U.S. patent number 3,683,932 [Application Number 05/041,890] was granted by the patent office on 1972-08-15 for implantable tissue stimulator.
This patent grant is currently assigned to Adcole Corporation. Invention is credited to Addison D. Cole.
United States Patent |
3,683,932 |
Cole |
August 15, 1972 |
IMPLANTABLE TISSUE STIMULATOR
Abstract
An implantable tissue stimulator comprising a metal case
enclosing a battery and a pulse generating circuit powered thereby,
in which the circuit includes a terminal common to the case and a
stimulating terminal extending through and insulated from the case,
a flexible probe assembly comprising an exposed electrode adapted
to be placed in proximity to and in electrical contact with tissue
to be stimulated, and an elongated flexible insulated cable
connecting the electrode to a connector part adapted to be secured
to the stimulating terminal during implantation.
Inventors: |
Cole; Addison D. (Natick,
MA) |
Assignee: |
Adcole Corporation (Waltham,
MA)
|
Family
ID: |
21918896 |
Appl.
No.: |
05/041,890 |
Filed: |
June 1, 1970 |
Current U.S.
Class: |
607/37 |
Current CPC
Class: |
A61N
1/37512 (20170801) |
Current International
Class: |
A61N
1/375 (20060101); A61N 1/372 (20060101); A61n
001/36 () |
Field of
Search: |
;128/404,418,419P,419R,421,422 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kamm; William E.
Claims
Having thus described my invention, what I claim is:
1. In a cardiac pacer, the combination of:
a body stimulating electrode;
an electrical contact element;
an elongated flexible insulated conductor having one end connected
to said electrode and a second end connected to said contact
element, said contact element being mounted in a surrounding plug
member of flexible insulating material;
a pair of spaced parallel cylindrical apertures formed in said plug
member, one of said apertures communicating with said contact
element;
a metal housing having a first terminal inside said housing and a
second terminal outside said housing;
a pair of metal posts mounted on and protruding from said housing,
said posts extending into and closing said apertures;
an insulated lead through one of said posts from said first
terminal to said second terminal, said second terminal engaging
said contact element; and
a pulse generating circuit located in said housing and having an
output circuit connected between said housing and said first
terminal.
2. The apparatus of claim 1, further comprising
means forming a threaded recess in said housing; and
screw means cooperating with said recess and securing said plug
member to said housing.
3. A cardiac pacer, comprising:
a connector plug comprising a body member of flexible insulating
material;
a pair of spaced apertures formed in said body and extending from
one side thereof along parallel axes from said side to terminations
within said body member;
an electrical contact element mounted in said body and
communicating with one of said apertures;
an electrode;
an elongated flexible conductor having one end electrically
connected to said contact element and a second end connected to
said electrode;
insulating means mounted on said flexible conductor;
a metal housing having a first terminal inside said housing and a
second terminal outside said housing;
a pair of metal posts mounted on and protruding from said housing
extending into and closing said apertures;
an insulated lead extending through one of said posts from said
first terminal to said second terminal, said second terminal
engaging said contact element; and
a pulse generating circuit located in said housing and having an
output circuit connected between said housing and said first
terminal.
4. The apparatus of claim 3, in which said flexible conductor
comprises
a tubiform metal helix forming a flexible passageway closed at the
electrode end by said electrode, and further comprising
means forming a mating passageway through said body member, whereby
a stiffener can be passed into said flexible conductor to
facilitate insertion of the electrode in a body sinus.
5. A cardiac pacer, comprising:
a conductive metal housing having a generally plane side;
a pulse generating circuit mounted in said housing and having a
first output terminal connected to said housing and a second output
terminal extending through and insulated from said housing;
a pair of spaced mounting posts formed on said side and projecting
from said housing, said second output terminal extending through
one of said posts;
a flexible probe assembly comprising an exposed electrode adapted
to be placed in proximity to and in electrical contact with cardiac
tissue to be stimulated;
a connector plug comprising a body member of flexible insulating
material having at least one generally plane side;
a pair of spaced, cylindrical apertures formed in said body for
receiving said posts and extending along parallel axes from said
plane side to terminations within said body member;
an electrical contact element mounted in said body, communicating
with one of said apertures, and connected to said second output
terminal; and
an elongated flexible insulated cable connecting said electrode to
said electrical contact element.
Description
My invention relates to electrical tissue stimulators, and
particularly to a novel implantable stimulator.
Great strides have been made in the development of cardiac
prosthetic devices for supplanting, supplementing or controlling
the action of the heart during periods of malfunction, disease or
radical functional disruption, as during surgery or the like. In
particular, a demand has arisen for heart pacers that will deliver
electrical stimulating pulses in place of natural pulses that fail
to occur under various pathological conditions. For many purposes,
it is essential that this supplementary stimulating function be
performed over relatively long periods of time inconsistent with
the use of external circuits and power supplies transcutaneously
connected to the stimulated tissue. Thus, a fully implantable,
self-contained pacer would be highly desirable.
One of the principal obstacles to the construction of a practical
implantable pacer is the physical size of the container for the
pulse generating circuit and its power source. There are numerous
requirements on such a container that are difficult to meet without
excessive size and weight. First, the container must present an
exterior that is fluid tight, electrically insulates the contained
circuit, and is chemically inert and thermally inactive. Those
requirements are generally met by encapsulating the electrical
contents of the container in a thermoplastic insulating material,
through which insulated electrical connector parts must be passed.
In general, the power supply and the electronic pulse generating
circuit must be implanted in the body at a distance from the
preferred site for stimulation. Thus, the stimulating electrode or
electrodes must be connected to the power package by a long,
flexible, insulated cable. The necessities of surgery dictate that
the assembly be separated before implantation, i. e., by providing
a separable electrical connector between the power package and the
flexible probe carrying the stimulating electrodes, so that those
elements can be separately installed and then connected together
after implantation. Since the connectors must maintain a fluid seal
between the internal electrical terminals of the pulse generating
circuit and the body, a relatively rugged, and therefore massive,
connector construction has been employed. The result has been that
practical pacers have tended to be limited in design by the maximum
size and weight that could be tolerated, rather than by the
performance criteria that would govern if space and weight were no
object. The objects of my invention are to decrease the size and
weight of implantable cardiac pacers while improving their
efficiency and service life.
Briefly, the above and other objects of my invention are attained
by a novel pacer construction in which the container for the power
supply and pulse generating circuits comprises a sealed metal
canister that also serves as one electrode of the stimulating
circuit. This container is not encapsulated in an insulating
plastic material, nor are the electronic components which it
surrounds preferably encapsulated. The container preferably
comprises a relatively thin, flat rectangular metal package formed
with retaining means for holding a circuit board of insulating
material inside the container in a fixed position. Mounted on this
board are the power supply and pulse generator circuit. The largest
single electrical element is the power supply, preferably a single
disk shaped mercury-zinc storage battery. Next in size is a pulse
transformer forming the output element of the pulse generator. The
battery and transformer together determine the basic size of the
housing, as other necessary circuit elements may be considerably
smaller and thus readily mounted in spaces available adjacent the
larger components. Two external mounting posts are preferably
connected to the housing. These posts are adapted to cooperate with
corresponding recesses in a thermoplastic connector plug. One
mounting post contains a central insulated conductor adapted to be
connected in circuit with the pulse transformer, and to engage a
contact in the connector plug that is in turn connected, through a
flexible insulated conductor, to a stimulating electrode.
Preferably, a fastener is provided to fix the connector plug to the
metallic housing after assembly, to prevent the parts from working
loose. Desirably, a passage is provided in the connector and the
adjoining flexible probe assembly to admit a stiffening wire to
facilitate insertion of the probe into a selected body sinus, such
as an artery or the like.
The manner in which the apparatus of my invention is constructed,
and its mode of operation, will best be understood in the light of
the following detailed description, together with the accompanying
drawings, of a preferred embodiment thereof.
In the drawings,
FIG. 1 is a wiring diagram of a conventional cardiac pacer of the
type with which my invention is concerned;
FIG. 2 is a composite waveform diagram illustrating the operation
of the circuit of FIG. 1;
FIG. 3 is a schematic fragmentary elevational view of a power
supply and pulse generating circuit forming a part of the apparatus
of my invention;
FIG. 4 is a schematic cross-sectional view of the apparatus of FIG.
3, taken substantially along the lines 4--4 in FIG. 3;
FIG. 5 is a schematic exploded perspective sketch of a pacer
housing assembly forming a part of the apparatus of my
invention;
FIG. 6 is a schematic cross-sectional view of the apparatus of FIG.
5, taken substantially along the lines 6--6 of FIG. 5 and showing
the apparatus of FIGS. 3 and 4 in place;
FIG. 7 is a schematic elevational view, with parts shown in cross
section and parts broken away, of a cardiac pacer in accordance
with my invention;
FIG. 8 is a detailed cross-sectional view, on an enlarged scale, of
a portion of the apparatus of FIG. 7, taken essentially along the
lines 8--8 in FIG. 7;
FIG. 9 is a plan view of the apparatus of FIG. 7 with the connector
removed, taken essentially along the lines 9--9 in FIG. 7;
FIG. 10 is an enlarged cross-sectional view of a portion of the
apparatus of FIG. 7, showing parts in more detail and including a
portion of a stiffener assembly; and
FIG. 11 is an end view, taken essentially along the lines 11--11 in
FIG. 10, showing a detail of the stiffener assembly.
Referring to FIG. 1, I have shown the essential elements of a
fixed-rate cardiac pacer. A primary source of energy 1
conventionally comprises one or more storage batteries. I prefer to
employ a single, disk-like mercury-zinc storage battery for the
purpose. The battery 1 energizes a pulse forming network comprising
a blocking oscillator 3, a pulse generator 5, and a pulse
transformer generally designated 7 and having a primary winding 9
and a secondary winding 11. The secondary winding 11 is adapted to
be connected in circuit with the heart by means of electrodes 13
and 15. As will appear, I prefer to make one of the electrodes such
as 13 serve to conduct current directly to the site to be
stimulated, and to make the second electrode 15 common to one
terminal of the battery 1, preferably the negative terminal.
FIG. 2 illustrates the basic mode of operation of the circuit of
FIG. 1. The blocking oscillator 3 produces a ramp signal, FIG.
2(a), having a period equal to that of the heart beat to be
simulated, i.e., typically 832 milliseconds for a normal 72 per
minute heartbeat. The trailing edge of the ramp signal causes the
pulse generator to produce a stimulating pulse, FIG. 2b, of
preferably about 4 volts at 13 milliamperes for about 1/2
millisecond. Average output power dissipation is thus about 31
microwatts.
FIGS. 3 and 4 illustrate the mounting of the principal parts of the
circuit of FIG. 1 in accordance with my invention. The largest
element is the battery 1, both as to size and weight. The next
element in point of size is the pulse transformer 7. These elements
are preferably mounted in adjacent, spaced relation on a board 17,
of any suitable insulating material such as phenolic resin, glass
fiber filled expoxy resin, or the like. Any suitable mounting or
adhesive means, such as an epoxy resin or the like, may be employed
to secure the parts together. Other electrical components, such as
capacitors, resistors, diodes, transistors and the like, being of
smaller size, may be disposed about the board 17 in any convenient
manner and interconnected by printed circuits mounted on the board
17, by separate insulated conductors, or by other conventional
techniques.
FIG. 5 illustrates the manner in which the board 17 and its
associated electrical parts is mounted and contained. A two-part
housing is formed by a generally rectangular container 19, of
stainless steel or the like, having one open end, and an end cap
generally designated 21, also of stainless steel or the like. The
end cap is adapted to engage the container 19 fairly snugly, and to
be sealed in place by welding, as will appear.
The container 19 is arranged to receive the board 17 and its
associated electronic parts. As shown in FIGS. 5 and 6, end walls
23 of the container 19 are formed with depressions such as 25,
creating ribs 27 to engage the edges of the board 17. A small
amount of epoxy resin or other desired adhesive is preferably used
to further secure the board 17 within the container 19, and to
inhibit vibration.
As best shown in FIGS. 5 and 10, the end cap 21 is formed with
downwardly depending side flanges 31 that are adapted to engage the
inner sides of the container 19. After assembly and electrical
connection of the other parts, in a manner to appear, the flanges
31 of the end plate 21 are welded to the sides of the container 19,
with the parts in the position shown in FIG. 10, to form a sealed
seam.
Referring to FIGS. 5, 7 and 10, the end cap 21 is formed with three
upstanding annular flanges 33, 35 and 37. To the flange 33 is
welded an upstanding post 39, of stainless steel or the like. An
externally similar conductor post 41 is welded into the flange 37.
To the flange 35 is welded a connector 43 that is threaded as
indicated at 45 in FIG. 10 to receive a cooperatively threaded bolt
47.
Referring to FIGS. 7 and 10, a separable connector plug 49, of
flexible, insulating, physiologically inert material, such as
silicone rubber or the like,is provided. The plug 49 serves to
establish a physical and insulated electrical connection between
the housing 19, its electrical contents, and a flexible elongated
probe 51.
The probe 51 essentially comprises a long, flexible electrical
conductor 53, of stainless steel or the like. The conductor 53 is
preferably wound in the form of a helix, as shown in FIG. 8. While
the details of the probe form no part of my invention, in practice
it is preferred that the helix 53 be formed of at least two
parallel congruent concentric contiguous helices made from two
parallel wires, in the manner shown and described in detail in
copending U. S. Pat. application Ser. No. 41,980, filed on June 6,
1970 by Jean Bellerose for Flexible Probe Construction and assigned
to the assignee of this application.
The probe 51 further comprises an outer insulating coating 55, of
silicone rubber or the like, which may be formed integral with the
plug 49. At or near the end of the probe 51 remote from the plug
49, there is formed an exposed electrode 59 of stainless steel,
platinum or the like. The electrode 59 is bonded to the silicone
rubber coating 55 and electrically connected, as by soldering or
brazing or the like, to the lead 53.
The flexible lead 53 is soldered or otherwise secured at its other
end to a metal contact element 61 located in a suitable recess in
the plug 49. For example, the element 61 may be molded into the
plug during the manufacture of the latter. As shown, a bore 63 in
the element 61 mates with corresponding bores 65 and 67 formed in
the plug 49 to form a passage admitting a stiffener 69, such as a
stainless steel wire or the like.
As indicated in FIGS. 8 and 10, the stiffener 69 extends through
the passage just described and thence through the inside of the
helical conductor 53 up into engagement with the electrode 59. A
suitable knob 71, FIGS. 10 and 11, is secured to the stiffener 69
to facilitate manipulation of the latter by an operator. In
practice, the stiffener is inserted into the plug and up through
the flexible probe 51 to stiffen the latter sufficiently to permit
it to be inserted into an artery or other body sinus to carry the
electrode 59 to the desired operating site. The stiffener is then
withdrawn to allow the probe to conform freely to the convolutions
of the sinus. Alternatively, it may be desired to omit the
stiffener and its function, and to draw the probe assembly into
position by means of a forceps.
As best shown in FIGS. 10, the posts 39 and 41 are preferably
formed with flanges such as 75, between which sealing washers 77 of
flexible insulating material are inserted. These washers 77 serve
to cooperate with bores 79 and 81 formed in the plug 49 to seal the
posts 39 and 41 and form a firm mechanical connection
therewith.
A central passage 89 is formed in the post 41. Supported within the
passage 89 by means such as an intermediate insulating glass seal
91 is a contact assembly generally designated 93 and comprising a
metal ball 95 within a cage 97 and urged by a spring 99 into
engagement with the contact element 61. The conductor from which
the cage 97 is formed extends down through the glass seal 91 and is
soldered or otherwise secured to the output lead 13 of the pulse
transformer 7.
In practice, the plug 49, probe 51 and electrode 59 are installed
in the body, and the case 19 and its contents are separately
installed. The plug 49 is then engaged with the posts 39 and 41.
The plug is then secured to the metal housing by means of the screw
47. Preferably, the screw 47 is made of stainless steel covered
with polytetrafluorethylene or the like. The relatively large
surface of the housing 19 makes a massive return electrode, so that
the principal resistance offered by the body to pulses produced by
the pacer circuit occurs at the interface between the electrode 59
and the adjacent tissue.
The apparatus of my invention is suitable for use in any
application requiring an implantable tissue stimulator. For
example, in addition to its use as a cardiac pacer, it is also
useful for stimulating other tissue, such as the carotid sinus
nerve.
While I have described my invention with respect to the details of
a preferred embodiment thereof, many changes and variations will
occur to those skilled in the art upon reading my description. Such
changes and variations can obviously be made without departing from
the scope of my invention.
* * * * *