Individualized Numerical Simulation Of The Artificial Grafts After The Operation Of The Total Arch Replacement With Stented "Elephant Trunk" Implantation

Objective:The total arch replacement with stented "elephant trank" implantation is a common procedure for the treatment of type A aortic dissection.Although the surgery has achieved good short-and middle-term efficacy,its long-term complications can not be ignored.At present,the mechanical properties between the artificial grafts and the natural aorta still do not match,and the hemodynamic changes will affect the long-term effect of the patient.Since the hemodynamic characteristics in the artificial grafts have not been completely elucidated,this study will analyze hemodynamic changes caused by artificial grafts through numerical simulation and provide a theoretical basis for the optimization and improvement of artificial grafts.This study will also explore the feasibility of evaluating surgical efficacy through numerical simulation techniques,in order to improve the long-term effect of the total arch replacement with stented "elephant trunk" implantation,and reduce the incidence of long-term complications related to artificial grafts.Method:Three healthy adults with no cardiovascular disease confirmed by CT,electrocardiogram and ultrasound were selected as the control group.Three patients who underwent total arch replacement with stented "elephant trunk" implantation were selected as the experimental group.CTA data were obtained from the control group and the experimental group 10 days after surgery,and the data was stored in DICOM format.The CTA data was imported into Mimics 19.0 software to create a personalized three-dimensional model of the whole aorta.The model will be exported as a CAD file in IGES format.After repairing the CAD files will be imported into ICEM CFD 17.0 software for 3D meshing.Importing the meshing model into CFX 17.0 and set the boundary conditions.Calculate and post-process the model.The hydrodynamic parameters of the control group and the experimental group at each time point were obtained.Results:(1)Individualized 3D models were successfully established using CTA data from the control and experimental groups.(2)By calculating the model of the control group and the experimental group,we obtained the corresponding hemodynamic parameters.The wall pressure,wall shear stress and distribution of blood flow fields in healthy adults and postoperative patients were demonstrated.(3)The hemodynamic characteristics of the control group were as follows:the wall pressure changed uniformly,and the pressure value gradually decreased from the inlet to the outlet.As for aortic arch,the wall pressure of the inner side wall is slightly lower than the outer side wall.The wall shear stress is higher at the aortic arch and the beginning of the three major branches.The wall shear stress is evenly distributed in the remaining parts.The blood flow field exhibits a stable laminar flow.The blood flow velocity in the center of the aorta is the largest,and the blood flow velocity is gradually reduced from the center to the periphery,the velocity of the layer near the tube wall is lowest.(4)The hemodynamic characteristics of the experimental group were as follows:the wall pressure gradually decreased from the inlet to the outlet,but the contour was very irregular.The wall pressure at the entrance of the aorta is highest,the wall pressure of the inner side wall is lower than the outer side wall.The wall shear stress is higher at the ascending aorta,the aortic arch,the beginning of the three major branches,and the beginning of the descending aorta.The wall shear stress is unevenly distributed in the remaining parts.The blood flow field exhibits an irregular flow state.Different degrees of turbulence occurred in the ascending aorta,the aortic arch,the proximal part of the three major branches,and the descending aorta.Conclusion:Although the operation reconstructed the blood flow channel from the heart to the whole body,it also produced obvious blood flow disturbances.By comparison with the control group,the distribution of aortic wall pressure and wall shear stress of the postoperative patients showed an irregular state.We found varying degrees of turbulence in the ascending aorta,the aortic arch,the proximal part of three major branches,and the descending aorta.Previous research shows the compliance of artificial grafts is much lower than that of the natural aorta,our study also confirms this conclusion.This study believes that the artificial grafts will bring significant blood flow disturbances,making the blood flow in the aorta "unphysiological" and will make adverse affect on the patient’s long-term prognosis.The new generation of artificial blood vessels should pay more attention to the compliance of artificial materials.Our research also confirmed that it is feasible to evaluate the surgical efficacy through numerical simulation.The numerical simulation can accurately reflect the hemodynamic state of the aorta in postoperative patients.