Cath Lab Digest

Abstract

Objective. We sought to report the successful intracranial placement of the Solitaire FR device (ev3, Inc., Irvine, California), a self-expanding stent-platform-based thrombectomy device that is fully recoverable after deployment, effecting complete recanalization of soft and firm clots in a canine stroke model.

Methods. Soft and firm clots were introduced in the target vessel to occlude the vessels completely in a mongrel dog. The clot was crossed with a SilverSpeed guidewire (ev3) and over the wire with a Rebar microcatheter (ev3). The Solitaire FR was deployed. The Solitaire FR and Rebar microcatheter were removed into the guide catheter while constant slow suction was maintained on the guide catheter. Angiographic runs were performed after deployment and retrieval of the Solitaire FR to assess recanalization, distal emboli, vessel damage, thrombosis and vasospasm.

Results. Successful delivery of the device with immediate thrombolysis in myocardial infarction (TIMI) 3 recanalization after deployment was achieved once in the intracranial anterior spinal artery (1.6 mm) and thrice in the extracranial vertebral artery (2.3–2.7 mm). In the case of the anterior spinal artery and when a soft clot was used in the vertebral artery, a second pass was required for complete clot recovery. No difficulty was encountered with respect to flexibility or maneuverability of the device. The distal markers were visible; the device was able to be reliably deployed and recovered within 2–4 minutes.

Conclusions. Use of this device in the intracranial vasculature of a canine stroke model was technically feasible and associated with a high success rate of recanalization after clot retrieval.

Key words: canine stroke model, clot retrieval, Solitaire™ FR
Revascularization Device, stent platform, thrombectomy device

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Retrievable, Detachable Stent-Platform-Based Thrombectomy Device (Solitaire™ FR) for Acute Stroke Revascularization: First Demonstration of Feasibility in a Canine Stroke Model

Introduction

Reestablishment of flow to perfuse salvageable brain tissues has been shown to significantly reduce the morbidity and mortality of ischemic stroke.^1,2 The Merci^® mechanical clot retriever (Concentric Medical, Mountain View, California) and the Penumbra device (Penumbra, Inc., Alameda, California) are thrombectomy devices that have increased the ability to recanalize acute thromboembolic occlusion in patients with ischemic stroke.^3,4 Self-expanding intracranial stents are being evaluated in this setting and their use has resulted in higher recanalization rates, albeit in small case series.^5–8 Concerns over stent-assisted recanalization are the need for dual antiplatelet therapy and the possibility of late in-stent stenosis. Hauck et al⁹ and Kelly et al¹⁰ reported the use of the Enterprise Stent (Codman Neurovascular, Raynham, Massachusetts) as a temporary endovascular bypass in acute stroke. In both reported cases, the stent was partially deployed for some time and then retrieved, with successful recanalization of the occluded vessel.

The Solitaire™ FR Revascularization Device (ev3, Inc., Irvine, California) (Figure 1) is a recoverable self-expanding thrombectomy device that can also be used as a temporary endovascular bypass. The Solitaire FR was developed as a result of the experience with the Solitaire™ AB Neurovascular Remodeling Device (ev3), which has been used for stent-assisted coiling.^11–13 We report the first successful delivery and recovery of the Solitaire™ FR Revascularization Device in the intracranial and extracranial vessels after the introduction of clots of varying consistencies in a canine stroke model.

Materials and Methods

The Solitaire FR Revascularization Device is packaged in a single unit consisting of the ev3 Solitaire AB stent, an introducer sheath and a detachable push wire. The stent is laser-cut from nickel-titanium alloy (nitinol). It is attached to a nitinol pushwire and has a closed-cell design and a slit along its longitudinal axis throughout its length. The slit allows the two circumferential ends of the stent to overlap when placed in a vessel. The extent of overlap depends on the extent of oversizing. As the deployed device traverses from a small vessel to a large vessel, its cell shape and configuration are retained, and the device unrolls to change the extent of overlap. This unique feature and resulting cell stability allow this device to reliably retain clot while traversing the vessel. The thickness of the stent wall is 50–70 microns, creating minimal intrusion on the lumen of the target vessel. The outer diameter of the stent is small enough to allow delivery through a 0.021- or 0.027-inch inner-diameter microcatheter for its 4 or 6 mm diameter sizes, respectively. It can be used with any appropriate microguidewire. The stent has a radiopaque marker at its proximal end and three or four radiopaque markers on its distal end for its 4 mm or 6 mm diameter sizes, respectively. The radial force per unit length is 0.011 Newtons (N)/mm and is comparable to that of the Wingspan stent (0.012 N/mm).