Incidence and risk factors for delayed structural changes in Pipeline Embolization Devices

BACKGROUND: Flow-diverting stents have transformed the management of intracranial aneurysms, but delayed structural changes of these devices, or delayed braid deformation (DBD), may compromise the parent vessel and increase thromboembolic risk. Data on the incidence, evolution, and predictors of DBD remain limited. METHODS: We retrospectively analyzed all Pipeline Embolization Device (PED) treatments for intracranial aneurysms at our institution from November 2011 to April 2024. Patients without follow-up imaging or treatment with other flow diverters were excluded. Demographic, aneurysm, and procedural variables were collected, including age, vessel-device size mismatch, and intraprocedural vasodilator use. Follow-up imaging was reviewed for DBD, parent-vessel narrowing, and angiographic or clinical sequelae. Multivariable logistic regression identified independent predictors. RESULTS: Among 566 PED treatments, DBD occurred in 59 (10.4%). Most cases were mild (≤49% luminal narrowing), but six (10.2%) showed ≥50% compromise, and two required balloon angioplasty for symptomatic flow limitation. Independent predictors included younger age (OR 1.51 per 10 year decrease, P<0.001) and device oversizing ≥1 mm (OR 3.14, P<0.001). The use of intraprocedural verapamil was not significant but showed a strong statistical trend (OR 2.31, P=0.053). Hypertension, aneurysm location, and PED generation were not associated with DBD. Among patients with imaging follow-up after diagnosis, >50% of non-treated cases showed spontaneous improvement or resolution. CONCLUSIONS: DBD of the PED after aneurysm treatment is relatively common but usually mild and self-limited. Younger age and device oversizing independently increase the risk of the phenomenon.