The Solitaire (Medtronic Inc, Mansfield, Massachusetts, USA) is a stentriever device for endovascular treatment of acute ischemic stroke. Temporary endovascular bypass and mechanical thrombectomy are well-described applications of this device. However, few reports of permanent stent placement have been published. We present a series of five cases in which the Solitaire stent was implanted to restore distal flow after failure of conventional mechanical thrombectomy. All patients presented with large vessel occlusions with thrombi that were resistant to retrieval or suction-aspiration. Immediately after implantation the patients were given a loading dose of abciximab and then transitioned to dual antiplatelet therapy within 24 hours. Our series suggests that permanent deployment of the Solitaire may be considered as a bailout technique in the treatment of cerebral large vessel occlusion. Long-term antiplatelet therapy is required after deployment.
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Endovascular treatment for acute ischemic stroke has rapidly evolved since the PROACT II trial in 1999, which demonstrated a 66% recanalization rate with intra-arterial chemical thrombolysis.1 Thrombolysis also achieved better clinical outcomes at 90 days, with 40% of these patients having a modified Rankin Scale (mRS) score of ≤2 compared with 25% of the control group. Over the past decade there have been significant advances in intra-arterial stroke devices.2–8 The use of an intracranial stent for temporary bypass was first described in 2008.9 Subsequent to this initial description, the use of stentrievers dramatically increased and vessel recanalization rates improved significantly.10 11 The effect of high recanalization rates has been shown to lead to better clinical outcomes in seven recently published large studies.12–18[ESCAPE, MR CLEAN, EXTEND IA, SWIFT PRIME, REVASCAT, THERAPY and THRACE]
The Solitaire stent (Medtronic Inc, Mansfield, Massachusetts, USA) is a self-expanding, closed-cell stent initially designed and approved as an adjunct in the coiling of intracranial aneurysms (Solitaire AB). More recently, its radial strength and flexibility have proved useful for revascularization of large vessel occlusions in the cerebral circulation. For this purpose, the Solitaire stent has been used in three ways.
The first technique is mechanical thrombectomy, in which the stent is deployed across the occlusion, and is then pulled back into the guide catheter together with the thrombus and removed.19 This may or may not include direct aspiration at the face of the clot (ie, ‘Solumbra’ technique) or may be used with a balloon guide catheter.
The second technique is temporary endovascular bypass (TEB), where the device is deployed across an acute thrombus to restore flow, and the stent is then removed.9 10 Although this technique was not originally described with the Solitaire stent, the principle remains the same with temporary deployment of a stent within a thrombus. Removal of the stent avoids complications associated with permanent stent implantation, while also predicting restoration of flow with detachment.
The third technique involves deploying and detaching the stent for permanent implantation across a thrombus in cases where other techniques are unsuccessful.10 19 This technique puts the patient at risk of developing complications associated with permanent stent placement, such as thromboembolic phenomena, antiplatelet therapy risks, and in-stent stenosis.
At our institution we have access to two on-label Solitaire devices, one marketed for stent-assisted aneurysm coil embolization (Solitaire AB or aneurysm bridging), and the other meant for thrombectomy (Solitaire FR or flow restoration). Historically, the original Solitaire devices were all detachable with the intended application of stent-assisted aneurysm treatment. This device has been modified into a stroke device by removing the detachability feature to avoid the potential risk of inadvertent detachment during thrombectomy deployment. The authors realise that both devices may not be universally available, but suggest this technique as a potential bailout option when thrombectomy has failed. This may provide impetus to consider evaluation of other stenting options. The benefits of using a Solitaire AB device, which requires electrolytic detachment, are the complete retrievability of the device to either reposition it or remove it entirely. There certainly are other devices with a higher radial force that may be more desirable, but these devices can not be retrieved once they have been completely deployed.
We present five cases of Solitaire stent deployment for large vessel occlusion and acute ischemic stroke. These cases were reviewed from a quality improvement perspective as they were cases in which mechanical thrombectomy had failed at our institution. Given this, institutional ethics approval was not obtained as it is waived at our institution for studies of quality improvement. Patient information is anonymized in this case series. In these cases, Solitaire devices were permanently placed as a last resort after traditional techniques failed to achieve distal flow. This case series is intended to contribute to the limited body of evidence on the effectiveness and safety of this technique, as well as post-implantation antiplatelet therapy management.
Patient 1 presented to the emergency department following a 45 min episode of acute onset bilateral leg weakness, right upper extremity weakness, and right facial droop. These symptoms had fully resolved at the time of medical assessment. Plain head CT showed no ischemic changes. However, CT angiography (CTA) showed an occlusive left M1 middle cerebral artery (MCA) thrombus (figure 1A). The patient was admitted to the neurology service and was given therapeutic intravenous heparin, aspirin, and clopidogrel. Magnetic resonance imaging 5 days after admission revealed multiple areas of left hemisphere infarct. The patient’s symptoms were minimal until 6 days after admission when the patient again developed a stuttering acute right-sided hemiparesis and worsening speech with a National Institutes of Health Stroke Scale (NIHSS) score of 16. Non-invasive CTA demonstrated a highly flow-limiting thrombus in the left M1 (figure 1B).
The patient was taken for immediate endovascular therapy. A 4×40 mm Solitaire stent was placed across the M1 occlusion with good restoration of flow initially, and 10 mg of abciximab and 5000 units of heparin were administered. After several minutes, distal flow decreased owing to thrombus propagation within the stent. The stent was removed, but no thrombus was retrieved. At this point the highly unstable thrombus further occluded the M1 (figure 1C). A second attempt at Solitaire placement again achieved good initial flow followed by thrombosis despite systemic anticoagulation, and the stent was removed. Clot aspiration was attempted with a 5Max catheter (Penumbra Inc, Alameda, California, USA) using a direct aspiration first pass technique (ADAPT), but this was unsuccessful. A Trevo device was also attempted twice, without successful recanalization. Finally, a 6 mm x 40 mm Solitaire AB stent was deployed from the distal M1 MCA to the internal carotid artery (ICA) and detached. Thrombolysis in Cerebral Infarction (TICI) grade 3 flow in the MCA was noted (figure 1D).
After the procedure the patient had a NIHSS score of 5. CT showed minor staining of the basal ganglia. At the time of discharge on day 7, the patient had an NIHSS score of 1. The modified Rankin Scale (mRS) score at 90 days was 2. The patient had been diagnosed with atrial fibrillation and anticoagulation started in the days following the thrombectomy procedure.
Patient 2 presented to hospital with acute onset aphasia and right-sided weakness. Past medical history included hypertension, and atrial fibrillation treated with sotalol and dabigatran. On examination, the NIHSS score was 14. A CT of the head demonstrated an Alberta Stroke Program Early CT Score (ASPECTS) of 8. CTA showed an extensive MCA and ICA clot (figure 1E, F), with good collateral flow. The patient was not a candidate for tissue plasminogen activator owing to treatment with dabigatran. The patient was referred for emergency endovascular therapy.
Under general anaesthesia a 6 French sheath was placed. A NeuronMax catheter was placed into the left ICA. Angiographic runs showed near-complete occlusion of the left ICA (figure 1G). Thrombectomy was attempted with a Penumbra ACE catheter with removal of thrombus, but occlusion persisted. The lesion was then passed with a Prowler plus microcatheter, Synchro2 wire, and a 6 mm × 20 mm Solitaire stent, with significant removal of thrombus, but the occlusion persisted. This was attempted three more times, followed by a 4 mm × 40 mm Solitaire stent. Each time thrombus was removed, but the occlusion remained after removal of the device. On two occasions a temporary bypass was performed with the Solitaire, and reperfusion was allowed for 20 min with one attempt and 20 mg of ReoPro was administered. On each removal the vessel re-occluded. The decision was then made to permanently place a 6 mm × 20 mm Solitaire stent in the M1 segment. With this, the MCA was patent, but the A1 segment of the anterior cerebral artery remained occluded. Runs from the contralateral ICA showed a patent anterior communicating artery, with adequate flow through bilateral A2 segments, and therefore a decision was made to detach the stent. Final angiographic runs showed good flow into the MCA territory and anterior cerebral artery territory through a patent anterior communicating artery. The final TICI score was 2b (figure 1H), compared with the pre-thrombectomy score of 0.
Repeat postoperative CT did not show any hemorrhagic transformation so the patient was given aspirin immediately, and Plavix 24 hours after the procedure, and continued to receive both for 1 year. The patient’s treatment was switched from dabigatran to warfarin for atrial fibrillation. The patient was discharged to rehabilitation with mild right facial weakness and mild right-sided ataxia. The mRS score at 90 days was 2.
Our series comprised four patients with MCA (80%) and one with basilar artery Solitaire implantation (table 1). Three of the patients were male (60%) with a mean age of 60 (50–83). The patients presented with significant deficits: NIHSS score 14–22 (mean 18) in the patients with anterior circulation occlusion, and coma in the patient with posterior circulation. ASPECT scores for anterior circulation strokes were high (8–9), with poor flow in the affected vessels in all cases (TICI 0–1). Good flow (TICI 2b–3) was successfully restored with stent implantation in four cases (80%), with one instance (20%) of TICI 2a flow after implantation. Postoperative mRS scores at 90 days were 0 for one patient (20%), 2 for two patients (40%), and 3 for two patients (40%). There was no incidence of postoperative symptomatic intracerebral hemorrhage in this series. Repeat vascular imaging showed patency of the stented vessel in all cases with available follow-up, with mild stenosis (<50%) in two cases.
Our case series illustrates permanent placement of the Solitaire when recanalization by other techniques was unsuccessful. The Solitaire stent has been shown to achieve high recanalization rates and good clinical outcomes as a stent retriever in large vessel occlusion.13–18 20 However, there is little information on outcomes when permanent stent placement is employed. In one series, 4/18 patients underwent permanent Solitaire placement and TICI grade 3 flow was restored.10 There are additional reports of permanent placement, including one series involving 6/50 treated patients,10 and another with 5/18 treated patients.19 These studies do not discuss the techniques, indications, or outcomes after permanent stentriever implantation. In contrast, our series shows that implantation with the Solitaire stent can achieve TICI grade 2b–3 flow in these difficult cases that are resistant to other revascularization techniques. With the recent convincing evidence demonstrating the effectiveness of endovascular therapy in acute stroke, the expansion of stroke therapy requires that various techniques be available to the operators.
The Solitaire stent has several characteristics that make it ideal for permanent implantation in cases resistant to conventional techniques. (1) The device can be delivered via a small, 0.021" microcatheter, which can be readily placed in the distal cerebral vasculature. (2) The majority of interventional operators have experience with the device for aneurysm bridging and use as a stentriever. (3) Unlike other stentrievers, the Solitaire AB can be electrolytically detached, allowing for its recapture or repositioning after complete deployment. The detachment zone is very strong and unexpected detachment is rare in our experience. (4) The Solitaire’s nitinol design makes it robust, and in cases of multiple failed stentriever attempts the same device can be permanently implanted without a problem—a cost-saving technique. (5) The Solitaire produces reasonable radial force, allowing for compaction of resistant, dense, or well-organized clots between the vessel wall and the stent. (6) The deployed Solitaire device can demonstrate whether there is flow before deployment (successful TEB), predicting success of bailout detachement. This is unknown with other stents, such as the Wingspan. (7) Using the same stent for bailout as for clot retrieval saves the cost of a subsequent stent.
Implantation of permanent stents for ischemic stroke requires dual antiplatelet therapy to be started immediately in cases of acute stroke. Therefore, we advocate this technique only when more conventional methods have failed. Our post-implantation management regimen is as follows: (1) we heparinize the patients to an activated clotting time twice that of baseline, and (2) patients receive a full loading dose of intra-arterial abciximab delivered directly into the vessel (0.25 mg/kg). Immediately after the procedure, the patients receive 325 mg of aspirin, either orally or rectally. Patients also receive postprocedure dual-volume CT at 6 hours. If the postoperative CT does not show evidence of intracranial haemorrhage, patients can then be loaded with Plavix, 600 mg, followed by daily aspirin and Plavix. Intraoperative CT was not consistently used as a decision-making tool as a number of our cases were performed on a biplane machine without CT capabilities. Despite the risk of hemorrhagic transformation of a large ischemic lesion, the decision to load with Plavix was based entirely on the absence of hemorrhage on the postoperative 6-hour CT scan as the risk of thromboembolic complications of stent implantation in a small MCA or basilar artery was felt to be higher than the risk of hemorrhage.
All patients in our series had neurologic improvement, and three patients returned to independent function. Although our experience with permanent implantation of the Solitaire device was successful, it is not without risk. Few data are available on the outcomes of permanent placement, especially in the long term. Patients may have complications of in-stent stenosis, and long-term antiplatelet therapy is required, thereby increasing their risk of intracerebral hemorrhage, especially in the setting of large, acute ischemic burden. Although stent delivery is straightforward, distal access is lost after implantation, which becomes a significant concern if the stent is detached and then occludes, and must be re-crossed. We did not encounter this problem in our series, but operators must be cognisant of losing distal access. We confirmed stent patency through TEB for 10–20 min before detachment in all cases, in order to mitigate the risk of stent re-occlusion. Given these risks, this approach should be considered only when other options for revascularization have been exhausted.
This case series suggests that permanent Solitaire deployment is an option for revascularization of intracranial large vessel occlusions that are resistant to stentriever or suction-aspiration techniques.
Contributors SUA, JM, JH, EB participated in the acquisition of data, interpretation and analysis of data, writing of the manuscript, editing of manuscript and agree to be accountable for the integrity of the work. MEK, LP participated in the conception of the manuscript, acquisition of data, interpretation and analysis of data, writing of the manuscript, editing of manuscript, and agree to be accountable for the integrity of the work.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests MEK: consultant, Medtronic; LP: consultant, Medtronic.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The authors are willing to share de-identified participant data acquired during the case series preparation with any one who wishes to access the data. Data will be available immediately after publication with no end date. All available anonymized data have been published in this manuscript, with the exception of radiological imaging. Requests should be submitted to email@example.com.
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