Study On Quantitative Analysis Of Blood Flow Interference In Type-B Aortic Dissection Based On Computer Simulation

Background: Cardiovascular disease is one of the leading causes of human death,and its incidence has been gradually increasing in recent years.Aortic dissection is a more serious type of cardiovascular disease,although its incidence is not high,but the mortality rate of patients without timely treatment is as high as 80%.The mechanism of the disease is that the blood flow’s impact causes aortic intimal tear,blood perfusion into the aorta and dissection to the proximal and distal,forming a false lumen independent of the original aorta(true lumen).The occurrence and development of this disease is closely related to the blood flow function in the aorta,and its severity is also closely related to the fluid exchange between true and false lumens.For the Stanford type-B aortic dissection the dissection from descending aorta,there are often multiple secondary tears in the thoracic aortic region.This study quantifies blood flow disturbances caused by tears at different locations to help establish studies on blood flow function for such diseases.Methods: This study reconstructed a specific three-dimensional model of the patient based on Computerized Tomography Angiography(CTA).Through the reverse engineering technique,three-dimensional models in which secondary tears appear at different positions were obtained.The flow field was solved based on the finite volume method.The relationship between the position of different secondary tears and blood flow function was discussed,and the coupling effects of aortic morphological parameters(such as curvature)and secondary cleft on aortic blood flow function were further studied..This study first established an analysis procedure of blood flow for the secondary tears in different locations in a single case.Secondly,a common analysis was conducted for multiple cases,and the main factors affecting aortic blood perfusion were proposed.Results: The results of a single case showed that: the blood movement in the true lumen(TL)is regular,while the blood flow in the false lumen(FL)is more disordered near the primary tear,and the blood flow velocity in TL is larger than that in the FL.When the position of the secondary tear is closer to the primary tear,the blood flow in the FL near the secondary tear is disordered,and when the secondary tear is located farther from the primary tear,the velocity of blood flowing into FL through the primary tear becomes larger.The blood flow into the false lumen is related to the position of the secondary tear.When the secondary tear is away from the primary tear,the blood flow into the FL becomes larger.The pressure in the TL is firstly larger than that in the FL;the number of zero points of the pressure difference is 1.When the position of the secondary tear is farthest from the primary tear,the position where pressure difference equals zero is moved downward.When the position of secondary tear is away from the primary tear,the wall shear stress becomes larger among the position in FL opposite to the primary tear.The results of the second part are: the velocity of blood in the TL is greater than that in the TL in 8 cases.In addition,all cases show that as the secondary tear moves down,the maximum flow velocity in the true lumen decreases.The blood flow into the FL is positively correlated with the low curvature of the secondary tear,and is highly negatively correlated with the area of secondary tear,and moderately positively correlated with the volume ratio of TL and FL above the secondary tear,and negatively correlated with the area of FL above the secondary tear.The position where the pressure difference equals zero is found changed in 6 cases.In these cases,as the position of the secondary tear moves down,the pressure in the true lumen of the blood vessel is stronger than that in the false cavity.In other cases,there is no significant change.In the 7 cases that have small primary tear,when the secondary tear is moved downward,the wall shearing stress among the position in FL opposite to primary tear is significantly increased,otherwise there is no significant change.Conclusion: Based on imaging and computational fluid dynamics,this paper quantitatively analyzes the different effects of secondary tears at different positions of the same patient on blood flow function,and analyzes the commonality of functional impact of secondary tears at different locations based on multiple case.In this study,the functional effects of secondary tears located in thoracic aorta on the overall blood flow function of the aortic dissection were preliminarily determined,and conclusions could provide guidance for risk assessment and stent intervention.