Abstract
PurposeThe main objective of this work is to investigate hemodynamics phenomena occurring in EVAS (Endo Vascular Aneurysm Sealing), to understand if and how they could lead to type 1a endoleaks and following re-intervention. To this aim, methods based on computational fluid mechanics are implemented as a tool for checking the behavior of a specific EVAS configuration, starting from the post-operative conditions. Pressure and velocity fields are detailed and compared, for two configurations of the Nellix, one as attained after correct implantation and the other in pathological conditions, as a consequence of migration or dislocation of endobags.MethodsThe computational fluid dynamics (CFD) approach is used to simulate the behavior of blood within a segment of the aorta, before and after the abdominal bifurcation. The adopted procedure allows reconstructing the detailed vascular geometry from high-resolution computerized tomography (CT scan) and generating the mesh on which the equations of fluid mechanics are discretized and solved, in order to derive pressure and velocity field during heartbeats.ResultsThe main results are obtained in terms of local velocity fields and wall pressures. Within the endobags, velocities are usually quite regular during the whole cardiac cycle for the post-implanted condition, whereas they are more irregular for the migrated case. The largest differences among the two cases are observed in the shape and location of the recirculation region in the rear part of the aorta and the region between the endobags, with the formation of a gap due to the migration of one or both of the two. In this gap, the pressure fields are highly different among the two conditions, showing pressure peaks and pressure gradients at least four times larger for the migrated case in comparison to the post-implanted condition.ConclusionsIn this paper, the migration of one or both endobags is supposed to be related to the existing differential pressures acting in the gap formed between the two, which could go on pushing the two branches one away from the other, thus causing aneurysm re-activation and endoleaks. Regions of flow recirculation and low-pressure drops are revealed only in case of endobag migration and in presence of an aneurysm. These regions are supposed to lead to possible plaque formation and atherosclerosis.
Highlights
IntroductionAND PURPOSESThere is a great debate on the effective reliability of the EVAS technique in the wide offer of endografts to treat an Abdominal Aortic Aneurysm (AAA), especially in comparison to fixed non-sealing devices. Both sealing and non-sealing systems require using endodevices, placed upstream of the aortic abdominal bifurcation, inserted through the femoral artery, and guided up to the aneurysm neck. The main advantages of such solutions reside in avoiding a local invasive operative procedure, in ensuring almost complete separation of the aneurysm from the local blood flow circulation, and in a rather simple positioning procedure.almost all configurations of endograft used to treat AAA, retain a significant risk of endoleak, which is a complication, due to antegrade or retrograde reperfusion of the sac, requiring a different kind of re-treatment
In this paper, the migration of one or both endobags is supposed to be related to the existing differential pressures acting in the gap formed between the two, which could go on pushing the two branches one away from the other, causing aneurysm re-activation and endoleaks
Since the volumetric flow rate is imposed at the inlet, the bulk velocity temporal profile is very similar in all considered conditions
Summary
AND PURPOSESThere is a great debate on the effective reliability of the EVAS technique in the wide offer of endografts to treat an Abdominal Aortic Aneurysm (AAA), especially in comparison to fixed non-sealing devices. Both sealing and non-sealing systems require using endodevices, placed upstream of the aortic abdominal bifurcation, inserted through the femoral artery, and guided up to the aneurysm neck. The main advantages of such solutions reside in avoiding a local invasive operative procedure, in ensuring almost complete separation of the aneurysm from the local blood flow circulation, and in a rather simple positioning procedure.almost all configurations of endograft used to treat AAA, retain a significant risk of endoleak, which is a complication, due to antegrade or retrograde reperfusion of the sac, requiring a different kind of re-treatment. There is a great debate on the effective reliability of the EVAS technique in the wide offer of endografts to treat an Abdominal Aortic Aneurysm (AAA), especially in comparison to fixed non-sealing devices.6 Both sealing and non-sealing systems require using endodevices, placed upstream of the aortic abdominal bifurcation, inserted through the femoral artery, and guided up to the aneurysm neck.. There are five different types of endoleaks, classified on the basis of features causing the back-flow into the aneurysm sac.. There are five different types of endoleaks, classified on the basis of features causing the back-flow into the aneurysm sac.13 Such endoleaks are coupled to high local pressures and require re-intervention after implantation, to prevent vascular rupture (around 1% of the total number of implantations after one year and rising to more than 2% after the third year) There are five different types of endoleaks, classified on the basis of features causing the back-flow into the aneurysm sac. Such endoleaks are coupled to high local pressures and require re-intervention after implantation, to prevent vascular rupture (around 1% of the total number of implantations after one year and rising to more than 2% after the third year)
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