Static anisotropic elastic properties of the aorta in living dogs.

Static anisotropic elasticity was studied in the middle descending thoracic aorta of 14 living dogs. Special transducers were used to measure radius and longitudinal stress at several pressures in situ in an isolated vessel segment. From these data, moduli describing elastic properties of the vessel wall were calculated. Results indicate that (1) at a physiologic pressure of 154 cm H2O (extension ratio of 1.52 circumferentially) the mean values for the incremental elastic moduli in the radial, circumferential, and longitudinal directions were 5480, 7510, and 10,100 g/cm-, respectively; (2) these moduli increased with an increase in intravascular pressure; and (3) the longitudinal modulus decreased when the vessel longitudinal tethering). was studied in vitro (from the removal of ADDITIONAL