Laurent Pierot
Endovascular treatment is now the first-line treatment for both ruptured and unruptured aneurysms.1,2 Some complex aneurysms (fusiform, wide-neck, large, and giant) are in some cases untreatable or difficult to treat with standard coiling. For this reason, more complex endovascular techniques have been developed, such as balloon-assisted coiling, stent-assisted coiling, and flow diversion.3,4
Although the treatment of wide-neck sidewall aneurysms has been facilitated by all these new techniques, the treatment of wide-neck bifurcation aneurysms using balloon-assisted coiling or stent-assisted coiling remains difficult, as several branches have to be protected. The safety and efficacy of flow diversion in such aneurysms is still controversial and has to be evaluated in large series.
Flow disruption with the Woven EndoBridge (WEB; Sequent Medical, Aliso Viejo, California) has emerged during the last 5 years as an innovative technique utilizing an intra-aneurysmal device placed inside the aneurysm sac at the level of the neck to disrupt the intra-aneurysmal flow and, subsequently, to create intra-aneurysmal (and intra-device) thrombosis.5 The surface exposed at the level of the neck is smooth, providing good support for the development of neointima. Several WEB devices are now available for aneurysm treatment, including dual-layer (WEB-DL) and single-layer (WEB-SL and WEB-SLS). Recently, EV (enhanced visualization) versions of these devices were developed with the introduction of platinum filaments to improve visualization of the devices during the treatment.
The treatment of aneurysms with the WEB is done using similar techniques as are used in the treatment of aneurysms with coils (eg, general anesthesia, intraoperative treatment with intravenous heparin, single or double femoral approach). Antiplatelet treatment is managed on a case-by-case basis according to aneurysm status, aneurysm anatomy, and potential alternative treatments. Sizing is an important part of the procedure. It is recommended that the WEB device be oversized compared to the diameter of the aneurysm; this is made possible by the fact that the radial force exerted by the WEB is distributed across the entire surface that is in contact with the aneurysm wall. Undersizing of the device will be associated with potentially insufficient coverage of the aneurysm neck and inadequate device seal against the aneurysm wall, leading to incomplete aneurysm treatment. On the other hand, if the initial device selected is too large, there is a risk of protrusion of the device into the parent vessel. The WEB is fully retrievable, so the physician may elect to replace the WEB with a different model or may attempt to reposition the WEB. The WEB has also been used in conjunction with both standard coils and stents. C-arm VasoCT (Philips Healthcare, Best, the Netherlands) is a helpful tool for the appropriate placement of the device in the aneurysm.6
According to the series published in the literature, current indications for WEB treatment are wide-neck aneurysms located at a bifurcation, middle cerebral artery, anterior communicating artery, internal carotid artery (terminus), and basilar artery.5,7,8 In contrast to stent-assisted coiling and flow diversion, where premedication with dual antiplatelet treatment is mandatory, WEB flow disruption can be used for the treatment of ruptured aneurysms.9
According to the literature, WEB treatment has a high feasibility (92.8%–100.0%), showing that, despite the fact that a large microcatheter is necessary for this type of treatment, WEB results are as successful as standard coiling.5,7–9 Failures were mostly encountered during initial experience with the device and were related to difficulties related to microcatheterization or inappropriate sizing.
Despite the most common aneurysm population being treated with the WEB (wide-neck bifurcation aneurysms), the rate of adverse events is relatively low. In the large French series, intraoperative complications occurred in 13.0% of patients. This rate is similar to what was observed in the ATENA (13.4%) or CLARITY (17.0%) trials.2,10 Intraoperative rupture occurred in a slightly lower percentage (1.3%) compared with ATENA (2.6%) and CLARITY (3.7%). Thromboembolic events occurred in 11.7% of patients, which is also similar to what was reported in ATENA (7.1%) and CLARITY (13.3%). Most of these thromboembolic events were “appearance of thrombus” during the procedure, and were successfully treated with intra-arterial or IV antiplatelet medications. Finally, the mortality was 0.0% in all series and morbidity was low (1.3% in the French series). These results are very similar to what was reported in large series with coiling and were also confirmed by the recent publication of the WEB prospective trial from the French Observatory.2,10,11 In this trial, it was also noteworthy that safety results were similar with both WEB-DL and WEB-SL/SLS, with a tendency for fewer thromboembolic complications with single-layer devices. WEB safety is still under