ABSTRACT
BACKGROUND:An inferior vena cava filter is an effective tool to prevent fatal pulmonary embolism. The existing filters have some shortcomings that limit their clinical application. OBJECTIVE:To evaluate the feasibility and capture efficiency of a new self-convertible inferior vena cava filter (SCF)in vivo. METHODS:L-lactide and ε-caprolactone were fused and polymerized to act as a degradable deformable switch of the filter. Medical stainless steel wire as the metal structure of the filter was combined with the degradable deformable switch to make the SCF. Eight SCFs were implanted into the inferior vena cava of eight adult Beagle dogs. The inferior vena cava angiography was performed to evaluate the release process, morphology and location of the filter. Venous angiography was performed 2 weeks later to evaluate the morphology and location of the filter and inferior vena cava patency. Detection of pulmonary embolism or other complications was performed at autopsy. RESULTS AND CONCLUSION:Eight SCFs were successfully implanted and positioned accurately with no tilt, and they were converted successfully at 2 weeks after the implantation, as assessed by the venous angiography. One of the eight SCFs migrated to the orifice of the right atrium, and caused asymptomatic inferior vena cava obstruction. The remaining SCFs were normally positioned with no tilt and local lesion or obstruction after deformation. No marked filling defect in the trunk of the pulmonary artery was shown by the pulmonary artery angiography. The autopsy report revealed that the filter arm had been endothelialized, and the inferior vena cava that was in contact with the filter arm had no obvious stenosis. Mild intimal hyperplasia, less than 1 mm in thickness, was found in the bottom of the filter arm, but it did not cause a stenosis in the lumen. No vena cava perforation, retroperitoneal hemorrhage, and injury of the surrounding viscera were found. Overall, the design of the SCF is feasible.
ABSTRACT
BACKGROUND: Inferior vena cava filter is an effective way to prevent fatal pulmonary embolism. The existing filters have some shortcomings that limit the clinical application. OBJECTIVE:To evaluate the feasibility and capture efficiency of a new self-convertible inferior vena cava filter(SCF)in vitro. METHODS: The biodegradable switch was constructed of a copolymer of ε-caprolactone and L-lactide (75%/25%, PCLA75). The biodegradable switch bound together with the apices of the convertible struts to make the self-convertible filter. The deformability and capture efficiency of the filter were tested in an in-vitro flow model with three different diameters (22, 25, 28 mm). A total of 15 filters were implanted both in the vertical and horizontal positions, and the tilt angle of the filter was tested after release. To accelerate switch degradation, a lipase perfusate was injected into the flow model and refreshed every 8 hours until conversion. RESULTS AND CONCLUSION: (1) All the filters were successfully implanted without tilting, both in the vertical and horizontal positions in the three different diameter models. (2) All the 15 SCFs were converted successfully without tilting, structural damage, and displacement. (3) The capture efficiency of the SCF had significant difference between the different diameter of the models, the size of the embolus and the position of the two models (P < 0.001). The mean capture efficiency was 82.5%, and the capture efficiency exhibited a downward trend with the increase of pipe diameter, the decrease of emboli size, and the position of pipeline changing from vertical to horizontal. All these results show that the SCF is feasible and highly efficient.
ABSTRACT
<p><b>BACKGROUND</b>People recently realized that it is important for artificial vascular biodegradable graft to bionically mimic the functions of the native vessel. In order to overcome the high risk of thrombosis and keep the patency in the clinical small-diameter vascular graft (SDVG) transplantation, a double-layer bionic scaffold, which can offer anticoagulation and mechanical strength simultaneously, was designed and fabricated via electrospinning technique.</p><p><b>METHODS</b>Heparin-conjugated polycaprolactone (hPCL) and polyurethane (PU)-collagen type I composite was used as the inner and outer layers, respectively. The porosity and the burst pressure of SDVG were evaluated. Its biocompatibility was demonstrated by the 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H tetrazolium bromide (MTT) test in vitro and subcutaneous implants in vivo respectively. The grafts of diameter 2.5 mm and length 4.0 cm were implanted to replace the femoral artery in Beagle dog model. Then, angiography was performed in the Beagle dogs to investigate the patency and aneurysm of grafts at 2, 4, and 8 weeks post-transplantation. After angiography, the patent grafts were explanted for histological analysis.</p><p><b>RESULTS</b>The double-layer bionic SDVG meet the clinical mechanical demand. Its good biocompatibility was proven by cytotoxicity experiment (the cell's relative growth rates (RGR) of PU-collagen outer layer were 102.8%, 109.2% and 103.5%, while the RGR of hPCL inner layer were 99.0%, 100.0% and 98.0%, on days 1, 3, and 5, respectively) and the subdermal implants experiment in the Beagle dog. Arteriography showed that all the implanted SDVGs were patent without any aneurismal dilatation or obvious anastomotic stenosis at the 2nd, 4th, and 8th week after the operation, except one SDVG that failed at the 2nd week. Histological analysis and SEM showed that the inner layer was covered by new endothelial-like cells.</p><p><b>CONCLUSION</b>The double-layer bionic SDVG is a promising candidate as a replacement of native small-diameter vascular graft.</p>