Numerical simulations of unsteady flows in a stenosed coronary bypass graft.

Using the finite element method, physiological blood flows through a three-dimensional model of a coronary graft are numerically analysed. The model includes a stenosis shape in the host artery upstream from the anastomosis. Recirculating areas, secondary flows, wall shear stress (WSS) and spatial wall shear stress gradients (WSSGs) are studied for different flow repartitions and at different times in the cycle. The temporal and spatial evolutions of the recirculating areas downstream from the stenosis, their interactions with the flow issued from the graft and their associated WSSs highlight that the presence of the stenosis in the recipient artery is essential for prediction of the evolution of a grafting at the beginning of its implantation. The areas downstream from the stenosis expansion, non-existent for a host artery without stenosis, are submitted to low and oscillating WSS between -0.5 and 0 Nm(-2). The stagnation point on the recipient artery floor is subjected to high positive and negative WSSGnd values, and its location is dependent on the residual flow through the stenosis.