Abstract
Endovascular Aneurysm Repair (EVAR), a method for repairing Abdominal Aortic Aneurysm (AAA), has increasingly been performed on patients with suitable anatomy, and has generated a great deal of interest toward enhancing minimallyinvasive therapeutics. However, there exist clinical cases of patients with large affected zones where one single oversized endograft does not provide a proper solution, often due to highly curved and irregular geometries. Therefore, the clinical practice of endograft implantation in patients with extended regions of arterial damage constitutes the use of multiple standard-sized endografts, usually overlapping to ensure a full coverage of the diseased areas. While being a clinically appealing practice, there exist reports on the confounding effects of using multiple, overlapping stents and the increased risk of adverse clinical outcome. The impacts of using multiple, overlapping stents on hemodynamics visa- vis cardiovascular mechanics have not been fully examined, and we speculate that resulting local flow complications contribute to the escalation of such cases. In this article, we review the arterial hemodynamic parameters in physiological conditions, as well as under employment of single and multiple stents, and highlight the major concerning impacts on the quantified flow parameters. Even though stent overlap cannot always be avoided in clinical practice, an improved stent design and overlapping deployment strategies could potentially minimize flow complications and compounding pathological effects.
Highlights
In 1991, the first aortic aneurysm repair using an aortic stent graft was reported [1,2]
Vascular diseases commonly occur at specific sites within the vascular system, such as bifurcations, stenotic necks and sacs, which are associated with abrupt disturbances to the blood flow, indicating that hemodynamic complications may play an important role in the development and progress of vascular diseases [15,16]
Several approaches have been reported in the literature to circumvent this limitation; for instance, conducting simulations on idealized geometries based on stent Coronary Artery Disease (CAD) data [69,70], on hybrid domains where the stent geometry is freely obtained by CT, or MRI as a contribution of a virtually-implanted stent [57,70], on ex vivo micro-Computed Tomography (mCT) data of explanted, stented arteries [21] or mCT images of stented in vitro artery models [22,63]
Summary
In 1991, the first aortic aneurysm repair using an aortic stent graft (endograft) was reported [1,2]. Using a three dimensional model of a patient with AAA, the mechanical interaction between hemodynamics and wall dynamics was studied by means of a computational coupled Fluid-Structure Interaction (FSI) analysis, providing actual 3D data of the AAA geometry using CT images [21]. One challenge with these types of techniques is the lack of a clinical imaging protocol that accurately establishes the precise location and orientation of the stent struts in relation to the arterial geometry. Additional considerations for stent design and optimization are suggested that could potentially enhance the clinical outcome on patients requiring multiple stent recruitment
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