An integrated fluid–structure interaction and thrombosis model for type B aortic dissection

Abstract

False lumen thrombosis (FLT) in type B aortic dissection has been associated with the progression of dissection and treatment outcome. Existing computational models mostly assume rigid wall behavior which ignores the effect of flap motion on flow and thrombus formation within the FL. In this study, we have combined a fully coupled fluid–structure interaction (FSI) approach with a shear-driven thrombosis model described by a series of convection–diffusion reaction equations. The integrated FSI-thrombosis model has been applied to an idealized dissection geometry to investigate the interaction between vessel wall motion and growing thrombus. Our simulation results show that wall compliance and flap motion can influence the progression of FLT. The main difference between the rigid and FSI models is the continuous development of vortices near the tears caused by drastic flap motion up to 4.45 mm. Flap-induced high shear stress and shear rates around tears help to transport activated platelets further to the neighboring region, thus speeding up thrombus formation during the accelerated phase in the FSI models. Reducing flap mobility by increasing the Young’s modulus of the flap slows down the thrombus growth. Compared to the rigid model, the predicted thrombus volume is 25% larger using the FSI-thrombosis model with a relatively mobile flap. Furthermore, our FSI-thrombosis model can capture the gradual effect of thrombus growth on the flow field, leading to flow obstruction in the FL, increased blood viscosity and reduced flap motion. This model is a step closer toward simulating realistic thrombus growth in aortic dissection, by taking into account the effect of intimal flap and vessel wall motion.

Shear-driven modelling of thrombus formation in type B aortic dissection

“…Furthermore, our simulation assumed a rigid wall. In a study using an idealised geometry, Chong et al (2022) demonstrated that accounting for wall compliance and flap motion can results in a 25% increase in the volume of thrombus formed. Flap stiffness varies from patient to patient, and tends to increase with the age of dissection ( Peterss et al, 2016 ), thus the flap may have been less mobile in this post-TEVAR case making the rigid wall assumption less impactful.…”

“… Menichini and Xu’s 2016 model requires five partial differential equations to be solved alongside the Navier-stokes equations, meaning simulations take on the order of 1–2 weeks to complete depending on patient-specific details such as cardiac cycle length. The computational cost increases even more when considering structural wall mechanics by performing fluid-structure-interaction (FSI) simulations - Chong et al (2022) performed an integrated FSI-thrombus study in an idealised geometry with Menichini and Xu’s 2016 model, with simulations taking 2–3 months to complete.…”

Effects of cardiac function alterations on the risk of postoperative thrombotic complications in patients receiving endovascular aortic repair

“…Thrombosis involves complex interlinked interactions between platelets, coagulation cascades, and the vascular wall (30). In this study, traditional hemodynamics parameters including WSS, OSI, and RRT did not precisely identified regions of thrombus formation, probably due to the lack of reflection of this complex reactions.…”

“…Besides, we ignored the arterial deformation in the 3D calculation. Future studies may combine fluid-structure interaction (FSI) models with mass transport models of thrombus to more realistically predict thrombus formation in deformed vessels (38,39).…”

The influence of minor aortic branches in Type-B Aortic Dissection: patient-specific flow simulations informed by 4D-Flow MRI

“…To date, minor branches have virtually always been neglected in simulations of the aorta due to limitations in medical image resolution, computational power, and a lack of available research on appropriate boundary conditions. Segmental arteries have been included as structural supports in aortic Fluid-Structure Interaction (FSI) studies 11,16 , but without haemodynamic assessment. The Inferior Mesenteric Artery (IMA) and a selection of FLbranching intercostal arteries were recently included in a TBAD simulation 3 .…”