Gender-specific Predicted Normal Aortic Size and Its Consequences of the Population-Based Prevalence of Abdominal Aortic Aneurysms

Abstract

To investigate if a relative-size-index of the abdominal aortic diameter influences the prevalence estimates of abdominal aortic dilatations compared to absolute diameters. Cross-sectional study. Participants from the Viborg Vascular Screening Trial, Viborg Women Cohort, and the Viborg Screening Program. Through multivariate linear regression analyses, two gender-specific prediction-equations were developed based upon body-surface area and age. The definitions of absolute and relative size of aortic ectasies were 25-29 mm and 1.25-1.49 x individual-predicted size (IPS), abdominal aortic aneurysm (AAA) 30 mm and 1.5 x IPS, and large repair-recommendable AAA ≥55mm or ≥ 2.75 x IPS, respectively. 19 269 males (69.6 years) and 2 426 females (67.1 years) attended the population- and ultrasound-based screening studies for AAA. The mean peak systolic abdominal anterior-posterior inner to inner diameter was 19.1mm (±5.3mm) and 16.6mm (±2.8mm) (P< .001) in males and females, respectively. Body surface area showed the strongest correlation with aortic diameters in both males (r=0.19, p< .001) and females (r=0.17, p< .001). Age correlated significantly with size, but only in males (r=0.03, p< .001). The prevalence in men of absolute-size-defined and relative-size-index-defined screening-detected aortic ectasies, AAAs and repair-recommendable AAAs were: 5.9% and 9.5% (p< .001), 3.3% and 4.2% (p< .001) and 9.9% and 15.2% (p= .004), respectively. Prevalence in females of absolute-size-defined and relative-size-index-defined screening-detected aortic ectasies, AAAs and repair-recommendable AAAs were 1.2% and 5.8% (p< .001), 0.5% and 1.3% (p= .003) and 0.0% and 23.1% (p= .553), respectively. Despite statistical differences, ultrasound-based absolute diameters to detect AAA seem acceptable in men. In females, poor agreements were noticed concerning all three categories of aneurysms, indicating that the current absolute diagnostic cut-points do not reflect female anatomy.