Histologic evaluation of platinum coil embolization in an aneurysm model in rabbits

PURPOSE: To characterize the histologic response to platinum coil embolizat ion by using a rabbit aneurysm model. MATERIALS AND METHODS: Saccular aneurysms were created in New Zealand White rabbits by using vessel ligation with intraluminal elastase incubation. An eurysms were subsequently embolized by using platinum coils. Subjects were sacrificed at various intervals up to 12 weeks following coil embolization. The aneurysm cavities and adjacent vessels were embedded in methylmethacry late, were sectioned, and were stained for histologic examination. RESULTS: Two weeks following coil implantation, aneurysms were filled predo minantly with unorganized thrombus. Six weeks following coil implantation, histologic features included complete filling of the aneurysm lumen with ei ther prominent laminated but unorganized thrombus or areas of unorganized t hrombus interspersed among areas of cellular infiltration. At 12 weeks foll owing coil implantation, aneurysms were filled with the loosely packed, dis ordered cells contained within the extracellular matrix. Fibrosis or smooth muscle cell infiltration was not present in any of the 6- or 12-week sampl es. CONCLUSION: Platinum coils placed into experimental saccular aneurysms in N ew Zealand White rabbits failed to elicit a fibrotic response. This model c an be used for the testing of biologic modifications of platinum coils aime d at increasing intraaneurysmal fibrosis.