U.S. patent application number 14/348035 was filed with the patent office on 2014-08-28 for energy delivery device and methods of use.
The applicant listed for this patent is COVIDIEN LP. Invention is credited to John P. Claude, Jonah Lepak, Emma Leung, Amr Salahieh, Tom Saul.
Application Number | 20140243821 14/348035 |
Document ID | / |
Family ID | 47143270 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140243821 |
Kind Code |
A1 |
Salahieh; Amr ; et
al. |
August 28, 2014 |
ENERGY DELIVERY DEVICE AND METHODS OF USE
Abstract
The present disclosure is directed to an expandable energy
delivery assembly adapted to deliver electrical energy to tissue.
The assembly includes an elongate device and an expandable portion.
The expandable portion includes an inflatable element, a single
helical electrode disposed on the inflatable element, and at least
one irrigation aperture within the inflatable element. The
inflatable element is secured to the elongate device and the single
helical electrode makes between about 0.5 and about 1.5 revolutions
around the inflatable element. The at least one irrigation aperture
is adapted to allow fluid to flow from within the inflatable
element to outside the inflatable element.
Inventors: |
Salahieh; Amr; (Saratoga,
CA) ; Lepak; Jonah; (Saratoga, CA) ; Leung;
Emma; (Saratoga, CA) ; Claude; John P.;
(Saratoga, CA) ; Saul; Tom; (Saratoga,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COVIDIEN LP |
Mansfield |
MA |
US |
|
|
Family ID: |
47143270 |
Appl. No.: |
14/348035 |
Filed: |
September 28, 2012 |
PCT Filed: |
September 28, 2012 |
PCT NO: |
PCT/US2012/057967 |
371 Date: |
March 27, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61541765 |
Sep 30, 2011 |
|
|
|
61593147 |
Jan 31, 2012 |
|
|
|
Current U.S.
Class: |
606/41 ;
29/829 |
Current CPC
Class: |
A61B 2018/00821
20130101; A61B 2090/3966 20160201; A61B 2018/00815 20130101; A61B
2018/0022 20130101; Y10T 29/49124 20150115; A61B 2018/00577
20130101; A61B 2018/00029 20130101; A61B 18/14 20130101; A61B
2018/00642 20130101; A61B 2018/00708 20130101; A61B 2018/1435
20130101; A61N 1/05 20130101; A61B 2018/00434 20130101; A61B
2090/064 20160201 |
Class at
Publication: |
606/41 ;
29/829 |
International
Class: |
A61B 18/14 20060101
A61B018/14; A61N 1/05 20060101 A61N001/05 |
Claims
1. An expandable energy delivery assembly adapted to deliver
electrical energy to tissue, comprising: an elongate device; and an
expandable portion comprising an inflatable element, a single
helical electrode disposed on the inflatable element, and at least
one irrigation aperture within the inflatable element, the
inflatable element secured to the elongate device, the single
helical electrode making between about 0.5 and about 1.5
revolutions around the inflatable element, and the at least one
irrigation aperture adapted to allow fluid to flow from within the
inflatable element to outside the inflatable element.
2. The assembly of claim 1 wherein the single helical electrode
makes between about 1 and about 1.25 revolutions around the
inflatable element.
3. The assembly of claim 1 further comprising a conductive material
disposed on the elongate device proximal to the expandable portion
to electrically couple the single helical electrode to an
electrical energy source.
4. The assembly of claim 3 wherein the conductive material is
disposed on substantially the entire elongate device proximal to
the expandable portion.
5. The assembly of claim 3 further comprising an insulation
material disposed on substantially all of the conductive material
on the elongate device.
6-7. (canceled)
8. The assembly of claim 1 wherein the expandable portion comprises
a proximal transition section covered with a conductive material
that electrically couples the helical electrode and the conductive
material on the elongate device.
9. The assembly of claim 8 further comprising an insulation
material disposed on the conductive material on the transition
shaped section.
10. The assembly of claim 1 wherein the inflatable element is a
balloon with a substantially cylindrical section, the single
helical electrode disposed on the substantially cylindrical
section.
11. The assembly of claim 1 wherein the at least one irrigation
aperture is in the inflatable element.
12. The assembly of claim 11 wherein the at least one irrigation
apertures is in the helical electrode.
13. The assembly of claim 11 wherein the at least one irrigation
aperture is not in the helical electrode.
14. The assembly of claim 11 wherein the at least one irrigation
aperture is adjacent the helical electrode.
15-27. (canceled)
28. A method of manufacturing an expandable energy delivery
assembly adapted to deliver energy to tissue, comprising: providing
an inflatable element secured to an elongate device; inflating the
inflatable element; and depositing a conductive material on an
exterior surface of the inflatable element to form a single helical
electrode making between about 0.5 and about 1.5 revolutions around
the inflatable element.
29. The method of claim 28 wherein depositing comprises one
selected from the group consisting of vapor deposition,
electroplating, electroless plating, pad printing, spraying, and
ink jet.
30. The method of claim 28 further comprising applying a mask to
the inflatable element before the depositing step.
31-32. (canceled)
33. The method of claim 30 further comprising removing the mask,
applying a second mask over the helical electrode, and depositing
an insulation material over substantially all of the elongate
device proximal to the inflatable element.
34. The method of claim 33 wherein depositing the insulation
material comprises depositing the insulation material over a
transition section of the inflatable element.
35. The method of claim 33 wherein applying the second mask
comprises applying the second mask over an entire intermediate
section of the inflatable element.
36-73. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of priority to
U.S. Provisional Application Ser. No. 61/541,765, filed on Sep. 30,
2011, and to U.S. Provisional Application Ser. No. 61/593,147,
filed on Jan. 31, 2012, with the entire contents of each of these
applications incorporated herein by reference. This application is
also related to and incorporates by reference herein the complete
disclosures of the following patent applications: U.S. Provisional
Pat. App. No. 61/113,228, filed Dec. 11, 2008; U.S. Provisional
Pat. App. No. 61/160,204, filed Mar. 13, 2009; U.S. Provisional
Pat. App. No. 61/179,654, filed May 19, 2009; U.S. Pat. App. Pub.
No. 2010/0204560, filed Nov. 11, 2009; U.S. Provisional Pat. App.
No. 61/334,154, filed May 12, 2010; and U.S. patent application
Ser. No. 13/106,658, filed May 12, 2011.
INCORPORATION BY REFERENCE
[0002] All publications and patent applications mentioned in this
specification are herein incorporated by reference to the same
extent as if each individual publication or patent application was
specifically and individually indicated to be incorporated by
reference.
TECHNICAL FIELD
[0003] The present disclosure relates generally to medical devices
and methods and more particularly to devices and methods for
applying radiofrequency energy to tissue.
BACKGROUND
[0004] Some medical treatment procedures involve the disruption of
a region of tissue. For example, medical treatment procedures
include the delivery of energy to disrupt a region of tissue.
Radiofrequency ("RF") energy devices are an example of devices that
can be used to perform such medical treatments.
[0005] Some RF energy devices have a single RF energy element or a
plurality of discrete RF energy elements that have to be repeatedly
moved within the subject in order to apply sufficient RF energy to
the entire region of the tissue. Such RF energy devices may need to
be moved within a patient during a given procedure, which can
increase the complexity, time, and energy required to perform a
given procedure.
SUMMARY
[0006] This description may use the phrases "in an embodiment," "in
embodiments," "in some embodiments," or "in other embodiments,"
which may each refer to one or more of the same or different
embodiments in accordance with the present disclosure. For the
purposes of this description, a phrase in the form "A/B" means A or
B. For the purposes of the description, a phrase in the form "A
and/or B" means "(A), (B), or (A and B)". For the purposes of this
description, a phrase in the form "at least one of A, B, or C"
means "(A), (B), (C), (A and B), (A and C), (B and C), or (A, B and
C)".
[0007] As used herein, the terms proximal and distal refer to a
direction or a position along a longitudinal axis of a catheter or
medical instrument. The term "proximal" refers to the end of the
catheter or medical instrument closer to the operator, while the
term "distal" refers to the end of the catheter or medical
instrument closer to the patient. For example, a first point is
proximal to a second point if it is closer to the operator end of
the catheter or medical instrument than the second point. The
measurement term "French", abbreviated Fr or F, is defined as three
times the diameter of a device as measured in mm. Thus, a 3 mm
diameter catheter is 9 French in diameter. The term "operator"
refers to any medical professional (i.e., doctor, surgeon, nurse,
or the like) performing a medical procedure involving the use of
aspects of the present disclosure described herein.
[0008] In an aspect of the present disclosure, an expandable energy
delivery assembly adapted to deliver electrical energy to tissue is
provided. The assembly includes an elongate device and an
expandable portion. The expandable portion includes an inflatable
element, a single helical electrode disposed on the inflatable
element, and at least one irrigation aperture within the inflatable
element. The inflatable element is secured to the elongate device
and the single helical electrode makes between about 0.5 and about
1.5 revolutions around the inflatable element. The at least one
irrigation aperture is adapted to allow fluid to flow from within
the inflatable element to outside the inflatable element.
[0009] The single helical electrode may make between about 1 and
about 1.25 revolutions around the inflatable element.
[0010] A conductive material may be disposed on the elongate device
proximal to the expandable portion to electrically couple the
single helical electrode to an electrical energy source, wherein
the conductive material is disposed on substantially the entire
elongate device proximal to the expandable portion. An insulation
material may be disposed on substantially all of the conductive
material on the elongate device.
[0011] The conductive material and the single helical electrode may
form a unitary conductive material without an electrical junction.
The conductive material and the helical electrode may be an
elastomeric ink.
[0012] The expandable portion may include a proximal transition
section covered with a conductive material that electrically
couples the helical electrode and the conductive material on the
elongate device. An insulation material may be disposed on the
conductive material on the transition shaped section.
[0013] The inflatable element is a balloon with a substantially
cylindrical section, where the single helical electrode is disposed
on the substantially cylindrical section. Additionally or
alternatively, the at least one irrigation aperture is in the
inflatable element, in the helical electrode, and/or adjacent the
helical electrode.
[0014] In certain embodiments, the elongate device includes an
irrigation lumen therein and an irrigation port therein. The
irrigation port can be disposed within the inflatable element and
can provide fluid communication between the irrigation lumen and
the interior of the inflatable element.
[0015] In another aspect of the present disclosure, an expandable
energy delivery assembly adapted to deliver energy to tissue is
provided. The assembly includes an elongate device and an
expandable element secured thereto. The assembly also includes a
unitary conductive material disposed on substantially all of the
elongate device proximal to the expandable element and on a portion
of the expandable element. The unitary conductor being void of an
electrical junction.
[0016] The expandable element may be an inflatable balloon. In some
embodiments, the conductive material on the expandable element
forms a single helix. The expandable element can include a
transition portion with the conductive material also being disposed
on the transition portion. An insulation material may be disposed
over substantially all of the conductive material on the elongate
device proximal to the expandable element. The transition portion
may include a conically-shaped portion.
[0017] In yet another aspect of the present disclosure, an
expandable energy delivery assembly adapted to deliver energy to
tissue is provided that includes an elongate device comprising an
irrigation lumen therethrough and an irrigation port proximal to a
distal end of the elongate device. An inflatable element is secured
to the elongate device such that the irrigation port is disposed
within a fluid chamber defined by the inflatable element. An
electrode is disposed on the inflatable element and at least one
irrigation aperture is provided and adapted to allow fluid to pass
from within the fluid chamber to outside the inflatable element.
The irrigation aperture is sized to maintain a pressure within the
inflatable element between about 0.5 atm and about 4 atm when a
substantially constant irrigation flow rate is between about 5
mL/min and about 15 mL/min.
[0018] The assembly may also include a temperature sensor adapted
to measure fluid temperature and may further include an energy
source and a controller, the controller being adapted to
automatically turn off the energy source if a sensed fluid
temperature is above a threshold limit. The temperature sensor can
be disposed within the inflatable element.
[0019] In some embodiments, the assembly includes a flow rate
sensor adapted to sense fluid flow rate and may further include an
energy source and a controller, the controller being adapted to
automatically turn off the energy source if a sensed flow rate
falls below a minimum value.
[0020] The assembly may include a pressure sensor adapted to sense
fluid pressure and may further include an energy source and a
controller, the controller being adapted to automatically turn off
the energy source if a sensed pressure falls below a minimum
value.
[0021] In yet another aspect of the present disclosure, a method of
manufacturing an expandable energy delivery assembly adapted to
deliver energy to tissue is provided. The method includes:
providing an inflatable element secured to an elongate device;
inflating the inflatable element; and depositing a conductive
material on an exterior surface of the inflatable element to form a
single helical electrode making between about 0.5 and about 1.5
revolutions around the inflatable element.
[0022] Depositing may include vapor deposition, electroplating,
electroless plating, pad printing, spraying, or ink jet. A mask may
be applied to the inflatable element before the depositing step. In
some embodiments, the depositing step includes depositing the
conductive material on substantially all of the elongate device
proximal to the inflatable device and on the inflatable element,
forming a unitary conductor. The depositing step may also include
depositing the conductive material on a conical section of the
inflatable element.
[0023] In some embodiments, the mask is removed, a second mask is
applied over the helical electrode, and an insulation material is
deposited over substantially all of the elongate device proximal to
the inflatable element. Depositing the insulation material can
include depositing the insulation material over a transition
section of the inflatable element. Additionally or alternatively,
applying the second mask can include applying the second mask over
an entire intermediate section of the inflatable element.
[0024] In yet another aspect of the present disclosure, a method of
manufacturing an expandable energy delivery assembly adapted to
deliver energy to tissue is provided that includes: providing an
inflatable element secured to an elongate device; inflating the
inflatable element; and depositing a conductive material on the
elongate device and a portion of the inflatable element in a single
depositing step to form a unitary conductor without an electrical
junction.
[0025] The depositing step may include depositing the conductive
material on substantially the entire elongate device proximal to
the inflatable element. Additionally or alternatively, depositing
may include depositing the conductive material in a helical pattern
on the inflatable element.
[0026] A mask may be applied over the inflatable element. In
certain embodiments, the depositing step also includes depositing
the conductive material over a transition section of the inflatable
element.
[0027] An insulation layer is deposited over the conductive
material on the elongate device.
[0028] The depositing step may include depositing an elastomeric
conductive material on the elongate device and a portion of the
inflatable element in a single depositing step to form an
elastomeric unitary conductor.
[0029] In some embodiments, depositing the conductive material
includes depositing the conductive material using vapor deposition,
electroplating, electroless plating, pad printing and spraying, or
ink jet.
[0030] In yet another aspect of the present disclosure, a method of
providing an irrigation fluid to an inflatable medical device
includes: providing an elongate device with an inflatable element
secured thereto, the inflatable element defining a fluid chamber
and comprising at least one irrigation aperture therein to allow a
fluid to flow through the inflatable element, the elongate device
comprising an irrigation lumen extending therethrough that provides
fluid communication to the inflatable chamber; continuously flowing
the fluid at a substantially constant flow rate between about 5
mL/min and about 15 mL/min from a fluid source and into the
irrigation lumen while allowing fluid to flow out of the fluid
chamber through the at least one irrigation aperture; and
maintaining a fluid pressure within the inflatable element between
about 0.5 atm and about 4 atm.
[0031] In yet another aspect of the present disclosure, a method of
providing an irrigation fluid to an inflatable medical device
includes: providing an elongate device with an inflatable element
secured thereto, the inflatable element defining a fluid chamber
and comprising at least one irrigation aperture therein to allow a
fluid to flow through the inflatable element, the elongate device
comprising an irrigation lumen extending therethrough that provides
fluid communication to the inflatable chamber; and maintaining a
substantially constant pressure between about 0.5 atm and about 4
atm within the inflatable element sufficient to maintain a flow
rate of between about 5 mL/min and about 15 mL/min through the
inflatable element and out of at least one irrigation aperture
[0032] In some embodiments, these methods include delivering RF
energy to tissue via an energy element disposed on the inflatable
element. Additionally or alternatively, a temperature of the fluid
may be sensed such that, for example, the delivery of RF energy can
be stopped if the sensed temperature is above a threshold
temperature. The delivery of RF energy may be stopped if the
pressure within the inflatable element falls outside of a control
range and/or if the flow through the inflatable element falls
outside of a control range. The RF energy may be delivered through
a unitary conductor comprising an electrode that may be, for
example, a helically-configured electrode.
[0033] In certain embodiments, these methods include endovascularly
disposing the inflatable element in a renal artery, applying RF
energy through an electrode on the inflatable element to renal
nerves to disrupt transmission of neural signals along the renal
nerves to treat hypertension.
[0034] In yet another aspect of the present disclosure, a method of
delivering RF energy to tissue includes: providing an elongate
device with an inflatable element secured thereto, the inflatable
element defining a fluid chamber and comprising at least one
irrigation aperture therein to allow the fluid to flow through the
inflatable element, the elongate device comprising an irrigation
lumen extending therethrough that provides fluid communication to
the inflatable chamber from a fluid source; continuously flowing a
fluid at a substantially constant flow rate from the fluid source;
sensing a temperature of the fluid; automatically stopping the
delivery of RF energy to an electrode on the inflatable element if
the sensed fluid temperature is above a threshold temperature.
[0035] Sensing a temperature of the fluid may include sensing a
temperature of the fluid within the fluid chamber. Delivery of RF
energy to an electrode on the inflatable element can be
automatically stopped if the sensed fluid temperature is above
about 60 degrees C.
[0036] In some embodiments, the method further includes
endovascularly positioning the inflatable element within a renal
artery, and RF energy is applied through the electrode on the
inflatable element to renal nerves to disrupt transmission of
neural signals along the renal nerves to treat hypertension. The RF
energy may be delivered through a unitary conductor including an
electrode that may be, for example, a helically-configured
electrode.
[0037] In yet another aspect of the present disclosure, a method of
treating hypertension is provided that includes: delivering RF
energy from a helically-configured electrode disposed on an
inflated element within a renal artery into a renal nerve to
disrupt renal nerve transmission to treat hypertension; and
substantially continuously flowing fluid through the inflated
element to cool tissue adjacent the helically-configured
electrode.
[0038] In yet another aspect of the present disclosure, a method of
treating hypertension is provided that includes: positioning a
unitary conductor comprising a helically-configured electrode
disposed on an inflated element within a renal artery; delivering
RF energy from the electrode and into a renal nerve to disrupt
renal nerve transmission to treat hypertension; and flowing fluid
through the inflated element to cool tissue adjacent the
helically-configured electrode.
[0039] In yet another aspect of the present disclosure, an RF
delivery device adapted to treat hypertension includes an
expandable element secured to an elongate device and a unitary
conductor disposed on a portion of the elongate device and a
portion of the inflatable element. An insulation material is
disposed on a portion of the unitary conductor, thereby forming a
helically-configured electrode disposed on the expandable element.
The expandable element includes a plurality of apertures
therein.
[0040] In yet another aspect of the present disclosure, an
expandable energy delivery assembly adapted to deliver electrical
energy to tissue includes an elongate device and an expandable
portion. The expandable portion includes an inflatable element, a
first helical electrode disposed on the inflatable element, a
second helical electrode disposed on the inflatable element and at
least one irrigation aperture within the inflatable element. The
inflatable element is secured to the elongate device, the first
helical electrode makes between about 0.5 and about 1.5 revolutions
around the inflatable element, the second helical electrode makes
between about 0.5 and about 1.5 revolutions around the inflatable
element, and the at least one irrigation aperture allows fluid to
flow from within the inflatable element to outside the inflatable
element.
[0041] In certain embodiments, the first helical electrode and the
second helical electrode may be configured to operate in a bipolar
mode or the first helical electrode or the second helical electrode
may be configured to operate in a monopolar mode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] FIGS. 1A, 1B, and 2 illustrate a portion of an energy
delivery device comprising a helical electrode on an expandable
element according to an embodiment of the present disclosure;
[0043] FIGS. 3A and 3B show a portion of an elongate device
according to an embodiment of the present disclosure;
[0044] FIG. 4 shows a portion of an energy delivery device
comprising a temperature sensor according to an embodiment of the
present disclosure;
[0045] FIG. 5 illustrates a portion of an energy delivery device
wherein portions of a helical electrode are covered with an
insulation material according to an embodiment of the present
disclosure;
[0046] FIG. 6 illustrates an system for delivering energy to tissue
according to an embodiment of the present disclosure;
[0047] FIG. 7 illustrates a cross section of an energy delivery
device with a helical electrode in use within a renal artery
according to an embodiment of the present disclosure;
[0048] FIGS. 8 and 9 illustrate a portion of an energy delivery
device wherein energy is delivered to renal nerves through
conductive fluid to the tissue according to an embodiment of the
present disclosure;
[0049] FIG. 10 is a photograph showing tissue ablation in a general
helical pattern caused by an energy delivery device with a helical
electrode according to an embodiment of the present disclosure;
[0050] FIGS. 11A-11H illustrate a method of manufacturing an energy
delivery device with a helical electrode on an expandable element
according to an embodiment of the present disclosure;
[0051] FIG. 12 represents an embodiment of a system similar to that
of FIG. 6 represented by the resistances of the various elements
according to an embodiment of the present disclosure;
[0052] FIG. 13 illustrates an alternative configuration in which a
capacitor, inductor, or both may be incorporated in the circuit
from FIG. 12;
[0053] FIGS. 14 and 15 illustrate an embodiment of a pressure
sensor according to an embodiment of the present disclosure;
and
[0054] FIG. 16 illustrates a portion of an energy delivery device
including a helical electrode pair on an expandable element
according to another embodiment of the present disclosure.
DETAILED DESCRIPTION
[0055] Particular embodiments of the present disclosure are
described hereinbelow with reference to the accompanying drawings;
however, the disclosed embodiments are merely examples of the
disclosure and may be embodied in various forms. Like reference
numerals may refer to similar or identical elements throughout the
description of the figures.
[0056] One aspect of the disclosure is a RF delivery device that is
adapted to deliver RF energy to tissue. FIG. 1A illustrates a side
view of a distal region of RF delivery device 10. Device 10 has
proximal region 2, intermediate region 4, and distal region 6.
Device 10 includes an elongate portion 12 and expandable portion 14
(shown in an expanded configuration) disposed on a distal region of
elongate portion 12. Expandable portion 14 includes inflatable
element 16 on which conductive material 18 is disposed.
[0057] FIG. 1B illustrates a perspective view of the portion of the
device shown in FIG. 1A, with a rectangular section of inflatable
element 16 removed to illustrate elongate portion 12 disposed
inside inflatable element 16.
[0058] FIG. 2 shows a sectional view of the portion of the device
shown in FIG. 1A. Expandable portion 14 includes a proximal
transition section 20, intermediate section 22, and distal
transition section 24. Proximal transition section 20 and distal
transition section 24 are shown with conical configurations
extending towards elongate portion 12 but are not limited to this
configuration. Intermediate section 22 is substantially
cylindrically-shaped when inflatable element 16 is in the expanded
configuration shown in FIGS. 1A, 1B, and 2. The proximal end of
inflatable element 16 and the distal end of inflatable element 16
are secured to catheter 26, which is part of elongate portion
12.
[0059] Conductive material 18 is disposed on catheter 26 proximal
to the expandable portion 14, and it is also disposed on the
cylindrical section of inflatable element 16 in a helical pattern
forming a helical electrode 19 as shown. In proximal region 2 and
in proximal section 20 of the expandable portion, insulation
material 34 is disposed on the layer of conductive material 18. In
the cylindrical intermediate section 22 of expandable portion 14,
insulation material 34 is not disposed on the helical electrode,
allowing energy to be delivered to tissue through conductive
material 18. In the proximal region 2 of the device, and in
proximal section 20 of expandable portion 14, conductive material
18 is covered with a layer of insulation, and thus energy is not
applied to tissue in those areas. The conductive material that is
not covered by dielectric material on the distal portion of the
system is considered an electrode. The conductive material and the
electrode are in this embodiment the same material.
[0060] The conductive material 18 is disposed on substantially the
entire catheter 26 in proximal region 2 of the device.
"Substantially the entire," or "substantially all," or derivatives
thereof as used herein include the entire surface of catheter 26,
but also includes most of the surface of the catheter. For example,
if a few inches of the proximal end of catheter 26 are not covered
with conductive material, conductive material is still considered
to be disposed on substantially all of the catheter. The conductive
material 18 and insulation material 34 extend 360 degrees around
the catheter shaft, as opposed to only covering discrete lateral
sections of the catheter. Alternatively, in some embodiments the
conductor covers only a portion of the lateral surface of the
catheter shaft. The conductive material and insulation material may
cover the entirety or only a portion of the proximal transition
section of the expandable portion. The insulation will typically
cover the entirety of the conductive material in this region. The
conductive material and insulation material could, however, also be
disposed on the distal section 24 of expandable portion 14.
[0061] In some embodiments the helical electrode makes about 0.5
revolutions to about 1.5 revolutions around the inflatable element.
The number of revolutions is measured over the length of the
helical electrode. The electrode may extend from the proximal
transition section to the distal transition section (as shown in
FIG. 2), but the electrode may extend over any section of the
inflatable element. For example, the proximal end of the electrode
may be disposed distal to the proximal transition section, and the
distal end of the electrode may be proximal to the distal
transition section.
[0062] One revolution traverses 360 degrees around the longitudinal
axis of the expandable element. One revolution of the electrode,
along an end-view of inflatable device, forms a circle, although
depending on the cross sectional shape of the expandable element,
the electrode can form any variety of shapes in an end-view. An
electrode making 0.5 revolutions therefore traverses one half of
360 degrees, or 180 degrees. An electrode making 0.5 revolutions
has distal and proximal ends that are on opposite sides of the
balloon. In an end-view of the inflatable element with a circular
cross section, an electrode making 0.5 revolutions has a
semi-circular, or C, shape.
[0063] The proximal end of the electrode can be disposed anywhere
on the expandable element and the distal end of the electrode can
be anywhere on the expandable element, as long as the proximal end
is proximal to the distal end. In some embodiments, the proximal
end of the electrode is at the boundary between the proximal
transition section and the cylindrical intermediate section of the
expandable element, and the distal end of the electrode is at the
boundary between the distal transition section and the cylindrical
intermediate section. In other embodiments the proximal end of the
electrode is disposed distal to the boundary between the proximal
intermediate section and the cylindrical intermediate section of
the expandable element, and the distal end is proximal to the
boundary between the distal transition section and the central
intermediate section of the expandable element. In these other
embodiments the electrode is considered to extend along a subset of
the length of the central intermediate section of the expandable
element. In the embodiment shown in FIG. 1B, the electrode makes
about 1 revolution around the inflatable element. In some
embodiments the electrode makes about 0.5 revolutions around the
inflatable element. In some embodiments the electrode makes about
0.75 revolutions around the inflatable element. In some embodiments
the electrode makes about 1 revolution around the inflatable
element. In some embodiments the electrode makes about 1.25
revolutions around the inflatable element. In some embodiments the
electrode makes about 1.5 revolutions around the inflatable
element.
[0064] The device is adapted to be coupled to an RF generator,
which supplies RF current through the conductive material 18 on
catheter 26 and inflatable element 16. In this manner RE current
can be delivered to the desired tissue. Energy is thus applied to
tissue in the configuration of the conductive material on the
intermediate section 22 of the expandable portion 14, which in this
embodiment is a helical, or spiral, configuration.
[0065] Within the expandable portion, catheter 26 is not covered
with conductive material or insulation material. Catheter 26
includes guide element lumen 36 and inflation lumen 28, also
referred to herein as irrigation lumen, extending therethrough.
Guide element lumen 36 extends from the proximal end of the device
(not shown) to the distal end. Irrigation lumen 28 extends from the
proximal end of catheter 26 (not shown) to a location within
inflatable element 16. Irrigation port 30 is located inside
inflatable element 16 and is in between proximal and distal ends of
irrigation lumen 28. Irrigation lumen 28 and irrigation port 30
provide for fluid communication between the irrigation lumen and
the interior of inflatable element 16. FIGS. 3A and 3B illustrate
additional views of guide element lumen 36, irrigation lumen 28,
and irrigation port 30. In some embodiments catheter 26 ranges in
size from 2 to 8 French, and in some embodiments is 4 Fr. In some
embodiments the guide wire lumen is between 1 and 4 Fr and in some
embodiments is 2.5 Fr.
[0066] Expandable portion 14 includes one or more irrigation
apertures 38 to allow irrigation fluid to pass from inside
inflatable element 16 to outside inflatable element 16. The
irrigation apertures can be formed only in the electrode section of
expandable portion 14 (see, for example, FIG. 1A), only in the
non-electrode section of inflatable portion 14, or in both the
electrode section and in the non-electrode section. The irrigation
fluid is adapted to cool the conductive material 18 and/or tissue.
The apertures allow for fluid to flow out of the balloon, allowing
either a continuous or non-continuous supply of fluid from a fluid
reservoir, through the lumen, and into the balloon. The irrigation
fluid is in some embodiments cooled prior to delivery.
[0067] FIG. 4 illustrates a portion of an embodiment of a RF
delivery device. Delivery device 110 is similar to the RF delivery
device shown in FIGS. 1-3. Device 110 includes catheter shaft 126
covered with conductive material 118, upon which insulation
material 134 is disposed. Insulation material 134 is also disposed
on the proximal transition section of the expandable portion 114,
similar to the embodiment shown in FIGS. 1-3. The inflatable
element also has conductive material 118 disposed on the inflatable
element in the form of a helical electrode. Catheter 126 has
guiding element lumen 136 and irrigation lumen 128 therein. Device
110 also includes at least one marker 127 disposed on catheter 126
such that the marker is within expandable portion 114 (shown as a
balloon). Device 110 also includes irrigation port 130 in fluid
communication with irrigation lumen 134. Device 110 also includes
temperature sensor 129, such as a thermocouple, a resistance
temperature detector, or a thermistor, that is electrically coupled
from the proximal end of the device (not shown) through irrigation
lumen 128, out of irrigation port 130, and is secured at its distal
region to catheter 126. The temperature sensor could alternatively
be disposed on the inner or outer surface of inflatable element
116. In some embodiments marker 127 is a radio opaque marker
comprised of Pt, PtIr, or other suitable radio opaque material. In
some embodiments the marker may also comprise features viewable
under fluoroscopy that allow for the visualization of the
rotational orientation of the marker, and therefore the expandable
section. This allows the physician to note the location of and/or
realign the expandable element and helical electrode as necessary
within the renal artery.
[0068] The irrigation fluid is adapted to cool the electrode on the
inflatable element. The irrigation fluid cools the RF electrode as
it flows within the inflatable element and after it passes through
the apertures as it flows across the outer surface of the
inflatable element. Temperature sensor 129 is adapted to sense the
temperature of the fluid within inflatable element 116. The signal
from the temperature sensor may be used in a feedback control
mechanism to control the flow of fluid from a fluid reservoir (now
shown) into the inflatable element. Alternatively, the irrigation
fluid may be delivered at a substantially constant rate and the
signal from the temperature sensor used as signal to automatically
shut off the RF generator if the sensed fluid temperature is above
a threshold limit, thereby terminating that portion of the
procedure. Such a condition is considered a fault and after
identification and resolution of a fault, a procedure may be
restarted. FIG. 5 illustrates a delivery device in which portions
of the helical conductor have been covered by insulation material
734, forming a plurality of discrete circularly-shaped windows
surrounding apertures 717 on electrical conductor 718. In this
fashion a single conductor can be used to create a number of
discrete burn zones following a helical path along and around a
vessel wall.
[0069] One aspect of the disclosure is a system to delivery RF
energy to treatment tissue. FIG. 6 illustrates a system 300 adapted
to deliver RF energy to treatment tissue. System 300 includes RF
energy delivery device 302, which can comprise any of the RF energy
delivery devices described herein. Delivery device 302 is shown
including inflatable element 316, helical energy delivery element
319, irrigation apertures 330, guidewire 310, and elongate member
312. System 300 also includes external housing 320, which includes
display 322 and controller 324. Housing includes connector 336,
which is adapted to connect to instrument interface cable 314.
System 300 also includes fluid reservoir 326, which is in fluid
communication with delivery device 302 via irrigation line 328. The
system also includes fluid pump 331, optional pressure sensor 332,
and optional bubble sensor 334. System 300 also includes a
grounding plate or set of grounding plates 340 interfaced to
controller 324 via connector 346.
[0070] An embodiment of pressure sensor 332 from the system in FIG.
6 is shown in FIGS. 14 and 15. Pressure sensor 332 includes a
housing, which comprises capture portion 335 and a force sensor
333. Capture portion 335 is configured to substantially surround
irrigation tube 328. Additionally, capture portion 335 captures
tubing 328 such that a portion of the wall of irrigation tube 328
is compressed against force sensor 333. The force experienced by
the force sensor is then a function of the force associated by the
compression of the irrigation tube and the pressure within the
irrigation tube. In operation, a measurement is made under a no
flow condition that describes the offset associated with the
compression of the irrigation tube. This offset measurement is made
prior to the initiation of a procedure and may be repeated at the
beginning of each power cycle. This value is then used as an offset
for subsequent measurements made under flow conditions. A
force/pressure calibration per tubing type or per tube is then used
to convert the force signal to a pressure value.
[0071] The disclosure includes methods of using any of the RF
delivery devices and systems herein. In some embodiments the
devices and/or systems are used to treat hypertension by disrupting
the transmission within renal nerves adjacent one or both renal
arteries.
[0072] The present methods control renal neuromodulation via
thermal heating mechanisms. Many embodiments of such methods and
systems may reduce renal sympathetic nerve activity.
Thermally-induced neuromodulation may be achieved by heating
structures associated with renal neural activity via an apparatus
positioned proximate to target neural fibers. Thermally-induced
neuromodulation can be achieved by applying thermal stress to
neural structures through heating for influencing or altering these
structures. Additionally or alternatively, the thermal
neuromodulation can be due to, at least in part, alteration of
vascular structures such as arteries, arterioles, capillaries, or
veins that perfuse the target neural fibers or surrounding
tissue.
[0073] Thermal heating mechanisms for neuromodulation include both
thermal ablation and non-ablative thermal alteration or damage
(e.g., via sustained heating or resistive heating). Thermal heating
mechanisms may include raising the temperature of target neural
fibers above a desired threshold to achieve non-ablative thermal
alteration, or above a higher temperature to achieve ablative
thermal alteration. For example, the target temperature can be
above body temperature (e.g., approximately 37 degrees C.) but less
than about 45 degrees C. for non-ablative thermal alteration, or
the target temperature can be about 45 degrees C. or higher for the
ablative thermal alteration.
[0074] The length of exposure to thermal stimuli may be specified
to affect an extent or degree of efficacy of the thermal
neuromodulation. For example, the duration of exposure can be as
short as about 5, about 10, about 15, about 20, about 25, or about
30 seconds, or could be longer, such as about 1 minute, or even
longer, such as about 2 minutes. In other embodiments, the exposure
can be intermittent or continuous to achieve the desired
result.
[0075] In some embodiments, thermally-induced renal neuromodulation
may be achieved via generation and/or application of thermal energy
to the target neural fibers, such as through application of a
"thermal" energy field, including, electromagnetic energy,
radiofrequency, ultrasound (including high-intensity focused
ultrasound), microwave, light energy (including laser, infrared and
near-infrared) etc., to the target neural fibers. For example,
thermally-induced renal neuromodulation may be achieved via
delivery of a pulsed or continuous thermal energy field to the
target neural fibers. The energy field can be sufficient magnitude
and/or duration to thermally induce the neuromodulation in the
target fibers (e.g., to heat or thermally ablate or necrose the
fibers). As described herein, additional and/or alternative methods
and systems can also be used for thermally-induced renal
neuromodulation.
[0076] The energy field thermally modulates the activity along
neural fibers that contribute to renal function via heating. In
several embodiments, the thermal modulation at least partially
denervates the kidney innervated by the neural fibers via heating.
This may be achieved, for example, via thermal ablation or
non-ablative alteration of the target neural fibers.
[0077] In some uses in which RF energy is used to ablate the renal
nerve, the RF delivery device is first positioned within one or
more renal arteries and RF energy is delivered into renal nerves to
disrupt the nerve transmission sufficiently to treat hypertension.
The disruption pattern within the artery preferably extends
substantially 360 degrees around the artery. Electrodes that treat
tissue falling diametrically in a single plane normal or oblique to
the longitudinal axis of the vessel have been shown to increase the
risk of stenosing a vessel treated with RF energy. Spiral, or
helical, patterns as described herein create patterns of treated
tissue for which the projection along the longitudinal axis is
circular and therefore have a high probability of treating any
renal nerve passing along the periphery of the renal artery. The
patterns, however, have minimal risk of creating a stenosis.
Previous attempts have used a point electrode at a distal end or
distal region of a device. In these attempts, the electrode is
disposed in the renal artery followed by RF energy delivery. To
disrupt renal nerve tissue in a non circumferential pattern using a
point electrode, the device is first positioned within the renal
artery adjacent arterial tissue. RF energy is then delivered to
disrupt a region of renal nerve. The device must then be moved
axially (distally or proximally) and rotated, followed by
additional RF delivery. The movement and RF delivery is repeated in
a pattern until the renal nerves have been sufficiently disrupted.
The repeated movements are time consuming and increase the
complexity of the overall process for the physician. During an
emergency situation the physician may lose track of the position
and sequence of previous burns thereby jeopardizing the likelihood
of creating a pattern sufficient to treat the neural tissue or be
forced to increase the number of burns thereby over-treating the
patient.
[0078] Utilizing a single helical electrode as described herein
provides procedural improvements over previous attempts. By using
an electrode with the configuration of the desired treatment
region, the device need not be moved to disrupt tissue in a desired
treatment configuration. In particular the device need not be moved
axially or rotated to treat an entire renal nerve treatment region.
This reduces the overall time of the treatment. Additionally, this
allows energy to be delivered to a desired treatment region in a
variety of patients with much greater predictability. Additionally,
if markers are used that allow for rotational alignment, the device
may be moved and/or removed and then replaced and realigned,
allowing the procedure to be restarted at a later time.
[0079] A method of using an RF delivery device to treat
hypertension is shown in FIG. 7, and will be described using the
device in FIG. 4 and the system shown in FIG. 6. The methods
described herein can be carried out by other systems and by other
RF delivery devices, such as the RF devices described herein.
[0080] The RF delivery device is positioned in a renal artery using
a percutaneous access through a femoral artery. The expandable
portion is delivered into the renal artery in a collapsed
configuration (not shown). Once the expandable portion is in
position, fluid from fluid reservoir 326 is pumped in an open loop
control configuration, under constant flow, through irrigation line
328 and into inflatable element 116 by pump 330. Fluid flow into
inflatable element 116 causes inflatable element 116 to expand.
Device 110 in FIG. 7 is in a delivered, or expanded, configuration
within renal artery 1000. The tunica intima 1001 is surrounded by
the tunica media 1002, which is in turn surrounded by adventitial
tissue 1003. Tissue renal nerves 1004 are shown within the
adventitial, and some renal nerves not shown will be found within
the tunica media.
[0081] The fluid continually passes through apertures 138 in the
expandable portion as it is replaced with new fluid from fluid
reservoir 326. Once fully expanded, the conductive material 118 on
the inflatable element fully assumes the helical configuration, as
shown in FIGS. 4 and 7. RF energy is then delivered to the helical
electrode on the inflatable element. Control unit 324 controls the
parameters of the RF alternating current being delivered through
the conductive material on the catheter and the helical electrode
on the inflatable element.
[0082] In general, the RF signal characteristics are chosen to
apply energy to depths at which the renal nerves are disposed to
effectively ablate the renal nerves. In general, the power is
selected to ablate a majority of the renal nerves adjacent to where
the device is positioned within the renal nerve. In some
embodiments the tissue is ablated to a depth of between about 3 mm
to about 7 mm from the tissue closest to the device in the renal
artery.
[0083] The RF signal can have the following characteristics, but
these are not intended to be limiting: the frequency is between
about 400 KHz to about 500 KHz and is a sine wave; the power is
between about 30 W to about 80 W, the voltage is between about 40 v
and about 80 v; and the signal is an intermittent signal.
[0084] Tissue treated by the RF energy via the helical electrode
comprised is shown as regions 1005, delineated by a dashed line. As
illustrated, a region of treated tissue 1005 adjacent to the cut
away section of conductor 118 includes nerve 1004. The device is
shown being used in monopolar mode with a return electrode 340
positioned somewhere on the patient's skin.
[0085] Control unit 324 controls the operation of pump 330 and
therefore controls the flow rate of the fluid from reservoir into
the inflatable element. In some embodiments the pump is
continuously pumping at constant flow rate such that the flow is
continuous from the reservoir, as is illustrated in FIG. 7. In some
embodiments the pump is operated in an open loop constant flow
configuration where pump rate is not adjusted as a function of any
control parameter other than an over-pressure condition sensed by
pressure sensor 332, in which case RF power delivery is terminated,
the pump is turned off, and an over-pressure condition reported to
the operator. The pump is typically operated for a period of time
which encompasses the delivery of the RF energy and turned off
shortly after the conclusion of the procedure or if the pressure
sensor senses an undesirable condition, discussed herein.
[0086] The irrigation fluid is delivered from the pump through
irrigation line 328 to irrigation lumen 128 to irrigation port 130
into the inflatable element 116, and then out of the inflatable
element through irrigation apertures 138. The pressure measured at
the pressure sensor is driven by flow rate and the series sum of
the fluid resistance of all of the elements in the fluid path. The
choice of fluid flow rate is driven by the required cooling rate
and limited by the amount of irrigant fluid that can be tolerated
by the patient which is delivered during the sum of treatments
cycles. The system is designed such that at the desired fluid flow
there is a defined operating pressure within the inflatable
element. An optimal inflatable element inflation pressure is a
pressure that is sufficient to completely inflate the inflatable
element such that the RF electrode engages the treatment tissue.
The operating pressure within the inflatable element will be driven
by the fluid flow, the number of apertures, and their cross
sections. The distribution, number, and cross section of the
irrigation apertures will be driven by the flow rate, the
configuration of the electrode, the intended operating pressure,
and the maximum desired exit velocity for the irrigation fluid. If
the number of apertures is too small and the distribution too
sparse some areas of the surface will not receive appropriate
irrigation and thereby be subject to overheating and possible
charring of tissue. For a set of circular apertures and a given
flow rate, the mean exit velocity for the irrigation fluid will
drop as the number of apertures is increased while decreasing the
cross sectional area of each aperture such that the fluid
resistance of the sum of apertures is appropriate to maintain the
desired inflation pressure. Minimizing the irrigation fluid exit
velocity minimizes or precludes the possibility that lesions will
be eroded through the treatment tissue.
[0087] A set of operating conditions and design parameters is now
provided, and is not meant to be limiting. An inflation pressure
between about 0.5 atm and less than about 4 atm used with a
noncompliant inflatable element of approximately 0.75 mil
(.about.19 um) thick ensures tissue engagement in a renal artery.
In some particular embodiments the inflation pressure is about 2
atm+/-0.5 atm. The irrigation fluid delivery rate is between about
1 mL/min and about 20 ml/min. In some particular embodiments the
delivery rate is about 10 mL/min+/-2 mL/min. The expandable portion
includes eight irrigation apertures about 2.6 mil (0.0026 inches)
in diameter distributed on either side of the helical electrode and
equally spaced along the edge of the electrode. In such a
configuration the mean exit velocity is about 6 msec. In some
embodiments the maximum mean fluid exit velocity is between about 1
m/sec and about 20 msec.
[0088] The above operating parameters are not intended to be
limiting. For example, the inflation pressure can be between about
0.5 atm (or less) and about 10 atm, the flow rate can be between
about 1 mL/min to about 50 mL/min, and any suitable number of
apertures with any suitable size can be incorporated into the
device. Apertures may be of the same size or of different sizes and
may also be uniformly or non-uniformly distributed through and/or
about the electrode. The apertures are sized such that the total
resistance of the set of apertures is appropriate to maintain the
pressures defined herein internal to the inflatable element at the
desired flows described herein. Alternatively, the total resistance
is such that the desired flows described herein are maintained at
the desired pressures described herein. The total resistance for
the parallel combination of apertures is calculated as the inverse
of the sum of the inverses of the individual aperture
resistances.
[0089] The system shown also includes pressure sensor 332, which is
adapted to determine if the pressure rises above or below threshold
limits. If the fluid pressure rises above an established limit, the
controller shuts off the RF energy, and fluid pump 330 is
automatically shut off. The pressure can elevate if one or more of
the apertures become blocked, preventing fluid from passing out of
the balloon, which can prevent the electrode from being cooled
sufficiently. Controller 324 therefore runs fluid pump 330 in a
binary manner, either open-flow or off.
[0090] The system as shown also includes a temperature sensor 129
secured to the catheter within the inflatable element. If the
sensed temperature of the fluid is above a threshold limit, the
fluid will not properly cool the electrode. If the sensed fluid
temperature is above a threshold limit, control unit 324 is adapted
to cease RF current delivery. The fluid temperature in the balloon
can rise if one or more apertures are blocked, preventing the
electrode from being properly cooled and also increasing the risk
of charring. The fluid pressure generally will rise above a
threshold limit if this occurs as well. In some embodiments the
system has only one of the temperature sensor and pressure
sensor.
[0091] The system may also include bubble sensor 334, which is
adapted to sense bubbles in the fluid line and communicates with
control unit 324 to shut off pump 330 if bubbles of sufficient
volume are detected.
[0092] The system can also include a flow sensor to determine if
the flow rate has gone below or above threshold limits. RF energy
delivery is automatically stopped and the pump is automatically
shut down if the flow rate goes above or below the threshold
limits.
[0093] In an alternate embodiment to that of FIG. 6 the constant
flow control of the system may be replaced by constant pressure
control. In such a system the reservoir 326 may be maintained at a
pressure within the prescribed pressure range using, for example
without limitation, an IV bag pressure cuff or other suitable
means, and the pump replaced by a flow sensor or flow controller.
In such a system pressure is maintained at a substantially constant
level within the prescribed range and flow rate monitored. When
flow rate falls outside of the proscribed range the RF power
delivery is terminated.
[0094] In general, using a greater number of smaller holes provides
substantially the same resistance as a fewer number of larger
holes, but mean fluid exit velocity is diminished.
[0095] FIG. 8 illustrates a portion of an embodiment of an RF
delivery device wherein the expandable portion has a general
dumbbell configuration, and energy is delivered through the
conductive fluid to the tissue. RF delivery device 210 includes
expandable portion 222 that comprises inflatable element 216 on
which is disposed conduction material 218 with a helical
configuration. The catheter has guiding element lumen 236 and
irrigation lumen 228. A conductive layer and an insulation layer
are disposed on the catheter as in the embodiment in FIGS. 1-5. The
proximal and distal portions of inflatable element 216 have
diameters that are greater than the intermediate section, such that
the expandable portion has a general dumbbell shape. When inflated,
larger diameter proximal and distal ends of the expandable portion
214 contact the vessel wall, while space is left between the
cylindrical section 222 of the expandable element and the vessel
wall as illustrated in FIG. 8. The irrigation fluid flowing through
irrigation apertures 238 fills the space between the cylindrical
section 222 and tissue, and current from the helical electrode is
carried through the conductive irrigation fluid and into the
adjacent tissue. In this configuration the helical electrode does
not contact tissue directly, therefore the uniformity of heating is
improved and the risk of charring or overheating the tissue is
reduced.
[0096] Device 210 is also adapted to query the nervous tissues
adjacent to the device, but need not include this functionality.
Device 210 includes nerve conduction electrodes 215 located on the
outer surface of the dumbbell shaped proximal and distal ends of
the expandable portion 214. In use, an electrical signal, typically
a low current pulse or group of pulses is transmitted to one of the
conduction electrodes. This triggers a response in adjacent renal
nerves, which then travels along the nerves and at some time "t"
later is sensed by the opposite electrode when the signal is
traveling in the appropriate direction. By alternating which
electrode is used as the exciter and which the sensor, both changes
in efferent and afferent nerve conduction in the renal nerves may
be monitored as a function of RF treatments induced by the RF
electrode. The conduction electrodes are wired to the sensing
circuits in the controller via wires traveling within the catheter
shaft, as in the irrigation lumen, or additional lumens (not
shown), or multiple conductors may be applied to the outer surface
of the shaft (not shown).
[0097] FIG. 9 illustrates the delivery device 210 in a delivered,
or expanded, configuration within a renal artery. Areas 1005
indicate tissue treated by the application of RF energy delivered
via the helical electrode. An area 1005 adjacent to conductor 218
surrounds a renal nerve 1004. Irrigation fluid movement is shown by
the arrows. The fluid enters the inflatable element 216 at
irrigation port 230 as shown by arrows 1006. The fluid then flows
out of inflatable element 216 at irrigation apertures 238, shown by
arrows 1007. The fluid then flows past conduction electrodes 215
into the blood stream, shown by arrows 1008.
[0098] In use, the dumbbell configuration creates a small space
between the helical electrode and the arterial wall. The irrigation
fluid, such as saline, can be used to act as a conductor and
transfer energy from the electrode to the tissue. In such a system,
the impedance variations, at the interface between the tissue and
the electrode, associated with surface irregularities and
variations in contact between the electrode and tissue will be
minimized. In this manner the fluid can act both to cool the
electrode and to transfer energy to tissue. The thin layer of fluid
between the electrode and tissue can also prevent sticking and add
lubrication.
[0099] Unless specifically stated to the contrary, the embodiment
of FIG. 7 includes features associated with the embodiment from
FIG. 4.
[0100] The configuration of RF delivery device 210 is less
dependent on considerations listed above with respect to the
embodiment in FIG. 4 as the irrigation fluid does not directly
impinge on the treatment tissue and is allowed circulate in the
space between the vessel wall and the cylindrical central section
222. Such a configuration additionally requires less irrigation
fluid to prevent charring as the electrode 129 does not contact the
tissue directly.
[0101] In use, the embodiment from FIG. 5 is used to create a
discontinuous helical burn pattern formed of a plurality of
discrete burn areas in the tissue. The helical burn pattern is
formed during a single treatment session and does not require the
device be moved to create the plurality of discrete burn areas.
[0102] FIG. 10 is a photograph of an RF delivery device 410 on top
of a piece of heart tissue 500 which has been ablated with RF
energy delivered by a device similar to that in FIG. 4 and a system
similar to that of FIG. 6. The heart tissue was originally cut as a
cylinder into the core of which the distal end 406 of the RF
delivery device 410 was deployed. RF energy comprising a signal of
400K Hz at 40 volts and 40 watts was then delivered to the tissue.
The cylinder of tissue was then cut along its length so that the
inner surface of the tissue cylinder could be visualized. Helical
burn zone 501 was created by helical electrode 419. The burn zone
has the same configuration as the helical electrode.
[0103] One aspect of the disclosure is a method of manufacturing RF
delivery devices. FIGS. 11A-11H illustrate a method of
manufacturing a portion of the RF delivery device 110 from FIG. 4.
In FIG. 11A, catheter 126 is provided and can be any suitable
catheter or other elongate device, such as a sheath. For example,
catheter 126 can be an extruded material, and optionally can have a
stiffening element therein such as a braided material. In this
embodiment catheter 126 is extruded with a guide element lumen and
an irrigation lumen formed therein (not shown), and the irrigation
port is formed therein (not shown). The irrigation lumen is closed
off at the distal end of the catheter to prevent fluid from
escaping the distal end of catheter, but the irrigation lumen can
stop at the irrigation port rather than continuing further towards
the distal end.
[0104] Inflatable element 116, which can be an inflatable balloon,
is then secured to the exterior of catheter 126 using any suitable
technique such that irrigation port 130 is disposed within
inflatable element 116. Next, mask 60 is applied or slid over
inflatable element 116. The mask is configured such that it covers
areas where the conductive material is not to be deposited and is
open where conductive material is to be applied. In FIG. 11C, mask
60 is configured with open area 61 to allow for the deposition of a
conductive element 118 in a helical configuration. Inflatable
element 116 is then inflated with a suitable inflation fluid (e.g.,
liquid or gas) delivered through the irrigation lumen and out port
130 to expand, or inflate, inflatable element 116, as shown in FIG.
11C. Additionally, mask 60 is typically configured to mask the
distal transition section of the expandable portion and the
catheter distal to the expandable portion. After mask 60 is
applied, conductive material 118 is then deposited, in a single
deposition step, onto substantially all of catheter 126, portions
of inflatable element 116, and mask 60. This forms a conductive
material layer on substantially all of catheter 26, proximal
portion of inflatable element 116, and in the helical pattern on
inflatable element 116. After the conduction material 118 is
deposited in the single step and allowed to dry sufficiently and or
cure, inflatable element 116 is deflated and the mask 60 is
removed. As shown in FIG. 11F, a second mask 70 is then applied
over those areas of conductive material 118 which are intended to
deliver energy directly to the tissue in the energy delivery
pattern, which is the helical pattern. The inflatable element 216
is then re-inflated and insulation material 34 is applied to
substantially the entire device in a single depositing step as
shown in FIG. 11G. This forms an insulation layer on substantially
the entire conductive material already deposited on catheter 126,
the proximal portion of the inflatable element, and the
intermediate portion of the inflatable element where mask 70 is not
disposed. Next, after appropriate drying and or curing the
inflatable element is deflated and the mask 70 removed as shown in
FIG. 11H. After mask 70 is removed, shaft 126, and proximal
transition section of inflatable element is encapsulated by
conductor 118 which are in turn encapsulated by dielectric 134,
while helical conductive electrode 118 on the inflatable element is
not covered with dielectric. The irrigation apertures are then
formed, such as by laser drilling.
[0105] In some embodiments of manufacturing the device, the layers
of conductive material and insulation material are between about
0.0001 and about 0.001 inches thick. In some embodiments the
conductive layer is about 0.0003 inches thick. In some embodiments
the insulation layer is about 0.0005 inches thick.
[0106] Alternate methods for deposition of the conductor and/or the
dielectric layers which that can be used and do not require masking
include ink jet and or pad printing techniques.
[0107] These methods of manufacturing form a unitary conductor. A
"unitary conductor" as described herein is a single conductive
material comprising both a conduction element and an electrode
element wherein the conductive element communicates energy between
the controller and the electrode element.
[0108] The conductive and insulation materials can each be
deposited on substantially all of elongate portion 112 (excluding
the portion within expandable portion 114) and expandable portion
114 in a single step, reducing the time necessary to form the
conductive and insulation layers, respectively. This can also
simplify the manufacturing process. To deposit the conductive and
insulation material, the device can be secured to a mandrel and
spun while the material is deposited, or the device can be secured
in place while the device used to deposit the material is moved
relative to the device, or a combination of the two steps. "Single
step" as used herein includes a step that applies the material
without stopping the deposition of material. For example, the
conductive material can be deposited on substantially all of the
catheter proximal to the inflatable element and to the inflatable
element in a single step. "Single step" as used herein also
includes applying a second or more coats to the elongate portion
and the expandable portion after initially ceasing the deposition
of material. For example, a process that applies a first coat of
conductive material to substantially all of the catheter proximal
to the inflatable element and to the inflatable element, followed
by a ceasing of the deposition, but followed by application of a
second coat to substantially the entire portion of the catheter
proximal to the inflatable element and to the inflatable element,
would be considered a "single step" as used herein. Some previous
attempts to form a conductive material on an elongate device formed
one or more discrete conductive elements on the elongate device,
thus complicating the deposition process. These and other attempts
failed to appreciate being able to form a single layer of
conductive material on substantially all of the catheter or other
elongate device. These attempts failed to appreciate being able to
form single layer of conductive material on the catheter and an
electrode element on an expandable element in a single step.
[0109] By disposing the conductive material on the external
surfaces of the catheter and inflatable element in a single step,
the creation of electrical junctions is avoided. For example, a
junction need not be formed between the conductive material on the
catheter and the conductive material on the inflatable element. As
used herein, electrical junction refers to a connection created
between two conductive materials, either the same or different
materials, that allows an electrical signal to be conducted from
one material to the other.
[0110] The inflatable element is, in some embodiments, an
inflatable balloon that is adapted to be inflated upon the delivery
of a fluid through the irrigation lumen and out of the irrigation
port. In the embodiment in FIGS. 1-11, the inflatable element is a
balloon made of non-elastic, or non-compliant, material, but it can
be a compliant, or elastic, material as well. Materials for a
non-compliant balloon include, without limitation, polyethylene,
polyethylene terephthalate, polypropylene, cross-linked
polyethylene, polyurethane, and polyimide. Materials for a
compliant balloon include, without limitation, nylon, silicon,
latex, and polyurethane.
[0111] In some embodiments of the embodiment in FIG. 4, the length
of the cylindrical intermediate portion of the inflatable element
is between about 1 cm and about 4 cm. In some embodiments the
inflatable element has a diameter between about 4 mm and about 10
mm. In some particular embodiments the length of the intermediate
portion of the inflatable element is about 20 mm and the diameter
is about 5 mm to about 7 mm.
[0112] The conductive material can be deposited onto the catheter
and/or expandable portion. Methods of depositing include, without
limitation, pad printing, screen printing, spraying, ink jet, vapor
deposition, ion beam assisted deposition, electroplating,
electroless plating, or other printed circuit manufacturing
processes.
[0113] In some embodiments the conductive material deposited is an
elastomeric ink and the dielectric material is an elastomeric ink.
They can be sprayed on the respective components. In some
embodiments the elastomeric ink is diluted with an appropriate
diluent to an appropriate viscosity then sprayed in a number of
coats while the delivery device is rotated beneath a linearly
translating spray head.
[0114] Conductive materials that can be deposited on the device to
form one or more conductive layers of the device include conductive
inks (e.g., electrically conductive silver ink, electrically
conductive carbon ink, an electrical conductive gold ink),
conductive powders, conductive pastes, conductive epoxies,
conductive adhesives, conductive polymers or polymeric materials
such as elastomers, or other conductive materials.
[0115] In some embodiments the conductive material comprises an
elastomeric matrix filled with conductive particles. Elastomeric
components include silicones and polyurethanes. Conductive
materials are conductive metals such as gold or silver. Conductive
inks that can be used are conductive ink CI-1065 and CI-1036
manufactured by ECM of Delaware Ohio. This ink is an extremely
abrasion resistant, flexible, and highly conductive elastomeric
ink. The ink has the following properties: 65% solids in the form
of silver flakes; 0.015 ohms/square (1 mil (0.001 inches) thick);
and a 10 minute cure time at 248 F.
[0116] The electrodes described herein can also be used as a
temperature sensor. Ablative electrodes are routinely used in wide
variety of surgical procedures. Many of these procedures are
performed percutaneously, and a subset are performed
endovascularly. In many of these procedures it is customary to
incorporate provisions to monitor the temperature of the ablative
electrodes. This temperature information is then used in some
fashion as an input in a control scheme to limit the maximum
temperature the electrode is allowed to attain. In this fashion a
number of mechanisms, that may be deleterious to the desired
outcome, may be controlled and or limited. Some of these effects,
which in some circumstances are considered deleterious are, tissue
charring, creation of steam, and the resultant uncontrolled, rapid,
or large changes in interface impedance.
[0117] The temperature monitoring is typically carried out by
incorporating and mounting some form of a temperature sensor such
as a thermocouple, an rdt, or a thermistor in proximity to, or on,
the electrode.
[0118] The electrodes are typically comprised of metals or metal
alloys which are either deposited as metals directly through
various metal deposition procedures such as, but not limited to
physical or chemical metal vapor deposition, or applied as a
component in a matrix such as but not limited to organic polymers
in the form of an ink. Such inks are deposited in many ways, a few
of which are, screening, spraying, ink jetting.
[0119] Metals, metal alloys, and other metal compound have
resistance characteristics which are dependent on temperature,
typically called the temperature coefficient of resistance or
"tempco." The magnitude and characteristics of these effects varies
and is often used in devices such as a resistance temperature
detector "RTD", such as a platinum rtd's, or in positive
temperature coefficient "PTC" or negative temperature coefficient
"NTC" thermistors.
[0120] The systems herein can therefore alternatively monitor
temperature by using the inherent tempco of the electrode itself as
a way of monitoring its temperature and or controlling its
impedance and thereby self-limiting its power output and thereby
its temperature.
[0121] FIG. 12 represents an embodiment of a system similar to that
of FIG. 6 represented by the resistances of the various elements.
The delivery RF lead which runs down catheter is represented as
resistance 626 and the electrode is represented by resistance 619.
In this embodiment there is an additional conductive element
running along the catheter shaft which is a return line represented
by resistance 650. In use the leads whose resistances are
represented by 626 and 650 may be sourced in parallel when RF is
delivered to electrode 619 and addressed separately when used to
characterize the resistance and hence temperature of the electrode
619. Alternatively one of them may be used solely for the purpose
of monitoring temperature and therefore left open circuited when RF
is being delivered. The design of the delivery system and electrode
will be such that the impedance 640 of the patient will be orders
of magnitude greater then the impedances for the delivery leads
626, 650, and the electrode 619. In one embodiment impedance 619
will be considerably greater than 626 or 650, or in some cases the
parallel combination of 626 and 650.
[0122] In one embodiment the electrode is comprised of a layer of
platinum and the temperature of the electrode may be characterized
by monitoring the voltage drop across the series resistances 626,
619, 650. This may be done intermittently, interspersed in the
delivery of the RF energy. As the electrode heats, its resistance
will increase in a well-known and repeatable fashion. As the leads
626 and 650 have lower resistance and will not self-heat
appreciable, the change in resistance will by primarily due to the
heating of electrode 619 and variation in its resistance. Many
other scenarios will be understood to those skilled in the art.
[0123] An alternate arrangement which relies on the use of a PTC
for the electrode relies on the rapid change in resistance of the
electrode past a particular set point which is a function of the
composition of the electrode. In this configuration the tempco of
the electrode is relatively small, for example, below about 40 C
but above about 40 C. In this temperature range the tempco rapidly
increases thereby limiting delivered power in a voltage-limited RF
configuration. Many alternate embodiments will be understood by
those skilled in the art.
[0124] FIG. 13 illustrates an alternative configuration in which a
capacitor 648, inductor (not shown), or both may be incorporated in
the circuit. In one embodiment the circuit may incorporate only one
source lead 621 and the inherent resonance of the circuit which
will depend on the varying impedance of the electrode resistance
623.
[0125] In yet another alternative the tempco associated with a
conductive ink such as the ECM CI-1036 may be used. Experimentally
the ECM CI-1036 demonstrated a 0.1% increase in impedance per
degree over the range of 30 C to 60 C.
[0126] As described above, devices capable of ablating renal nerves
surrounding the renal arteries are useful in treating hypertension.
The device disclosed in FIG. 16 is another embodiment of a device
adapted for such purpose. The device described herein comprises a
bipolar electrode pair disposed on the outer surface of an
expandable structure comprised of an inflatable balloon. A bipolar
electrode pair provides for both a more controlled burn and a
shallower burn than a comparable monopolar electrode. The device is
configured for endovascular delivery to a renal artery. Each of the
individual electrodes comprising the bipolar set is in turn
comprised of a unitary electrode/conductor.
[0127] Referring to FIG. 16, detailed description of the distal
features of an embodiment of the device is as follows. The distal
portion of an bipolar RF delivery device 810 includes an expandable
section 850 including a balloon, and a catheter shaft section 820
including an inner shaft 830 and an outer shaft 840. The inner
lumen of the inner shaft 830 includes a guidewire lumen 822. The
annular gap between the inner and outer shafts includes an
irrigation lumen 821. The outer shaft 840 also includes an
irrigation outflow 812 (e.g., an irrigation port) located near its
distal end such that it is disposed within the balloon. A
temperature sensor 811 may be located within the balloon 850 and
interconnecting leads of the temperature sensor 811 may be routed
through the irrigation lumen outflow 812 and irrigation lumen
821.
[0128] Prior to assembly, a conductive material is deposited on
substantially the entire inner shaft 830. A dielectric material is
then deposited on the conductive material except at the distal most
end of the inner shaft 830. The inner shaft 830 is then fitted
within the outer shaft 840 and the two are affixed to one another
such that the inner shaft 830 extends beyond the most distal
portion of the outer shaft 840 and the balloon 850. The dielectric
on the inner shaft 830 is deposited on at least the portions of the
surface of the conductor on the inner shaft 830 that would contact
irrigation fluid, thus preventing the conductive material on the
inner shaft 830 from coming into contact with irrigation fluid. The
distal end of the inner shaft 830, which extends distal to the
outer shaft 840, is not coated with dielectric. This allows the
inner shaft 830 to be in electrical communication with the inner
sourced electrode as described below.
[0129] Next, the outer shaft 840 and balloon 850 are coated with an
elastomeric ink, and then, subsequently, by a dielectric as
described above. The conductive coating is deposited on the outer
shaft 840, all or a portion of the proximal cone 843 of the balloon
850, and on the balloon 850, forming a conductive material that
includes an outer sourced spiral electrode 842. This conductive
material can be deposited in a unitary manner, as is described
above and in the materials incorporated by reference herein.
Conductive material is also deposited on the most distal section of
the shaft assembly, the distal cone portion 833 of the balloon 850,
and the balloon 850, forming a conductive material that includes an
inner sourced electrode 832. This conductor can also be formed in a
unitary manner. The conductive material that forms the inner
sourced electrode can be the same material that is used for the
outer sourced electrode. When the distal conductor (which includes
the inner sourced electrode 832) is formed, it interfaces
electrically with the conductor on the inner shaft 830 that extends
distal to the balloon 850. The conductive materials can be selected
such that when the conductive materials are deposited, the
interface is a single layer of the same material rather than two
distinct layers. The conductor and dielectric structures can be
fabricated as described above. When used in bipolar mode, energy
passes from one spiral electrode 832 or 842, through renal nerve
tissue, to the other electrode. The electrodes 832, 842 can be used
in a bipolar manner, or each electrode can be used in monopolar
mode. Bipolar mode can be used if the tissue burn need not be as
deep as may be needed if using a monopolar mode. Bipolar mode
generally allows more control in the tissue burn. Additionally or
alternatively, the electrodes 832, 842 can be used together as a
single monopolar electrode (e.g., by feeding both electrodes with
the same frequency and RF energy such that the electrodes appear to
be one electrode).
[0130] In an alternative embodiment, the inner shaft is not coated
with a conductor (or dielectric) and, instead, a wire extends
through the irrigation lumen, and interfaces the conductor that
includes the inner sourced electrode.
[0131] Although not shown in FIG. 16, irrigation ports as described
above can be situated such that they pass through the electrode
structures, sit adjacent to the electrode structures such as in the
space between them or exterior to the pair, or both.
[0132] One or more radio opaque markers 813 may be affixed to the
outer shaft.
[0133] While several embodiments of the disclosure have been shown
in the drawings and/or discussed herein, it is not intended that
the disclosure be limited thereto, as it is intended that the
disclosure be as broad in scope as the art will allow and that the
specification be read likewise. Therefore, the above description
should not be construed as limiting, but merely as exemplifications
of particular embodiments. Those skilled in the art will envision
other modifications within the scope and spirit of the claims
appended hereto.
* * * * *