The Preliminary Research On The Mechanical Properties Of Aortic Wall And The Latent Relationship With Aortic Dissection Formation

Objective To study the mechanical properties of human aortic media in layers and the latent relationship betweenm the mechanical properties and aortic dissection formation. Methods The average dissecting force (ADF) and interlamellar shear stress of each interspace in the media were measured using a tensile strength tester, and the the final shape-changed strength ratio of each layer was calculated before and after melting the tissue with collagenase and elastase. Results As compared with the same ADF on different segment of the aorta, the ADF (middle) on the ascending aorta was much higher than that on the upper and lower descending thoracic aorta respectively. As compared with the corresponding longitudinal ADF on the same site, the circumferential ADF (outer) on ascending aorta, ADF (inner) on the upper descending thoracic aorta and the lower descending thoracic aorta were significantly reduced. The interlamellar shear stress between the middle two layers was lower than that between the inner and outer two layers respectively. The longitudinal final shape-changed strength ratio of the aorta was lower than the circumferential one. The longitudinal final shape-changed strength ratio on the dorsal part of the ascending aorta and the upper thoracic aorta was also lower than that on the ventral part. The mean value of longitudinal final shape-changed strength ratio of the second layer labeled from adventitia to intima is lower than any other layer on dorsal part of the ascending aorta and the upper thoracic aorta. There were no significent differences of the longitudinal final shape-changed strength ratio among four layers on the dorsal part after enzyme melting. Conclusion The dissection occurred in the middle and inner part media had a propensity to extend to the distal aorta. The dissection on ascending aorta is easier to rupture than that on other segments. The latent dissection happened most commonly in the middle part of the media on the dorsal part of upper thoracic aorta. 4. The second stripe nearing the adventitia might break first in same stress setting. The discrepancy of the longitudinal final shape-changed strength ratio across the media might be caused by the uneven distribution of the collagen.