Abstract 13737: Abdominal Aortic Aneurysm Growth is Predicted by Uptake of Ultrasmall Superparamagnetic Particles of Iron Oxide
Background: Abdominal aortic aneurysms are a major cause of death. Prediction of aneurysm expansion and rupture is challenging and currently relies on the simple measure of aneurysm diameter. Using magnetic resonance imaging, we aimed to assess whether areas of cellular inflammation correlated with the rate of abdominal aortic aneurysm expansion.
Methods: Stable patients (n=29; 27 male; aged 70±5 years) with asymptomatic abdominal aortic aneurysms (4–6.6 cm) were recruited from a surveillance programme and were imaged in a 3T magnetic resonance imaging scanner before and 24–36 h after administration of ultrasmall superparamagnetic particles of iron oxide (USPIO). The change in T2* value on T2*-weighted imaging was used to detect accumulation of USPIO within the abdominal aortic aneurysm. The aneurysm growth rate was calculated from serial ultrasound measurements. In patients undergoing surgery, a sample of aortic wall was fixed and stained for CD68 (macrophages) and Prussian blue (iron).
Results: Histological examination of aneurysm tissue confirmed co-localisation and uptake of USPIOs in areas with macrophage infiltration. Patients with distinct hotspots of USPIO uptake (n=13, Figure (a)) had a three-fold higher growth rate (0.66 cm/yr; P=0.020) than those with no (n=7; 0.22 cm/yr; Figure (b)) or with non-specific USPIO uptake (n=9; 0.24 cm/yr; Figure (c)) despite having similar aneurysm diameters (P=ns). In one patient with an inflammatory aneurysm, there was a strong and widespread uptake of USPIO (Figure (d)) extending beyond the aortic wall (arrows).
Conclusions: Uptake of USPIOs in abdominal aortic aneurysms identifies cellular inflammation and appears to distinguish those patients with more rapidly progressive abdominal aortic aneurysm expansion. This technique holds major promise as a new method of risk-stratifying patients with abdominal aortic aneurysms that extends beyond the simple anatomical measure of aneurysm diameter.
- © 2010 by American Heart Association, Inc.