Preliminary Study On Numerical Simulation Of Stanford Type A Aortic Dissection

Objective:The pathogenesis of Stanford A type aortic dissection is not yet fully understood,and its hemodynamic changes are closely related to disease progression.Numerical simulation of blood flow in the aorta combined with fluid mechanics methods,analysis of the influence of wall pressure,shear stress,blood flow velocity and other parameters on the aorta,discussion of the application value of numerical simulation methods in the study of aortic dissection,and analysis Its effect on evaluating the prognosis of patients.Method:10 cases of Stanford type A aortic dissection patients and 10 cases of ascending aortic aneurysm diagnosed based on aortic CTA and ultrasound were selected as the experimental group,and 10 healthy adults without aortic disease and heart disease were selected as the control group,and the experimental group was collected.The CTA results before and within 2 weeks after the operation,and the CTA results of some patients during the half-year follow-up after the operation were used as experimental data.The peak values of the aorta,innominate artery,common carotid artery,and subclavian artery measured by transthoracic Doppler ultrasound were collected The blood flow velocity is used as the boundary condition,and the imaging results are saved in DICOM format.First,import the CTA data of the research object into Mimics 21.0 to construct an individualized aortic three-dimensional model,ranging from the ascending aorta to the descending aorta,including the aortic arch and the proximal end of the three branches,and output as a CAD format file.Secondly,combined with the use of ANSYS software for meshing,input the inlet and outlet blood flow velocity and other parameters into the calculation software,set reasonable boundary conditions,calculate the hemodynamic parameters through the CFX software,and the statistical processing of mechanical parameters is performed to evaluate the influence of wall pressure and shear stress changes on the vessel wall.Results:(1)Three-dimensional images of the aorta of the three groups of subjects were reconstructed by Mimics software and CTA data.(2)Combined with the computational fluid dynamics method,the reconstructed three-dimensional model is used to simulate the corresponding blood flow state,and the blood flow velocity changes at different times,the distribution of wall pressure and shear stress are calculated,and an intuitive hemodynamic distribution map is obtained.(3)The blood flow state of aortic dissection is more disordered than that of ascending aortic aneurysm.There is a difference between the three groups of preoperative wall pressure and shear stress.Within a cardiac cycle,the dissection group is the highest,and the normal person The lowest;surgery can effectively reduce the wall pressure and shear stress of the ascending aorta segment,both in the two groups are lower than before surgery,surgery cannot completely restore the blood flow in the aorta.After the operation,the wall pressure of the two groups decreased gradually from the proximal end of the ascending aorta to the distal end.The higher the blood flow velocity,the higher the pressure,and the three-branch opening showed greater shear stress,and the systole was broken.The shear stress was the largest near the mouth position,and there was no significant difference between the dissection group and the ascending aortic aneurysm group.Due to the shape of the blood vessel and the presence of the trunk stent at the artificial blood vessel anastomosis,it will show a state of local high shear stress.Conclusion:Surgery can reconstruct the aortic vessel,is an effective strategy for the treatment of type A dissection.After the operation,the wall pressure and shear stress of the patient are effectively reduced,but the blood flow is still different from the normal thoracic aortic blood flow,and the blood flow state will be abnormal locally.Artificial blood vessels and stents used in surgery can replace diseased tissue blood vessels to a certain extent,but due to problems such as their shape and compliance,they are still different from normal people after surgery.Numerical simulation methods provide an important method for hemodynamic research.Changes in mechanical parameters have an important relationship with the occurrence and development of aortic dissection.It has a certain prompting effect on the pathogenesis of the disease,and it is also expected to become an important method for evaluating long-term prognosis..