Flow diverters can occlude aneurysms and preserve arterial branches: a new experimental model

Abstract

Background and purpose: FDs are new intracranial stents designed to occlude aneurysms while preserving flow to jailed arterial branches. We tested this fundamental principle in a new aneurysm model.

Materials and methods: Canine lateral wall aneurysms, featuring a branch located immediately opposite the aneurysm, were created in 16 animals to study the effects on aneurysm or branch occlusion using single HP stents (n = 4), 2 overlapping HP stents (n = 4), or an FD (n = 8). Two other animals, in which an efferent arterial branch was anastomosed to the aneurysm fundus, were also treated with FDs. Angiographic results after deployment, at 2 weeks, and at 3 months were scored using an ordinal scale. The metal porosity of the FSS and the amount of FSS neointima formation was determined by postmortem photography.

Results: FDs led to better angiographic occlusion scores compared with HP stents (P = .026). FDs were significantly more likely to occlude the aneurysm than the branch (P = .01). When the branch was switched to originate from the aneurysm fundus, the FDs became ineffective (0/2). Neointimal closure of the aneurysm ostium was significantly better with FDs than with single or double HP stents (P = .039). Angiographic occlusion correlated with metallic porosity and neointimal tissue coverage (Spearman ρ = -0.81; P = .001).

Conclusions: In this study, flow diverters occluded lateral wall aneurysms more readily than branches. Metal device porosity strongly influenced the occlusion rate.

Fig 1.

A, Experimental canine model featuring a branch immediately opposite a lateral wall aneurysm, allowing the direct comparison of aneurysm with branch occlusion rates. B, Variant of model, where efferent branch is anastomosed to aneurysm fundus to test the effect of arterial flow patterns on aneurysm occlusion.

Fig 2.

Macroscopic en-face photography of aneurysm (A1) and branch ostium (A2), 3 months after treatment with FD stent compared with aneurysm (B1) and branch ostium (B2) of animals treated with double overlapping HP stents. Angiographic branch patency was maintained in all cases, despite a substantial amount of neointimal coverage of the branch orifice.

Fig 3.

Three-month angiographic and pathologic comparison of flow diverter treatment with (A) lateral wall aneurysm and (B) lateral wall aneurysm with efferent branch flow from the aneurysm fundus. Note complete occlusion of aneurysm (A1) with full neointimal closure of the FSS (A2). When an arterial outflow is present, the aneurysm remains patent (B1) with incomplete neointimal closure or leaks (B2, arrow) in the FSS.

Fig 4.

Comparison of pathologic outcomes after aneurysm treatment with (A) a single HP stent, (B) double overlapping HP stents, or (C) an FD stent, showing increasing neointima formation with decreasing porosity.