Initial results of ultrasound screening for aneurysm of the abdominal aorta in Western Australia: relevance for endoluminal treatment of aneurysm disease

Background. Increased life expectancy in men during the last thirty years i s largely due to the decrease in mortality from cardiovascular disease in t he age group 29-69 yr. This change has resulted in a change in the disease profile of the population with conditions such as aneurysm of the abdominal aorta (AAA) becoming more prevalent. The advent of endoluminal treatment f or AAA has encouraged prophylactic intervention and fuelled the argument to screen for the disease. The feasibility of inserting an endoluminal graft is dependent on the morphology and growth characteristics of the aneurysm. This study used data from a randomized controlled trial of ultrasound scree ning for AAA in men aged 65-83 yr in Western Australia for the purpose of d etermining the norms of the living anatomy in the pressurized infrarenal ao rta. Aims. To examine (1) the diameters of the infra-renal aorta in aneurysmal a nd non-aneurysmal cases, (2) the implications for treatment modalities, wit h particular reference to endoluminal grafting, which is most dependent on normal and aneurysmal morphology, and (3) any evidence to support the notio n that northern Europeans are predisposed to aneurysmal disease. Methods. Using ultrasound, a randomized control trial was established in We stern Australia to assess the value of a screening program in males aged 65 -83 yr, The infra-renal aorta was defined as aneurysmal if the maximum diam eter was 30 mm or more. Aortic diameter was modelled both as a continuous t in mm) and as a binary outcome variable, for those men who had an infra-ren al diameter of 30 mm or more. ANOVA and linear regression were used for mod elling aortic diameter as a continuum, while chi-square analysis and logist ic regression were used in comparing men with and without the diagnosis of AAA. Findings. By December 1998, of 19.583 men had been invited to undergo ultra sound screening for AAA, 12.203 accepted the invitation (corrected response fraction 70.8%). The prevalence of AAA increased with age from 4.8% at 65 yr to 10.8% at 80 yr (chi (2) = 77.9, df = 3, P<0.001). The median (IQR) di ameter for the non-aneurysmal group was 21.4 mm (3.3 mm) and there was an i ncrease (<chi>(2) = 76.0, df = 1, P<0.001) in the diameter of the infra-ren al aorta with age. Since 27 mm is the 95th centile for the non-aneurysmal i nfra-renal aorta, a diameter of 30 mm or more is justified as defining an a neurysm. The risk of AAA was higher in men of Australian (OR = 1.0) and nor thern European origin (OR = 1.0, 95%CL: 0.9. 1.2) compared with those of Me diterranean origin (OR = 0.5, 99%CL: 0.4, 0.7). Conclusion. Although screening has not yet been shown to reduce mortality f rom AAA. these population-based data assist the understanding of aneurysmal disease and the further development and use of endoluminal grafts for this condition. (C) 2001 Published by Elsevier Science Ltd on behalf of The Int ernational Society for Cardiovascular Surgery.