Objective Two different venous models,one with and one without a venous sinus,each containing two pairs of adjacent orthogonal venous valves,were constructed.Using fluid-structure interaction(FSI)simulations,the influence of the venous sinus structure on blood flow in the lower limb venous system was studied,and the role of the venous sinus structure in the process of venous valve opening and closing was analyzed.Methods Based on ultrasound images and anatomical images of animals,two distinct three-dimensional(3D)geometric models of the venous system were constructed using modeling software.Using the immersed boundary method,FSI simulations of venous valves were performed to obtain hemodynamic parameters,such as changes in valve morphology,flow streamline distribution,wall shear stress(WSS)distribution,and Q-criterion intensity distribution.Results The geometric opening area of the valve in the model with sinuses was larger than that in the model without sinuses.The distribution of blood streamlines demonstrated the existence of vortices in the sinus region and helical flow within the vessel.The same venous valve pair exhibited an asymmetric distribution of WSS,with the region of high WSS behind the venous valve and the Q-criterion intensity between the far and near end valves being smaller in the sinus model compared to the non-sinus model.Conclusions The blood flow between two adjacent pairs of orthogonal venous valves exhibits a helical flow characteristics.The venous sinus structure facilitates the opening of the venous valve and the generation of vortices in the sinus region.However,the venous sinus structure may somewhat weaken the helical flow produced by the orthogonal venous valves.The venous sinus has a critical influence on the hemodynamics of the venous system,and in the study of venous valves,the venous sinus structure should be considered as an indispensable component.

Objective To understand the changing profiles of antimicrobial susceptibility of the bacterial strains isolated from patients at Liuzhou Workers'Hospital in Guangxi from 2020 to 2022.Methods The bacteria were isolated,identified,and underwent antimicrobial susceptibility testing using VITEK 2 Compact,disk diffusion method,or E-test.The results were interpreted according to the breakpoints recommended by CLSI M100 32nd Edition in 2022.The data were analyzed using WHONET 5.6 software.Results A total of 26 254 nonduplicate strains were collected from 2020 to 2022,including Gram-positive bacteria(27.9％)and gram-negative bacteria(72.1％).The prevalence of methicillin-resistant strains was 20.0％in SS.aureus(MRSA),and 72.2％in coagulase-negative Staphylococcus(MRCNS).Methicillin-resistant staphylococcal strains were more resistant to most antimicrobial agents than methicillin-susceptible strains(MSSA and MSCNS).None of the staphylococcal strains was resistant to vancomycin,linezolid or tigecycline.Enterococcus faecium strains showed higher resistance rates to most antimicrobial agents than Enterococcus faecalis.None of enterococcal strains was resistant to vancomycin.A few enterococcal strains were resistant to linezolid.Overall,691 strains of the non-meningitis Streptococcus pneumoniae were isolated from children and 123 strains were isolated from adults.The prevalence of penicillin-resistant SS.pneumoniae(PRSP)was 0.4％in the strains from children and 1.6％in the strains from adults.None of S.pneumoniae strains was intermediate to penicillin.The prevalence of carbapenem-resistant Klebsiella pneumoniae(CRKpn)was 1.2％,1.2％,and 13.8％in 2020,2021,and 2022,respectively.The prevalence of carbapenem-resistant P.aeruginosa(CRPae)and carbapenem-resistant Acinetobacter baumannii(CRAba)was 10.7％and 68.4％in 2020,17.5％and 75.2％in 2021,14.3％and 77.3％in 2022,respectively.About 84.6％of the 1 269 strains of Haemophilus influenzae were isolated from children and 15.4％isolated from adults.The prevalence of beta-lactamase-producing strains was 39.4％in the isolates from children and 46.8％in the isolates from adults.The β-lactamase-producing H.influenzae was resistant to ampicillin.Furthermore,some β-lactamase-nonproducing ampicillin-resistant(BLNAR)H.influenzae strains(27.0％)were also identified.Conclusions Antimicrobial resistance is still serious in this hospital,especially high prevalence of carbapenem-resistant organisms(CRO).Hospital infection prevention and control measures,antibiotic stewardship,and proactive CRO screening should be strengthened.More clinical specimens should be collected for suspected infections.Antimicrobial treatment should be prescribed empirically in time and adjusted when the results of antimicrobial susceptibility testing are available.

Objective To understand the changing profiles of antimicrobial susceptibility of the bacterial strains isolated from patients at Liuzhou Workers'Hospital in Guangxi from 2020 to 2022.Methods The bacteria were isolated,identified,and underwent antimicrobial susceptibility testing using VITEK 2 Compact,disk diffusion method,or E-test.The results were interpreted according to the breakpoints recommended by CLSI M100 32nd Edition in 2022.The data were analyzed using WHONET 5.6 software.Results A total of 26 254 nonduplicate strains were collected from 2020 to 2022,including Gram-positive bacteria(27.9％)and gram-negative bacteria(72.1％).The prevalence of methicillin-resistant strains was 20.0％in SS.aureus(MRSA),and 72.2％in coagulase-negative Staphylococcus(MRCNS).Methicillin-resistant staphylococcal strains were more resistant to most antimicrobial agents than methicillin-susceptible strains(MSSA and MSCNS).None of the staphylococcal strains was resistant to vancomycin,linezolid or tigecycline.Enterococcus faecium strains showed higher resistance rates to most antimicrobial agents than Enterococcus faecalis.None of enterococcal strains was resistant to vancomycin.A few enterococcal strains were resistant to linezolid.Overall,691 strains of the non-meningitis Streptococcus pneumoniae were isolated from children and 123 strains were isolated from adults.The prevalence of penicillin-resistant SS.pneumoniae(PRSP)was 0.4％in the strains from children and 1.6％in the strains from adults.None of S.pneumoniae strains was intermediate to penicillin.The prevalence of carbapenem-resistant Klebsiella pneumoniae(CRKpn)was 1.2％,1.2％,and 13.8％in 2020,2021,and 2022,respectively.The prevalence of carbapenem-resistant P.aeruginosa(CRPae)and carbapenem-resistant Acinetobacter baumannii(CRAba)was 10.7％and 68.4％in 2020,17.5％and 75.2％in 2021,14.3％and 77.3％in 2022,respectively.About 84.6％of the 1 269 strains of Haemophilus influenzae were isolated from children and 15.4％isolated from adults.The prevalence of beta-lactamase-producing strains was 39.4％in the isolates from children and 46.8％in the isolates from adults.The β-lactamase-producing H.influenzae was resistant to ampicillin.Furthermore,some β-lactamase-nonproducing ampicillin-resistant(BLNAR)H.influenzae strains(27.0％)were also identified.Conclusions Antimicrobial resistance is still serious in this hospital,especially high prevalence of carbapenem-resistant organisms(CRO).Hospital infection prevention and control measures,antibiotic stewardship,and proactive CRO screening should be strengthened.More clinical specimens should be collected for suspected infections.Antimicrobial treatment should be prescribed empirically in time and adjusted when the results of antimicrobial susceptibility testing are available.

Objective Two different venous models,one with and one without a venous sinus,each containing two pairs of adjacent orthogonal venous valves,were constructed.Using fluid-structure interaction(FSI)simulations,the influence of the venous sinus structure on blood flow in the lower limb venous system was studied,and the role of the venous sinus structure in the process of venous valve opening and closing was analyzed.Methods Based on ultrasound images and anatomical images of animals,two distinct three-dimensional(3D)geometric models of the venous system were constructed using modeling software.Using the immersed boundary method,FSI simulations of venous valves were performed to obtain hemodynamic parameters,such as changes in valve morphology,flow streamline distribution,wall shear stress(WSS)distribution,and Q-criterion intensity distribution.Results The geometric opening area of the valve in the model with sinuses was larger than that in the model without sinuses.The distribution of blood streamlines demonstrated the existence of vortices in the sinus region and helical flow within the vessel.The same venous valve pair exhibited an asymmetric distribution of WSS,with the region of high WSS behind the venous valve and the Q-criterion intensity between the far and near end valves being smaller in the sinus model compared to the non-sinus model.Conclusions The blood flow between two adjacent pairs of orthogonal venous valves exhibits a helical flow characteristics.The venous sinus structure facilitates the opening of the venous valve and the generation of vortices in the sinus region.However,the venous sinus structure may somewhat weaken the helical flow produced by the orthogonal venous valves.The venous sinus has a critical influence on the hemodynamics of the venous system,and in the study of venous valves,the venous sinus structure should be considered as an indispensable component.

Objective To establish an ideal model of the mitral valve,including the left heart and blood,and study the motion characteristics of the mitral valve in blood flow using the fluid-structure interaction(FSI)simulation.Methods Based on anatomical parameters,models of the mitral valve,left heart,and blood were established.The finite-elements combined immersed boundary method was used for FSI to simulate the motion of the mitral valve using the LS-DYNA software.Morphological,mechanical,and hemodynamic parameters were compared with those obtained from structural simulations.Results The morphological results of the mitral valve from the two simulations differed significantly,and the FSI results matched the ultrasound images.The stress distributions of the leaflets in the FSI and structural simulations were consistent.The maximum first principal stresses calculated by FSI and structural simulations were 1.48 MPa and 1.53 MPa,respectively,with a relative error of 3.27％.The fluid field in the left heart was complex with vortex structures,and the maximum mitral flow velocity was 1.02 m/s during diastole,consistent with the physiological data of healthy humans(0.89±0.15 m/s).Conclusions The morphological results of the mitral valve obtained from the FSI simulation were closer to those in the physiological state.FSI simulations can provide flow patterns that are indispensable for clinical diagnosis.Structural simulations are more efficient for studying leaflet stress distribution.

Objective To noninvasively assess the cerebral ischemic status using the velocity profile of the carotid and vertebral arteries measured by Doppler ultrasound and a neural network model.Methods Imaging data were collected from patients who underwent computed tomography perfusion(CTP)and Doppler ultrasound.Hemodynamic parameters were extracted from the ultrasound images.These parameters were used to train a fully connected neural network model.The model was validated using the CTP results.Results Sixty-two eligible patients were included;44 were randomly selected as the training dataset and 18 were designated for validation.In the training set,the area under the curve(AUC)of the receiver operating characteristic,sensitivity,specificity,and accuracy were 0.95,0.833,0.923,and 0.886,respectively.In the test set,the AUC,sensitivity,specificity,and accuracy were 0.860,0.714,1.000,and 0.889,respectively.Conclusions The model based on Doppler ultrasound and neural network was clinically verified and had good accuracy for assessing cerebral ischemia,showing its clinical potential for the early screening of cerebral ischemia.

Objective To explore hemodynamics of the aortic arch and supraarch vessels after thoracic endovascular aortic repair with fenestration and parallel grafts techniques, and compare the differences of these techniques. Methods Four patients with aortic arch lesions whose supraarch vessels were reconstructed by different surgical techniques (fenestration, chimney and periscope) were studied, and three-dimensional (3D) geometric models were established based on postoperative image data. The physiological flow obtained from two dimensional (2D) phase contrast magnetic resonance imaging were imposed on the ascending aorta inlet and the supraarch vessels outlets. The pressure waveform of 3-element Windkessel model was imposed on the descending aorta outlet. Through computational fluid dynamics ( CFD ) simulations, the hemodynamic parameters were obtained, including the pressure of supraarch vessels, the velocity vector of the stent inlet, and the relative residence time. Results The pressure change of the periscope stent was the largest, followed by the fenestration stent, and the pressure change of the chimney stent was the smallest. The velocity of the fenestration and periscope stent inlet was uneven, which might form vortex. The velocity of the chimney stent inlet was even. The high relative residence time concentrated in distal end of the fenestration stent outer wall, the ‘gutter’ part, and the place where the chimney and periscope stent adhered to the vessel wall. Conclusions The pressure difference between the inner and outer walls of the fenestration and periscope stent was high, so it was recommended to use the balloon-expandable stent. The pressure difference between the inner and outer walls of the chimney stent was low, so it was recommended to use the self-expanding stent. The predicted location of thrombosis was consistent with the clinical follow-up data, so it may be used for surgical planning and risk assessment of interventional treatment of aortic arch lesions.

Objective To study the process of single stent and double-stent thrombectomy at the Y-shaped bifurcation of the ideal internal carotid artery by finite element simulation, analyze the stent-thrombus-vessel interaction during the thrombectomy process based on the simulation results, and provide guidance for improving the effect of stent thrombectomy at the bifurcation. Methods The CAD software was used to build the model and the finite element analysis software was used to simulate the process of single stent and double-stent thrombectomy. Results Thrombectomy was unsuccessful in single stent model and successful in double-stent model, and the maximum stress of thrombus during embolus retrieval was twice that of single stent, the maximum strain was 1.12 times that of single stent, and the maximum contact pressure on the surface of vessel was approximately twice that of single stent. Conclusions Double Solitaire stents can effectively prevent thrombus displacement at the bifurcation and successfully retrieve the thrombus, but there is a risk of fracture due to the high stress level in the middle section of the thrombus. The contact pressure of the vessel on the anterior artery side is higher during thrombectomy, and the risk of vessel damage is greater. Therefore, it is necessary to optimize the design of the stent-retriever to improve its flexibility.

OBJECTIVE: In daily life, the movement of the neck will cause certain deformation of the blood vessel and the stent. This study explores the quantitative influence of the torsion deformation of the blood vessel on the mechanical properties of the stent. METHODS: In the finite element simulation software Abaqus, the numerical simulation of the crimping and releasing process of the stent, the numerical simulation of the torsion process of the blood vessel with the stent, and the numerical simulation of the pressure loading process of the outer wall of the blood vessel were carried out. RESULTS: After the stent was implanted, when a load was applied to the outer surface of the blood vessel wall, when the applied load did not change, as the torsion angle increased, the smallest cross-sectional area in the blood vessel decreased. CONCLUSIONS After the stent is placed, when the external load is fixed, the radial support capacity of the stent will decrease as the torsion angle increases.
Computer Simulation ; Finite Element Analysis ; Humans ; Stents ; Stress, Mechanical

Objective To study mechanical properties of polyethylene terephthalate (PET)-based textile valves woven with nickel-titanium (NiTi) wires by finite element method, and combined with in vitro hemodynamic testing, to analyze the effect of wire quantity and woven position on hemodynamic performance of PET textile valve. Methods The three-dimensional (3D) geometric models of PET valves without wires and models of PET valves with wires by different numbers and distributions in radial direction were constructed using modeling software. Material properties of PET valves and wires were given based on the literature and experimental data. The transvalvular pressure difference curves of PET valves obtained from in vitro pulsatile flow experiments were used as boundary conditions. Stress distributions of the valve during peak systole and diastole were studied by finite element analysis software. Hydrodynamic performance of the valve with wires was evaluated by in vitro pulsatile flow experiments. ResultsThe finite element analysis results showed that the radially woven NiTi wires could enhance support for the PET textile valve, and support force and area of the valve in belly region of the valve leaflet with evenly distributed metal wires increased with the number of metal wires. The situation of support force was similar for silk distributions on both sides of the belly. The weaving of wires reduced stress concentration on the PET textile valve to a certain extent. The pulsatile flow experiment results showed that the stability of opening and closing shapes, effective opening area (EOA), regurgitation fraction (RF) and transvalvular pressure differences for two kinds of the PET valves with woven wires were better than those of the PET valves without wires. Conclusions Weaving metal wires in radial direction of the PET textile valve can effectively reduce stress concentrations on the PET textile valve during the cardiac cycle, and reduce tearing possibility of the valve leaflet. The woven metal wires can improve opening and closing stability of PET textile valve in in vitro hydrodynamic test, increase EOA and reduce RF and transvalvular pressure difference of the PET valve.