Invited commentary
Article Outline
Surgeons have known for many years that maximal aneurysm diameter is a poor predictor of rupture for any particular individual patient. However, we continue to use maximal diameter as our determinant of recommendation for aneurysm repair because we are unable to translate several new concepts, such as finite element analysis,1 shape changes,2 and serum markers,3 into clinically meaningful predictions.
Reeps et al describe a small series of patients with aneurysms in which they have examined the aneurysms with fluorodeoxyglucose F 18 (FDG)-positron emission tomography (PET)/computed tomography (CT) scanning and then correlated areas of maximal FDG uptake with histologic markers of inflammation and wall degradation in surgically obtained aneurysm wall biopsy specimens. FDG-PET scanning is an established technique that is available in most hospitals and can be used to detect increased glucose accumulation, reflecting increased metabolic rate, in vivo.
Other preliminary studies have suggested that increased aneurysm metabolism may be related to inflammatory changes within the aneurysm, but this study is novel. Not only have the authors shown that aneurysms have significantly greater metabolic activity compared with normal aorta, and symptomatic aneurysms have greater activity compared to quiescent aneurysms, but the authors also correlate metabolic activity with increased inflammatory cell density, increased matrix metalloproteinase (MMP)-2 and MMP-9 expression, and decreased collagen and smooth muscle cells in the aneurysm. In particular, these histologic changes occurred precisely in the area localized by the FDG-PET scan, validating this technique with clinically relevant and previously reported pathologic changes.
Several limitations of this study need additional confirmation before we can apply FDG-PET to select patients for aneurysm repair. The small number of symptomatic patients needs to be increased, correlation with finite element analysis and plasma levels of MMP-2 and MMP-9 would be helpful, and infection needs to be excluded, notwithstanding the confounding Chlamydia hypothesis. Scientifically, it would be nice to see additional studies confirming protein detection with more quantitative Western blot analysis as well as analysis of gene expression.
However, this seminal report shows that aneurysm activity correlates with FDG uptake on PET scan. If validated, these findings could lead to a paradigm shift in how we select patients for early repair.
References
- . In vivo analysis of mechanical wall stress and abdominal aortic aneurysm rupture risk. J Vasc Surg. 2002;36:589–597
- . Beyond fusiform and saccular: a novel quantitative tortuosity index may help classify aneurysm shape and predict aneurysm rupture potential. Ann Vasc Surg. 2008;22:88–97
- . Serum elastin peptides in the preoperative evaluation of abdominal aortic aneurysms. Eur J Vasc Endovasc Surg. 2001;22:546–550
PII: S0741-5214(08)00510-7
doi:10.1016/j.jvs.2008.04.001
© 2008 The Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.
