U.S. patent application number 09/751472 was filed with the patent office on 2002-07-04 for tissue ablation apparatus with a sliding ablation instrument and method.
This patent application is currently assigned to AFx, Inc.. Invention is credited to Berube, Dany, Mody, Dinesh, Norris, Nancy.
Application Number | 20020087151 09/751472 |
Document ID | / |
Family ID | 25022126 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020087151 |
Kind Code |
A1 |
Mody, Dinesh ; et
al. |
July 4, 2002 |
Tissue ablation apparatus with a sliding ablation instrument and
method
Abstract
A system and method for ablating a selected portion of a contact
surface of biological tissue is provided. The system includes an
elongated ablation sheath having a preformed shape adapted to
substantially conform a predetermined surface thereof with the
contact surface of the tissue. The ablation sheath defines an
ablation lumen sized to slideably receive an elongated ablative
device longitudinally therethrough. The ablative device includes a
flexible ablation element selectively generating an ablative field
sufficiently strong to cause tissue ablation. Advancement of the
ablation element slideably through the ablation lumen of the
ablation sheath selectively places the ablation element along the
ablation path for guide ablation on the contact surface when the
predetermined surface is in strategic contact therewith. The
ablation lumen and the ablative device cooperate to position the
ablation element proximate to the ablation sheath predetermined
surface for selective ablation of the selected portion within the
ablative field.
Inventors: |
Mody, Dinesh; (Pleasanton,
CA) ; Berube, Dany; (Fremont, CA) ; Norris,
Nancy; (Fremont, CA) |
Correspondence
Address: |
AFX INC.
47929 FREMONT BLVD
FREMONT
CA
94538
US
|
Assignee: |
AFx, Inc.
|
Family ID: |
25022126 |
Appl. No.: |
09/751472 |
Filed: |
December 29, 2000 |
Current U.S.
Class: |
606/15 ; 606/33;
606/41 |
Current CPC
Class: |
A61B 18/1492 20130101;
A61B 2017/00243 20130101; A61B 2018/00839 20130101; A61B 2018/00375
20130101; A61B 18/18 20130101; A61B 2018/1407 20130101; A61B 18/02
20130101; A61B 18/1815 20130101; A61B 2018/1497 20130101; A61B
2018/0212 20130101 |
Class at
Publication: |
606/15 ; 606/33;
606/41 |
International
Class: |
A61B 018/18; A61B
018/24; A61B 018/14 |
Claims
In the claims:
1. A method of ablating tissue within a body of a patient
comprising: providing an elongated flexible tubular member having
at least one lumen and a distal end portion; providing an ablative
device which is configured to be longitudinally received within
said at least one lumen of said flexible tubular member, said
ablative device having an energy delivery portion which is coupled
to a source of ablative energy; introducing said flexible tubular
member into the patient's body and positioning the distal end
portion of the tubular member adjacent to or in contact with a
tissue region to be ablated; transluminally positioning the
ablative device through the at least one lumen of the flexible
tubular member until the energy delivery portion is located at
least partially within said distal end portion; and delivering
ablative energy to said energy delivery portion to ablate said
tissue region.
2. The method of claim 1 wherein the distal end portion is
pre-shaped.
3. The method of claim 1 wherein the distal end portion is
malleable.
4. The method of claim 1 wherein said introducing said flexible
tubular member into the patient's body comprises introducing the
flexible tubular member through an opening in the body of the
patient.
5. The method of claim 4 wherein said opening in the body is
located in the chest of the patient.
6. The method of claim 5 wherein said flexible tubular member is
inserted through a partial or median sternotomy opening in the
chest.
7. The method of claim 5 wherein said flexible tubular member is
inserted through a thorascopic opening in the chest.
8. The method of claim 5 wherein said flexible tubular member is
inserted through a percutaneous portal access opening in the
chest.
9. The method of claim 1 wherein said tissue region to be ablated
is a tissue region located within or on an organ or vessel selected
from the group consisting of a heart, a stomach, a liver, a
pancreas, a kidney, an esophagus, an intestine, a uterus, a spleen,
a prostate, or a brain.
10. The method of claim 4 further comprising positioning the distal
end portion of the flexible tubular member adjacent to or in
contact with an epicardium of the heart of the patient.
11. The method of claim 10 wherein the heart remains beating during
said positioning of the distal end portion.
12. The method of claim 10 further comprising: positioning the
distal end portion of the flexible tubular member adjacent to or in
contact with at least a portion of the transverse sinus preparatory
to treating atrial fibrillation.
13. The method of claim 10 wherein said distal end portion is
positioned adjacent to or in contact with at least a portion of the
oblique sinus preparatory to treating atrial fibrillation.
14. The method of claim 10 wherein said distal end portion is
positioned adjacent to or in contact with a posterior wall of a
left atrium proximate to a junction between a pulmonary vein and
the left atrium of the heart.
15. The method of claim 10 wherein said distal end portion is
positioned substantially adjacent to a pulmonary vein on an
epicardial surface of the heart.
16. The method of claim 15 further comprising repeating said
positioning the distal end portion and said delivering ablative
energy two or more times to create a substantially annular ablation
around one or more pulmonary veins of the heart of the patient.
17. The method of claim 4 further comprising forming a penetration
through a muscular wall of the heart into an interior chamber
thereof and positioning the distal end portion of the flexible
tubular member through the penetration.
18. The method of claim 17 further comprising positioning the
distal end portion of the elongated tubular member adjacent to or
in contact with a tissue surface of an interior wall of an interior
chamber of the heart.
19. The method of claim 18 further comprising positioning the
distal end portion of the elongated tubular member adjacent to or
in contact with a tissue surface of an interior wall of a hollow
organ.
20. The method of claim 18 wherein the interior chamber is selected
from a right atrium or a left atrium.
21. The method of claim 20 wherein the distal end portion is
pre-shaped to extend at an angle of from between about 0 and 90
degrees relative to a longitudinal axis of the tubular member.
22. The method of claim 20 wherein the distal end portion is
annular shaped.
23. The method of claim 1 wherein said energy delivery portion is
flexible.
24. The method of claim 1 wherein said energy delivery portion is
unidirectional.
25. The method of claim 1 wherein said energy delivery portion
comprises a microwave ablation element.
26. The method of claim 25 wherein said microwave ablation element
is flexible.
27. The method of claim 25 wherein said microwave ablation element
is directional
28. The method of claim 1 wherein said energy delivery portion
comprises a radiofrequency ablation element.
29. The method of claim 28 wherein said radiofrequency ablation
element is flexible.
30. The method of claim 28 wherein said radiofrequency ablation
element is directional.
31. The method of claim 1 wherein said energy delivery portion
comprises an ultrasound ablation element.
32. The method of claim 31 wherein said ultrasound ablation element
is flexible.
33. The method of claim 31 wherein said ultrasound ablation element
is directional.
34. The method of claim 1 wherein said energy delivery portion
comprises a laser ablation element.
35. The method of claim 34 wherein said laser ablation element is
flexible.
36. The method of claim 34 wherein said laser ablation element is
directional.
37. The method of claim 1 wherein said energy delivery portion
comprises a fluid delivery element.
38. The method of claim 37 wherein said fluid delivery element is
flexible.
39. The method of claim 37 wherein said fluid delivery element is
directional.
40. The method of claim 1 wherein said energy delivery portion
comprises a cryogenic ablation element.
41. The method of claim 40 wherein said cryogenic ablation element
is flexible.
42. The method of claim 40 wherein said cryogenic ablation element
is directional.
43. The method of claim 1 further comprising repositioning the
energy delivery portion of the ablative device within the distal
end portion of the flexible tubular member at least once to form a
plurality of strategically positioned lesions along said tissue
region.
44. The method of claim 43 wherein at least a portion of respective
ones of said plurality of lesions overlap one another to form a
continuous lesion.
45. The method of claim 44 wherein said plurality of lesions are
formed in a substantially rectilinear pattern.
46. The method of claim 44 wherein said plurality of lesions are
formed in a substantially curvilinear pattern.
47. The method of claim 44 wherein said plurality of lesions are
formed in a substantially annular pattern.
48. The method of claim 1 further comprising positioning the distal
end portion of the flexible tubular member adjacent to or in
contact with a tissue region within an interior chamber of the
heart of a patient.
49. The method of claim 4 wherein said energy delivery portion
comprises a microwave ablation element.
50. The method of claim 49 wherein said microwave ablation element
is directional.
51. The method of claim 24 wherein said flexible tubular member
includes a key assembly to properly align the energy delivery
portion within the distal end portion of the flexible tubular
member such that the predetermined direction of the ablative energy
aligns with the tissue region to be ablated.
52. The method of claim 49 wherein said microwave ablation element
comprises a microwave antenna which is located within an antenna
assembly of the instrument for generating an electromagnetic field
sufficient to cause ablation of said tissue region, said antenna
assembly being adapted to direct the majority of the
electromagnetic field generally in a predetermined direction across
the distal end portion of the flexible tubular member.
53. The method of claim 52, wherein said antenna is configured to
generate said electromagnetic field substantially radially from a
longitudinal axis of the antenna, and said antenna assembly
includes an elongated shield extending partially around and
generally in the direction of the longitudinal axis of the antenna,
said shield defining an opening adapted to direct said majority of
the electromagnetic field generally in said predetermined
direction.
54. The method of claim 52 wherein said flexible tubular member
includes a key assembly to properly align the antenna assembly
within the distal end portion of the flexible tubular member such
that the predetermined direction of the electromagnetic field
aligns with the tissue region to be ablated.
55. The method of claim 4 wherein said energy delivery portion
comprises a laser ablation element.
56. The method of claim 55 wherein said laser ablation element is
directional.
57. The method of claim 55 wherein said laser ablation element
comprises a laser emitting element which is located within a laser
emitting assembly of the instrument for generating an
electromagnetic field sufficient to cause ablation of said tissue
region, said laser emitting assembly being adapted to direct the
majority of the electromagnetic field generally in a predetermined
direction across the distal end portion of the flexible tubular
member.
58. The method of claim 57, wherein said laser emitting element is
configured to generate said electromagnetic field substantially
radially from a longitudinal axis of the laser emitting element,
and said laser emitting assembly includes an elongated reflector
extending partially around and generally in the direction of the
longitudinal axis of the laser emitting element, said shield
defining an opening adapted to direct said majority of the
electromagnetic field generally in said predetermined
direction.
59. The method of claim 57 wherein said flexible tubular member
includes a key assembly to properly align the laser emitting
assembly within the distal end portion of the flexible tubular
member such that the predetermined direction of the electromagnetic
field aligns with the tissue region to be ablated.
60. The method of claim 4 wherein said energy delivery portion
comprises a ultrasound ablation element.
61. The method of claim 60 wherein said ultrasound ablation element
is directional.
62. The method of claim 60 wherein said ultrasound ablation element
comprises at least one ultrasound transducer which is located
within an ultrasound ablation assembly of the instrument for
generating an acoustic pressure wave sufficient to cause ablation
of said tissue region, said ultrasound ablation assembly being
adapted to direct the majority of the acoustic pressure wave
generally in a predetermined direction across the distal end
portion of the flexible tubular member.
63. The method of claim 62, wherein said ultrasound transducer is
configured to generate said acoustic pressure wave substantially
radially from a longitudinal axis of the ultrasound ablation
element, and said ultrasound ablation assembly includes an good
echogenic material extending partially around and generally in the
direction of the longitudinal axis of the ultrasound transducer,
said echogenic material defining an opening adapted to direct said
majority of the acoustic pressure wave generally in said
predetermined direction.
64. The method of claim 62 wherein said flexible tubular member
includes a key assembly to properly align the ultrasound ablation
assembly within the distal end portion of the flexible tubular
member such that the predetermined direction of the acoustic
pressure wave aligns with the tissue region to be ablated.
65. The method of claim 4 wherein said energy delivery portion
comprises a cryoablation element.
66. The method of claim 65 wherein said cryoablation element is
directional.
67. The method of claim 65 wherein said cryoablation element
comprises a decompression chamber which is located within a
cryoablation assembly of the instrument for generating a thermal
sink sufficient to cause ablation of said tissue region, said
cryoablation assembly being adapted to direct the majority of the
thermal conduction generally in a predetermined direction across
the distal end portion of the flexible tubular member.
68. The method of claim 67, wherein said decompression chamber is
configured to generate said thermal sink substantially radially
from a longitudinal axis of the cryoablation element, and said
cryoablation assembly includes an elongated thermal isolating
element extending partially around and generally in the direction
of the longitudinal axis of the cryoablation element, said thermal
isolating element defining an opening adapted to direct said
majority of the thermal conduction generally in said predetermined
direction.
69. The method of claim 67 wherein said flexible tubular member
includes a key assembly to properly align the cryoablation assembly
within the distal end portion of the flexible tubular member such
that the predetermined direction of the thermal conduction aligns
with the tissue region to be ablated.
70. The method of claim 1 wherein said flexible tubular member
comprises one or more electrodes coupled to said distal end portion
of the flexible tubular member, said method further comprising
sensing contact between the flexible tubular member and the tissue
region to be ablated using said one or more electrodes.
71. The method of claim 1 wherein said distal end portion of the
flexible tubular member includes at least first and second
sections, said first section having a loop configuration sized and
dimensioned to substantially encircle an opening to a pulmonary
vein, and said second section extending from said first section and
having a substantially longitudinal configuration.
72. The method of claim 71 wherein said second section includes at
least one electrode.
73. The method of claim 71 further comprising introducing the
distal end portion of the flexible tubular member into an atrium of
the heart such that the first section substantially encircles the
opening to the pulmonary vein and said second section extends a
short distance into the vein through the opening thereof.
74. The method of claim 73 further comprising sensing electrical
activity within the pulmonary vein with said at least one
electrode.
75. The method of claim 73 further comprising assessing the
electrical isolation of the pulmonary vein by using said at least
one electrode to attempt to pace the heart from within the
pulmonary vein.
76. The method of claim 73 further comprising assessing the
electrical isolation of the pulmonary vein by using said at least
one electrode to attempt to monitor the electrical activation from
the left atrium.
77. The method of claim 73 further comprising introducing at least
one contrast agent through said at least one lumen of the flexible
tubular member into the pulmonary vein.
78. The method of claim 1 wherein said distal end portion of the
flexible tubular member includes at least one temperature sensor,
said method further comprising measuring a temperature of the
tissue region using said temperature sensor.
79. The method of claim 1 wherein said ablative device includes at
least one temperature sensor, said method further comprising
measuring a temperature from within the flexible tubular member at
one or more locations within the tubular member using the
temperature sensor.
80. The method of claim 1 further comprising: providing a guide
sheath having a pre-shaped distal end portion; providing an
introducer sheath having a distal end; introducing the introducer
sheath into an interior chamber of the heart; telescopically
introducing the guide sheath through the introducer sheath such
that the pre-shaped distal end portion of the guide sheath extends
a short distance beyond the distal end of the introducer sheath in
a direction which is sufficient to direct the distal end portion of
the flexible tubular member towards the tissue region to be
ablated; and telescopically introducing the flexible tubular member
through the guide catheter to position the distal end portion
adjacent to or in contact with the tissue region to be ablated.
81. The method of claim 80 wherein the interior chamber is selected
from a right atrium or a left atrium.
82. The method of claim 80 wherein the interior chamber is selected
from a right ventricle or a left ventricle.
83. The method of claim 80 wherein said introducer sheath is sized
and dimensioned to extend into an interior chamber of the heart
from a peripheral access vessel in the arm or leg of the
patient.
84. The method of claim 80 wherein said introducer sheath is sized
and dimensioned to extend into an interior chamber of the heart of
the patient from a jugular vein of the patient.
85. The method of claim 80 wherein said introducer sheath is sized
and dimensioned to extend into an interior chamber of the heart of
the patient from a subclavian vein of the patient.
86. The method of claim 1 further comprising: providing a guide
sheath having a pre-shaped distal end portion; introducing the
guide sheath into an interior chamber of the heart such that the
distal end portion extends in a direction which is sufficient to
direct the distal end portion of the flexible tubular member
towards the tissue region to be ablated; and telescopically
introducing the flexible tubular member through the guide sheath to
position the distal end portion adjacent to or in contact with the
tissue region to be ablated.
87. The method of claim 86 wherein the interior chamber is selected
from a right atrium or a left atrium.
88. The method of claim 86 wherein the interior chamber is selected
from a right ventricle or a left ventricle.
89. The method of claim 86 wherein said guide catheter is sized and
dimensioned to extend into an interior chamber of the heart from a
peripheral access vessel in the arm or leg of the patient.
90. The method of claim 86 wherein said introducer sheath is sized
and dimensioned to extend into an interior chamber of the heart of
the patient from a jugular vein of the patient.
91. The method of claim 86 wherein said introducer sheath is sized
and dimensioned to extend into an interior chamber of the heart of
the patient from a subclavian vein of the patient.
92. The method of claim 1, wherein said tubular member includes a
window portion in a portion of a side wall of the tubular member
near the distal end portion of the tubular member, and said
positioning the tubular member comprises positioning the window
portion adjacent to or in contact with the tissue region to be
ablated.
93. The method of claim 92, wherein said transluminally positioning
the ablative device through the tubular member comprises
positioning at least a portion of the energy delivery portion of
the ablative device proximate to said window portion.
94. The method of claim 93, wherein said window portion is formed
of a material used to obtain a good energy transfer between the
ablative device and the tissue to ablate.
95. The method of claim 93, wherein said window portion is formed
of a material with a low water absorption coefficient.
96. The method of claim 94, wherein said ablative device comprises
at least one ultrasonic ablation element.
97. The method of claim 93, wherein said window portion comprises a
removed portion of the side wall of the tubular member and wherein
said ablative device comprises a ultrasonic ablation element.
98. The method of claim 93, wherein said window portion is formed
of a laser transparent material and said ablative device comprises
a laser emitting element.
99. The method of claim 93, wherein said window portion comprises a
removed portion of the side wall of the tubular member and wherein
said ablative device comprises a laser ablation element.
100. The method of claim 93, wherein said window portion is formed
of a electrically conductive material and said ablative device
comprises a RF ablation element.
101. The method of claim 93, wherein said window portion is formed
of a dielectric material having a low loss-tangent at microwave
frequencies and said ablative device comprises a microwave ablation
element.
102. The method of claim 93, wherein said window portion comprises
a removed portion of the side wall of the tubular member and
wherein said ablative device comprises a microwave ablation
element.
103. The method of claim 93, wherein said window portion comprises
a removed portion of the side wall of the tubular member and
wherein said ablative device comprises a microwave ablation
element.
104. The method of claim 93, wherein said window portion is formed
of a good thermal conductor material and said ablative device
comprises a cryoablation element.
105. The method of claim 93, wherein said window portion comprises
a removed portion of the side wall of the tubular member and
wherein said ablative device comprises a cryoablation element.
106. A method of ablating tissue comprising: positioning a
pre-shaped distal end portion of a guide catheter proximate to a
tissue region to be ablated of a body structure; transluminally
positioning an energy delivery portion of an ablative device
through said guide catheter until said energy delivery portion is
located within at least a portion of said distal end portion;
delivering sufficient energy to said energy delivery portion to
ablate said tissue region through said distal end portion of the
guide catheter.
107. A method of ablating tissue within an interior chamber of a
patent's heart comprising: providing a flexible tubular member
having a distal end portion which is shaped to substantially
conform the distal end portion to a tissue region within an atrial
chamber of the patient's heart; introducing the flexible tubular
member into an atrial chamber of the heart and positioning the
distal end portion adjacent to or in contact with the tissue
region; transluminally positioning an energy delivery portion of an
ablative device through said flexible tubular member until said
energy delivery portion is at least partially located within said
distal end portion; delivering ablative energy to said energy
delivery portion to ablate said tissue region.
108. A system for ablating tissue within a body of a patient
comprising: an elongated flexible tubular member having at least
one lumen and including a pre-shaped distal end portion which is
shaped to be positioned adjacent to or in contact with a selected
tissue region within the body of the patient; and an ablative
device which is configured to be slideably received longitudinally
within said at least one lumen and having an energy delivery
portion located near a distal end portion of said ablative device
which is adapted to be coupled to an ablative energy source.
109. The system of claim 108 wherein said energy delivery portion
and ablative energy source are working together to produce the
ablation of said selected tissue region.
110. The system of claim 108 wherein said flexible tubular member
includes at least one radio-opaque element.
111. The system of claim 110 wherein said radio-opaque element can
be used to assess the shape of the flexible tubular member during a
fluoroscopic procedure.
112. The system of claim 108 wherein said energy delivery portion
includes at least one radio-opaque element.
113. The system of claim 112 wherein said radio-opaque element is
strategically located to identify the extremities of said energy
delivery portion.
114. The system of claim 112 wherein said radio-opaque element is
strategically located to identify the ablation location.
115. The system of claim 116 further including an introducer which
is configured to longitudinally receive said flexible tubular
member.
116. The system of claim 115 wherein said introducer has a
pre-shaped distal end portion which is configured to be manipulated
to direct the flexible tubular member towards the selected tissue
region to be ablated following insertion of the distal end portion
of the introducer into an interior chamber of the heart.
117. The system of claim 108 wherein said distal end portion of the
flexible tubular member has a distal end which is closed.
118. The system of claim 108 wherein said energy delivery portion
is flexible.
119. The system of claim 108 wherein said energy delivery portion
is unidirectional.
120. The system of claim 108 wherein said energy delivery portion
comprises a microwave ablation element.
121. The system of claim 120 wherein said microwave ablation
element is flexible.
122. The system of claim 120 wherein said microwave ablation
element is directional
123. The system of claim 108 wherein said ablative device is a
laser ablation element.
124. The system of claim 123 wherein said laser ablation element is
flexible.
125. The system of claim 123 wherein said laser ablation element is
directional.
126. The system of claim 108 wherein said energy delivery portion
comprises a radiofrequency ablation element.
127. The system of claim 126 wherein said radiofrequency ablation
element is flexible.
128. The system of claim 126 wherein said radiofrequency ablation
element is directional.
129. The system of claim 108 wherein said energy delivery portion
comprises an ultrasound ablation element.
130. The system of claim 129 wherein said ultrasound ablation
element is flexible.
131. The system of claim 129 wherein said ultrasound ablation
element is directional.
132. The system of claim 108 wherein said energy delivery portion
comprises an cryoablation element.
133. The system of claim 132 wherein said cryoablation element is
flexible.
134. The system of claim 132 wherein said cryoablation element is
directional.
135. The system of claim 108 wherein said energy delivery portion
comprises an fluid delivery element.
136. The system of claim 135 wherein said fluid delivery element is
flexible.
137. The system of claim 135 wherein said fluid delivery element is
directional.
138. The system of claim 108 wherein said distal end portion of the
flexible tubular member includes at least first and second
sections, said first section having a loop configuration sized and
dimensioned to substantially encircle an opening to a pulmonary
vein, said second section extending from said first section and
having a substantially longitudinal configuration.
139. The system of claim 138 wherein said second section includes
at least one electrode.
140. The system of claim 108 wherein said distal end portion of the
flexible tubular member is shaped to substantially encircle two or
more pulmonary veins on an epicardial surface of the heart of the
patient.
141. The system of claim 108 wherein said ablative device comprises
a microwave ablation element.
142. The system of claim 108 wherein said flexible tubular member
is sized and dimensioned to be transluminally positioned in an
atrial chamber of the heart from a peripheral access vessel.
143. The system of claim 142 wherein said peripheral access vessel
is a femoral artery in a leg of the patient.
144. The system of claim 142 wherein said peripheral access vessel
is a femoral vein in a leg of the patient.
145. The system of claim 142 wherein said peripheral access vessel
is a radial artery or vein in an arm of the patient.
146. The system of claim 142 wherein said peripheral access vessel
is a jugular artery or vein in a neck region of the patient.
147. The system of claim 108 wherein said flexible tubular member
further comprises at least one electrode.
148. The system of claim 108 wherein said ablative device comprises
at least one electrode.
149. The system of claim 108 wherein said distal end portion of the
flexible tubular member includes at least one temperature sensor
for measuring a temperature of the tissue region during ablation
thereof.
150. The system of claim 108 wherein said ablative device includes
at least one temperature sensor which is adapted to measure a
temperature from within the flexible tubular member at one or more
locations along a length of the tubular member.
151. The system of claim 108 wherein said distal end portion of the
flexible tubular member includes at least first and second
sections, said first section having a loop configuration sized and
dimensioned to substantially encircle an opening to a pulmonary
vein, said second section extending distally from said first
section and having a substantially longitudinal configuration.
152. The system of claim 151 wherein said second section includes
at least one electrode
153. The system of claim 108 wherein said flexible tubular member
includes a key assembly to properly align the energy delivery
portion within the distal end portion of the flexible tubular
member such that the predetermined direction of the ablative energy
aligns with the tissue region to be ablated.
154. The system of claim 141 wherein said microwave ablation
element comprises a microwave antenna which is located within an
antenna assembly of the instrument for generating an
electromagnetic field sufficient to cause ablation of said tissue
region, said antenna assembly being adapted to direct the majority
of the electromagnetic field generally in a predetermined direction
across the distal end portion of the flexible tubular member.
155. The system of claim 154 wherein said antenna is configured to
generate said electromagnetic field substantially radially from a
longitudinal axis of the antenna, and said antenna assembly
includes an elongated shield extending partially around and
generally in the direction of the longitudinal axis of the antenna,
said shield defining an opening adapted to direct said majority of
the electromagnetic field generally in said predetermined
direction.
156. The system of claim 154 wherein said flexible tubular member
includes a key assembly to properly align the antenna assembly
within the distal end portion of the flexible tubular member such
that the predetermined direction of the electromagnetic field
aligns with the tissue region to be ablated.
157. The system of claim 123 wherein said laser ablation element
comprises a laser emitting element which is located within a laser
emitting assembly of the instrument for generating an
electromagnetic field sufficient to cause ablation of said tissue
region, said laser emitting assembly being adapted to direct the
majority of the electromagnetic field generally in a predetermined
direction across the distal end portion of the flexible tubular
member.
158. The system of claim 157, wherein said laser emitting element
is configured to generate said electromagnetic field substantially
radially from a longitudinal axis of the laser emitting element,
and said laser emitting assembly includes an elongated reflector
extending partially around and generally in the direction of the
longitudinal axis of the laser emitting element, said shield
defining an opening adapted to direct said majority of the
electromagnetic field generally in said predetermined
direction.
159. The system of claim 157 wherein said flexible tubular member
includes a key assembly to properly align the laser emitting
assembly within the distal end portion of the flexible tubular
member such that the predetermined direction of the electromagnetic
field aligns with the tissue region to be ablated.
160. The system of claim 132 wherein said ultrasound ablation
element comprises at least one ultrasound transducer which is
located within an ultrasound ablation assembly of the instrument
for generating an acoustic pressure wave sufficient to cause
ablation of said tissue region, said ultrasound ablation assembly
being adapted to direct the majority of the acoustic pressure wave
generally in a predetermined direction across the distal end
portion of the flexible tubular member.
161. The system of claim 160, wherein said ultrasound transducer is
configured to generate said acoustic pressure wave substantially
radially from a longitudinal axis of the ultrasound ablation
element, and said ultrasound ablation assembly includes an good
echogenic material extending partially around and generally in the
direction of the longitudinal axis of the ultrasound transducer,
said echogenic material defining an opening adapted to direct said
majority of the acoustic pressure wave generally in said
predetermined direction.
162. The system of claim 160 wherein said flexible tubular member
includes a key assembly to properly align the ultrasound ablation
assembly within the distal end portion of the flexible tubular
member such that the predetermined direction of the acoustic
pressure wave aligns with the tissue region to be ablated.
163. The system of claim 132 wherein said cryoablation element
comprises a decompression chamber which is located within a
cryoablation assembly of the instrument for generating a thermal
sink sufficient to cause ablation of said tissue region, said
cryoablation assembly being adapted to direct the majority of the
thermal conduction generally in a predetermined direction across
the distal end portion of the flexible tubular member.
164. The system of claim 163, wherein said decompression chamber is
configured to generate said thermal sink substantially radially
from a longitudinal axis of the cryoablation element, and said
cryoablation assembly includes an elongated thermal isolating
element extending partially around and generally in the direction
of the longitudinal axis of the cryoablation element, said thermal
isolating element defining an opening adapted to direct said
majority of the thermal conduction generally in said predetermined
direction.
165. The system of claim 163, wherein said flexible tubular member
includes a key assembly to properly align the cryoablation assembly
within the distal end portion of the flexible tubular member such
that the predetermined direction of the majority of the thermal
conduction aligns with the tissue region to be ablated.
166. The system of claim 108 wherein said flexible tubular member
is substantially transparent to allow visualization of the ablative
device within said tubular member.
167. The system of claim 120 wherein said flexible tubular member
is made from a material which has a low loss tangent.
168. The system of claim 108 wherein said flexible tubular member
is made from a material which has a low water absorption
coefficient.
169. The system of claim 123 wherein said flexible tubular member
is made from a material which has a low scattering coefficient.
170. The system of claim 126 wherein said flexible tubular member
is made from a material which has a electrical conductivity.
171. The system of claim 129 wherein said flexible tubular member
is made from a material working to provide a good mechanical
impedance matching between the tissue and the ultrasound ablation
element.
172. The system of claim 108, wherein said tubular member further
includes a window portion in a portion of a side wall of the
tubular member which extends longitudinally along at least a
portion of the distal end portion of the tubular member.
173. The system of claim 172, wherein said energy delivery portion
of the ablative device is configured to be exposed through the
window portion of the tubular member for effecting ablation of
tissue proximate to the window portion.
174. The system of claim 172, wherein said window portion is formed
of a material used to obtain a good energy transfer between the
ablative device and the tissue to ablate.
175. The system of claim 172, wherein said window portion is formed
of a material with a low water absorption coefficient.
176. The system of claim 175, wherein said ablative device
comprises at least one ultrasonic ablation element.
177. The system of claim 172, wherein said window portion comprises
a removed portion of the side wall of the tubular member and
wherein said ablative device comprises a ultrasonic ablation
element.
178. The system of claim 172, wherein said window portion is formed
of a laser transparent material and said ablative device comprises
a laser emitting element.
179. The system of claim 172, wherein said window portion comprises
a removed portion of the side wall of the tubular member and
wherein said ablative device comprises a laser ablation
element.
180. The system of claim 172, wherein said window portion is formed
of a electrically conductive material and said ablative device
comprises a RF ablation element.
181. The system of claim 172, wherein said window portion is formed
of a dielectric material having a low loss-tangent at microwave
frequencies and said ablative device comprises a microwave ablation
element.
182. The system of claim 172, wherein said window portion comprises
a removed portion of the side wall of the tubular member and
wherein said ablative device comprises a microwave ablation
element.
183. The system of claim 172, wherein said window portion comprises
a removed portion of the side wall of the tubular member and
wherein said ablative device comprises a microwave ablation
element.
184. The system of claim 122, wherein said window portion is formed
of a good thermal conductor material and said ablative device
comprises a cryoablation element.
185. The system of claim 172, wherein said window portion comprises
a removed portion of the side wall of the tubular member and
wherein said ablative device comprises a cryoablation element.
186. A system for ablating tissue within a body of a patient
comprising: an elongated flexible tubular member having at least
one lumen and including a malleable distal end portion which is
shaped to be positioned adjacent to or in contact with a selected
tissue region within the body of the patient; and an ablative
device which is configured to be slideably received longitudinally
within said at least one lumen and having an energy delivery
portion located near a distal end portion of said ablative device
which is adapted to be coupled to an ablative energy source.
187. The system of claim 186 wherein said energy delivery portion
and ablative energy source are working together to produce the
ablation of said selected tissue region.
188. The system of claim 189 wherein said distal end portion of the
flexible tubular member has a distal end which is closed.
189. The system of claim 186 wherein said energy delivery portion
comprises a microwave ablation element.
190. The system of claim 189 wherein said microwave ablation
element is flexible.
191. The system of claim 189 wherein said microwave ablation
element is directional
192. The system of claim 186 wherein said ablative device is a
laser ablation element.
193. The system of claim 192 wherein said laser ablation element is
flexible.
194. The system of claim 192 wherein said laser ablation element is
directional.
195. The system of claim 186 wherein said energy delivery portion
comprises a radiofrequency ablation element.
196. The system of claim 195 wherein said radiofrequency ablation
element is flexible.
197. The system of claim 195 wherein said radiofrequency ablation
element is directional.
198. The system of claim 186 wherein said energy delivery portion
comprises an ultrasound ablation element.
199. The system of claim 198 wherein said ultrasound ablation
element is flexible.
200. The system of claim 198 wherein said ultrasound ablation
element is directional.
201. The system of claim 186 wherein said energy delivery portion
comprises an cryoablation element.
202. The system of claim 201 wherein said cryoablation element is
flexible.
203. The system of claim 201 wherein said cryoablation element is
directional.
204. The system of claim 86 wherein said energy delivery portion
comprises an fluid delivery element.
205. The system of claim 204 wherein said fluid delivery element is
flexible.
206. The system of claim 204 wherein said fluid delivery element is
directional.
207. A guide sheath comprising a proximal end portion, a distal end
portion, and at least one lumen extending between the proximal and
distal end portions, said at least one lumen being sized and
dimensioned to longitudinally slideably receive an ablative device
therethrough, said distal end portion having a preformed shape
which is moveable between a substantially linear configuration for
insertion into and through an introducer which is adapted to
deliver the guide sheath into a selected chamber within a heart of
a patient, and an operable configuration wherein said distal end
portion has a loop shape configuration which is sized and
dimensioned to substantially encircle an opening to a pulmonary
vein.
208. The guide sheath of claim 207 further including a second
section extending from said first section and having a
substantially longitudinal configuration.
209. The guide sheath of claim 208 wherein said distal end portion
has a distal end which is closed.
210. The guide sheath of claim 208 wherein said second section
includes at least one electrode.
211. The guide sheath of claim 207 wherein said guide sheath
further includes a lumen used to inject a contrast agent.
212. The guide sheath of claim 207 wherein said loop shape
configuration section includes at least one electrode.
213. The guide sheath of claim 208 wherein said second section is
configured to extend a short distance within the opening to the
pulmonary vein when said first section is located at or near the
tissue region extending about the periphery of the opening to the
pulmonary vein.
214. The guide sheath of claim 213 wherein said electrode is
configured to monitor electrical signals within the pulmonary
vein.
215. A guide sheath comprising a proximal end portion, a distal end
portion, and at least one lumen, the distal end portion having a
pre-shaped configuration including at least first and second
sections, said first section having a loop configuration sized and
dimensioned to substantially encircle an opening to a pulmonary,
said second section extending from said first section and having a
substantially linear configuration, said second section including
at least one electrode.
216. A guide sheath comprising a proximal end portion, a distal end
portion, and at least one lumen extending between the proximal and
distal end portions, said at least one lumen being sized and
dimensioned to longitudinally slideably receive an ablative device
therethrough, said distal end portion having a preformed shape
which is moveable between a substantially linear configuration for
insertion into and through an introducer which is adapted to
deliver the guide sheath into a selected chamber within a heart of
a patient, and an operable configuration wherein said distal end
portion has a curvilinear shape configuration which is sized and
dimensioned to substantially follow the wall of a interior cardiac
chamber.
217. The guide sheath of claim 216 wherein said interior cardiac
chamber is selected from a right or a left atrium.
218. The guide sheath of claim 216 wherein said interior cardiac
chamber is selected from a right or a left ventricle.
219. The guide sheath of claim 216 wherein said distal end portion
includes at least one electrode.
220. The guide sheath of claim 216 wherein said curvilinear shape
is configured to substantially follow the posterior wall of the
left atrium between two pulmonary veins.
221. The guide sheath of claim 216 wherein said curvilinear shape
is configured to substantially follow the posterior wall of the
left atrium between a pulmonary vein and the mitral valve.
222. The guide sheath of claim 216 wherein said curvilinear shape
is configured to substantially follow the posterior wall of the
left atrium between a pulmonary vein and the left atrial
appendage.
223. The guide sheath of claim 216 wherein said curvilinear shape
is configured to substantially follow the isthmus between the
inferior caval vein and the tricuspid valve.
224. The guide sheath of claim 216 wherein said curvilinear shape
is configured to substantially follow the lateral right free wall
between the superior and inferior caval veins.
225. A method of conducting a surgical ablation procedure on a
heart of a patient comprising: providing an ablation sheath
comprising a proximal end portion a distal end portion and at least
one lumen; providing an ablative device which is configured to be
longitudinally received within said at least one lumen of said
ablation sheath, said ablative device having an energy delivery
portion which is adapted to be coupled to a source of ablative
energy;. making at least one incision in a patient's chest to
access the heart; introducing the ablation sheath through said
incision and positioning the distal end portion of the sheath
adjacent to or in contact with a tissue surface of the heart;
advancing said ablative device through the ablation sheath such
that the energy delivery portion of the device is located at least
partially within said distal end portion of the sheath; and forming
at least one lesion along the tissue surface of the heart by
applying energy to said energy delivery portion to effect ablation
of tissue.
226. The method of claim 225 wherein said distal end portion is
pre-shaped.
227. The method of claim 225 wherein said distal end portion is
malleable.
228. The method of claim 225 wherein said distal end portion is
flexible.
229. The method of claim 225 further comprising forming at least
one penetration in a wall of the heart into an interior chamber
thereof and introducing the ablation sheath through the penetration
to perform an ablative procedure within the internal chamber of the
heart.
230. The method of claim 229 wherein the internal chamber is
selected from the right atrium or left atrium.
231. The method of claim 229 wherein the internal chamber is
selected from the right ventricle or left ventricle.
232. The method of claim 229 wherein said forming at least one
penetration in a wall of the heart is performed using a cutting
member on a distal end of the ablation sheath.
233. The method of claim 225 wherein the heart remains beating
during the ablation procedure.
234. The method of claim 225 further comprising arresting the
patient's heart prior to said forming at least one lesion.
235. The method of claim 225 wherein said incision is a median or
partial sternotomy incision.
236. The method of claim 225 wherein said incision is a minimal
thoracotomy.
237. The method of claim 225 wherein the size of said incision is
not substantially greater than about 12 cm.
238. The method of claim 225 wherein the formation of said at least
one lesion is visualized by a thoracoscope.
239. The method of claim 225 further comprising performing at least
one portion of a coronary artery bypass graft procedure prior to or
after said formation of at least one lesion.
240. The method of claim 225 further comprising repeating said
forming at least one lesion at least one or more times to form two
or more overlapping lesions on the heart.
241. The method of claim 225 wherein said distal end portion of the
sheath is positioned adjacent to or in contact with at least a
portion of the transverse sinus preparatory to treating atrial
fibrillation.
242. The method of claim 225 wherein said distal end portion of the
sheath is positioned adjacent to or in contact with at least a
portion of the oblique sinus preparatory to treating atrial
fibrillation.
243. The method of claim 225 wherein said distal end portion of the
sheath is positioned adjacent to or in contact with at least a
portion of the tissue connecting a pulmonary vein to the left
appendage.
244. The method of claim 225 wherein said positioning the distal
end portion of the sheath comprises puncturing at least one portion
of the pericardial reflexion.
245. The method of claim 244 wherein said portion of the
pericardial reflexion is located around a pulmonary vein.
246. The method of claim 240 wherein at least a portion of
respective ones of said plurality of lesions overlap one another to
form a continuous lesion.
247. The method of claim 246 wherein said plurality of lesions are
formed in a substantially rectilinear pattern.
248. The method of claim 246 wherein said plurality of lesions are
formed in a substantially curvilinear pattern.
249. The method of claim 246 wherein said plurality of lesions are
formed in a substantially annular pattern.
250. The method of claim 225 wherein said ablative device comprises
a microwave ablation element.
251. The method of claim 225 wherein said ablative device comprises
a radiofrequency ablation element.
252. The method of claim 225 wherein said ablative device comprises
an ultrasound element.
253. The method of claim 225 wherein said ablative device comprises
a laser emitting element.
254. The method of claim 225 wherein said ablative device comprises
a fluid delivery probe.
255. The method of claim 225 wherein said ablative device comprises
a cryogenic element.
256. A system for ablating tissue within a body of a patient
comprising: an elongated rail device adapted to be positioned
proximate and adjacent to a selected tissue region to be ablated
within the body of the patient; and an ablative device having a
receiving passage configured to slideably receive said rail device
longitudinally therethrough to slideably position the ablative
device substantially adjacent to or in contact with the selected
tissue region, said ablative device having an energy delivery
portion which is adapted to be coupled to an ablative energy
source.
257. The system of claim 256 wherein said ablative device and
ablative energy source are working together to produce the ablation
of said selected tissue region.
258. The system of claim 256 wherein said ablative energy source is
a microwave generator and said ablative device includes a microwave
ablation element.
259. The system of claim 256 wherein said ablative energy source is
a radiofrequency generator and said ablative device includes a
radiofrequency ablation element.
260. The system of claim 256 wherein said ablative energy source is
a ultrasound generator and said ablative device includes a
ultrasound ablation element.
261. The system of claim 256 wherein said ablative energy source is
a laser generator and said ablative device includes a laser
ablation element.
262. The system of claim 256 wherein said ablative energy source
includes a compressor and a compressible gas, and said ablative
device includes a cryoablation element.
263. The system of claim 256, wherein said rail device includes a
pre-shaped distal portion.
264. The system of claim 256, wherein said rail device includes a
malleable distal portion
265. The system of claim 256, wherein said ablative device is
flexible.
266. The system of claim 256, wherein said ablative device is
adapted to directionally emit the ablative energy from the energy
delivery portion.
267. The system of claim 266 further including: a key assembly
cooperating between the ablative device and the rail member to
properly align the directionally emitted ablative energy toward the
tissue region to be ablated.
268. The system of claim 267, wherein the rail device includes a
non-circular transverse cross-sectional dimension, and the
receiving passage of the ablative device includes a substantially
similarly shaped non-circular transverse cross-sectional dimension
to enable sliding of the ablative device in a manner continuously
aligning the directionally emitted ablative energy toward the
tissue region to be ablated as the ablative device advances along
the rail device.
269. The system of claim 268, wherein the transverse
cross-sectional dimensions of the rail device and the receiving
passage are rectangular-shaped.
270. The system of claim 268, wherein the transverse
cross-sectional dimensions of the rail device and the receiving
passage are oval-shaped.
271. The system of claim 267, wherein one of the rail device and an
interior wall, defining receiving passage of the ablative device,
includes a key notch, and the other of the interior wall and the
rail device defines a matching keyway to continuously align the
directionally emitted ablative energy toward the tissue region to
be ablated as the ablative device advances along the rail
device.
272. The system of claim 267 wherein said energy delivery portion
is provided by a microwave ablation element.
273. The system of claim 272 wherein said microwave ablation
element comprises a microwave antenna which is located within an
antenna assembly of the ablative device for generating an
electromagnetic field sufficient to cause ablation of said tissue
region, said antenna assembly being adapted to direct the majority
of the electromagnetic field generally in a predetermined direction
across the distal end portion of the flexible tubular member.
274. The system of claim 273 wherein said antenna is configured to
generate said electromagnetic field substantially radially from a
longitudinal axis of the antenna, and said antenna assembly
includes an elongated shield extending partially around and
generally in the direction of the longitudinal axis of the antenna,
said shield defining an opening adapted to direct said majority of
the electromagnetic field generally in said predetermined
direction.
275. A method of ablating tissue within a body of a patient
comprising: providing an elongated rail device having a distal
portion; providing an ablative device having a receiving passage
configured to slideably receive said rail device longitudinally
therethrough, said ablative device having an energy delivery
portion which is adapted to be coupled to an ablative energy
source; introducing said rail device into the patient's body and
positioning the distal portion thereof proximate and adjacent to a
selected tissue region to be ablated; slideably positioning the
ablative device along the rail until the energy delivery portion is
located substantially adjacent to or in contact with the selected
tissue region; and delivering ablative energy to said energy
delivery portion to ablate said tissue region.
276. The method of claim 275 wherein the distal end portion is
pre-shaped.
277. The method of claim 275 wherein the distal end portion is
malleable.
278. The method of claim 275 wherein said introducing said rail
device into the patient's body comprises introducing the rail
device through an opening in the body of the patient.
279. The method of claim 275 further comprising repositioning the
energy delivery portion of the ablative device along the distal end
portion of the rail device at least once to form a plurality of
strategically positioned lesions along said tissue region.
280. The method of claim 279 wherein at least a portion of
respective ones of said plurality of lesions overlap one another to
form a continuous lesion.
281. The method of claim 275, wherein said ablative device is
adapted to directionally emit the ablative energy from the energy
delivery portion; further including: aligning the directionally
emitted ablative energy toward the tissue region to be ablated
through a key assembly cooperating between the ablative device and
the rail member to properly.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates, generally, to ablation
instrument systems that use ablative energy to ablate internal
bodily tissues. More particularly, the present invention relates to
preformed guide apparatus which cooperate with energy delivery
arrangements to direct the ablative energy in selected directions
along the guide apparatus.
[0003] 2. Description of the Prior Art
[0004] It is well documented that atrial fibrillation, either alone
or as a consequence of other cardiac disease, continues to persist
as the most common cardiac arrhythmia. According to recent
estimates, more than two million people in the U.S. suffer from
this common arrhythmia, roughly 0.15% to 1.0% of the population.
Moreover, the prevalence of this cardiac disease increases with
age, affecting nearly 8% to 17% of those over 60 years of age.
[0005] Atrial arrhythmia may be treated using several methods.
Pharmacological treatment of atrial fibrillation, for example, is
initially the preferred approach, first to maintain normal sinus
rhythm, or secondly to decrease the ventricular response rate.
Other forms of treatment include drug therapies, electrical
cardioversion, and RF catheter ablation of selected areas
determined by mapping. In the more recent past, other surgical
procedures have been developed for atrial fibrillation, including
left atrial isolation, transvenous catheter or cryosurgical
ablation of His bundle, and the Corridor procedure, which have
effectively eliminated irregular ventricular rhythm. However, these
procedures have for the most part failed to restore normal cardiac
hemodynamics, or alleviate the patient's vulnerability to
thromboembolism because the atria are allowed to continue to
fibrillate. Accordingly, a more effective surgical treatment was
required to cure medically refractory atrial fibrillation of the
Heart.
[0006] On the basis of electrophysiologic mapping of the atria and
identification of macroreentrant circuits, a surgical approach was
developed which effectively creates an electrical maze in the
atrium (i.e., the MAZE procedure) and precludes the ability of the
atria to fibrillate. Briefly, in the procedure commonly referred to
as the MAZE III procedure, strategic atrial incisions are performed
to prevent atrial reentry circuits and allow sinus impulses to
activate the entire atrial myocardium, thereby preserving atrial
transport function postoperatively. Since atrial fibrillation is
characterized by the presence of multiple macroreentrant circuits
that are fleeting in nature and can occur anywhere in the atria, it
is prudent to interrupt all of the potential pathways for atrial
macroreentrant circuits. These circuits, incidentally, have been
identified by intraoperative mapping both experimentally and
clinically in patients.
[0007] Generally, this procedure includes the excision of both
atrial appendages, and the electrical isolation of the pulmonary
veins. Further, strategically placed atrial incisions not only
interrupt the conduction routes of the common reentrant circuits,
but they also direct the sinus impulse from the sinoatrial node to
the atrioventricular node along a specified route. In essence, the
entire atrial myocardium, with the exception of the atrial
appendages and the pulmonary veins, is electrically activated by
providing for multiple blind alleys off the main conduction route
between the sinoatrial node to the atrioventricular node.
[0008] Atrial transport function is thus preserved postoperatively
as generally set forth in the series of articles: Cox, Schuessler,
Boineau, Canavan, Cain, Lindsay, Stone, Smith, Corr, Change, and
D'Agostino, Jr., The Surgical Treatment Atrial Fibrillation (pts.
1-4), 101 THORAC CARDIOVASC SURG., 402-426, 569-592 (1991).
[0009] While this MAZE III procedure has proven effective in
ablating medically refractory atrial fibrillation and associated
detrimental sequelae, this operational procedure is traumatic to
the patient since this is an open-heart procedure and substantial
incisions are introduced into the interior chambers of the Heart.
Consequently, other techniques have been developed to interrupt
atrial fibrillation restore sinus rhythm. One such technique is
strategic ablation of the atrial tissues through ablation
catheters.
[0010] Most approved ablation catheter systems now utilize radio
frequency (RF) energy as the ablating energy source. Accordingly, a
variety of RF based catheters and power supplies are currently
available to electrophysiologists. However, radio frequency energy
has several limitations including the rapid dissipation of energy
in surface tissues resulting in shallow "burns" and failure to
access deeper arrhythmic tissues. Another limitation of RF ablation
catheters is the risk of clot formation on the energy emitting
electrodes. Such clots have an associated danger of causing
potentially lethal strokes in the event that a clot is dislodged
from the catheter. It is also very difficult to create continuous
long lesions with RF ablation instruments.
[0011] As such, catheters which utilize other energy sources as the
ablation energy source, for example in the microwave frequency
range, are currently being developed. Microwave frequency energy,
for example, has long been recognized as an effective energy source
for heating biological tissues and has seen use in such
hyperthermia applications as cancer treatment and preheating of
blood prior to infusions. Accordingly, in view of the drawbacks of
the traditional catheter ablation techniques, there has recently
been a great deal of interest in using microwave energy as an
ablation energy source. The advantage of microwave energy is that
it is much easier to control and safer than direct current
applications and it is capable of generating substantially larger
and longer lesions than RF catheters, which greatly simplifies the
actual ablation procedures. Such microwave ablation systems are
described in the U.S. Pat. Nos. 4,641,649 to Walinsky; 5,246,438 to
Langberg; 5,405,346 to Grundy, et al.; and 5,314,466 to Stem, et
al, each of which is incorporated herein by reference.
[0012] Most of the existing microwave ablation catheters
contemplate the use of longitudinally extending helical antenna
coils that direct the electromagnetic energy in all radial
directions that are generally perpendicular to the longitudinal
axis of the catheter. Although such catheter designs work well for
a number of applications, such radial output is inappropriate when
the energy needs to be directed toward the tissue to ablate
only.
[0013] Consequently, microwave ablation instruments have recently
been developed which incorporate microwave antennas having
directional reflectors. Typically, a tapered directional reflector
is positioned peripherally around the microwave antenna to direct
the waves toward and out of a window portion of the antenna
assembly. These ablation instruments, thus, are capable of
effectively transmitting electromagnetic energy in a more specific
direction. For example, the electromagnetic energy may be
transmitted generally perpendicular to the longitudinal axis of the
catheter but constrained to a selected radial region of the
antenna, or directly out the distal end of the instrument. Typical
of these designs are described in the U.S. patent application Ser.
Nos.: 09/178,066, filed Oct. 23, 1998; and 09/333,747, filed Jun.
14, 1999, each of which is incorporated herein by reference.
[0014] In these designs, the resonance frequency of the microwave
antenna is preferably tuned assuming contact between the targeted
tissue or blood and a contact region of the antenna assembly
extending longitudinally adjacent to the antenna longitudinal axis.
Hence, should a portion of, or substantially all of, the exposed
contact region of the antenna not be in contact with the targeted
tissue or blood during ablation, the resonance frequency will be
adversely changed and the antenna will be untuned. As a result, the
portion of the antenna not in contact with the targeted tissue or
blood will radiate the electromagnetic radiation into the
surrounding air. The efficiency of the energy delivery into the
tissue will consequently decrease which in turn causes the
penetration depth of the lesion to decrease.
[0015] This is particularly problematic when the microwave antenna
is not in the blood pool, or when the tissue surfaces are
substantially curvilinear, or when the targeted tissue for ablation
is difficult to access, such as in the interior chambers of the
Heart. Since these antenna designs are generally relatively rigid,
it is often difficult to maneuver substantially all of the exposed
contact region of the antenna into abutting contact against the
targeted tissue. In these instances, several ablation instruments,
having antennas of varying length and shape, may be necessary to
complete just one series of ablations.
SUMMARY OF THE INVENTION
[0016] Accordingly, a system for ablating a selected portion of a
contact surface of biological tissue is provided. The system is
particularly suitable to ablate cardiac tissue, and includes an
elongated ablation sheath having a preformed shape adapted to
substantially conform a predetermined surface thereof with the
contact surface of the tissue. The ablation sheath defines an
ablation lumen extending therethrough along an ablation path
proximate to the predetermined surface. An elongated ablative
device includes a flexible ablation element which cooperate with an
ablative energy source which is sufficiently strong for tissue
ablation. The ablative device is formed and dimensioned for
longitudinal sliding receipt through the ablation lumen of the
ablation sheath for selective placement of the ablative device
along the ablation path created by the ablation sheath. The
ablation lumen and the ablative device cooperate to position the
ablative device proximate to the ablation sheath predetermined
surface for selective ablation of the selected portion
[0017] Accordingly, the ablation sheath in its preshaped form
functions as a guide device to guide the ablative device along the
ablation path when the predetermined surface of the ablation sheath
properly contacts the biological tissue. Further, the cooperation
between the ablative device and the ablation lumen, as the ablative
device is advanced through the lumen, positions the ablative device
in a proper orientation to facilitate ablation of the targeted
tissue during the advancement. Thus, once the ablation sheath is
stationed relative the targeted contact surface, the ablative
device can be easily advanced along the ablation path to generate
the desired tissue ablations.
[0018] In one embodiment, the ablative device is a microwave
antenna assembly which includes a flexible shield device coupled to
the antenna substantially shield a surrounding area of the antenna
from the electromagnetic field radially generated therefrom while
permitting a majority of the field to be directed generally in a
predetermined direction toward the ablation sheath predetermined
surface. The microwave antenna assembly further includes a flexible
insulator disposed between the shield device and the antenna. A
window portion of the insulator is defined which enables
transmission of the directed electromagnetic field in the
predetermined direction toward the ablation sheath predetermined
surface. The antenna, the shield device and the insulator are
formed for manipulative bending thereof, as a unit, to one of a
plurality of contact positions to generally conform the window
portion to the ablation sheath predetermined surface as the
insulator and antenna are advanced through the ablation lumen.
[0019] In another embodiment, to facilitate alignment of the
ablative device assembly in the ablation lumen, the ablative device
provides a key device which is slideably received in a mating slot
portion of the ablation lumen. In still another embodiment, the
system includes a guide sheath defining a guide lumen formed and
dimensioned for sliding receipt of the ablation sheath
therethrough. The guide sheath is pre-shaped to facilitate
positioning of the ablation sheath toward the selected portion of
the contact surface when the ablation sheath is advanced through
guide lumen.
[0020] The ablation sheath includes a bendable shape retaining
member extending longitudinally therethrough which is adapted to
retain the preformed shape of the ablation sheath once positioned
out of the guide lumen of the guide sheath.
[0021] The ablative energy is preferably provided by a microwave
ablative device. Other suitable tissue ablation devices, however,
include cryogenic, ultrasonic, laser and radiofrequency, to name a
few.
[0022] In another aspect of the present invention, a method for
treatment of a Heart includes forming a penetration through a
muscular wall of the Heart into an interior chamber thereof; and
positioning a distal end of an elongated ablation sheath through
the penetration. The ablation sheath defines an ablation lumen
extending along an ablation path therethrough. The method further
includes contacting, or bringing close enough, a predetermined
surface of the elongated ablation sheath with a first selected
portion of an interior surface of the muscular wall; and passing a
flexible ablative device through the ablation lumen of the ablation
sheath for selective placement of the ablative device along the
ablation path. Once these events have been performed, the method
includes applying the ablative energy, using the ablative device
and the ablation energy source, which is sufficiently strong to
cause tissue ablation.
[0023] In one embodiment, the passing is performed by incrementally
advancing the ablative device along a plurality of positions of the
ablation path to produce a substantially continuous lesion. Before
the positioning event, the method includes placing a distal end of
a guide sheath through the penetration, and then positioning the
distal end of the ablation sheath through the guide lumen of the
guide sheath.
[0024] In still another embodiment, before the placing event,
piercing the muscular wall with a piercing sheath. The piercing
sheath defines a positioning passage extending therethrough, The
placing the distal end of a guide sheath is performed by placing
the guide sheath distal end through the positioning passage of the
piercing sheath.
[0025] In yet another configuration, the positioning the distal end
event includes advancing the ablation sheath toward the first
selected portion of the interior surface of the muscular wall
through a manipulation device extending through a second
penetration into the Heart interior chamber independent from the
first named penetration.
[0026] In another embodiment, a system for ablating tissue within a
body of a patient is provided including an elongated rail device
and an ablative device. The raidl device is adapted to be
positioned proximate and adjacent to a selected tissue region to be
ablated within the body of the patient. The ablative device
includes a receiving passage configured to slideably receive the
rail device longitudinally therethrough. This enables the ablative
device to be slideably positioned along the rail substantially
adjacent to or in contact with the selected tissue region. The
ablative device, having an energy delivery portion which is adapted
to be coupled to an ablative energy source, can then be operated to
ablate the selected tissue region.
[0027] In this configuration, the ablative device is adapted to
directionally emit the ablative energy from the energy delivery
portion. A key assembly cooperates between the ablative device and
the rail member, thus, to properly align the directionally emitted
ablative energy toward the tissue region to be ablated. This
primarily performed by providing a rail device with a non-circular
transverse cross-sectional dimension. The receiving passage of the
ablative device further includes a substantially similarly shaped
non-circular transverse cross-sectional dimension to enable sliding
of the ablative device in a manner continuously aligning the
directionally emitted ablative energy toward the tissue region to
be ablated as the ablative device advances along the rail
device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The assembly of the present invention has other objects and
features of advantage which will be more readily apparent from the
following description of the best mode of carrying out the
invention and the appended claims, when taken in conjunction with
the accompanying drawing, in which:
[0029] FIGS. 1A and 1B are fragmentary, top perspective views,
partially broken-away, of the ablation system constructed in
accordance with the present invention, and illustrating advancement
of a bendable directional reflective microwave antenna assembly
through an ablation lumen of a ablation sheath.
[0030] FIGS. 2A-2D is series of fragmentary, side elevation views,
in partial cross-section, of the Heart, and illustrating
advancement of the ablation system of present invention into the
left atrium for ablation of the targeted tissue.
[0031] FIG. 3 is a fragmentary, side elevation view, in partial
cross-section, of the Heart showing a pattern of ablation lesions
to treat atrial fibrillation.
[0032] FIGS. 4A and 4B are a series of enlarged, fragmentary, top
perspective view of a pigtail ablation sheath of the ablation
system of FIGS. 2C and 2D, and exemplifying the ablation sheath
being advanced into one of the pulmonary vein orifices.
[0033] FIG. 5 is a front schematic view of a patient's
cardiovascular system illustrating the positioning of a transseptal
piercing sheath through the septum wall of the patient's Heart.
[0034] FIG. 6 is a fragmentary, side elevation view, in partial
cross-section, of another embodiment of the ablation sheath of the
present invention employed for lesion formation.
[0035] FIG. 7 is a fragmentary, side elevation view, in partial
cross-section, of yet another embodiment of the ablation sheath of
the present invention employed for another lesion formation.
[0036] FIG. 8 is an enlarged, front elevation view, in
cross-section, of the ablation system of FIG. 1 positioned through
the trans-septal piercing sheath.
[0037] FIG. 9 is an enlarged, front elevation view, in
cross-section, of the ablation sheath and the antenna assembly of
the ablation system in FIG. 8 contacting the targeted tissue.
[0038] FIG. 10 is an enlarged, front elevation view, in
cross-section, of the antenna assembly taken substantially along
the plane of the line 10-10 in FIG. 9.
[0039] FIG. 11 is a diagrammatic top plan view of an alternative
embodiment microwave ablation instrument system constructed in
accordance with one embodiment of the present invention.
[0040] FIG. 12 is an enlarged, fragmentary, top perspective view of
the ablation instrument system of FIG. 11 illustrated in a bent
position to conform the ablation sheath to a surface of the tissue
to be ablated.
[0041] FIGS. 13A-13D is a series of side elevation views, in
cross-section, of the ablation sheath of the present invention
illustrating advancement of the ablation device incrementally
through the ablation sheath to form plurality of overlapping
lesions.
[0042] FIG. 14A is a fragmentary, side elevation view of a
laser-type ablation device of the present invention.
[0043] FIG. 14B is a front elevation view of the laser-type energy
delivery portion taken along the plane of the line 14B-14B in FIG.
14A.
[0044] FIG. 15A is a fragmentary, side elevation view of a
cryogenic-type ablation device of the present invention.
[0045] FIG. 15B is a front elevation view of the cryogenic-type
energy delivery portion taken along the plane of the line 15B-15B
in FIG. 15A.
[0046] FIG. 16 is a fragmentary, side elevation view, in
cross-section, of an ultrasonic-type ablation device of the present
invention.
[0047] FIG. 17 is an enlarged, fragmentary, top perspective view of
an alternative embodiment ablation sheath having an opened window
portion.
[0048] FIG. 18 is a fragmentary, side elevation view of an
alternative embodiment ablation assembly employing a rail
system.
[0049] FIG. 19 is a front elevation view of the energy delivery
portion of the ablation rail system taken along the plane of the
line 19-19 in FIG. 18.
[0050] FIGS. 20A-20C are cross-sectional views of alternative key
systems in accordance with the present invention.
[0051] FIG. 21 is a fragmentary, diagrammatic, front elevation view
of a torso applying one embodiment of the present invention through
a minimally invasive technique.
[0052] FIG. 22 is a top plan view, in cross-section of the
fragmentary, diagrammatic, top plan view of the torso of FIG. 21
applying the minimally invasive technique.
DETAILED DESCRIPTION OF THE INVENTION
[0053] While the present invention will be described with reference
to a few specific embodiments, the description is illustrative of
the invention and is not to be construed as limiting the invention.
Various modifications to the present invention can be made to the
preferred embodiments by those skilled in the art without departing
from the true spirit and scope of the invention as defined by the
appended claims. It will be noted here that for a better
understanding, like components are designated by like reference
numerals throughout the various Figures.
[0054] Turning generally now to FIGS. 1A-2D, an ablation system,
generally designated 20, is provided for transmurally ablating a
targeted tissue 21 of biological tissue. The system 20 is
particularly suitable to ablate the epicardial or endocardial
tissue 40 of the heart, and more particularly, to treat medically
refractory atrial fibrillation of the Heart. The ablation system 20
for ablating tissue within a body of a patient includes an
elongated flexible tubular member 22 having at least one lumen 25
(FIGS. 1A, 1B, 8 and 9) and including a pre-shaped distal end
portion (E.g., FIGS. 2C, 6 and 7) which is shaped to be positioned
adjacent to or in contact with a selected tissue region 21 within
the body of the patient. An ablative device, generally designated
26, is configured to be slideably received longitudinally within
the at least one lumen 25, and includes an energy delivery portion
27 located near a distal end portion of the ablative device 26
which is adapted to be coupled to an ablative energy source (not
shown).
[0055] The ablative device is preferably provided by a microwave
ablation device 26 formed to emit microwave energy sufficient to
cause tissue ablation. As will be described in greater detail
below, however, the ablative device energy may be provided by a
laser ablation device, a Radio Frequency (RF) ablation device, an
ultrasound ablation device or a cryoablation device.
[0056] The tubular member 22 is in the form of an elongated
ablation sheath having, in a preferred embodiment, a resiliently
preformed shape adapted to substantially conform a predetermined
contact surface 23 of the sheath with the targeted tissue region
21. In another embodiment, the ablation sheath is malleable. Yet,
in another embodiment, the ablation sheath is flexible. The lumen
25 of the tubular member extends therethrough along an ablation
path proximate to the predetermined contact surface. Preferably, as
will be described in more detail below, the ablative device 26
includes a flexible energy delivery portion 27 selectively
generating an electromagnetic field which is sufficiently strong
for tissue ablation. The energy delivery portion 27 is formed and
dimensioned for longitudinal sliding receipt through the ablation
lumen 25 of the ablation sheath 22 for selective placement of the
energy delivery portion along the ablation path. The ablation lumen
25 and the ablative device 26 cooperate to position the energy
delivery portion 27 proximate to the ablation sheath 22
predetermined contact surface 23 of the sheath for selective
transmural ablation of the targeted tissue 21 within the
electromagnetic field when the contact surface 23 strategically
contacts or is positioned close enough to the targeted tissue
21.
[0057] Accordingly, in one preferred embodiment, the pre-shaped
ablation sheath 22 functions to unidirectionally guide or position
the energy delivery portion 27 of the ablative device 26 properly
along the predetermined ablation path 28 proximate to the targeted
tissue region 21 as the energy delivery portion 27 is advanced
through the ablation lumen 25. By positioning the energy delivery
portion 27, which is preferably adapted to emit a directional
ablation field, at one of a plurality of positions incrementally
along the ablation path (FIGS. 1A and 1B) in the lumen 25, a single
continuous or plurality of spaced-apart lesions can be formed. In
other instances, the antenna length may be sufficient to extend
along the entire ablation path 28 so that only a single ablation
sequence is necessary.
[0058] While the method and apparatus of the present invention are
applicable to ablate any biological tissue which requires the
formation of controlled lesions (as will be described in greater
detail below), this ablation system is particularly suitable for
ablating endocardial or epicardial tissue of the Heart. For
example, the present invention may be applied in an intra-coronary
configuration where the ablation procedure is performed on the
endocardium of any cardiac chamber. Specifically, such ablations
may be performed on the isthmus to address atrial flutter, or
around the pulmonary vein ostium, electrically isolating the
pulmonary veins, to treat medically refractory atrial fibrillation
(FIG. 3). This procedure requires the precise formation of
strategically placed endocardial lesions 30-36 which collectively
isolate the targeted regions. By way of example, any of the
pulmonary veins may be collectively isolated to treat chronic
atrial fibrillation. The annular lesion isolating one or more than
one pulmonary vein can be linked with another linear lesion joining
the mitral valve annulus. In another example, the annular lesion
isolating one or more than one pulmonary vein can be linked with
another linear lesion joining the left atrium appendage.
[0059] In a preferred embodiment, the pre-shaped ablation sheath 22
and the sliding ablative device 26 may applied to ablate the
epicardial tissue 39 of the Heart 40 as well (FIG. 12). An annular
ablation, for instance, may be formed around the pulmonary vein for
electrical isolation from the left atrium. As another example, the
lesions may be created along the transverse sinus and oblique sinus
as part of the collective ablation pattern to treat atrial
fibrillation for example.
[0060] The application of the present invention, moreover, is
preferably performed through minimally invasive techniques. It will
be appreciated, however, that the present invention may be applied
through open chest techniques as well.
[0061] Briefly, to illustrate the operation of the present
invention, a flexible pre-shaped tubular member (i.e., ablation
sheath 22) in the form of a pigtail is shown in FIGS. 2C and 2d
which is specifically configured to electrically isolate a
pulmonary vein of the Heart 40. The isolating lesions are
preferably made on the posterior wall of the left atrium, around
the ostium of one, or more than one of a pulmonary vein.
[0062] In this example and as illustrated in FIGS. 4A and 4B, a
distal end of the pigtail-shaped ablation sheath or tubular member
22 is positioned into the left superior pulmonary vein orifice 37
from the left atrium 41. As the ablation sheath 22 is further
advanced, a predetermined contact surface 23 of the ablation sheath
is urged adjacent to or into contact with the endocardial surface
of the targeted tissue region 21 (FIGS. 2D and 4B). Once the
ablation sheath 22 is properly positioned and oriented, the
ablative device 26 is advanced through the ablation lumen 25 of the
ablation sheath 22 (FIGS. 1A and 1B) which moves the energy
delivery portion 27 of the ablative device along the ablation path.
When the energy delivery portion 27 is properly oriented and
positioned in the ablation lumen 25, the directional ablation field
may be generated to incrementally ablate (FIGS. 13A-13D) the
epicardial surface of the targeted tissue 21 along the ablation
path to isolate the Left Superior Pulmonary Vein (LIPV)
[0063] Accordingly, as shown in FIGS. 13A-13D, as the energy
delivery portion 27 is incrementally advanced through the lumen 25,
overlapping lesion sections 44-44"' are formed by the ablation
field which is directional in one preferred embodiment.
Collectively, a continuous lesion or series of lesions can be
formed which essentially three-dimensionally "mirror" the shape of
the contact surface 23 of the ablation sheath 22 which is
positioned adjacent to or in contact with the targeted tissue
region. These transmural lesions may thus be formed in any shape on
the targeted tissue region such as rectilinear, curvilinear or
circular in shape. Further, depending upon the desired ablation
lines pattern, both opened and closed path formation can be
constructed.
[0064] Referring now to FIGS. 2A, 2D and 5, a minimal invasive
application of the present invention is illustrated for use in
ablating Heart tissue. By way of example, a conventional
transseptal piercing sheath 42 is introduced into the femoral vein
43 through a venous cannula 45 (FIG. 5). The piercing sheath is
then intravenously advanced into the right atrium 46 of the Heart
40 through the inferior vena cava orifice 47. These piercing
sheaths are generally resiliently pre-shaped to direct a
conventional piercing device 48 toward the septum wall 50. The
piercing device 48 and the piercing sheath 42 are manipulatively
oriented and further advanced to pierce through the septum wall 50,
as a unit, of access into the left atrium 41 of the Heart 40 (FIG.
2A).
[0065] These conventional devices are commonly employed in the
industry for accessing the left atrium or ventricle, and have an
outer diameter in the range of about 0.16 inch to about 0.175 inch,
while having an inner diameter in the range of about 0.09 inch to
about 0.135 inch.
[0066] Once the piercing device 48 is withdrawn from a positioning
passage 51 (FIG. 8) of the piercing sheath 42, a guide sheath 52 of
the ablation system 20 is slideably advanced through the
positioning passage and into a cardiac chamber such as the left
atrium 41 thereof (FIG. 2B). The guide sheath 52 is essentially a
pre-shaped, open-ended tubular member which is inserted into the
coronary circulation to direct and guide the advancing ablation
sheath 22 into a selected cardiac chamber (i.e., the left atrium,
right atrium, left ventricle or right ventricle) and toward the
general direction of the targeted tissue. Thus, the guide sheath 52
and the ablation sheath 22 telescopically cooperate to position the
predetermined contact surface 23 thereof substantially adjacent to
or in contact with the targeted tissue region.
[0067] Moreover, the guide sheath and the ablation sheath cooperate
to increase the structural stability of the system as the ablation
sheath is rotated and manipulated from its proximal end into
ablative contact with the targeted tissue 21 (FIG. 2A). As the
distal curved portions of the ablation sheath 22, which is
inherently longer than the guide sheath, is advanced past the
distal lumen opening of the guide sheath, these resilient curved
portions will retain their original unrestrained shape.
[0068] The telescopic effect of these two sheaths is used to
position the contact surface 23 of the ablation sheath 22
substantially adjacent to or in contact with the targeted tissue.
Thus, depending upon the desired lesion formation, the same guide
sheath 52 may be employed for several different procedures. For
example, the lesion 30 encircling the left superior pulmonary vein
ostium and the Left Inferior Pulmonary Vein Ostium (RIPVO) lesion
31 (FIG. 3) may be formed through the cooperation of the pigtail
ablation sheath 22 and the same guide sheath 52 of FIGS. 2B and 2D,
while the same guide sheath may also be utilized with a different
ablation sheath 22 (FIG. 4) to create the long linear lesion 34 as
shown in FIG. 3.
[0069] In contrast, as illustrated in FIG. 7, another guide sheath
52 having a different pre-shaped distal end section may be applied
to direct the advancing ablation sheath 22 back toward the in the
left and right superior pulmonary vein orifices 53, 55. Thus,
several pre-shaped guide sheaths, and the corresponding ablation
sheaths, as will be described, cooperate to create a predetermined
pattern of lesions (E.g., a MAZE procedure) on the tissue.
[0070] In the preferred embodiment, the guide sheath 52 is composed
of a flexible material which resiliently retains its designated
shape once external forces urged upon the sheath are removed. These
external forces, for instance, are the restraining forces caused by
the interior walls 56 of the transseptal piercing sheath 42 as the
guide sheath 52 is advanced or retracted therethrough. While the
guide sheath 52 is flexible, it must be sufficiently rigid so as to
substantially retain its original unrestrained shape, and not to be
adversely influenced by the ablation sheath 22, as the ablation
sheath is advanced through the lumen of the guide sheath. Such
flexible, biocompatible materials may be composed of braided Pebax
or the like having an outer diameter formed and dimensioned for
sliding receipt longitudinally through the positioning passage 51
of the transseptal piercing sheath 42. The outer dimension is
therefore preferably cylindrical having an outer diameter in the
range of about 0.09 inch to about 0.145 inch, and more preferably
about 0.135", while having an inner diameter in the range of about
0.05 inch to about 0.125 inch, and more preferably about 0.115".
This cylindrical dimension enables longitudinal sliding receipt, as
well as axial rotation, in the positioning passage 51 to properly
place and advance the guide sheath 52. Thus, the dimensional
tolerance between the cylindrical-shaped, outer peripheral wall of
the guide sheath 52 and the interior walls 56 of the transseptal
piercing sheath 42 should be sufficiently large to enable
reciprocal movement and relative axial rotation therebetween, while
being sufficiently small to substantially prevent lateral
displacement therebetween as the ablation sheath 22 is urged into
contact with the targeted tissue 21. For example, the dimensional
tolerance between the transverse cross-sectional periphery of the
interior walls 56 of the positioning passage 51 and that of the
substantially conforming guide sheath 52 should be in the range of
about 0.005 inches to about 0.020 inches.
[0071] To increase the structural integrity of the guide sheath 52,
metallic braids 57 are preferably incorporated throughout the
sheath when the guide sheath is molded to its preformed shape.
These braids 57 are preferably provided by 0.002" wires composed of
304 stainless steel evenly spaced about the sheath.
[0072] Once the guide sheath 52 is properly positioned and oriented
relative the transseptal sheath 42, the ablation sheath 22 is
advanced through a guide lumen 54 (FIG. 8) of the guide sheath 52
toward the targeted tissue. Similar to the pre-shaped guide sheath
52, the ablation sheath 22 is pre-shaped in the form of the desired
lesions to be formed in the endocardial surface of the targeted
tissue 21. As best viewed in FIGS. 2D, 6 and 7, each ablation
sheath 52 is adapted facilitate an ablation in the targeted tissue
21 generally in the shape thereof. Thus, several pre-shaped
ablation sheaths cooperate to form a type of steering system to
position the ablation device about the targeted tissue.
Collectively, a predetermined pattern of linear and curvilinear
lesions (E.g., a MAZE procedure) can be ablated on the targeted
tissue region.
[0073] Again, similar to the guide sheath 52, the ablation sheath
22 is composed of a flexible material which resiliently retains its
designated shape once external forces urged upon the sheath are
removed. These external forces, for instance, are the restraining
forces caused by the interior walls 59 defining the guide lumen 54
of the guide sheath 52 as the ablation sheath 22 is advanced or
retracted therethrough. Such flexible, biocompatible materials may
be composed of Pebax or the like having an outer diameter formed
and dimensioned for sliding receipt longitudinally through the
guide lumen 54 of the ablation sheath 22. As mentioned, the inner
diameter of the guide lumen 54 is preferably in the range of about
0.050 inch to about 0.125 inch, and more preferably about 0.115",
while the ablation sheath 26 has an outer diameter in the range of
about 0.40 inch to about 0.115 inch, and more preferably about
0.105".
[0074] The concentric cylindrical dimensions enable longitudinal
sliding receipt, as well as axial rotation, of the ablation sheath
22 in the guide lumen 54 to properly place and advance the it
toward the targeted tissue 21. Thus, the dimensional tolerance
between the cylindrical-shaped, outer peripheral wall of the
ablation sheath 22 and the interior walls 59 of the guide lumen 54
of the guide sheath 52 should be sufficiently large to enable
reciprocal movement and relative axial rotation therebetween, while
being sufficiently small to substantially prevent lateral
displacement therebetween as the ablation sheath 22 is urged into
contact with the targeted tissue 21. For example, the dimensional
tolerance between the transverse cross-sectional periphery of the
guide lumen 54 and that of the substantially conforming energy
delivery portion 27 should be in the range of about 0.001 inches to
about 0.005 inches.
[0075] As above-indicated, the pre-shaped ablation sheath 22
facilitates guidance of the ablative device 26 along the
predetermined ablation path 28. This is primarily performed by
advancing the energy delivery portion 27 of the ablative device 26
through the ablation lumen 25 of the ablation sheath 22 which is
preferably off-set from the longitudinal axis 78 thereof. As best
viewed in FIGS. 8 and 9, this off-set positions the energy delivery
portion 27 relatively closer to the predetermined contact surface
23 of the ablation sheath 22, and hence the targeted tissue 21.
Moreover, when using directional fields such as those emitted from
their energy delivery portion 27, it is important to provide a
mechanism for continuously aligning the directional field of the
energy delivery portion 27 with the tissue 21 targeted for
ablation.
[0076] Thus, in this design, the directional field must be
continuously aligned with the predetermined contact surface 23 of
the ablation sheath 22 as the energy delivery portion 27 is
advanced through the ablation lumen 25 since the ablation sheath
contact surface 23 is designated to contact or be close enough to
the targeted tissue.
[0077] If the directional field is not aligned correctly, for
example, the energy may be transmitted into surrounding fluids and
tissues designated for preservation rather than into the targeted
tissue region. Therefore, in accordance with another aspect of the
present invention, a key structure 48 (FIGS. 1, 8 and 9) cooperates
between the ablative device 26 and the ablation lumen 25 to orient
the directive energy delivery portion 27 of the ablative device
continuously toward the targeted tissue region 21 as it is advanced
through the lumen. This key structure 48, thus, only allows receipt
of the energy delivery portion 27 in the lumen in one orientation.
More particularly, the key structure 48 continuously aligns a
window portion 58 of the energy delivery portion 27 substantially
adjacent the predetermined contact surface 23 of the ablation
sheath 22 during advancement. This window portion 58, as will be
described below, enables the transmission of the directed ablative
energy from the energy delivery portion 27, through the contact
surface 23 of the ablation sheath 22 and into the targeted tissue
region. Consequently, the directional ablative energy emitted from
the energy delivery portion will always be aligned with the contact
surface 23 of the ablation sheath 22, which is positioned adjacent
to or in contact with the targeted tissue region 21, to maximize
ablation efficiency. By comparison, the ablation sheath 22 is
capable of relatively free rotational movement axially in the guide
lumen 54 of the guide sheath 52 for maneuverability and positioning
of the ablation sheath therein.
[0078] As mentioned, the transverse cross-sectional dimension of
the energy delivery portion 27 is configured for sliding receipt in
the ablation lumen 25 of the ablation sheath 22 in a manner
positioning the directional ablative energy, emitted by the energy
delivery portion, continuously toward the predetermined contact
surface 23 of the ablation sheath 22. In one example, as shown in
FIGS. 8 and 9, the transverse peripheral dimensions of the energy
delivery portion 27 and the ablation lumen 25 are generally
D-shaped, and substantially similar in dimension. Thus, the window
portion 58 of the insulator 61, as will be discussed, is preferably
semi-cylindrical and concentric with the interior wall 62 defining
the ablation lumen 25 of the ablation sheath 22. It will be
appreciated, however, that any geometric configuration may be
applied to ensure unitary or aligned insertion. As another example,
one of the energy delivery portion and the interior wall of the
ablation lumen may include a key member and corresponding receiving
groove, or the like. Such key and receiving groove designs,
nonetheless, should avoid relatively sharp edges to enable smooth
advancement and retraction of the energy delivery portion in the
ablation lumen 25.
[0079] This dimension alignment relationship can be maintain along
the length of the predetermined contact surface of the ablation
sheath 22 as the energy delivery portion 27 is advanced through the
ablation lumen whether in the configuration of FIGS. 2, 6, 7 or 12.
In this manner, a physician may determine that once the
predetermined contact surface 23 of the ablation sheath 22 is
properly oriented and positioned adjacent or in contact against the
targeted tissue 21, the directional component (as will be
discussed) of the energy delivery portion 27 will then be
automatically aligned with the targeted tissue as it is advanced
through the ablation lumen 25. Upon selected ablation by the
ablative energy, a series of overlapping lesions 44-44"' (FIGS.
13A-13D) or a single continuous lesion can then be generated.
[0080] It will further be appreciated that the dimensional
tolerances therebetween should be sufficiently large to enable
smooth relative advancement and retraction of the energy delivery
portion 27 around curvilinear geometries, and further enable the
passage of gas therebetween. Since the ablation lumen 25 of the
ablation sheath 22 is closed ended, gases must be permitted to flow
between the energy delivery portion 27 and the interior wall 62
defining the ablation lumen 25 to avoid the compression of gas
during advancement of the energy delivery portion therethrough.
Moreover, the tolerance must be sufficiently small to substantially
prevent axial rotation of the energy delivery portion in the
ablation lumen 25 for alignment purposes. The dimensional tolerance
between the transverse cross-sectional periphery of the ablation
lumen and that of the substantially conforming energy delivery
portion 27, for instance, should be in the range of about 0.001
inches to about 0.005 inches.
[0081] To further facilitate preservation of the fluids and tissues
along the backside of the ablation sheath 22 (i.e., the side
opposite the contact surface 23 of the sheath), a thermal isolation
component (not shown) is disposed longitudinally along, and
substantially adjacent to, the ablation lumen 25. Thus, during
activation of the ablative device, the isolation component and the
directive component 73 of the energy ablation portion 27 cooperate
to form a thermal barrier along the backside of the ablation
sheath.
[0082] For instance, the isolation component may be provided by an
air filled isolation lumen extending longitudinally along, and
substantially adjacent to, the ablation lumen 25. The
cross-sectional dimension of the isolation lumen may be C-shaped or
crescent shaped to partially surround the ablation lumen 25. In
another embodiment, the isolation lumen may be filled with a
thermally refractory material.
[0083] In still another embodiment, a circulating fluid, which is
preferably biocompatible, may be disposed in the isolation lumen to
provide to increase the thermal isolation. Two or more lumens may
be provided to increase fluid flow. One such biocompatible fluid
providing suitable thermal properties is saline solution.
[0084] Similar to the composition of the guide sheath 52, the
ablation sheath 22 is composed of a flexible bio-compatible
material, such as PU Pellethane, Teflon or polyethylent, which is
capable of shape retention once external forces acting on the
sheath are removed. By way of example, when the distal portions of
the ablation sheath 22 are advanced past the interior walls of the
guide lumen 54 of the guide sheath 52, the ablation sheath 22 will
return to its preformed shape in the interior of the Heart.
[0085] To facilitate shape retention, the ablation sheath 22
preferably includes a shape retaining member 63 extending
longitudinally through the distal portions of the ablation sheath
where shape retention is necessary. As illustrated in FIGS. 1, 8
and 9, this retaining member 63 is generally extends substantially
parallel and adjacent to the ablation lumen 25 to reshape the
predetermined contact surface 23 to its desired pre-shaped form
once the restraining forces are removed from the sheath. While this
shape-memory material must be sufficiently resilient for shape
retention, it must also be sufficiently bendable to enable
insertion through the guide lumen 54 of the guide sheath 52. In the
preferred form, the shape retaining member is composed of a
superelastic metal, such as Nitinol (NiTi). Moreover, the preferred
diameter of this material should be in the range of 0.020 inches to
about 0.050 inches, and more preferably about 0.035 inches.
[0086] When used during a surgical procedure, the ablation sheath
22 is preferably transparent which enables a surgeon to visualize
the position of the energy delivery portion 27 of the ablative
device 26 through an endoscope or the like. Moreover, the material
of ablation sheath 22 must be substantially unaffected by the
ablative energy emitted by the energy delivery portion 27. Thus, as
will be apparent, depending upon the type of energy delivery
portion and the ablative source applied, the material of the
tubular sheath must exhibit selected properties, such as a low loss
tangent, low water absorption or low scattering coefficient to name
a few, to be unaffected by the ablative energy.
[0087] As previously indicated, the ablation sheath 22 is advanced
and oriented, relative to the guide sheath 52, adjacent to or into
contact with the targeted tissue region 21 to form a series of
over-lapping lesions 44-44"', such as those illustrated in FIGS. 3
and 13A-13D. Preferably, the contact surface 23 of the pre-shaped
ablation sheath 22 is negotiated into physical contact with the
targeted tissue 21. Such contact increases the precision of the
tissue ablation while further facilitating energy transfer between
the ablation element and the tissue to be ablated, as will be
discussed.
[0088] To assess proper contact and positioning of the contact
surface 23 of the ablation sheath 22 against the targeted tissue
21, at least one positioning electrode, generally designated 64, is
disposed on the exterior surface of the ablation sheath for contact
with the tissue. Preferably a plurality of electrodes are
positioned along and adjacent the contact surface 23 to assess
contact of the elongated and three dimensionally shaped contact
surface. These electrodes 64 essentially measure whether there is
any electrical activity (or electrophysiological signals) to one or
the other side of the ablation sheath 22. When a strong electrical
activation signal is detected, or inter-electrode impedance is
measured when two or more electrodes are applied, contact with the
tissue can be assessed. Once the physician has properly situated
and oriented the sheath, they may commence advancement of the
energy delivery portion 27 through the ablation lumen 25.
Additionally, these positioning electrodes may be applied to map
the biological tissue prior to or after an ablation procedure, as
well as be used to monitor the patient's condition during the
ablation process.
[0089] To facilitate discussion of the above aspects of the present
invention, FIG. 10 illustrates two side-by-side electrodes 64, 65
configured for sensing electrical activity in substantially one
direction, in accordance with one aspect of the present invention.
This electrode arrangement generally includes a pair of
longitudinally extending electrode elements 66, 67 that are
disposed on the outer periphery of the ablation sheath 22. The pair
of electrode elements 66, 67 are positioned side by side and
arranged to be substantially parallel to one another. In general,
splitting the electrode arrangement into a pair of distinct
elements permits substantial improvements in the resolution of the
detected electrophysiological signals. Therefore, the pair of
electrode elements 66, 67 are preferably spaced apart and
electrically isolated from one another. It will be appreciated,
however, that only one electrode may be employed to sense proper
tissue contact. It will also be appreciated that ring or coiled
electrodes can also be used.
[0090] The pair of electrode elements 66, 67 are further arranged
to be substantially parallel to the longitudinal axis of the
ablation sheath 22. In order to ensure that the electrode elements
are sensing electrical activity in substantially the same
direction, the space between electrodes should be sufficiently
small. It is generally believed that too large space may create
problems in determining the directional position of the catheter
and too small a space may degrade the resolution of the detected
electrophysiological signals. By way of example, the distance
between the two pair of electrode elements may be between about 0.5
and 2.0 mm.
[0091] The electrode elements 66, 67 are preferably positioned
substantially proximate to the predetermined contact surface 23 of
the ablation sheath 22. More preferably, the electrode elements 66,
67 are positioned just distal to the distal end of the
predetermined contact surface 23 since it is believed to be
particularly useful to facilitate mapping and monitoring as well as
to position the ablation sheath 22 in the area designated for
tissue ablation. For example, during some procedures, a surgeon may
need to ascertain where the distal end of the ablation sheath 22 is
located in order to ablate the appropriate tissues. In another
embodiment, the electrode elements 66, 67 may be positioned
substantially proximate the proximal end of the predetermined
contact surface 23, at a central portion of the contact surface 23
or a combination thereof. For instance, when attempting to contact
the loop-shaped ablation sheath 22 employed to isolate each of left
and inferior pulmonary vein orifices 37, 38, a central location of
the electrodes along the looped-shape contact surface 23 may best
sense contact with the targeted tissue. Moreover, while not
specifically illustrated, a plurality of electrode arrangements may
be disposed along the ablation sheath as well. By way of example, a
first set of electrode elements may be disposed distally from the
predetermined contact surface, a second set of electrode elements
may be disposed proximally to the contact surface, while a third
set of electrode elements may be disposed centrally thereof. These
electrodes may also be used with other types of mapping electrodes,
for example, a variety of suitable mapping electrode arrangements
are described in detail in U.S. Pat. No. 5,788,692 to Campbell, et
al., which is incorporated herein by reference in its entirety.
Although only a few positions have been described, it should be
understood that the electrode elements may be positioned in any
suitable position along the length of the ablation sheath.
[0092] The electrode elements 66, 67 may be formed from any
suitable material, such as stainless steel and iridium platinum.
The width (or diameter) and the length of the electrode may vary to
some extent based on the particular application of the catheter and
the type of material chosen. Furthermore, in the preferred
embodiment where microwave is used as the ablative energy, the
electrodes are preferably dimensioned to minimize electromagnetic
field interference, for example, the capturing of the microwave
field produced by the antenna. In most embodiments, the electrodes
are arranged to have a length that is substantially larger than the
width, and are preferably between about 0.010 inches to about 0.025
inches and a length between about 0.50 inch to about 1.0 inch.
[0093] Although the electrode arrangement has been shown and
described as being parallel plates that are substantially parallel
to the longitudinal axis of the ablation sheath 22 and aligned
longitudinally (e.g., distal and proximal ends match up), it should
be noted that this is not a limitation and that the electrodes can
be configured to be angled relative to the longitudinal axis of the
ablation sheath 22 (or one another) or offset longitudinally.
Furthermore, although the electrodes have been shown and described
as a plate, it should be noted that the electrodes may be
configured to be a wire or a point such as a solder blob.
[0094] Each of the electrode elements 66, 67 is electrically
coupled to an associated electrode wire 68, 70 and which extend
through ablation sheath 22 to at least the proximal portion of the
flexible outer tubing. In most embodiments, the electrode wires 68,
70 are electrically isolated from one another to prevent
degradation of the electrical signal, and are positioned on
opposite sides of the retaining member 63. The connection between
the electrodes 64, 65 and the electrode wires 68, 70 may be made in
any suitable manner such as soldering, brazing, ultrasonic welding
or adhesive bonding. In other embodiments, the longitudinal
electrodes can be formed from the electrode wire itself. Forming
the longitudinal electrodes from the electrode wire, or out of wire
in general, is particularly advantageous because the size of wire
is generally small and therefore the longitudinal electrodes
elements may be positioned closer together thereby forming a
smaller arrangement that takes up less space. As a result, the
electrodes may be positioned almost anywhere on a catheter or
surgical tool. These associated electrodes are described in greater
detail in U.S. patent application Ser. No.: 09/548,331, filed Apr.
12, 2000, and entitled "ELECTRODE ARRANGE-MENT FOR USE IN A MEDICAL
INSTRUMENT", and incorporated by reference.
[0095] Referring now to FIGS. 1, 8, 9 and 11, the ablative device
26 is preferably in the form of an elongated member, which is
designed for insertion into the ablation lumen 25 of the ablation
sheath 22, and which in turn is designed for insertion into a
vessel (such as a blood vessel) in the body of a patient. It will
be understood, however, that the present invention may be in the
form of a handheld instrument for use in open surgical or minimally
invasive procedures (FIG. 12).
[0096] The ablative device 26 typically includes a flexible outer
tubing 71 (having one or several lumens therein), a transmission
line 72 that extends through the flexible tubing 71 and an energy
delivery portion 27 coupled to the distal end of the transmission
line 72. The flexible outer tubing 71 may be made of any suitable
material such as medical grade polyolefins, fluoropolymers, or
polyvinylidene fluoride. By way of example, PEBAX resins from
Autochem of Germany have been used with success for the outer
tubing of the body of the catheter.
[0097] In accordance with another aspect of the present invention,
the ablative energy emitted by the energy delivery portion 27 of
the ablative device 26 may be one of several types. Preferably, the
energy delivery portion 27 includes a microwave component which
generates a electromagnetic field sufficient to cause tissue
ablation. As mentioned, as will be discussed in greater detail
below, the ablative energy may also be derived from a laser source,
a cryogenic source, an ultrasonic source or a radiofrequency
source, to name a few.
[0098] Regardless of the source of the energy, a directive
component cooperates with the energy source to control the
direction and emission of the ablative energy. This assures that
the surrounding tissues of the targeted tissue regions will be
preserved. Further, the use of a directional field has several
potential advantages over conventional energy delivery structure
that generate uniform fields about the longitudinal axis of the
energy delivery portion. For example, in the microwave application,
by forming a more concentrated and directional electromagnetic
field, deeper penetration of biological tissues is enabled, and the
targeted tissue region may be ablated without heating as much of
the surrounding tissues and/or blood. Additionally, since
substantial portions the radiated ablative energy is not emitted in
the air or absorbed in the blood or the surrounding tissues, less
power is generally required from the power source, and less power
is generally lost in the microwave transmission line.
[0099] In the preferred form, the energy delivery portion 27 of the
ablative device 26 is an antenna assembly configured to
directionally emit a majority of an electromagnetic field from one
side thereof. The antenna assembly 27, as shown in FIGS. 9 and 11,
preferably includes a flexible antenna 60, for generating the
electromagnetic field, and a flexible reflector 73 as a directive
component, for redirecting a portion of the electromagnetic field
to one side of the antenna opposite the reflector. Correspondingly,
the resultant electromagnetic field includes components of the
originally generated field, and components of the redirected
electromagnetic field. During aligned insertion of the antenna
assembly 27 into the ablation lumen 25, via the key structure 48,
the directional field will thus be continuously aligned toward the
contact surface 23 of the ablation sheath 22 as the antenna
assembly is incrementally advanced through the ablation lumen
25.
[0100] FIG. 11 illustrates that the proximal end of the antenna 60
is preferably coupled directly or indirectly to the inner conductor
75 of a coaxial transmission line 72. A direct connection between
the antenna 60 and the inner conductor 75 may be made in any
suitable manner such as soldering, brazing, ultrasonic welding or
adhesive bonding. In other embodiments, antenna 60 can be formed
from the inner conductor 75 of the transmission line 72 itself.
This is typically more difficult from a manufacturing standpoint
but has the advantage of forming a more rugged connection between
the antenna and the inner conductor. As will be described in more
detail below, in some implementations, it may be desirable to
indirectly couple the antenna to the inner conductor through a
passive component, such a capacitor, an inductor or a stub tuner
for example, in order to provide better impedance matching between
the antenna assembly and the transmission line, which is a coaxial
cable in the preferred embodiment.
[0101] Briefly, the transmission line 72 is arranged for actuating
and/or powering the antenna 60. Typically, in microwave devices, a
coaxial transmission line is used, and therefore, the transmission
line 72 includes an inner conductor 75, an outer conductor 76, and
a dielectric material 77 disposed between the inner and outer
conductors. In most instances, the inner conductor 75 is coupled to
the antenna 60. Further, the antenna 60 and the reflector 73 are
enclosed (e.g., encapsulated) in a flexible insulative material
thereby forming the insulator 61, to be described in greater detail
below, of the antenna assembly 27.
[0102] The power supply (not shown) includes a microwave generator
which may take any conventional form. When using microwave energy
for tissue ablation, the optimal frequencies are generally in the
neighborhood of the optimal frequency for heating water. By way of
example, frequencies in the range of approximately 800 MHz to 6 GHz
work well. Currently, the frequencies that are approved by the
Federal Communication Commission (FCC) for experimental clinical
work includes 915 MHz and 2.45 GHz. Therefore, a power supply
having the capacity to generate microwave energy at frequencies in
the neighborhood of 2.45 GHz may be chosen. A conventional
magnetron of the type commonly used in microwave ovens is utilized
as the generator. It should be appreciated, however, that any other
suitable microwave power source could be substituted in its place,
and that the explained concepts may be applied at other frequencies
like about 434 MHz or 5.8 GHz (ISM band).
[0103] In the preferred embodiment, the antenna assembly 27
includes a longitudinally extending antenna wire 60 that is
laterally offset from the transmission line inner conductor 75 to
position the antenna closer to the window portion 58 of the
insulator 61 upon which the directed electric field is transmitted.
The antenna 60 illustrated is preferably a longitudinally extending
exposed wire that extends distally (albeit laterally offset) from
the inner conductor. However it should be appreciated that a wide
variety of other antenna geometries may be used as well. By way of
example, helical coils, flat printed circuit antennas and other
antenna geometries will work as well.
[0104] Briefly, the insulator 61 is preferably provided by a good,
low-loss dielectric material which is relatively unaffected by
microwave exposure, and thus capable of transmission of the
electromagnetic field therethrough. Moreover, the insulator
material preferably has a low water absorption so that it is not
itself heated by the microwaves. Incidentally, when the emitted
ablative energy is microwave in origin, the ablation sheath must
also include these material properties. Finally, the insulation
material must be capable of substantial flexibility without
fracturing or breaking. Such materials include moldable TEFLON.TM.,
silicone, or polyethylene, polyimide, etc.
[0105] As will be appreciated by those familiar with antenna
design, the field generated by the illustrated antenna will be
generally consistent with the length of the antenna. That is, the
length of the electromagnetic field is generally constrained to the
longitudinal length of the antenna. Therefore, the length of the
field may be adjusted by adjusting the length of the antenna.
Accordingly, microwave ablation elements having specified ablation
characteristics can be fabricated by building them with different
length antennas. Additionally, it should be understood that
longitudinally extending antennas are not a requirement and that
other shapes and configurations may be used.
[0106] The antenna 60 is preferably formed from a conductive
material. By way of example, copper or silver-plated metal work
well. Further, the diameter of the antenna 60 may vary to some
extent based on the particular application of the catheter and the
type of material chosen. In microwave systems using a simple
exposed wire type antenna, for instance, wire diameters between
about 0.010 to about 0.020 inches work well. In the illustrated
embodiment, the diameter of the antenna is about 0.013 inches.
[0107] In a preferred embodiment, the antenna 60 is positioned
closer to the area designated for tissue ablation in order to
achieve effective energy transmission between the antenna 60 and
the targeted tissue 21 through the predetermined contact surface 23
of the ablation sheath 22. This is best achieved by placing the
antenna 60 proximate to the outer peripheral surface of the antenna
insulator 61. More specifically, a longitudinal axis of the antenna
60 is preferably off-set from, but parallel to, a longitudinal axis
78 of the inner conductor 75 in a direction away from the reflector
73 and therefore towards the concentrated electromagnetic field
(FIGS. 8 and 9). By way of example, placing the antenna between
about 0.010 to about 0.020 inches away from the outer peripheral
surface of the antenna insulator works well. In the illustrated
embodiment, the antenna is about 0.013 inches away from the outer
peripheral surface of the antenna insulator 61. However, it should
be noted that this is not a requirement and that the antenna
position may vary according to the specific design of each
catheter.
[0108] Referring now to the directive component or reflector 73, it
is positioned adjacent and generally parallel to a first side of
the antenna, and is configured to redirect those components of the
electromagnetic field contacting the reflector back towards and out
of a second side of the antenna assembly 27 opposite the reflector.
A majority of the electromagnetic field, consequently, is directed
out of the window portion 58 of the insulator 61 in a controlled
manner during ablation.
[0109] To reduce undesirable electromagnetic coupling between the
antenna and the reflector 73, the antenna 60 is preferably off-set
from the reflector 73 (FIGS. 8 and 9). This off-set from the
longitudinal axis 78 further positions the antenna 60 closer to the
window portion 58 to facilitate ablation by positioning the antenna
60 closer to the targeted tissue region. It has been found that the
minimum distance between the reflector and the antenna may be
between about 0.020 to about 0.030 inches, in the described
embodiment, in order to reduce the coupling. However, the distance
may vary according to the specific design of each ablative
device.
[0110] The proximal end of the reflector 73 is preferably coupled
to the outer conductor 76 of the coaxial transmission line 72.
Connecting the reflector to the outer conductor serves to better
define the electromagnetic field generated during use. That is, the
radiated field is better confined along the antenna, to one side,
when the reflector is electrically connected to the outer conductor
of the coaxial transmission line. The connection between the
reflector 73 and the outer conductor 76 may be made in any suitable
manner such as soldering, brazing, ultrasonic welding or adhesive
bonding. In other embodiments, the reflector can be formed from the
outer conductor of the transmission line itself. This is typically
more difficult from a manufacturing standpoint but has the
advantage of forming a more rugged connection between the reflector
and the outer conductor.
[0111] In one embodiment, to improve flexibility at the electrical
connection with the outer conductor 76 and entirely along the
energy delivery device, the proximal end of the reflector 73 is
directly contacted against the outer conductor without applying
solder or such conductive adhesive bonding. In this design, the
insulator material of the insulator 61 functions as the adhesive to
maintain electrical continuity. This is performed by initially
molding the antenna wire in the silicone insulator. The reflector
73 is subsequently disposed on the molded silicone tube, and is
extended over the outer conductor 76 of coaxial cable transmission
line 72. A heat shrink tube is then applied over the assembly to
firmly maintain the electrical contact between the reflector 73 and
the coaxial cable outer conductor 76. In other embodiments, the
reflector may be directly coupled to a ground source or be
electrically floating.
[0112] As previously noted, the antenna 60 typically emits an
electromagnetic field that is fairly well constrained to the length
of the antenna. Therefore, in some embodiments, the distal end of
the reflector 73 extends longitudinally to at about the distal end
of the antenna 60 so that the reflector can effectively cooperate
with the antenna. This arrangement serves to provide better control
of the electromagnetic field during ablation. However, it should be
noted that the actual length of the reflector may vary according to
the specific design of each catheter. For example, catheters having
specified ablation characteristics can be fabricated by building
catheters with different length reflectors.
[0113] Furthermore, the reflector 73 is typically composed of a
conductive, metallic material or foil. However, since the antenna
assembly 27 must be relatively flexible in order to negotiate the
curvilinear ablation lumen 25 of the ablation sheath 22 as the
ablative device it is advanced therethrough, the insulator 61, the
antenna wire and the reflector must collectively be relatively
flexible. Thus, one particularly material suitable for such a
reflector is a braided conductive mesh having a proximal end
conductively mounted to the distal portion of the outer conductor
of the coaxial cable. This conductive mesh is preferably thin
walled to the shield assembly yet provide the appropriate microwave
shielding properties, as well as enable substantial flexibility of
the shield device during bending movement. For example, a suitable
copper mesh wire should have a diameter in the range of about 0.005
inches to about 0.010 inches, and more preferably about 0.007
inches. A good electrical conductor is generally used for the
shield assembly in order to reduce the self-heating caused by
resistive losses. Such conductors includes, but are not restricted
to copper, silver and gold.
[0114] Another suitable arrangement may be thin metallic foil
reflector 73 which is inherently flexible. However, to further
increase flexibility, the foil material can be pleated or folded
which resists tearing during bending of the antenna assembly 27.
These foils can be composed of copper that has a layer of silver
plating formed on its inner peripheral surface. Such silver
plating, which can also be applied to the metallic mesh material,
is used to increase the conductivity of the reflector. It should be
understood, however, that these materials are not a limitation.
Furthermore, the actual thickness of the reflector may vary
according to the specific material chosen.
[0115] Referring back to FIG. 11, the reflector 73 is preferably
configured to have an arcuate or meniscus shape (e.g., crescent),
with an arc angle that opens towards the antenna 60. Flaring the
reflector towards the antenna serves to better define the
electromagnetic field generated during use. Additionally, the
reflector functions to isolate the antenna 60 from the restraining
member 63 of the ablation sheath 22 during ablation. Since the
restraining member 63 is preferably metallic in composition (most
preferably Nitinol), it is desirable minimize electromagnetic
coupling with the antenna. Thus, the reflector 73 is preferably
configured to permit at most a 180.degree. circumferential
radiation pattern from the antenna. In fact, it has been discovered
that arc angles greater than about 180.degree. are considerably
less efficient. More preferably, the arc angle of the radiation
pattern is in the range of about 90.degree. to about
120.degree..
[0116] While the reflector is shown and described as having an
arcuate shape, it will be appreciated that a plurality of forms may
be provided to accommodate different antenna shapes or to conform
to other external factors necessary to complete a surgical
procedure. For example, any flared shape that opens towards the
antenna may work well, regardless of whether it is curvilinear or
rectilinear.
[0117] Further still, it should be noted that the shape of the
reflector need not be uniform. For example, a first portion of the
reflector (e.g., distal) may be configured with a first shape
(e.g., 90.degree. arc angle) and a second portion (e.g., proximal)
of the reflector may be configured with a second shape (e.g.,
120.degree. arc angle). Varying the shape of the reflector in this
manner may be desirable to obtain a more uniform radiated field. It
is believed that the energy transfer between the antenna and the
tissue to be ablated tends to increase by decreasing the coverage
angle of the reflector, and conversely, the energy transfer between
the antenna and the tissue to be ablated tends to decrease by
increasing the coverage angle of the reflector. Accordingly, the
shape of the reflector may be altered to balance out
non-uniformities found in the radiated field of the antenna
arrangement.
[0118] In another configuration, the directive component 73 for the
microwave antenna assembly 27 can be provided by another dielectric
material having a dielectric constant different than that of the
insulator material 67. Indeed, a strong reflection of
electromagnetic wave is observed when the wave reaches an interface
created by two materials with a different dielectric constant. For
example, a ceramic loaded polymer can have a dielectric constant
comprised between 15 and 55, while the dielectric of a
fluoropolymer like Teflon or is comprised between 2 and 3. Such an
interface would create a strong reflection of the wave and act as a
semi-reflector.
[0119] It should also be noted that the longitudinal length of the
reflector need not be uniform. That is, a portion of the reflector
may be stepped towards the antenna or a portion of the reflector
may be stepped away from the antenna. Stepping the reflector in
this manner may be desirable to obtain a more uniform radiated
field. While not wishing to be bound by theory, it is believed that
by placing the reflector closer to the antenna, a weaker radiated
field may be obtained, and that by placing the reflector further
away from the antenna, a stronger radiated field may be obtained.
Accordingly, the longitudinal length of the reflector may be
altered to balance out non uniformities found in the radiated field
of the antenna arrangement. These associated reflectors are
described in greater detail in U.S. patent application Ser. Nos.:
09/178,066, entitled "DIRECTIONAL REFLECTOR SHIELD ASSEMBLY FOR A
MICROWAVE ABLATION INSTRUMENT, and 09/484,548 entitled "A MICROWAVE
ABLATION INSTRUMENT WITH FLEXIBLE ANTENNA ASSEMBLY AND METHOD",
each of which is incorporated by reference.
[0120] In a typical microwave ablation system, it is important to
match the impedance of the antenna with the impedance of the
transmission line. As is well known to those skilled in the art, if
the impedance is not matched, the catheter's performance tends to
be well below the optimal performance. The decline in performance
is most easily seen in an increase in the reflected power from the
antenna toward the generator. Therefore, the components of a
microwave transmission system are typically designed to provide a
matched impedance. By way of example, a typical set impedance of
the microwave ablation system may be on the order of fifty (50)
ohms.
[0121] Referring back to FIGS. 10 and 11, and in accordance with
one embodiment of the present invention, an impedance matching
device 80 may be provided to facilitate impedance matching between
the antenna 60 and the transmission line 72. The impedance matching
device 80 is generally disposed proximate the junction between the
antenna 60 and the inner conductor 75. For the most part, the
impedance match is designed and calculated assuming that the
antenna assembly 27, in combination with the predetermined contact
surface 23 of the ablation sheath 22, is in resonance to minimize
the reflected power, and thus increase the radiation efficiency of
the antenna structure.
[0122] In one embodiment, the impedance matching device is
determined by using a Smith Abacus Model. In the Smith Abacus
Model, the impedance matching device may be ascertained by
measuring the impedance of the antenna with a network analyzer,
analyzing the measured value with a Smith Abacus Chart, and
selecting the appropriate device. By way of example, the impedance
matching device may be any combination of a capacitor, resistor,
inductor, stub tuner or stub transmission line, whether in series
or in parallel with the antenna. An example of the Smith Abacus
Model is described in Reference: David K. Cheng, "Field and Wave
Electromagnetics," second edition, Addison-Wesley Publishing, 1989,
which is incorporated herein by reference. In one preferred
implementation, the impedance matching device is a serial capacitor
having a capacitance in the range of about 0.6 to about 1.0
picoFarads. In the illustration shown, the serial capacitor has a
capacitance of about 0.8 picoFarads.
[0123] As above-mentioned, the impedance will be matched assuming
flush contact between the antenna assembly 27 and the ablation
sheath (FIG. 9). In accordance with the present invention, as the
antenna assembly 27 is advanced through the ablation lumen 25,
before selective ablation, it is desirable to position the window
portion 58 of the flexible antenna insulator 61 in flush contact
against the interior wall 62 of the ablation lumen 25, opposite the
predetermined contact surface 23. This arrangement may
substantially reduce the impedance variance caused by the interface
between insulator 61 and the ablation sheath 22 as the directional
field is transmitted therethrough. In comparison, if the window
portion 58 were not required to be positioned in flush contact
against the interior wall 62 of the ablation lumen, pockets of air
or fluid, or the like, may be disposed intermittently therebetween
which would result in a greater degree of impedance variations at
this interface. Consequently, the above-indicated impedance
matching techniques would be less effective.
[0124] To assure such flush contact during selective directional
ablation and advancement along the sheath ablation lumen, the
ablation system 20 preferably incorporates a forcing mechanism 81
(FIGS. 8 and 9) adapted to urge the window portion 58 of the
antenna assembly 27 into flush contact against the interior wall 62
of the ablation sheath. Preferably, the forcing mechanism
cooperates between a support portion 82 of the interior wall 62 of
the ablation lumen 25 and the forcing wall portion 83 of the
antenna assembly.
[0125] When not operational, the forcing mechanism permits relative
axial displacement between the ablative device 26 and the ablation
sheath for repositioning of the antenna assembly 27 along the
ablation path 28 (FIG. 8). Upon selective operation, the forcing
mechanism 81 contacts the forcing wall portion 83 to urge window
portion 58 flush against the interior wall 62 opposite the
predetermined contact surface 23. Consequently, the impedance match
between the antenna and the transmission line is properly achieved
and stable even when the antenna is moving in the ablation
sheath.
[0126] In one embodiment, the forcing mechanism may be provided by
an inflatable structure acting between the support portion 82 of
the interior wall 62 of the ablation lumen 25 and the forcing wall
portion 83 of the antenna assembly device. Upon selective inflation
of forcing mechanism 81 (FIG. 9), the window portion 58 will be
urged into flush contact with the interior wall 62 of the ablation
lumen. Upon selective deflation of the forcing mechanism 81 (FIG.
8), relative axial displacement between the antenna assembly 27 and
the ablation sheath may commence. The forcing mechanism can be
provided by other techniques such as spring devices or the
like.
[0127] In accordance with another aspect of the present invention,
the ablative energy may be in the form of laser energy sufficient
to ablate tissue. Example of such laser components include CO.sub.2
or Nd:YAG lasers. To transmit the beams, the transmission line 72
is preferably in the form of a fiber optic cable or the like.
[0128] In this design, as shown in FIGS. 14A and 14B, the directive
component 73 may be provided by a reflector having a well polished
smooth reflective or semi-reflective surface. This preferably
metallic reflective surface is configured to reflect the emitted
laser energy toward the targeted tissue region. By way of example,
functional metallic materials include silver or platinum. In
another configuration, similar to the difference in dielectric
constants of the microwave ablation device 26, the directive
component of the laser ablative device may be provided between two
layers of dielectric materials with a sufficient difference between
the refractory indexes. Here, at least one dielectric directive
component layer functions like the outer dielectric layer of the
fiber optic transmission line 72 to obtain "total internal
reflection". Consequently, the laser energy can be emitted away
from the dielectric layer. By providing more than one dielectric
layer, "total internal reflection" may be attained at several
angles of incidence. Again, the reflection of the electromagnetic
wave is caused by the interface between two media having different
dielectric constants. Generally speaking, the higher is the
difference between the dielectric constants, the more significant
is the internal reflection. In addition, when more than one
dielectric layer are involved, interference can be used to direct
the laser energy in a preferred direction.
[0129] Moreover, when the ablative energy is laser based, it will
be appreciated that it is desirable that both the ablation sheath
22 and the ablation device be composed of materials which have a
low scattering coefficient and a low factor of absorption. In
addition, it is also preferable to use material with low water
absorption.
[0130] It will be appreciated that a plurality of designs can be
used for the laser energy delivery portion. For example, the laser
energy delivery portion can consist of multiple reflective
particles embedded in a laser transparent material. The laser wave
is propagating from the laser generator to the optic fiber
transmission line and enter in the laser energy delivery portion.
The embedded reflective particles diffracts the light, which is
reflected toward the tissue to be ablated by the directive
component 73.
[0131] In yet another alternative embodiment, cryogenic energy may
be employed as an ablative energy. Briefly, as shown in FIGS. 15A
and 15B, in these cryogenic ablation device designs, a cryogenic
fluid, such as a pressurized gas (E.g., Freon) is passed through an
inflow lumen 90 in the ablation device transmission line 72. The
distal ablative device 26 is preferably provided by a decompression
chamber which decompresses the pressurized gas from the inflow
lumen 90 therein. Upon decompression or expansion of the
pressurized gas in the decompression chamber 91, the temperature of
the exterior surface 92 of the decompression chamber is
sufficiently reduced to cause tissue ablation upon contact thereof.
The decompressed gas is then exhausted through the outflow lumen 93
of the transmission line 72.
[0132] FIG. 15B illustrates that the directive component 73 is in
the form of a thermal insulation layer extending longitudinally
along one side of the energy delivery portion 27. By forming a good
thermal insulator with a low thermal conductivity, the C-shaped
insulation layer 73 will substantially minimize undesirable
cryogenic ablation of the immediate tissue surrounding of the
targeted tissue region. In one configuration, the isolation layer
may define a thin, elongated gap 95 which partially surrounds the
decompression chamber 91. This gap 95 may then be filled with air,
or an inert gas, such as CO.sub.2, to facilitate thermal isolation.
The isolation gap 95 may also be filled with a powder material
having relatively small solid particulates or by air expended
polymer. These materials would allow small air gaps between the
insulative particles or polymeric matrix for additional insulation
thereof. The isolation layer may also be provided by a refractory
material. Such materials forming an insulative barrier include
ceramics, oxides, etc.
[0133] Referring now to FIG. 16, an ultrasound ablation device may
also be applied as another viable source of ablation energy. For
example, a piezoelectric transducer 96 may be supplied as the
ablative element which delivers acoustic waves sufficient to ablate
tissue. These devices emit ablative energy which can be directed
and shaped by applying a directive echogenic component to reflect
the acoustic energy. Moreover, a series or array of piezoelectric
transducers 96, 96' and 96" can be applied to collectively form a
desired radiation pattern for tissue ablation. For example, by
adjusting the delay between the electrical exciting signal of one
transducer and its neighbor, the direction of transmission can be
modified. Typical of these transducers include piezoelectric
materials like quartz, barium oxides, etc.
[0134] In this configuration, the directive component 73 of the
ultrasonic ablation device may be provided by an echogenic material
(73-73") positioned proximate the piezoelectric transducers. This
material reflects the acoustic wave and which cooperates with the
transducers to direct the ablative energy toward the targeted
tissue region. By way of example, such echogenic materials are
habitually hard. They include, but are not restricted to metals and
ceramics for example.
[0135] Moreover, when the ablative energy is ultrasonic based, it
will be appreciated that it is desirable that both the ablation
sheath 22 and the ablation device be composed of materials which
have low absorption of the acoustic waves, and that provide a good
acoustic impedance matching between the tissue and the transducer.
In that way, the thickness and the material chosen for the ablation
sheath play in important role to match the acoustic properties of
the tissue to be ablated and the transducer. An impedance matching
jelly can also be used in the ablation sheath to improve the
acoustic impedance matching.
[0136] Lastly, the ablation device may be provided by a
radiofrequency (RF) ablation source which apply RF conduction
current sufficient to ablate tissue. These conventional ablation
instruments generally apply conduction current in the range of
about 450 kHz to about 550 kHz. Typical of these RF ablation
devices include ring electrodes, coiled electrodes or saline
electrodes.
[0137] To selectively direct the RF energy, the directive component
is preferably composed of an electrically insulative and flexible
material, such as plastic or silicone. These biocompatible
materials perform the function of directing the conduction current
toward a predetermined direction.
[0138] In an alternative embodiment, as best viewed in FIG. 17, the
window portion 58 of the ablation sheath 22 is provided by an
opening in the sheath along the ablation path, as opposed to being
merely transparent to the energy ablation devices. In this manner,
when the ablation sheath 22 is properly positioned with the window
portion placed proximate and adjacent the targeted tissue, the
energy delivery portion 27 of the ablation device 26 may be
slideably positioned into direct contact with the tissue for
ablation thereof. Such direct contact is especially beneficial when
it is technically difficult to find a sheath that is merely
transparent to the used ablative energy. For example, it would be
easier to use a window portion when RF energy is used. The ablative
RF element could directly touch the tissue to be ablated while the
directive element would be the part of the ablation sheath 22
facing away the window portion 58. Furthermore, during surgical
ablation, the window portion could be used by the surgeon to
indicate the area where an ablation can potentially be done with
the energy ablation device.
[0139] In yet another embodiment, the ablation system 20 may be in
the form of a rail system including a rail device 96 upon which the
ablation device 26 slides therealong as compared to therethrough.
FIGS. 18 and 19 illustrate the rail device 96 which is preferably
pre-shaped or bendable to proximately conform to the surface of the
targeted tissue. Once the rail device 96 is positioned, the
ablation device can be advanced or retracted along the path defined
by the rail device for ablation of the targeted tissue 21.
[0140] The ablation device 26 in this arrangement includes a body
portion 98 housing the energy delivery portion 27 therein. The
window portion 58 is preferably extend longitudinally along the
outer surface of one side of the housing. An opposite side of the
housing, and longitudinally oriented substantially parallel to the
window portion 58 is a rail receiving passage 97 formed and
dimensioned to slideably receive and slide over the rail device 96
longitudinally therethrough. In one configuration, the energy
delivery portion 27 may be advanced by pushing the body portion 98
through the transmission line 72. Alternatively, the energy
delivery portion 27 may be advanced by pulling the body portion 98
along the path of the rail system 20.
[0141] As best viewed in FIG. 19, the directive component 73 of the
ablation device 26 is integrally formed with the body portion 98 of
the ablation device. This preferably C-shaped component extends
partially peripherally around the energy delivery portion 27 to
shield the rail device 96 from exposure to the ablative energy.
Depending upon the type of ablative energy employed, the material
or structure of the directive component 73 can be constructed as
set forth above.
[0142] To assure the directional position and orientation of the
window portion 58 of the ablative device toward the targeted
tissue, a key structure 48 is employed. Generally, the transverse
cross-sectional dimension of the rail device 96 and matching rail
receiving passage 97 is shaped to assure proper directional
orientation of the ablative energy. Examples of such key forms are
shown in FIGS. 20A-20B.
[0143] As with the previous embodiments, the open window embodiment
and the rail system embodiment may employ multiple ablative element
technology. These include microwave, radiofrequency, laser,
ultrasound and cryogenic energy sources.
[0144] In accordance with another aspect of the present invention,
the tissue ablation system further includes a temperature sensor
which is applied to measure the temperature of the ablated tissue
during the ablation. In one embodiment, the temperature sensor is
mounted to the ablation device proximate the energy delivery
portion 27 so that the sensor moves together with the energy
delivery portion as it is advanced through the ablation sheath. In
another embodiment, the temperature sensor is attached on the
ablation sheath.
[0145] To determine the temperature of the ablated tissue, a
mathematical relationship is used to calculate the tissue
temperature from the measured temperature. Typical of such
temperature sensors include a metallic temperature sensor, a
thermocouple, a thermistor, or a non-metallic temperature sensor
such as fiber optic temperature sensor.
[0146] In accordance with the present invention, the guide sheath
52 and the ablation sheath 22 can be designed and configured to
steer the ablative device along any three dimensional path. Thus,
the tissue ablation system of present invention may be adapted for
an abundance of uses. For instance, the distal end portion of the
ablation sheath can be configured to form a closed ablation path
for the ablation device. This design may be employed to ablate
around an ostium of an organ, or to electrically isolate one or
several pulmonary veins to treat atrial fibrillation. A closed
ablation path may also utilized to ablate around an aneurysm, such
as a cardiac aneurysm or tumor, or any kink of tumor. In other
example, the ablation sheath can be inserted in an organ in order
to ablate a deep tumor or to perform any surgical treatment where a
tissue ablation is required.
[0147] In other instances, the distal end portion of the ablation
sheath 22 may define a rectilinear or curvilinear open ablation
path for the ablation device. Such open ablation paths may be
applied to ablate on the isthmus between the inferior caval vein
(IVC) and the tricuspid valve (TV), to treat regular flutter, or to
generate a lesion between the IVC and the SVC, to avoid
macro-reentry circuits in the right atrium. Other similar ablation
lesions can be formed between: any of the pulmonary vein ostium to
treat atrial fibrillation; the mitral valve and one of the
pulmonary veins to avoid macro-reentry circuit around the pulmonary
veins in the left atrium; and the left appendage and one of the
pulmonary veins to avoid macro-reentry circuit around the pulmonary
veins in the left atrium.
[0148] The ablation apparatus may be applied through several
techniques. By way of example, the ablation apparatus may be
inserted into the coronary circulation to produce strategic lesions
along the endocardium of the cardiac chambers (i.e., the left
atrium, the right atrium, the left ventricle or the right
ventricle). Alternatively, the ablation apparatus may be inserted
through the chest to produce epicardial lesions on the heart. This
insertion may be performed through open surgery techniques, such as
by a sternotomy or a thoracotomy, or through minimally invasive
techniques, applying a cannula and an endoscope to visualize the
location of the ablation apparatus during a surgery.
[0149] The ablation apparatus is also suitable for open surgery
applications such as ablating the exterior surfaces of an organ as
well, such as the heart, brain, stomach, esophagus, intestine,
uterus, liver, pancreas, spleen, kidney or prostate. The present
invention may also be applied to ablate the inside wall of hollow
organs, such as heart, stomach, esophagus, intestine, uterus,
bladder or vagina. When the hollow organ contains bodily fluid, the
penetration port formed in the organ by the ablation device must be
sealed to avoid a substantial loss of this fluid. By way of
example, the seal may be formed by a purse string, a biocompatible
glue or by other conventional sealing devices.
[0150] As mentioned, the present invention may be applied in an
intra-coronary configuration where the ablation device is used to
isolate the pulmonary vein from the left atrium. FIG. 2C
illustrates that a distal end of the ablation sheath 22 is adapted
for insertion into the pulmonary vein. In this embodiment, the
distal end of the ablation device may include at least one
electrode used to assess the electrical isolation of the vein. This
is performed by pacing the distal electrode to "capture" the heart.
If pacing captures the heart, the vein is not yet electrically
isolated, while, if the heart cannot be captured, the pulmonary
vein is electrically isolated from the left atrium. As an example,
a closed annular ablation on the posterior wall of the left atrium
around the ostium of the pulmonary vein by applying the pigtail
ablation sheath 22 of FIGS. 2 and 4.
[0151] In yet another configuration, the ablation device may
include a lumen to inject a contrasting agent into the organ. For
instance, the contrasting agent facilitates visualization of the
pulmonary vein anatomy with a regular angiogram technique. This is
important for an intra-coronary procedure since fluoroscopy is used
in this technique. The premise, of course, is to visualize the
shape and the distal extremity of the sheaths, as well as the
proximal and distal part of the sliding energy delivery portion
during an ablative procedure under fluoroscopy. It is essential for
the electrophysiologist to be able to identify not only the
ablative element but also the path that the ablation sheath will
provide to guide the energy delivery portion 27 therealong.
[0152] Another visualization technique may be to employ a plurality
of radio-opaque markers spaced-apart along the guide sheath to
facilitate location and the shape thereof. By applying the
radio-opaque element that will show the shape of the sheath. This
element can be a metallic ring or soldering such as platinum which
is biocompatible and very radio-opaque. Another example of a
radio-opaque element would be the application of a radio-opaque
polymer such as a beryllium loaded material. Similarly,
radio-opaque markers may be disposed along the proximal, middle and
distal ends of the energy delivery portion 27 to facilitate the
visualization and the location of the energy delivery portion when
the procedure is performed under fluoroscopy.
[0153] To facilitate identification of the distal end portion of
the ablation sheath, a fluoro-opaque element may be placed at the
distal extremity. Another implementation of this concept would be
to have different opacities for the ablation sheath and the energy
delivery portion 27. For example, the energy delivery portion may
be more opaque than that of the ablation sheath, and the ablation
sheath may be more opaque than the transseptal sheath, when the
latter is used.
[0154] The surgical ablation device of the present invention may
also be applied minimally invasively to ablate the epicardium of a
beating heart through an endoscopic procedure. As view in FIGS. 21
and 22, at least one intercostal port 85 or access port is formed
in the thorax. A dissection tool (not shown) or the like may be
utilized to facilitate access the pericardial cavity. For instance,
the pericardium may be dissected to enable access to the epicardium
of a beating heart. The pericardial reflections may be dissected in
order to allow the positioning of the ablation device 26 around the
pulmonary veins. Another dissection tool (not shown) may also be
utilized to puncture the pericardial reflection located in
proximity to a pulmonary vein. After the puncture of the
pericardial reflection, the ablation sheath can be positioned
around one, or more than one pulmonary veins, in order to produce
the ablation pattern used to treat the arrhythmia, atrial
fibrillation in particular.
[0155] For example, a guide sheath 52 may be inserted through the
access port 85 while visualizing the insertion process with an
endoscopic device 86 positioned in another access port 87. Once the
guide sheath 52 is properly positioned by handle 88, the ablation
sheath 22 may be inserted through the guide sheath, while again
visualizing the insertion process with the endoscopic system to
position the ablation sheath on the targeted tissue to ablate. The
ablation device may then be slid through the ablation lumen of the
ablation sheath and adjacent the targeted tissue. Similar to the
previous ablation techniques, the ablative element of the ablation
device may be operated and negotiated in an overlapping manner to
form a gap free lesion or a plurality of independent lesions. The
ablation sheath may also be malleable or flexible. The surgeon can
use a surgical instrument, like a forceps, to manipulate, bend and
position the ablation sheath.
[0156] In accordance with yet another aspect of the present
invention, the guide sheath, ablation sheath, or ablation element
could be controlled by a robot during a robotic minimally invasive
surgical procedure. The robot could telescopically translate or
rotate the guide sheath, the ablation sheath, or the ablation
element in order to position the ablation sheath and the ablation
element correctly to produce the ablation of tissue. The robot
could also perform other tasks to facilitate the access of the
ablation sheath to the tissue to be ablated. These tasks include,
but are not limited to: performing the pericardial reflection in
the area of a pulmonary vein; performing an incision on the
pericardial sac; manipulating, bending or shaping the ablation
sheath; or performing an incision on an organ to penetrate the
ablation sheath through the penetration hole.
[0157] In accordance with yet another aspect of the present
invention, the concept of using a sliding ablation element in an
ablation sheath to ablate from the epicardium of a beating heart
can also be applied in open chest surgery. In this procedure, a
malleable ablation sheath may be beneficial, as compared to a
pre-shaped ablation sheath. For example, a malleable metallic wire
(e.g., copper, stainless steel, etc.) could be integrated into the
ablation sheath. The cardiac surgeon will then shape the ablation
sheath to create the ablation path that he wants and will finally
produce the ablation line by overlapping several ablations
[0158] In this technique, it is important to note that the ablation
sheath must be stabilized against the epicardium since the ablation
sheath will define the ablation path of the energy delivery
portion. Should the ablation sheath be inadvertently move during
the process, the final ablation line may be undesirably
discontinuous. Thus, a securing device may be applied to secure the
ablation sheath against the epicardium. Such a securing device may
include stitches or the like which may be strung through receiving
holes or cracks placed in the ablation sheath. Another device to
anchor the ablation sheath to the epicardium may be in the form of
a biocompatible adhesive, or a suction device.
[0159] In accordance with yet another aspect of the present
invention, a way to visually locate the ablation element within the
ablation sheath is provided to the surgeon. In one embodiment of
the invention, the ablation sheath is transparent and the ablation
element can be directly visualized, or indirectly visualized via an
endoscope. In yet another embodiment of the application, a marking
element that can be directly visually identify along the ablation
sheath, or indirectly visualized via an endoscope, is used to
identify the location of the ablation element within the sheath.
The marking element is sliding with the ablation element to show
the location of the ablation element.
[0160] In accordance with yet another aspect of the present
invention, a way to indirectly locate the ablation element within
the ablation sheath is provided to the surgeon. A position finding
system is incorporated in the handle of the device to indicate the
position of the ablation element within the ablation sheath. At
least one marker can be directly visually, or indirectly visually
identified. These markers can be used in collaboration with the
position finding system as reference points to identify the
location of the ablation element.
[0161] While the present invention has been primarily described and
applied for epicardial tissue ablations, it will be appreciated
that the ablation system 20 may just as easily apply to endocardial
tissue ablations as well. The tissue ablations may be performed
through either open surgery techniques or through minimal invasive
techniques.
[0162] Although the foregoing invention has been described in some
detail for purposes of clarity of understanding, it will be
apparent that certain changes and modifications may be practiced
within the scope of the appended claims.
* * * * *