Elsevier

World Neurosurgery

Volume 82, Issue 6, December 2014, Pages 1120-1126
World Neurosurgery

Peer-Review Report
Flow Diversion of Giant Curved Sidewall and Bifurcation Experimental Aneurysms with Very-Low-Porosity Devices

https://doi.org/10.1016/j.wneu.2013.09.036Get rights and content

Objective

Flow diverters (FDs) are increasingly used to treat difficult intracranial aneurysms. The objective of this study was to test whether treatment challenges posed by giant curved sidewall (cSW) and endwall bifurcation (EwB) aneurysms can be overcome with the use of very-low-porosity devices.

Methods

Large and giant EwB (n = 12) and cSW aneurysms (n = 5) were constructed in 17 dogs. EwB aneurysms were treated with 48 (n = 4), 64 (n = 4), or two overlapping 64-wire low-porosity devices (n = 4), whereas all cSW aneurysms were treated with single 64-wire devices. Angiographic results were recorded immediately and at 12 weeks before euthanasia. Pathologic specimens were photographed and neointimal coverage of devices measured and scored.

Results

By 12 weeks, 1 of 12 EwB and 1 of 5 cSW aneurysms were occluded. All other aneurysms were patent. Device-related arterial stenoses occurred in 13 of 17 animals, hemodynamically significant in two. All branches jailed by the FDs remained patent. There was a significant correlation between angiographic scores and the degree of neointima formation on the device (Rho = 0.527; P = 0.04). Failures of aneurysm occlusion could be explained by holes, sometimes barely visible, in the neointima that formed over FDs.

Conclusion

Low-porosity FDs fail to reliably occlude experimental giant EwB and cSW aneurysms.

Introduction

Flow diverters (FDs) are increasingly used to treat large or giant aneurysms, and more recently, bifurcation aneurysms 2, 12. The optimal device porosity and pore density that will successfully occlude all aneurysms while sparing jailed branches, if it exists, remains unknown. Optimal FD characteristics may vary from one case to another, depending on aneurysm size, type, and flow patterns.

Previous studies in a modular carotid aneurysm model have shown that FDs made from 36 braided wires are capable of occluding straight lateral wall aneurysms but fail when implanted across curved sidewall or bifurcation aneurysms (4). Increasing the number of metallic filaments (from 36 to 48 and 64 wires), thus increasing pore density and decreasing pore size and porosity, or multiplying devices (2 × 64-wire FDs) in an overlapping fashion could, at least in theory, overcome the challenges posed by such difficult aneurysms. The present work explored devices of decreasing porosity and increasing pore density in the treatment of challenging giant curved sidewall (cSW) and endwall bifurcation (EwB) aneurysm models. Our hypotheses were that (1) decreasing FD porosity would lead to occlusion of cSW aneurysms and; (2) the EwB aneurysms could not successfully be occluded with FDs without jeopardizing the branch jailed by the device. Experimental results did not confirm our hypotheses: low porosity-flow diversion could not achieve reliable occlusion of these difficult aneurysms, no matter what device or combination of devices was used.

Section snippets

In Vitro Studies

The 2 FDs that were used (48- and 64-wire braided devices) are stent-in-stent constructions made of an outer high-porosity stent (LVIS; Microvention Inc., Tustin, California, USA) and an inner low-porosity FD made of either 48 or 64 braided wires. FDs were placed into 3.5-mm diameter straight glass tubes, magnified, and photographed with an overlaid 1 × 1 mm2 reference square. The square area occupied by the metal struts within the reference square was subtracted from the total square area

In Vitro

The measured porosity and pore density for the 48 wire devices in 3.5-mm straight glass tubes were 70.3 ± 2.8%, 8.2 ± 2.2 pores/mm2, and 66.0 ± 2.6%, 10.2 ± 2.9 pores/mm2 for the 64-wire device. In the 90-degree curved 3.5-mm glass tubes, the porosity and pore density were 71.3 ± 3.2%, 6.9 ± 3.1 pores/mm2, and 69.0 ± 3.4%, 7.3 ± 2.8 pores/mm2 for the 48 and 64-wire devices, respectively. In vitro measurement of porosity and pore density for the double overlapping 64-wire devices was not

Discussion

The main finding of this work is that increasing the metal content of FDs (from 48- to 64-wire and then to double overlapping 64-wire devices) remained insufficient to reliably cause giant EwB aneurysm occlusion. Low-porosity FDs (64 wires) were also insufficient to occlude giant cSW aneurysms. Angiography at 3 months in most cases showed widely patent aneurysms; microscopic photography consistently revealed apertures through the neointima covering the devices, permitting blood flow to keep

Conclusions

FDs of low nominal porosity were not able to reliably occlude large and giant canine cSW or EwB aneurysms.

References (13)

  • F. Bing et al.

    Stents and flow-diverters in the treatment of aneurysms: device deformation in vivo and impact on porosity

    Neuroradiology

    (2013)
  • Byrne JV, Szikora I: Flow diverters in the management of intracranial aneurysms: a review. EJMINT 2012:1225000057 (22nd...
  • T.E. Darsaut et al.

    Flow diversion to treat aneurysms: the free segment of stent

    J Neurointerv Surg

    (2013)
  • T.E. Darsaut et al.

    Flow diverters fail to occlude experimental bifurcation or curved side-wall aneurysms: an in vivo study in canines

    J Neurosurg

    (2012)
  • T.E. Darsaut et al.

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

    AJNR Am J Neuroradiol

    (2012)
  • D.F. Kallmes et al.

    A new endoluminal, flow-disrupting device for treatment of saccular aneurysms

    Stroke

    (2007)
There are more references available in the full text version of this article.

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Conflict of interest statement: This work was supported by a grant from the Heart and Stroke Foundation of Alberta to T.E.D. and by a grant from Le Fonds de Recherche du Québec - Santé (FRQS) to J.R.

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