U.S. patent application number 11/058108 was filed with the patent office on 2005-11-03 for methods and devices for ablation.
Invention is credited to Anderson, Scott C., Champsaur, Gerard, Crowe, John E., Miller, Gary Henry, Morse, Stephen A., Podmore, Jonathan L., Sliwa, John W. JR., Vaska, Matthias.
Application Number | 20050245918 11/058108 |
Document ID | / |
Family ID | 46278852 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050245918 |
Kind Code |
A1 |
Sliwa, John W. JR. ; et
al. |
November 3, 2005 |
Methods and devices for ablation
Abstract
An ablating device has a cover which holds an interface material
such as a gel. The cover contains the interface material during
initial placement of the device. The ablating device may also have
a removable tip or a membrane filled with fluid. In still another
aspect, the ablating device may be submerged in liquid during
operation.
Inventors: |
Sliwa, John W. JR.; (Los
Altos, CA) ; Vaska, Matthias; (Palo Alto, CA)
; Podmore, Jonathan L.; (Millbrae, CA) ; Miller,
Gary Henry; (Milpitas, CA) ; Anderson, Scott C.;
(Sunnyvale, CA) ; Champsaur, Gerard; (Palo Alto,
CA) ; Crowe, John E.; (Palo Alto, CA) ; Morse,
Stephen A.; (Menlo Park, CA) |
Correspondence
Address: |
HOEKENDIJK & LYNCH, LLP
P.O. BOX 4787
BURLINGAME
CA
94011-4787
US
|
Family ID: |
46278852 |
Appl. No.: |
11/058108 |
Filed: |
February 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11058108 |
Feb 15, 2005 |
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10238821 |
Sep 10, 2002 |
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10238821 |
Sep 10, 2002 |
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10077470 |
Feb 15, 2002 |
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6840936 |
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10077470 |
Feb 15, 2002 |
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09884435 |
Jun 19, 2001 |
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6719755 |
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09884435 |
Jun 19, 2001 |
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09614991 |
Jul 12, 2000 |
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6805128 |
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09614991 |
Jul 12, 2000 |
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09507336 |
Feb 18, 2000 |
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09507336 |
Feb 18, 2000 |
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09356476 |
Jul 19, 1999 |
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6311692 |
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09356476 |
Jul 19, 1999 |
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09157824 |
Sep 21, 1998 |
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6237605 |
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09157824 |
Sep 21, 1998 |
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08943683 |
Oct 15, 1997 |
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6161543 |
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08943683 |
Oct 15, 1997 |
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08735036 |
Oct 22, 1996 |
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Current U.S.
Class: |
606/32 ;
606/41 |
Current CPC
Class: |
A61B 18/02 20130101;
A61B 2018/00023 20130101; A61N 1/056 20130101; A61B 2017/00252
20130101; A61B 2018/142 20130101; A61B 2018/00654 20130101; A61B
2018/00898 20130101; A61B 2017/00247 20130101; A61B 2090/3782
20160201; A61B 2018/00577 20130101; A61B 2090/395 20160201; A61B
18/04 20130101; A61B 2018/00797 20130101; A61B 34/20 20160201; A61B
2018/00005 20130101; A61B 2218/007 20130101; A61B 2017/22077
20130101; A61B 2018/00214 20130101; A61N 1/06 20130101; A61B
17/2251 20130101; A61B 2018/00375 20130101; A61B 2018/00982
20130101; A61B 2090/3614 20160201; A61B 18/24 20130101; A61N 1/3629
20170801; A61N 2007/0078 20130101; A61B 17/22012 20130101; A61B
2018/1472 20130101; A61B 2017/00243 20130101; A61B 2017/2253
20130101; A61B 2017/003 20130101; A61B 2018/0016 20130101; A61B
2018/1213 20130101; A61B 18/1482 20130101; A61B 2018/1861 20130101;
A61B 18/00 20130101; A61B 18/1815 20130101; A61B 2018/00392
20130101; A61B 5/287 20210101; A61B 2017/3419 20130101; A61B
2018/00285 20130101; A61B 2018/00363 20130101; A61B 2018/147
20130101; A61B 18/18 20130101; A61B 18/20 20130101; A61B 18/148
20130101; A61B 2018/00261 20130101; A61B 2018/00351 20130101; A61B
2218/002 20130101; A61B 2018/00291 20130101; A61B 2018/00839
20130101; A61B 18/1402 20130101; A61B 2018/2283 20130101; A61N 7/02
20130101; A61B 18/1492 20130101; A61B 2018/00232 20130101; A61B
17/2202 20130101; A61B 2018/1467 20130101 |
Class at
Publication: |
606/032 ;
606/041 |
International
Class: |
A61B 018/14 |
Claims
1-20. (canceled)
21. A device for ablating a target tissue, comprising: a plurality
of ablating elements; an emitter which emits energy toward the
target tissue; a receiver which receives energy transmitted through
the target tissue; a control system coupled to the ablating
elements, the emitter, and the receiver, the control system
determining a change in an energy characteristic of the energy
transmitted from the emitter to the receiver.
22. The device of claim 21, wherein: the control system has an
indicator which indicates the energy characteristic, the indicator
providing the user with an indication of a change in the energy
characteristic.
23. The device of claim 21, wherein: at least one of the ablating
element acts as the receiver.
24. The device of claim 21, wherein: the control system controls
the ablating element to stop emitting ablating energy while
receiving energy transmitted through the target tissue from the
emitter.
25. The device of claim 21, wherein: at least one of the ablating
elements acts as the emitter.
26. The device of claim 25, wherein: the control system controls
the ablating element to emit ablating energy which is different
than energy emitted which is received by the receiver.
27. The device of claim 21, wherein: at least one of the ablating
element acts as the receiver. at least one of the ablating elements
acts as the emitter.
28. The device of claim 21, wherein: the indicator provides an
indication of the magnitude of the energy received by the
receiver.
29. The device of claim 21, wherein: the indicator provides an
indication of the frequency of the energy passing through the
target tissue.
30. The device of claim 21, further comprising: an intravascular
device which acts as at least one of the emitter and receiver.
31. A method of ablating cardiac tissue, comprising the steps of:
providing an ablating device having at least one ablating element,
the ablating element having a focus; positioning the ablating
device on a epicardial surface, wherein the focus is positioned at
an angle with respect to the epicardial surface; and ablating
tissue with the ablating element with the device positioned on the
epicardial surface to form a first lesion.
32. The method of claim 31, wherein: the positioning step is
carried out with the focus being angled with respect to the
epicardial surface so that the focus extends through a substantial
portion of the thickness of the target tissue.
33. The method of claim 31, wherein: the positioning step is
carried out with the focus being angled with respect to the
epicardial surface so that the focus extends through the entire
thickness of the target tissue.
34. The method of claim 31, wherein: the providing step is carried
out with the angle of the ablating element being adjustable so that
the angle of the focus relative to the target tissue may be
varied.
35. The method of claim 31, further comprising the step of: moving
the ablating element; and ablating tissue again after the moving
step to form a second lesion continuous with the first lesion.
36. The method of claim 31, wherein: the moving step is carried out
with the ablating element continuing to ablate tissue.
37. The method of claim 31, wherein: the moving step is carried out
by moving the ablating device across the epicardial surface.
38. The method of claim 31, wherein: the providing step is carried
out with the ablating device being coupled to a guide member; and
the moving step is carried out with the ablating device being moved
relative to the guide member.
39. The method of claim 38, further comprising: positioning the
guide member at a fixed position relative to the target tissue; the
moving step being carried out a number of times with the guide
member being at the fixed position.
40. The method of claim 31, wherein: the providing step is carried
out with the ablating element producing focused ultrasound.
41. A device for ablating tissue, comprising: a shaft; and a
plurality of ablating elements coupled to the shaft, the plurality
of ablating elements being configured to produce a continuous
lesion in a target tissue.
42-59. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of
application Ser. No. 09/884,435, filed Jun. 19, 2001, which is a
continuation-in-part of application Ser. No. 09/614,991, filed Jul.
12, 2000, which is a continuation-in-part of application Ser. No.
09/507,336 filed Feb. 18, 2000 which is a continuation-in-part of
application Ser. No. 09/356,476, filed Jul. 19, 1999, which is a
continuation-in-part of application Ser. No. 09/157,824, filed Sep.
21, 1998, which is a continuation-in-part of application Ser. No.
08/943,683, filed Oct. 15, 1997, which is a continuation-in-part of
application Ser. No. 08/735,036, filed Oct. 22, 1996, the full
disclosures of which are incorporated herein by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] This invention relates generally to devices and methods for
ablating tissue. The diagnosis and treatment of
electrophysiological diseases of the heart, and more specifically
to devices and methods for epicardial mapping and ablation for the
treatment of atrial fibrillation, are described in connection with
the devices and methods of the present invention.
[0004] 2. Description of Related Art
[0005] Atrial fibrillation results from disorganized electrical
activity in the heart muscle, or myocardium. The surgical maze
procedure has been developed for treating atrial fibrillation and
involves the creation of a series of surgical incisions through the
atrial myocardium in a preselected pattern so as to create
conductive corridors of viable tissue bounded by scar tissue.
[0006] As an alternative to the surgical incisions used in the maze
procedure, transmural ablation of the heart wall has been proposed.
Such ablation may be performed either from within the chambers of
the heart (endocardial ablation) using endovascular devices (e.g.
catheters) introduced through arteries or veins, or from outside
the heart (epicardial ablation) using devices introduced into the
chest. Various ablation technologies have been proposed, including
cryogenic, radiofrequency (RF), laser and microwave. The ablation
devices are used to create elongated transmural lesions--that is,
lesions extending through a sufficient thickness of the myocardium
to block electrical conduction--which form the boundaries of the
conductive corridors in the atrial myocardium. Perhaps most
advantageous about the use of transmural ablation rather than
surgical incisions is the ability to perform the procedure on the
beating heart without the use of cardiopulmonary bypass.
[0007] In performing the maze procedure and its variants, whether
using ablation or surgical incisions, it is generally considered
most efficacious to include a transmural incision or lesion that
isolates the pulmonary veins from the surrounding myocardium. The
pulmonary veins connect the lungs to the left atrium of the heart,
and join the left atrial wall on the posterior side of the heart.
This location creates significant difficulties for endocardial
ablation devices for several reasons. First, while many of the
other lesions created in the maze procedure can be created from
within the right atrium, the pulmonary venous lesions must be
created in the left atrium, requiring either a separate arterial
access point or a transeptal puncture from the right atrium.
Second, the elongated and flexible endovascular ablation devices
are difficult to manipulate into the complex geometries required
for forming the pulmonary venous lesions and to maintain in such
positions against the wall of the beating heart. This is very
time-consuming and can result in lesions which do not completely
encircle the pulmonary veins or which contain gaps and
discontinuities. Third, visualization of endocardial anatomy and
endovascular devices is often inadequate and knowing the precise
position of such devices in the heart can be difficult, resulting
in misplaced lesions. Fourth, ablation within the blood inside the
heart can create thrombus which, in the right chambers, is
generally filtered out by the lungs rather than entering the
bloodstream. However, on the left side of the heart where the
pulmonary venous lesions are formed, thrombus can be carried by the
bloodstream into the coronary arteries or the vessels of the head
and neck, potentially resulting in myocardial infarction, stroke or
other neurologic sequelae. Finally, the heat generated by
endocardial devices which flows outward through the myocardium
cannot be precisely controlled and can damage extracardiac tissues
such as the pericardium, the phrenic nerve and other
structures.
[0008] What are needed, therefore, are devices and methods for
forming lesions that isolate the pulmonary veins from the
surrounding myocardium which overcome these problems. The devices
and methods will preferably be utilized epicardially to avoid the
need for access into the left chambers of the heart and to minimize
the risk of producing thrombus.
[0009] Additional aspects of the present invention are directed to
devices and methods for ablating tissue. Ablation of heart tissue
and, specifically, ablation of tissue for treatment of atrial
fibrillation is developed as a particular use of these other
aspects of the present invention.
SUMMARY
[0010] The present invention meets these and other objectives by
providing epicardial ablation devices and methods useful for
creating transmural lesions for the treatment of atrial
fibrillation.
[0011] In a first embodiment, a method of forming a transmural
lesion in a wall of the heart adjacent to the pulmonary veins
comprises the steps of placing at least one ablation device through
a thoracic incision and through a pericardial penetration so that
at least one ablation device is disposed in contact with an
epicardial surface of the heart wall; positioning at least one
ablation device adjacent to the pulmonary veins on a posterior
aspect of the heart while leaving the pericardial reflections
intact; and ablating the heart wall with at least one ablating
device to create at least one transmural lesion adjacent to the
pulmonary veins. While the method may be performed with the heart
stopped and circulation supported with cardiopulmonary bypass, the
method is preferably performed with the heart beating so as to
minimize morbidity, mortality, complexity and cost.
[0012] In another aspect of the invention, an apparatus for forming
a transmural lesion in the heart wall adjacent to the pulmonary
veins comprises, in a preferred embodiment, an elongated flexible
shaft having a working end and a control end; an ablation device
attached to the working end for creating a transmural lesion in the
heart wall; a control mechanism at the control end for manipulating
the working end; and a locating device near the working end
configured to engage one or more of the pulmonary veins, or a
nearby anatomical structure such as a pericardial reflection, for
positioning the working end adjacent to the pulmonary veins. The
locating device may comprise a catch, branch, notch or other
structure at the working end configured to engage one or more of
the pulmonary veins or other anatomical structure such as the
inferior vena cava, superior vena cava, aorta, pulmonary artery,
left atrial appendage, right atrial appendage, or one of the
pericardial reflections. The ablation device may be a
radiofrequency electrode, microwave transmitter, cryogenic element,
laser, ultrasonic transducer or any of the other known types of
ablation devices suitable for forming transmural lesions.
Preferably, the apparatus includes a plurality of such ablation
devices arranged along the working end in a linear pattern suitable
for forming a continuous, uninterrupted lesion around or on the
pulmonary veins.
[0013] The working end may additionally include one or more movable
elements that are manipulated from the control end and which may be
moved into a desired position after the working end has been
located near the pulmonary veins. Slidable, rotatable, articulated,
pivotable, bendable, pre-shaped or steerable elements may be used.
Additional ablation devices may be mounted to these movable
elements to facilitate formation of transmural lesions. The movable
elements may be deployed to positions around the pulmonary veins to
create a continuous transmural lesion which electrically isolates
the pulmonary veins from the surrounding myocardium.
[0014] In addition, a mechanism may be provided for urging all or
part of the working end against the epicardium to ensure adequate
contact with the ablation devices. This mechanism may be, for
example, one or more suction holes in the working end through which
suction may be applied to draw the working end against the
epicardium, or an inflatable balloon mounted to the outer side of
the working end such that, upon inflation, the balloon engages the
inner wall of the pericardium and forces the working end against
the epicardium. This also functions to protect extracardiac tissues
such as the pericardium from injury by retracting such tissues away
from the epicardial region which is being ablated, and, in the case
of the balloon, providing an insulated barrier between the
electrodes of the ablation probe and the extracardiac tissues.
[0015] The apparatus may be either a single integrated device or
two or more devices which work in tandem. In either case, the
apparatus may have two or more tips at the working end which are
positioned on opposing sides of a tissue layer such as a
pericardial reflection. A device may be provided for approximating
the two free ends on opposing sides of the tissue layer, such as an
electromagnet mounted to one or both of the free ends. In this way,
a continuous lesion may be created in the myocardium from one side
of the pericardial reflection to the other without puncturing or
cutting away the pericardial reflection.
[0016] The apparatus may further include a working channel through
which supplemental devices may be placed to facilitate
visualization, tissue manipulation, supplementary ablation,
suction, irrigation and the like.
[0017] The apparatus and methods of the invention are further
useful for mapping conduction pathways in the heart (local
electrograms) for the diagnosis of electrophysiological diseases.
Any of the electrodes on the apparatus may be individually selected
and the voltage may be monitored to determine the location of
conduction pathways. Alternatively, the apparatus of the invention
may be used for pacing the heart by delivering current through one
or more selected electrodes at levels sufficient to stimulate heart
contractions.
[0018] Additionally, although the ablation apparatus and methods of
the invention are preferably configured for epicardial use, the
principles of the invention are equally applicable to endocardial
ablation catheters and devices. For example, an endocardial
ablation apparatus according to the invention would include a
locating device configured to engage an anatomical structure
accessible from within the chambers of the heart such as the
coronary sinus (from the right atrium), pulmonary artery (from the
right ventricle), or the pulmonary veins (from the left atrium),
and the ablation device would be positionable in a predetermined
location relative to the locating device. The endocardial apparatus
could further include suction holes, expandable balloons, or other
mechanisms for maintaining contact between the ablation device and
the interior surface of the heart wall.
[0019] In another aspect of the present invention, an anchor is
used to hold part of the device while displacing another part of
the device. The anchor is preferably a balloon but may also be
tines, a suction port or a mechanically actuated device. After
actuating the anchor, a proximal portion of the device may be moved
by simply manipulating the device or by advancement or withdrawal
of a stylet.
[0020] The present invention is also related to a method of
creating a continuous ablation lesion in tissue underlying a
pericardial reflection without penetrating the pericardial
reflection. First and second ablating devices are introduced into
the space between the pericardium and the epicardium. The first
ablating device is positioned on one side of the pericardial
reflection and the second ablating device is positioned on the
other side of the pericardial reflection. Tissue beneath the
pericardial reflection is then ablated with one or both of the
devices to create a continuous lesion beneath the pericardial
reflection. The devices may be aligned across the pericardial
reflection by any suitable method such as with magnetic force, use
of an emitter and sensor, or by marking the pericardial reflection
on one side and locating the mark from the other side of the
pericardial reflection. The emitter and sensor may work with
electromagnetic radiation such as light, ultrasound, magnetic
field, and radiation.
[0021] In yet another aspect of the invention, the ablating device
may have a guide portion which aligns the device between the
pericardium and epicardium. The guide portion may be a continuous
strap or a number of discrete guide portions. The guide portions
may be fins, wings or one or more laterally extending elements such
as balloons. The guide portions may be individually actuated to
align the device and ablate discrete locations of the tissue along
the ablating device.
[0022] The ablating device may also be advanced into position over
a guide. The guide is preferably a guidewire but may be any other
suitable structure. The guide may also lock into position with a
coaxial cable or locking arm. The guide is advanced ahead of the
ablation device and positioned along the desired ablation path. The
ablating device is then advanced or retracted along the guide. The
ablating device preferably includes a device for locating
previously formed lesions so that subsequent lesions will merge
with a previously formed lesion to create a continuous, transmural
lesion. The device for locating previously created lesions may be
pacing and sensing electrodes or electrodes which simply measure
electrical impedance.
[0023] Although cutting through the pericardial reflections has
certain risks, the methods and devices of the present invention
may, of course, be practiced while cutting through the pericardial
reflections. After penetrating through the pericardial reflection,
the ablating device may interlock with another part of the same
device or with a separate device.
[0024] In another method and device of the present invention,
another ablating device is provided which may be used to ablate any
type of tissue including heart tissue for the reasons described
herein. The ablating device has a suction well and an ablating
element. The suction well adheres the device to the tissue to be
ablated. The device is preferably used to ablate cardiac tissue
from an epicardial location to form a transmural lesion. The device
preferably includes a number of cells which each have a suction
well and at least one ablating element. The cells are coupled
together with flexible sections which permit the cells to displace
and distort relative to one another. The device preferably has
about 5-30 cells, more preferably about 10-25 cells and most
preferably about 16 cells. The suction well has an inner lip and an
outer lip. The inner lip forms a closed wall around the ablating
element.
[0025] The device also has a fluid inlet and a fluid outlet for
delivering and withdrawing fluid from within the closed wall formed
by the inner lip. The fluid is preferably a conductive fluid, such
as hypertonic saline, which conducts energy from the ablating
element, such as an RF electrode, to the tissue. The fluid is
preferably delivered along a short axis of the ablating element so
that the temperature change across the ablating element is
minimized.
[0026] The ablating elements are preferably controlled by a control
system. One or more temperature sensors on the device are coupled
to the control system for use as now described. The control system
may control ablation in a number of different ways. For example,
the control system may activate one or more pairs of adjacent cells
to form continuous lesions between the adjacent cells. After
ablation at the one or more adjacent cells, another pair of
adjacent cells is activated to form another continuous ablation
segment. This process is continued until a continuous lesion of the
desired geometry is produced. In another mode of operation, the
control system may activate every other or every third cell. Still
another mode of operation is to activate only the ablating elements
which have low temperatures by using a multiplexer coupled to the
temperature sensors.
[0027] The control system may also conduct a thermal response
analysis of the tissue to be ablated to determine the appropriate
ablation technique. The tissue to be ablated is heated, or cooled,
and the temperature response of the tissue over time is recorded.
The temperature response is then analyzed to determine the
appropriate ablation technique. The analysis may be a comparison of
the temperature response against a database of temperature
responses or may be a calculation which may require user input as
described below.
[0028] In a further aspect of the invention, the ablating element
preferably produces focused ultrasound in at least one dimension.
An advantage of using focused ultrasound is that the energy can be
concentrated within the tissue. Another advantage of using focused
ultrasound is that the energy diverges after reaching the focus
thereby reducing the possibility of damaging tissue beyond the
target tissue as compared to collimated ultrasonic energy. When
ablating epicardial tissue with collimated ultrasound, the
collimated ultrasound energy not absorbed by the target tissue
travels through blood and remains concentrated on a relatively
small area when it reaches another surface such as the endocardial
surface on the other side of a heart chamber. The present invention
reduces the likelihood of damage to other structures since the
ultrasonic energy diverges beyond the focus and is spread over a
larger area. The focused ultrasound has a focal length of about 2
to 20 mm, more preferably about 2 to 12 mm and most preferably
about 8 mm in at least one dimension. The focused ultrasound also
forms an angle of 10 to 170 degrees, more preferably 30 to 90
degrees and most preferably about 60 degrees as defined relative to
a focal axis. The focused ultrasound preferably emits over 90%, and
more preferably over 99%, of the energy within the angles and focal
lengths described above. The focused ultrasound may be produced in
any manner and is preferably produced by a curved transducer with a
curved layer attached thereto. The ultrasound is preferably not
focused, and may even diverge, when viewed along an axis transverse
to the focal axis.
[0029] The ultrasound transducers are preferably operated while
varying one or more characteristics of the ablating technique such
as the frequency, power, ablating time, and/or location of the
focal axis relative to the tissue. In a first treatment method, the
transducer is activated at a frequency of 2-7 MHz, preferably about
3.5 MHz, and a power of 80-140 watts, preferably about 110 watts,
in short bursts. For example, the transducer may be activated for
0.01-1.0 second and preferably about 0.4 second. The transducer is
inactive for 2-90 seconds, more preferably 5-80 seconds, and most
preferably about 45 seconds between activations. Treatment at this
frequency in relatively short bursts produces localized heating at
the focus. Energy is not absorbed as quickly in tissue at this
frequency as compared to higher frequencies so that heating at the
focus is less affected by absorption in the tissue.
[0030] In a second treatment method, the transducer is operated for
longer periods of time, preferably about 1-4 seconds and more
preferably about 2 seconds, to distribute more ultrasound energy
between the focus and the near surface. The frequency during this
treatment is also 2-14 MHz, more preferably 3-7 MHz and preferably
about 6 MHz. The transducer is operated for 0.7-4 seconds at a
power of 20-60 watts, preferably about 40 watts. The transducer is
inactive for at least 3 seconds, more preferably at least 5 seconds
and most preferably at least 10 seconds between each
activation.
[0031] In a third treatment method, the ultrasonic transducer is
activated at a higher frequency to heat and ablate the near
surface. The transducer is preferably operated at a frequency of at
least 6 MHz and more preferably at least 10 MHz and most preferably
about 16 MHz. The transducer is operated at lower power than the
first and second treatment methods since ultrasound is rapidly
absorbed by the tissue at these frequencies so that the near
surface is heated quickly. In a preferred method, the transducer is
operated at 2-10 watts and more preferably about 5 watts. The
transducer is preferably operated until the near surface NS
temperature reaches 70-85 degrees C.
[0032] In general, the treatment methods described above deliver
energy closer and closer to the near surface NS with each
subsequent treatment method. Such a treatment method may be
practiced with other devices without departing from this aspect of
the invention and, as mentioned below, may be automatically
controlled by the control system.
[0033] The device preferably has a number of cells with each cell
having at least one ablating element. After ablating tissue with
all of the cells, gaps may exist between adjacent ablations. The
tissue in the gaps is preferably ablated by moving at least one of
the ablating elements. In one method, the entire device is shifted
so that each cell is used a second time to ablate one of the
adjacent gaps. Yet another method of ablating tissue in the gaps is
to tilt one or more of the ablating elements to direct the
ultrasound energy at the gaps between cells. The ablating element
may be moved, tilted or pivoted in any suitable manner and is
preferably tilted with an inflatable membrane. The transducer may
also simply be configured to direct ultrasound energy to tissue
lying beneath the gaps between adjacent transducers. In this
manner, the device does not need to be moved or tilted.
[0034] The device may be adhered to tissue with suction although
suction is not required. The device may also have a membrane filled
with a substance which transmits the ultrasound energy to the
tissue. The membrane conforms to the tissue and eliminates air gaps
between the device and tissue to be ablated. Alternatively, the
device may have a solid element which contacts the tissue and
transmits the ultrasound energy to the tissue. The device may also
be used with a gel applied to the tissue which transmits the
ultrasound energy and eliminates air gaps.
[0035] The device may also have a number of ultrasound transducers
with varying characteristics. For example, the device may have
cells which provide focused ultrasound having different focal
lengths or which are intended to operate at different frequencies
or power. In this manner, the user may select the appropriate cell
to ablate a particular tissue structure. For example, it may be
desirable to select an ablating element with a small focal length
and/or low power when ablating thin tissue.
[0036] An advantage of using ultrasound for ablating tissue is that
the transducer may be used for other measurements. For example, the
transducer may be used to provide temperature, tissue thickness,
thickness of fat or muscle layers, and blood velocity data. The
ultrasound transducer may also be used to assess the adequacy of
contact between the device and the tissue to be ablated. These
features find obvious use in the methods described herein and all
uses of ultrasound mentioned here, such as temperature feedback
control, may be accomplished using other methods and devices.
[0037] In another aspect of the invention, the ablating device has
a cover which extends over the bottom surface of the ablating
device. A fluid cavity is defined by a space between the cover and
bottom surface. A flowable material is positioned in the cavity.
The device is positioned in the desired ablation position and the
cover is then moved to expose the bottom surface while leaving the
flowable material positioned between the ablating device and the
tissue to be ablated.
[0038] In still another aspect of the present invention, the device
has a flexible tip which facilitates advancement of the device. The
tip preferably extends for at least two inches and is free of any
ablating elements. The tip is also preferably removable so that the
tip also does not interfere with creating a closed loop.
[0039] In yet another aspect of the present invention, a fluid
environment is created around the heart and the ablating device is
submerged in the fluid environment. The fluid environment helps to
ensure that no air bubbles or gaps are present and also can help to
regulate the temperature by controlling the fluid temperature.
[0040] In still another aspect, a fluid-filled membrane is provided
at the contact or bottom surface of the device. The membrane
preferably conforms to the shape of the tissue to be ablated and
may form a convex contact surface. A fluid may also be circulated
through the membrane to provide cooling as necessary. The membrane
may also have holes or may be permeable to permit some of the fluid
to leak from the membrane into contact with the tissue being
ablated.
[0041] Other aspects and advantages of the invention are disclosed
in the following detailed description and in the accompanying
drawings.
DESCRIPTION OF DRAWINGS
[0042] FIG. 1A is side view of a left ablation probe according to
the invention.
[0043] FIG. 1B is a side view of a right ablation probe according
to the invention.
[0044] FIGS. 2A-2F are side views of a working end of the left
ablation probe of FIG. 1A in various configurations thereof.
[0045] FIG. 3 is a side cross-section of the working end of the
left ablation probe of FIG. 1A.
[0046] FIG. 4 is a transverse cross-section of the shaft of the
left ablation probe of FIG. 1A.
[0047] FIGS. 5A-C are partial side cross-sections of the working
end of the left ablation probe of FIG. 1A, showing the deployment
of a superior sub-probe and inner probe thereof.
[0048] FIG. 6 is a side view of the left ablation probe of FIG.
1A.
[0049] FIG. 7 is a partial side cross-section of the handle of the
left ablation probe of FIG. 1A.
[0050] FIG. 8 is an anterior view of the thorax of a patient
illustrating the positioning of the left and right ablation probes
according to the method of the invention.
[0051] FIG. 9 is a side view of the interior of a patient's thorax
illustrating the positioning of the left and right ablation probes
according to the method of the invention.
[0052] FIG. 10 is a posterior view of a patient's heart
illustrating the use of the left and right ablation probes
according to the method of the invention.
[0053] FIG. 11 is a posterior view of a patient's heart
illustrating a transmural lesion formed according to the method of
the invention.
[0054] FIGS. 12 and 13 are side views of the left ablation probe of
the invention positioned on a patient's heart, showing a balloon
and suction ports, respectively, on the inner probe.
[0055] FIG. 14A shows the ablating device having a pre-shaped
distal portion.
[0056] FIG. 14B shows an alternative anchor.
[0057] FIG. 14C shows another anchor.
[0058] FIG. 14D shows still another anchor.
[0059] FIG. 15 shows the ablating device having a flexible distal
portion which is shaped with a stylet.
[0060] FIG. 16 is a cross-sectional view of the ablating device of
FIGS. 14 and 15 with three chambers of the balloon inflated.
[0061] FIG. 17 is a cross-sectional view of the ablating device of
FIGS. 14 and 15 with two chambers of the balloon inflated.
[0062] FIG. 18 shows the ablating device advanced into the
transverse pericardial sinus with the balloon deflated.
[0063] FIG. 19 shows the ablating device advanced into the
transverse pericardial sinus with the balloon inflated.
[0064] FIG. 20 shows the ablating device extending between the left
and right inferior pulmonary veins and another ablating device
having an end superior to the right superior pulmonary vein.
[0065] FIG. 21 shows the ablating device moved toward the right
superior and right inferior pulmonary veins.
[0066] FIG. 22 shows one of the ablating devices having an emitter
and the other ablating device having a sensor for aligning the
devices across a pericardial reflection.
[0067] FIG. 23 shows the ablating device having a needle to deliver
a marker which is located on the other side of the pericardial
reflection.
[0068] FIG. 24 shows the ablating device having a number of
discrete guide portions.
[0069] FIG. 25 shows the guide portions being inflatable
balloons.
[0070] FIG. 26 shows selective inflation of the balloons for
selective ablation along the ablating device.
[0071] FIG. 27A shows the guide portions used when ablating around
the pulmonary veins.
[0072] FIG. 27B shows the guide portions being inflatable when
ablating around the pulmonary veins.
[0073] FIG. 28 is a bottom view of another ablating device which is
advanced over a guide.
[0074] FIG. 29 is a top view of the ablating device of FIG. 28.
[0075] FIG. 30 is a cross-sectional view of the ablating device of
FIGS. 28 and 29 along line A-A of FIG. 29.
[0076] FIG. 31 is another cross-sectional view of the ablating
device of FIGS. 28 and 29 along line B-B of FIG. 29.
[0077] FIG. 32 shows the guide advanced to a desired location with
the balloon deflated.
[0078] FIG. 33 shows the ablating device advanced over the guide
and creating a first lesion.
[0079] FIG. 34 shows the ablating device creating a second lesion
continuous with the first lesion.
[0080] FIG. 35 shows the ablating device creating a third lesion
continuous with the second lesion.
[0081] FIG. 36 shows another ablating device having an expandable
device movable thereon.
[0082] FIG. 37 is a cross-sectional view of the ablating device of
FIG. 36.
[0083] FIG. 38 is an enlarged view of the cross-sectional view of
FIG. 37.
[0084] FIG. 39 shows the ablating device with a piercing element in
a retracted position.
[0085] FIG. 40 shows the ablating device aligned across the
pericardial reflection.
[0086] FIG. 41 shows the ablating device interlocked with another
ablating device on opposite sides of the pericardial
reflection.
[0087] FIG. 42 shows a mechanism for locking the first and second
ablating devices together.
[0088] FIG. 43 shows the piercing element engaging a lock on the
other ablating device.
[0089] FIG. 44 shows the ablating device passing through the
pericardial reflection and interlocking with itself.
[0090] FIG. 45 shows the ablating devices interlocked across the
pericardial reflections.
[0091] FIG. 46 shows the ablating device adhered to a pericardial
reflection with suction.
[0092] FIG. 47 shows the penetrating element penetrating the
pericardial reflection.
[0093] FIG. 48 shows the ablating device passing through the
pericardial reflection.
[0094] FIG. 49 shows another ablating device.
[0095] FIG. 50 shows a buckle for forming a closed loop with the
ablating device.
[0096] FIG. 51 shows another buckle for forming the closed loop
with the ablating device.
[0097] FIG. 52 shows a bottom side of the ablating device of FIG.
49.
[0098] FIG. 53A is a cross-sectional view of the ablating device
along line C-C of FIG. 52.
[0099] FIG. 53B is an alternative cross-sectional view of the
ablating device along line C-C of FIG. 52.
[0100] FIG. 54 is a cross-sectional view of the ablation device
along line D-D of FIG. 53A showing a fluid inlet manifold.
[0101] FIG. 55 is a cross-sectional view of an alternative
embodiment of the device.
[0102] FIG. 56 shows a system for controlling the ablation device
of FIG. 55.
[0103] FIG. 57 shows the device having two sets of lumens extending
from each end of the device toward the middle of the device.
[0104] FIG. 58 shows another ablating device.
[0105] FIG. 59 is an exploded view of a cell of the ablating
device.
[0106] FIG. 60 is a cross-sectional view of the ablating device of
FIG. 60.
[0107] FIG. 61 is a perspective view of a transducer with a layer
attached thereto.
[0108] FIG. 62 is an end view of the transducer and layer.
[0109] FIG. 63 is a plan view of the transducer and layer.
[0110] FIG. 64 shows another ablating device with a membrane filled
with a substance with transmits energy from the transducer to the
tissue.
[0111] FIG. 65 shows the membrane inflated to move the focus
relative to the tissue.
[0112] FIG. 66 shows another ablating device with a membrane which
tilts the device when inflated.
[0113] FIG. 67 shows another ablating device.
[0114] FIG. 68 shows still another ablating device having at least
two ablating elements which have different ablating
characteristics.
[0115] FIG. 69 is an isometric view of another ablating element
which diverges in at least one dimension to ablate tissue beneath
gaps between ablating elements.
[0116] FIG. 70 is a side view of the ablating element of FIG.
69.
[0117] FIG. 71 shows still another device for ablating tissue.
[0118] FIG. 72 is a partial cross-sectional view showing three
ablating elements which are movable within a body of the
device.
[0119] FIG. 73 shows the ablating elements with the body
removed.
[0120] FIG. 74 shows the ablating device having a cover.
[0121] FIG. 75 shows a system for ablating tissue which provides a
liquid environment around the heart.
[0122] FIG. 76 shows another system for providing a liquid
environment around the heart.
[0123] FIG. 77 shows another system for ablating tissue with a
membrane extending over the ablating element.
[0124] FIG. 78 shows the membrane extending over a number of
ablating elements.
[0125] FIG. 79 shows a flexible skirt surrounding the ablating
element.
[0126] FIG. 80 shows another embodiment of the flexible skirt.
[0127] FIG. 81A shows an ablating element which moves along a guide
member and travels toward and away from the target tissue.
[0128] FIG. 81B shows another ablating element moving along another
guide member.
[0129] FIG. 82 is a partial cut-away of the guide member with
another ablating element contained therein having a focus which is
tilted relative to the target tissue.
[0130] FIG. 83 is a partial cut-away of the guide member with
another ablating element contained therein.
[0131] FIG. 84 shows another guide member with another ablating
element.
[0132] FIG. 85 shows another ablating device which has a shaft for
stabilizing the device.
[0133] FIG. 86 shows a bottom view of the ablating device of FIG.
85
[0134] FIG. 87 shows still another ablation device;
[0135] FIG. 88 shows the distal end of the ablation device
DETAILED DESCRIPTION
[0136] FIGS. 1A-1B illustrate a first embodiment of the apparatus
of the invention. In this embodiment, the apparatus comprises a
left ablation probe 20, shown in FIG. 1A, and a right ablation
probe 22, shown in FIG. 1B, which work in tandem to form a
transmural lesion isolating the pulmonary veins from the
surrounding myocardium. Left ablation probe 20 has a flexible shaft
21 extending to a working end 24 configured for insertion into the
chest cavity through a small incision, puncture or access port.
Opposite working end 24, shaft 21 is attached to a control end 26
used for manipulating the working end 24 from outside the chest.
Shaft 21 is dimensioned to allow introduction through a small
incision in the chest, preferably in a subxiphoid location, and
advanced to the pulmonary veins on the posterior side of the heart.
Preferably, shaft 21 is configured to be flexible about a first
transverse axis to allow anterior-posterior bending and torsional
flexibility, but relatively stiff about a second transverse axis
perpendicular to the first transverse axis to provide lateral
bending stiffness. In an exemplary embodiment, shaft 21 has a
length in the range of about 10-30 cm, and a guide portion 25
having a rectangular cross-section with a width-to-height ratio of
about 2-5, the cross-sectional width being about 6-35 mm and the
cross-sectional height being about 3-17 mm. The guide portion 25
aligns the device between the epicardium and pericardium to ablate
tissues as described below. Shaft 21 is made of a flexible
biocompatible polymer such as polyurethane or silicone, and
preferably includes radiopaque markers or a radiopaque filler such
as bismuth or barium sulfate.
[0137] Working end 24 includes a plurality of ablating elements 27.
The ablating elements 27 are preferably a plurality of electrodes
28 for delivering radiofrequency (RF) current to the myocardium so
as to create transmural lesions of sufficient depth to block
electrical conduction. Electrodes 28 may be partially-insulated
solid metal rings or cylinders, foil strips, wire coils or other
suitable construction for producing elongated lesions. Electrodes
28 are spaced apart a distance selected so that the lesions created
by adjacent electrodes contact or overlap one another, thereby
creating a continuous, uninterrupted lesion in the tissue
underlying the electrodes. In an exemplary embodiment, electrodes
28 are about 2-20 mm in length and are spaced apart a range of 1-6
mm. It is understood that the term electrodes 28 as used herein may
refer to any suitable ablating element 27. For example, as an
alternative to RF electrodes, the ablating elements 27 may be
microwave transmitters, cryogenic element, laser, heated element,
ultrasound, hot fluid or other types of ablation devices suitable
for forming transmural lesions. The heated element may be a
self-regulating heater to prevent overheating. Electrodes 28 are
positioned so as to facilitate lesion formation on the
three-dimensional topography of the left atrium. For example,
lateral electrodes 28a face medially to permit ablation of the
myocardium on the lateral side of the left inferior pulmonary vein
and medial electrodes 28b face anteriorly to permit ablation of the
posterior surface of the myocardium adjacent to the left inferior
pulmonary vein.
[0138] Working end 24 further includes a locating mechanism which
locates the working end at one of the pulmonary veins and helps to
maintain it in position once located. In a preferred embodiment,
working end 24 is bifurcated into two branches 30, 32, and the
locating mechanism is a notch 34 disposed between the two branches.
Notch 34 tapers into a concave surface 36 so as to receive one of
the pulmonary veins between branches 30, 32 and to atraumatically
engage the pulmonary vein against concave surface 36. In an
exemplary embodiment, notch 34 is about 10 to 30 mm in width at its
widest point between branches 30, 32 and tapers toward concave
surface 36 which has a radius of curvature of about 4 to 15 mm, so
as to conform to the outer curvature of the pulmonary vein.
Preferably, notch 34 is sized and positioned for placement against
the left inferior pulmonary vein, as described more fully below.
Alternatively, the locating mechanism may be configured to engage
another anatomic structure such as the inferior vena cava, superior
vena cava, pericardial reflections, pulmonary vein, aorta,
pulmonary artery, atrial appendage, or other structure in the space
between the pericardium and the myocardium. The various shapes of
the ablating devices described and shown herein are, of course,
useful in locating various structures to position the ablating
elements against predetermined tissues to be ablated.
[0139] Working end 24 further includes a superior sub-probe 38 and
an inferior sub-probe 40 which are slidably extendable from working
end 24, as further described below.
[0140] Control end 26 includes a handle 42 and a plurality of
slidable actuators 44A-44E, which are used to extend superior
sub-probe 38 and inferior sub-probe 40 from working end 24, and to
perform other functions as described below. An electrical connector
46 suitable for connection to an RF generator is mounted to handle
42 and is electrically coupled to electrodes 28 at working end 24.
Also mounted to handle 42 are a working port 48 in communication
with a working channel 92, described below, and a connector 50 for
connection to a source of inflation fluid or suction, used for
purposes described below.
[0141] Right ablation probe 22 has a flexible shaft 52 extending
from a control end 54 to a working end 56. Working end 56 has a
cross-member 58 to which are mounted a plurality of electrodes 60.
Cross member 58 preferably has tips 59 which are pre-shaped or
deflectable into a curve so as to conform to the right lateral
walls of the right pulmonary veins, and which are separated by a
distance selected so that the two right pulmonary veins may be
positioned between them, usually a distance of about 20-50 mm.
Electrodes 60 are sized and positioned so as to create a continuous
lesion along the right side (from the patient's perspective) of the
pulmonary veins as described more fully below. In an exemplary
embodiment, electrodes 60 are about 2-20 mm in length, and are
spaced apart about 1-6 mm. Shaft 52 is dimensioned to allow
introduction through a small incision in the chest, preferably in a
subxiphoid location, and advanced to the pulmonary veins on the
posterior side of the heart. Shaft 52 will have dimensions,
geometry and materials like those of shaft 21 of left ablation
probe 20, described above.
[0142] Control end 54 includes a handle 62. An electrical connector
64 adapted for connection to an RF generator is attached to handle
62 and is electrically coupled to electrodes 60 at working end 56.
An inflation or suction connector 65 is mounted to handle 62 and
adapted for connection to a source of inflation fluid or suction,
for purposes described below. Handle 62 may further include a
working port (not shown) like working port 48 described above in
connection with left ablation probe 20.
[0143] FIGS. 2A-2E illustrate the deployment of the various
components of working end 24 of left ablation probe 20. Superior
sub-probe 38 is slidably extendable from working end 24 as shown in
FIG. 2B. A plurality of electrodes 66 are mounted to superior
sub-probe 38 and are sized and positioned to create a continuous
lesion along the left side of the pulmonary veins. Superior
sub-probe 38 has an articulated or steerable section 68 which can
be selectively shaped into the position shown in FIG. 2C, with its
distal tip 70 pointing in a lateral direction relative to the more
straight proximal portion 72.
[0144] As shown in FIG. 2D, an inner probe 74 is slidably
extendable from superior sub-probe 38 and is directed by steerable
section 68 in a lateral direction opposite notch 34. Inner probe 74
is separated from notch 34 by a distance selected such that inner
probe 74 may be positioned along the superior side of the pulmonary
veins when the left inferior pulmonary vein is positioned in notch
34. In an exemplary embodiment, the maximum distance from concave
surface 36 to inner probe 74 is about 20-50 mm. A plurality of
electrodes 76 are mounted to inner probe 74 and positioned to
enable the creation of a continuous transmural lesion along the
superior side of the pulmonary veins as described more fully
below.
[0145] Referring to FIG. 2E, inferior sub-probe 40 is slidably
extendable from working end 24. Its distal tip 78 is attached to a
tether 80 extending through a lumen in shaft 21. Tether 80 may be
selectively tensioned to draw distal tip 78 away from inner probe
74 (toward control end 26), imparting a curvature to inferior
sub-probe 40. Inferior sub-probe 40 is constructed of a resilient,
bendable plastic which is biased into a straight configuration.
When inferior sub-probe 40 has been advanced sufficiently, tether
80 may be released, whereby the resiliency of inferior sub-probe 40
causes it to conform to the pericardial reflection and the medial
and/or inferior sides of the four pulmonary veins. Inferior
sub-probe 40 further includes a plurality of electrodes 82 sized
and positioned to produce a continuous transmural lesion in the
myocardium along the inferior side of the pulmonary veins, as
described more fully below.
[0146] Referring to FIGS. 3 and 4, superior sub-probe 38 is
slidably disposed in a first lumen 84 and inferior sub-probe 40 is
slidably disposed in a second lumen 86 in shaft 21. Electrodes 28
along notch 34 are coupled to wires 88 disposed in a wire channel
90 running beneath electrodes 28 and extending through shaft 21.
Each electrode is coupled to a separate wire to allow any electrode
or combination of electrodes to be selectively activated. Shaft 21
also includes a working channel 92 extending to an opening 94 in
working end 24 through which instruments such as endoscopes,
suction/irrigation devices, mapping and ablation devices, tissue
retraction devices, temperature probes and the like may be
inserted. Superior sub-probe 38 has an inner lumen 96 in which
inner probe 74 is slidably disposed. Electrodes 76 on inner probe
74 are coupled to wires 98 extending through inner probe 74 to
connector 46 on handle 42, shown in FIG. 1A. Similarly, electrodes
66 on superior sub-probe 38 are coupled to wires 99 (FIG. 4) and
electrodes 82 on inferior sub-probe 40 are coupled to wires 100,
both sets of wires extending to connector 46 on handle 42. Tether
80 slidably extends through tether lumen 102 in shaft 21.
[0147] The distal end of inner probe 74 has a tip electrode 104 for
extending the transmural lesion produced by electrodes 76.
Preferably, inner probe 74 further includes a device for
approximating the tip of inner probe 74 with the superior tip 106
of right ablation probe 22 (FIG. 1B) when the two are separated by
a pericardial reflection. In a preferred embodiment, a first
electromagnet 108 is mounted to the distal end of inner probe 74
adjacent to tip electrode 104. First electromagnet 108 is coupled
to a wire 110 extending to handle 42, where it is coupled to a
power source and a switch (not shown) via connector 46 or a
separate connector. Similarly, a second electromagnet 112 is
mounted to distal tip 78 of inferior sub-probe 40, adjacent to a
tip electrode 114, which are coupled to wires 116, 118 extending to
a connector on handle 42. As shown in FIG. 1B, a third
electromagnet 120 is mounted to superior tip 106 of right ablation
probe 22, and a fourth electromagnet 122 is mounted to inferior tip
124 of right ablation probe 22. Electromagnets 120, 122 are coupled
to wires (not shown) extending to a connector on handle 62 for
coupling to a power source and switch. In this way, superior tip
106 and inferior tip 124 may be approximated with inner probe 74
and inferior sub-probe 40 across a pericardial reflection by
activating electromagnets 108, 112, 120, 122.
[0148] It should be noted that thermocouples, thermistors or other
temperature monitoring devices may be mounted to the working ends
of either left or right ablation probes 20, 22 to facilitate
temperature measurement of the epicardium during ablation. The
thermocouples may be mounted adjacent to any of the electrodes
described above, or may be welded or bonded to the electrodes
themselves. The thermocouples will be coupled to wires which extend
through shafts 21, 52 alongside the electrode wires to connectors
46, 64 or to separate connectors on handles 42, 62, facilitating
connection to a temperature monitoring device.
[0149] FIGS. 5A-5C illustrate the operation of superior sub-probe
38. Superior sub-probe 38 has a pull wire 126 movably disposed in a
wire channel 128 in a sidewall adjacent to inner lumen 96. Pull
wire 126 is fixed at its distal end 130 to steerable section 68 of
superior sub-probe 38. Steerable section 68 is constructed of a
flexible, resilient plastic such that by tensioning pull wire 126,
steerable section 68 may be deformed into a curved shape to direct
inner probe 74 in a transverse direction relative to the straight
proximal portion 72, as shown in FIG. 5B. Once in this curved
configuration, inner probe 74 may be slidably advanced from
superior sub-probe 38 as shown in FIG. 5C.
[0150] Referring to FIG. 6, actuator 44D is slidably disposed in a
longitudinal slot 132 in handle 42 and is coupled to the proximal
end of inferior sub-probe 40. Actuator 44E is slidably disposed in
a longitudinal slot 134 in handle 42 and is coupled to the proximal
end of tether 80. When sub-probe 40 is to be deployed, actuator 44D
is slid forward, advancing inferior sub-probe 40 distally. Actuator
44E may be allowed to slide forward as well, or it may be held in
position to maintain tension on tether 80, thereby bending
sub-probe 40 into the curved shape shown in FIG. 2E. When sub-probe
40 has been fully advanced, actuator 44E may be released, allowing
distal end 78 of sub-probe 40 to engage the pericardial reflection
along the inferior surfaces of the pulmonary veins, as further
described below.
[0151] Actuators 44A-C are slidably disposed in a longitudinal slot
136 in handle 42, as more clearly shown in FIG. 7. Actuator 44A is
attached to the proximal end of superior sub-probe 38, and may be
advanced forward to deploy the sub-probe from working end 24, as
shown in FIG. 2A. Actuator 44B is attached to inner probe 74, which
is frictionally retained in inner lumen 96 such that it is drawn
forward with superior sub-probe 38. Actuator 44C is attached to
pull wire 126 which is also drawn forward with superior sub-probe
38. In order to deflect the steerable section 68 of superior
sub-probe 38, actuator 44C is drawn proximally, tensioning pull
wire 126 and bending steerable section 68 into the configuration of
FIG. 2C. Finally, to deploy inner probe 74, actuator 44B is pushed
forward relative to actuators 44A and 44C, advancing inner probe 74
from superior sub-probe 38 as shown in FIG. 2D.
[0152] The slidable relationship between the shafts and probes 74,
40, 38 helps to guide and direct the probes to the tissues to be
ablated. The shafts have various features, including the ablating
elements 27, however, the shafts may be simple sheaths which locate
structures and/or direct the probes into various regions of the
pericardial space.
[0153] Referring now to FIGS. 8-11, a preferred embodiment of the
method of the invention will be described. Initially, left ablation
probe 20 and right ablation probe 22 are connected to an RF
generator 140. RF generator 140 will preferably provide up to 150
watts of power at about 500 kHz, and will have capability for both
temperature monitoring and impedance monitoring. A suitable
generator would be, for example, a Model No. EPT-1000 available
from the EP Technologies Division of Boston Scientific Corp. of
Natick, Mass. Retraction, visualization, temperature monitoring,
suction, irrigation, mapping or ablation devices may be inserted
through working port 142. Left ablation probe 20 may further be
connected to a source of suction or inflation fluid 144, for
reasons described below. If electromagnets are provided on left and
right ablation probes 20, 22 as described above, an additional
connection may be made to a power supply and switch for operating
the electromagnets, or power may be supplied by RF generator 140
through connectors 46, 64.
[0154] A subxiphoid incision (inferior to the xiphoid process of
the sternum) is made about 2-5 cm in length. Under direct vision
through such incision or by visualization with an endoscope, a
second small incision is made in the pericardium P (FIG. 9). Left
ablation probe 20 is introduced through these two incisions and
advanced around the inferior wall of the heart H to its posterior
side under fluoroscopic guidance using fluoroscope 146. Alternative
methods of visualization include echocardiography, endoscopy,
transillumination, and magnetic resonance imaging. Left ablation
probe 20 is positioned such that left inferior pulmonary vein LI is
disposed in notch 34 as shown in the posterior view of the heart in
FIG. 10.
[0155] Superior sub-probe 38 is then advanced distally from working
end 24 until its steerable section 68 is beyond the superior side
of the left superior pulmonary vein LS. Steerable section 68 is
then deflected into the curved configuration shown in FIG. 10 such
that its distal end 70 is superior to the left superior pulmonary
vein LS and pointing rightward toward the right superior pulmonary
vein RS. Inner probe 74 is then advanced toward the right until its
distal tip is very close to or contacting the pericardial
reflection PR superior to the right superior pulmonary vein RS.
[0156] Inferior sub-probe 40 is next advanced from working end 24
while maintaining tension on tether 80 such that the inferior
sub-probe engages and conforms to the shape of the pericardial
reflection PR between the left inferior and right inferior
pulmonary veins. When inferior sub-probe 40 has been fully
advanced, tension is released on tether 80 so that distal tip 78
moves superiorly into engagement with the right inferior pulmonary
vein RI adjacent to pericardial reflection PR inferior thereto.
[0157] Right ablation probe 22 is placed through the subxiphoid
incision and pericardial incision and advanced around the right
side of the heart as shown in FIG. 8. Under fluoroscopic guidance,
right ablation probe 22 is positioned such that cross-member 58
engages the right superior and inferior pulmonary veins, as shown
in FIG. 10. In this position, superior tip 106 and inferior tip 124
should be generally in opposition to distal tip 75 of inner probe
74 and distal tip 78 of inferior sub-probe 40, respectively,
separated by pericardial reflections PR. In order to ensure close
approximation of the two tip pairs, electromagnets 108, 120, 114,
122 may be energized, thereby attracting the tips to each other
across the pericardial reflections RS.
[0158] It should be noted that the pericardium P attaches to the
heart at the pericardial reflections PR shown in FIGS. 10-11.
Because of the posterior location of the pulmonary veins and the
limited access and visualization available, cutting or puncturing
the pericardial reflections in the vicinity of the pulmonary veins
poses a risk of serious injury to the heart or pulmonary veins
themselves. The apparatus and method of the present invention avoid
this risk by allowing the pericardial reflections to remain intact,
without any cutting or puncturing thereof, although the pericardial
reflections may also be cut without departing from the scope of the
invention.
[0159] RF generator 140 is then activated to deliver RF energy to
electrodes 28, 60, 66, 76, 82, 104, and 112 on left and right
ablation probes 20, 22, producing the transmural lesion L shown in
FIG. 11. Preferably, power in the range of 20-150 watts is
delivered at a frequency of about 500 kHz for a duration of about
30-180 seconds, resulting in localized myocardial temperatures in
the range of 45-95.degree. C. Ultrasound visualization may be used
to detect the length, location and/or depth of the lesion created.
Lesion L forms a continuous electrically-insulated boundary
encircling the pulmonary veins thereby electrically isolating the
pulmonary veins from the myocardium outside of lesion L.
[0160] Ablation probes 20, 22 may further be used for mapping
conduction pathways in the heart (local electrocardiograms) for the
diagnosis of electrophysiological abnormalities. This is
accomplished by selecting any of the electrodes on the ablation
probes and monitoring the voltage. A commercially available
electrophysiology monitoring system is utilized, which can select
any electrode on the ablation probes and monitor the voltage.
Various electrodes and various locations on the heart wall may be
selected to develop a map of potential conduction pathways in the
heart wall. If ablation treatment is then required, the steps
outlined above may be performed to create transmural lesions at the
desired epicardial locations.
[0161] During any of the preceding steps, devices may be placed
through working port 142 and working channel 92 to assist and
supplement the procedure. For example, a flexible endoscope may be
introduced for visualization to assist positioning. Ultrasound
probes may be introduced to enhance visualization and for measuring
the location and/or depth of transmural lesions. Suction or
irrigation devices may be introduced to clear the field and remove
fluid and debris. Tissue manipulation and retraction devices may be
introduced to move and hold tissue out of the way. Cardiac mapping
and ablation devices may also be introduced to identify conduction
pathways and to supplement the ablation performed by left and right
ablation probes 20, 22.
[0162] Furthermore, mapping and ablation catheters, temperature
monitoring catheters, and other endovascular devices may be used in
conjunction with the left and right ablation probes of the
invention by introducing such devices into the right atrium or left
atrium either through the arterial system or through the venous
system via the right atrium and a transeptal puncture. For example,
an ablation catheter may be introduced into the left atrium to
ablate any region of the myocardium not sufficiently ablated by
left and right ablation probes 20, 22 in order to ensure complete
isolation of the pulmonary veins. Additionally, ablation catheters
may be introduced into the right chambers of the heart, or
epicardial ablation devices may be introduced through incisions in
the chest, to create other transmural lesions.
[0163] In some cases, it may be desirable to actively ensure
adequate contact between the epicardium and the electrodes of left
and right ablation probes 20, 22. For this purpose, left ablation
probe 20 and/or right ablation probe 22 may include one or more
expandable devices such as balloons which are inflated in the space
between the heart and the pericardium to urge the ablation probe
against the epicardial surface. An exemplary embodiment is shown in
FIG. 12, in which a balloon 150 is mounted to the outer surface of
inner probe 74 opposite electrodes 76 on left ablation probe 20.
Inner probe 74 further includes an inflation lumen 152 in
communication with an opening 154 within balloon 150 and extending
proximally to inflation fitting 50 on handle 42, through which an
inflation fluid such as liquid saline or gaseous carbon-dioxide may
be delivered. When inflated, balloon 150 engages the inner surface
of the pericardium P and urges inner probe 74 against the
epicardial surface of heart H. This ensures close contact between
electrodes 76 and the epicardium, and protects extracardiac tissue
such as the pericardium and phrenic nerve from injury caused by the
ablation probes. Balloons or other expandable devices may similarly
be mounted to superior sub-probe 38, inferior sub-probe 40, or
right ablation probe 22 to ensure sufficient contact between the
epicardium and the electrodes on those components.
[0164] Alternatively or additionally, suction ports may be provided
in the ablation probes of the invention to draw the electrodes
against the epicardium, as shown in FIG. 13. In an exemplary
embodiment, suction ports 156 are disposed in inner probe 74
between or adjacent to electrodes 76. Suction ports 156 are in
communication with a suction lumen 158 which extends proximally to
suction fitting 48 on handle 42. In this way, when suction is
applied through suction port 156, inner probe 74 is drawn tightly
against the heart, ensuring good contact between electrodes 76 and
the epicardium. In a similar manner, superior sub-probe 38,
inferior sub-probe 40 and right ablation probe 22 may include
suction ports adjacent to the electrodes on those components to
enhance contact with the epicardium.
[0165] Referring to FIGS. 14A, 15, 16 and 17, the ablating device
20 is shown with various features described above. The embodiments
are specifically referred to as ablating device 20A and like or
similar reference numbers refer to like or similar structure. The
ablating device 20A may have any of the features of the ablating
devices 20, 22 described above and all discussion of the ablating
devices 20, 22 or any other ablating device described herein is
incorporated here. As mentioned above, the ablating device 20A may
have a pre-shaped portion 160 or a flexible or bendable portion 162
as shown in FIGS. 14 and 15, respectively. A stylet 164 or sheath
(not shown) is used to shape the ablating device 20A as described
below. The stylet 164 passes through a working channel 166 which
may receive other devices as described above. The working channel
166 may also be coupled to a source of fluid 169, such as
fluoroscopic contrast, which may be used for visualization. The
contrast may be any suitable contrast including barium, iodine or
even air. The fluoroscopic contrast may be introduced into the
pericardial space to visualize structures in the pericardial
space.
[0166] Referring to FIG. 14A, the pre-shaped portion 160 has a
curved or L-shape in an unbiased position. The distal portion of
the device 20A may have any other shape such as a hook or C-shape
to pass the device 20A around a structure. The stylet 164 holds the
pre-shaped portion 160 in any other suitable geometry, such as
dotted-line 167, for introduction and advancement of the ablating
device 20A. The stylet 164 may also be malleable. When the ablating
device 20A is at the appropriate position, the stylet 164 is
withdrawn thereby allowing the distal end 160 to regain the angled
or curved shape. The device 20A may also be shaped with a sheath
(not shown) through which the device 20A passes in a manner similar
to the manner of FIGS. 2 and 5.
[0167] Referring to FIG. 15, the ablating device 20A has the
flexible distal portion 162 which is shaped by the stylet 164 into
the dotted line 168 position. The pre-shaped portion 160 may be
used to position or advance the ablating device 20A between the
epicardium and pericardium. FIG. 18 shows the pre-shaped portion
positioned around the left superior pulmonary vein as described
below. A number of different stylets 164 may be used to shape the
flexible portion 162 around various structures.
[0168] The ablating device 20A also has an anchor 170 to anchor a
portion of the device 20A while moving another part of the device
20A. When the anchor 170 is the balloon 150, the balloon may have a
number of chambers 171, preferably three, which can be inflated as
necessary to position the device as shown in FIGS. 16 and 17. The
chambers 171 are coupled to a source of inflation fluid 173 via
inflation lumens 175. The anchor 170 is preferably an expandable
element 172 such as the balloon 150, but may also be tines which
grab the epicardium, pericardium or pericardial reflection. The
anchor 170 may also be one or more suction ports 156, as described
above (see FIG. 13). The suction ports 156 may be used to anchor
the device to the pericardium, epicardium, pericardial reflection
or any other structure in the space between the pericardium and
epicardium. Although only one anchor 170 is located at the distal
end, the anchor 170 may be positioned at any other location and
more than one anchor 170 may be provided without departing from the
scope of the invention.
[0169] Referring to FIGS. 18-21, a specific use of the ablating
device 20A is now described. The ablating devices described herein
may, of course, be used to ablate other tissues when positioned in
the space between the epicardium and pericardium. The ablating
device 20A is preferably introduced in the same manner as the
ablating device 20 or in any other suitable manner. When the
ablating device 20A is at the entrance to the transverse
pericardial sinus, the ablating device 20A may be given the angled
or curved shape by advancing or withdrawing the stylet 164 (see
FIGS. 14 and 15) or with the sheath (see FIGS. 2 and 5). The device
20A is then advanced until the tip meets the pericardial reflection
at the end of the sinus as shown in FIG. 18. The anchor 170, such
as the balloon 150, is then actuated to resist movement of the
distal end when displacing other parts of the ablating device 20A
(FIG. 19). At this time, the ablating device 20A may be used to
ablate tissue in the manner described above from a position
superior to the right superior pulmonary vein, around the left
superior pulmonary vein and to the left inferior pulmonary vein.
Thus, the ablating device 20A is similar to the ablating device 20
described above in that the device 20A extends through the
transverse pericardial sinus and to the left inferior pulmonary
vein.
[0170] The ablating device 20A, like the ablating device 20, may
also have a portion 176 which is moved to ablate tissue inferior to
the left and right inferior pulmonary veins. Stated another way,
the portion 176 is moved to a position inferior to the inferior
pulmonary veins. The portion 176 is moved into the position shown
in FIG. 20 by simply pushing the device 20A to displace the portion
176 or by advancing or withdrawing the stylet 164. After the
ablating device 20A is properly positioned, the ablating elements
27 are activated as described above to create transmural
lesions.
[0171] Still referring to FIG. 20, another ablating device 22A may
also be used to ablate tissue in the same manner as the ablating
device 22 described above. The ablating device 22A is introduced in
the manner described above and is advanced until distal end 177 is
positioned at a desired location. FIG. 20 shows the distal end 177
superior to the right superior pulmonary vein adjacent to the
pericardial reflection. A portion 179 of the ablating device 20A is
then moved to the position of FIG. 21 in any manner described above
such as by introduction or withdrawal of the stylet 164. The
ablating device 20A is then used to ablate tissue as described
above.
[0172] The ablating device 20A, 22A are also similar to the
ablating devices 20, 22 in that the ablating devices 20A, 22A
create continuous lesions on both sides of the pericardial
reflections extending between the vena cava and the right superior
and right inferior pulmonary veins. Tissue beneath the pericardial
reflections is ablated using at least one of the ablating devices
20A, 22A. The ablating devices 20A, 22A may be approximated using
any suitable technique or device such as with magnetic force
described above. Other methods and devices for creating a
continuous lesion beneath a pericardial reflection are described
below.
[0173] Referring now to FIG. 22, another system and method for
approximating the ablating devices 20, 22 and 20A, 22A is now
described. An energy emitter 180, such as a light source 182, emits
energy from the ablating device 20A which is received by a sensor
184 on the other ablating device 22A to determine when the devices
20A, 22A are positioned on opposite sides of a pericardial
reflection. The emitter 180 and sensor 184 preferably pass through
the working channel 166 but may also be integrated into the devices
20A, 22A. When the ablating devices 20A, 22A are aligned across the
pericardial reflection, the sensor 184 detects proper alignment so
that the lesion may be formed continuously on both sides of the
pericardial reflection.
[0174] Yet another method to make sure that the ablating devices
20A, 22A are aligned across a pericardial reflection is to mark a
location on the pericardial reflection where a lesion has been
created as shown in FIG. 23. The device 20A has a needle 185
introduced through the working channel 166. The needle 185 delivers
a marker 186, such as a radioopaque dye, which can be visualized.
The device 20A may also deliver a solid marker such as a platinum
wire. An advantage of using the marker 186 is that both ablating
devices 20A, 22A do not need to be positioned on opposite sides of
the pericardial reflection at the same time. Thus, only one
ablating device 20A may be necessary to create a continuous lesion
beneath the pericardial reflection since the same device 20A can
mark the pericardial reflection on one side, locate the mark 186 on
the other side, and continue the lesion on the other side of the
pericardial reflection.
[0175] Referring again to FIG. 10, the ablating device 20 has the
guide portion 25. As mentioned above, the guide portion 25
preferably has a width to height ratio of about 2 to 5. The guide
portion 25 aligns the ablating element 27 against a predetermined
structure, such as the pulmonary veins, to ablate tissue. The
relatively flat configuration of the guide portion 25 aligns the
device 20 between the epicardium and the pericardium so that the
ablating elements 27 are directed toward the myocardium.
[0176] Referring now to FIG. 24, an ablating device 20B is shown
which has a number of discrete guide portions 25A. Four guide
portions 25A are shown in FIG. 24 with each guide portion 25A being
shaped similar to a fin 29. The ablating device 20A may also have a
beaded or scalloped appearance. The ablating device 20A preferably
has flexible sections 188 between the guide portions 25A which
provide torsional flexibility so that the guide portions 25A can
rotate relative to one another. The guide portions 25A may be
positioned between the pulmonary veins as shown in FIG. 27A. The
ablating device 20B may have any of the features of the other
ablating devices 20, 20A described herein.
[0177] Referring to FIG. 25, another ablating device 20C is shown
which has guide portions 25B which may also be deployed after the
ablating device 20C has been positioned so that the guide portion
25B does not interfere with advancement and placement. The guide
portion 25B has one or more expanding elements 192, such as the
balloons 150, which may be expanded during advancement or after the
device 20A is at the desired location. The expanding elements 192
are positioned on opposite sides of the ablating device 20C,
however, the expanding elements 192 may be positioned only on one
side of the device 20C. The guide portions 25A may be positioned
between the pulmonary veins as shown in FIG. 27B. The expanding
elements 192 may also be mechanically actuated elements such as
bending arms or an expandable mesh.
[0178] The expanding elements 192 may also be inflated at selected
locations corresponding to discrete ablation sites as shown in FIG.
26. An advantage of individual expansion of the expanding elements
192 is that other portions of the device 20C may rotate and
displace as necessary to provide good contact at the desired
ablation site 193.
[0179] Another ablating device 20D is now described with reference
to FIGS. 28-31. The ablating device 20D is advanced over a guide
200 which is advanced ahead of the device 199. The guide 200 is
preferably a guidewire 202 having the anchor 170 to anchor an end
204 of the guide 200. The guide 200 is advanced and positioned
along the intended ablation path. The ablating device 20D is then
retracted or advanced along the guide 200 to create a continuous
lesion along the intended ablation path. The guide 200 may also be
locked into a desired orientation with a coaxial cable or with a
mechanism similar to locking arms used to hold surgical devices.
The ablating device 20D has an expanding device 201, such as the
balloon 150, to move the ablating element 27 into contact with the
tissue to be ablated. The balloon 150 preferably has a number of
chambers 203, preferably at least two, coupled to inflation lumens
205, 207 which are coupled to the source of inflation fluid 173
(FIG. 14A). Electrodes 191, 193 are coupled to wires 209, 211
passing through the device 20D. The guide 200 passes through the
working channel 166. Wires 213 are also provided to steer, rotate
and position the device 20D.
[0180] The ablating device 20D and/or the guide 200 preferably
includes a device 206 for aligning the ablating element with a
previously created lesion. The aligning device 206 may be
electrodes 191, 193 which simply measure electrical impedance. When
the electrodes 191, 193 measure a large increase in electrical
impedance an ablation is positioned beneath the electrodes 191,
193. In this manner, the ablating element 27 can be aligned and
positioned to create a continuous lesion through the tissue.
Referring to FIG. 29, the electrodes 191, 193 may also be used to
locate the previously created lesion 195 as shown in FIG. 29. The
electrode 191 will sense a higher amplitude of activity than the
electrode 193 since the electrode is positioned over the previously
created lesion while the electrode 191 is not.
[0181] Still referring to FIG. 28, the ablating device 20D may have
first and second electrodes 194, 196 on opposite sides of the
ablating element 27. The first electrode 194 may be a pacing
electrode 195 which emits an electrical impulse and the second
electrode 196 may be a sensing electrode 197 which receives
electrical impulses. When the first electrode 194 emits a stimulus,
launching a cardiac impulse, the impulse is transmitted through
tissue to the sensing electrode 197 if a discontinuity exists in
the lesion. A number of sensing electrodes 197 may be positioned
along the ablating device 20A which may be used to determine the
location of a discontinuity. Both electrodes 194, 196 may also be
sensing electrodes 197 with both electrodes 194, 196 merely sensing
normal activity. When only one of the electrodes 194, 196 senses
the activity an effective, continuous, transmural lesion has been
created. The electrodes described herein may be coupled to any
suitable device including an ECG with electrogram amplitudes being
measured.
[0182] The electrodes 194, 196 may also be used to locate the end
of a previously created lesion. The time between emission of the
pacing stimulus to receipt of the cardiac impulse at the sensing
electrode increases when a transmural ablation has been created
between the electrodes 194, 196. When such an increase is detected,
it is known that the previously created lesion is positioned
between the electrodes 194, 196. The time between emission and
receipt of the cardiac impulse may also be used in simple time of
flight analysis to determine the location of a discontinuity in the
ablation. For example, the electrodes 194, 196 are positioned at a
discontinuity in an ablation when the time of flight is lowest.
[0183] A method of using the device is shown in FIGS. 32-35. The
guide 200 is advanced to a desired location and the anchor 170 is
actuated. The ablating device 20D is then advanced over the guide
200, the balloon 150 is inflated, and a first ablation 215 is
performed. The balloon 150 is then deflated and the ablating device
20C is then moved to another location. The electrodes 191, 193 or
194, 196, or other suitable aligning device, is used to position
and align the ablating device 20D and a second ablation 217 is then
performed which is continuous with the first ablation 215. The
device 20D is then moved again and a third ablation 219 is formed
continuous with the second ablation 217.
[0184] Referring to FIGS. 36-38, another ablating device 210 is
shown wherein the same or similar reference numbers refer to the
same or similar structure. The ablating device 210 has an
expandable structure 209, preferably a balloon 150A, movable along
the ablating device 210 to selectively anchor and align the device
210. An advantage of the system of FIGS. 36-38 is that the
structure 209 can be moved to various locations on the ablating
device 210 for moving various ablating elements into contact with
tissue to be ablated. The ablating device 210 also has the anchor
170, such as the balloon 150B, to anchor a part of the ablating
device 210 and to move the ablating elements 27 into contact with
the tissue to be ablated. The balloon 150B is coupled to a source
of inflation fluid 211 via inflation lumen 223.
[0185] The expandable device 209 is mounted to a body 211 having a
scalloped appearance to provide flexibility although any other
suitable design may be used. The body 211 has a C-shaped
cross-section which engages a flange 221 on the ablating device
210. The expandable device 209 is preferably the balloon 150A but
may be a mechanically actuated device. For example, the expandable
device 209 can be an extendable arm, a wire loop or an expandable
mesh. The anchor 170 may be selectively expandable to guide,
rotate, and move the ablating device 210 as necessary. The balloon
150A preferably has at least two separately inflatable chambers 212
and FIG. 38 shows the balloon 150A having three independently
inflatable chambers 212. The chambers 212 are coupled to inflation
lumens 219 which are coupled to a source of inflation fluid 213.
The chambers 212 may be inflated as necessary to move and rotate
the ablating device 210 and press the ablating element 27 against
the tissue to be ablated. The expandable structure 209 is moved to
various positions along the ablating device 210 to move various
ablating elements 27 into contact with the tissue. The body 211 may
also have pull wires 218 for further manipulation of the ablating
device 210.
[0186] As mentioned above, penetrating the pericardial reflections
carries inherent risks. However, the methods and devices of the
invention may, of course, be used when penetrating the pericardial
reflections. The ablating devices 20, 22, 20A, 22A may have a
penetrating element 220 as shown in FIGS. 39-43 for penetrating the
pericardial reflections. The penetrating element 220 is movable
from a retracted position (FIG. 40) to an extended position (FIG.
41). The penetrating element 220 passes through the working channel
166 of the ablating device 20A. The penetrating element 220 is
preferably positioned in the working channel 166 but may also be
integrated into the ablating device 20A or may be a separate device
altogether. The first and second ablating devices 20A, 22A are
positioned on opposite sides of the pericardial reflection as shown
in FIG. 40 using the emitter and sensor arrangement described above
in connection with FIG. 22 although any other devices or techniques
may be used. The penetrating element 220 is then used to penetrate
the pericardial reflection and the two devices 20A, 22A are
interlocked as shown in FIG. 41.
[0187] Referring to FIGS. 42 and 43, the ablating device 22A has a
locking mechanism 224 which holds the penetrating element 220. The
locking mechanism 224 has a stationary jaw 230 and a movable jaw
231. The movable jaw 231 is movable in the direction of arrow 223
for releasing the device 20A. The locking mechanism 224 is also
positioned in the working channel 166 of the ablating device 22A
but may be integral with the device 22A. The penetrating element
220 preferably has a conical tip 222 or other cutting element for
piercing the pericardial reflection but may also be a laser,
ultrasonic dissector, or electrosurgical device. The penetrating
element 220 may also be a blade, needle or other structure for
cutting or piercing the pericardial reflection. After ablating
tissue, the locking mechanism 224 is released, the penetrating
element 220 is retracted and the ablating devices 20A, 22A are
removed. The ablating devices 20A, 22A may have any other
interlocking configuration and the ablating device 22A may
interlock with some other structure other than the penetrating
element 220. Referring to FIG. 48, the ablating devices 20, 22 may
interlock with one another in the manner described above. Referring
to FIG. 44, the ablating device 20 may penetrate through one or
more pericardial reflections and interlock with another part of the
ablating device 20. Referring to FIG. 45, the ablating device 20
and the ablating device 22 may also interlock across the
pericardial reflections using the penetrating element 220 or other
suitable device.
[0188] Referring to FIGS. 46-49, another method of penetrating and
advancing through the pericardial reflection is shown. The end of
the ablating device 20A may be adhered to the pericardial
reflection using suction through the working channel 166. The
penetrating element 220 is then advanced through the working
channel 166 while suction is maintained so that the piercing
element is guided directly to the pericardial reflection. The
penetrating element 220 is then used to penetrate the pericardial
reflection as shown in FIG. 45. The ablating device 20A is then
advanced through the pericardial reflection as shown in FIG.
46.
[0189] Referring to FIG. 14B, another anchor 170A for anchoring the
device is shown. Any of the anchors described herein may be used
with any of the devices described herein without departing from the
scope of the invention. The anchor 170A is a relatively flat
balloon having a thickness of about 1 cm and a width of about 0.3
cm when the balloon is inflated. Referring to FIG. 14C, yet another
inflatable anchor 170B is shown which forms a hook-shaped element
171 which can engage a vessel such as the aorta, superior or
inferior vena cava or any other vessel mentioned herein. Referring
to FIG. 14D, still another anchor 170C is shown which has a
mechanically expanding coiled section 173. As mentioned above, the
anchors of the present invention are expanded to hold the devices
at a particular location. For example, the anchors may be used to
anchor a part of the device between blood vessels such as the
superior vena cava and the aorta. When positioned between blood
vessels or when engaging a vessel with the hook-shaped element of
FIG. 14C, tension may be applied to the device to wrap the device
around a vessel or vessels, such as the pulmonary veins, in the
manner described above.
[0190] Referring to FIG. 49-54, another device 300 for ablating
tissue, such as cardiac tissue, is shown. The device 300 may also
be used in any manner described herein and may have the features
and dimensions of other devices described herein without departing
from the scope of the invention. The device 300 encircles the
pulmonary veins and is particularly suited for conventional open
chest surgery but may also be used in less and minimally invasive
procedures. Although ablation of tissue around the pulmonary veins
is described as a specific use of the device 300, the device 300
may be used on other parts of the heart and in other areas of the
body.
[0191] The device 300 has a body 302 having a length of 5-12
inches, preferably about 10 inches, and a width of 0.2-0.7 inch
preferably about 0.5 inch. The body 302 is preferably made of an
polymeric material such as silicone or urethane and is formed by
injection molding although any suitable material and method may be
used to form the body 302. The body 302 has a number of cells 304
coupled together by integrally formed hinges 303 in the body 302.
Of course, the cells 304 may be coupled together with mechanical
connections rather than the integrally formed hinges 303 without
departing from the scope of the invention. The device 300
preferably has 5-30 cells, more preferably 10-25 cells and most
preferably about 16 cells although any number of cells 304 may be
used depending upon the specific application. For example, the
device 300 may be used to extend around a single vessel, such as
the aorta, pulmonary vein, SVC or IVC in which case the device 300
preferably has 4-12 cells 304 and preferably about 8 cells 304.
[0192] The device 300 has a locking mechanism 306, preferably a
buckle 308, which engages another part of the device 300 to form a
closed loop 307. Referring to FIG. 49, the device 300 extends
around the pulmonary veins with the locking mechanism 306 to form
the closed loop 307 around the pulmonary veins. The buckle 308
forms a side-by-side (FIG. 50) or one on top of the other (FIG. 51)
locking engagement with another part of the device 300. Although
the buckle 308 is preferred, the locking mechanism 306 may have any
other suitable structure for locking one part of the device 300 to
another part of the device 300.
[0193] Referring now to FIGS. 49, 52, 53A and 54, the cells 304
have a suction well 310 for adhering the device to the tissue to be
ablated. The suction well 310 may take any form and is preferably
formed between an inner lip 312 and an outer lip 314. The suction
well 310 has a suction port 316 coupled to a vacuum source 318
through a lumen 320. The vacuum source 318 is activated to cause
the suction well 310 to hold the cell 304 against the tissue to be
ablated. The lumen 320 is preferably formed by a separate tube 322
bonded to the body 302. The lumen 320 may, of course, be formed
integral with the rest of the body 302. The upper surface of the
cells 304 has three longitudinal recesses 324 in which the tubes
322, 326, 328 are positioned. The tubes 322, 326, 328 have slack
between the cells 304 to permit the cells 304 to wrap around
structures without significant resistance from the tubes 322, 326,
328.
[0194] The suction port 316 preferably has a cross-sectional size
which is no more than 10% of the cross-sectional size of the lumen
320. In this manner, if suction is lost at one of the cells 304,
suction can be maintained at the other cells 304 since the
relatively small suction port 316 produces low flow. Of course,
another part of the vacuum flow path 317 other than the suction
port 316 may be sized small to reduce losses through cells 304 not
adhered to the tissue.
[0195] An ablating element 311 is positioned within a closed wall
319 formed by the inner lip 312 so that the ablating element 311 is
surrounded by the suction well 310. The ablating element 311 may be
any ablating element mentioned herein and a preferred element is an
RF electrode 330. The RF electrode 330 is coupled to an RF
generator 332 which transmits RF energy to the electrode. The RF
electrode 330 is preferably a stainless steel or gold plated copper
electrode although any suitable electrode may be used. The ablating
element 311 preferably has a width of 1-6 mm, preferably about 3
mm, and a length of 2-25 mm, preferably about 12 mm. When the
ablating element 311 is the RF electrode, the ablating element 311
is preferably spaced apart from the target tissue, or from a bottom
of the inner lip 312, by a distance of 0.5-3 mm and more preferably
about 1.5 mm. The locking mechanism 306 preferably has at least one
ablating element 311 to create a continuous lesion in tissue
beneath the locking mechanism 306.
[0196] The ablating elements 311 are coupled to a control system
334 with wires 345. The control system 334 controls ablation in the
manner described below. The RF generator 332 may form part of the
control system 334 or may be separate from the control system 334.
One or more temperature sensors 336, preferably thermocouples 338,
are positioned within recesses in the inner and/or outer lips 312,
314 to measure temperature. The temperature sensors 336 are coupled
to the control system 334 for use as described below. Wires 340
extending through the tube 326 couple the temperature sensors 336
to the control system 334.
[0197] Fluid is delivered to cool the tissue and/or conduct energy
from the ablating element 311 to the tissue. Fluid is supplied from
a source of fluid 342 to an inlet lumen 344 formed by tube 328.
Fluid is withdrawn through the lumen 320 in the tube 322 so that
the lumen 320 produces suction at the suction well 310 and
withdraws fluid. As mentioned above, the lumens 344, 346 are
preferably formed by the tubes 322, 328 but may be integrally
formed with the rest of the body 302. The fluid is preferably a
conductive solution, such as saline or hypertonic saline, which
conducts RF energy from the electrode 330 to the tissue to be
ablated.
[0198] Referring to FIGS. 53A and 54, fluid flows from the inlet
lumen 344 into an inlet manifold 350 which distributes fluid along
the length of the ablating element 311 as shown in the
cross-sectional view of FIG. 54. Fluid then flows into a fluid
chamber 348 formed between the ablating element 311, inner lip 312
and tissue. Fluid passes across the fluid chamber 348 and is
received at a fluid outlet manifold 352. The fluid outlet manifold
352 is coupled to the lumen 320 so that the lumen 320 withdraws
fluid and provides suction for the suction well 310 as mentioned
above.
[0199] The fluid inlet and outlet 350, 352 are preferably
positioned on opposite sides of the short axis of the fluid chamber
348, however, the fluid inlet and fluid outlet 350, 352 may be
positioned anywhere within the fluid chamber 348 without departing
from the scope of the invention. Fluid is preferably supplied at an
average flow rate of at least 0.24 cc/sec, more preferably at least
0.50 cc/sec and most preferably at least 1.0 cc/sec to each cell
304 although lower or higher flows may be used. Fluid is preferably
delivered to the inlet lumen 344 at a set pressure which results in
the desired average flow rate through the cells 304. The fluid may
be cooled, or even heated, by passing the fluid through a heat
exchanger 354. The fluid is preferably delivered at a temperature
of no more than 40.degree. C. and more preferably no more than
20.degree. C. to cool the tissue and/or ablating element 311. A
fluid permeable, porous structure, such as gauze (not shown), may
be positioned in the fluid chamber 348 to hold the fluid and
prevent direct contact between the ablating element 311 and
tissue.
[0200] Referring to FIG. 53B, the device 300E may also provide
cooling to a backside 353 of the ablating element 311. Fluid from
the inlet lumen 344 passes across the backside 353 of the ablating
element 311 and is removed on the other side through the lumen 320.
The embodiment of FIG. 53B may include any of the features and
advantages of the embodiment of FIG. 35, for example, the fluid
flow rate and temperature may be the same as described in relation
to FIG. 53A. The inlet lumen 344 is also coupled to the suction
well 310 via a conduit 355 for supplying fluid to the suction well
310. In this manner, the fluid may also be used to cool tissue
adjacent to the ablating element 311. Fluid introduced into the
suction well 310 is withdrawn through the lumen 320 in the manner
described above. Although the fluid in the suction well 310 is
exposed to the near surface NS of the tissue, the cooling fluid may
also be contained within a closed circuit so that the near surface
NS of the tissue is not in direct contact with the fluid.
Furthermore, the fluid preferably cools tissue around the entire
ablating element 311 but may also cool tissue only along one side
of the device or only on the two lateral sides of the device
without departing from the scope of the invention.
[0201] Referring to FIGS. 55 and 56, another device 300E is shown
where the same or similar reference numbers refer to the same or
similar structure. Use and dimensions of the device 300 are equally
applicable for the device 300E. The device 300E has a lumen 356
contained within a cavity 358 in the body 302E. The lumen 356
carries the wires 340, 345 for the temperature sensors 336 and
ablating elements 311. The lumen 356 is coupled to the control
system 334 for control in the manner described below. The lumen 346
is a dedicated lumen for withdrawing fluid so that the fluid can be
recycled as shown in FIG. 56. The system of FIG. 56 is described in
greater detail below in connection with use of the devices 300,
300E. The lumen 356, wires 340, 345, ablating elements 311, and
temperature sensors 336 form a strip 359 which is bonded to the
rest of the body 302, preferably with an interlocking
engagement.
[0202] A pair of wires 360, 362 is positioned across a gap 361 in
suction path 363 (shown in dotted-line) to determine when the inner
lip 312 is not adequately adhered to the tissue. When the inner lip
312 is not adequately adhered to the tissue, fluid leaks under the
inner lip 312 and is drawn into the vacuum outlet 316. The fluid,
which is preferably cooled hypertonic saline, conducts electricity
across the gap 361 thereby indicating that the inner lip 312 may
not be adequately sealed. The wires 360, 362 may be embedded in the
body 302E or may travel through one or more of the lumens.
[0203] Referring to FIG. 57, another device 300F is shown which has
two sets of lumens 364, 368 extending from both ends of the device
300F. The two sets of lumens 364, 368 perform the same functions as
the lumens described above and all discussion of the device 300 is
equally applicable here. An advantage of using two sets of lumens
364, 368 is that suction and/or fluid containment does not need to
be maintained at all cells 304 at the same time. Connectors 370 at
the buckle 308 are disconnected to wrap the device 300F around the
pulmonary veins and are then reconnected to form the closed loop.
Each set of lumens 364, 368 terminates near the middle of the
device 300F at ends 372. Valves 374 are provided to selectively
couple the lumens 362, 368 to the vacuum source 318 and/or fluid
supply 342.
[0204] Referring to FIGS. 49 and 52-57 the control system 334 is
coupled to the temperature sensors 336, ablating elements 311,
fluid source 342 and vacuum source 318 for controlling the devices
300, 300E, 300F. The control system 334 may also be coupled to a
pressure sensor 376 and/or a flow rate sensor 378 positioned along
the inlet line of the vacuum source 318 (FIGS. 56 and 57). The
pressure and/or flow rate sensors 376, 378 determine when the cells
304 are adequately secured to the tissue. If suction is not
adequate, the pressure and/or flow rate will be higher than
expected. Fluid flow indicators 380 can also be used to measure
fluid flow into and out of the devices 300E, 300F to determine
whether fluid is leaking from the cells 304 which also indicates a
poor seal.
[0205] The cells 304 are preferably numbered and the control system
334 indicates whether each cell 304 is adequately adhered to the
tissue. In this manner, the user may apply manual pressure to a
particular cell 304 if an adequate seal is not present. The readout
may be a digital readout 377 or lights 379 for each cell 304. The
control system 334 also preferably has a temperature display 335
and a timer 337 for timing the duration of ablation.
[0206] The control system 334 preferably activates the ablating
elements 311 in a predetermined manner. In one mode of operation,
ablation is carried out at adjacent cells 304. Ablation may also be
carried out at a number of pairs of adjacent cells such as the
first and second cells 304 and the fifth and sixth cells 304. After
ablation is carried out at these adjacent cells 304, another pair
or pairs of adjacent cells are activated such as the third and
fourth cells 304 and the seventh and eighth cells 304. The
continuity of the ablation between the adjacent cells 304 may be
confirmed in any suitable manner including those described herein.
In another mode of operation, the control system 334 energizes
every other cell, every third cell or a limited number of cells 304
such as no more than four. The control system 334 may also activate
less than 50% and even less than 30% of the total ablation area at
one time. For the device 300, a percentage of the total ablation
area is essentially a percentage of the total number of ablation
elements 311.
[0207] The ablation at each cell 304 may be controlled based on
temperature measured at the temperature sensors 336. For example,
the control system 334 may be configured to maintain a near surface
NS temperature of 0-80.degree. C., more preferably 20-80.degree. C.
and most preferably 40-80.degree. C. The temperature can be
adjusted by changing the fluid flow rate and temperature and/or the
power delivered to the ablating element 311. The control system 334
may also have a multiplexer 333 which delivers energy to only the
cells 304 having a temperature below the threshold temperature.
Alternatively, the multiplexer 333 may deliver energy to only the
coldest cells 304 or only a number of cells 304 which register the
coolest temperatures.
[0208] The control system 334 may also be configured to measure a
temperature response of the tissue to be ablated. The temperature
response of the tissue is measured to provide a tissue
characterization which can be used to select the appropriate
ablation technique. The ablation technique is primarily selected to
produce a temperature of at least 50.degree. C. at the far surface
FS of the tissue. When ablating cardiac tissue, for example, the
control system 334 determines the ablation technique required to
form a transmural lesion which requires a far surface FS
temperature of 50-80.degree. C. and more preferably 50-60.degree.
C. Measuring temperature at the far surface FS is somewhat
difficult so the temperature of the near surface NS is used in
conjunction with the methods and devices described herein. Of
course, the temperature of the far surface FS may be measured to
determine when the ablation is complete rather than using the
temperature response described below.
[0209] The temperature response of the tissue is performed in the
following manner. The tissue to be ablated is heated or cooled and
the temperature response over time is measured with the temperature
sensors 336. The temperature response over time at the near surface
NS provides a rough indication of the thermal properties of the
tissue to be ablated. The thermal properties of the tissue is
affected by a number of variables including tissue thickness,
amount of fat and muscle, blood flow through the region and blood
flow and temperature at the far surface FS. These factors all play
a role in the temperature response of the tissue. The tissue
thickness, for example, affects the temperature response in the
following manner. When a thin tissue layer is heated, the
temperature at the near surface will generally increase more slowly
than with a thick layer since the flow of blood at the far surface
will draw heat away quicker with the thin tissue layer. The control
system preferably measures the temperature response for at least
two temperature sensors 336 for each ablating element with one of
the temperature sensors being positioned laterally spaced to
measure the temperature change at adjacent portions of the
tissue.
[0210] After measuring the temperature change over time, the
temperature response is then analyzed to determine the appropriate
ablation technique. The analysis may be a comparison of the
temperature response with temperature response curves of known
tissue types. The temperature response curves may be developed
empirically or may be calculated. The temperature response may also
consider other variables input by the user including blood
temperature and flow rate and the presence and amount of fat. When
assessing the temperature response during heating with the ablating
element, the amount of energy delivered to the tissue may also be
used to characterize the tissue.
[0211] Using the results of the temperature response assessment,
the control system 334 determines the appropriate ablation
technique to produce the desired far surface FS temperature. In one
mode of operation, the control system 334 determines the amount of
time required to reach a desired far surface FS temperature when
the near surface NS is maintained at a temperature of less than
60.degree. C. The control system 334 preferably maintains an
adequate flowrate and temperature of fluid to maintain the desired
near surface NS temperature. The control system 334 monitors the
temperature of the near surface NS with temperature sensors 336.
After the period of time has elapsed, the control system 334
automatically stops ablating. Alternatively, the ablation may take
place until the near surface NS reaches a target temperature. The
continuity of the ablation may then be checked in any manner
described herein.
[0212] In use, the devices 300, 300E, 300F are wrapped around a
structure, such as the pulmonary veins, with the locking mechanism
306 to form the closed loop 307. The vacuum source 318 is then
activated to adhere the cells 304 to the epicardium. Manual
pressure can be applied to cells 304 which are not sufficiently
adhered to the tissue. The control system 334 then ablates tissue
while delivering fluid to cool the tissue and conduct RF energy to
the tissue. The continuity of ablation is then assessed by any
suitable method including those described herein.
[0213] Referring to FIG. 58-63, still another device 400 is shown
for ablating tissue wherein the same or similar reference numbers
refer to the same or similar structure. The device 400 is
particularly useful for ablating cardiac tissue but may be used for
any other purpose without departing from various aspects of the
invention. In a specific embodiment, the device 400 is used to
ablate tissue around the pulmonary veins. The ablating device 400
has a number of cells 402 similar to the cells described above and
description of the preferred characteristics above are equally
applicable here. For example, the cells 402 may have the preferred
dimensions and features of the cells 304 described above. The
ablating device 400 has an ablating element 404 which is preferably
an ultrasonic transducer 406 although various features of the
invention may be practiced with any other type of ablating element
464 (FIG. 68).
[0214] The device 400 preferably delivers ultrasound which is
focused in at least one dimension. In particular, the device 400
preferably delivers focused ultrasound having a focal length of
about 2 to 20 mm, more preferably about 2 to 12 mm and most
preferably about 8 mm. Stated another way, a focal axis FA is
spaced apart from a bottom or contact surface 405 of the device
within the stated ranges. The focused ultrasound also forms an
angle of 10 to 170 degrees, more preferably 30 to 90 degrees and
most preferably about 60 degrees as defined relative to the focal
axis A. The ultrasonic transducer 406 is preferably a piezoelectric
element 408. The transducer 406 is mounted within a housing 410.
The housing 410 has an enclosure 412 and a top 414 which fits over
the enclosure 412. The enclosure 412 has curved lips 416 on both
sides of the enclosure 412 which generally conform to the curvature
of the transducer 406. The transducer 406 is curved to focus the
ultrasound energy for the reasons discussed below. The transducer
406 has a length of about 0.43 inch, a width of about 0.35 inch and
a thickness of about 0.017 inch. The transducer 406 has a radius of
curvature R (FIG. 62) consistent with the preferred focal lengths
described above. The transducer 406 forms an angle A with the focus
F within the preferred angle ranges described above.
[0215] A layer 418, which is preferably aluminum but may be any
other suitable material, is bonded or otherwise acoustically
coupled to a concave side 423 of the transducer 406. The layer 418
has a length of about 0.51 inch, a width of about 0.43 inch and a
thickness of about 0.012 inch. The layer 418 preferably has the
same radius of curvature as the transducer 406 so that the layer
418 mates with the transducer 406. The layer 418 is attached to the
curved lips 416 of the enclosure 412 with an epoxy.
[0216] An advantage of using focused ultrasonic energy is that the
energy can be concentrated within the tissue. Another advantage of
using focused ultrasound is that the energy diverges after reaching
the focus thereby reducing the possibility of damaging tissue
beyond the target tissue as compared to collimated ultrasonic
energy. When ablating epicardial tissue with collimated ultrasound,
the collimated ultrasound energy not absorbed by the target tissue
travels through the heart chamber and remains concentrated on a
relatively small area when it reaches the endocardial surface on
the other side of the chamber. The present invention reduces the
likelihood of damage to other structures since the ultrasonic
energy diverges beyond the focus and is spread over a larger
area.
[0217] Although the focused ultrasonic energy is preferably
produced with the curved transducer 406 and the layer 418, the
focused ultrasonic energy may be produced with any suitable
structure. For example, acoustic lensing may be used to provide
focused ultrasound. The acoustic lens can be used with a flat
piezoelectric element and matching layer. Furthermore, although the
ultrasound energy is preferably emitted directly toward the tissue
the ultrasound energy may also be reflected off a surface and
directed toward the tissue without departing from the scope of the
invention. The energy may also be produced by a number of small
transducers which are oriented to focus or concentrate ultrasonic
energy, such as at least 90% of the energy, within the preferred
angle ranges and radius of curvature described herein when viewed
along a longitudinal axis 419 or along the focal axis FA. For
example, a multielement acoustic phased array may be used to
provide an acoustic beam-steering capability from one or more
cells. One skilled in the art can also appreciate the use of
multiple matching layers, focusing acoustic lenses and non-focusing
acoustic windows and the like. Thus, the focused energy may be
produced in a number of different ways, including other ways not
mentioned here, without departing from the scope of the
invention.
[0218] A distributing element 420 is attached to the transducer 406
at two locations to distribute energy that drives the transducer
406. The element 420 is preferably a piece of copper ribbon 0.020
inch wide and 0.0005 inch thick soldered to the transducer 406 at
two locations. A coaxial cable 422 delivers power to the transducer
406 from a source of power 421 and also provides a ground path. The
coaxial cable 422 has a power lead 424 coupled to the distributing
element 420 to power the transducer 406. A braided portion 426 of
the cable 422 serves as a ground. The braided portion 426 is
soldered to a tube 428 and/or the top 414. The ground path leads
from the transducer 406 to the layer 418 and then to the housing
410 at the curved lips 416. The ground path then passes to the top
414 and finally to the braided portion 426 either directly or via
the tube 428. The tube 428 and top 414 are preferably made of brass
and the enclosure 412 is preferably made of aluminum although any
other suitable materials may be used. Polyimide tape 430 is adhered
to the inside of the enclosure 412 and on the transducer 406 to
electrically separate the two structures.
[0219] The transducer 406 may be cooled during operation although
cooling may not be required. A cooling inlet 432 having an inlet
lumen 440 extends through the top 414 and is coupled to a source of
cooling medium 434. The cooling medium, which is preferably forced
air, passes into a chamber 436 so that the cooling medium is in
direct contact with the transducer 406. A cooling outlet 438 having
an outlet lumen 442 removes the cooling medium from the chamber
436. Although the lumens 440, 442 are preferably separate and
independent from the housing 420, the lumens 440, 442 may also be
integrated into the housing 420 without departing from the scope of
the invention.
[0220] The cells 402 may also be adhered or acoustically coupled to
the tissue with suction in the manner described above although
various features of the invention may be practiced without using
suction. The housing 410 is mounted within an opening 446 in a
suction body 448. The body 448 has a port 449 coupled to a lumen
452 leading to the vacuum source 318. The lumen 452 is coupled to
the outlet lumen 442 with tubing 443 so that the outlet lumen 442
provides suction and withdraws the cooling medium (FIG. 59). Of
course, the lumen 452 may also be completely independent of the
outlet lumen 442. FIG. 58 shows separate cooling outlet and vacuum
lumens. The port 450 leads to recesses 454 on two sides of the
transducer 406. The recesses 454 also may be formed by individual
suction pods, a linear segment, or any other suitable structure
without departing from the scope of the invention. A channel 456
extends from one side of the enclosure 412 to provide communication
between the two recesses 454. The channel 456 prevents only one
recess 454 from being adhered to the tissue. The body 448 is
preferably made of polycarbonate but may be made of any other
suitable material.
[0221] The ablating device 400 may also be used with a substance,
such as a gel or saline, applied to the target tissue to eliminate
air gaps between the transducer 406 and target tissue. Air gaps
between the transducer 406 and target tissue impede delivery of
ultrasonic energy to the tissue. When using suction as described
below, use of the substance may be unnecessary since the transducer
406 assembly can be forced into intimate contact with the target
tissue with the suction force.
[0222] The ablating device 400 may also have a membrane 460 (FIG.
64) filled with the substance 458 or a solid element 459 (FIG. 65)
which transmits the ultrasonic energy to the tissue. An advantage
of the membrane 460 is that the membrane 460 may be made flexible
and compliant to conform to the tissue. Another advantage of the
membrane 460 is that the distance between the transducer 406 and
the tissue may be varied. When ablating thick tissue, the membrane
460 can be deflated so that the transducer 406 is close to the
tissue (FIG. 64). When ablating thin tissue, the membrane 460 is
inflated so that the transducer 406 is further from the tissue
(FIG. 66). Adjacent cells preferably maintain contact with the
tissue to maintain the orientation of the device. The membrane 460
may also be inflated and deflated during or between activations of
the transducer 406 to move the focus relative to the tissue. For
example, the membrane 460 may be inflated and deflated to move the
focus relative to the tissue and, in particular, to different
depths. The membrane 460 is adhered to the device around the bottom
of the enclosure 412. The membrane 460 is preferably compliant and
may be made of any suitable material such as silicone or urethane.
The membrane 460 may be pre-filled with the substance or the
substance may be added later through another lumen (not shown).
[0223] Referring to FIG. 67, the membrane 460 may also take a shape
which tilts the transducer 406. The transducer 406 is preferably
tilted to direct the ultrasound energy to tissue positioned beneath
gaps between adjacent transducers 406 as will be explained in
greater detail below. A flexible flange 461 deflects to permit
tilting of the device. The transducer 406 may be angled, pivoted or
tilted in any other suitable manner. For example, the transducer
406 may have a mechanical pivot which moves the transducer 406 or a
movable foot on the bottom of the device 400 which is advanced and
retracted to tilt the transducer 406.
[0224] Referring to FIG. 68, another device 462 for ablating tissue
is shown wherein the same or similar reference numbers refers to
the same or similar structure. The device 462 has the ablating
element 404 which is preferably an ultrasonic transducer 463. The
transducer 463 is designed to deliver ultrasonic energy to tissue
beneath the transducer 463 and to tissue beneath the gaps between
adjacent cells 402. In this manner, the device may be operated
without moving or tilting the transducers 463 to create a
continuous lesion beneath the device. The transducer 463 is a flat
transducer 463 with a layer 464 attached thereto. The layer has a
flat bottom portion 466 and angled sides 468 which direct energy at
tissue lying beneath the gaps between adjacent transducers 463. The
device 462 has a membrane 470 adhered over the bottom of the cell
402. The membrane 460 is filled with a substance 472, such as a gel
or saline, which transmits the ultrasonic energy to the tissue. The
device 462 may be operated in any mode or method described
herein.
[0225] Referring to FIGS. 69-70, another transducer 474 is shown
which may be used with any of the devices described herein and is
particularly useful with the devices of FIGS. 59-68 and all uses
and features of the devices described herein are incorporated here.
The transducer 474 preferably provides focused ultrasound relative
to a focal axis FA within focal lengths and/or angle ranges
described above. The transducer 474 also provides diverging
ultrasound energy when viewed along an axis transverse to the focal
axis (FIG. 70). The ultrasound diverges to form an angle A2 of
about 10 to 120 degrees and preferably about 45 degrees. The
focused and diverging ultrasound is preferably formed with the
saddle-shaped transducer 474 with a similarly shaped layer 476
attached or otherwise acoustically coupled thereto. Of course, the
focused and diverging ultrasound may be produced in any other
suitable manner including those described herein. An advantage of
the diverging nature of the ultrasound energy is that tissue lying
beneath gaps between cells can be ablated with the ablating
elements while still providing a relatively focused energy. The
term focal axis FA, as defined herein, is intended to include both
linear and non-linear shapes. For example, the focal axis FA of the
transducer of FIGS. 69 and 70 is curved.
[0226] Referring to FIGS. 71-73, still another ablating device 478
is shown wherein the same or similar reference numbers refer to the
same or similar structure. The ablating device 478 has a first
ablating element 480, a second ablating element 482 and a third
ablating element 484 which differ. Although only three different
ablating elements are shown, the device 478 could include any
number of ablating elements. The ablating elements differ to
provide different ablating characteristics. For example, the
ablating elements may produce focused ultrasound with the first
ablating element having a different focal length than the second or
third ablating elements. Such a configuration permits the user to
select the appropriate ablating element for the particular tissue
structure. The ablating elements 480, 482 and 434 may also be
designed to operate at different frequencies and/or powers.
[0227] The ablating elements are movable within a lumen 486 in a
body 488. The body 488 forms two suction channels 490 to adhere the
device to the target tissue. The body 488 preferably forms a closed
loop but may be shaped in any other manner. Each of the ablating
elements has an element 492 which transmits the ultrasound energy
to the target tissue. The ablating elements may also have the
membrane (see FIG. 64) or may be used without the element or
membrane (see FIG. 60). Lumens 491 for supply of energy, suction
and inlet and outlet for the cooling medium are provided. The
lumens 491 extend through a manipulator 493. The manipulator 493
forms a seal with the body 488 to adhere the body 488 to the tissue
with a suction.
[0228] An advantage of using ultrasound for ablation is that the
transducer may also be used to measure temperature. Measuring
temperature is particularly helpful in operating the transducer for
feedback control of the ablating element in any manner described
above. Of course, the thermocouples described above or any other
suitable methods or devices for measuring temperature may be
used.
[0229] Another advantage of using the transducer is that the
transducer can be used to determine whether the transducer itself
is in good contact with the tissue to be ablated. Any air gap
between the transducer and the near surface NS can dramatically
affect the ability to deliver the ultrasonic energy in a controlled
manner. The adequacy of contact is determined by measuring the
electrical impedance which is generally large when an air gap
exists between the transducer and tissue. Monitoring suction as
described above is another method of assessing contact between the
device and tissue.
[0230] Yet another advantage of using the transducer is that the
transducer can provide flow velocity data using conventional
doppler techniques. The doppler flow techniques can be used to
characterize the amount of cooling at the far surface FS which can
be used to select the appropriate tissue ablation technique.
[0231] Still another advantage of the transducer is that the
transducer can provide the thickness of one or more layers of
tissue using known pulse-echo or a-line techniques. For example,
the transducer may be operated to provide total tissue thickness or
the thickness of fat and muscle or other layers. The thickness of
fat, muscle, and total thickness may be used when characterizing
the tissue to determine the appropriate ablation technique. For
example, the ablating element may be operated in response to the
tissue thickness measurement with or without one or more additional
measurements. A single transducer may be used to emit ultrasonic
energy and receive reflected energy or one transducer may emit and
a different transducer can receive the reflected ultrasound
energy.
[0232] The transducer may also be used to determine the distance to
tissue beyond the target tissue such as endocardial tissue on the
opposite side of a cardiac chamber. Such measurements can be useful
in selecting the appropriate transducer. For example, if the tissue
structure beyond the target tissue is relatively far away, a longer
focal length can be used since the ultrasound energy will be spread
over a larger area. On the other hand, if the tissue structure is
near the target tissue, shorter focal lengths may be preferred to
avoid damaging the tissue structure beyond the target tissue.
[0233] These above-described aspects of the ablating element may be
combined with any of the other features and advantages of the
invention. For example, the transducer 406 may be used for
temperature feedback control of the control system 334 in any
manner described herein and the flow velocity measurements may be
used to characterize the amount of blood cooling at the far surface
FS.
[0234] A method of ablating tissue is now described. The method is
described in connection with the ablating device 400 described
above, however, the method may be practiced with any other suitable
structure or device. The ablating device 400 is positioned against
tissue to be ablated and suction is initiated to hold the cells 402
to the tissue to be ablated. The ablating device 400 may use any of
the methods and devices described above, such as temperature
feedback control or methods of checking the adequacy of contact,
which are incorporated here. As will be explained below, the
transducer 406 itself may be used to determine the adequacy of the
contact between the device and the tissue. In particular, the
transducer 406 may also be used to determine whether any air gaps
exist between the transducer 406 and the tissue. After it has been
determined that the cells 402 are adequately adhered to the tissue,
one or more of the cells 402 are activated to begin ablating
tissue.
[0235] In another aspect of the invention, the device is operated
during two different time periods while varying at least one
characteristic of the device such as the frequency, power, position
of the focus relative to the tissue and/or ablating time. For
example, the ablating device 400 may be operated at varying
frequencies over time to ablate tissue in a controlled manner.
Specifically, the ablating device is preferably operated to create
a transmural lesion by controlling the delivery of energy to the
tissue. Although it is preferred to vary the frequency when
ablating the tissue, the device may, of course, be operated at a
single frequency without departing from various other aspects of
the invention
[0236] In a first treatment method of the present invention, the
transducer 406 is activated at a frequency of 2-7 MHz, preferably
about 3.5 MHz, and a power of 80-140 watts, preferably about 110
watts, in short bursts. For example, the transducer 406 may be
activated for 0.01-1.0 second and preferably about 0.4 second. The
transducer 406 is inactive for about 2-90 seconds, more preferably
5-80 seconds, and most preferably about 45 seconds between
activations. In this manner, a controlled amount of accumulated
energy can be delivered to the tissue in short bursts to heat
tissue at and near the focus and minimizes the impact of blood
cooling at the far surface FS. Ablation at this frequency may
continue until a controlled amount of energy is delivered such as
about 0.5-3 kilojoules. Treatment at this frequency in relatively
short bursts produces localized heating at the focus. At the first
frequency, energy is not absorbed as quickly in tissue as it is at
higher frequencies so that heating at the focus is not
significantly affected by absorption of ultrasound energy in tissue
before reaching the focus.
[0237] Following treatment at the first frequency, the transducer
406 is operated for longer periods of time, preferably about 1-4
seconds and more preferably about 2 seconds, to ablate tissue
between the focus and the transducer 406. The frequency during this
treatment is also 2-14 MHz, more preferably 3-7 MHz and preferably
about 6 MHz. The transducer 406 is operated for 0.7-4 seconds at a
power of 20-60 watts, preferably about 40 watts. The transducer 406
is inactive for at least 3 seconds, more preferably at least 5
seconds and most preferably about 10 seconds between each
activation. In this manner, a controlled amount of energy can be
delivered to heat tissue between the focus and the transducer. The
treatment at this frequency may continue until a controlled amount
of total energy is delivered such as about 750 joules.
[0238] As a final treatment, the ultrasonic transducer is activated
at a higher frequency to heat and ablate the near surface NS. The
transducer is preferably operated at a frequency of at least 6 MHz
and more preferably at least 10 MHz and most preferably about 16
MHz. The transducer 406 is operated at lower power than the
treatment methods above since the ultrasonic energy is rapidly
absorbed by the tissue at these frequencies so that the near
surface NS is heated quickly. In a preferred method, the transducer
is operated at 2-10 watts and more preferably about 5 watts. The
transducer 406 is preferably operated until the near surface NS
temperature reaches 70-85 degrees C.
[0239] Each of the treatments described above may be used by itself
or in combination with other treatments. Furthermore, the
combination of transducer size, power, frequency, activation time,
and focal length may all be varied to produce the desired delivery
of ultrasound energy to the tissue. As such, it is understood that
the preferred embodiment may be adjusted by simply adjusting one or
more of the characteristics and, thus, these parameters may be
changed without departing from various aspects of the invention.
The treatment sequence described above generally deliver energy
closer to the near surface NS during the second treatment and even
closer to the near surface NS for the third treatment.
[0240] The focus of the ultrasound energy may also be moved
relative to the tissue to deliver energy to different depths in the
tissue. When using the devices of FIGS. 66 and 67, for example, the
device can be moved closer to and farther away from the target
tissue with the membrane 460 conforming to the required shape to
fill the gap between the transducer 406 and the tissue. The
membrane is preferably inflated and deflated to move the focus,
however, the device may also be moved with any other suitable
mechanism such as the threaded foot described above. The focus may
be moved while the ablating element is activated or may be moved
between activations of the ablating element. Moving the focus of
the ultrasound energy may be sufficient to create a transmural
lesion without changing frequencies or may be used together with a
change in frequencies as described above. The focus may be moved in
any other manner such as with a phased array or variable acoustic
lensing.
[0241] Referring again to FIG. 60, after the ablating elements have
been activated to ablate tissue it may be necessary to ablate
tissue in gaps between ablations from each of the cells. In one
method, the entire device is shifted so that each of the ablating
elements is positioned to ablate tissue beneath one of the gaps.
Thus, after ablating tissue with all of the cells, the device is
shifted and all of the cells are activated again to create a
continuous lesion. Another method to ablate tissue beneath the gaps
is to tilt the cells to ablate tissue beneath the gaps. In this
manner, the device does not need to be moved. When using the device
of FIG. 67, for example, the membrane is inflated to tilt the
transducer which directs the ultrasound energy toward tissue
beneath gaps between transducers.
[0242] The control system 334 may be designed to automatically
ablate in any manner described herein. For example, the control
system can change the frequency, power, focal length and/or
operating time to provide the desired ablating technique. The
change in frequency and power may be completely automatic or may
require some user input such as visual indications of fat and/or
tissue thickness. For example, the control system 334 may be
designed to automatically sequence through two or more different
ablating techniques such as those described above. Other
techniques, of course, may be used depending on the tissue
characteristics and the type and characteristics of the one or more
ultrasound transducers 406. The control system 334 may also utilize
feedback, such as temperature-based feedback or electrical
impedance, to actively control the ablations. Furthermore, although
various methods have been described, the corresponding
functionality of the control system is provided. Thus, all methods
of the present invention provide corresponding devices and systems
as controlled by the control system.
[0243] In still another aspect of the present invention, a cover
500 is provided in which an ablating device 502 is positioned
during initial positioning of the device as shown in FIG. 74. The
cover 500 may extend over only the bottom or contact surface of the
ablating device 502 or may be a sleeve 501 which surrounds the
device 502. The ablating device 502 may be any of the ablating
devices, elements or systems described herein or any other suitable
system and all aspects of the ablating devices described herein are
incorporated here specifically for the ablating device 502. The
cover 500 has a cavity 503 which contains a flowable material 504.
The flowable material 504 provides an interface between the
ablating device 502 and the tissue to be ablated. The ablating
device 502 is loaded into the cover 500 to help reduce or eliminate
air bubbles or gaps contained in the flowable material 504. Air
bubbles or air gaps can reduce the performance of various energy
sources such as RF and ultrasound.
[0244] The cover 500 is positioned at or near the desired ablating
location and the cover 500 is then pulled, retracted or otherwise
moved to expose the ablating device 502. When the cover 500 is
moved to expose the ablating device 502, the flowable material 504
conforms to the shape of the target tissue to provide an interface
of the flowable material 504 between the ablating device 502 and
the target tissue. The cover 500 is moved by simply pulling the
sleeve over the end of the ablating device 502 while maintaining
the ablating device in substantially the desired ablating position.
Alternatively, the ablating device 502 may be moved out of the
cover 500, however, removal of the cover 500 is preferred to
prevent loss of the flowable material 504 as the ablating device
502 is moved along the target tissue. The flowable material 504 may
be any suitable material depending upon the ablating energy being
used. When ultrasound energy is used, the flowable material is
preferably PEG (polyethyleneglycol) or glycerine. The flowable
material also preferably has a relatively high boiling point such
as at least 100 degrees C. and a vapor pressure lower than that of
water.
[0245] In still another aspect of the present invention, the
ablating device 502 may also have a tip 510 which provides a
flexible, atraumatic distal end as shown in FIG. 74. The flexible
tip 510 facilitates advancement of the device 502 through the space
between the epicardium and pericardium without damaging the heart
or pericardium. The tip 510 may be removable so that the tip 510
does not interfere with the ablating process and can make it easier
to form a closed loop as is shown in various embodiments contained
herein. It can be appreciated that the tip 510 may be used with any
of the ablating devices, systems or methods described herein
without departing from this aspect of the invention. The tip 510
preferably has a length of at least two inches and more preferably
at least four inches from the distal end 511. The tip 510 is
preferably free of any ablating elements.
[0246] In another aspect of the present invention, another system
and method for ablating tissue is shown in FIGS. 75 and 76. The
system 512 provides a liquid environment around the heart. The
liquid environment may help in energy transfer when using certain
energy types, such as RF or ultrasound, and/or may serve to simply
eliminate air bubbles or gaps which can hinder energy transfer. The
liquid environment also helps in controlling the temperature since
the temperature of the liquid can be regulated. For example, the
liquid can be circulated through a heat exchanger 514 which heats
or cools the liquid as desired. In one aspect of the invention, the
liquid is cooled to remove heat generated by the ablating device
502. The temperature may be controlled in any manner described
herein and such methods are specifically incorporated here.
[0247] The system 512 includes a liquid delivery element 516, such
as a tube 518, connected to a liquid source 520, preferably sterile
saline. Of course, the liquid must also be delivered and/or
withdrawn with the ablating device 502. Liquid is delivered as
necessary with conventional valves 522 and clamps 524 controlling
the flow of liquid. The ablating device 502 is submerged within the
liquid environment and may be any device described herein or other
suitable device. The liquid delivery element 516 may form a fluid
tight seal with the pericardium or the patient may be positioned so
that the liquid environment can be created by penetrating the
pericardium at an elevated position which does not require a
hemostatic seal. The system 512 may be used in an open chest
procedure with a rib retractor 515 as shown in FIG. 76. The
pericardium is snared, sutured or otherwise anchored or suspended
as is known in the art. The system 512 may also be used in a less
or minimally invasive manner as shown in FIG. 75 wherein the chest
is accessed via a subxyphoid approach. The delivery element 516 has
two lumens with one of the lumens 517 being an outlet lumen coupled
to openings 519.
[0248] In another aspect of the invention, any of the ablating
devices described herein may have a convex contact surface 520 as
shown in FIGS. 73 and 74. The convex contact surface 520 helps to
squeeze or eliminate air bubbles or gaps from the area between the
device and the target tissue. Air bubbles or gaps can inhibit
energy transfer and, in particular, can reduce the efficiency of
ultrasound and RF energy transfer. The convex surface 520 may form
part of the ablating element itself or may be a separate element
that is adhered, mounted or otherwise coupled to the ablating
device as described above. Of course, the convex contact surface
520 may be used with any of the ablating devices described herein
and is shown specifically in FIGS. 73 and 74. The convex contact
surface 520 may be made of any suitable material such as
polyurethane.
[0249] Referring to FIGS. 77 and 78, another ablating device 522 is
shown which is similar to the device of FIG. 64 wherein all aspects
of the device of FIG. 64 are incorporated here. The ablating device
522 has the membrane 460 which is spaced apart from the ablating
element to form a fluid cavity 524 therebetween. The fluid cavity
524 contains a fluid 526 which can serve any one or more of the
following functions. The fluid 526, of course, transmits energy
from the ablating element. The membrane 460 also conforms to the
shape of the target tissue. The fluid 526 may be delivered from the
source of cooling medium 434 having a suitable heat exchanger as
discussed above. The temperature of the fluid 526 may be controlled
in any manner described herein and all such descriptions are
incorporated specifically here for all purposes. For example,
temperature control of the fluid provides the ability to control
the near surface temperature of the tissue in any manner described
herein.
[0250] Referring to FIG. 77, each fluid cavity 524 may extend over
a single ablating element with each of the fluid cavities 524 being
coupled to a common inlet lumen 530 and outlet lumen 531.
Alternatively, the membrane 460 may extend over a number of
ablating elements or along the entire device as shown in FIG. 78.
The fluid 526 is circulated through the fluid cavity 524 from an
inlet lumen 525 attached to one end and an outlet lumen 527
attached to the other end of the device. The fluid 526 is
circulated through the fluid cavity 524 using the source of cooling
medium 434. The membrane 460 may also have openings 462 (FIG. 77)
therein or may be permeable so that some of the fluid 526 leaks
through the membrane 460. The fluid 526 may help conduct energy or
may simply reduce or eliminate air gaps. The membrane 460 may also
form the convex contact surface 520 naturally or when fluid
pressure is applied. The fluid 526 may also be pulsed to provide
intermittent weeping or leaking of the fluid through the membrane
460. The pulsed fluid flow may also be used to deform the membrane
by partially inflating/deflating the membrane which may help to
sweep away bubbles or provide a flushing action for the fluid.
[0251] Referring now to FIG. 79, a flexible skirt 536 may be
provided around the ablating element. The flexible skirt 536 may be
used to contain the fluid 526 which is supplied in any suitable
manner such as those described herein. Referring to FIG. 80, the
flexible skirt may be used in connection with the convex contact
surface 520. The fluid 526, or other flowable material, is
introduced through an inlet 540 and travels down lumen 542 to the
contact surface 520. The skirt 536 helps to contain the fluid 526
to inhibit the fluid 526 from flowing freely outward.
[0252] Referring to FIG. 81A, still another ablation device 540 is
shown which may be used in any manner described herein. The
ablation device 540 has an ablating element 542, such as the
focused ultrasound element described herein, which moves along a
guide member 544. The guide member 544 may be any suitable element
such as a tube, track, wire, rail, catheter, or chain. Similar to
other embodiments described herein, the guide member 544 is
positioned along a desired ablation path and is then fixed relative
to the heart. The guide member 544 may have a locking mechanism to
lock one part of the guide member 544 to another part to form a
closed loop like the device of FIGS. 56-58. Alternatively or in
addition to the locking mechanism, the guide member 544 may use
suction to adhere to the target tissue similar to other embodiments
described herein.
[0253] The ablating element 542 moves toward and away from the
epicardial surface to distribute the energy through the target
tissue similar to other devices described herein. Of course, the
ablating element 542 may maintain communication with the target
tissue via a transmission medium, such as a liquid or gelm as
described above. The transmission medium may be contained within
the guide member 544. The ablating element 542 is mounted on wheels
546 at an offset location relative to the wheel axis which causes
the ablating element 542 to move along an arc. The ablating element
542 is located at the same relative position on both wheels so that
the ablating element 542 maintains the same orientation relative to
the epicardial surface while moving along the guide member 544. The
ablating element 542 may be moved with simple push-pull elements
547 or by using an internal or external drive system. The push-pull
elements 547 may also have the various lumens, control and sensing
wires, energy transmission elements and the like which may be
bundled together. All of the various features of the invention
described herein may be used with the guide element 544 and
ablating element 542.
[0254] Referring to FIG. 81B, another ablation device 541 is shown
which moves toward and away from the target tissue. The ablation
device 541 also tilts relative to the tissue while moving along
guide element 543. The guide element 543 has a track 545 which
undulates to cause the ablation element 540 to move toward and away
from the tissue and tilt.
[0255] Referring to FIG. 82, still another ablation device 548 is
shown. The ablation device 548 also has the guide member 544 and
the ablation element 542. The ablation element 542 moves along the
guide member 544 similar to other devices described herein. The
ablation element 542, such as a focused ultrasound element,
produces focused energy having a focus which is tilted or angled
relative to the target tissue so that the focal energy is
distributed throughout at least part of the thickness of the target
tissue and preferably throughout the entire thickness of the target
tissue. The ablation element 542 is advanced through the guide
member 544 using the push-pull elements 547 or any other suitable
system. The guide member 544 may be filled with a fluid, such as
saline, which transmits the energy to the target tissue or the
ablating element may have a transmission element 545 coupled to the
ablating element 542 which transmits the energy to the target
tissue. The guide member 544 may be fixed relative to the heart in
any manner such as with the locking device, suction or any other
suitable method. The device 548 may have a number of elements which
are angled differently to provide the ability to use a different
ablating element for differing tissue thickness.
[0256] The transmission element 545 may be solid or may be filled
with a liquid or gel to form a compliant contact surface. For
example, the ablation element 542 may have a chamber 550 which
holds a fluid which transmits energy to the target tissue rather
than filling the entire guide member with the fluid as shown in
FIG. 83. The chamber 550 may fully contain the fluid or may have
one or more openings which permit the fluid to weep or flow out of
the chamber 550 as described above. The fluid may also be
circulated through the chamber 550 in any manner described above
for cooling or heating the ablating element 542 or target tissue.
The fluid may be delivered through one or more lumens 551. The
ablation element 542 is moved along the target tissue to form a
continuous lesion.
[0257] The ablation element 542 may be moved to discrete locations
to ablate while the ablation element 542 is still. The ablation
element 542 may also be moved during ablation with the velocity of
the ablation element 542 being controlled. The ablation element 542
is moved at a velocity which may be controlled by any of the
control system or methods described herein. The velocity may be set
based upon any of the various parameters described herein such as
with the electrodes, sensors, temperature sensors, or thickness
determinations.
[0258] Referring to FIG. 84, still another ablation device 552 is
shown which may be used in any manner described herein. The
ablation device 552 has an ablation element 554, such as a laser
555 as mentioned above, which moves along a guide member 556 which
is positioned along a desired ablation path. The guide member 556
has an elongate opening 558 on a side facing the target tissue. The
ablation element 554 directs the ablating energy, such as laser
energy, through the opening 558 to the target tissue. The laser 555
may direct the energy at the target tissue or the energy may be
reflected off a mirror 557 toward the target tissue.
[0259] Referring again to FIGS. 56-58, another aspect of the
present invention is now described which relates to monitoring the
progress of an ablation. As mentioned above, monitoring the
ablation may be helpful since it is desirable to ablate through at
least a substantial portion of the tissue thickness and preferably
through the entire thickness of the tissue. To monitor the progress
of the ablation, energy is passed through the target tissue and
monitored after passing through the target tissue to detect a
change in an energy characteristic. A change in the energy
characteristic, such as the energy magnitude, frequency or a phase
shift or delay, helps the user monitor the ablation and determine
when the ablation may be complete. The characteristic is indicated
to the user by an indicator 560 which may be part of the control
system 334. The indicator 560 may show the characteristic in any
suitable manner such as numerically or schematically with a color
code or graphic bars. The indicator 560 may be part of the control
system which also include the features of any of the other control
systems described herein. Of course, the control system may turn
the ablating elements on and off, or may move the ablating
elements, automatically in accordance with any of the methods
described herein wherein the change may or may not be indicated to
the user.
[0260] In one application of the invention, the characteristic is
simply the amount of energy transmitted through the target tissue.
When using ultrasound ablating elements described herein, for
example, the amount of energy transmitted through the target tissue
tends to decrease when the tissue is ablated. The change in the
amount of energy transmitted through the target tissue can be
monitored to provide an indication of the progression of the
ablation and when the ablation procedure is complete. In another
aspect, the frequency or phase shift may be measured.
[0261] The ablation elements may themselves act as an emitter 562
and/or the receiver 564 or separate emitters and receivers may be
used. When using the ablation elements 404 (see FIG. 59) to emit
and/or receive the energy, one or more of the ablating elements 404
may receive energy from active ablating element 404 to monitor
changes in the transmitted energy as the ablation progresses. The
ablating element 404 may also periodically emit energy having
different characteristics than the ablation energy. For example,
the power may be reduced or the frequency changed. An advantage of
using ultrasound is that the ablating element 404 may periodically
change energy characteristics for a very short time to provide
virtually continuous ablating. Of course, any suitable ablating
element, including any of those described herein, may be used
without departing from the scope of the invention.
[0262] The ablating element 404 may also receive energy so that the
ablating element 404 itself acts as the receiver 564. The ablating
element may stop emitting ablating energy for a short time to act
as the receiver 564 to receive energy. When using ultrasound, the
ablating element 404 may be periodically stopped for a very short
period to receive energy (rather than emit) to provide virtually
continuous ablating. For example, energy may be terminated for 1 to
100 msec periodically.
[0263] The ablation device may include a number of emitters 562 and
receivers 564. For example, one of the ablating elements 404 may
emit energy while a number of the receivers 564 receive the energy.
In this manner, a number of receivers 564, such as a number of the
ablating elements 404, may be used to monitor the change in energy
characteristics. Of course, various different energy sources for
the ablating elements 404 may be used in connection with this
method.
[0264] In another aspect of the invention, an intravascular device
570 may be positioned within the patient's vascular system, such as
a chamber of the heart, to act as the emitter 562 and/or receiver
564. The device may be introduced directly into the heart through
the chest and into the vascular system through a direct penetration
in the heart or great vessel. Alternatively, the intravascular
device 570 may be introduced and advanced through a peripheral
vessel, such as a femoral vessel, and into the heart. The
intravascular device 570 may either be the emitter 562 or the
receiver 564, and when using ultrasound it may, of course, be both.
The intravascular device 570 may be used in any manner described
herein where the intravascular device 570 replaces functions of the
emitter 562 and/or receiver 564. For example, the intravsacular
device 570 may emit energy which is received by the ablating device
or simply receive energy from the ablating element 404.
[0265] Referring to FIGS. 85 and 86, another ablating device 572 is
shown wherein the same or similar reference numbers refer to the
same or similar structure. The ablating device 572 has a shaft 574
which extends out of the patient's chest. The shaft may 574 be
hand-held or coupled to a retractor, trocar or the like which fixes
the shaft relative to the patient's heart. The shaft 574 has a
multi-link configuration, as is known in the art, which is either
flexible or fixed in position by manipulating an actuator 576. Of
course, the shaft 574 may be articulated, flexible, malleable or
may also be a simple, straight shaft.
[0266] The device 572 may be used in the same manner as described
herein except that the device 572 is periodically moved to a new
location to form a continuous lesion. The device 572 preferably has
three ablating elements 404 although any number may be provided.
The device 572 also has the control system 334 described above in
connection with FIGS. 56 and 57 and all aspects of the control
system and related structure is incorporated here. It is understood
that all features of the similar or same structure described herein
may be used with the ablating device 572. For example, FIG. 86 is
similar to FIG. 28 and the aspects and features relating to FIG. 28
are applicable here. FIG. 28 also shows the electrodes 191, 193,
195, 196 which are used in the manner described above corresponding
to FIG. 28. The electrodes may be used to either simply sense
electrical activity or may emit pulses which are then monitored at
other electrodes. For example, the electrodes 191, 193 are used to
help position the device 572 at an appropriate location to form a
continuous lesion. Electrodes 195, 196 are positioned on opposite
sides of the ablation and help to determine whether the lesion is
continuous and whether the ablation electrically isolates one side
of the ablation from the other. Thus, it can be appreciated that
the ablating device 572 any number of features and aspects
described herein and such features and aspects are specifically
incorporated here.
[0267] Referring to FIGS. 87 and 88, another ablation device 580 is
shown. The ablation device 580 has at least one ablation element
582 and the device 580 has two ablation elements 582 but may, of
course, have more than two. The ablation element 582 may be any
suitable element such as the ultrasound elements described herein
which are incorporated here. Furthermore, the device 580 may have
the sensors and electrodes operated in the manner described above.
All of such features are specifically incorporated into the
ablation device 580. The device 580 has a connector 583 for
coupling the device to fluid delivery and withdrawal and/or suction
as described herein. The device 580 also has a connector 585 for
connecting the device 580 to any one of the control systems
described herein for controlling the device 580, receiving data
from sensors, and the ablating elements 582.
[0268] The device 580 has a shaft 584 which is relatively rigid
with a flexible distal portion 586. The distal portion 586 can be
shaped by a user into a variety of positions to accommodate the
angle of introduction and target surface orientation. The distal
portion 586 has a stacked coil 588 contained within a sheath 560
which can be deformed by a user and retains the deformed shape. The
ablation elements 582 may be fixed relative to one another or may
have a flexible or malleable connection therebetween to adjust the
relative orientation or position of the ablation elements 582.
[0269] Finally, although the present methods have been described in
connection with creating a continuous lesion around the pulmonary
veins, it is understood that the methods are equally applicable for
only ablating partially around the pulmonary veins or along only a
segment. Furthermore, other lesions may be beneficial in treating
electrophysiological conditions and the devices and methods
described herein may be useful in creating such other lesions.
Thus, the present invention should not be construed as being
limited to creating lesions completely around the pulmonary
veins.
[0270] While the above is a complete description of the preferred
embodiments of the invention, various alternatives, substitutions
and modifications may be made without departing from the scope
thereof, which is defined by the following claims. For example, any
of the ablating devices described herein may have the anchor, fins,
lateral balloons, sensors, and/or electrodes without departing from
the scope of the invention
* * * * *