A medical lead and a method of making the medical lead, the medical lead having a proximal end for electrical connection to a medical device and a distal end implantable proximate a target tissue. The lead includes a conductor and a sheath disposed over the conductor, the sheath comprising a polymer and a filler mixed in the polymer. The filler has a dielectric constant that is different from a dielectric constant of the polymer. The weight percentage of the filler in the sheath is selected such that energy induced by an external disruptive energy field in the conductor that is absorbed by the target tissue proximate the distal end of the lead is below a predetermined threshold energy.
