Computational modelling of endoleak after endovascular repair of abdominal aortic aneurysms

To better understand the effects of endoleak on the aneurysm intrasac pressure, previously, in a small number of studies, numerical models have been developed for the simulation of endoleak based on coupled fluid-structure interaction (FSI). Although such models can provide useful information on the fluid dynamics and structural deformations in aneurysms after endovascular repair (EVAR), they may computationally be too expensive if one is solely interested in the effects of endoleak on the risk of aneurysm rupture. To assess the value of computationally more efficient lumped parameter models in the simulation of endoleak, in the current study, a lumped parameter-based computational model of an incompletely excluded abdominal aortic aneurysm is developed as well as one based on coupled FSI. Both models are used to study the aneurysm intrasac pressure as a function of the degree of endoleak and the stent-graft compliance. Based on the agreement of the results of the two models it is concluded that the lumped parameter modelling method provides a useful alternative to coupled FSI for modelling the aneurysm intrasac pressure in the presence of endoleak. The modelled pressure could be used as a boundary condition for solid stress analyses to predict the risk of aneurysm rupture after EVAR

Biomechanical analysis for abdominal aortic aneurysm risk stratification

No abstract

Endovascular management of traumatic ruptures of the thoracic aorta:A retrospective multicenter analysis of 28 cases in The Netherlands

Background. Minimally invasive endovascular treatment of a traumatic rupture of the thoracic aorta is a new strategy in the care of multitrauma patients. We report the experience in The Netherlands with endovascular management of patients with acute traumatic ruptures of the thoracic aorta. Methods. We reviewed 28 patients with a traumatic thoracic aortic rupture treated with a thoracic aortic endograft between June 2000 and April 2004. All patients underwent treatment at one of the four participating level I trauma centers. Data collected included age, sex, injury severity score, type of endovascular graft, endovascular operation time, length of stay, length of stay in the intensive care unit, and mortality. Follow-up data consisted of computed tomographic angiography and plain chest radiographs at regular intervals. Results. All patients (mean age, 40.9 years; SD, 18.5 years) experienced severe traumatic injury, and the mean injury severity score was 37.1 (SD, 7.8). All endovascular procedures were technically successful, and the median operating time for the endovascular procedure was 58 minutes (interquartile range, 47-88 minutes). The overall hospital mortality was 14.3% (n = 4), and all deaths were unrelated to the aortic rupture or stent placement. There was no intervention-related mortality during a median follow-up of 26.5 months (interquartile range, 10-34.6 months). Postoperative data showed no severe endovascular graft- or procedure-related morbidity, except for one patient with an asymptomatic collapse of the endovascular graft during regular follow-up. This was corrected by placing a second graft. Conclusions. This study shows that the results of immediate endovascular repair of a traumatic aortic rupture are at least equal to those of conventional open surgical repair. Especially in these multitrauma patients with traumatic ruptures of the thoracic aorta, endovascular therapy seems to be preferable to conventional open surgical repair

Wall stress analysis of abdominal aortic aneurysms using 3D ultrasound

\u3cp\u3eWall stress analysis of abdominal aortic aneurysms is a novel tool that has proven high potential to improve risk stratification of abdominal aortic aneurysms (AAAs). Wall stress analysis is based on computed tomography (CT) and magnetic resonance imaging, however, 3D ultrasound (US) has not been used yet. In this study, the feasibility of 3D US based wall stress analysis is investigated and compared to CT. Three-dimensional US and CT data were acquired in 15 patients (diameter 35 - 90 mm). US data were segmented manually and compared to automatically acquired CT geometries by calculating the similarity index (SI) and Hausdorff distance (HD). Wall stresses were simulated at p = 140 mmHg using a non-linear material model (Raghavan & Vorp). The SI of US vs CT was 0.75 - 0.91, with a median HD of 5 - 15 mm, with the higher values found at the proximal and distal sides of the AAA. Wall stresses were in accordance with literature and a good agreement was found between US and CTbased median stresses and inter-quartile stresses. Stress values of US were typically higher, the result of geometrical irregularities, caused by the manual segmentation of the US data. In future work, an automated segmentation approach is the essential point of improvement.\u3c/p\u3

Initial stress and nonlinear material behavior in patient-specific AAA wall stress analysis

An abdominal aortic aneurysm (AAA) is a local dilation in the abdominal aorta of more than 50% of the original diameter and occurs in about 1 of 20 men over 65 years of age [1]. The largest threat for an AAA is rupture. Aortic repair is considered when the risk of rupture exceeds the risk of the surgical procedure. Currently, clinicians use the maximum AAA diameter as rupture risk estimator. A higher sensitivity and specificity was reached by computing the maximum AAA wall stress with finite element analysis, thus incorporating the total AAA geometry [2]