A combined experimental and computational study of the flow characteristics in a Type B aortic dissection: Effect of primary and secondary tear size

Abstract

Aortic dissection is related to the separation of the tunica intima from the aortic wall, which can cause blood to flow through the newly formed lumen, thereby further damaging the torn vessel. This type of pathology is the most common catastrophic event that affects the aorta and is associated with complications such as malperfusion. In this work, an idealised, simplified geometric model of Type B aortic dissection is investigated experimentally using particle image velocimetry (PIV) and numerically using computational fluid dynamic (CFD) simulations. The flow characteristics through the true and false lumina are investigated parametrically over a range of tear sizes. Specifically, four different tear sizes and size ratios are considered, each representing a different dissection case or stage, and the experimental and numerical results of the flow-rate profiles through the two lumina in each case, along with the phase-averaged velocity vector maps at mid-acceleration, mid-deceleration, relaminarisation and peak systole, and their corresponding velocity profiles are compared. The experimental and numerical results are in good qualitative as well as quantitative agreement. The flow characteristics found here provide insight into the importance of the re-entry tear. We observe that an increase in the re-entry tear size increases considerably the flow rate in the false lumen, decreases significantly the wall shear stress (WSS) and decreases the pressure difference between the false and the true lumen. On the contrary, an increase in the entry tear, increases the flow rate through the false lumen, increases slightly the WSS and increases the pressure difference between the false and the true lumen. These are crucial findings that can help interpret medical diagnosis and accelerate prevention and treatment, especially in high-risk patients.

A Combined In Vivo, In Vitro, In Silico Approach for Patient-Specific Haemodynamic Studies of Aortic Dissection

“…22 PIV was recently used to study the impact of tear size on the flow in an idealised model of AD using computations and experiments. 30 However, to date, PIV has not been used in any patient-specific in vitro AD work.…”

Experimental evaluation of the patient-specific haemodynamics of an aortic dissection model using particle image velocimetry

“…In order to overcome these, AD benchtop experiments – either employing an ex-vivo vessel or a synthetic replica – started to be employed and allowed the study of haemodynamic variables through different measurement techniques (e.g. Ultrasound (US) Chung et al, 2000a , magnetic resonance imaging (MRI) Birjiniuk et al, 2017 and, only recently, Particle Image Velocimetry (PIV) Zadrazil et al, 2020 ).…”

“…Parametric studies with idealised artificial phantoms have increased the understanding of the pathology and have highlighted the importance of morphological features on the haemodynamic variables ( Chung et al, 2000b , Rudenick et al, 2013 , Marconi et al, 2017 , Zadrazil et al, 2020 ) ( Table 1 ). Parametric studies can also be used to assess possible treatment methods and their impact on parameters of interest (e.g.…”

An in vitro Assessment of the Haemodynamic Features Occurring Within the True and False Lumens Separated by a Dissection Flap for a Patient-Specific Type B Aortic Dissection

“…A haemodynamic study was also conducted within an in vitro patient-specific Type B aortic dissection phantom model under steady ( 14 ) and pulsatile ( 15 ) flow conditions with undocumented stiffness or compliance values. Zadrazil et al ( 16 ) performed steady flow computational and experimental simulations on an idealised Type B aortic dissection without branching vessels. Patient-specific computational studies incorporating branching vessels along a Type B dissection have previously been reported ( 17 , 18 ).…”