Arterial Anatomy and Atherosclerotic Lesion Localization: a Finite Element Study of Mechanical Factors.

Abstract

Theories of atherogenesis related to mechanical factors may be useful in explaining the location of certain atherosclerotic lesions. The mechanical factor considered here is the stretching of the artery during the cardiac cycle. In particular, evidence from the literature suggests that excessive endothelial stretch contributes to atherosclerosis. Certain anatomical features may locally alter the otherwise uniform deformation of an artery. This investigation examines the manner in which these features could affect the local endothelial stretch. The thoracic aorta forms the basis for the models. Externally tethered models and models having locally thinned walls are studied. The finite element method is used to quantify the stretch of the inner surface of the models. Models with rigid tethering stretch a relatively large amount at the edge of the tethered region--approximately 14% more than a uniform cylinder model. "Soft" tethering is modeled with spring elements. Radially oriented springs alone approximate a sliding boundary constraint, while the addition of tangential springs causes the stretch pattern to resemble more closely that of the rigid models. Models of arteries with thinned sections stretch considerably in the thinned region--40%-100% more than a uniform cylinder. The stretch reaches a peak at the edge of the thinned section. These results demonstrate that external tethering and thinned sections do affect the modeled mechanical behavior of an artery. Because it is likely that the stretch of the endothelium affects the transport of cholesterol and other substances into the arterial wall, these findings relate to the hypothesis that mechanical factors contribute to atherogenesis.