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 s
afe 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 instanc
es of abdominal aortic aneurysm rupture were identified during the 7-year p
eriod of follow-up (1991-1998). Almost all patients (98%) had initial aneur
ysm 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 diame
ter. Kaplan-Meier survival and Cox regression analysis were used to identif
y 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 significan
tly associated with female sex (p < 0.001), larger initial aneurysm diamete
r (p < 0.001), lower FEV1 (p = 0.004), current smoking (p = 0.001), and hig
her 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 aneury
sm rupture than men. Effective control of blood pressure and cessation of s
moking are likely to diminish the risk of rupture.