A simplified method to account for wall motion in patient-specific blood flow simulations of aortic dissection: Comparison with fluid-structure interaction

Abstract

Aortic dissection (AD) is a complex and highly patient-specific vascular condition difficult to treat. Computational fluid dynamics (CFD) can aid the medical management of this pathology, yet its modelling and simulation are challenging. One aspect usually disregarded when modelling AD is the motion of the vessel wall, which has been shown to significantly impact simulation results. Fluid-structure interaction (FSI) methods are difficult to implement and are subject to assumptions regarding the mechanical properties of the vessel wall, which cannot be retrieved non-invasively. This paper presents a simplified 'moving-boundary method' (MBM) to account for the motion of the vessel wall in type-B AD CFD simulations, which can be tuned with non-invasive clinical images (e.g. 2D cine-MRI). The method is firstly validated against the 1D solution of flow through an elastic straight tube; it is then applied to a type-B AD case study and the results are compared to a state-of-the-art, full FSI simulation. Results show that the proposed method can capture the main effects due to the wall motion on the flow field: the average relative difference between flow and pressure waves obtained with the FSI and MBM simulations was less than 1.8% and 1.3%, respectively and the wall shear stress indices were found to have a similar distribution. Moreover, compared to FSI, MBM has the advantage to be less computationally expensive (requiring half of the time of an FSI simulation) and easier to implement, which are important requirements for clinical translation.

Residual type B aortic dissection FSI modeling

“…At t ¼ 0.3 s, recirculating area occurring for rigid case within the FL does not develop for FSI one. In agreement with literature (Bonfanti et al 2018) rigid hypothesis overestimates WSS value on average. However, at ETs, FSI modeling induces higher WSS values as reported in Table 1.…”

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

“…12 Recently, the limitation of the rigid wall assumption has also been overcome, with the implementation of fluid structure interaction (FSI) models able to simulate the motion of the aortic wall and IF. 1,2,4 Experimental investigations of flow in simplified models of AD have increased the general understanding of the pathology and highlighted the influence of morphological features on the involved fluid dynamic variables. 3,23 However, patient-specific, complex flow fields have not been measured in physical AD models yet.…”

Patient-specific haemodynamic simulations of complex aortic dissections informed by commonly available clinical datasets

“…However, the majority of published AD models [12][13][14][15][16][17] assumes rigid-walls and neglects compliance effects on the predicted pressures. Advanced CFD models of AD account for the motion of the vessel walls using fluidstructure interaction (FSI) or moving boundary approaches [11,[18][19][20] which, in order to be patient-specific, need to be informed by nonroutine displacement data obtained, for example, via cine-MRI.…”