SELF-EXPANDING AND BALLOON-EXPANDABLE STENTS IN THE TREATMENT OF CAROTID ANEURYSMS - AN EXPERIMENTAL-STUDY IN A CANINE MODEL

PURPOSE: To assess the efficacy of metal stents for the treatment of d ifferent forms and sires of carotid aneurysms. METHODS: A total of 14 experimentally constructed aneurysms in dogs were treated with transfe morally placed balloon-expandable tantalum and self-expanding nitinol stents. RESULTS: In 10 cases, stenting produced either immediate compl ete occlusion of the aneurysm (n = 7) or complete delayed thrombosis a fter 7 to 10 days (n = 3). In two cases treated with balloon-expandabl e tantalum endoprostheses, repeated angiography showed a persistent an eurysmal neck with a diameter of 1 mm. No incompletely occluded aneury sms were visible after implantation of nitinol stents. Nine-month angi ographic follow-up revealed maximal stenosis of the stented vessel seg ment of up to 40% after placement of tantalum endoprostheses. However, no more than 15% stenosis followed the deployment of nitinol stents. Histologic examination confirmed these findings. Significantly greater intimal fibrocellular tissue growth surrounded tantalum filaments tha n nitinol filaments, which were covered with a smooth, thin neointimal layer. In two carotid arteries a subtotal and total occlusion of the parent vessel occurred after the insertion of a tantalum and nitinol s tent, respectively. No recanalization of completely occluded aneurysms or delayed migration of a stent was observed. CONCLUSIONS: Porous, tu bular self-expanding nitinol stents may become the treatment of choice for broad-based and fusiform aneurysms of the internal carotid artery . However, blood flow dynamics of the aneurysms must be studied carefu lly in order to select an appropriate mesh size for complete occlusion while preserving the parent vessel. Improvements in the introducing s ystem, stent material, and stent shape are required for simple implant ation and reduction of intimal hyperplasia.