Hemodynamics-simulation-based cardiovascular surgical planning.which is the patient-specific surgical hemodynamics optimization based on medical image,is the further development of clinical-applica-tion-oriented computational hemodynamics,it is very helpful for cardiovascular surgical decision-making.The art-in-work of hemodynamics-simulation-based cardiovascular surgical planning in both domestic and over-seas research was reviewed,the key problems and solutions involved were analyzed,and the further develo-ping objectives were presented.

Geometrically virtual models of three-dimensional blood flow field and eight types of mesh stent (different porosity and different stent shape) were constructed using SoildWorks software, and simulation of stented models were performed respectively using finite element software ANSYS11.0 according to computation fluid dynamics method. The flow resistance of the semi-circular section stent model of blood flow from the semi-circular planar surface was greater than the reverse in a certain range of permeability. However, the result was the opposite when the porosity increased to a specific value. For both grid-stent model and sine-stent model, flow resistance of blood that flowed from the stent in both directions increased with the porosity reduction. Under the same porosity and the direction of blood flow from the same stent, the flow resistance of the grid stent model was 1.5 times greater than the sine-stent model. Results showed that there are different effects on the flow resistance in blood flow in different directions from the semi-circular section stent model.

Aortic dissection is a common disease which is very dangerous,with high mortality rate.Bypass graft for the treatment of DeBakey Ⅲ dissection has outstanding advantages than the ordinary replacement of thoracic aorta,and some patients will inevitably require the use of the procedure.The purpose of this study was to explore the impact of the subclavian artery-abdominal aorta bypass graft on hemodynamic parameters in the false lumen and the effectiveness of surgical treatment.First of all,the idealized three-dimensional geometric models of DeBakey Ⅲ aortic dissection and its subclavian artery-abdominal aorta bypass graft operation were constructed,respectively.Then the models were imported into ANSYS 11.0 for finite element analysis.Results of numerical simulation showed that both velocity and pressure of the blood flow were reduced after bypass graft at the entrance and in the internal sac of false lumen,which is very favorable for reducing the impact of blood flow on false lumen,slowing down the further expansion of entrance,preventing the breakdown of false lumen,and promoting the healing of dissection.Therefore,the subclavian artery-abdominal aorta bypass graft operation is an effective surgical method for the treatment of DeBakey Ⅲ aortic dissection in some particular cases.This operation is with great prospects for clinical application.

To provide a reference basis for the structural design and optimization of endovascular stent by analyzing the flow resistance of the new stent with triangle cross-section using numerical simulation method, and finding out the stent structure which will influence hemodynamic parameters. Four kinds of models of the triangle cross-section bare stent were constructed in infinite flow field using solidworks software. Numerical simulations of the four models were performed respectively using ANSYS finite element software. Steady flows and transient flows in these models were studied. Hemodynamics data in the four models were collected, such as the flow patterns, the distribution of pressure and the flow resistance of the new stents. The stent with triangular wire cross-section can be applied to cover aneurysm cavity because that resistance of blood inflow to aneurysm was large and outflow from aneurysm was small. Thus, it was easy to outflow than inflow. Thereby blood perfusion and flow of aneurysm cavity was restrained, and the pressure of aneurysm cavity was reduced, which plays a certain effect on the treatment of aneurysm. This result provides some instructions for the design of stent structure.

For the purpose of improving the hemodynamics of CABG, the authors presented a new amelioration measurement of symmetric 2-way bypass graft. The physiological blood flow in 1-way and 2-way bypass graft of coronary is simulated with finite element method, and the data on computational hemodynamics of these two cases were compared. The temporal-spatial distributions of hemodynamics during the cardiac cycle such as flow patterns and wall shear stress in the vicinity of anastomosis were analyzed. The study results showed that 2-way bypass graft was of more rational hemodynamics when compared with 1-way bypass graft, and it could improve the flow conditions and decrease the probability of restenosis.
Anastomosis, Surgical ; Blood Flow Velocity ; Coronary Artery Bypass ; methods ; Coronary Circulation ; Humans ; Saphenous Vein ; transplantation

Objective To establish a method for non-invasive calculation of fractional flow reserve (FFRCT) with the shape resistance of coronary artery stenosis as boundary condition, and to verify the accuracy of this method. Methods CT angiography images of 16 patients with coronary artery disease were reconstructed; the mathematical model of shape resistance was established by considering the minimum cross-sectional area and the length of stenosis of coronary artery stenosis, the induced pressure difference as the boundary condition was applied to calculate FFRCT (named as shape resistance method ). The values of clinical FFR were taken as the gold standard, previous diameter method and volume method were taken as control method, and accuracy of shape resistance method was investigated from the aspects of mean error rate, accuracy rate, sensitivity rate, positive prediction rate and negative prediction rate. Results The mean error rate of calculated FFRCT by the diameter method, volume method and shape resistance method were 11.76%, 10.46%, 4.82%, the accuracy rates were 85%, 65%, 90%, the sensitivity rates were 87.5%, 66.7%, 87.5%, the positive prediction rate were 75%, 25%, 87.5%, respectively, while the negative prediction rates were all 91.6%. Conclusions The established shape resistance method is better than the diameter method and volume method from the aspects of mean error rate, accuracy rate, sensitivity rate and positive prediction rate; the FFRCT based on the shape resistance method and clinical FFR have good consistency, and this work may provide a new way for the calculation and application of FFRCT.

Endovascular stent is a new technique for the treatment of aortic arch aneurysms. The present simulation study of endovascular stent treatment for aneurysms in the inner bend of aortic arch is initiated by the fact that no one has ever investigated the hemodynamics of stented aortic arch aneurysm harboring a bleb. For the comparative convenience, a stented and a nonstented aortic arch aneurysm models were constructed respectively. Physiological blood flows in both models were simulated using the computational fluid dynamics method. The detailed flow patterns, pressure and wall shear stress distributions around the aneurysm of both models were compared and analyzed so as to evaluate the effectiveness of endovascular stent treatment for aortic arch aneurysms. Results showed that the stented model is attributed to substantially different intra-aneurysmal flow patterns versus the nonstented model. Flow activities within the stented aneurysmal sacs are markedly diminished, specifically the pressure and wall shear stress in the bleb were significantly decreased. These phenomena allow us to conclude that endovascular stent can promote intra-aneurysmal thrombus development and attenuating aneurysm rupture risk.
Aortic Aneurysm, Thoracic ; physiopathology ; surgery ; Computer Simulation ; Hemodynamics ; physiology ; Humans ; Models, Cardiovascular ; Shear Strength ; Stents ; Stress, Mechanical

A new stent with triangular wire cross-section was proposed. The new stents were compared with traditional circular wire cross-section stent in the same porosity in order to investigate its effectiveness in treating intracranial aneurysms. Three models were established separately, including the aneurysm model with circle cross section stent, the aneurysm model with triangular cross section stent and the aneurysm model with non-stent. Then the same boundary conditions were set to contrast the resistance to flow, velocity, pressure, wall shear stress and total mesh displacement. The resistance to flow of triangular cross section stent was lower than circle cross section stent and the velocity, pressure, total mesh displacement of aneurysm model with triangular cross section stent were all higher than those of the model with circle cross section stent. Moreover, the peak value and valley value of wall shear stress in aneurysm model with triangular cross section stent were higher than those of the other. Triangular cross section stent might play a negative role to aneurysm rupturing. Thus, the therapeutic effect of stent with triangle cross section was not better than the stent with circle cross section. In the clinical application, doctors should consider the various factors, and choose the most suitable one.
Aneurysm ; therapy ; Computer Simulation ; Hemorheology ; physiology ; Humans ; Intracranial Aneurysm ; therapy ; Prosthesis Design ; Stents

The graft diameter plays a critically important role in the long-term patency rates of bypass surgery. To clarify the influence of graft diameter on the blood flows in the femoral 2-way bypass surgery, the physiologically pulsatile flows in two femoral bypass models were simulated with numerical methods. For the sake of comparison, the models were constructed with identical geometry parameters except the different diameters of grafts. Two models with small and large grafts were studied. The boundary conditions for the simulation of blood flow were constant for both models. The maximum Reynolds number was 832.8, and the Womersley number was 6.14. The emphases of results were on the analysis of flow fields in the vicinity of the distal anastomosis. The temporal-spatial distributions of velocity vectors, pressure drop between the proximal and distal toe, wall shear stresses, wall shear stress gradients and oscillating shear index were compared. The present study indicated that femoral artery bypassed with a large graft demonstrated disturbed axial flow and secondary flow at the distal anastomosis while the axial flow at its downstream of toe was featured with larger and more uniform longitudinal velocities. Meanwhile, the large model exhibits less refluences, relatively uniform wall shear stresses, lower pressure and smaller wall shear stress gradients, whereas it does not have any advantages in the distributions of secondary flow and the oscillating shear index. In general, the large model exhibits better and more uniform hemodynamic phenomena near the vessel wall and may be effective in preventing the initiation and development of postoperative intimal hyperplasia and restenosis.
Anastomosis, Surgical ; Arterial Occlusive Diseases ; surgery ; Blood Flow Velocity ; physiology ; Blood Vessel Prosthesis ; Blood Vessel Prosthesis Implantation ; methods ; Femoral Artery ; physiopathology ; surgery ; Humans ; Models, Cardiovascular ; Shear Strength ; Stress, Mechanical

Objective To compare and analyze the mechanical performance of a new biodegradable stent and a common stent and their effects on treating the stenotic vessels. Methods Using finite numerical simulation, the new stent and the common stent were implanted into vessels with a diameter stenosis of 30%, and their support performance and influences on reshaping the stenotic vessels were investigated. Results The radial recoiling ratio and dog-boning ratio of the new stent were decreased by 26.6% and 34.7%, respectively, compared with the common stent. Besides, the stenotic vessel deployed with the new stent recoiled less and had a flatter and larger lumen. Conclusions Compared with the common stent, the new stent has stronger scaffold performance and a better therapeutic effect on stenotic vessels. The new stent with stronger scaffold performance is highly expected to be an alternative choice in interventional surgeries.