Potential biomechanical roles of risk factors in the evolution of thrombus‐laden abdominal aortic aneurysms

Abstract

Abdominal aortic aneurysms (AAAs) typically harbour an intraluminal thrombus (ILT), yet most prior computational models neglect biochemomechanical effects of thrombus on lesion evolution. We recently proposed a growth and remodelling model of thrombus-laden AAAs that introduced a number of new constitutive relations and associated model parameters. Because values of several of these parameters have yet to be elucidated by clinical data, and could vary significantly from patient to patient, the aim of this study was to investigate the possible extent to which these parameters influence AAA evolution. Given that some of these parameters model potential effects of factors that influence the risk of rupture, this study also provides insight into possible roles of common risk factors on the natural history of AAAs. Despite geometrical limitations of a cylindrical domain, findings support current thought that smoking, hypertension, and female sex likely increase the risk of rupture. Although thrombus thickness is not a reliable risk factor for rupture, the model suggests that the presence of ILT may have a destabilizing effect on AAA evolution, consistent with histological findings from human samples. Finally, simulations support two hypotheses that should be tested on patient-specific geometries in the future. First, ILT is a potential source of the staccato enlargement observed in many AAAs. Second, ILT can influence rupture risk, positively or negatively, via competing biomechanical (e.g., stress shielding) and biochemical (i.e., proteolytic) effects. Although further computational and experimental studies are needed, the present findings highlight the importance of considering ILT when predicting aneurysmal enlargement and rupture risk.

Global Sensitivity Analysis of a Homogenized Constrained Mixture Model of Arterial Growth and Remodeling

“…It should also be noted that in clinical practice many larger AAAs contain intraluminal thrombi, which were not considered herein. Their effect on aneurysmal expansion is, however, often not thought to be primarily a mechanical one [104][105][106] but rather a biochemical one [21,29,56]. That is, it should translate into changes of the parameter T and k σ in our model and is thus at least implicitly covered by this study to some extent.…”

Fluid–structure interaction study for biomechanics and risk factors in Stanford type A aortic dissection

“…This low TAWSS in the false lumen contributes to future lumen expansion and increases the risk of rupture. Furthermore, low WSS and lumen expansion can also cause recirculation in the lumen, hence leading to platelet accumulation in the recirculation zone, with potential to form thrombosis 101 . Therefore, patients with type A dissection who do not receive clinical intervention face high risk of rapid dilation in the false lumen 60 ; however, the true lumen size remains stable over the follow‐up period.…”

Intraluminal thrombus effect on the progression of abdominal aortic aneurysms by using a multistate continuous-time Markov chain model

“…Once the initial ILT accumulation occurs (usually in the transition between the 'early' to 'mild' state), these current results have shown that the next transition stage would be sensitive to the amount of lumen area covered by the thrombus (area frac ). The intraluminal thrombus is a complex biological entity composed of many inflammatory cells, including macrophages and neutrophils, 25 which not only interfere with the direct wall shear stress and strain relationship between the lumen wall and blood flow, but they also interact biochemically (promoting wall thinning, cell inflammation, degradation of the extracellular matrix 26 ) and biomechanically (modifying wall shear stress 27 ) with the arterial wall. It is then understandable that a larger area covered by thrombus would have a greater impact on the AAA growth process and thus in the transition time.…”