Structures and methods relating to electrodes for incorporation into a feedthrough with a profile adapted for subcutaneous sensing of physiologic and cardiac signals. Electrode assemblies are adapted for integration with feedthroughs and provide reliable insulation from the implantable medical device housing. Various structures and manufacturing processes are implemented to provide a large sensing surface with a low profile. The subcutaneous sensing electrode assembly can provide a leadless sensing system and further enhances installation and follow-up procedures.