Difference in neointimal coverage at chronic stage between bare metal stent and sirolimus-eluting stent evaluated at stent-strut level by optical coherence tomography

Abstract

Compared with the bare metal stent (BMS), suppression of neointimal growth in the sirolimus-eluting stent (SES) reduced restenosis at the cost of more exposed struts that could impose the risk of stent thrombosis. The present study was conducted to analyze neointimal coverage patterns of stents at a strut-level after implantation of BMS or SES with the use of optical coherence tomography (OCT). We enrolled 35 patients and analyzed neointimal coverage of every strut from 41 stents (BMS: n = 8, SES: n = 33) by using OCT at follow-up of the stent implantation. All of the 371 struts from eight BMSs were covered with ≥100 μm of neointima, while 19.8 and 3.5% of 3,478 struts from 33 SESs were uncovered (neointimal thickness of <10 μm) and malapposed, respectively. The histogram of neointimal thickness showed basically normal distribution in BMS but skewed in SES. No regional difference in neointimal thickness was observed in BMS (proximal, 535.7 ± 25.2 μm; body, 532.4 ± 17.0 μm; distal, 485.8 ± 27.0 μm). In SES, however, the body segment showed thinner neointima [median 40 μm (interquartile range (IQR) 10-90 μm)] than proximal [60 μm (IQR 10-140 μm), p < 0.001] or distal [50 μm (IQR 10-110 μm), p < 0.001] segment, while uncovered and malapposed struts were more frequent in the proximal and body segments. In conclusion, SES, compared with BMS, showed more suppressed neointimal growth with regional variation: neointimal thickness was the least in the body part while the ratio of exposed and malapposed struts was minimal in the distal segment. OCT was useful for a strut-level analysis of neointimal coverage over the whole stent.