A system including an implantable defibrillation electrode includes a first layer of porous Polytetrafluoroethylene (PTFE) adjacent to at least one surface of the defibrillation electrode, the first layer of porous PTFE having a fibril length adapted to bleed gas away from the at least one surface of the defibrillation electrode, and a second layer of porous PTFE formed over the first layer, the second layer of porous PTFE having a fibril length adapted to prevent substantially all tissue in-growth.