Neointimal coverage of sirolimus-eluting stents 6 months and 12 months after implantation: evaluation by optical coherence tomography.

Background: Optical coherence tomography (OCT) is a new imaging modality with resolution of approximately 10 microm and can be employed to visualize intracoronary characteristics. Sirolimus-eluting stents (SES) are susceptible to late thrombosis due to delayed re-endothelialization over the stent struts, which may result in acute myocardial infarction or death. This study was designed to evaluate the re-endothelialization and neointimal coverage of SES with OCT 6 months and 12 months after implantation.

Methods: A total of 36 patients enrolled in the study underwent OCT examination 6 months (17 patients) and 12 months (19 patients) after SES implantation. The strut apposition to the vessel wall and neointimal coverage on SES struts were evaluated by OCT.

Results: Forty-six SES and 6561 struts were analyzed. At 6 months, 3041 struts (98.7%) were well-apposed and 39 struts (1.3%) were malapposed. At 12 months, 3434 struts (98.6%) were well-apposed and 47 struts (1.4%) were malapposed. Furthermore, only 4 SES at 6 months (18.2%) and 10 SES at 12 months (41.7%) were fully covered by neointimal growth. The average neointimal thicknesses covering the analyzed struts at 6 months and 12 months were (42+/-28) microm and (88+/-32) microm, respectively. There were 1989 struts at 6 months (72.1%) and 1461 struts at 12 months (45.6%) with neointimal thickness <100 microm.

Conclusions: OCT was able to visualize the strut apposition to the vessel wall and neointimal coverage on SES struts. At 6-month and 12-month follow-up examinations most struts were covered with thin neointima, but few of the entire SES showed full coverage. To prevent late-stent thrombosis in the presence of uncovered stent struts, longer dual antiplatelet drugs therapy should be recommended.