Mechanical and histological characteristics of aortic dissection tissues

Aims: This study investigated the association between the macroscopic mechanical response of aortic dissection (AoD) flap, its fibre features, and patient physiological features and clinical presentations. Methods: Uniaxial test was performed with tissue strips in both circumferential and longitudinal directions from 35 patients with (AoD:CC) and without (AoD:w/oCC) cerebral/coronary complications, and 19 patients with rheumatic or valve-related heart diseases (RH). A Bayesian inference framework was used to estimate the expectation of material constants ( C 1 , D 1 , and D 2 ) of the modified Mooney-Rivlin strain energy density function. Histological examination was used to visualise the elastin and collagen in the tissue strips and image processing was performed to quantify their area percentages, fibre misalignment and waviness. Results: The elastin area percentage was negatively associated with age ( p = 0.008), while collagen increased about 6% from age 40 to 70 ( p = 0.03). Elastin fibre was less dispersed and wavier in old patients and no significant association was found between patient age and collagen fibre dispersion or waviness. Features of fibrous microstructures, either elastin or collagen, were comparable between AoD:CC and AoD:w/oCC group. Elastin and collagen area percentages were positively correlated with C 1 and D 2 , respectively, while the elastin and collagen waviness were negatively correlated with C 1 and D 2 , respectively. Elastin dispersion was negatively correlated to D 2 . Multivariate analysis showed that D 2 was an effective parameter which could differentiate patient groups with different age and clinical presentations, as well as the direction of tissue strip. Conclusion: Fibre dispersion and waviness in the aortic dissection flap changed with patient age and clinical presentations, and these can be captured by the material constants in the strain energy density function.

Automated summary

This study investigated the association between the macroscopic mechanical response of aortic dissection (AoD) flap, its fibre features, and patient physiological features and clinical presentations. The study found that fibre dispersion and waviness in the aortic dissection flap changed with patient age and clinical presentations. The elastin and collagen area percentages were positively correlated with material constants, while the elastin and collagen waviness were negatively correlated with material constants. The study also found that D2 was an effective parameter to differentiate patient groups with different age and clinical presentations.