Risk factors for aneurysm rupture in patients kept under ultrasound surveillance

Objective To investigate risk factors associated with aneurysm rupture using patients randomized into the U.K. Small Aneurysm Trial (n = 1090) or monitored for aneurysm growth in the associated study(n = 1167), Summary Background Data The U.K. 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 1%. Methods In the cohort of 2257 patients (79% male), aged 59 to 77 years, 103 instances of abdominal aortic aneurysm rupture were identified during the 7-year period of follow-up (1991-1998). Almost all patients (98%) had initial aneurysm diameters in the range of 3 to 6 cm, and the majority of ruptures (76%) occurred in patients with aneurysms greater than or equal to 5 cm in diameter. Kaplan-Meier survival and Cox regression analysis were used to identify baseline risk factors associated with aneurysm rupture. Results After 3 years, the annual rate of aneurysm rupture was 2.2% (95% confidence interval 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), lower FEV1 (p = 0.004), current smoking (p = 0.001), 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. Conclusions Within this cohort of patients, women had a threefold higher risk of aneurysm rupture than men. Effective control of blood pressure and cessation of smoking are likely to diminish the risk of rupture.