A header assembly for connecting a conductor terminating at a body organ with an implantable medical device is described. The header assembly comprises a base plate, a feedthrough subassembly disposed in the base plate and comprising a ceramic-to-metal seal with first and second feedthrough wires passing through the ceramic-to-metal seal a first electrically conductive terminal connected to a distal end of the first feedthrough wire and having a first lead opening sized to receive a first portion of a lead for the conductor a second electrically conductive terminal connected to a distal end of the second feedthrough wire and having a second lead opening sized to receive a second portion of the lead for the conductor a body of polymeric material molded in a two-part construction to encase the conductive terminals and their feedthrough wires except for a first bore communicating from outside the polymeric body to the first and second lead openings aligned in a first co-axial relationship. Preferably, the polymeric body comprises a first polymeric material such as Techothane® or Polysulfone® encasing the terminals except the bore and an epoxy as a second polymeric material molded over the first polymeric material.
