11B-5 Pulse Wave Imaging Of Abdominal Aortic Aneurysms: Comparison Between Control And Angiotensin II-Treated Mice In Vivo

Abstract

The abdominal aortic aneurysm (AAA) is a common vascular disease. AAA disease leads to changes in the mechanical properties of the aortic wall. Pulse-wave imaging (PWI) has been developed by our group to noninvasively and visually map the pulse-wave propagation along the aortic wall in mice at a frame rate of 8 kHz in vivo. By using a retrospective electrocardiogram (ECG) gating technique, the radio-frequency (RF) signals over one cardiac cycle were obtained in murine aortas at the extremely high frame rate of 8 kHz and with a field- of-view of 12times12 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The incremental displacements of the aortic wall were estimated using an RF-based speckle tracking method. An Angiotensin II (AngII) infusion-based AAA model was used in this paper. In the normal and sham aortas, the propagation of the pulse wave was relatively uniform, with a higher PWV. In the AngII-treated aortas, the propagation of the pulse was nonuniform while the PWV was significantly lower. The displacements induced by the pulse wave were smaller and the pulse wave moved nonuniformly along the AngII-treated aorta, with the lowest displacements at the aneurysmal regions. A student's t-test on five (n=5) sham and seventeen (n=17) AngII- treated aortas demonstrated the capability of PWI in differentiating AngII-treated from sham aortas. The regional- displacement discrepancy and the nonuniform pulse-wave propagation indicated the inhomogeneities in the aortic wall properties, and the reduced PWV and displacements suggested the change in aortic wall stiffness. This novel PWI technique may thus constitute an early detection tool of vascular degeneration as well as serve as a potentially suitable predictor of AAA rupture.