Toward Better Understanding of Flow Diversion in Bifurcation Aneurysms

Abstract

BACKGROUND AND PURPOSE:Flow diversion is being increasingly used to treat bifurcation aneurysms. Empiric approaches have generally led to encouraging results, and a growing body of animal and ex vivo literature addresses the fate of target aneurysms and covered branches. Our prior investigations highlighted the dynamic nature of metal coverage provided by the Pipeline Embolization Device and suggested strategies for creating optimal single and multidevice constructs. We now address the geometric and hemodynamic aspects of jailing branch vessels and neighboring target aneurysms. MATERIALS AND METHODS:Fundamental electric and fluid dynamics principles were applied to generate equations describing the relationships between changes in flow and the degree of vessel coverage in settings of variable collateral support to the jailed territory. Given the high complexity of baseline and posttreatment fluid dynamics, in vivo, we studied a simplified hypothetic system with minimum assumptions to generate the most conservative outcomes. RESULTS:In the acute setting, Pipeline Embolization Devices modify flow in covered branches, principally dependent on the amount of coverage, the efficiency of collateral support, and intrinsic resistance of the covered parenchymal territory. Up to 30% metal coverage of any branch territory is very likely to be well-tolerated regardless of device or artery size or the availability of immediate collateral support, provided, however, that no acute thrombus forms to further reduce jailed territory perfusion. CONCLUSIONS:Basic hemodynamic principles support the safety of branch coverage during aneurysm treatment with the Pipeline Embolization Device. Rational strategies to build bifurcation constructs are feasible. ABBREVIATIONS: FD ϭ flow diverter; PcomA ϭ posterior communicating artery; PED ϭ Pipeline Embolization Device

Expanding Indications for Flow Diverters: Distal Aneurysms, Bifurcation Aneurysms, Small Aneurysms, Previously Coiled Aneurysms and Clipped Aneurysms, and Carotid Cavernous Fistulas

“…18,19,22,29,30 This observation has been confirmed by experimental models showing that patency or occlusion of the jailed bifurcation branches may be predicted on the basis of collateral circulation. 31 In addition, the effect of flow diversion also depends on the local stent porosity that is influenced by the stent sizing: undersized stents are associated with a shorter deployment, more condensed pores, and higher mesh density, resulting in increased risks of side branch occlusion. 32 Interestingly, the fate of the bifurcation branches coming from the aneurysms may also influence the aneurysm occlusion, as the jailed vessel may maintain the flow towards the aneurysm.…”

Vertebral artery dissection and associated ruptured intracranial pseudoaneurysm successfully treated with coil assisted flow diversion

“…[ 37 ] Management of perforators and the brainstem vasculature is of considerable concern, as occlusion may result in devastating neurologic deficits. [ 7 8 9 12 20 35 39 ]…”

“…[ 40 ] The overall high rate of aneurysm occlusion, long-term durability, and excellent safety profile has driven its application to the management of challenging off-label lesions. [ 7 8 9 12 20 35 39 ] The scaffolding properties that promote endothelialization and vessel reconstruction lend to its utility in treating pathology of the vessel wall. [ 7 8 9 ] Due to the DAPT requirement, significant controversy continues to exist pertaining to the use of stent-assisted coil (SAC) embolization and FD technology in the setting of acute aSAH.…”

Complex Wide-necked and Lobulated Aneurysm of the Middle Cerebral Artery Bifurcation

“…Flow diversion is being increasingly used to treat bifurcation aneurysms. In cases of MCA bifurcation aneurysms, FD treatment is feasible with good angiographic results and acceptable complication rates; however, compared to the results of other endovascular techniques and to surgery, total occlusion seems to be less frequent [ 3 , 19 , 20 ]. Most of these new tools available on the market target the temporary or permanent reconstruction of the aneurysmal neck [ 21 , 22 ], the parent artery or both but in certain scenarios, alternative or combination techniques are mandatory to secure the patency of the incorporated branches and deal with the troublesome anatomy.…”