The Effect of Helical and Vortical Structures on Lagrangian Behavior of Particles in the End-to-Side Anastomosis Using Discrete-Phase Modeling

Abstract

Anastomotic blood flow patterns have been extensively studied in relationship to graft failure with the objective of understanding the specific flow environment underlying the stenosis formation at the anastomosis. In the present study, computational modeling of blood flow along with discrete-phase modeling of low-density protein (LDL) and platelets for end-to-side anastomosis was conducted to assess the effect of vortical/helical structure and hemodynamic parameters on Lagrangian behavior of particles identified by particle residence time (PRT). Simulations were carried out for four models, generated based on two main features of “anastomosis angle” and “the presence of blood flow at distal venous segment”. The transport equations were solved in the Eulerian frame of reference, and the discrete phase was simulated in the Lagrangian frame of reference. The continuous phase was assessed using helicity-based descriptors, visualization of the vortical structure, and wall shear stress. Results indicated that the presence of the side vortex observed in 70:30 cases increased the helicity intensity and PRT with forcing particles wrapping around it. With respect to the comparison of anastomosis angle, larger flow separation, flow reversal, and higher helicity intensity in 65° cases resulted in higher PRT. A smaller anastomotic angle lowered peak wall shear stress, the flow separation area, and disturbances at the toe. Hemodynamics of a larger number of models should be studied to elucidate the connection between helical/vortical structures and Lagrangian residence time of particles that can contribute to activation of platelets and deposition of LDL particles.