Assessment Of The Ascending Aorta Wall Function By Two-dimensional Speckle Tracking Imaging

[Background and purpose] Cardiovascular Surgeons have been facing the challenges of a growing number of aortic diseases. Structure and its function of the aortic wall has become the focus of research in the pathogenesis of aortic disease. Assessment of regional myocardial motion and deformation using two-dimensional speckle tracking imaging (2D-STI) could be simple, fast and accurate without any angular dependence. The application of this technology in the assessment of aortic function is also expanding gradually. This study measured the velocity, strain, strain rate and stiffness of the ascending aorta wall by2D-STI, aimed to:1, explore the application of2D-STI in quantitatively assessment of the ascending aorta wall function;2, deliberate the movement and deformation characteristics of aortic wall;3, discover the abnormal changes of radial velocity, strain and strain rate of ascending aorta in patients with dilated aorta;4, explore the differences of the ascending aorta wall function between patients with severe aortic stenosis and those with severe aortic regurgitation.[Methods] TTE was performed in29patients (17males, mean age of62.7±17.7yrs) with dilated ascending aorta(experimental group) and30subjects (15males, mean age of43.1±10.8yrs) without any structural and functional abnormalities (control group) in Huashan Hospital during October2011and April2012. The ascending aortic long axis, short axis dynamic images and M-mode images of the ascending aorta were acquired with color Doppler ultrasonic system (GE Vivid7) using2.5MHz transducer, and then analyzed offline with the Research Arena software. The stiffness, area change of ascending aortic wall were measured, the movement features and elastic property of aortic wall were analyzed, and were compared between the2study groups and between the subgroups of severe aortic stenosis and of severe aortic regurgitation to probe into the value of2D-STI in assessment of ascending aortic wall.[Results] 1) Ascending aortic wall motion featuresThe radial velocity of the ascending aorta wall displayed as a regular wave pattern, composed of one systolic negative wave and two diastolic positive waves. The anterior and posterior walls moved in coordinated mode, with systolic forward and diastolic backward. The peak systolic velocity, peak diastolic velocity and displacement of the anterior wall were higher than those of posterior wall in long axis, while the velocities of the anterior and right-anterior segments were higher than remainders in short axis.The radial strain and radial strain rate of anterior and right-anterior segments were lower than those of other segments, which were no significant differences between each other.2) Functional changes of aorta wall in patients with dilated ascending aortaThe end-systolic area and end-diastolic area increased in patients with dilated ascending aorta, while fractional area change and systolic dA/dt decreased.The systolic and diastolic peak radial velocity and displacement of anterior and posterior segments also decreased, as well as the values of the peak radial velocity, strain and strain rate of anterior and right-anterior segments in short axis.Distensibility of dilatated ascending aorta decreased, while the stiffness increased.3) Aortic wall functional differences in patients with different type of aortic valve diseaseCompared with severe AS patients, severe AR patients had larger diameter and area, and greater dA/dt-s. The systolic and diastolic radial velocities, radial strain and radial strain rate of anterior and posterior segments were higher in severe AR patients. Compared to the severe AR patients, the ascending aorta wall was stiffer in severe AS patients, with worse distensibility.4) Variability of2D-STI parameters was excellent. The distensibility and stiffness index measured by2D-STI correlated well with which derived from M-mode with a systematic difference.[Conclusion]1)2D-STI is valuable in noninvasive assessment of the ascending aorta wall function with low variability. The stiffness index and distensibility derived from2D-STI correlated well with those from M-mode, despite of the systematic difference.2) The normal ascending aortic wall reveals the regular pattern of motion and deformation.3) The wall of dilated ascending aorta was stiffer than those of the control, with impaired movement and deformation function, indicated by the reduced radial velocity, strain and strain rate of the anterior and right-anterior segments.4) Significant differences of aortic wall functions could be found between patients with severe AS and those with severe AR, more rigid in the former while more dilated in the later.