A mathematical model to predict the in vivo pulsatile drag forces acting on bifurcated stent grafts used in endovascular treatment of abdominal aortic aneurysms (AAA)

Morris, Liam; Delassus, Patrick; Walsh, Michael T.; McGloughlin, Timothy M.

doi:10.1016/j.jbiomech.2003.11.014

Cited by 125 publications

(115 citation statements)

References 32 publications

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“…7 A number of factors hypothesized to affect device migration have been clinically investigated, including aortic neck diameter, length, and angulation; neck calcification and thrombus; neck enlargement; inadequate proximal and distal fixation length; and neck enlargement. [8][9][10] In-vitro 11 and in-vivo experimental studies, 12 as well as theoretical 13 and computational studies, [14][15][16][17][18][19] have been conducted to investigate the magnitude of the loads acting on endografts. These loads have been referred to as migration forces, displacement forces, or drag forces.…”

mentioning

confidence: 99%

Effect of Curvature on Displacement Forces Acting on Aortic Endografts: A 3-Dimensional Computational Analysis

Figueroa

Taylor

Yeh

et al. 2009

Journal of Endovascular Therapy

112

114

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¤ ¤Purpose: To determine the effect of curvature on the magnitude and direction of displacement forces acting on aortic endografts in 3-dimensional (3D) computational models.Method: A 3D computer model was constructed based on magnetic resonance angiography data from a patient with an infrarenal aortic aneurysm. Computational fluid dynamics tools were used to simulate realistic flow and pressure conditions of the patient. An aortic endograft was deployed in the model, and the displacement forces acting on the endograft were calculated and expressed in Newtons (N). Additional models were created to determine the effects of reducing endograft curvature, neck angulation, and iliac angulation on displacement forces. Results: The aortic endograft had a curved configuration as a result of the patient's anatomy, with curvature in the anterolateral direction. Total displacement force acting on the endograft was 5.0 N, with 28% of the force in a downward (caudal) direction and 72% of the force in a sideways (anterolateral) direction. Elimination of endograft curvature (planar graft configuration) reduced total displacement force to 0.8 N, with the largest component of force (70%) acting in the sideways direction. Straightening the aortic neck in the curved endograft configuration reduced the total force acting on the endograft to 4.2 N, with a reduction of the sideways component to 55% of the total force. Straightening the iliac limbs of the endograft reduced the total force acting on the endograft to 2.1 N but increased the sideways component to 91% of the total force. Conclusion: The largest component of the force acting on the aortic endograft is in the sideways direction, with respect to the blood flow, rather than in the downward (caudal) direction as is commonly assumed. Increased curvature of the aortic endograft increases the magnitude of the sideways displacement force. The degree of angulation of the proximal and distal ends of the endograft influence the magnitude and direction of displacement force. These factors may have a significant influence on the propensity of endografts to migrate in vivo.

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mentioning

confidence: 99%

Effect of Curvature on Displacement Forces Acting on Aortic Endografts: A 3-Dimensional Computational Analysis

Figueroa

Taylor

Yeh

et al. 2009

Journal of Endovascular Therapy

112

114

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“…Such an approach, in combination with Bernoulli's equation to link velocities and pressures, has been successfully used by various authors [9][10][11][12][13] to estimate distraction forces in endovascular [9][10][11] or endoluminal 12 stents or in modeling of hemodynamic forces in the aortic arch, 13 for example. Hemodynamic distraction forces are generated by blood pressure and blood flow and may encourage migration of the C__Users_HLS352_Dropbox_Research%20Projects_Nellix_Relining%20forces_15-5604%20Swaelens%20EDIT [1].doc -page 4 stent-graft.…”

Section: Methodsmentioning

confidence: 99%

Type IIIb Endoleak and Relining

et al. 2016

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Purpose: To examine the changes in distraction force following relining of a conventional abdominal aortic stent-graft with a type IIIb endoleak using the Nellix endovascular sealing device compared to a unilateral stent-graft. Methods:Relining is often used to repair type IIIb endoleaks, but the consequences to graft stability are unknown. A mathematical model was constructed based on pressure and volume flow through the stent-grafts, incorporating recognized distraction force equations. Steady flow was presumed at peak systolic pressures to calculate the maximum distraction force, with gravity ignored. Distraction forces for 28-to 36-mmdiameter stent-graft bodies with 16-mm limbs were calculated and compared to forces following relining with single and double Nellix devices or the Renu unilateral device.Results: Distraction forces for the 28-, 32-, and 36-mm stent-grafts prior to relining were 5.99, 10.21, and 14.99 N, respectively. Similar forces were reported after relining with bilateral Nellix devices (5.86, 10.08, and 14.86 N, respectively). However, use of a unilateral Nellix increased the distraction forces to 9.92, 14.14, and 18.92 N, respectively. These were comparable to the increase observed after relining with a Renu unilateral stent-graft (9.87, 14.09, and 18.86 N, respectively). The proportional increase in distraction force for a unilateral relining ranged from 26% to 66%, with the greatest increase noted in the smaller diameter main bodies. Conclusion:Relining a stent-graft with a type IIIb endoleak using bilateral Nellix devices does not increase the distraction force. However, a unilateral Nellix device or the Renu system could theoretically increase the distraction force by up to 66%, potentially risking migration and type Ia endoleak. In clinical practice, these results suggest that a relining with bilateral Nellix may have benefits over the Renu unilateral stent-graft.

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“…The first auxiliary equation to predict these four unknowns was obtained by setting the outlet pressure of the two limbs equal, similar to the analytical works by Liffman et al [5], Finol et al [6], and Morris et al [7]. While the latter two groups studied symmetric geometry, Liffman et al included asymmetric geometries in their analytical work.…”

Section: Figurementioning

confidence: 99%

“…The coefficients for this Fourier series were supplied by T. McGloughlin through direct correspondence [28] and were those used in his previously published study [7]. Velocity vectors on mid-coronal (z = 0) plane for severeredundancy configuration under equal-mass flow (left) and equal-pressure (right) conditions.…”

Section: List Of Tablesmentioning

confidence: 99%

Computational Fluid Dynamics Modeling of Redundant Stent-Graft Configurations in Endovascular Aneurysm Repair

Tse

Shek

Nabovati

et al. 2010

Volume 2: Biomedical and Biotechnology Engineering

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During endovascular aneurysm repair (EVAR), if the stent-graft device is too long for a given patient the redundant (extra) length adopts a convex configuration in the aneurysm.Based on clinical experience, we hypothesize that redundant stent-graft configurations increase the downward force acting on the device, thereby increasing the risk of device dislodgement and failure. This work numerically studies both steady-state and physiologic pulsatile blood flow in redundant stent-graft configurations. Computational fluid dynamics simulations predicted a peak downward displacement force for the zero-, moderate-and severe-redundancy configurations of 7.36, 7.44 and 7.81 N, respectively for steady-state flow; and 7.35, 7.41 and 7.85 N, respectively for physiologic pulsatile flow. These results suggest that redundant stent-graft configurations in EVAR do increase the downward force acting on the device, but the clinical consequence depends significantly on device-specific resistance to dislodgement.ii

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A mathematical model to predict the in vivo pulsatile drag forces acting on bifurcated stent grafts used in endovascular treatment of abdominal aortic aneurysms (AAA)

Cited by 125 publications

References 32 publications

Effect of Curvature on Displacement Forces Acting on Aortic Endografts: A 3-Dimensional Computational Analysis

Effect of Curvature on Displacement Forces Acting on Aortic Endografts: A 3-Dimensional Computational Analysis

Type IIIb Endoleak and Relining

Computational Fluid Dynamics Modeling of Redundant Stent-Graft Configurations in Endovascular Aneurysm Repair

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