In-vitro evaluation of a new inferior vena cava filter-the stent-filter

Inferior vena cava filters are indicated for the prevention of pulmonary embolism when anticoagulation using heparin has failed or is contraindicated. The aim of this study was to assess in an in-vitro setting the efficiency of a new inferior vena cava filter to intercept emboli. The new filter, stent-filter, was inserted into a pulsating flow circuit. Then thrombi were produced by introducing sheep's blood into silicon tubes with 3 mm diameter. A combination of 9% saline solution with 40% glycerol was used as the isosmotic fluid in the circuit. A total of 150 thrombi were introduced into the circuit in 3 stages of 50 events each. The flow rate in each of the 3 stages was altered; initially a rate of 1.0 liter per minute was chosen, and after this, it was increased to 1.5 liters and finally 2.0 liters per minute. The percentage of interceptions was used for statistical analysis. In the in-vitro experiment, the filter captured 94%, 90%, and 92% of the thrombi at flow rates of 1.0, 1.5, and 2.0 liters per second, respectively. In conclusion the new filter was effective in the interception of the thrombi when it was evaluated in in-vitro conditions.