 1778. The RF channels 1776,
the switches and/or multiplexor 1778 may be controlled by a central
controller 1774 (for example the central controller 1774 may
include a processor, for example a microcontroller and/or
single-board computer). The control unit may include receiver that
is able to measure temperature inside the lumen (for example by
means of a thermocouple attached at the location of one, some or
all of the electrodes and/or at other locations). The control unit
may include a user interface 1780, for example a graphical user
interface (GUI), e.g. presented on a touch screen.
[0137] In some embodiments, electrode impedance measurements may be
used to estimate contact between electrode and tissue.
Alternatively or additionally impedance measurements may be used as
surrogate for thermal contact between electrode interface and
target tissue. Optionally, RF power, electrode temperature, and
electrode impedance may be used to estimate power being converted
to heat at electrode/tissue interface. The estimated contact and/or
estimated power may optionally be used to calculate energy
transferred to target tissue and/or resulting target tissue
temperature. Temperature and/or impedance measurements may be used
in real-time to determine whether to apply unipolar or bipolar
ablation. Optionally, other sensors inputs may be used in real-time
to determine whether to apply unipolar or bipolar ablation. In some
embodiments, the operator (e.g., a physician) may determine whether
to apply unipolar or bipolar ablation, optionally based on
temperature and/or impedance measurements which may be displayed to
the operator. Additionally or alternatively, temperature and/or
impedance measurements may be used in real-time to control power
and duration of ablation. The power and/or duration of ablation may
optionally be used to ensure quality of lesion formation. The
generator may estimate lesion quality for an individual electrode
and/or for an area between electrodes. The algorithms may
optionally alert a user that lesion formation has been completed
when the quality of lesion at each electrode location reaches a
predetermined range. The algorithm may change the electrodes being
powered and/or the power level and/or frequency dependent on the
differential progress of ablation. In some embodiments, the
algorithm may recommend changes to a use and wait for user input
before making changes. For example, if ablation is progressing
faster at a first electrode of a pair of electrodes than at a
second electrode, the algorithm may recommend switching to unipolar
ablation at the second electrode and/or may automatically switch.
For example, if ablation is localized too much at the electrode
locations, the algorithm may recommend changing to a frequency that
penetrates tissue better.
[0138] In some embodiments, the control unit may measure complex
bipolar and/or unipolar electrode impedance. For example impedance
may be measured at the ablation frequency and/or at another
frequency. Optionally, measurements may be made while ablating
based on the ablation signal. Alternatively or additionally,
impedance measurements may be made when not ablating. For example,
during a interruption in ablation, impedance may be measured using
an auxiliary signal. The auxiliary signal may be generated by an RF
generator of one or more of channels 1776. The auxiliary signal may
optionally meet the requirements of an auxiliary current not meant
to cause any physiological effect. In some embodiments, electrode
Impedance measurements shall be possible within the 100.OMEGA. to 1
k.OMEGA. range with a minimum accuracy of 5%, and within the
1001.OMEGA. to 2 k.OMEGA. range with a minimum accuracy of 10%.
Minimum repeatability within the 100.OMEGA. to 2 k.OMEGA. range may
optionally be 5%. In some embodiments, ablation interruptions of
less than 100 ms may be made for measuring impedance during
ablation segments. Optionally, an auxiliary signal for impedance
measurements may have the same frequency as ablation signals and/or
an auxiliary signal for impedance measurements may have a different
frequency from an ablation signal. Optionally, impedance
measurements may be conveyed between a pair of electrodes being
used for an ablation and/or an impedance measurement may be
conveyed between electrodes between which there is no current
ablation treatment. For example, during an interruption in bipolar
ablation impedance may be measured between a disperse electrode and
one ablation electrode of the active bipolar pair. Optionally,
impedance measurements may be taken at a rate greater than 100
samples/s.
6 Evoked Response
[0139] In some embodiments, evoked response may be used for
determining a treatment location and/or measuring ablation
progress. For example a catheter may be supplied with an apparatus
for measuring vasoconstriction (for example through balloon
pressure, strain on supports, pressure on a transducer [for example
measuring blood pressure in the lumen being ablated and/or
elsewhere], electrical signals [picked up for example by an antenna
and/or an electrode in the catheter or elsewhere] and/or impedance
measurements, for example as illustrated in FIG. 20 and FIGS.
21A-B). Target sites may optionally be located by finding regions
where electrical stimulation delivered through the electrodes
causes a significant vasocontractile response. Once ablation is
started, changes in vasocontractile response to stimulation may be
used to control the delivery of energy until a certain dampening of
the vasocontractile response indicates desired extent of the effect
of the ablation. Alternatively or additionally, the evoked
electrical response to stimulus may be measured to find ablation
sites and/or to estimate the extent of the effect of the
ablation.
[0140] FIG. 18 illustrates an exemplary method of finding a
receptor (for example a receptor may include perivascular renal
nerve) and/or ascertaining ablation progress via evoked response,
in accordance with some embodiments of the invention. In some
embodiments, a stimulation electrode (which could include for
example an ablation electrode) is positioned 1844 at a location
wherein there may be an ablation candidate receptor and the tissue
may be stimulated 1846 for example via an electrical signal. The
response may be measured 1848 (for example the vasoconstriction
and/or the electrical response). For example, a fast and/or strong
response may indicate the presence of a receptor. If a receptor is
not found 1850, then the simulation electrode is positioned 1844 at
a new location. If a receptor is found 1850, then the ablation 1813
may proceed. Ablation 1813 may include bipolar ablation (for
example bipolar ablation 112 as described hereinabove) and/or
unipolar ablation (for example unipolar ablation 114 as described
hereinabove). In place of and/or in addition to the tests described
herein above evoked response may be used to measure ablation
progress. During ablation, current application may be interrupted
and an electrical signal may be transmitted to stimulate 1852 the
tissue. The evoked response to stimulation may then be measured
1854 (for example the vasoconstriction and/or the electrical
response). If the response is not yet damped 1856 enough, then
ablation 1813 may continue. If the response is damped 1856 enough,
then the process ends (for example either the ablation session ends
and/or the process restarts finding another site and optionally
ablating that site).
[0141] In some embodiments, the method illustrated in FIG. 18 may
be used for determining a treatment location in a body of a treated
patient e.g., by stimulating a tissue and detecting the elicited
vasocontractile response. Treatment locations may be located by
finding regions where electrical stimulation delivered through the
electrodes causes a significant vasocontractile response. Once
ablation is started, changes in vasocontractile response to
stimulation may be used to control the delivery of energy for
example until a certain dampening of the vasocontractile response
indicates desired extent of lesion formation. Optionally, the
evoked response may be measured in the intravascular space (for
example by a blood pressure sensor in the catheter) and/or
elsewhere in the body (for example through a blood pressure or
blood flow sensor elsewhere in the body and/or from a location
external to the body, for example through a blood pressure sensor,
heart rate sensor, or plethysmography sensor).
[0142] In some embodiments, an evoked response may include an
electrical reaction signal produced in response to a stimulus.
Optionally, the stimulus may be applied inside a lumen of the
patient, for example by a device on the ablation catheter.
Optionally, a target site may be identified as a region where
delivering a stimulation causes a significant evoked response. For
example, a target for ablation may include a nerve terminal.
Optionally, the stimulus may include an electrical signal. The
evoked response may be measured for example as an electrogram.
Optionally, the evoked response may be measured in the
intravascular space (for example by electrodes of the catheter)
and/or elsewhere in the body (for example at a nerve location
elsewhere in the body and/or external to the body (for example
using an external electrode). Once ablation is started, changes in
evoked response to stimulation may optionally be used to control
the delivery of energy until a certain dampening of the evoked
response is detected. The dampened response may optionally indicate
a desired extent of lesion formation. When sufficient dampening is
detected, ablation may optionally be stopped.
[0143] FIG. 19 illustrates an exemplary stimulation and evoked
response, in accordance with some embodiments of the invention. For
example, curve 1961a illustrates a stimulation to the receptors
before ablation (either while searching for receptors or at the
beginning of ablation). The abscissa shows time (for example a few
milliseconds) and the ordinate may include for example the voltage
of the signal and/or the current. The measured return signal is
represented by graph 1962. The measured signal may include a change
in pressure in a balloon due to vasoconstriction and/or a stress
and/or a strain on a support of a basket (for example support 432)
and/or a change electrical potential and/or impedance measured on
the tissue. For example, curve 1961b illustrates a stimulation to
the receptors after ablation. For example, curve 1964 illustrates
the dampening of the return signal after successful ablation.
[0144] FIG. 20 illustrates an ablation device 2000 capable of
measuring evoked response in accordance with some embodiments of
the current invention. Ablation device 2000 may, for example,
include a support structure similar to that of FIG. 4C (for example
including struts 432). Ablation device 2000 may option include
markers (for example similar to markers 455a,b--not illustrated),
electrodes 436, an insulator (for example a membrane 434) and/or
other components or structures described above. For example, the
support structure, markers, electrodes 436 and/or insulator may be
similar to one, some and/or any of the embodiments above.
Optionally, ablation device 2000 may include one or more sensors to
sense evoked response. For example, a strain gauge 2070 may measure
evoked vasoconstriction response and/or resultant squeezing of the
support structure. Alternately or additionally, ablation device
2000 may include a pressure transducer to measure the fluid
pressure inside a lumen. Ablation device 2000 may include exemplary
thermocouples 2072 for measuring temperature near the ablation
electrodes 436.
[0145] FIGS. 21A-B illustrate a perspective and a cross sectional
view respectively of an alternate ablation device 2100 capable of
measuring evoked response in accordance with some embodiments of
the invention. Ablation device 2100 may, for example, include a
malecot support structure similar to that of FIGS. 14A-C (for
example including struts 1432). Ablation device may option include
markers (for example similar to markers 455a,b--not illustrated),
electrodes 1336 and/or an insulator 2134. Ablation device 2100 may
include other components or structures described above. For
example, the support structure, markers, sensors, electrodes
sensors and/or insulator may be similar to one, some and/or any of
the embodiments above. Optionally, ablation device 2100 may be
configured to sense evoked response. For example, insulator may be
configured to sense pressure and/or shape changes caused by evoked
vasoconstriction response and/or resultant squeezing of the support
structure. For example, insulator 2134 may include an internal
liquid filled cavity 2179. Changes in the shape of insulator 2134
may induce changes in the internal pressure in cavity 2179 and may
be sensed by a pressure transducer. Alternately or additionally,
ablation device 2100 may be constructed of multiple layers of
material which may produce an electrical response (for example a
change in resistance) under strain. The electrical response may be
sensed and/or used detect an evoked response. The materials of
insulator 2134 and or the fluid between layers may be chosen to
provide a heat sink and/or heat conductor, for example for
conducting heat away from the ablation zone. Insulator 2134 may
include a central passageway 2177 through which lumen fluids may
flow 2139. Optionally, struts 1432 may pass through support lumens
2175 in insulator 2134.
[0146] It is expected that during the life of a patent maturing
from this application many relevant technologies will be developed
and the scope of the terms used herein is intended to include all
such new technologies a priori. As used herein the term "about"
refers to .+-.10%.
[0147] The terms "comprises", "comprising", "includes",
"including", "having" and their conjugates mean "including but not
limited to".
[0148] The term "consisting of" means "including and limited
to".
[0149] The term "consisting essentially of" means that the
composition, method or structure may include additional
ingredients, steps and/or parts, but only if the additional
ingredients, steps and/or parts do not materially alter the basic
and novel characteristics of the claimed composition, method or
structure.
[0150] As used herein, the singular form "a", "an" and "the"
include plural references unless the context clearly dictates
otherwise. For example, the term "a compound" or "at least one
compound" may include a plurality of compounds, including mixtures
thereof.
[0151] Throughout this application, various embodiments of this
invention may be presented in a range format. It should be
understood that the description in range format is merely for
convenience and brevity and should not be construed as an
inflexible limitation on the scope of the invention. Accordingly,
the description of a range should be considered to have
specifically disclosed all the possible subranges as well as
individual numerical values within that range. For example,
description of a range such as from 1 to 6 should be considered to
have specifically disclosed subranges such as from 1 to 3, from 1
to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as
well as individual numbers within that range, for example, 1, 2, 3,
4, 5, and 6. This applies regardless of the breadth of the
range.
[0152] Whenever a numerical range is indicated herein, it is meant
to include any cited numeral (fractional or integral) within the
indicated range. The phrases "ranging/ranges between" a first
indicate number and a second indicate number and "ranging/ranges
from" a first indicate number "to" a second indicate number are
used herein interchangeably and are meant to include the first and
second indicated numbers and all the fractional and integral
numerals therebetween.
[0153] As used herein the term "method" refers to manners, means,
techniques and procedures for accomplishing a given task including,
but not limited to, those manners, means, techniques and procedures
either known to, or readily developed from known manners, means,
techniques and procedures by practitioners of the chemical,
pharmacological, biological, biochemical and medical arts.
[0154] As used herein, the term "treating" includes abrogating,
substantially inhibiting, slowing or reversing the progression of a
condition, substantially ameliorating clinical or aesthetical
symptoms of a condition or substantially preventing the appearance
of clinical or aesthetical symptoms of a condition.
[0155] It is appreciated that certain features of the invention,
which are, for clarity, described in the context of separate
embodiments, may also be provided in combination in a single
embodiment. Conversely, various features of the invention, which
are, for brevity, described in the context of a single embodiment,
may also be provided separately or in any suitable subcombination
or as suitable in any other described embodiment of the invention.
Certain features described in the context of various embodiments
are not to be considered essential features of those embodiments,
unless the embodiment is inoperative without those elements.
[0156] Although the invention has been described in conjunction
with specific embodiments thereof, it is evident that many
alternatives, modifications and variations will be apparent to
those skilled in the art. Accordingly, it is intended to embrace
all such alternatives, modifications and variations that fall
within the spirit and broad scope of the appended claims.
* * * * *