Comparison of shape memory polymer foam versus bare metal coil treatments in an in vivo porcine sidewall aneurysm model

Abstract

The endovascular delivery of platinum alloy bare metal coils has been widely adapted to treat intracranial aneurysms. Despite the widespread clinical use of this technique, numerous suboptimal outcomes are possible. These may include chronic inflammation, low volume filling, coil compaction, and recanalization, all of which can lead to aneurysm recurrence, need for retreatment, and/or potential rupture. This study evaluates a treatment alternative in which polyurethane shape memory polymer (SMP) foam is used as an embolic aneurysm filler. The performance of this treatment method was compared to that of bare metal coils in a head-to-head in vivo study utilizing a porcine vein pouch aneurysm model. After 90 and 180 days post-treatment, gross and histological observations were used to assess aneurysm healing. At 90 days, the foam-treated aneurysms were at an advanced stage of healing compared to the coil-treated aneurysms and showed no signs of chronic inflammation. At 180 days, the foam-treated aneurysms exhibited an 89-93% reduction in cross-sectional area; whereas coiled aneurysms displayed an 18-34% area reduction. The superior healing in the foam-treated aneurysms at earlier stages suggests that SMP foam may be a viable alternative to current treatment methods. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1892-1905, 2017.

Shape memory polyurethane‐urea foams with improved toughness

“…SMPs are materials that have the ability to transition between a primary and secondary shape after application of an external stimulus, such as heat . The new SMP‐based aneurysm occlusion device comprises a SMP foam crimped over a nickel‐titanium (nitinol) and platinum wire backbone . These devices are delivered in their low‐profile secondary, crimped shape to the aneurysm via a micro‐catheter, after which they expand in response to heating at body temperature to space‐fill the aneurysm.…”

“…These devices are delivered in their low‐profile secondary, crimped shape to the aneurysm via a micro‐catheter, after which they expand in response to heating at body temperature to space‐fill the aneurysm. SMP‐coated coils show rapid clotting, improved volumetric filling, and superior healing in comparison to bare metal coils …”

Particulate Release From Nanoparticle-Loaded Shape Memory Polymer Foams

“…In comparison to alloy-based embolization devices, which are the most comparable existing devices, SMP foams promote significantly improved clotting and healing [27]. Additionally, their unique shape memory properties enable their catheter delivery through tortuous vasculature to the desired treatment site, where they expand to fill the site and promote clotting.…”

In vitro performance of a shape memory polymer foam-coated coil embolization device

“…[12, 13] SMP foams have been reported with increased angiographic occlusion, more advanced healing marked by mature connective tissue, and a thicker neointima layer compared to bare metal coils in porcine saccular aneurysm models. [9, 10] Though both SMP foams and hydrogels exhibit volume-filling capability, SMP foams exhibit interconnected pores with diameters in the hundreds of microns, compared to hydrogel pore sizes less than 10 µm in diameter. [12, 14] This interconnected porosity of the SMP foams acts as a scaffold for blood flow, thrombus formation, and tissue healing throughout the material volume.…”

“…[12, 14] This interconnected porosity of the SMP foams acts as a scaffold for blood flow, thrombus formation, and tissue healing throughout the material volume. [9, 10]…”