Encapsulated intraluminal stent-graft and methods of making same

An endoluminal prosthesis comprising:

• a self-expanding stent, characterized by having substantially the same longitudinal length in a radially contracted and expanded state;
• a seamless expanded polytetrafluoroethylene covering, exhibiting a node and fibril microstructure with fibrils oriented in a generally uniaxial direction, the covering comprising extruded luminal and abluminal tubular layers of expanded polytetrafluoroethylene intimately joined to one another through the walls of the stent;
• and
• an interlayer member disposed between the abluminal tubular layer of expanded polytetrafluoroethylene and the stent, comprising a pair of unsintered expanded polytetrafluoroethylene rings;
• wherein the prosthesis has a contracted first diametrical dimension and an expanded second diametrical dimension, the prosthesis being adapted to expand from the first diametrical dimension to the second diametrical dimension without plastically deforming the expanded polytetrafluoroethylene covering.