A Comparison of 2 Stroke Devices: The New Aperio Clot-Removal Device and the Solitaire AB/FR

Revascularization Devices

The Solitaire AB/FR device is a laser-cut self-expanding split-design closed-cell nitinol stent device. It is available with a diameter of 4 mm (length, 15 or 20 mm) or 6 mm (length, 20 or 30 mm) and is delivered through a 0.021- or 0.027-inch microcatheter.

The Aperio is a self-expanding nitinol laser-cut stentlike thrombectomy device. It contains 3 distal device markers to indicate device expansion (Fig 1B, gray arrow) as well as a proximal and distal wire marker (Fig 1B, white and black arrows). The device has a hybrid design with a mixture of closed and partially open cells. The small closed cells (Fig 1A, small black circle) are supposed to optimize vessel adaption; the wider hybrid cells, clot-catching cells (Fig 1A, large black circle), contain an anchoring element for optimal clot fixation in tortuous vessels. It is available with a diameter of 4.5 mm and a length of 40 mm for the treatment of vessels ranging from 2 to 4 mm. It is bundled with the 0.027-inch Acandis microcatheter, which has a length of 1550 mm and is compatible with 0.010- to 0.014-inch guidewires and 6F guiding catheters.

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Fig 1.

A, The small circle shows the smaller closed cells with a diameter of 1.7 mm; the larger circle illustrates the larger hybrid (clot-catching) cells for better thrombus fixation in tortuous vessel segments (3.7 mm). B, The Aperio device in its unfolded state. The white and black arrows mark the distal and proximal radiopaque wire markers; the gray arrow shows the radiopaque markers at the end of the device, indicating complete device unfolding.

Animal Care

All procedures were conducted according to international guidelines. Eight swine ranging from 35 to 50 kg were used in this study. Each animal had free access to food and water until the morning of the angiography.

Sedation was induced by a mixture of ketamine (KetaVet, 30 mg/kg) and xylazine (TranquiVed, 2.5 mg/kg) and atropine (0.05 mg/kg). Endotracheal intubation was performed. General anesthesia was maintained by IV infusion of thiopental (Trapanal, 2.6-g/100 mL sodium chloride solution, 15–20 mL/hr). After the swine was put under general anesthesia, the femoral artery and vein were exposed surgically and an 8F sheath (Avanti+ Introducer, Cordis, Bridgewater, New Jersey) and a 4F (Cordis) sheath, respectively, were introduced into the vessels. As a guiding catheter, an 8F balloon catheter (Merci; Concentric Medical, Mountain View, California) was used. The procedures were performed with the swine under systemic heparinization.

Vital parameters such as arterial blood pressure, heart rate, and expired oxygen and carbon dioxide levels were continuously recorded. The expired oxygen levels were kept at 30% of the expired vol. After the experiments, the animals were euthanized with an IV injection of pentobarbital.

Angiography

Selective intra-arterial DSA was performed on a high-resolution angiographic system (Ziehm Vision imaging, Nuremberg, Germany); Ultravist-370 (iopromide; Bayer Schering Pharma, Berlin, Germany) was used for vessel contrast. Selective occlusion of vessels in the subclavian or carotid vasculature within a 2- to 4-mm size range was performed. These vessel regions simulate the anatomic setting of an occlusion of the MCA and the basilar artery in the human circulation. The guiding catheter was pulled back into a larger vessel segment to restore arterial flow. The occluded vessel segment was then navigated with a 0.21-inch microcatheter (Rebar 18, ev3) for the deployment of the Solitaire device or with the microcatheter that comes with the Aperio device, both in combination with a 0.014-inch microwire (Traxcess; MicroVention, Aliso Viejo, California).

Preparation of the Experimental Thrombi

The thrombi used for the trial were prepared with a modified method of the Chandler loop,^15,16 with the help of a dynamic clot-generating system (Thrombus Loop, Acandis). A polyvinyl chloride tubing with an inner diameter of 5 mm and a length of 50 cm was filled with 3 mL of blood from the corresponding swine for the trial. For better fluoroscopic visibility, the blood was mixed with 300 mg of BaSo₄ /12 mL of blood. The tubing rotated at a rate of 20 rpm in a water basin at 37°C. After 15 minutes, the thrombi were drained and rinsed with physiologic saline solution and stored in a basin with the same solution at room temperature for 60 minutes.

Thrombus Application

After cutting the thrombi in lengths of 10 mm, we injected the thrombi, with help of polytetrafluoroethylene tubing (4-mm inner diameter) with a 20-mL syringe, both filled with physiologic saline solution to avoid air embolism, via a long 6F sheath (Strada; St Jude Medical, St Paul, Minnesota) into the target vessel.

Mechanical Thrombectomy

An 8F balloon catheter (Merci) was advanced into the proximal subclavian artery and the proximal common carotid artery, respectively. The target vessel occlusion was verified angiographically and rated with the help of the TICI scale.¹⁷ The thrombus was passed with a microcatheter (3F Microcatheter, Acandis; Rebar, ev3) with a 0.014-inch microwire (Traxcess; SilverSpeed, ev3). After placement of the microcatheter distal to the thrombus, verified by intra-arterial contrast medium injection, we advanced the device through the microcatheter and placed it with the proximal third within the thrombus. A control angiogram was obtained after successful unfolding of the device to evaluate re-establishment of flow and again after 3 and 5 minutes. Then the balloon at the tip of the guiding catheter was inflated, and the device was pulled back in its unleashed state under continuous aspiration with a 50-mL syringe together with the microcatheter into the guiding sheath. After removal of the device and the microcatheter, another 50 mL was aspirated from the guiding sheath to prevent re-embolization of a possibly lost clot. If the following control angiogram showed a TICI score lower than 2, the procedure was repeated until a TICI score of 2 or 3 was achieved.

Measurement of Outcome

The time to recanalization, the number of attempts to reach recanalization, device deployment, and the rate of device-related complications were recorded. For device-related complications, we noted vasospasm, vascular perforation, intramural arterial dissection, or embolization of a previously uninvolved territory.

The DSAs were analyzed by 2 experienced neuroradiologists (M.S. and W.R.), who were blinded to the devices used, on a MacPro workstation (Apple, Bothell, Washington) running OsiriX 3.8.1 open-source DICOM software (Pixmeo, Geneva, Switzerland). The angiograms were carefully read for any sign of postinterventional vasospasm, dissection, or vessel perforation. The evaluation of embolization of previously uninvolved vessel territories during the retrieval attempt was done by reading the unsubtracted images for radiopaque clot as well as reading the subtracted images for newly occluded branches.