Three-dimensional numerical simulation of blood flow in the aortic arch during cardiopulmonary bypass

Objective: To better understand the mechanism of stroke during cardiopulmonary bypass, it is necessary to obtain information on the location of turbulence, wall pressure, and flow distribution within the aortic arch. Methods: Blood flow was numerically simulated using the finite element method in the following representative case: a curved arterial cannula was inserted into the anterior wall of the distal ascending aorta 2 cm below the orifice of brachiocephalic artery. Perfusion was performed, with a bypass flow index of 2.5 l min^-1 m^-2. Computational grids, consisting of 1,493,297 tetrahedral elements, were generated. Results: The highest wall pressure (3104.8 Pa) was observed at the superior-posterior wall of the aorta below the orifice of the brachiocephalic artery where jet flow impingement occurred. The maximum wall shear stress was 25.1 Pa. High velocity vortex started below the orifice of the brachiocephalic artery. The turbulent flows continued along the posterior wall and then mainly flowed off into the left subclavian artery. Therefore, in the present case, an embolic event in the territory of the left subclavian artery could occur if a plaque was present at the superior-posterior wall of the aorta below the orifice of the brachiocephalic artery. The flow rates in each of the branches were 132, 613, 175, and 821 ml/min for the right subclavian, right common carotid, left common carotid, and left subclavian artery, respectively. Conclusion: This study confirmed that blood flow during cardiopulmonary bypass can be simulated and visualized. Computational fluid dynamics could be applied in the future to assess an individual's risk of stroke. Further multiple representative cases need to be simulated.