Predictors of cerebral aneurysm persistence and occlusion after flow diversion: a single-institution series of 445 cases with angiographic follow-up

OBJECTIVE Flow diversion requires neointimal stent overgrowth to deliver aneurysm occlusion. The existing literature on aneurysm occlusion is limited by heterogeneous follow-up, variable antiplatelet regimens, noninvasive imaging modalities, and nonstandard occlusion assessment. Using a large, single-center cohort with low attrition and standardized antiplatelet tapering, the authors evaluated outcomes after flow diversion of anterior circulation aneurysms to identify predictors of occlusion and aneurysm persistence. METHODS Data from a prospective, IRB-approved database was analyzed for all patients with anterior circulation aneurysms treated by flow diversion with the Pipeline embolization device (PED) at the authors' institution. Follow-up consisted of catheter cerebral angiography at 6 and 12 months postembolization. Clopidogrel was discontinued at 6 months and aspirin was reduced to 81 mg daily at 12 months. Occlusion was graded as complete, trace filling, entry remnant, or aneurysm filling. Multivariate logistic regression was performed to identify predictors of aneurysm persistence. RESULTS Follow-up catheter angiography studies were available for 445 (91%) of 491 PED procedures performed for anterior circulation aneurysms between August 2011 and August 2016. Three hundred eighty-seven patients accounted for these 445 lesions with follow-up angiography. The population was 84% female; mean age was 56 years and mean aneurysm size was 6.6 mm. Aneurysms arose from the internal carotid artery (83%), anterior cerebral artery (13%), and middle cerebral artery (4%). Morphology was saccular in 90% of the lesions, and 18% of the aneurysms has been previously treated. Overall, complete occlusion was achieved in 82% of cases at a mean follow-up of 14 months. Complete occlusion was achieved in 72%, 78%, and 87% at 6, 12, and 24 months, respectively. At 12 months, adjunctive coiling predicted occlusion (OR 0.260, p = 0.036), while male sex (OR 2.923, p = 0.032), aneurysm size (OR 3.584, p = 0.011), and incorporation of a branch vessel (OR 2.206, p = 0.035) predicted persistence. Notable variables that did not predict aneurysm occlusion were prior treatments, vessel of origin, fusiform morphology, and number of devices used. CONCLUSIONS This is the largest single-institution study showing high rates of anterior circulation aneurysm occlusion after Pipeline embolization. Predictors of persistence after flow diversion included increasing aneurysm size and incorporated branch vessel, whereas adjunctive coiling predicted occlusion.