Serial Changes of Neointimal Tissue after Everolimus-Eluting Stent Implantation in Porcine Coronary Artery: An Optical Coherence Tomography Analysis

Purposes. The serial changes in neointimal tissues were compared between everolimus-eluting stent (EES) and bare-metal stent (BMS) in the porcine coronary artery using optical coherence tomography (OCT). Methods. Serial (1, 3, and 6 month follow-up after stent implantation) OCT examinations were performed in 15 swine with 15 BMS- and 15 EES-treated lesions in porcine coronary arteries. Results. In BMS-implanted lesions, neointimal volume decreased from 7.3 mm³ to 6.9 mm³ and 6.4 mm³ at 1, 3, and 6 months follow-up without statistical significance (P=0.369). At the time points of 1, 3, and 6 months, neointimal tissue appearance was mainly a homogeneous pattern (80.0%, 93.3%, and 100%, resp.), while the other pattern was layered. In contrast, in EES-implanted lesions, neointimal volume significantly increased from 4.8 mm³ to 9.8 mm³ between 1 and 3 months but significantly decreased to 8.6 mm³ between 3 and 6 months (P<0.001). Between 1 and 3 months, the layered pattern of neointimal tissue increased from 26.7% to 66.7% but decreased to 20.0% between 3 and 6 months. Conclusions. EES had a biphasic pattern of neointimal amounts that correlated with changes in neointimal morphology.