Most of use have had trouble threading a Picc wire @ one time or another. What are some reasons this occurs, besides scar tissue or plaque in the vein? Â You visualize a good size vein and enter it without difficulty and get a great blood return, but you are unable to thread the wire. I have tried both retracting styletÂ Â slightly from the veinÂ and repositioning the angle of the stylet but without success. Any suggestions on how to get wire to advance without giving up and making another insertion site?