Experience with the Amplatz retrievable vena cava filter
The vena cava filter, a device implanted in the main vein of the body, the vena cava, prevents emboli (fragments of a blood clot) from traveling through the heart and becoming trapped in the small capillary spaces of the lungs (pulmonary emboli). The preferred treatment for the prevention of pulmonary emboli is the vena cava filter. The fact that there are many competing filters indicates the difficulty in developing a suitable device that prevents such complications as migration, insertion difficulty, and clotting of the vena cava with the possibility of occlusion (complete closure of the vessel by a clot). The Amplatz filter is inserted through the skin (percutaneous) into a major vein (either in the groin or neck) and guided into its final site in the vena cava. The design of the filter allows it to be repositioned or removed through the same percutaneous venous approach that is used for insertion. The current study looks at 52 patients who had Amplatz filters placed in their bodies. No deaths occurred as a result of the filter placement. The position of the device and its physiologic status was confirmed by the use of various medical imaging methods and by autopsy. A large clot was found in 17.5 percent of the cases; this was most likely due to the progression of a clot trapped by the device, perhaps as a result of the geometry of the device. Retrieval of the device was considered in eight patients and was performed in five patients in whom the filter had been inserted from one to sixteen days previously. The replacement procedure was well tolerated by all patients and no deaths were attributed to the insertion or retrieval of the device. Neither the current design, nor the designs of other known systems appears to be ideal with regard to clot trapping and lysis. In general the ability of the filters to stop the migration of emboli to the lungs, even if this results in blockage, is the single most important design concern. The efficacy of the current Amplatz caval filter is unsure; final FDA approvals have not been given and changes to the final design are under evaluation.
Publication Name: Radiology
Inferior vena cava filter: search for an ideal device
Since the 1940s researchers have tried to develop a surgical procedure to place a baffle in the inferior vena cava (the main vein which returns blood to the heart) to prevent clots or venous thrombi from entering the right side of the heart and, through it, the lungs. Difficulties with this task caused researchers to intensify their search for an ideal filter. The ideal filter should be based on several concepts: (1) it should not increase instances of clot formation; (2) it should break the large cross-sectional face of the vena cava into smaller channels so as to prevent the movement of large clots; and (3) it should be able to be placed without extensive surgery. Several filters have been developed and tried, and although good results have been recorded with most, there are considerable risks and unanswered questions regarding their use and time of removal. Several can now be installed and removed through a simple needle-like inserter system through the skin. Several devices under study have either been modified or withdrawn from further study. It has not yet been determined which of the commercially available devices and methods are best. A collaborative, multicenter study to evaluate these important devices is proposed.
Publication Name: Radiology
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