Role of regional aortic wall properties in the pathogenesis of thoracic aortic dissection.

Objectives: The mechanisms of the location and extension of acute aortic dissection (AD) are only poorly understood. The aim of this study was to compare the cohesion of the non-coronary aortic sinus (NAS) and the ascending aortic wall (AA) using the Dissectometer - a new device for analyses of the mechanical properties of the aorta.

Design: The properties of the aortic wall were analyzed with the "Dissectometer" (parameters P7, P8 and P9) in adult patients undergoing aortic root (AR) replacement in two different segments: NAS and AA. The aortic wall thickness (AWT) was measured with a micrometer.

Results: Thirty-three adult patients (mean age 65 ± 14 years, 80% male) were included in this study. The aortic wall of the NAS was significantly thinner than that of the AA (1.9 ± 0.4 vs. 2.3 ± 0.4, p < 0.01). In contrast, mechanical stability assessed by cohesion testing was diminished in AA samples compared to NAS samples (P7: 86.0 ± 55.0 vs. 152.3 ± 89.2, p < 0.01; P8: 2.5 ± 1.3 vs. 6.0 ± 3.1, p < 0.01; P9: 3.6 ± 1.4 vs. 7.8 ± 3.2, p < 0.01).

Conclusions: This study shows that the wall of the AR is characterized by a thin but stable wall, whereas AA was found to be weaker despite its greater thickness. This difference might be involved in the development and spreading of aortic dissections.