Outcome of conservative medical treatment of patients with infrarenal abdominal aortic aneurysms

Objective: Since non-invasive diagnostic methods have become available and screening programs have become popular, abdominal aortic aneurysms are more frequently being detected at an early stage of the disease. We analyzed the course of conservatively treated patients with infrarenal abdominal aortic aneurysms (AAA), and determined independent risk factors for aneurysm expansion. Methods: The study was designed as a retrospective-cohort study including 110 consecutive patients with AAA. Cardiovascular risk factors, comorbidities, current medication, and the findings of color coded duplex sonography and computed tomography were recorded. Ninety-two conservatively treated patients were re-investigated every 6 or 12 months (depending on an initial aneurysm size of > 45 mm or < 45 mm respectively) after initial detection by color coded duplex sonography. We performed a multivariate Cox regression analysis to determine independent predictors of diameter progression (diameter increase greater than or equal to 5 mm). Results: We found AAA expansion in 46 conservatively treated patients (50%) during the median follow up period of 23 months (IQR 13 to 33), but no rupture occurred. Baseline diameter >45mm (HR 2.3, 95% CI 1.0 to 5.3, P = .04) and signs of aortic dissection in duplex ultrasound (HR 2.2, 1.0 to 4.6, P = .04) were independently associated with aneurysm expansion. The presence of an intraluminal thrombus showed a trend towards higher rates of disease progression (HR 2.6, 95% CI 0.9 to 7.6, P = .08). Conclusion: Patients with an aneurysm diameter >45 mm or ultrasound signs of aortic dissection have an increased risk for AAA progression and need careful evaluation, optimization of risk factors and close (six-month) follow-up intervals. For patients with an aneurysm diameter below 45 mm and without additional risk factors, follow-up intervals of 12 months seem to be safe.