November 16, 2006

Small AAA Expansion Rates in Current Practice

Joel E. Barbato, MD, Jonathan Small, BS, Michael Go, MD, Jae Cho, MD, Robert Y. Rhee, MD, Michel S. Makaroun, MD.
University of Pittsburgh, Pittsburgh, PA, USA.

Objectives: New standards for measuring abdominal aortic aneurysms include use of the minor axis for better accuracy. Small aneurysm management would benefit from an estimate of the rate of growth using this standard as all previous reports used maximal diameter.
Methods: A retrospective review of AAA patients referred for intervention was performed. Patient characteristics, including age, sex, CAD, history of smoking, hypertension, diabetes, and COPD were collected. Multivariate analysis of the effect on growth rate was compared with both linear and logistic regression models.
Results: A total of 246 patients had “small” aneurysms followed with serial radiographs (over a total of 616 patient years). Mean age was 73.0±8.6 years and 68.7% were male. Hypertension and smoking were associated with a non-significant trend toward increase in aneurysm growth rates of 0.04 mm/year, whereas diabetes appeared to have a protective effect of 1.0 mm/year (p=0.06). Hypertension however significantly predicted growth with an odds ratio of 2.19 (p=0.024) in those patients whose aneurysms demonstrated expansion. Mean aneurysm growth rate was only 0.30±0.34 cm/year and was related to initial size.
Mean rate of growth by initial documented aneurysm size


Initial aneurysm size (minor axis)	Mean rate of minor axis growth (cm/yr)	p-value
3.0-3.9 (n=98)	0.26±0.31	0.069*
4.0-4.4 (n=83)	0.30±0.33	0.022†
4.5-5.0 (n=47)	0.41±0.45

*overall test †test for trend
Conclusions: Aneurysms grow at a faster rate as size increases which should dictate a different follow-up schedule for each range. Only aneurysms exceeding 4.5 cm in minor axis expand at 0.4 cm/year. Hypertension is a predictor of expansion.

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