Abstract
Protrusion of scaffold struts is related with local coronary flow dynamics that can promote scaffold restenosis and thrombosis. That fact has prompted us to investigate in vivo the protrusion status of different types of scaffolds and their relationship with endothelial shear stress (ESS) distributions. Six Absorb everolimus-eluting Bioresorbable Vascular Scaffolds (Absorb, Abbott Vascular) and 11 Mirage sirolimus-eluting Bioresorbable Microfiber Scaffolds (Mirage, Manli Cardiology) were implanted in coronaries of eight mini pigs. Optical coherence tomography (OCT) was performed post-scaffold implantation and obtained images were fused with angiographic data to reconstruct the three dimensional coronary anatomy. Blood flow simulation was performed and ESS distribution was estimated for each scaffold. Protrusion distance was estimated using a dedicated software. Correlation between OCT-derived protrusion and ESS distribution was assessed for both scaffold groups. A significant difference was observed in the protrusion distances (156 ± 137 µm for Absorb, 139 ± 153 µm for Mirage; p = 0.035), whereas difference remained after adjusting the protrusion distances according to the luminal areas. Strut protrusion of Absorb is inversely correlated with ESS (r = −0.369, p < 0.0001), whereas in Mirage protrusion was positively correlated with EES (r = 0.192, p < 0.0001). Protrusion distance was higher in Absorb than in Mirage. The protrusion of the thick quadratic struts of Absorb has a tendency to lower shear stress in the close vicinity of struts. However, circular shape of the less thick struts of Mirage didn’t show this trend in creating zone of recirculation around the struts. Strut geometry has different effect on the relationship between protrusion and shear stress in Absorb and Mirage scaffolds.
Highlights
A permanent metallic stent constitutes a foreign structure in the vessel wall that induces inflammatory reactions increasing the thrombosis risk at post-implantation follow up [1]
Observational atherosclerosis studies have proposed that low endothelial shear stress (ESS) promotes atherosclerotic plaque growth in native vessel segments [9, 10] and neointimal hyperplasia in scaffolded segments after percutaneous coronary intervention (PCI) [8]
We investigated the relationship between struts protrusion and local shear stress distributions in the vessel segments implanted with Absorb and Mirage
Summary
A permanent metallic stent constitutes a foreign structure in the vessel wall that induces inflammatory reactions increasing the thrombosis risk at post-implantation follow up [1]. Bioresorbable scaffolds (BRS) have been introduced to address the disadvantages of metallic drug-eluting stents (DES) [2]. Embedment of the stent/scaffold is one of the surrogate factor affecting the vessel wall reaction after. The vessel wall stretch and injury have been shown to be related with the embedment status of the device [5, 6]. The strut protrusion and related local coronary flow hemodynamics, endothelial shear stress (ESS) influence biological response of the vessel wall [7, 8]. Observational atherosclerosis studies have proposed that low ESS promotes atherosclerotic plaque growth in native vessel segments [9, 10] and neointimal hyperplasia in scaffolded segments after percutaneous coronary intervention (PCI) [8]
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