A haemodynamic predictor of intraluminal thrombus formation in abdominal aortic aneurysms

Abstract

Intraluminal thrombus (ILT) is present in over 75% of all abdominal aortic aneurysms (AAAs) and probably contributes to the complex biomechanics and pathobiology of these lesions. A reliable predictor of thrombus formation in enlarging lesions could thereby aid clinicians in treatment planning. The primary goal of this work was to identify a new phenomenological metric having clinical utility that is motivated by the hypothesis that two basic haemodynamic features must coincide spatially and temporally to promote the formation of a thrombus on an intact endothelium-platelets must be activated within a shear flow and then be presented to a susceptible endothelium. Towards this end, we propose a new thrombus formation potential (TFP) that combines information on the flow-induced shear history experienced by blood-borne particles that come in close proximity to the endothelium with information on both the time-averaged wall shear stress (WSS) and the oscillatory shear index (OSI) that locally affect the endothelial mechanobiology. To illustrate the possible utility of this new metric, we show computational results for 10 carotid

A comparison of hemodynamic metrics and intraluminal thrombus burden in a common iliac artery aneurysm

“…The methodology used in this study to assess the site specificity of ILT may be simplified. The recent work of Di Achille et al [36] further scales the ECAP by the platelet activation potential recently proposed by Shadden & Hendabadi [71] to calculate a new thrombus formation potential. By combining information on the flow-induced shear history of wall-proximal platelets with information on the thrombotic susceptibility (ECAP) of the endothelial layer, a single, simple measure can be produced.…”

“…The ECAP is the ratio between the OSI and TAWSS, and is used to characterise the artery wall's degree of 'thrombotic susceptibility' in one index [36]. We know from previous work that artery wall regions of TAWSS below 0.36 Pa expect monocyte/cell adhesion to occur [47,[59][60][61] and the OSI describes maximum WSS vector oscillation, and atheroprone behaviour, at a value of 0.5 [34,62].…”

“…Averaging for 10 cardiac cycles is traditionally quite conservative with many studies taking these fields over three or five cycles (i.e. [5,35,36]). However, in light of a recent study by Poelma et al [54], we investigated the statistical convergence of these variables, as it had become clear that the systolic pulses were creating fluctuations within the CIAA that continued through diastole.…”

“…As a means to quantify this behaviour in transient simulations of blood flow, the time-averaged wall shear stress (TAWSS) and the oscillatory shear index (OSI) [34] are often used to measure the interaction between the flow field and the artery wall (i.e. [5,[35][36][37][38]). Doyle et al showed, via a serial CFD study of a patientspecific AAA over 2.5 years, the direct spatial relationship between low TAWSS, local aneurysm expansion and localised in vivo ILT development [5].…”

Relative Roles of Mechanics and Biochemistry in the Initiation and Progression of Cerebral Aneurysm Thrombosis

“…Various computational models have been developed in effort to elucidate features of aneurysm thrombosis [9]- [13]. Even though they have been developed with different goals in mind, they all make a contribution to the effort of elucidating aneurysm thrombosis.…”