U.S. patent application number 13/074867 was filed with the patent office on 2011-09-29 for indifferent electrode pad systems and methods for tissue ablation.
This patent application is currently assigned to ESTECH, Inc. (Endoscopic Technologies, Inc.). Invention is credited to David K. Swanson, Hans van den Biggelaar.
Application Number | 20110238058 13/074867 |
Document ID | / |
Family ID | 44657255 |
Filed Date | 2011-09-29 |
United States Patent
Application |
20110238058 |
Kind Code |
A1 |
van den Biggelaar; Hans ; et
al. |
September 29, 2011 |
INDIFFERENT ELECTRODE PAD SYSTEMS AND METHODS FOR TISSUE
ABLATION
Abstract
Systems and methods for transmitting energy through patient
tissue involve the use of an indifferent pad assembly in
conjunction with an ablation probe. Systems may include an
electrical surgical unit having a power output connector, a first
power return connector, and a second power return connector.
Systems may also include an ablation probe coupleable with the
power output connector of the electrical surgical unit, and an
indifferent pad assembly having a conductive mechanism coupled with
an electrical and thermal insulator mechanism, and a wire assembly
coupled with the conductive mechanism. The wire assembly can
include a first connector coupleable with the first power return
connector of the electrical surgical unit, and a second connector
coupleable with the second power return connector of the electrical
surgical unit.
Inventors: |
van den Biggelaar; Hans;
(Haaren, NL) ; Swanson; David K.; (Campbell,
CA) |
Assignee: |
ESTECH, Inc. (Endoscopic
Technologies, Inc.)
San Ramon
CA
|
Family ID: |
44657255 |
Appl. No.: |
13/074867 |
Filed: |
March 29, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61318474 |
Mar 29, 2010 |
|
|
|
Current U.S.
Class: |
606/33 ;
606/41 |
Current CPC
Class: |
A61B 2018/1253 20130101;
A61B 18/1233 20130101; A61B 2018/165 20130101; A61B 18/16
20130101 |
Class at
Publication: |
606/33 ;
606/41 |
International
Class: |
A61B 18/18 20060101
A61B018/18; A61B 18/14 20060101 A61B018/14 |
Claims
1. A method of transmitting energy through a left atrial wall
tissue of a patient, the method comprising the steps of:
positioning an indifferent pad assembly within the patient's
pericardial space, so that a conductive mechanism of the pad
assembly faces toward an external side of the left atrial wall
tissue, an insulative mechanism of the pad assembly faces toward
the patient's esophagus, and a return line of the pad assembly is
coupled with the conductive mechanism; advancing an ablation probe
of an electrophysiological device through an opening in the
patient's left atrium; positioning the ablation probe within the
left atrium at an internal side of the left atrial wall tissue, so
that the left atrial wall tissue is disposed between the ablation
probe and the conductive mechanism of the pad assembly;
transmitting energy from the ablation probe of the
electrophysiological device through the left atrial wall tissue and
to the conductive mechanism of the pad assembly, while shielding
the esophagus with the insulative mechanism of the pad assembly;
and returning energy from the conductive mechanism of the pad
assembly to an electrosurgical unit via the return line.
2. The method according to claim 1, wherein the step of
transmitting energy comprises transmitting RF energy from the
ablation probe of the electrophysiological device through the left
atrial wall tissue and to the conductive mechanism of the pad
assembly.
3. The method according to claim 1, wherein the step of
transmitting energy through the left atrial wall tissue creates a
lesion in the left atrial wall tissue.
4. The method according to claim 1, wherein the step of
transmitting energy through the left atrial wall tissue creates a
lesion in a posterior aspect of the left atrial wall tissue.
5. A system for transmitting energy through a tissue of a patient,
the system comprising: an electrical surgical unit having a power
output connector, a first power return connector, and a second
power return connector; an ablation probe coupleable with the power
output connector of the electrical surgical unit; and an
indifferent pad assembly comprising a conductive mechanism coupled
with an electrical and thermal insulator mechanism, and a wire
assembly coupled with the conductive mechanism, wherein the wire
assembly comprises a first connector coupleable with the first
power return connector of the electrical surgical unit, and a
second connector coupleable with the second power return connector
of the electrical surgical unit.
6. The system according to claim 5, wherein the conductive
mechanism and the electrical and thermal insulator mechanism are
configured for placement between the pulmonary veins of the
patient.
7. The system according to claim 5, wherein the electrical surgical
unit is configured to sense current individually through the first
and second power return connectors, and to shut off power if
current to either return connector exceeds a predetermined amount
of current.
8. The system according to claim 7, wherein the predetermined
amount of current comprises one ampere.
9. A method of transmitting energy through a left atrial wall
tissue of a patient, the method comprising the steps of:
positioning an indifferent pad assembly within the patient's
pericardial space, so that a conductive mechanism of the pad
assembly faces toward an external side of the left atrial wall
tissue, and an insulative mechanism of the pad assembly faces
toward the patient's esophagus; advancing an ablation probe of an
electrophysiological device through an opening in the patient's
left atrium; positioning the ablation probe within the left atrium
at an internal side of the left atrial wall tissue, so that the
left atrial wall tissue is disposed between the ablation probe and
the conductive mechanism of the pad assembly; and transmitting
energy from the ablation probe of the electrophysiological device
through the left atrial wall tissue and to the conductive mechanism
of the pad assembly, while shielding the esophagus with the
insulative mechanism of the pad assembly.
10. The method according to claim 9, wherein the step of
transmitting energy comprises transmitting RF energy from the
ablation probe of the electrophysiological device through the left
atrial wall tissue and to the conductive mechanism of the pad
assembly.
11. The method according to claim 9, wherein the step of
transmitting energy through the left atrial wall tissue creates a
lesion in the left atrial wall tissue.
12. The method according to claim 9, wherein the step of
transmitting energy through the left atrial wall tissue creates a
lesion in a posterior aspect of the left atrial wall tissue.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a nonprovisional of, and claims the
benefit of priority to, U.S. Provisional Patent Application No.
61/318,474 filed Mar. 29, 2010 (docket no. 87512-784699; previously
021063-003500US). This application is also related to U.S. patent
application Ser. No. ______ filed Mar. 29, 2011 (docket no.
87512-798150; previously 021063-004100US) and U.S. Pat. No.
7,288,090, the content of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] Embodiments of the present invention related to medical
devices and methods, and in particular to cardiac ablation systems
and methods.
[0003] Atrial fibrillation (AF) is a common clinical condition, and
presents a substantial medical issue to aging populations. AF is
costly to health systems, and can cause complications such as
thrombo-embolism, heart failure, electrical and structural
remodeling of the heart, and even death.
[0004] For many years, the main treatment for atrial fibrillation
(AF) involved pharmacological intervention. More recently, the
focus has shifted toward surgical or catheter ablation options to
treat or effect a cure for AF. The ablation techniques for
producing lines of electrical isolation are now replacing the
so-called Maze procedure. The Maze procedure uses a set of
transmural surgical incisions on the atria to create fibrous scars
in a prescribed pattern. This procedure was found to be highly
efficacious but was associated with a high morbidly rate. The more
recent approach of making lines of scar tissue with modern ablation
technology has enabled the electrophysiologist or cardiac surgeon
to create the lines of scar tissue more safely. Ideally, re-entrant
circuits that perpetuate AF can be interrupted by the connected
lines of scar tissue, and the goal of achieving normal sinus rhythm
in the heart may be achieved.
[0005] Triggers for intermittent AF and drivers for permanent AF
can be located at various places on the heart, such as the atria.
For example, where triggers or drivers are located near the
pulmonary veins, it follows that treatment may involve electrical
isolation of the pulmonary veins.
[0006] Certain cardiac surgical procedures involve administering
ablative energy to the cardiac tissue in an attempt to create a
transmural lesion on the tissue. However, some monopolar approaches
may present a risk of injury or damage to tissue located near the
treatment site. Relatedly, some current bipolar approaches may be
limited due to structural constraints associated with the use of a
clamping device. For example, although bipolar radiofrequency can
be a reliable way to create transmural atrial scars, the clamping
design of bipolar devices can limit its use in certain anatomical
applications. Hence, there continues to be a need for improved
systems and methods that can safely and effectively deliver
ablative energy to patient tissue in a uniform and reproducible
manner.
[0007] Although current and proposed treatments may provide real
benefits to patients in need thereof, still further advances would
be desirable. For example, it would be desirable to provide
improved systems and methods for delivering ablation treatment
while reducing the risk of damage to tissue surrounding the
treatment site. Embodiments of the present invention provide
solutions that address the problems described above, and hence
provide answers to at least some of these outstanding needs.
BRIEF SUMMARY OF THE INVENTION
[0008] Embodiments of the present invention encompass ablation
systems and methods involving the use of a flexible indifferent
electrode pad assembly. In some cases, the indifferent electrode
pad assembly is shaped to fit in the pericardial space and conform
to the posterior portion of the left atrium and right atrium. The
pad assembly can include a conductive surface on the side of the
pad that faces the atria, in combination with an electrical and
thermal insulator. Relatedly, the pad can provide a return path in
the pericardial space. The conductive surface can be electrically
coupled with a thin flexible cable that connects to an Electrical
Surgical Unit (ESU) to return current originating from a separate
ablation device or probe. The pad assembly can operate to prevent
or inhibit potential damage to the esophagus and to other
non-cardiac tissues or devices, for example by isolating those
tissues or preventing transmitted ablation energy from reaching
them. The pad assembly, used in combination with an endocardial
surgical ablation monopolar probe, can also enhance the effect of
the ablation because current spread can be less than would
otherwise occur when a monopolar probe is used in conjunction with
a return electrode placed on the patient's skin. For lesions
applied near the posterior aspect of the atria, system embodiments
can produce lesions similar to those made by bipolar clamping
devices, while maintaining the benefit of easy application of all
ablation lines used for a modified MAZE procedure. Hence,
embodiments of the present invention provide an efficient and safe
ablation treatment, without the geometric constraints or
limitations associated with some bipolar treatments, and without
the risk of complication sometimes associated with other monopolar
treatments.
[0009] In an exemplary approach, an indifferent pad assembly may be
used in conjunction with a monopolar probe or wand device such as
the COBRA.RTM. Surgical Probe (Estech, San Ramon, Calif.), a
malleable epicardial or endocardial probe that utilizes multiple
electrodes to create uniform, reproducible linear lesions. This
combination enables the flexibility and ease of use of monopolar
ablation and the efficacy of the bipolar clamping devices.
Relatedly, combination indifferent pad assembly and monopolar probe
systems can be used to safely treat patient tissue with reduced
risk to surrounding tissue. For example, the pad assembly and probe
can be used to treat atrial tissue, without a high risk of damage
to non-cardiac tissue such as the esophagus, lung, and the
like.
[0010] In one aspect, embodiments of the present invention
encompass methods of transmitting energy through a left atrial wall
tissue of a patient. Exemplary methods may include positioning an
indifferent pad assembly within the patient's pericardial space, so
that a conductive mechanism of the pad assembly faces toward an
external side of the left atrial wall tissue, and an insulative
mechanism of the pad assembly faces toward the patient's esophagus.
The pad assembly may include a return line or wire that is coupled
with or in electrical connectivity with the conductive mechanism.
Methods may also include advancing an ablation probe of an
positioning an electrophysiological device through an opening in
the patient's left atrium, positioning the ablation probe within
the left atrium at an internal side of the left atrial wall tissue,
so that the left atrial wall tissue is disposed between the
ablation probe and the conductive mechanism of the pad assembly,
and transmitting energy from the ablation probe of the
electrophysiological device through the left atrial wall tissue and
to the conductive mechanism of the pad assembly, while shielding
the esophagus with the insulative mechanism of the pad assembly.
Exemplary techniques may include returning energy from the
conductive mechanism of the pad assembly to an electrosurgical unit
via the return line. In some cases, the step of transmitting energy
includes transmitting RF energy from the ablation probe of the
electrophysiological device through the left atrial wall tissue and
to the conductive mechanism of the pad assembly. In some cases, the
step of transmitting energy through the left atrial wall tissue
creates a lesion in the left atrial wall tissue. Optionally, the
step of transmitting energy through the left atrial wall tissue may
create a lesion in a posterior aspect of the left atrial wall
tissue.
[0011] In another aspect, embodiments of the present invention
encompass systems for transmitting energy through a tissue of a
patient. Exemplary systems may include an electrical surgical unit
having a power output connector, a first power return connector,
and a second power return connector. Systems may also include an
ablation probe coupleable with the power output connector of the
electrical surgical unit. Further, systems may include an
indifferent pad assembly having a conductive mechanism coupled with
an electrical and thermal insulator mechanism, and a wire assembly
coupled with the conductive mechanism. The wire assembly can have a
first connector coupleable with the first power return connector of
the electrical surgical unit, and a second connector coupleable
with the second power return connector of the electrical surgical
unit. In some cases, the conductive mechanism and the electrical
and thermal insulator mechanism can be configured for placement
between the pulmonary veins of the patient. In some cases, the
electrical surgical unit can be configured to sense current
individually through the first and second power return connectors,
and to shut off power if current to either return connector exceeds
a predetermined amount of current. Optionally, the predetermined
amount of current can be one ampere.
[0012] For a fuller understanding of the nature and advantages of
the present invention, reference should be had to the ensuing
detailed description taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIGS. 1-4 illustrate aspects of ablation treatment systems
and methods according to embodiments of the present invention.
[0014] FIG. 5 is a front elevation view of an electrosurgical unit
in accordance with embodiments of the present invention.
[0015] FIG. 6 shows an indifferent pad assembly according to
embodiments of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Embodiments of the present invention encompass indifferent
electrode pad systems and methods for performing endocardial
ablation in a patient in need thereof. For example, such techniques
are well suited for treating patients who present with atrial
fibrillation and other electrical abnormalities of the heart such
as incessant ventricular tachycardia. Cardiac conditions such as
these can lead to thrombo-embolisms, heart failure, and other
complications in a patient. These treatment approaches provided
herein can result in electrical isolation or blockage between
various portions of cardiac tissue, optionally via the creation of
transmural ablations at selected locations on the endocardium. For
example, methods and systems can be used to create scars that
produce lines of electrical isolation, so as to inhibit or prevent
electrical activity which may otherwise lead to or perpetuate
atrial fibrillation, or so as to promote or maintain normal sinus
rhythm in the patient. In some cases, these techniques can be used
to form lesions at or near the pulmonary veins, the left atrial
appendage, or the mitral valve, for example. Techniques can be used
to treat patients presenting with paroxysmal or intermittent atrial
fibrillation, as well as persistent or long lasting persistent
atrial fibrillation.
[0017] Soft tissue coagulation that is performed using electrodes
to transmit energy to tissue, whether catheter-based or surgical
probe-based, may be performed in both bi-polar and uni-polar modes.
In the uni-polar mode, energy emitted by the electrodes supported
on the catheter or surgical probe is returned through one or more
indifferent electrodes. In some cases, a uni-polar mode is useful
because the uni-polar mode allows for individual electrode
control.
[0018] Embodiments of the present invention provide techniques for
applying endocardial lesions to tissue at or near the pulmonary
vein (PV) ostia and other locations of the heart, to cause or
enhance conduction block at the junction of the PV and left atrium
as well as other blocking lesions. Such techniques are well suited
for use with patients presenting with paroxysmal (focal) atrial
fibrillation. Exemplary embodiments involve the administration of
precisely controlled ablative energy, or controlled power, to
create reproducible, uniform transmural lesions during cardiac
surgery. Such techniques enable rapid and effective ablative
lesions in a variety of clinical situations, including endocardial
and epicardial ablations. By forming the transmural ablations,
surgeons are able to achieve conduction block in the patient.
Advantageously, embodiments of the present invention can be used to
create complete lesion sets and reliably produce transmural lesions
on a beating heart. According to embodiments disclosed herein,
transmural lesions across the atrial wall can be performed reliably
and efficiently. Relatedly, although many of the examples described
herein are with reference to ablation of cardiac tissue such as the
left atrial wall, embodiments of the present invention encompass
systems and methods for ablating other tissues in the body, such as
the tissue wall of various hollow organs.
[0019] Embodiments also includes ablation systems having an
ablation energy source for providing energy to the ablation device.
An ablation energy source is typically suited for use with ablation
apparatus as described herein using RF energy. With regard to RF
ablation, a typical RF ablation system includes a RF generator
which feeds current to an ablation device, including those
described in this application, containing a conductive electrode
for contacting targeted tissue. The electrical circuit can be
completed by a return path to the RF generator, provided through
the patient and a large conductive plate, which is typically in
contact with the patient's back. Embodiments encompass ablation
using RF electrodes, including single RF ablation electrodes.
Although ablation energy is often described herein in terms of RF
energy, it is understood that embodiments are not limited to such
ablation modalities, and other kinds of ablation energy sources and
ablation devices may be used. Hence, with regard to the ablation
techniques disclosed herein, other suitable ablation elements or
mechanisms, instead or in addition to an RF electrode, can be used.
Embodiments of the present invention therefore encompass any of a
variety of ablation techniques, including without limitation
irreversible electroporation, infrared lasers, high intensity
focused ultrasound (HIFU), microwave, Cryoablation (killing or
damaging the tissue by freezing), radiation, and the like. In some
cases, an ablation mechanism can include an ablation element that
transmits or delivers RF energy to patient tissue. Optionally,
suitable ablation elements can transmit or deliver high voltage
pulses, infrared laser energy, high intensity focused ultrasound
(HIFU) energy, microwave energy, Cryoablation energy, radiation
energy, and the like. Embodiments encompass ablation mechanisms
having multiple ablation elements, such as multiple RF electrodes.
According to some embodiments, an ablation element may include a
monopolar electrode. Any of these modalities is well suited for use
in endocardial ablation techniques resulting in electrical
isolation and transmurality.
[0020] Turning now to the drawings, FIG. 1 illustrates aspects of
ablation treatment systems and methods according to embodiments of
the present invention. FIG. 1 illustrates a posterior view of the
heart, as viewed through the rear ribs or backbone. As shown here,
a pad assembly 100 can be positioned anterior to the esophagus and
posterior to the heart. An exemplary pad assembly 100 may include a
conductive mechanism or surface 110 on the side of the pad assembly
that faces toward the atria, an electrical and thermal insulator
mechanism 120 on the side of the pad assembly that faces toward the
esophagus, and an electrical wire assembly 130 that provides
electrical connectivity between the conductive mechanism 110 and an
Electrical Surgical Unit (ESU). A portion of the pad is disposed
central to the four pulmonary veins (PV's). For example, in some
cases, the pad spans or covers at least about 80% of the area
between the right and left pulmonary veins. It is understood that
the pulmonary veins, esophagus, pericardium, skeleton, and other
anatomical features may not be rigidly attached with one another,
the heart may move relative to the esophagus due to a variety of
factors, including gravity, patient swallowing, or other movement
of the patient during surgery. Hence, the pad can be configured to
cover a selected amount of space between the pulmonary veins, to
accommodate for the shifting of such anatomical features while
still providing protection to the esophagus or other tissue during
an ablation treatment.
[0021] Pad assemblies may be used in concomitant cardiac surgery
cases, for example in patients undergoing mitral valve repair or
replacement, aortic valve replacement, and/or coronary artery
bypass grafting (CABG) surgery concomitant with ablative therapy.
Such treatments can involve creating a medial stenotomy or large
incision splitting the breastbone, and placing the pad assembly
within the pericardial space. In some cases, the surgeon may
prepare a pericardial cradle, splitting the pericardium, and
suspending the split or cut edges to provide a sling that supports
or holds the heart. The pad assembly can be placed to the left of
heart, slipped around a region proximal to left atrial appendage,
and directed into position between the two sets of pulmonary veins.
In some instances, the pad assembly can be advanced from the apical
side of heart, pushed toward the base, guided behind the heart, and
moved slightly toward the surgeon, thus disposing the pad assembly
between the right and left pulmonary veins, such that the pad
assembly terminates or is placed against the pericardial
reflection. In some cases, the pad assembly may contact the left
ventricle, and may be supported or at least partially held in place
by the left ventricle. In some cases, a lower tail 150 of the pad
assembly can help to provide mechanical stability when the pad
assembly is positioned within the patient's body.
[0022] Treatment systems which include a pad assembly and ablation
probe may be used to create lesions in any of a variety of tissues,
including atrium or ventricle tissue, on either of the right or
left sides. The pad assembly can operate to physically or
geometrically constrain the application of the ablation by the
probe. In some cases, patients presenting certain diseases may have
larger or smaller than normal heart dimensions. For example, a
particular patient may have a left atrium that is larger than
normal. Hence, pad assemblies can be configured in a variety of
shapes and sizes for use suitable with a particular patient.
Typically, the pad assembly has a size and shape that covers a
certain percentage of the posterior atrial surface. In some cases,
the pad assembly can have a size and shape that covers about 80% or
more of the tissue area located between the pulmonary veins.
[0023] FIG. 2 illustrates a top view of a transverse section of a
patient 201. As shown here, a pad assembly 200 can be positioned
anterior to the esophagus and posterior to the heart, for example
in the pericardial space. FIG. 2 also depicts an ablation probe 205
disposed within an interior chamber of the heart. Indifferent
electrode pad assembly 200 provides a return path in the
pericardial space. Pad assembly 200 can be shaped to fit in the
pericardial space and conform to the posterior portion of the left
atrium and right atrium. Pad assembly 200 can include a conductive
surface on the side of the pad assembly that faces toward the
atria, and an electrical and thermal insulator mechanism 220 on the
side of the pad assembly that faces toward the esophagus.
Conductive surface or mechanism 210 can be electrically coupled
with a thin flexible cable 230 that connects to an Electrical
Surgical Unit (ESU) 240 to return current originating from a
separate ablation device or probe. Pad assembly 200 can operate to
prevent or inhibit potential damage to the esophagus and to other
non-cardiac tissue.
[0024] Conductive mechanism or surface 210 can include a flexible
conductor material, and electrical and thermal insulator mechanism
220 can include a foam or other material which prevents or inhibits
the flow or transfer of heat or electricity. The electrical
insulating properties can help prevent or inhibit heating when
current is passed through the assembly. The thermal insulating
properties can help prevent or inhibit thermal transfer which may
cause tissue char. The conductive material can have a thickness
within a range from about 0.002 to about 0.008 inches. In some
cases, the thickness of the conductive material is about 0.005
inches. The conductive material may include any of a variety of
conductive components, such as stainless steel, nickel coated
copper, platinum, gold, or any other nontoxic conductive materials.
The structure of the surface conductor can be a mesh, film, or the
like. The insulating material can have a thickness within a range
from about 0.5 mm to about 1.5 mm. In some cases, the thickness of
the conductive material is about 1 mm. The insulating material may
include any of a variety of insulating components, such as
polyurethane foam or the like.
[0025] Pad assembly 200, used in combination with an endocardial
surgical ablation probe such as probe 205, can also enhance the
effect of the ablation because current will not spread as much as
current would otherwise spread in the situation where a return
electrode is placed on the patient's skin. An ESU can be configured
to provide power control using standard power delivery algorithms.
Typically, the ESU is configured to operate in a stable matter
during ablation procedures involving any of a variety of tissue
types having different degrees of thermal capacity.
[0026] In some instances, conductive mechanism or surface 210 can
be coated with a conductive coating, such as a conductive hydrogel.
Such hydrogels can be configured to provide about 500 ohm-cm
resistivity. Optionally, the resistivity of the hydrogel can be
configured to match the resistivity of the tissue which it
contacts. In this way, electrical discontinuity between the pad
assembly and the tissue surface is reduced or minimized, to reduce
edge currents, i.e. the very high current densities (and high
heating) that would otherwise occur at the edge of the electrical
pad assembly.
[0027] An exemplary surgical procedure may include opening the
pericardium, inserting the pad assembly 200 along the posterior
aspect of the left ventricle, and advancing the pad assembly
adjacent the right coronary to position the pad assembly posterior
to the heart, for example posterior to the left atrial
appendage.
[0028] A surgeon may use a pad assembly and ablation provide during
a treatment procedure in which the left atrium is open. For
example, a cardiopulmonary bypass technique can be used to remove
blood from the heart, and an ablation probe device 205, which may
include a monopolar probe, can be inserted within the heart
chamber. Optionally, the surgeon may use a visualization device as
an aid in positioning the ablation probe or pad assembly. In some
cases, the surgeon may view or evaluate the heart tissue curvature
or contour, and bend or form the ablation electrode device to
provide a corresponding curvature or contour in the device. The
surgeon may then contact the atrial wall or tissue with the formed
device. According to some embodiments, the pad assembly is placed
within the pericardial space, between the pericardium and the
heart, and ablations are performed in the left atrium. During the
ablation procedure, the ablation probe can be moved and positioned
within the heart chamber and relative to the pad assembly, as
desired. Hence, the pad assembly can be placed near the posterior
part of atrium, and the probe device can be moved independent of
the pad assembly. In this way, the surgeon is free to create
lesions at any of a variety of locations, such as at or near the
mitral valve annulus, which may otherwise be difficult using some
known bipolar clamping devices.
[0029] Typically, a pad assembly conductive mechanism is much more
conductive than the patient tissue, and behaves like an
isopotential surface. When the ablation probe electrode is
positioned directly across from the pad assembly, the ablation
probe device and return pad assembly combination can operate in a
fashion similar to that of a bipolar ablation system, with current
remaining within a constrained region, passing from the ablation
probe, directly through the tissue, and to the pad assembly. When
the ablation probe electrode and pad assembly are positioned at a
further distance from one another, the ablation probe device and
return pad assembly combination can operate in a fashion similar to
that of a monopolar ablation system, where the current traveling
from the ablation probe and spreading out in all directions, with
current density (and heating rate) decreasing rapidly as a function
of distance from the ablation probe. Put another way, as the
distance between the ablation electrode and the pad assembly
becomes greater, there is a corresponding transition from a bipolar
lesioning configuration to a monopolar lesioning configuration.
Relatedly, the heat generated is proportional to the square of the
current. Hence, if a current is distributed in a way to provide 10%
of an original amount of current, the resulting rate of heat
generation will be about 1% of original rate of heating. As noted
elsewhere herein, the indifferent pad assembly can operate to
prevent or inhibit noncardiac tissue, such as the esophagus, from
being damaged during an ablation procedure.
[0030] In some cases, tissue positioned between the pad assembly
and the ablation electrode may provide minimal or nominal
resistance. For example, a tissue such as the atrial wall may
provide about 10 ohms of resistance. Relatedly, certain ESU devices
may not operate effectively in low resistance circumstances. For
example, ESU devices may not operate as desired when the resistance
is less than about 25 ohms. With continued reference to FIG. 2, in
some embodiments pad assembly 200 may include one or more
noninductive power resistors 260 in operative association with the
return lines. As shown here, the pad assembly can include two
return lines 230, and each of these lines may include two
noninductive power resistors 260. Each of the resistors may
provide, for example, between about 10 and about 50 ohms of
resistance. In some cases, the pad assembly 200 is configured to
allow up to 2 amps of current equally distributed in each of two
return lines.
[0031] An ESU can be configured to monitor return current
separately from two return paths. If the current exceeds a
predetermined threshold, the ESU may be configured to automatically
reduce or terminate power delivery.
[0032] FIG. 3 illustrates an anterior view of the heart, as viewed
through the front ribs or sternum. As shown here, a monopolar probe
assembly 310 can be placed within an interior chamber of the heart,
and a pad assembly can be placed posterior to the heart. A
pericardial reflection is typically present between the right and
left pulmonary veins. The process of ablating between the right and
left pulmonary veins, for example as illustrated by lesion or
ablation pattern, may involve a concomitant dissection of the
pericardial reflection between the right and left pulmonary veins
at or near the epicardium. The pericardial reflection presents a
ridge or line of attachment between the right and left pulmonary
veins. For example, FIG. 3 illustrates a pericardial reflection
between the right pericardial veins and the left pericardial veins.
Embodiments of the present invention provide systems and methods
for performing any of a variety of lesions or lesion sets on heart
tissue. For example, embodiments encompass the performance of a
posterior left atrial connection (PLAC) between 2 PV-encircling
ablations epicardially. Embodiments may also encompass the
performance of left atrial ablations. Embodiments also encompass
the creation of any of the lesions sets described in U.S. patent
application Ser. Nos. 12/124,743 and 12/124,766 filed May 21, 2008,
the disclosures of which are incorporated herein by reference.
[0033] FIG. 4 illustrates aspects of ablation treatment systems and
methods according to embodiments of the present invention.
Specifically, FIG. 4 depicts a posterior view of the heart, as
viewed through the rear ribs or backbone. As shown here, a pad
assembly 400 can be positioned anterior to the esophagus and
posterior to the heart. An exemplary pad assembly 400 may include a
conductive mechanism or surface 410 on the side of the pad assembly
that faces toward the atria, an electrical and thermal insulator
mechanism 420 on the side of the pad assembly that faces toward the
esophagus, and an electrical wire assembly 430 that provides
electrical connectivity between the conductive mechanism 410 and an
Electrical Surgical Unit (ESU). A portion of the pad is disposed
central to the four pulmonary veins (PV's). For example, in some
cases, the pad spans or covers at least about 80% of the area
between the right and left pulmonary veins. It is understood that
the pulmonary veins, esophagus, pericardium, skeleton, and other
anatomical features may not be rigidly attached with one another,
the heart may move relative to the esophagus due to a variety of
factors, including gravity, patient swallowing, or other movement
of the patient during surgery. Hence, the pad can be configured to
cover a selected amount of space between the pulmonary veins, to
accommodate for the shifting of such anatomical features while
still providing protection to the esophagus or other tissue during
an ablation treatment.
[0034] Indifferent pad assemblies can be used in conjunction with
an electrosurgical unit (ESU) such as the ESU 500 shown in FIG. 5.
ESU 500 can be used to supply and control power to a surgical probe
or other electrophysiological device, and may include a plurality
of displays 522, as well as buttons 524, 526 and 528 that are
respectively used to control which of the electrodes on the
electrophysiological device receive power, the level of power
supplied to the electrodes, and the temperature at the electrodes.
Power is supplied to the surgical probe or other
electrophysiological device by way of a power output connector 530.
Lesion creation procedures sometimes require that up to 2 amperes
be returned to the ESU 500 and, to that end, an indifferent pad
assembly that can handle up to 2 amperes can be placed within the
patient's body and connected with the ESU. The indifferent pad
assembly electrodes can be connected to a pair of power return
connectors 532 and 534 on the ESU 500. The power return connectors
532 and 534 in the exemplary ESU 500 illustrated in FIG. 5 has a
rectangular profile and recessed male pins 536, while the power
output connector 530 has a circular profile. In order to mate with
the rectangular power return connectors 532 and 534, the connector
160 (shown in FIG. 1) of the pad assembly includes a mating portion
162 with a rectangular profile and longitudinally extending female
pin-connects 164. The profile need not be perfectly rectangular so
long as the profile substantially corresponds to that of the power
return connectors 532 and 534. For example, the middle of the top
and bottom surfaces of mating portion 168 may include
longitudinally extending grooves for mechanical keying with the
corresponding connector. The shape and style of the power return
connectors 532 and 534 and the corresponding mating portion 162 on
the connector 160 need not be rectangular. However, in many cases,
both will have the same general shape and this shape will be
different than the shape of the power output connector 530, which
need not be circular, to prevent users from attempting to plug an
indifferent pad assembly into a power output connector and/or an
electrophysiological device into a power return connector.
Alternatively, the power output power return connectors could have
the same general shape and noticeably different sizes to prevent
confusion. Color coding may also be used.
[0035] FIG. 6 illustrates aspects of an indifferent pad assembly
600 according to embodiments of the present invention. Pad assembly
600 may include a conductive mechanism or surface 610 on the side
of the pad assembly that faces toward the atria, an electrical and
thermal insulator mechanism 620 on the side of the pad assembly
that faces toward the esophagus, and an electrical wire assembly
630 that provides electrical connectivity between the conductive
mechanism 610 and an Electrical Surgical Unit (ESU). Conductive
mechanism or surface 610 can include a flexible conductor material,
and electrical and thermal insulator mechanism 620 can include a
foam or other material which prevents or inhibits the flow or
transfer of heat or electricity. As shown here, wire assembly 630
may include a cable 632 having two wire mechanisms 634 and 636
extending from the pad or conductive mechanism 620. The cable
splits at a "Y", and two separated cable sections 644 and 646
terminate at connectors 650 and 660, respectively, which in turn
may be connected with, for example, power return connectors 532 and
534, respectively, of the ESU shown in FIG. 5. The ESU can be
configured to sense current individually to each connection and
shut off power if current to either return connection exceeds a
predetermined amount, for example 1 ampere. As described elsewhere
herein, in some situations for the pad assembly, ablation will
occur at the return indifferent pad assembly, which can correspond
to a bipolar mode technique.
[0036] In some cases, embodiments of the present invention can
incorporate various aspects of treatment systems and methods which
are disclosed in previously incorporated U.S. patent application
Ser. No. ______ filed Mar. 29, 2011 (docket no. 87512-798150).
[0037] Individual system elements or aspects of a tissue treatment
computer system may be implemented in a separated or more
integrated manner. In some embodiments treatment systems, which may
include computer systems, which may be part of or operatively
associated with an electrosurgical unit (ESU) such as the ESU 500
shown in FIG. 5, also include software elements, for example
located within a working memory of a memory, including an operating
system and other code, such as a program designed to implement
method embodiments of the present invention. In some cases,
software modules implementing the functionality of the methods as
described herein, may be stored in a storage subsystem. It is
appreciated that systems can be configured to carry out various
method aspects described herein. Each of the devices or modules of
the present invention can include software modules on a computer
readable medium that is processed by a processor, hardware modules,
or any combination thereof. Any of a variety of commonly used
platforms, such as Windows, MacIntosh, and Unix, along with any of
a variety of commonly used programming languages, such as C or C++,
may be used to implement embodiments of the present invention. In
some cases, tissue treatment systems include FDA validated
operating systems or software/hardware modules suitable for use in
medical devices. Tissue treatment systems can also include multiple
operating systems. For example, a tissue treatment system can
include a FDA validated operating system for safety critical
operations performed by the treatment system, such as data input,
power control, diagnostic procedures, recording, decision making,
and the like. A tissue treatment system can also include a
non-validated operating system for less critical operations. In
some embodiments, a computer system can be in integrated into a
tissue treatment system, and in some embodiments, a computer system
can be separate from, but in connectivity with, a tissue treatment
system. It will be apparent to those skilled in the art that
substantial variations may be used in accordance with any specific
requirements. For example, customized hardware might also be used
and/or particular elements might be implemented in hardware,
software (including portable software, such as applets), or both.
Further, connection to other computing devices such as network
input/output devices may be employed. Relatedly, any of the
hardware and software components discussed herein can be integrated
with or configured to interface with other medical treatment or
information systems used at other locations.
[0038] While the exemplary embodiments have been described in some
detail, by way of example and for clarity of understanding, those
of skill in the art will recognize that a variety of modification,
adaptations, and changes may be employed. Hence, the scope of the
present invention should be limited solely by the claims.
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