Local hemodynamic analysis after coronary stent implantation based on Euler-Lagrange method

Volumetric mass density measurements of mesenchymal stem cells in suspension using a density meter

To use regeneratively active cells for cell therapeutic applications, the cells must be isolated from their resident tissues. Different isolation procedures subject these cells to varying degrees of mechanical strain, which can affect the yield of cell number and viability. Knowledge of cell volumetric mass density is important for experimental and numerical optimization of these procedures. Although methods for measuring cell volumetric mass density already exist, they either consume much time and cell material or require a special setup. Therefore, we developed a user-friendly method that is based on the use of readily available instrumentation. The newly developed method is predicated on the linear relationship between the volumetric mass density of the cell suspension and the volumetric mass density, number, and diameter of the cells in the suspension. We used this method to determine the volumetric mass density of mesenchymal stem cells (MSCs) and compared it to results from the established density centrifugation.

Risk factors for in-stent restenosis after coronary stent implantation in patients with coronary artery disease: A retrospective observational study

To explore the risk factors for in-stent restenosis (ISR) after stent implantation in patients with coronary heart disease (CHD) using logistic regression analysis. From February 2020 to February 2022, 350 patients with CHD after percutaneous coronary intervention (PCI) were divided into a stent stenosis group and a stent nonstenosis group based on coronary angiography results performed 2 years after PCI. Univariate and multivariate logistic regressions were used to analyze the factors related to ISR after coronary stent implantation in patients with CHD. This study was approved by the Ethics Committee of Shandong University of Traditional Chinese Medicine. Patient signed informed consent. Of the 350 patients with CHD, 138 (39.43%) had stent restenosis while 212 did not. Univariate analysis showed that a family history of CHD, history of type 2 diabetes, hypertension, smoking, and drinking, discontinuation of aspirin, use of conventional dose statins, calcified lesions, ≥ 3 implanted stents, stent length ≥ 30 mm, stent diameter < 3 mm, and tandem stent increased the risk of restenosis. The incidence of restenosis was higher in the stent group than that in the nonstent group (P < .05). There were no significant differences in the blood lipid level, left ventricular ejection fraction, clopidogrel/ticagrelor or beta-blocker withdrawal, location of culprit vessels, and thrombotic lesions between the 2 groups (P > .05). Multivariate logistic regression analysis showed that family history of CHD, history of type 2 diabetes, hypertension, smoking, and drinking, aspirin withdrawal, use of conventional doses of statins, calcified lesions, ≥ 3 implanted stents, stent length ≥ 30 mm, stent diameter < 3 mm, and tandem stenting were risk factors for ISR within 2 years after PCI. A family history of CHD, history of type 2 diabetes, hypertension, smoking, and drinking, discontinuation of aspirin, use of conventional dose statins, calcified lesions, ≥ 3 stent implantations, stent length ≥ 30 mm, stent diameter < 3 mm, and tandem stenting are risk factors for ISR within 2 years after PCI in patients with CHD.

Red blood cells tracking and cell-free layer formation in a microchannel with hyperbolic contraction: A CFD model validation

BACKGROUND AND OBJECTIVE

In recent years, progress in microfabrication technologies has attracted the attention of researchers across disciplines. Microfluidic devices have the potential to be developed into powerful tools that can elucidate the biophysical behavior of blood flow in microvessels. Such devices can also be used to separate the suspended physiological fluid from whole in vitro blood, which includes cells. Therefore, it is essential to acquire a detailed description of the complex interaction between erythrocytes (red blood cells; RBCs) and plasma. RBCs tend to undergo axial migration caused by occurrence of the Fåhræus-Lindqvist effect. These dynamics result in a cell-free layer (CFL), or a low volume fraction of cells, near the vessel wall. The aim of the paper is to develop a numerical model capable of reproducing the behavior of multiphase flow in a microchannel obtained under laboratory conditions and to compare two multiphase modelling techniques Euler-Euler and Euler-Lagrange.

METHODS

In this work, we employed a numerical Computational Fluid Dynamics (CFD) model of the blood flow within microchannels with two hyperbolic contraction shapes. The simulation was used to reproduce the blood flow behavior in a microchannel under laboratory conditions, where the CFL formation is visible downstream of the hyperbolic contraction. The multiphase numerical model was developed using Euler-Euler and hybrid Euler-Lagrange approaches. The hybrid CFD simulation of the RBC transport model was performed using a Discrete Phase Model. Blood was assumed to be a nonhomogeneous mixture of two components: dextran, whose properties are consistent with plasma, and RBCs, at a hematocrit of 5% (percent by volume of RBCs).

RESULTS

The results show a 5 μm thick CFL in a microchannel with a broader contraction and a 35 μm thick CFL in a microchannel with a narrower contraction. The RBC volume fraction in the CFL is less than 2%, compared to 7-8% in the core flow. The results are consistent for both multiphase simulation techniques used. The simulation results were then validated against the experimentally-measured CFL in each of the studied microchannel geometries.

CONCLUSIONS

Reasonable agreement between experiments and simulations was achieved. A validated model such as the one tested in this study can expedite the microchannel design process by minimizing the need to prefabricate prototypes and test them under laboratory conditions.