Improved reliability of ultrasonic surveillance of abdominal aortic aneurysms

Objectives:

Small abdominal aortic aneurysms (AAA) are usually managed conservatively by serial ultrasound examinations to assess size. The development of the size of the AAA will determine whether the patient is a candidate for surgery. The precision of measurement is therefore of considerable importance. The aim of this study was to evaluate the accuracy and the reproducibility of a newly developed echo-tracking ultrasonic system in the size evaluation of AAA.

Design:

Prospective study at a University Hospital.

Material and methods:

An echo-tracking ultrasound system with a 3.5 MHz transducer was used in 54 patients with AAA. Thirty-six patients had repeated measurements by one technician to evaluate the intra-observer variability. In another 18 patients with aortic dilatation/AAA, the measurements were repeated by a second technician in a blinded fashion with calculation of inter-observer variability. The reproducibility was evaluated both using linear regression and plots according to the method described by Bland and Altman.

Results:

The mean diameter of the aorta was 37 mm (range 21–51 mm). The coefficient of correlation of repetitive measurements with one observer was r = 0.99 and with two observers r = 0.99. The intra-observer variability was 0.78 mm (s.d.) and the inter-observer variability 0.93 mm (s.d.). The intra- and inter-observer coefficient of variation (CV) was 2–3%.

Conclusions:

The newly developed echo-tracking ultrasonography seems at present to be the most accurate and reliable method to follow the diameter of an abdominal aortic aneurysm detecting relevant changes in the diameter exceeding 2 mm (2 s.d.). Thus it fulfils the requirements both for follow-up of conservatively managed AAAs and endovascularly treated aneurysms.