Blood Rheology Influence on False Lumen Thrombosis in Type B Aortic Dissection

Abstract

Aortic dissection is a disease caused by the occurrence of a rupture in the innermost layer of the aortic wall. Due to the pulsation of the heart, blood penetrates through the tear between the layers of the aortic wall, which causes a new, so-called false lumen (FL). The local haemodynamic conditions in the FL significantly contribute to clotting of blood, so the formation of a thrombus. The level of thrombosis in the FL affects patients' prognosis and chances of survival, in which a complete thrombosis is usually beneficial. In recent studies on platelet deposition in the FL, it is demonstrated that haemodynamic conditions influence on platelet activation and aggregation, effectively boosting in regions of recirculation. Blood coagulation has the highest chance of occurrence in these recirculation regions within the FL. Considering the dominant influence of shear rate in FL thrombosis, the non-Newtonian rheological properties and behaviour of blood play a crucial role. The most important rheological factor is the volume fraction of red blood cells in the blood, i.e., the haematocrit value (HCT), which affects the shear rate dependent viscosity and the yield stress observed in regions of low shear rate and stress, respectively, in the blood flow. In the current work, the influence of the haematocrit value on thrombosis in the FL is simulated. The simulations are done in idealized aortic dissection phantom models employing HCT-dependent non-Newtonian haemodynamics. The value for the HCT was varied within a physiological range. On the one hand, an increase in the total volume of thrombus in time was found for all HCT values. On the other hand, with increasing HCT values, less thrombus is formed in the FL. This suggests that high HCT values impede thrombus formation due to rheological effects and that patients with higher haematocrit values have less chance of benefiting from complete thrombosis in the FL.

Morphological parameters affecting false lumen thrombosis following type B aortic dissection: a systematic study based on simulations of idealized models

“…where the rheological model parameters 0 , ∞ , , and n were determined from experimental data in (Jafarinia et al 2020). The values of the parameters are listed in Table 4.…”

“…The volume percentage of the thrombus th (t) and the growth rate φth (t) have concise information about the FL thrombosis status to account for thrombus formation in the FL (Jafarinia et al 2020;Melito et al 2020). The volume percentage of thrombus th (t) is defined by Jafarinia et al (2020) where V FL is the volume of the FL. However, in this study, due to the chosen 2D idealized geometries, the volume V FL is expressed as FL area A FL multiplied with the unit depth.…”

“…A thrombus formation model was incorporated into computational fluid dynamics (CFD) simulations and a parameterization of morphologies representing TBAD was developed. The simulations are performed in the open-source software OpenFOAM (Weller et al 1998) implementing the combination of a non-Newtonian blood flow behavior (Jafarinia et al 2020) and the phenomenological hemodynamic-based model for thrombus formation developed by . We employ this phenomenological thrombus formation model since detailed modeling of the biochemical interactions between blood species involved in the hemostasis process would be computationally intractable Chong et al 2022).…”

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

“…The model parameters η 0 , η ∞ , λ, and n η were determined from experimental data, as reported by Jafarinia et al (2020). The values are listed in Table 2.…”

“…In the model, thrombus formation depends on local hemodynamic conditions in the FL, which are influenced by the dissection morphology, such as the location, size, number of intimal tears, and the dimensions of the FL. Among the quantities related to hemodynamic conditions, shear rate and shear stress play a significant role in driving FL thrombosis ( Menichini et al, 2016 ; Menichini and Xu, 2016 ; Menichini et al, 2018 ; Jafarinia et al, 2020 ; Armour et al, 2022 ).…”