Abstract 2777: Optimal Expansion of the Stent is a Major Contributor to the Neointimal Coverage Following Sirolimus-eluting Stent Implantation: A Combined Study of Angioscopy and Intravascular Ultrasound

Background: Although sirolimus-eluting stent (SES) has significantly reduced in-stent restenosis by inhibiting neointimal hyperplasia, insufficient neointimal coverage after stenting may result in adverse outcomes. Determinants of neointimal coverage following SES, however, are poorly understood. Methods: We evaluated 28 SES lesions using both angioscopy and intravascular ultrasound (IVUS). Degree of neointimal coverage was judged by angioscopy at follow-up (11 ± 6 months): complete/incomplete coverage, based on whether the stent struts were embedded by the neointima. Minimal stent area (MSA), external elastic membrane (EEM), lumen cross-sectional area (CSA) and plaque burden (EEM minus lumen/EEM CSA) were measured by IVUS at stent implantation. Both proximal and distal references were used. Stent expansion was assessed by stent expansion index (SEI) as MSA/reference EEM CSA. Under-expansion was defined as SEI < 0.4. Incomplete apposition was defined as the lack of contact between any strut and the underlying vessel wall. Results: Complete coverage was identified in 10 (36%), and incomplete coverage in 18 (64%). Time from the stenting to angioscopy (10 ± 5 versus 11 ± 7 months, p=0.8) as well as the lesion and procedural characteristics was similar between the complete/incomplete coverage groups. IVUS parameters were also similar, except for the final MSA (7.0±1.8mm 2 in complete versus 5.3±1.9mm 2 in incomplete , p=0.02) and lumen CSA at the distal reference site (6.1±1.4mm 2 in complete versus 4.9 ±1.2mm 2 in incomplete , p= 0.02). The frequency of incomplete apposition was similar between the groups (20% in complete versus 39% in incomplete , P= 0.4); however, SEI was significantly larger in the complete coverage than in the incomplete coverage group (0.52 ± 0.11 versus 0.39 ± 0.09, p=0.002). Stent under-expansion was identified only in 2 (20%) of the complete coverage, as compared to 67% of the incomplete coverage group (P=0.046). By multivariate logistic regression analysis, large SEI was strongly associated with complete neointimal coverage (P=0.04). Conclusion: Optimal expansion of the stent is a major contributor to the complete neointimal coverage following sirolimus-eluting stent implantation.