Systems and methods for exploiting the tip or ring conductor of an implantable medical device lead during an MRI to reduce lead heating and the risks of MRI-induced stimulation

A lead for use with an implantable medical device for implant within a patient, the lead comprising:

• first and second electrodes for placement adjacent patient tissues;
• an inner conductor for routing signals along the lead between the first electrode and the implantable medical device;
• an outer conductor for routing signals along the lead between the second electrode and the implantable medical device;
• an insulator interposed between the outer conductor and patient tissues;
• and
• an electrical device connected along the outer conductor between the second electrode and the implantable medical device and operative to selectively control the conduction of signals along the outer conductor in response to the presence of particular electromagnetic fields to selectively convert the outer conductor into an electromagnetic signal shield;
• wherein the lead is a bipolar lead, wherein the first electrode is a tip electrode and the second electrode is a ring electrode, wherein the tip electrode and ring electrode are pacing and/or sensing electrodes, and wherein the inner conductor is a tip conductor and the outer conductor is a ring conductor;
• and
• wherein the bipolar lead is a coaxial lead wherein the tip conductor is mounted coaxially inside the ring conductor.