U.S. patent application number 10/158435 was filed with the patent office on 2002-10-03 for surgical devices and methods for use in tissue ablation procedures.
This patent application is currently assigned to Lotek, Inc.. Invention is credited to Adelman, Thomas G., Foley, Frederick J., Hoey, Michael F., Reeve, Lorraine E., Sharrow, James S..
Application Number | 20020143326 10/158435 |
Document ID | / |
Family ID | 27539057 |
Filed Date | 2002-10-03 |
United States Patent
Application |
20020143326 |
Kind Code |
A1 |
Foley, Frederick J. ; et
al. |
October 3, 2002 |
Surgical devices and methods for use in tissue ablation
procedures
Abstract
Devices and a method are provided to assist a surgeon in
ablating conduction paths in tissue, such as a heart. A device can
be configured to operate as a template that adheres to the tissue
surface, and allows the surgeon to more easily sever the conduction
path to form a lesion in a desired location. In particular, the
template can be used to guide the surgeon's use of a surgical
instrument along a desired ablation path. In some case, the
template may incorporate hardware that structurally supports the
instrument for travel along the ablation path. A surgical
instrument such as an ablation probe, e.g., radio frequency, laser,
ultrasonic, microwave, thermal, chemical, mechanical, or cryogenic
ablation probe, may be used to sever the conduction paths.
Measurements made substantially contemporaneously with the
conduction path ablation operation may be used to evaluate whether
the desired degree of ablation has been achieved. The device may
also incorporate feedback to compare the desired degree of
conduction path ablation with the measured degree, and may
deactivate the surgical instrument when the desired degree has been
achieved. In some cases, the template device can be configured to
provide local stabilization of organ tissue, particularly for a
moving organ such as a beating heart. In other cases, the template
device may provide little or no stabilization, but provide a guide
structure for placement of the ablation probe in the same frame of
motion as the moving tissue. Also, for some applications, the
template device may be arranged to facilitate application of other
therapeutic devices, such as diagnostic probes, pacing leads, and
drug delivery devices, to the surface of a moving organ.
Inventors: |
Foley, Frederick J.;
(Bedford, NH) ; Sharrow, James S.; (Bloomington,
MN) ; Reeve, Lorraine E.; (Dexter, MI) ;
Adelman, Thomas G.; (West Baldwin, ME) ; Hoey,
Michael F.; (Shoreview, MN) |
Correspondence
Address: |
SHUMAKER & SIEFFERT, P. A.
8425 SEASONS PARKWAY
SUITE 105
ST. PAUL
MN
55125
US
|
Assignee: |
Lotek, Inc.
Edina
MN
|
Family ID: |
27539057 |
Appl. No.: |
10/158435 |
Filed: |
May 28, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10158435 |
May 28, 2002 |
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09649998 |
Aug 28, 2000 |
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60217304 |
Jul 11, 2000 |
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60206081 |
May 22, 2000 |
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60190411 |
Mar 17, 2000 |
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60181895 |
Feb 11, 2000 |
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Current U.S.
Class: |
606/41 ; 606/10;
606/21 |
Current CPC
Class: |
A61B 2017/22067
20130101; A61B 2018/00291 20130101; A61B 2018/0022 20130101; A61B
2017/320052 20130101; A61B 2017/003 20130101; A61B 18/1492
20130101; A61B 2018/00261 20130101; A61B 2018/00214 20130101; A61B
2018/00285 20130101; A61B 2018/00875 20130101; A61B 2018/1475
20130101; A61B 2017/0243 20130101 |
Class at
Publication: |
606/41 ; 606/10;
606/21 |
International
Class: |
A61B 018/18 |
Claims
1. A surgical device for use in a tissue ablation procedure, the
device comprising a contact member that engages tissue near a
location where the tissue is to be ablated, the contact member
defining a guide that indicates, upon engagement of the contact
member with the tissue, a location where tissue is to be ablated,
and provides a path for travel of a tissue ablation device.
2. The device of claim 1, wherein the contact member includes a
substantially compliant and tacky interface element for engagement
with the tissue.
3. The device of claim 2, wherein the contact member includes a
frame formed of a material that is substantially more rigid that
the interface element, the interface element being coupled to the
frame.
4. The device of claim 1, further comprising a length indicator
formed on the contact member that indicates a desired tissue
ablation length along the path for travel of the tissue ablation
device.
5. The device of claim 4, wherein the length indicator includes one
or more visible markings.
6. The device of claim 4, wherein the length indicator includes a
stop structure formed on the contact member, the stop structure
extending into the path for travel of the ablation device and being
oriented for abutment with the ablation device.
7. The device of claim 1, further comprising a length indicator
along the contact member, the length indicator indicating a desired
lesion length.
8. The device of claim 1, wherein a portion of the contact member
that engages the tissue is curved to allow the contact member to
conform to the shape of the tissue.
9. The device of claim 8, wherein a portion of the contact member
that engages the heart is curved to allow the contact member to
conform to the shape of the heart.
10. The device of claim 1, wherein the contact member defines an
interior chamber and a vacuum port in fluid communication with the
interior chamber, the interior chamber being capable of delivering
vacuum pressure to the contact member to thereby promote
vacuum-assisted adherence of the contact member to the tissue.
11. The device of claim 1, wherein the contact member defines an
interior chamber, the device further comprising a vacuum port in
fluid communication with the interior chamber, the vacuum port
allowing connection to a source of vacuum pressure to provide
vacuum pressure to the contact member and thereby promote
vacuum-assisted adherence to the tissue.
12. The device of claim 1, wherein the contact member includes an
adhesive material that promotes adherence of the contact member to
the tissue.
13. The device of claim 1, wherein the contact member includes an
adhesive material that promotes repositionable adherence of the
contact member to the tissue.
14. The device of claim 1, further comprising an adhesive member
that extends outward from the contact member for engagement with
the tissue, the adhesive member being sufficiently compliant and
tacky so as to promote adhesion of the contact member to a beating
heart.
15. The device of claim 1, wherein the contact member is
substantially annular-shaped, the device further comprising a
skirt-like member that extends outward from the annular-shaped
contact member for contact with the tissue, the skirt-like member
being substantially compliant and tacky, thereby promoting adhesion
of the contact member with the tissue.
16. The device of claim 15, wherein the skirt-like member is formed
from a compliant, tacky silicone gel.
17. The device of claim 1, wherein the contact member is
substantially annular-shaped.
18. The device of claim 1, wherein the contact member is
substantially U-shaped.
19. The device of claim 1, wherein the contact member includes a
first contact foot and a second contact foot extending outward from
a common shaft, each of the first foot and the second foot
including a compliant and tacky material that promotes adhesion of
the contact member to the tissue.
20. The device of claim 1, wherein the contact member defines an
opening through which the tissue may be accessed, and a port for
removal of fluid proximate the tissue surface.
21. The device of claim 1, wherein the contact member is
substantially ring-shaped and includes an annular chamber, the
device further comprising a vacuum port in fluid communication with
the annular chamber for delivery of vacuum pressure to the chamber,
thereby promoting vacuum-assisted adherence of the contact member
to the tissue.
22. The device of claim 21, wherein the substantially ring-shaped
contact member includes an outer diameter edge and an inner
diameter edge, the device further comprising an inner skirt-like
member coupled to the inner diameter edge and an outer skirt-like
member coupled to the outer diameter edge, the skirt-like members
being substantially compliant and tacky to promote adhesion of the
contact member to the tissue.
23. The device of claim 22, wherein the skirt-like members are
formed from a compliant, tacky silicone gel.
24. The device of claim 1, wherein the contact member is
substantially U-shaped and defines a substantially U-shaped
chamber, the device further comprising a vacuum port in fluid
communication with the chamber for delivery of vacuum pressure to
the chamber, thereby promoting vacuum-assisted adherence of the
contact member to the tissue.
25. The device of claim 24, further comprising a skirt-like member
coupled to the contact member at a periphery of the chamber, the
skirt-like member being substantially compliant and tacky to
promote adhesion of the contact member to the tissue.
26. The device of claim 25, wherein the adhesive material is formed
from a compliant, tacky silicone gel.
27. The device of claim 1, further comprising a sensor that
indicates whether a desired degree of tissue ablation has been
achieved.
28. The device of claim 27, wherein the sensor includes a first
electrode capable of transmitting a first electrical signal and a
second electrode capable of receiving a second electrical
signal.
29. The device of claim 28, wherein the first electrode is disposed
adjacent a first side of the contact member and the second
electrode is disposed adjacent a second side of the contact member
opposite the first side, whereby first and second electrodes are
disposed on opposite sides of the location for ablation during use
of the device.
30. The device of claim 28, wherein the distance between the first
electrode and the second electrode is known.
31. The device of claim 28, wherein the distance between the first
electrode and the second electrode is relatively fixed.
32. The device of claim 28, wherein the sensor includes apparatus
electrically coupled to the electrodes to measure at least one of
conduction time, conduction distance and conduction velocity based
on the second electrical signal.
33. The device of claim 28, wherein the sensor includes apparatus
electrically coupled to the electrodes to measure at least one of
phase angle and impedance.
34. The device of claim 28, further comprising a processor coupled
to at least the second electrode, the processor receiving signals
from the second electrode and, based on the signals, determining
whether the desired ablation has been achieved to a satisfactory
degree.
35. The device of claim 34, wherein the processor includes one of a
computer, microprocessor, a microcontroller, and discrete logic
circuitry arranged to measure the extent of the tissue ablation
procedure based on the signals received from the second
electrode.
36. The device of claim 34, further comprising a measurement device
coupled to the first electrode and the second electrode, wherein
the first electrode and the second electrode serve as probes for
the measurement device.
37. The device of claim 36, wherein the processor is electrically
coupled to the measurement device, the measurement device
transmitting data to the processor based on signals generated at
the second electrode.
38. The device of claim 36, wherein the processor controls the
operation of the measurement device.
39. The device of claim 34, wherein the processor is coupled to an
input device.
40. The device of claim 34, wherein the processor is coupled to an
output device.
41. The device of claim 34, wherein the processor controls the
activation of a tissue ablation device that performs the ablation
procedure.
42. The device of claim 41, wherein the processor deactivates the
tissue ablation device based upon the data received from the
measurement device.
43. The device of claim 28, further comprising a processor coupled
to receive an indication of signals generated at the second
electrode, the processor measuring the extent of the tissue
ablation procedure based on the signals.
44. An apparatus for determining whether conduction paths within
heart tissue have been adequately severed during a surgical
procedure, the apparatus comprising a first electrode capable of
transmitting a first electrical signal adjacent the tissue to be
severed; a second electrode capable of receiving a second
electrical signal adjacent the tissue to be severed; a measuring
device electrically coupled to at least the second electrode to
receive the second electrical signal from the second electrode, the
measuring device determining the extent to which the tissue has
been severed; and an output device that provides an indication of
extent to which the tissue is severed.
45. The apparatus of claim 44, wherein the measuring device
includes a measuring circuit that generates a third electrical
signal indicating the degree of tissue severing, and a processor
that determines whether the tissue has been adequately severed
based on the third electrical signal.
46. The apparatus of claim 44, wherein the measuring device
measures at least one of electrical conduction time, electrical
conduction distance and electrical conduction velocity through the
severed tissue based on the second electrical signal.
47. The apparatus of claim 44, wherein the measuring device
measures at least one of phase angle and impedance based on the
second electrical signal.
48. The apparatus of claim 44, wherein the first electrode is
disposed on a first side of tissue to be severed and the second
electrode is disposed on a second side of the tissue to be severed
opposite the first side.
49. The apparatus of claim 44, wherein the distance between the
first electrode and the second electrode is known.
50. The apparatus of claim 44, wherein the distance between the
first electrode and the second electrode is relatively fixed.
51. The apparatus of claim 44, wherein the first electrode and the
second electrode serve as probes for the measuring device.
52. The apparatus of claim 44, further comprising a processor
coupled to at least the second electrode the processor receiving
signals from the second electrode and, based on the signals,
determining whether the desired ablation has been achieved to a
satisfactory degree.
53. A method for ablation of conduction paths within tissue
comprising: placing a first device near the target conduction paths
to be severed, using the first device as a guide for an ablation
probe to sever the target conduction paths, and measuring
electrical tissue characteristics proximate the target conduction
paths to determine whether the desired severing has been
achieved.
54. The method of claim 53, wherein the first device and the second
device are coupled to one another.
55. The method of claim 53, wherein measuring comprises measuring
at least one of phase angle and impedance.
56. The method of claim 53, wherein measuring comprises measuring
at least one of conduction time, conduction distance or conduction
velocity.
57. The method of claim 53, further comprising comparing the
desired degree of ablation with the measured degree of
ablation.
58. The method of claim 53, further comprising discontinuing
ablation when the desired degree of ablation has been achieved.
59. The method of claim 58, further comprising automatically
discontinuing ablation when the desired degree of ablation has been
achieved.
60. A method for determining the effectiveness of a tissue ablation
procedure in ablation conduction paths in the heart, the method
comprising: measuring at least one of electrical impedance and
electrical phase angle across the ablated tissue; and determining
the effectiveness of the tissue ablation procedure based on the
measurement.
61. The method of claim 60, further comprising prior to ablation,
disposing a first electrode on a first side of tissue to be ablated
and disposing a second electrode on a second side of the tissue,
the second side being opposite the first side following
ablation.
62. The method of claim 61, further comprising measuring the
distance between the electrodes.
63. The method of claim 61, further comprising prior to ablation
measuring electrical impedance between the electrodes, this
measurement to serve as a baseline measurement.
64. The method of claim 61, further comprising prior to ablation
measuring phase angle between the electrodes, this measurement to
serve as a baseline measurement.
65. The method of claim 60, further comprising calculating an
impedance value that will be measured when the tissue ablation
procedure has been effectively performed.
66. The method of claim 60, further comprising performing tissue
ablation and discontinuing tissue ablation when a predetermined
impedance is measured.
67. The method of claim 60, further comprising calculating a phase
angle value that will be measured when the tissue ablation
procedure has been effectively performed.
68. The method of claim 60, further comprising performing tissue
ablation and discontinuing tissue ablation when a predetermined
phase angle is measured.
69. A method for determining the effectiveness of a tissue ablation
procedure in ablation conduction paths in the heart, the method
comprising: measuring at least one of electrical conduction
velocity, electrical conduction time, and electrical conduction
distance across the ablated tissue as a parameter; and determining
the effectiveness of the tissue ablation procedure based on the
measured parameter.
70. The method of claim 69, further comprising prior to ablation,
disposing a first electrode on a first side of tissue to be ablated
and disposing a second electrode a second side of the tissue, the
second side being opposite the first side following ablation.
71. The method of claim 69, further comprising measuring the
distance between the electrodes.
72. The method of claim 69, further comprising prior to ablation,
measuring at least one of electrical conduction velocity,
electrical conduction time, and electrical conduction distance,
this measurement to serve as a baseline measurement.
73. The method of claim 69, further comprising calculating a value
that will be measured when the tissue ablation procedure has been
effectively performed, of at least one of electrical conduction
velocity, electrical conduction time, and electrical conduction
distance.
74. The method of claim 69, further comprising performing tissue
ablation and discontinuing tissue ablation when a predetermined
value is measured of at least one of electrical conduction
velocity, electrical conduction time, and electrical conduction
distance.
75. A method for ablating heart tissue to ablate conduction paths,
the method comprising: placing a guide in contact with the tissue
to be ablated; applying an ablation probe to the tissue using the
guide to assist in control of movement of the ablation probe;
measuring the effectiveness of the ablation probe in ablation of
the conduction paths; and deactivating the ablation probe when the
measured effectiveness meets a desired level.
76. The method of claim 75, wherein measuring the effectiveness of
the ablation probe in ablation of the conduction paths includes
measuring at least one of electrical impedance, electrical phase
angle, electrical conduction velocity, electrical conduction time,
and electrical conduction distance across the tissue to be
ablated.
77. The method of claim 75, wherein measuring the effectiveness of
the ablation probe in ablation of the conduction paths includes
measuring impedance across the tissue to be ablated.
78. The method of claim 75, wherein measuring the effectiveness of
the ablation probe in ablation of the conduction paths includes
measuring the phase angle across the tissue to be ablated.
79. The method of claim 75, wherein the measurement is made using
electrodes that are structurally integrated with the guide.
80. The method of claim 75, wherein the ablation probe is
deactivated automatically when the measured effectiveness meets a
desired level.
81. A tissue ablation system, the system comprising: an ablation
probe that generates energy for ablation of the tissue at an
ablation site; a contact member for engagement with the tissue
adjacent the ablation site, the contact member defining a guide for
movement of the ablation probe during tissue ablation; first and
second electrodes integrated with the contact member, the
electrodes being disposed on opposite sides of the ablation site; a
measurement device that measures at least one of electrical
impedance, electrical phase angle, electrical conduction velocity,
electrical conduction time, and electrical conduction distance
across the ablation site to measure an extent of the ablation
procedure; and a controller that deactivates the ablation probe
when the measurement device measures an extent of the ablation
procedure that meets a desired level.
82. A method for performing surgery on moving organ tissue
comprising: affixing a contact member on a moving tissue surface;
providing a surgical instrument that is attached to the contact
member to place the surgical instrument in substantially the same
frame of motion as the tissue surface; and performing a surgical
procedure with the surgical instrument.
83. The method of claim 82, wherein the moving organ tissue is
beating heart tissue.
84. The method of claim 82, wherein the surgical instrument is an
ablation probe, and performing the surgical procedure includes
forming a tissue lesion with the ablation probe to sever desired
conduction paths within the tissue.
85. The method of claim 84, wherein the ablation probe includes one
of a radio frequency, laser, ultrasonic, microwave, thermal,
chemical, mechanical, and cryogenic ablation probe.
86. The method of claim 84, further comprising moving the ablation
probe along the tissue surface relative to the contact member to
form the tissue lesion along a desired ablation track.
87. A surgical device for use on moving organ tissue, the device
comprising: a contact member for affixation to a tissue surface;
and a surgical instrument mounted on the contact member, thereby
placing the surgical instrument in substantially the same frame of
motion as the tissue surface.
88. The device of claim 87, wherein the surgical instrument is an
ablation probe that forms a tissue lesion to sever desired
conduction paths within the tissue.
89. The device of claim 84, wherein the ablation probe includes one
of a radio frequency, laser, ultrasonic, microwave, thermal,
chemical, mechanical, and cryogenic ablation probe.
90. The device of claim 84, further comprising moving the ablation
probe along the tissue surface relative to the contact member to
form the tissue lesion along a desired ablation track.
Description
RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Application Serial No. 60/217,1304, filed Jul. 11, 2000; U.S.
Provisional Application Serial No. 60/206,081, filed May 22, 2000;
U.S. Provisional Application Serial No. 60/190,411, filed Mar. 17,
2000; and U.S. Provisional Application Serial No. 60/181,895, filed
Feb. 11, 2000, the entire content of each of which is incorporated
herein by reference.
TECHNICAL FIELD
[0002] The invention generally relates to surgical devices and,
more particularly, to surgical devices and methods for use in
procedures performed on moving tissue.
BACKGROUND
[0003] Some forms of surgery involve ablation to kill tissue in an
organ in order to achieve a therapeutic result. Ablation can be
achieved by various techniques, including the application of radio
frequency energy, lasers, cryogenic probes, and ultrasound. Thus,
the term "ablation," as used herein refers to any of a variety of
methods used to kill tissue within an organ. To be successful,
ablation treatment may require considerable precision. The surgeon
must target a particular region, and be careful not to cause
unnecessary trauma to other areas of the patient's body near the
target area. Just as important, the surgeon must be confident that
the procedure within the target area has been appropriately
performed. For example, the surgeon may need to determine whether
the tissue has been ablated to an appropriate degree. The surgery
may be made more difficult if the target area is moving.
[0004] One such surgical procedure in which a surgeon may wish to
ablate moving tissue is an operation to correct an abnormal
heartbeat. To function efficiently, the heart atria must contract
before the heart ventricles contract. As blood returns to the heart
and enters the atria, blood also flows through the atrioventricular
(AV) valves and partially fills the ventricles. Following an
electrical excitation by the sinoatrial (SA) node, the atria
contract in unison, expelling blood into the ventricles to complete
ventricular filling. The ventricles then become excited and
contract in unison. Ventricular contraction ejects the blood out of
the heart. Blood ejected from the right ventricle enters the
pulmonary arteries for oxygenation by the lungs, and blood ejected
from the left ventricle enters the main aorta and is distributed to
the rest of the body. If the timing of cardiac functions is
impaired, such as by the atria not contracting in unison or by the
ventricles contracting prematurely, then the operation of the heart
is impaired.
[0005] The synchronization of heart functions is initiated by an
excitation from the SA node, which is the heart's natural
pacemaker. The excitation propagates along an interatrial pathway,
extending from the SA node in the right atrium to the left atrium.
The excitation then spreads across gap junctions throughout the
atria, causing the atria to contract in unison. The excitation
further travels down an internodal pathway to the AV node, which
transmits the excitation to the ventricles along the bundle of His
and across the myocardium via the Purkinje fibers. In an aging
heart, the atria may stretch, and the conduction paths by which the
excitations travel may become lengthened. As a result, the
excitations have a longer distance to travel, and this may affect
the timing of the heart contractions and may create an arrhythmia.
The term "arrhythmia" is used to describe any variation from normal
rhythm and sequence of excitation of the heart.
[0006] One form of arrhythmia is atrial fibrillation. Atrial
fibrillation is characterized by chaotic and asynchronized atrial
cell contractions resulting in little or no effective blood pumping
into the ventricle. Ventricular contractions are not synchronized
with atrial contractions, and ventricular beats may come so
frequently that the heart has little time to fill with blood
between beats. Atrial fibrillation may occur if conduction blocks
form within the tissue of the heart, causing the electrical
excitations to degenerate into flurries of circular wavelets, or
"reentry circuits," which interfere with atrial activity.
Initiation or maintenance of atrial fibrillation may be facilitated
if atria become enlarged. Atrial enlargement increases the time
required for the electrical impulse to travel across the atria.
This allows sufficient time for the cells that contracted initially
to repolarize and allows the re-entry circuit to be maintained.
[0007] One surgical procedure for treating some forms of arrhythmia
is to disrupt conduction paths in the heart tissue by severing the
paths at selected regions of the atrial myocardium. Selective
disruption of the conduction pathways permits impulses to propagate
from the SA node to activate the atria and the AV node, but
prevents the propagation of aberrant impulses from other anatomic
sites in the atria. Severing may be accomplished, for example, by
incising the full thickness of the myocardial tissue followed by
closing the incision with sutures. The resultant scar permanently
disrupts the conduction paths. As an alternative, permanent
lesions, in which tissue is killed, can be created by ablation. The
ablation process involves creating a lesion that extends from the
top surface of the myocardium to the bottom surface (endocardial
surface). Thus, the purpose of ablation is to create one or more
lesions that sever certain paths for the excitations while keeping
other paths intact. In the case of atrial fibrillation, for
example, the lesions may interrupt the reentry circuit pathways
while leaving other conduction pathways open. By altering the paths
of conduction, the synchronization of the atrial contractions with
the ventricular contractions may be restored. A plurality of
lesions may be needed to achieve the desired results.
[0008] Incision through the myocardium, referred to as the "maze
procedure," requires suturing to restore the integrity of the
myocardium, and exposes the patient to considerable risk and
morbidity. In contrast, thermal or other forms of ablation can
create effective lesions without the need for sutures or other
restorative procedures. Consequently, ablation can be performed
more quickly and with far less morbidity. For these reasons,
ablation is becoming a preferred method for severing conduction
paths. The surgical ablation procedure may be performed during
open-heart surgery. In a typical open-heart surgery, the patient is
placed in the supine position. The surgeon must then obtain access
to the patient's heart. One procedure for obtaining access is the
median sternotomy, in which the patient's chest is incised and
opened. Thereafter, the surgeon may employ a rib-spreader to spread
the rib cage apart, and may incise the pericardial sac to obtain
access to the cardiac muscle.
[0009] For some forms of open-heart surgery, the patient is placed
on cardiopulmonary bypass (CPB) and the patient's heart is
arrested. CPB is preferred for many coronary procedures because the
procedure is difficult to perform if the heart continues to beat.
CPB, however, entails trauma to the patient with attendant side
effects and risks.
[0010] In some circumstances, the patient may be treated by a
procedure less invasive than the procedure described above. One
such less invasive procedure may be a lateral thoracotomy. The
heart may be accessed through a comparatively small opening in the
chest and accessed through the ribs. In such a procedure, arrest of
the patient's heart may not be feasible, and if the heart cannot be
arrested, the surgery must be performed while the heart continues
to beat. Other procedures for access to the heart include
sternotomy, thoracoscopy, transluminal, or combinations
thereof.
[0011] Once the surgeon has obtained access to the heart, ablation
can be carried out with a probe that delivers ablative energy. The
ablative energy may take the form of electromagnetic radiation
generated by a laser or radio frequency antenna. Other techniques
for achieving ablation include the application of ultrasound energy
or very low temperature. For the procedure to be successful, the
created lesions should sever the targeted conduction paths.
Typically, the surgeon must create a lesion of a particular length
to create the desired severance. The surgeon must also create a
lesion of a particular depth in order to prevent the electrical
impulses from crossing the lesion. In particular, when the
myocardial tissue is ablated, the lesion must be transmural, i.e.,
the tissue must be killed in the full thickness of the myocardium
to prevent conduction across the ablation line.
SUMMARY
[0012] The present invention is directed to surgical devices and
methods useful in guiding surgical instruments during procedures on
internal organs such as the heart. The device may take the form of
a surgical "template" device that is attached to the surface of an
organ. The device can be configured to facilitate surgical
procedures such as tissue ablation. For example, a surgical
template can be used as a guide for travel of a surgical or
ablative probe along a path to aid a surgeon in ablation of tissue
to sever conduction paths in the heart and thereby alleviate
arrhythmia. A surgical template device may be especially useful in
operations where the organ tissue being treated is moving, e.g.,
for so-called beating heart surgery. The surgical template device
may be effective in providing local stabilization of the tissue to
which the tissue ablation procedure is directed. The devices and
methods also may find use in procedures in which the pertinent
organ is not moving.
[0013] Alternatively, the device may be configured to provide
little or no stabilization, but provide guide structure for
placement of the ablation probe in the same frame of motion as the
moving tissue. In some cases, the template may incorporate hardware
that structurally supports the instrument for travel along the
ablation path. The template devices and methods can be configured
for application of other types of therapeutic devices, such as
diagnostic probes, pacing leads, and drug delivery devices, to the
surface of a moving organ. To promote adhesion, in some
embodiments, the device may be equipped with a compliant, tacky
material that forms a seal for contact with tissue. The device also
may be equipped with one or more vacuum ports that make use of
vacuum pressure to enhance the attachment to the organ tissue.
Adhesion refers to the ability of the device to hold fast to an
organ on a temporary basis, either with the benefit of an adhesive
or vacuum pressure or both. The present invention also is directed
to surgical devices and methods useful in determining the
effectiveness of a tissue ablation procedure. In some embodiments,
a sensor may be integrated with a surgical template device as
described above to assist the surgeon by making measurements that
gauge whether the surgical procedure has been satisfactorily
performed. For example, the surgical device may be configured to
measure the effectiveness of an ablation procedure in terms of
ablation length, depth or width. For example, the sensor may
measure electrical characteristics of the tissue proximate the
target conduction paths, e.g., tissue impedance, tissue conduction
velocity, or tissue conduction time, as an indication of the
effectiveness of the procedure. The information obtained by the
sensor can be used as the basis for feedback to the surgeon, e.g.,
in audible and/or visible form. Moreover, the sensor information
can be used as feedback for the closed-loop control of the tissue
ablation probe. The sensor may be employed independently of a
surgical template device.
[0014] As a further aid to the surgeon, the surgical template
device may include indicators such as visible markings that show
the targeted length of the ablation. The visible markings can be
used as a reference by the surgeon during movement of the ablation
probe within the template area provided by the device. Also, the
template device may include a structure that physically restricts
the length of travel of the ablation probe, as well as the shape of
the path along which the probe travels. In particular, the length
indicator may include a stop structure that extends into the path
for travel of the ablation device and is oriented for abutment with
the ablation device. In some embodiments, for example, the ablation
template device may provide a linear path for travel of the
ablation probe. In other embodiments, however, the template device
may define a non-linear, e.g., curved, path for travel of the
ablation probe.
[0015] Further, the present invention is directed to surgical
devices and methods for manipulation of the heart and local
stabilization of heart tissue for a tissue ablation procedure. In
this aspect, the present invention may make use of a surgical
template device that provides not only a guide for a tissue
ablation procedure but also a structure that provides local
stabilization of heart tissue within the operative area. In some
embodiments, the ablation template device may be accompanied by a
surgical manipulation device that adheres to the heart tissue and
enables manipulation of the heart to provide the surgeon with a
desired access orientation for the procedure. The manipulation
device may permit lifting, pushing, pulling, or turning of the
pertinent organ to provide the surgeon with better access to a
desired area. For both the template and manipulation device, to
promote adhesion, a compliant, tacky interface material can be
provided for contact with tissue, along with one or more vacuum
ports for use of vacuum pressure.
[0016] In addition to providing a guide for a procedure, a template
device and associated methods can be arranged to provide structure
that supports instruments such as ablation probes, diagnostic
probes, pacing leads, and drug delivery devices, for application to
the surface of a moving organ and active guidance along a path. For
some surgical procedures, it is necessary to bring surgical
instruments into contact with the surface of a particular organ. In
addition to the ablation application described above, one example
is the placement of one or more electrodes within or in contact
with organ tissue to deliver electrical impulses to the organ
tissue for various purposes, such as a pacing to control the
beating of the heart. Another example is the placement of a syringe
needle to deliver a medicament to a specific location on an organ.
Although all these procedures could be performed manually by the
surgeon when the body cavity is opened during surgery, each is made
more difficult when performed via a small opening in the body
cavity, usually through an endoscopy port. Moreover, such
procedures are particularly complicated when the surface of the
pertinent organ is moving, as with a beating heart.
[0017] Recently, some types of cardiac surgery have been performed
through access ports or rather small incisions in the rib cage,
instead of in the open field created by cutting through the sternum
(a sternotomy) and spreading open the rib cage with a mechanical
device. In these situations, there are occasions when surgical
devices (diagnostic, therapeutic, etc.) will need to be affixed to
a particular location on the heart surface without direct contact
of the human hand. This might also be done while the heart is still
beating. There is an increasing frequency of coronary artery bypass
surgery done on beating hearts to avoid the morbidity associated
with stopping the heart and placing the patient on cardiopulmonary
bypass. Some surgeries on the beating heart are also performed
using the traditional sternotomy. Access procedures such as
sternotomy, thoracotomy, thoracoscopy, and percutaneous
transluminal are contemplated.
[0018] To facilitate such procedures, a template device is provided
to fix a particular surgical tool or diagnostic or therapeutic
device within a defined operative path for the tool or device.
There are some surgical procedures performed on a beating heart, or
other organ, that will require the fixation of a surgical
instrument, diagnostic device or therapeutic device to accomplish a
specific surgical procedure, diagnostic measurement, or delivery of
some therapeutic product or method. This is particularly true when
such procedures, measurements, or deliveries are performed under
minimally invasive conditions, such as through narrow tubes or
ports that penetrate the skin and enter the abdominal or thoracic
cavities. Template devices and associated methods, in accordance
with the present invention, are useful in guiding surgical
instruments, certain diagnostic sensors, or mechanisms for delivery
of medicaments on the surface of internal organs, such as the
heart.
[0019] The template devices and methods are particularly useful in
attaching such instruments to the surface of the beating heart
without any additional manual assistance of the surgeon, thereby
facilitating certain procedures carried out both in open and
minimally invasive procedures. Notable features of the template
device include conformability to the contours of the organ, such as
the heart, the ability to fix the device in place using vacuum,
mechanical pressure, or adhesives, and a traumatic attachment by
virtue of specific soft polymeric interfaces and shapes. The
template device can be configured to attach to various surfaces of
the heart using a vacuum seal. This device provides two or more
vacuum ports surrounded by a conformable, compressible silicone gel
or elastomer. As in the ablation template, these seals contain
integrated electrodes for sending and receiving an electrical
signal for the purpose of measuring impedance or conductance time
or velocity across tissue in a treatment area. The electrodes may
be surface or interstitial. Also, the electrodes may be multipolar,
e.g., bipolar. In some embodiments, a single electrode within the
seal may be sufficient with a reference electrode located
elsewhere. A vacuum port or other fluid removal device may be
desirable to remove fluids from the chamber to avoid the effects of
such fluids on the electrical performance of the electrode(s) or
electrical ablation devices. The ports can be attached to a single
or multiple independent vacuum lines.
[0020] In some embodiments of the invention, ablation is performed
on the interior surfaces of the tissues. For example, an ablating
instrument may be directed transluminally, such as by way of a
catheter, near the ostia of the pulmonary veins in the left atrium
of the heart. Following the ablation and creation of a lesion,
electrodes delivered by the catheter may be used to measure the
efficacy of the ablation.
[0021] For radio frequency ablation, for example, enclosed in the
body of the device can be a channel in which is located a moveable
cable housing a radio frequency (RF) antenna for delivery of RF
energy to the myocardium. The device allows the RF antenna to be
moved by a remote control unit on the distal end of the cable. The
cable can be moved through its channel by the controller in
response to feedback from the sensors on the vacuum seals. As a
lesion becomes transmural in one location, the sensors detect
either decreases in impedance or increases in conduction time. This
information is processed by the controller, and the RF antenna is
moved by a motor that advances the cable assembly along a track in
the device. Such a device is suitable for use in both open and
minimally invasive procedures for the creation of linear transmural
lesions for the treatment of atrial fibrillation.
[0022] Another embodiment is a similar device, which contains
malleable metal elements that allow the device to be formed into an
arc (like a shepherd's crook) whose circumference can match the
outer circumference of the base of the pulmonary vein. This device
is similar in construction to the embodiment described above,
except that it is attached to a rod suitable for insertion into a
port access device for entry into the thorax or for manual
manipulation by a surgeon in an open procedure. The device is
brought into contact with the base of the pulmonary vein, and
vacuum is used to attach it to a portion of the basal circumference
of the vein. RF energy is delivered controllably as described
above. When a full thickness lesion is created on one side of the
vein, the vacuum is released, and the device moved so that its arc
rests over the side of the vein that has not been treated. A full
thickness lesion can then be created on that side.
[0023] For some applications, the surgeon may manually control
advance of the radio frequency antenna within the template device,
and control further movement with a remote control device. In
particular, the surgeon can also utilize manual movement of the RF
antenna assembly through a joystick or other actuation transducer
that advances the RF antenna. The joystick is operated by the
surgeon in response to an indicator (light, etc.) that responds to
the appropriate decrease in impedance or increase in conductance
time detected by the sensors mounted in the vacuum seals. As an
alternative, the surgeon may simply monitor the advance of the
radio frequency antenna visually, and actuate a joystick or similar
device. In either case, the template device operates as both a
guide and an automated actuator to translate the radio frequency
antenna (or other device) along a desired path. Notably, the
template device is affixed to the pertinent tissue and provides
automated movement of the instrument, reducing motion problems
relative to the instrument offering enhanced precision.
[0024] In one embodiment, the present invention provides a surgical
device for use in a tissue ablation procedure. The device includes
a contact member that engages the tissue near a location where the
tissue is to be ablated. The contact member defines a guide that
indicates, upon engagement of the contact member with the tissue,
the location where the tissue is to be ablated, and provides a path
for travel of a tissue ablation probe. The contact member of the
device may include a compliant and tacky interface element for
engagement with the tissue. The device may further define an
interior chamber, and may include a vacuum port in fluid
communication with the interior chamber. The interior chamber may
be capable of delivering vacuum pressure to the contact member,
thereby promoting vacuum assisted adherence of the contact member
to the tissue. In addition, the device may include a sensor that
may indicate whether the desired degree of tissue ablation has been
achieved.
[0025] In another embodiment, the present invention provides an
apparatus for determining whether conduction paths within heart
tissue have been adequately ablated during a surgical procedure.
The apparatus includes a first electrode capable of transmitting a
first electrical signal adjacent the tissue to be ablated, a second
electrode capable of receiving a second electrical signal adjacent
the tissue to be ablated and a measuring device electrically
coupled to at least the second electrode to receive the second
electrical signal from the second electrode. The measuring device
may determine whether the extent to which the tissue has been
ablated to a sufficient degree based on the second electrical
signal. The apparatus further includes an output device that
provides an indication of extent, e.g., depth, to which the tissue
is ablated. In order to measure impedance when using RF ablation,
it may be necessary to use an energy frequency outside of the
ablation energy frequency range or pulse or ablation energy and
measure impedance during the quiescent period between ablation
pulses.
[0026] In another embodiment, the present invention provides a
method for severing conduction paths within tissue. The method
involves placing a first device near the target conduction paths to
be severed, using the first device as a guide to sever the target
conduction paths, and with a second device, measuring to determine
whether the desired severing has been achieved. In this embodiment,
the target conduction paths may be severed by tissue ablation.
Measurement may involve determining whether the lesion depth is
sufficient to sever the target conduction paths.
[0027] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a perspective view of an ablation template device
in accordance with an embodiment of the present invention placed on
a heart for purposes of illustration.
[0029] FIG. 2 is an enlarged perspective view of an ablation
template device as shown in FIG. 1, showing use of a surgical
instrument.
[0030] FIG. 3A is a top view of an ablation template device in
accordance with an embodiment of the invention.
[0031] FIG. 3B is a side view of an ablation template device in
accordance with an embodiment of the invention.
[0032] FIG. 3C is a cross-sectional side view of the device of
FIGS. 3A and 3B.
[0033] FIG. 4 is a conceptual diagram illustrating an ablation
template device in accordance with an embodiment of the
invention.
[0034] FIG. 5 is another conceptual diagram illustrating an
ablation template device in accordance with an embodiment of the
invention.
[0035] FIG. 6 is a perspective view of an ablation template device
in accordance with an alternative embodiment of the invention
placed on a heart for purposes of illustration.
[0036] FIG. 7 is a top view of an ablation template device in
accordance with an embodiment of the invention.
[0037] FIG. 8 is a top view of an ablation template device in
accordance with an embodiment of the invention.
[0038] FIG. 9A is a perspective top view of an ablation template
device in accordance with an embodiment of the invention.
[0039] FIG. 9B is a perspective bottom view of an ablation template
device as shown in FIG. 9A.
[0040] FIG. 10 is a perspective view of an ablation template device
in accordance with an embodiment of the invention.
[0041] FIG. 11 is a perspective view of an ablation template device
in accordance with an embodiment of the present invention, placed
on a heart for purposes of illustration, used in cooperation with
another device that permits manipulation of the heart.
[0042] FIG. 12 is a cross-sectional side view of a cup-like
manipulation device.
[0043] FIG. 13 is a cross-section side view of another cup-like
manipulation device.
[0044] FIG. 14 is a perspective view of an ablation template device
incorporating structure for accommodating an ablation probe;
[0045] FIG. 15 is a cross-sectional view of the device of FIG. 14,
taken at point 145.
[0046] FIG. 16 is a cross-sectional view of a shaft incorporated in
the device of FIG. 14, taken at point B.
[0047] FIG. 17 is a perspective view of an arcuate ablation
template device incorporating structure for accommodating an
ablation probe.
[0048] FIG. 18 is a perspective view of an added ablation template
device incorporating structure for accommodating an ablation
probe.
[0049] FIG. 19 is a cross-sectional view of the device of FIG. 18,
taken along line 210-210'.
[0050] FIG. 20 is a bottom view of the device of FIG. 18.
[0051] FIG. 21 is a perspective view of an ablation template device
incorporating a movable carriage for support of an ablation
probe.
[0052] FIG. 22 is a cross-sectional view of the device of FIG. 21,
taken along line 250-250'.
[0053] FIG. 23 is a cross-sectional view of the device of FIG. 21,
taken along line 244-244'.
[0054] FIG. 24 is a cross-sectional front view of an ablation
template device having an internal ablation probe.
[0055] FIG. 25 is a cross-sectional side view of the ablation
template device of FIG. 24.
[0056] FIG. 26 is a cross-sectional side view of a catheter-mounted
ablation device.
[0057] FIG. 27 is a side view of a catheter-mounted ablation
device.
[0058] FIG. 28 is a side view of a catheter-mounted ablation
device.
[0059] FIG. 29 is a cross-sectional side view of a catheter-mounted
ablation device.
[0060] FIG. 30 is a side view of a catheter-mounted ablation
device.
[0061] In general, like reference numerals are used to refer to
like components.
DETAILED DESCRIPTION
[0062] FIG. 1 is a perspective view of an ablation template device
14 in accordance with an embodiment of the present invention. In
FIG. 1, ablation template device 14 is shown placed on a heart 10
for purposes of illustration. In particular, heart 10 has been
exposed by an open-chest surgical technique and ablation template
device 14 has been affixed to the right atrium 12 of the heart. In
some embodiments, ablation template device 14 includes a contact
member 17 that engages the tissue. In the example of FIG. 1,
contact member 17 takes the form of a substantially ovular ring.
Inner and outer diameters 20, 21 of the ring-like contact member 17
define an annular chamber for engagement with tissue on the surface
of heart 10.
[0063] Contact member 17 may be affixed to the surface 15 of atrium
12 in many ways, such as by application of an adhesive at the inner
and outer diameters 20, 21, or by application of vacuum pressure to
the annular chamber. Another way to achieve adherence between
contact member 17 and the surface tissue 15 is to include a seal
member 23 formed from an adhesive material in the contact member.
One example of an adhesive material is a coating of compliant,
tacky material, such as silicone gel, at the interface between the
contact member 17 and the tissue on the surface 15 of atrium 12. In
this case, contact member 17 may include a semi-rigid frame member
25 and a compliant, tacky seal member. The compliant, tacky seal
member 23 provides intrinsic adhesive properties, and aids
conformability and sealing to surface 15, while the frame 25
imparts structural integrity to contact member 17. Each of frame 25
and seal member 23 has a substantially annular shape. In
particular, seal member 23 may include inner and outer portions 27,
29 disposed at the inner and outer diameters 20, 21 of contact
member 17.
[0064] With a silicone gel, intrinsic adherence of seal member 23
may be sufficient that ablation template device 14 remains affixed
to the heart 10 in spite of contractions of atrium 12 and in spite
of the use of device 14 in surgical procedures described below.
Nevertheless, application of vacuum pressure will be desirable in
many applications to provide secure adherence. Although the
adherence should be secure, the adherence preferably is not
permanent. Rather, adherence between device 14 and the tissue may
be discontinued as desired without serious trauma to the tissue,
and the device repositioned and adhered anew at a different
location. As an alternative, ablation template device 14 can be
forced against atrium 12 to provide pressure contact with heart 10.
In such a case, ablation template device 14 may have a local
stabilizing effect on the contact region of heart 10 despite
continued beating of the heart. Ablation template device 14 may be
sized or shaped to allow it to mold to the contours of the atrium
12. Ablation template device 14 can be made principally of
nonconductive materials, such as polyurethane, silicone, or natural
or synthetic rubber. Shore A 50-80 silicone elastomer may be used,
for example, to form frame 25 of device 14. Metal such as annealed
stainless steel or zinc or polymeric reinforcing members may be
incorporated in device 14, e.g., embedded within the molded
elastomer, to resist excessive deformation or collapse during use.
Shape memory alloys, in particular, may be useful in imparting a
desired shape to device 14 during use, and permit collapse and
unfolding to the desired position for endoscopic deployment in
minimally invasive techniques.
[0065] An electrode 16 can be affixed to device 14, e.g., within
seal member 23 or frame member 25, and placed in contact with the
surface 15 of the heart 10. The electrode 16 may send signals
across the tissue of the heart 10 to be received by a second
electrode (not shown in FIG. 1). These signals will traverse the
tissue area being ablated. The associated circuitry for the
electrodes may reach device 14 by way of a connective tube 18. As
will be described, electrode 16 may form part of a sensor for
determining the effectiveness of a tissue ablation procedure. In
particular, the electrodes can be used to measure electrical
properties (such as impedance, phase angle, conduction time,
conduction velocity, capacitance) of the local tissue area being
ablated, and thereby indicate whether an effective lesion has been
formed in the tissue. In some embodiments, ablation template device
14 may have multiple sets of electrodes situated at different
positions along the major axis of the device. In this case, such
electrodes may take the same types of measurements at different
positions, or different types of measurements such as impedance,
conduction velocity, and conduction time.
[0066] If ablation template device 14 is attached with the
assistance of vacuum pressure, connective tube 18 may also serve
the purpose of attaching the interior chamber formed by contact
member 17 to an external source of vacuum pressure (not shown).
Ablation template device 14 may be shaped to define an interior
chamber that is enclosed upon engagement of the device with the
tissue. In the example of FIG. 1, the chamber is substantially
annular. Application of vacuum pressure may cause the enclosed
chamber to slightly deform, creating a vacuum seal and causing the
device 14 to become more affixed to the tissue. With added
compliance from seal member 23, in particular, contact member 17
can conform to tissue surface 15 to achieve an effective seal. At
the same time, the compliant seal member 23 distributes sealing
force across the tissue to reduce tissue trauma.
[0067] As shown in FIG. 1, contact member 17 of ablation template
device 14 generally may have a somewhat annular shape, with
substantially oval-shaped inner and outer diameters, and an opening
31 through which the tissue of atrium 12 may be accessed. The
lengths of the major and minor axes of annular-shaped device 14 may
vary to provide opening 31 with varying sizes according to the
characteristics of the particular procedure to be performed. In
some applications, opening 31 may define a narrow, linear track for
travel of an ablation probe. In other applications, opening 31 may
be much wider or define nonlinear tracks for travel of an ablation
probe. Other shapes for contact member 17 beside the annular shape
may also be suitable.
[0068] A closer perspective view of ablation template device 14
appears in FIG. 2. In FIG. 2, a surgeon's fingers 24 hold a
surgical instrument shown as an ablation probe 22 that may be used
to ablate the tissue of the heart 10. Even though the heart 10 is
beating, the surgeon 24 may position the probe 22 within the
opening 31 with relative ease. The surgeon 24 may also use the
probe 22 to ablate a particular area of the atrium 12, even though
the atrium 12 is in the process of contracting and relaxing, by
using the inside edge 26 of the device 14 as a guide for travel of
the probe. Again, opening 31 may define a substantially linear path
for travel of an ablation probe. Alternatively, opening 31 can be
non-linear, e.g., curved, or have other shapes appropriate for
given surgical applications. In either case, the surgeon man use
opening 31 as a guide, even resting the ablation probe 22 against
the inside edge 26 of contact member 17 in some cases. Because
significant heat may be generated by RF, laser, and ultrasonic
energy, it may be desirable to provide ablation probe 22 with a
thermally insulative sleeve that extends downward to the tip of the
probe, thereby protecting the inside edge 26 of contact member 17.
Also, inner edge 26 of contact member 17 can be coated with or
coupled to an insulative material for contact with ablation probe
22.
[0069] If ablation template device 14 is fixed to a point of
reference, it may provide a local stabilizing effect that holds the
tissue within opening 31 substantially stationary, or at least
constrains the local area against excessive movement, despite
continued beating of heart 10. For example, ablation template
device 14 may be pushed against heart 10 to apply stabilizing
pressure to the local area of contact. Alternatively, ablation
template device 14 can make use of suction or adherence in
combination with either a pushing or pulling force to provide a
stabilizing effect.
[0070] Ablation probe 22 may use a number of methods to achieve
ablation. The probe 22 may, for example, use a laser to ablate
tissue. As another alternative, the probe may incorporate an
antenna that emits radio frequency (RF) energy to ablate tissue.
The amount of power delivered by the ablation probe may vary. A
typical RF probe, for example, may deliver from 5 to 50 watts. In
this alternative, the probe 22 may include an electrode at its tip.
An electrode can be provided within ablation template device 14 to
provide circuit completion for a probe using RF energy. For
example, a passive electrode forming part of the sensor described
above could be used as the return electrode. As a further
alternative, probe 22 could take the form of an ultrasound probe
that emits ultrasound energy, or a cryosurgical probe that cools
the tissue to ultra-low temperatures. Thermal, chemical, and
mechanical probes for obtaining or incising tissue are also
contemplated. In each case, opening 31 of ablation template device
14 provides a guide for travel of probe 22, enabling greater
precision in the ablation of conduction paths within the heart
tissue.
[0071] Other views of ablation template device 14 appear in FIGS.
3A and 3B. In these views, the device is shown in a top view, FIG.
3A, and a side view, FIG. 3B. FIG. 3C is a cross-sectional side
view of the device of FIGS. 3A and 3B. Inner seal member 27 is
indicated by dashed line 33. The interior chamber of contact member
17 is indicated by reference numeral 35. Ablation template device
14 may be flexible, and its relaxed shape may be curved as shown in
FIG. 3B to more readily conform to the surface of the heart. The
exemplary annular shape allows first electrode 16 and second
electrode 30 to be located opposite to each other across the
opening 31. The distance between the electrodes 16, 30 may be a
known, fixed distance. The interior edges 26, 32 of the opening 31
preferably have sufficient rigidity to serve as a guide for travel
of a probe or other surgical instrument. Although seal member 23
may be substantially compliant and conformable, the inner edge of
frame member 25 may provide the degree of rigidity desirable to
support the probe. In addition, ablation template device 14 may
include one or several length indicators in the form of visible
markings 28, to assist the surgeon in forming a lesion of a desired
length.
[0072] A surgeon desiring to make a lesion of a particular length
may use the markings 28 as a guide for manipulating the probe.
Thus, the guide provided by opening 31 is useful in guiding both
the direction of travel of the probe and the extent of travel.
Also, the template device 14 may include a structure that
physically restricts the length of travel of the ablation probe, as
well as the shape of the path along which the probe travels.
Substantially straight ablation tracks ordinarily will be
desirable. Accordingly, the guide surface on the interior of the
opening may be substantially straight. In other applications,
however, it may be desirable to effect a curved ablation track.
Therefore, the shape of the guide within opening 31 may vary
according to the application. Furthermore, because ablation
typically causes a change in tissue color, the markings 28 may
provide the surgeon with information as to the actual length of the
lesion.
[0073] In one aspect, the invention can be useful in determining
whether the conduction path has indeed been cut. Ordinarily, a
surgeon cannot visually gauge the depth of a lesion. The guide
defined by ablation template device 14 may provide an indication of
the length of a lesion. A lesion of an insufficient depth may
result in currents that pass under or over the lesion, however, and
may thus be incapable of disrupting the reentry circuits or other
undesirable current pathways. The myocardium consists of interlaced
bundles of cardiac muscle fibers. Within the fibers, cardiac muscle
cells are joined by intercalated discs, which include areas of low
electrical resistance known as gap junctions. Gap junctions permit
excitations or action potentials to propagate from one cell to
another. A lesion created by ablation may destroy the tissue and
the gap junctions, effectively interrupting electrical conduction.
Thus, determination of whether the conduction paths are indeed
ablated may be crucial to a successful treatment.
[0074] As shown in FIGS. 3A and 3B, ablation template device 14 may
include at least two electrodes, 16, 30 that operate as part of a
sensor. A sensor may be used to indicate to the surgeon whether a
desired degree of tissue ablation has been achieved. Electrodes 16,
30 preferably are integrated with ablation template device 14 to
reduce the number of instruments that need to be introduced in to
the surgical field. In particular, electrodes 16, 30 can be molded
into the material forming seal member 23 or frame member 25, and
have conducting members that extend away from the tissue site via
tube 18. A tip portion of each electrode may be exposed beyond the
surface of seal member 23 to enable sufficient electrical contact
with the tissue to which contact member 17 is attached.
[0075] In other embodiments, however, electrodes 16, 30 may be
introduced independently of ablation template device 14. FIGS. 3A
and 3B show an exemplary embodiment of the present invention, and
other embodiments may incorporate more than two electrodes. After
an ablation is performed inside the opening 31, and during
ablation, electrodes 16 and 30 may be located on opposite sides of
the lesion. The distance between electrodes 16 and 30 may be a
known distance and relatively fixed. The electrodes 16, 30 may be
used to determine whether the conduction path has been severed by
ablation to the desired degree.
[0076] One way to make the determination is to use the electrodes
16, 30 as probes for an impedance-measuring instrument. Electrodes
16, 30 may be electrically coupled to the impedance-measuring
instrument. The impedance of the area of tissue may be measured
before any ablation is made, and this measurement may be used as a
baseline. The impedance may be measured again after the ablation is
made and may be compared with the baseline measurement to determine
whether the conduction path has been severed. Moreover, it may be
desirable to measure impedance during an ablation procedure to
assess progress in producing an effective lesion. During ablation,
impedance measured from one side of the lesion to the other side
will decrease as ablation ruptures cell membranes, permitting
dissolved ions to move with less restriction. Impedance will
generally decrease until impedance reaches a minimum value when the
lesion becomes transmural. One way to determine whether the
ablation is complete is to look for the point at which the
impedance measurement levels off. For example, a baseline
measurement on canine atrial myocardium may show an impedance of
240 ohms, but measurements taken during the ablation may how a
steady decline in impedance, eventually leveling off at 150 ohms
after about 90 seconds. It may also be possible in some
circumstances to evaluate the ablation process on the basis of a
percentage change of impedance or on the basis that a predetermined
impedance value has been reached. Parameters such as the baseline
value, the leveling off value and the time needed to produce a
transmural lesion are dependent upon the patient being treated, the
tissue being ablated, the distance of the electrodes, the thickness
of the tissue, and other factors. In the case of the heart, for
example, not all hearts have the same impedance, and different
sections of a single heart may also have varying impedance. In such
cases a baseline measurement may be desirable, with transmural
penetration indicated by the leveling off of impedance
measurements.
[0077] In addition to measuring impedance or as an alternative to
measuring impedance, alternating current (ac) phase angle may be
measured. In a capacitive circuit, the voltage lags the current,
and the amount of lag is often expressed in the form of a phase
angle. In a purely capacitive circuit, the voltage is 90.degree.
behind the current, expressed as a phase angle of -90.degree.. A
phase angle of 0.degree. means the circuit is purely resistive. A
phase angle between 0.degree. and -90.degree. means the circuit is
partly resistive and partly capacitive. Typically a phase angle
measurement across tissue will be between 0.degree. and
-90.degree., indicating some capacitive nature of the tissue. As
ablation proceeds, cell membranes are ruptured, making the tissue
less capacitive. Accordingly, the phase angle across the ablative
lesion will become more positive (i.e., will approach zero) as
cells die in the lesion. One way to determine whether the ablation
is complete is to look for the point at which the phase angle
measurement levels off. A baseline measurement of canine
myocardium, for example, may show a phase angle of -13.1.degree..
Measurements taken during the ablation may show the phase angle
becoming more positive, eventually leveling off at -12.degree.
after about 20 seconds. As with impedance measurements, phase angle
measurements are dependent upon many factors.
[0078] Another way to make the determination is to use the
electrodes to measure conduction distance by measuring conduction
time. A signal traveling on a conduction path propagates as an
action potential and propagates via gap junctions. The length of a
conduction path, the speed of conduction and the time taken for a
signal to travel the path are related by the simple formula
D=RT
[0079] where D is the distance traveled by the signal, R is the
rate of speed of the signal, and T is the time taken for the signal
to travel the distance. In the case of an actual operation, a
particular value of D or T may be desired. A value for R may be
obtained by sending a test signal from one electrode, receiving it
at the other electrode, the distance between the electrodes being
known and relatively fixed, and measuring the time of conduction.
In many cases, however, a relative measure of conductive velocity
or time is sufficient, and therefore the distance between
electrodes need not be known absolutely so long as it remains
fixed. This measurement may then be used as a baseline measurement.
Again, a baseline measurement may be desirable, because not all
hearts have the same conduction speed, and different sections of a
single heart may also have varying conduction speeds. The time of
conduction may be measured again after the ablation is made and may
be compared with the desired value of D or T. In general,
conduction time increases and conduction velocity decreases as the
ablation proceeds, and one way to determine whether the ablation is
complete is to look for the point at which the measured quantity
levels off. For example, a conduction time of 15 ms may be measured
as a baseline. During ablation, conduction time may increase,
eventually leveling off at around 30 ms. The leveling off indicates
the ablation is transmural.
[0080] In the case of measurement of conduction time, velocity, or
distance, electrode 30 may be a single electrode or a bipolar or
multipolar electrode. Thus, in the description of this invention,
it is to be understood that the transmitting electrode 16
positioned on one side of the ablation track may be unipolar, while
the measurement or "recording" electrode 30 positioned on the
opposite side of the ablation track can be unipolar, bipolar, or
multipolar, depending upon the electrical measurement that is
utilized to determine if the conduction paths have been severed or
ablation of the target tissue has been transmural, and desired
precision. With a unipolar recording electrode 16, an electrical
signal transmitted into the tissue by the transmitting electrode is
first sensed as an electrical signal that is then followed by a
depolarization wavefront that propagates through the cells disposed
between electrodes 16, 30. It is the depolarization wavefront that
is detected to measure conduction time.
[0081] A unipolar recording electrode 30 simply measures whether
the depolarization wavefront exceeds a given threshold. With a
bipolar recording electrode 30, however, the two electrodes can be
used to measure current flow or a voltage potential between them.
The two electrodes of the bipolar recording electrode 30 can be
oriented in a line substantially parallel to the ablation track,
and thereby form a "T" with the transmitting electrode 16. As the
depolarization wavefront propagates through the cells positioned
between transmitting electrode 16 and recording electrode 30, the
cells disposed between two recording electrodes of bipolar
recording electrode 30 depolarize, producing a difference in
current flow between the two recording electrodes. This bipolar
arrangement enables measurement of an increase in the intensity of
current flow between the two electrodes of bipolar recording
electrode 30, and more precision in the measurement. In particular,
an intensity threshold can be set. Conduction time can be measured
between the time at which transmitting electrode 16 transmits the
initial signal and the time at which current flow between the two
electrodes of bipolar recording electrode 30 exceeds the threshold.
Again, the initial signal transmitted by transmitting electrode 16
and sensed by the recording electrode 30 can be ignored. Rather,
the depolarization wavefront typically will be the event of
interest in determining conduction time.
[0082] A method of using measurement of impedance or conductance
variables to determine the transmurality of a lesion may also be
employed using bipolar radio frequency electrosurgical ablation
devices. For example, separate electrodes, using an electrical
frequency different from the frequency used by the ablation device,
can be mounted on the device and used to form a separate measuring
circuit for impedance for the purpose of measuring the distance
ablated. A typical bipolar device could have two electrode
surfaces, one for one side of a tissue surface and one for the
other side of a planar tissue surface, such as the myocardium, or a
vascular structure. One transmitting electrode, or a plurality of
electrodes, can be mounted with one of the surgical electrodes, and
a receiving or "recording" electrode, which could be bipolar or
multipolar, or a plurality of unipolar, bipolar, or multipolar
electrodes, can be mounted on the opposite surgical electrode.
Impedance or conductance, such as time, distance, or velocity, can
be measured as described herein and can be used to determine
transmurality, and shut off power to the ablation device as
described. It is envisioned that one specific application of such a
bipolar device would be for deployment through a puncture hole in
the myocardium. The ablation device could be equipped with "jaws"
that carry the electrodes. Entry of one of the "jaws" of the
surgical RF device could be either from the endocardial or
epicardial surfaces. After deployment, there would be a surgical
electrode on both the epicardial surface and the endocardial
surface. As RF power is supplied to the surgical ablation device,
the tissue between the two surgical electrodes is heated and
killed, creating a lesion for the purpose of interrupting
conductance pathways. The transmurality of this lesion at different
points along its length can be measured simultaneously or at time
intervals during ablation using measurement of impedance or
conductance variables with the separate circuits defined by the
transmitting and recording electrodes placed along the path of the
surgical electrodes and the underlying lesion.
[0083] FIG. 4 shows a conceptual diagram of an implementation of an
aspect of the invention. Electrodes 16, 30 shown in FIG. 3 may
serve as probes 34 for a measurement device 36. The measurement
device 36 may measure a quantity related to conduction, such as
impedance or conduction time or conduction velocity. Data measured
by measurement device 36 may be fed into a processor 38. Processor
38 may be in the form of a generalized computing device, such as a
personal computer. Alternatively, processor 38 may be in the form
of a smaller and more specialized computing device, such as a
microprocessor or an application-specific integrated circuit. As a
further alternative, processor 38 could be realized by discrete
logic circuitry configured appropriately to perform the necessary
measurement control and processing functions. Accordingly,
processor 38 need not be embodied by integrated circuitry, so long
as it capable of functioning as described herein.
[0084] In addition, processor 38 may take an active role in the
measurement process and may control measurements made by
measurement device 36 through probes 34. In particular, processor
38 may control a current or voltage source to apply electrical
current or voltage to one of electrodes 16, 30. Two representative
instances where the processor 38 may actively control the
measurement process are in the taking of a baseline measurement,
and in the taking of periodic measurements during the ablation
procedure to monitor progress. Processor 38 may further perform
calculations as needed, and may provide output to the surgeon by
way of an output device 40 such as a display. In addition,
processor 38 may receive input from an additional input device 42,
which may include, for example, a keyboard or a touch screen. Using
input device 42, the surgeon may, for example. input the length of
a desired lesion, and the processor 38 may be able to provide
feedback to the surgeon via output device 40 as to whether the
desired lesion has been created. Output device 40 may provide
audible and/or visible output such as beeps, flashing light
emitting diodes (LED's), speech output, display graphics, and the
like, to provide feedback to the surgeon. Output device 40 can be
mounted in a housing associated with processor 38, or integrated
with the ablation probe 22. For example, one or more LED's could be
mounted on the ablation probe in view of the surgeon.
[0085] FIG. 5 shows another conceptual block diagram of an
implementation of an aspect of the invention. FIG. 5 is similar to
FIG. 4, except that the processor 38 is connected to the ablation
device 44. Ablation device 44 may be any device intended to sever
conduction paths by killing tissue, such as the RF, laser,
ultrasonic, or cryogenic probe 22 depicted in FIG. 2. In each case,
ablation device 44 may be in the form of a powered instrument such
as a laser, RF, or ultrasonic electrosurgical probe, or be coupled
to a cryogenic supply. Processor 38 may control ablation device 44
by, for example, cutting off power or supply to the ablation device
once the desired lesion has been created. In this manner, the
surgeon can take advantage of closed-loop, real-time control of the
output of ablation device 44, ensuring ablation to a proper level
of effectiveness and avoiding excessive ablation. The result may be
the creation of an effective lesion in a shorter time period,
reducing the time necessary for access to the patient's heart
tissue. The system may be even more effective if multiple electrode
pairs are mounted along opening 31 to measure the effectiveness of
ablation in creating a lesion along a continuous track.
[0086] The system shown in FIG. 5 may be useful for dynamic
monitoring and control of the surgical procedure. The surgeon may
choose an ablation device 44, such as a laser, that will not
interfere with the operation of the probes 34. Alternatively, if
interference is created by an RF probe, power can be intermittently
turned off to enable measurement. By any combination of taking a
baseline measurement or receiving input through input device 42,
the processor 38 may determine what measurements received from
measurement device 36 will satisfy the conditions for a successful
surgical procedure. Processor 38 may continuously or frequently
monitor the measurements received from measurement device 36 to
determine whether the criteria for a successful surgical procedure
have been met. When those criteria have been met, processor 38 may
cut off power to, or otherwise interrupt the operation of, ablation
device 44. In other words, processor 38 may use a feedback system
as part of its control of ablation device 44 for either automated
control or manual control by the surgeon.
[0087] One advantage of this system is the speed by which the
surgeon may perform the ablation procedure. Speed is of a
considerable advantage to the patient in several respects. First,
risks attendant to surgery may be minimized if the time spent on
the operating table is reduced. Second, a procedure performed on
moving tissue such as a beating heart may be more efficient if done
quickly.
[0088] Once ablation template device 14 is placed into position, a
baseline measurement may be taken, and the surgeon may then proceed
to make the ablation, using ablation template device 14 as a
template or a guide. Use of the device 14 as a template or guide is
one factor enhancing the speed of the procedure. The surgeon may
use markings 28 on ablation template device 14 to get a general
idea of where to begin and end the ablation. The processor 38 may
be used to suggest to the surgeon via output device 40 suitable
markings 28 for beginning and ending the ablation pass. The surgeon
may then make a pass with the ablation device 44. If the pass is
too long, the processor 38 may interrupt the function of the
ablation device 44 before the pass is completed. If the pass is too
short, the processor 38 may assist the surgeon in determining the
best approach for a second pass. Again, the length determination
may be aided by the use of a series of electrode pairs along an
ablation track. The use of dynamic processing and feedback further
enhance the speed of the procedure. FIG. 6 is a perspective view of
an ablation template device 50 in accordance with an alternative
embodiment of the present invention. Like ablation template device
14 in FIG. 1, ablation template device 50 is shown placed on the
right atrium 12 of a heart 10 in FIG. 6 for purposes of
illustration. In particular, heart 10 has been exposed and ablation
template device 50 has been affixed to the right atrium 12 of the
heart. Ablation template device 50 includes a contact member 51
which may engage and may be affixed to the surface 15 of atrium 12
by being pushed against the heart. Because ablation template device
50 generally has a U-shaped shape, contact member 51 includes two
contact tines or contact "feet" 53.
[0089] Electrodes used to take the measurements described herein
may take the form of discrete electrodes that operate in pairs to
transmit and receive signals across the ablated tissue region.
Alternatively, one or more of the electrodes may take the form of
bipolar or multi-polar electrodes that are integrated in a common
electrode package and positioned in very close proximity to one
another. With the closer spacing available in a bipolar package,
for example, the signal transmitted by one electrode and received
by the other as an EMG potential can be cleaner in terms of having
a reduced degree of background noise due to surrounding electrical
potentials produced by the heart. Instead, the bipolar electrode is
capable of more effectively measuring the local signal conduction
time. Also, in some embodiments, series of electrodes on each side
of the ablation track can be realized by a continuous electrode
component that includes conductive electrode regions and insulating
regions disposed therebetween. Again, this sort of component can
permit closer electrode spacing. In this case, however, the closer
spacing is not between transmitting and receiving electrodes but
between adjacent transmitting electrodes and adjacent receiving
electrodes extending parallel to the ablation track. The closer
spacing permits a higher degree of resolution in monitoring the
progress of the ablation procedure along the ablation track, and
thus the length of the resulting lesion. The closer spacing permits
more precise feedback and control of the ablation probe by the
surgeon or by an automated controller.
[0090] To maintain its position relative to the heart 10, ablation
template device 50 may, in addition, have a compliant, tacky
material such as silicone gel at the point of contact between
contact member 51 and the surface 15 of the atrium 12, providing a
compliant, tacky interface. Ablation template device 50 may remain
substantially affixed to the heart 10 in spite of contractions of
atrium 12 and in spite of the use of ablation template device 50 in
surgical procedures described such as those described above. By
being forced against the heart, ablation template device 50 may
have a stabilizing effect on the contact region of heart 10 despite
continued beating of the heart. Shaft 52, made of a rigid material
and formed in any suitable shape, may be used to press ablation
template device 50 against atrium 12 and hold the device in
place.
[0091] Although ablation template device 50 may be more rigid than
ablation template device 14 in FIG. 1, ablation template device 50
may be sized or shaped to allow it to mold to the contours of the
atrium 12. Like ablation template device 14 in FIG. 1, ablation
template device 50 can be made (with the exception of the
compliant, tacky interface) principally of substantially rigid,
nonconductive materials, and may include a first electrode 56 and a
second electrode (not shown in FIG. 6). The associated circuitry
for the electrodes may reach ablation template device 50 by way of
shaft 52. The general U-shape of ablation template device 50
includes an opening 54 through which the tissue of atrium 12 is
accessible. The dimensions of ablation template device 50 and
opening 54 may vary. Other shapes beside the U-shape may also be
suitable for the device 50, such as the annular shape, and the
opening 54 may be in other suitable shapes as well.
[0092] A top view of ablation template device 50 appears in FIG. 7.
The exemplary U-shape allows first electrode 56 and second
electrode 58 to be located opposite to each other across the
opening 54. The distance between the electrodes 56, 58 may be a
known, fixed distance. The interior edges 60, 62 of the opening 54
have sufficient rigidity to serve as a guide for travel of a probe
or other surgical instrument. In addition, like ablation template
device 14, ablation template device 50 may include several length
indicators 64, to assist the surgeon in forming a lesion of a
desired length.
[0093] A top view of a variation of ablation template device 50
appears in FIG. 8. Ablation template device 50 is like the same
device depicted in FIG. 7, except the first electrode 56 and second
electrode 58 are not rigidly affixed to the body of the device 50.
Electrodes 56, 58 are electrically coupled to ablation template
device 50 by way of electrical connectors 66, 68. Electrical
connectors 66, 68 may be flexible wires, and may allow a surgeon to
place electrodes 56, 58 at a desired location on the tissue or at a
desired distance apart. Alternatively, electrical connectors 66, 68
may be spring-like connectors, that may appear somewhat like insect
antennae, and which may force the electrodes 56, 58 against the
tissue when the ablation template device 50 is pressed against the
tissue to enhance electrical coupling pressure and surface area. As
shown in FIG. 8, electrodes 56, 58 may be deployed within the
opening 54. Electrodes 56, 58 may also be deployed at other
locations as well.
[0094] FIGS. 9A and 9B show an ablation template device 69, which
is similar to the ablation template device 14 shown in FIG. 1.
However, FIGS. 9A and 9B illustrates a frame member 75 and a seal
member 77 in somewhat greater detail. FIG. 9A is a perspective top
view of device 69, while FIG. 9B is a perspective bottom view of
device 69. FIGS. 9A and 9B differ slightly in the shape of device
69. Specifically, device 69 of FIG. 9A is shown as having a
somewhat curved contour for conformability to the surface of the
tissue.
[0095] Frame member 75 can be formed from a semi-rigid material
that lends structural integrity to contact member 73, while seal
member 77 is formed from a more compliant material that facilitates
conformance of the contact member to the tissue surface and
promotes a seal that is generally atraumatic and more effective.
Seal member 77 includes an inner skirt-like member 70 coupled to
and extending around the inner edge of contact member 73 that acts
as an interface with the tissue. Skirt-like member 70 may function
in part as a seal gasket. Ablation template device 69 also includes
an outer skirt-like member 72, coupled to and extending around the
outer edge of the contact member 73. Skirt-like members 70, 72
define annular vacuum chamber 76. Inside of skirt-like member 70,
contact member 73 defines opening 81 for access to a tissue site.
Skirt-like members 70, 72 may be composed of a material that is
generally more compliant and conformable than the rest of contact
member 73.
[0096] Use of Shore A 5-10 durometer silicone elastomer for the
skirt-like member 70, 72 may be appropriate for some applications.
Silicone gels are preferred, however, due to the intrinsic
compliance and tackiness provided by such materials. Like silicone
elastomers, silicone gels can be manufactured with a range of
crosslink densities. Silicone gels, however, do not contain
reinforcing filler and therefore have a much higher degree of
malleability and conformability to desired surfaces. As a result,
the compliance and tackiness of silicone gel materials can be
exploited in skirt-like members 70, 72 to provide a more effective
seal. An example of one suitable silicone gel material is MED 6340,
commercially available from NUSIL Silicone Technologies, of
Carpinteria, Calif. The MED 6340 silicone gel is tacky and exhibits
a penetration characteristic such that a 19.5 gram shaft with a
6.35 mm diameter has been observed to penetrate the gel
approximately 5 mm in approximately 5 seconds. This penetration
characteristic is not a requirement, but merely representative of
that exhibited by the commercially available MED 6340 material.
[0097] Metal or polymeric reinforcing tabs can be incorporated in
skirt-like members 70, 72 to prevent collapse, and promote
structural integrity for a robust seal. Skirt-like members 70, 72
can be compliant, tacky silicone gel molded about the reinforcing
tabs. In particular, for manufacture, frame member 75 can be molded
about reinforcing tabs or springs, allowing a portion of the tabs
or springs to extend downward, to one or both of the inner diameter
or outer diameter side of the annular contact member. Then, one or
both skirt-like members 70, 72 can be molded onto frame member 75,
encasing the exposed portions of the tabs or springs. In the
example of FIG. 9, outer skirt-like member 72 and the outer
diameter side of frame member 75 are molded about and encase a
continuous spring member, shown partially in FIG. 9 and indicated
by reference numeral 79. Spring member 79 can be shaped from a
continuous length or one or more segments of spring steel, or other
materials capable of exerting a spring bias on contact member
73.
[0098] When ablation template device 69 is placed in contact with
tissue, skirt-like members 70, 72 may promote adherence between the
tissue and the device. Furthermore, ablation template device 69 may
include a vacuum port 74. When vacuum pressure is supplied by
connective tube 71 to vacuum port 74, skirt-like members 70, 72 may
promote the creation of a seal, further enhancing the adherence of
device 69 to the tissue. Upon application of vacuum pressure,
skirt-like members 70, 72 may deform slightly, conforming to the
surface of the tissue and helping define a sealed vacuum chamber 76
having a substantially annular shape. Skirt-like members 70, 72 may
therefore improve adherence to the tissue in two ways: by being
tacky and compliant, and by assisting the creation of a vacuum
seal. Silicone gels, such as NuSil 6340, may be especially well
suited for this function, providing a quality of adherence and
compressibility appropriate for the intended purposes.
[0099] FIG. 10 shows a perspective view of an ablation template
device 80, which is similar to ablation template device 50 shown in
FIG. 6. The contact member 82 of the device 80 has been supplied
with a thin layer of a compliant, tacky substance 84 such as a
silicone gel. When ablation template device 80 is held by pressure
against tissue using shaft 86, tacky layer 84 may provide added
adherence between the device and the tissue, and may reduce the
risk of slippage. The tacky material may be included at every point
of contact between the tissue and contact member 82, or at selected
sites of contact.
[0100] FIG. 11 is a perspective view of an ablation template device
100, shown placed on a heart 10 for purposes of illustration.
Ablation template device 100 is like ablation template device 69
shown in FIG. 9. Contact member 102 has been placed against the
surface 15 of the right atrium 12. Inner skirt-like member 104,
extending around the inner edge of contact member 102, and outer
skirt-like member 106, extending around the outer edge of contact
member 102, assist in substantially affixing device 100 to the
heart 10. Vacuum pressure supplied to vacuum port 108 via
connecting tube 110 may promote additional adherence between
contact member 102 and heart surface 15.
[0101] It may be difficult for a surgeon to obtain direct access to
the tissue of the atrium 12 where ablation is to be performed. It
may be necessary for the surgeon to manipulate or move the heart so
that access may be obtained. FIG. 11 illustrates the use of a
surgical manipulating device 120, whereby the apex 122 of the heart
10 is held and manipulated, allowing the surgeon to obtain access
to the desired site on the atrium 12. It is known that some
significant portion of the aberrant impulses responsible for atrial
fibrillation can originate in myocardial cells that have migrated
to the inner base of the pulmonary veins. Accordingly, it is
important that ablation lines be drawn in such a way as to isolate
the pulmonary veins and prevent those impulses from traveling into
the atrial tissue. Accomplishing this isolation requires that the
ablation lines be drawn relatively close to the base of the
pulmonary veins.
[0102] The use of surgical manipulating device 120 and similar
devices described herein enables the surgeon to grasp the apex 122
of the beating or stopped heart 10 and access the base of the
pulmonary veins, e.g., by lifting, pulling, and/or turning the
beating heart to expose the pulmonary veins. Important additional
benefits of device 120 and similar devices described herein may
include the ability to lift and manipulate the heart 10 without
causing significant trauma to the epicardium and with minimal or no
disturbance of hemodynamics, reducing the overall risk of the
procedure to the patient. The rigid handle 127 on device 120
permits the surgeon to apply axial (i.e., along axis from top of
heart to apex) tension to the beating heart while lifting the heart
10 from the pericardial cavity. Maintaining axial tension while
lifting the heart from the supine position to a position 90-110
degrees from the spine prevents distortion of valves and the
decline in cardiac output that occurs when the heart is lifted by
the surgeon's hand alone.
[0103] In some embodiments, two suction devices, e.g., like
surgical manipulating device 120, can be used to access the
posterior of the heart and the base of the pulmonary veins. One
device may be applied to the apex of the heart and the second
device may be applied to a suitable location on the anterior
surface of the heart, such as the area between the right and left
ventricles (interventricular groove). Both devices can then be
manually manipulated in concert so that the heart can be raised to
a vertical position, i.e., close to 90 degrees from its ordinary
anatomic orientation, without distorting the axis that runs from
the apex to the great vessels. In addition, manual manipulation of
both devices simultaneously permits the surgeon to move the raised
heart from left to right inside the thoracic cavity. The use of the
second device on the anterior surface of the heart keeps the
chambers and valves in the heart from being compressed or
distorted, and permits elevation and rotation of the heart without
compromising blood flow. No decline in blood pressure (measured
just below the aortic arch with an intravascular transducer) is
observed when these manipulations are performed with the two
devices used in concert. The two devices (each of which may conform
substantially to device 120) can also be secured by a suitable
clamp or frame that is anchored to the operating table or the chest
retractor.
[0104] Manipulating device 120, as shown in FIG. 11, may define a
cup-like chamber 123 having a vacuum port 125 coupled to a vacuum
tube 127. Chamber 123 can be formed from a cup frame 121 formed
with semi-rigid material and a compliant, tacky skirt-like member
129. Vacuum tube 127 may be coupled to an external vacuum source
for delivery of vacuum pressure to the interior of chamber 123.
[0105] Compliant, tacky skirt-like member 129 can be formed, for
example, from silicone gel, and can be attached to an outer wall
defined by chamber 123 to provide a sealing interface with tissue
at apex 122 of heart 10. Skirt member 129 can be molded, cast,
deposited or otherwise formed about the wall of chamber 123, or
adhesively bonded to the chamber wall. Although the tackiness of
skirt member 129 promotes adherence, adherence may be improved by
application of the vacuum pressure via tube 127 and port 125. Upon
application of vacuum pressure, at least a portion of the seal
member 129 deforms and substantially forms a seal against the
surface. Device 120, in various embodiments, may correspond
substantially to similar devices described in the U.S. provisional
application serial No. 60/181,925, filed Feb. 11, 2000, to Sharrow
et al., entitled "DEVICES AND METHODS FOR MANIPULATION OF ORGAN
TISSUE," and bearing attorney docket no. 11031-004P01, the entire
content of which is incorporated herein by reference.
[0106] The semi-rigid chamber 123 imparts structural integrity to
the device 120, while the tacky, deformable material forming the
skirt-like member 129 provides a seal interface with the heart
tissue that is both adherent and adaptive to the contour of the
heart. Moreover, as the skirt-like member 129 deforms, it produces
an increased surface area for contact with the heart tissue. The
increased surface area provides a greater overall contact area for
adherence, and distributes the coupling force of the vacuum
pressure over a larger tissue area to reduce tissue trauma. In
general, the structure of device 120 can be helpful in avoiding
ischemia, hematoma or other trauma to the heart 10. Device 120
provides a grasping point, however, for manipulation of heart 10 to
provide better access to a desired surgical site, e.g., by lifting,
turning, pulling, pushing, and the like. Once the desired
presentation of heart 10 is achieved using device 120, the heart
can be held relatively stationary, e.g., by fixing vacuum tube 127
to a more stationary object such as a rib spreader. Device 120 and
similar devices described herein can be used to stabilize the heart
in a similar manner by grasping the apex and/or other suitable
locations on the heart, such as the anterior interventricular
groove, and attaching the device to a stationary object. In this
manner, it is possible to use one or more devices such as device
120 and similar embodiments in concert with the various embodiments
of tissue ablation templates described herein placed at a variety
of suitable locations on the heart to create a relatively stable
epicardial surface for ablation. Such stabilization allows the
surgeon to complete the manual ablation or other surgical
procedures more easily and more quickly than without stabilization.
For example, using a first device 120 on a suitable ventricular
surface and a second device 120 on the apex permits the surgeon to
elevate the heart and stabilize it to permit ablation with an
ablation template on the posterior side of the heart. Addition of a
flexible joint between vacuum tube 127 and member 121 may allow the
heart to maintain its normal movement resulting from contraction
further reducing trauma to the heart.
[0107] In some embodiments, device 120 and an ablation template
device as described herein may be appropriately miniaturized to
permit deployment via port-access methods, such as small
thoracotomies. An ablation template device as described herein also
could be appropriately miniaturized for application on the
endocardial surface of the heart, e.g., using transluminal
approaches. For endocardial application, an ablation probe such as
an RF antenna can be integrated with the ablation template device,
which could be made substantially flexible but incorporate shape
memory elements or elasticity to expand following transluminal
deployment.
[0108] In alternative embodiments, no external vacuum pressure need
be applied. Instead, as shown in the cross-sectional side view of
FIG. 12, a device 120' can be configured to incorporate a
mechanical structure that permits variation of the volume within
the chamber 123', e.g., by actuation of a piston-like member or
modulation of a fluid chamber. For example, a shaft 130 can be
mounted within chamber 123' substantially where vacuum port 125 and
vacuum tube 127 are located in FIG. 11. A distal end 131 of the
shaft 130 is positioned to engage a flexible membrane 132 within
chamber 123'. An attachment pad can be placed between distal end
131 of shaft 130 and flexible membrane 132 to permit adhesive or
thermal attachment. Upon actuation of the shaft 130, the membrane
132 can be moved inward and outward relative to the interior of
chamber 123', and thereby change the volume and, as a result,
pressure within the chamber 123'.
[0109] As an illustration, upon engagement of seal member 129 with
heart 10, shaft 130 and cup 121 are pushed onto heart surface 15.
Retracting shaft 130 draws membrane 132 and heart surface 15 into
the chamber defined by cup 121. Upon release of shaft 130,
elasticity of membrane 132 biases the membrane and shaft 130 back
to their original positions, increasing the volume and decreasing
the pressure within chamber 123'. As a result, chamber 123'
produces a suction effect without application of external negative
pressure that enhances the seal provided by the tacky skirt-like
member 129. Thus, the shaft 130 and membrane 132 can be used to
create a negative pressure within chamber 123' that serves to aid
adhesion of the tacky skirt-like gasket member 129 to apex 122
(shown in FIG. 11). FIG. 12 also illustrates internal attachment of
skirt-like member 129 with cup frame 121. In particular, as shown
in FIG. 12, skirt-like member 129 can be molded about the outer lip
133 of cup frame 121. Also, an insert 135 formed from a metal or
polymeric material can be embedded within cup frame 121 and
skirt-like member 129 to provide added structural integrity to
device 120'.
[0110] FIG. 13 illustrates another embodiment of a device 120'
incorporating a limpet-like structure. In the example of FIG. 13,
instead of a shaft 130 as shown in FIG. 12, chamber 123 receives a
fluid tube 134 at port 125. Fluid tube 134 permits inflow and
outflow of fluid 136 into the internal cavity 138 defined by
membrane 132 and the inner wall 140 of chamber 123. In this case,
internal cavity 138 can be normally filled with a fluid 136 such as
saline. When fluid is drawn from device 120 through fluid tube 134,
membrane 132 is drawn toward port 125, decreasing the volume of the
portion 138 of chamber 123 that engages heart 10. In this manner,
pressure within chamber 123 is reduced, creating a suction effect
that aids the sealing pressure of skirt-like member 129 at apex
122. A stopping mechanism such as a valve or stopcock (not shown)
may be employed to stop the flow of fluid through fluid tube 134,
and thereby fixing the sealing pressure.
[0111] FIG. 14 depicts a device 141 that permits attachment of an
antenna for delivery of radio frequency (RF) energy to the surface
of a heart for the purpose of creating a linear lesion of dead
tissue that is transmural. FIG. 15 shows a cross section at point
145 on device 140 of FIG. 14. The body 147 of the device 140 can be
made of a suitable flexible polymeric material such as silicone
elastomer. A shaft 142, made of either a rigid or flexible
material, depending upon application, can be used to position the
device 140 in either an open or minimally invasive surgical
procedure. The diameter of shaft 142 would be sized differently for
each of these applications. In the example of FIGS. 14 and 15,
shaft 142 also contains a moveable inner catheter 143 that contains
the RF antenna and, if appropriate, a fluid delivery lumen 148. In
addition to the catheter 143, shaft 142 can provide a vacuum
connection to device 140, which may define one or more inner
chambers. The device 140 can be attached to the heart using two
vacuum ports 144, 146 connected to one or more seal members 149,
151. Vacuum pressure can be provided to ports 144, 146 via tubes
150, 152, which are coupled to an external vacuum source and branch
off from shaft 142.
[0112] The body 147 of device 140 can be molded to define two
vacuum chambers 154, 156 and a central lumen 158, which opens to a
base side 160 of the device and forms a continuous track for
accommodation of catheter 143. Malleable metal shafts 162, 163, 164
can be inserted into the body 147 to provide shaping capability and
added structural integrity, but may not be necessary to achieve
compatibility with all desired contours and positions on the heart.
Vacuum pressure delivered through vacuum chambers 154, 156 via
vacuum ports 144, 146 is used to attach the device 140 to the
heart. Flexible seal members 166, 168, and 170, 172 are disposed
adjacent each vacuum chamber 154, 156, respectively, and conform to
the surface of the heart and function as seals 149, 151. Seal
members 166, 168, 170, 172 can be made of silicone elastomers as
soft as 5 on the Shore A scale, or can be made of silicone gel. A
suitable silicone elastomer material may have a durometer, for
example, in the range of 5 to 30 Shore A. An example of one
suitable silicone gel material is MED 6340, commercially available
from NUSIL Silicone Technologies, of Carpinteria, Calif. The MED
6340 silicone gel is tacky and exhibits a penetration
characteristic such that a 19.5 gram shaft with a 6.35 mm diameter
has been observed to penetrate the gel approximately 5 mm in
approximately 5 seconds. This penetration characteristic is not a
requirement, but merely representative of that exhibited by the
commercially available MED 6340 material. These materials can
conform to the irregular shape of the myocardium under negative
pressure created by the vacuum source and, if formed from silicone
gel, may provide tackiness that aids the seal.
[0113] The seal members 166, 168, 170, 172 can be partially shaped
and stiffened, if necessary by fins 174, 176, 178, 180,
respectively, placed at different intervals along the length of the
seal members. These fins can be made of flexible metal or can be
part of the material forming body 147 of device 140 and integrally
molded therewith. Seal members 166, 168, 170, 172 and associated
vacuum chambers 154, 156 may extend along the length of body 147,
like central lumen 158, to define elongated tracks. Upon
application of vacuum pressure to vacuum ports 144, 146, vacuum
chambers 154, 156 serve to hold device 140 tightly against the
surface of the heart. Device 140 may be sized and structured to
provide a local stabilizing effect on the tissue to which the
device is attached, e.g., for beating heart surgical applications.
In many embodiments, however, stabilization will not be necessary.
Rather, it is sufficient that device 140 fix a surgical instrument,
e.g., RF antenna 141, in the same frame of motion as the moving
tissue. In this manner, an instrument can be applied with precision
to the surface of the heart without significant relative
motion.
[0114] In the central lumen 158 is inserted catheter 143, which, in
the example of FIGS. 14 and 15, contains RF antenna 141. Antenna
141 may, itself, enclose fluid delivery lumen 148. RF antenna 141
is shown in FIGS. 14 and 15 at the end of catheter 143, where the
antenna emerges at an angle to the catheter and protrudes through
the track defined by central lumen 158 of device 140. By sliding
catheter 143 along the track defined by lumen 158, the tip 182 of
antenna 141 can move along the track and deliver energy to the
tissue with which it is in contact, creating a lesion that can
extend the full thickness of the myocardium. An RF antenna is one
example of an ablation probe suitable for use with device 140 to
ablate tissue. Other ablation instruments could be placed in
catheter 143, however, including laser, ultrasonic, and cryogenic
probes, all, all of which could create a lesion in a similar
fashion.
[0115] In some embodiments, catheter 143 can be moved through lumen
158 either manually by a surgeon by grasping the proximal end of
the catheter or by a mechanical device connected to the catheter,
e.g., at its distal end. For example, a variety of electrical
motors could be used to drive catheter 143 along central lumen 158,
e.g., directly via a worm gear drive or indirectly via pulley or
gear arrangements. The motors can be driven either automatically,
or at the direction of the surgeon using a joystick or other manual
controls. Electrodes 184, 186 can be mounted on an inner surface of
the innermost seal members 168, 170 for contact with the
myocardium. Electrodes 184, 186 are connected to conductors 188,
190, respectively, which extend out of device body 147 and continue
into shaft 142. Electrode 184 and conductor 188 on one side of the
device 140 can be used to send an electric signal across the lesion
area formed by antenna 141 for detection on the other side of the
device by another electrode 186 and conductor 190.
[0116] FIG. 16 is a cross section at point B on shaft 142 of FIG.
14. Conductors 188, 190 can be connected via a cable 192 to
appropriate instrumentation. Such conductor/electrode sets can be
used to measure impedance across the lesion or conduction velocity
across the lesion. These measurements can be used to determine if
the lesion is truly transmural, that it extends the full thickness
of the myocardium. Conductors 188, 190 can be ultimately connected
to an external control unit which is capable of using impedance or
conductance time or velocity measurements to generate either a
signal observable by the surgeon or a signal for control of a
device responsible for advancing catheter 143 along central lumen
158 when a transmural lesion has been created in one region. To
that end, a plurality of electrodes 184, 186 can be placed on
respective sides of central lumen 158 to take measurements at
several positions along the length of the lesion track, thereby
driving controlled advancement of catheter 143 as an effective
lesion is formed at each position. Again, advancement of catheter
143 can be automated or manual. In either case the surgeon can be
assured during the procedure that an effective lesion has been
formed.
[0117] As shown in FIG. 16, outer shaft 142 may contain two
separate lumens 194, 196, which provide vacuum pressure to chambers
154, 156 via tubes 150, 152. FIG. 16 also shows a cable with a
wiring bundle including conductors 188, 190, for electrical
communication with electrodes 184, 186 (FIG. 15). The number of
conductors may be dependent upon the number of electrodes placed on
each side of the inner sealing members 168, 170. For example, each
electrode 184, 186 preferably is coupled to an individual conductor
188, 190, respectively. Alternatively, a single continuous
electrode could be disposed on one side of central lumen 158 and
coupled to a single conductor. In this case, a series of electrodes
at various positions on one side of central lumen 158 would
transmit signals to the continuous electrode on the other side or
vice versa. Catheter 143 fits in the central lumen 158 of shaft 142
and, in this example, contains RF antenna 141 and fluid lumen 148.
Again, other embodiments could have different types of ablation
probes built into catheter 143.
[0118] FIG. 17 shows a specialized form of a device 140' as shown
in FIG. 14. In this embodiment, the device body 147' is shaped in a
substantially semicircular form to facilitate contact around the
base of the pulmonary vein or similar structure. Device body 147'
is moved into position via shaft 142' and vacuum is used to affix
it to its first location on the vein. In this case, a catheter is
translated around the arcuate path defined by a central lumen. The
catheter carries an RF antenna or other ablation probe that is
exposed via opening for contact with the outer wall of the
pulmonary vein. Lesion generation is carried out on the full
thickness of the vein wall in one location by energization of the
RF antenna or activation of other suitable probe. As shown in FIG.
17, vacuum pressure can be applied via vacuum chambers 154', 156'
with seal members 166', 168', 170', 172' providing an effective
seal. When vacuum pressure is released, device 140' can be moved
via shaft 142' to another location to create a lesion continuous
with the previous one until a circumferential lesion is created all
the way around the base of the pulmonary vein. As in the example of
FIGS. 14-16, device 140 can be fixed in the same frame of motion as
the pulmonary vein, eliminating significant relative motion to
enhance precision in creation of the lesion. The interior of device
140' is identical to that of device 140 as shown in FIG. 15, with
two modifications. The malleable metal inserts 162, 164 are
replaced with shaped memory metal inserts, which cause 140' to
assume an arcuate shape shown in FIG. 17. Malleable insert 163 is
replaced with a semi-rigid metal rod which can be withdrawn through
shaft 142' to allow elements 162, 164 to assume their arcuate shape
and cause device 140' to also assume an arcuate shape. Insertion of
the semi-rigid rod causes device 140' to straighten into a linear
shape that would permit device 140' to entry into or withdraw from
a tubular access port used in minimally invasive surgical
procedures.
[0119] Although device 140 is depicted as having a "shepherd's
crook" shape, that shape is merely an exemplary embodiment of the
invention. The ablative device may take other forms such as a loop,
hook, ess or snare. In any of these configurations, electrode sets
may be placed on the device so as to have a one or more
transmitting electrodes on one side of the lesion and one or more
receiving electrodes on the opposite side of the lesion to measure
the effectiveness of the ablation.
[0120] FIGS. 18-20 illustrate another embodiment of an ablation
template device 200. FIG. 18 is a perspective side view of device
200. FIG. 19 is a cross-sectional side view of device 200 taken at
line 210-210' in FIG. 18. FIG. 20 is a bottom view of device 200.
As shown in FIGS. 18-20, device 200 includes a ring-like contact
member 202 defining an annular but generally oval-shaped chamber
204. Contact member 202 may include a frame 204 formed from a
semi-rigid material, and seal members 206, 208 formed at the inner
and outer diameters of frame 204. Seal members 206, 208 can be
formed, for example, from a silicone gel material. A vacuum tube
212 is mounted in a vacuum port 214 that communicates with an
interior chamber 216 defined by frame 204 and seal members 206,
208. A cover 218 can be mounted within the central aperture 220
defined by frame 204, or integrally formed with the frame, e.g., by
molding. Cover 218 includes a slot-like track 222 that extends
along the major axis of contact member 202. Track 222 accommodates
an ablation probe 224.
[0121] Ablation probe 224 may take the form of an RF, laser,
ultrasonic, or cryogenic probe, and includes upper and lower
flanges 226, 228 that hold the probe within track. In particular,
upper flange 226 bears on an upper surface of cover 218 adjacent
track 222, while lower flange 228 bears on a lower surface of the
cover. Ablation probe 224 is slidable along track 222, however, to
define a lesion path for an ablation procedure. In particular, a
surgeon can simply slide ablation probe 224 along track 222.
Electrodes 230, 232 on opposite sides of track 222 can be
electrically coupled to electronics that provide measurements,
e.g., impedance, conduction velocity, and conduction time, to
assess the effectiveness of the ablation procedure. In response to
indications provided based on the electrode measurements, the
surgeon advances ablation probe 224 along track 222. Alternatively,
ablation probe 224 can be advanced automatically along track 222 in
response to such indications. In some embodiments, tip 234 of
ablation probe 224 may contact tissue.
[0122] FIGS. 21-23 illustrate another ablation template device 240.
FIG. 21 is a partial perspective view of device 240. FIG. 22 is a
partial cross-sectional side view of device 240 of FIG. 21 taken at
line 242-242'. FIG. 23 is a cross-sectional front view of device
240 of FIG. 21 taken at line 244-244'. As shown in FIGS. 21-23,
device 240 includes a contact member 246 mounted on an elongated
guide member 248 that extends through bore 249. Contact member 246
may be slidable along guide member 248 or fixed. The contact member
includes a frame 250 formed of a flexible material, and a seal
member 252 formed from a compliant, tacky material such as silicone
gel. The seal member 252 interfaces with tissue, e.g., on the
surface of the heart. Frame 250 further defines one or more rails
254 that extend radially outward relative to contact member 246 and
longitudinally relative to guide member 248. A carriage 256 is
mounted on rails 254, e.g., via inner grooves that engage the
rails, and defines a lateral flange 258 designed to hold an
ablation probe 260. As shown in FIGS. 21 and 23, in particular,
ablation probe 260 protrudes downward from lateral flange 258 for
contact with organ tissue.
[0123] Ablation probe 260 can be molded into or otherwise encased
in lateral flange 258 of carriage 256. A second lateral flange 262
(FIG. 23) can be provided, along with a counter probe 264, to
contact tissue and thereby balance device 240 on a side of carriage
256 opposite lateral flange 258. Ablation probe 260 may take the
form of an RF, laser, ultrasonic, or cryogenic probe designed to
ablate tissue. Ablation probe 260 may have electric conductors that
run along the length of guide member 248 to an external power
supply, in the case of an RF or ultrasonic probe. Alternatively, an
optical fiber or fiber bundle may be coupled between ablation probe
260 and an external source of laser energy. As a further
alternative, a fluid line may extend between ablation stylus and a
cryogenic source. In each case, device 240 can be sized and
arranged to permit deployment by endoscopic or other minimally
invasive techniques to an ablation site, e.g., on the surface of
the heart. Thus, in one application, device 240 can be deployed and
affixed to the surface of a beating heart, and fix the ablation
probe 260 in the same frame of motion as the heart.
[0124] Seal member 252 may define a plurality of vacuum ports 266
coincident with vacuum ports in guide member 248. A vacuum tube
resides within an inner lumen 270 of guide member 248 and includes
one or more output ports that apply vacuum pressure to vacuum ports
266. To perform an ablation procedure, device 240 is deployed to a
desired site on the surface of an organ such as the heart. Vacuum
pressure is applied to affix contact member 246 to the tissue
surface via the seal interface provided by seal member 252. At the
same time, ablation probe 260 is brought in contact with the tissue
surface. Ablation probe 260 is then energized to ablate the local
tissue area proximate the tip of the probe. A guide wire or other
elongated member can be coupled to carriage 256, which preferably
is slidable along rails 254 defined by contact member 252. By
translating the guide wire, carriage 256 can be moved relative to
contact member 252 and thus relative to the tissue surface, thereby
creating an ablation track. As in other embodiments, electrodes can
be integrated with seal member 252 to measure the extent of
ablation. Again, the measurements can be used as the basis for
manual or automated control of the guide wire, and resulting
movement of carriage 256.
[0125] FIGS. 24 and 25 illustrate another ablation template device
272. FIG. 24 is a cross-sectional front view of device 272, while
FIG. 25 is a fragmentary cross-sectional side view. Device 272 is
somewhat similar to device 240 of FIGS. 21-23. However, device 272
need not incorporate a carriage. Rather, device 272 provides an
internal optical waveguide 274 mounted within a guide member 276
that transmits laser radiation. Waveguide 274 may be housed in a
cannula 278. Waveguide 274 may incorporate a reflector 280 at its
distal end 282 that reflects laser energy downward through a
chamber defined by seal member 284 to ablate tissue. Seal member
284 may be substantially compliant and tacky and may be attached to
a semi-rigid frame 286 that is coupled to or integrated with guide
member 276. Cannula 278 and waveguide 274 preferably are movable
along the length of guide member 276, as indicated by arrow 288.
Optical waveguide 274 can be mounted within an outer vacuum lumen
290 that delivers vacuum pressure to affix device 272 to the tissue
292 via seal member 284. To form an ablation track, optical
waveguide 274 can be translated within guide member 276, as
indicated by arrow 288. Once again, electrodes can be integrated
with seal member to enable manual or automated control of waveguide
movement.
[0126] Ablation, and measurement of impedance or conduction time to
assess ablation lesion depth, can also be performed along the
interior surfaces of a structure. For example, a linear RF
electrode can be transluminally introduced via a catheter into the
atria of the heart and positioned on the endocardium in appropriate
locations. Ablative energy from the RF electrode can then be
applied. Electrode sets used to measure impedance or conduction
time or other electrical properties can be integrated into the
catheter body parallel to but insulated from the active RF
electrode at the distal end of the catheter. These electrode sets
can be utilized as described above to both measure lesion depth
(from the endocardial to the epicardial surface) and to control
delivery of energy.
[0127] Transluminal introduction, therefore, represents an
additional way to create a lesion around the base of the pulmonary
veins, and thereby treat atrial fibrillation. The lesion may be
created on the interior surfaces of the heart or pulmonary veins,
rather than the heart's or veins' exterior surfaces. The treatment
entails ablating the endocardial tissue near the ostia of the
pulmonary veins in the left atrium. Typically the ablation
apparatus is delivered to the site on the distal end of a steerable
catheter introduced into the atrium or the pulmonary veins, and is
manipulated and controlled at the proximal end of the catheter.
[0128] FIG. 26 is a side view of an apparatus that may be directed
transluminally near the ostia of the pulmonary veins in the left
atrium. The device of FIG. 26 may conform substantially to the
device shown in U.S. Pat. No. 5,938,660 to Swartz et al. In the
example of FIG. 26, however, the device has been adapted in
accordance with the present invention to incorporate components for
measurement of ablation depth or effectiveness. In particular,
electrodes have been positioned on the device so as to come into
contact with tissue on opposing sides of a lesion created by the
ablative components.
[0129] FIG. 26 depicts a distal end of a catheter body 300, with
balloons 302, 304 on the catheter body 300 shown inflated. Fluid
medium introduced through catheter lumen 306 at the proximal end
emerges at the distal end through openings 308, thus inflating the
balloons 302, 304. Inflation causes balloons 302, 304 to lodge
against the tissue. Catheter 300 may include a tip electrode 310
for sensing electrical activity. Catheter 300 may also include RF
electrode 312, which performs the actual ablation. After balloons
302, 304 are inflated, ablation may be accomplished by introducing
a conductive media through catheter 300, which emerges at the
distal end through openings 318. Application of RF energy follows,
and the tissue between the balloons 302, 304 is ablated.
[0130] Electrodes 314, 316 are mounted on the surface of the
balloons 302, 304 at the circumference of the balloons. Electrodes
314, 316 are insulatively separated from RF electrode 312 and tip
electrode 310. Electrodes 314, 316 may be uni-polar or multi-polar.
Connecting leads 320 and 322 are coupled to electrodes 314 and 316
respectively. Leads 320, 322 may be wires or conductors printed on
the surface of balloons, or a combination of both. Leads 320, 322
travel from electrodes 314, 316 toward proximal end of catheter
300, and emerge from proximal end of catheter where leads are
electrically coupled to a measuring device such as an impedance
meter or conduction time measuring device. Following measurements
that show a successful ablation, the conductive media may be
withdrawn, balloons 302, 304 may be deflated, and the catheter may
be extracted.
[0131] Many variations are possible. For example, a plurality of
electrodes can be mounted on the surface of balloons 302, 304.
Flexible disks or other extendable members could be used in place
of balloons. The RF electrode may be extended or unfolded from the
body of the catheter or otherwise steered into proximity with the
tissue surface. Ultrasound energy or other energy forms may be used
in place of RF. Sites other than the ostium may be treated. In each
of these variations, however, electrodes can be used to measure the
efficacy of the treatment.
[0132] FIG. 27 is a side view of an additional apparatus that may
be directed transluminally near the ostia of the pulmonary veins in
the left atrium. The device of FIG. 27 may conform substantially to
the device shown in U.S. Pat. No. 6,024,740 to Lesh et al. and to
the device shown in U.S. Pat. No. 6,012,457 to Lesh. In the example
of FIG. 27, however, the device has been adapted in accordance with
the present invention to incorporate components for measurement of
ablation depth or effectiveness. In particular, electrodes have
been positioned on the device so as to come into contact with
tissue on opposing sides of a lesion created by the ablation
element.
[0133] FIG. 27 depicts a distal end of a catheter 330, with balloon
332 on the catheter body 330 shown inflated. Fluid medium
introduced through catheter lumen 334 at the proximal end inflates
balloon 332, causing balloon 332 to lodge against the tissue,
preferably but not necessarily at the ostia of the pulmonary veins.
Catheter 330 may also include RF electrode 336, which contacts the
tissue. Catheter 330 may further include a proximal perfusion port
338 and a distal perfusion port 340 connected by a perfusion lumen
342.
[0134] Electrodes 344, 346 are mounted on the surface of balloon
332, and contact the tissue. Electrodes 344, 346 are insulatively
separated from RF electrode 336. Electrodes 344, 346 may be
uni-polar or multi-polar. A plurality of such electrode pairs could
be employed. Connecting leads 348 and 350 are coupled to electrodes
344 and 346, respectively, and travel from electrodes 344, 346
toward proximal end of catheter 330. At the proximal end of
catheter, leads 348, 350 are electrically coupled to a measuring
device such as an impedance meter or conduction time measuring
device. Following measurements that show a successful ablation, the
balloon 332 may be deflated and the catheter may be extracted. As
with the apparatus shown in FIG. 26, many variations are
possible.
[0135] FIG. 28 is a side view of a further apparatus that may be
directed transluminally to various locations within either atrium.
FIG. 28 depicts a distal end of a catheter body 360. Catheter 360
is steerable, allowing it to be positioned against the tissue. An
energy delivery means such as an RF electrode 362 performs the
ablation.
[0136] Electrodes 364, 366 may be independently controlled from the
proximal end of the catheter and may be extended from or retracted
into lumens 368, 370. Electrodes 364, 366 may be uni-polar or
multi-polar. Electrodes 364, 366 extend toward proximal end of
catheter 360, where they are electrically coupled to a measuring
device such as an impedance meter or conduction time measuring
device. Electrode tips 372, 374 can be of various shapes to
facilitate insertion into the tissue. For example, electrode tips
372, 374 may have needle-like shapes or screw-like shapes. Being
independently extendable and retractable, electrodes 364, 366 may
be directed to different sites along a lesion and may be used to
make measurements at multiple locations along a lesion. There could
also be a plurality of such electrodes to provide electrical
measurements at various sites along a lesion.
[0137] FIG. 29 shows another apparatus that may be used
transluminally in either atrium. The device of FIG. 29 may conform
substantially to the device shown in U.S. Pat. No. 5,676,662 to
Fleischhacker et al. In the example of FIG. 29, however, the device
has been adapted in accordance with the present invention to
incorporate components for measurement of ablation depth or
effectiveness. In particular, electrodes have been positioned on
the device so as to come into contact with tissue on opposing sides
of a lesion created by the helical ablation element.
[0138] FIG. 29 shows a distal end of a catheter body 380. Catheter
380 is steerable, allowing it to be positioned against the tissue.
An RF electrode 382 in the form of helical coils 384 performs the
ablation. Coils 384 are electrically isolated from each other by an
insulating substance 386.
[0139] Electrodes 388, 390, which may be uni-polar or multi-polar,
are mounted on opposing sides of catheter 380 and are electrically
isolated from helical coils 384. Electrodes 388, 390 are connected
to leads 392, 394, which extend toward proximal end of catheter
380. At the proximal end of catheter, leads 392, 394 are
electrically coupled to a measuring device such as an impedance
meter or conduction time measuring device.
[0140] FIG. 30 is a side view of a further apparatus that may be
directed transluminally, and may also be positioned on the atrial
endocardium via thoracoscope or port access. The device of FIG. 30
may conform substantially to the device shown in U.S. Pat. No.
5,916,213 to Haissaguerre et al. In the example of FIG. 30,
however, the device has been adapted in accordance with the present
invention to incorporate components for measurement of ablation
depth or effectiveness. In particular, electrodes have been
positioned on the device so as to come into contact with tissue on
opposing sides of a lesion created by the ablation elements.
[0141] FIG. 30 depicts a distal end of a steerable catheter body
400. Catheter 400 includes two energy delivery surfaces 402, 404
such as RF electrodes, which perform the ablation. Energy delivery
surfaces 402, 404 are mounted on movable arms 406, 408
respectively. Arms 406, 408 can be manipulated through a yoke 410,
which is coupled to a cable 412 leading to the proximal end of the
catheter. By manipulation of cable 412 and yoke 410, arms 406, 408
can be drawn into the tip of catheter body 400 and placed in a
closed position parallel to catheter body 400. Cable 412 may also
be used to supply power to energy delivery surfaces 402, 404. Arms
406, 408 can be extended from the tip of catheter body 400 and
placed in an open position perpendicular to catheter body 400. When
arms 406, 408 are in the open position, catheter 400 can be steered
to press energy delivery surfaces 402, 404 against the epicardium
or endocardium. Once energy delivery surfaces 402, 404 are in
place, energy may be applied to energy delivery surfaces 402, 404
to effect the ablation and create a lesion.
[0142] Electrodes 414 and 416 are mounted on opposite sides of arm
406 and electrodes 418 and 420 are mounted on opposite sides of arm
408. Electrodes 414, 416, 418, 420 may be uni-polar or multi-polar.
Connecting leads 422, 424, 426 and 428 are coupled to electrodes
414, 416, 418 and 420 respectively, and travel from electrodes 414,
416, 418 and 420 toward proximal end of the catheter. At the
proximal end of the catheter, leads 422, 424, 426 and 428 are
electrically coupled to one or more measuring devices such as an
impedance meter or conduction time measuring device. Leads 422 and
424 carry information pertaining to the lesion created by energy
surface 402, and leads 426 and 428 carry information pertaining to
the lesion created by energy surface 404.
[0143] Many of the devices described above, such as those depicted
in FIGS. 28, 29 and 30, may be used with epicardial applications as
well as endocardial applications. The devices described above may
also be applied to tissues other than cardiac tissues. The
electrode sets may be used with or without a surgical template.
Although only one set of electrodes is shown in the figures for
clarity, a plurality of electrode sets can be used in any
embodiment. The electrode sets may be also be deployed
independently of the ablative energy delivery system, and may be
used with any ablative energy delivery system. Furthermore, in the
devices described above, the electrode sets may be used as probes
to control the delivery of energy as outlined in FIGS. 4 and 5. The
specific embodiments described above are intended to be
illustrative of the general principle and are not intended to be
limited to a particular device or to a particular template or to a
particular ablative energy delivery system.
[0144] A number of embodiments of the present invention have been
described. Other embodiments are within the scope of the following
claims.
* * * * *