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Rupture Risk for Abdominal Aortic Aneurysms: Size Matters

Large abdominal aortic aneurysms had a high incidence of rupture at 1 year and the strongest predictor of rupture was initial AAA diameter.

There are few data on the rupture rate of large abdominal aortic aneurysms (AAA). These authors conducted a prospective, observational study of patients at 47 Veteran Affairs Medical Centers who had AAAs 5.5 cm and refused (42.6%) or were deemed medically unfit (81.3%) for elective repair, or both. Exclusion criteria were symptoms or radiologic evidence of rupture, prior aortic surgery, dissection of the thoracic aorta, known conditions associated with secondary AAA, or death expected within 30 days. Ruptures were defined as definite (confirmed by autopsy, surgery, or computed tomography) or probable (patient died with symptoms that were consistent with rupture but no objective confirmation). Ultrasonography was performed every 6 months.

During a mean follow-up of 1.5 years (range, 6-42 months), 112 of the 198 patients (57%) died. Forty-five patients (23%) had definite or probable rupture. The 1-year incidence of rupture was 9.4% for AAAs with an initial diameter of 5.5-5.9 cm, 10.2% for those 6.0-6.9 cm, 19.1% for those 6.5-6.9 cm, and 32.5% for those 7.0 cm. The 6-month incidence of rupture for AAAs that attained a diameter of 8 cm was 25.7%. Predictors of rupture included relatively large AAA diameter (relative risk, 1.39 per 1 cm) and renal artery involvement (RR, 2.36). The median rate of change in diameter (0.43 cm/year) was significantly higher for AAAs that ruptured (mean enlargement rate, 0.75 cm/year) than for those that did not (0.41 cm/year).

Comment: The rupture rate of large AAAs in patients with high operative risk is substantial. Not surprisingly, the factor most predictive of risk is the diameter of the AAA.

— John A. Marx, MD, FACEP

Published in Journal Watch Emergency Medicine August 28, 2002

Citation(s):

Lederle FA et al. Rupture rate of large abdominal aortic aneurysms in patients refusing or unfit for elective repair. JAMA 2002 Jun 12; 287:2968-72.

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