The natural history of abdominal aortic aneurysms and their risk of rupture.

The UK Small Aneurysm Trial has shown that ultrasound surveillance is a safe management option for patients with small abdominal aortic aneurysms (4.0 to 5.5 cm in diameter), with an annual rupture rate of only 1%. We investigated baseline risk factors associated with aneurysm rupture in the 1090 trial patients and an additional 1167 patients enrolled in the UK Small Aneurysm Study. In this cohort of 2257 patients there were 103 cases of aneurysm rupture. After 3 years the annual rate of rupture was 2.2% (95% CI 1.7 to 2.8). The risk of rupture was independently and significantly associated with female sex (p < 0.001), larger initial aneurysm diameter (p < 0.001), current smoking (p = 0.01) and higher mean blood pressure (p = 0.01). Age, body mass index, serum cholesterol concentration and ankle/brachial pressure index were not associated with an increased risk of aneurysm rupture. The most surprising finding was that women had a 3-fold higher risk of aneurysm rupture than men. Effective control of blood pressure and cessation of smoking are two simple measures that are likely to diminish the risk of aneurysm rupture and improve the cardiovascular health of patients with abdominal aortic aneurysm.