The body 66 may comprise any of a variety of suitable, biocompatible materials such as various densities of polyethylenes, nylon, polyethylene terephthalate, pebax, and others apparent to those of skill in the art. [0097] Alternatively, the forming element 56 and support 58 may be surrounded by a tubular jacket of ePTFE or a polyester fabric such as DACRON, or other material which is wrapped or st