Key result
Small abdominal aortic aneurysm growth rates increased with size, indicating safe ultrasound surveillance intervals of 60, 17, 11, and 5 months for sizes <3.5, 3.5-3.9, 4.0-4.4, and 4.5-4.9 cm.
Why the study?
What are the appropriate ultrasound screening intervals for small abdominal aortic aneurysms based on their growth rate?
Observational (n=252)
What are the appropriate ultrasound screening intervals for small abdominal aortic aneurysms based on their growth rate?
The growth rate of small AAAs increases with baseline size, suggesting that surveillance intervals can be tailored from 5 years for AAAs <3.5 cm to shorter intervals for larger aneurysms.
May support size-based AAA surveillance intervals; leaves open prospective validation before practice change.
The management of small abdominal aortic aneurysms (AAA) is by ultrasound surveillance. The study aimed to calculate their growth rate, identify risk factors and determine appropriate screening intervals. The local screening programme and hospital records were used to identify patients with a small (< 5.5 cm) AAA. The dates and maximum diameter of serial scans of patients with two or more scans were obtained. Patients were subdivided by 0.5 cm increments above 3.0 cm. The rate of growth was calculated by linear regression for each patient using both the absolute measurements and logarithmically (ln) transformed measurements. The 95th centile of growth rate within each subgroup was used to estimate the minimum time to grow to 5.5 cm. A total of 252 were included. The mean (± SD) AAA size on the initial scan was 3.9 (± 0.7) cm. Statin use and initial size were predictive factors for the growth rate. The median rate of growth increased according to size from 0.075 to 0.432 cm/year for AAA < 3.5 cm and > 5.0 cm, respectively. It also steadily increased for ln measurements from 0.022 (or 2.2%/year) to 0.078 or (7.8%/year). The minimum time (months) to reach 5.5 cm was 61, 17, 11 and 5 for AAA < 3.5 cm, 3.5-3.9 cm, 4.0-4.4 cm and 4.5-4.9 cm, respectively. Based on ln measurements, the times were similar at 60, 17, 10 and 4 months. In conclusion, the rate of growth increased steadily with AAA size. An aneurysm < 3.5 cm does not require a repeat scan for 5 years, while those measuring 3.5-3.9 cm and 4.0-4.4 cm require a repeat scan after 17 and 11 months.
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Badger et al. (2011) conducted an observational in Small abdominal aortic aneurysms (AAA) (n=252). Ultrasound surveillance was evaluated on Rate of growth and minimum time to grow to 5.5 cm. Small abdominal aortic aneurysm growth rates increased with size, indicating safe ultrasound surveillance intervals of 60, 17, 11, and 5 months for sizes <3.5, 3.5-3.9, 4.0-4.4, and 4.5-4.9 cm.
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