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Patient-specific coronary endothelial shear stress (ESS) calculations using Newtonian and non-Newtonian rheological models were performed to assess whether the common assumption of Newtonian blood behavior offers similar results to a more realistic but computationally expensive non-Newtonian model. 16 coronary arteries (from 16 patients) were reconstructed from optical coherence tomographic (OCT) imaging. Pulsatile CFD simulations using Newtonian and the Quemada non-Newtonian model were performed. Endothelial shear stress (ESS) and other indices were compared. Exploratory indices including local blood viscosity (LBV) were calculated from non-Newtonian simulation data. Compared to the Newtonian results, the non-Newtonian model estimates significantly higher time-averaged ESS (1.69 (IQR 1.36)Pa versus 1.28 (1.16)Pa, p < 0.001) and ESS gradient (0.90 (1.20)Pa/mm versus 0.74 (1.03)Pa/mm, p < 0.001) throughout the cardiac cycle, under-estimating the low ESS (p < 0.001). Similar results were also found in the idealized artery simulations with non-Newtonian median ESS being higher than the Newtonian median ESS (healthy segments: 0.8238Pa versus 0.6618Pa, p < 0.001 proximal; 0.8179Pa versus 0.6610Pa, p < 0.001 distal; stenotic segments: 0.8196Pa versus 0.6611Pa, p < 0.001 proximal; 0.2546Pa versus 0.2245Pa, p < 0.001 distal) On average, the non-Newtonian model has a LBV of 1.45 times above the Newtonian model with an average peak LBV of 40-fold. Non-Newtonian blood model estimates higher quantitative ESS values than the Newtonian model. Incorporation of non-Newtonian blood behavior may improve the accuracy of ESS measurements. The non-Newtonian model also allows calculation of exploratory viscosity-based hemodynamic indices, such as local blood viscosity, which may offer additional information to detect underlying atherosclerosis.

Aims: The aim of this study was to assess the acute performance of the 95 mu m ArterioSorb oriented poly L-lactic acid (PLLA) scaffold in comparison with the XIENCE metallic drug-eluting stent (DES) in porcine coronary arteries.Methods and results: In 15 non-atherosclerotic Yucatan mini pigs, the ArterioSorb (3.0/14 mm) and XIENCE (3.0/15 mm) were implanted in 25 and 15 vessels, respectively. Acute performance was evaluated by using quantitative coronary angiography (QCA) and optical coherence tomography (OCT). Following three-dimensional reconstruction of the coronary arteries, endothelial shear stress (ESS) was quantified using non-Newtonian steady-flow simulation. Acute recoil measured by QCA was comparable in the two aims. Post-procedural flow and scaffold/stent area by OCT did not differ between the two devices. ESS post procedure was comparable between ArterioSorb and XIENCE (2.21 +/- 1.97 vs 2.25 +/- 1.71 Pa, p=0.314).Conclusions: Acute recoil, luminal dimensions and ESS in the ArterioSorb oriented PLLA scaffold with thin struts of 95 mu m were comparable to those in the XIENCE metallic DES.