Long-Term Angiographic and Histological Results of a New Hydrogel-Containing Filling Coil in Experimental Rabbit Aneurysms

Background: The aim of this study was to compare the performance of a new filling coil, the HydroFill device, to historical results of HydroSoft and bare platinum coil devices in experimental rabbit aneurysms. Methods: Experimental aneurysms were constructed in rabbits and embolized with HydroFill (n = 32), HydroSoft (n = 48), or bare platinum coil (n = 47) devices. Angiographic occlusion was evaluated post-treatment and at 1 month (n = 55), 3 month (n = 20), 6 month (n = 35), and 12 month (n = 12) follow-ups according to the Raymond scale. The aneurysms were analyzed histologically for neointima formation, thrombus organization, and inflammation. Continuous and discrete results were compared using ANOVA/t-test and chi(2) tests, respectively. Results: Volumetric occlusion of the aneurysm sac was increased in the HydroFill group compared to the HydroSoft and platinum coil groups. Protrusions into the parent artery were common in all treatment groups due to the treatment of wide-necked aneurysms without the use of balloons or stents. Although angiographic occlusion post-treatment scores were reduced in the HydroFill group compared to the HydroSoft and platinum coil groups, stable/progressive occlusion was increased in the HydroFill group compared to the platinum coil group. Histologically, neointima formation and thrombus organization scores were increased in the HydroFill and HydroSoft groups compared to the platinum coil group at 3 months. Although there were some differences in the scoring, inflammation was generally minimal to mild in all three groups. Conclusion: The HydroFill device, with its high levels of volumetric filling, increased stable/progressive occlusion at follow-up, increased neointima formation, and increased thrombus organization, shows promise for clinical use.