Growth Rate and Associated Factors in Small Abdominal Aortic Aneurysms

Abstract 

Objective

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 <5cm in diameter in two groups. Group I (AAA 3–3.9cm, n=246) underwent annual ultrasound scans. Group II (AAA 4–4.9cm, 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±3.23mm/year; p<0.0001). Group II had a greater percentage of patients with rapid aneurysm expansion (>4mm/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 (≤4mm/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±6.11mm/year; p=0.032).

Conclusions

The expansion rate of small AAA increases with the AAA size. AAA with a diameter of 3–3.9cm expand slowly, and they are very unlikely to require surgical repair in 5 years. Many 4–4.9cm 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.

Keywords: Small abdominal aortic aneurysm, Growth rate, Risk factors