Background The low profile visualized intraluminal support (LVIS) device is being increasingly used for the treatment of intracranial aneurysms. Its application in the basilar artery (BA) has not yet been reported.
Objective To evaluate the safety and early efficacy of the LVIS device for the treatment of BA aneurysms.
Methods A prospectively maintained database was retrospectively reviewed for all patients with BA aneurysms treated by LVIS stents at our institution. Angiographic results were evaluated using the modified Raymond–Roy classification (mRRC).
Results 23 patients (mean age 52.8 years) with a BA aneurysm that was treated by LVIS stent implantation, with (n=21) or without (n=2) adjunctive coiling, were included in our study. 7 aneurysms were treated in the setting of subarachnoid hemorrhage (SAH). 10 aneurysms were located at the basilar tip, 10 at the basilar trunk, and 3 at the superior cerebellar artery. Procedure related complications developed in three patients (13%), including two perforator infarction and one worsening mass effect. Complications resulted in permanent morbidity (4%) in one case. One fatality was related to severe poor grade SAH. At a mean follow-up of 6.9 months, 13 of the 20 patients were mRRC I closure, 3 were mRRC II closure with an improvement from class IIIa, 3 were observed to be recanalized from class IIIa to IIIb, and 1 with stenting only was still patent similar to the immediate angiography.
Conclusion The LVIS stent represents a feasible and safe option for endovascular embolization of BA aneurysms. Although recanalization may occur after LVIS treatment, the mid term complete occlusion rate was acceptable.
- basilar artery
- endovascular treatment
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Posterior circulation aneurysms suffer from a poor natural history relative to the anterior circulation.1 The management of posterior circulation aneurysms is particularly challenging. Even though endovascular therapy is frequently chosen over microsurgery because of the lower morbidity, conventional methods such as primary coil embolization, and stent assisted or balloon assisted coiling have significant risks of recanalization and retreatment.2 3Flow diverters, as a treatment option for challenging aneurysms in the anterior circulation, have recently been used in the posterior circulation. However, the application of flow diverters in the posterior circulation is still associated with a risk of periprocedural stroke and high overall mortality.4–8
The low profile visualized intraluminal support (LVIS) device (MicroVention Terumo, Tustin, California, USA) is a new generation of self-expanding intracranial stent indicated for use in conjunction with coil embolization for the treatment of intracranial aneurysms. Its small cell structure (0.8 mm) and high metal coverage (approximately 28%) were found to provide slightly less flow diversion than approved flow diverters but nominally higher than that of other currently available coil assist stents. The LVIS stent has a better crossing profile for microcatheters, better wall apposition, and less perforator coverage than a flow diverter (flow redirection endoluminal device (FRED); MicroVention).9 These are desirable features in territories with high densities of perforators, such as the posterior circulation. We have reviewed our results with the use of the LVIS stent in intracranial vertebral artery dissecting aneurysms which showed good short term angiographic and clinical outcomes.10 However, its safety and efficacy in the basilar artery (BA) have yet to be described. We sought to evaluate the preliminary experience of this device for the treatment of BA aneurysms.
A retrospective review of a prospectively maintained single center database was performed for all patients with BA aneurysms treated by LVIS stents at our institution between October 2015 and October 2017. Institutional review board approval was obtained in our hospital. Individual patient consent was not required because clinical data are collected in a de-identified manner during our routine clinical practice. A multidisciplinary team, including neurosurgeons and neuroradiologists, determined the optimal aneurysm management after careful risk–benefit analysis of different treatment modalities, such as surgical clipping and various endovascular options.
Patients with unruptured BA aneurysms were treated with aspirin 100 mg and clopidogrel 75 mg for a minimum of 3 days prior to the intervention. Platelet function testing was performed routinely before the procedure from August 2016. Ticagrelor was used to replace clopidogrel if the patient was not sensitive to cloplidogrel. However, for patients with acutely ruptured aneurysms, 0.1 µg/kg/min of glycoprotein IIb/IIIa antagonist (tirofiban) was injected intravenously after deployment of the stent. Then, a loading dose of clopidogrel and aspirin (300 mg each) was administered orally 6 hours before stenting. After achieving groin access with a 6 F sheath, heparin was intravenously infused with the goal of achieving an activated clotting time of 2–2.5 times that of baseline during the procedure. Heparinization was discontinued at the end of the procedure. Regardless of whether the aneurysm was ruptured, all patients were administrated a daily dose of aspirin (100 mg) and clopidogrel (75 mg) postoperatively for 6 weeks followed by aspirin alone, which was maintained indefinitely.
All embolizations were performed under general anesthesia using biplane angiographic equipment. Endovascular strategy included stent implantation with or without an adjunctive coiling technique. In general, we used a Headway-21 microcatheter (Microvention/Terumo, Tustin, California, USA) for stenting and an Enchelon-10 microcatheter (Covidien/ev3, Irvine, California, USA) for coiling. A Prowler Select Plus microcatheter (Codman, Raynham, Massachusetts, USA) was used to deploy the LVIS stent in the setting where an Enterprise stent had been deployed first. Twenty-one patients had adjunctive coiling through a modified stent assisted semi-jailing technique, as previously described.11 12 For basilar apex aneurysms, the LVIS stent was often used to create a ‘shelf’ across the aneurysm neck sufficient to prevent coil prolapse, especially when bilateral posterior cerebral arteries were incorporated into the aneurysm dome. A Y stenting technique was not used in this case series.
Consideration was given to both the degree of initial occlusion (contrast stasis) and the patency of branch arteries when additional stent application was manipulated. For the lesion with a potential risk of parent or perforating arteries occlusion, staged stent implantation was required. In our series, overlapping stents were deployed in six cases with an additional LVIS (n=4) or Enterprise (Codman and Shurtleff Inc, Raynham, Massachusetts, USA) stent (n=2), respectively. Staged LVIS stent assisted coiling was performed in two patients with a 1 month interval. The remaining aneurysms were treated in a single session.
Procedural assessment and follow-up
Aneurysm occlusion after initial treatment and during follow-up was found to be unchanged (patent), or was evaluated using the validated modified Raymond–Roy classification (mRRC)13 where mRRC I closure indicates complete occlusion, mRRC II closure indicates opacification of the aneurysm neck, mRRC IIIa closure indicates opacification within the interstices of the coil mass, and mRRC IIIb closure indicates opacification between the coil mass and aneurysm wall. Angiographic follow-up was assessed by MR angiography or DSA routinely at 3–12 months. Clinical outcome was evaluated using the modified Rankin Scale (mRS) score at discharge and during follow-up.
Baseline patient and aneurysm characteristics
Patient demographics, clinical presentation, and aneurysm characteristics are summarized in table 1. Twenty-three consecutive patients, including 18 women and five men, ranging in age from 17 to 76 years (mean 52.8), were included in the study. Seven patients presented with subarachnoid hemorrhage (SAH). All aneurysms were located at the BA (basilar tip, n=10; basilar trunk, n=10; superior cerebellar artery, n=3). Aneurysm size ranged from 2 to 27 mm (mean 9.3 mm). Large or giant aneurysms were found in 8 (35%) patients. With respect to morphology, 5 were fusiform, 5 were acute dissecting, and 13 were wide necked saccular. No dolichoectatic aneurysms were treated.
An LVIS blue stent was used in this case series. The LVIS stent was deployed into the correct position across the whole length of the aneurysm in all patients successfully. In all cases, the LVIS stent covered at least one third of the BA. Procedural details and outcomes are summarized in table 2. Post-procedurally, 3 of the cases were graded as mRRC I closure, 5 as mRRC II closure, and the remaining 13 as mRRC IIIa embolization. In the two patients treated by stenting alone, the aneurysms were still patent, while contrast residual time within the aneurysm was increased moderately after stent placement (figure 1). At the end of the procedure, parent vessel and covered daughter vessel patency was observed for all lesions with no evidence of an associated decrement in flow in the covered vessel.
After discharge, during a mean follow-up of 6.9 months (range 3–20 months), angiographic follow-up was available for 20 of 23 patients at different time intervals. Seventeen patients were followed-up with DSA and three with MR angiography. mRRC grade I occlusion was observed in 13 (65%) of 20 patients. Three patients were graded as mRRC II closure with an improvement from class IIIa. Three (15%) aneurysms were observed to be recanalized from mRRC class IIIa to IIIb, including an aneurysm at the basilar apex and two at the basilar trunk. In the remaining case with stenting only, there was persistent patency without any improvement or progression on the 20 month follow-up DSA. Retreatment with an additional stent with adjunctive coiling occurred in two basilar trunk aneurysms. The parent vessels of all cases were patent, with no evidence of in-stent stenosis on follow-up. In three patients, however, no follow-up imaging was available. Figure 2 shows a representative case of a patient successfully treated with an LVIS stent with adjunctive coiling for a saccular basilar apex aneurysm.
Procedural complications and clinical outcome
Procedural complications occurred in three cases (13%), including two ischemic strokes and one brainstem compression (table 3). There were no intracranial hemorrhages or SAHs. In patients with thromboembolic events, platelet function testing was performed with thromboelastography (TEG Hemostasis System, Haemoscope Corporation, Niles, Illinois, USA) with none showing a poor response to antiplatelet therapy. Major complications occurred in one patient (4%) who experienced delayed perforator infarction after retreatment of a large basilar trunk aneurysm (case No 2 in table 3). This patient initially presented with acute SAH. DSA demonstrated a 15 mm mid-basilar aneurysm with a small daughter sac arising from the proximal portion of the aneurysmal neck which was considered to be responsible for the SAH. Endovascular treatment with a single LVIS stent and adjunctive coils was uneventful. The initial angiographic result was mRRC IIIa closure. Follow-up DSA was performed 4 months later confirming recanalization (mRRC IIIb). The patient was retreated with another LVIS stent and coils. Two months after treatment, the patient suffered a sudden attack of aphasia and left-sided hemiplegia. Emergent DSA demonstrated a patent BA and recanalization of the aneurysm. MRI disclosed pontine infarction and the patient was discharged home with a mRS score of 3.
One patient developed ischemic complications immediately after the procedure. This patient had a 15 mm fusiform mid-basilar aneurysm which was treated with two overlapping LVIS devices and adjunctive coils. The patient developed weakness of the left-sided limbs 12 hours after the procedure at which time MRI disclosed pontine infarct secondary to perforator occlusion which recovered at the last follow-up (mRS score of 0) (figure 3, case No 3 in table 3).
Another complication developed in an additional patient who experienced unilateral oculomotor nerve palsy 3 days after LVIS stent assisted coiling of a giant basilar tip saccular aneurysm because of brainstem compression (MRI conformed no infarction). Steroid therapy was initiated. The patient was seen at our clinic 18 months after the procedure and still had oculomotor nerve palsy on the right, approximately similar to the status at discharge (mRS score of 2) (case No 4 in table 3).
Inhospital mortality occurred in one patient as a result of complications of severe poor grade SAH (case No 1 in table 3). Neither rebleeding nor device related mortality was observed. No severe procedural complications, such as aneurysm rerupture or side branch occlusion, occurred in any patient. The median clinical follow-up was 16 months (range 6–30 months) and was available for all 22 survivors. A favorable clinical outcome (mRS ≤2) was observed in all patients except for one case with major complication (mRS 3).
In this study, we describe our preliminary experience of using the LVIS stent to treat patients with BA aneurysms. Overall, the results of this small series suggest that LVIS deployment in the BA is feasible and safe, with good clinical outcomes and acceptable occlusion rates after mid term follow-up. This represents the first series to date.
Recent years have witnessed a conceptual change in aneurysmal treatment from traditional intraluminal embolization towards reconstruction of the parent artery and aneurysmal neck. Flow diversion, which emerged as a reconstructive technique for intracranial aneurysms a few years ago, is gradually changing the paradigm of aneurysmal treatment. Flow diverters (FDs) have proved to be reliable tools for the treatment of anterior circulation aneurysms, but their use in the BA remains controversial. Available studies reporting on the use of FDs in the posterior circulation show highly variable results and complication rates. Table 4 summarizes large series (>5 cases) on the use of FDs for BA aneurysms. We found these searching the PubMed database using the keywords ‘posterior circulation/basilar flow diverter’, ‘posterior circulation/basilar flow diversion’. While there are limitations for direct comparison of these results owing to the heterogeneity of the aneurysms, the retrospective analysis, and the relatively small total numbers, comparison of the results between the FD studies and ours may provide valuable insights regarding different clinical strategies. As with all new technologies, incorporation into common practice often clarifies the strengths and limitations of these devices and techniques.
One of the important observations from the overall outcomes is that procedural complications appeared to be higher with FD implantation (31%), which led to unfavorable mortality of 14.3% and morbidity of 11.5%. Thromboembolic events are the main source of poor outcomes. Compromise of perforating arteries and consequent infarction because of struts coverage and delayed neointimal proliferation over the perforator ostia were the most common complications. Generally, porosity of the stent induces neck coverage and the possibility of flow stasis in the aneurysm, which plays an important role in thrombosis.14 The metal coverage rate of FDs was reported to be 30–40%. This is in contrast with the currently available stents Enterprise, Neuroform, Solitaire, and LVIS jr, which have 12% and lower metallic coverage. As previously mentioned, the LVIS stent has a nominal intermediate coverage of 28%, similar to the FDs. Matsuda et al demonstrated that the LVIS stent showed less perforator coverage than the FRED stent when deployed from the posterior cerebral artery to the BA in a fresh frozen cadaver using OCT intravascular imaging.9 This result suggests that the LVIS stent could reduce ischemic complications related to perforators seen with the use of FDs in the BA. Several studies have reported the application of LVIS stents in the posterior circulation.15–17 Poncyljusz et al reported 14 cases with LVIS/LVIS Jr stents deployed in BAs and no major adverse events occurred, similar to our results.17 In the present study, the rate of procedural complications with LVIS stents was relatively lower (13%) and no mortality or major morbidity events occurred.
In our study, the complete occlusion rate was 65% with LVIS stent implantation. Despite the slightly high recurrence rate, the mid term efficacy with LVIS stents was acceptable in comparison with FDs (71.3%). FDs demonstrated a high occlusion rate for BA aneurysms in most studies. An important reason is that a high pore density with FDs provides better flow diversion and scaffolding for endothelialization and vessel wall healing. According to a computational fluid dynamics study in virtual models, a single LVIS stent caused more flow reductions than the double Enterprise stent but less than that of a pipeline embolization device.14 Although this lower flow diversion versus FDs may decrease the occlusion rate, the LVIS stent facilitates improved flow diversion over other currently available coil assist stents and a higher aneurysm occlusion rate might be anticipated compared with conventional stents. In addition, the braided properties of the stent allow for easily changed cell size and crossing with microcatheters through the stent cells to place coils in aneurysms. When recanalization of an aneurysm treated with the LVIS stent is recognized, retreatment by a trans cell approach is possible.
Although recent case series and reports have demonstrated the relatively safe use of FDs in the posterior circulation, these usages were ‘off label’.5 18 19 As illustrated in our case series, the use of the LVIS stent for the treatment of BA aneurysms resulted in acceptable occlusion rates with a low frequency of major complications. Furthermore, the LVIS stent can be delivered through lower profile microcatheters (0.021 inch) than the FD (0.027 inch), which means easier access to deploy the stent into BAs and for use as an adjunctive method. Moreover, the LVIS stent showed better wall apposition than the FRED stent in a cadaver experiment.9 However, insufficient opening and incomplete apposition of the FD were reported in up to 10% of cases.20 The risk of thrombus formation and subsequent parent artery occlusion is high if wall apposition is not adequate. Thus better wall apposition in the LVIS stent might also reduce ischemic complications.
Our study has various inherent limitations. This main limitations are the small number of patients and the retrospective collection of the cases. In addition, the follow-up period was quite short; a longer follow-up is essential to assess the long term stability of adequate occlusion. Monitoring the dual antiplatelet therapy response was not standard procedure in this case series. A clinical trial using different devices by way of comparison should be examined.
The LVIS stent represents a feasible and safe option as a coil adjunct for endovascular embolization of BA aneurysms. Although recanalization may occur after LVIS treatment, the mid term complete occlusion rate was acceptable. Larger cohort studies are required to validate these results.
CW and YW contributed equally.
Contributors CW and YW: drafting of the article and design of the data collection. JW and ZF: design of the data collection. RZ, QL, BH, YX, and QH: interpretation of the radiological results. YF and JL: revision of the article and final approval of the version to be published.
Funding This work was supported in part by the National Key R&D program of China (2016YFC1300700), National Natural Science Foundation of China (No 81301004), and project on research and application of effective intervention techniques for high risk population of stroke from the National Health and Family Planning Commission in China (GN-2016R0012).
Competing interests None declared.
Patient consent Not required.
Ethics approval The study was approved by the ethics committee of Changhai Hospital.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Additional documentation from this study is available on request to the corresponding author.
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