Time-resolved simulation of blood flow through left anterior descending coronary artery: effect of varying extent of stenosis on hemodynamics.

BACKGROUND AND OBJECTIVES: Real-time blood flow variation is crucial for understanding the dynamic development of coronary atherosclerosis. The main objective of this study is to investigate the effect of varying extent of stenosis on the hemodynamic features in left anterior descending coronary artery. METHODS: Various Computational fluid dynamics (CFD) models were constructed with patient-specific CT image data, using actual fractional flow reserve (FFR) as boundary conditions to provide a real-time quantitative description of hemodynamic properties. The hemodynamic parameters, such as the local and instantaneous wall shear stress (WSS), oscillating shear index (OSI) and relative residence time (RRT), blood flow velocity and pressure drop during various phases of cardiac cycle were provided in detail. RESULTS: There was no evident variation in hemodynamic parameters in the cases of less than 50% stenosis while there were abrupt and dramatic changes in hemodynamics when the stenosis aggravated from 60 to 70%. Furthermore, when the stenosis was beyond 70%, there existed substantial pressure difference, WSS, and blood flow velocity in the center of the stenosis. Although OSI and RRT increased along with the aggravation of stenosis, they appeared with obvious abnormalities across all cases, even in mild stenosis. CONCLUSION: The simulation could present a dynamic and comprehensive profile of how hemodynamic parameters vary in accordance with divergent severities of stenosis, which could serve as an effective reference for the clinicians to have a deeper insight into the pathological mechanism of coronary atherosclerosis and stenosis.

Computational fluid dynamics simulation of time-resolved blood flow in Budd-Chiari syndrome with inferior vena cava stenosis and its implication for postoperative efficacy assessment.

BACKGROUND: This study aimed to adopt computational fluid dynamics to simulate the blood flow dynamics in inferior vena cava stenosis based on time-dependent patient-specific models of Budd-Chiari syndrome as well as a normal model. It could offer valuable references for a retrospective insight into the underlying mechanisms of Budd-Chiari syndrome pathogenesis as well as more accurate evaluation of postoperative efficacy. METHODS: Three-dimensional inferior vena cava models of Budd-Chiari syndrome patient-specific (preoperative and postoperative) and normal morphology model were reconstructed as per magnetic resonance images using Simpleware. Moreover, computational fluid dynamics of time-resolved inferior vena cava blood flow were simulated using actual patient-specific measurements to reflect time-dependent flow rates. FINDINGS: The assessment of the preoperative model revealed the dramatic variations of hemodynamic parameters of the stenotic inferior vena cava. Moreover, the comparison of the preoperative and postoperative models with the normal model as benchmark showed that postoperative hemodynamic parameters were markedly ameliorated via stenting, with the attenuation of overall velocity and wall shear stress, and the increase of pressure. However, the comparative analysis of the patient-specific simulations revealed that some postoperative hemodynamic profiles still bore some resemblance to the preoperative ones, indicating potential risks of restenosis. INTERPRETATION: Computational fluid dynamics simulation of time-resolved blood flow could reveal the tight correlation between the hemodynamic characteristics and the pathological mechanisms of inferior vena cava stenosis. Furthermore, such time-resolved hemodynamic profiles could provide a quantitative approach to diagnosis, operative regimen and postoperative evaluation of Budd-Chiari syndrome with inferior vena cava stenosis.

Fractional flow reserve-based 4D hemodynamic simulation of time-resolved blood flow in left anterior descending coronary artery.

BACKGROUND: The purpose of this study was to investigate the feasibility of the non-invasive assessment of hemodynamic parameters with computational fluid dynamics in left anterior descending coronary artery based on invasive fractional flow reserve. METHODS: A left coronary artery model based on computed tomography angiography was reconstructed using MIMICS 18.0 for computational fluid dynamics analysis. With actual fractional flow reserve measured from the patient, 4D hemodynamic profiles of time-resolved blood flow were simulated. FINDINGS: The 4D blood flow simulation could provide extensive information of blood flow status. Hemodynamic parameters, such as velocity, wall shear stress and pressure were simulated throughout the cardiac cycle. There might be high flow velocities and high wall shear stress in the stenotic region throughout the whole cycle, both of which peaked in the case of the maximum inlet differential pressure. The reverse flow and vortex were detectable at the downstream areas beneath the stenotic site. The pressure remarkably increased near the proximal stenotic end and declined in the mid-stenosis. Moreover, the simulation results provided detailed and accurate mass flow measurements of hemodynamic parameters as well. INTERPRETATION: The computational fluid dynamics analysis of 4D blood flow based on fractional flow reserve is feasible in left anterior descending coronary artery. It presents the merits of providing both qualitative and quantitative information for further investigation of the links between hemodynamic parameters and left anterior descending artery stenosis.

[Investigation of FTIR spectra analysis of gallstones from Xuzhou region by solvent extraction].

The present paper is a preliminary exploration of the possible way the gallstones are formed. Five categories of gallstones from clinical surgery in Xuzhou region were extracted by a series of solvents. Fourier transform infrared spectroscopy (FTIR) was used to characterize the structure of morphological changes between gallstone and residue by extracting. The gallstone samples are from clinical surgeries in Xuzhou region where gallstone disease is quite common. Samples were extracted with a series of solvents, and then FTIR and other instrumental analysis were applied to characterize the composition, structure and morphological changes of the samples both before and after the extraction. The results show that the gallstone samples can be classified as 5 types: cholesterol-type, cholesterol-based hybrid type with salt, bilirubin and protein as its insoluble substances, brown pigment type and black pigment type gallstones. The results also indicate that protein plays a key role in gallstone nucleation process by providing a sediment matrix for the formation of gallstones. Both cholesterol and carbonated hydroxyapatite are found in the insoluble substances of the samples. It is possible that cholesterol was accompanied by carbonated hydroxyapatite and there are interactions between them, and these interactions contribute to the crystallization process and speed up the formation of gallstones. All the results above may provide useful references for the clinical diagnosis, treatment and prevention of gallstones.