Bioengineering (Basel)
April 2023
The low long-term patency of bypass grafts is a major concern for cardiovascular treatments. Unfavourable haemodynamic conditions in the proximity of distal anastomosis are closely related to thrombus creation and lumen lesions. Modern graft designs address this unfavourable haemodynamic environment with the introduction of a helical component in the flow field, either by means of out-of-plane helicity graft geometry or a spiral ridge.
View Article and Find Full Text PDFBackground: The Altura (Alt) endograft is a new design, lacking the classic main body with the flow divider. Instead, 2 proximal D-shaped endografts form a round circumference in the aortic neck for secure sealing and land in the iliac arteries in a cross-limb fashion. The aim of this computational study was to compare hemodynamically this model with the classic bifurcated (Bif) and cross-limb (Cx) endograft designs of equal total length.
View Article and Find Full Text PDFPurpose: To use computational simulations to compare the hemodynamic characteristics of a classic bifurcated stent-graft to an equally long endograft design with "dog bone"-shaped limbs (DB), which have large diameter proximal and distal ends and significant narrowing at the midsection to accommodate aneurysms with an extremely narrow bifurcation.
Materials And Methods: A 3-dimensional model was constructed using commercially available validated software. Inlet and outlet diameters were 28 and 14 mm, respectively.
Background: We conducted a computational study to assess the hemodynamic impact of variant main body-to-iliac limb length (L1/L2) ratios on certain hemodynamic parameters acting on the endograft (EG) either on the normal bifurcated (Bif) or the cross-limb (Cx) fashion.
Methods: A customary bifurcated 3D model was computationally created and meshed using the commercially available ANSYS ICEM (Ansys Inc., Canonsburg, PA, USA) software.
Purpose: This study investigated the impact of the variant angulations on the values and distribution of wall shear stress on the renal branches and the mating vessels of a pivotal fenestrated design.
Methods: An idealized endograft model of two renal branches was computationally reconstructed with variable angulations of the left renal branch. These ranged from the 1:30' to 3:30' o'clock position, corresponding from 45° to 105° with increments of 15°.
Purpose: To evaluate the flow phenomena within an aortic endograft with crossed-limbs, comparing to an endograft with the ordinary limb bifurcation.
Methods: An endograft model with crossed-limbs was computationally reconstructed based on Computed Tomography patient-specific data, using commercially available software. Accordingly, its analogue model was reconstructed in the ordinary fashion (ordinary bifurcation).
Purpose: To investigate the factors influencing the hydrostatic pressure exerted within the venous aneurysms (VA) of an arteriovenous fistula (AVF).
Methods: Ideal models of a side-to-end brachial-cephalic AVF were computationally constructed and typical values for the length and the local diameters were considered for both the artery and vein sections of the models. Three VA configurations were reconstructed (spherical, fusiform and curved) and hydrostatic pressure was assessed with respect to different degrees of the outflow vein stenosis, ranging from 25% to 95%, and VA maximum diameters, using validated, commercially available software.
Purpose: To compare the hemodynamic behavior between an aortic endograft model in the "crossed-limbs" configuration and the customary bifurcated deployment position under the influence of several geometric factors.
Methods: A crossed-limbs graft and its analogue model with uncrossed limbs were computationally reconstructed. The displacement forces acting over the entire endograft and at the bifurcation and iliac sites separately were calculated using a fluid structure interaction simulation under a range of specific geometric characteristics, namely, the lateral and anteroposterior (AP) neck angulation, the iliac bifurcation angulation, and the endograft curvature.
Purpose: To evaluate the displacement forces acting on an aortic endograft when the iliac limbs are crossed ("ballerina" position).
Methods: An endograft model was computationally reconstructed based on data from a patient whose infrarenal aortic aneurysm had an endovascular stent-graft implanted with the iliac limbs crossed. Computational fluid dynamics analysis determined the maximum displacement force on the endograft and separately on the bifurcation and iliac limbs.
Using knowledge gained from bioengineering studies, current vascular research focuses on the delineation of the natural history and risk assessment of clinical vascular entities with significant morbidity and mortality, making the development of new, more accurate predictive criteria a great challenge. Additionally, conclusions derived from computational simulation studies have enabled the improvement and modification of many biotechnology products that are used routinely in the treatment of vascular diseases. This review highlights the promising role of the bioengineering applications in the vascular field.
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