Delayed Neointimalization on Drug-Eluting Stents

rug-eluting stents (DES) have made innovativesuccess in suppressing neointimal proliferation with reduced target lesion revascularization.Long term safety, however, becomes the major concern due to persistent incidence of very late stent thrombosis.By intravascular ultrasound (IVUS) examinations, most DES appears uncovered by neointima at a chronic stage, even though it is difficult to evaluate the extent or thickness of neointimal coverage due to its limited resolution.Since 2004, optical coherence tomography (OCT), which has almost 10 times higher resolution than IVUS, became available for coronary evaluation and its image acquisition method is in progress.1 Matsumoto et al reported that when using OCT for a 6-month follow-up period, 89% of the sirolimus-eluting stents (SES) lesion were covered by thin neointima and 64% of neointima covering the struts were less than 100 μm thickness, which was undetectable by IVUS.Thus, most of the SES lesions appeared to be covered by thin neointima.However, the frequency of full covered SES was only 16% at 6 months.2 Thus, most of the SES are supposed to have partial uncovered struts at 6 months.As a result, the more important question was proposed; when will most of SES be fully covered by neointima?