Experimental Evaluation of a Retrievable Vena Cava Filter

A new retrievable filter, consisting of a helical basket of ten stainless steel wires and a retrieval cable, was tested in 7 adult sheep. The filter was inserted into the infrarenal vena cava through a 9-F sheath and fixed subcutaneously by a stabilizing ball at the skin insertion site. An average of 15.6 days after the filter placement, a follow-up cavography and clot-trapping tests were performed. The filter was retrieved through a 9-F sheath. Although all of the filters were free of thrombi and all of the inferior venae cavae were patent with good flow, two caval stenoses were noted below the filter. All 4 x 30 mm clots were trapped by the filter. Five filters were retrieved successfully; however, two filters could not be retrieved. Although these initial animal studies have shown this basket-type filter to be less than ideal, the development of a filter than can be successfully retrieved is essential for expanding the application of vena cava filters.