Introduction

The Solitaire stent (ev3, Irvine, CA, USA) is a self-expanding, electrically detachable stent for cerebral vessels. It is retrievable even after complete deployment, if not detached3,4,6. Recently, we used this device for mechanical thrombectomies in patients with acute strokes due to embolic occlusions of the middle cerebral artery (MCA). In this article, we describe our experience with the Solitaire stent system in revascularization after acute stroke in two patients.

Illustrative cases

Case 1

An 81-year-old male presented with sudden onset right-side hemiparesis and a drowsy mental status within a 2 h window. The patient? initial National Institutes of Health Stroke Score (NIHSS) was 22. Diffusion magnetic resonance imaging (MRI) revealed an acute infarction in the left insular and superior parietal cortex. Perfusion MRI showed a perfusion decrease in the territory of the left MCA and a MR angiogram demonstrated complete occlusion of the mid M1 segment of the left MCA. The patient was diagnosed with acute ischemic stroke (AIS) due to a large artery occlusion, and so we performed an emergency intra-arterial thrombolysis (IAT). An angiogram showed occlusion of the mid M1(Fig. 1A). A microcatheter was advanced to the thrombus under the guidance of a microwire. A Solitaire stent was deployed over the whole length of the thrombus and then withdrawn with a microcatheter. The whole thrombus was captured by the stent(Fig. 1B). Complete recanalization of thrombolysis in cerebral infarction (TICI) grade 3 was achieved(Fig. 1C). There were no distal emboli. The procedural time was 17 min from femoral puncture to recanalization. The immediate post-procedural NIHSS improved to 17.

Case 2

A 78-year-old male patient presented with the clinical signs of an awakening stroke. The initial NIHSS was 24. Diffusion MRI showed an acute infarction in the left basal ganglia and the corona radiata. A MR angiogram demonstrated complete occlusion of the proximal M1 segment of the left MCA. There was a large diffusion-perfusion mismatch and so an emergency IAT was performed. A basal angiogram showed occlusion of the proximal M1(Fig. 2A). A microcatheter was advanced to the thrombus under the guidance of a microwire. A Solitaire stent was deployed over the whole length of the thrombus (Fig. 2B). Temporary reperfusion flow was observed on a manual angiogram(Fig. 2C). The stent was then withdrawn with a microcatheter through a guiding catheter outside of the body. The whole thrombus was captured by the stent (Fig. 2D). Complete recanalization of TICI grade 3 was achieved(Fig. 2E). No emboli were visible on the final angiogram. The procedural time was 30 min from femoral puncture to recanalization. The immediate post-procedural NIHSS improved to 19.

IAT criteria and common technical details of the two cases

The indications for IAT were: 1) large cerebral artery occlusion, 2) 3-8 h time window, 3) no intracranial hemorrhage, 4) perfusion-diffusion mismatch on MRI, 5) initial NIHSS ≥ 4, and 6) no response to intravenous tissue plasminogen activator (IVtPA), if indicated.

Endovascular procedures were performed through a femoral artery under local anesthesia. A biplane angiography unit (Integris Allura 12/12; Philips, Netherlands) was used. No heparin was given during the procedure except for a heparinized saline solution that was continuously perfused through the catheter. After placing the femoral sheath, a diagnostic cerebral angiography was performed to visualize the occlusion site and the collateral channels. A 9Fr balloon-guiding catheter was then introduced. The occluding clot extent was visualized by selective angiography using a microcatheter (Excelsior 10; Boston Scientific, Natick, MA, USA). In our cases, a Prowler Select Plus microcatheter (Cordis, Bridgewater, NJ, USA) was used as the delivery catheter of the Solitaire stent. The stent was advanced and fully deployed a few millimeters distal to the clot. In our cases, the clot length was shorter than the stent length (20 mm), and so the stent covered the whole clot. Immediate flow restoration after stent deployment was observed even though the procedure was not complete. The stent was kept deployed for 2 or 3 min before retrieval. The microcatheter and the stent were then withdrawn slowly while the balloon of the guiding catheter was inflated in order to block anterograde ICA flow. To further reduce the chance of distal migration of the captured thrombi, we applied negative pressure through the guiding catheter using an aspiration gun device that held a 50 cc syringe with a locking system.

Discussion

Mechanical thrombolysis has been the actively preferred method of thrombolysis because of limitations with pharmacological thrombolysis.2)5)11)15) Various mechanical devices have been introduced, including wires, coils, balloons, and capture or aspiration devices. In the case of AIS patients with large artery occlusions, theoretically and practically, removing the occluding thrombi from the cerebral arteries by methods that involve aspiration or capture of the thrombi are the best ways to treat acute stroke, since these methods reduce the thrombi burden directly and rapidly. In contrast, fibrinolytic drugs require a long time and are often ineffective.

In this report, we present a new thrombectomy technique using the Solitaire stent. Above all, the technique was simple regarding the technical aspects and rapid in the completion of effective recanalization. The time for recanalization was very short: 17 min for one patient and 30 min for the other patient. The initial flow restoration time, if partial reopening was included, was shorter as it occurred immediately with stent opening. In large artery occlusion cases, the impact of timely reperfusion is very critical for brain survival.7-8)14) The ability to restore flow immediately, even though it may only be temporary, is a great advantage.3) In addition, in a published study and in our report, it was shown that the procedural time from groin puncture to recanalization was short, even with the temporary reperfusion.3)15) We suggest that the speed and simplicity of the present technique may make thrombolytic procedures easier. In addition, in this system, we believe the use of a microcatheter as a guide for the Solitaire stent allows easier navigation and safer manipulation because of its flexibility, and may reduce the chance of a thrombolysis failure in difficult cases such as elderly patients with tortuous vessels.10) Unlike other self-expandable stents such as the Enterprise stent (Cordis), which has retrieval limitations, the Solitaire stent can always be retrieved if it is not detached, allowing the opportunity to try other thrombolytic procedures if necessary and reducing stent-related complications such as in-stent thrombosis. Although suction thrombectomy has been used to aspirate or capture the thrombus in AIS patients, this method is sometimes not suitable for thrombi at the carotid siphon and in the small or tortuous proximal MCA because of decreased transmission of the negative pressure from the proximal to the distal tip caused by vessel curvature, long distance to the occlusion site, and/or the use of small caliber aspiration catheters. On the other hand, in the above situation, the technique using the Solitaire stent was performed well because the thrombus was captured through the strut of the stent and not by negative pressure. However, this method has limitations in covering the whole thrombus due to the limitation of the stent length (15 or 20 mm).

Another advantage of this technique is that there is little chance of intra-arterial chemical thrombolysis. To the best of our knowledge, IAtPA has been used in just two of the 20 total cases in the published literature for this technique to date.3) This technique was performed as a rescue and adjuvant therapy after IAtPA was used in the two cases. In the present two cases, an intra-arterial chemical agent was not used. The less a chemical agent is used in thrombolysis, the less intracranial hemorrhage occurs,12)18)19) and post-operative symptomatic hemorrhages very much affect the clinical outcome in AIS patients.9)17) Like other mechanical thrombectomy techniques, one of the problems to consider is fragmentation of the thrombi and distal migration. Thrombi at distal vessels are difficult to open in many cases. We used a balloon-guiding catheter and applied negative suction pressure through the guiding catheter by using an aspiration gun device. These procedures in our technique are thought to reduce migration of the fragmented thrombus.13)16)

The next steps following this report trial are to collect more data, follow patients longer, conduct a multi-institute study, and conduct a prospective study to assess the feasibility, safety, and effectiveness of this technique. Nevertheless, we suggest that this technique may have potential as a novel technique that may produce better clinical outcomes for AIS patients with large artery occlusions based on its many advantages and the similar results of another published study.3)

References

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