Purpose: Early repair of abdominal aortic aneurysms (AAA) is particularly appropriate for those that are most likely to expand. Our aim was to define features on computed tomography (CT) scanning associated with subsequent rapid aneurysm expansion.
Methods: We reviewed CT scans of 80 patients with AAA (> 3.0 cm) who underwent CT scanning of the abdomen and pelvis two times, at least 6 months apart, between 1986 and 1992. The aneurysms initially measured 4.4 +/- 0.6 cm, and the mean interval between obtaining scans was 22 +/- 12 months. Clinical variables assessed included age, sex, medical risk factors, underlying cardiovascular and pulmonary diseases, and administration of beta blockers and lipid-lowering agents. Computer-aided measurements on each CT scan section included the maximal and minimal diameters and area of the aneurysm. Dimensions of the luminal thrombus and the arc of aneurysm wall covered by thrombus (TARC). Maximal aneurysm dimensions were related to juxtarenal aortic and second lumbar vertebral body dimensions.
Results: Mean aneurysm expansion was 0.26 +/- 0.25 cm/yr. CT scanning variables that correlated significantly with rate of expansion included the mean TARC (r = 0.43, p < 0.001), thrombus volume fraction (r = 0.37, p < 0.001), TARC on the largest aneurysm cross section (r = 0.34, p < 0.01), and thrombus area fraction (r = 0.30, p < 0.01). Rapid expansion (> 0.5 cm/yr) occurred in 15 (19%) aneurysms. The two predictors for rapid expansion on logistic regression analysis were mean TARC (p < 0.005) and the presence of carotid artery disease (p < 0.05).
Conclusion: An increased AAA thrombus load is associated with a higher likelihood of rapid expansion and should weigh in favor of early surgical repair.