Flow diverters failing to occlude experimental bifurcation or curved sidewall aneurysms: an in vivo study in canines

Object Flow diverters (FDs) are increasingly used to treat complex intracranial aneurysms, but preclinical studies that could guide clinical applications are lacking. The authors designed a modular aneurysm model in canines to address this problem. Methods Three variants of one modular aneurysm model were constructed in 21 animals. Sidewall (n = 5), curved sidewall (n = 5), and end-wall bifurcation (n = 7) aneurysms were treated with prototype 36-wire FDs. Four more end-wall bifurcation aneurysms were treated with prototype 48-wire lower-porosity FDs. Angiographic results postimplantation and at 3 months were scored with an ordinal scale. Animals were euthanized at 3 (n = 17) or 6 (n = 3) months, and the FD covering the aneurysm ostium was photographed to analyze metallic porosity and amount of neointima formation. Results Straight sidewall aneurysms were better occluded than curved sidewall and end-wall bifurcation aneurysms at the 3-month angiography follow-up (p = 0.010). Flow diverters failed to occlude curved sidewall aneurysms (n = 0/5) and all but one (n = 1/7) end-wall bifurcation aneurysm. Angiographic results were no better (n = 0/4) using a 48-wire FD (p = 0.788). Branches jailed by the FD (n = 16) remained patent in all cases. Metallic porosity was decreased (p = 0.014) and neointimal closure of the aneurysm ostium was more complete (p = 0.040) in sidewall aneurysms than in curved or bifurcation variants of the model. Conclusions Flow diverters may succeed in treating straight sidewall aneurysms, but the same device repeatedly fails to occlude curved sidewall and end-wall bifurcation aneurysms. In vivo studies can be designed to test basic principles that, once validated, may serve to guide clinical use of new devices.