Abstract 13012: Layer-Specific Mechanical Properties of Ascending Thoracic Aortic Aneurysms
Aim: No previous studies have documented the layer-specific mechanical properties of ascending thoracic aortic aneurysms (ATAA) or even abdominal aortic aneurysms, for which there is a greater number of reports. Such knowledge is, however, vital, as it is acknowledged that ATAA dissection is caused by a circumferential or, less frequently, transverse tear of the inner aortic wall layers. Accordingly, this study investigated the mechanical properties of the three basic layers (intima, media, and adventita) of ATAA wall.
Methods: ATAA wall specimens were obtained from 8 patients (age: 62±5 y, ATAA diameter: 5.9±0.6 cm) during graft replacement for degenerative ATAA, dissected into layers, and categorized by direction: circumferential (CIRC) vs. longitudinal (LONG) and layer: intima (nCIRC=48; nLONG=48) vs. media (nCIRC=48; nLONG=48) vs. adventitia (nCIRC=48; nLONG=48). Mechanical tests of the individual layers were conducted with a tensile tester up to rupture, calculating tissue strength, maximum stiffness, and extensibility.
Results: The intima displayed significantly lower extensibility (CIRC: 0.48±0.03; LONG: 0.44±0.03) than the media (CIRC: 0.66±0.03; LONG: 0.63±0.03) and adventitia (CIRC: 0.68±0.03; LONG: 0.65±0.03). Higher were the tissue strength (CIRC: 262.4±19.2; LONG: 198.8±20.9 N/cm2) and stiffness (CIRC: 1121.5±90.8; LONG: 882.8±101.2 N/cm2) in the adventitia than the intima (CIRC: 107.5±12.9; LONG: 71.7±7.9 N/cm2 and CIRC: 598.4±73.4; LONG: 476.1±59.5 N/cm2, respectively) and media (CIRC: 146.7±14.4; LONG: 52.4±6.1 N/cm2 and CIRC: 732.5±83.4; LONG: 199.3±21.9 N/cm2, respectively). In most layers, strength and stiffness were significantly higher in CIRC than LONG specimens.
Conclusions: The present findings highlight that the mechanical properties of ATAA vary notably across wall thickness. Dissection/rupture of ATAA may be ascribed to those differences and particularly to the lower strength of the inner layers. This is the first study to place emphasis on the layer-specific mechanical properties of human aneurysmal aorta that may be expected to shed light into the mechanisms promoting aneurysm dissection/rupture.
- © 2012 by American Heart Association, Inc.