The Elastic Symmetry of Arterial Segments in Dogs

Elastic symmetry was studied in the middle descending thoracic aorta, abdominal aorta, and left common carotid artery under physiologic ranges of loading in ten dogs. A segment of the blood vessel was isolated and hung vertically. As the segment was pressurized, the radius, length, and the rotation of the lower end of the vessel were measured with respect to the fixed upper end. In addition, the angular displacement of a glass whisker initially placed perpendicularly through the wall was measured. From these data it was possible to calculate the values of shearing strains and elongating strains associated with pressurization and various imposed longitudinal stresses. The values of shearing strain varied from 0.003 to 0.115 over pressure ranges of 3 to 270 cm H 2 O. In all instances the values of shearing strain were much smaller than the corresponding elongating strains. It was concluded that the vessel has elastic properties that are nearly symmetrical about the planes perpendicular to principal stresses under physiologic loading, i.e., the vessel may be treated as a cylindrically orthotropic tube.