Gigantic 25-cm abdominal aortic aneurysm

A two-scale numerical study on the mechanobiology of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are a serious condition whose pathophysiology is related to phenomena occurring at different length scales. To gain a better understanding of the disease, this work presents a multi-scale computational study that correlates AAA progression with microstructural and mechanical alterations in the tissue. Macro-scale geometries of a healthy aorta and idealized aneurysms with increasing diameter are developed on the basis of existing experimental data and subjected to physiological boundary conditions. Subsequently, microscopic representative volume elements of the abluminal side of each macro-model are employed to analyse the local kinematics at the cellular scale. The results suggest that the formation of the aneurysm disrupts the micromechanics of healthy tissue, which could trigger collagen growth and remodelling by mechanosensing cells. The resulting changes to the macro-mechanics and microstructure of the tissue seem to establish a new homeostatic state at the cellular scale, at least for the diameter range investigated.

Open repair of a type Ia endoleak with a giant abdominal aortic aneurysm sac

Endovascular aneurysm repair (EVAR) has been widely accepted as a safe and effective treatment for abdominal aortic aneurysm. Endoleaks are the most common complication after EVAR and require urgent interventions. Usually endoleaks can be treated with endovascular procedures using a variety of techniques. Despite these interventions, if the endoleak still persists, conventional open surgery should be evaluated. A 67-year-old man had been treated with EVAR after a ruptured abdominal aortic aneurysm 7 years ago. Later on, a type II endoleak was detected due to the inferior mesenteric artery and treated with coil embolization at the first follow-up year. The patient was admitted to our emergency department due to abdominal pain. Computed tomography angiography demonstrated a type Ia endoleak from the posterior side of the graft with a huge abdominal aortic aneurysm sac (22.9 cm) without rupture. The patient was hemodynamically unstable, and open surgical repair was performed via left anterolateral thoracotomy and laparotomy. Here we report a case where we performed open repair of a type Ia endoleak and discuss the repairing techniques for type Ia endoleak in the light of the literature.

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

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 (eg, stress shielding) and biochemical (ie, 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.