Long (>wavelength/4) actively-tracked metallic-backbone or metallic-braided cardiovascular devices are not used in MRI-guided interventions due to surrounding-tissue heating concerns. Such devices may be used if induced currents on the metallic-backbone and internal cables are sufficiently attenuated. At ISMRM 2018 we demonstrated a miniaturized resonant floating Balun (MBalun), and two actively-tracked MRI-guided metallic interventional devices built using MBaluns. MBaluns were constructed with loosely-wound solenoids overlaid on the metallic-backbones, generating strong transverse magnetic fields that attenuated surface currents and internal-cable common-mode currents. We now provide electromagnetic simulation revealing MBalun critical dimensions, along with phantom heating and swine experiments that validate the designs.