Formation of web- and membrane-like structures on the edges of bare-metal coronary stents

Web-like (W) and membrane-like (M) structures have been observed on coronary stent edges on angioscopy but their incidence and mechanisms remain obscure.

First, 26 patients [acute coronary syndromes (ACS) in 10 and stable angina (SA) in 16] underwent angioscopy of the stented coronary artery immediately after, and 32 patients (ACS in 18 and SA in 14) 6 months after insertion of bare-metal stents. Second, angioscopy of the stented coronary artery was performed in 4 beagles 5 h after, and in 9 beagles 1 month after stenting. W and M were observed in patients with ACS and those with SA (80.0% vs 18.7%; P<0.05) immediately after and 6 months after stenting (55.5% vs 28.5%; NS). They were stained with Evans blue that selectively stains fibrin immediately after stent insertion, but not 6 months later. In beagles, W and M were observed in 75.0% at 5 h and in 66.6% 1 month later. Histologically, W and M were composed of fibrin at 5 h, whereas they were composed of collagen fibers at 1 month.

W and M were frequently formed on the edges of coronary stents. They were formed with fibrin in the acute phase, whereas this fibrin was replaced by collagen fibers in the chronic phase.