Importance

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Abstract

MP35N (35% Co, 35% Ni, 20% Cr, 10% Mo) wires (solid and clad) are widely used for leads in cardiac rhythm management (CRM) and neurological electrical stimulation devices. Over the typical lifetime of a CRM device, a lead wire is subjected to stress cycling imposed by the heartbeat and is expected to survive 300 million stress cycles, or more. Premature fatigue fracture of a lead is sometimes caused by surface imperfections in the wire that has been coiled into the lead. The imperfections can result in concentration of stresses at a specific location on the wire surface. A vexing type of imperfection is a tiny surface fissure that is commonly referred to as a chevron. Wire drawing processes that are commonly used to form wires for manufacturing an implantable lead inherently produce a distribution of tiny chevrons on the wire surface. According to the present invention, removing chevrons and other surface imperfections using an electropolishing process helps reduce or eliminate premature fatigue failure initiated by such surface imperfection.

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First Claim