Dispersive Aortic Cannulas Reduce Aortic Wall Shear Stress Affecting Atherosclerotic Plaque Embolization *†‡Alexander Assmann, §Fethi Gül, §Ali Cemal Benim, ¶Franz Joos, *Payam Akhyari, and *Artur Lichtenberg *Research Group for Experimental Surgery and Department of Cardiovascular Surgery, Medical Faculty, Heinrich Heine University; §Computational Fluid Dynamics Lab, Department of Mechanical and Process Engineering, Düsseldorf University of Applied Sciences, Düsseldorf; ¶Laboratory of Turbomachinery, Helmut Schmidt University, Hamburg, Germany; †Department of Medicine, Center for Biomedical Engineering, Brigham and Women’s Hospital, Harvard Medical School, Boston; and ‡Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA Abstract: Neurologic complications during on-pump car- diovascular surgery are often induced by mobilization of atherosclerotic plaques, which is directly related to enhanced wall shear stress. In the present study, we numerically evaluated the impact of dispersive aortic can- nulas on aortic blood flow characteristics, with special regard to the resulting wall shear stress profiles. An ideal- ized numerical model of the human aorta and its branches was created and used to model straight as well as bent dispersive aortic cannulas with meshlike tips inserted in the distal ascending aorta. Standard cannulas with straight beveled or bent tips served as controls. Using a recently optimized computing method, simulations of pulsatile and nonpulsatile extracorporeal circulation were performed. Dispersive aortic cannulas reduced the maximum and average aortic wall shear stress values to approximately 50% of those with control cannulas, while the difference in local values was even larger. Moreover, under pulsatile circulation, dispersive cannulas shortened the time period during which wall shear stress values were increased. The turbulent kinetic energy was also diminished by utilizing dispersive cannulas, reducing the risk of hemolysis. In summary, dispersive aortic cannulas decrease aortic wall shear stress and turbulence during extracorporeal circula- tion and may therefore reduce the risk of endothelial and blood cell damage as well as that of neurologic complica- tions caused by atherosclerotic plaque mobilization. Key Words: Aortic blood flow—Aortic cannula— Extracorporeal circulation—Computational fluid dynamics—Wall shear stress—Plaque embolization. One of the major adverse events that may occur during extracorporeal circulation (ECC) in cardiac surgery is arterial embolization of atherosclerotic plaques resulting in stroke or ischemia of other organs such as kidney, liver, or intestine. Besides being manually mobilized during cross-clamping of the aorta, plaques may delaminate or rupture due to the jet stream of the aortic inlet cannula of the heart– lung machine. This sandblastlike effect not only negatively affects atherosclerotic plaques but also damages healthy endothelium in the area in which the cannula jet hits the aortic wall (1). Enhanced maximum wall shear stress (WSS) values have been reported to be correlated with the rupture of atherosclerotic plaques (2,3). Recently, our group has developed and validated a numerical model for simulating different ECC conditions in human aortic geometries (4,5). Using this model, it has been shown that nonpulsatile ECC remarkably reduces maximum WSS values as compared with pul- satile ECC. Previous simulation studies have under- lined the importance of the cannulation site with regard to changes in the aortic blood flow profile (6,7). Another important component influencing the ECC-generated blood flow in the aorta is the tip shape of the arterial cannula. In experimental in vitro settings, different tip geometries have been tested, doi:10.1111/aor.12359 Received March 2014; revised April 2014. Address correspondence and reprint requests to Dr. Alexander Assmann, Department of Cardiovascular Surgery, Medical Faculty, Heinrich Heine University, Moorenstr. 5, D–40225 Düsseldorf, Germany. E-mail: alexander.assmann@med.uni- duesseldorf.de Copyright © 2014 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc. Artificial Organs 2015, 39(3):203–211