Endothelial shear stress (ESS) plays a key role in the clinical outcomes in native and stented segments; however, their implications in bypass grafts and especially in a synthetic biorestorative... Show moreEndothelial shear stress (ESS) plays a key role in the clinical outcomes in native and stented segments; however, their implications in bypass grafts and especially in a synthetic biorestorative coronary artery bypass graft are yet unclear. This report aims to examine the interplay between ESS and the morphological alterations of a biorestorative coronary bypass graft in an animal model. Computational fluid dynamics (CFD) simulation derived from the fusion of angiography and optical coherence tomography (OCT) imaging was used to reconstruct data on the luminal anatomy of a bioresorbable coronary bypass graft with an endoluminal "flap" identified during OCT acquisition. The "flap" compromised the smooth lumen surface and considerably disturbed the local flow, leading to abnormally low ESS and high oscillatory shear stress (OSI) in the vicinity of the "flap". In the presence of the catheter, the flow is more stable (median OSI 0.02384 versus 0.02635, p < 0.0001; maximum OSI 0.4612 versus 0.4837). Conversely, OSI increased as the catheter was withdrawn which can potentially cause back-and-forth motions of the "flap", triggering tissue fatigue failure. CFD analysis in this report provided sophisticated physiological information that complements the anatomic assessment from imaging enabling a complete understanding of biorestorative graft pathophysiology. Show less
OBJECTIVES: This study aimed to investigate the impact of mechanical factors at baseline on the patency of a restorative conduit for coronary bypass grafts in an ovine model at serial follow-up up... Show moreOBJECTIVES: This study aimed to investigate the impact of mechanical factors at baseline on the patency of a restorative conduit for coronary bypass grafts in an ovine model at serial follow-up up to 1 year.METHODS: The analyses of 4 mechanical factors [i.e. bending angle, superficial wall strain and minimum and maximum endothelial shear stress (ESS)] were performed in 3D graft models reconstructed on baseline (1-month) angiograms frame by frame by a core laboratory blinded for the late follow-up. The late patency was documented by Quantitative Flow Ratio (QFR (R)) that reflects the physiological status of the graft. The correlation between 4 mechanical factors and segmental QFR (Delta QFR) were analysed on 10 equal-length segments of each graft.RESULTS: A total of 69 graft geometries of 7 animals were performed in the study. The highest Delta QFR at 12 months was colocalized in segments of the grafts with the largest bending angles at baseline. Higher Delta QFR at 3 months were both at the anastomotic ends and were colocalized with the highest superficial wall strain at baseline. High baseline ESS was topographically associated with higher Delta QFR at the latest follow-up. Correlations of minimum and maximum ESS with Delta QFR at 3 months were the strongest among these parameters (rho = 0.30, 95% CI [-0.05 to 0.56] and rho = 0.27, 95% CI [-0.05 to 0.54], respectively).CONCLUSIONS: Despite the limited number of grafts, this study suggests an association between early abnormal mechanical factors and late flow metrics of the grafts. The understanding of the mechanical characteristics could help to improve this novel conduit. Show less
