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Technical Briefs

Increase in Opening Angle in Hypertension Off-Loads the Intimal Stress: A Simulation Study

[+] Author and Article Information
Chong Wang

Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA

Ghassan S. Kassab1

Department of Biomedical Engineering, Department of Surgery, Cellular and Integrative Physiology and Indiana Center for Vascular Biology and Medicine, IUPUI, Indianapolis, IN 46202gkassab@iupui.edu

1

Corresponding author.

J Biomech Eng 131(11), 114502 (Oct 26, 2009) (3 pages) doi:10.1115/1.4000085 History: Received January 01, 2009; Revised May 22, 2009; Posted September 01, 2009; Published October 26, 2009

The stress distribution in the vessel wall has important bearing on vascular function including intima, media, and adventitia. The residual strain in the vessel wall has been thought to largely normalize the transmural stress distribution with slightly higher values at the intima. In hypertension, the compensatory increase in opening angle is thought to maintain a uniform stress distribution. We have recently shown that the circumferential stress at adventitia may exceed that at intima at physiological loading due to large opening angle (OA) in normal porcine coronary arteries. The objective of this study was to show that increases in opening angle subsequent hypertension can further shift the stress from the intima to the adventitia. The change in stress distribution during acute hypertension was calculated using available data on the changes in vessel geometry, material property, and internal pressure during hypertension. It was found that the increase in OA following acute hypertension off-loads the stress from intima to adventitia, therefore, relieving some of the stress increase in the intimal layer induced by the sudden pressure increase. This has important implications for hypertension where it may shift the excessive stress from the inner layer to the outer layer. This may be a protective mechanism for the intima layer in hypertension.

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Copyright © 2009 by American Society of Mechanical Engineers
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Grahic Jump Location
Figure 1

Acute hypertension during the first two days. (a) Ratio of inner-to-outer circumferential length in the zero-stress state. (b) The fraction (%) of the stress at the intima and adventitia layer taking into account the changes in opening angle. (c) The fraction (%) of stress at the intima and adventitia layer if there is no change in opening angle. The circumferential stress at inner and outer boundaries of the vessel wall was considered as the stress in the intima and adventitia layer, respectively. The fraction value is the ratio of individual layer stress to the sum of stresses in both layers.

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