Influence of aortic outflow cannula orientation on epiaortic flow pattern during pulsed cardiopulmonary bypass

Cerebral hypoperfusion that may occur during linear cardiopulmonary bypass (CPB) is often responsible for mnemonic problems, loss of neural functions, or coma. Pulsed CPB might provide better organ protection, especially to the brain. The present work numerically investigates how the CPB cannula orientation influences blood flow in aortic and epiaortic vessels during pulsed CPB, realized using the intra-aortic balloon pump (IABP). The computational fluid dynamics (CFD) model consisted of a three-dimensional (3D) patient-specific aorta with three epiaortic vessels, a 40-cm3 intra-aortic balloon, and a 24 Fr arterial cannula in the traditional position and orientation (tilt angle of 45°, case I) and with a greater inclination (tilt angle of 60°, case II). Comparative multi-scale studies, realized by coupling a 3D CFD analysis and a lumpedparameters model, were carried out to establish the hemodynamic modifications due to changes in the cannula orientation. A comparison between the two cases revealed that when the cannula flow was directed to the epiaortic vessels (case I), the mean flows of the left subclavian artery and the thoracic aorta increased by about 2.08 and 7.50 %, respectively. When the flow cannula collided with the aortic arch concavity (case II), this area presented high wall shear stress (WSS) values and a greater amount of blood occurred in the ascending aorta, where it stagnated, although the mean flows of the innominate and left common carotid arteries increased by about 6.25 and 3.13 %, respectively. Pulsed CPB may reduce brain damage during heart surgery, so the evaluation of epiaortic flow during the extracorporeal circulation with various arterial cannula orientations is useful for the analysis of hemodynamic modifications.