Aortic haemodynamics and wall stress analysis following arch aneurysm repair using a single-branched endograft

Figure 1. The NEXUS™ device selected for TEVAR, highlighting its features and different components.

Figure 2. The various stages of treatment and follow-ups for the patient examined. PRE: Pre-TEVAR geometry indicating presence of aneurysm, POST: Post-TEVAR geometry following a successfully completed procedure, FU1: First follow-up scan which indicated negative results in the form of the carotid-carotid bypass being compromised, FU2: The final clinical images obtained from the patient indicating the formation of an aneurysmal sac in the ascending aorta.

Figure 3. Central line view of the whole aorta: (left) proximal to distal aorta with three marked levels. (A)—just beyond LSA, (B)—just before IA, (C)—proximal landing zone, 35 mm from IA proximally to the ascending aorta. The length between (B) and (C) is 35 mm, and (B) and (A) is 70.7 mm. (Right) Transverse view of levels (B) and (C) with a cross-sectional measurement of aortic diameter 37.9 × 37.7 mm and 37.0 × 39.5 mm, respectively.

Figure 4. Pre-TEVAR (left) and post-TEVAR (right) models reconstructed from the corresponding CT scans, and the prescribed 3-EWM boundary conditions at the model outlets.

Figure 5. 3d geometry for structural domain, with unstructured mesh shown on the left, and segments of different material highlighted on the right. The uniform thickness of the geometry can be seen clearly on the right with the branch inlets and outlets serving as regions of fixed points to tether the geometry in place.

Figure 6. Representative 3D inlet velocity profile imposed at model inlet showing velocity distribution at different stages of the systolic phase of the cardiac cycle.

Figure 7. Instantaneous velocity streamlines at peak systole for the pre-TEVAR (PRE—top left) and post-TEVAR (POST—top right) and follow-up (FU1—bottom right) models. This indicates the exclusion of the aneurysm in the inner curvature of the arch following the procedure and the flow patterns observed at the follow-up examination following the compromise of the carotid-subclavian bypass.

Figure 8. Volumetric flowrate in the RCC for the pre-TEVAR (PRE) case, post-TEVAR (POST) and follow-up (FU1) cases (bottom). The length of the cardiac cycle was based on clinical measurements (1.23 s for pre-TEVAR and 1.4 s for post-TEVAR).

Figure 9. Vortical structures within the vessel represented as isosurfaces using the λ2 criterion for pre-TEVAR (left) and post-TEVAR (right) stages.

Figure 10. Comparison of time-averaged WSS between pre-TEVAR (top) and post-TEVAR (bottom) stages.

Figure 11. Comparison of wall shear stress-related metrics between post-TEVAR and follow-up stages with time-averaged WSS (top), transverse WSS (middle) and endothelial cell activation potential (bottom) maps all showing similar spatial distribution and patterns between the two cases.

Figure 12. Time-dependent displacement forces acting on the ascending module of the device, shown for POST, decomposed into x-, y- and z-components with peak values in each direction indicated on the plot. The direction of the resultant force is shown on the geometric model.