Late stent thrombosis related to delayed endothelialization is a major concern after drug-eluting stent (DES) implantation. The long-term vascular response towards DES implantation remains unclear. Optical coherence tomography (OCT) is a high-resolution imaging modality which provides new opportunities for evaluating neointimal coverage and stent strut apposition after stent implantation.Methods
Fifty two patients who accepted 64 sirolimus-eluting stents (SESs, Cypher Select) were enrolled in the study. The OCT procedure was performed in 20 patients at 12 months (group 1), 17 patients at 24 months (group 2), and 15 patients at 48 months (group 3) after SESs implantation, respectively. The neointimal hyperplasia (NIH) thickness and stent strut apposition were assessed at 1-mm interval, and the presence of thrombus was observed in each stent.Results
The NIH thickness was significantly higher at 48 months than that of 12 months (0.1694 ± 0.1455 mm in G3 vs. 0.1455 ± 0.1373 mm in G1, P < 0.01) and 24 months (0.1514 ± 0.1296 mm in G2, P <0.01) after SESs implantation, but no significant difference existed between that of 12 months and 24 months (P > 0.05). Longer follow-up time was associated with significant decrease in the prevalence of uncovered struts (17.3% in group 1 vs. 8.8% in group 2 vs. 2.6% in group 3, P < 0.01) and malapposed struts (14.2% in group 1 vs. 10.3% in group 2 vs. 4.7% in group 3, P < 0.01). The incidence of intracoronary thrombus steadily decreased from 3.6% at 12 months to 2.4% at 24 months, and to 0.8% at 48 months (P < 0.01).Conclusion
Neointimal growth continued for as long as 48 months after SES implantation. NIH thickness increased insignificantly from 12 to 24 months, but markedly increased at 48 months after stent implantation. Late neointimal growth was accompanied by a higher rate of covered struts and lower rate of malapposed stent struts. © 2012 Wiley Periodicals, Inc.