In vitro flow phantom analysis and clot-capturing ability of incompletely opened Vena Tech-LGM vena caval filters

It has been shown recently that Vena Tech-LGM (B. Braun Vena Tech, Evanston, IL) filters inserted into the inferior vena cava via the jugular route may be deployed sometimes in an incompletely opened (IO) position. The flow characteristics and clot capturing ability of IO Vena Tech-LGM filters are not clearly understood. Using a vena cava flow phantom, the clot-capturing abilities of the IO and opened Vena Tech-LGM filters were assessed. For 5 x 5-mm clots, the IO Vena Tech-LGM filter captured only 40% of thrombi compared with a 90% capture rate for the opened filter. The capture rates were 90 and 100% for the IO and opened filter, respectively, for larger 5 x 15-mm clots. It was found that the IO filter could capture 2-7 x 25 mm thrombi prior to the development of a turbulent bypass channel which prevented subsequent clot capture. Using 5 x 15 mm clots, this same phenomenon occurred with the capture of 6 and 11 thrombi by the IO and opened Vena Tech-LGM filters, respectively. Our results suggest a significantly reduced filtering efficiency for the IO Vena Tech-LGM device. However, there is a high rate of clot capture with the opened Vena Tech-LGM filter.