Risk Factors for Rupture of an Abdominal Aortic Aneurysm

 

Risk factors for rupture:

(1) diameter of the aneurysm (see below)

(2) mean blood pressure (diastolic hypertension; the mean blood pressure for a blood pressure of 140/90 is 107 mm Hg)

(3) smoking and COPD

(4) family history of a ruptured aneurysm (this could be restricted to a rupture of an abdominal aortic aneurysm)

(5) expansion rate (in SESAP, > 0.5 cm in 6 months)

(6) female gender (although aneurysms are more common in men)

 

Other factors:

(1) inflammation within the aortic wall

(2) thrombus free surface area of the aneurysm sac

 

Diameter of the aneurysm:

(1) Aneurysms with a diameter of < 4 cm have a low rate of rupture.

(2) Aneurysms with a diameter of >= 6 cm have a high rate of rupture, which increases exponentially.

(3) Problems with data: reported over a diameter range (for example 4-4.9 cm), for different time periods (for example, for 1 or 5 years).

(4) Monitoring should be standardized to minimize variation (differences from using different scanning methods and observers).

Diameter in cm	Rate of Rupture in 1 Year
5.0	4%
6.0	10%
7.0	15%
8.0	30%
9.0	60%
10.0	90%

from Figure page 1194, Thompson and Bell (2000)

 

Implications for a patient with an abdominal aortic aneurysm:

(1) Hypertension should be controlled.

(2) Smoking should be stopped.

(3) Patients with a large aneurysm or an increase in a size of an aneurysm should be evaluated for elective repair.

(4) The UK Small Aneurysm Trial showed that patients with aneurysms measuring 4.0 to 5.5 cm in diameter could be followed safely with ultrasound.