The value of volume over maximum diameter for following abdominal aortic aneurysm growth and reducing surveillance visits in patients with a subthreshold aneurysm.

Abstract

To describe and compare abdominal aortic aneurysm (AAA) volume to maximum diameter regarding follow-up of AAA progression and investigate its added value in AAA surveillance. This prospective, observational cohort study included 126 patients enrolled in the multicenter BIOMArCS-AAA study (Study of Biomarker Profiling to Unravel the Intertwined Pathophysiology of Coronary Artery Disease and Abdominal Aortic Aneurysm) who were under surveillance for an AAA. Participants underwent computed tomography scans at study inclusion and after 1 and 2 years, alongside computed tomography scans for clinical care. Maximum diameter and total volume were measured after center lumen line reconstruction. Mixed-effects regression was used to evaluate the maximum diameter and volume changes over time. The value of volume alongside the maximum diameter to distinguish patients who will or will not experience the composite end point (qualifying for surgery, or AAA rupture/AAA-related death) was evaluated using Cox models and cumulative incidence-based positive and negative predictive values. A median of three scans were available per patient. The baseline median (25th, 75th percentile) maximum diameter and volume were 48 mm (45, 52 mm) and 109 mL (90, 130 mL), respectively. The observed median (25th, 75th percentile) growth at the 1-year follow-up was 2.3 mm (1.3, 3.1 mm) in maximum diameter, and 10.8 mL (7.0, 16.4 mL) in volume. Changes in aneurysm size at the next recommended surveillance visit lay within the boundaries of the interobserver variability for 81 patients (65%) when measuring maximum diameter, compared with 43 patients (34%) when measuring volume (P < .001). Using a single maximum diameter measurement, 32 patients (26%) could be exempt from surveillance imaging at 1 year, while ensuring that the risk of qualifying for surgery remains below 10%. When combining this with a simultaneous volume measurement, 54 patients (44%) could similarly be safely exempt from surveillance imaging (P = .002). Moreover, simultaneously measuring volume refines the identification of patients that will qualify for surgery at 2 years (positive predictive value diameter alone vs diameter and volume, 57.7% and 72.5%, respectively; P < .001). AAA volume is more sensitive to detect small changes in aneurysm size at the currently recommended surveillance intervals, and could be used to safely prolong surveillance intervals for patients with a small AAA. The use of volume should be encouraged in research and could prove valuable in AAA surveillance.