Intra-aneurysmal flow reductions in a thin film nitinol flow diverter

Abstract

A novel hyper-elastic thin film nitinol (HE-TFN) covered stent has been developed topromote aneurysm occlusion by diminishing flow in the aneurysm. Laboratory aneurysmmodels were used to assess the flow changes produced by stents covered with differentpatterns of HE-TFN placed across the aneurysm neck in the parent vessel. The flowdiverters were constructed by covering Wingspan stents (Boston Scientific) withdifferent HE-TFNs (i.e., of 82% and 77% porosity) and deployed in both in vitrowide-neck and fusiform glass aneurysm models. In wide-neck aneurysms, the 82%porous HE-TFN stent reduced mean flow velocity in the middle of the sac by86 ± 1%, while the 77% porous stent reduced the velocity by93 ± 5% (n = 3). Local wall shear rates were also significantly reduced by about 98%in this model after device placement. Tests conducted on the fusiformaneurysm revealed smaller intra-aneurysmal flow velocity reduction by48 ± 3% for the 82% porousstent and by 59 ± 7% for the 77% porous stent. The wall shear was reduced by approximately 50% by HE-TFNstents in fusiform models. These results suggest that HE-TFN covered stents have thepotential to promote thrombosis in both wide-neck and fusiform aneurysm sacs.