Predictors of Abdominal Aortic Aneurysm Progression in Men with small Infrarenal Aortic Diameters at Screening.

Abstract

Objective: Screening for abdominal aortic aneurysm defined as an infrarenal aortic diameter ≥30 mm reduces mortality, but managing patients with diameters of 25-29 mm is debated. Incorporating body surface area into diagnostic criteria may improve identification of those at risk of developing treatment-requiring aneurysms in this group. In a previous study, we defined a relative abdominal aortic aneurysm as an infrarenal aortic diameter ≥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 25-29 mm at screening.

Methods: A cohort study was conducted on men with abdominal aortic diameters of 25-29 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 non-relative 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.

Results: In a cohort of 270 men, three developed abdominal aortic aneurysms ≥55 mm. Baseline growth rate was 0.1 mm/year (95% 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. Median time to reach IAD ≥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 IAD ≥40 mm for relative aneurysms was 2.77 (95% CI: 1.34-5.74, p=.006) compared to those without.

Conclusion: In men with diameters of 25-29 mm at screening for abdominal aortic aneurysms, the use of an individualised diagnostic criterion, based on height and weight, could identify those with increased aneurysm growth and a significantly shorter time to reach 40 mm compared to baseline. The relative aortic diameter, beyond the absolute diameter, appeared 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.