The concept of a topocatheter extension added to a standard angiographic catheter involves the production of a high strength thin walled tapered tube attached to the end of a standard catheter. Suction on the catheter causes the thin wall portion to collapse and invert itself until it lines the distal end of the catheter. Flow out of the catheter causes the thin wall to valve shut and evert again. When the thin wall everts it rolls onto the inside of the vessel wall with no relative wall motion hence no friction. The rolling wall is advanced by the pressure of the fluid inside so that the extension enters and follows small or tortuous vessles with ease. We are continuing to supply collagen extension catheters to Dr. Doppman but other applications that do not require protection from ballooning and obstruction of flow can be met by returning to the plain polyurethane thin wall catheter. New tubing of high quality Tecoflex has been drawn to produce higher quality catheters and solution casting or dip coating have been demonstrated to produce catheters that promise easy and rapid fabrication so that made to order devices can be tailored to specific clinical problems. In addition to catheter production from collagen the tubes made have been slightly modified to make 3mm tubes that have been supplied to the surgical service for testing as vascular prosthesis. The strength texture and future holding qualities have been reported to be superior and animal implants have remained patent for a short time which is relatively encouraging for this size vessel.
