Learning from failure: persistence of aneurysms following pipeline embolization

OBJECTIVE A detailed analysis was performed of anterior circulation aneurysms treated with a Pipeline Embolization Device (PED) that did not progress to complete occlusion by 1-year follow-up. Angiography was performed with the purpose of identifying specific factors potentially responsible for these failed outcomes. METHODS From among the first 100 patients with anterior circulation aneurysms, 92 underwent 1-year follow-up angiography and were individually studied through review of their pre- and postembolization studies. RESULTS Nineteen aneurysms (21%) remained unoccluded at 12 months. Independent predictors of treatment failure, identified by logistic regression analysis, were found to be fusiform aneurysm morphology, decreasing dome-to-neck ratio, and the presence of a preexisting laser-cut stent. Further examination of individual cases identified several common mechanisms—device malapposition, inadequate coverage of the aneurysm neck with persistent exchange across the device, and the incorporation of a branch vessel into the aneurysm fundus—potentially contributing to failed treatment in these settings. CONCLUSIONS Attention to specific features of the aneurysm and device construct can frequently identify cases predisposed to treatment failure and suggest strategies to maximize favorable outcomes.