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(Stroke. 2005;36:1933.)
© 2005 American Heart Association, Inc.

Original Contributions

Role of the Bloodstream Impacting Force and the Local Pressure Elevation in the Rupture of Cerebral Aneurysms

Masaaki Shojima, MD; Marie Oshima, PhD; Kiyoshi Takagi, MD, PhD; Ryo Torii, PhD; Kazuya Nagata, MD, PhD; Ichiro Shirouzu, MD, PhD; Akio Morita, MD, PhD Takaaki Kirino, MD, PhD

From the Department of Neurosurgery (M.S., A.M., T.K.), Faculty of Medicine, and the Institute of Industrial Science (M.S., M.O., R.T.), University of Tokyo, Japan; the Department of Neurosurgery (K.T.), Faculty of Medicine, Teikyo University, Tokyo, Japan; and Departments of Neurosurgery (K.N.) and Radiology (I.S.), Kanto Medical Center NTT EC, Tokyo, Japan.

Correspondence to Masaaki Shojima, MD, Department of Neurosurgery, Faculty of Medicine, University of Tokyo, Japan, 7-3-1, Hongo, Bunkyo-ku, Tokyo, Japan 113-8655. E-mail mshoji-tky{at}umin.ac.jp

Background and Purpose— Inertial force of the bloodstream results in the local elevation of intravascular pressure secondary to flow impact. Previous studies suggest that this "impacting force" and the local pressure elevation at the aneurysm may have a large contribution to the development of cerebral aneurysms. The goal of the present study is to evaluate how the bloodstream impacting force and the local pressure elevation at the aneurysm influences the rupture of cerebral aneurysms.

Methods— A total of 29 aneurysms were created in 26 patient-specific vessel models, and computer simulations were used to calculate pressure distributions around the vessel branching points and the aneurysms.

Results— Direct impact of the parent artery bloodstream resulted in local elevation in pressure at branch points, and bends in arteries (231.2±198.1 Pa; 100 Pa=0.75 mm Hg). The bloodstream entered into the aneurysm with a decreased velocity after it impacted on the branching points or bends. Thus, the flow impact at the aneurysm occurred usually weakly. At the top or the rupture point of the aneurysm, the flow velocity was always delayed. The local pressure elevation at the aneurysm was 119.3±91.2 Pa.

Conclusions— The pressure elevation at the area of flow impact and at the aneurysm constituted only 1% to 2% of the peak intravascular pressure. The results suggest that the bloodstream impacting force and the local pressure elevation at the aneurysm may have less contribution to the rupture of cerebral aneurysms than was expected previously.

Key Words: blood pressure • computer simulation • hemodynamic phenomena • intracranial aneurysm • stress, mechanical

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