US20050256557A1

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Publication number: US20050256557A1
Application number: US11/074,572
Authority: US
Inventors: Bradley Wessman; Peter Pohndorf
Original assignee: Individual
Current assignee: Advanced Neuromodulation Systems Inc
Priority date: 2000-09-26
Filing date: 2005-03-08
Publication date: 2005-11-17
Also published as: US6952616B2; US20020038139A1

Abstract

The present invention provides a medical lead for implantation within a patient. The medical lead has a seem-less lead body having one or more electrodes secured to the distal end and one or more connector bands attached to the proximal end of the lead.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a medical leads and particularly to medical leads having unitary construction.

2. Description of the Related Art

Implantable leads form an electrical connection between a pulse generator or other electronic device and a tissue or structure in the body. For example, leads transmit electric signals used to stimulate cardiac or nerve tissue in one direction and signals generated by sensors placed in proximity to particular organs or tissues in the opposite direction. Leads typically include one or more electrodes at the lead's distal end. The electrodes are designed to form an electrical connection with a tissue or organ. In addition, most leads also include a lead connector at the lead body's proximal end. Lead connectors are adapted to electrically and mechanically connect leads to the pulse generators or other electronic medical devices. A conductor connects the electrode to the lead connector. Commonly, the conductor takes the form of a single or multifilar wire coil. Although, there is an increasing interest in using stranded cables as conductors. Regardless of the conductor's form, an insulating material typically surrounds the conductors. Spinal chord stimulation leads are typically formed with individually insulated conductors surrounded by a separate lead body tube. Together, the conductor and the insulating material form the lead body. The lead body couples the lead connector at the proximal end with the electrode at the distal end.

Present lead designs frequently electrically connect a separate electrode assembly to the distal end of the lead. This results in an electrical connection and a seam between the electrode assembly and the lead body. Other current lead designs add ring electrodes over the lead body's distal end. To access the wound conductors within the lead body, the conductors are pulled from the lead body for welding to the edge of the ring electrode. The removal of the conductors from the lead body may result in a breach of the lead body's insulator that must later be sealed creating a seam. These seams and other junctions provide a potential point for failure and the potential for electrical leakage. Therefore, a need exists for a lead having a seam-less or unitary construction.

Further, manufacturing leads is costly. A significant portion of the cost is allocated to electrically connecting the conductors to the various electrodes, sensors and connectors used in the industry. Forming a secure electrical junction has proven difficult and time consuming. Laser welds are commonly used to connect the conductors to the electrodes. The conductors are typically helically wound into a coil for increased reliability and flexibility. Band electrodes are typically connected to conductors by welding in an operation separate from the application of the lead body tube. Once the band electrodes are connected to the conductors, an extruded tube is placed over the conductor coil and welded band electrodes are connected to the lead body tube by insert molding or RF welding. Band electrodes may also be connected to a conductor by etching away a region of insulator, applying a coating of electrically conductive adhesive, and then placing the band electrode around the conductor. This etching method is complex, not amenable to automation, and expensive. Therefore, a need exists for a method that reduces complexity and is easily automated to reduce production costs.

In another method of attachment, band electrodes are electrically connected to coiled conductors by placing a soft metal in a hole cut into an insulating sleeve. An electrode is placed over the metal and crimped or swaged to bring the electrode, soft metal and coiled conductors into electrical contact and to secure the electrode to the lead body. The crimping or swaging method of connection results in electrical connections between the conductor and the band electrode that may fail. Further, swaging to electrically connect an electrode to a conductor is time consuming and difficult to implement with the modern reduced diameter leads. Hence, a need exists for an improved manufacturing technique to secure band electrodes to conductors that reduces the time, complexity and cost while increasing reliability.

In addition, current manufacturing techniques frequently require adding elements, such as collars, when connecting a band electrode to a coil. The added elements increase the lead's diameter near the weld. In application, a uniform diameter weld would result in a smaller lead. A smaller diameter lead is desired to allow placement in restricted spaces such as the epidural space or cardiac veins to reduce the effects of implanted lead on the patient. Further, a smaller lead allows for a smaller introducer that reduces the trauma associated with implantation and similarly a smaller removal sheath when explanting the lead. Hence, there exists a need to reduce the diameter of the welds used to secure electrodes to conductors in implantable medical leads.

The present invention meets the above-referenced needs and provides other advantages and improvements that will be evident to those skilled in the art.

SUMMARY OF THE INVENTION

The present invention provides a medical lead having a novel seam-less design which electrically connects the electrodes, connectors and/or sensors to the conductors through the insulator of the lead body. A medical lead in accordance with the present invention includes a lead body, at least one band electrode and at least one band conductor. The lead body extends the length of the lead and includes a seamless insulator between the proximal and distal ends of the lead insulating at least one conductor within the lead body. At least one band electrode and at least one band connector are secured between the proximal and distal end of the lead body and electrically connected to the conductor. Typically, the band connector is positioned adjacent the proximal end of the lead body and the band electrode is positioned adjacent the distal end of the lead body. Further, the band electrode and the band connector may be electrically connected to the conductor by welding to a conductive pad within a welding region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a lead in accordance with the present invention;

FIG. 2 illustrates a longitudinal cross-sectional view of a of a lead showing an embodiment of the connection between a coiled conductor and a band with a conductive pad;

FIG. 3 illustrates a top view of a lead, as shown inFIG. 2, without the band;

FIG. 4 illustrates a longitudinal cross-sectional view of a of a lead showing the connection between a coiled conductor and a band with an elongated conductive element;

FIG. 5 illustrates a top view of a lead, as shown inFIG. 4, without the band;

FIG. 6A illustrates a cross-sectional longitudinal view of a band electrode, as shown inFIGS. 4 and 5; and

FIG. 6B illustrates and end view of the band electrode, as inFIG. 6A.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a medical lead and a method for lead manufacture. The invention is described generally in the context of a neurostimulating lead and a method for manufacturing a neurostimulating lead as a specific example for illustrative purposes only. The appended claims are not intended to be limited to any specific example or embodiment described in this patent. It will be understood by those skilled in the art that leads in accordance with the present invention may be used for a wide variety of applications including, but not limited to, leads and catheters for use with cardiac monitoring devices, cardiac rhythm management devices, ablation devices, mapping devices, neurostimulating devices, neuromonitoring devices or other medical devices using leads or catheters. Further, in the drawings described below, the reference numerals are generally repeated where identical elements appear in more than one figure.

FIG. 1 illustrates an embodiment of aseam-less lead10 in accordance with the present invention. Leads designed for neurostimulation typically have two or more longitudinally spacedband electrodes14 at the lead's distal end and an equivalent number ofband connectors15 at the proximal end to connect the lead to the particular medical device.Lead10 includes alead body12, fourband electrodes14 and fourconnector bands15, for exemplary purposes.Connector bands15 are shown disposed about asleeve19 secured over the lead body to increase the diameter allowing insertion of a reduced diameter lead's connector into a standard connector port of a medical device. Typically, one ormore band electrodes14 and one ormore band connectors15 are provided.Lead10 is generally configured to transmit an electric signal from a pulse generator (not shown) to a spinal nerve or peripheral nerve. Thus,band electrodes14 are typically located at the distal end oflead10. Leadbody12 includes a flexible lead insulator surrounding one or more conductors. The conductors are electrically coupled toband electrodes14 at the distal end andband connectors15 at the proximal end oflead10.

Typically,lead body12 is a flexible, elastomeric structure having a round cross-section. Alternatively, lead body's cross-section could be any number of shapes appropriate for the specific application. The diameter oflead body12 may vary between the proximal end and distal end oflead10. Depending on the particular application, the diameter oflead body12 may be smaller than 2 French for neurological and myocardial mapping/ablation leads and can be sizes larger than 12 French for other applications. The lead insulator is generally configured to insulate the conductors and to present a smooth biocompatible external surface to body tissues and form a continuous and seam-less structure between the proximal and distal ends oflead10. When a plurality of conductors form a multipolar lead, individual conductors are typically electrically isolated from one another within the insulator. The insulator material is typically selected based on biocompatibility, biostability and durability for the particular application. The insulator material may be silicone, polyurethane, polyethylene, polyimide, polyvinylchloride, PTFE, ETFE, or other materials known to those skilled in the art. Moreover, alloys and blends of these materials may also be formulated to control the relative flexibility, torqueability, and pushability of the lead.

Theconductors22 may take the form of solid wires, drawn-filled-tube (DFT), drawn-brazed-strand (DBS), stranded cables or other forms that will be recognized by those skilled in the art. The conductors may be composed of stainless steel, MP35N, or other conductive materials known to those skilled in the art. The number, size, and composition of the conductors will depend on particular application for the lead.

At least oneband electrode14 is positioned at the distal end oflead body12 to electrically contact a target tissue or organ and at least oneband connector15 is positioned at the proximal end oflead body12 to electrically connect the conductors to the neurostimulator. Theband electrodes14 andband connectors15 are typically made of a conductive material such as platinum, gold, silver, platinum-iridium, stainless steel, MP35N or other conductive metals or alloys thereof known to those skilled in the art.Band electrodes14 andband connectors15 are typically composed of a material thin enough to allow for welding of the elements to the underlying conductive pad, as discussed below. For neurostimulation,band electrodes14 are typically between 1 and 10 millimeters long and have a diameter between about 2 and about 8 French but are more typically between 4 and 6 French. Typically,band connectors15 have a size and configuration appropriate to connect the lead to a particular neurostimulator.

FIG. 2 illustrates the details of an embodiment of the connection between aconductor22 andband electrode14 in accordance with the present invention. For purposes of the followingdescription band electrodes14 andband connectors15 should be considered synonymous andband electrode14 will be used throughout the remainder of the description.Band electrode14 is disposed about lead body. Leadbody12 is shown with fourspirally wound conductors22 connected at two locations to bandelectrode14.Band electrode14 is connectedlead body12 atwelding regions20 by a weld throughband electrode14 to electrically connect the band toconductive pad24. The distal end and proximal end ofband electrode14 are positioned to extend overwelding regions20.Band electrode14 is connected to thesame conductor22 twice for exemplary purposes. A single band may be connected to multiple conductors if desired.

FIG. 3 illustrates a top view of a lead body having the insulating material removed to formwelding region20 by exposingconductor22.Welding region20 provides access to conductor(s)22 for electrically connectingband electrode14 toconductor22.Welding region20 is typically formed by removing the insulating material fromlead body10. The insulating material is removed to expose small sections of theindividual conductors22 without breaching an inner lumen, if present. Typically, an excimer laser is used to remove the insulating material. When the insulator is removed by laser,welding region20 may be in the form of a groove in the insulator. Alternatively,welding region20 may take a variety of forms and orientations that expose a sufficient surface area ofconductor22 to form an electrical connection with a conductive pad, discussed below. When in the form of a groove,welding region20 is typically formed such that the groove runs parallel toconductor22. Regardless of the form ofwelding region20, sufficient surface area ofconductor22 is exposed to secure aconductive pad22 or an elongatedconductive element34, shown inFIG. 4, toconductor22.

Referring toFIGS. 2 and 3, aconductive pad24 is positioned within weldingregion20 during manufacture to facilitate the electrical connection ofband electrode14 andconductor22.Conductive pad24 may be formed by centering a length of wire or other piece of material over the welding region and melting the wire or material at a point over thewelding region20. As the material melts, the ends of the wire are drawn into the welding region to form the conductive pad. Aweld26 is typically used to secure theconductive pad24 in electrical contact withconductor22. Alternatively,conductive pad24 may be secured using an adhesive.Conductive pad22 may be composed of any of a variety of conductive materials that can be welded or secured with adhesives. Some suitable metals include stainless steel, MP35N, Pt—Ir, platinum, silver, gold, copper, vanadium or other metal that will be recognized by one skilled in the art upon review of this disclosure.Conductive pad24 is positioned within weldingregion20 so thatconductive pad24 is in electrical contact withconductor22. Typically,conductive pad24 is welded to the conductor prior to placingband electrode14 over the welding regions andconductive pads24. A pulsed Neodymium:yttrium-arsenic-garnet (YAG) laser may be used to weldconductive pad24 toconductor22.FIG. 2 shows a side view of a cross-section of twogrooves20 that expose two regions of thesame conductor22.Conductive pads24 are welded toconductor22 withingrooves20.Band electrode14 is placed overlead body12 oflead10 and welded toconductive pads24, thereby securingband electrode14 to leadbody12 and electrically connectingconductor22 andband electrode14.Band electrode14 may be further secured to leadbody12 by swaging, crimping and/or adhesives. Alternatively, the band electrode may be secured to the lead body by heating the lead body. Heating the lead body stress-relieves the plastic increasing the outside diameter and securing the band electrode over the lead body. In addition, heating the lead body may be used to create a lead having a uniform diameter betweenband electrode14 andlead body12.

FIGS. 4 and 5 illustrate the details of another embodiment of a connection betweenconductor22 and aband electrode14 in accordance with the present invention. In the embodiments shown inFIGS. 4 and 5, an elongatedconductive element34 is used to electrically connectband electrode14 toconductor22. The elongated conductive element may be in the form of a wire, a ribbon wire, or a cable. The metal may be stainless steel, MP35N, Pt—Ir, platinum, silver, gold, copper, vanadium or other metal that will be recognized by one skilled in the art upon review of this disclosure. A distal end of elongatedconductive element34 is electrically connected to bandelectrode14. Typically, the electrical connection employs aweld28, although a conductive adhesive or other method of conductively attaching may be used.FIG. 4 shows a longitudinal cross-section of a lead body having four spirally wound conductors. One ormore welding regions20 are formed through the insulating material by removing the insulating material fromlead body10. Typically, the insulating material is removed with a laser. The proximal end of elongatedconductive element34 is positioned within weldingregion20 so that the proximal end is in electrical contact withconductor22. Typically, the proximal end is secured toconductor22 prior to placingband electrode14 overlead body12. Again, the proximal end is typically welded although a conductive adhesive or other method of conductively attaching the proximal end may be used. The elongatedconductive element34 and attached proximal end are typically configured to allowband electrode14 to pass over elongatedconductive element34 during assembly. The distal ends of elongatedconductive elements34 may then be electrically connected to bandelectrode14.

FIGS. 4 and 5 illustrate a single exemplary connection betweenconductor22 andband electrode14 by

welds

26 and28. Thus,FIG. 4 shows only onegroove20 exposingconductor22. The proximal end of elongatedconductive element24 is positioned withingroove20 is welded toconductor22.Band electrode14 is placed overlead body12 and welded to elongatedconductive element34, thereby electrically connectingconductor22 andband electrode14.Band electrode14 may be further secured to leadbody12 by swaging, crimping, adhesives and/or insert molding. In addition, swaging may reduce the outside diameter ofband electrode14 to permit the manufacture of a lead of uniform diameter. Alternatively,lead body12 may be expanded by heating to create a uniform diameter betweenband electrode14 andlead body12.

FIGS. 6A and 6B illustrate a novel embodiment ofband electrode14 which may be used in conjunction with the present invention.Band electrode14 includes aninner wall42 defining alumen44. At least oneprojection46 is formed on theinner wall42.Projections46 define a space betweeninner wall42 and an outer surface of the lead body during assembly.Projections46 may be molded on the inner surface; formed by crimping the exterior surface of the band; or added as separate elements secured to the inner surface of the band.Projections46 have aheight45 which defines the amount of space between the outer surface of the lead body andinner wall42.Height45 is generally selected to allowconductive pads24 and/orconductive elements34 to pass beneath the inner wall during assembly. Typically, three projections are provided at positions around the circumference ofband electrode14 tocenter band electrode14 overlead body12 during assembly. Centeringband electrode14 so thatheight45 is substantially the same around the circumference of the lead body assures clearance of the conductive element during assembly.

Claims

1.-2. (canceled)

3. A method of forming a medical lead, the method comprising:

forming a welding region within insulating material in a lead body of the medical lead to expose a conductor;

forming a conductive pad within the welding region by melting conductive material at a point over the welding region to form the conductive pad and electrically connecting the conductive pad to the conductor; and

electrically connecting an electrode to the conductive pad.

4. A method in accordance withclaim 3 wherein the welding region is formed using a laser.

5. A method in accordance withclaim 3 wherein the conductive material comprises a conductive metal selected from the group consisting of stainless steel, MB35N, Pt—Ir, platinum, silver, gold, copper and vanadium.

6. A method in accordance withclaim 3 wherein the welding region is in the shape of a groove.

7. A method in accordance withclaim 3 further comprising:

welding the electrode to the conductive pad.

8. A method in accordance withclaim 3 wherein forming the conductive pad further comprises melting and welding the conductive pad to the conductor using a laser.

9. A method in accordance withclaim 3 wherein forming the conductive pad further comprises;

placing a length of wire over the welding region; and

melting the wire at a point such that ends of the wire are drawn into the welding region to form the conductive pad.

10. A method of forming a medical lead, the method comprising:

forming a first welding region within insulating material in a lead body of the medical lead to expose a conductor;

forming a second welding region within the insulating material in the lead body of the medical lead to expose the conductor;

forming a first conductive pad within the first welding region by melting a first conductive material at a point over the first welding region to form the first conductive pad and electrically connecting the first conductive pad to the conductor;

forming a second conductive pad within the second welding region by melting a second conductive material at a point over the second welding region to form the second conductive pad and electrically connecting the second conductive pad to the conductor; and

electrically connecting an electrode to the first conductive pad and the second conductive pad.

11. A method in accordance withclaim 10 wherein the first and second welding regions are formed using a laser.

12. A method in accordance withclaim 10 wherein the first and second conductive material each comprise a conductive metal selected from the group consisting of stainless steel, MB35N, Pt—Ir, platinum, silver, gold, copper and vanadium.

13. A method in accordance withclaim 10 wherein the first and second welding regions are in the shape of a groove.

14. A method in accordance withclaim 10 further comprising:

welding the electrode to the first conductive pad; and

welding the electrode to the second conductive pad.

15. A method in accordance withclaim 10 wherein forming the first conductive pad further comprises melting and welding the first conductive pad to the conductor using a laser, and forming the second conductive pad further comprises melting and welding the second conductive pad to the conductor using a laser.

16. A method in accordance withclaim 10 wherein forming the first conductive pad further comprises,

placing a length of first wire over the first welding region; and

melting the first wire at a point such that ends of the first wire are drawn into the first welding region to form the first conductive pad; and

wherein forming the second conductive pad further comprises,

placing a length of second wire over the second welding region; and

melting the second wire at a point such that ends of the second wire are drawn into the second welding region to form the second conductive pad

17. A method of forming a medical lead, the method comprising:

forming, using a laser, a conductive pad within the welding region by melting wire conductive material within the welding region to form the conductive pad thereby welding the conductive pad to the conductor; and

welding an electrode to the conductive pad.

18. A method in accordance withclaim 17 wherein the welding region is formed using a laser.

19. A method in accordance withclaim 17 wherein the conductive material comprises a conductive metal selected from the group consisting of stainless steel, MB35N, Pt—Ir, platinum, silver, gold, copper and vanadium.

20. A method in accordance withclaim 17 wherein forming the conductive pad further comprises;

placing a length of wire over the welding region; and