Portal de Periódicos da CAPES

Letter

2015; Lippincott Williams & Wilkins; Volume: 77; Issue: 4 Linguagem: Inglês

10.1227/neu.0000000000000880

1524-4040

Laurent Pierot,

Aortic Disease and Treatment Approaches

To the Editor: I have read with a great interest the impressive article by Cognard and Januel1 titled "Remnants and Recurrences After the Use of the WEB Intrasaccular Device in Large-Neck Bifurcation Aneurysms." The authors are to be congratulated for their very precise analysis of the anatomic follow-up in patients with wide-neck bifurcation aneurysms treated with WEB. WEB Flow Disruption is an innovative treatment for wide-neck bifurcation aneurysms that has been evaluated in multiple retrospective and prospective series.2-7 Initial evaluation has shown good safety. Efficacy was evaluated in short- and mid-term follow-up, which showed appropriate stability of aneurysm occlusion (see below), knowing that wide-neck aneurysms are prone to recanalization.4,8 Cognard and Januel report results that are not in line with previously published data regarding the stability of aneurysm occlusion. Of note, their article presents a single-center, retrospective series with a small number of patients (15), with long-term follow-up obtained in only 7 of them. Anatomic results were self-evaluated. This series consists of the first cases treated in the center during the learning curve, which certainly affect the anatomic results (see below). For these reasons, this single-center series is certainly difficult to compare with good clinical practice multicenter European and French studies conducted soon after the introduction of the WEB device after it received the Conformité Européenne mark (WEB Clinical Assessment of Intrasaccular Aneurysm [WEBCAST] and French Observatory).6,7 As mentioned by the authors, some, but not all, of their patients were included in these studies. One interesting point is that the authors were trying to define a postoperation aneurysm occlusion status by combining 3 different factors: end-of-procedure positioning of the WEB cage at the aneurysm neck on angiography, high-resolution contrast-enhanced flat-panel detector computed tomography, and 1-day time-of-flight magnetic resonance imaging. The manner in which the authors used these factors is not described. In fact, WEB induces progressive stagnation of blood inside the aneurysm, followed by intra-aneurysmal and intradevice thrombosis. The duration of this process is variable as a result of several factors, including the aneurysm anatomy and antiaggregation status of the patient. For these reasons, contrast flow inside the aneurysm and the device is currently seen on the last angiography run, and the aneurysm occlusion status is extremely difficult to evaluate accurately at the end of the procedure, as is the case after flow diversion treatment. One-day magnetic resonance imaging is probably the most accurate technique, but its sensitivity and specificity were not evaluated vs the gold standard, which is angiography. Because the postoperative status cannot be defined, it is not possible to evaluate the evolution between the postoperative period and the short-term follow-up. Therefore, the alleged 71.5% worsening of the occlusion between postoperative baseline and 3- to 6-month follow-up is not relevant. Unfortunately, only a limited number of patients (7) had long-term follow-up, and in this small group, worsening of the aneurysm status was observed in 57.2% of cases. The WEB device has a concave proximal surface that creates a proximal recess often visible on follow-up examinations. In the initial clinical experience, this recess was often classified as neck remnant. For this reason and because WEB treatment is a completely new approach for the treatment of wide-neck bifurcation aneurysm, short- and mid-term anatomic follow-up was carefully evaluated in a retrospective multicenter European study with independent evaluation of the anatomic results and is evaluated in WEBCAST and French Observatory. To precisely analyze the evolution of the proximal recess, a 4-grade scale was used to evaluate the aneurysm occlusion, including 1 grade that was opacification of the proximal recess (besides complete occlusion, neck remnant, and aneurysm remnant). Importantly, between the short-term (median, 6 months) and mid-term (median, 13 months) follow-up, all opacification of the proximal recesses was stable. If they are included as complete occlusion, the aneurysm status at the short-term follow-up was complete occlusion in 56.7%, neck remnant in 24.3%, and aneurysm remnant in 18.9%. At the mid-term follow-up, the aneurysm occlusion status was complete occlusion in 69.0%, neck remnant in 20.7%, and aneurysm remnant in 10.3%. Worsening of aneurysm occlusion between short- and mid-term results was observed in 7.1% of cases. Follow-up at 6 months was already obtained in WEBCAST with results similar to those of the retrospective series: complete occlusion in 56.1%, neck remnant in 29.3%, and aneurysm remnant in 14.6%. One-year anatomic results in both WEBCAST and French Observatory are currently under evaluation and will be published in the next months. There is clearly a large discrepancy between the results reported by Cognard and Januel and those of the retrospective series and WEBCAST. This discrepancy is probably explained by several factors. First, the selection of aneurysms treated with WEB is probably different from one series to another. As stated by Cognard and Januel, WEB treatment was selected only when all other options were considered impossible, including other endovascular and surgical options. On the basis of the Cognard and Januel figures, the aneurysms contained in their series were probably more challenging than those included in WEBCAST and the retrospective series. Second, in Table 1 of the Cognard and Januel article, it seems that in several cases the device was undersized (when we compare the sizes of the aneurysm and the device). Experience has shown that oversizing the device by approximately 1 mm in diameter is necessary to obtain appropriate anatomic results, but this was clearly not done in all patients treated in the Cognard and Januel series. Finally, Cognard and Januel report for the first time a phenomenon that has not been described in the literature before, which they called compression. It is a decrease in height of the device or, more likely, a deepening of the proximal and distal concave device recesses during the follow-up that can be analyzed on nonsubtracted images. This phenomenon was observed in 57.2% at first follow-up and 42.8% at second follow-up (with a new compression in 1 case, 14.3%). It is in fact difficult to analyze on nonsubtracted images because it requires exactly the same view from one examination to another. For this reason, this evolution is difficult to depict in WEBCAST and French Observatory. To carefully estimate the frequency of this phenomenon, it is probably necessary to use more sophisticated tools to evaluate the volume of the device. Moreover, the term compression is probably not appropriate because it relates to a given mechanism (water-hammer effect) that is presently not demonstrated. Further studies are needed to determine whether it is effectively a true compression or another mechanism like a retraction of the marker recesses related to thrombus evolution and to carefully analyze the relationship between this phenomenon and the anatomic evolution. The Cognard and Januel article is certainly useful to stress again the importance of careful prospective evaluation of new aneurysm technologies in terms of aneurysm occlusion stability, evaluation that is already under way for WEB through WEBCAST, French Observatory, and now WEBCAST 2. In each of these studies, a very long-term follow-up (up to 5 years) is planned. Disclosures Dr Pierot is consultant for Sequent and the principal investigator for WEBCAST, French Observatory, and WEBCAST2. He has no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.