Note: Descriptions are shown in the official language in which they were submitted.
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Descri~-tion
Implantable Cardiac Defibrillating Electrode
Technical Field
It is well known -that cardiac arrhythmias,
such as atrial or ventricular fibrillation, can be
overcome by applying electrical energy to the fibril-
lating myocardium. This procedure, defibrillation,
can be accomplished by applying the elec-trical energy
either to the chest of the patient by means of
conductive-metal paddles held in place by medical
personnel or, during the course of cardiac surgery,
by holding conductive~me-tal paddles in direct con-tact
with the surface of the heart. Such procedures are
well known and have been found to be generally effective.
More recently, implantable defibrillators
have been proposed for automatically detecting -the
onset of -the cardiac arrhythmia and for automatically
correcting such arrhythmia. These automatic defibril-
lators may employ conformal electrodes, which are
maintained in contact with the surface of -the heart
or/ electrodes on an intravascular cath~ter, or some
combination of these. In any case, the electrodes
act to impart the desired electrical energy -to the
heart muscle to achieve defibrillation.
With the intravascular catheter electrode
approach, i-t has been found that although less elec-
trical energy need be imparted to the heart than in
the exterior chest paddles approach, more energy is
needed than in the system wherein the electrodes are
placed directly in contact wi~ the heart surface.
In other words, it has been found that physically
placing the electrodes in cont~ct with the exterior
~k~
I ~ 8253~
of the heart will provide a more efficient use of the
electrical energv, thereby reducing the amount of
energy required. Obviously, energy consumption is of
the utmost importance in any implanted medical~
electronic device.
In the automatic defibrillators, previously
under consideration, the defibrillation electrodes
have been designed for application to the hear-t by
entering the chest cavity and by sewing the electrodes
to the heart or positioning the electrodes on the
surface of the heart. At times, such elec-trode
implantation may be accomplished during the course of
cardiac surgery, such as during a bypass operatlon.
However, even when such heart surgery is not indepen-
dently requirPd, the previous surface electrodesrequired that the chest cavity be opened in order to
implant the defibrillating electrodes. This surgical
procedure requires intubation of the lungs and e~poses
the surfaces of the lungs to possible infec-tion.
Additionally, in order for the surgeon to have sufficient
working space to effectively pOSitiOIl and apply the
electrodes, it may be necessary to perform an additional
surgical procedure involving spreading two adjacent
ribs or splitting the sternum. Accordingly, at the
present time, in order to apply any type of cardiac
electrodes to the surface of the heart, it is necessary
to perform major surgery. Nevertheless, it is desirable
to be able to implant the electrodes without the
necessity of entering the pleural space, thereby
maintaining the inte~rity o~ the pleural cavity.
Moreover, known surface electrodes suffer
from the disadvantage that less than uniform energy
density results from a discharge. Higher energy
densities appear at the electrode edges, and at
higher discharge levels, damaged tissue could result
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at the heart surface. It is, of course, desirable that the
discharge be uniform over the entire electrode surface and
that no regions of high energy density be present.
Dis^losure of the_Invention
The present invention i5 generally related to the
field of electrical defibrillation and, more specifically, to
particular cardioverting electrode configurations for use in
implantable defibrillators.
"Cardioverting" or "cardioversion" as used herein is
intended to emcompass the correction of a number of arrhythmic
heart conditions, both lethal and nonlethal. Those arrhythmic
heart conditions include atrial tachycardia, atrial flutter,
atrial fibrillation, junctional rhythms, ventricular
tachycardia, ventricular flutter, ventricular fibrillation,
and any other non-pacemaking related arrhythmic condition
which may be corrected by applying electrical shocks, which
are of a magnitude substantially greater than pacing shocks,
to the heart. Obviously then "defibrillation" is included in
the term cardioversion as a method o~ applying electrical
shocks to the heart to defibrillate fibrillating atria or
fibrillation ventricles.
The present invention provides an implantable
cardioverting electrode assembly for placement pro~imate the
heart and ~or connection to a suitable cardioverting s~stem,
the assembly compri 5 ing:
a flexible electrically conductive planar electrode
means for placement proximate the heart,
i 3 ~
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electrical conductor means arranged to electrically
connect said electrode means and said cardioverting system,
means arranged on the surface of said electrode means
proximate the heart for providing an increased electrical
impedance in the region surrounding the perimeter of said
electrode means, thereby maintaing substantially constant the
current density over the surface of said planar electrode
means, and wherein said means arranged on the surface of said
electrode comprises a layer of electrical insulation material
having at leas-t one open central area to permit the central
portion of said electrode to be exposed and substantially
covering the perimeter portion of said electrode, said
insulation material having a plurality of small apertures
therein located about said perimeter portion of said electrode
for also exposing the electrode surface therethrough, whereby
said plurality of small apertures substantially eliminates
edge effect current concentrations.
According to the present invention there is further
provided an electrode of the type for implantation in a
patient for connection to an electrical cardioverting system.
said electode comprising:
a planar electrical conductor,
a first layer of electrical insulating material
arranged in contact with and entirely convering one side of
said planar electrical conductor,
a second layer of electrical insulating material of
substantially the same size as said first layer; having at
5 3 ~
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least one large aperture therein for exposing the central
portion of said conductor and covering a perimeter portion of
said conductor and having a plurality of small apertures
therein located above said peri~eter portion for exposing
portions of said conductor therethrough, thereby substantially
elim:inating edge effect current concentrations, and
flexible electrical conductor means connected to said
planar electrical conductor and the electrical cardioverting
system, whereby sai.d electrode may be arranged in contact with
the heart for effecting cardioversion.
There is further provided an electrode of the type
for implantation in a patient for connection to an electrical
cardioverting system, said electrode comprising-
a planar electrical conductor,
a first layer of electrical insulating material
arranged in contact with and entirely covering one side of
said planar electrical conductor,
a second layer of electrical insulating ma-terial of
substantially the same size as te first layer, having at least
one large aperture therein for exposing the central portion of
said conductor and covering a perimeter of said conductor,
flexible electrical conductor means for electrically
connecting to the electrical cardioverting system, and
joint means interposed between said first and second
layers for electrically connecting said flexibl.e electrical.
conductor means to said planar electrical conductor in a joint
area where said planar electrical conductor is between said first
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-3c-
and second layers, whereby said electrode is adapted to be
arranged in contact with the heart for effecting cardioversion.
Further provided is a cardiac tissue-contacting
electrode of the type for implantation in a patient for connection
to an electrical cardi.overting system, said electrode comprising:
a planar electrically conductive metallic mesh having a
tissue-contacting surface and an insular-contacting surface,
a first layer of electrieal insulating material arranged
in contact with and entirely covering said insulator-contacting
surface,
a second layer of eleetrical insulating material of
substantially the same size as said first layer arranged in
contact with and peripherally covering said tissue-contacting
surface, said second layer having at least one large aperture
therein for exposing the eentral portion of said tissue-
eontaeting surfaee and eovering a perimeter portion of said
tissue-contacting surfaee, and
seeuring means disposed aeross said exposed central
portion of said mesh for maintaining said insulator-conducting
surfaee of said mesh in intimate eontact with said first layer of
eleetrieal insulating material to prevent ~issue from growing
between and separating said mesh and said first layer while
permitting said exposed portion of said tissue-contacting surfaee
to be in eonduetive eontaet with eardiac tissue, and
i ~8253~
-3d-
means arranged on the insulator covering said perimeter
portion for providing an increased electical impedance in the
region surrounding the perimeter of the electrode means, by
substantially eliminating the edge effect current concentrations,
thereby maintaining substantially constant the current density
over the surface of the planar electrode means.
In one embodiment, the cardiove~ting electrode is of
rectangular shape which is designed for insertion through the
soft tissues outside the pleural cavity and then to be arranged
in contact with the heart. The electrode has a specific
configuration which enhances energy efficiency, while providing
optimum transfer of electrical energy to the heart, and
preventing high-current densities from existing at the edges of
the electrode.
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The electrode is formed of a metallic mesh
or screen which is sandwiched between two layers of a
chemically inert, electrical insulation material. In
this manner, the portions of the electrode facing
away from, i.e., not in contact with the heart surface,
are electrically insulated from the body. An alternative,
yet a somewhat less efficient, embodiment is to use
only a single layer of insulation on the back and to
stitch such layer to the screen. The defibrillation
electrode may be provided with an additional electrode,
which is utilized -to provide a cardiac pacing function.
Means are also provided to permit disconnection of
the electrical lead to the pacing tip, after the
surgical implantation has taken place, at such time
when it may be reasonably assumed that cardiac pacing
is not required.
Additionally, the ele-ctrode may
also be used as a pick~up electrode in an electro-
cardiogram (ECG) system to detect the electrical
activity of the heart. Since both functions need not
occur simultaneously, the same electrical lead can be
used both in the defibrillator function and in the
ECG function.
Implantation of the electrode
consists of the steps of first making a skin
incision on the interior -thoracic or abdominal wall,
and then positioning the electrode on the surface of
the heart by using-a hand-held instrument to separate
the tissue planes and to create a tunnel inside the
thorax, but outside the pleural cavity, through the
soft tissues surrounding the heart. Upon creating
the tunnel, one or more electrodes may be placed into
the tunnel and arranged proximate the surface of the
heart. In one embodiment, two electrodes are placed
on opposing sides of the heart and means are provided
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whereby the proximal ends of the electrodes may be
sutured to the adjacent tissue, in order to provide
positive electrode fixation. In another manner of
practicing the method, a first tunneled
space is located between the interior surface of the
sternum and the exterior surface of the heart's
pericardium, and a second tunnel is created on the
heart's inferior surface between the pericardium and
the diaphragm.
In order to perform the inventive method
described above, a specialized inventive implantation
tool is provided which cooperates with the electrode
being implanted to permit relatively easy placement
of the electrode in relation to the heart and subseguent
withdrawal of the implantation tool.
In one embodiment of the electrode, the
edge surface of the electrode is constructed so as -to
have a higher impedance to current flow than the
central portion, thereby providing efficient, and
relatively uniform, energy transfer by eliminating
the so-called "edge effect". Such impedance is
controlled by the use of a mechanically embodied
electrical filter having spaced holes located over
the edges of the mesh electrode.
It is, therefore, one object of the present
invention to provide defibrillating electrodes, which
are highly efficient in transferring electrical
energy to the heart.
Another object of the present invention is
to provide defibrillator electrodes, which minimize
any electrical damage that may be done to the heart
muscle during defibrillation.
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The manner in which these and other objects
are accomplished by the present invention, as well as
the many attendant advantages thereof, will become
more readily apparent when reference is made to the
following description, taken in conjunction with the
accompanying drawings, of preferred er~odiments of the
present invention.
Brief Description of Drawinqs
Figure l is a perspective of an
electrode;
~igure 2 is a cross section through the
electrode of Figure l taken along sight line 2-2;
Figure 3 is a perspective of the bottom
surface of the elec-trode of Figure l;
Figure 4 is a perspective of a tool suitable
for inserting the electrode;
Figure 5 is a cross section of the insertion
tool of Figure 4 taken along plane 5-5;
Figure 6 is a perspective view of another
embodiment of a tool suitable ~or in~erting the
electrode;
Figure 7 (drawn on sheet 3 adjacent Fig. 9)
is a schematic representation showing the insertion of the
electrode into the body;
Figure 8 is a schematic representation showing
another manner of insertion of the electrode into the body;
Figure 9 (drawn on sheet 3 adjacent Fig. 7) is a
perspective of the electrode arranged on the insertion tool
prior to implantation of the electrode; and
Figure 10 is a cross-sectional view of the separable
coupler utilized in the embodiment of Figure l; and
Figure ll i5 a perspective of another embodiment of
the electrode.
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(
Best Mode or Carrying Out -the Invention
Referring first to Figure 1, the
electrode 10 is formed in a substantially rectangular
configuration, with side dimensions ranging from
approximately 1.5 to 4 cm and 3 to 6 cms, respectively.
Preferably, the electrode 10 is approximately 4 x 6
cm. In special cases the electrode may also be
formed as a square. The actual metallic electrode
element is a mesh or screen 12, which may be formed
of ti-tanium or platinum. Alternately, the electrode
may be formed of expanded platinum. The mesh is a
150 mesh, having 150 elements or individual wires per
inch. The wire diameter is chosen to be be-tween 1
and 3 mils. The electrode mesh 12 is first prepared
by spot welding together the wires located around the
periphery of the mesh. After spot welding, the
excess lengths of wires are then ground or machined
flush, so as to produce a smooth edge and to form a
continuous border.
The body of the electrade may be formed of
two layers of Silastic (~rade Mark) ~th the metallic electrode
element sandwiched therebetween. The electrode 10 is
formed by providing a first bottom layer 14 then
applying the titanium mesh 12 and, finally, having a
top layer 16 applied thereupon. The thickness of the
assembly should be approximately 0.1 to 0. 3 cm. The top
layer 16 has a rectangular aperture cut into it so
that the titanium mesh 12 may make electrical contact
with the surface of the heart. In order to provide
structural strength, a r~inforcing mesh of ~acron (I~ad~k) may
be embedded in both of the Silastic layers and, at
the very least, should be used in the bottom layer
14.
The electrode 10 may also be
provided with a pacing button 18, which is centrally
3 2
arranged in the metal mesh 12, and which is electrically
insulated from the mesh 12 by means of a suitable
insulator 20. The pacing button 18 may be formed of
platinum or some other suitably inert conductor. The
pacing button 18 should extend approximately 1 to 3
millimeters above the surface of the titanium mesh
12. The electrical lead for the pacing button 18 is
seen at 22 and is provided with a specialized detachable
coupler 24, located at the end of the conductor 22.
The detachable coupler 24 will be further described
and shown in more detail hereinbelow. Issuing from
this connector 24 is another conductor 26 which is
connected to a suitable plug 28 for connection to the
appropriate electronic cardiac pacing apparatus.
Upon implanting the electrode 10, the conductor 26 is
arranged externally to the patient with the coupler
24 located just inside the skin of the patient. In
this way, if necessary following surgery, the lead 26
is available to make a connection for the heart
pacing functionO Subsequently, after the patient's
condition has been stabilized, and when it appears to
the physician that the pacing function will not be
required, the lead 26 may be pulled from the coupler
24 with no additional surgical procedures required.
The mesh 12 of the electrode 10 is connected
to the proper source of electrical current through an
insulated cable 30 having a suitable electrical
connector 32 located at one end. The other end of
the cable 30 is electrically connected to the mesh 12
at a lo~ resistance joint located inside an insulated
boot 33.
The electrode 10 is an energy efficient
electrode which does not re~uire creating large
incisions or openings in the thorax, in order to
~ lB2532
_9_
effect direct surgical placement of the electrodes.
Such electrodes can be constructed so as to minimize the
possiblity of any damage to the heart caused when
using the electrode for defibrillation. In this regard,
it has been found that when employing defibrillation
electrodes having opposed conducto~s~ there is
presenc in the electric field between those two
conductors a phenomenon commonly associated with
parallel plate capacitors, to wit, the edge effect.
Briefly stated the edge effect involves the electric
field between two plates of a capacitor wherein the
electric field is normal to the plates except near
the plate edges, at which place the electric-field
lines tend to bulge outwardly. These bulging field
lines which are concentrated near the edges of the
capacitor plates (in the present case they are located
near the edges of the titanium mesh) produce a higher
current density than that which is present over the
central portion of the metal electrode surface.
In order to eliminate the adverse eEfects
of higher current densities due to the edge effect,
as well as to simultaneously maximize the surface
area available to reduce the current densities over
the metallic electrode surface, the present elec-trode
provides a plurality of holes, which are cut through
the top layer 16 of Silastic (Trad~k) dcw~ to the surface of
the mesh 12, in the vicinity of the edges of the
mesh. These holes are shown typically at 34 in
Figure 1 and, as may be seen, the surface of the
titanium mesh screen 12 is exposed therethrough. It
has been found that by means of these holes 34, the
edge effect which creates high current densities can
be substantially eliminated and also that the mesh
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--10--
12, which shows through the holes 34, increases the
surface area of the electrode which is available to
contact the heart surface, thereby also tending to
lower the current densities on the metallic electrode
elemen-ts.
The two layers and the metallic mesh may be
securely fastened together by placing stitches 36
around the periphery of the electrode 10 with a
conventional sewing machine using Dacron thread or
the like.
The leads 22, 30 are preferably formed of a
special, extremely flexible, electric cable, which is
particularly suitable for use with implanted cardiac
electrodes. Such flexibility is extremely important
so as to permit cardiac activity without trauma.
This cable is commonly known as tinsel and is formed
having a central strand of a polyester yarn and
around such central strand are wound six or more
conductive strands of silver. Each conductive strand
comprises, in turn, its own polyester yarn core and
concentrically wound conductive strands. This tinsel
wire has an exceedingly long life in the face of
mechanical stress, such as flexure. Additionally,
since it is formed of silver, the tinsel wire has an
extremely low electrical resistance. The tinsel wire
cable 30 must be electrically connected to the titanium
mesh 12 and this operation is accomplished on the
bottom surface of the mesh by crimping, welding, or
some other similar electrical connecting operation.
L82~2
Turning now to Figure 2, the arrangement of
the various elemen-ts making up the electrode 10 of
Figure 1 is shown in cross section, taken along sight
line 2-2 of Figure 1. In such cross section, the top
Silastic (Trad Æ k) layer 16 is bonded to the bottom Si]astic (Trad Æ k)
layer 14 and the titanium mesh electrode 12 is sandwiched
therebetween. It is seen that the holes 34 expose an
additional surface area of the mesh 12 to the heart
surface. The pacing tip 18 is connected to its
flexible cable 22 and the tip 18 is electrically
insulated from the mesh 12 by means of an insulator
20.
A]so seen in the cross section of Figure 2
is a layar of Dacron (Trade~rk) mPsh which may be u~lized as a
strengthening element in either or both Silas-tic (Trad Æ k)
layers of the sandwich. In this embodiment the mesh
is placed in the lower layer 14 and is seen in cross
section at 42 and at the leading edge of the assembly
where stresses occur during implanting. Similar Dacron
(Trad Æ k) mesh could also be used to strengthen the top
layer 16. The specialized pouch or pocket arrangement
44 which interacts with the specialized insertion or
implantation tool, for placement of the electrode 10
with minimum surgical involvemen-t, is shown in cross
section also. The pocket or pouch 44 is formed by
continuing the top layer 16 of Silastic (Trad Æ k) d~n cv~r ~e
leading edge of the electrode so as to form a lip 48
which extends parallel to the bottom layer 14 of the
electrode, thereby forming a pocket 50 across the
entire width of the electrode to receive the insertion
tool. Additionally, a portion of Dacron (Trad Æ k) me.sh 52 may
be embedded in the pocket or pouch 44 in order to
provide added strength to the pocket to prevent
tearing by the insertion tool.
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(
Fiyure 3 is a perspective from the bottom
of the electrode 10 and in this view the
pocket arrangement 44 is seen in more detail. Also
seen in Figure 3 is ~he Dacron (Trad~k) mesh 42, which is
5 embedded inside the bottom Silastic (Trad~k) layer 14. The
specialized pocket 44, which is intended for use
during insertion of the inventive electrodes, is
raised above the bottom layer 14 so as to form the
desired pocket 50. The opening of the pocket 50 must
be directed backwards and opening towards the rear of
the electrode, for reasons which will become clear
below. The additional Dacron (TradeNark) mesh streng~enin~
layer is seen at 52. The location of the joint
between the electrical conductor 30 and the wire mesh
12 is in the area shown generally at 54 and, after
such suitable electrical connection, the boot 33 is
placed over the joint area to provide both electrical
insulation and mechanical strain relief.
The pre~erred method for implanting the
present defibrillation electrode and pacer tip will
be set forth below, however, preliminarily thereto it
is necessary to show and describe a preferred embodi-
ment of a suitable insertion tool for use in practicing
such inventive method. Figure 4 shows a perspective
view of a preferred embodiment of the insertion tool
which is formed essentially as an elongated, flat,
mandrel-type probe 60. The prohe 60 has an elongated
flat handle portion 62 and a blunt but rigid leading
edge 64 which is utilized to form a tunnel through
the soft-tissue plane during the electrode insertion
process. The plane of the handle 62 changes somewhat
to form the upraised leading edge 64.
Figure 5 is a cross section of ~ portion of
the insertion tool 60 of Figure 4 and shows the
location of the upraised leadiny edge portion 64, in
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relation to the plane of handle 62. The leading edge
portion 64 is provided to interact with the pocket 50
formed in the bottom surface of the electrode lO and,
as may be seen by comparing Figures 2 and 5, in ~uch
interaction portion 64 will slide easily into the
pocket 50 in one direction and the electrode will
then lie parallel the plane of the handle 62. Accord-
ingly, the relative motion which is possible between
the insertion tool 60 and the electrode lO is uni-
directional. After insertion of the electrode, thetool 60 is withdrawn, thereby permitting the leading
edge portion 64 to slip out of the pocket 50, while
the electrode is retained in place next to the hear-t.
Additionally, upon insertion of the leading edge
portion 64 into the pocket 50 of the electrode lO,
the electrode itself becomes part of the means for
insertion into the human body
Figure 6 shows another embodiment of an
insertion tool 70, which has an elongated handle
portion 72 and a leading edge portion 74. The leading
edge portion 74 is inserted into the pocket 50 in the
electrode. This insertion tool 70 is formed as a
planar instrument.
As descrihed herein there is
25 - provided a method of Lmplanting a
defibrillation electrode system by making only a skin
incision, iOe., not involving major chest surgery, on
ei-ther the interior thoracic or abdominal wall.
EIence, by means of a specially provided hand-held
instrument, the tissue planes are separated and a
tunnel is created inside the thorax but outside the
pleural cavity through the soft tissues which surround
the heart. After forming a tunnel, one or more
electrodes may be inserted into the tunnel and arranged
proxirnate the surface of the heart.
3 ~
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~ lso contemplated is the forming of one tunnel
between the interior surface of the thorax and the
exterior surface of the heart's pericardium and,
attendantly, the insertion of one or more electrodes
through such tunnel for ultimate placement proximate
the heart. Additionally, the present disclosure
teaches another tunnel created on the poste.rior
surface of the heart's pericardium, between the
pericardium and the diaphragm, and also placement of
cardiac electrodes through this second tunnel.
Turning to Figure 7, the silhouette of the
thoracic region of a patient 100 is shown and the
incision locations are shown at 102 and 104. In the
silhouette of Figure 7 the location and general
outline of the patient's heart is seen at 106. In
regard to the abdominal incision 102, whereat the
incision tool 62 may be seen par-tially protruding
through this incision, the tunnel is bPing created
which is located on the inferior surface of -the
heart's pericardium between the pericardium and the
diaphragm. The electrode 10 is shown in
position and retained on the insertion tool 60. The
two leads 22 and 30 are also shown p.rotruding from
the incision 102.
Referring for a moment to Figure 8, the
electrode 10 is shown installed on the
specialized insertion tool 60 and the leading edge 64
of the insertion tool 60 having been inserted into
the pocket 50 formed in the back surface o~ the
: electrode 10. As may be seen in phantom,
the leading hard edge 64 of the insertion tool 60 is
at the front of the electrode 10. During insertion
thxough the soft tissue planes, the electrode 10 and
the hard leading edge 64 of the insertion tool cooperate
to form the tunnel.
3 2
--15--
Referring back to Figure 7, it may be seen
that the tunnels are being formed as indicated above.
In relation to the upper incision 104, which is made
in the interior thoracic region, a tunnel 110, similar
to 108, is being created between the interior surface
of the thorax and the anterior surface of the heart's
pericardium and the handle 62 of the insertion tool
60 is shown protruding through the incision 104, as
are the leads 22 and 30.
In Figure 9, it may be seen that by complete-
ly inserting -the insertion tool 60 the tunnels 108
and 110 are fully formed, and upon withdrawing the
insertion tool 60, the leading edge portion 64 of the
tool slips out of the pocket 50 of the electrode 10
and the electrode remains at its original location.
Figure 9 shows the electrodes in place after having
been inserted through the tunnels formed in the soft
tissue planes and after having the insertion tool
withdrawn frQm the tunnels. In Figure 9, the leads
are shown extending through the incisions; however,
these leads will be ultimately disposed of in accordance
with the desired ou-tcome, i.e., whether or not pacing
is reguired and whether or not the defibrillator is
of a completely implanted type.
There are also other procedures which may
be followed in applying the present electrodes to
the heart and the apparent order of combination
preEerences might be as follows. A superior vena
cava electrode in combination with a tunneled diaphrag-
matic electrode. Another combination might be a
substernal patch in combination with a diaphra~matic
patch, wherein both electrodes were introduced via a
subziphoid route. Of course, the locations as shown
in Fig. 9 are another combination.
5 3 2
-16-
Figure 10 is a cross sectional view of the
releasable lead coupling, shown at 24 in
Figure 1. As mentioned above, this type of coupling
is intended for use with the pacer tip so that after
implantation o the present electrode an electrical
connection is available for quick hook-up to a heart
pacing device so that if necessary, cardiac pacing
may be easily and ~lickly achieved. The present
coupling is provided so that when it becomes clear
that cardiac pacing will not be required, the lead
may be pulled free, with the coupling remaining in
the patient, and no further sur~ery will be re~uired.
In Figure 10, an ou-ter casing 130 of the
coupling 24 surrounds a female-type metallic connector
132 which is electrically connected to the pacing
lead 22. Forming an electrical joint with the female
connector 132 is a male plug 134 which is electrically
connected by either soldering or crimping to the
external pacing lead 26. The casing 130 of the
coupling i5 constructed such that there is a tight
mechanical bond formed at 136 between the pacing lead
insulation 22 and the casing 130, whereas in the case
of the external pacing lead 26, the housing 130 is
formed having an excessively large passage, shown
typically at 138, which is of greater diameter than
the outside diameter of the pacing lead 26. Such
greater diameter is provided so that when it is
desired to disconnect the external pacing lead, a
tensional force may be applied to the external lead
26 so that parts 132 and 134 will be separated,
th~reby permitting the external lead 26 to be withdrawn
from the patient's body.
Figure 11 shows an alternate embodiment of
the inventive electrode. In this embodiment, the
electrode 150 is constructed as was electrode 10 of
-17-
Fig. 1, except that top layer 16 is provided with a
plurality of apertures 152 in place of the single
large opening. These apertures 152 are formed by
crossing members 154 formed in the top layer 14.
This multiple aperture embodiment still permits use
of the pacing tip 18, which is then relocated in one
of the several available apertures.
These cross members 154 and additlonal
stitches 156 have been found advantageous in maintain-
ing the original form and function of the electrode.After implantation of an electrode the tissue acljacent
to the metallic mesh has been found -to adhere and
grow on and through the metallic mesh. ~hen this
happens, the tissue gets behind the mesh and tends to
force it away from the back layer. This ultimately
distorts the electrode shape and degrades its per-
formance by adversely affecting the contact surface.
The additional stitches 156 keep the mesh firmly
affixed to the back portion.
It is, of course, understood that the above
detailed descrip-tion is intended by way of example
only and is no-t intended to limit the present invent,ion
in any way, except as set forth in -the following
claims.
Thus, as shown ~n the dra~ings there IS
provided a defi~rillation electrode which ~ay be implanted
and arrang~d next to tha ~eart ~n a ~anner req~iring only
a minimum amount of surger~;
Also illustrated and described are a
specialized tool for use in ~nserting the electrode
~y means of the method; a defibrillating electrode
having a hear-t-pacing tip wherein the lead connec-tin~
the pacing tip to the pacing apparatus, locat2d
externally of the patient, is provided with a separable
connector so that after surgery a temporar,v pacin~ lead
-18-
may be disconnected and removed; and an implantable
defibrillation electrode having a specialized
receiving pocket at its forward most end to receive
the leading edge of an implantation tool, which will
permit insertion of the electrode through the soft
tissues of the thorax, while permitting the insertion
tool to be withdrawn after placement of the electrode.
