Predictors of abdominal aortic aneurysm progression in men with small infrarenal aortic diameters at screening

Screening for abdominal aortic aneurysm (AAA) defined as an infrarenal aortic diameter (IAD) of ≥30 mm reduces mortality, but managing patients with diameters of 25 to 29 mm is debated. Incorporating body surface area into the diagnostic criteria may improve the identification of those at risk of developing treatment-requiring aneurysms in this group. In a previous study, we defined a relative AAA as an IAD ≥150% larger than expected, with the normal diameter calculated using body surface area as a scaling factor. This study aimed to determine if this criterion could identify those at risk of aneurysmal development among patients with aortic diameter of 25 to 29 mm at screening.

A cohort study was conducted on men with abdominal aortic diameters of 25 to 29 mm at AAA screening in Malmö, Sweden, with a median follow-up of 9.9 years. Growth rates were compared between the relative aneurysm group and the nonrelative aneurysm group using a linear mixed-effects model to account for both fixed and random effects. Time and hazard ratio to reach 40 mm, a marker of significant aneurysmal progression, were assessed using a log-rank test and a Cox proportional hazards model, both adjusted for smoking status and diabetes.

In a cohort of 270 men, three developed AAAs ≥55 mm. The baseline growth rate was 0.1 mm/year (95% confidence interval [CI], 0.0-0.3). Growth rates were increased by 0.4 mm/year (95% CI, 0.0-0.7) in the relative aneurysm group, and by 0.4 mm/year (95% CI, 0.2-0.7) in smokers. The median time to reach an IAD of ≥40 mm was 11.5 years for relative aneurysms and was not reached for those without, with a significant difference shown by a log-rank test stratified for smoking (P = .009). Hazards ratio to reach an IAD of ≥40 mm for relative aneurysms was 2.77 (95% CI, 1.34-5.74; P = .006) compared with those without.

In men with diameters of 25 to 29 mm at screening for AAAs, the use of an individualized diagnostic criterion, based on height and weight, could identify those with increased aneurysm growth and a significantly shorter time to reach 40 mm compared with baseline. The relative aortic diameter, beyond the absolute diameter, seemed to be important for aneurysmal development. However, the differences were likely too small to warrant changes in clinical practice, highlighting the need for further research to establish clinical relevance.