On the importance of tunica intima in the aging aorta: a three-layered in silico model for computing wall stresses in abdominal aortic aneurysms.

Layer-specific experimental data for human aortic tissue suggest that, in aged arteries and arteries with non-atherosclerotic intimal thickening, the innermost layer of the aorta increases significantly its stiffness and thickness, becoming load-bearing. However, there are very few computational studies of abdominal aortic aneurysms (AAAs) that take into account the mechanical contribution of the three layers that comprise the aneurysmal tissue. In this paper, a three-layered finite element model is proposed from the simplest uniaxial stress state to geometrically parametrized models of AAAs with different asymmetry values. Comparisons are made between a three-layered artery wall and a mono-layered intact artery, which represents the complex behavior of the aggregate adventitia-media-intima in a single layer with averaged mechanical properties. Likewise, the response of our idealized geometries is compared with similar experimental and numerical models. Finally, the mechanical contributions of adventitia, media and intima are analyzed for the three-layered aneurysms through the evaluation of the mean stress absorption percentage. Results show the relevance and necessity of considering the inclusion of tunica intima in multi-layered models of AAAs for getting accurate results in terms of peak wall stresses and displacements.

Results of Transarterial Embolization for Treating Type 2 Endoleaks: A Single-Center Experience.

BACKGROUND: Type 2 endoleaks (T2Es) are the main cause of reintervention after endovascular repair of abdominal aortic aneurysms (EVAR). The objective of this study is to quantify success rates of T2E treatment. METHODS: This study involves a retrospective analysis of a prospectively maintained database containing data on all consecutive patients treated for a T2E between 2003 and 2017 in a single center. Technical success was defined as absence of endoleak in the final angiographic control after treatment. Clinical success was defined as absence of sac growth over 5 mm in the contrast-enhanced computed tomography performed a year thereafter. Statistics included Kaplan-Meier survival estimates. RESULTS: A total of 528 elective EVARs were performed in the period. Thirty-six of these (6.8%) developed a T2E requiring reintervention, a median of 37.9 months after EVAR. Twenty-five percent of the treatments were performed more than 5 years after intervention. Twenty-eight of the 36 treatments were performed via transarterial embolization. For this technique, technical success was 71.4% and clinical success was 62.5%. A subsequent reintervention was required in 35.7% of patients. In this cohort, the rate of aneurysm rupture was 10.7% (n = 3/28), open surgical conversion was needed in 2 of 28 cases (7.1%), and rate of aneurysm-related death was 14.3% (n = 4/28) over follow-up. CONCLUSIONS: A high percentage of patients are at risk of adverse outcomes after T2E treatment. Strict imaging follow-up is still needed in this population.