The In Vitro Study Of A New Eccentric Self-convertible Vena Cava Filter

Backgrounds: Pulmonary embolism(PE) is one of the most serious complications occurs in trauma patients and some elder patients who needs bedridden. Nearly 90% of clots caused PE are from deep venous thrombosis(DVT). Inferior vena cava filter(IVCF) is an efficient device to prevent PE, it was widely used in cilnical trials. However, with the increased us of IVCF, some applications associate with IVCF such as recurrence of DVT and postcava occlusion were reported in many medical center. The research about IVCF found that the instructure of the filter and thrombosis the filter captured hindered the bloodstream in the postcava, which may lead to DVT and other IVCF related complications. The widely use of Retrievable inferior vena cava filters(RIVCF) may readuce the reates of complications, but the clinical data show a low recovery of RIVCF, some patients have no indication to retrive the filter. To solve the problem from the resource, we desigened a new type filter which have a unique instructure, we expect this filter may make some help to reduce the occurrence of IVCF related complications.Objective: We designed the Eccentric Self-convertible Vena Cava Filter(ESCF), to evaluate the clot capture efficency and the function to guide the clots adherence the cava wall of the ESCF by using mimical fliud modal. To evaluate the hemodynamics of the ESCF by using three-dimensional computational fluid dynamics.Methods:(1) Test the ESCF in a mimical fliud model, the cava of the model have two different diamter and three different positions. Use two different sizes of thrombosis to evaluate the clot capture rates and the rates of adhered clos.(2) Three-dimensional computational models of the ESCF and the Trap Ease filter, three sphere clots with different volume and a 23 mm diamter cava were constructed by Solidwork2013. The hemodynamics of steady-state flow were examined for unocculed and partially occuled filter by Ansys14.5.Results:(1) The total clot capture rates is 82.6%(595/720), the dimater of the cava, the size of clots,the position of the cava and the ESCF have prominent influence to the clot capture rates. The rates of adhered clots is 84.7%(504/595). The catched clots are more likely adhere to the cava wall when the cava position is horizontal, and the big clots have higher adherence rates.(2)The fluid inside the ESCF can still keep steady, but in the Trap Ease filter the fluid was disturbed slightly by the tips of the filter. Disturbed flow can be found in the downstream of both partially occuled filter, and the area of the unsteady flow grow fast with the increased of clot dimater. The bypass flow caused by clots which adherenced to the cava wall is gentle than the clots in the central of the cava. The wall share stress of the downstream of the adhered clot are lower than normal.Conclusions: The clot capture rates of ESCF is high enough for prevent PE, this filter have the ability of guiding clots to adhere the wall, but both of those two functions influenced by the position of the cava and ESCF, we should better put ESCF in a proper position in our further trials. The simple structure of ESCF have less impact to steady flow than Trap Ease filter. Fewer disturbed flow occuered at downstream of adhered clots. The low share stress may favor the hemostasis and the hyperplasia endothelialis, which will make sure that adherenced clot do not defulvium from the cava wall after the transformation of ESCF.