The shear stess profile of the pivotal fenestrated endograft at the level of the renal branches: A computational study for complex aortic aneurysms

Georgakarakos, Efstratios; Xenakis, Antonios; Bisdas, Theodosios; Georgiadis, George S.; Schoretsanitis, Nikolaos; Antoniou, George Α.; Lazarides, Miltos K.

doi:10.1177/1708538115598726

Cited by 9 publications

(4 citation statements)

References 31 publications

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“…32 Fluid simulation, which may seem essential to simulate biological conditions, was employed in only 1 of 7 FEVAR studies and 4 of 11 PG studies. Probably due to the different nature of both techniques, while different CFD simulation studies to investigate possible devices' behavior can be found regarding FEVAR, [33][34][35][36][37] none of the same nature was found analyzing the PG technique. Although excluded from the present analyses due to the lack of benchtop testing, CFD studies may represent a valuable tool to analyze SG behavior in diverse preselected patients' anatomy.…”

Section: Discussionmentioning

confidence: 99%

Systematic Review of the Current In Vitro Experience of the Endovascular Treatment of Juxtarenal Abdominal Aortic Aneurysms by Fenestrated and Parallel Endografting

et al. 2022

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Objective: To identify and analyze the published in vitro benchtop experiments for the assessment of endovascular techniques used for the treatment of juxtarenal abdominal aortic aneurysms (jAAAs). Data sources: Scopus, PubMed, and Web of Science. Review methods: A systematic literature search was carried out throughout March 2021 following PRISMA guidelines. Two investigators independently performed title and abstract screening to reveal all benchtop testing evaluating the endovascular treatment of jAAA. Results: A total of 19 studies were included, 8 evaluating fenestrated (FEVAR) and 11 parallel grafts (PGs). FEVAR studies used different custom testing apparatus (n=7) or 3D-printed models (n=1) to analyze dislodgement and migration resistance, misalignment consequences and causation, and bridging stents’ radial force, flareability, fatigue, and fracture resistance. All PG studies used silicone-based models to analyze optimal oversizing, sealing length, gutter behavior, and possible reduction. Test evaluation in FEVAR in vitro testing was based on pullout force analysis (N=5), photo evaluation (n=1), fluoroscopy (n=1), X-rays (n=4), CT analysis (n=3), macro- and microscopic evaluation (n=4), water permeability (n=1), and fatigue simulator testing (n=1), while it was based on CT analysis in all PG studies adding ECG-gate in one study. The most frequently tested devices were Zenit (Cook) (n=7), Endurant (Medtronic) (n=5), and Excluder (Gore) (n=5) as main grafts, and Advanta V12 (n=14) as the bridging device. Conclusions: This systematic review presents a broad analysis of the current in vitro methods evaluating the endovascular treatment of jAAA. Fundamental issues have been benchtop tested in both FEVAR and PGs. The analysis of the included studies allowed to recommend an optimal testing design. In vitro testing is a potential tool to further elucidate points of attention hard to investigate in vivo to finally enhance the endovascular treatment outcomes. Future in vitro studies are needed to evaluate the in vitro performance of all indistinctively used devices in the clinical practice.

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Section: Discussionmentioning

confidence: 99%

Systematic Review of the Current In Vitro Experience of the Endovascular Treatment of Juxtarenal Abdominal Aortic Aneurysms by Fenestrated and Parallel Endografting

et al. 2022

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“…The proximal component was exposed to distraction forces of 1.3 to 15.7 N, depending on the inlet cross-sectional area. Georgakarakos et al 12 examined the differences in intraluminal flow dynamics between conventional and pivot fEVAR in a virtual 3-dimensional model. In this estimation of intraluminal wall shear stress, values between 6.3 and 12.48 Pa were measured.…”

Section: Discussionmentioning

confidence: 99%

Performance of BeGraft and BeGraft+ Stent-Grafts as Bridging Devices for Fenestrated Endovascular Aneurysm Repair: An In Vitro Study

et al. 2019

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Purpose: To investigate 2 generations of balloon-expandable covered stents as potential bridging devices using an in vitro model of stent-graft fenestrations. Materials and Methods: Twenty BeGraft and 20 BeGraft+ cobalt-chromium stents covered in expanded polytetrafluoroethylene (ePTFE) in 6- and 8-mm diameters were tested in sheets mimicking stent-graft fenestrations. Microscopy and radiography were employed to evaluate stent morphology after flaring. In vitro bench tests measured maximum pullout (perpendicular displacement) and the shear stress (axial displacement) forces needed to dislocate the stents. Results: No alteration of ePTFE coverage was detected in the flared stents. Digital radiography and computed tomography showed marked alteration of the stent geometry, which was more pronounced in the BeGraft group. No fractures were detected. Median (minimum–maximum) pullout forces for the 6-mm stent-grafts were 17.1 N (15.8–19.6) for the BeGraft device and 30.4 N (20.2–31.9) for the BeGraft+ device (p=0.006). Median (minimum–maximum) pullout forces for the 8-mm stent-grafts were 11.3 N (11–12.1) for the BeGraft device and 21.8 N (18.2–25.5) for the BeGraft+ device (p<0.001). The shear stress test showed median forces of 10.5 vs 15.28 N at 150% of the stent diameter for the 6-mm BeGraft and BeGraft+ stent-grafts, respectively, and 15.23 vs 20.72 N at 150% stent diameter for the 8-mm models (p=0.016 and 0.017, respectively). Conclusion: Flaring changed the stent geometry but did not provoke stent fractures. The BeGraft+ is superior to the BeGraft in terms of pullout and shear stress forces, demonstrating greater resilience.

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“…A number of CFD studies have been done on FSGs to evaluate their efficacy for FEVAR. For example, Avrahami et al, 10 Georgakarakos et al, 11 , 12 Kandail et al, 13 , 14 Sun et al, 15 and Sutalo et al, 16 among others, performed CFD simulations on either patient-specific or ideal models of FSGs to shed light on hemodynamic conditions within the fenestrated endoprostheses. With the exception of Sun et al, 15 most of these studies, however, neglected the effect of a flared renal stent.…”

Section: Introductionmentioning

confidence: 99%

Effect of a Flared Renal Stent on the Performance of Fenestrated Stent-Grafts at Rest and Exercise Conditions

Kandail

Hamady

2016

J Endovasc Ther

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Purpose: To quantify the hemodynamic impact of a flared renal stent on the performance of fenestrated stent-grafts (FSGs) by analyzing flow patterns and wall shear stress–derived parameters in flared and nonflared FSGs in different physiologic scenarios. Methods: Hypothetical models of FSGs were created with and without flaring of the proximal portion of the renal stent. Flared FSGs with different dilation angles and protrusion lengths were examined, as well as a nonplanar flared FSG to account for lumbar curvature. Laminar and pulsatile blood flow was simulated by numerically solving Navier-Stokes equations. A physiologically realistic flow rate waveform was prescribed at the inlet, while downstream vasculature was modeled using a lumped parameter 3-element windkessel model. No slip boundary conditions were imposed at the FSG walls, which were assumed to be rigid. While resting simulations were performed on all the FSGs, exercise simulations were also performed on a flared FSG to quantify the effect of flaring in different physiologic scenarios. Results: For cycle-averaged inflow of 2.94 L/min (rest) and 4.63 L/min (exercise), 27% of blood flow was channeled into each renal branch at rest and 21% under exercise for all the flared FSGs examined. Although the renal flow waveform was not affected by flaring, flow within the flared FSGs was disturbed. This flow disturbance led to high endothelial cell activation potential (ECAP) values at the renal ostia for all the flared geometries. Reducing the dilation angle or protrusion length and exercise lowered the ECAP values for flared FSGs. Conclusion: Flaring of renal stents has a negligible effect on the time dependence of renal flow rate waveforms and can maintain sufficient renal perfusion at rest and exercise. Local flow patterns are, however, strongly dependent on renal flaring, which creates a local flow disturbance and may increase the thrombogenicity at the renal ostia. Smaller dilation angles, shorter protrusion lengths, and moderate lower limb exercise are likely to reduce the risk of thrombosis in flared geometries.

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The shear stess profile of the pivotal fenestrated endograft at the level of the renal branches: A computational study for complex aortic aneurysms

Abstract: The variant horizontal branch orientation influences the wall shear stress distribution across its length and affects its values only at its transition with the mating vessel. These findings and their potential association with adverse effects deserve further clinical validation.

Cited by 9 publications

References 31 publications

Systematic Review of the Current In Vitro Experience of the Endovascular Treatment of Juxtarenal Abdominal Aortic Aneurysms by Fenestrated and Parallel Endografting

Systematic Review of the Current In Vitro Experience of the Endovascular Treatment of Juxtarenal Abdominal Aortic Aneurysms by Fenestrated and Parallel Endografting

Performance of BeGraft and BeGraft+ Stent-Grafts as Bridging Devices for Fenestrated Endovascular Aneurysm Repair: An In Vitro Study

Effect of a Flared Renal Stent on the Performance of Fenestrated Stent-Grafts at Rest and Exercise Conditions

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