Implantable electrical lead wire

Abstract

Implantable electrical lead wires, such as cobalt-chromium-molybdenum alloy wires, are coated with a metal, ceramic, or carbon to a thickness of about 100 nm or less to provide a non-reactive interface to polyurethane sheathing materials. Preferred is sputter coating an amorphous carbon intermediate the alloy wire and the polyurethane sheath.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority from provisional application Ser. No. 60 / 512,741, filed Oct. 20, 2003.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to implantable electrical lead wires such as those used in cardiac pacing and neurostimulation. More particularly, the present invention relates to a solution to the chronic compatibility problems of lead wires with the materials used to insulate them. [0004] The primary requirements of lead wires are conductivity and fatigue resistance. Because lead wires are designed so that body fluids never come into contact with the conductor material, biocompatibility has only been considered a secondary requirement. However, with the introduction of polyurethane as an insulator for lead wires, it is now known that an interaction can be initiated at the conductor / insulator interface in which the insulator material is degraded by a metal ion oxidation ...

AI Technical Summary

Benefits of technology

[0011] Polyurethane insulator degradation is prevented by means of a barrier coating consisting of a very thin sputtered film of selected metal, ceramic, and carbon in the form of amorphous carbon, turbostratic carbon, diamond-like carbon, and the like. These films are characterized by very good hardness, durability, and adhesion. When applied as a thin film, they readily conform to the lead wire metal surface as the wire is formed into a coil. At very thin film thicknesses, the films readily adapt to the stresses of coiling a wire into a helical shape to provide an effective barrier layer.

Problems solved by technology

The disadvantage is that the very desirable fatigue resistance of nickel, cobalt, chromium, and molybdenum materials and their alloys is lost.

The disadvantage of using titanium and platinum as coating materials, however, is that they can be damaged during the coating process and lead assembly, as well as by the stylet during implantation.

Another disadvantage is their generally poor adhesion to the wire throughout the deformation process during coiling to low diameter coils.

The deformation process can also result in the development of small breaches or cracks in the titanium and platinum coating.

Even in the absence of an insulative outer layer, the typical cracks and breaches in the sputtered coating due to winding are unlikely to produce significant areas of contact between the base metal of the coil and the polyurethane insulation.”

Any degree of compromise in the insulation layer is cause for concern.

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