Computational Fluid Dynamics Simulation of Hemodynamic Impact and Geometric Thresholds in Stenotic Coronary Distal Side‐to‐Side Anastomoses

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Abstract
Background: Distal side‐to‐side anastomosis is an effective technique for coronary artery bypass grafting; however, restrictive suturing may adversely affect graft patency. In this study, we evaluated ex vivo side‐to‐side models through numerical simulations of fluid dynamics to compare varying degrees of anastomotic stenosis and predict their hemodynamic consequences. Methods: A carotid artery was grafted onto a porcine coronary artery in a side‐to‐side configuration, with the vessels filled with liquid silicone. Ultra‐high‐resolution computed tomography was employed to acquire the reference side‐to‐side image, and stenotic models were developed with longitudinal shortening and bilateral narrowing at 25%, 50%, and 75% stenosis, alongside 90% coronary artery stenosis. Hemodynamic analysis was conducted using computational fluid dynamics simulations to calculate streamlines, wall shear stress, and oscillatory shear index. Results: In the reference model, graft inflow impinged on the coronary artery floor, generating a recirculating vortex at the heel and blind end of the graft while maintaining laminar flow. Longitudinal stenosis resulted in a steeper graft flow angle, whereas bilateral stenosis induced helical flow along the lateral arterial wall, exacerbating with increased stenosis. At 75% longitudinal or 50% bilateral stenosis, a region of flow separation was observed, characterized by low wall shear stress and high oscillation regions distal to the toe of the anastomosis. Conclusions: Computational fluid dynamics simulations indicate that anastomotic stenosis with longitudinal length ratios less than 1.6 and bilateral width ratios less than 0.73 relative to coronary diameter is at risk of intimal hyperplasia leading to graft failure, whereas larger ratios suggest acceptable hemodynamics. Future research should investigate long‐term clinical outcomes associated with suboptimal side‐to‐side anastomotic construction.
Funding Information
  • Japan Society for the Promotion of Science (JP23K08231)

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