High-Frequency Murine Ultrasound Provides Enhanced Metrics of BAPN-Induced AAA Growth

An abdominal aortic aneurysm (AAA), defined as a pathological expansion of the largest artery in the abdomen, is a relatively common disease that frequently leads to death if rupture occurs. Once diagnosed, clinicians often evaluate the rupture risk based on the maximum diameter of the aneurysm, a limited metric that is not accurate for all patients. In this study, we worked to provide additional distinguishing factors between growing and stable AAAs to aid in clinical rupture risk assessment. We utilized a relatively new murine model that uses surgical application of topical elastase to cause initial aortic expansion, and a lysyl oxidase inhibitor, β-aminopropionitrile (BAPN), in the drinking water to promote AAA growth. We further sought to develop and demonstrate applications of advanced imaging approaches, including four-dimensional ultrasound (4DUS), to obtain and evaluate alternative geometric and biomechanical parameters between 1) growing AAAs, 2) stable AAAs, and 3) non-aneurysmal control mice. Our study confirmed the reproducibility of the model and found reduced strain values, greater tortuosity, and decreased elastin health in mice with aneurysms. We also found expanding murine AAAs to have increased peak wall stress and surface area per length compared to stable aneurysms. The results from this work help provide a better understanding of the growth patterns associated with elastase-BAPN murine aneurysms and demonstrate the capabilities of high-frequency ultrasound. Eventually these data could help lay the groundwork for improving insight into clinical prediction of AAA expansion.