Evaluation of a spiral nitinol temporary inferior vena caval filter

Rationale and Objectives. The authors performed this study to evaluate the (a) ability of a prototype temporary inferior vena caval (IVC) filter to tr ap and retain emboli in an ex vivo flow circuit, (b) feasibility of filter placement and removal via a superficial vein in sheep, and (c) intermediate -term effects of the filter on the insertion vein and at the filter site. Materials and Methods. In an iliocaval circuit, embolus capture with the pr ototype filter was compared to that with a Greenfield filter. In addition, prototype filters were placed into the infrarenal IVC in six sheep. Placeme nt via a superficial venous route was initially attempted. Inferior vena ca vography was performed weekly, and filters were removed after 2, 3, or 4 we eks (n = 2 each). Two weeks after the filters were removed, vena cavograms were obtained, the animals were sacrificed, and the IVC was evaluated at pa thologic examination. Results. The prototype filter captured all emboli, and the Greenfield filte r captured 70%-100% of emboli. Successful placement via a superficial venou s route was accomplished in only two sheep owing to small vein caliber; fou r filters were placed via a deep vein. Adverse events included perifilter t hrombus, insertion site infection, and caudal migration. Two sheep died bef ore filter removal owing to sepsis and anesthetic complications. The filter s in the remaining four sheep were easily and successfully removed. Five sh eep had stenosis at the filter site, and fibrosis with acute and chronic in flammation was seen at microscopic examination. Conclusion. The prototype filter trapped emboli as well as the Greenfield f ilter. Insertion via a superficial route, however, is possible only if the access vein is of an adequate size.