Background . Single ventricle disease is treated by Glenn surgery. It is generally accompanied by stenosis on a pulmonary artery or its branches, which has great effect on hemodynamics. This study investigated the hemodynamic influence of different pulmonary stenosis degree in Glenn procedure. Materials . Four three-dimensional Glenn models with different left pulmonary artery stenosis rates as, respectively, 0% (model 1), 25% (model 2), 50% (model 3), and 75% (model 4) by the diameter were generated. Method . Geometric multiscale analysis method was used in the numerical simulations by coupling the lumped parameter model (LPM) and three-dimensional model. Results . During one cardiac cycle, the flow ratio between left pulmonary artery and superior vena cava was about 0.49 for models 1, 2, and 3, while the ratio decreased to 0.34 for model 4. On the other hand, hemodynamics parameters like power loss and oscillation shear index show complications of the stenosis to the postoperative development. Conclusion . When the stenosis rate is above 75%, it is suggested to treat stenosis before Glenn procedure, while when the stenosis rate is below 50%, there is no necessity to pay attention to it due to the little effect it makes.

The modified Blalock–Taussig (BT) shunt is a palliative surgery which can help the tetralogy of Fallot (TOF) patient increase the blood oxygen saturation by interposing a systemic-to-pulmonary artery shunt. Two typical anastomotic shapes are frequently used in clinical practice: the end-to-side (ETS) and the side-to-side (STS) anastomosis. This paper examines the hemodynamic influence of the anastomotic shape in the modified BT shunt. Three models with different anastomotic shapes were reconstructed. The ETS anastomoses were applied in the first model. For the innominate artery (IA) and the pulmonary artery (PA) in the second model, the ETS and the STS anastomosis were applied, respectively. Finally, the STS anastomoses were applied in the third model. The 0D/3D coupling method was used to perform a numerical simulation by coupling the three-dimensional (3D) artery model with a zero-dimensional (0D) lumped parameter model for the cardiovascular system. The simulation results showed that the perfusion into the left and right PA in Model 1 was unbalanced. Swirling flow appeared in the shunt in Model 3, but the shunt flow rate in Model 3 was lower. The ETS anastomosis at the PA may cause unbalanced blood perfusion into the left and right PA. Conversely, the STS anastomosis can make the blood perfusion more balanced. Otherwise, the STS anastomosis at the IA could generate a swirling flow in the shunt which may provide a better hemodynamic environment while decreasing the pulmonary perfusion.

Purpose: Hypoplastic left heart syndrome (HLHS) is a congenital heart disease and is usually associated with pulmonary artery stenosis. The superior vena cava-to-pulmonary artery (bidirectional Glenn) shunt is used primarily as a staging procedure to the total cava-to-pulmonary connection for single-ventricle complex. When HLHS coexists with pulmonary artery stenosis, the surgeons then face a multiple problem. This leads to high demand of optimized structure of Glenn surgery. The objective of this article is to investigate the influence of various anastomotic structures and the direction of superior vena cava (SVC) in Glenn on hemodynamics under pulse inflow conditions and try to find an optimal structure of SVC in Glenn surgery with unilateral pulmonary artery stenosis.Method: First, 3D patient-specific models were constructed from medical images of a HLHS patient before any surgery by using the commercial software Mimics, and another software Free-form was used to deform the reconstructed models in the computer. Four 3D patient-specific Glenn models were constructed: model-1 (normal Glenn), model-2 (lean the SVC back to the stenotic pulmonary artery), model-3 (lean the SVC towards the stenotic pulmonary artery), model-4 (add patch at junction of the SVC toward stenosis at pulmonary artery). Second, a lumped parameter model (LPM) was established to predict boundary conditions for computational fluid dynamics (CFD). In addition, numerical simulations were conducted using CFD through the finite volume method. Finally, hemodynamic parameters were obtained and evaluated.Results: It was showed that model-4 have relatively balanced vena cava blood perfusion into the left pulmonary artery (LPA) and right pulmonary artery (RPA), this may be due to less helical flow and the patch at junction of the SVC. Near stenosis of pulmonary artery, model-4 performed with the higher wall shear stress (WSS), which would benefit endothelial cell function and gene expression. In addition, results showed that model-4 performed with the lower oscillatory shear index (OSI) and wall shear stress gradient (WSSG), which would decrease the opportunity of vascular intimal hyperplasia.Conclusion: It is benefited that surgeons adds patch at junction of the SVC towards stenosis at pulmonary artery. These results can impact the surgical design and planning of the Glenn surgery with unilateral pulmonary artery stenosis.

Objective To analyze and compare hemodynamic features of two different options for modified B-T shunt( MBTS) surgery,namely end-to-side( ETS) and side-to-side( STS),so as to provide references for clinical treatment of single ventricle heart defect syndrome. Methods The real geometric model was reconstructed by medical images obtained from a patient with hypoplastic left heart syndrome( HLHS); MBTS surgery was simulated through virtual operations; a lumped parameter model( LPM) was constructed based on physiological data of the patient; the post-operational boundary conditions of computational fluid dynamics( CFD) models( namely STS model and ETS model) were predicted based on the LPM; numerical simulation was conducted on two CFD models by using finite volume method. Results Flow details and wall shear stress distributions were all obtained for two models. The mean oscillatory shear index( OSI) of ETS model and STS model in part of pulmonary arteries was 3. 058 × 10- 3and 13. 624 × 10- 3,respectively,while the energy loss was 116.5 and 94.8 mW,respectively,and blood flow rate ratios of left pulmonary artery to right pulmonary artery( RRPA /LPA) were 0.8 and 1.72,respectively. Conclusions There were nearly no differences between two CFD models in energy loss,which led to a relatively small impact on the surgery. The STS model had a more balanced pulmonary artery blood perfusion and a smaller mean OSI in part of pulmonary arteries,therefore,the STS model was superior to the ETS model. This study provides an important theoretical support and reference for treating patients with HLHS.

Objective Modified B-T shunt(MBTS) and central shunt(CS) are two common surgical procedures for the treatment of tetralogy of fallot(TOF).The purpose is to analyze and compare the hemodynamic features of MBTS and CS.Methods 3D anatomy was reconstructed by medical images obtained from a patient with TOF,and two computational models were generated through virtual operations.A lumped parameter model was constructed to predict the post-operational boundary conditions.Computational fluid dynamics(CFD) was performed for the two models.Results A persistent pulmonary blood perfusion was observed in each model both during the systolic phase and diastolic phase,but the maximum velocities in the shunt were different for the two models.The pressure drop of the shunt in CS model was higher than that in MBTS model.The wall shear stress of the shunt in the MBTS model ranged unevenly from 0.025 to 340 Pa,while the wall shear stress in CS model ranged relatively evenly from 32.2 to 72.6 Pa.Conclusions Pulmonary artery blood was increased effectively for both options.The blood perfusion of right upper extremity was decreased in the MBTS model.More blood was directed into the pulmonary artery in CS model.Attention should be paid to the fact that the pressure gradient was large at the proximal anastomosis in both models in clinic.This study provides important theoretical references for surgeons to make choice from the surgery options in the treatment with TOF.

The study of hemodynamics,which refers to dynamics inside the blood circulation,mainly includes the flow rate,flow resistance,pressure,shear stress,disturbed flow,as well as their associations in between. Therefore,with its important significance in the clinical treatments of vessel curvature,arterial stenosis or occlusion,pathological artery branches and aneurism,study about hemodynamics is essential to human health. Currently,extensive researches on hemodynamics have been conducted with respect to artery bypass,coronary arterial stenosis,abdominal aortic aneurysm,atherosclerosis,cerebral aneurysm and swirling flow. With the development of such research on hemodynamics,surgical planning and interventional therapy have improved rapidly. The influence mechanism of hemodynamic parameters,including pressure,flow resistance,flow rate,wall shear stress,blood viscosity,flow separation,turbulent flow,vortex on the post-operation complications could be deeply explored with the help of more and more clinical apparatus and have gained some achievements.

Objective To study the hemodynamics of central shunt( CS) by numerical simulation and investigate the effects of the elastic and rigid vessel wall on distributions of hemodynamic parameters in the vessel. Methods Two idealized CS models were constructed,one with a rigid wall( the rigid model) and the other with an elastic wall( the elastic model). Numerical calculation was conducted by the finite element method,and the elastic model adopted the fluid-structure interaction. Results The distribution of flow velocity and pressure in both models were generally the same. About 68. 9% of the aortic blood was directed into the pulmonary artery for the rigid model,as compared to 70% for the elastic model. The pressure drops within the shunt for the elastic model and rigid model were about 7. 668 8 kPa and 7. 222 3 kPa,respectively. The maximum variation in the average crosssections along the shunt was about 2. 2% for the elastic model,appearing at the proximal end to side( ETS) anastomosis. The maximum difference of wall shear stress( WSS) between the two models at five key regions of each was about 16. 1%. Conclusions Generally,the global flow structure in both the CS models remains unchanged; the elasticity of the vessel wall slightly influenced the flow distributions and pressure drop of the shunt; the effect from elasticity of the vessel wall on average cross-sections along the shunt was higher at the proximal ETS anastomosis than that at the distal ETS anastomosis; the hypothesis that the vessel wall is rigid is acceptable in CS numerical simulations for the treatment of tetralogy of Fallot( TOF). However,the coupling of flow dynamics and wall mechanics may lead to a more reliable simulation result in the CS.

Objective Based on time-coupled multiscale coupling algorithm,to simulate the hemodynamics after systemic-pulmonary shunt procedure on single ventricular patient so as to obtain the local three-dimensional( 3D) fluid field and global hemodynamic information before and after surgery. Methods Firstly,the 0D-3D coupled multiscale hemodynamic model of systemic-pulmonary shunt procedure was established based on the lumped parameter model( 0D) before surgery and the shunt model( 3D),then the 0D-3D interface coupling condition and the time coupling algorithm were discussed. Secondly,the multiscale simulation of 3D CFD( computational fluid dynamics) model coupled with 0D lumped parameter model was realized based on lattice Boltzmann method. Finally,the multiscale simulation results were compared with patient's 0D simulation results to study the hemodynamic changes before and after surgery. Results The global hemodynamic change and local 3D flow pattern were obtained by this multiscale simulation. The pulmonary blood flow distribution ratio was increased from 32. 21% to 57. 8%. Conclusions The systemic-pulmonary shunt procedure can effectively increase the blood supply of pulmonary circulation by implanting the shunt between the systematic circulation and pulmonary circulation. The geometrical multiscale method can effectively simulate both the coarse global and detailed local cardiovascular hemodynamic changes,which is of great significance in pre-operation planning of cardiovascular surgery.

Objective To predict the influence of connecting position between left superior vena cava(LSVC) and pulmonary artery on bilateral bidirectional Glenn(BBDG) shunt by numerical simulation.Methods Firstly,a 3D anatomical geometrical model was reconstructed by the medical images of a hypoplastic left heart syndrome(HLHS) patient with LSVC.Secondly,based on haptic deformations,several computational models were virtually generated,and computational fluid dynamics(CFD) numerical simulations were conducted using finite volume method.Finally,hemodynamic parameters were analyzed and evaluated.Results Flow recirculation was observed in the pulmonary artery between the LSVC and right superior vena cava(RSVC).The diameter of RSVC was defined as D.Varying the distance between LSVC and RSVC from 2D to 3.5D resulted in the least energy dissipation at 3D and the most at 2D.The blood flow rate ratios of left pulmonary artery to right pulmonary artery(LPA/RPA) ranged from 0.65-1.11.Conclusions Too close distance between LSVC and RSVC would bring out unfavorable hemodynamic distributions and consume more energy in the treatment of BBDG shunt.This study is of significance for surgeons to evaluate the optimal Fontan options in the treatment of HLHS accompanied by LSVC.