Circulating markers of abdominal aortic aneurysm presence and progression.

Over the last decade, abdominal aortic aneurysm (AAA) has increasingly been recognized as an important cause of mortality in older persons. In 1999, for example, AAA was noted to be the 15th leading cause of mortality in the United States.1 Exact estimates of AAA-related fatalities are hampered by the low rate of postmortems when sudden death occurs in elderly subjects; however, recent figures suggest that AAA accounts for 15 000 deaths annually in the United States despite the increasing number of elective AAA repairs.2,3 Approximately 25 000 endovascular and open AAA repairs are performed annually in the United States.3 Ultrasound screening of men 65 years of age has been demonstrated to reduce AAA-related mortality, and selective screening (of men 65 of age who have ever smoked) has been introduced in the United States.4 Most screen-detected AAAs are small ( 55 mm), and surgery for these AAAs has not been demonstrated to improve outcome.5–7 In a screening study of 12 203 men 65 years of age performed in Australia, for example, 814 (6.7%) had a small AAA measuring 30 to 54 mm, but only 61 (0.5%) had a large AAA ( 55 mm).8 The increase in identification of small AAAs resulting from screening programs, in association with an ageing population, highlights the number of deficiencies in the current diagnosis and management of this condition. First, there are no accurate nonimaging methods of diagnosing small AAAs, with clinical examination being inaccurate.9 Second, prognostic determinants for AAA are relatively poorly defined.10 Approximately 70% of 40to 55-mm AAAs expand within 10 years to a size requiring treatment.6,7 There are, however, large intrapatient and interpatient variations in rates of expansion of small AAAs during follow-up.10 To date, only initial aortic diameter has consistently been shown to predict a subsequent increase in aortic diameter.10–13 Smoking has been associated with increased and diabetes with decreased AAA expansion in some but not all studies.10–13 More accurate prognostic predictors would offer the possibility of selecting patients for different management pathways rather than relying on aortic diameter alone.10 Finally, the management of small AAAs remains controversial despite randomized controlled trials indicating that open surgical repair of 40to 55-mm AAAs does not reduce mortality.6,7 Many centers manage all AAAs 55 mm conservatively. Estimates based on the UK Small Aneurysm Trial support repeat imaging for 30to 40-, 41to 45-, 46to 50-, and 51to 55-mm AAAs at 24-, 12-, 6-, and 3-month intervals, respectively.10 The increasing use of endovascular repair of AAA, with its lower perioperative mortality, has been suggested as more appropriate management for small AAAs, particularly those in the 50to 55-mm range.14,15 At present, however, no randomized controlled trial examining the outcome of endovascular repair of small AAAs has been completed, although 1 such study is expected to report soon.16 The lack of any proven medical therapy for prevention of the progression and rupture of AAAs represents an important challenge.17 Only 1 randomized trial has examined the value of a medication (propranolol) for small AAAs in a cohort of a reasonable size ( 500 subjects).18