Different levels of spatiotemporal heterogeneity characterize the aneurysmal and healthy ascending aorta hemodynamics, reflecting on wall shear stress topological skeleton. Peculiar wall shear stress topological skeleton features are linked to local ascending thoracic aortic aneurysms stiffness. The topological shear variation index, a measure of wall shear stress luminal contraction/expansion action variation along the cardiac cycle, is an indicator of local aortic wall degradation, performing better than canonical wall shear stress-based descriptors of flow disturbances. Wall shear stress topological skeleton analysis, combined with Complex Networks theory, contributes to better determine whether arterial wall degeneration, in combination with hemodynamic insult, leads to aneurysmal progression/rupture.
Endovascular aneurysm repair (EVAR) has disseminated rapidly as an alternative to open surgical repair for the treatment of abdominal aortic aneurysms (AAAs), because of its reduced invasiveness, low mortality and morbidity rate. The effectiveness of the endovascular devices used in EVAR is always at question as postoperative adverse events can lead to re-intervention or to a possible fatal scenario for the circulatory system. Motivated by the assessment of the risks related to thrombus formation, here the impact of two different commercial endovascular grafts on local hemodynamics is explored through 20 image-based computational hemodynamic models of EVAR-treated patients (N=10 per each endograft model). Hemodynamic features, susceptible to promote thrombus formation, such as flow separation and recirculation, are quantitatively assessed and compared with the local hemodynamics established in image-based infrarenal abdominal aortic models of healthy subjects (N=10). The hemodynamic analysis is complemented by a geometrical characterization of the EVAR-induced reshaping of the infrarenal abdominal aortic vascular region. The findings of this study indicate that: (1) the clinically observed propensity to thrombus formation in devices used in EVAR strategies can be explained in terms of local hemodynamics by means of image-based computational hemodynamics approach; (2) reportedly pro-thrombotic hemodynamic structures are strongly correlated with the geometry of the aortoiliac tract postoperatively. In perspective, our study suggests that future clinical follow up studies could include a geometric analysis of the region of the implant, monitoring shape variations that can lead to hemodynamic disturbances of clinical significance.
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