Evaluating Growth Patterns of Abdominal Aortic Aneurysm Diameter With Serial Computed Tomography Surveillance

IMPORTANCE: Small abdominal aortic aneurysms (AAAs) are common in the elderly population. Their growth rates and patterns, which drive clinical surveillance, are widely disputed. OBJECTIVE: To assess the growth patterns and rates of AAAs as documented on serial computed tomography (CT) scans. DESIGN, SETTING, AND PARTICIPANTS: Cohort study and secondary analysis of the Non-Invasive Treatment of Abdominal Aortic Aneurysm Clinical Trial (N-TA3CT), a randomized, double-blind placebo-controlled clinical trial conducted from 2013 to 2018, with CT imaging every 6 months for 2 years. The trial was a multicenter, observational secondary analysis, not related to treatment hypotheses of data collected in the N-TA3CT. Participants included 254 patients with baseline AAA diameter between 3.5 and 5.0 cm. EXPOSURES: Patients received serial CT scan measurements, analyzed for maximum transverse diameter, at 6-month intervals. MAIN OUTCOMES AND MEASURES: The primary study outcome was AAA annual growth rate. Secondary analyses included characterizing AAA growth patterns, assessing likelihood of AAA diameter to exceed sex-specific intervention thresholds over 2 years. RESULTS: A total of 254 patients, 35 women with baseline AAA diameter 3.5 to 4.5 cm and 219 men with baseline diameter 3.5 to 5.0 cm, were included. Yearly growth rates of AAA diameters were a median of 0.17 cm/y (interquartile range [IQR], 0.16) and a mean (SD), 0.19 (0.14) cm/y. Ten percent of AAAs displayed minimal to no growth (0.25 cm/y). Baseline AAA diameter accounted for 5.4% of variance of growth rate (P