FDG PET hot spots spell risk of rupture in abdominal aortic aneurysm

A higher risk of aneurysm is on the menu for patients who test positive for abdominal aortic inflammation and other cellular changes, according to a study published online Sept. 5 in the Journal of Nuclear Medicine.

The 13th leading cause of death in Western countries is the rupturing of an abdominal aortic aneurysm (AAA). F-18 FDG uptake in the abdominal aortic is present in a significant number of patients at high risk for rupture. Research scientist Audrey Courtois from the Laboratory of Connective Tissues Biology, GIGA-R at the University of Liege in Sart-Tilman, Belgium, and colleagues found strong inflammatory and other potentially damaging processes in the aortic wall that explained the association.

“The metabolically active spots detected by the uptake of F-18 FDG display striking alterations potentially related to medial degeneration and significant degradation of the fibrillar structures of the adventitia, which may ultimately lead to rupture,” wrote Courtois et al.

A total of 28 patients were included in the study. Eight subjects tested positive for F-18 FDG uptake as a result of PET/CT imaging and 10 tested negative for FDG uptake. Biopsies and immunohistochemistry were performed both at the areas of substantial uptake and in control sections that were negative for FDG. Results of the study showed that areas of clear uptake were overrun by adventitial inflammatory cells and were characterized by a dramatic dip in smooth muscle cells.

“It is worth noting that we were able to correlate the hot spots of F-18 FDG uptake with high peak wall stress that, in some cases, corresponded to the point of rupture of the aneurysm,” wrote the authors. “The uptake of F-18 FDG is likely related to the massive infiltrate of lymphocytes observed in the positive sites of the adventitia, which are probably activated as indicated by their increased proliferative activity and the increased number of plasmocytes. Moreover, macrophages present in the positive media in higher number may also incorporate F-18 FDG as previously reported.”

This and further study could one day help identify patients at risk for AAA rupture by pinpointing areas of active inflammation in deteriorating abdominal aortic walls.