Computational Fluid Dynamic Evaluation of Deep Inferior Epigastric Artery Perforator (DIEP) Flap End-to-Side Anastomosis.

Background End-to-side (ETS) microvascular anastomoses are utilized within deep inferior epigastric artery perforator (DIEP) flap breast reconstruction procedures. Optimization of these anastomoses via a computational fluid dynamic (CFD) model can minimize ischemia and contribute to flap success. Methods  A CFD model of a deep inferior epigastric artery to internal mammary artery anastomosis was constructed with OpenFOAM software (OpenCFD Ltd., Bracknell, UK). Blood was modelled as an incompressible Newtonian fluid. Viscosity and density were assumed to be constant throughout the simulation. Mean arterial pressure was held constant at 100 mmHg. Individual virtual meshes were created for 30-, 45-, 60-, 75-, and 90-degree anastomotic angle simulations. Fluid flow was visualized with line integral convolution (LIC) and pure fluid velocity (PFV) techniques. Vessel wall shear stress (WSS) was also visualized. Results  The LIC revealed blood recirculation was associated with large anastomotic angles with minimal to no recirculation seen in the 45- and 30-degree simulations. Any recirculation visualized was confined to the toe of the bifurcation. This recirculation was associated with stagnation in the toe of the graft vessel as well, as visualized by the PFV model. A linear relationship was identified between anastomotic angle and percentage of stagnant fluid, with stagnation increasing as the anastomotic angle increased. Wall shear stress increased with the anastomotic angle and was concentrated in the heel and toe of the model. Conclusions  The CFD modelling shows that increased acuity of anastomotic angles in ETS DIEP flaps is essential to minimize stagnation, recirculation, and WSS. Successful implementation of this recommendation may directly decrease the risk of flap failure from ischemia.