Haemodynamic Analysis of the Relationship between the Morphological Alterations of the Ascending Aorta and the Type A Aortic-Dissection Disease

Type A aortic dissection (AD) is one of the most serious cardiovascular diseases, whose risk predictors are controversial. The purpose of this research was to investigate how elongation accompanied by dilation of the ascending aorta (AAo) affects the relevant haemodynamic characteristics using image-based computational models. Five elongated AAos with different levels of dilation have been reconstructed based on the centerlines data of an elderly and an AD patient. Numerical simulations have been performed assuming an inflow waveform and a Windkessel model with three elements for all outflow boundaries. The numerical results have revealed that the elongation of AAo can disturb the systolic helical flow pattern between the root of AAo and the aortic arch. The helical flow inside the AAo starts to develop into a vortex flow when the elongated AAo becomes dilated. The vortex gives rise to a localized oscillatory shear index at the ostia of the brachiocephalic artery (BA) and the inner curve of the aortic arch. This study suggests that abnormal growth of AAo, especially accompanied by its moderate dilation, can be considered as morphological risk factors of AD.