Graft Modification Strategies to Improve Patency of Prosthetic Arteriovenous Grafts for Hemodialysis

Moufarrej, Andrew; Tordoir, Jan H.M.; Mees, Barend

doi:10.5301/jva.5000526

Cited by 10 publications

(9 citation statements)

References 57 publications

(70 reference statements)

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“…Hemodynamically optimized graft designs have been proposed to increase AVG longevity by reducing hemodynamic disturbances near the graft-vein anastomosis [ 3 ]. The hemodynamic benefit of these grafts is typically assessed and demonstrated using computational fluid dynamics (CFD) simulations [ 4 – 11 ], because, as opposed to experimental in vitro techniques, CFD modelling allows for straightforward, high resolution assessment of WSS parameters and for simultaneous evaluation of multiple graft designs.…”

Section: Introductionmentioning

confidence: 99%

A realistic arteriovenous dialysis graft model for hemodynamic simulations

et al. 2022

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Objective The hemodynamic benefit of novel arteriovenous graft (AVG) designs is typically assessed using computational models that assume highly idealized graft configurations and/or simplified boundary conditions representing the peripheral vasculature. The objective of this study is to evaluate whether idealized AVG models are suitable for hemodynamic evaluation of new graft designs, or whether more realistic models are required. Methods An idealized and a realistic, clinical imaging based, parametrized AVG geometry were created. Furthermore, two physiological boundary condition models were developed to represent the peripheral vasculature. We assessed how graft geometry (idealized or realistic) and applied boundary condition models of the peripheral vasculature (physiological or distal zero-flow) impacted hemodynamic metrics related to AVG dysfunction. Results Anastomotic regions exposed to high WSS (>7, ≤40 Pa), very high WSS (>40 Pa) and highly oscillatory WSS were larger in the simulations using the realistic AVG geometry. The magnitude of velocity perturbations in the venous segment was up to 1.7 times larger in the realistic AVG geometry compared to the idealized one. When applying a (non-physiological zero-flow) boundary condition that neglected blood flow to and from the peripheral vasculature, we observed large regions exposed to highly oscillatory WSS. These regions could not be observed when using either of the newly developed distal boundary condition models. Conclusion Hemodynamic metrics related to AVG dysfunction are highly dependent on the geometry and the distal boundary condition model used. Consequently, the hemodynamic benefit of a novel graft design can be misrepresented when using idealized AVG modelling setups.

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Section: Introductionmentioning

confidence: 99%

A realistic arteriovenous dialysis graft model for hemodynamic simulations

et al. 2022

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“…NIH development is believed to be triggered by disturbed blood flow and non‐physiological wall shear stresses (WSS) around the venous anastomosis 1,2 . Although the exact haemodynamic trigger for NIH development is unknown, 3 various novel graft designs have been proposed to reduce disturbed flow and non‐physiological WSS at the graft‐vein anastomosis 4 …”

Section: Introductionmentioning

confidence: 99%

Haemodynamic optimisation of a dialysis graft design using a global optimisation approach

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Delhaas

Mees

et al. 2020

Numer Methods Biomed Eng

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Disturbed flow and the resulting non‐physiological wall shear stress (WSS) at the graft‐vein anastomosis play an important role in arteriovenous graft (AVG) patency loss. Modifying graft geometry with helical features is a popular approach to minimise the occurrence of detrimental haemodynamics and to potentially increase graft longevity. Haemodynamic optimisation of AVGs typically requires many computationally expensive computational fluid dynamics (CFD) simulations to evaluate haemodynamic performance of different graft designs. In this study, we aimed to develop a haemodynamically optimised AVG by using an efficient meta‐modelling approach. A training dataset containing CFD evaluations of 103 graft designs with helical features was used to develop computationally low‐cost meta‐models for haemodynamic metrics related to graft dysfunction. During optimisation, the meta‐models replaced CFD simulations that were otherwise needed to evaluate the haemodynamic performance of possible graft designs. After optimisation, haemodynamic performance of the optimised graft design was verified using a CFD simulation. The obtained optimised graft design contained both a helical graft centreline and helical ridge. Using the optimised design, the magnitude of flow disturbances and the size of the anastomotic areas exposed to non‐physiological WSS was successfully reduced compared to a regular straight graft. Our meta‐modelling approach allowed to reduce the total number of CFD model evaluations required for our design optimisation by approximately a factor 2000. The applied efficient meta‐modelling technique was successful in identifying an optimal, helical graft design at relatively low computational costs. Future studies should evaluate the in vivo benefits of the developed graft design.

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“…Most research on minimising disturbed flow and normalising WSS patterns at the graft-vein anastomosis has focused on modifying graft geometry. 4 Strikingly, the impact of haemodialysis (HD) needle flow on AVG haemodynamics is often neglected, even though it has been shown that needle flow can result in increased flow disturbance. 5e7 Most HD patients receive dialysis according to intermittent or daily dialysis programs that amount to 12e36 h per week.…”

Section: Introductionmentioning

confidence: 99%

Computational Modelling Based Recommendation on Optimal Dialysis Needle Positioning and Dialysis Flow in Patients With Arteriovenous Grafts

Quicken

Huberts

Tordoir

et al. 2020

European Journal of Vascular and Endovascular Surgery

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WHAT THIS PAPER ADDSThis work has demonstrated that blood flow near the venous anastomosis of arteriovenous grafts deteriorates considerably as a result of flow from the venous dialysis needle. Since disturbed flow is believed to be the initiating event of venous neointimal hyperplasia, this finding suggests that dialysis needle flow can play an important role in graft patency loss. The negative effects of dialysis flow can be mitigated by ensuring the venous needle is in the centre of the graft's lumen, by decreasing dialysis flow, or by increasing the distance between graft cannulation and the venous anastomosis.Objective: Arteriovenous grafts (AVGs) typically lose patency within two years of creation due to venous neointimal hyperplasia, which is initiated by disturbed haemodynamics after AVG surgery. Haemodialysis needle flow can further disturb haemodynamics and thus impact AVG longevity. In this computational study it was assessed how dialysis flow and venous needle positioning impacts flow at the graft-vein anastomosis. Furthermore, it was studied how negative effects of dialysis needle flow could be mitigated. Methods: Non-physiological wall shear stress and disturbed blood flow were assessed in an AVG model with and without dialysis needle flow. Needle distance to the venous anastomosis was set to 6.5, 10.0, or 13.5 cm, whereas dialysis needle flow was set to 200, 300 or 400 mL/min. Intraluminal needle tip depth was varied between superficial, central, or deep. The detrimental effects of dialysis needle flow were summarised by a haemodynamic score (HS), ranging from 0 (minimal) to 5 (severe). Results: Dialysis needle flow resulted in increased disturbed flow and/or non-physiological wall shear stress in the venous peri-anastomotic region. Increasing cannulation distance from 6.5 to 13.5 cm reduced the HS by a factor 4.0, whereas a central rather than a deep or superficial needle tip depth reduced the HS by a maximum factor of 1.9. Lowering dialysis flow from 400 to 200 mL/min reduced the HS by a factor 7.4. Conclusion:Haemodialysis needle flow, cannulation location, and needle tip depth considerably increase the amount of disturbed flow and non-physiological wall shear stress in the venous anastomotic region of AVGs. Negative effects of haemodialysis needle flow could be minimised by more upstream cannulation, by lower dialysis flow and by ensuring a central needle tip depth. Since disturbed haemodynamics are associated with neointimal hyperplasia development, optimising dialysis flow and needle positioning during haemodialysis could play an important role in maintaining AVG patency.

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Graft Modification Strategies to Improve Patency of Prosthetic Arteriovenous Grafts for Hemodialysis

Cited by 10 publications

References 57 publications

A realistic arteriovenous dialysis graft model for hemodynamic simulations

A realistic arteriovenous dialysis graft model for hemodynamic simulations

Haemodynamic optimisation of a dialysis graft design using a global optimisation approach

Computational Modelling Based Recommendation on Optimal Dialysis Needle Positioning and Dialysis Flow in Patients With Arteriovenous Grafts

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