Key result
Aortic root in-plane motion increased the longitudinal stress of the proximal ascending aorta by less than 5%, compared to a 40% increase caused by axial motion, suggesting neither directly leads to dissection.
Why the study?
Axial motion of the aortic root was suggested to contribute to ascending aorta dissection, but the effects of aortic root in-plane motion on ascending aorta stresses have never been studied.
Cross-Sectional (n=25)
No
Absolute Event Rate: 5% vs 40%
Aortic root in-plane motion does not significantly elevate ascending aorta stress levels compared to axial motion, suggesting neither directly leads to aortic dissection in healthy individuals.
Aortic root motion unlikely causative for dissection; leaves open alternative biomechanical triggers in diseased human aortas.
BACKGROUND: The axial motion of aortic root (AR) due to ventricular traction was previously suggested to contribute to ascending aorta (AA) dissection by increasing its longitudinal stress, but AR in-plane motion effects on stresses have never been studied. The objective is to investigate the contribution of AR in-plane motion to AA stress levels. METHODS: The AR in-plane motion was assessed on magnetic resonance imagining data from 25 healthy volunteers as the movement of the AA section centroid. The measured movement was prescribed to the proximal AA end of an aortic finite element model to investigate its influences on aortic stresses. The finite element model was developed from a patient-specific geometry using LS-DYNA solver and validated against the aortic distensibility. Fluid-structure interaction (FSI) approach was also used to simulate blood hydrodynamic effects on aortic dilation and stresses. RESULTS: The AR in-plane motion was 5.5 ± 1.7 mm with the components of 3.1 ± 1.5 mm along the direction of proximal descending aorta (PDA) to AA centroid and 3.0 ± 1.3 mm perpendicularly under the PDA reference system. The AR axial motion elevated the longitudinal stress of proximal AA by 40% while the corresponding increase due to in-plane motion was always below 5%. The stresses at proximal AA resulted approximately 7% less in FSI simulation with blood flow. CONCLUSIONS: The AR in-plane motion was comparable with the magnitude of axial motion. Neither axial nor in-plane motion could directly lead to AA dissection. It is necessary to consider the heterogeneous pressures related to blood hydrodynamics when studying aortic wall stress levels.
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Wei et al. (2019) conducted a cross-sectional in Healthy (n=25). Aortic root in-plane motion vs. Aortic root axial motion was evaluated on Increase in longitudinal stress of the proximal ascending aorta. Aortic root in-plane motion increased the longitudinal stress of the proximal ascending aorta by less than 5%, compared to a 40% increase caused by axial motion, suggesting neither directly leads to dissection.
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