Computational prediction of hemodynamical and biomechanical alterations induced by aneurysm dilatation in patient‐specific ascending thoracic aortas

• Published in: International journal for numerical methods in biomedical engineering Vol. 36; no. 6; pp. e3326 - n/a
• Main Authors: Jayendiran, Raja, Condemi, Francesca, Campisi, Salvatore, Viallon, Magalie, Croisille, Pierre, Avril, Stéphane
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.06.2020; Wiley Subscription Services, Inc; John Wiley and Sons
• Subjects: 4D MRI; Aneurysms; Aorta; Aortic aneurysms; ascending thoracic aortic aneurysm; biomechanical descriptors; Biomechanics; Blood flow; Cardiology and cardiovascular system; CFD; Computational Engineering, Finance, and Science; Computational fluid dynamics; Computer applications; Computer Science; Computer simulation; Engineering Sciences; FEA; Flow mapping; Fluid dynamics; Fluids mechanics; Helicity; Hemodynamics; Human health and pathology; Hydrodynamics; Life Sciences; Magnetic resonance imaging; Mathematical analysis; Mechanical properties; Mechanics; Morphology; Patients; rupture index; Sex; Shear stress; Thorax; Wall shear stresses; CFD; FEA; rupture index; 4D MRI; biomechanical descriptors; ascending thoracic aortic aneurysm
• ISSN: 2040-7939; 2040-7947; 2040-7947
• DOI: 10.1002/cnm.3326

The aim of the present work is to propose a robust computational framework combining computational fluid dynamics (CFD) and 4D flow MRI to predict the progressive changes in hemodynamics and wall rupture index (RPI) induced by aortic morphological evolutions in patients harboring ascending thoracic aortic aneurysms (ATAAs). An analytical equation has been proposed to predict the aneurysm progression based on age, sex, and body surface area. Parameters such as helicity, wall shear stress (WSS), time‐averaged WSS, oscillatory shear index, relative residence time, and viscosity were evaluated for two patients at different stages of aneurysm growth, and compared with age‐sex‐matched healthy subjects. The study shows that evolution of hemodynamics and RPI, despite being very slow in ATAAs, is strongly affected by morphological alterations and, in turn could impact biomechanical factors and aortic mechanobiology. An aspect of the current work is that the patient‐specific 4D MRI data sets were obtained with a follow‐up of 1 year and the measured time‐averaged velocity maps and flow eccentricity were compared with the CFD simulation for validation. The computational framework presented here is capable of capturing the blood flow patterns and the hemodynamic descriptors during the various stages of aneurysm growth. Further investigations will be conducted in order to verify these results on a larger cohort of patients and with long follow‐up times to finally elucidate the link between deranged hemodynamics, AA geometry, and wall mechanical properties in ATAAs. The comparison between the time‐averaged velocity maps and the flow eccentricity data measured using 4D flow MRI showed good correlation, elucidating that our computational framework is plausible and can be used for future study. The ascending thoracic aortic diameter and inlet angle have a major effect on the blood flow pattern in the diseased subject. The ascending thoracic aortic aneurysm subjects showed decreased wall shear stress, elevated relative residence time, and rupture index near the ascending aortic region compared to healthy subjects.