Numerical Simulation of Physiological Blood Flow in 2-way Coronary Artery Bypass Grafts

Abstract

Abstract. The Coronary Artery Bypass Graft (CABG) yields excellent results and remains the modern standard of care for treatment of occlusive disease in the cardiovascular system. However, the development of anastomotic Intimal Hyperplasia (IH) and restenosis can compromise the mediumand-long term effects of the CABG. This problem can be correlated with the geometric configuration and hemodynamics of the bypass graft. A novel geometric configuration was proposed for the CABG with two symmetrically implanted grafts for the purpose of improving the hemodynamics. Physiological blood flows in two models of bypass grafts were simulated using numerical methods. One model was for the conventional bypass configuration with a single graft (1-way model); the other model was for the proposed bypass configuration with two grafts (2-way model). The temporal and spatial distributions of hemodynamics, such as flow patterns and Wall Shear Stress (WSS) in the vicinity of the distal anastomoses, were analyzed and compared. Calculation results showed that the 2-way model possessed favorable hemodynamics with uniform longitudinal flow patterns and WSS distributions, which could decrease the probability of restenosis and improve the effect of the surgical treatment. Concerning the limitations of the 2-way bypass grafts, it is necessary to perform animal experiments to verify the viability of this novel idea for the CABG.

Blood Flow in an Out-of-Plane Aorto-left Coronary Sequential Bypass Graft

“…In the case of sequential bypass grafting, the flow splitting in the graft causes the parabolic graft flow profile to change to a flat profile thus resulting in a plug flow and consequential reduction of the velocity gradient. Hence the influence of the side-to-side anastomosis B on the end-to-side anastomosis C contributes to better WSSG environment which is in agreement with other reports [18]. These findings are also in agreement with Pietrabissa et al [19] who also showed that sequential bypasses exhibited better hemodynamics (velocity, WSS, and spatial WSSG) in the graft segments upstream from the first anastomosis (side-to-side anastomosis).…”

“…Lei et al [21] have shown that in disturbed flow regions the elongation and alignment of endothelial cells are difficult to achieve because of high WSS gradients. Another numerical study on flow in two-way bypass grafts [18] reported that spatial WSSG could best relate to the initiation of disease formation, and the decrease of spatial WSSG may contribute to the improved hemodynamic condition. From this, we may infer that the toe and the floor of the end-to-side anastomosis region (in the sequential grafting) are more Fig.…”

An S-type bypass can improve the hemodynamics in the bypassed arteries and suppress intimal hyperplasia along the host artery floor

“…To optimize venous anastomoses and improve the patency rate of the bypassed arteries, many computational simulation studies have been conducted (Krueger et al, 2002;Qiao et al, 2005;Qiao and Liu, 2006). In the present study, 4 end-to-side bypass models, namely the conventional 301, 451, 601 and the S-type anastomoses were compared in terms of IH and flow pattern in the host artery.…”

Computational Comparisons of Hemodynamics between 3D and 2D Models of CABG

“…The graft meets the host artery with a side-to-end anastomosis at a junction angle of β (20°≤β≤45°). When γ≥0.8, the circular cross-section of graft turns into an ellipse whose short axis is 80% of the diameter of host artery [5]. This configuration approximates the Taylor patch model which is commonly considered to be effective for improving the hemodynamics of bypass graft [6].…”