WEB Device for Endovascular Treatment of Wide-Neck Bifurcation Aneurysms

Procedure Duration/Patient Selection

The procedure duration may be reduced compared with other available techniques. If one considers that we have included only patients with complex IAs that would “classically” require a several-hour procedure (either surgical or endovascular), the use of the WEB, in general, brings a significant improvement in treatment time to this subgroup of patients. This might decrease the procedure-related morbidity by reducing thromboembolic events and anesthesia time. However, in 2 patients (patients 7 and 8), the procedure was significantly longer because of the difficulty associated with delivery and satisfactory positioning/deployment of the WEB in these aneurysms. This occurred because the long axis of the aneurysm was not in line with the center line of the parent artery, resulting in the need for repositioning and/or catheter shaping. In these 2 patients, the angle between the microcatheter axis and the long axis of the aneurysm was close to 45° so that during initial WEB deployment the device would have had some contact with the aneurysm wall. As a remedy, the delivery catheter had to be reshaped and the WEB had to be repositioned several times to finally allow a safe deployment.

EVT with the WEB

Despite the small size of the present series, our results show that EVT of IAs with the WEB is a feasible new technique. Moreover, the availability of the WEB might enlarge indications of EVT because it allows treating IAs that are not amenable to conventional endovascular techniques. Indeed, wide-neck terminal/bifurcation IAs require treatment with a Y- or X-stent placement or even the waffle-cone technique.^4,5 These techniques may be difficult in some IAs and also have other major limitations, including the need for dual antiplatelet medication, which may be associated with higher complication rates,⁶ the unknown long-term tolerance of 2 stents within the same vessel, and the high rate of recanalization with the waffle-cone technique.^4,5 Therefore, the WEB might have potential advantages over these techniques, but this needs to be confirmed in larger studies evaluating the efficacy and stability of this new therapeutic option.

From a technical point of view, the key points for EVT with the WEB are the support of the delivery microcatheter and the WEB size selection. A telescopic access system is very useful to ensure stable navigation and deployment of the WEB. For adequate WEB sizing, the width of the device should be equal to or greater than the aneurysm width. If the device is larger than the sac, it will elongate, and care must be taken after delivery to assess whether there is any significant parent artery intrusion at the aneurysm ostium. If this is present, the device may be removed and a smaller size WEB may be deployed. In most instances, upsizing the device by 1 mm, when the first device is too small, is sufficient and appropriate. However, as seen in the case to be described below, it would be beneficial to be able to upsize, in some aneurysms, by 0.5 mm. We experienced 1 failure in patient 18, who had an aneurysm with a 5.5-mm width that was not suitable for either a 5- or a 6-mm WEB. These half-millimeter sizes are expected to be available soon. Fortunately, the WEB is fully retrievable once deployed, and it may be exchanged for a more optimal device if sizing is not correct. As shown in 2 of our patients, should there be inadvertent intrusion of the WEB into the parent artery or adjacent branches, a stent may be used to avoid flow obstruction (patients 5 and 11). Last but not least, the use of a WEB does not prevent using other conventional embolic material such as detachable coils if the aneurysm occlusion is incomplete (Fig 3).

Anatomic Outcome

Our anatomic results are encouraging if one considers the anatomic features of the aneurysms in this series (ie, patients with unruptured bifurcation/terminal-type aneurysms, having wide necks and a mean size of 9 mm). Indeed, in this group of IAs that have the highest recanalization rate when treated with coils, near-complete occlusion was immediately achieved in most patients, and it either improved or remained stable at follow-up in most cases. Moreover, the small remnant at the base of the sac was frequently due to the design of the WEB device that has a concave proximal recess that is filled with contrast material. At follow-up, most of these remnants remained stable or even remodeled positively. In time, modification of the WEB design may further reduce this feature. It could be, however, that the current design is beneficial to aneurysm/device stability or that this type of small-neck remnant, adjacent to the very low porosity of the base of the WEB, is irrelevant to the stability of treatment. We are optimistic that the use of an intrasaccular flow disrupter with the physical characteristics of the WEB (an elasticity that resists deformation) will be associated with stable anatomic results because the mechanisms that lead to aneurysm occlusion are different from those associated with coiling. Also, the fact that the WEB resists deformation (Fig 1D, -F; arrows) would seem to offer hope that it will not, as do coils, undergo compaction so as to allow aneurysm recanalization.

Finally, our preliminary experience suggests that in patients who need to receive IV abciximab (and perhaps other powerful antiplatelet medication) immediate complete aneurysm occlusion may be difficult. Nevertheless, follow-up controls in the 2 such patients in our series showed a satisfactory aneurysm occlusion that either remained stable or improved.

Much more data and experience with the device are now needed to evaluate the real efficacy and long-term results of this new therapeutic approach.