Ww. Reed et al., LEARNING FROM THE LAST ULTRASOUND - A POPULATION-BASED STUDY OF PATIENTS WITH ABDOMINAL AORTIC-ANEURYSM, Archives of internal medicine, 157(18), 1997, pp. 2064-2068
Background: Patients with abdominal aortic aneurysm often are followed
up with serial ultrasound examinations, but published studies usually
describe rupture risk according to the diameter of the abdominal aort
ic aneurysm at diagnosis rather than by most recent ultrasound. Inform
ation in this form is misleading when used to predict prognosis. Metho
ds: We used data from the population-based cohort of residents of Roch
ester, Minn, diagnosed as having abdominal aortic aneurysm who have ha
d at least 1 ultrasound measurement. Of the 181 patients who were enro
lled in this cohort between January 1, 1974, and December 31, 1988, 5
had clinical evidence of rupture at entry. Analysis of a cohort define
d by size category at ''last ultrasound'' was undertaken to assess rup
ture risk and growth rate. Results: Median overall aneurysmal growth r
ate was 0.21 cm/y. Initial growth rate did not correlate with subseque
nt growth rate (r=0.18; P=.14) or with initial size (r=-0.12; P=.22).
Only 1 aneurysm ruptured when last ultrasound was less than 5 cm, and
this occurred 3 1/2 years after this ultrasound. Estimated rupture ris
k by last ultrasound was 0% per year (95% confidence interval [CI], 0%
-5%) when less than 4.00 cm, 1.0% per year (95% CI, 0%-5%) when 4.00 t
o 4.99 cm, and 11% per year (95% CI, 1%-21%) when 5.00 to 5.99 cm. Con
clusions: The most clinically useful approach to estimating the risk o
f abdominal aortic aneurysm rupture is according to size at last ultra
sound. Aneurysm growth rate is predicted neither by size nor by initia
l growth rate.