Introduction Stents reduce the rate of angiographic recurrence of intracranial aneurysms. The newest stent for intracranial use is the Low-profile Visible Intraluminal Support device (LVIS Jr).
Objective To assess the efficacy of the new stent in a multicenter retrospective registry.
Materials and method Centers across Canada using LVIS Jr were contacted and asked to participate in a retrospective registry of consecutive patients treated with LVIS Jr for intracranial aneurysms between January 2013 and July 2015.
Results A total of 102 patients, with saccular aneurysms in 100 patients (72 women; age range 21–78 years; mean 56.0 years; median 57.5 years) were treated with a LVIS Jr stent. The mean maximum diameter of the dome and neck of the aneurysm and dome to neck ratios were 8.3 mm±7.7 mm, 4.4 mm±1.9 mm, and 1.86±1.22, respectively. Angiographic complications arose in 23 patients, clinical complications in 9 patients, and only 3% of permanent neurological deficits occurred. Death occurred in 1 patient, unrelated to the stent. The ruptured status of the aneurysms (OR=3.29; p=0.046) and use of LVIS Jr for bailout (OR=2.54; p=0.053) showed a trend towards significant association with higher angiographic complications. At the last available follow-up, 68 class I, 20 class II, and 12 class III results were seen.
Conclusions The LVIS Jr stent is a safe and effective device for stent-assisted coiling, with 3% permanent neurological complications. Stent-assisted coiling continues to be technically challenging in cases of ruptured aneurysms and bailout situations.
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Stents are used to form a scaffold across the neck of an aneurysm to prevent coils from coming back into the parent artery. Stent assistance is used for coiling of wide-neck intracranial aneurysms. Stents significantly reduce the rate of angiographic recurrence.1–3 Different types of stents are used for treatment of intracranial aneurysms.4–9 Many intracranial stents are limited by their visualization under fluoroscopy. Radio-opacity of the stent has been a field of constant evolution.
The newest stent for intracranial use is the Low-profile Visible Intraluminal Support device (LVIS Jr, MicroVention-Terumo, Tustin, California, USA).10 ,11 The larger LVIS device is a braided stent meant for use with a larger diameter (2.5–4.5 mm) parent artery and needs a 0.021″ Headway microcatheter (MicroVention-Terumo) for deployment. This has four distal and four proximal radiopaque markers. The LVIS Jr device is also a braided stent meant for a smaller (diameter 2.5–3.5 mm), more distal parent artery but can be deployed through a 0.017″ inner diameter Headway 17 microcatheter (MicroVention-Terumo) or Scepter occlusion balloon microcatheter (MicroVention-Terumo). The LVIS Jr stent has three radiopaque strands and three distal and proximal radiopaque markers. LVIS Jr has a larger cell size (1.5 mm) than the LVIS device cell (1 mm) for easier catheterization through the stent struts.
Compared with many other intracranial stents, this stent is much more visible under fluoroscopy. However, the safety and efficacy of these stents has not been studied and reported across multiple centers and multiple operators. The purpose of our study was to report the safety and efficacy of the LVIS Jr stent in the Canadian Registry of LVIS Jr for Treatment of Intracranial Aneurysms (CaRLA).
Materials and method
CaRLA is a retrospective registry of consecutive patients with intracranial aneurysms treated with LVIS Jr in six centers across Canada between January 2013 and July 2015. All 10 centers in Canada using the LVIS Jr were contacted to contribute to our registry. However, despite multiple attempts, we were unable to get information on about 50 other patients treated with LVIS Jr in this time interval. Individual operators at each center were contacted to fill out a case report form for patients in their center. The image analysis was performed by individual operators. The information was then collected and analyzed. All patients were followed up according to the standard of care of the individual institution. At the end of December 2015, all case report forms were sent to Halifax, Nova Scotia, where the final analysis was performed. Approval from local research ethics boards was obtained. For this study, the data were anonymized and pooled for retrospective analysis.
Individual operators decided whether to use a stent for an intracranial aneurysm and whether to use LVIS Jr stent, based on their judgment of the aneurysm morphology and the operator's experience with stents. The antiplatelet regimen was also decided by individual operators. For electively planned cases, the standard antiplatelet regimen included daily dual antiplatelet medication (81 mg of aspirin and 75 mg of Plavix) starting 4 days before the procedure. When LVIS Jr stents were used in patients with acutely ruptured aneurysms (13 patients), they were loaded with 650 mg of aspirin and 300 mg of Plavix before the coiling procedure. A similar antiplatelet regimen was used through a nasogastric tube in bailout situations, in which the LVIS Jr stent was used to trap herniated coil loops into the parent artery. In all patients, dual antiplatelet medication (81 mg of aspirin and 75 mg of Plavix) was continued up to 3 months after the procedure. After 3 months, most patients were maintained with only one of the two drugs for life.
LVIS Jr stents were deployed using a Headway 17 microcatheter (MicroVention-Terumo) through a standard guide catheter. The stent was deployed using standard push and pull technique for braided stents. The number of stents deployed was only one for each aneurysm except in patients where an X or Y configuration of the stent was planned. Creation of a ‘shelf’11 using the stent for more neck coverage was also left to the operator's discretion.
In most situations, the same Headway 17 microcatheter was then used for coiling of the aneurysm. The use of adjuvant coils was at the discretion of the treating physician. Baseline characteristics were recorded, including patient demographics, mode of presentation, and specific details of the aneurysm, such as location, largest diameter (mm), neck width (mm), and morphology. Periprocedural morbidity and mortality (within 30 days of the treatment) were recorded, as were any significant clinical events through follow-up. Radiographic follow-up consisted of a combination of contrast-enhanced magnetic resonance angiography (CE-MRA), time-of-flight magnetic resonance angiography, and digital subtraction angiography (DSA). Follow-up paradigms—in particular, technique and timing—varied among centers. Aneurysm closure was judged using all available radiographic modalities. Aneurysm filling was categorized based on the Raymond classification12 as residual aneurysm, residual neck, or complete occlusion (no filling).
All data were analyzed using the STATA V.13.0 software package. Continuous variables were recoded as categorical variables for the purpose of analysis. Univariate and multivariate analyses of outcomes were done using Mantel–Haenszel tests and logistic regression respectively. A χ2 test and independent t test were also used, where appropriate. A p value of 0.05 was considered significant.
We received a total of 102 patients in our registry. Two patients, one with a fusiform internal carotid artery aneurysm and another with a dissecting middle cerebral artery aneurysm, were excluded from further analysis. A total of 100 patients (M: 28; F: 72; age range 21–78 years; mean 56.0 years; median 57.5 years) with intracranial saccular aneurysms were treated at the participating centers between January 2013 and July 2015. Details of aneurysm characteristics and their treatment with a LVIS stent are shown in table 1.
Presentations of the patients are summarized in table 1. Most of these aneurysms were saccular, except for one fusiform and one dissecting aneurysm. For statistical calculations, we included only the 100 saccular aneurysms. Only 13 patients were treated for acutely ruptured aneurysms. The remaining 87 patients were treated on an elective basis. Forty-one patients (41%) were treated for a recurrent aneurysm after prior coil embolization without stent assistance. The average diameter of the dome of the aneurysm was 8.3 mm (±7.7 mm; range 2–67 mm). The average diameter of the neck of the aneurysms was 4.4 mm (±1.9 mm; range 1.8–11 mm). The average dome to neck ratio was 1.86 (±1.22; range 0.33–10.63). A detailed summary of the aneurysm location is shown in table 1. The most common location was the anterior communicating artery followed by the basilar tip. Most aneurysms were wide-neck aneurysms (58%) with an unfavorable dome to neck ratio (47%).
A total of 120 LVIS Jr stents were used in 100 patients. Nineteen patients had an X or Y stent configuration. In one patient, there was inadvertent distal deployment of the stent and another stent was needed to cover the neck of the aneurysm. All 120 LVIS Jr stents were successfully deployed and none failed to open.
The majority of the aneurysms were coiled using bare platinum coils. Only six patients were treated with coated coils. In 32 patients, LVIS Jr was used for bailout and a stent was delivered through a Scepter balloon (MicroVention). LVIS Jr was delivered after coiling of the aneurysm in 35 patients. Most of the time, complete opening of the stent was confirmed on fluoroscopy or biplane angiography, except in 15 patients for whom dynaCT was used for this confirmation.
Angiographic complications, from asymptomatic movement of the stent to a thromboembolic phenomenon, were seen in 23% of patients (table 2). The most common angiographic complications were thromboembolic, seen in 14 patients. All of these patients were successfully treated using IA anti-IIb–IIIa agents. Only 9% of patients had clinical complications, with most of them being minor (table 2). Neurological complications were seen in 6% of patients. Half of these (3%) improved within 24 hours of onset of symptoms, resulting in only 3% of permanent neurological deficits. Of these, one patient developed right hemiparesis 1 day after treatment, one patient developed a small cerebellar stroke 4 days after the procedure, and one patient developed an ischemic stroke immediately after the procedure.
Only one death occurred in the series of 100 saccular aneurysms in which LVIS Jr was used. This patient presented with poor grade subarachnoid hemorrhage (World Federation of Neurosurgery (WFNS) grade 5) and underwent balloon-assisted coiling of a ruptured anterior communicating artery aneurysm. At the end of the coiling, the A2 segment was compressed and occluded by the coil mass and LVIS Jr was used as a bailout procedure through the Scepter balloon (MicroVention). The A2 could be opened after deployment of LVIS Jr, but the patient died from complications of severe subarachnoid hemorrhage. In another patient, LVIS Jr was used to try to open the in-stent stenosis within a flow diverter used for treatment of a fusiform carotid cave aneurysm. The in-stent stenosis could not be improved and the patient died 8 days after the procedure. This patient had a fusiform aneurysm and thus was excluded from our final study. Moreover, this complication occurred owing to in-stent stenosis of a flow diverter and not because of the LVIS Jr stent.
On univariate analysis (table 3), the ruptured status of the aneurysms (OR=3.29; p=0.046) and the situation in which LVIS Jr was used for bailout (OR=2.54; p=0.053) showed some trend towards significant association with higher angiographic complications. However, neither showed any significant association with angiographic complications when other parameters were controlled in a multivariate analysis (table 4).
At the most recent follow-up (mean 7.52 months; median 12 months), there were no further angiographic or clinical complications. The overall mortality and permanent morbidity in our series were 1% (one patient) and 3% (three patients), respectively.
Radiological outcomes were evaluated using the Raymond classification.12 Post-coiling angiography showed a class I result in 52, class II in 35, and class III result in 13 patients. Follow-up was carried out using only CE-MRA in 32, only DSA in 21, and both DSA and CE-MRA in 29 patients. The median follow-up for the entire cohort was 1 year (range 0.25–2 years). At the last available follow-up, 68 class I, 20 class II, and 12 class III results were seen. None of these patients needed re-treatment.
Post-marketing surveillance of new devices after regulatory approval is important, both for continued evaluation of the efficacy of the device and for the safety of patients. Many new devices claim superiority without any assessment of their claim. These products could be assessed either in a prospective or retrospective multicenter registry, preferably the former. We report the results of a retrospective registry in Canada using the LVIS Jr stent. To our knowledge, this is the largest reported case series of the use of the LVIS Jr stent for intracranial saccular aneurysms.
In our series, LVIS Jr had a technical success rate of 100%. In the previous series, the technical success was reported to be 91%.13 The lower technical success in the previous series was possibly because a previous version of LVIS stents was included. Our series used only LVIS Jr ‘C’ stents. The previous version of LVIS has shown incomplete opening, possibly from a lower radial force. In a smaller number of patients when LVIS Jr ‘C’ was used, the technical success was also 100% in the previous series,13 possibly owing to the improved radial force in LVIS Jr ‘C’ stents. A systematic review of all LVIS stents showed technical success of 96.8%.14 The technical success rates have been reported to be 94% with Neuroform,7 95% with Enterprise stents,5 and 100% with Solitaire stents.9
The designs of LVIS Jr stents enable their delivery into small arteries. They can be deployed into arteries with diameters as small as 1.5 mm to treat wide-neck aneurysms and can be delivered through microcatheters with an internal diameter of 0.0165 inches, which facilitates navigation in small-sized vessels. This feature is unlike Enterprise, Neuroform, or Solitaire, which need larger caliber microcatheters to be delivered. Another low-profile self-expandable stent is the LEO baby stent (Balt, Montmorency, France), for which a technical success rate of 97.5% has been reported.15
In our series, use of LVIS Jr was associated with 3% permanent neurological deficits and 1% mortality. One patient with a ruptured anterior communicating artery aneurysm in WFNS grade 5 died on the day after coiling of the aneurysm. LVIS Jr was used for bailout to open the A2 segment from the protruding coil mass. The patient never improved from his presenting clinical grade and died. We believe that this was not directly related to complications from use of the LVIS Jr stent, but we report this as an LVIS Jr stent was used in that patient. The previous series reported no permanent morbidity and mortality, but had a smaller number of patients than in our series.13
A systemic review of the use of LVIS stents reported a thromboembolic rate of 4.9% and hemorrhagic complication rate of 2.1%.14 Mocco et al5 reported 2.8% permanent morbidity and 2% mortality associated with use of Enterprise stents. Biondi et al7 reported procedural morbidity of 4.8% and 2.4% mortality with use of Neuroform stents. Jeong and Seung9 reported one thromboembolic (2%) and three hemorrhagic complications (6%) with use of the Solitaire AB stent. One of the largest series of patients treated with stent-assisted coiling reported a complication rate of 4.2%.3 The permanent morbidity rate with LEO baby stents has been reported to be 3.8% with no mortality.15 Although not directly comparable, the low complication rate in our series might reflect the overall improvement of treatment outcome, proper patient selection, and potentially, the properties of the LVIS Jr stents.
The angiographic complications of 23% were very high in our series, mainly because we included any technical problems encountered, irrespective of their clinical manifestations (table 2). This resulted in only 3% permanent neurological deficits. We believe this made our angiographic complication rate higher than those previously reported. The most common angiographic complication was thromboembolism seen in 14% of patients. Thromboembolic phenomenon without clinical manifestations is usually not reported. The thromboembolic complications were weakly associated with rupture status of the aneurysm (OR=3.29; p=0.046) and with use of the LVIS Jr for bailout (OR=2.29; p=0.08). In both situations, patients were loaded with antiplatelet medication either immediately before, or at the time of, coiling. The potentially inadequate antiplatelet response and use of stent itself are possible reasons for thromboembolic phenomenon in these subsets of patients. Geyik et al3 has also reported higher thromboembolic rates in these subsets of patients and they even considered these thromboembolic events to be unrelated to stent placement. Higher complication rates have also been reported when stents were used for bailout.16
The LVIS Jr is visible under fluoroscopy. It is important to check for complete opening and complete wall apposition of the stent just before releasing the last portion of the stent. This can be checked on either unsubtracted anteroposterior and lateral images or on dynaCT. We believe that some of the thromboembolic complications could be explained by incomplete opening of the stent. However, we did not find this to be significant in our analysis (p=0.579). Once noticed, the incompletely opened stent can be easily opened further by manipulating the stent itself or by manipulation of microcatheter or micro-guidewire within the stent.
The X or Y configurations of stent placement to improve neck coverage of the aneurysms are technically complicated and have been reported to be challenging.17–20 These configurations are used with very wide-neck bifurcation aneurysms. Nineteen of our patients were treated with X or Y configuration of stents. However, owing to mutability of the braided design of the LVIS Jr stent, a shelf technique can be used for wide-neck bifurcation aneurysms.11 This technical modification obviates the need for complicated stent configurations and can potentially reduce the angiographic complications.
The efficacy of the 88% class I and II results in our series is similar to, if not better than, that reported in previous series—76% with Enterprise stents,5 80% with Neuorform stents,7 88% with LVIS stents,13 90% with Solitaire stents,9 and 85.7% with LEO baby stents.15 No patients in our series needed re-treatment. The series with LEO baby stents reported a re-treatment rate of 5.2%.15
Our study was limited by selection bias, as we could not report on all patients in Canada for whom the LVIS Jr stent was used during the study period. Our study might also have information bias, as outcomes were reported by the operators themselves and these findings were not verified independently. However, this reflects the real-world scenario, where operators report their own outcomes. Moreover, the Canadian interventional group has carried out several registries of honest self-reporting of outcomes.21 ,22 The retrospective nature of reporting adds another layer of bias. We recommend a prospective registry for future device surveillance.
The LVIS Jr stent is a safe and effective device for stent-assisted coiling of saccular intracranial aneurysms, with 3% permanent neurological complication and 1% mortality. Stent-assisted coiling continues to be technically challenging in cases of ruptured aneurysms and bailout situations.
Thank you to Jillian Banfield for assistance with manuscript revision and submission.
Contributors JJSS: conception, data acquisition, data analysis and interpretation, drafting, revising, and approving the manuscript. AQ, AW, DT, MDPC, RF, SP, ZK, CL, HL, UA, LP, MEK: conception, data acquisition, and approving the manuscript. DI: conception, data acquisition, revising and approving the manuscript.
Competing interests JJSS is a proctor for LVIS Jr stents in Canada and has received an honorarium for his proctorship. He has also received a MicroVention education grant.
Ethics approval Each center's respective board.
Provenance and peer review Not commissioned; externally peer reviewed.