EMBEDMENT ANALYSIS OF ABSORB BVS AND MIRAGE BRMS-THE RELATION WITH SHEAR STRESS: INSIGHTS FROM HISTOLOGY IN PORCINE CORONARY MODELS

Background and Aim:Bioresorbable_scaffolds have been introduced to address some limitations of metallic drug-eluting stents.Scaffold apposition status is related with coronary flow behaviors in treated segments.Emerging scaffold_thrombosis cases have inspired us to investigate embedment/protrusion status of different types of scaffolds and its relations with endothelial_shear_stress (ESS) distributions.Method:Six Absorb_BVS and 11 Mirage_BRMS were implanted in epicardial_coronaries of eight mini-pigs.Optical_coherence_tomography(OCT)was performed post-scaffold implantation and obtained images were fused with angiographic data to reconstruct 3D-coronary_anatomy. Blood_flow_simulation was performed and ESS was estimated for each scaffold.A dedicated software for quantitative evaluation of embedment of struts by OCT was used. Two_animals were sacrificed at 30-day post-implantation for histopathological analyses in Absorb_BVS(n=2) and Mirage_BRMS(n=2).In linear_mixed-effects analysis,embedment/protrusion data and ESS were compared between groups.Results:In mixed_effects model,mean_ESS were comparable between Absorb_BVS and Mirage_BRMS(0.73±2.19 vs 0.93±1.83,respectively;p=0.142).Embedment_depths were comparable between Absorb and Mirage scaffolds(22±37µm vs 17±33µm,respectively;p=0.45).There was significant difference between scaffolds for protrusion_heights(160.61±171.28µm for Absorb_BVS,139.69±153.31µm for Mirage_BRMS;p=0.035).After adjusting protrusion distances according to luminal_diameters in OCT difference remained its significance(0.050±3.08 for Absorb_BVS vs 0.041±3.95 for Mirage_BRMS;p<0.0001).ESS was significantly related with protrusion and protrusion/lumen diameter_ratio inversely in Absorb_BVS and positively in Mirage_BRMS.Histopatholohgical_examination revealed minimal_inflammatory changes in both groups.At 30-day,endothelial_coverage was less in Absorb_BVS.Increased fibrin_accumulation was noticed around the struts in Absorb_BVS.Due to increased neointimal_hyperplasia,diameter_stenosis was higher in Mirage.Conclusion:Despite similar embedment levels,protrusion_distance was higher in Absorb BVS.Embedment/protrusion levels have different relations with ESS in Absorb BVS and Mirage BRMS.Discrepancy in the correlation of ESS with protrusion_distances should be due to different geometries of the scaffold struts.