Abstract: Apparatus and method according to the disclosure relate to minimizing gaps between a substantially planar cardiac-sensing electrode and a shroud member utilizing a so-called interference-fit. For example, a relatively recessed area or aperture formed in an exemplary resin-based shroud member has slightly reduced dimensions relative to the electrode and requires compression forces during assembly (e.g., manually or in an automated process including a press, a tool or other means). The interference-fit promotes a very tight fit (or seal) between the metallic electrode and the resin-based shroud member and, importantly, minimizes gaps. Additionally, discrete interference structures promote fluid tight seals between the electrode and a recess or aperture adapted to receive the electrode.

Abstract: The invention provides diverse ways to reduce if not eliminate the possibility of an errant electrical path from one or more conductors of the shroud to a portion of the conductive housing of its corresponding IMD. That is—as described hereinbelow prior to backfilling the shroud with medical adhesive as a final fabrication step—according to various forms of the invention biocompatible electrical insulation is added between an IMD housing and the elongated conductors that couple to the surface electrodes. For example, a parylene coating can be added to the outside of the IMD housing using a simple spraying procedure and/or dip coating the IMD housing into the parylene. Parylene is a proven biocompatible, electrically insulative material. In addition to or in lieu of a coating or layer of parylene, a dielectric layer such as titanium nitride (TiN) or the like can be sputtered to the elongated conductors.