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Ischemic stroke
Original research
Solitaire stents for the treatment of complex symptomatic intracranial stenosis after antithrombotic failure: safety and efficacy evaluation
  1. Guoli Duan1,
  2. Zhengzhe Feng1,
  3. Lei Zhang1,
  4. Ping Zhang2,
  5. Lei Chen2,
  6. Bo Hong1,
  7. Yi Xu1,
  8. Wenyuan Zhao1,
  9. Jianmin Liu1,
  10. Qinghai Huang1
  1. 1Department of Neurosurgery, Changhai Hospital, Second Military Medical University, Shanghai, China
  2. 2Department of Neurology, Changhai Hospital, Second Military Medical University, Shanghai, China
  1. Correspondence to Professor Qinghai Huang or Professor Jianmin Liu, Department of Neurosurgery, Changhai Hospital, Changhai Road 168, Shanghai 200433, China; ocinhqh{at}163.com; chstroke@163.com

Abstract

Objectives To evaluate the feasibility, safety, and efficacy of Solitaire stent placement after balloon angioplasty for the treatment of complex symptomatic intracranial atherosclerotic stenosis (ICAS).

Methods We retrospectively reviewed the clinical data from 44 patients who underwent Solitaire stent placement for complex symptomatic ICAS at our department between November 2010 and March 2014, with focus on the clinical factors, lesion characteristics, treatment results, and periprocedural complications. We also summarized the early outcomes and imaging findings during the follow-up period.

Results Overall, the technical success rate was 100% (44/44). Post-stenting residual stenosis ranged from 0% to 40% (mean 15.00±12.94%). The overall 30-day rate of procedure-related complications was 9.09% (4/44). The incidence of recurrent ischemic events related to the territory artery was 4.55% during a mean clinical follow-up period of 25.5 months. Five patients (11.36%) developed in-stent restenosis during a mean angiographic follow-up period of 9.3 months.

Conclusions This is the first case series study of ICAS treated by Solitaire stent placement. Deployment of a Solitaire stent with balloon angioplasty in the treatment of complex severe intracranial stenosis appears safe and effective, with a high technical success rate, relatively low periprocedural complication rate, and favorable outcome during follow-up.

https://doi.org/10.1136/neurintsurg-2015-011734

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    Introduction

    Intracranial atherosclerotic stenosis (ICAS) is an important cause of ischemic stroke among Asians, especially among Chinese populations.1 ,2 Although in patients with ICAS aggressive medical management proved superior to percutaneous transluminal angioplasty and stenting (PTAS),3 the latter remains an alternative for stroke prevention in patients with severe stenosis or an ineffective response to drug therapy.4–7

    The self-expanding Wingspan stent (Stryker Neurovascular, Freemont, California, USA), a dedicated stent system approved by the US FDA for patients with transient ischemic attack (TIA) or stroke secondary to stenosis of a major intracranial artery,8 ,9 appears structurally unsuited for treatment of complex ICAS, yielding a lower success rate in complex lesions such as long, bifurcation, or tip lesions and those with tortuous access, and a higher rate of periprocedural complications than in simple lesions.10 ,11

    In contrast, the unit design of the Solitaire AB device (ev3, Irvine, California, USA) is laser cut from a nitinol plate into a honeycomb pattern resulting in a self-expanding overlap platform that allows for versatility in multiple applications, including treatment of intracranial aneurysms and mechanical thrombectomy in acute intracranial artery occlusion.12 ,13 Due to its relatively low radial force, high flexibility, thin wall, and the special structure of the release system, it appears better suited for the treatment of complex ICAS.

    The present study therefore retrospectively investigated whether endovascular treatment of complex symptomatic ICAS using the Solitaire AB device would combine higher procedural safety and efficacy with better follow-up results.

    Materials and methods

    This retrospective study was approved by the Institutional Review Board at our hospital, all patients signed a general informed consent, and no research was conducted outside the country of residence.

    Patients

    From July 2010 to March 2014, of the 334 patients with ICAS who were treated by PTAS, 44 (8.24%) had complex symptomatic lesions that were treated with Solitaire stents and met the following inclusion criteria: (1) arterial stenosis >70% as determined by CT angiography (CTA) or digital subtraction angiography (DSA) using the formulas described by the Warfarin Aspirin Symptomatic Intracranial Disease (WASID) method14 and the presence of atherosclerotic risk factors; (2) recurrent low-flow TIAs or non-disabling ischemic stroke despite antiplatelet or anticoagulation therapy (at our center, patients with symptomatic ICAS undergo close outpatient follow-up and aggressive medical management according to the guidelines for the prevention of stroke in patients with stroke and TIA15 ,16); and (3) stenosis located in lesions that are long, at the bifurcation or tip of the artery, and with tortuous access, rendering them unsuitable for Wingspan stent use. Patients with any of the following were excluded: (1) severe disability because of stroke or dementia; (2) total occlusive lesion; or (3) inability to provide informed consent.

    Interventional procedure

    Before the procedure, brain CT and MRI/MR angiography (MRA) were performed in all patients and CT perfusion and diagnostic cerebral angiography was performed in most patients. All patients were pretreated with dual antiplatelet therapy (clopidogrel 75 mg and aspirin 300 mg daily) for at least 3 days prior to the endovascular procedure.

    The procedures were performed by experienced interventional neuroradiologists, each with more than 15 years’ experience in neurointervention. Briefly, access was typically achieved through the common femoral artery. Heparin was titrated during the procedure to achieve an activated clotting time 2–2.5 times that of baseline. Almost all the procedures were performed through a 6 Fr guiding catheter or a long-sheath system. After conventional catheter-based angiography, a microcatheter (Prowler 14, Cordis Neurovascular, Miami, Florida, USA; or Echelon 10, ev3/Neurovascular, Irvine, California, USA) was manipulated across the target lesion using a 0.014 inch (300 cm) microwire (Transend Floppy, Boston Scientific, Fremont, California, USA). The microcatheter was then exchanged for a Gateway angioplasty balloon (Boston Scientific, Natick, Massachusetts, USA). The balloon length was selected to match the lesion length. The balloon diameter was selected to match the DSA-based distal artery diameter by 80–100%, except for cases of very severe stenosis (7 in this study) in which the distal artery may have shrunk, and vessel diameter was also determined using high-resolution MRI vessel wall imaging to select balloon diameter. Angioplasty was typically performed with a slow, graded inflation of the balloon to a pressure between 5 and 12 atm, which was then maintained for 15–30 s. Following angioplasty, the balloon was removed and conventional angiography was repeated. A Rebar-18 microcatheter (ev3) was then placed through the lesion site into the normal distal artery with the support of a 0.014 Synchro micro-guidewire (Boston Scientific). Next, a Solitaire stent (ev3) was delivered through the Rebar-18 microcatheter. The Perclose device (Abbott Vascular Devices, Redwood City, California, USA) was then used for closure of the femoral access site.

    Residual postprocedural stenosis and the degree of vascular patency were assessed by angiography. Stent morphology was evaluated by flat panel angiography CT scanning (DynaCT, Siemens Healthcare Solutions, Malvern, Pennsylvania, USA). Balloon post-dilation was used if necessary.

    Aspirin was maintained at a daily dose of 300 mg for at least 6 months after the procedure until follow-up angiography was performed. In cases where no in-stent restenosis (ISR) developed, 100 mg of aspirin daily lifelong was recommended. Clopidogrel was usually maintained for 6 weeks after the procedure and then discontinued. Risk factors for atherosclerosis were controlled in accordance with pertinent guidelines.

    Evaluation of outcomes and clinical and angiographic follow-up

    Technical success of the procedure was defined as performing the balloon angioplasty and placing the stent across the target lesion with less than 50% immediate residual stenosis.

    The study clinical outcomes were any stroke or death within 30 days of the procedure and the occurrence of ipsilateral ischemic stroke after the procedure; any TIA in the territory of the stented artery and ischemic stroke outside the territory of the stented artery during follow-up were also included. Other procedure-related complications such as arterial dissection, vasospasm, vessel perforation, groin hematoma, and pseudoaneurysm were also documented. The initial and follow-up clinical evaluations were performed by two neurologists.

    Imaging follow-up was scheduled as follows: DSA after 6 months, and CTA and CT perfusion after 12 months and subsequent years. If ISR was questionable after CTA, DSA was recommended for confirmation. ISR was defined as a lesion demonstrating >50% stenosis (ie, within or immediately adjacent to within 5 mm to the stent) and >20% absolute luminal loss at follow-up imaging (ie, >20% increase in post-treatment stenosis).17

    Statistical methods

    Continuous variables are presented as mean±SD or as median and IQR for those with skewed distributions, while nominal variables are presented as percentages. The Fisher exact test, χ2 test, or continuity adjusted χ2 test was used to compare the data; p values <0.05 were considered statistically significant. Statistical analyses were performed using SAS V.9.1 (SAS Institute, Cary, North Carolina, USA).

    Results

    Patient characteristics

    The study cohort included 44 patients (31 men and 13 women) with a mean age of 62.50±11.72 years (range 37–79 years). All patients presented with an ischemic stroke (19 patients, 43.18%) or TIA (25 patients, 56.82%) in the territory of a suspected 70–99% stenotic intracranial artery. The stenting procedure was performed at 49.31±11.65 days (range 7–69 days) from the qualifying event (large-scale cerebral infarction with modified Rankin Scale score >2). Because of concern over hyperperfusion after stroke, stenting procedures were performed after the patient status had improved at a rehabilitation center. The general characteristics of the patients studied are summarized in table 1.

    View this table:
    Table 1

    Demographic and clinical characteristics of the 44 patients studied

    Lesion and angiographic characteristics

    All 44 patients underwent DSA preoperatively. The degree of stenosis was determined using the formulas described in the WASID trial method.14 The distal artery diameter based on DSA imaging was defined as the reference artery diameter. Lesion classification was based on the location, morphology, and access (LMA) criteria system, as described by Jiang et al.18 The lesion characteristics are summarized in table 2.

    View this table:
    Table 2

    Lesion characteristics of the 44 patients studied

    Procedural outcomes and periprocedural complications

    The overall technical success rate was 100% (44/44). The post-balloon dilation residual stenosis ranged from 15% to 60% (mean 35.50±19.94%) and post-stenting residual stenosis ranged from 0% to 40% (mean 15.00±12.94%). The median duration of hospitalization, defined as time from arrival in our center to discharge, including imaging evaluation, procedure and postprocedural short-term observation, was 8.5 days (range 3–23 days).

    The overall rate of procedure-related complications during the periprocedural period (30 days) was 9.09% (4/44): the four patients had a non-fatal ischemic stroke with symptoms in the territory of the stented artery and all recovered without overt neurological sequelae. Three patients (6.82%) developed a groin hematoma after the procedure and recovered after hemostasis by compression and one patient (2.27%) developed pneumonia because he was bedridden. No patient suffered a hemorrhagic stroke, myocardial infarction, or died during the periprocedural period. The results are detailed in table 3.

    View this table:
    Table 3

    Procedural outcomes and periprocedural complications of the 44 patients studied

    Clinical and angiographic follow-up results

    Forty-four patients were available for a clinical follow-up visit 3–60 months (mean 25.5 months) after treatment. Thirty-two patients had their follow-up visit more than 12 months after the procedure. The incidence of recurrent ischemic events related to the territory artery was 4.55% during the mean clinical follow-up period of 25.5 months. There were no deaths during the follow-up period.

    Overall, 37 patients (84.09%) underwent DSA follow-up examinations and seven patients underwent CTA at least once during the follow-up period. The average follow-up period was 9.3 months (range 3–27 months). At mean 6.2 months follow-up, five patients (11.36%) developed recurrent restenosis, defined as an in-stent stenotic lesion of >50% on follow-up DSA series. Two (4.55%) of these recurrent lesions were symptomatic with minor stroke in the dependent vascular territory, of which one required balloon angioplasty (pre/post retreatment stenosis, 70/30%) (figures 1 and 2).

    Figure 1
    Figure 1

    A 47-year-old man with severe stenosis of the M1 segment of the right middle cerebral artery (MCA) was referred for evaluation of stroke. Diagnostic cerebral angiography confirmed a pre-occlusive (>80%) stenosis of the right MCA (A). The patient underwent percutaneous transluminal angioplasty and Solitaire stent placement. The subtracted image demonstrates postprocedural residual stenosis of nearly 15% (B). The DynaCT scan shows the morphology of the stent after placement (C). The 7 month follow-up angiogram shows complete patency of the stented segment (D) and good morphology of the stent (E).

    Figure 2
    Figure 2

    A 64-year-old man with severe stenosis of the M1 segment of the right middle cerebral artery (MCA) was referred for evaluation of stroke. Diagnostic cerebral angiography confirmed a pre-occlusive (>80%) stenosis of the right MCA (A). The patient underwent percutaneous transluminal angioplasty and Solitaire stent placement. The subtracted image demonstrates near-complete resolution of the stenosis (B). The DynaCT scan shows the morphology of the stent after placement (C). After 4 months, the patient experienced transient ischemic attacks in the dependent territory and the follow-up angiography (D) revealed an in-stent restenosis (>80%) and diffuse intimal hyperplasia throughout the entire stented segment (E).

    Discussion

    Angioplasty and stenting of intracranial arteries is a controversial therapy for stroke risk reduction in patients with recent symptomatic intracranial stenosis, especially after the Stenting and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Arterial Stenosis (SAMMPRIS) trial proved that, in patients with intracranial stenosis, aggressive medical management was superior to PTAS.3 ,19 However, for patients with severe stenosis and an ineffective response to drug therapy, angioplasty and stenting of intracranial arteries remains an alternative for stroke prevention under the premise of reduction or prevention of periprocedural complications.

    Although the self-expanding Wingspan stent was the first dedicated stent system approved by the FDA for patients with stenosis of the intracranial artery and has been widely used in multiple stroke centers,7–9 ,20 ,21 after the SAMMPRIS study the FDA limited the indications for use of the Wingspan stent because of its high periprocedural complication rate.19 The main concern regarding angioplasty and stenting of intracranial arteries has therefore been to reduce the procedure-related complication rate and improve patient safety and technical outcomes.

    In the present study, albeit retrospectively assessed, the rate of periprocedural complications for the Solitaire stent was lower than for the Wingspan arm, but was still higher than that of the medical treatment arm of the SAMMPRIS trial. Reasons for the latter might be that, in the present study, all patients had stenosis in complex lesions that were long (4.20–21.11 mm; mean 15.83±3.85 mm), located at the bifurcation or distal end of the artery, and with tortuous access. In addition, the percentage of severe stenosis (90–99%) was more than twice that in the medical group of the SAMMPRIS trial (27.27% vs 12.3%).3 Most of all, in patients with antithrombotic failure, interventional treatment of lesions is more challenging from a safety perspective.

    The LMA classification described by Jiang et al18 has been helpful in predicting the likelihood of technical and clinical success, thereby informing individual therapy. To this end, type B and C lesions have a lower technical success rate and a higher risk of periprocedural stroke, which has been correlated with ISR and mortality.18 ,22 In the present study, the technical success rate was 100% (10/10) in type III access while the periprocedural complication rate was 6.82% (3/26) in type C morphology, which is significantly lower than that documented for the Wingspan stent.18

    The Solitaire self-expanding stent, which has been widely used in intracranial aneurysm treatment and mechanical thrombectomy in acute intracranial artery occlusion,23–25 has many advantages including ease of delivery, high wall apposition and bending stiffness, and relatively lower radial strength.26 Because of the latter properties, we use the Solitaire stent at our center to treat complex intracranial stenosis for which the Wingspan stent appears unsuited. The results of the present study indicate that deployment of a Solitaire stent with balloon angioplasty is safe and effective for complex severe intracranial stenosis with a higher technical success rate, relatively lower periprocedural complication rate, and lower ISR rate than the Wingspan stent.7 ,27

    Although the biggest concern in using the Solitaire or Enterprise (Cordis Neurovascular) stents is the relatively lower radial force to effectively reduce vascular elasticity recoil and remolding, maintain blood flow and prevent vascular restenosis, the results of the present study suggest that the Solitaire stent releases the vascular diameter to a greater extent than simple balloon dilation.

    Another major drawback of the Wingspan stent is the high rate of recurrent stenosis.28 Development of intimal hyperplasia is the main cause of recurrent stenosis, which may be related to dilation trauma, thrombogenicity of the deployed stent, and inflammatory reactions of the vessel wall toward the stent.29 ,30 A previous study suggested that the restenosis rate might be related to stent oversizing,31 and our previous studies documented that stent diameter and the ratio of reference artery diameter to stent diameter were associated with recurrent stenosis, presumably because the intramural wall stress from the stent caused more damage to the vessel wall and subsequent excessive repair, ultimately leading to ISR.20 ,21 A high recurrence rate appeared to be associated with high radial force in other previous studies.32 ,33 In the present study the ISR rate of Solitaire stents was lower than that of Wingspan stents used at the same center,20 ,21 possibly because of the relatively lower radial strength reducing chronic stimulation and inflammatory response toward the stent.

    Interestingly, the radial force of the Enterprise stent, another self-expanding closed-cell design stent, is less than that of the Solitaire stent. In a recent study, patients with intracranial atherosclerotic arterial stenosis were treated with the Enterprise stent33 and the results showed a relatively lower ISR rate than with Wingspan stents but a higher rate than in our present study. This raises the question of whether the radial force is really associated with restenosis. However, the occurrence of ISR is associated with multiple risk factors including clinical, lesion and procedural characteristics, so choosing a stent with appropriate radial force to reduce procedure-related injury and effectively controlling clinical risk factors may reduce the incidence of ISR.

    The limitations of this study should be noted. First, angiographic follow-up of all patients has not yet been completed. Second, the sample size was small and should be increased in future studies to strengthen the results. Third, this is a retrospective analysis so selection bias may be built into the data. Thus, further long-term follow-up and increased sample size will be important in future studies to provide more adequate statistical evidence to support our findings. Moreover, although long-term outcome data appear to favor the Solitaire over the Wingspan stent for the treatment of complex ICAS, it remains to be determined if the same applies to other intracranial atherosclerosis lesions.

    Acknowledgments

    Thanks are due to Benqiang Deng for valuable discussion.

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    Footnotes

    • GD and ZF are joint first authors.

    • Contributors GD and QH contributed equally to the preparation of the manuscript; ZF, GD and LZ contributed equally to data collection; PZ and LC contributed equally to clinical follow-up; and QH, BH and JL contributed equally to interventional procedures.

    • Funding This research was supported by the 1255 Project of Changhai Hospital (Grant No. CH125550400), Shanghai Shenkang Research Fund (Grant No. SHDC12012103), Major Project of Shanghai Committee of Science and Technology (Grant No.13411950300). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

    • Competing interests None declared.

    • Patient consent Obtained.

    • Ethics approval Ethics approval was obtained from the Institutional Review Board of Changhai Hospital.

    • Provenance and peer review Not commissioned; externally peer reviewed.