U.S. patent application number 12/902597 was filed with the patent office on 2011-02-03 for electrosurgical systems and methods for removing and modifying tissue.
Invention is credited to Philip E. Eggers, Hira V. Tapliyal, Craig Tsuji, Jean Woloszko.
Application Number | 20110028970 12/902597 |
Document ID | / |
Family ID | 27391584 |
Filed Date | 2011-02-03 |
United States Patent
Application |
20110028970 |
Kind Code |
A1 |
Woloszko; Jean ; et
al. |
February 3, 2011 |
ELECTROSURGICAL SYSTEMS AND METHODS FOR REMOVING AND MODIFYING
TISSUE
Abstract
The present invention provides systems, apparatus and methods
for selectively applying electrical energy to body tissue in order
to ablate, contract, coagulate, or otherwise modify a tissue or
organ of a patients. An electrosurgical apparatus includes an
electrode support bearing an active electrode in the form of a
plasma blade or hook having an active edge and first and second
blade sides. The active edge is adapted for severing a target
tissue via localized molecular dissociation of tissue components.
The first and second blade sides are adapted for engaging against,
and coagulating, the severed tissue. A method of the present
invention comprises positioning an electrosurgical probe adjacent
to the target tissue so that a blade- or hook-like active electrode
is brought into at least close proximity to the target tissue in
the presence of an electrically conductive fluid. A high frequency
voltage is applied between the active electrode and a return
electrode to effect cool ablation or other modification of the
target tissue. During application of the high frequency voltage,
the electrosurgical apparatus may be translated, reciprocated, or
otherwise manipulated such that the active edge is moved with
respect to the tissue. The present invention volumetrically ablates
or otherwise modifies the target tissue with minimal or no damage
to surrounding, non-target tissue.
Inventors: |
Woloszko; Jean; (US)
; Tsuji; Craig; (US) ; Tapliyal; Hira V.;
(US) ; Eggers; Philip E.; (US) |
Correspondence
Address: |
ARTHROCARE CORPORATION;ATTN: Matthew Scheele
7500 Rialto Boulevard, Building Two, Suite 100
Austin
TX
78735-8532
US
|
Family ID: |
27391584 |
Appl. No.: |
12/902597 |
Filed: |
October 12, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10339470 |
Jan 9, 2003 |
7824398 |
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12902597 |
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09780745 |
Feb 9, 2001 |
6770071 |
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10339470 |
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09162117 |
Sep 28, 1998 |
6117109 |
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09780745 |
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08977845 |
Nov 25, 1997 |
6210402 |
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09162117 |
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08562332 |
Nov 22, 1995 |
6024733 |
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08977845 |
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60182751 |
Feb 16, 2000 |
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Current U.S.
Class: |
606/45 ;
606/49 |
Current CPC
Class: |
A61B 2018/00029
20130101; A61B 2218/003 20130101; A61B 18/1206 20130101; A61B
18/1402 20130101; A61B 2018/00148 20130101; A61B 18/1485 20130101;
A61F 2/2493 20130101; A61B 2018/00875 20130101; A61B 2018/162
20130101; A61B 2018/00827 20130101; A61B 2018/1472 20130101; A61B
2018/00327 20130101; A61B 2018/00392 20130101; A61B 2018/00178
20130101; A61B 2018/00505 20130101; A61B 2018/00726 20130101; A61B
2018/00601 20130101; A61B 2018/124 20130101; A61B 18/148 20130101;
A61B 2018/00476 20130101; A61B 2018/00625 20130101; A61B 2018/00678
20130101; A61B 2017/00247 20130101; A61B 2018/0016 20130101; A61B
2018/1407 20130101; A61B 2018/00702 20130101; A61B 2018/126
20130101; A61B 2018/1273 20130101; A61B 2018/00583 20130101; A61B
2018/1253 20130101; A61B 2018/0047 20130101; A61B 18/1482 20130101;
A61B 2017/00084 20130101; A61B 2218/002 20130101; A61B 2018/00119
20130101; A61B 2018/1422 20130101; A61B 18/149 20130101; A61B
2017/00101 20130101; A61B 2018/00577 20130101; A61B 2018/00821
20130101; A61B 2018/00797 20130101; A61B 2018/1467 20130101; A61B
2218/007 20130101; A61B 2018/00791 20130101; A61B 2018/1213
20130101; A61B 18/1492 20130101; A61B 2018/00404 20130101; A61B
2018/165 20130101; A61B 18/042 20130101; A61B 2018/1412 20130101;
A61B 2017/00026 20130101; A61B 2018/00083 20130101; A61B 2018/00815
20130101 |
Class at
Publication: |
606/45 ;
606/49 |
International
Class: |
A61B 18/14 20060101
A61B018/14 |
Claims
1. An electrosurgical probe, comprising: a shaft having a shaft
distal end portion and a shaft proximal end portion; an aspiration
lumen in fluid communication with a distal aspiration port; at
least one electrode support affixed to the shaft distal end
portion; a blade electrode affixed to the at least one electrode
support, wherein the blade electrode comprises a first electrode
arm, a second electrode arm, and a crosspiece extending between the
first and second electrode arms; and wherein the crosspiece
comprises at least one active edge of the blade electrode operable
for dissecting tissue via molecular dissociation of tissue
components.
2. The electrosurgical probe of claim 1, wherein the blade
electrode further comprises a first blade side and a second blade
side operable for engaging and coagulating severed tissue.
3. The electrosurgical probe of claim 1, wherein the at least one
electrode support comprises a first electrode support and a second
electrode support, and wherein the first electrode arm and the
second electrode arm are affixed to the first electrode support and
the second electrode support, respectively.
4. The probe of claim 1, wherein the crosspiece is substantially
orthogonal to the first electrode arm and to the second electrode
arm.
5. The probe of claim 1, wherein the at least one active edge
comprises a distal active edge operable for resection, transection,
or dissection of tissue.
6. The probe of claim 1, wherein the distal aspiration port is
located proximal to the crosspiece, and the crosspiece spans the
distal aspiration port.
7. The probe of claim 1, wherein the blade electrode extends
distally from the electrode support by a distance in the range of
from about 0.1 mm to about 10 mm.
8. The probe of claim 1, wherein the shaft distal end portion is
curved.
9. The probe of claim 1, wherein the shaft distal end portion
terminates in a beveled edge and the at least one electrode support
is disposed on the beveled edge.
10. The probe of claim 1, wherein the blade electrode comprises a
single metal blade having a shape selected from the group
consisting of: substantially semicircular, substantially
rectangular, hooked, and arcuate.
11. The probe of claim 1, further comprising a fluid delivery unit
associated with the shaft.
12. The probe of claim 11, wherein the fluid delivery unit includes
an outer sheath situated external to the shaft and forming an
annular fluid delivery lumen between the outer sheath and the
shaft, the annular fluid delivery lumen terminating in a fluid
delivery port.
13. The probe of claim 12, wherein the fluid delivery port is
located at the shaft distal end portion proximal to a return
electrode.
14. An electrosurgical apparatus, comprising: a shaft having a
shaft distal end portion and a shaft proximal end portion; an
electrode support arranged terminally on the shaft distal end
portion; a blade electrode disposed on the distal terminus of the
electrode support, the blade electrode comprises a first electrode
arm, a second electrode arm, and a crosspiece extending between the
first and second electrode arms, the crosspiece including a distal
active edge operable for localized ablation of tissue via molecular
dissociation of tissue components; and wherein the blade electrode
has a contact surface operable for severing and coagulating
tissue.
15. The apparatus of claim 14, further comprising an aspiration
lumen in fluid communication with a distal aspiration port, wherein
the distal aspiration port is located proximal to the crosspiece,
and the crosspiece spans the distal aspiration port.
16. The apparatus of claim 14, wherein the blade electrode
comprises a single metal blade having a shape selected from the
group consisting of: substantially semicircular, substantially
rectangular, hooked, and arcuate.
17. An electrosurgical system, comprising: a plasma blade
electrosurgical probe, the probe comprising: a shaft having a shaft
distal end portion and a shaft proximal end portion; a shaft having
a shaft distal end portion and a shaft proximal end portion; an
aspiration lumen in fluid communication with a distal aspiration
port; at least one electrode support affixed to the shaft distal
end portion; a blade electrode affixed to the at least one
electrode support, wherein the blade electrode comprises a first
electrode arm, a second electrode arm, and a crosspiece extending
between the first and second electrode arms; wherein the crosspiece
comprises at least one active edge of the blade electrode operable
for severing tissue via molecular dissociation of tissue
components; and a generator comprising a high frequency power
supply, the high frequency power supply electrically coupled to the
blade electrode.
18. The system of claim 17, wherein the high frequency power supply
is operable to apply pulses of high frequency voltage to the blade
electrode.
19. The system of claim 17, wherein the blade electrode has a shape
selected from the group consisting of: substantially rectangular,
substantially semicircular, hooked, and arcuate.
20. The system of claim 17, wherein the blade electrode comprises a
material selected from the group consisting of platinum, tungsten,
palladium, iridium, and titanium.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/339,470, filed Jan. 9, 2003, which is a
divisional of U.S. patent application Ser. No. 09/780,745, filed
Feb. 9, 2001, now U.S. Pat. No. 6,770,071, which claims the benefit
of U.S. Provisional Patent Application No. 60/182,751 filed Feb.
16, 2000. application Ser. No. 09/780,745 is also a
continuation-in-part of U.S. patent application Ser. No.
09/162,117, filed Sep. 28, 1998, now U.S. Pat. No. 6,117,109, which
is a continuation in part of U.S. patent application Ser. No.
08/977,845, filed Nov. 25, 1997, now U.S. Pat. No. 6,210,402, which
is a continuation-in-part of U.S. patent application Ser. No.
08/562,332, filed Nov. 22, 1995, now U.S. Pat. No. 6,024,733, all
of which are herein incorporated by reference for all purposes.
[0002] The present invention is also related to commonly assigned
U.S. Provisional Patent Application No. 60/062,996, filed Oct. 23,
1997, and U.S. patent application Ser. No. 08/990,374, filed Dec.
15, 1997, now U.S. Pat. No. 6,109,268, which is a continuation in
part of U.S. patent application Ser. No. 08/485,219, filed on Jun.
7, 1995, now U.S. Pat. No. 5,697,281; U.S. patent application Ser.
No. 09/109,219, filed on Jun 30, 1998, now abandoned; U.S. patent
application Ser. No. 09/058,571, filed Apr. 10, 1998, now U.S. Pat.
No. 6,142,992; U.S. patent application Ser. No. 08/874,173, filed
Jun. 13, 1997, now U.S. Pat. No. 6,179,824; and U.S. patent
application Ser. No. 09/002,315, filed Jan. 2, 1998, now U.S. Pat.
No. 6,183,469, and U.S. patent application Ser. No. 09/054,323,
filed on Apr. 2, 1998, now U.S. Pat. No. 6,063,079; U.S. patent
application Ser. No. 09/010,382, filed Jan. 21, 1998, now U.S. Pat.
No. 6,190,381; and U.S. patent application Ser. No. 09/032,375,
filed Feb. 27, 1998, now U.S. Pat. No. 6,355,032; U.S. patent
application Ser. No. 08/977,845, filed on Nov. 25, 1997, now U.S.
Pat. No. 6,210,402; U.S. application Ser. No. 08/942,580, filed on
Oct. 2, 1997, now U.S. Pat. No. 6,159,194, U.S. application Ser.
No. 08/753,227, filed on Nov. 22, 1996, now U.S. Pat. No.
5,873,855; U.S. application Ser. No. 08/687,792, filed on Jul. 18,
1996, now U.S. Pat. No. 5,843,019; and International Application,
No. PCT/US94/05168, filed on May 10, 1994; U.S. patent application
Ser. No. 08/446,767, filed Jun. 2, 1995, now U.S. Pat. No.
5,697,909; U.S. patent application Ser. No. 08/059,681, filed on
May 10, 1993, now abandoned, which is a continuation-in-part of
U.S. patent application Ser. No. 07/958,977, filed on Oct. 9, 1992,
now U.S. Pat. No. 5,366,443, which is a continuation-in-part of
U.S. patent application Ser. No. 07/817,575, filed on Jan. 7, 1992,
now abandoned, the complete disclosures of which are incorporated
herein by reference for all purposes. The present invention is also
related to commonly assigned U.S. patent application Ser. No.
08/562,331, filed Nov. 22, 1995, now U.S. Pat. No. 5,683,366, the
complete disclosure of which is incorporated herein by reference
for all purposes.
BACKGROUND OF THE INVENTION
[0003] The present invention generally relates to electrosurgical
systems and methods for ablating, severing, dissecting,
contracting, or otherwise modifying target tissues or organs. The
invention relates more particularly to electrosurgical apparatus
and methods for modifying a tissue or organ via molecular
dissociation of tissue components, wherein the apparatus includes
an active electrode in the form of a plasma blade or hook. The
present invention further relates to electrosurgical instruments
and methods for harvesting blood vessels such as the internal
mammary artery, the saphenous vein, or the like, for use in
coronary artery bypass graft procedures.
[0004] Conventional electrosurgical instruments and techniques are
widely used in surgical procedures because they generally reduce
patient bleeding and trauma associated with cutting operations, as
compared with mechanical cutting and the like. Conventional
electrosurgical procedures may be classified as operating in
monopolar or bipolar mode. Monopolar techniques rely on external
grounding of the patient, where the surgical device defines only a
single electrode pole. Bipolar devices have two electrodes for the
application of current between their surfaces. Conventional
electrosurgical devices and procedures, however, suffer from a
number of disadvantages. For example, conventional electrosurgical
cutting devices typically operate by creating a voltage difference
between the active electrode and the target tissue, causing an
electrical arc to form across the physical gap between the
electrode and the tissue. At the point of contact of the electric
arcs with the tissue, rapid tissue heating occurs due to high
current density between the electrode and the tissue. This high
current density causes cellular fluids to rapidly vaporize into
steam, thereby producing a "cutting effect" along the pathway of
localized tissue heating. Thus, the tissue is parted along the
pathway of evaporated cellular fluid, inducing undesirable
collateral tissue damage in regions surrounding the target
tissue.
[0005] Further, monopolar electrosurgical devices generally direct
electric current along a defined path from the exposed or active
electrode through the patient's body to the return electrode, the
latter externally attached to a suitable location on the patient.
This creates the potential danger that the electric current will
flow through undefined paths in the patient's body, thereby
increasing the risk of unwanted electrical stimulation to portions
of the patient's body. In addition, since the defined path through
the patient's body has a relatively high electrical impedance,
large voltage differences must typically be applied between the
return and active electrodes in order to generate a current
suitable for ablation or cutting of the target tissue. This
current, however, may inadvertently flow along body paths having
less impedance than the defined electrical path, which will
substantially increase the current flowing through these paths,
possibly causing damage to or destroying surrounding tissue.
[0006] Bipolar electrosurgical devices have an inherent advantage
over monopolar devices because the return current path does not
flow through the patient. In bipolar electrosurgical devices, both
the active and return electrode are typically exposed so that both
electrodes may contact tissue, thereby providing a return current
path from the active to the return electrode through the tissue.
One drawback with this configuration, however, is that the return
electrode may cause tissue desiccation or destruction at its
contact point with the patient's tissue. In addition, the active
and return electrodes are typically positioned close together to
ensure that the return current flows directly from the active to
the return electrode. The close proximity of these electrodes
generates the danger that the current will short across the
electrodes, possibly impairing the electrical control system and/or
damaging or destroying surrounding tissue.
[0007] In addition, conventional electrosurgical methods are
generally ineffective for ablating certain types of tissue, and in
certain types of environments within the body. For example, loose
or elastic connective tissue, such as the synovial tissue in
joints, is extremely difficult (if not impossible) to remove with
conventional electrosurgical instruments because the flexible
tissue tends to move away from the instrument when it is brought
against this tissue. Since conventional techniques rely mainly on
conducting current through the tissue, they are not effective when
the instrument cannot be brought adjacent to, or in contact with,
the elastic tissue for a sufficient period of time to energize the
electrode and conduct current through the tissue.
[0008] A prevalent form of cardiovascular disease is
atherosclerosis in which the cardiovascular system leading to the
heart is damaged or obstructed as a result of occluding material in
the blood stream. Vascular complications produced by
atherosclerosis, such as stenosis, aneurysm, rupture, or occlusion,
increase the likelihood of angina, stroke, and heart attacks. In
many cases, the obstruction of the blood stream leading to the
heart can be treated by a coronary artery bypass graft (CABG)
procedure.
[0009] In a conventional CABG procedure, the obstruction is
bypassed by a vascular conduit established between an arterial
blood source and the coronary artery to a location beyond the
obstruction. The vascular conduit is typically a non-critical
artery or vein harvested from elsewhere in the body. In a procedure
known as "free bypass graft", the saphenous vein is harvested from
the patient's leg and is used as the vascular conduit. One end of
the saphenous vein is anastomosed to the aorta and the other end is
anastomosed to the diseased coronary artery at a location past the
obstruction. In a procedure known as "in situ bypass graft", an
internal mammary artery (IMA) is used as the bypass conduit. In an
in situ bypass graft procedure, the surgeon dissects a sufficient
length of the artery from its connective tissue, then transects the
artery and connects the transected end to the diseased coronary
past the obstruction, and leaves the other end of the IMA attached
to the arterial supply.
[0010] The internal mammary arteries are particularly desirable for
use as in situ bypass grafts, as they are conveniently located,
have diameters and blood flow volumes that are comparable to those
of coronary arteries, and have superior patency rates. Use of the
left or right IMA as a bypass graft first involves harvesting the
IMA from the inside chest wall.
[0011] In conventional CABG procedures, access to the IMA is
typically obtained either through a sternotomy or a gross
thoracotomy. In the sternotomy or gross thoracotomy, the surgeon
typically uses a saw or other cutting instrument to cut the sternum
longitudinally to allow two opposing halves of the anterior portion
of the rib cage to be spread apart. The opening into the thoracic
cavity is created so that the surgeon may directly visualize the
heart and thoracic cavity. However, such methods suffer from
numerous drawbacks. For example, the longitudinal incision in the
sternum often results in bone bleeding, which is difficult to stop.
The bone bleeding can produce a high degree of trauma, a larger
risk of complications, an extended hospital stay, and a painful
recovery period for the patient. Once the surgeon has accessed the
thoracic cavity, the conventional method of harvesting the IMA
involves the use of scalpels or conventional electrosurgical
devices. A number of disadvantages inherent in conventional
electrosurgical devices have been set forth hereinabove.
[0012] Thus, there is a need for an electrosurgical apparatus which
can be used for the precise removal or modification of tissue at a
specific location, wherein a target tissue or organ can be
dissected, transected, incised, contracted, and/or coagulated, with
minimal, or no, collateral tissue damage. The instant invention
provides such an apparatus and related methods, wherein tissue may
be ablated or otherwise modified by a first region or element of a
blade active electrode, and the modified tissue can be further
modified by a second region or element of the blade active
electrode, and wherein the quantity and quality of the tissue
modification can be accurately controlled.
SUMMARY OF THE INVENTION
[0013] The present invention generally provides systems, apparatus,
and methods for selectively applying electrical energy to cut,
incise, ablate, or otherwise modify a tissue or organ of a patient.
In one aspect, the electrosurgical systems and methods of the
invention are useful for harvesting and dissecting veins and
arteries of a patient, such as the saphenous vein or an IMA for use
in a CABG procedure.
[0014] In one aspect, the present invention provides a method of
creating an incision in a body structure. An electrosurgical probe
is positioned adjacent the target tissue so that one or more active
electrode(s) are brought into at least partial contact or close
proximity with the target tissue. High frequency voltage is then
applied between the active electrode(s) and one or more return
electrode(s) and the active electrode(s) are moved, translated,
reciprocated, or otherwise manipulated to cut through a portion of
the tissue. In some embodiments, an electrically conductive fluid,
e.g., isotonic saline or conductive gel, is delivered or applied to
the target site to substantially surround the active electrode(s)
with the fluid. In other embodiments, the active electrode(s) are
immersed within the electrically conductive fluid. In both
embodiments, the high frequency voltage may be selected to locally
ablate or sever a target tissue, and/or to effect a controlled
depth of hemostasis of severed blood vessels within the tissue. In
another aspect, the electrosurgical systems and methods of the
invention are useful for harvesting and dissecting veins and
arteries of a patient, such as the saphenous vein or the IMA for
use in a CABG procedure.
[0015] In one aspect, tissue is cut or otherwise modified by
molecular dissociation or disintegration processes. (In contrast,
in conventional electrosurgery tissue is cut by rapidly heating the
tissue until cellular fluids explode, producing a cutting effect
along the pathway of localized heating.) The present invention
volumetrically removes the tissue along the cutting pathway in a
cool ablation process that minimizes thermal damage to surrounding
tissue. In these embodiments, the high frequency voltage applied to
the active electrode(s) is sufficient to vaporize the electrically
conductive fluid (e.g., gel or saline) between the active
electrode(s) and the tissue. Within the vaporized fluid, a plasma
is formed and charged particles (e.g., electrons) cause the
molecular breakdown or disintegration of the tissue, perhaps to a
depth of several cell layers. This molecular dissociation is
accompanied by the volumetric removal of the tissue, e.g., along
the incision of the tissue. This process can be precisely
controlled to effect the volumetric removal of tissue as thin as 10
microns to 150 microns with minimal heating of, or damage to,
surrounding or underlying tissue structures. A more complete
description of this phenomenon is described in commonly assigned
U.S. Pat. No. 5,683,366, the complete disclosure of which is
incorporated herein by reference.
[0016] In a specific embodiment, the present invention provides a
method of accessing a patient's thoracic cavity. The active
electrode(s) are positioned in contact or in close proximity to a
surface of the sternum. A high frequency voltage is applied between
the active electrode(s) and a return electrode. The active
electrodes are moved across the sternum to create an incision. In a
specific configuration, the sides of the active electrode are
slidingly engaged with the sternum as the incision is being made,
so as to cause coagulation and hemostasis within the sternum.
[0017] In another exemplary embodiment, the present invention
provides a method for harvesting the IMA from a patient. The
electrosurgical probe is positioned adjacent the IMA and high
frequency electrical energy is applied between one or more active
electrode(s) and one or more return electrode(s). The probe is then
moved so that the active electrode(s) volumetrically removes
connective tissue adjacent to the IMA so that the IMA is free from
connective tissue along a portion of its length. In an exemplary
embodiment, the probe is positioned adjacent to the IMA, and
advanced along the length of the IMA while high frequency
electrical energy is applied between the active electrode(s) and a
return electrode to remove or cut the connective tissue or other
structures surrounding the IMA. The residual heat from the
electrical energy also provides simultaneous hemostasis of severed
blood vessels, which increases visualization and improves recovery
time for the patient. In addition, the ability to simultaneously
cut through tissue on either side of the IMA decreases the length
of the procedure, which further improves patient recovery time.
After a suitable length of the IMA has been dissected, it may be
transected, and anastomosed to a diseased coronary artery using
known methods. In some embodiments, an electrically conductive
fluid (liquid, gas, or gel) is placed at the target site adjacent
to the IMA so as to provide a current flow path between the return
electrode and the active electrode.
[0018] Apparatus according to the present invention generally
include an electrosurgical instrument, such as a probe or catheter,
having a shaft with proximal and distal ends, one or more active
electrode(s) at the distal end and one or more connectors coupling
the active electrode(s) to a source of high frequency electrical
energy. The active electrode(s) are preferably designed for cutting
tissue; i.e., they typically have a distal edge or point. In one
embodiment, a plurality of active electrodes are aligned with each
other to form a linear electrode array for cutting a path through
the tissue. In another exemplary embodiment, the active
electrode(s) include a sharp distal point to facilitate the cutting
of the target tissue. In one specific configuration, the active
electrode is a blade having a sharp distal point and sides. As the
sharp distal point incises the tissue, the sides of the blade
slidingly contact the incised tissue. The electrical current flows
through that portion of the tissue in the vicinity of the active
electrode and/or the conductive fluid to the return electrode, such
that the target tissue is first severed, and then the severed
tissue is coagulated.
[0019] The apparatus can further include a fluid delivery element
for delivering electrically conductive fluid to the active
electrode(s) and the target site. The fluid delivery element may be
located on the probe, e.g., a fluid lumen or tube, or it may be
part of a separate instrument. Alternatively, an electrically
conductive gel or spray, such as a saline electrolyte or other
conductive gel, may be applied the target site. In this embodiment,
the apparatus may not have a fluid delivery element. In both
embodiments, the electrically conductive fluid preferably provides
a current flow path between the active electrode(s) and one or more
return electrode(s). In an exemplary embodiment, the return
electrode is located on the probe and spaced a sufficient distance
from the active electrode(s) to substantially avoid or minimize
current shorting therebetween and to shield the return electrode
from tissue at the target site.
[0020] In a specific configuration, the electrosurgical probe
includes an electrically insulating electrode support member having
a tissue treatment surface at the distal end of the probe. One or
more active electrode(s) are coupled to, or integral with, the
electrode support member such that the active electrode(s) are
spaced from the return electrode. In one embodiment, the probe
includes a plurality of active electrode(s) having distal edges
linearly aligned with each other to form a sharp cutting path for
cutting tissue. The active electrodes are preferably electrically
isolated from each other, and they extend about 0.2 mm to about 10
mm distally from the tissue treatment surface of the electrode
support member. In this embodiment, the probe may further include
one or more lumens for delivering electrically conductive fluid to
one or more openings around the tissue treatment surface of the
electrode support member. In an exemplary embodiment, the lumen
extends through a fluid tube exterior to the probe shaft that ends
proximal to the return electrode.
[0021] In another aspect of the invention, the electrode support
member comprises a plurality of wafer layers bonded together, e.g.,
by a glass adhesive or the like. The wafer layers each have
conductive strips plated or printed thereon to form the active
electrode(s) and the return electrode(s). In one embodiment, the
proximal end of the wafer layers will have a number of holes
extending from the conductor strips to an exposed surface of the
wafer layers for connection to electrical conductor lead traces in
the electrosurgical probe or handpiece. The wafer layers preferably
comprise a ceramic material, such as alumina, and the electrode
will preferably comprise a metallic material, such as gold,
platinum, tungsten, palladium, silver or the like.
[0022] In another aspect of the invention, there is provided an
electrosurgical probe having a blade-like active electrode affixed
to an electrically insulating electrode support on the distal end
of a shaft. In a specific configuration, the active electrode is in
the form of a plasma blade comprising a substantially flat metal
blade having at least one active edge and first and second blade
sides. In one embodiment, the active electrode comprises a hook.
The hook may include a curved portion. One or more portions of the
hook may have a serrated edge. The return electrode is typically
located on the shaft distal end proximal to the electrode support.
In use, the active electrode and the return electrode are coupled
to opposite poles of a high frequency power supply. The active edge
may have a variety of shapes, and is adapted for generating high
current densities thereon, and for precisely severing or ablating
tissue or an organ in a highly controlled manner via molecular
dissociation of tissue components. The first and second blade sides
are adapted for engaging with tissue, such as tissue severed by the
active edge, and for coagulating tissue engaged therewith.
[0023] The probe may be provided in various configurations, for
example, according to a particular procedure to be performed. Thus,
the electrode support may be arranged terminally or laterally on
the probe, and the blade active electrode may be arranged
terminally or laterally on the electrode support. The active
electrode may be provided in various forms, such as a metal blade
of unitary construction, e.g., a metal disc or portion thereof, a
crosspiece supported by at least one electrode arm, or a hook. The
shaft distal end may have a beveled end, a distal curve, and/or a
laterally compressed region. Each of these features or elements of
the probe may facilitate accessing a tissue or organ targeted for
treatment or modification by the probe. In addition, the laterally
compressed region may be adapted for accommodating the electrode
support.
[0024] According to one aspect of the invention, there is provided
a method for modifying a tissue using an electrosurgical probe
having an active electrode in the form of a single blade which
includes at least one active edge and first and second blade sides.
The method involves positioning the probe such that the active
electrode makes contact with, or is in close proximity to, a target
tissue; and applying a high frequency voltage between the active
and return electrodes sufficient to precisely sever or remove
target tissue via molecular dissociation of tissue components
adjacent to the active edge. The probe may be manipulated during
the application of the high frequency voltage such that the active
electrode is moved with respect to the target tissue. According to
one aspect of the invention, the configuration of the active
electrode (e.g., a hook shaped electrode) is adapted for severing
tissue as the probe distal end is drawn or pulled towards the
operator of the probe. In this manner, the extent to which the
tissue is severed can be precisely controlled. Thereafter, the
severed tissue may be coagulated upon engagement of the tissue
against the first and second blade sides of the active
electrode.
[0025] In another aspect of the invention, there is provided a
method of harvesting a tissue or organ using an electrosurgical
probe having an active electrode in the form of a single blade,
wherein the single blade electrode includes an active edge and
first and second blade sides. In situations where the tissue to be
harvested is concealed by an overlying tissue, the tissue to be
harvested must first be accessed by incising or removing the
overlying tissue. Removal of the overlying tissue may be performed
in various ways, including: 1) mechanically, e.g. using a scalpel,
rongeur, surgical saw or drill, etc. or a combination thereof; 2)
via conventional electrosurgery, e.g., a Bovie; or 3) using an
electrosurgical probe of the instant invention adapted for severing
tissue in a cool ablation process. Once the tissue or organ to be
harvested is accessible, the tissue or organ to be harvested may be
dissected by juxtaposing the active edge of the active electrode
against the surrounding connective tissue, and applying a high
frequency voltage between the active and return electrodes
sufficient to cause molecular dissociation of connective tissue
components. In this way, the connective tissue adjacent to the
active electrode is ablated at a temperature in the range of
40.degree. C. to 70.degree. C., with no, or minimal, thermal damage
to the tissue to be harvested.
[0026] The electrosurgical probe of the invention is also
applicable to a broad range of other procedures, including without
limitation: cutting, resection, ablation, and/or hemostasis of
tissues and organs such as prostate tissue, scar tissue, myocardial
tissue, and tissues of the knee, shoulder, hip, and other joints;
procedures of the head and neck, such as of the ear, mouth, throat,
pharynx, larynx, esophagus, nasal cavity, and sinuses; as well as
procedures involving skin tissue removal and/or collagen shrinkage
in the epidermis or dermis. A more detailed account of various
treatments and procedures which may be carried out according to the
invention is set forth in enabling detail hereinbelow.
[0027] For a further understanding of the nature and advantages of
the invention, reference should be made to the following
description taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a perspective view of an electrosurgical system
incorporating a power supply and an electrosurgical probe for
tissue ablation, resection, incision, contraction, vessel
harvesting, and hemostasis, according to the present invention;
[0029] FIG. 2 is a side view of an electrosurgical probe according
to the present invention;
[0030] FIG. 3 is an end view of the distal portion of the probe of
FIG. 2;
[0031] FIG. 4 is a cross sectional view of the distal portion of
the electrosurgical probe of FIG. 2;
[0032] FIG. 5 is an exploded view of a proximal portion of the
electrosurgical probe;
[0033] FIG. 6 is an end view of an exemplary electrode support
comprising a multi-layer wafer with plated conductors for
electrodes;
[0034] FIGS. 7 and 8 are side views of the electrode support of
FIG. 7;
[0035] FIGS. 9A-13 are side views of the individual wafer layers of
the electrode support;
[0036] FIGS. 9B-12B are cross-sectional views of the individual
wafer layers;
[0037] FIGS. 14 and 15 illustrate an alternative multi-layer wafer
design according to the present invention;
[0038] FIG. 16 is a perspective view of an electrosurgical probe
having an elongated, blade-like active electrode;
[0039] FIGS. 17A-17C are cross-sectional views of the distal
portions of three different embodiments of an electrosurgical probe
according to the present invention;
[0040] FIG. 18 illustrates an electrosurgical probe with a
90.degree. distal bend and a lateral fluid lumen;
[0041] FIG. 19 illustrates an electrosurgical system with a
separate fluid delivery instrument according to the present
invention;
[0042] FIGS. 20A and 20B are cross-sectional and end views,
respectively, of yet another electrosurgical probe incorporating
flattened active electrodes;
[0043] FIG. 21 is a detailed end view of an electrosurgical probe
having an elongate, linear array of active electrodes suitable for
use in surgical cutting;
[0044] FIG. 22 is a detailed view of a single active electrode
having a flattened end at its distal tip;
[0045] FIG. 23 is a detailed view of a single active electrode
having a pointed end at its distal tip;
[0046] FIG. 24 is a perspective view of the distal portion of
another electrosurgical probe according to the present
invention;
[0047] FIG. 25 illustrates another embodiment of the probe of the
present invention, specifically designed for creating incisions in
external skin surfaces;
[0048] FIG. 26 is a perspective view of another embodiment of an
electrosurgical probe for use in dermatology procedures;
[0049] FIGS. 27A-27C are exploded, isometric views of the probe of
FIG. 26;
[0050] FIG. 28 is a cross-sectional view of another alternative
electrosurgical probe;
[0051] FIG. 29 illustrates another embodiment of the
electrosurgical probe of the present invention, incorporating
additional active electrodes;
[0052] FIG. 30 is a perspective view of an electrosurgical probe
having a blade electrode;
[0053] FIG. 31A is a perspective view, and FIG. 31B is a lateral
view, of a blade electrode, according to one embodiment of the
invention;
[0054] FIGS. 32A, 32B, and 32C are a side view, a plan view, and an
end view, respectively, of an electrosurgical probe having a blade
electrode;
[0055] FIGS. 33A and 33B are a side view and a plan view,
respectively, of the distal end of an electrosurgical probe having
a terminal blade electrode, according to one embodiment of the
invention;
[0056] FIGS. 33C-33E each show a side view of the distal end of an
electrosurgical probe having a terminal blade electrode, according
to three different embodiments of the invention;
[0057] FIGS. 34A, 34B, and 34C are a side view, a plan view, and an
end view, respectively, of an electrosurgical probe having a
terminal electrode support and a lateral blade electrode, according
to another embodiment of the invention;
[0058] FIGS. 35A, 35B, and 35C are a side view, a plan view, and an
end view, respectively, of an electrosurgical probe having a
lateral electrode support and a lateral blade electrode, according
to another embodiment of the invention;
[0059] FIGS. 36A and 36B each show a side view of the distal end of
an electrosurgical probe having a blade electrode, according to two
different embodiments of the invention;
[0060] FIGS. 37A, and 37B are a side view and an end view,
respectively, of an electrosurgical probe having a lumen external
to the probe shaft, according to one embodiment of the
invention;
[0061] FIGS. 38A, and 38B are a side view and an end view,
respectively, of an electrosurgical probe having an outer sheath
surrounding the probe shaft, according to another embodiment of the
invention;
[0062] FIGS. 39A, 39B, and 39C schematically represent a
perspective view, a longitudinal sectional view, and an end view,
respectively, of an electrosurgical probe, according to another
embodiment of the invention;
[0063] FIG. 39D shows detail of the distal portion of the probe of
FIGS. 39A-C;
[0064] FIGS. 40A and 40B schematically represent a longitudinal
sectional view, and an end view, respectively, of an
electrosurgical probe, according to another embodiment of the
invention;
[0065] FIG. 40C shows detail of the distal portion of the probe of
FIGS. 40A, 40B;
[0066] FIGS. 41A, 41B, and 41C each show detail of the distal
portion of an electrosurgical probe, according to three different
embodiments of the invention;
[0067] FIGS. 42A and 42B schematically represent a procedure for
incising and coagulating tissue with an electrosurgical probe
having a blade electrode, according to one embodiment of the
invention;
[0068] FIG. 43A schematically represents a number of steps involved
in a method of treating a patient with an electrosurgical probe
having a blade electrode, according to one embodiment of the
invention;
[0069] FIG. 43B schematically represents a number of steps involved
in a method of concurrently severing and coagulating tissue,
according to one embodiment of the invention; and
[0070] FIG. 44 schematically represents a number of steps involved
in a method of dissecting a tissue or organ of a patient with an
electrosurgical probe, according to another embodiment of the
invention.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0071] The present invention provides systems and methods for
selectively applying electrical energy to a target location within
or on a patient's body, particularly for cutting, ablating, and/or
coagulating a tissue using a blade-like electrode. The instant
invention also provides apparatus and methods for making incisions
to access a tissue or organ within a patient's body, to dissect or
harvest the tissue or organ from the patient, and to transect or
otherwise modify the tissue or organ. In one aspect, the invention
provides apparatus and methods for dissecting and harvesting blood
vessels from a patient.
[0072] The present invention is useful in procedures where the
target tissue or organ is, or can be, flooded or submerged with an
electrically conductive fluid, such as isotonic saline. In
addition, tissues which may be treated by the system and method of
the present invention further include, but are not limited to,
tissues of the heart, chest, knee, shoulder, ankle, hip, elbow,
hand or foot; as well as prostate tissue, leiomyomas (fibroids)
located within the uterus, gingival tissues and mucosal tissues
located in the mouth, tumors, scar tissue, myocardial tissue,
collagenous tissue within the eye; together with epidermal and
dermal tissues on the surface of the skin. The present invention is
also useful for resecting tissue within accessible sites of the
body that are suitable for electrode loop resection, such as the
resection of prostate tissue, leiomyomas (fibroids) located within
the uterus, or other tissue to be removed from the body.
[0073] The present invention is also useful for procedures in the
head and neck, such as the ear, mouth, throat, pharynx, larynx,
esophagus, nasal cavity, and sinuses. These procedures may be
performed through the mouth or nose using speculae or gags, or
using endoscopic techniques, such as functional endoscopic sinus
surgery (FESS). These procedures may include the removal of swollen
tissue, chronically-diseased inflamed and hypertrophic mucus
linings, polyps and/or neoplasms from the various anatomical
sinuses of the skull, the turbinates and nasal passages, in the
tonsil, adenoid, epi-glottic and supra-glottic regions, and
salivary glands, submucus resection of the nasal septum, excision
of diseased tissue and the like. In other procedures, the present
invention may be useful for cutting, resection, ablation and/or
hemostasis of tissue in procedures for treating snoring and
obstructive sleep apnea (e.g., UPPP procedures), for gross tissue
removal, such as tonsillectomies, adenoidectomies, tracheal
stenosis and vocal cord polyps and lesions, or for the resection or
ablation of facial tumors or tumors within the mouth and pharynx,
such as glossectomies, laryngectomies, acoustic neuroma procedures
and nasal ablation procedures. In addition, the present invention
is useful for procedures within the ear, such as stapedotomies,
tympanostomies, myringotomies, or the like.
[0074] The present invention may also be useful for cosmetic and
plastic surgery procedures in the head and neck. For example, the
present invention is particularly useful for ablation and sculpting
of cartilage tissue, such as the cartilage within the nose that is
sculpted during rhinoplasty procedures. The present invention may
also be employed for skin tissue removal and/or collagen shrinkage
in the epidermis or dermis tissue in the head and neck region,
e.g., the removal of pigmentations, vascular lesions, scars,
tattoos, etc., and for other surgical procedures on the skin, such
as tissue rejuvenation, cosmetic eye procedures (blepharoplasties),
wrinkle removal, tightening muscles for facelifts or browlifts,
hair removal and/or transplant procedures, etc.
[0075] The present invention is also useful for harvesting blood
vessels, such as a blood vessel to be used as a graft vessel during
the CABG procedure, e.g., the saphenous vein and the internal
mammary artery (IMA). One or more embodiments of the invention may
be used as follows: i) to access the blood vessel to be harvested,
e.g., by opening the leg to access the saphenous vein, or opening
the chest (either via a longitudinal incision of the sternum during
an open-chest procedure, or during a minimally invasive
inter-costal procedure); ii) to dissect the blood vessel to be
harvested from the surrounding connective tissue along at least a
portion of its length; and iii) to transect the dissected blood
vessel at a first position only in the case of a pedicled graft
(IMA), or at the first position and at a second position in the
case of a free graft (saphenous vein). In each case i) to iii), as
well as for other embodiment of the invention, the procedure
involves removal of tissue by a cool ablation procedure in which a
high frequency voltage is applied to an active electrode in the
vicinity of a target tissue, typically in the presence of an
electrically conductive fluid. The cool ablation procedure of the
invention is described fully elsewhere herein. The electrically
conductive fluid may be a bodily fluid such as blood or synovial
fluid, intracellular fluid of the target tissue, or isotonic saline
delivered to the target tissue during the procedure. The present
invention is also useful for coagulating blood or blood vessels,
for example, to minimize bleeding in the sternum during an
open-chest procedure.
[0076] Although certain parts of this disclosure are directed
specifically to creating incisions for accessing a patient's
thoracic cavity and the harvesting and dissection of blood vessels
within the body during a CABG procedure, systems and methods of the
invention are equally applicable to other procedures involving
other organs or tissues of the body, including minimally invasive
procedures (e.g., minimally invasive CABG procedures), other open
procedures, intravascular procedures, urological procedures,
laparascopy, arthroscopy, thoracoscopy or other cardiac procedures,
cosmetic surgery, orthopedics, gynecology, otorhinolaryngology,
spinal and neurologic procedures, oncology, and the like.
[0077] In methods of the present invention, high frequency (RF)
electrical energy is usually applied to one or more active
electrodes in the presence of an electrically conductive fluid to
remove and/or modify target tissue, an organ, or a body structure.
Depending on the specific procedure, the present invention may be
used to: (1) create incisions in tissue; (2) dissect or harvest
tissue; (3) volumetrically remove tissue or cartilage (i.e., ablate
or effect molecular dissociation of the tissue); (4) cut, transect,
or resect tissue or an organ (e.g., a blood vessel); (5) create
perforations or holes within tissue; and/or (6) coagulate blood and
severed blood vessels.
[0078] In one method of the present invention, the tissue
structures are incised by volumetrically removing or ablating
tissue along a cutting path. In this procedure, a high frequency
voltage difference is applied between one or more active electrode
(s) and one or more return electrode(s) to develop high electric
field intensities in the vicinity of the target tissue site. The
high electric field intensities lead to electric field induced
molecular breakdown of target tissue through molecular dissociation
(rather than thermal evaporation or carbonization). Applicant
believes that the tissue structure is volumetrically removed
through molecular disintegration of larger organic molecules into
smaller molecules and/or atoms, such as hydrogen, oxides of carbon,
hydrocarbons and nitrogen compounds. This molecular disintegration
completely removes the tissue structure, as opposed to dehydrating
the tissue material by the removal of liquid within the cells of
the tissue, as is typically the case with electrosurgical
desiccation and vaporization.
[0079] The high electric field intensities may be generated by
applying a high frequency voltage that is sufficient to vaporize an
electrically conductive fluid over at least a portion of the active
electrode(s) in the region between the tip of the active
electrode(s) and the target tissue. The electrically conductive
fluid may be a gas or liquid, such as isotonic saline, delivered to
the target site, or a viscous fluid, such as a gel, that is located
at the target site. In the latter embodiment, the active
electrode(s) are submersed in the electrically conductive gel
during the surgical procedure. Since the vapor layer or vaporized
region has a relatively high electrical impedance, it minimizes the
current flow into the electrically conductive fluid. Within the
vaporized fluid a plasma is formed, and charged particles (e.g.,
electrons) cause the localized molecular dissociation or
disintegration of components of the target tissue, to a depth of
perhaps several cell layers. This molecular dissociation results in
the volumetric removal of tissue from the target site. This
ablation process, which typically subjects the target tissue to a
temperature in the range of 40.degree. C. to 70.degree. C., can be
precisely controlled to effect the removal of tissue to a depth as
little as about 10 microns, with little or no thermal or other
damage to surrounding tissue. This cool ablation phenomenon has
been termed Coblation.RTM..
[0080] While not being bound by theory, applicant believes that the
principle mechanism of tissue removal in the Coblation.RTM.
mechanism of the present invention is energetic electrons or ions
that have been energized in a plasma adjacent to the active
electrode(s). When a liquid is heated sufficiently that atoms
vaporize from the liquid at a greater rate than they recondense, a
gas is formed. When the gas is heated sufficiently that the atoms
collide with each other and electrons are removed from the atoms in
the process, an ionized gas or plasma is formed. (A more complete
description of plasmas (the so-called "fourth state of matter") can
be found in Plasma Physics, by R. J. Goldston and P. H. Rutherford
of the Plasma Physics Laboratory of Princeton University (1995),
the complete disclosure of which is incorporated herein by
reference). When the density of the vapor layer (or within a bubble
formed in the electrically conductive liquid) becomes sufficiently
low (i.e., less than approximately 1020 atoms/cm3 for aqueous
solutions), the electron mean free path increases to enable
subsequently injected electrons to cause impact ionization within
these regions of low density (i.e., vapor layers or bubbles). Once
the ionic particles in the plasma layer have sufficient energy,
they accelerate towards the target tissue. Energy evolved by the
energetic electrons (e.g., 3.5 eV to 5 eV) can subsequently bombard
a molecule and break its bonds, dissociating a molecule into free
radicals, which then combine into final gaseous or liquid
species.
[0081] Plasmas may be formed by heating and ionizing a gas by
driving an electric current through it, or by transmitting radio
waves into the gas. Generally, these methods of plasma formation
give energy to free electrons in the plasma directly, and then
electron-atom collisions liberate more electrons, and the process
cascades until the desired degree of ionization is achieved. Often,
the electrons carry the electrical current or absorb the radio
waves and, therefore, are hotter than the ions. Thus, in
applicant's invention, the electrons, which are carried away from
the tissue towards the return electrode, carry most of the plasma's
heat with them, allowing the ions to break apart the tissue
molecules in a substantially non-thermal manner.
[0082] The energy evolved by the energetic electrons may be varied
by adjusting a variety of factors, such as: the number of active
electrodes; electrode size and spacing; electrode surface area;
asperities and sharp edges on the electrode surfaces; electrode
materials; applied voltage and power; current limiting means, such
as inductors; electrical conductivity of the fluid in contact with
the electrodes; density of the fluid; electrical insulators over
the electrodes; and other factors. Accordingly, these factors can
be manipulated to control the energy level of the excited
electrons. Since different tissue structures have different
molecular bonds, the present invention can be configured to break
the molecular bonds of certain tissue, while having too low an
energy to break the molecular bonds of other tissue. For example,
fatty tissue, (e.g., adipose tissue) contains a large amount of
lipid material having double bonds, the breakage of which requires
an energy level substantially higher than 4 eV to 5 eV.
Accordingly, the present invention can be configured such that
lipid components of adipose tissue are selectively not ablated. Of
course, the present invention may be used to effectively ablate
cells of adipose tissue such that the inner fat content of the
cells is released in a liquid form. Alternatively, the invention
can be configured (e.g., by increasing the voltage or changing the
electrode configuration to increase the current density at the
electrode tips) such that the double bonds of lipid materials are
readily broken leading to molecular dissociation of lipids into low
molecular weight condensable gases, generally as described
hereinabove. A more complete description of the Coblation.RTM.
phenomenon can be found in commonly assigned U.S. Pat. No.
5,683,366, and U.S. patent Application Ser. No. 09/032,375, filed
Feb. 27, 1998, now U.S. Pat. No. 6,355,032, the complete
disclosures of which are incorporated herein by reference.
[0083] Methods of the present invention typically involve the
application of high frequency (RF) electrical energy to one or more
active electrodes in the presence of an electrically conductive
fluid to remove (i.e., resect, incise, perforate, cut, or ablate) a
target tissue, structure, or organ; and/or to seal transected
vessels within the region of the target tissue. The present
invention is particularly useful for sealing larger arterial
vessels, e.g., having a diameter on the order of 1 mm or greater.
In some embodiments, a high frequency power supply is provided
having an ablation mode, wherein a first voltage is applied to an
active electrode sufficient to effect molecular dissociation or
disintegration of the tissue; and a coagulation mode, wherein a
second, lower voltage is applied to an active electrode (either the
same or a different electrode) sufficient to achieve hemostasis of
severed vessels within the tissue. In other embodiments, an
electrosurgical probe is provided having one or more coagulation
electrode(s) configured for sealing a severed vessel, such as an
arterial vessel, and one or more active electrodes configured for
either contracting the collagen fibers within the tissue or
removing (ablating) the tissue, e.g., by applying sufficient energy
to the tissue to effect molecular dissociation. In the latter
embodiments, the coagulation electrode(s) may be configured such
that a single voltage can be applied to both coagulate with the
coagulation electrode(s), and to ablate or contract tissue with the
active electrode(s). In other embodiments, the power supply is
combined with the coagulation probe such that the coagulation
electrode is used when the power supply is in the coagulation mode
(low voltage), and the active electrode(s) are used when the power
supply is in the ablation mode (higher voltage).
[0084] In one method of the present invention, one or more active
electrodes are brought into close proximity to tissue at a target
site, and the power supply is activated in the ablation mode such
that sufficient voltage is applied between the active electrodes
and the return electrode to volumetrically remove the tissue
through molecular dissociation, as described above. During this
process, vessels within the tissue are severed. Smaller vessels may
be automatically sealed with the system and method of the present
invention. Larger vessels and those with a higher flow rate, such
as arterial vessels, may not be automatically sealed in the
ablation mode. In these cases, the severed vessels may be sealed by
actuating a control (e.g., a foot pedal) to reduce the voltage of
the power supply into the coagulation mode. In this mode, the
active electrodes may be pressed against the severed vessel to
provide sealing and/or coagulation of the vessel. Alternatively, a
coagulation electrode located on the same or a different probe may
be pressed against the severed vessel. Once the vessel is
adequately sealed, the surgeon may activate a control (e.g.,
another foot pedal) to increase the voltage of the power supply
back into the ablation mode.
[0085] The present invention is also useful for removing or
ablating tissue around nerves, such as spinal, or cranial nerves,
e.g., the hypoglossal nerve, the optic nerve, facial nerves,
vestibulocochlear nerves and the like. This is particularly
advantageous when removing tissue that is located close to nerves.
One of the significant drawbacks with the conventional RF devices,
scalpels, and lasers is that these devices do not differentiate
between the target tissue and the surrounding nerves or bone.
Therefore, the surgeon must be extremely careful during these
procedures to avoid damage to the nerves within and around the
target tissue. In the present invention, the Coblation.RTM. process
for removing tissue results in no, or extremely small amounts, of
collateral tissue damage, as described above. This allows the
surgeon to remove tissue close to a nerve without causing
collateral damage to the nerve fibers and surrounding tissue.
[0086] In addition to the generally precise nature of the novel
mechanisms of the present invention, applicant has discovered an
additional method of ensuring that adjacent nerves are not damaged
during tissue removal. According to the present invention, systems
and methods are provided for distinguishing between the fatty
tissue immediately surrounding nerve fibers and the normal tissue
that is to be removed during the procedure. Peripheral nerves
usually comprise a connective tissue sheath, or epineurium,
enclosing the bundles of nerve fibers, each bundle being surrounded
by its own sheath of connective tissue (the perineurium) to protect
these nerve fibers. The outer protective tissue sheath or
epineurium typically comprises a fatty tissue (e.g., adipose
tissue) having substantially different electrical properties than
the normal target tissue that is treated. The system of the present
invention measures the electrical properties of the tissue at the
tip of the probe with one or more active electrode(s). These
electrical properties may include electrical conductivity at one,
several, or a range of frequencies (e.g., in the range from 1 kHz
to 100 MHz), dielectric constant, capacitance or combinations of
these. In this embodiment, an audible signal may be produced when
the sensing electrode(s) at the tip of the probe detects the fatty
tissue surrounding a nerve, or direct feedback control can be
provided to only supply power to the active electrode(s) either
individually or to the complete array of electrodes, if and when
the tissue encountered at the tip or working end of the probe is
normal tissue based on the measured electrical properties.
[0087] In one embodiment, the current limiting elements are
configured such that the active electrodes will shut down or turn
off when the electrical impedance reaches a threshold level. When
this threshold level is set to the impedance of the fatty tissue
surrounding nerves, the active electrodes will shut off whenever
they come in contact with, or in close proximity to, nerves.
Meanwhile, the other active electrodes, which are in contact with
or in close proximity to target tissue, will continue to conduct
electric current to the return electrode. This selective ablation
or removal of lower impedance tissue in combination with the
Coblation.RTM. mechanism of the present invention allows the
surgeon to precisely remove tissue around nerves or bone. Applicant
has found that the present invention is capable of volumetrically
removing tissue closely adjacent to nerves without impairing the
function of the nerves, and without significantly damaging the
tissue of the epineurium.
[0088] The present invention can be also be configured to create an
incision in a bone of the patient. For example, the systems of the
present invention can be used to create an incision in the sternum
for access to the thoracic cavity. Applicant has found that the
Coblation .RTM. mechanism of the present invention allows the
surgeon to precisely create an incision in the sternum while
minimizing or preventing bone bleeding. The high frequency voltage
is applied between the active electrode(s) and the return
electrode(s) to volumetrically remove the bone from a specific site
targeted for the incision. As the active electrode(s) are passed
through the incision in the bone, the sides of the active
electrodes (or a third coagulation electrode) slidingly contact the
bone surrounding the incision to provide hemostasis in the bone. A
more complete description of such coagulation electrodes can be
found in U.S. patent application Ser. No. 09/162,117, filed Sep.
28, 1998, now U.S. Pat. No. 6,117,109, the complete disclosure of
which is incorporated herein by reference.
[0089] The present invention can also be used to dissect and
harvest blood vessels from the patient's body during a CABG
procedure. The system of the present invention allows a surgeon to
dissect and harvest blood vessels, such as the right or left IMA or
saphenous vein, while concurrently providing hemostasis at the
harvesting site. In some embodiments, a first high frequency
voltage, can be delivered in an ablation mode to effect molecular
disintegration of connective tissue adjacent to the blood vessel
targeted for harvesting; and a second, lower voltage can be
delivered to achieve hemostasis of the connective tissue adjacent
to the blood vessel. In other embodiments, the targeted blood
vessel can be transected at one or more positions along its length,
and one or more coagulation electrode(s) can be used to seal the
transected blood vessel at the site of transection. The coagulation
electrode(s) may be configured such that a single voltage can be
applied to the active electrodes to ablate the tissue and to
coagulate the blood vessel and target site.
[0090] The present invention also provides systems, apparatus, and
methods for selectively removing tumors or other undesirable body
structures while minimizing the spread of viable cells from the
tumor. Conventional techniques for removing such tumors generally
result in the production of smoke in the surgical setting, termed
an electrosurgical or laser plume, which can spread intact, viable
bacterial or viral particles from the tumor or lesion to the
surgical team, or viable cancerous cells to other locations within
the patient's body. This potential spread of viable cells or
particles has resulted in increased concerns over the proliferation
of certain debilitating and fatal diseases, such as hepatitis,
herpes, HIV and papillomavirus. In the present invention, high
frequency voltage is applied between the active electrode(s) and
one or more return electrode(s) to volumetrically remove at least a
portion of the tissue cells in the tumor or lesion by the molecular
dissociation of tissue components into non-condensable gases. The
high frequency voltage is preferably selected to effect controlled
removal of these tissue cells while minimizing substantial tissue
necrosis to surrounding or underlying tissue. A more complete
description of this phenomenon can be found in U.S. patent
application Ser. No. 09/109,219, filed Jun. 30, 1998, now
abandoned, the complete disclosure of which is incorporated herein
by reference.
[0091] A current flow path between the active electrode(s) and the
return electrode(s) may be generated by submerging the tissue site
in an electrically conductive fluid (e.g., within a viscous fluid,
such as an electrically conductive gel) or by directing an
electrically conductive fluid along a fluid path to the target site
(i.e., a liquid, such as isotonic saline, or a gas, such as argon).
This latter method is particularly effective in a dry field
procedure (i.e., the tissue is not submersed in fluid). The use of
a conductive gel allows a slower, more controlled delivery rate of
conductive fluid as compared with a liquid or a gas. In addition,
the viscous nature of the gel may allow the surgeon to more easily
contain the gel around the target site (e.g., as compared with
containment of isotonic saline). A more complete description of an
exemplary method of directing electrically conductive fluid between
the active and return electrodes is described in U.S. Pat. No.
5,697,281, the full disclosure of which is incorporated herein by
reference. Alternatively, the body's natural conductive fluids,
such as blood, may be sufficient to establish a conductive path
between the return electrode(s) and the active electrode(s), and to
provide the conditions for establishing a vapor layer, as described
above. However, conductive fluid that is introduced into the
patient is generally preferred over blood because blood will tend
to coagulate at certain temperatures. Advantageously, a liquid
electrically conductive fluid (e.g., isotonic saline) may be used
to concurrently "bathe" the target tissue surface to provide an
additional means for removing any tissue, and to cool the tissue at
or adjacent to the target site.
[0092] In some embodiments of the invention, an electrosurgical
probe includes an electrode support for electrically isolating the
active electrode(s) from the return electrode, and a fluid delivery
port or outlet for directing an electrically conductive fluid to
the target site or to the distal end of the probe. The electrode
support and the fluid outlet may be recessed from an outer surface
of the instrument to confine the electrically conductive fluid to
the region immediately surrounding the electrode support. In
addition, a shaft of the instrument may be shaped so as to form a
cavity around the electrode support and the fluid outlet. This
helps to assure that the electrically conductive fluid will remain
in contact with the active electrode(s) and the return electrode(s)
to maintain the conductive path therebetween. In addition, this
will help to maintain a vapor layer and subsequent plasma layer
between the active electrode(s) and the tissue at the treatment
site throughout the procedure, thereby reducing any thermal damage
that might otherwise occur if the vapor layer were extinguished due
to a lack of conductive fluid. Provision of the electrically
conductive fluid around the target site also helps to maintain the
tissue temperature at desired levels.
[0093] The electrically conductive fluid should have a threshold
conductivity to provide a suitable conductive path between the
return electrode and the active electrode(s). The electrical
conductivity of the fluid (in units of milliSiemens per centimeter
or mS/cm) will usually be greater than 0.2 mS/cm, preferably will
be greater than 2 mS/cm and more preferably greater than 10 mS/cm.
In an exemplary embodiment, the electrically conductive fluid is
isotonic saline, which has a conductivity of about 17 mS/cm.
[0094] An electrosurgical probe or instrument of the invention
typically includes a shaft having a proximal end and a distal end,
and one or more active electrode(s) disposed at the shaft distal
end. The shaft serves to mechanically support the active
electrode(s) and permits the treating physician to manipulate the
shaft distal end via a handle attached to the proximal end of the
shaft. The shaft may be rigid or flexible, with flexible shafts
optionally being combined with a generally rigid external tube for
mechanical support. Flexible shafts may be combined with pull
wires, shape memory actuators, and other known mechanisms for
effecting selective deflection of the distal end of the shaft to
facilitate positioning of the electrode array. The shaft will
usually have one or more wires, electrode connectors, leads, or
other conductive elements running axially therethrough, to permit
connection of the electrode(s) to a connection block located at the
proximal end of the instrument. The connection block is adapted for
coupling the electrode(s) to the power supply or controller.
Typically, the connection block is housed within the handle of the
probe.
[0095] The shaft of an instrument under the invention may assume
various configurations. Generally, the shaft will have a suitable
diameter and length to allow the surgeon to access the target site
with the distal or working end of the shaft. Thus, the shaft may be
provided in a range of sizes according to the particular procedure
or tissue targeted for treatment. Typically, the shaft will have a
length in the range of from about 5 cm to 30 cm, and have a
diameter in the range of from about 0.5 mm to 10 mm. Specific shaft
designs will be described in detail in connection with the drawings
hereinafter.
[0096] The present invention may use a single active electrode or a
plurality of electrodes distributed across a contact surface of a
probe (e.g., in a linear fashion). In the latter embodiment, the
electrode array usually includes a plurality of independently
current-limited and/or power-controlled active electrodes to apply
electrical energy selectively to the target tissue while limiting
the unwanted application of electrical energy to the surrounding
tissue and environment resulting from power dissipation into
surrounding electrically conductive liquids, such as blood, normal
saline, electrically conductive gel and the like. The active
electrodes may be independently current-limited by isolating the
terminals from each other and connecting each terminal to a
separate power source that is isolated from the other active
electrodes. Alternatively, the active electrodes may be connected
to each other at either the proximal or distal ends of the probe to
form a single wire that couples to a power source.
[0097] In one configuration, each individual active electrode is
electrically insulated from all other active electrodes within the
probe and is connected to a power source which is isolated from
each of the other active electrodes in the array, or to circuitry
which limits or interrupts current flow to the active electrode
when low resistivity material causes a low impedance path between
the return electrode and the individual active electrode. The
isolated power sources for each individual active electrode may be
separate power supply circuits having internal impedance
characteristics which limit power to the associated active
electrode when a low impedance return path is encountered. By way
of example, the isolated power source may be a user selectable
constant current source. In this embodiment, lower impedance paths
will automatically result in lower resistive heating levels since
the heating is proportional to the square of the operating current
times the impedance. Alternatively, a single power source may be
connected to each of the active electrodes through independently
actuatable switches, or by independent current limiting elements,
such as inductors, capacitors, resistors and/or combinations
thereof. The current limiting elements may be provided in the
probe, connectors, cable, power supply or along the conductive path
from the power supply to the distal tip of the probe.
Alternatively, the resistance and/or capacitance may occur on the
surface of the active electrode(s) due to oxide layers which form
selected active electrodes (e.g., titanium or a resistive coating
on the surface of metal, such as platinum).
[0098] The distal end of the probe may comprise many independent
active electrodes designed to deliver electrical energy in the
vicinity of the distal end. The selective application of electrical
energy to the conductive fluid is achieved by connecting each
individual active electrode and the return electrode to a power
source having independently controlled or current limited channels.
The return electrode(s) may comprise a single tubular member of
electrically conductive material at the distal end of the probe
proximal to the active electrode(s). The same tubular member of
electrically conductive material may also serve as a conduit for
the supply of the electrically conductive fluid between the active
and return electrodes. The application of high frequency voltage
between the return electrode(s) and the active electrode(s) results
in the generation of high electric field intensities at the distal
tip of the active electrode(s), with conduction of high frequency
current from each active electrode to the return electrode. The
current flow from each active electrode to the return electrode(s)
is controlled by either active or passive means, or a combination
thereof, to deliver electrical energy to the surrounding conductive
fluid while minimizing energy delivery to surrounding (non-target)
tissue.
[0099] The application of a suitable high frequency voltage between
the return electrode(s) and the active electrode(s) for appropriate
time intervals effects cutting, removing, ablating, shaping,
contracting or otherwise modifying the target tissue. In one
embodiment, the tissue volume over which energy is dissipated
(i.e., over which a high current density exists) may be precisely
controlled, for example, by the use of a multiplicity of small
active electrodes whose effective diameters or principal dimensions
range from about 5 mm to 0.01 mm, preferably from about 2 mm to
0.05 mm, and more preferably from about 1 mm to 0.1 mm. Electrode
areas for both circular and non-circular terminals will have a
contact area (per active electrode) below 25 mm2, preferably being
in the range from 0.0001 mm2 to 1 mm2, and more preferably from
0.005 mm2 to 0.5 mm2. The circumscribed area of the electrode array
is in the range from 0.25 mm2 to 75 mm2, preferably from 0.5 mm2 to
40 mm2. In one embodiment the probe may include a plurality of
relatively small active electrodes disposed over the distal contact
surfaces on the shaft. The use of small diameter active electrodes
increases the electric field intensity and reduces the extent or
depth of tissue heating as a consequence of the divergence of
current flux lines which emanate from the exposed surface of each
active electrode.
[0100] The portion of the electrode support on which the active
electrode(s) are mounted generally defines a tissue treatment
surface of the probe. The area of the tissue treatment surface can
vary widely, and the tissue treatment surface can assume a variety
of geometries, with particular areas and geometries being selected
for specific applications. The area of the tissue treatment surface
can range from about 0.25 mm2 to 75 mm2, usually being from about
0.5 mm2 to 40 mm2. The geometries of the active electrode(s) can be
planar, concave, convex, hemispherical, conical, a linear "in-line"
array, or virtually any other regular or irregular shape. Most
commonly, the active electrode(s) will be located at the shaft
distal end of the electrosurgical probe, frequently having planar,
disk-shaped, or hemispherical surfaces for use in reshaping
procedures, ablating, cutting, dissecting organs, coagulating, or
transecting blood vessels. The active electrode(s) may be arranged
terminally or laterally on the electrosurgical probe (e.g., in the
manner of a scalpel or a blade). However, it should be clearly
understood that the active electrode of the invention does not cut
or sever tissue mechanically as for a scalpel blade, but rather by
the localized molecular dissociation of tissue components due to
application of high frequency electric current to the active
electrode. In one embodiment, a distal portion of the shaft may be
flattened or compressed laterally (e.g., FIGS. 32A-32C). A probe
having a laterally compressed shaft may facilitate access to
certain target sites or body structures during various surgical
procedures.
[0101] In embodiments having a plurality of active electrodes, it
should be clearly understood that the invention is not limited to
electrically isolated active electrodes. For example, a plurality
of active electrodes may be connected to a single lead that extends
through the probe shaft and is coupled to a high frequency power
supply. Alternatively, the probe may incorporate a single electrode
that extends directly through the probe shaft or is connected to a
single lead that extends to the power source. The active electrode
may have a planar or blade shape, a screwdriver or conical shape, a
sharpened point, a ball shape (e.g., for tissue vaporization and
desiccation), a twizzle shape (for vaporization and needle-like
cutting), a spring shape (for rapid tissue debulking and
desiccation), a twisted metal shape, an annular or solid tube
shape, or the like. Alternatively, the electrode may comprise a
plurality of filaments, a rigid or flexible brush electrode (for
debulking a tumor, such as a fibroid, bladder tumor or a prostate
adenoma), a side-effect brush electrode on a lateral surface of the
shaft, a coiled electrode, or the like.
[0102] In one embodiment, the probe comprises a single blade active
electrode that extends from an insulating support member, spacer,
or electrode support, e.g., a ceramic or silicone rubber spacer
located at the distal end of the probe. The insulating support
member may be a tubular structure or a laterally compressed
structure that separates the blade active electrode from a tubular
or annular return electrode positioned proximal to the insulating
member and the active electrode. The blade electrode may include a
distal cutting edge and sides which are configured to coagulate the
tissue as the blade electrode advances through the tissue. In yet
another embodiment, the catheter or probe includes a single active
electrode that can be rotated relative to the rest of the catheter
body, or the entire catheter may be rotated relative to the
electrode lead(s). The single active electrode can be positioned
adjacent the abnormal tissue and energized and rotated as
appropriate to remove or modify the target tissue.
[0103] The active electrode(s) are preferably supported within or
by an insulating support member positioned near the distal end of
the instrument shaft. The return electrode may be located on the
instrument shaft, on another instrument, or on the external surface
of the patient (i.e., a dispersive pad). For certain procedures,
the close proximity of nerves and other sensitive tissue makes a
bipolar design more preferable because this minimizes the current
flow through non-target tissue and surrounding nerves. Accordingly,
the return electrode is preferably either integrated with the
instrument body, or located on another instrument. The proximal end
of the probe typically includes the appropriate electrical
connections for coupling the return electrode(s) and the active
electrode(s) to a high frequency power supply, such as an
electrosurgical generator.
[0104] One exemplary power supply of the present invention delivers
a high frequency current selectable to generate average power
levels ranging from several milliwatts to tens of watts per
electrode, depending on the volume of target tissue being treated,
and/or the maximum allowed temperature selected for the instrument
tip. The power supply allows the user to select the voltage level
according to the specific requirements of a particular otologic
procedure, neurosurgery procedure, cardiac surgery, arthroscopic
surgery, dermatological procedure, ophthalmic procedures, open
surgery or other endoscopic surgery procedure. For cardiac
procedures and potentially for neurosurgery, the power source may
have an additional filter, for filtering leakage voltages at
frequencies below 100 kHz, particularly voltages around 60 kHz.
Alternatively, a power supply having a higher operating frequency,
e.g., 300 kHz to 500 kHz may be used in certain procedures in which
stray low frequency currents may be problematic. A description of
one suitable power supply can be found in U.S. patent application
Ser. Nos. 09/058,571 and 09/058,336, filed Apr. 10, 1998, now U.S.
Pat. Nos. 6,142,992, and 6,235,020, respectively, the complete
disclosures of which are incorporated herein by reference for all
purposes.
[0105] The voltage difference applied between the return
electrode(s) and the active electrode(s) will be at high or radio
frequency, typically between about 5 kHz and 20 MHz, usually being
between about 30 kHz and 2.5 MHz, preferably being between about 50
kHz and 500 kHz, often less than 350 kHz, and often between about
100 kHz and 200 kHz. The RMS (root mean square) voltage applied
will usually be in the range from about 5 volts to 1000 volts,
preferably being in the range from about 10 volts to 500 volts
depending on the active electrode size, the operating frequency,
and the operation mode of the particular procedure or desired
effect on the tissue (e.g., contraction, coagulation, cutting or
ablation). Typically, the peak-to-peak voltage for ablation or
cutting will be in the range of 10 volts to 2000 volts and
preferably in the range of 200 volts to 1800 volts, and more
preferably in the range of about 300 volts to 1500 volts, often in
the range of about 500 volts to 900 volts peak to peak (again,
depending on the electrode size, the operating frequency and the
operation mode). Lower peak-to-peak voltages will be used for
tissue coagulation or collagen contraction and will typically be in
the range from 50 to 1500, preferably 100 to 1000, and more
preferably 120 to 600 volts peak-to-peak.
[0106] The voltage is usually delivered in a series of voltage
pulses or alternating current of time varying voltage amplitude
with a sufficiently high frequency (e.g., on the order of 5 kHz to
20 MHz) such that the voltage is effectively applied continuously
(as compared with e.g., lasers claiming small depths of necrosis,
which are generally pulsed about 10 Hz to 20 Hz). In addition, the
duty cycle (i.e., cumulative time in any one-second interval that
energy is applied) is on the order of about 50% for the present
invention, as compared with pulsed lasers which typically have a
duty cycle of about 0.0001%.
[0107] The power supply may include a fluid interlock for
interrupting power to the active electrode(s) when there is
insufficient conductive fluid around the active electrode(s). This
ensures that the instrument will not be activated when conductive
fluid is not present, minimizing the tissue damage that may
otherwise occur. A more complete description of such a fluid
interlock can be found in commonly assigned U.S. application Ser.
No. 09/058,336, filed Apr. 10, 1998, now U.S. Pat. No. 6,235,020,
the complete disclosure of which is incorporated herein by
reference.
[0108] The power supply may also be current limited or otherwise
controlled so that undesired heating of the target tissue or
surrounding (non-target) tissue does not occur. In a presently
preferred embodiment of the present invention, current limiting
inductors are placed in series with each independent active
electrode, where the inductance of the inductor is in the range of
10 uH to 50,000 uH, depending on the electrical properties of the
target tissue, the desired tissue heating rate and the operating
frequency. Alternatively, capacitor-inductor (LC) circuit
structures may be employed, as described previously in U.S. Pat.
No. 5,697,909, the complete disclosure of which is incorporated
herein by reference. Additionally, current limiting resistors may
be selected. Preferably, these resistors will have a large positive
temperature coefficient of resistance so that, as the current level
begins to rise for any individual active electrode in contact with
a low resistance medium (e.g., saline irrigant or blood), the
resistance of the current limiting resistor increases
significantly, thereby minimizing the power delivery from the
active electrode into the low resistance medium (e.g., saline
irrigant or blood).
[0109] In some procedures, it may also be necessary to retrieve or
aspirate the electrically conductive fluid and/or the
non-condensable gaseous products of ablation. In addition, it may
be desirable to aspirate small pieces of tissue or other body
structures that are not completely disintegrated by the high
frequency energy, or other fluids at the target site, such as
blood, mucus, purulent fluid, the gaseous products of ablation, or
the like. Accordingly, the system of the present invention may
include one or more suction lumen(s) in the instrument, or on
another instrument, coupled to a suitable vacuum source for
aspirating fluids from the target site. In addition, the invention
may include one or more aspiration electrode(s) coupled to the
distal end of the suction lumen for ablating, or at least reducing
the volume of, non-ablated tissue fragments that are aspirated into
the lumen. The aspiration electrode(s) function mainly to inhibit
clogging of the lumen that may otherwise occur as larger tissue
fragments are drawn therein. The aspiration electrode(s) may be
different from the ablation active electrode(s), or the same
electrode(s) may serve both functions. A more complete description
of instruments incorporating aspiration electrode(s) can be found
in commonly assigned application Ser. No. 09/010,382, filed Jan.
21, 1998, now U.S. Pat. No. 6,190,381, the complete disclosure of
which is incorporated herein by reference.
[0110] During a surgical procedure, the distal end of the
instrument and the active electrode(s) may be maintained at a small
distance away from the target tissue surface. This small spacing
allows for the continuous flow of electrically conductive fluid
into the interface between the active electrode(s) and the target
tissue surface. The continuous flow of the electrically conductive
fluid helps to ensure that the thin vapor layer will remain between
the active electrode(s) and the tissue surface. In addition,
dynamic movement of the active electrode(s) over the tissue site
allows the electrically conductive fluid to cool the tissue
underlying and surrounding the target tissue to minimize thermal
damage to this surrounding and underlying tissue. Accordingly, the
electrically conductive fluid may be cooled to facilitate the
cooling of the tissue. Typically, the active electrode(s) will be
about 0.02 mm to 2 mm from the target tissue and preferably about
0.05 mm to 0.5 mm during the ablation process. One method of
maintaining this space is to move, translate and/or rotate the
probe transversely relative to the tissue, i.e., for the operator
to use a light brushing motion, to maintain a thin vaporized layer
or region between the active electrode and the tissue. Of course,
if coagulation or collagen shrinkage of a deeper region of tissue
is necessary (e.g., for sealing a bleeding vessel embedded within
the tissue), it may be desirable to press the active electrode(s)
against the tissue to effect joulean heating therein.
[0111] Referring to FIG. 1, an exemplary electrosurgical system 11
for cutting, ablating, resecting, or otherwise modifying tissue
will now be described in detail. Electrosurgical system 11
generally comprises an electrosurgical handpiece or probe 10
connected to a power supply 28 for providing high frequency voltage
to a target site, and a fluid source 21 for supplying electrically
conductive fluid 50 to probe 10. In addition, electrosurgical
system 11 may include an endoscope (not shown) with a fiber optic
head light for viewing the surgical site. The endoscope may be
integral with probe 10, or it may be part of a separate instrument.
The system 11 may also include a vacuum source (not shown) for
coupling to a suction lumen or tube 211 (see FIG. 2) in the probe
10 for aspirating the target site.
[0112] As shown, probe 10 generally includes a proximal handle 19
and an elongate shaft 18 having one or more active electrodes 58 at
its distal end. A connecting cable 34 has a connector 26 for
electrically coupling the active electrodes 58 to power supply 28.
In embodiments having a plurality of active electrodes, active
electrodes 58 are electrically isolated from each other and the
terminal of each active electrode 58 is connected to an active or
passive control network within power supply 28 by means of a
plurality of individually insulated conductors (not shown). A fluid
supply tube 15 is connected to a fluid tube 14 of probe 10 for
supplying electrically conductive fluid 50 to the target site.
[0113] Power supply 28 has an operator controllable voltage level
adjustment 30 to change the applied voltage level, which is
observable at a voltage level display 32. Power supply 28 also
includes first, second, and third foot pedals 37, 38, 39 and a
cable 36 which is removably coupled to power supply 28. The foot
pedals 37, 38, 39 allow the surgeon to remotely adjust the energy
level applied to active electrode(s) 58. In an exemplary
embodiment, first foot pedal 37 is used to place the power supply
into the "ablation" mode and second foot pedal 38 places power
supply 28 into the "coagulation" mode. The third foot pedal 39
allows the user to adjust the voltage level within the ablation
mode. In the ablation mode, a sufficient voltage is applied to the
active electrodes to establish the requisite conditions for
molecular dissociation of the tissue (i.e., vaporizing a portion of
the electrically conductive fluid, ionizing the vapor layer and
accelerating charged particles against the tissue). As discussed
above, the requisite voltage level for ablation will vary depending
on the number, size, shape and spacing of the electrodes, the
distance in which the electrodes extend from the support member,
etc. When the surgeon is using the power supply in the ablation
mode, voltage level adjustment 30 or third foot pedal 39 may be
used to adjust the voltage level to adjust the degree or
aggressiveness of the ablation.
[0114] Of course, it will be recognized that the voltage and
modality of the power supply may be controlled by other input
devices. However, applicant has found that foot pedals are
convenient means for controlling the power supply while
manipulating the probe during a surgical procedure.
[0115] In the coagulation mode, the power supply 28 applies a low
enough voltage to the active electrode(s) (or the coagulation
electrode) to avoid vaporization of the electrically conductive
fluid and subsequent molecular dissociation of the tissue. The
surgeon may automatically toggle the power supply between the
ablation and coagulation modes by alternately stepping on foot
pedals 37, 38, respectively. This allows the surgeon to quickly
move between coagulation and ablation in situ, without having to
remove his/her concentration from the surgical field or without
having to request an assistant to switch the power supply. By way
of example, as the surgeon is sculpting soft tissue in the ablation
mode, the probe typically will simultaneously seal and/or
coagulation small severed vessels within the tissue. However,
larger vessels, or vessels with high fluid pressures (e.g.,
arterial vessels) may not be sealed in the ablation mode.
Accordingly, the surgeon can simply step on foot pedal 38,
automatically lowering the voltage level below the threshold level
for ablation, and apply sufficient pressure onto the severed vessel
for a sufficient period of time to seal and/or coagulate the
vessel. After this is completed, the surgeon may quickly move back
into the ablation mode by stepping on foot pedal 37. A specific
design of a suitable power supply for use with the present
invention can be found in Provisional Patent Application No.
60/062,997, filed Oct. 23, 1997, previously incorporated herein by
reference.
[0116] FIG. 2 shows an electrosurgical probe 20 according to one
embodiment of the invention. Probe 20 may be used in conjunction
with a system similar or analogous to system 11 (FIG. 1). As shown
in FIG. 2, probe 20 generally includes an elongated shaft 100 which
may be flexible or rigid, a handle 204 coupled to the proximal end
of shaft 100 and an electrode support member 102 coupled to the
distal end of shaft 100. Shaft 100 may comprise a plastic material
that is easily molded into the shape shown in FIG. 3, or shaft 100
may comprise an electrically conductive material, usually a metal,
such as tungsten, stainless steel alloys, platinum or its alloys,
titanium or its alloys, molybdenum or its alloys, and nickel or its
alloys. In the latter case (i.e., shaft 100 is electrically
conductive), probe 20 includes an electrically insulating jacket
108, which is typically formed as one or more electrically
insulating sheaths or coatings, such as polytetrafluoroethylene,
polyimide, and the like. The provision of electrically insulating
jacket 108 over shaft 100 prevents direct electrical contact
between the metal shaft and any adjacent body structure or the
surgeon. Such direct electrical contact between a body structure
(e.g., heart, bone, nerves, skin, or other blood vessels) and an
exposed electrode could result in unwanted heating and necrosis of
the structure at the point of contact.
[0117] Handle 204 typically comprises a plastic material that is
easily molded into a suitable shape for handling by the surgeon.
Handle 204 defines an inner cavity (not shown) that houses an
electrical connections unit 250 (FIG. 5), and provides a suitable
interface for coupling probe 20 to power supply 28 via an
electrical connecting cable. Electrode support member 102 extends
from the distal end of shaft 100 (usually about 1 mm to 20 mm), and
provides support for an active electrode or a plurality of
electrically isolated active electrodes 104. In the specific
configuration shown in FIG. 2, probe 20 includes a plurality of
active electrodes. As shown in FIG. 2, a fluid tube 233 extends
through an opening in handle 204, and includes a connector 235 for
connection to a fluid supply source for supplying electrically
conductive fluid to the target site. Fluid tube 233 is coupled to a
distal fluid tube 239 that extends along the outer surface of shaft
100 to an opening 237 at the distal end of the probe 20, as will be
discussed in detail below. Of course, the invention is not limited
to this configuration. For example, fluid tube 233 may extend
through a single lumen (not shown) in shaft 100, it may be coupled
to a plurality of lumens (also not shown) that extend through shaft
100 to a plurality of openings at its distal end, or the fluid tube
may be completely independent of shaft 100. Probe 20 may also
include a valve or equivalent structure for controlling the flow
rate of the electrically conductive fluid to the target site.
[0118] As shown in FIGS. 3 and 4, electrode support member 102 has
a substantially planar tissue treatment surface 212 and comprises a
suitable insulating material (e.g., a ceramic or glass material,
such as alumina, zirconia and the like) which could be formed at
the time of manufacture in a flat, hemispherical or other shape
according to the requirements of a particular procedure. The
preferred support member material is alumina (Kyocera Industrial
Ceramics Corporation, Elkgrove, Ill.), because of its high thermal
conductivity, good electrically insulative properties, high
flexural modulus, resistance to carbon tracking, biocompatibility,
and high melting point. Electrode support member 102 is adhesively
joined to a tubular support member (not shown) that extends most or
all of the distance between support member 102 and the proximal end
of probe 20. The tubular member preferably comprises an
electrically insulating material, such as an epoxy or
silicone-based material.
[0119] In a preferred construction technique, active electrodes 104
extend through pre-formed openings in the support member 102 so
that they protrude above tissue treatment surface 212 by the
desired distance. The electrodes are then bonded to the tissue
treatment surface 212 of support member 102, typically by an
inorganic sealing material. The sealing material is selected to
provide effective electrical insulation, and good adhesion to both
support member 102 and active electrodes 104. In one embodiment,
active electrodes 104 comprise an electrically conducting,
corrosion resistant metal, such as platinum or titanium. The
sealing material additionally should have a compatible thermal
expansion coefficient and a melting point well below that of
platinum or titanium and alumina or zirconia, typically being a
glass or glass ceramic.
[0120] In the embodiment shown in FIGS. 2-5, probe 20 includes a
return electrode 112 for completing the current path between active
electrodes 104 and a high frequency power supply 28 (see FIG. 1).
As shown, return electrode 112 preferably comprises an annular
conductive band coupled to the distal end of shaft 100 at a
location proximal to tissue treatment surface 212 of electrode
support member 102, typically about 0.5 mm to 10 mm proximal to
surface 212, and more preferably about 1 mm to 10 mm proximal to
surface 212. Return electrode 112 is coupled to a connector 258
that extends to the proximal end of probe 20, where it is suitably
connected to power supply 28 (FIGS. 1 and 2).
[0121] As shown in FIG. 2, return electrode 112 is not directly
connected to active electrodes 104. To complete this current path
so that active electrodes 104 are electrically connected to return
electrode 112, electrically conductive fluid (e.g., isotonic
saline) is caused to flow therebetween. In the representative
embodiment, the electrically conductive fluid is delivered through
an external fluid tube 239 to opening 237, as described above
(FIGS. 2 and 4). Alternatively, the fluid may be continuously
delivered by a fluid delivery element (not shown) that is separate
from probe 20.
[0122] In alternative embodiments, the fluid path may be formed in
probe 20 by, for example, an inner lumen or an annular gap between
the return electrode and a tubular support member within shaft 100
(not shown). This annular gap may be formed near the perimeter of
the shaft 100 such that the electrically conductive fluid tends to
flow radially inward towards the target site, or it may be formed
towards the center of shaft 100 so that the fluid flows radially
outward. In both of these embodiments, a fluid source (e.g., a bag
of fluid elevated above the surgical site or having a pumping
device), is coupled to probe 20 via a fluid supply tube (not shown)
that may or may not have a controllable valve. A more complete
description of an electrosurgical probe incorporating one or more
fluid lumen(s) can be found in U.S. Pat. No. 5,697,281, the
complete disclosure of which is incorporated herein by
reference.
[0123] Referring to FIGS. 3 and 4, the electrically isolated active
electrodes 104 are preferably spaced from each other and aligned to
form a linear array 105 of electrodes for cutting a substantially
linear incision in the tissue. The tissue treatment surface and
individual active electrodes 104 will usually have dimensions
within the ranges set forth above. Active electrodes 104 preferably
have a distal edge 107 to increase the electric field intensities
around terminals 104, and to facilitate cutting of tissue. Thus,
active electrodes 104 have a screwdriver shape in the
representative embodiment of FIGS. 2-4. In one representative
embodiment, the tissue treatment surface 212 has a circular
cross-sectional shape with a diameter in the range of about 1 mm to
30 mm, usually about 2 mm to 20 mm. The individual active
electrodes 104 preferably extend outward from tissue treatment
surface 212 by a distance of about 0.1 mm to 8 mm, usually about 1
mm to 4 mm. Applicant has found that this configuration increases
the high electric field intensities and associated current
densities around active electrodes 104 to facilitate the ablation
of tissue as described in detail above.
[0124] Probe 20 may include a suction or aspiration lumen 213 (see
FIG. 2) within shaft 100 and a suction tube 211 (FIG. 2) for
aspirating tissue, fluids and/or gases from the target site. In
this embodiment, the electrically conductive fluid generally flows
from opening 237 of fluid tube 239 radially inward and then back
through one or more openings (not shown) in support member 102.
Aspirating the electrically conductive fluid during surgery allows
the surgeon to see the target site, and it prevents the fluid from
flowing into the patient's body (e.g., the thoracic cavity). This
aspiration should be controlled, however, so that the conductive
fluid maintains a conductive path between the active electrode(s)
and the return electrode. In some embodiments, the probe 20 will
also include one or more aspiration electrode(s) (not shown)
coupled to the aspiration lumen for inhibiting clogging during
aspiration of tissue fragments from the surgical site. A more
complete description of these embodiments can be found in commonly
assigned U.S. Pat. No. 6,190,381, the complete disclosure of which
is incorporated herein by reference for all purposes.
[0125] FIG. 5 illustrates the electrical connections 250 within
handle 204 for coupling active electrodes 104 and return electrode
112 to the power supply 28. As shown, a plurality of wires 252
extend through shaft 100 to couple electrodes 104 to a plurality of
pins 254, which are plugged into a connector block 256 for coupling
to a connecting cable 22 (FIG. 1). Similarly, return electrode 112
is coupled to connector block 256 via a wire 258 and a plug
260.
[0126] According to the present invention, probe 20 further
includes an identification element that is characteristic of the
particular electrode assembly so that the same power supply 28 can
be used for different electrosurgical operations. In one
embodiment, for example, probe 20 includes a voltage reduction
element or a voltage reduction circuit for reducing the voltage
applied between the active electrodes 104 and the return electrode
112. The voltage reduction element serves to reduce the voltage
applied by the power supply so that the voltage between the active
electrodes and the return electrode is low enough to avoid
excessive power dissipation into the electrically conductive medium
and/or the tissue at the target site. The voltage reduction element
primarily allows the electrosurgical probe 10/20 to be compatible
with a range of different power supplies that are adapted to apply
higher voltages for ablation or vaporization of tissue (e.g.,
various power supplies or generators manufactured by ArthroCare
Corporation, Sunnyvale, Calif.). For contraction of tissue, for
example, the voltage reduction element will serve to reduce a
voltage of about 100 to 135 volts RMS (which corresponds to a
setting of 1 on the ArthroCare Model 970 and 980 (i.e., 2000)
Generators) to about 45 to 60 volts RMS, which is a suitable
voltage for contraction of tissue without ablation (e.g., molecular
dissociation) of the tissue.
[0127] Again with reference to FIG. 5, n the representative
embodiment the voltage reduction element is a dropping capacitor
262 which has a first leg 264 coupled to the return electrode wire
258 and a second leg 266 coupled to connector block 256. Of course,
the capacitor may be located in other places within the system,
such as in, or distributed along the length of, the cable, the
power supply, the connector, etc. In addition, it will be
recognized that other voltage reduction elements, such as diodes,
transistors, inductors, resistors, capacitors or combinations
thereof, may be used in conjunction with the present invention. For
example, probe 20 may include a coded resistor (not shown) that is
constructed to lower the voltage applied between return electrode
112 and active electrodes 104 to a suitable level for contraction
of tissue. In addition, electrical circuits may be employed for
this purpose.
[0128] Alternatively or additionally, the cable 22 that couples the
power supply 28 to probe 10/20 may be used as a voltage reduction
element. The cable has an inherent capacitance that can be used to
reduce the power supply voltage if the cable is placed into the
electrical circuit between the power supply, the active electrodes
and the return electrode. In this embodiment, the cable 22 may be
used alone, or in combination with one of the voltage reduction
elements discussed above, e.g., a capacitor.
[0129] Further, it should be noted that various electrosurgical
probes of the present invention can be used with a particular power
supply that is adapted to apply a voltage within a selected range
for a certain procedure or treatment. In which case, a voltage
reduction element or circuitry may not be necessary nor
desired.
[0130] With reference to FIGS. 6-8, electrode support member 70
according to one embodiment includes a multi-layer substrate
comprising a suitable high temperature, electrically insulating
material, such as ceramic. The multi-layer substrate is a thin or
thick-film hybrid having conductive strips that are adhered to the
ceramic wafer layers (e.g., thick-film printed and fired onto or
plated onto the ceramic wafers). The conductive strips typically
comprise tungsten, gold, nickel, silver, platinum or equivalent
materials. In the exemplary embodiment, the conductive strips
comprise tungsten, and they are co-fired together with the wafer
layers to form an integral package. The conductive strips are
coupled to external wire connectors by holes or vias that are
drilled through the ceramic layers, and plated or otherwise covered
with conductive material. A more complete description of such
support members 370 can be found in U.S. patent application Ser.
No. 08/977,845, filed Nov. 25, 1997, now U.S. Pat. No. 6,210,402,
the entire disclosure of which is incorporated herein by
reference.
[0131] In the representative embodiment, support member 70
comprises five ceramic layers 200, 202, 204, 206, 208 (see FIGS.
6-10), three gold plated active electrodes 210a, 210b, 210c and
first and second gold plated return electrodes 216, 218. As shown
in FIGS. 9A and 9B, a first ceramic layer 200, which is one of the
outer layers of support 70, includes first gold plated return
electrode 216 on a lateral surface 220 of layer 200. First ceramic
layer 200 further includes a gold conductive strip 222 extending
from return electrode 216 to the proximal end of layer 200 for
coupling to a lead wire (not shown), and three gold conductive
lines 224, 226, 228 extending from a mid-portion of layer 200 to
its proximal end. Conductive strips 224, 226, 228 are each coupled
to one of the active electrodes 210a, 210b, 210c by conductive
holes or vias 230, 232, 234, respectively. As shown, all three vias
230, 232, 234 extend through wafer layer 200.
[0132] Referring to FIGS. 10A and 10B, a second wafer layer 202 is
bonded between first outer wafer layer 200 and a middle wafer layer
204 (See FIGS. 11A and 11B). As shown, first active electrode 210a
is attached to the distal surface of second wafer layer 202, and a
conductive strip 240 extends to via 230 to couple active electrode
210a to a lead wire. Similarly, wafer layers 204 and 206 (FIGS.
11A, 11B, 12A, and 12B) each have an active electrode 210b, 210c
plated to their distal surfaces, and a conductive strip 242, 244,
respectively, extending to one of the vias 232, 234, respectively.
Note that the vias only extend as far as necessary through the
ceramic layers. As shown in FIG. 13, a second outer wafer layer 208
has a second return electrode 218 plated to the lateral surface 250
of layer 208. The second return electrode 218 is coupled directly
to the first return electrode 216 through a via 252 extending
through the entire ceramic substrate.
[0133] Of course, it will be recognized that a variety of different
types of single layer and multi-layer wafers may be constructed
according to the present invention. For example, FIGS. 14 and 15
illustrate an alternative embodiment of the multi-layer ceramic
wafer, wherein the active electrodes comprise planar strips 280
that are plated or otherwise bonded between the ceramic wafer
layers 282. Each of the planar strips 280 has a different length,
as shown in FIG. 15, so that the active electrodes can be
electrically isolated from each other, and coupled to lead wires by
vias (not shown).
[0134] FIG. 16 illustrates an electrosurgical probe 20' according
to another embodiment of the present invention. Probe 20' generally
includes handle 104 attached to shaft 100, and has a single, thin,
elongated active blade electrode 58. Active electrode 58 is
mechanically and electrically separated from return electrode 112
by a support structure 102. The active blade electrode 58 has a
sharp distal edge 59 which helps facilitate the cutting process,
and sides 62 which contact the tissue (e.g., bone) as the blade
electrode 58 passes through the tissue or body structure. By
contacting the sides of the blade electrode 58 directly with the
tissue or body structure, the electrical power supplied to
electrode 58 by power supply 28 can provide hemostasis to the body
structure during the cutting process. Optionally, probe 20' can
further include one or more coagulation electrode(s) (not shown)
configured to seal a severed vessel, bone, or other tissue that is
being incised. Such coagulation electrode(s) may be configured such
that a single voltage can be applied to coagulate with the
coagulation electrode(s) while ablating tissue with the active
electrode(s). According to one aspect of the invention, probe 20'
is particularly useful for creating an incision in a patient's
chest. For example, in an open-chest CABG procedure a median
sternotomy is first performed in which the sternum is sectioned
longitudinally so as to allow the chest to be opened for access to
the thoracic cavity. Active electrodes 58 include distal edge 59
suitable for sectioning the sternum, and sides 62 suitable for
arresting bone bleeding within the incised sternum. Sides 62 are
configured to slidably engage the sternum as active electrode 58 is
moved with respect to the sternum. Return electrode 112 is spaced
proximally from active electrode 58 such that the electrical
current is drawn away from the surrounding tissue. Alternatively,
the return electrode 112 may be a dispersive pad located on the
external surface of the patient's body. By minimizing bleeding of
the sternum during an open-chest procedure, the patient's recovery
time can be substantially shortened and patient suffering is
alleviated.
[0135] FIGS. 17A-17C schematically illustrate the distal portion of
three different embodiments of a probe 90 according to the present
invention. As shown in FIG. 17A, active electrodes 104 are anchored
in a support 102 of suitable insulating material (e.g., ceramic or
glass material, such as alumina, zirconia and the like) which could
be formed at the time of manufacture in a flat, hemispherical or
other shape according to the requirements of a particular
procedure. In one embodiment, the support material is alumina,
available from Kyocera Industrial Ceramics Corporation, Elkgrove,
Ill., because of its high thermal conductivity, good electrically
insulative properties, high flexural modulus, resistance to carbon
tracking, biocompatibility, and high melting point. The support 102
is adhesively joined to a tubular support member 78 that extends
most or all of the distance between matrix 102 and the proximal end
of probe 90. Tubular member 78 preferably comprises an electrically
insulating material, such as an epoxy or silicone-based
material.
[0136] According to one construction technique, active electrodes
104 extend through pre-formed openings in the support 102 so that
they protrude above tissue treatment surface 212 by the desired
distance. The electrodes are then bonded to the tissue treatment
surface 212 of support 102, typically by an inorganic sealing
material 80. Sealing material 80 is selected to provide effective
electrical insulation, and good adhesion to both the support 102
and the platinum or titanium active electrodes. Sealing material 80
additionally should have a compatible thermal expansion
coefficient, and a melting point well below that of platinum or
titanium and alumina or zirconia, typically being a glass or glass
ceramic.
[0137] In the embodiment shown in FIG. 17A, return electrode 112
comprises an annular member positioned around the exterior of shaft
100 of probe 90. Return electrode 112 may fully or partially
circumscribe tubular member 78 to form an annular gap 54
therebetween for flow of electrically conductive liquid 50
therethrough, as discussed below. Gap 54 preferably has a width in
the range of 0.25 mm to 4 mm. Alternatively, probe 90 may include a
plurality of longitudinal ribs between tubular member 78 and return
electrode 112 to form a plurality of fluid lumens extending along
the perimeter of shaft 100. In this embodiment, the plurality of
lumens will extend to a plurality of openings.
[0138] Return electrode 112 is disposed within an electrically
insulative jacket 17, which is typically formed as one or more
electrically insulative sheaths or coatings, such as
polytetrafluoroethylene, polyimide, and the like. The provision of
the electrically insulative jacket 17 over return electrode 112
prevents direct electrical contact between return electrode 112 and
any adjacent body structure. Such direct electrical contact between
a body structure (e.g., the heart) and an exposed electrode member
112 could result in unwanted heating and necrosis of the structure
at the point of contact.
[0139] As shown in FIG. 17A, return electrode 112 is not directly
connected to active electrodes 104. To complete a current path so
that active electrodes 104 are electrically connected to return
electrode 112, electrically conductive liquid 50 (e.g., isotonic
saline) is caused to flow along fluid path(s) 83. Fluid path 83 is
formed by annular gap 54 between outer return electrode 112 and
tubular support member 78. The electrically conductive liquid 50
flowing through fluid path 83 provides a pathway for electrical
current flow between active electrodes 104 and return electrode
112, as illustrated by the current flux lines 60 in FIG. 17A. When
a voltage difference is applied between active electrodes 104 and
return electrode 112, high electric field intensities will be
generated at the distal tips of active electrodes 104 with current
flow from electrodes 104 through the target tissue to the return
electrode, the high electric field intensities causing ablation of
tissue 52 in zone 88.
[0140] FIG. 17B illustrates another alternative embodiment of
electrosurgical probe 90 which has a return electrode 112
positioned within tubular member 78. Return electrode 112 may
comprise a tubular member defining an inner lumen 57 for allowing
electrically conductive liquid 50 (e.g., isotonic saline) to flow
therethrough in electrical contact with return electrode 112. In
this embodiment, a voltage difference is applied between active
electrodes 104 and return electrode 112 resulting in electrical
current flow through the electrically conductive liquid 50 as shown
by current flux lines 60. As a result of the applied voltage
difference and concomitant high electric field intensities at the
tips of active electrodes 104, tissue 52 becomes ablated or
transected in zone 88.
[0141] FIG. 17C illustrates another embodiment of probe 90 that is
a combination of the embodiments in FIGS. 17A and 17B. As shown,
this probe includes both an inner lumen 57 and an outer gap or
plurality of outer lumens 54 for flow of electrically conductive
fluid. In this embodiment, the return electrode 112 may be
positioned within tubular member 78 as in FIG. 17B, outside of
tubular member 78 as in FIG. 17A, or in both locations.
[0142] FIG. 18 illustrates another embodiment of probe 90 where the
distal portion of shaft 100 is bent so that active electrodes
extend transversely to the shaft. Preferably, the distal portion of
shaft 100 is perpendicular to the rest of the shaft so that tissue
treatment surface 212 is generally parallel to the shaft axis. In
this embodiment, return electrode 112 is mounted to the outer
surface of shaft 100 and is covered with an electrically insulating
jacket 17. The electrically conductive fluid 50 flows along flow
path 83 through return electrode 112 and exits the distal end of
electrode 112 at a point proximal of tissue treatment surface 212.
The fluid is directed exterior of shaft to surface 212 to create a
return current path from active electrodes 104, through the fluid
50, to return electrode 112, as shown by current flux lines 60.
[0143] FIG. 19 illustrates another embodiment of the invention
where electrosurgical system 11 further includes a liquid supply
instrument 64 for supplying electrically conductive fluid 50
between active electrodes 104 and a return electrode 112'. Liquid
supply instrument 64 comprises an inner tubular member or return
electrode 112' surrounded by an electrically insulating jacket 17.
Return electrode 112' defines an inner passage 83 for flow of fluid
50. As shown in FIG. 19, the distal portion of instrument 64 is
preferably bent so that liquid 50 is discharged at an angle with
respect to instrument 64. This allows the surgical team to position
liquid supply instrument 64 adjacent tissue treatment surface 212
with the proximal portion of supply instrument 64 oriented at a
similar angle to probe 90.
[0144] The present invention is not limited to an electrode array
disposed on a relatively planar surface at the distal tip of probe
90, as described above. Referring to FIGS. 20A and 20B, an
alternative probe 90 includes a pair of electrodes 105a, 105b
mounted to the distal end of shaft 100. Electrodes 105a, 105b are
electrically connected to a power supply, as described above, and
preferably have tips 107a, 107b having a screwdriver shape. The
screwdriver shape provides a greater amount of "edges" to
electrodes 105a, 105b, to increase the electric field intensity and
current density at tips 107a, 107b, thereby improving the cutting
ability as well as the ability to provide hemostasis of the incised
tissue.
[0145] FIG. 21 illustrates yet another embodiment designed for
cutting of body tissue, organs, or structures. In this embodiment,
the active electrodes 104 are arranged in a linear or columnar
array of one of more closely spaced columns so that as the
electrodes 104 are moved along the longer axis (denoted by arrow
160 in FIG. 21), the current flux lines are narrowly confined at
the tip of the active electrodes 104 and result in a cutting effect
in the body structure being treated. As before, the current flux
lines 60 emanating from the active electrodes 104 pass through the
electrically conductive liquid to the return electrode structure
112 located proximal to the probe tip.
[0146] Referring now to FIGS. 22 and 23, alternative geometries are
shown for the active electrodes 104. These alternative electrode
geometries allow the electrical current densities emanating from
the active electrodes 104 to be concentrated to achieve an
increased ablation rate and/or a more concentrated ablation effect
due to the fact that sharper edges (i.e., regions of smaller radii
of curvature) result in higher current densities. FIG. 22
illustrates a flattened extension of a round wire active electrode
104 which results in higher current densities at the edges 180.
Another example is shown in FIG. 23 in which the active electrode
104 is formed into a cone shaped point 182 resulting in higher
current densities at the tip of the cone.
[0147] Another embodiment of the electrosurgical probe is
illustrated in FIG. 24. The electrosurgical probe 90 comprises a
shaft 100 and at least two active electrodes 104 extending from a
support 102 at the distal end of the shaft. The active electrodes
104 preferably define a distal edge 600 for making an incision in
tissue. The edges 600 of the active electrodes 104 are
substantially parallel with each other and usually spaced a
distance of about 4 mm to 15 mm apart, preferably about 8 mm to 10
mm apart. The edges 600 extend from the distal end of support 102
by a distance of about 0.5 mm to 10 mm, preferably about 2 mm to 5
mm. In the exemplary embodiment, probe 90 will include a return
electrode 112 spaced proximally from the active electrodes 104. In
an alternative embodiment (not shown), one of the active electrodes
104 may function as a return electrode, or the return electrode may
be a dispersive pad located on an external surface of the patient's
body.
[0148] FIG. 25 illustrates a distal portion of an electrosurgical
probe 500 according to another embodiment of the present invention
The embodiment of FIG. 25 is particularly useful for cutting or
creating incisions in tissue structures. Probe 500 comprises a
support member 502 coupled to a shaft or disposable tip (not shown)
as described in previous embodiments. Support member 502 preferably
comprises an inorganic electrically insulating material, such as
ceramic, glass or glass-ceramic. In this embodiment, however,
support member 502 may comprise an organic material, such as
plastic, because the active electrode 506 and return electrode 508
are both spaced away from support member 502. Thus, the high
intensity electric fields may be far enough away from support
member 502 so as to allow an organic material.
[0149] An electrode assembly 504 extends from a distal end of
support member 502, preferably by a distance of about 2 mm to 20
mm. Electrode assembly 504 comprises a single, active electrode 506
and a return electrode sleeve 508 spaced proximally from active
electrode 506 by an insulation member 510, which preferably
comprises an inorganic material, such as ceramic, glass or
glass-ceramic. As shown, active electrode 506 preferably tapers to
a sharp distal end 512 to facilitate the cutting or incising of
tissue. In the exemplary embodiment, active electrode 506 has a
proximal diameter of about 0.2 to 20 mm and a distal diameter of
less than about 0.2 mm. Return electrode 508 is spaced from active
electrode 506 a sufficient distance to prevent shorting or arcing
therebetween at sufficient voltages to allow the volumetric removal
of tissue. In the representative embodiment, the distal exposed
portion of return electrode 508 is spaced about 0.5 to about 5 mm
from the proximal exposed portion of active electrode 506. Of
course, it will be recognized that the present invention is not
limited to the particular dimensions and configuration of the
electrode assembly 504 described herein, and a variety of different
configurations may be envisioned depending on the surgical
application.
[0150] As shown, probe 500 includes a fluid lumen 520 passing
through support member 502 to a distal opening (not shown) at the
distal end of support member 502. Fluid lumen 520 is coupled to a
supply of electrically conductive fluid, such as isotonic saline,
or other suitable conductive fluid for delivery of such fluid to
the target site. In the exemplary embodiment, probe 500 is designed
such that lumen 520 will be positioned above electrode assembly 504
during use such that the conductive fluid exiting the distal
opening of lumen 520 will naturally pass over return electrode 508
and active electrode 506 thereby creating a current path
therebetween. In addition, the conductive fluid will be sufficient
to cover the active electrode 506 such that the conditions for
plasma formation can be met, as described in detail above.
[0151] FIGS. 26 and 27A-C illustrate another exemplary
electrosurgical probe 310 for cutting, incising, or removing tissue
structures. Probe 310 comprises a shaft or disposable tip 313
removably coupled to a proximal handle 312, and an electrically
insulating electrode support member 370 extending from tip 313 for
supporting a plurality of active electrodes 358. Tip 313 and handle
312 typically comprise a plastic material that is easily molded
into a suitable shape for handling by the surgeon. As shown in
FIGS. 27A and 27B, handle 312 defines an inner cavity 372 that
houses the electrical connections 374, and provides a suitable
interface for connection to electrical connecting cable 34 (see
FIG. 1). In the exemplary embodiment, handle 312 is constructed of
a steam autoclavable plastic or metal (e.g., polyethylether ketone,
or a stable metal alloy containing aluminum and/or zince) so that
it can be re-used by sterilizing handle 312 between surgical
procedures. High service temperature materials are preferred, such
as a silicone cable jacket and a poly-ether-imide handpiece or
ULTEM.RTM. that can withstand repeated exposure to high
temperatures.
[0152] Referring to FIGS. 27A-27C, tip 313 preferably comprises
first and second housing halves 500, 502 that snap fit together,
and form a recess 404 therebetween for holding electrode support
member 370 within the tip 313. Electrode support member 370 extends
from the distal end of tip 313, usually by about 0.5 mm to 20 mm,
and provides support for a plurality of electrically isolated
active electrodes 358 and one or more return electrodes 400.
Alternatively, electrode support member 370 may be recessed from
the distal end of tip 313 to help confine the electrically
conductive fluid around the active electrodes 358 during the
surgical procedure, as discussed above. Electrode support member
370 has a substantially planar tissue treatment surface 380 that is
usually disposed at an angle of about 10 to 90 degrees relative to
the longitudinal axis of handle 312 to facilitate handling by the
surgeon. In the exemplary embodiment, this function is accomplished
by orienting tip 313 at an acute angle relative to the longitudinal
axis of handle 312.
[0153] In the embodiment shown in FIGS. 26-27C, probe 310 includes
a single annular return electrode 400 for completing the current
path between active electrodes 358 and power supply 28 (see FIG.
1). As shown, return electrode 400 preferably has a fluid contact
surface slightly proximal to tissue treatment surface 380,
typically by about 0.1 mm to 2 mm, and preferably by about 0.2 mm
to 1 mm. Return electrode 400 is coupled to a connector 404 that
extends to the proximal end of handle 313, where it is suitably
connected to power supply 28 (FIG. 1).
[0154] Referring again to FIGS. 27A-27C, tip 313 further includes a
proximal hub 506 for supporting a male electrical connector 508
that holds a plurality of wires 510 each coupled to one of the
active electrodes 358 or to return electrode 400 on support member
370. A female connector 520 housed within handle 312 is removably
coupled to male connector 508, and a plurality of wires 522 extend
from female connector 520 through a strain relief 524 to cable 334.
Both sets of wires 510, 522 are insulated to prevent shorting in
the event of fluid ingress into the probe 310. This design allows
for removable connection of the electrodes in tip 313 with the
connector 520 within handle 312 so that the handle can be re-used
with different tips 313. Probe 310 will preferably also include an
identification element, such as a coded resistor (not shown), for
programming a particular voltage output range and mode of operation
for the power supply. This allows the power supply to be employed
with a variety of different probes for a variety of different
applications.
[0155] In the representative embodiment, probe 310 includes a fluid
tube 410 (FIG. 26) for delivering electrically conductive fluid to
the target site. Fluid tube 410 is sized to extend through a groove
414 in handle 313 and through an inner cavity 412 in tip 312 to a
distal opening 414 (FIG. 26) located adjacent electrode support
member 370. Tube 410 extends all the way through inner cavity 412
to opening 414 to eliminate any possible fluid ingress into cavity
412. Fluid tube 410 includes a proximal connector for coupling to
an electrically conductive fluid source 321.
[0156] Probe 310 will also include a valve or equivalent structure
for controlling the flow rate of the electrically conductive fluid
to the target site. In the representative embodiment shown in FIGS.
27A-27C, handle 312 comprises a main body 422 coupled between
distal hub 418 and strain relief 420, and a rotatable sleeve 416
around main body 422. Distal hub 418 has an opening 419 for
receiving proximal hub 506 of tip 313 for removably coupling the
tip 313 to the handle 312. Sleeve 416 is rotatably coupled to
strain relief 420 and distal hub 418 to provide a valve structure
for fluid tube 410. As shown in FIG. 27A, fluid tube 410 extends
through groove 414 from strain relief 420, through main body 422
and distal hub 420 to tip 313. Rotation of sleeve 416 will impede,
and eventually obstruct, the flow of fluid through tube 410. Of
course, this fluid control may be provided by a variety of other
input and valve devices, such as switches, buttons, etc.
[0157] In alternative embodiments, the fluid path may be directly
formed in probe 310 by, for example, a central inner lumen or an
annular gap (not shown) within the handle and the tip. This inner
lumen may be formed near the perimeter of the probe 310 such that
the electrically conductive fluid tends to flow radially inward
towards the target site, or it may be formed towards the center of
probe 310 so that the fluid flows radially outward. In addition,
the electrically conductive fluid may be delivered from a fluid
delivery element (not shown) that is separate from probe 310. In
arthroscopic surgery, for example, the body cavity will be flooded
with isotonic saline and the probe 310 will be introduced into this
flooded cavity. Electrically conductive fluid will be continually
resupplied to maintain the conduction path between return electrode
400 and active electrodes 358. A more complete description of
alternative electrosurgical probes incorporating one or more fluid
lumen(s) can be found in commonly assigned U.S. patent application
Ser. No. 08/485,219, filed on Jun. 7, 1995, now U.S. Pat. No.
5,697,281, the complete disclosure of which is incorporated herein
by reference.
[0158] Referring now to FIG. 26, electrically isolated active
electrodes 358 are spaced apart over tissue treatment surface 380
of electrode support member 370, preferably in a linear array. In
the representative embodiment, three active electrodes 358, each
having a substantially conical shape, are arranged in a linear
array extending distally from surface 380. Active electrodes 358
will usually extend a distance of about 0.5 mm to 20 mm from tissue
treatment surface 380, preferably about 1 mm to 5 mm. Applicant has
found that this configuration increases the electric field
intensities and associated current densities at the distal edges of
active electrodes 358, which increases the rate of tissue cutting.
In the representative embodiment, the tissue treatment surface 380
has a circular cross-sectional shape with a diameter in the range
of about 0.5 mm to 20 mm (preferably about 2 mm to 10 mm). The
individual active electrodes 358 preferably taper outward as shown,
or they may form a distal edge, such as the electrodes shown in
FIGS. 3 and 24.
[0159] Probe 430 of FIG. 28 includes a shaft 432 coupled to a
proximal handle 434 for holding and controlling shaft 432. Probe
430 includes an active electrode array 436 at the distal tip of
shaft 432, an annular return electrode 438 extending through shaft
432 and proximally recessed from the active electrode array 436,
and an annular lumen 442 between return electrode 438 and an outer
insulating sheath 446. Probe 430 further includes a liquid supply
conduit 444 attached to handle 434 and in fluid communication with
lumen 442, and a source of electrically conductive fluid (not
shown) for delivering the fluid past return electrode 438 to the
target site on the tissue 440. Electrode array 436 is preferably
flush with the distal end of shaft 432 or distally extended from
the distal end by a small distance (on the order of 0.005 inches)
so as to minimize the depth of ablation. Preferably, the distal end
of shaft 432 is beveled to improve access and control of probe 430
while treating the target tissue.
[0160] Yet another embodiment of the present invention is shown in
FIG. 29. Auxiliary active electrodes 458, 459 are positioned at the
distal tip 70 of the probe. Auxiliary active electrodes 458, 459
may be the same size as ablation active electrodes 58, or larger as
shown in FIG. 29. One operating arrangement is to connect auxiliary
active electrodes 458, 459 to two poles of a high frequency power
supply to form a bipolar circuit allowing current to flow between
the terminals of auxiliary active electrodes 458, 459 as shown by
current flux lines 460. Auxiliary active electrodes 458, 459 are
electrically isolated from ablation electrodes 58. By proper
selection of the inter-electrode spacing, W2, and electrode width,
W3, and the frequency of the applied voltage, the current flux
lines 460 can be caused to flow below the target layer as described
above.
[0161] The voltage will preferably be sufficient to establish high
electric field intensities between the active electrode array 436
and the target tissue 440 to thereby induce molecular breakdown or
disintegration of several cell layers of the target tissue. As
described above, a sufficient voltage will be applied to develop a
thin layer of vapor within the electrically conductive fluid and to
ionize the vaporized layer or region between the active
electrode(s) and the target tissue. Energy in the form of charged
particles are discharged from the vapor layer to ablate the target
tissue, thereby minimizing necrosis of surrounding tissue and
underlying cell layers.
[0162] With reference to FIG. 30, there is shown in perspective
view an electrosurgical probe 700, according to another embodiment
of the invention. Probe 700 includes a shaft 702 having a shaft
distal end portion 702a and a shaft proximal end portion 702b.
Shaft 702 is affixed at its proximal end 702b to a handle 704.
Shaft 702 typically comprises an electrically conductive material,
usually a metal, such as tungsten, stainless steel, platinum or its
alloys, titanium or its alloys, molybdenum or its alloys, nickel or
its alloys. An electrically insulating electrode support 710 is
disposed at shaft distal end 702a. An active electrode 712 is
disposed on electrode support 710. Active electrode 712 comprises a
blade electrode (e.g., FIGS. 31A, 31B). An electrically insulating
sleeve 716 covers a portion of shaft 702, and terminates at sleeve
distal end 716a to define an exposed portion of shaft 702 extending
between electrode support proximal end 710b and sleeve distal end
716a. This exposed portion of shaft 702 defines a return electrode
718 on shaft distal end portion 702a. (In an alternative
embodiment, the return electrode may take the form of an annular
band of an electrically conductive material, e.g., a platinum
alloy, disposed on the exterior of the shaft distal end). A cavity
within handle 704 accommodates a connection block 706 which is
connected to active electrode 712 and return electrode 718 via
electrode leads (not shown). Connection block 706 provides a
convenient mechanism for coupling active electrode 712 and return
electrode 718 to opposite poles of a power supply (e.g., power
supply 28, FIG. 1).
[0163] FIG. 31A is a perspective view of an active electrode 712 of
probe 700, according to one embodiment of the invention. Active
electrode 712 is in the form of a single blade electrode which
extends from electrode support 710 to a distance, Hb. The distance
Hb may vary, for example, according to the intended applications of
probe 700, and the value of Hb is at least to some extent a matter
of design choice. Typically, for a broad array of electrosurgical
procedures, the distance Hb is in the range of from about 0.02 mm
to about 5 mm. Active electrode 712 includes an active edge 713
which is adapted for generating high current densities thereat upon
application of a high frequency voltage from the power supply
between active electrode 712 and return electrode 718. In this way,
active edge 713 can efficiently effect localized ablation of
tissues via molecular dissociation of tissue components which
contact, or are in close proximity to, active edge 713. A process
for ablation of tissues via molecular dissociation of tissue
components has been described hereinabove.
[0164] As best seen in FIG. 31B, the blade-like active electrode
712 further includes first and second blade sides, 714a, 714b,
respectively. First and second blade sides 714a, 714b are separated
by a maximum distance, Wb. The distance Wb is typically in the
range of from about 0.1 mm to about 2.5 mm. In the embodiment of
FIG. 31B, first and second blade sides 714a, 714b are substantially
parallel to each other. Each of first and second blade sides 714a,
714b are adapted for engaging tissue severed, ablated, or otherwise
modified by active edge 713, and for coagulating tissue engaged by
first blade side 714a and/or second blade side 714b. In this way,
active electrode 712 can precisely and effectively sever, ablate,
or otherwise modify a target tissue with active edge 713 to form a
first-modified tissue, and at the same time, or shortly thereafter,
further modify the first-modified tissue by means of first and
second blade sides 714a, 714b. For example, active edge 713 can
make an incision in a target tissue via localized molecular
dissociation of target tissue components, while first and second
blade sides 714a, 714b can effect hemostasis in the severed
tissue.
[0165] FIGS. 32A, 32B, and 32C are a side view, a plan view, and an
end view, respectively, of electrosurgical probe 700 having a
blade-like active electrode 712, according to one embodiment of the
invention. In the embodiment of FIGS. 32A-C, electrode support 710
is disposed at the terminus of shaft 702, and active electrode 712
is affixed to support distal end 710a (e.g., FIG. 33A). However,
other arrangements for electrode support 710 and active electrode
712 are within the scope of the invention (e.g., FIGS. 34A-C,
35A-C). Active electrode 712 is in the form of a substantially flat
metal blade. Active electrode 712 is shown as being substantially
rectangular as seen from the side (FIG. 32A). However, various
other shapes for active electrode 712 are within the scope of the
invention (e.g., FIGS. 33C-E). FIG. 32C is an end view of probe 700
as seen along the lines 32C-32C of FIG. 32B, showing a laterally
compressed region 703 of shaft 702. Laterally compressed region 703
may be adapted for housing electrode support 710. Laterally
compressed region 703 may also facilitate manipulation of shaft
distal end portion 702a of probe 700 during various surgical
procedures, particularly in situations where accessibility of a
target tissue is restricted.
[0166] FIGS. 33A and 33B are a side view and a plan view,
respectively, of the distal end of probe 700, showing details of
shaft distal end portion 702a and terminally disposed blade active
electrode 712, according to one embodiment of the invention. Blade
electrode 712 is substantially rectangular in shape as seen from
the side (FIG. 33A). The distal end of shaft 702 includes laterally
compressed region 703. As seen from the side (FIG. 33A), laterally
compressed region 703 appears wider than more proximal portions of
shaft 702. FIG. 33B is a plan view of probe 700 as seen along the
lines 33B-33B of FIG. 33A, in which laterally compressed region 703
appears narrower than more proximal portions of shaft 702.
Electrode support 710 is mounted to the distal end of laterally
compressed region 703. Typically, electrode support 710 comprises a
durable, electrically insulating, refractory material having a
certain amount of flexibility. For example, electrode support 710
may comprise a material such as a silicone rubber, a polyimide, a
fluoropolymer, a ceramic, or a glass.
[0167] FIGS. 33C-33E each show a side view of the distal end of
probe 700 having a terminal blade active electrode 712, according
to three different embodiments of the invention. Electrode support
710 is mounted terminally on shaft 702, and includes a support
distal end 710a and a support proximal end 710b. In the embodiment
of FIG. 33C, active edge 713 of active electrode 712 is arcuate,
convex, or substantially semi-circular in shape. In the embodiment
of FIG. 33D, active electrode 712 has a pointed active edge 713,
while in the embodiment of FIG. 33E, the active edge 713 of active
electrode 712 is serrated.
[0168] FIG. 34A shows in side view an electrosurgical probe 700
having electrode support 710 mounted terminally on shaft 702 and
blade active electrode 712 disposed laterally on electrode support
710, according to another embodiment of the invention. FIG. 34B is
a plan view of probe 700 taken along the lines 34B-34B of FIG. 34A.
FIG. 34C is an end view taken along the lines 34C-34C of FIG. 34A.
In the embodiments of FIGS. 34A-C, electrode 712 is in the form a
substantially flat, metal blade having first and second blade sides
714a, 714b, substantially parallel to each other. First and second
blade sides 714a, 714b are adapted for engaging and coagulating
severed or modified tissue, as described hereinabove.
[0169] FIG. 35A shows in side view an electrosurgical probe 700
having electrode support 710 mounted laterally on the distal end of
shaft 702, according to another embodiment of the invention. Blade
active electrode 712 is mounted laterally on electrode support 710.
FIG. 35B is a plan view of probe 700 taken along the lines 35B-35B
of FIG. 35A. FIG. 35C is an end view taken along the lines 35C-35C
of FIG. 35A. Active electrode 712 is in the form a substantially
flat, metal blade having first and second blade sides 714a, 714b,
substantially parallel to each other. Electrode support 710 is
mounted laterally on laterally compressed region 703 of shaft
702.
[0170] FIG. 36A shows a side view of the distal end of an
electrosurgical probe 700, wherein shaft 702 includes a beveled end
728 to which electrode support 710 is mounted. Blade active
electrode 712 is disposed on electrode support 710. The arrangement
of electrode support 710 and electrode 712 on beveled end 728 may
facilitate access of shaft distal end portion 702a in general, and
of electrode 712 in particular, to a target tissue during various
surgical procedures, particularly in situations where accessibility
is restricted. FIG. 36B shows a side view of the distal end of an
electrosurgical probe 700, according to another embodiment of the
invention. Shaft 702 includes a curved distal end 702a'. Electrode
support 710 is mounted on distal end 702a', and blade active
electrode 712 is affixed to electrode support 710. Curved distal
end 702a' facilitates access of electrode 712 to a target tissue
during various surgical procedures.
[0171] Although in the embodiments of FIGS. 34A-C, 35A-C, and 36A-B
active electrode 712 is shown as being substantially rectangular,
this representation should not be construed as limiting these
embodiments to a rectangular active electrode 712. Indeed, each of
the embodiments of FIGS. 34A-C, 35A-C, and 36A-B may have an active
electrode 712 in a broad range of shapes, including those
represented in FIGS. 33C-E.
[0172] FIG. 37A shows in side view an electrosurgical probe 700
having an exterior tube 724 arranged on shaft 702 and coupled at
its proximal end to a connection tube 720 at handle 704. Exterior
tube 724 may comprise a plastic tube of suitable length
commensurate with the size of probe 700. Exterior tube 724 defines
a lumen 726, and typically terminates at shaft distal end 702a at a
location somewhat proximal to electrode support 710. In some
embodiments, probe 700 may include two or more exterior tubes 724,
each exterior tube 724 having lumen 726. Each lumen 726 may serve
as a conduit for an aspiration stream, or as a conduit for delivery
of an electrically conductive fluid to the shaft distal end,
generally as described hereinabove. FIG. 37B is an end view of
probe 700 taken along the lines 37B-37B of FIG. 37A, showing
exterior tube 724 and lumen 726 in relation to shaft 702. The
diameter of exterior tube 724 is, at least to some extent, a matter
of design choice. Exterior tube 724 may comprise a substantially
rigid or somewhat flexible plastic tube comprising polyethylene, a
polyimide, a fluoropolymer, and the like.
[0173] FIG. 38A shows, in side view, an electrosurgical probe 700
having an outer sheath 722 surrounding the exterior of a portion of
shaft 702, according to another embodiment of the invention. Outer
sheath 722 is coupled at its proximal end to a connection tube 720
at handle 704. Outer sheath 722 may comprise a plastic tube of
suitable length and having a diameter larger than that of shaft
702. Together with the exterior of shaft 702, outer sheath 722
defines a lumen 726' in the form of an annular void. Typically,
outer sheath 722 terminates at shaft distal end 702a at a location
proximal to electrode support 710. Lumen 726' typically serves as a
conduit for delivery of an electrically conductive fluid to the
shaft distal end. FIG. 38B is an end view of probe 700 taken along
the lines 38B-38B of FIG. 38A, showing outer sheath 722 and lumen
726' in relation to shaft 702. The diameter of outer sheath 722 is,
at least to some extent, a matter of design choice. Outer sheath
722 may comprise a substantially rigid or somewhat flexible plastic
tube comprising polyethylene, a polyimide, and the like.
[0174] FIG. 39A schematically represents an electrosurgical probe
700, according to another embodiment of the invention. Probe 700
includes shaft 702 and handle 704 affixed at shaft proximal end
702b. A first electrode support 711a and a second electrode support
711b are disposed at shaft proximal end 702a. A blade active
electrode 712 is arranged on first and second electrode supports,
711a, 711b. Each of first and second electrode supports 711a, 711b
may comprise a refractory and electrically insulating material,
such as a silicone rubber or the like, as described hereinabove. A
return electrode 718 is located at shaft distal end 702 proximal to
first and second electrode supports 711a, 711b. Return electrode
718 may comprise an exposed portion of shaft distal end 702a (e.g.,
FIGS. 32A-C). Blade active electrode 712 typically extends distally
from electrode support 710 by a distance in the range of from about
0.1 mm to about 10 mm, an more typically from about 2 mm to 10
mm.
[0175] Blade active electrode 712 and return electrode 718 may be
independently coupled to opposite poles of a high frequency power
supply via electrode leads (not shown) and a connection block
(e.g., FIG. 30). In one embodiment, an active electrode lead is
coupled to one of first and second electrode arms 715a, 715b, and
the other arm terminates in a free, electrically isolated end, for
example, within first electrode support 711a or second electrode
support 711b. Blade active electrode 712 includes a crosspiece 715c
(FIGS. 39B-D) located distal to aspiration port 734. A fluid
delivery element or unit including an outer sheath 722' (e.g., FIG.
39B) is omitted from FIG. 39A for the sake of clarity.
[0176] FIG. 39B is a partial sectional view of probe 700 of FIG.
39A as seen from the side. Outer sheath 722' defines an annular
fluid delivery lumen 726' between sheath 722' and shaft 702. Lumen
726' terminates in an annular fluid delivery port 725 at shaft
distal end 702a. Fluid delivery lumen 726' is in communication
proximally with a fluid delivery tube 721. Solid arrows indicate
the direction of flow of an electrically conductive fluid (e.g.,
isotonic saline) within fluid delivery lumen 726'. Aspiration port
734 is in communication proximally with an aspiration lumen 732 and
an aspiration tube 730. Solid arrows within aspiration lumen 732
indicate the direction of flow of an aspiration stream, which flows
from aspiration port 734 towards a source of vacuum (not shown),
the latter coupled to aspiration tube 730. FIG. 39C is an end view
of probe 700 taken along the lines 39C-39C of FIG. 39B. Active
electrode 712 includes crosspiece 715c extending between first and
second electrode arms 715a, 715b, respectively (FIG. 39D). Active
electrode 712 further includes first and second blade sides 714a,
714b. In some embodiments, first and second blade sides 714a, 714b
are adapted for engaging tissue that has been severed, and for
coagulating the severed tissue. Crosspiece 715c at least partially
spans aspiration port 734. Typically, active electrode 712
comprises a single metal blade, comprising a material such as
platinum, tungsten, palladium, iridium, or titanium, or their
alloys.
[0177] FIG. 39D shows detail of the distal portion of probe 700 of
FIGS. 39A-C including blade active electrode 712. As shown, first
and second electrode arms 715a, 715b are disposed on first and
second electrode supports 711a, 711b, respectively. In an
alternative embodiment, first and second electrode arms 715a, 715b
may be disposed on a single annular electrode support having a
substantially central void defining aspiration port 734. In one
embodiment, active electrode 712 includes both a distal active edge
713a, and a proximal active edge 713b. Distal active edge 713a, in
particular, is adapted for aggressively ablating tissue via
molecular dissociation of tissue components and for severing tissue
targeted for resection, transection, dissection, or other
treatment.
[0178] FIG. 40A is a partial sectional view of an electrosurgical
probe 700 according to another embodiment of the invention. Probe
700 of FIG. 40A generally includes shaft 702 and handle 704,
together with a fluid delivery element, and an aspiration unit,
essentially as for the embodiment described with reference to FIGS.
39A-D. In the interests of brevity these elements and features will
not described in detail with reference to FIGS. 40A-C. The
embodiment of FIG. 40A differs from other embodiments described
herein in having an active electrode in the form of a plasma hook
712'. Hook 712' is in some respects analogous to plasma blade
electrodes described hereinabove. For example, in one respect hook
712' is analogous to a truncated version of electrode 712 of the
embodiment of FIGS. 39A-D in which one of arms 715a or 715b is
omitted leaving one electrode arm affixed to crosspiece 715c. From
a functional standpoint, hook 712' allows the operator (surgeon) to
ablate tissue by drawing the instrument towards himself/herself. In
this manner, greater control is exerted over the amount or extent
of tissue removed or severed by probe 700. Hook 712' includes a
first axial portion 712'a (FIG. 40C) in contact at its proximal end
with electrode support 710. Hook 712' may further include a second
portion 712'b extending from the distal portion of first axial
portion 712'a. In some embodiments, second portion 712'b is
arranged substantially orthogonal to first axial portion 712'a. In
one embodiment, second portion 712'b may be structurally similar or
analogous to crosspiece 715c of the embodiment of FIGS. 39A-D.
Second portion 712'b at least partially spans aspiration port 734
(FIG. 40B). Electrode support 710 may comprise a refractory and
electrically insulating material, such as a silicone rubber or the
like, as described hereinabove.
[0179] FIG. 40B shows an end view of probe 700 taken along the
lines 40B-40B of FIG. 40A. Hook 712' includes first and second
blade sides 714a, 714b. Second portion 712'b extends at least
partially across aspiration port 734. FIG. 40C shows detail of the
distal end portion of probe 700 of FIGS. 40A, 40B, including hook
712'. Hook 712' includes a distal active edge 713a, a proximal
active edge 713b, and an active tip 713c. Return electrode 718 is
located proximal to electrode support 710. Upon application of a
high frequency voltage between hook 712' and return electrode 718,
a high current density may be generated at each of distal active
edge 713a, proximal active edge 713b, and active tip 713c. Each of
distal active edge 713a, proximal active edge 713b, and active tip
713c may be adapted for severing tissue via electrosurgical
molecular dissociation of tissue components.
[0180] FIGS. 41A, 41B, and 41C each show detail of the distal end
portion of an electrosurgical probe including a hook electrode
712', according to three different embodiments of the invention. In
the embodiment of FIG. 41A, hook 712' is curved, having a convex
distal edge 713a, and a concave proximal edge 713b. In the
embodiment of FIG. 41B, proximal edge 713b includes serrations
thereon. In an alternative embodiment (not shown), distal edge
713a, and/or active tip 713c may be similarly serrated. In the
embodiment of FIG. 41C, hook 712' is curved, having a concave
distal edge 713a, and a convex proximal edge 713b. According to
various embodiments of probe 700, second portion 712'b may have a
length which is less than, equal to, or greater than the diameter
of shaft 702. In the latter case, second portion 712'b extends
laterally beyond the exterior surface of shaft 702 (e.g., FIG.
41C). In each of the embodiments of FIGS. 41A-C, hook 712'
typically comprises a single blade having first and second blade
sides 714a, 714b (e.g., FIG. 40B). Hook 712' typically comprises a
metal such as platinum, tungsten, palladium, iridium, or titanium,
or their alloys.
[0181] FIGS. 42A-B schematically represent a process during
treatment of a patient with electrosurgical probe 700. Blade active
electrode 712 is affixed to support 710 on shaft 702. Blade active
electrode 712 includes active edge 713 and first and second blade
sides, 714a, 714b (e.g., FIGS. 31A-B). Referring to FIG. 42A,
active edge 713 forms an incision, I, in a target tissue, T, via
localized molecular dissociation of tissue components upon
application of a high frequency voltage between active electrode
712 and return electrode 718. (The localized molecular dissociation
may be facilitated by the delivery of a suitable quantity of an
electrically conductive fluid (e.g. isotonic saline) to form a
current flow path between active electrode 712 and return electrode
718.) With reference to FIG. 42B, as the incision I is deepened
within tissue T, first and second blade sides, 714a, 714b engage
severed tissue in regions indicated by the arrows labeled E. In
this way, the severed tissue is coagulated by first and second
blade sides, 714a, 714b, thereby effecting hemostasis at the point
of incision of the tissue.
[0182] FIG. 43A schematically represents a number of steps involved
in a method of treating a patient with an electrosurgical probe,
wherein step 1000 involves positioning the distal end of the probe
adjacent to target tissue such that an active electrode of the
probe is in contact with or in close proximity to the target
tissue. In one embodiment, the active electrode is spaced a short
distance from the target tissue, as described hereinabove.
Typically, step 1000 involves positioning the probe such that an
active edge of the active electrode makes contact with, or is in
close proximity to, the target tissue. Step 1002 involves
delivering an electrically conductive fluid to the distal end of
the probe in the vicinity of the active electrode and the return
electrode, such that the electrically conductive fluid forms a
current flow path between the active electrode and the return
electrode. The electrically conductive fluid may be delivered via
an exterior tube disposed on the outside of the shaft (e.g., FIGS.
37A, 37B), or an outer sheath external to the shaft and forming an
annular fluid delivery lumen (e.g., FIGS. 38A, 38B). The
electrically conductive fluid may be a liquid, a gel, or a gas.
Apart from providing an efficient current flow path between the
active and return electrodes, a clear, colorless electrically
conductive liquid, such as isotonic saline, exhibits the added
advantage of increasing the visibility of the surgeon at the target
site. However, in situations where there is an abundance of
electrically conductive body fluids (e.g., blood, synovial fluid)
already present at the target site, step 1002 may optionally be
omitted.
[0183] Step 1004 involves applying a high frequency voltage between
the active electrode and the return electrode sufficient to ablate
or otherwise modify the target tissue via localized molecular
dissociation of target tissue components. By delivering an
appropriate high frequency voltage to a suitably configured probe,
the target tissue can be incised, dissected, transected,
contracted, or otherwise modified. In addition, the modified tissue
can also be coagulated (e.g., FIG. 42B). The frequency of the
applied voltage will generally be within the ranges cited
hereinabove. For example, the frequency will typically range from
about 5 kHz to 20 MHz, usually from about 30 kHz to 2.5 MHz, and
often between about 100 kHz and 200 kHz. The root mean square (RMS)
voltage that is applied in step 1004 is generally in the range of
from about 5 volts to 1000 volts RMS, more typically being in the
range of from about 10 volts to 500 volts RMS. The actual voltage
applied may depend on a number of factors, including the size of
the active electrode, the operating frequency, and the particular
procedure or desired type of modification of the tissue (incision,
contraction, etc.), as described hereinabove.
[0184] Step 1006 involves manipulating the probe with respect to
the tissue at the target site. For example, the probe may be
manipulated such that an active edge of a blade or hook electrode
reciprocates with respect to the target tissue, such that the
target tissue is severed, incised, or transected at the point of
movement of the active edge by a process involving molecular
dissociation of tissue components. In embodiments where the active
electrode is in the form of a hook, step 1006 may involve engaging
the hook against the target tissue and drawing the hook towards the
operator in order to cut or sever the tissue. In this manner, the
extent of cutting or severing can be precisely controlled. In one
embodiment, step 1006 involves reciprocating an active edge in a
direction parallel to a surface of the target tissue. Typically,
step 1006 is performed concurrently with step 1004. Step 1002 may
be performed at any stage during the procedure, and the rate of
delivery of the electrically conductive fluid may be regulated by a
suitable mechanism, such as a valve.
[0185] Step 1008 involves modifying the target tissue as a result
of the high frequency voltage applied in step 1004. The target
tissue may be modified in a variety of different ways, as referred
to hereinabove. The type of tissue modification achieved depends,
inter alia, on the voltage parameters of step 1004; the shape,
size, and composition of the active electrode; and the manner in
which the probe is manipulated by the surgeon in step 1006. At
relatively high voltage levels, tissue components typically undergo
localized molecular dissociation, whereby the target tissue can be
dissected, incised, transected, etc. At a lower voltage, or at a
lower current density on the active electrode surface, the target
tissue can be contracted (e.g., by shrinkage of collagen fibers in
the tissue), or a blood vessel can be coagulated. For example, in
step 1010 the first and second blade sides of the active electrode
may be engaged against a region of the target tissue which has been
modified as a result of localized molecular dissociation of tissue
components in step 1008. The first and second blade sides are
substantially flat metal plates having lower current densities than
the active edge. In this manner, the lower current densities of the
first and second blade sides cause further modification (e.g.,
coagulation) of the previously modified (e.g., severed) target
tissue (step 1012).
[0186] FIG. 43B schematically represents a number of steps involved
in a method of severing tissue with an electrosurgical probe via a
process involving molecular dissociation of tissue components, and
of coagulating the severed tissue with the same electrosurgical
probe during a single procedure, according to one embodiment of the
invention. The electrosurgical probe typically comprises an active
electrode in the form of a single, substantially flat metal hook or
blade having at least one active edge adapted for electrosurgically
severing the tissue, and first and second blade sides adapted for
effecting hemostasis of the severed tissue. Steps 1000' through
1006' are substantially the same or analogous to steps 1000 through
1006, as described hereinabove with reference to FIG. 43A. Step
1008' involves severing the target tissue via localized molecular
dissociation of tissue components due to high current densities
generated at the position of an active edge upon execution of step
1004'. Step 1010' involves engaging the first and second blade
sides against the tissue severed in step 1008', whereby blood/blood
vessels in the severed tissue are coagulated as a result of the
relatively low current densities on the first and second blade
sides (step 1012').
[0187] FIG. 44 schematically represents a number of steps involved
in a method of dissecting a tissue or organ of a patient with an
electrosurgical probe having a hook or blade active electrode,
according to one embodiment of the invention, wherein step 1100
involves accessing an organ or tissue. Typically, accessing an
organ or tissue in step 1100 involves incising an overlying tissue
which conceals the organ or tissue to be dissected. As an example,
in an open chest procedure involving a median sternotomy, the
thoracic cavity is accessed by making a longitudinal incision
though the sternum. Incising an overlying tissue in step 1100 may
be performed generally according to the methods described with
reference to FIGS. 43A or 43B. Step 1102 involves positioning the
distal end of the electrosurgical probe, and in particular an
active edge of the hook or blade active electrode, in at least
close proximity to connective tissue adjacent to the tissue or
organ to be dissected. As an example, the connective tissue may be
soft tissue, such as adipose tissue, or relatively hard tissue such
as cartilage or bone. Optional step 1104 involves delivering an
electrically conductive fluid to the distal end of the probe such
that the electrically conductive fluid forms a current flow path
between the active electrode and the return electrode, generally as
described for step 1002, supra. Step 1106 involves applying a high
frequency voltage between the active electrode and the return
electrode, generally as described for step 1004, supra.
[0188] Depending on the type of procedure, e.g., the nature of the
tissue or organ to be dissected, optional step 1108 may be
performed, in which the probe is manipulated such that an active
edge of the active electrode is moved with respect to the
connective tissue adjacent to the tissue or organ to be dissected.
Where the active electrode comprises a hook, the hook may be
engaged against the connective tissue and drawn towards the
operator of the probe to precisely control the degree of cutting or
tissue removal. Step 1110 involves electrosurgically ablating, via
molecular dissociation of connective tissue components, at least a
portion of the connective tissue adjacent to the tissue or organ to
be dissected. As an example, connective tissue adjacent to the
internal mammary artery may be dissected by a process involving
molecular dissociation of connective tissue components, in either
an open-chest or a minimally invasive procedure, such that the IMA
is substantially free from connective tissue over a portion of its
length.
[0189] It is to be understood that the electrosurgical apparatus of
the invention, e.g., probe 700, is by no means limited to those
methods described with reference to FIGS. 42A-44. Thus, as stated
hereinabove, embodiments of an electrosurgical probe having an
active electrode in the form of a blade or hook are applicable to a
broad range of surgical procedures, such as ablation, incision,
contraction, coagulation, or other modification of: connective
tissue, including adipose tissue, cartilage, and bone; dermal
tissue; vascular tissues and organs, including arteries and veins;
and tissues of the shoulder, knee, and other joints. Thus, while
the exemplary embodiments of the present invention have been
described in detail, by way of example and for clarity of
understanding, a variety of changes, adaptations, and modifications
will be apparent to those of skill in the art. Therefore, the scope
of the present invention is limited solely by the appended
claims.
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