Serial Evaluation of Vascular Response After Implantation of a New Sirolimus-Eluting Stent With Bioabsorbable Polymer (MISTENT): an optical coherence tomography and histopathological study.

Background: Novel vascular scaffolds aim at equipoise between safety and efficacy. Intravascular optical coherence tomography (OCT) allows in-vivo serial assessment of stent-vessel interactions with high resolution and frequent sampling and may complement histology assessment. We investigated the vascular response to a novel absorbable coating sirolimus-eluting stent (AC-SES) by means of serial OCT and histology evaluation in a porcine model.
Methods: One AC-SES and one bare-metal stent (BMS) were implanted in separate coronary arteries of three Yucatan mini-swine. Serial OCT was performed post procedure and at 3-, 28-, 90-, and 180-day follow-up. Normalized optical density (NOD) was used for the assessment of tissue response over time. Histological evaluation was performed at day 180.
Results: A total of 6408 stent struts were analyzed. OCT revealed 100% of struts covered at 28 days, and a significant difference in NOD from 3 to 28 days (0.64 ± 0.07 vs 0.71 ± 0.05, respectively; P<.001) in the AC-SES group. Neointimal thickness was 0.14 ± 0.08 mm, 0.17 ± 0.11 mm, and 0.16 ± 0.09 mm in the AC-SES group and 0.18 ± 0.10 mm, 0.14 ± 0.09 mm, and 0.10 ± 0.08 mm in the BMS group, while rates of uncovered struts were 0%, 0%, and 3.1% and 1.4%, 7.8%, and 21.5%, respectively, at 28, 90, and 180 days. Minimal inflammation and a mature endothelialization were demonstrated in both groups by histology.
Conclusion: OCT serial assessment of vascular response suggested NIH maturation 28 days following AC-SES implantation in pigs. These findings, coupled with histological demonstration of low inflammation scores and complete endothelial coverage as measured at 180 days, suggest a satisfactory healing response to AC-SES.