Long-term follow-up of neointimal coverage of sirolimus-eluting stents--evaluation with optical coherence tomography.

BACKGROUND Late stent thrombosis related to delayed neointimal growth is a major concern after drug-eluting stent (DES) implantation. The time course of neointimal growth and risk factors of uncovered stent struts after sirolimus-eluting stent (SES) was studied using optical coherence tomography (OCT). METHODS AND RESULTS The 60 patients were enrolled and classified into G1 (follow-up period <9 months, n=27), G2 (9-24 months, n=18), and G3 (>25 months, n=15). The time elapsed since SES implantation was associated with a significant increase in mean neointimal area and neointimal thickness, and also with a significant decrease in the number of uncovered stent struts (G1: 14.8%, G2: 11.7%, and G3: 4.1%, P<0.001). However, only 17.6% of implanted SES was completely covered by neointima, even in the G3 period. Small-diameter SES, complex coronary lesions with lipid and calcium content adjacent to stent struts, and diabetes predicted delayed neointimal coverage of SES struts in G1. CONCLUSIONS Neointima inside SES progressively increases after the routine follow-up period, but only a few SES were completely covered at 3 years after implantation. OCT is a useful modality for assessing neointimal formation after SES implantation, and may give important information about the strategy of antiplatelet therapy after DES implantation.