Filament inadequate wall apposition of the different ends of flow diverters in the abdominal aorta of rabbits

Background Flow diverters (FDs) with flared ends (FEs) or straight ends (SEs) are used either alone or when overlapped to treat complex intracranial aneurysms. We evaluated filament inadequate wall apposition (IWA) of the FEs and SEs of FDs in vivo. Methods A total of 24 FDs with FEs and SEs were placed in an overlapping manner in the abdominal aortae of six rabbits (two sets per rabbit). Digital subtraction angiography was performed immediately after stent insertion and three months later. The anatomical and histopathological aortic features at FEs and SEs were evaluated. Results Angiography revealed no significant difference in terms of changes in arterial diameter between the FE and SE groups ( p = 0.877). Gross anatomical evaluation revealed IWA of the different ends of FDs but no thrombi or bleeding, showing that the metallic filaments were not in touch with the vessel wall and nor had they penetrated the vessel wall. The filaments’ IWA rates of FEs and SEs were 8.33% and 8.85%, respectively. The IWA rate at overlapping ends was lower than that at non-overlapping ends. The maximum neo-intimal thickness at FEs was greater than that at SEs (149.4 ± 48.9 and 98.6 ± 26.6 µm, respectively; p < 0.001). Conclusions Both the FEs and SEs of FDs can exhibit IMA. IWA events are reduced at the overlapped regions. On pathological evaluation, FEs increased neo-intimal thicknesses more than SEs did, but hyperplasia was minimal on angiography.