Pathology of Stented Common Carotid Aneurysm in Dogs. Comparison between Stenting and Stent-Assisted Coiling

To elucidate focal successive histological responses of the neck of wide-necked aneurysm after single stent implantation and stent-assisted coiling, an experimental wide-necked aneurysm model was surgically created in bilateral common carotid arteries of adult dogs. Balloon-expandable porous stents were positioned across the aneurysm necks on both sides. The aneurysm cavity of one side was additionally loosely coiled with Gugliemi detachable coils after stent implantation. The dogs were followed up with ultrasonography and angiography, then sacrificed at two days, one month, and one year and the aneurysm specimen was subjected to macro, micro, and electron microscopic observation. Stent implantation and coiling was successful in eight dogs. This investigation observed that single stent implantation slowed down the blood flow within the aneurysm, but barely induced thrombosis within the aneurysm. There was neointima formation over the stent mesh without thrombus within the aneurysm cavity, but it did not cover the whole aneurysm neck at one year.Aneurysms treated with stent-assisted coiling showed thrombosis within the aneurysms and neointima formation over the whole aneurysm orifice. These results suggest that the neointima could develop over bare stent filament without thrombus within the aneurysm cavity, coils could enhance thrombosis within the aneurysm cavity and facilitate neointima formation over the aneurysm orifice. Stent-assisted coiling may be an alternative option for the treatment of wide-necked aneurysms.