U.S. patent application number 10/954136 was filed with the patent office on 2006-03-30 for methods and apparatus for tissue cryotherapy.
This patent application is currently assigned to Scimed Life Systems, Inc.. Invention is credited to Boaz Avitall, Daniel M. Lafontaine.
Application Number | 20060069385 10/954136 |
Document ID | / |
Family ID | 36100257 |
Filed Date | 2006-03-30 |
United States Patent
Application |
20060069385 |
Kind Code |
A1 |
Lafontaine; Daniel M. ; et
al. |
March 30, 2006 |
Methods and apparatus for tissue cryotherapy
Abstract
A method for performing cryotherapy on a target tissue region in
a body includes positioning a first cooling element in a first
location in a body adjacent a target tissue region, positioning a
second cooling element in a second location in the body adjacent
the target tissue region, and cooling the respective first and
second cooling elements so as to cool the target tissue region.
Inventors: |
Lafontaine; Daniel M.;
(Plymouth, MN) ; Avitall; Boaz; (Whitefish Bay,
WI) |
Correspondence
Address: |
Bingham McCutchen, LLP;Suite 1800
Three Embarcadero
San Francisco
CA
94111-4067
US
|
Assignee: |
Scimed Life Systems, Inc.
Maple Grove
MN
|
Family ID: |
36100257 |
Appl. No.: |
10/954136 |
Filed: |
September 28, 2004 |
Current U.S.
Class: |
606/21 ;
606/23 |
Current CPC
Class: |
A61B 18/02 20130101;
A61B 2017/00243 20130101; A61B 2018/0212 20130101; A61B 2017/22051
20130101; A61B 2090/3954 20160201; A61B 2017/00101 20130101; A61B
2018/0022 20130101; A61B 90/39 20160201 |
Class at
Publication: |
606/021 ;
606/023 |
International
Class: |
A61B 18/02 20060101
A61B018/02 |
Claims
1. A method for performing cryotherapy on a target tissue region in
a body, comprising: positioning a first cooling element in a first
location in a body adjacent a target tissue region; positioning a
second cooling element in a second location in the body adjacent
the target tissue region; and cooling the respective first and
second cooling elements so as to cool the target tissue region.
2. The method of claim 1, wherein the target tissue region is
sufficiently cooled to be ablated.
3. The method of claim 1, wherein the target tissue region is
proximate an annulus of a mitral valve connecting a left atrium and
left ventricle of a heart.
4. The method of claim 3, wherein the target tissue region
comprises a left atrial isthmus of the heart.
5. The method of claim 1, wherein the target tissue region is
proximate an annulus of a tricuspid valve connecting a right atrium
and right ventricle of a heart.
6. The method of claim 1, wherein the first location is in a
coronary sinus and the second location is in a left atrium.
7. The method of claim 6, wherein positioning the first cooling
element in the coronary sinus comprises inserting the first cooling
element in the coronary sinus and adjacent the target tissue region
when the first cooling element is in a collapsed profile, and
expanding the first cooling element to an expanded profile that
substantially occludes the coronary sinus.
8. The method of claim 1, wherein one or both of the cooling
elements are expandable.
9. The method of claim 1, wherein one or both of the first and
second cooling elements are inflatable.
10. The method of claim 1, one or both of the first and second
locations comprising an atrium or ventricle of a heart.
11. The method of claim 1, one or both of the first and second
locations comprising a pulmonary vein or pulmonary vein
opening.
12. The method of claim 1, wherein cooling of the first cooling
element is controlled independent of cooling of the second cooling
element.
13. The method of claim 1, wherein positioning the second cooling
element comprises locating a portion of the first cooling element
and verifying that the located portion is in contact with, or
otherwise adjacent to, the target tissue region.
14. The method of claim 13, wherein the portion of the first
cooling element is located using a fluoroscope.
15. The method of claim 13, wherein the portion of the first
cooling element is located using ultrasound.
16. The method of claim 13, wherein the portion of the first
cooling element is located using electromagnetic or radiofrequency
energy.
17. The method of claim 13, wherein cooling the first cooling
element comprises cooling the located portion.
18. The method of claim 1, further comprising verifying a selected
portion of the first cooling element is positioned proximate a
selected portion of the second cooling element while or after the
respective cooling elements are positioned adjacent the target
tissue region.
19. The method of claim 1, wherein the first location is inside a
heart, and the second location is adjacent or on a surface of the
heart.
20. The method of claim 19, wherein the first location is inside an
atria.
21. The method of claim 19, wherein the second location is on an
epicardium of the heart or within a pericardial sac.
22. A method for treating atrial fibrillation, comprising:
positioning a first cooling element in a patient's coronary sinus
adjacent a target tissue region at least partially connecting the
patient's left atrium and left ventricle; positioning a second
cooling element in the patient's left atrium adjacent the target
tissue region; and cooling the respective first and second cooling
elements so as to ablate the target tissue region.
23. The method of claim 22, wherein the target tissue region
comprises the patient's left atrial isthmus.
24. The method of claim 22, wherein positioning the first cooling
element in the coronary sinus comprises inserting the first cooling
element in the coronary sinus and adjacent the target tissue region
when the first cooling element is in a collapsed profile, and
expanding the first cooling element to an expanded profile that
substantially occludes the coronary sinus.
25. The method of claim 24, wherein the first cooling element is
expanded by inflating the first cooling element.
26. The method of claim 22, wherein one or both of the first and
second cooling elements are expandable.
27. The method of claim 26, wherein cooling of the first cooling
element is controlled independent of cooling of the second cooling
element.
28. The method of claim 22, further comprising locating a portion
of the first cooling element and verifying that the located portion
is in contact with, or otherwise adjacent to, the target tissue
region.
29. The method of claim 28, wherein cooling the first cooling
element comprises cooling the located portion.
30. The method of claim 22, further comprising verifying a selected
portion of the first cooling element is positioned proximate a
selected portion of the second cooling element while or after the
respective cooling elements are positioned adjacent the target
tissue region.
31. The method of claim 30, wherein cooling the first and second
cooling elements comprises cooling the respective selected
portions.
32. The method of claim 22, wherein the target tissue region is
ablated by being synergistically cooled using the first and the
second cooling elements.
33. Apparatus for performing cryotherapy on a target tissue region
in a body, comprising: a first cooling element configured for
positioning in a first location in a body adjacent a target tissue
region, the first cooling element comprising a locatable portion; a
second cooling element configured for positioning in a second
location in a body adjacent the target tissue region, the second
cooling element comprising a locatable portion; each of the first
and second cooling elements being in fluid communication with a
coolant source; and one or more controllers for controlling cooling
of the first and second cooling elements independent of each
other.
34. The apparatus of claim 33, wherein the first location is in a
coronary sinus and the second location is in a left atrium.
35. The apparatus of claim 34, wherein the first cooling element
may be configured in a collapsed profile for positioning in the
coronary sinus adjacent the target tissue region, and in an
expanded profile that substantially occludes the coronary
sinus.
36. The apparatus of claim 33, wherein one or both of the first and
the second cooling elements are expandable.
37. The apparatus of claim 33, wherein one or both of the first and
second cooling elements are inflatable.
38. The apparatus of claim 33, further comprising a system for
verifying whether the locatable portion of the first cooling
element is in contact with, or otherwise adjacent to, the target
tissue region.
39. The apparatus of claim 33, wherein the locatable portion of the
first cooling element may be selectively cooled.
40. The apparatus of claim 33, further comprising a system for
verifying whether the locatable portion of the first cooling
element is positioned proximate the locatable portion of the second
cooling element.
41. The apparatus of claim 33, further comprising a third cooling
element, wherein the first, second, and third cooling elements are
configured such that two of the cooling elements are alternately
placed in contact with the target tissue region while the remaining
cooling element is being positioned.
42. The apparatus of claim 33, wherein the first location is inside
a heart and the second location is outside the heart.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to therapeutic
cooling of body tissue, and more particularly, to methods and
apparatus for deploying a plurality of cooling elements to at least
partially surround and cool, e.g., to ablate by cryoplasty, a
selected tissue region.
BACKGROUND OF THE INVENTION
[0002] A number of medical conditions may be treated using ablative
techniques or devices. Ablative therapy generally involves the
killing of abnormal tissue at an area of interest, thereby
resulting in an efficacious treatment for a medical condition. For
example, atrial fibrillation may be treatable by ablation of the
abnormal tissue within the left atrium and/or the pulmonary
vein.
[0003] Atrial fibrillation is a serious medical condition that is
the result of abnormal electrical activity within the heart. This
abnormal activity may occur at regions of the heart including the
sino-atrial (SA) node, the atriovenricular (AV) node, or within
other areas of cardiac tissue. Moreover, atrial fibrillation may be
caused by abnormal activity within one or more isolated focal
centers within the heart. It is believed that these foci can
originate from within the pulmonary vein, particularly the superior
pulmonary veins.
[0004] Ablation catheters have been used in minimally invasive
techniques to ablate target tissue, e.g., foci having abnormal
electrical activity. The techniques typically are characterized by
application of energy to create lesions at the foci or other areas
possessing abnormal electrical activity. Ablation catheters can
also be used to create lesions at the heart to block electrical
signals or to alter a travel path of electrical signals at the
heart.
[0005] Some ablation devices utilize radio frequency (RF) energy
for ablation, including the device disclosed in U.S. Pat. No.
6,024,740 to Lesh et al. The RF energy devices may be used to
ablate an area of interest with heat. The use of RF energy for
ablation may, however, lead to untoward healing responses such as
collagen build up at the area of interest after treatment. In some
cases, RF ablation may create lesions that cause occlusion of the
coronary sinus in post procedure healing. A need, therefore, exists
for ablative devices and methods that include improved healing
responses.
[0006] An alternative treatment strategy has been developed that
uses cooling energy for ablation. This method, termed cryoplasty or
cryotherapy, may be used to cool or otherwise freeze a portion of
target tissue to ablate the target tissue. For example, cryoplasty
may be used to cool or freeze and simultaneously dilate a lesion
within a blood vessel that might otherwise lead to restenosis or
recoil. Cryotherapy may also be used to create lesions at a heart
to treat atrial fibrillation. However, creating lesions in a heart
using cryotherapy poses a challenge in that it may be difficult to
deliver sufficient cooling to create a transmural (i.e., a through
thickness) lesion. In addition, blood delivered to and from the
heart constantly provides heat to a target site at the heart,
thereby counteracting against the cooling being delivered by the
cryotherapy, and limiting the amount of cooling that can be
delivered to the target site. This in turn, further prevents a
transmural lesion, or lesion of a desired size or characteristic,
from being created at the target tissue.
[0007] Thus, there is currently a need for an improved device and
method to perform ablation therapy.
SUMMARY OF THE EMBODIMENTS
[0008] In accordance with some embodiments, a method for performing
cryotherapy on a target tissue region in a body includes
positioning a first cooling element in a first location in a body
adjacent a target tissue region, positioning a second cooling
element in a second location in the body adjacent the target tissue
region, and cooling the respective first and second cooling
elements so as to cool the target tissue region.
[0009] In accordance with other embodiments, a method for treating
atrial fibrillation includes positioning a first cooling element in
a patient's coronary sinus adjacent a target tissue region at least
partially connecting the patient's left atrium and left ventricle,
positioning a second cooling element in the patient's left atrium
adjacent the target tissue region, and cooling the respective first
and second cooling elements so as to ablate the target tissue
region.
[0010] In accordance with other embodiments, an apparatus for
performing cryotherapy on a target tissue region in a body includes
a first cooling element configured for positioning in a first
location in a body adjacent a target tissue region, the first
cooling element comprising a locatable portion, a second cooling
element configured for positioning in a second location in a body
adjacent the target tissue region, the second cooling element
comprising a locatable portion, each of the first and second
cooling elements being in fluid communication with a coolant
source, and one or more controllers for controlling cooling of the
first and second cooling elements independent of each other.
[0011] Other and further aspects and features of the invention will
be evident from reading the following detailed description of the
preferred embodiments, which are intended to illustrate, not limit,
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The drawings illustrate the design and utility of preferred
embodiments of the present invention. It should be noted that the
figures are not drawn to scale and that elements of similar
structures or functions are represented by like reference numerals
throughout the figures. In order to better appreciate how the
above-recited and other advantages and objects of the present
inventions are obtained, a more particular description of the
present inventions briefly described above will be rendered by
reference to specific embodiments thereof, which are illustrated in
the accompanying drawings. Understanding that these drawings depict
only typical embodiments of the invention and are not therefore to
be considered limiting of its scope, the invention will be
described and explained with additional specificity and detail
through the use of the accompanying drawings in which:
[0013] FIG. 1 is a perspective view of a tissue ablation system in
accordance with some embodiments of the invention, showing the
tissue ablation system having two ablation devices;
[0014] FIG. 2 is a cross sectional view of one of the ablation
devices of FIG. 1;
[0015] FIG. 3 is a perspective view of an ablation device having an
array of sensors in accordance with other embodiments of the
invention;
[0016] FIG. 4 is a perspective view of a variation of the ablation
device of FIG. 3;
[0017] FIG. 5 is a perspective view of a tissue ablation device in
accordance with other embodiments of the invention, showing the
tissue ablation device having three cryo balloons;
[0018] FIGS. 6A and 6B are end views of the tissue ablation device
of FIG. 5, showing the tissue ablation device being used to create
lesions;
[0019] FIGS. 7A and 7B are cross-sectional views, showing a method
for treating tissue, in accordance with some embodiments of the
invention;
[0020] FIG. 8 shows, in diagrammatic form, anatomic landmarks for
lesion formation in left and right atriums;
[0021] FIG. 9A and 9B show representative lesion patterns in a left
atrium that may be formed using the tissue ablation system of FIG.
1; and
[0022] FIG. 10A-10C show representative lesion patterns in a right
atrium that may be formed using the tissue ablation system of FIG.
1.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0023] Various embodiments of the present invention are described
hereinafter with reference to the figures. It should be noted that
the figures are not drawn to scale and elements of similar
structures or functions are represented by like reference numerals
throughout the figures. It should also be noted that the figures
are only intended to facilitate the description of specific
embodiments of the invention. They are not intended as an
exhaustive description of the invention or as a limitation on the
scope of the invention. In addition, an aspect described in
conjunction with a particular embodiment of the present invention
is not necessarily limited to that embodiment and can be practiced
in any other embodiments of the present invention.
[0024] FIG. 1 illustrates a tissue ablation system 10 in accordance
with some embodiments of the invention. The tissue ablation system
10 includes a first and a second ablation devices 12, 52 configured
for introduction into the body of a patient for ablative treatment
of target tissue. The tissue ablation system 10 also includes a
coolant supply 80 configured for supplying cooling energy to the
ablation devices 12, 52 during use. In the illustrated embodiments,
the coolant supply 80 provides cooling media to both the first and
the second ablation devices 12, 52. Alternatively, each of the
first and the second ablation devices 12, 52 can have its own
coolant supply.
[0025] The first ablation device 12 includes a shaft 16 having a
proximal end 18, a distal end 20, and a lumen 21 extending between
the proximal and the distal ends 18, 20, and terminating at a
distal port 44. The proximal end 18 of the shaft 16 has an
extension 40 with a guidewire port 42 that is in fluid
communication with the lumen 21 of the shaft 16. During use, a
guidewire 120 can be inserted through the distal port 44 and exits
through the guidewire port 42 at the proximal end 18 of the shaft
16 (FIG. 2). As shown in FIG. 2, the shaft 16 also includes a media
delivery channel 130 and a suction channel 140 disposed within a
wall 142 of the shaft 16. The media delivery channel 130 and the
suction channel 140 extend along the length of the shaft 16 and
terminate at a delivery port 132 and a suction port 142,
respectively, located at the distal end 20 of the shaft 16. In
other embodiments, instead of having the channels 130, 140 within
the wall 142 of the shaft 16, the first ablation device 12 can
include a fluid delivery tube and a drainage tube. The delivery
tube and the drainage tube can be secured to an exterior surface of
the shaft 16, or alternatively, be disposed within the lumen 21 of
the shaft 16. Also, in other embodiments, a cooling tube having a
coil configuration, such as that described in U.S. patent
application Ser. No. 10/231,738, can be provided. The entire
disclosure of U.S. patent application Ser. No. 10/231,738 is
expressly incorporated by reference herein.
[0026] The first ablation device 12 also includes a cryo balloon
22. The cryo balloon 22 has a proximal end 102 and a distal end 104
that are both secured to the distal end 20 of the shaft 16, and a
lumen 106 that is in fluid communication with the delivery port 132
and the suction port 142. In the illustrated embodiments, the cryo
balloon 22 has a configuration that resembles an elliptical shape.
Alternatively, the cryo balloon 22 can have other shapes, such as a
spherical shape, an elongate shape, or other customized shapes.
During use, coolant is delivered from the coolant supply 80 via the
media delivery channel 130 and exits through the delivery port 132
to inflate the cryo balloon 22. The delivered coolant can be
drained or vacuumed through the suction port 142 to circulate
coolant through the cryo balloon 22 and/or to deflate the cryo
balloon 22.
[0027] In some embodiments, the first ablation device 12 further
includes one or more steering wires disposed within the wall 142 of
the shaft 16, with the distal end(s) of the steering wire(s)
secured to the distal end 20 of the shaft 16. In such cases,
tension can be applied to the steering wire(s) to bend the distal
end 20 of the shaft 16, thereby steering the cryo balloon 22.
[0028] The first ablation device 12 also includes an access cannula
30 having a distal end 32, a proximal end 34, and a lumen 36
extending between the distal and the proximal ends 32, 34. The
shaft 16 is located coaxially within the lumen 36 of the cannula
30, and is slidable relative to the cannula 30. During use, the
cryo balloon 22 initially-in its deflated configuration, is resided
within the lumen 36 of the cannula 30. After the distal end 32 of
the-cannula 30 has been desirably positioned, the shaft 16 is then
advanced distally relative to the cannula 30 (or the cannula 30 is
retracted proximally relative to the shaft 16) to push the cryo
balloon 22 out of the distal end 32 of the cannula 30, and the cryo
balloon 22 is then inflated to perform ablative therapy. In some
embodiments, the cannula 30 can further include one or more
steering wires (not shown) having distal end(s) that is secured to
the distal end 32 of the cannula 30. The steering wire(s) can be
tensioned to bend the distal end 32, thereby steering the distal
end 32 of the cannula 30 during use.
[0029] In other embodiments, the first ablation device 12 can
further include an outer member (not shown) disposed over the cryo
balloon 22. Also, in other embodiments, the first ablation device
12 can further include an outer shaft (not shown ) disposed
coaxially outside the shaft 16. During use, a vacuum can be created
in the lumen that is between the shaft 16 and the outer shaft,
thereby providing both thermal insulation and gas isolation between
the coolant and the patient. The outer shaft can be made from a
biocompatible material known to those skilled in the art of
catheter construction, and should be sufficiently rigid to prevent
the outer shaft from collapsing when a vacuum is created within the
lumen of the outer shaft.
[0030] The above and similar devices have been disclosed in U.S.
Pat. No. 6,666,858, and U.S. patent application Ser. No.
10/126,027, the entire disclosures of which are expressly
incorporated by reference herein.
[0031] Returning to FIG. 1, the second ablation device 52 also
includes a shaft 56 having a proximal end 58, a distal end 60, and
a lumen 61 extending between the proximal and the distal ends 58,
60, and terminating at a port 84. The proximal end 58 of the shaft
56 has an extension 80 with a guidewire port 82 that is in fluid
communication with the lumen 61 of the shaft 56. The second
ablation device 52 also includes a cryo balloon 62 secured to the
distal end 60 of the shaft 56, and an access cannula 70 having a
distal end 72, a proximal end 74, and a lumen 76 extending between
the distal and the proximal ends 72, 74. The shaft 56 is located
coaxially within the lumen 76, and is slidable relative to the
cannula 70. The second ablation device 52 is similar to the first
ablation device 12, and therefore, will not be described in further
details.
[0032] The first and the second cryo balloons 22, 62 are adapted to
be placed relative to each other such that they at least partially
surround a target tissue to be ablated. In the illustrated
embodiments, the first and the second ablation devices 12, 52
further include a first element 110 and a second element 112,
respectively, for assisting placement of the cryo balloons 22, 62
relative to each other. The first and the second elements 110, 112
can be radio opaque markers that can be visualized under x-ray or
fluoroscope. Alternatively, the first and the second elements 110,
112 can be a signal transmitter, and a signal receiver,
respectively, or vice versa. For example, the first element 110 can
be an ultrasound signal transmitter that transmits ultrasound
signals, and the second element 112 can be an ultrasound signal
sensor for sensing ultrasound signals. In such cases, based on a
time difference between the first element 110 transmitting an
ultrasound signal and the second element 112 receiving the
ultrasound signal, a distance between the first and the second
elements 110, 112 (and therefore, between the cryo balloons 22, 62)
can then be determined. Also in other embodiments, multiple
receivers could be used to triangulate position(s) of the cryo
balloons 22, 62.
[0033] In other embodiments, the first element 110 can be a magnet
(e.g., a permanent magnet or an electromagnet), and the second
element 112 can be a magnetic field sensor, or vice versa. In such
cases, based on a sensed magnetic field by the magnetic field
sensor, a distance between the cryo balloons 22, 62 can be
determined (e.g., a stronger magnetic field indicates that the cryo
balloons 22, 62 are closer to each other, and vice versa).
[0034] In other embodiments, the first element 110 can be a
radiofrequency energy transmitter, and the second element 112 can
be a radiofrequency energy sensor, or vice versa. In such cases,
based on a strength of the radiofrequency energy sensed by the
sensor, a relative distance between the first and the second
elements 110, 112 (and therefore, a relative position between the
cryo balloons 22, 62) can be determined.
[0035] Also, in other embodiments, both the first and the second
elements 110, 112 can be magnets (e.g., permanent magnets or
electromagnets). In such cases, during use, the magnets
mechanically attract the first and the second cryo balloons 22, 62
towards each other, thereby positioning the cryo balloons 22, 62
close to each other. In some embodiments, the cryo balloons 22, 62
are placed on opposite sides of target tissue. In such cases, the
magnets will cause the cryo balloons 22, 62 to move towards each
other and make contact with opposite sides of the target
tissue.
[0036] In the above described embodiments, the first and the second
elements 110, 112 are secured to the distal ends 20, 60 of the
respective shafts 16, 56. Alternatively, the first and the second
elements 110, 112 can be secured to the cryo balloons 22, 62,
respectively. Furthermore, instead of the first and the second
elements 110, 112, in other embodiments, the first and the second
ablation devices 12, 52 can include other systems or devices known
in the art for determining a relative position or distance between
portions of the respective ablation devices 12, 52.
[0037] In other embodiments, instead of, or in addition to, having
the navigation assisting elements 110, 112, the first and the
second ablation devices 12, 52 can each include one or more
sensor(s) for sensing a characteristic of target tissue being
ablated, a temperature of the cryo balloon, a temperature of the
coolant within the lumen of the cryo balloon, and/or a
characteristic of an environment in which the tissue is being
ablated. FIG. 3 shows an ablation device 200 in accordance with
other embodiments of the invention. The ablation device 200 can be
used in substitute of either of the ablation devices 12, 52 of FIG.
1. The ablation device 200 includes an array 202 of sensors 204
secured to a cryo balloon 208. The sensors 204 can be, for example,
temperature sensors for sensing temperature of tissue being
ablated, temperature of the cryo balloon 208, and/or temperature of
coolant within the cryo balloon 208. Alternatively, the sensors 204
can be impedance sensors for sensing impedance of tissue being
ablated. In other embodiments, the sensors 204 can be other types
of sensors for sensing electrical activity of cardiac tissue. In
the illustrated embodiments, the array 202 of sensors 204 are
secured to an exterior surface of the cryo balloon 208.
Alternatively, the sensors 204 can be disposed within a wall of the
cryo balloon 208, or be secured to an interior surface of the cryo
balloon 208. Also, in other embodiments, the sensors 204 can be
secured to the shaft 210. In the illustrated embodiments, the array
202 includes a plurality of splines 206 to each of which, three
sensors 204 are secured. In other embodiments, each spline 206 can
carry other number of sensors 204. Also, in other embodiments, the
array 202 of sensors 204 can be arranged in a staggered
configuration (FIG. 4), which allows the sensors 204 to be more
uniformly spaced. Although a plurality of sensors 204 are shown, in
alternative embodiments, the ablation device 200 can include a
single sensor 204. In some embodiments, the sensor 204 can be
slidable relative to the shaft 210. For example, the sensor 204 can
be slidably coupled to the shaft 210. Alternatively, the sensors
204 can be mounted on an entirely different member (not shown),
such as another catheter, that is positionable relative to the
shaft 210.
[0038] In the illustrated embodiments, the sensors 204 are
electrically coupled to a controller (not shown), which is
configured to control a temperature of the coolant being delivered
to the cryo balloon 208 in response to signals received from the
sensors 204. For example, if a sensor 204 senses a temperature
indicating that the temperature of the delivered coolant is above a
prescribed threshold, the controller then lowers the temperature of
the coolant at the source 80 until the temperature of the delivered
coolant is within the prescribed threshold. In other embodiments,
the controller can be configured to control a flow rate of the
coolant being delivered by the source 80 based on signals received
from the sensors 204.
[0039] Although the first and the second ablation devices 12, 52
have been described as each having a single cryo balloon, in
alternative embodiments, either or both of the ablation devices 12,
52 can each have more than one cryo balloon. FIG. 5 shows an
ablation device 300 in accordance with other embodiments of the
invention. The ablation device 300 can be used in substitute of
either of the ablation devices 12, 52 of FIG. 1. The ablation
device 300 has three cryo balloons 302, 304, 306 secured to distal
ends 310, 312, 314 of respective shafts 320, 322, 324. The ablation
device 300 further includes a cannula 330 having a distal end 332,
a proximal end 334, and a lumen 336 extending between the distal
and the proximal ends 332, 334. During use, the cryo balloons 302,
304, 306 are pushed out of the distal end 332 of the cannula 330
and are inflated by coolant. The balloons 302, 304, 306 are then
placed against target tissue to create a lesion 340 at the target
tissue by cryolysis (FIG. 6A). During the ablation procedure, the
shafts 320, 322, 324 can be sequentially positioned to place the
respective balloons 302, 304, 306 at different target tissue. For
example, after the lesion 340 has been created by the balloons 302,
304, 306, the third balloon 306 is then placed adjacent the first
balloon 302 to create another lesion 342. While the third balloon
306 is used to create the lesion 342, the first and the second
balloons 302, 304 remain in their initial positions to further
ablate the target tissue and to increase the size of the first
lesion 340. In a similar fashion, the second balloon 304 can next
be placed adjacent the third balloon 306 to create another lesion
344 (FIG. 6B). In some embodiments, the shafts 320, 322, 324 can be
coupled to an inner tube (not shown) that is disposed within the
lumen 336 of the cannula 330. In such cases, the inner tube can be
rotated coaxially within the cannula 330 to sequentially place the
balloons 302, 304, 306 against different target tissue. As should
be understood by those skilled in the art, use of a plurality of
balloons is advantageous because it allows target tissue be cooled
synergistically.
[0040] Referring now to FIGS. 7A and 7B, the operation of the
tissue ablation system 10 will now be described with reference to
cardiac ablation therapy, and more specifically, to creating a
lesion at a left atrial isthmus of a heart. However, it should be
understood by those skilled in the art that the tissue ablation
system 10 can also be used to treat tissue at other locations at
the heart, such as an annulus of a mitral valve connecting a left
atrium and a left ventricle, or an annulus of a tricuspid valve
connecting the an atrium and a right ventricle of the heart. In
other embodiments, the tissue ablation system 10 can also be used
to treat tissue at other locations within a body.
[0041] When using the system 10 to create a lesion at the left
atrial isthmus, the first cannula 30 is inserted through the right
atrium via jugular or femoral vein access to the vena cava, and is
steered into the coronary sinus (CS). The second cannula 70 is also
inserted through a main vein, and is steered into a right atrium
(RA) of a heart. The cannulas 30, 70 can be steered by using a
guidewire in a conventional manner, or by applying tension to
steering wire(s) (if the steering wire(s) is provided). After the
distal end 72 of the cannula 70 has reached the right atrium, a
needle can be inserted into the lumen 76 of the cannula 70 and
exits from the distal end 72 to puncture an atrial septum (AS) that
separates the right atrium and left atrium (LA). Alternatively, the
cannula 70 can be advanced through a guiding sheath placed
transeptally into the LA. The distal end 72 of the cannula 70 is
then advanced through the atrial septum, and into the left atrium.
At the left atrium, the distal end 72 of the cannula 70 is steered
to adjacent a treatment site (TS) (FIG. 7A). If the cannula 30, 70
are not steerable, separate cannulas that are steerable, or have a
pre-bent configuration, can be used to access the coronary sinus
and the left atrium. In such cases, after the separate cannulas
have reached the coronary sinus and the left atrium, the cannulas
30, 70 are then inserted into the separate cannulas and are
advanced distally until the distal ends 32, 72 exit from the
separate cannulas at the coronary sinus and the left atrium,
respectively.
[0042] Next, the first and the second cryo balloons 22, 62, in
their collapsed configuration, are inserted into the lumens 36, 76
of the respective cannulas 30, 70, and are advanced distally within
the respective lumens 36, 76 until they reach the distal ends 32,
72 of the cannulas 30, 70. Alternatively, the cryo balloons 22, 62
can be housed within the lumens 36, 76 of the respective cannulas
30, 70 while the cannulas 30, 70 are steered to the treatment site.
The cannulas 30, 70 are then retracted relative to the cryo
balloons 22, 62 (or the cryo balloons 22, 62 are advanced distally
relative to the cannulas 30, 70), thereby exposing the cryo
balloons 22, 62.
[0043] Next, the cryo balloons 22, 62 are positioned relative to
each other such that they are substantially next to each other and
are on opposite sides of target tissue. For example, the cryo
balloons 22, 62 can be positioned by operating the proximal ends
18, 58 of the respective shafts 16, 56. The cryo balloons 22, 62
can also be steered by using guidewires that are disposed within
the respective lumens 21,61 of the shafts 16, 56 in a conventional
manner. If the first and the second ablation devices, 12, 52
include steering wires, tension can be applied to the steering
wires to steer the cryo balloons 22, 62, and place the cryo
balloons 22, 62 at desired locations. The navigation assisting
elements 110, 112 can be used to assist placement of the cryo
balloons 22, 62 such that the cryo balloons 22, 62 are
substantially next to, or at least proximate, each other on
opposite sides of the target tissue. Also, mapping catheter 200 or
similar may be used to verify placement.
[0044] Next, inflation fluid is delivered under positive pressure
by the coolant source 80 to urge the cryo balloons 22, 62 to expand
(FIG. 7B). After the first cryo balloon 22 has been expanded, the
first cryo balloon 22 substantially occludes the coronary sinus,
thereby preventing or substantially reducing flow of blood through
the coronary sinus. Such technique is advantageous because it
limits the amount of blood that carries heat from passing through
target tissue, thereby allowing more cooling energy be delivered to
the target tissue. As shown in FIG. 7B, after the cryo balloons 22,
62 have been expanded, the first cryo balloon 22 is in contact with
a first surface 400 of target tissue at the left atrial isthmus,
and the second cryo balloon 62 is in contact with a second surface
402 that is on an opposite side of the target tissue. If the cryo
balloons 22, 62 each includes the sensor(s) 204, the sensor(s) 204
can be used to sense a temperature or an electrical activity to
determine whether the cryo balloons 22, 62 are in contact with
target tissue to be ablated. The cryo balloons 22, 62 can be
further positioned until they are in contact with target tissue to
be ablated.
[0045] In the illustrated embodiments, the inflation fluid is a low
freezing point liquid such as an ethanol mixture, or a liquified
gas such as N.sub.2O or CO.sub.2. The coolant is one which will
provide the appropriate heat transfer characteristics consistent
with the goals of treatment. Liquid N.sub.2O can be used as a
general purpose coolant, and is particularly useful when freezing
of cells is desired. When liquid N.sub.2O is used, it can be
transported to the cryo balloons 22, 62 in the liquid phase where
it evaporates at the port 132 and exits into the port 142 as a gas.
Freon, and other types of gas can also be used as coolants. Other
coolants that could be used include cold alcohol/saline solution,
Fluisol (a freon based blood substitute), or a mixture of saline
solution and ethanol. One skilled in the art would appreciate that
other coolants could be used in a similar manner to achieve one or
more of the treatment goals. In some embodiments, regulated back
pressure may be maintained along the path followed by the coolant
in order to prevent freezing of coolant (i.e., dry ice formation)
within the respective shafts 16, 56.
[0046] After the cryo balloons 22, 62 have been inflated and
desirably positioned, the cryo balloons 22, 62 may then be used to
cool target tissue to create a cold-induced lesion at the target
site. Particularly, the coolant cools the cryo balloons 22, 62,
which in turn, cool the target tissue at the left atrial isthmus
that is between the cryo balloons 22, 62. In the illustrated
embodiments, the target tissue is cooled to a temperature that is
approximately between -20.degree. C. to -100.degree. C., and more
preferably, between -40.degree. C. to -80.degree. C., such that at
least part of the target tissue is ablated by cryolysis. As shown
in the illustrated embodiments, by using two cryo balloons that are
placed on opposite sides of target tissue to cool the target
tissue, sufficient cooling can be delivered to create a transmural
(i.e., a through thickness) lesion at the target tissue. It is
believed that, by using two cryo balloons (instead of one),
synergistic cooling can be delivered to the target tissue, thereby
improving the lesion creation process.
[0047] In some embodiments, if the second ablation device 52 (or
the first ablation device 12) includes the sensor(s) 204, the
sensor(s) 204 can be used to sense a temperature or an electrical
characteristic of the tissue being ablated during the ablation
procedure. The sensor(s) 204 then transmit a signal representative
of the sensed temperature or electrical characteristic to a
controller (not shown) that is coupled to the source 80 of coolant.
In response to the signal, the controller regulates the temperature
and/or the flow rate of the coolant that is being delivered to the
second cryo balloon 62 (or the first cryo balloon 22). In other
embodiments, if the cryo balloons 22, 62 each includes the
sensor(s) 204, the controller can independently control the
temperatures and/or the flow rates of the coolants that are being
delivered to the respective cryo balloons 22, 62.
[0048] In many cases, a single ablation may be sufficient to create
a desired lesion. However, if it is desired to perform further
ablation to increase the lesion size or to create lesions at
different site(s) within the treatment region or elsewhere, the
cryo balloons 22, 62 may be placed at different target site(s), and
the same steps discussed previously may be repeated. When a desired
lesion at treatment region has been created, the cryo balloons 22,
62 are deflated and retracted into the respective shaft lumens 36,
76, and the ablation devices 12, 52 are removed from the treatment
region.
[0049] The system 10 and method described previously can be also
used to create lesions at other locations of the heart. For
example, the system 10 and similar method can be used to create
lesions inside the left atrium between the pulmonary veins and the
mitral valve annulus. Tissue nearby these anatomic structures are
recognized to develop arrhythmia substrates causing atrial
fibrillation. Lesions in these tissue regions block reentry paths
or destroy active pacemaker sites, and thereby prevent the
arrhythmia from occurring. FIG. 8 shows (from outside the heart H)
the location of major anatomic landmarks for lesion formation in
the left atrium. The landmarks include the right inferior pulmonary
vein (RIPV), the right superior pulmonary vein (RSPV), the left
superior pulmonary vein (LSPV), the left inferior pulmonary vein
(LIPV); and the mitral valve annulus (MVA). FIGS. 9A and 9B show
examples of lesion patterns formed inside the left atrium based
upon these landmarks.
[0050] In FIG. 9, the lesion pattern comprises a first leg L1
between the right inferior pulmonary vein (RIPV) and the right
superior pulmonary vein (RSPV); a second leg L2 between the RSPV
and the left superior pulmonary vein (LSPV); a third leg L3 between
the left superior pulmonary vein (LSPV) and the left inferior
pulmonary vein (LIPV); and a fourth leg L4 leading between the LIPV
and the mitral valve annulus (MVA). The first, second, and third
legs L1-L3 can be created by placing the first cryo balloon 22 at
the left atrium (LA), and the second cryo balloon 62 inside the
left ventrical (LV), the right ventrical (RV), or the coronary
sinus (CS). The fourth leg L4 can be created by placing the first
cryo balloon 22 at the LA, and the second cryo balloon 62 inside
the CS. In alternative methods, the positions of the first and the
second cryo balloons 22, 62 described previously may be
exchanged.
[0051] FIG. 9B shows a criss-crossing lesion pattern comprising a
first leg L1 extending between the RSPV and LIPV; a second leg L2
extending between the LSPV and RIPV; and a third leg L3 extending
from the LIPV to the MVA. The first and second legs L1, L2 can be
created by placing the first cryo balloon 22 at the LA, and the
second cryo balloon 62 inside the LV, RV, or the CS. The third leg
L3 can be created by placing the first cryo balloon 22 at the LA,
and the second cryo balloon 62 inside the CS. In alternative
embodiments, the positions of the first and the second cryo
balloons 22, 62 described previously may be exchanged.
[0052] The system 10 described previously can also be used to
create lesions inside the right atrium. FIG. 8 shows (from outside
the heart H) the location of the major anatomic landmarks for
lesion formation in the right atrium. These landmarks include the
superior vena cava (SVC), the tricuspid valve annulus (TVA), the
inferior vena cava (IVC), and the coronary sinus (CS). Tissue
nearby these anatomic structures have been identified as developing
arrhythmia substrates causing atrial fibrillation. Lesions in these
tissue regions block reentry paths or destroy active pacemaker
sites and thereby prevent the arrhythmia from occurring.
[0053] FIGS. 10A to 10C show representative lesion patterns formed
inside the right atrium based upon these landmarks. FIG. 10A shows
a representative lesion pattern L that extends between the superior
vena cava (SVC) and the tricuspid valve annulus (TVA). The lesion L
can be created by placing the first cryo balloon 22 at the LA, and
the second cryo balloon 62 inside the LV or the RV. In an
alternative embodiment, the positions of the first and the second
cryo balloons 22, 62 may be exchanged.
[0054] FIG. 10B shows a representative lesion pattern that extends
between the interior vena cava (IVC) and the TVA. The lesion L can
be created by placing the first cryo balloon 22 at the LA, and the
second cryo balloon 62 inside the LV or the RV. In an alternative
embodiment, the positions of the first and the second cryo balloons
22, 62 may be exchanged.
[0055] FIG. 10C shows a representative lesion pattern L that
extends between the coronary sinus (CS) and the tricuspid valve
annulus (TVA). The lesion L can be created by placing the first
cryo balloon 22 at the right atrium (RA), and the second cryo
balloon 62 inside the LV, the RV, or the CS. In an alternative
embodiment, the positions of the first and the second cryo balloons
22, 62 may be exchanged.
[0056] Although several examples of lesions that can be created
using the above-described system have been discussed, the above
described system and method can also be used to create lesions at
other locations of the heart. For example, in one embodiment, one
of the first and the second cryo balloons 22, 62 can be placed at
the atrium at the base of a heart, while the other of the first and
the second cryo balloons 22, 62 is placed at the LV. Such placement
of the first and the second cryo balloons 22, 62 allows a lesion to
be created at the intersection of the atria and the ventricle. In
another embodiment, one of the cryo balloons 22, 62 can be placed
at the RV next to the septum, while the other of the cryo balloons
22, 62 is placed at the LV. Such placement of the cryo balloons 22,
62 allows a lesion to be created at the ventricular septum. In
addition, although the above described system and method have been
described in the context of cardiac ablation therapy, e.g., for
treating arrhythmias, such as ventricular tachycardia (VT),
post-myocardial infraction, atrial fibrillation, supra-VT, flutter,
and other heart conditions, the system 10 may also be used in many
different environments and/or applications. For example, the system
10 may also be used to create lesions, such as transmural lesions,
at different locations within the body.
[0057] Although particular embodiments of the present invention
have been shown and described, it should be understood that the
above discussion is not intended to limit the present invention to
these embodiments. It will be obvious to those skilled in the art
that various changes and modifications may be made without
departing from the spirit and scope of the present invention. For
example, in alternative embodiments, instead of using cryo
balloons, other cooling elements, such as cooling tubes, can be
used to deliver cooling energy to ablate target tissue. In
addition, an illustrated embodiment needs not have all the aspects
or advantages of the invention shown. An aspect or an advantage
described in conjunction with a particular embodiment of the
present invention is not necessarily limited to that embodiment and
can be practiced in any other embodiments of the present invention
even if not so illustrated. Thus, the present invention is intended
to cover alternatives, modifications, and equivalents that may fall
within the spirit and scope of the present invention as defined by
the claims.
* * * * *