A RETRIEVABLE NITINOL VENA-CAVA FILTER - EXPERIMENTAL AND INITIAL CLINICAL-RESULTS

PURPOSE: The authors describe the properties of a new retrievable niti nol vena cava filter and report experimental and initial clinical resu lts. MATERIALS AND METHODS: The filters, made of nitinol monofilament wire that forms a spiral cone and retrieval wire, were introduced thro ugh an indwelling 5.5-F transfemoral sheath into the infrarenal portio n of the inferior vena cava in 10 sheep. In seven animals, four 4 x 30 -mm radiopaque clots were injected below the filter to test its thromb us-trapping efficacy. Aspiration thrombectomy was then attempted, and the filter was removed. Follow-up venography was performed 1 week afte r placement in three other animals. After successful preclinical testi ng, the filter was implanted and retrieved in two patients. RESULTS: A ll 10 filters were successfully and easily placed in sheep. All filter s were thrombus-free at follow-up venography. All clots injected in th e iliac veins were trapped by the filter and successfully removed by m eans of aspiration thrombectomy. All 10 filters were retrieved without difficulty. Temporary filter implantation and retrieval were accompli shed in two patients for 5 and 7 days. In one patient, infrafilter thr ombus was aspirated. Perisheath thrombosis occurred in both patients. One patient subsequently underwent permanent filter placement. CONCLUS ION: Temporary vena cava filtration is feasible. Potential advantages include easy placement, surveillance, and retrieval. One current limit ation is pericatheter thrombosis, which may be eliminated by a less th rombogenic sheath.