I was inserting a PICC and afterpassing it theough the introducer I lost patency. I retracted it some and checked patency and found that i aslo could not flush it. I manipulated it to no avail. Finally I went to remove it and found that I could not. I removed the introducer over the catheter and the catheter came out. To my amazement, the end was in a complete knot!!!! I understand how it could happen, but in over 5K insertions, I have never seen it. But when I saw it all I could think was OMG!!!