Improved reliability of ultrasonic surveillance of abdominal aortic aneurysms.

Abstract

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. Prospective study at a University Hospital. 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. 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%. 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.