Quantitative assessment of aortic elastic properties with aging by velocity-vector imaging and its correlation with histologic analysis

Abstract

Backgrounds: The loss of aortic elasticity with aging, which impact on ventricular load and coronary perfusion is known to be strong determinant of cardiovascular events. Objectives: To determine the decisive method for quantification of aortic elastic properties with aging, we assessed the feasibility of a novel echo-tracking technique with velocity-vector imaging (VVI) and its correlation with tissue characterization.Methods: Fourteen mongrel dogs were classified with 7 young dogs (age 1 to 2 years, female, weighing 22 to 29kg) and 7 senescent dogs (age 8 to 11 years, female, weighing 36 to 45kg). Under general anesthesia, transesophageal echocardiography was performed to obtain the short-axis image of proximal descending thoracic aorta (DTA) for VVI analysis with identification of the location using fluoroscopic guidance. Then, the proximal DTA was excised to quantify tissue contents as collagen and elastin and assessed the correlation with the global and segmental aortic indices of elastic properties using VVI.Results: The mean aortic area was more dilated and fractional area change as global measure of VVI was significantly reduced in the senescent group than young group. When each aorta was divided into 6 segments, the segmental radial velocity (RV), circumferential strain and strain rate of VVI were also significantly reduced in the senescent group. For histologic correlation, RV and circumferential strain of VVI showed independent associations with the collagen contents of the corresponding segment of the DTA. Contrary to collagen content, mean or segmental content of elastin showed no significant correlations with any aortic indices of elastic properties.Conclusion: Alteration of aortic elastic properties with aging assessed by VVI was dilation and stiffening of aortic wall. VVI is a feasible, in vivo method for quantification of aortic elastic properties and the magnitude of VVI-derived parameters showed independent associations with tissue collagen content of vessel wall.