Ultrasonic measurement of abdominal aortic aneurysm wall compliance: a reproducibility study

The purpose of this study was to examine the intraobserver and interobserver error associated with ultrasonic echo-tracking compliance measurement in patients with abdominal aortic aneurysm.

Two observers independently measured brachial blood pressure by sphygmomanometer and maximum aortic diameter, pressure strain elastic modulus (Ep) and stiffness using an ultrasonic echo-tracker. The observer was blind to several variables: pulse pressure, diameter change, Ep, and stiffness. In study 1, observer A measured compliance in 13 patients at 30 to 60 minutes apart. In study 2, observers A and B each measured compliance on 23 patients at two visits, 2 weeks apart.

There were no significant differences within observer A's compliance measurements. The coefficients of variation of method error (CV(ME)) for directly measured variables were systolic blood pressure, 7.3%; diastolic blood pressure, 5.4%; and maximum aortic diameter, 2.6%. CV(ME) values for derived variables were Ep, 21.2%, and stiffness, 17.6%. No differences were found between observers A and B and visits 1 and 2. CV(ME) values were 7.9% or less for directly measured variables and 32.7% or less for derived variables. These CV(ME) values were greatly reduced when the calculation was made with the use of log transformed data.

The high CV(ME) value for derived variables is largely due to their wide variation within this population. This technique can measure abdominal aortic aneurysm diameter and compliance with an acceptable level of intraobserver and interobserver error.