Computational modelling of blood flow through sutured and coupled microvascular anastomoses

Abstract

The research presented in this thesis uses Computational Fluid Dynamics (CFD) to model blood flow through idealised sutured and coupled microvascular Anastomoses to investigate the affect of each surgical technique on the flow within the vessel. Local flow phenomena are examined in detail around suture and coupler sites to study characteristics that could potentially initiate thrombus formation; for example, changes in velocity profile, wall shear stress or recirculating flow (vorticity).

Idealised geometries of sutured and coupled blood vessels were created using CFD software with dimensions identical to microvascular suture material and coupling devices. Vessels were modelled as non‐compliant 1mm diameter ducts, and blood was simulated as a Newtonian fluid, in keeping with previous similar studies. All analyses were steady-state and performed on arteries.

Comparison of the sutured and coupled techniques in the simulated microarterial anastomoses revealed a reduced boundary velocity profile; high Wall Shear Stress (WSS); high Shear StrainRate(SSR);and elevated vorticity at the suturesites. The coupled anastomosis simulation showed a small increase in maximum WSS at the anastomotic region compared to a pristine vessel. However, this was less than half that of the sutured model. The coupled vessel displayed an average WSS equal to a pristine vessel.

Taken together, these observations demonstrate an increased thrombogenic profile in the sutured anastomosis when compared to a pristine, or indeed a coupled vessel. Data from the simulations on a coupled anastomosis reveal a profile that is less thrombogenic than that of the sutured anastomosis, and one that is nearly equivalent to that of a pristine vessel.

Overall, it can be concluded that, within the limits of CFD simulations and the assumptions taken in this study, a sutured anastomosis is potentially more likely to generate an intravascular thrombosis than a coupled anastomosis.