Background: Until recently, the principle prognostic indicator of progression and complications of abdominal aortic aneurysm (AAA) has been the maximum antero-posterior aortic diameter. However, evidence has accumulated that comprehensive assessment of risk of rupture must also consider peak stress on the aortic wall derived from local hemodynamic forces and material properties of the arterial wall. In the present study we show that M-mode high frequency ultrasound (HF-u/s) measurements of radial wall velocity (RWV), and anterior wall displacement (AWD) normalized to the diastolic diameter (DiasD), are strong predictors of AAA progression in the angiotensin-II-infused apolipoprotein E-deficient (Apo-E-/-) mouse model.
Methods: AAA was induced in Apo-E-/- mice (age16-20 weeks [w]) by infusion of angiotensin-II using osmotic minipumps (Alzet, model 2004, 1000ng/kg/min, 4w). M-mode HF-u/s (40MHz, 0.01mm resolution, Vevo-770, VisualSonics) was used to measure systolic and diastolic diameter, anterior and posterior wall displacement, and radial wall velocity (SysD, DiasD, AWD, PWD, and RWV, respectively) at baseline, 2, and 4 weeks. Mice with aortas that developed >35% maximal suprarenal aortic expansion at 2w over baseline (by B-mode HF-u/s) were included in this study (n=21).
Results: The greatest change in all M-mode parameters occurred at 2w over baseline, with significant changes at 4w being limited only to diameter measurements by B-mode. AWD/DiasD and RWV were dramatically decreased, while PWD/AWD was significantly increased, at 2w over baseline (baseline vs 2w [mean±SD]: AWD/DiasD [%] = 20±6 vs 6±4, pConclusions: Cofactoring M-mode with B-mode ultrasonography provides important additional information related to compromise of biomechanical integrity during aneurysm progression of potential relevance to prediction of rupture.
