Systems and methods for shielding implantable leads from magnetic fields during medical procedures such as magnetic resonance imaging (MRI) are described. In various embodiments, the lead includes an inner conductor that is helically shaped and radially surrounded, at least in part, by one or more outer shielding conductors. The pitch of the inner conductor, and in some cases also the outer conductor, can be varied (e.g., continuously or at certain points) along the length of the lead, forming a plurality of high impedance points along the length of the lead which result in the dissipation of electromagnetic energy at an interrogation frequency of a magnetic resonance imaging device (e.g., 64 MHz, 128 MHz, or the like). In some embodiments, the variance in the pitch of the inner conductor follows a sinusoidal function, a modified square-wave function, or some other repeating pattern.
