## 3 Results
### Stress Analysis  
Finally, we analysed changes in WSS to compare distribution of stresses during blood flow before and after TEVAR for the thoracic trunk and renal arteries. We observed a significant decrease in WSS values post-TEVAR compared to pre-TEVAR (1.34 \(\pm\) 0.20 Pa vs. 3.80 \(\pm\) 0.59 Pa, respectively, \(p\) = 0.0001). This decrease was associated with an increase in true lumen diameter and a decrease in blood velocity in this area.  
Moreover, a significant decrease of WSS values was observed in the thoracic aorta post-TEVAR compared to pre-TEVAR (1.34 \(\pm\) 0.11 Pa and 3.10 \(\pm\) 0.27 Pa, respectively, \(p\) = 0.043). A similar tendency was observed for the renal arteries (1.50 \(\pm\) 0.22 Pa and 4.40 \(\pm\) 0.25 Pa, post-TEVAR and pre-TEVAR, respectively, \(p\) = 0.043). The changes in WSS contour distribution in the thoracic aorta and left renal artery are presented in Figures 4 and 5, respectively. At each time for all analysed patients, the  
Figure 3: Changes in blood velocity contours of the left renal artery for a representative patient. **(top)**: velocity contour distribution in the left renal artery for representative time points before and 7 months after TEVAR; **(bottom)**: the average velocity changes in the left renal artery for one cardiac cycle. Changes in velocity contours were presented for the anterior and posterior position in the left renal artery. Numerical simulations calculated using ANSYS FLUENT software.  
pre-operative aorta had an irregular shape with numerous narrowing areas and unstable flow forced by the appearance of the two lumens (true and false). In our study the dissecting membrane created an artificial barrier characterized by high-WSS in the areas adjacent to the wall (4.7 Pa, Figure 4). Therefore, in the true lumen, WSS was much lower than expected. The endovascular intervention for all five patients separated the false lumen and directed blood flow through the true lumen leaving one channel. This smoothed the blood flow in each analysed patient and caused a noticeable change in WSS from 3.5 Pa to 1.3 Pa after TEVAR.  
Figure 4: Changes in wall shear stress (WSS) contour distribution in the thoracic aorta for a representative patient. **(top)**: WSS contour distribution in the thoracic aorta for representative time points before and 7 months after TEVAR; **(bottom)**: the average velocity changes in the thoracic aorta for one cardiac cycle. Changes in WSS contours were presented for the anterior and posterior position in the left renal artery. Numerical were simulations calculated using ANSYS FLUENT software.  
The second critical area affected by aorta dissection before TEVAR was the renal arteries. Prior to intervention, the left renal artery had an irregular shape with numerous stenotic areas, which resulted in high average WSS values (4.4 Pa) (Figure 5). The endovascular intervention led to an alignment of the artery and 57% increase in the average channel cross-section. Free passage through the left renal artery also lowered the average WSS in this area (Figure 5). Moreover, there was a 3.2-fold decrease in the average WSS from 4.4 Pa to 1.4 Pa (Figure 5). The distribution of the WSS contours post- and pre-TEVAR is presented in Figure 5. Moreover, in patients where the stent was placed in the left renal artery, WSS decreased by 3.1-2.3 Pa.  
Figure 5: Changes in WSS contour distribution in the left renal artery for a representative patient. **(top)**: WSS contour distribution in the left renal artery for representative time points before and 7 months after TEVAR; **(bottom)**: the average velocity changes in the left renal artery for one cardiac cycle. Changes in WSS contours are presented for the anterior and posterior position in the left renal artery. Numerical simulations were calculated in ANSYS FLUENT software.