Morphological And Hemodynamic Study Of Type Stanford B Aortic Dissection

Objective:To investigate the differences in aortic morphology between native patients with acute Stanford type B aortic dissection（ATBAD）and controls,and to establish a morphological prediction model for ATBAD.A related ideal model of the aorta was constructed,and the underlying mechanisms that may be related to the pathogenesis of ATBAD were further explored through hemodynamic analysis.By comparing the hemodynamic parameters of dissecting aorta before and after stent implantation,we determined the hemodynamic risk factors related to reverse tear type A aortic dissection（RTAD）.Materials and Methods:In the first part of the ATBAD morphological study,237 ATBAD patients and 544 normal aortic controls were retrospectively collected.Using the PMS propensity score,109 cases in each of the dissection group and the control group were finally included.The clinical data and aorta-related morphological parameters of the subjects were collected through the electronic case system of the Second Affiliated Hospital of Xiangya.Univariate analysis was used to obtain the factors with statistical differences between the two groups and perform univariate logistic regression analysis.The screened morphological parameters of interest were subjected to multivariate logistic regression analysis,and the finally obtained meaningful parameters were used for predictive model modeling.,the prediction model is displayed in the form of a nomogram,and the model performance is detected by the ROC curve.In the second part,based on the results of the first part of the study,an ideal model series of the aorta related to the volume of the proximal aortic segment and the length of the distal aortic arch was constructed respectively,and the hemodynamic parameters were quantitatively analyzed using Fluent software.In the third part of the clinical event simulation fluid dynamics study,from the database of acute aortic Stanford B dissection in our hospital,4 cases of Stanford type A reverse tear after receiving aortic stent implantation were screened out.They were matched according to age and sex.Four patients with ATBAD who underwent endoluminal stent implantation did not develop reverse tear Stanford A aortic dissection three years later.Mimics,geomagic,and Ansys software were used to process graphics,analyze hemodynamic data,and analyze the preoperative and postoperative aortic time-averaged wall shear force and shear shock index in the two groups.Statistical analysis was performed using SPSS and R language,and P<0.05was considered statistically significant.Results:The first part of the study found that the length of the distal aortic arch（L₂）,the cross-sectional diameter of the aorta at the proximal end of the left carotid artery opening（D₄）,the cross-sectional diameter of the aorta at the distal end of the left subclavian artery opening（D₆）,the The proximal aortic arch volume（LV）was a positive independent risk factor for acute type B dissection,and the aortic cross-sectional diameter（D₅）at the distal end of the left carotid artery was a negative independent risk factor for acute type B dissection.In this study,we constructed a diagnostic prediction model of acute Stanford type B dissection by incorporating four morphological factors of L₂,D₄,D₆,and LV,and its diagnostic performance was satisfactory（ROC-AUC=0.88）.The second part found that the volume of the proximal aorta increased,the overall kinetic energy（Kinetic energy）increased,the time-averaged time-averaged wall shear stress（TAWSS）and the oscillatory shear index（OSI）of the downstream distal aortic arch segment were found.)will also increase accordingly.The length of the distal aortic arch segment increases,and the wall fluid energy loss（Energy loss）,time-averaged shear stress（TAWSS）,oscillatory shear index（OSI）,and low oscillatory shear（LOS）all increase accordingly.The third step found that in the reverse tear type A dissection group,the postoperative TAWSS increased compared with that before the operation,while in the control group,this trend was just the opposite.The OSI before and after surgery did not show a consistent change.Conclusions:The aortic arch diameter,enlarged proximal aortic segment volume,and distal descending aorta lengthening are associated with the occurrence of acute type B aortic dissection and are helpful in screening individuals at high risk for acute type B aortic dissection.Computer-assisted hemodynamics（CFD）is an effective tool to help us understand disease mechanisms.The increased TAWSS of the aortic arch after TEVAR may provide an evaluation method for predicting the occurrence of RTAD.