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.

Effects of size and location of distal tear on hemodynamics and wave propagation in type B aortic dissection

The type B aortic dissection(TBAD)is a perilous disease with high morbidity and mortality rates.The hemodynamics of TBAD in different scenarios has been widely studied by computational fluid dynamics(CFD)research.However,the flow pattern and wave propagation characteristics in the cardiovascular system with TBAD are not yet clear,and the effect of the distal tear is still unknown.In this work,a onedimensional(1D)cardiovascular system model coupling with a zero-dimensional(0D)lumped-parameter model is introduced to study the hemodynamics and wave propagation in the cardiovascular system.The results show that the proposed 0D-1D method well captures the oscillation and retrograde characteristics for the flow in the false lumen(FL),and the smaller distal tear damps the retrograde flow.Besides,the distal tear should also be paid attention to,and the wave intensity(WI)can be used as an access mark of the degree of the aortic dissection(AD).

Study of Effect of Boundary Conditions on Patient-Specific Aortic Hemodynamics

Cardiovascular computational fluid dynamics(CFD)based on patient-specific modeling is increasingly used to predict changes in hemodynamic parameters before or after surgery/interventional treatment for aortic dissection(AD).This study investigated the effects of flow boundary conditions(BCs)on patient-specific aortic hemodynamics.We compared the changes in hemodynamic parameters in a type A dissection model and normal aortic model under different BCs:inflow from the auxiliary and truncated structures at aortic valve,pressure control and Windkessel model outflow conditions,and steady and unsteady inflow conditions.The auxiliary entrance remarkably enhanced the physiological authenticity of numerical simulations of flow in the ascending aortic cavity.Thus,the auxiliary entrance can well reproduce the injection flow fromthe aortic valve.In addition,simulations of the aortic model reconstructed with an auxiliary inflow structure and pressure control and the Windkessel model outflow conditions exhibited highly similar flow patterns and wall shear stress distribution in the ascending aorta under steady and unsteady inflow conditions.Therefore,the inflow structure at the valve plays a crucial role in the hemodynamics of the aorta.Under limited time and calculation cost,the steady-state study with an auxiliary inflow valve can reasonably reflect the blood flow state in the ascending aorta and aortic arch.With reasonable BC settings,cardiovascular CFD based on patient-specific ADmodels can aid physicians in noninvasive and rapid diagnosis.