USE OF STENTS COVERED WITH POLYTETRAFLUOROETHYLENE IN EXPERIMENTAL ABDOMINAL AORTIC-ANEURYSM

PURPOSE: To establish the effectiveness of covered stents in the treat ment of aortic aneurysms, to investigate the histopathologic healing p atterns of the device, and to determine the long-term endurance and in tegrity of modified polytetrafluoroethylene (PTFE). MATERIALS AND METH ODS: Experimental aneurysms were created in dogs by enlarging the aort ic lumen with a patch of abdominal fascia. After 5 months, eight anima ls underwent an endoluminal bypass, The bypass device consisted of a 6 -cm-long stent covered with thin PTFE, After surgery, the animals were killed at 3, 6, and 12 months in groups of three, three, and two, res pectively, Specimens were processed for luminal surface studies and cr oss-sectional histologic study. Explanted PTFE material was analyzed f or its physical characteristics and performance and was compared with retained control samples, RESULTS: Before the animals were killed, aor tography showed patent bypass conduits in all animals, although two of eight had leaks into the aneurysmal sac. Endothelialized neointima la rgely covered the luminal surface of the PTFE stent, The percentage of prosthetic surface covered by tissue did not change from 3 months to 1 year, Physical testing of the explanted PTFE material showed no stru ctural deterioration and no change in the internodal distance, Thickne ss and axial tensile strength varied 12% and 17% from controls, respec tively. CONCLUSION: Thin-walled PTFE seems to have physicochemical cha racteristics that make this material adequate for endovascular use, Th ough limited, this study supports the establishment of preliminary cli nical evaluation of metallic stents combined with PTFE for the treatme nt of abdominal aortic aneurysm.