Difference in haemodynamic microenvironment in vessels scaffolded with Absorb BVS and Mirage BRMS: insights from a preclinical endothelial shear stress study

In silico studies have provided robust evidence that stent design affects local haemodynamic forces, which appear as a major determinant of clinical outcomes following stent implantation. However, the implications of different stent/scaffold configurations on local haemodynamic forces have not yet been investigated in vivo in a comparative fashion. The aim of this study was to compare the ESS distribution in two differently shaped scaffolds using OCT-based modelling.Eight healthy mini pigs were implanted with six Absorb everolimus-eluting bioresorbable vascular scaffolds (Absorb BVS) and five Mirage sirolimus-eluting bioresorbable microfibre scaffolds (Mirage BRMS). Optical coherence tomography (OCT) was performed and strut protrusion was assessed post scaffold implantation. Following the reconstruction of coronary anatomy, blood flow simulation was performed and endothelial shear stress (ESS) was estimated on top of the struts and at luminal surface between the struts in each scaffold. The thicker struts in Absorb (152±140 μm) resulted in an increased protruded distance compared to Mirage (117±123 μm) (p=0.003). This had an effect on the local haemodynamic microenvironment. ESS at the top of the struts was higher in Absorb (1.69±1.20 Pa) than in Mirage (1.53±0.91 Pa) (p<0.001), but lower at inter-strut zones (0.60±0.51 Pa vs. 0.63±0.50 Pa; p<0.01) compared to Mirage. Both scaffold types revealed comparable percentages of vessel luminal surface exposed to recirculation.Absorb demonstrated higher shear stress on top of the struts compared to Mirage. However, in the inter-strut zones shear stress was higher in Mirage than in Absorb. Further research is required to examine the potential value of in vivo computational modelling in optimising scaffold configuration and clinical outcomes.