Body Tissue Electrode And Device For Screwing The Electrode Into Body Tissue

Abstract

A body implantable electrode comprising a flexible insulated conductor having a proximal end adapted for connection to a power supply and a distal end portion comprising an uninsulated, conductive, rigid helix adapted for attachment to body tissue. Means located and engageable at substantially the distal end portion are provided for facilitating the screwing of the helix into body tissue. A device is provided with means for firmly holding the means for facilitating the screwing of the helix into body tissue. The device also has means for holding the conductor and for preventing the transmission of torque to the proximal end of the conductor when the helix is being screwed into body tissue.

Description

BACKGROUND OF THE INVENTION

Electrical stimulation of body tissue and organs as a method of treating various pathological conditions is becoming quite common-place. Such stimulation generally entails making some type of electrical contact with the body tissue or organ. In particular, with respect to the heart, electrical leads have been developed in which an electrode formed on the end of the lead are physically implanted into the myocardial tissues. Various electrode structures and various techniques for implanting those structures into the myocardium have been developed. One such technique required a plurality of stab wounds to be made in the myocardium both for the location of the electrode as well as the suturing of the lead to myocardial tissue. Obviously, such wounds are undesirable for a variety of reasons. Other techniques have included the percutaneous insertion through the chest wall or an open wound by means of a hollow needle with the subsequent placement of the electrode into the myocardial tissue. Still another technique involved the deformation or flattening of one convolution of a rigid helix serving as the electrode so that a keyed stylet could engage the deformed convolution to permit the electrode to be screwed into the myocardial tissue. However, this technique requires that the stylet be in physical contact with the helix during insertion into the myocardium and in addition has the undesirable effect of imparting torque to the proximal end of the coiled conductor.

SUMMARY OF INVENTION

In the present invention a body implantable electrode assembly is provided in which a flexible insulated electrical conductor has a proximal end thereof adaptable for connection to a power supply and a rigid helix serving as the distal end portion thereof. The rigid helix serves as the electrode to be screwed into the body tissue. This procedure is facilitated by a tool or member which is substantially cylindrically-shaped and having a slot located in one end surface thereof, the slot being substantially orthogonal to the longitudinal axis of the member. A groove is located in the outer surface of the member and extends from the end surface opposite the slotted end surface to just short of the slotted end surface and lies in a plane substantially parallel to the longitudinal axis. Also, starting in the same end surface as the groove is a bore extending for the entire length of the member for receiving the proximal end of the conductor.

The assembly is used during the implantation of the electrode into body tissue. A raised portion on the conductor near the distal end thereof is fitted into the slotted end of the cylindrically-shaped member. The insulated portion of the conductor is fitted into the groove and the remaining proximal portion of the conductor is inserted into the bore, connector end first. In this position the electrode comprising the rigid helix is securely held by the tool and by applying a twisting or rotation of the tool, the helical electrode may be screwed into the tissue, which in the case of the heart is the myocardium. When the electrode is securely screwed into the tissue, the portion of the conductor lying in the groove is removed and then the slotted end of the member is removed from the raised portion of the conductor.

The present invention has a number of

advantages and features which include: (1) the tool used in facilitating the screwing-in of the electrode into the tissue or organ never contacts the electrode; (2) the configuration of the cylindrically-shaped member and the positioning of the conductor with respect thereto prevents any torque from being imparted to the conductor along its entire length during the rotation of the member; (3) the electrode assembly permits the use of wrapped on tinsel wire, rather than a coiled wire, which has great strength and a very good flex tolerance; (4) the electrode is extremely easy to install, reduces patient trauma, effects a very sound electrical connection with body tissue and at the same time minimizes the amount of surgery with respect to the handling of the particular body tissue or organ involved; and (5) the tool may be used in periodically producing a tunnel in subcutaneous tissue and in guiding the connector end of the conductor through the tunnel for connection to a power supply.

With these and other objects, advantages and features in view, as will hereinafter more fully appear, and which will be more particularly pointed out in the appended claims, reference is now made to the following description taken in connection with the accompanying drawings.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a diagram of an implantable lead in accordance with the present invention;

FIG. 2 illustrates an embodiment of the device used in conjunction with the lead of FIG. 1 for screwing the electrode into body tissue;

FIG. 3 is a cross-sectional view of the device shown in FIG. 2; and

FIG. 4 illustrates the lead of FIG. 1 and the device of FIGS. 2 and 3 in operative relationship for the insertion of the electrode into body tissue .

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows an implantable lead 10 which includes a flexible electrical conductor 12. Conductor 12 may, for example, be made of wrapped platinum wire or other suitable conducting material adaptable to the internal environment of a human or animal body. Wrapped platinum wire is generally comprised of a plurality of platinum ribbons each helically wound around a separate electrically non-conductive core and then all the platinum ribbons are helically wound around a central electrically non-conductive core. A specific description of this type of conductor may be found in my U.S. Pat. No. 3,572,344, issued Mar. 23, 1971, and entitled "Electrode Apparatus With Novel Lead Construction." Affixed to the proximal end of conductor 12 is an electrical connector 14 having a tip or extension 16 which may be connected to a suitable implantable or external power supply. Affixed to and serving as the distal end portion of conductor 12 is a rigid helical electrode 18 having several convolutions. Helical electrode 18 is a rigid coil which may, for example, be made of platinum irridium, and terminates in a sharply pointed end 19. Electrode 18 serves as the distal end portion of conductor 12 which may be screwed into body tissue as will be explained later. Electrode 18 and conductor 12 are electrically joined together by conductive epoxy (not shown) substantially orthogonally with respect to one another and this electrical junction is contained in a rubber boot 20.

Conductor 12, connector 14 and boot 20 are covered with a relatively transparent, flexible insulating covering being relatively inert with respect to the body, which, for example, may be a silicone rubber casing 22. The portion of casing 22 surrounding boot 20 forms a raised portion or projection 24. Formed on both sides of projection 24 are three spaced, substantially vertical ribs 25 which are adapted to permit projection 24 to be more securely engaged as will be explained. The distal portion of casing 22 is terminated and shaped as a circular disc 26 through which helical electrode 18 projects. Helical electrode 18 projects through disc 26 at substantially a right angle to conductor 12. Affixed to the under surface of disc 26 is a circular sheet of netting 28, which may, for example, be made of Dacron which is a trademark of E. I. Du Pont De Nemours and Company for a type of polyester fiber. Netting 28 enhances fibrotic growth, further insuring a secure connection of the electrode to the tissue.

FIGS. 2 and 3 illustrate the device used in conjunction with lead 10 to facilitate the screwing of electrode 18 into body tissue. Device 40 comprises a substantially cylindrically-shaped member or tool having a longitudinal axis 42 and end surfaces 44 and 46. Member 40 may be made, for example, of a hard plastic material such as Delrin which is a trademark of the E. I. Du Pont De Nemours and Company for acetal resins. Preferably member 40 should be made of a autoclavable material. Formed in end surface 44 is a slot 48. Slot 48 is shaped so as to be adapted to substantially conform to and securely engage ribs 25 of raised portion 24 of lead 10. The edge defined by end surface 46 is rounded in order to permit member 40 to be used for surgically producing a tunnel in subcutaneous tissue without causing severe tissue damage. Formed in the outer surface of member 40, lying in a plane substantially parallel to axis 42, and extending from end surface 46 for substantially the entire length of member 40 is a groove 50. Groove 40 is substantially aligned with slot 48. Groove 50 is adaptable to receive and securely engage at least a portion of the length of the insulated portion of lead 10 housed in casing 22. Also formed in end surface 46 is an axial opening or bore 52 extending the entire length of member 40 from end surface 46 to slot 48. Bore 52 is adapted to receive at least a portion of the proximal end of lead 10 including connector 14 and tip 16.

FIG. 4 illustrates the operative relationship between lead 10 and member 40 as will now be described. Raised portion 24 is first inserted into slot 48 so that the surfaces defining slot 48 firmly grip ribs 25 to provide a friction fit and securely hold projection 24 in the slot. A small loop is left in the portion of casing 22 immediately proximal to raised portion 24 and then casing 22 is worked into groove 50 so as to be securely held in the groove against movement. Then connector 14 and tip 16 are inserted into bore 52 as far as they will go. In this position the electrode 18 is positioned substantially along longitudinal axis 42 of member 40 and the assembly is now ready for the electrode to be screwed into body tissue.

Pointed end 19 is placed against the tissue or organ and member 40 is rotated as indicated by the curved arrow. The diameter of the wound is confined to the diameter of the wire of which helical electrode 18 is formed. As member 40 is rotated, helical electrode 18 is firmly screwed into the tissue or organ until netting 28 firmly contacts the outer surface of the organ. Netting 28 helps to provide a more secure and permanent placement of electrode 18 in the tissues in that the netting promotes more rapid fibrosis in and around the netting, as well as around disc 26 and raised portion 24 of casing 22.

When electrode 18 is firmly screwed into the tissue and netting 28 firmly seated against the outer surface of the tissue or organ, the connector-end of lead 10 is removed from bore 52, the portion of casing 22 lying in groove 50 is removed from the groove, and then slot 48 is disengaged from projection 24 thereby freeing lead 10 from member 40. With the use of the procedure described, since projection 24 and a substantial portion of casing 22 are firmly secured during the rotation of member 40, no torque is transmitted to lead 10 and consequently to conductor 12. In addition, before, during, and after the insertion procedure, member 40 in no way contacts the helical convolutions of electrode 18, permitting a very positive action in screwing electrode 18 into the tissue at substantially a 90.degree. angle. Then, if desired, end surface 46 of member 40 may be used to provide a tunnel in the subcutaneous layers. The connector-end of lead 10 may then be inserted into bore 52 and member 40 guided back through the tunnel in order to facilitate connecting tip 16 of conductor 14 to a power supply to be implanted under the skin.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings even though only one embodiment of the invention has been shown. For example, the presence and use of bore 52 are entirely optional and do not affect the screwing of the electrode into body tissue. Also, the exact shape and size of the projection 24 and the matching slot 48, as well as the shape, size and extent of groove 50, are all subject to modification within the scope of the present invention. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims

What is claimed is:

1. In a body implantable electrode assembly that includes a flexible electrical conductor means having a proximal end thereof adaptable for connection to a power supply and wherein the distal end portion of the conductor comprises an uninsulated, conductive, rigid helix adapted for attachment to body tissue, the improvement which comprises:

means located and engageable at substantially said distal end portion for facilitating the screwing of said helix into body tissue and for preventing the transmission of torque to said proximal end of said conductor means when said helix is being screwed into body tissue, said means including further friction increasing means adapted to be firmly held by means used for screwing said helix into body tissue, said means and said further means being substantially inert to body fluids and tissue; and

means substantially inert to body fluids and tissue enclosing substantially the entire length of said conductor means except for said distal end portion for permitting said electrode assembly to be implanted within the body.

2. The invention as set forth in claim 1 wherein:

said means located and engageable at the distal end portion comprises a raised section of insulation surrounding the conductor, and wherein;

said further means comprises at least one rib on the outer surface of said raised section adapted to frictionally fit with a member having a slot defined therein for receiving said raised section and said at least one rib.

3. The invention as set forth in claim 1 wherein:

said conductor comprises a plurality of electrically non-conducting cores, a plurality of conductive metal ribbons, each of said ribbons being helically wound around a separate one of said electrically non-conducting cores, and a central electrically non-conducting core, said plurality of ribbons wound on said cores being helically wound around said central core.

4. The invention as set forth in claim 3 wherein:

said ribbons are made of platinum.

5. A device for use in screwing the conductive uninsulated distal end portion of a body implantable electrode assembly into body tissue, said assembly being of the type including a flexible insulated electrical conductor having a proximal end thereof adaptable for connection to a power supply, said device comprising:

first means for firmly holding a portion of said electrode assembly near said uninsulated distal end portion thereof, said first means contacting only an insulated portion of said electrical conductor; and

second means adapted to contact an insulated portion of said insulated conductor for holding said conductor to facilitate the screwing of said distal end portion into body tissue and for preventing the transmission of torque to said proximal end of said conductor means when said distal end portion is being screwed into body tissue.

6. A device for use in screwing the conductive, uninsulated distal end portion of a body implantable electrode assembly into body tissue, said assembly being of the type including a flexible insulated electrical conductor having a proximal end thereof adaptable for connection to a power supply, said device comprising:

a substantially cylindrically-shaped member having a pair of end surfaces;

one end surface of said member having a slot defined therein for engagement with a portion of said electrode assembly located proximally with respect to said distal end portion thereof; and

the outer surface of said member having a groove formed therein, said groove lying substantially parallel to the longitudinal axis of said member, said groove being engageable with a portion of said insulated conductor, whereby rotation of said member about said longitudinal axis permits said distal end portion to be screwed into body tissue without said member contacting said distal end portion and without imparting any torque to said conductor along its length.

7. The device as set forth in claim 6 wherein:

said member has an axially-extending opening extending from said one end surface to said other end surface.

8. The device as set forth in claim 6 wherein:

said groove extends from said other end surface toward said one end surface.

9. The combination of a body implantable electrode assembly including a flexible insulated electrical conductor means having a proximal end thereof adaptable for connection to a power supply and a conductive uninsulated distal end portion and a device for use in screwing the conductive, uninsulated distal end portion of said assembly into body tissue, said combination comprising:

an electrical conductor having its uninsulated distal end portion formed as a rigid helix;

slot engageable means surrounding said conductor proximally with respect to said distal end portion;

first means defining a slot for rigidly engaging said slot engageable means; and

second means formed integrally with said first means for rigidly engaging a portion of said insulated conductor, whereby rotation of said first and second means permits said distal end portion to be screwed into body tissue without said first and second means coming into contact with said distal end portion and without imparting any torque to said conductor along its length.

10. The combination as set forth in claim 9 wherein:

said device for screwing comprises a substantially cylindrically-shaped member having an axially-extending bore, said bore extending from said one end surface to said other end surface of said member, said bore being adapted to receive the proximal end of said conductor;

said first means comprises one end surface of said member having said slot formed therein; and

said second means comprises the outer surface of said member having a groove formed therein, said groove lying substantially parallel to the longitudinal axis of said member and extending from the other end surface of said member toward said one end surface.