Abstract
Objective
This Woven EndoBridge Database (W-EB DB) study was conducted using data from a nationwide, multicenter database to evaluate the safety and efficacy of the W-EB device (MicroVention, Aliso Viejo, CA, USA; distributed by Terumo, Tokyo, Japan) for the treatment of wide-neck intracranial bifurcation aneurysms in Japanese patients. In this paper, we confirm the clinical usefulness of the W-EB device in Japanese patients based on the comparable 1-year post-procedure outcomes to those reported from overseas.
Methods
This W-EB DB study was a post-marketing, open-label, non-randomized cohort study conducted using the database of the Japanese Society of Neuroendovascular Therapy (JSNET). A total of 128 participants (including 103 patients with unruptured aneurysms and 25 patients with ruptured aneurysms) treated with the W-EB device between December 2020 and December 2025 at any of the 12 participating centers were included in this study. Clinical data collected from the database consisted of the patient demographics, comorbidities, aneurysm characteristics (location, size, and neck width), procedural details, and follow-up outcomes. The safety endpoints were the incidences of subarachnoid hemorrhage (SAH), rebleeding, cerebral infarction, and other adverse events occurring within 1 year after the procedure. The efficacy endpoints were the aneurysm occlusion rates and retreatment rates at 180 days and 1 year after the procedure; the aneurysm occlusion status was determined in accordance with the W-EB Occlusion Scale (WOS). We used descriptive statistics to analyze the results. The research within our submission was approved by the institutional ethics review board of Kyoto University (Approval No. R2088).
Results
In regard to the safety endpoints, SAH occurred in 1 patient (1.0%) with an unruptured aneurysm, and rebleeding occurred in 1 patient (4.0%) with a ruptured aneurysm. The incidence of cerebral infarction was 7.0%. Most other adverse events were mild, and no new device-related risks were identified. In regard to the efficacy of the device, at 1 year post-procedure, complete occlusion (WOS grade A or B) was achieved in 58 of 95 lesions (61.1%) and adequate occlusion (WOS grade A, B, or C) was achieved in 79 of 95 lesions (83.2%). Retreatment was needed for 5 of 126 lesions (4.0%). The safety and efficacy outcomes were comparable to those reported from multicenter studies conducted in Europe and the United States, with slightly higher complete occlusion rates and similar adequate occlusion and retreatment rates.
Conclusion
Favorable safety and effectiveness of the W-EB device were observed at 1 year after device deployment in Japanese patients with wide-neck intracranial aneurysms. These findings are consistent with international reports and support the clinical utility of the W-EB device, given the low incidence of serious complications.
Keywords: Woven-EndoBridge device, wide-necked bifurcation aneurysm, intracranial aneurysm
Introduction
Endovascular coil embolization has long been widely used for the treatment of intracranial aneurysms. However, for wide-neck bifurcation aneurysms, conventional coil embolization is often technically challenging or inadequate,1,2) and more complex endovascular techniques, including balloon-assisted coil embolization, stent-assisted coil embolization, and flow diverter placement, have been developed to address these difficulties.3–9)
The Woven EndoBridge (W-EB) device (MicroVention, Aliso Viejo, CA, USA; distributed by Terumo, Tokyo, Japan), first introduced in Japan in the year 2020, is an intrasaccular flow-disruption device designed to promote thrombosis by directly disrupting blood flow within the aneurysm sac. It is indicated for the treatment of wide-neck intracranial aneurysms (defined as aneurysms with a neck width of ≥4 mm and/or dome-to-neck ratio of <2) located at bifurcation sites in either the anterior or posterior circulation. Multiple clinical trials and observational studies conducted in Europe have reported the aneurysm occlusion rates and safety outcomes, including the incidence of complications such as subarachnoid hemorrhage (SAH), in intracranial aneurysm patients treated with the W-EB device.10–14) However, real-world clinical data from Japan remain limited, and the usefulness of the W-EB device for the treatment of wide-neck intracranial aneurysms in Japanese patients has still not been established.
Given this background, the present study was aimed at evaluating the clinical utility of the W-EB device for the treatment of wide-neck intracranial aneurysms in Japanese patients through an analysis of the 1-year post-procedure outcomes, including the post-procedure aneurysm occlusion rates and safety profiles, in patients selected from a nationwide W-EB database (W-EB DB) in Japan.
Materials and Methods
Study design
This W-EB DB study was a post-marketing, open-label, non-randomized observational cohort study evaluating the safety and effectiveness of the W-EB device (MicroVention) for the treatment of wide-neck intracranial aneurysms. The treatment target was wide-neck intracranial aneurysms, defined as aneurysms with a neck width of ≥4 mm and/or a dome-to-neck ratio of <2, located at bifurcation sites in either the anterior or posterior intracranial circulation. The study was based on an analysis of the data of patients registered in the Japan Society of Neuroendovascular Therapy (JSNET) database. We applied for and obtained approval from the JSNET Database Management Committee for use of the database.
The study within our submission was approved by the institutional ethics review board of Kyoto University (Approval No. R2088).
Eligible participants were those who underwent treatment with the W-EB device during the study period and provided consent for registration in the database. Eligibility for the study was not restricted by age. As a comprehensive registry-based approach was adopted, no exclusion criteria were defined.
The study period covered a 6-year period following the commercial launch of the W-EB device, and each participant was followed up for up to 3 years from the date of implantation of the W-EB device. Aneurysm occlusion was evaluated independently at each participating institution based on the imaging findings, without the services of a central core laboratory. The planned sample size for the study was 125 participants (including 100 patients with unruptured aneurysms and 25 patients with ruptured aneurysms), and patient enrollment began on December 1, 2020, using an all-case surveillance approach.
JSNET database
The JSNET database study was conducted in accordance with the Declaration of Helsinki (October 2013 revision by the World Medical Association) and the Ethical Guidelines for Medical and Health Research Involving Human Subjects (December 22, 2014; partially revised on February 28, 2017). Although the new Ethical Guidelines for Human Genome/Gene Analysis Research and Life Sciences/Medical Research Involving Human Subjects came into effect on June 30, 2021, this study had already commenced by then under the previous guidelines and was therefore continued with the adoption of transitional measures.
The principal investigators at each participating institution provided potential patient participants with a written explanation about the study, and written informed consent from each participating patient was obtained prior to enrollment in the study.
This study was registered in the University Hospital Medical Information Network (UMIN) clinical trials registry (UMIN000041023).
Number of participants and rationale
To assess the safety of the W-EB device, we considered it essential to evaluate the occurrence rate of SAH resulting from aneurysm rupture in patients with unruptured aneurysms, and the occurrence rate of rebleeding in patients with ruptured aneurysms. According to data reported from the WEB Intrasaccular Therapy Study (WEB-IT) clinical trial that were used for obtaining regulatory approval for the W-EB device, the incidence of SAH occurring within 1 year of device deployment among patients with unruptured aneurysms was 2.1% (3/141 patients).11) We assumed an SAH incidence of 3.0% based on this result, determined that a study cohort of 99 patients would be required to detect at least 1 event with 95% probability, and set the target sample size at 100 patients for evaluating the safety of the W-EB device in patients with unruptured aneurysms.
On the other hand, data from the same WEB-IT trial mentioned above also revealed that none of the participants with previously ruptured aneurysms (0%, 0/9 patients) developed SAH (rebleeding) within 1 year of device deployment.11) Therefore, we assumed a rebleeding rate of 12.0% based on a prior report on stent-assisted coil embolization of an early rebleeding rate of 11.1% (5/45 patients),15) determined that a study cohort of 24 patients would be required to detect at least 1 event with 95% probability, and set the target sample size at 25 patients for evaluating the safety of the W-EB device in patients with ruptured aneurysms.
Collected data
The following data about each participant patient were collected from the database: age and sex; medical history and comorbidities; status of rupture of the aneurysm; aneurysm characteristics (location, size, and neck width); date of the deployment of the W-EB device and procedural details (procedure time, fluoroscopy time, success or failure of device deployment); the type of device used (SL or SLS); antiplatelet medications used; intra- and post-procedure adverse events; presence/absence of any additional devices used during the procedure; and the modified Rankin Scale (mRS) scores obtained preoperatively, at discharge/on post-procedure day 7, and on post-procedure days 30, 180, and 365 (1 year).
Study outcomes
Technical success was defined as appropriate device deployment into the target lesion.
We evaluated both the safety and effectiveness outcomes.
The primary safety endpoints set were the incidence of SAH occurring within 1 year after deployment of the device in patients with unruptured aneurysms, and the incidence of rebleeding occurring within 1 year of device deployment in patients with ruptured aneurysms. Only events for which a causal relationship with the W-EB device could not be excluded were considered in the analysis. Other safety endpoints were the incidence of cerebral infarction and changes in the mRS scores over time after deployment of the W-EB device.
To determine the effectiveness of the W-EB device, the aneurysm occlusion status was assessed on the day of deployment of the W-EB device, and at 6 months and 1 year after the device deployment procedure. The occlusion status was determined according to the W-EB Occlusion Scale (WOS),16) a classification system specifically developed based on the design and deployment characteristics of the device. The WOS consists of 4 grades (A–D): grades A and B indicate complete occlusion, grade C indicates a residual neck, and grade D indicates a residual aneurysm.
The frequency distributions of lesions treated with the W-EB device for which complete occlusion (WOS grade A or B) was achieved and for which adequate occlusion (WOS grade A, B, or C) was achieved were calculated. We also assessed the retreatment status of each target aneurysm at discharge, and at 30 days, 6 months, and 1 year after the device deployment procedure, and recorded the number and proportion of retreated cases.
Statistical analysis
A conventional frequentist analytical approach was used. Descriptive statistics for continuous variables include the mean, standard deviation, median, interquartile range, and range. Categorical and ordinal variables were summarized using frequencies and percentages.
Primary analyses were performed by Mebix (Tokyo, Japan), in accordance with a statistical analysis plan agreed in advance, using SAS software version 9.4 (SAS Institute, Cary, NC, USA). Subgroup analyses stratified by rupture status, presented in Tables 1–3, were performed by Terumo using R software version 4.4.1 (R Core Team, 2024; R Foundation for Statistical Computing, Vienna, Austria).
Table 1. Patient backgrounds.
| Ruptured aneurysms (n = 25) |
Unruptured aneurysms (n = 103) |
Total (n = 128) |
|
|---|---|---|---|
| Age (years) | |||
| Mean ± SD | 61.8 ± 14.9 | 67.2 ± 13.0 | 66.2 ± 13.5 |
| Min, max | 22, 83 | 57, 77 | 22, 90 |
| Gender, n (%) | |||
| Female | 16 (64.0%) | 66 (64.1%) | 82 (64.1%) |
| Comorbidities, n (%) | 11 (44.0%) | 73 (70.9%) | 84 (65.6%) |
| Comorbidities (categories), n (%) | |||
| Cardiovascular disease | 1 (4.0%) | 7 (6.8%) | 8 (6.3%) |
| Hypertension | 7 (28.0%) | 60 (58.3%) | 67 (52.3%) |
| Dyslipidemia | 3 (12.0%) | 34 (33.0%) | 37 (28.9%) |
| Diabetes mellitus | 1 (4.0%) | 8 (7.8%) | 9 (7.0%) |
| Ischemic stroke | 1 (4.0%) | 2 (1.9%) | 3 (2.3%) |
| Hemorrhagic stroke | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Kidney disease | 1 (4.0%) | 1 (1.0%) | 2 (1.6%) |
| Liver/splenic disease | 0 (0.0%) | 2 (1.9%) | 2 (1.6%) |
| Others | 1 (4.0%) | 13 (12.6%) | 14 (10.9%) |
| Previous history of neurosurgical procedures (other than the target intracranial aneurysm), n (%) | 2 (8.0%) | 6 (5.8%) | 8 (6.3%) |
| Previous history of neurosurgical procedures (categories), n (%) | |||
| Endovascular coil embolization | 2 (8.0%) | 3 (2.9%) | 5 (3.9%) |
| Cerebrovascular surgery (e.g., clipping) | 1 (4.0%) | 1 (1.0%) | 2 (1.6%) |
| Others | 0 (0.0%) | 2 (1.9%) | 2 (1.6%) |
n (%), n represents the number of patients, and % indicates the proportion relative to the total study population.
SD, standard deviation
Table 2. Lesion characteristics and procedural details.
| Ruptured aneurysms (n = 25) |
Unruptured aneurysms (n = 104) |
Total (n = 129) |
|
|---|---|---|---|
| Number of patients, n | |||
| With 1 lesion | 25 | 102 | 127 |
| With 2 lesions | 0 | 1 | 1 |
| Rupture status by phase, n (%) | |||
| Ruptured (acute phase: within 14 days prior to the procedure) | 22 (88.0%) | 0 (0.0%) | 22 (17.1%) |
| Ruptured (non-acute phase) | 3 (12.0%) | 0 (0.0%) | 3 (2.3%) |
| Unruptured | 0 (0.0%) | 104 (100.0%) | 104 (80.6%) |
| Previous history of neurosurgical procedures, n (%) | 4 (16.0%) | 2 (1.9%) | 6 (4.7%) |
| Previous history of neurosurgical procedures (categories), n (%) | |||
| Endovascular coil embolization | 4 (16.0%) | 1 (1.0%) | 5 (3.9%) |
| Cerebrovascular surgery (e.g., clipping) | 0 (0.0%) | 1 (1.0%) | 1 (0.8%) |
| Others | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Lesion location (vessel), n (%) | |||
| BA bifurcation (BA top) | 7 (28.0%) | 23 (22.1%) | 30 (23.3%) |
| MCA | 5 (20.0%) | 30 (28.8%) | 35 (27.1%) |
| ACOMA | 6 (24.0%) | 36 (34.6%) | 42(32.6%) |
| ICA bifurcation (ICA top) | 0 (0.0%) | 3 (2.9%) | 3 (2.3%) |
| Others | 7 (28.0%) | 12 (11.5%) | 19 (14.7%) |
| Lesion laterality, n (%) | |||
| Right | 6 (24.0%) | 26 (25.0%) | 32 (24.8%) |
| Left | 6 (24.0%) | 18 (17.3%) | 24 (18.6%) |
| Midline (e.g., BA, ACOMA) | 13 (52.0%) | 60 (57.7%) | 73 (56.6%) |
| Aneurysm height (mm), mean ± SD | 5.32 ± 1.38 | 5.34 ± 1.58 | 5.34 ± 1.54 |
| Maximum aneurysm diameter (mm), mean ± SD | 6.81 ± 2.11 | 6.75 ± 1.96 | 6.77 ± 1.98 |
| Aneurysm dome width (mm), mean ± SD | 4.93 ± 1.58 | 5.59 ± 1.74 | 5.47 ± 1.72 |
| Neck diameter (mm), mean ± SD | 4.19 ± 1.54 | 4.34 ± 1.34 | 4.31 ± 1.38 |
| Dome-to-neck ratio, mean ± SD | 1.25 ± 0.32 | 1.31 ± 0.30 | 1.30 ± 0.31 |
| Technical success (successful device deployment), n (%) | |||
| Success | 25 (100.0%) | 101 (97.1%) | 126 (97.7%) |
| Unsuccess | 0 (0.0%) | 3 (2.9%) | 3 (2.3%) |
| Technical unsuccessful reasons, n (%) | |||
| Adverse event | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Device malfunction | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Others | 0 (0.0%) | 3 (2.9%) | 3 (2.3%) |
n (%), n represents the number of lesions, and % indicates the proportion relative to the total number of target lesions.
ACOMA, anterior communicating artery; BA, basilar artery; ICA, internal carotid artery; MCA, middle cerebral artery; SD, standard deviation
Table 3. Status of antiplatelet medication.
| Day before the procedure | Day of the procedure | At discharge/post-procedure day 7 | Post-procedure day 30 | Post-procedure day 180 | Post-procedure year 1 | |
|---|---|---|---|---|---|---|
| Ruptured aneurysms | ||||||
| Number of patients, n | 25 | 25 | 25 | 23 | 21 | 17 |
| Distribution of patients by number of agents, n (%) | ||||||
| 0 agents | 21 (84.0%) | 17 (68.0%) | 7 (28.0%) | 14 (60.9%) | 16 (76.2%) | 12 (70.6%) |
| 1 agent | 1 (4.0%) | 3 (12.0%) | 14 (56.0%) | 6 (26.1%) | 2 (9.5%) | 3 (17.6%) |
| 2 agents | 3 (12.0%) | 5 (20.0%) | 4 (16.0%) | 3 (13.0%) | 3 (14.3%) | 2 (11.8%) |
| 3 agents | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| 4 agents | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Distribution of patients by specific agent, n (%) | ||||||
| Aspirin | 4 (16.0%) | 8 (32.0%) | 9 (36.0%) | 9 (39.1%) | 5 (23.8%) | 4 (23.5%) |
| Clopidogrel | 3 (12.0%) | 3 (12.0%) | 2 (8.0%) | 2 (8.7%) | 0 (0.0%) | 0 (0.0%) |
| Cilostazol | 0 (0.0%) | 1 (4.0%) | 10 (40.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Prasugrel | 0 (0.0%) | 1 (4.0%) | 1 (4.0%) | 1 (4.3%) | 3 (14.3%) | 3 (17.6%) |
| Unruptured aneurysms | ||||||
| Number of patients, n | 103 | 103 | 101 | 99 | 97 | 87 |
| Distribution of patients by number of agents, n (%) | ||||||
| 0 agents | 3 (2.9%) | 3 (2.9%) | 12 (11.9%) | 19 (19.2%) | 54 (55.7%) | 62 (71.3%) |
| 1 agent | 24 (23.3%) | 25 (24.3%) | 49 (48.5%) | 45 (45.5%) | 29 (29.9%) | 20 (23.0%) |
| 2 agents | 72 (69.9%) | 71 (68.9%) | 39 (38.6%) | 34 (34.3%) | 14 (14.4%) | 5 (5.7%) |
| 3 agents | 4 (3.9%) | 4 (3.9%) | 1 (1.0%) | 1 (1.0%) | 0 (0.0%) | 0 (0.0%) |
| 4 agents | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Distribution of patients by specific agent, n (%) | ||||||
| Aspirin | 96 (93.2%) | 96 (93.2%) | 85 (84.2%) | 75 (75.8%) | 37 (38.1%) | 19 (21.8%) |
| Clopidogrel | 64 (62.1%) | 59 (57.3%) | 31 (30.7%) | 29 (29.3%) | 15 (15.5%) | 6 (6.9%) |
| Cilostazol | 3 (2.9%) | 3 (2.9%) | 2 (2.0%) | 2 (2.0%) | 1 (1.0%) | 2 (2.3%) |
| Prasugrel | 17 (16.5%) | 21 (20.4%) | 12 (11.9%) | 10 (10.1%) | 4 (4.1%) | 3 (3.4%) |
| Total | ||||||
| Number of patients, n | 128 | 128 | 126 | 122 | 118 | 104 |
| Distribution of patients by number of agents, n (%) | ||||||
| 0 agents | 24 (18.8%) | 20 (15.6%) | 19 (15.1%) | 33 (27.0%) | 70 (59.3%) | 74 (71.2%) |
| 1 agent | 25 (19.5%) | 28 (21.9%) | 63 (50.0%) | 51 (41.8%) | 31 (26.3%) | 23 (22.1%) |
| 2 agents | 75 (58.6%) | 76 (59.4%) | 43 (34.1%) | 37 (30.3%) | 17 (14.4%) | 7 (6.7%) |
| 3 agents | 4 (3.1%) | 4 (3.1%) | 1 (0.8%) | 1 (0.8%) | 0 (0.0%) | 0 (0.0%) |
| 4 agents | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Distribution of patients by specific agent, n (%) | ||||||
| Aspirin | 100 (78.1%) | 104 (81.3%) | 94 (74.6%) | 84 (68.9%) | 42 (35.6%) | 23 (22.1%) |
| Clopidogrel | 67 (52.3%) | 62 (48.4%) | 33 (26.2%) | 31 (25.4%) | 15 (12.7%) | 6 (5.8%) |
| Cilostazol | 3 (2.3%) | 4 (3.1%) | 12 (9.5%) | 2 (1.6%) | 1 (0.8%) | 2 (1.9%) |
| Prasugrel | 17 (13.3%) | 22 (17.2%) | 13 (10.3%) | 11 (9.0%) | 7 (5.9%) | 6 (5.8%) |
Results
Cleaned data entered into the JSNET database between December 1, 2020 (W-EB DB study initiation date), and December 25, 2025, were extracted. A total of 128 participants registered from 12 participating institutions were selected, including 103 patients with unruptured wide-neck intracranial bifurcation aneurysms and 25 patients with ruptured wide-neck intracranial bifurcation aneurysms (Fig. 1).
Fig. 1. Study flow diagram. A flow diagram illustrating the participant selection process in the study. With follow-up: Patient vital status (alive or deceased) was available at each observation time point. Without follow-up: Patient vital status (alive or deceased) was unavailable at each observation time point.
IA, intracranial aneurysm; JSNET, Japanese Society for Neuroendovascular Therapy; W-EB, Woven EndoBridge, MicroVention, Aliso Viejo, CA, USA, distributed by Terumo, Tokyo, Japan
Patient backgrounds
The patient characteristics are summarized in Table 1.
A total of 128 patients were enrolled, with a mean age of 66.2 years (range: 22–90); 82 patients (64.1%) were female. Comorbidities were observed in 84 patients (65.6%), the most common being hypertension in 67 patients (52.3%), followed in frequency by dyslipidemia in 37 patients (28.9%), diabetes mellitus in 9 patients (7.0%), cardiovascular disease in 8 patients (6.3%), ischemic stroke in 3 patients (2.3%), renal disease in 2 patients (1.6%), and hepatic or splenic disease in 2 patients (1.6%). Other comorbidities were reported in 14 patients (10.9%).
Eight patients (6.3%) had a previous history of neurosurgical procedures performed for lesions other than the target aneurysm.
The lesion characteristics and procedural details are presented in Table 2. Of the 129 aneurysms in the 128 enrolled patients, 104 (80.6%) were unruptured and 25 (19.4%) were ruptured lesions. Among the ruptured aneurysms, 22 lesions (17.1%) presented in the acute phase (within 14 days prior to the procedure), while 3 lesions (2.3%) presented after the acute phase. Six aneurysms (4.7%) had a history of prior neurovascular interventions, such as coil embolization or cerebrovascular surgery.
In regard to the aneurysm location, the most common site was the anterior communicating artery (42 lesions, 32.6%), followed in frequency by the middle cerebral artery (35 lesions, 27.1%), basilar artery bifurcation (30 lesions, 23.3%), and internal carotid artery bifurcation (3 lesions, 2.3%). Other locations accounted for 19 of the 129 lesions (14.7%).
The aneurysm dimensions were as follows (mean ± standard deviation [SD]): height, 5.34 ± 1.54 mm; maximum diameter, 6.77 ± 1.98 mm; dome width, 5.47 ± 1.72 mm; neck diameter, 4.31 ± 1.38 mm; and dome-to-neck ratio 1.3 ± 0.31.
Analyses were conducted on a per-lesion basis. Technical success was achieved for 126 of the 129 lesions (97.7%). For the 3 lesions (2.3%), the procedure proved unsuccessful due to device size mismatch or post-deployment device instability, and the device placement was ultimately abandoned.
Antiplatelet drug use in the patients is summarized in Table 3.
The most common antiplatelet regimen was dual-agent therapy on the day before and the day of the procedure. This transitioned to single-agent therapy at discharge through post-procedure day 30, and to no antiplatelet therapy at post-procedure day 180 and 1 year. None of the patients received 4 or more antiplatelet agents at any time point.
In patients with unruptured intracranial aneurysms, dual antiplatelet therapy was predominantly administered before and during the procedure.
In contrast, in patients with ruptured intracranial aneurysms, antiplatelet therapy was not administered in most cases before or during the procedure; however, dual antiplatelet therapy was predominantly used at discharge or on post-procedural day 7.
Safety outcomes
Among the 103 patients with unruptured intracranial aneurysms, 1 participant (1.0%) developed SAH that was considered possibly related to the W-EB device (MicroVention). This event occurred when the aneurysm was perforated by the microcatheter during navigation of the device into the lesion. Although hemostasis was subsequently established, the patient developed increased intracranial pressure and required ventricular drainage, mechanical ventilation, and systemic management, and died on post-procedure day 5.
Among the 25 patients with ruptured intracranial aneurysms, 1 patient (4.0%) developed rebleeding that was considered possibly related to the W-EB device. This event developed on post-procedure day 15, but the patient’s family declined further surgical intervention, and conservative management was continued. The patient subsequently developed hypotension due to brain herniation and died on post-procedure day 23.
Changes in functional status evaluated using the mRS are presented in Table 4. At discharge (or on post-procedure day 7 for patients who had not yet been discharged), mRS score improvement was observed in 11 patients (8.7%), whereas worsening was observed in 8 patients (6.3%). On post-procedure day 30, improvement of the score was observed in 14 patients (12.5%) and worsening of the score in 5 patients (4.5%). On post-procedure day 180, 17 patients (14.7%) showed improvement, and 2 patients (1.7%) showed worsening. At 1 year post-procedure, 17 patients (16.7%) showed improved mRS scores, while none of the patients showed worsening of the scores.
Table 4. Changes in mRS scores.
| Preoperative | Post-procedure day 7 | Post-procedure day 30 | Post-procedure day 180 | Post-procedure year 1 | ||
|---|---|---|---|---|---|---|
| Ruptured aneurysms | ||||||
| Number of patients assessed for mRS, n | 25 | 25 | 23 | 20 | 19 | |
| Distribution of patients by mRS scores, n (%) | ||||||
| mRS 0 | 3 (12.0%) | 12 (48.0%) | 13 (56.5%) | 16 (80.0%) | 16 (84.2%) | |
| mRS 1 | 8 (32.0%) | 2 (8.0%) | 3 (13.0%) | 0 (0.0%) | 0 (0.0%) | |
| mRS 2 | 6 (24.0%) | 4 (16.0%) | 1 (4.3%) | 1 (5.0%) | 2 (10.5%) | |
| mRS 3 | 2 (8.0%) | 1 (4.0%) | 3 (13.0%) | 1 (5.0%) | 0 (0.0%) | |
| mRS 4 | 1 (4.0%) | 2 (8.0%) | 1 (4.3%) | 2 (10.0%) | 1 (5.3%) | |
| mRS 5 | 5 (20.0%) | 3 (12.0%) | 1 (4.3%) | 0 (0.0%) | 0 (0.0%) | |
| mRS 6 | 0 (0.0%) | 1 (4.0%) | 1 (4.3%) | 0 (0.0%) | 0 (0.0%) | |
| Number of patients assessed for mRS at both preoperative and the corresponding post-procedure time point, n | — | 25 | 23 | 20 | 19 | |
| Distribution of patients by mRS scores change, n (%) | ||||||
| Improved | — | 11 (44.0%) | 13 (56.5%) | 16 (80.0%) | 16 (84.2%) | |
| Unchanged | — | 11 (44.0%) | 7 (30.4%) | 4 (20.0%) | 3 (15.8%) | |
| Worsened | — | 3 (12.0%) | 3 (13.0%) | 0 (0.0%) | 0 (0.0%) | |
| Unruptured aneurysms | ||||||
| Number of patients assessed for mRS, n | 102 | 103 | 90 | 97 | 84 | |
| Distribution of patients by mRS scores, n (%) | ||||||
| mRS 0 | 97 (95.1%) | 93 (90.3%) | 85 (94.4%) | 92 (94.8%) | 82 (97.6%) | |
| mRS 1 | 3 (2.9%) | 7 (6.8%) | 3 (3.3%) | 2 (2.1%) | 2 (2.4%) | |
| mRS 2 | 1 (1.0%) | 1 (1.0%) | 0 (0.0%) | 1 (1.0%) | 0 (0.0%) | |
| mRS 3 | 1 (1.0%) | 1 (1.0%) | 1 (1.1%) | 1 (1.0%) | 0 (0.0%) | |
| mRS 4 | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | |
| mRS 5 | 0 (0.0%) | 0 (0.0%) | 1 (1.1%) | 0 (0.0%) | 0 (0.0%) | |
| mRS 6 | 0 (0.0%) | 1 (1.0%) | 0 (0.0%) | 1 (1.0%) | 0 (0.0%) | |
| Number of patients assessed for mRS at both preoperative and the corresponding post-procedure time point, n | — | 102 | 89 | 96 | 83 | |
| Distribution of patients by mRS scores change, n (%) | ||||||
| Improved | — | 0 (0.0%) | 1 (1.1%) | 1 (1.0%) | 1 (1.2%) | |
| Unchanged | — | 97 (95.1%) | 86 (96.6%) | 93 (96.9%) | 82 (98.8%) | |
| Worsened | — | 5 (4.9%) | 2 (2.2%) | 2 (2.1%) | 0 (0.0%) | |
| Total | ||||||
| Number of patients assessed for mRS, n | 127 | 128 | 113 | 117 | 103 | |
| Distribution of patients by mRS scores, n (%) | ||||||
| mRS 0 | 100 (78.7%) | 105 (82.0%) | 98 (86.7%) | 108 (92.3%) | 98 (95.1%) | |
| mRS 1 | 11 (8.7%) | 9 (7.0%) | 6 (5.3%) | 2 (1.7%) | 2 (1.9%) | |
| mRS 2 | 7 (5.5%) | 5 (3.9%) | 1 (0.9%) | 2 (1.7%) | 2 (1.9%) | |
| mRS 3 | 3 (2.4%) | 2 (1.6%) | 4 (3.5%) | 2 (1.7%) | 0 (0.0%) | |
| mRS 4 | 1 (0.8%) | 2 (1.6%) | 1 (0.9%) | 2 (1.7%) | 1 (1.0%) | |
| mRS 5 | 5 (3.9%) | 3 (2.3%) | 2 (1.8%) | 0 (0.0%) | 0 (0.0%) | |
| mRS 6 | 0 (0.0%) | 2 (1.6%) | 1 (0.9%) | 1 (0.9%) | 0 (0.0%) | |
| Number of patients assessed for mRS at both preoperative and the corresponding post-procedure time point, n | — | 127 | 112 | 116 | 102 | |
| Distribution of patients by mRS scores change, n (%) | ||||||
| Improved | — | 11 (8.7%) | 14 (12.5%) | 17 (14.7%) | 17 (16.7%) | |
| Unchanged | — | 108 (85.0%) | 93 (83.0%) | 97 (83.6%) | 85 (83.3%) | |
| Worsened | — | 8 (6.3%) | 5 (4.5%) | 2 (1.7%) | 0 (0.0%) | |
mRS assessment: The denominator is the number of patients assessed for mRS at each evaluation time point. Changes from the preoperative assessment: The denominator is the number of patients assessed for mRS at both preoperative and the corresponding post-procedure time point (the sum of those classified as improved, unchanged, or worsened).
mRS, modified Rankin Scale
In patients with unruptured intracranial aneurysms, mRS scores showed a gradual improvement trend from the preoperative period through 1 year after the procedure.
In patients with ruptured intracranial aneurysms, the proportion of patients with an mRS score of ≥3 at baseline was higher than that in patients without ruptured lesions. However, during the follow-up period from post-procedure day 7 to 1 year, the proportion of patients with an mRS score of ≥3 showed a decreasing trend.
Across the entire cohort, adverse events were reported in 19 patients (14.8%), with a total of 22 events. On a per-patient basis, the most frequent adverse event was cerebral infarction, which occurred in 9 patients (7.0%). This was followed by SAH in 3 patients (2.3%) and hydrocephalus in 2 patients (1.6%). Of the 9 patients in whom a cerebral infarction occurred, 6 developed it on the day of treatment or the following day. In contrast, cerebral infarction occurred in 3 patients between approximately 8 and 30 days postoperatively; of these 3 patients, 2 had ruptured intracranial aneurysms, and neither had received single antiplatelet therapy (SAPT) or antiplatelet therapy. The 1 patient with an unruptured intracranial aneurysm developed an incidental acute myocardial infarction on the 4th postoperative day, and cerebral infarction occurred after transfer to another hospital; however, the details were reported as unknown.
In patients with unruptured intracranial aneurysms, cerebral infarction occurred in 6 patients and SAH in 2 patients. Among these events, those for which a causal relationship with the W-EB device could not be excluded were cerebral infarction in 4 patients and SAH in 1 patient. Of the 2 patients for whom a relationship to the device was excluded, 1 involved a cerebral infarction related to the procedure for positioning the device, and a causal relationship with the procedure could not be excluded; the other was reported as a cerebral infarction caused by epileptic seizures.
In patients with ruptured intracranial aneurysms, cerebral infarction was observed in 3 patients, hydrocephalus in 2 patients, and SAH in 1 patient. Among these events, those for which a causal relationship with the W-EB device could not be excluded were cerebral infarction in 1 patient and SAH in 1 patient. The 2 patients with ruptured intracranial aneurysms, for whom a causal relationship to the device was excluded were reported to have cerebral infarctions associated with SAH.
For hydrocephalus, a causal relationship with the W-EB device was assessed as unlikely in both cases.
Overall, 3 deaths were reported in the entire cohort. One death occurred in a patient with an unruptured intracranial aneurysm and was associated with SAH for which a causal relationship with the W-EB device could not be excluded. In this patient, a W-EB device was immediately placed to address an intraoperative rupture, and hemostasis was achieved using a balloon catheter; however, the patient reportedly died a few days later due to severe brain damage caused by the SAH.
Another death occurred in a patient with a ruptured intracranial aneurysm and was associated with rebleeding for which a causal relationship with the W-EB device could not be excluded. The remaining death occurred in a patient with an unruptured intracranial aneurysm after transfer to another hospital, and the cause of death was unknown.
Device malfunction was noted in 1 patient (0.8%)—incomplete detachment was observed after deployment and the device position was corrected using a snare; the patient developed a minor embolic infarction in the right middle cerebral artery territory, but recovered 6 days later. No other cases of device malfunction were encountered.
Efficacy outcomes
The number of patients in whom the device was successfully deployed, the number of patients who underwent WOS evaluations, and the number of patients who required retreatment at each assessment time point are presented in Table 5. Assessments were performed for 126 lesions in 125 participants immediately after the procedure, for 87 lesions in 86 patients on post-procedure day 180, and for 95 lesions in 94 patients at 1 year post-procedure.
Table 5. WOS classification and retreatment status at each evaluation time point.
| Procedure | Post-procedure day 180 | Post-procedure year 1 | |
|---|---|---|---|
| Ruptured aneurysms | |||
| Number of lesions with successful device deployment (number of patients),* n (n) | 25 (25) | 22 (22) | 19 (19) |
| Number of lesions assessed for WOS (number of patients), n (n) | 25 (25) | 12 (12) | 17 (17) |
| WOS classification of lesions, n (%) | |||
| WOS grade A: Complete occlusion | 0 (0.0%) | 3 (25.0%) | 11 (64.7%) |
| WOS grade B: Complete occlusion | 0 (0.0%) | 2 (16.7%) | 3 (17.6%) |
| WOS grade C: Residual neck | 2 (8.0%) | 0 (0.0%) | 2 (11.8%) |
| WOS grade D: Residual aneurysm | 20 (80.0%) | 7 (58.3%) | 1 (5.9%) |
| Unassessable | 3 (12.0%) | 0 (0.0%) | 0 (0.0%) |
| WOS A+B complete occlusion | 0 (0.0%) | 5 (41.7%) | 14 (82.4%) |
| WOS A+B+C adequate occlusion | 2 (8.0%) | 5 (41.7%) | 16 (94.1%) |
| Retreatment—Yes, n (%) | — | 2 (9.1%) | 0 (0.0%) |
| Unruptured aneurysms | |||
| Number of lesions with successful device deployment (number of patients),* n (n) | 101 (100) | 100 (99) | 93 (92) |
| Number of lesions assessed for WOS (number of patients), n (n) | 101 (100) | 75 (74) | 78 (77) |
| WOS classification of lesions, n (%) | |||
| WOS grade A: Complete occlusion | 19 (18.8%) | 25 (33.3%) | 26 (33.3%) |
| WOS grade B: Complete occlusion | 15 (14.9%) | 13 (17.3%) | 18 (23.1%) |
| WOS grade C: Residual neck | 3 (3.0%) | 22 (29.3%) | 19 (24.4%) |
| WOS grade D: Residual aneurysm | 58 (57.4%) | 14 (18.7%) | 15 (19.2%) |
| Unassessable | 6 (5.9%) | 1 (1.3%) | 0 (0.0%) |
| WOS A+B complete occlusion | 34 (33.7%) | 38 (50.7%) | 44 (56.4%) |
| WOS A+B+C adequate occlusion | 37 (36.6%) | 60 (80.0%) | 63 (80.8%) |
| Retreatment—Yes, n (%) | — | 1 (1.0%) | 2 (2.2%) |
| Total | |||
| Number of lesions with successful device deployment (number of patients),* n (n) | 126 (125) | 122 (121) | 112 (111) |
| Number of lesions assessed for WOS (number of patients), n (n) | 126 (125) | 87 (86) | 95 (94) |
| WOS Classification of lesions, n (%) | |||
| WOS grade A: Complete occlusion | 19 (15.1%) | 28 (32.2%) | 37 (38.9%) |
| WOS grade B: Complete occlusion | 15 (11.9%) | 15 (17.2%) | 21 (22.1%) |
| WOS grade C: Residual neck | 5 (4.0%) | 22 (25.3%) | 21 (22.1%) |
| WOS grade D: Residual aneurysm | 78 (61.9%) | 21 (24.1%) | 16 (16.8%) |
| Unassessable | 9 (7.1%) | 1 (1.1%) | 0 (0.0%) |
| WOS A+B complete occlusion | 34 (27.0%) | 43 (49.4%) | 58 (61.1%) |
| WOS A+B+C adequate occlusion | 39 (31.0%) | 65 (74.7%) | 79 (83.2%) |
| Retreatment—Yes, n (%) | — | 3 (2.5%) | 2 (1.8%) |
Denominator for WOS assessment: The denominator is the number of lesions assessed for WOS at each evaluation time point. Denominator for retreatment: The denominator is the number of lesions with successful device deployment at each evaluation time point.
*In this table, the “Number of lesions with successful device deployment (number of patients)” includes only successfully treated lesions (patients) in which survival was confirmed beyond predefined time thresholds (i.e., ≥38 days for Post-procedure day 180 and ≥223 days for Post-procedure year 1).
W-EB, Woven EndoBridge, MicroVention, Aliso Viejo, CA, USA, distributed by Terumo, Tokyo, Japan; WOS, W-EB Occlusion Scale
Immediately after the procedure, the occlusion status evaluated according to the WOS in 126 lesions revealed grade A occlusion in 19 lesions (15.1%), grade B occlusion in 15 lesions (11.9%), grade C occlusion in 5 lesions (4.0%), and grade D occlusion in 78 lesions (61.9%); 9 lesions (7.1%) were deemed as being unevaluable. The combined number of lesions showing complete occlusion (grade A or B) was 34 (27.0%), and the combined number of lesions showing adequate occlusion (grade A, B, or C) was 39 (31.0%).
On post-procedure day 180, assessment of the occlusion status according to the WOS of 87 lesions showed grade A occlusion in 28 lesions (32.2%), grade B occlusion in 15 lesions (17.2%), grade C occlusion in 22 lesions (25.3%), and grade D occlusion in 21 lesions (24.1%); 1 lesion (1.1%) was deemed as being unevaluable. Complete occlusion (grade A or B) was achieved in 43 lesions (49.4%), and adequate occlusion (grade A, B, or C) was observed in 65 lesions (74.7%).
At 1 year post-procedure, assessment of the occlusion status according to the WOS of 95 lesions indicated grade A occlusion in 37 lesions (38.9%), grade B occlusion in 21 lesions (22.1%), grade C occlusion in 21 lesions (22.1%), and grade D occlusion in 16 lesions (16.8%). The total number of lesions showing complete occlusion (grade A or B) was 58 (61.1%), while the total number of cases that showed adequate occlusion (grade A, B, or C) was 79 (83.2%).
Retreatment was performed for 5 lesions (4.0%) within 1 year after the device deployment procedure. Three lesions in 3 patients required retreatment within 180 days post-procedure, while 2 lesions in 2 patients required retreatment within 1 year after the procedure. Among the 5 lesions that required retreatment, 3 were treated by stent-assisted coil embolization, 1 was treated by coil embolization alone, and 1 was treated by coil embolization combined with flow diverter placement.
Discussion
Safety outcomes
In this W-EB DB study, SAH within 1 year of device deployment for which a causal relation to the device could not be ruled out occurred in 1 patient (1.0%) among all the patients with unruptured intracranial aneurysms. This incidence was lower than the 2.1% reported from the WEB-IT study,11) which was used as the reference to determine the sample size. Among patients with ruptured intracranial aneurysms, 1 patient (4.0%) developed rebleeding within 1 year of device deployment that was considered possibly related to the device; this incidence was also lower than the 11.1% reported from the reference study.15) In contrast, recently published systematic reviews and meta-analyses of treatment outcomes with the W-EB device have reported rebleeding rates in patients with ruptured intracranial aneurysms ranging from 0.33% to 1.0%.17–19)
Because the number of patients in the ruptured intracranial aneurysm cohort was limited in the present study, the precision of the estimated rebleeding rate is subject to inherent limitations. Therefore, the results should be interpreted with caution, and further studies involving larger patient populations are warranted to more accurately assess the risk of rebleeding.
The incidence of cerebral infarction developing post-procedure was 7.0% (9/128 patients), with the infarction considered as possibly being related to the device deployment in 5 of the 9 cases. A systematic review published in 2017 reported a thromboembolic event rate of 8.0% within 30 days after the procedure.20) Based on the comparable incidences between this aforementioned study and our study, the rate of cerebral infarction observed in this study was not considered as a safety concern. Furthermore, in the present study, no cerebral infarction was observed in association with the stepwise reduction of antiplatelet therapy over time. These findings suggest that, when appropriate antiplatelet therapy is administered, endovascular treatment using the W-EB device (MicroVention) is associated with a very low incidence of cerebral infarction.
No other adverse events or device malfunctions suggesting new safety concerns associated with the device were identified.
Although the effectiveness of balloon catheters in managing intraoperative ruptures is believed to be similar to that observed during coil embolization, the number of cases in this study is limited. Therefore, we believe it is necessary to gather and analyze further data regarding injuries caused by intraoperative ruptures and hemostasis when using the W-EB device.
Regarding factors contributing to worsening mRS scores, in patients with unruptured intracranial aneurysms, adverse events related to the procedure or W-EB device were the primary causes, while worsening at a later stage was reported to be due to incidental adverse events. In patients with ruptured intracranial aneurysms, reports have indicated that, in addition to brain damage caused by the underlying condition, patients may also develop cerebral infarction.
Efficacy outcomes
In this W-EB DB study, by 1 year after the device deployment procedure, complete occlusion was achieved in 58 of 95 lesions (61.1%) and adequate occlusion in 79 of 95 lesions (83.2%). In previous multicenter studies that similarly included both unruptured and ruptured wide-neck bifurcation aneurysms, such as the French Observatory,10) WEBCAST2,13) and WEB-IT11) studies, the 1-year complete occlusion rates ranged from 51.7% to 54.0%, and the 1-year adequate occlusion rates ranged from 79.3% to 85.4%. As compared with these results, the complete occlusion rate observed in the present study was slightly higher (61.1% vs. 51.7%–54.0%), while the adequate occlusion rate was comparable (83.2% vs. 79.3%–85.4%).
Retreatment due to recanalization was performed for 5 lesions (4.0%) within 1 year after the device deployment procedure. All retreatments, including coil embolization, coil embolization combined with flow diverter placement, and stent-assisted coil embolization, were completed safely without associated adverse events. The reported 1-year retreatment rates from other multicenter studies10,11,13) range from 3.2% to 8.0%. Thus, the retreatment rate observed in the present study (4.0%) was comparable to these previous reports.
In summary, in this study, the incidence of SAH possibly related to use of the W-EB device occurring within 1 year of device deployment in patients with unruptured aneurysms was 1.0%, which is lower than the rate of 2.1% reported by the WEB-IT study.11) The incidence of rebleeding possibly related to use of the W-EB device occurring within 1 year of device deployment in patients with ruptured aneurysms was 4.0%, which was also lower than the rate of 11.1% reported from the reference study.15) The complete occlusion rate was slightly higher than the rates reported from previous studies (61.1% vs. 51.7%–54.0%),10,11,13) while the adequate occlusion rate was comparable (83.2% vs. 79.3%–85.4%). The retreatment rate was also comparable to previous reports (4.0% vs. 3.2%–8.0%).10,11,13) These findings collectively demonstrate the safety and efficacy of the W-EB device in Japanese patients with wide-neck intracranial bifurcation aneurysms.
The W-EB-17 device, which is compatible with a 0.017-inch microcatheter, has recently been approved in Japan. This low-profile device is expected to improve access to smaller and more distal vessels. Future studies are needed to evaluate the advantages of the device reported from international studies, such as reduced requirement of adjunctive device use and a lower incidence of thromboembolic events,21) in the Japanese population.
Limitations of the study
This W-EB DB study had several limitations. First, because an appropriate control group that can be compared with the deviceuse group was not registered in the database, while it was possible to calculate the incidence rates of adverse events in the study cohort, it was not possible to compare the safety and efficacy—specifically, the incidence of SAH, which serves as a key safety endpoint—with those of similar devices already on the market. Furthermore, because the number of patients in the ruptured intracranial aneurysm cohort was limited in the present study, the precision of the estimated rebleeding rate and the proportion of patients with mRS worsening are subject to certain limitations. Therefore, the interpretation of these results should be approached with caution. Additionally, although the aneurysm occlusion status was a mandatory survey item, this was an observational study without intervention, and the results relied on measurements performed by the treating physicians in real-world clinical practice. Moreover, variations in the measured results could have occurred in this study because no independent central core laboratory was designated for the imaging assessments. The absence of an independent safety committee could also have limited the rigor of the safety evaluations. Finally, comparisons of the results with existing reports must be conducted with caution, as differences in editorial standards and methodological aspects could interfere with the validity of such comparisons.
Conclusion
This study was aimed at clarifying the safety and efficacy of the W-EB device (MicroVention) used in Japanese patients with wide-neck intracranial bifurcation aneurysms through an analysis of the 1-year post-procedure outcomes of patients registered in the W-EB DB. In regard to safety, the incidences of SAH and rebleeding were lower than the anticipated rates prior to initiation of the W-EB DB study. The efficacy outcomes were comparable to those reported from previous studies conducted in Western countries. Taken together, these findings demonstrate the clinical utility of the W-EB device for Japanese patients with wide-neck intracranial bifurcation aneurysms.
Disclosure Statement
Yuji Matsumaru serves as a consultant to Terumo Corporation and Medtronic Japan and received lecture fees from Terumo Corporation and Medtronic Japan. Akira Ishii received lecture fees from Terumo Corporation, Medtronic Japan, Stryker Japan, and Kaneka Medics. Shigeru Miyachi received lecture fees from Medtronic Japan and Kaneka Medics. Tomoji Takigawa received lecture fees from Terumo Corporation. Nobuyuki Sakai received lecture fees from Medtronic Japan, SB Kawasumi, and Stryker, and research fundings from Century Medical, Kaneka Medics, Penumbra, and Toro Neurovascular. Chiaki Chiba and Hiroyuki Seki are employees of Terumo Corporation. The first author and the other authors have no conflict of interest. This W-EB DB study was conducted by Terumo Corporation using data purchased from JSNET.
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