Aims: We sought to investigate two-year clinical and serial optical coherence tomography (OCT) outcomes after implantation of a fully bioresorbable vascular scaffold (BVS) or a cobalt-chromium everolimus-eluting stent (CoCr-EES). Methods and results: In the ABSORB Japan trial, 400 patients were randomised in a 2:1 ratio to BVS (N=266) or CoCr-EES (N=134). A pre-specified OCT subgroup (N=125, OCT-1 group) underwent angiography and OCT post procedure and at two years. Overall, the two-year TLF rates were 7.3% and 3.8% in the BVS and CoCr-EES arms (p=0.18), respectively. Very late scaffold thrombosis (VLST) beyond one year was observed in 1.6% (four cases: all in non-OCT-1 subgroups) of the BVS arm, while there was no VLST in the CoCr-EES arm. In three cases, OCT at the time of or shortly after VLST demonstrated strut discontinuities, malapposition and/or uncovered struts. However, the vessel healing by two-year OCT was nearly complete in both BVS and CoCr-EES arms with almost fully covered struts, and minimal malapposition. The flow area by two-year OCT was smaller in the BVS arm than in the CoCr-EES arm, mainly due to tissue growth inside the device. However, there were no differences between the BVS and CoCr-EES with regard to the quality of homogenous tissues growing inside the devices. Conclusions: The rate of TLF was numerically higher in the BVS arm than in the CoCr-EES arm, although this difference was not statistically significant. VLST was observed only in the BVS arm at a rate of 1.6% between one and two years. Further studies are mandatory to investigate the risk of BVS relative to metallic stents for VLST, and the underlying mechanisms of BVS VLST.
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