Predicting abdominal aortic aneurysm progression via metabolic and haemodynamic markers

Introduction Since abdominal aortic aneurysms (AAA) rupture is associated with high mortality, early diagnosis and risk stratification are essential for timely elective intervention. At present, the aneurysm maximum diameter is the only imaging-based metric used to evaluate rupture risk. However, other factors, such as inflammation and haemodynamics, may provide relevant insights about aneurysm growth. Purpose To explore the potential role of glucose uptake and blood flow dynamics on AAA progression. Methods Patients diagnosed with AAA underwent a hybrid 18F-fluorodesoxyglucose Positron Emission Tomography (18F-FDG PET) and cardiovascular magnetic resonance (CMR) imaging scan, including a 4D flow sequence (Fig. 1A). Patients were monitored over time to measure the rate of AAA diameter expansion. Haemodynamics and 18F-FDG PET target-to-background (TBR) were quantified at 28 standardised regions in the abdominal aorta (Fig. 1C, 1D and 1E). Correlations between baseline aortic diameter, haemodynamics, and TBR in the aneurysm and AAA growth rate were analysed using bivariate and multivariate linear regression models. Results Thirty-two AAA patients (84.4% men) with a median age of 73, inter-quartile range [68; 77] years were prospectively enrolled. At baseline, the AAA maximum diameter was 48.1 [44.8; 55.0] mm, and the aneurysm expanded at a rate of 2.7 [1.3; 4.0] mm/year over a prospective follow-up period of 2.0 [1.1; 3.5] years. Bivariate analysis showed significant correlations between growth rate and baseline AAA maximum diameter (R=0.443, p=0.011) and flow vorticity (R=0.453, p=0.009). After adjusting for aneurysm diameter, helicity density was correlated with growth rate (p=0.045), while thrombus volume was inversely correlated with it (p=0.042). Notably, aneurysms with negative helicity density (counterclockwise rotation) grew significantly faster (p=0.042) than those with positive helicity. In multivariate analysis, larger baseline diameter predicted faster future growth, whereas greater thrombus volume, higher helicity density, and elevated TBR were associated with slower aneurysm progression (Fig. 2). Conclusions Integrating flow, inflammatory and thrombus information may enhance the prediction of AAA growth rate, beyond the maximum aneurysm diameter.Fig 1:PET/CMR Analysis Flowchart Fig 2:High vs Low Aneurysm Growth Rates