WEB (Woven EndoBridge) SL / SLS / WEB 17

2018), CE Mark, NMPA | Evidence Level: Level 1 (WEB-IT, CLARYS, CLEVER, 5-Year Follow-Up Data)

5.1.1 Design and Engineering: Generation Evolution The WEB (Woven EndoBridge) device, manufactured by MicroVention, consists of a selfexpanding nitinol braided mesh structure designed to be deployed within the aneurysm sac. The device has evolved through several generations, beginning with the WEB DL (Dual Layer): the first-generation device featured a dual-layer design with an inner and outer braided nitinol mesh. The WEB is an intrasaccular, spherically shaped, self-expanding, braided device with a dense mesh constructed from a large number of extremely fine nitinol wires. This construct disrupts blood flow at the level of the aneurysm neck, promoting intrasaccular thrombosis. The current commercially available WEB generations are: Model

Shape

Delivery System

Key Feature

WEB SL (Single Layer)

Sphere

0.021"–0.027" MC

Main workhorse; sphere conforms to sac

WEB SLS (Single

Prolate sphere

0.021"–0.027" MC

For taller

Layer Sphere) WEB 17

aneurysms Sphere/barrel

0.017" MC

For smaller aneurysms; low profile

The WEB device is designed to treat brain aneurysms inside the aneurysm sac, disrupting blood flow while sealing the neck and protecting the dome with MicroVention’s MicroBraid Technology. The WEB device provides proven, long-term durability with its five-year followup results demonstrating long-term safety and effectiveness and is the only 17-system compatible intrasaccular flow disruptor. WEB is now also available in two new sizes (SL 6×2 and SL 7×2), continuing to allow for the treatment of different sizes and shapes of aneurysms. The WEB device sizes range from \(4 \times 3\) mm to \(11 \times 9\) mm, covering a broad spectrum of aneurysm morphologies. Sizes range from 4×3 mm to 11×9 mm, and the devices are braided composites made from nitinol and platinum.

5.1.2 Evidence Base: The WEB Evidence Pyramid With five-year clinical trial data, WEB is the most well-studied intrasaccular device available in the marketplace today, with 7 good clinical practice (GCP) studies and over 200 peerreviewed publications. WEB-IT: The US Pivotal Trial (J Neurointerv Surg 2019) The U.S. pivotal trial WEB-IT showed complete or adequate occlusion in 84.6% of aneurysms at 12 months. The WEB-IT study enrolled 150 patients with 152 wide-neck bifurcation aneurysms (MCA, basilar tip, AComm) across 14 US centers. It used an independent core laboratory for angiographic assessment and was the basis for FDA approval of the WEB device in December 2018. The trial defined “adequate occlusion” as complete occlusion or neck remnant on core-lab-adjudicated DSA. WEB-IT: 5-Year Follow-Up (JNIS 2023) The most comprehensive long-term data comes from the 5-year WEB-IT follow-up publication: Five-year follow-up data from the WEB-IT study demonstrated that the WEB device was safe and effective when used in the treatment of WNBAs. Aneurysm occlusion rates achieved at 1 year follow-up were durable, with rates of progressive thrombosis far exceeding rates of recurrence over time.

At 5-year follow-up, complete occlusion was observed in 58.1% and adequate occlusion in 87.2% of cases. For patients with both 1-year and 5-year occlusion statuses available, 76.8% (63/82) of aneurysms remained stable or improved with no retreatment. Long-Term Single-Center 5-Year Experience In one series, a total of 66 patients (72.7% female) with 66 intracranial aneurysms (n = 25 acutely ruptured) were treated with WEB, with a mean patient age of 55.6 years and mean aneurysm neck width of 4.5 mm. Of the aneurysms analyzed at 5 years, including those that required retreatment, 47.3% were occluded completely, 36.4% had neck remnant, and 16.3% had recanalized. 83.7% of aneurysms were occluded adequately. None of the aneurysms rebled after initial treatment with WEB. Recanalization appears to be unlikely after the first two years post-treatment. Retreatment Meta-Analysis (Interventional Neuroradiology 2023) A systematic review including 11 studies found an overall retreatment rate of 171/1875 aneurysms (10.3%; 95% CI 8.3–12.9%). Stent-assisted coiling was used to treat 59 retreated aneurysms (36.7%), and flow diverters were used to treat 44 aneurysms (18.7%). Following retreatment, the complete occlusion rate was 57/91 aneurysms (62.8%) and the adequate occlusion rate was 24/91 aneurysms (26.4%). Multicenter Retrospective Study (n = 412, 22 centers, 2025) This multicenter, retrospective study analyzed 405 patients with 412 aneurysms treated with the WEB device across 22 neurovascular centers. Clinical and radiologic data were reviewed to identify factors influencing patients’ clinical outcome and target aneurysmal occlusion at short-term (within 6 months) and long-term (beyond 1 year) follow-up. Occlusion status of target aneurysms was analyzed in relation to various clinical and morphological factors. Outcomes were also compared based on institutional treatment volume. Centers with higher WEB treatment volumes (more than 30 cases) demonstrated lower thromboembolic events with sequelae. CLEVER Study: WEB 17 (2024) The CLEVER study was an observational, multicenter, prospective study conducted in 17 European investigational sites using the WEB 17 device for the treatment of ruptured and unruptured aneurysms. The WEB device demonstrated efficacy and safety for both unruptured and ruptured aneurysms. The study objective was to provide safety and efficacy data on the WEB 17 device in the treatment of wide-neck bifurcation aneurysms.

WEB-IT China: First Chinese GCP Study The WEB-IT China study was the first and only good clinical practice (GCP) study of intrasaccular flow disruption devices conducted in China, with the purpose of evaluating the safety and effectiveness of the WEB device for treating patients with WNBAs in the Chinese population. WEB-IT China was a prospective, single-arm confirmatory study conducted in 8 centers in China between June 2017 and August 2019.

5.1.3 CLARYS Study: The Ruptured Aneurysm Evidence Base One of the most clinically important applications of the WEB device is in acutely ruptured wide-neck bifurcation aneurysms, where DAPT avoidance is especially critical. The CLARYS study is a prospective multicenter study conducted in 13 European centers. The study enrolled 60 patients with 60 ruptured aneurysms of the anterior and posterior circulation. The study was conducted with an independent assessment of safety outcomes and imaging. The CLARYS study, focused on ruptured aneurysms, showed complete or adequate occlusion in 81.1% at 12 months. At 30 days, among patients with follow-up, 76% received no antiplatelet, 18% received a single antiplatelet, and 6% were on dual antiplatelets. This antiplatelet profile is fundamentally safer than stent-assisted coiling or flow diversion in the acute SAH setting. The interim results of CLARYS show that the endovascular treatment of ruptured bifurcation aneurysms with the WEB is safe and effective and, in particular, provides effective protection against rebleeding. It may induce profound change in the endovascular management of ruptured bifurcation aneurysms. Updated WEB Meta-Analysis in Ruptured Aneurysms (2025) Twenty-five studies with 1,065 patients (1,077 aneurysms) were included. The implantation success rate was 98.04%, and rebleeding occurred in only 0.33% of cases. Adequate and complete occlusion at 12 months were 83.77% and 59.42%, respectively. Good functional outcomes at 90 days were 87.27%, with a retreatment rate of 7.54%. Procedure-related mortality and morbidity were 0.39% and 1.39%. The overall complication rate was 12.82%, with thromboembolic and hemorrhagic events in 4.55% and 1.05% of cases, respectively.

5.1.4 WEB Shape Modification (WSM): A Surveillance Consideration WEB shape modification (WSM) has previously been associated with aneurysm recurrence. A 5-year experience of WEB device use with a quantitative approach to the WSM phenomenon has been reported.

During the total follow-up period, WSM was observed in 35/48 aneurysms (72.9%). Adequate occlusion rates were 87.0% and 92.6% with and without WSM, respectively (P = 0.65). WSM was observed in more than half of cases but without significant influence on adequate occlusion rate. This quantitative approach to WSM shows that this phenomenon appears to be early and progressive over time. The practical implication is that WSM seen on 6-month follow-up DSA should not automatically prompt retreatment, as it does not correlate with worse occlusion outcomes. The absence of WSM does not predict better outcomes. Surveillance should use a standardized occlusion grading scale (modified O’Kelly-Marotta scale), not WSM morphology alone.

5.1.5 Sizing Principles and Deployment Sequence Sizing Table Measurement

Rule

Width

Oversize 1 mm vs. widest sac diameter

Height

Match or slightly undersize to sac height

Delivery (WEB 17)

0.017" microcatheter

Delivery (WEB SL/SLS)

0.021"–0.027" microcatheter

Deployment Sequence

Measure sac width and height on biplane 3D-DSA working projection; select device by manufacturer sizing chart Navigate microcatheter into sac; deploy device, confirming neck coverage and intrasaccular seating Assess marker position and “WEB bulge” sign; if mal-sized, fully resheath and exchange Detach electrothermally once position is confirmed Critical Tech Tip: The most common sizing error is under-sizing height, causing the device to compress too tall and protrude into the parent vessel. Always re-measure on a workingprojection 3D run, not a single 2D view. Warning: Incomplete neck coverage predicts recurrence. If the device bulges beyond the neck plane or a residual neck remnant persists, consider resheathing and resizing rather than accepting a suboptimal result.

5.1.6 Expanded Indications: Beyond Classic WNBAs The possibility to extend the indications of WEB devices for the treatment of distally located or more complex aneurysms has been highlighted. The future role of intrasaccular flow disruptors in intracranial aneurysm treatment has yet to be defined but will likely expand significantly in the future. Investigators have started to report the use of WEB beyond the traditional proximal bifurcation anatomy studied in the prospective trials, with successful applications reported in side-wall and more distal bifurcation aneurysms. Results suggest that deployment technique and device stability may be more critical determinants of long-term outcomes than aneurysm morphology. The WEB device performs reliably across a spectrum of aneurysm shapes, and this versatility broadens the indications for the WEB system, underscoring its potential utility in cases previously deemed unsuitable for intrasaccular flow disruption. WEB-Assisted Microcatheterization A WEB placed inside the sac, blocking the aneurysm neck and providing a contact surface to redirect the microwire across the aneurysm, represents an alternative strategy for the treatment of complex aneurysms. This novel technique leverages the WEB’s neck-covering mesh as a scaffold to guide wire and microcatheter navigation in challenging aneurysm geometries. ──────────────────────────────────────────────────