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

Abstract

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.

Computationally guided in-vitro vascular growth model reveals causal link between flow oscillations and disorganized neotissue

“…After the dynamic culture, constructs and supernatants are collected and processed for further analysis. a is derived from Quicken et al 19 with permission . …”

“…A CFD model of the full geometry with a rigid wall assumption was used to obtain proper boundary conditions for the FSI model and to estimate the wall shear stresses in the graft. At the inlet boundary of the CFD model, a Doppler ultrasound-based velocity profile was prescribed, whereas at the proximal venous outlet a zero-pressure boundary condition was prescribed 19 . To mimic the peripheral bed and collateral venous flow, a six elements lumped parameter model was coupled to the distal arterial and venous outlets.…”

“…The ε strain metric is equivalent to engineering strain and combines both longitudinal and circumferential strain in a single scalar metric. For detailed information regarding the methodology of the simulations, the reader is referred to Quicken et al 15 , 19 .…”

“…After 3 days of static culture, the constructs were mounted in the culture chambers of the bioreactor for the application of hemodynamic loading 21 , 22 . To determine the loading conditions that mimic the conditions in vivo, we first examined the expected hemodynamic loads at the vein–graft anastomosis, as computed from the CFD and FSI simulations 15 , 19 . The samples were allocated to the different experimental conditions in a non-blinded, random way.…”

“…All computational methods used in this paper to perform the CFD and FSI simulations were peer-reviewed and are extensively described in Quicken et al 15 , 19 . The data and methods required to reproduce Fig.…”