Coronary Bypass Anastomoses (deSTS vs ETS) in Pulsatile Flow: Paper Validation

Description

This project presents a computational fluid dynamics (CFD) simulation based on the reference study "Analysis of Computational Fluid Dynamics and Particle Image Velocimetry Models of Distal-End Side-to-Side and End-to-Side Anastomoses for Coronary Artery Bypass Grafting in a Pulsatile Flow" by Shintani et al. (Circulation Journal, 2018).

The objective was to reproduce and validate the hemodynamic behavior of two coronary artery bypass grafting (CABG) configurations: the distal-end side-to-side (deSTS) and end-to-side (ETS) anastomoses. Using ANSYS Fluent, the simulation results were benchmarked against the reference data to confirm the numerical methodology's accuracy. The study examined steady, laminar, incompressible flow conditions to evaluate velocity profiles and wall shear stress (WSS) distributions, verifying the CFD approach's reliability for modeling physiological blood flow through coronary bypass geometries.

Geometry and Mesh

The geometry was built in ANSYS Design Modeler using coronary artery and graft dimensions consistent with those described by Shintani et al. The model featured a circular graft connected to the host artery at a physiologically realistic angle, capable of representing both the ETS and deSTS configurations.

An unstructured tetrahedral mesh was generated in ANSYS Meshing to accurately resolve flow gradients near the anastomotic junction, consisting of approximately 2,049,525 elements. Fine mesh resolution near the vessel wall enabled precise evaluation of velocity distribution and wall shear stress, ensuring mesh-independent, high-quality results suitable for validation.

Model and Solver Settings

The fluid was modeled as laminar, incompressible, and Newtonian, with blood-like properties: a density of 1060 kg/m³ and a dynamic viscosity of 0.004 Pa·s. An inlet velocity of 0.0097 m/s was applied, along with a pressure outlet boundary condition set to 0 Pa gauge pressure. Vessel walls were treated as rigid with no-slip conditions.

Simulations were run using ANSYS Fluent's pressure-based solver under steady-state conditions, with convergence defined as all residuals falling below 1×10⁻⁵ — ensuring numerically stable, accurate predictions of the velocity field and wall shear stress distribution across the anastomotic region.

Results

The CFD results showed strong agreement with the data reported by Shintani et al., confirming the reliability of the numerical approach. Velocity profiles closely matched the reference comparison at both evaluated sections, correctly capturing flow behavior at the anastomotic junctions.

The dimensionless wall shear stress comparison likewise validated the model, with low WSS regions identified near the graft's heel and distal end — areas typically associated with disturbed flow — while higher WSS values appeared along regions of direct flow impingement. These results confirm the CFD model's ability to accurately capture the complex hemodynamic behavior characteristic of coronary bypass flow.