. . "The illustrative device 10 preferably comprises a standard exchange wire guide, e. g., 480 cm or 260 cm in length, with a solid core wire 11, formed from a metal such as nitinol, and a coating 12 on the wire 11, comprising a polymer such as a fluoropolymer, e.g. polytetrafluoroethylene (PTFE), that is shrink-wrapped over the wire." . .