Assessment of Matrix coils in a canine model of a large bifurcation aneurysm

Introduction Controversy exists as to whether Matrix coils are an improvement over bare platinum coils in preventing aneurysm recanalization in endosaccularly coiled large aneurysms. We investigated Matrix coils in a dog model of a wide-necked large bifurcation aneurysm. Methods Six experimental aneurysms were created in dogs and these aneurysms were endosaccularly coiled with 100% Matrix coils. Angiographic and histopathological data were analyzed at 2 weeks and at 3 months. Results Average aneurysm dimensions were length 17.8 mm, width 8.3 mm, and neck 6.2 mm. Aneurysm coil filling ranged 24.1 - 41.8% by volume. At 14 days, three of six Matrix-treated aneurysms showed coil compaction and aneurysm recanalization. At 3 months, one additional Matrix-treated aneurysm showed delayed coil compaction and aneurysm recanalization. At 3 months, in three harvested aneurysms, the average measured neck neointima was 0.150 +/- 0.14 mm. However, in two of the three aneurysms harvested at 3 months, aneurysm recanalization had occurred with neointimal tissue not completely covering the aneurysm orifice. Thick connective fibrous intercoil tissue was observed. No immediate or delayed thrombus formation had occurred. Conclusion Based on limited data in an experimental bifurcation aneurysm in dogs, Matrix coils appear to induce a thicker aneurysm neck neointima tissue and intercoil granulation response but appear prone to coil compaction and aneurysm recanalization. Modifications to the Matrix coil are likely needed to improve angiographic results in large aneurysms.