Vena caval filter to prevent pulmonary embolism: experimental study. Work in progress.

A new inferior vena caval filter was tested in an experimental series of 23 dogs and in an in vitro study. The filter consists of a pliable basket and anchoring legs made of stainless steel. It can be inserted percutaneously in an antegrade or retrograde fashion through a 10-F Teflon catheter and can be retrieved with a snare or forceps. The filter is self-orienting in the inferior vena cava, becomes securely the inferior vena cava, becomes securely fixed to the wall, and has exhibited no tendency to migrate. It is highly effective in capturing small and large emboli. There was no significant elevation in upstream hydrostatic pressure following entrapment of emboli. Spontaneous thrombus formation within the basket was observed in two of six dogs who had short-term follow-up. In dogs who had long-term follow-up, the filter remained patent. Microscopically, the filter caused sclerosis of the intima where the wire was in contact with the vessel wall. Breakage of an anchor leg and separation at the fusion between anchor and basket were seen in the study. They were eliminated by improvement of the prototype, which is now ready for clinical application.