To study the growth rate and factors influencing progression of small infrarenal abdominal aortic aneurysms (AAA).
Design
Observational, longitudinal, prospective study.
Patients and methods
We followed patients with AAA <5 cm in diameter in two groups. Group I (AAA 3–3.9 cm, n=246) underwent annual ultrasound scans. Group II (AAA 4–4.9 cm, n=106) underwent 6-monthly CT scans.
Results
We included 352 patients (333 men and 19 women) followed for a mean of 55.2±37.4 months (6.3–199.8). The mean growth rate was significantly greater in group II (4.72±5.93 vs. 2.07±3.23 mm/year; p<0.0001). Group II had a greater percentage of patients with rapid aneurysm expansion (>4 mm/year) (36.8 vs. 13.8%; p<0.0001). The classical cardiovascular risk factors did not influence the AAA growth rate in group I. Chronic limb ischemia was associated with slower expansion (≤4 mm/year) (OR 0.47; CI 95% 0.22–0.99; p=0.045). Diabetic patients in group II had a significantly smaller mean AAA growth rate than non-diabetics (1.69±3.51 vs. 5.22±6.11 mm/year; p=0.032).
Conclusions
The expansion rate of small AAA increases with the AAA size. AAA with a diameter of 3–3.9 cm expand slowly, and they are very unlikely to require surgical repair in 5 years. Many 4–4.9 cm AAA can be expected to reach a surgical size in the first 2 years of follow-up. Chronic limb ischemia and diabetes are associated with reduced aneurysm growth rates.