Introduction Evaluation of the angiographic outcomes for intracranial aneurysms treated with the WEB endosaccular device (Sequent Medical, Inc., Aliso Viejo, CA, USA) is different compared to coiling. As the WEB is a new device, other scales are needed and several have been and will likely be proposed. By the way, a consensus grading scale has emerged and is currently used for the clinical registries WEBCAST, WEBCAST2, WEB-IT. The objectives of the present study were to analyze the histological results for healing of the aneurysms and correlate angiographic follow-up based on the consensus scale and histologic findings in a large experimental series of WEB devices used for the treatment of elastase induced aneurysms in rabbits.

Material and methods Intracranial aneurysms were created using the elastase model in 80 rabbits and were treated with WEB devices. DSA was performed just after the deployment of the device and at long-term follow-up (mean follow-up: 100 days, 30–365). The rabbits were sacrificed at last follow-up for histological evaluation. Four investigators independently and retrospectively twice examined the post-treatment and follow up DSA to grade occlusion status accordingly to the Web Occlusion Scale. This scale is with 4 points as follow: complete aneurysm occlusion, complete occlusion with recess filling, aneurysm neck remnants and aneurysm remnants. Complete aneurysm occlusion and complete occlusion with recess filling are considered good angiographic outcomes according to previous studies. One histopathologist blinded to the angiographic results, independently graded the occlusion based on histological findings, according to a 4 point histological scale patterned on the angiographic Web Occlusion Scale. For DSA evaluation, intra and inter-observers agreement were evaluated. Follow-up angiographic grading and histological evaluation were compared using the histological grading as the gold standard, in order to determine the accuracy of the angiographic scale.

Results At last follow-up, good angiographic outcomes (complete occlusion or recess filling) were observed in 46.2% of cases (295/639 readings), 30.8%(197/639) had an aneurysm neck remnant and 23.0% (147/639) had aneurysm remnants. Histological evaluation found 40.0% of cases (32/80 aneurysms) had a good results with complete healing or only proximal recess persistence, 13.8% of cases (11/80) had aneurysm neck remnants and 46.2% (37/80) had aneurysm remnants. The inter-observers weighted kappa coefficient for agreement of the occlusion grade according to the angiographic WEB occlusion scale was 0.76, indicating substantial to almost perfect agreement between readers (range 0.68 to 0.81). Intra-observer kappa for the two sequential readings of the angiographic results was also substantial at 0.76 ranging from 0.58 to 0.85. The weighted kappa between DSA and histological occlusion evaluations was moderate at 0.47 (IC 95%: 0.42 – 0.52). Sensitivity of the DSA evaluation for complete occlusion was high at 75% and moderate at 45% for aneurysm remnant.

Conclusion DSA assessment of occlusion for aneurysms treated with the WEB device is different than coiling. The WEB occlusion scale appears to be consistent, reliable and overall accurate when compared to a histological gold standard. However, DSA readings did tend to overestimate the number of neck remnants and underestimated the number of aneurysm remnants.

Disclosures A. Rouchaud: None. D. Dai: None. Y. Ding: None. W. Brinjikji: None. Y. Zhu: None. R. Lingineni: None. D. Kallmes: 1; C; Research grant from Sequent.. R. Kadirvel: None.