OBJECTIVE The Pipeline Embolization Device (PED) is now a well-established option for the treatment of giant or complex aneurysms, especially those arising from the anterior circulation. Considering the purpose of such treatment is to maintain patency of the parent vessel, postembolization occlusion of the parent artery can be regarded as an untoward outcome. Antiplatelet therapy in the posttreatment period is therefore required to minimize such events. Here, the authors present a series of patients with anterior circulation aneurysms treated with the PED who subsequently experienced parent vessel occlusion (PVO). METHODS The authors performed a retrospective review of all anterior circulation aneurysms consecutively treated at a single institution with the PED through 2014, identifying those with PVO on follow-up imaging. Aneurysm size and location, number of PEDs used, and follow-up digital subtraction angiography results were recorded. When available, pre- and postembolization platelet function testing results were also recorded. RESULTS Among 256 patients with anterior circulation aneurysms treated with the PED, the authors identified 8 who developed PVO after embolization. The mean aneurysm size in this cohort was 22.3 mm, and the number of PEDs used per case ranged from 2 to 10. Six patients were found to have asymptomatic PVO discovered incidentally on routine follow-up imaging between 6 months and 3 years postembolization, 3 of whom had documented "delayed" PVO with prior postembolization angiograms confirming aneurysm occlusion and a patent parent vessel at an earlier time. Two additional patients experienced symptomatic PVO, one of which was associated with early discontinuation of antiplatelet therapy. CONCLUSIONS In this large series of anterior circulation aneurysms, the authors report a low incidence of symptomatic PVO, complicating premature discontinuation of postembolization antiplatelet or anticoagulation therapy. Beyond the subacute period, asymptomatic PVO was more common, particularly among complex fusiform or very large-necked aneurysms, highlighting an important phenomenon with the use of PED for the treatment of anterior circulation aneurysms, and suggesting that extended periods of antiplatelet coverage may be required in select complex aneurysms.
Keywords: ICA = internal carotid artery; MCA = middle cerebral artery; MPED = minimally porous endoluminal device; PED = Pipeline Embolization Device; PRU = platelet reactivity units; PVO = parent vessel occlusion; Pipeline Embolization Device; aneurysm; flow diversion; internal carotid artery; parent vessel occlusion; vascular disorders.