An electrical lead including a conductor assembly, an electrode, and a thermally sensitive material. The conductor assembly has one or more conductors. The electrode is in electrical communication with one of the conductors and has an outer contact adapted for contacting adjacent body tissue of a patient. The thermally sensitive material is electrically connected between the one conductor and the electrode outer contact, and is configured to exhibit high impedance in the presence of currents considered unsafe to the patient, thereby preventing the unsafe currents from flowing through the thermally sensitive material and through the electrode outer contact potentially causing the adjacent body tissue to increase in temperature to an unsafe level. The unsafe currents cause the thermally sensitive material to increase in temperature, thereby causing the material to transition to a high impedance state.