Abstract 2697: Non-Invasive Imaging of the Aortic Pulse-Wave Propagation for the Detection of Abdominal Aortic Aneurysms In Vivo
OBJECTIVE: Pulse wave velocity (PWV) has long been used as an indicator of aortic compliance, which is an early predictor of cardiovascular mortality. A novel, ultrasound-based technique for non-invasive imaging of the pulse-wave propagation (PWP) may detect mechanical properties of the aortic wall in the presence and absence of abdominal aortic aneurysm (AAA).
METHODS: Wild-type mice were treated by infusing angiotensin II (Ang II) or saline (sham). Thirty-five Ang II-treated and five sham mice aortas were scanned using 30 MHz ultrasound (Vevo 770, Visualsonics, Inc.) at 8000 frames/s with an ECG gating technique. Incremental displacements of the aortic wall were estimated using a 1D cross-correlation method. Color-coded ciné-loops of the displacement images showed the PWP along the aortic wall (see figure⇓). The PWV was estimated through a linear regression.
RESULTS: Local AAA was formed in 17 Ang II-treated mice and confirmed by histopathology whereas aneurysm formation was observed in the sham mice. The PWP occurred from proximal (heart) to distal (renal) in the sham mice at 2.13 ± 0.82 m/s (r2 = 0.86 ± 0.09), and in the AAA mice at 0.92 ± 0.92 m/s (r2 =0.51 ± 0.18). The maximum displacements were 1.59 ± 0.72 um (proximal wall), 0.93 ± 0.37 um (middle wall), 1.08 ± 0.48 um (distal wall) in the AAA mice, with the smallest displacements occurring in the aneurysm (see figure⇓), and 2.36 ± 0.98 um in the sham mice, respectively. The difference between these two groups was significant (p < 0.01).
CONCLUSION: The PWP was successfully imaged in mice using high frame-rate ultrasound. This novel imaging technique may be capable of detecting the AAA based on the distinct mechanical wall properties.