Abstract 2884: Angiographic Lumen Changes From Oversized Neuroform Stent Implantation

Abstract

Introduction: The effect of oversized intracranial stent implantation, and the potential for excessive neointimal hyperplasia from the resulting chronic outward radial force, has not been previously reported. We sought to compare the angiographic narrowing associated with implantation of oversized Neuroform stents overlapping vessels of different diameters. Methods: We reviewed an aneurysm database and identified patients treated with stent-assisted coil embolization involving stent placement overlapping a vessel size transition. Patient demographics and lesion characteristics were extracted from chart review. A submillimeter digital caliper was used for angiogram measurement of lumen diameter at four sites ( figure ). The relationship between lumen diameter and stent oversizing was compared with student’s t-test and Pearson’s correlation. Results: Twenty vessels were identified in 18 patients, providing 80 paired data points. Mean age was 52 years (SD 12), with mean follow-up time of 8 months (SD 6). The distribution of vessel transitions included BA to PCA (n = 8), A1 to A2 or M1 to M2 (n = 8), ICA to ACA or MCA (n = 3), and Vertebral artery to PICA (n = 1). Stent diameter ranged from 3 mm to 4.5 mm, and the average oversizing in the smaller diameter parent vessel landing-zone was 1.75 mm (range 0.8 to 2.9 mm) greater than the vessel diameter. The mean change in lumen size from pre-stent implantation to follow-up was not significantly different for any of the four sites; the proximal end-stent decreased by 5.5% (SD 19.7), proximal mid-stent increased by 7.3% (SD 18.8), distal mid-stent increased by 14.7% (SD 13.8), and the distal end-stent decreased by 0.9% (SD 13.1). Stent oversizing by less than a factor of 1.65 resulted in a mean lumen loss of 4.1% (SD 15.6), while oversizing by greater than a factor of 1.65 resulted in a mean lumen gain of 11.1% (SD = 17.2), (p = 0.006). Conclusions: These data suggest oversized Neuroform stent implantation within the intracranial vasculature does not lead to increased stenosis. Stent oversizing by a factor of 1.65 or more leads to significant persistent luminal gain. The non-significant trend toward lumen loss at the stent tines suggests diminished radial force or greater neointimal hyperplasia at these sites, however persistent luminal gain from the oversized stent radial force likely predominates over any neointimal hyperplasia. Figure . A NF stent overlapping the M1 and M2 segments (A, tines indicated by white arrows). Four points of measurement (B), proximal tines (1.), mid-stent in proximal landing zone (2.), mid-stent in distal landing zone (3.), and distal tines (4.).