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

Purpose: The purpose of this study was to examine the intraobserver and int erobserver error associated with ultrasonic echo-tracking compliance measur ement in patients with abdominal aortic aneurysm. Methods: Two observers independently measured brachial blood pressure by sp hygmomanometer and maximum aortic diameter, pressure strain elastic modulus (Ep) and stiffness using an ultrasonic echo-tracker. The observer was blin d to several variables: pulse pressure, diameter change, Ep, and stiffness. In study 1, observer A measured compliance in 13 patients at 30 to 60 minu tes apart. In study 2, observers A and B each measured compliance on 23 pat ients at two visits, 2 weeks apart. Results: There were no significant differences within observer A's complian ce measurements. The coefficients of variation of method error (CVME) for d irectly measured variables were systolic blood pressure, 7.3%; diastolic bl ood pressure, 5.4%; and maximum aortic diameter, 2.6%. CVME values for deri ved variables were Ep, 21.2%, and stiffness, 17.6%. No differences were fou nd between observers A and B and visits 1 and 2. CVME values were 7.9% or l ess for directly measured variables and 32.7% or less for derived variables . These CVME values were greatly reduced when the calculation was made with the use of log transformed data. Conclusion: The high CVME value for derived variables is largely due to the ir wide variation within this population. This technique can measure abdomi nal aortic aneurysm diameter and compliance with an acceptable level of int raobserver and interobserver error.