The preparation of biodegradable vena cava filter and the study of its properties / 中华放射学杂志

ABSTRACT

Objective To investigate the preparation of biodegradable vena cava filter(BVCF) with poly-l-lactic acid (PLLA),and to evaluate its mechanical properties,delivery performance,the ability of capturing thrombus and the degradation property.Methods Three-dimensional design software was used to design the shape of BVCF.The BVCF was prepared by using PLLA with molecular weight of 100 000 unit.Twelve minipigs were used to test the feasibility of this BVCF.They were randomly divided into four groups.At first the BVCFs were placed into the inferior vena cava of pigs in three experimental groups.The fourth group was used as a blank control group.The thrombi were injected into all pigs after 1 week,and CT examinations were performed at different time points to observe the filter locations and pulmonary artery.The animals were sacrificed according to a fixed time table for histopathological assessment.Results The BVCF was successfully designed and produced,which could expand by stretching the center-thread.In vitro test results showed the radial force of BVCF was approximately 1.6 N and could capture the thrombus more than 5 mm in diameter,and it was easy to release.Through the animal experiment confirmed that the filter could capture the lethal thrombus and all 9 pigs of experimental groups were survived,two of those had the symptoms of respiratory frequency and heartbeat accelerated slightly in the operation.In control group,the symptoms such as accelerate of respiratory rate,shortness of breath were observed in varying degree.The pig which was injected with 8 strips of thrombus died in the same day after surgery.Postoperative CT and pathological examinations showed that 2 pigs in the experimental group developed peripheral pulmonary embolism,while the dead pig in the control group developed central pulmona-y embolism.Histological findings showed that the intima covered the BVCF lateral branch partly after one week,and thoroughly after six weeks.The vessel wall structure remained normal and no signs of the obvious inflammatory cells infiltration were detected.Twelve weeks after the implantation,the vessel wall structure was normal,and the lumen was unobstructed,and the collateral of the filter was partly degradated.Conclusions The BVCF has the advantage of good mechanical strength and good biocompatibility.It is easy to release and can capture the lethal thrombus,but its degradation performance remains to be studied.