Hindawi Publishing Corporation Te Scientifc World Journal Volume 2013, Article ID 601470, 9 pages http://dx.doi.org/10.1155/2013/601470 Research Article Preliminary Computational Hemodynamics Study of Double Aortic Aneurysms under Multistage Surgical Procedures: An Idealised Model Study Yosuke Otsuki, 1 Nhat Bui Minh, 2 Hiroshi Ohtake, 3 Go Watanabe, 3 and Teruo Matsuzawa 4 1 School of Information Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1211, Japan 2 Department of Simulation Analysis, Fujitsu Systems East, 1415 Tsuruga Midori, Nagano 380-0813, Japan 3 Department of General and Cardiothoracic Surgery, Graduate School of Medical Science, 13-1 Takara, Kanazawa 920-1192, Japan 4 Research Center for Simulation Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1211, Japan Correspondence should be addressed to Yosuke Otsuki; yosuke otsuki@jaist.ac.jp Received 2 August 2013; Accepted 19 September 2013 Academic Editors: H.-C. Han, M. Ohta, and A. Qiao Copyright © 2013 Yosuke Otsuki et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Double aortic aneurysm (DAA) falls under the category of multiple aortic aneurysms. Repair is generally done through staged surgery due to low invasiveness. In this approach, one aneurysm is cured per operation. Terefore, two operations are required for DAA. However, post-frst-surgery rupture cases have been reported. Although the problems involved with managing staged surgery have been discussed for more than 30 years, investigation from a hemodynamic perspective has not been attempted. Hence, this is the frst computational fuid dynamics approach to the DAA problem. Tree idealized geometries were prepared: presurgery, thoracic aortic aneurysm (TAA) cured, and abdominal aortic aneurysm (AAA) cured. By applying identical boundary conditions for fow rate and pressure, the Navier-Stokes equation and continuity equations were solved under the Newtonian fuid assumption. Average pressure in TAA was increased by AAA repair. On the other hand, average pressure in AAA was decreased afer TAA repair. Average wall shear stress was decreased at the peak in post-frst-surgery models. However, the wave profle of TAA average wall shear stress was changed in the late systole phase afer AAA repair. Since the average wall shear stress in the post-frst-surgery models decreased and pressure at TAA afer AAA repair increased, the TAA might be treated frst to prevent rupture. 1. Introduction An aortic aneurysm is abnormal dilatation on the aortic wall. Te formation and growth process are not fully understood although some fundamental biological evidence has been identifed [1]. Lasheras stated that repeatedly applied shear force stifens the aortic wall by changing the biomechanical reaction and when the aneurysm wall strength can no longer tolerate the mechanical load, it ruptures. Moreover, he also mentioned that atherosclerotic plaque was responsible for the growth since it was found in the majority of aneurysms. Te death rate due to rupture is high; according to Shek, it reaches 85% if an abdominal aortic aneurysm (AAA) is lef untreated [2]. Te size of an aneurysm is closely related to the rupture risk. Choke et al. demonstrated the relationship between the size of AAA and the annual risk of rupture [3]. From their research, the rupture risk increased as the aneurysm diameter increased. Population-based research shows that aneurysms are frequently formed at the aortic arch and abdominal wall [4]. To cure an aneurysm, stent-graf implantation or artifcial graf replacement is the common surgical procedure. Since the frst procedure is less invasive, it is frequently used. Frauenfelder et al. illustrated the reduction in AAA pressure by stent-graf implantation through their fuid structure interaction model and validation experiment [5]. If more than one aortic aneurysm is found, the condition is called multiple aortic aneurysms (MAA). Crawford and