The external lumen of a stent [defined as extra-stent lumen (ESL)] assessed by optical coherence tomography (OCT) may be related to the risk of thrombus formation after sirolimus-eluting stent (SES) implantation. An everolimus-eluting stent (EES) might provide relatively minimal inflammatory reaction and appropriate neointimal coverage. The purpose of this study was to compare the neointimal thickness and ESL between SES and EES. Patients who underwent OCT examination more than 7 months after either SES or EES implantation were enrolled. Stent area (SA), lumen area (LA), neointimal area (NIA) and neointimal thickness (NIT) of each strut were measured at 1-mm intervals between stented segments. The area, angle (summation per cross-section) and depth (maximum distance from adjacent vessel surface to the outline of stent) of ESL were analyzed. A total of 49 lesions were included (SES n = 20, EES n = 29). Mean follow-up period was 11 months. A total of 998 cross-sections and 9874 struts were analyzed. There were no differences in stent area, lumen area and neointimal area (SA: 6.01 ± 1.60 vs. 6.02 ± 1.40 mm(2), p = 0.572, LA: 5.37 ± 1.52 vs. 5.29 ± 1.34 mm(2), p = 0.692, NIA: 0.64 ± 0.49 vs. 0.72 ± 0.37 mm(2), p = 0.493). Mean NIT of SES and EES were 0.11 ± 0.05 and 0.10 ± 0.05 mm, respectively (p = 0.367). Conversely, area, angle and depth of ESL in SES group were significantly greater than those in EES group (0.20 ± 0.39 vs. 0.03 ± 0.09 mm(2), p < 0.001, 56.2 ± 59.1° vs. 20.1 ± 41.9°, p < 0.001, 0.10 ± 0.09 vs. 0.03 ± 0.03 mm, p < 0.001). OCT showed that the efficacy of neointimal growth suppression is similar between SES and EES, whereas the adverse vascular response after EES implantation is smaller than that after SES implantation.
Keywords: Drug-eluting stent; Extra-stent lumen; Neointimal thickness; Optical coherence tomography; Stent coverage.