Abstract: Objective To design a new biodegradable vena cava filter which could degrade and be absorbed slowly when the risk of pulmonary embolism (PE) has passed. Methods The filters were handmade, and consisted of two parts: the cone was constructed of six polyglycolic acid polymer strands anchored to a handmade absorbable stent. Central inferior vena cava fixation were accomplished by the absorbable stent which was made of polycaprolactone. The filters were inserted to the inferior vena cava of ten dogs under ultrasound guidance. The filters were operatively retrieved at 6 weeks after implantation .The inferior vena cava were subsequently analyzed using light microscopy. The lungs were also removed to observe any pulmonary embolism caused by the degradation products of the biodegradable filter. Results Biodegradable vena cava filters were successfully made and implanted in 10 adult dogs. None of the 10 dogs had abnormal vital signs except one dog had lower extremity swelling. ① Migration:All the filters migrated cephalad. One filter migrated into the right atrioventricular orifice, the other 9 filters migrated cephalad approximately < 2 cm and remained below the renal vein ostia. ② Naked-eye observation:In 8 of the 9 remaining filters, the absorbable strands had completely dissolved. One specimen had evidence of incorporated residual strands within the caval wall on gross examination, resulting in 70% stenosis of inferior vena cava. All of the biodegradable stents were embedded into the caval wall. The caval wall became thick at the level of filter placement without significant lumen narrowing. ③ Hematoxylin and eosin (HE) staining:Intense inflammatory response with significant thickened intima and media was seen on HE staining. There was no evidence of pulmonary embolism or inflammatory response caused by degradation products of the absorbable strands. Conclusion We had designed a biodegradable inferior vena cava filter successfully, the biodegradability and biocompability had been proven through in vivo studies.

Key words: vena cava filter, biodegradable, deep venous thrombosis, pulmonary embolism