Background:
Defining the biomechanical properties of the infrarenal aorta plays a crucial roll in stratifying of aortic aneurysm rupture risk. The aim of this study was to evaluate the bedside applicability of 4D speckle tracking ultrasound in analysing biomechanical properties of the aorta, in view of stratifying infrarenal aortic aneurysm rupture risk.

Material and Methods
65 persons were examined with a commercial 4D speckle tracking ultrasound system and analysed in three groups: patients with infrarenal aortic aneurysm (Group I, n=19), with normal aortic diameter younger than 60 years (Group II , n = 21) and with normal aortic diameter older than 60 years (Group III, n = 25). Based on the 4D speckle tracking derived finite element model heterogeneity and dyssynchrony of infrarenal aorta was evaluated.

Result
The analysis of biomechanical properties displayed increasing heterogeneity and dyssynchrony of circumferential strain with increasing patient age (p<0.05). The local peak strain was higher in Group II (0.26±0.17) compared to Groups I (0.16±0.1) and III (0.16±0.07) (p<0.05), with no significant difference between Groups I and III. Spatial dyssynchrony described by the systolic dyssynchrony index significantly differed between the young (Group II, 0.13±0.1) and old, regardless of aortic diameter.

Conclusion
4D ultrasound speckle tracking enables description of global biomechanical properties of the infrarenal aorta and advances the possibility to evaluate individual aortic aneurysm rupture risk by analysis of global (circumferential) strain amplitude, the spatial heterogeneity index and the ratio of local peak and global mean strain.