Fluid displacement from intraluminal thrombus of abdominal aortic aneurysm as a result of uniform compression

Abstract

Objectives The results after aneurysm repair with an endovascular aneurysm sealing (EVAS) system are dependent on the stability of the aneurysm sac and particularly the intraluminal abdominal aortic thrombus (ILT). The postprocedural ILT volume is decreased compared with preprocedural ILT volume in aortic aneurysm patients treated with EVAS. We hypothesize that ILT is not stable in all patients and pressurization of the ILT may result in displacement of fluids from the ILT, no differently than serum is displaced from whole blood when it settles. To date, the mechanism and quantification of fluid displacement from ILT are unknown. Methods The study included 21 patients who underwent elective open abdominal aortic aneurysm repair. The ILT was harvested as a routine procedure during the operation. After excision of a histologic sample of the ILT specimen in four patients, ILT volume was measured and the ILT was compressed in a dedicated compression setup designed to apply uniform compression of 200 mmHg for 5 min. After compression, the volumes of the remaining thrombus and the displaced fluid were measured. Results The median (interquartile-range) of ILT volume before compression was 60 (66) mL, and a median of 5.7 (8.4) mL of fluid was displaced from the ILT after compression, resulting in a median thrombus volume decrease of 11% (10%). Fluid components can be up to 31% of the entire ILT volume. Histologic examination of four ILT specimens showed a reduction of the medial layer of the ILT after compression, which was the result of compression of fluid-containing canaliculi. Conclusions Applying pressure of 200 mmHg to abdominal aortic aneurysm ILT resulted in the displacement of fluid, with a large variation among patients. Fluid displacement may result in decrease of ILT volume during and after EVAS, which might have implications on pre-EVAS volume planning and on stability of the endobags during follow-up which may lead to migration, endoleak or both.

Computational Simulation of Abdominal Aortic Aneurism and Its Assessment to Medical Treatment

“…Displacement in aneurysms generates instabilities which may lead to its rupture [8]. On simulations, the greatest instability occurs when the thrombus is not taken into account, with a displacement value of 3.7210 -4 ± 2.0010 -4 mm, followed by an aneurysm when the blood flows through the wall 5.9610 -5 ± 3.2110 -5 mm and of the aneurysm with the thrombus with 6.1010 -5 ± 3.2910 -5 mm.…”

Anatomical Predictors of Endoleaks or Migration After Endovascular Aneurysm Sealing

“…Studies have shown that intraluminal thrombus cannot be addressed as a rigid structure and might change over time. [11][12][13] This spongelike effect in combination with a larger AAA diameter might result in bending of the stent frames into the thrombus and parting of the stent frames, which can make the EVAS configuration unstable. A low amount of polymer surrounding the stent frames in small flow lumens might also induce instability into the EVAS configuration.…”