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BACKGROUND OF THE INVENTION
1. Field Of The Invention
The present invention relates to the field of implantable bipolar or
multipolar electrode leads and, more particularly, to a structure for
providing electrical connection with one of a plurality of conductors in
such leads.
2. The Prior Art
Permanent implantable multiple conductor electrode leads are well known in
the art and are used for a variety of purposes. A common use of such leads
is in connection with pacemakers in which the lead is connected at a
proximal end to a pacemaker, and has a distal end implanted in the heart
for appropriate stimulus. Such a lead may simultaneously provide for
monitoring of body function through additional conductors separate from
those used to carry pulses generated by the pacemaker. However, a problem
has arisen in balancing the benefits of multiconductor electrode leads
with their larger diameters against the benefits of using as small a
diameter lead as possible so as to facilitate ease of passage through and
implantation in the body.
A further problem arises with respect to providing electrical connection
between the implantable lead and proximal or distal tips. It is known to
provide swaged connectors which may also include an auxiliary support,
such as tubing. Of course, bipolar and multipolar leads require two or
more such swaged conductors. Such a construction, however, tends to render
the electrode lead thick and bulky compared to the veins through which it
must pass.
As the number of conductors within the lead increases, so does the bulk of
the resultant lead. Attempts have been made to render the lead, itself,
conductive so as to eliminate the need for discrete connectors.
Nevertheless, a need remains for an implantable electrode lead having a
plurality of both implantation in the body and conductors yet permitting
ease of connection to other structures. This need is particularly strong
in the case of multiconductor leads, such as bipolar electrode leads for
cardiac pacemakers.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an implantable
electrode lead having multiple conductors and a small diameter connector.
It is another object of the present invention to provide connection with
multiconductor electrode leads without adding to the diameter or bulk of
such leads.
A further object of the present invention is to provide a connector for a
multiconductor lead which is sealed against infiltration by body fluids
and the like.
Additional objects and advantages of the present invention will be set
forth in part in the description that follows and in part will be obvious
from the description or may be learned by practice of the invention.
To achieve the objects and in accordance with the purpose of the invention
as embodied and as broadly described herein, a body implantable electrode
lead is provided which comprises: a first layer of non-conductive material
forming an elongated tube; a plurality of layered conductors wound about
the first layer, the outermost one of the plurality of conductors
comprising a first conductor and a second layer of body-compatible non
conductive material formed over the plurality of conductors and the first
layer, with an annular portion of the second layer having been removed to
expose a section of the first conductor and facilitate electrical
connection therewith. The exposed section of the first conductor can be
used as a ring electrode, itself, or a discrete ring electrode may be
provided affixed thereto and sealed against invasion of body fluids.
The accompanying drawings, which are incorporated in and constitute a part
of this specification, illustrate presently preferred embodiments of the
invention and, together with the description, serve to explain the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of an implantable electrode lead according
to the present invention;
FIG. 2 is a cross-sectional view of an implantable electrode lead of the
present invention in which the first conductor is closely wound to form a
ring electrode;
FIG. 3 is a cross-sectional view of an implantable electrode lead of the
present invention in which a separate coiled conductor is provided as a
ring electrode;
FIG. 4 is a cross-sectional view of an implantable electrode lead of the
present invention showing a swaged electrode ring;
FIG. 5 is a cross-sectional view of another implantable electrode lead
according to another embodiment of the present invention;
FIG. 6 is a perspective view of a ring electrode for use with the lead of
FIG. 5;
FIG. 7 is a cross sectional view of an implantable electrode lead according
to a further embodiment of the present invention;
FIG. 8 is a perspective view of an electrode ring for use with the lead of
FIG. 7;
FIG. 9 is a cross-sectional view showing the lead of FIG. 7 with the ring
of FIG. 8 in place;
FIG. 10 is a cross-sectional view of a proximal electrode tip coupled to a
lead incorporating the teachings of the present invention;
FIG. 11 is a cross-sectional view of a distal electrode tip coupled to a
lead incorporating the teachings of the present invention;
FIGS. 12a and 12b are, respectively, perspective and cross-sectional views
of a multiconductor electrode lead usable with the present invention;
FIGS. 13 and 14 are, respectively, cross-sectional and perspective views
illustrating a commercially preferred embodiment of an electrode lead
incorporating the teachings of the present invention; and
FIG. 15 is a cross-sectional view of a multiconductor electrode lead usable
with the present invention according to a further embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference will now be made in detail to the presently preferred embodiments
of the invention, examples of which are illustrated in the accompanying
drawings. Throughout the drawings, like reference characters are used to
designate like elements.
FIG. 1 is a cross-sectional view of a portion of a body implantable
electrode lead 10 which incorporates the teachings of the present
invention. While it is to be understood that electrode lead 10 has a
proximal end, which can be connected to a cardiac pacemaker or other
circuitry, and a distal end, which is suitable for implantation in the
body, these are not illustrated in FIG. 1 since their disclosure is not
necessary to understand the invention.
In the illustrated lead, a first layer of non-conductive material forming
an elongated tube is provided. As embodied in FIG. 1, a first layer 12 is
shown by way of example. Layer 12 is preferably comprised of polyurethane
or a similar insulation material. Layer 12 may also be provided with a
lumen 14 to permit passage of fluids or to provide for a conductor, such
as a helically wound coil 16.
A plurality of layered conductors are provided disposed about the first
layer, the outermost one of the plurality of conductors comprising a first
conductor. In the embodiment of FIG. 1, a plurality of layered conductors
18 and 20 are illustrated. Both conductors 18 and 20 are wound in a
regularly disposed coil-like fashion about first layer 12. Conductors 18
and 20 are preferably made of a conductive material such as platinum,
platinum/iridium alloy, tungsten, copper, gold, silver, MP35N, titanium,
carbon, stainless steel or a composite or mixture of these or other
materials. In the illustrated embodiment of FIG. 1, conductor 18 may be
considered to be a "first conductor" as that term is used in the claims,
since conductor 18 is the outermost conductor relative to the group of
layered conductors 18, 20. Although only two conductors are illustrated in
FIG. 1, it should be appreciated that more conductors can be provided
without departing from the spirit or scope of the invention.
A second layer of body-compatible non-conductive material is provided
formed over the plurality of conductors and the first layer. As shown in
FIG. 1, a second layer 22 is provided over conductors 18, 20 and first
layer 12. Preferably, layer 22 is a polyurethane coat that can be readily
cut. Other biocompatible material suitable for these purposes are known in
the art and need not be described in detail for purposes of understanding
the present invention.
As can be appreciated from FIG. 1, conductors 18, 20 are provided in a
multilayer fashion, with each one being separated from the other by an
insulating layer 24. This insulating layer 24 can be of a material similar
to that of first layer 12 or other suitable insulating material.
Additionally, since conductors 18, 20 are provided in a coiled fashion,
each conductor is embedded within a respective intermediate silicone layer
26, 28. This arrangement ensures stability of the conductors and
contributes to overall strength of the lead.
It should be appreciated that the number of layers of conductors and
corresponding insulation can easily be increased to any desired number. It
should also be appreciated that various types of "conductors" can be
employed, at least with respect to interior conductors such as coil 16,
other than electrical conductors; for example, chemical or optical means
such as tubes and optical fibers, could be used. Such modifications are
considered within the scope and spirit of the present invention.
Means for manufacturing such a lead, including coiled multilayered
conductors, is disclosed in P.C.T. Berkley application Ser. No. US83/00827
which was published on Dec. 8, 1983 under Publ. No. WO 83/04182. The
Berkley application is hereby expressly incorporated herein by reference.
According to the invention, an annular portion of the second layer is
removed to expose a section of the first conductor and facilitate
electrical connection therewith. As shown in FIG. 1, a portion of layer 22
has been removed, leaving a correspondingly annular exposed section 30 of
the first conductor 18. Such removal can be accomplished by cutting and
stripping of layer 22. In so doing, it is noted that intermediate silicone
26 is also removed to a depth sufficient to expose first conductor 18.
According to another method of construction, exposed section 30 can be
formed concurrently during manufacture of the electrode lead, e.g., either
by not forming the overlying insulation material from the outset or by
removing it during the manufacturing process.
According to a presently preferred embodiment, exposed section 30 is
approximately 6 mm in length, although this dimension is subject to
variations depending upon the particular application of the lead, for
example. To expose first conductor 18, it is necessary to remove all of
layer 22 within section 30; however, layer 26 need not be fully removed,
but instead only partially removed to a depth sufficient to expose
conductor 18. In the alternate construction method disclosed above, layer
26 could instead be only half formed, i.e., deposited to half or other
sufficient depth, suitable for leaving conductor 18 exposed within section
30.
The exposed section 30 is used to provide electrical connection between
first conductor 18 and, for example, the body tissue in which the lead has
been implanted. This can be accomplished either directly, i.e. through use
of the first conductor 18 itself, or through an intermediate ring
electrode as described further below.
FIG. 2 illustrates an embodiment in which first conductor 18 has a small
pitch throughout exposed section 30. That is, the pitch of first conductor
18 in the sections of electrode lead 10 still covered by layer 22 is
greater than that within exposed section 30. Preferably, the coils of
first conductor 18 are wound so as to actually contact one another within
exposed section 30 whereby conductor 18 effectively comprises a ring
electrode within region 30. A method and apparatus for changing the pitch
in a coiled conductor of an electrode lead is described in the
aforementioned Berkley PCT application.
The embodiment illustrated in FIG. 2 is highly desirable in that the
diameter of section 30 where electrical connection is made is actually
smaller than that of the other portions of the electrode lead. This is
directly opposite to typical prior art arrangements in which the
electrical connection portion is of a greater diameter than the electrode
lead.
Another embodiment of the present invention is shown in FIG. 3, in which a
second conductor 32 is provided coaxially about an exposed section 30 of
first conductor 18. Conductor 32 may comprise material similar to that of
first conductor 18 and is preferably tightly coiled so as to form an
effective electrode ring. By drawing second conductor 32 tightly into
contact with first conductor 18 within exposed section 30, electrical
contact between conductors 18 and 32 is ensured. Second conductor 32 may
be provided by means of coiled wire, ribbon, mesh or other suitably shaped
material to electrically engage first conductor 18.
Another embodiment of a second electrode according to this invention is
illustrated in FIG. 4, in which a second conductor is designated by
reference character 34. According to this embodiment, second conductor 34
is a conductive ring that is swaged in place contacting first conductor
18. Through use of swaging techniques that are well known in the art,
electrode lead 10 can be passed through the conductive ring forming second
conductor 34 until the ring is positioned over exposed section 30.
Thereafter, the ring can be swaged so as to force it into electrical and
mechanical contact with first conductor 18.
Preferably, the ring comprising second conductor 34 is formed of a
conductive material such as platinum. Ring 34 may further be fixed in
place by means of an adhesive 36 which serves to smooth out the surface of
the overall electrode lead and prevents the ingress of fluids underneath
the ring. Biocompatible adhesives suitable for such purposes are well
known in the art and need not be described further.
Another embodiment of an implantable electrode lead having a connector as
illustrated in FIGS. 5 and 6 will now be described. According to this
embodiment of the invention, a conductive ring is positioned coaxially
over the exposed section of the first conductor and over the edges of the
second layer adjacent the exposed section. As illustrated in FIG. 6, by
way of example, a conductive ring 38 is formed of a conducting material,
such as platinum. Ring 38 has an internal diameter of a size sufficient to
permit electrode lead 10 to pass therethrough. As shown best in FIG. 5,
the length of ring electrode 38 is slightly greater than that of exposed
section 30, such that ring 38 also covers the edges of second layer 22
immediately adjacent exposed section 30.
Ring electrode 38 is provided with two diametrically opposed holes 40. Once
ring 38 is positioned coaxially over exposed section 30, a conductive
adhesive 42 is introduced into the void between ring electrode 38 and
first conductor 18 via holes 40. Preferably, this is done by injecting
adhesive 42 through one hole and permitting it to exit via the other hole.
Suction can be enlisted to assist this procedure. Adhesive 42 is
conductive and is preferably biocompatible so as to provide both
electrical and mechanical coupling between ring electrode 38 and first
conductor 18. For example, adhesive 42 may be silicon rubber filled with a
biocompatible conductive powder, such as platinum, carbon or the like.
To further strengthen the mechanical attributes of ring electrode 38, it
may be affixed to second layer 22 via adhesive 36 of a type described
previously. This arrangement also serves to ensure sealing of the entire
connector and to prevent ingress of body fluids.
Another embodiment of the present invention is illustrated in FIGS. 7-9.
According to this embodiment, a conductive ring is positioned coaxially
over the exposed section of the first conductor and over the edges of the
second layer adjacent the exposed section, with the first conductor being
partially unwound and disposed in a slot formed in the ring so as to
facilitate electrical connection. As illustratively shown in FIGS. 7-9, a
conductive ring is of a construction similar to that described above with
respect to ring 38, with diametrically opposed holes 40. However, ring 38
has a longitudinal slot 48. First conductor 18 is cut and partially
unwound within exposed section 30, resulting in a plurality of radially
disposed aligned ends 46. Ring 44 is slid over electrode lead 10 such that
the exposed conductor ends 46 are introduced into slot 48. Mechanical and
electrical connection between ring 44 and the first conductor 18 can be
accomplished by welding, swaging, or otherwise compressing ring 44 so as
to firmly encapture exposed ends 46. Alternately, or in addition to these
mechanical coupling arrangements, the void between ring 48 and first
conductor 18 can be filled with a conductive adhesive 42, as illustrated
best in FIG. 9. To accomplish this filling, holes 40 are used in the same
manner as described above. Additionally, a biocompatible adhesive 36 can
be used to seal the ends of ring 42 to outer layer 22 in the manner
described above.
FIG. 10 illustrates a proximal connector affixed to an electrode lead by
means of a ring electrode as described above with regard to FIGS. 7-9. A
bipolar arrangement is illustrated in the drawing, including a proximal
ring 50 and a proximal pin 52. Ring 50 is electrically connected to first
conductor 18 by means of a conductive ring of the type described above
with respect to FIGS. 5-6 or FIGS. 7-9. Proximal pin 52 can be coupled to
inner helix 16 by first placing a support pin 54 centrally within helix 16
and then swaging proximal pin 52 thereover. This arrangement causes helix
16 to be tightly trapped between pins 52, 54. The overall configuration of
a proximal connector suitable for connecting an implantable electrode lead
with other apparatus is well known and need not be described in further
detail for purposes of this invention.
A distal tip electrode for use with an electrode lead incorporating the
teachings of the present invention is shown in FIG. 11 and is generally
designated by reference character 56. Distal electrode 56 is designated
for use with a corresponding ring electrode (not shown) of a type
described above. Thus, since this ring electrode is coupled to first
conductor 18, distal electrode 56 is typically coupled to inner helix 16.
As shown in FIG. 11, distal electrode 56 comprises a distal tip 58 swaged
over a pin 60 positioned inside inner helix 16. Through this arrangement,
distal tip 58 is brought into electrical contact with inner helix 16. To
complete the assembly, a tine structure 62 is glued over electrode tip 22
via a biocompatible adhesive 36. The trailing end of tine assembly 62 is
also preferably sealed with biocompatible adhesive 36.
In known fashion, distal tip 22 is preferably made of a biocompatible
conducting material such as platinum, platinum/ iridium alloy or the like,
while support pin 60 can be made from a variety of suitable conducting
materials.
FIGS. 12a and 12b illustrate another type of multiconductor cable which can
be used according to the present invention. In this cable, a
multiconductor electrode lead is provided in which an inner conductor 20
is helically wound about a first insulating layer 12, with an outer
conductor 18 helically wound about both. An intermediate insulating sheath
64 separates the inner and outer conductors 18, 20, while an outer
insulation sheath 22 covers the entire assembly. Material suitable for
these purposes has been described above.
As shown in FIGS. 12a and 12b outer conductor 18 may be helically wound
about inner conductor 20 so that the former is in the interstices formed
between the later. By cutting through a portion of outer layer 22 so as to
expose an annular section of inner conductor 18, the foregoing electrode
structures can be utilized to facilitate connection to the outer conductor
18.
Another embodiment of an electrode lead according to the present invention
is illustrated in FIGS. 13 and 14, with particular emphasis being placed
on providing a commercially desirable product. FIG. 13 illustrates details
of an electrode lead for use with a connector of the type illustrated and
referred to throughout the foregoing drawings and description, including
an exposed portion 30 in which insulation has been removed from first
conductor 18. In the embodiment illustrated in FIG. 13, a further outer
insulating layer 66 has been provided on top of exposed portion 30 and
contiguous with outer layer 22. Thus, a void 68 is formed underneath
annular layer 66 and above first conductor 18. As shown in FIG. 14, a
electrode lead can thus be provided with a plurality of such regions 66
and corresponding voids 68 spaced at regular intervals so that first
conductor 18 can readily be exposed at whichever point is expedient. In
use, a physician can easily locate region 66 and quickly remove it,
thereby exposing first conductor 18 for facilitating electrical connection
in one of the aforedescribed methods. To enable ease in locating regions
66, marker lines 70 can be provided along the edges between each region 66
and the adjacent outer layer 22, for example.
FIG. 15 illustrates a further embodiment of a multi-conductor lead
according to the present invention. In this embodiment, a plurality of
conductors 18a-18h are disposed parallel to each other and aligned with
the longitudinal axis of lead 10. First and second insulating layers 12
and 18 are effectively joined so as to encapsulate fully conductors
18a-18h. According to the invention, an annular portion of outer
insulating layer 22 is selectively removed to a level as indicated by the
dashed line in FIG. 15, thereby exposing conductors 18a-18h for contact
with surrounding tissues or for electrical connection in a manner as
described previously with respect to the embodiments shown in FIGS. 1-14.
While eight conductors have been illustrated in FIG. 15, it should be
appreciated that more or fewer conductors may be used. Further, the
conductors can either be connected to a common source or to different
sources individually or to any combination thereof. All of these changes
are considered to be within the spirit and scope of the present invention.
From the foregoing, it should be appreciated that an implantable electrode
lead according to the present invention provides for connection to an
inner conductor without markedly increasing the diameter of the electrode
lead so as to make implantation difficult. It will be apparent to those
skilled in the art that modifications and variations can be made in the
electrode lead apparatus of thus invention. The invention in its broader
aspects is, therefore, not limited to the specific details, representative
methods and apparatus, and illustrate examples shown and described above.
Thus, it is intended that all matter contained in the foregoing
description or shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
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