Biomechanical changes during abdominal aortic aneurysm growth

The biomechanics-based Abdominal Aortic Aneurysm (AAA) rupture risk assessment has gainedconsiderable scientific and clinical momentum. However, such studies have mainly focused oninformation at a single time point, and little is known about how AAA properties change over time.Consequently, the present study explored how geometry, wall stress-related and blood flow-relatedbiomechanical properties change during AAA expansion. Four patients with a total of 23 ComputedTomography-Angiography (CT-A) scans at different time points were analyzed. At each time point,patient-specific properties were extracted from (i) the reconstructed geometry, (ii) the computedwall stress at Mean Arterial Pressure (MAP), and (iii) the computed blood flow velocity atstandardized in and out flow conditions. Testing correlations between these parameters identifiedseveral non-intuitive dependencies. Most interestingly, the Peak Wall Rupture Index (PWRI) and themaximum Wall Shear Stress (WSS) independently predicted AAA volume growth. Similarly, Intra-luminal Thrombus (ILT) volume growth depended on both the maximum WSS and the ILT volumeitself. In addition, ILT volume, ILT volume growth and maximum ILT layer thickness correlated withPWRI as well as AAA volume growth. Consequently, a large ILT volume as well as fast increase of ILTvolume over time may be a risk factor for AAA rupture. However, tailored clinical studies would berequired to test this hypothesis and to clarify whether monitoring ILT development has any clinicalbenefit.QC 20170116