In vitro study of guide wire entrapment in currently available inferior vena cava filters

Guide wire entrapment by some older inferior vena cava (IVC) filters is known to occur, particularly with J-tipped wires. Three new IVC filters have recently been approved for use in the United States. An in vitro study was performed to compare the risk of engaging and entrapping guide wires in eight of the IVC filters currently available in the United States.

Titanium Greenfield, over-the-wire stainless-steel Greenfield, Simon nitinol, Bird's Nest, Vena Tech LGM, Vena Tech LP, TrapEase, and Günther Tulip IVC filters were deployed separately in an in vitro IVC flow model. Four different wires (15-mm, 3-mm, and 1.5-mm J-tipped, and straight) were passed 100 times each through the filters (50 from a jugular approach and 50 from a femoral approach). The frequency and specific patterns of engagement of the wires by the filters were recorded. Engagement was defined as a filter/wire interaction that caused either the filter or the wire to be deformed. The second part of the experiment measured the force (in pounds) that was required to release wires that became engaged in the filters with use of an electromechanical test stand with a specially designed low-capacity load cell of 20 pounds. Entrapment was defined as inability to separate an engaged wire from the filter without damage to either the wire or filter.

Guide wire engagement occurred in all filters tested with the 15-mm, 3-mm, and 1.5-mm J-tipped wires. The straight wire did not engage any of the filters. The wires engaged the TrapEase filter with the greatest frequency overall (72.8%; 291 of 400). The 15-mm J wire engaged the filters more often than the other wires (98.5%; 788 of 800), but never became entrapped in a filter. The Vena Tech LP and Günther Tulip filters did not entrap any of the wires. The TrapEase filter, the stainless-steel Greenfield filter, and the Vena Tech LGM filter entrapped the 3-mm and 1.5-mm J wires. The force required to disengage the wires from these filters exceeded 4 pounds and resulted in structural damage to the wire and/or filter.

Among the IVC filters recently approved by the Food and Drug Administration, the TrapEase filter entrapped 3-mm and 1.5-mm J-tipped guide wires, whereas the Vena Tech LP and Günther Tulip filters did not. This study corroborates previously described wire entrapment by the stainless-steel Greenfield and Vena Tech LGM devices.