RT Journal Article SR Electronic T1 P-013 Predicting Mass Effect Exacerbation after Pipeline Embolization of Intracranial Aneurysms JF Journal of NeuroInterventional Surgery JO J NeuroIntervent Surg FD BMJ Publishing Group Ltd. SP A27 OP A27 DO 10.1136/neurintsurg-2014-011343.49 VO 6 IS Suppl 1 A1 Raychev, R A1 Tateshima, S A1 Jahan, R A1 Gonzalez, N A1 Szeder, V A1 Vinuela, F A1 Duckwiler, G YR 2014 UL http://jnis.bmj.com/content/6/Suppl_1/A27.1.abstract AB Introduction In this study, we investigated the clinical and procedural predictors associated with interval growth manifested as new or worsened mass effect after Pipeline Embolization Device (PED) placement for treatment of intracranial aneurysms Methods We evaluated the baseline clinical and procedural characteristics of 46 consecutive patients who underwent 48 PED procedures. The clinical factors analyzed included age, history of smoking, history of hypertension, aneurysm size, pre-existing mass effect, platelet aggregation measured by ADP% inhibition, and administration of alternative antiplatelet treatment. Procedural factors included fluoroscopy time, adjunctive coiling, and device balloon angioplasty for optimal wall apposition. Univariate analyzes using Chi-square and T-test were conducted for categorical and continuous variables, respectively. Multivariate regression model was used to determine the strongest predictor of interval growth or worsened mass effect after PED placement. The logistic regression equation was used to determine cut off values for continuous variables included in the model. Results The median age was 58 (5–88), 35/46 (76%) patients were female, and the median aneurysm size was 14.5 mm (2–38 mm). PED angioplasty was performed in 21/48 (44%) procedures, and adjunctive coiling was performed in 13/48 (27%) procedures. The median fluoroscopy time was 39 (15–314) min. 15/46 (33%) of patients had pre-existing mass effect prior to PED placement, of which 3 had worsened symptoms and 2 had new mass effect after the procedure. Of the 5 patients who had new or worsened mass effect, 4 experienced complete symptomatic resolution, while 1 had a delayed aneurysm rupture requiring vessel sacrifice. 7/15 (46%) patients with pre-existing mass effect eventually experienced symptomatic improvement. Complete aneurysm occlusion rate at 6 months was 32/43 (74%). Among all baseline clinical and procedural factors, the strongest predictor of interval growth, manifested as new or worsened mass effect, was aneurysm size larger than 18mm (OR 15.51, p = 0.018). Conclusions 1. New or worsened mass effect after PED placement may be anticipated in patients with intracranial aneurysm exceeding 18 mm in size. Although this phenomenon is uncommon and transient in most cases, physicians should be aware as pre-procedural counselling, administration of steroids, or close follow may be warranted. 2. Overall, PED placement is an effective treatment of symptomatic mass effect from intracranial aneurysms with 46% success rate in our cohort. Disclosures R. Raychev: None. S. Tateshima: 2; C; Covidien; Stryker; Penumbra; Reverse Medical; Pulsar Vascular. R. Jahan: 2; C; Covidien. N. Gonzalez: None. V. Szeder: None. F. Vinuela: None. G. Duckwiler: 2; C; Sequent; Covidien; Asahi.