Investigating heartbeat-related in-plane motion and stress levels induced at the aortic root

Abstract

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. Electronic supplementary material The online version of this article (10.1186/s12938-019-0632-7) contains supplementary material, which is available to authorized users.

Three-Dimensional Characterization of Aortic Root Motion by Vascular Deformation Mapping

“…Most studies thus far have characterized aortic root motion using 2D approaches [ 5 , 7 , 8 , 9 , 17 , 42 , 43 ]. However, extracting aortic root motion from 2D images without accounting for the full 3D motion of the aorta may provide a distorted assessment.…”

“…Electrocardiogram (ECG)-gated computed tomography angiography (CTA) affords the opportunity to visualize motion of the thoracic aorta throughout the cardiac cycle and is capable of depicting such dynamic aortic root motion in a three-dimensional (3D) manner [ 4 ]. Abnormalities in aortic root motion have been proposed to be a potential risk factor for disease progression and complications in thoracic aortic disease [ 5 , 6 , 7 , 8 ].…”

“…However, some studies have used idealized aortic models rather than patient-specific anatomy [ 5 ]. Furthermore, most techniques used to extract and quantify aortic root motion are based on 2D imaging and thus lack a comprehensive description of the multi-directional components of aortic root motion [ 5 , 6 , 7 , 8 , 9 ]. An accurate 3D assessment of cyclic motion of the ATAA could have significant implications for estimating mechanical properties of the aorta, informing computational simulations, endovascular device design, and, importantly, for refining diameter-based assessment of disease severity.…”

Biomechanical Characterisation of Thoracic Ascending Aorta with Preserved Pre-Stresses

“…Therefore, the aorta did not experience any axial stretch while deforming from an unloaded configuration to the configuration at the diastolic pressure. Nevertheless, the importance of axial stretch has been acknowledged since it affects transverse deformation in the radial direction due to the Poisson's effect as well as induced longitudinal stresses [19,20]. Besides prescribing the axial stretch directly, ventricular traction force causing the aortic root displacement could also be utilised as a boundary condition to determine the axial stretch.…”

Influence of the aortic morphological changes in aging on aortic flow

“…The blood flow is governed by the Navierstokes equations. The fluid was set to resemble to the blood (Newtonian fluid) with constant viscosity of 0.0045 Pa/s and a density of 1050 kg/m 3 (Wei et al 2019;Tokuda et al 2008).…”