Circumferential strain distribution in rabbit thoracic aorta using novel observation technique

The purpose of this study was to reveal circumferential strain distributions in aortas by using a newly designed observation technique. Six cylindrical descending thoracic aortas were excised from Japanese white rabbits and stretched in the longitudinal direction to their in vivo length. Five-millimeter long needles (phi 0.4 mm) were penetrated into the aorta as a marker of circumferential displacement of the aorta. During application of internal pressure ranging from 0 to 200 mmHg, displacements of needles were recorded with a CCD camera from longitudinal direction of the aorta and with other two CCD cameras from both lateral sides of aorta. The images of cameras were used to determine the penetration points of all needles. From the penetration points, we calculated the local circumferential lengths of aorta and circumferential local stretch ratios. As a result, circumferential stretch ratio of ventral side of aorta was significantly higher than that of dorsal side (p < 0.05). This result suggests that nonuniform strain distributions exist in the circumferential direction of aortas. The present method was useful to measure the detailed mechanical property of blood vessels and to understand vascular mechanics.