Growth rates and risk of rupture of abdominal aortic aneurysms

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Abstract
Background: Early identification of abdominal aortic aneurysms (AAAs) may reduce the risk of death from rupture by providing the opportunity for elective repair. Before a screening policy for AAA is implemented, the growth rates of AAAs and the accompanying risk of rupture without intervention should be established. Methods: The growth rates of AAAs were calculated using longitudinal aneurysmal growth data from screening studies in Chichester and Huntingdon. Estimates of the growth rates of AAAs and the risks of rupture over time were made taking measurement error and individual variability into account. Results: Growth rate estimates were found to vary by initial aortic diameter, with a more rapid growth seen in large aneurysms (50 mm or more). The rate of aneurysm growth did not differ with age or sex. The estimated risk of rupture of an AAA with an initial diameter of 45 mm did not exceed 20·5 per cent over 5 years. An AAA with an initial diameter of 30 mm has a 4·0 per cent or less chance of rupture over 5 years. Conclusion: The study provides a more accurate assessment of the risk of aneurysm rupture without surgery and helps to define rescreening intervals for those with an enlarged aortic diameter.