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MEDICAL ELECTRICAL LEAD AND METHOD FOR MAKING THE SAME

IP.com Disclosure Number: IPCOM000011021D
Publication Date: 2003-Feb-06
Document File: 3 page(s) / 9K

Publishing Venue

The IP.com Prior Art Database

Abstract

A medical implantable electrical lead exhibits uniform mechanical properties throughout the entire lead body, thereby providing superior steerability and torquability features. The uniform mechanical properties are realized by making the lead body as a single unit. To make the lead body, individual wires are first coated with an insulative thermoplastic material. A multifilar coil is then wound using the coated wires to achieve a desired outer diameter, inner diameter, and pitch. The multifilar coil is then coextruded in a jacket of insulative thermoplastic material. The insulative thermoplastic material has a melting temperature that is lower than the melting temperature of the thermoplastic material that coats the individual wires. A mandrel may be placed in the inner diameter of the coil during the coextrusion process to ensure the patency of the inner lumen. The coextruded lead is placed in a fixture to determine the location of the wires for exposure for subsequent electrode connection. The outer jacket insulation is removed using a suitable removal process, and ring electrodes are positioned along the lead body so as to align with the locations where the insulation has been removed. The electrodes are then electrically and mechanically bonded to the lead body. Finally, any voids or gaps between the ring electrodes and the outer jacket insulation are filled with a suitable thermoplastic. The above process results in a single unit construction that provides a torque ratio that approaches 1:1.

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MEDICAL ELECTRICAL LEAD AND METHOD FOR MAKING THE SAME

Summary

The present invention relates to medical implantable leads for use with neural stimulation systems, and more particularly to a medical electrical lead having uniform mechanical properties throughout the entire lead body. Such uniform lead advantageously offers superior steerability and torqueability features when compared to a lead that does not have uniform mechanical properties throughout the entire lead body.

The uniform mechanical properties made possible by the present invention are realized by making the lead body as a single unit. A single unit construction includes the following: a medical implantable electrical lead exhibits uniform mechanical properties throughout the entire lead body, thereby providing superior steerability and torqueability features; and the uniform mechanical properties are realized by making the lead body as a single unit.

A single unit construction, in accordance with the present invention, includes some or all of the following manufacturing steps: (1) individual wires are coated with an insulative thermoplastic material; (2) a multifilar coil is wound using the coated wires to achieve a desired outer diameter, inner diameter, and pitch; (3) the multifilar coil is coextruded in a jacket of insulative thermoplastic material, wherein the insulative thermoplastic material has a melting temperature that is lower than the melting temperature of the insulative thermoplastic material used to coat the individual wires; (4) a mandrel is placed in the inner diameter of the coil during the coextrusion process to ensure the patency of the inner lumen; (5) the coextruded lead is placed in a fixture and the location of the wires for exposure for subsequent electrode connection is determined; (6) the outer jacket insulation is removed using a suitable removal process; (7) ring electrodes are positioned along the lead body so as to align with the locations where the insulation has been removed; (8) the electrodes are then electrically and mechanically bonded to the lead body; and (9) any voids or gaps between the ring electrodes and the outer jacket insulation are filled.

The process outlined above results in a single unit construction that provides a torque ratio that approaches 1:1. (A torque ratio of 1:1 means that the same torque applied to one end of the lead is transferred to the other end of the lead.) Such torque ratio makes the lead much easier to steer during implantation.

Detailed Description

Desirable features for medical electrical leads, specifically those used for spinal cord stimulation, include steerability, small size (diameter 1 mm), multiple electrodes (4+), reliability, and visibility. Many of these features are inversely related to one another. For example, multiple electrodes and reliability are inversely related to small size in terms of ease of manufacturing. To a certain extent visibility versus size, and multiple electrodes versus steerab...