Long-term efficacy,safety and biocompatibility of a novel sirolimus eluting iron bioresorbable scaffold in a porcine model

Iron is considered as an attractive alternative material for bioresorbable scaffolds(BRS).The sirolimus eluting iron bioresorbable scaffold(IBS),developed by Biotyx Medical(Shenzhen,China),is the only iron-based BRS with an ultrathin-wall design.The study aims to investigate the long-term efficacy,safety,biocompatibility,and lumen changes during the biodegradation process of the IBS in a porcine model.A total of 90 IBSs and 70 cobaltchromium everolimus eluting stents(EES)were randomly implanted into nonatherosclerotic coronary artery of healthy mini swine.The multimodality assessments including coronary angiography,optical coherence tomography,micro-computed tomography,magnetic resonance imaging,real-time polymerase chain reaction(PCR),and histopathological evaluations,were performed at different time points.There was no statistical difference in area stenosis between IBS group and EES group at 6 months,1year,2 years and 5 years.Although the scaffolded vessels narrowed at 9 months,expansive remodeling with increased mean lumen area was found at 3 and 5 years.The IBS struts remained intact at 6 months,and the corrosion was detectable at 9 months.At 5 years,the iron struts were completely degraded and absorbed in situ,without in-scaffold restenosis or thrombosis,lumen collapse,aneurysm formation,and chronic inflammation.No local or systemic toxicity and abnormal histopathologic manifestation were found in all experiments.Results from real-time PCR indicated that no sign of iron overload was reported in scaffolded segments.Therefore,the IBS shows comparable efficacy,safety,and biocompatibility with EES,and late lumen enlargement is considered as a unique feature in the IBS-implanted vessels.