Longitudinal braid stability of Surpass Evolve®: In the aspect of Fish-mouthing deformation

Fish-mouthing (FM), defined as focal end convergence of a flow diverter(FD) with or without associated biological changes such as in-stent stenosis, has been increasingly reported with newer-generation devices and has gained increasing clinical attention. However, data regarding FM associated with the Surpass Evolve(SE) FD remain limited. This study aimed to evaluate the incidence, temporal changes, and risk factors of FM.

We retrospectively reviewed 124 patients who underwent single SE (Stryker Neurovascular, Kalamazoo, MI, USA) implantation for the treatment of cerebral aneurysms. Serial follow-up skull X-rays or computed tomography(CT) were systematically reviewed. FM was defined as a ≥25% reduction in the diameter of either end. Patient demographics, aneurysm characteristics and procedure-related factors were analyzed to identify predictors of FM.

Of the 124 patients, 94 patients (with 115 aneurysms) completed 1-month follow-up. Most aneurysms (107 cases, 93%) were located in the internal carotid artery(ICA), with a median size of 10.03 mm (range, 2.39-28.61). At 1 month, FM was identified in 19 patients (20.21%). At 1 year, FM was observed in 6 patients (6.96%). One of the patients with FM experienced mild visual disturbance symptom. Complete occlusion was seen in 87.1% of cases at 1 year. Univariate analysis showed associations between proximal FM and fusiform shaped aneurysm, multiple aneurysms and middle cerebral artery located aneurysm.

FM deformities were observed in 20.21% of SE cases at 1month and decreased to 6.98% at 1 year. Fusiform shaped aneurysm, multiple aneurysms and middle cerebral artery located aneurysm were identified as possible risk factors of proximal FM. Further studies investigating these biomechanical mechanisms are warranted to identify additional risk factors.