Numerical and Physical Models of Distal Anastomosis in Coronary Artery Bypass Grafting

Abstract

Abstract-The progressive anastomotic intimal hyperplasia has been considered as a major failure reason for coronary artery bypass grafting (CABG), which is associated with the abnormality of the hemodynamic conditions. We designed a set of plexiglass models which can serve as in vitro cells or tissue culture bioreactors, also serve as mechanical flow chambers in a physical perfusion system of CABG. The models of distal anastomosis with different angles were made of plexiglass material. The anastomotic angles α in three models are 60°, 30° and 15°, respectively. The numerical simulation models, reproducing from these physical models, were set up using a computer fluid dynamic (CFD) software. First, the numerical results showed that in the model with α=60° there is a high velocity characteristic on the floor of the host artery opposite the graft orifice, where significant intimal thickening is likely to occur. Decreasing α, the peak velocity will move to the outlet of host artery. Second, the stagnant flow region depends directly on the distance D (The distance from the heel of the graft to the center of stenosed site), the larger is the value of D, and the longer is the stagnant region. We also found the residual flow which is harmful to the orifice region and the distal portion of anastomotic gradually became more slender as severity of the stenosis increased. The results suggest that anastomotic angle and stenosed site are very important factors for preoperative investigation. A smaller α can eliminate the stagnation and decrease the risk of intimal thickening at the anastomotic junction, while a shorter D can decrease stagnant region. The results also showed that our perfusion system and the physical models are feasible for CABG studies.