We investigated the association between the inflow angle of aneurysms and their occlusion status at 1 and 2years after flow diverter (FD) treatment. We retrospectively analyzed 42 consecutive patients from a single center with 43 untreated, unruptured internal carotid artery (ICA) proximal to communicating segment, saccular aneurysms sized <12mm. At 1year posttreatment, the complete occlusion (CO) rate was 58.1%. On univariate analyses, the proportion of inflow angle >90° was significantly lower in the CO group than in the incomplete occlusion group (20.0% VS. 83.3%; P < 0.001). The CO incidence decreased with a height-width (H/W) ratio of <1.2 (P= 0.059). On multivariate analysis, an H/W ratio of <1.2 (odds ratio [OR], 0.076; P= 0.027) and an inflow angle of >90° (OR, 0.020; P= 0.0011) significantly influenced CO at 1year post FD. At 2years posttreatment, the CO rate was 76.3% (29/38 cases with available follow-up data). On univariate analyses, in the CO group compared to the incomplete occlusion group, the proportion of H/W ratio <1.2 was significantly lower (P= 0.005) and the proportion of inflow angle >90° was significantly lower (P= 0.021); aneurysm dome size tended to be larger (8.5mm vs. 7.1mm; P= 0.080). On multivariate analysis, an H/W ratio <1.2 (OR, 0.042; P= 0.015) and an inflow angle >90° (OR: 0.088; P= 0.031) significantly influenced CO at 2years post FD. The inflow angle of >90° and H/W ratio <1.2 may significantly influence the CO rate in small- or medium-sized internal carotid artery aneurysms 1 and 2 years post FD.
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